Update to MediaWiki 1.20.2

this update includes:
* adjusted Arch Linux skin
* updated FluxBBAuthPlugin
* patch for https://bugzilla.wikimedia.org/show_bug.cgi?id=44024

18 files changed, 9804 insertions, 0 deletions

diff --git a/includes/filebackend/FSFile.php b/includes/filebackend/FSFile.php
new file mode 100644
index 00000000..e07c99d4
--- /dev/null
+++ b/includes/filebackend/FSFile.php
@@ -0,0 +1,252 @@
+<?php
+/**
+ * Non-directory file on the file system.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ */
+
+/**
+ * Class representing a non-directory file on the file system
+ *
+ * @ingroup FileBackend
+ */
+class FSFile {
+	protected $path; // path to file
+
+	/**
+	 * Sets up the file object
+	 *
+	 * @param $path string Path to temporary file on local disk
+	 * @throws MWException
+	 */
+	public function __construct( $path ) {
+		if ( FileBackend::isStoragePath( $path ) ) {
+			throw new MWException( __METHOD__ . " given storage path `$path`." );
+		}
+		$this->path = $path;
+	}
+
+	/**
+	 * Returns the file system path
+	 *
+	 * @return String
+	 */
+	public function getPath() {
+		return $this->path;
+	}
+
+	/**
+	 * Checks if the file exists
+	 *
+	 * @return bool
+	 */
+	public function exists() {
+		return is_file( $this->path );
+	}
+
+	/**
+	 * Get the file size in bytes
+	 *
+	 * @return int|bool
+	 */
+	public function getSize() {
+		return filesize( $this->path );
+	}
+
+	/**
+	 * Get the file's last-modified timestamp
+	 *
+	 * @return string|bool TS_MW timestamp or false on failure
+	 */
+	public function getTimestamp() {
+		wfSuppressWarnings();
+		$timestamp = filemtime( $this->path );
+		wfRestoreWarnings();
+		if ( $timestamp !== false ) {
+			$timestamp = wfTimestamp( TS_MW, $timestamp );
+		}
+		return $timestamp;
+	}
+
+	/**
+	 * Guess the MIME type from the file contents alone
+	 * 
+	 * @return string 
+	 */
+	public function getMimeType() {
+		return MimeMagic::singleton()->guessMimeType( $this->path, false );
+	}
+
+	/**
+	 * Get an associative array containing information about
+	 * a file with the given storage path.
+	 *
+	 * @param $ext Mixed: the file extension, or true to extract it from the filename.
+	 *             Set it to false to ignore the extension.
+	 *
+	 * @return array
+	 */
+	public function getProps( $ext = true ) {
+		wfProfileIn( __METHOD__ );
+		wfDebug( __METHOD__.": Getting file info for $this->path\n" );
+
+		$info = self::placeholderProps();
+		$info['fileExists'] = $this->exists();
+
+		if ( $info['fileExists'] ) {
+			$magic = MimeMagic::singleton();
+
+			# get the file extension
+			if ( $ext === true ) {
+				$ext = self::extensionFromPath( $this->path );
+			}
+
+			# mime type according to file contents
+			$info['file-mime'] = $this->getMimeType();
+			# logical mime type
+			$info['mime'] = $magic->improveTypeFromExtension( $info['file-mime'], $ext );
+
+			list( $info['major_mime'], $info['minor_mime'] ) = File::splitMime( $info['mime'] );
+			$info['media_type'] = $magic->getMediaType( $this->path, $info['mime'] );
+
+			# Get size in bytes
+			$info['size'] = $this->getSize();
+
+			# Height, width and metadata
+			$handler = MediaHandler::getHandler( $info['mime'] );
+			if ( $handler ) {
+				$tempImage = (object)array();
+				$info['metadata'] = $handler->getMetadata( $tempImage, $this->path );
+				$gis = $handler->getImageSize( $tempImage, $this->path, $info['metadata'] );
+				if ( is_array( $gis ) ) {
+					$info = $this->extractImageSizeInfo( $gis ) + $info;
+				}
+			}
+			$info['sha1'] = $this->getSha1Base36();
+
+			wfDebug(__METHOD__.": $this->path loaded, {$info['size']} bytes, {$info['mime']}.\n");
+		} else {
+			wfDebug(__METHOD__.": $this->path NOT FOUND!\n");
+		}
+
+		wfProfileOut( __METHOD__ );
+		return $info;
+	}
+
+	/**
+	 * Placeholder file properties to use for files that don't exist
+	 *
+	 * @return Array
+	 */
+	public static function placeholderProps() {
+		$info = array();
+		$info['fileExists'] = false;
+		$info['mime'] = null;
+		$info['media_type'] = MEDIATYPE_UNKNOWN;
+		$info['metadata'] = '';
+		$info['sha1'] = '';
+		$info['width'] = 0;
+		$info['height'] = 0;
+		$info['bits'] = 0;
+		return $info;
+	}
+
+	/**
+	 * Exract image size information
+	 *
+	 * @param $gis array
+	 * @return Array
+	 */
+	protected function extractImageSizeInfo( array $gis ) {
+		$info = array();
+		# NOTE: $gis[2] contains a code for the image type. This is no longer used.
+		$info['width'] = $gis[0];
+		$info['height'] = $gis[1];
+		if ( isset( $gis['bits'] ) ) {
+			$info['bits'] = $gis['bits'];
+		} else {
+			$info['bits'] = 0;
+		}
+		return $info;
+	}
+
+	/**
+	 * Get a SHA-1 hash of a file in the local filesystem, in base-36 lower case
+	 * encoding, zero padded to 31 digits.
+	 *
+	 * 160 log 2 / log 36 = 30.95, so the 160-bit hash fills 31 digits in base 36
+	 * fairly neatly.
+	 *
+	 * @return bool|string False on failure
+	 */
+	public function getSha1Base36() {
+		wfProfileIn( __METHOD__ );
+
+		wfSuppressWarnings();
+		$hash = sha1_file( $this->path );
+		wfRestoreWarnings();
+		if ( $hash !== false ) {
+			$hash = wfBaseConvert( $hash, 16, 36, 31 );
+		}
+
+		wfProfileOut( __METHOD__ );
+		return $hash;
+	}
+
+	/**
+	 * Get the final file extension from a file system path
+	 * 
+	 * @param $path string
+	 * @return string
+	 */
+	public static function extensionFromPath( $path ) {
+		$i = strrpos( $path, '.' );
+		return strtolower( $i ? substr( $path, $i + 1 ) : '' );
+	}
+
+	/**
+	 * Get an associative array containing information about a file in the local filesystem.
+	 *
+	 * @param $path String: absolute local filesystem path
+	 * @param $ext Mixed: the file extension, or true to extract it from the filename.
+	 *             Set it to false to ignore the extension.
+	 *
+	 * @return array
+	 */
+	public static function getPropsFromPath( $path, $ext = true ) {
+		$fsFile = new self( $path );
+		return $fsFile->getProps( $ext );
+	}
+
+	/**
+	 * Get a SHA-1 hash of a file in the local filesystem, in base-36 lower case
+	 * encoding, zero padded to 31 digits.
+	 *
+	 * 160 log 2 / log 36 = 30.95, so the 160-bit hash fills 31 digits in base 36
+	 * fairly neatly.
+	 *
+	 * @param $path string
+	 *
+	 * @return bool|string False on failure
+	 */
+	public static function getSha1Base36FromPath( $path ) {
+		$fsFile = new self( $path );
+		return $fsFile->getSha1Base36();
+	}
+}
diff --git a/includes/filebackend/FSFileBackend.php b/includes/filebackend/FSFileBackend.php
new file mode 100644
index 00000000..93495340
--- /dev/null
+++ b/includes/filebackend/FSFileBackend.php
@@ -0,0 +1,986 @@
+<?php
+/**
+ * File system based backend.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Class for a file system (FS) based file backend.
+ *
+ * All "containers" each map to a directory under the backend's base directory.
+ * For backwards-compatibility, some container paths can be set to custom paths.
+ * The wiki ID will not be used in any custom paths, so this should be avoided.
+ *
+ * Having directories with thousands of files will diminish performance.
+ * Sharding can be accomplished by using FileRepo-style hash paths.
+ *
+ * Status messages should avoid mentioning the internal FS paths.
+ * PHP warnings are assumed to be logged rather than output.
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+class FSFileBackend extends FileBackendStore {
+	protected $basePath; // string; directory holding the container directories
+	/** @var Array Map of container names to root paths */
+	protected $containerPaths = array(); // for custom container paths
+	protected $fileMode; // integer; file permission mode
+	protected $fileOwner; // string; required OS username to own files
+	protected $currentUser; // string; OS username running this script
+
+	protected $hadWarningErrors = array();
+
+	/**
+	 * @see FileBackendStore::__construct()
+	 * Additional $config params include:
+	 *   - basePath       : File system directory that holds containers.
+	 *   - containerPaths : Map of container names to custom file system directories.
+	 *                      This should only be used for backwards-compatibility.
+	 *   - fileMode       : Octal UNIX file permissions to use on files stored.
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+
+		// Remove any possible trailing slash from directories
+		if ( isset( $config['basePath'] ) ) {
+			$this->basePath = rtrim( $config['basePath'], '/' ); // remove trailing slash
+		} else {
+			$this->basePath = null; // none; containers must have explicit paths
+		}
+
+		if ( isset( $config['containerPaths'] ) ) {
+			$this->containerPaths = (array)$config['containerPaths'];
+			foreach ( $this->containerPaths as &$path ) {
+				$path = rtrim( $path, '/' );  // remove trailing slash
+			}
+		}
+
+		$this->fileMode = isset( $config['fileMode'] ) ? $config['fileMode'] : 0644;
+		if ( isset( $config['fileOwner'] ) && function_exists( 'posix_getuid' ) ) {
+			$this->fileOwner = $config['fileOwner'];
+			$info = posix_getpwuid( posix_getuid() );
+			$this->currentUser = $info['name']; // cache this, assuming it doesn't change
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::resolveContainerPath()
+	 * @param $container string
+	 * @param $relStoragePath string
+	 * @return null|string
+	 */
+	protected function resolveContainerPath( $container, $relStoragePath ) {
+		// Check that container has a root directory
+		if ( isset( $this->containerPaths[$container] ) || isset( $this->basePath ) ) {
+			// Check for sane relative paths (assume the base paths are OK)
+			if ( $this->isLegalRelPath( $relStoragePath ) ) {
+				return $relStoragePath;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * Sanity check a relative file system path for validity
+	 *
+	 * @param $path string Normalized relative path
+	 * @return bool
+	 */
+	protected function isLegalRelPath( $path ) {
+		// Check for file names longer than 255 chars
+		if ( preg_match( '![^/]{256}!', $path ) ) { // ext3/NTFS
+			return false;
+		}
+		if ( wfIsWindows() ) { // NTFS
+			return !preg_match( '![:*?"<>|]!', $path );
+		} else {
+			return true;
+		}
+	}
+
+	/**
+	 * Given the short (unresolved) and full (resolved) name of
+	 * a container, return the file system path of the container.
+	 *
+	 * @param $shortCont string
+	 * @param $fullCont string
+	 * @return string|null
+	 */
+	protected function containerFSRoot( $shortCont, $fullCont ) {
+		if ( isset( $this->containerPaths[$shortCont] ) ) {
+			return $this->containerPaths[$shortCont];
+		} elseif ( isset( $this->basePath ) ) {
+			return "{$this->basePath}/{$fullCont}";
+		}
+		return null; // no container base path defined
+	}
+
+	/**
+	 * Get the absolute file system path for a storage path
+	 *
+	 * @param $storagePath string Storage path
+	 * @return string|null
+	 */
+	protected function resolveToFSPath( $storagePath ) {
+		list( $fullCont, $relPath ) = $this->resolveStoragePathReal( $storagePath );
+		if ( $relPath === null ) {
+			return null; // invalid
+		}
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $storagePath );
+		$fsPath = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		if ( $relPath != '' ) {
+			$fsPath .= "/{$relPath}";
+		}
+		return $fsPath;
+	}
+
+	/**
+	 * @see FileBackendStore::isPathUsableInternal()
+	 * @return bool
+	 */
+	public function isPathUsableInternal( $storagePath ) {
+		$fsPath = $this->resolveToFSPath( $storagePath );
+		if ( $fsPath === null ) {
+			return false; // invalid
+		}
+		$parentDir = dirname( $fsPath );
+
+		if ( file_exists( $fsPath ) ) {
+			$ok = is_file( $fsPath ) && is_writable( $fsPath );
+		} else {
+			$ok = is_dir( $parentDir ) && is_writable( $parentDir );
+		}
+
+		if ( $this->fileOwner !== null && $this->currentUser !== $this->fileOwner ) {
+			$ok = false;
+			trigger_error( __METHOD__ . ": PHP process owner is not '{$this->fileOwner}'." );
+		}
+
+		return $ok;
+	}
+
+	/**
+	 * @see FileBackendStore::doStoreInternal()
+	 * @return Status
+	 */
+	protected function doStoreInternal( array $params ) {
+		$status = Status::newGood();
+
+		$dest = $this->resolveToFSPath( $params['dst'] );
+		if ( $dest === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		if ( file_exists( $dest ) ) {
+			if ( !empty( $params['overwrite'] ) ) {
+				$ok = unlink( $dest );
+				if ( !$ok ) {
+					$status->fatal( 'backend-fail-delete', $params['dst'] );
+					return $status;
+				}
+			} else {
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		}
+
+		if ( !empty( $params['async'] ) ) { // deferred
+			$cmd = implode( ' ', array( wfIsWindows() ? 'COPY' : 'cp',
+				wfEscapeShellArg( $this->cleanPathSlashes( $params['src'] ) ),
+				wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
+			) );
+			$status->value = new FSFileOpHandle( $this, $params, 'Store', $cmd, $dest );
+		} else { // immediate write
+			$ok = copy( $params['src'], $dest );
+			// In some cases (at least over NFS), copy() returns true when it fails
+			if ( !$ok || ( filesize( $params['src'] ) !== filesize( $dest ) ) ) {
+				if ( $ok ) { // PHP bug
+					unlink( $dest ); // remove broken file
+					trigger_error( __METHOD__ . ": copy() failed but returned true." );
+				}
+				$status->fatal( 'backend-fail-store', $params['src'], $params['dst'] );
+				return $status;
+			}
+			$this->chmod( $dest );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FSFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseStore( $errors, Status $status, array $params, $cmd ) {
+		if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
+			$status->fatal( 'backend-fail-store', $params['src'], $params['dst'] );
+			trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doCopyInternal()
+	 * @return Status
+	 */
+	protected function doCopyInternal( array $params ) {
+		$status = Status::newGood();
+
+		$source = $this->resolveToFSPath( $params['src'] );
+		if ( $source === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+			return $status;
+		}
+
+		$dest = $this->resolveToFSPath( $params['dst'] );
+		if ( $dest === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		if ( file_exists( $dest ) ) {
+			if ( !empty( $params['overwrite'] ) ) {
+				$ok = unlink( $dest );
+				if ( !$ok ) {
+					$status->fatal( 'backend-fail-delete', $params['dst'] );
+					return $status;
+				}
+			} else {
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		}
+
+		if ( !empty( $params['async'] ) ) { // deferred
+			$cmd = implode( ' ', array( wfIsWindows() ? 'COPY' : 'cp',
+				wfEscapeShellArg( $this->cleanPathSlashes( $source ) ),
+				wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
+			) );
+			$status->value = new FSFileOpHandle( $this, $params, 'Copy', $cmd, $dest );
+		} else { // immediate write
+			$ok = copy( $source, $dest );
+			// In some cases (at least over NFS), copy() returns true when it fails
+			if ( !$ok || ( filesize( $source ) !== filesize( $dest ) ) ) {
+				if ( $ok ) { // PHP bug
+					unlink( $dest ); // remove broken file
+					trigger_error( __METHOD__ . ": copy() failed but returned true." );
+				}
+				$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+				return $status;
+			}
+			$this->chmod( $dest );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FSFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseCopy( $errors, Status $status, array $params, $cmd ) {
+		if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+			trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doMoveInternal()
+	 * @return Status
+	 */
+	protected function doMoveInternal( array $params ) {
+		$status = Status::newGood();
+
+		$source = $this->resolveToFSPath( $params['src'] );
+		if ( $source === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+			return $status;
+		}
+
+		$dest = $this->resolveToFSPath( $params['dst'] );
+		if ( $dest === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		if ( file_exists( $dest ) ) {
+			if ( !empty( $params['overwrite'] ) ) {
+				// Windows does not support moving over existing files
+				if ( wfIsWindows() ) {
+					$ok = unlink( $dest );
+					if ( !$ok ) {
+						$status->fatal( 'backend-fail-delete', $params['dst'] );
+						return $status;
+					}
+				}
+			} else {
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		}
+
+		if ( !empty( $params['async'] ) ) { // deferred
+			$cmd = implode( ' ', array( wfIsWindows() ? 'MOVE' : 'mv',
+				wfEscapeShellArg( $this->cleanPathSlashes( $source ) ),
+				wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
+			) );
+			$status->value = new FSFileOpHandle( $this, $params, 'Move', $cmd );
+		} else { // immediate write
+			$ok = rename( $source, $dest );
+			clearstatcache(); // file no longer at source
+			if ( !$ok ) {
+				$status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
+				return $status;
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FSFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseMove( $errors, Status $status, array $params, $cmd ) {
+		if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
+			$status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
+			trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doDeleteInternal()
+	 * @return Status
+	 */
+	protected function doDeleteInternal( array $params ) {
+		$status = Status::newGood();
+
+		$source = $this->resolveToFSPath( $params['src'] );
+		if ( $source === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+			return $status;
+		}
+
+		if ( !is_file( $source ) ) {
+			if ( empty( $params['ignoreMissingSource'] ) ) {
+				$status->fatal( 'backend-fail-delete', $params['src'] );
+			}
+			return $status; // do nothing; either OK or bad status
+		}
+
+		if ( !empty( $params['async'] ) ) { // deferred
+			$cmd = implode( ' ', array( wfIsWindows() ? 'DEL' : 'unlink',
+				wfEscapeShellArg( $this->cleanPathSlashes( $source ) )
+			) );
+			$status->value = new FSFileOpHandle( $this, $params, 'Copy', $cmd );
+		} else { // immediate write
+			$ok = unlink( $source );
+			if ( !$ok ) {
+				$status->fatal( 'backend-fail-delete', $params['src'] );
+				return $status;
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FSFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseDelete( $errors, Status $status, array $params, $cmd ) {
+		if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
+			$status->fatal( 'backend-fail-delete', $params['src'] );
+			trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doCreateInternal()
+	 * @return Status
+	 */
+	protected function doCreateInternal( array $params ) {
+		$status = Status::newGood();
+
+		$dest = $this->resolveToFSPath( $params['dst'] );
+		if ( $dest === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		if ( file_exists( $dest ) ) {
+			if ( !empty( $params['overwrite'] ) ) {
+				$ok = unlink( $dest );
+				if ( !$ok ) {
+					$status->fatal( 'backend-fail-delete', $params['dst'] );
+					return $status;
+				}
+			} else {
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		}
+
+		if ( !empty( $params['async'] ) ) { // deferred
+			$tempFile = TempFSFile::factory( 'create_', 'tmp' );
+			if ( !$tempFile ) {
+				$status->fatal( 'backend-fail-create', $params['dst'] );
+				return $status;
+			}
+			$bytes = file_put_contents( $tempFile->getPath(), $params['content'] );
+			if ( $bytes === false ) {
+				$status->fatal( 'backend-fail-create', $params['dst'] );
+				return $status;
+			}
+			$cmd = implode( ' ', array( wfIsWindows() ? 'COPY' : 'cp',
+				wfEscapeShellArg( $this->cleanPathSlashes( $tempFile->getPath() ) ),
+				wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
+			) );
+			$status->value = new FSFileOpHandle( $this, $params, 'Create', $cmd, $dest );
+			$tempFile->bind( $status->value );
+		} else { // immediate write
+			$bytes = file_put_contents( $dest, $params['content'] );
+			if ( $bytes === false ) {
+				$status->fatal( 'backend-fail-create', $params['dst'] );
+				return $status;
+			}
+			$this->chmod( $dest );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FSFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseCreate( $errors, Status $status, array $params, $cmd ) {
+		if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
+			$status->fatal( 'backend-fail-create', $params['dst'] );
+			trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doPrepareInternal()
+	 * @return Status
+	 */
+	protected function doPrepareInternal( $fullCont, $dirRel, array $params ) {
+		$status = Status::newGood();
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+		$existed = is_dir( $dir ); // already there?
+		if ( !wfMkdirParents( $dir ) ) { // make directory and its parents
+			$status->fatal( 'directorycreateerror', $params['dir'] ); // fails on races
+		} elseif ( !is_writable( $dir ) ) {
+			$status->fatal( 'directoryreadonlyerror', $params['dir'] );
+		} elseif ( !is_readable( $dir ) ) {
+			$status->fatal( 'directorynotreadableerror', $params['dir'] );
+		}
+		if ( is_dir( $dir ) && !$existed ) {
+			// Respect any 'noAccess' or 'noListing' flags...
+			$status->merge( $this->doSecureInternal( $fullCont, $dirRel, $params ) );
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doSecureInternal()
+	 * @return Status
+	 */
+	protected function doSecureInternal( $fullCont, $dirRel, array $params ) {
+		$status = Status::newGood();
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+		// Seed new directories with a blank index.html, to prevent crawling...
+		if ( !empty( $params['noListing'] ) && !file_exists( "{$dir}/index.html" ) ) {
+			$bytes = file_put_contents( "{$dir}/index.html", $this->indexHtmlPrivate() );
+			if ( $bytes === false ) {
+				$status->fatal( 'backend-fail-create', $params['dir'] . '/index.html' );
+				return $status;
+			}
+		}
+		// Add a .htaccess file to the root of the container...
+		if ( !empty( $params['noAccess'] ) && !file_exists( "{$contRoot}/.htaccess" ) ) {
+			$bytes = file_put_contents( "{$contRoot}/.htaccess", $this->htaccessPrivate() );
+			if ( $bytes === false ) {
+				$storeDir = "mwstore://{$this->name}/{$shortCont}";
+				$status->fatal( 'backend-fail-create', "{$storeDir}/.htaccess" );
+				return $status;
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doPublishInternal()
+	 * @return Status
+	 */
+	protected function doPublishInternal( $fullCont, $dirRel, array $params ) {
+		$status = Status::newGood();
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+		// Unseed new directories with a blank index.html, to allow crawling...
+		if ( !empty( $params['listing'] ) && is_file( "{$dir}/index.html" ) ) {
+			$exists = ( file_get_contents( "{$dir}/index.html" ) === $this->indexHtmlPrivate() );
+			if ( $exists && !unlink( "{$dir}/index.html" ) ) { // reverse secure()
+				$status->fatal( 'backend-fail-delete', $params['dir'] . '/index.html' );
+				return $status;
+			}
+		}
+		// Remove the .htaccess file from the root of the container...
+		if ( !empty( $params['access'] ) && is_file( "{$contRoot}/.htaccess" ) ) {
+			$exists = ( file_get_contents( "{$contRoot}/.htaccess" ) === $this->htaccessPrivate() );
+			if ( $exists && !unlink( "{$contRoot}/.htaccess" ) ) { // reverse secure()
+				$storeDir = "mwstore://{$this->name}/{$shortCont}";
+				$status->fatal( 'backend-fail-delete', "{$storeDir}/.htaccess" );
+				return $status;
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doCleanInternal()
+	 * @return Status
+	 */
+	protected function doCleanInternal( $fullCont, $dirRel, array $params ) {
+		$status = Status::newGood();
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+		wfSuppressWarnings();
+		if ( is_dir( $dir ) ) {
+			rmdir( $dir ); // remove directory if empty
+		}
+		wfRestoreWarnings();
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doFileExists()
+	 * @return array|bool|null
+	 */
+	protected function doGetFileStat( array $params ) {
+		$source = $this->resolveToFSPath( $params['src'] );
+		if ( $source === null ) {
+			return false; // invalid storage path
+		}
+
+		$this->trapWarnings(); // don't trust 'false' if there were errors
+		$stat = is_file( $source ) ? stat( $source ) : false; // regular files only
+		$hadError = $this->untrapWarnings();
+
+		if ( $stat ) {
+			return array(
+				'mtime' => wfTimestamp( TS_MW, $stat['mtime'] ),
+				'size'  => $stat['size']
+			);
+		} elseif ( !$hadError ) {
+			return false; // file does not exist
+		} else {
+			return null; // failure
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doClearCache()
+	 */
+	protected function doClearCache( array $paths = null ) {
+		clearstatcache(); // clear the PHP file stat cache
+	}
+
+	/**
+	 * @see FileBackendStore::doDirectoryExists()
+	 * @return bool|null
+	 */
+	protected function doDirectoryExists( $fullCont, $dirRel, array $params ) {
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+
+		$this->trapWarnings(); // don't trust 'false' if there were errors
+		$exists = is_dir( $dir );
+		$hadError = $this->untrapWarnings();
+
+		return $hadError ? null : $exists;
+	}
+
+	/**
+	 * @see FileBackendStore::getDirectoryListInternal()
+	 * @return Array|null
+	 */
+	public function getDirectoryListInternal( $fullCont, $dirRel, array $params ) {
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+		$exists = is_dir( $dir );
+		if ( !$exists ) {
+			wfDebug( __METHOD__ . "() given directory does not exist: '$dir'\n" );
+			return array(); // nothing under this dir
+		} elseif ( !is_readable( $dir ) ) {
+			wfDebug( __METHOD__ . "() given directory is unreadable: '$dir'\n" );
+			return null; // bad permissions?
+		}
+		return new FSFileBackendDirList( $dir, $params );
+	}
+
+	/**
+	 * @see FileBackendStore::getFileListInternal()
+	 * @return array|FSFileBackendFileList|null
+	 */
+	public function getFileListInternal( $fullCont, $dirRel, array $params ) {
+		list( $b, $shortCont, $r ) = FileBackend::splitStoragePath( $params['dir'] );
+		$contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
+		$dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
+		$exists = is_dir( $dir );
+		if ( !$exists ) {
+			wfDebug( __METHOD__ . "() given directory does not exist: '$dir'\n" );
+			return array(); // nothing under this dir
+		} elseif ( !is_readable( $dir ) ) {
+			wfDebug( __METHOD__ . "() given directory is unreadable: '$dir'\n" );
+			return null; // bad permissions?
+		}
+		return new FSFileBackendFileList( $dir, $params );
+	}
+
+	/**
+	 * @see FileBackendStore::getLocalReference()
+	 * @return FSFile|null
+	 */
+	public function getLocalReference( array $params ) {
+		$source = $this->resolveToFSPath( $params['src'] );
+		if ( $source === null ) {
+			return null;
+		}
+		return new FSFile( $source );
+	}
+
+	/**
+	 * @see FileBackendStore::getLocalCopy()
+	 * @return null|TempFSFile
+	 */
+	public function getLocalCopy( array $params ) {
+		$source = $this->resolveToFSPath( $params['src'] );
+		if ( $source === null ) {
+			return null;
+		}
+
+		// Create a new temporary file with the same extension...
+		$ext = FileBackend::extensionFromPath( $params['src'] );
+		$tmpFile = TempFSFile::factory( 'localcopy_', $ext );
+		if ( !$tmpFile ) {
+			return null;
+		}
+		$tmpPath = $tmpFile->getPath();
+
+		// Copy the source file over the temp file
+		$ok = copy( $source, $tmpPath );
+		if ( !$ok ) {
+			return null;
+		}
+
+		$this->chmod( $tmpPath );
+
+		return $tmpFile;
+	}
+
+	/**
+	 * @see FileBackendStore::directoriesAreVirtual()
+	 * @return bool
+	 */
+	protected function directoriesAreVirtual() {
+		return false;
+	}
+
+	/**
+	 * @see FileBackendStore::doExecuteOpHandlesInternal()
+	 * @return Array List of corresponding Status objects
+	 */
+	protected function doExecuteOpHandlesInternal( array $fileOpHandles ) {
+		$statuses = array();
+
+		$pipes = array();
+		foreach ( $fileOpHandles as $index => $fileOpHandle ) {
+			$pipes[$index] = popen( "{$fileOpHandle->cmd} 2>&1", 'r' );
+		}
+
+		$errs = array();
+		foreach ( $pipes as $index => $pipe ) {
+			// Result will be empty on success in *NIX. On Windows,
+			// it may be something like "        1 file(s) [copied|moved].".
+			$errs[$index] = stream_get_contents( $pipe );
+			fclose( $pipe );
+		}
+
+		foreach ( $fileOpHandles as $index => $fileOpHandle ) {
+			$status = Status::newGood();
+			$function = '_getResponse' . $fileOpHandle->call;
+			$this->$function( $errs[$index], $status, $fileOpHandle->params, $fileOpHandle->cmd );
+			$statuses[$index] = $status;
+			if ( $status->isOK() && $fileOpHandle->chmodPath ) {
+				$this->chmod( $fileOpHandle->chmodPath );
+			}
+		}
+
+		clearstatcache(); // files changed
+		return $statuses;
+	}
+
+	/**
+	 * Chmod a file, suppressing the warnings
+	 *
+	 * @param $path string Absolute file system path
+	 * @return bool Success
+	 */
+	protected function chmod( $path ) {
+		wfSuppressWarnings();
+		$ok = chmod( $path, $this->fileMode );
+		wfRestoreWarnings();
+
+		return $ok;
+	}
+
+	/**
+	 * Return the text of an index.html file to hide directory listings
+	 *
+	 * @return string
+	 */
+	protected function indexHtmlPrivate() {
+		return '';
+	}
+
+	/**
+	 * Return the text of a .htaccess file to make a directory private
+	 *
+	 * @return string
+	 */
+	protected function htaccessPrivate() {
+		return "Deny from all\n";
+	}
+
+	/**
+	 * Clean up directory separators for the given OS
+	 *
+	 * @param $path string FS path
+	 * @return string
+	 */
+	protected function cleanPathSlashes( $path ) {
+		return wfIsWindows() ? strtr( $path, '/', '\\' ) : $path;
+	}
+
+	/**
+	 * Listen for E_WARNING errors and track whether any happen
+	 *
+	 * @return bool
+	 */
+	protected function trapWarnings() {
+		$this->hadWarningErrors[] = false; // push to stack
+		set_error_handler( array( $this, 'handleWarning' ), E_WARNING );
+		return false; // invoke normal PHP error handler
+	}
+
+	/**
+	 * Stop listening for E_WARNING errors and return true if any happened
+	 *
+	 * @return bool
+	 */
+	protected function untrapWarnings() {
+		restore_error_handler(); // restore previous handler
+		return array_pop( $this->hadWarningErrors ); // pop from stack
+	}
+
+	/**
+	 * @return bool
+	 */
+	private function handleWarning() {
+		$this->hadWarningErrors[count( $this->hadWarningErrors ) - 1] = true;
+		return true; // suppress from PHP handler
+	}
+}
+
+/**
+ * @see FileBackendStoreOpHandle
+ */
+class FSFileOpHandle extends FileBackendStoreOpHandle {
+	public $cmd; // string; shell command
+	public $chmodPath; // string; file to chmod
+
+	/**
+	 * @param $backend
+	 * @param $params array
+	 * @param $call
+	 * @param $cmd
+	 * @param $chmodPath null
+	 */
+	public function __construct( $backend, array $params, $call, $cmd, $chmodPath = null ) {
+		$this->backend = $backend;
+		$this->params = $params;
+		$this->call = $call;
+		$this->cmd = $cmd;
+		$this->chmodPath = $chmodPath;
+	}
+}
+
+/**
+ * Wrapper around RecursiveDirectoryIterator/DirectoryIterator that
+ * catches exception or does any custom behavoir that we may want.
+ * Do not use this class from places outside FSFileBackend.
+ *
+ * @ingroup FileBackend
+ */
+abstract class FSFileBackendList implements Iterator {
+	/** @var Iterator */
+	protected $iter;
+	protected $suffixStart; // integer
+	protected $pos = 0; // integer
+	/** @var Array */
+	protected $params = array();
+
+	/**
+	 * @param $dir string file system directory
+	 * @param $params array
+	 */
+	public function __construct( $dir, array $params ) {
+		$dir = realpath( $dir ); // normalize
+		$this->suffixStart = strlen( $dir ) + 1; // size of "path/to/dir/"
+		$this->params = $params;
+
+		try {
+			$this->iter = $this->initIterator( $dir );
+		} catch ( UnexpectedValueException $e ) {
+			$this->iter = null; // bad permissions? deleted?
+		}
+	}
+
+	/**
+	 * Return an appropriate iterator object to wrap
+	 *
+	 * @param $dir string file system directory
+	 * @return Iterator
+	 */
+	protected function initIterator( $dir ) {
+		if ( !empty( $this->params['topOnly'] ) ) { // non-recursive
+			# Get an iterator that will get direct sub-nodes
+			return new DirectoryIterator( $dir );
+		} else { // recursive
+			# Get an iterator that will return leaf nodes (non-directories)
+			# RecursiveDirectoryIterator extends FilesystemIterator.
+			# FilesystemIterator::SKIP_DOTS default is inconsistent in PHP 5.3.x.
+			$flags = FilesystemIterator::CURRENT_AS_SELF | FilesystemIterator::SKIP_DOTS;
+			return new RecursiveIteratorIterator(
+				new RecursiveDirectoryIterator( $dir, $flags ),
+				RecursiveIteratorIterator::CHILD_FIRST // include dirs
+			);
+		}
+	}
+
+	/**
+	 * @see Iterator::key()
+	 * @return integer
+	 */
+	public function key() {
+		return $this->pos;
+	}
+
+	/**
+	 * @see Iterator::current()
+	 * @return string|bool String or false
+	 */
+	public function current() {
+		return $this->getRelPath( $this->iter->current()->getPathname() );
+	}
+
+	/**
+	 * @see Iterator::next()
+	 * @return void
+	 */
+	public function next() {
+		try {
+			$this->iter->next();
+			$this->filterViaNext();
+		} catch ( UnexpectedValueException $e ) {
+			$this->iter = null;
+		}
+		++$this->pos;
+	}
+
+	/**
+	 * @see Iterator::rewind()
+	 * @return void
+	 */
+	public function rewind() {
+		$this->pos = 0;
+		try {
+			$this->iter->rewind();
+			$this->filterViaNext();
+		} catch ( UnexpectedValueException $e ) {
+			$this->iter = null;
+		}
+	}
+
+	/**
+	 * @see Iterator::valid()
+	 * @return bool
+	 */
+	public function valid() {
+		return $this->iter && $this->iter->valid();
+	}
+
+	/**
+	 * Filter out items by advancing to the next ones
+	 */
+	protected function filterViaNext() {}
+
+	/**
+	 * Return only the relative path and normalize slashes to FileBackend-style.
+	 * Uses the "real path" since the suffix is based upon that.
+	 *
+	 * @param $path string
+	 * @return string
+	 */
+	protected function getRelPath( $path ) {
+		return strtr( substr( realpath( $path ), $this->suffixStart ), '\\', '/' );
+	}
+}
+
+class FSFileBackendDirList extends FSFileBackendList {
+	protected function filterViaNext() {
+		while ( $this->iter->valid() ) {
+			if ( $this->iter->current()->isDot() || !$this->iter->current()->isDir() ) {
+				$this->iter->next(); // skip non-directories and dot files
+			} else {
+				break;
+			}
+		}
+	}
+}
+
+class FSFileBackendFileList extends FSFileBackendList {
+	protected function filterViaNext() {
+		while ( $this->iter->valid() ) {
+			if ( !$this->iter->current()->isFile() ) {
+				$this->iter->next(); // skip non-files and dot files
+			} else {
+				break;
+			}
+		}
+	}
+}
diff --git a/includes/filebackend/FileBackend.php b/includes/filebackend/FileBackend.php
new file mode 100644
index 00000000..76c761b0
--- /dev/null
+++ b/includes/filebackend/FileBackend.php
@@ -0,0 +1,1173 @@
+<?php
+/**
+ * @defgroup FileBackend File backend
+ * @ingroup  FileRepo
+ *
+ * File backend is used to interact with file storage systems,
+ * such as the local file system, NFS, or cloud storage systems.
+ */
+
+/**
+ * Base class for all file backends.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Base class for all file backend classes (including multi-write backends).
+ *
+ * This class defines the methods as abstract that subclasses must implement.
+ * Outside callers can assume that all backends will have these functions.
+ *
+ * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
+ * The "<path>" portion is a relative path that uses UNIX file system (FS)
+ * notation, though any particular backend may not actually be using a local
+ * filesystem. Therefore, the relative paths are only virtual.
+ *
+ * Backend contents are stored under wiki-specific container names by default.
+ * For legacy reasons, this has no effect for the FS backend class, and per-wiki
+ * segregation must be done by setting the container paths appropriately.
+ *
+ * FS-based backends are somewhat more restrictive due to the existence of real
+ * directory files; a regular file cannot have the same name as a directory. Other
+ * backends with virtual directories may not have this limitation. Callers should
+ * store files in such a way that no files and directories are under the same path.
+ *
+ * Methods of subclasses should avoid throwing exceptions at all costs.
+ * As a corollary, external dependencies should be kept to a minimum.
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+abstract class FileBackend {
+	protected $name; // string; unique backend name
+	protected $wikiId; // string; unique wiki name
+	protected $readOnly; // string; read-only explanation message
+	protected $parallelize; // string; when to do operations in parallel
+	protected $concurrency; // integer; how many operations can be done in parallel
+
+	/** @var LockManager */
+	protected $lockManager;
+	/** @var FileJournal */
+	protected $fileJournal;
+
+	/**
+	 * Create a new backend instance from configuration.
+	 * This should only be called from within FileBackendGroup.
+	 *
+	 * $config includes:
+	 *   - name        : The unique name of this backend.
+	 *                   This should consist of alphanumberic, '-', and '_' characters.
+	 *                   This name should not be changed after use.
+	 *   - wikiId      : Prefix to container names that is unique to this wiki.
+	 *                   It should only consist of alphanumberic, '-', and '_' characters.
+	 *   - lockManager : Registered name of a file lock manager to use.
+	 *   - fileJournal : File journal configuration; see FileJournal::factory().
+	 *                   Journals simply log changes to files stored in the backend.
+	 *   - readOnly    : Write operations are disallowed if this is a non-empty string.
+	 *                   It should be an explanation for the backend being read-only.
+	 *   - parallelize : When to do file operations in parallel (when possible).
+	 *                   Allowed values are "implicit", "explicit" and "off".
+	 *   - concurrency : How many file operations can be done in parallel.
+	 *
+	 * @param $config Array
+	 * @throws MWException
+	 */
+	public function __construct( array $config ) {
+		$this->name = $config['name'];
+		if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
+			throw new MWException( "Backend name `{$this->name}` is invalid." );
+		}
+		$this->wikiId = isset( $config['wikiId'] )
+			? $config['wikiId']
+			: wfWikiID(); // e.g. "my_wiki-en_"
+		$this->lockManager = ( $config['lockManager'] instanceof LockManager )
+			? $config['lockManager']
+			: LockManagerGroup::singleton()->get( $config['lockManager'] );
+		$this->fileJournal = isset( $config['fileJournal'] )
+			? ( ( $config['fileJournal'] instanceof FileJournal )
+				? $config['fileJournal']
+				: FileJournal::factory( $config['fileJournal'], $this->name ) )
+			: FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
+		$this->readOnly = isset( $config['readOnly'] )
+			? (string)$config['readOnly']
+			: '';
+		$this->parallelize = isset( $config['parallelize'] )
+			? (string)$config['parallelize']
+			: 'off';
+		$this->concurrency = isset( $config['concurrency'] )
+			? (int)$config['concurrency']
+			: 50;
+	}
+
+	/**
+	 * Get the unique backend name.
+	 * We may have multiple different backends of the same type.
+	 * For example, we can have two Swift backends using different proxies.
+	 *
+	 * @return string
+	 */
+	final public function getName() {
+		return $this->name;
+	}
+
+	/**
+	 * Get the wiki identifier used for this backend (possibly empty)
+	 *
+	 * @return string
+	 * @since 1.20
+	 */
+	final public function getWikiId() {
+		return $this->wikiId;
+	}
+
+	/**
+	 * Check if this backend is read-only
+	 *
+	 * @return bool
+	 */
+	final public function isReadOnly() {
+		return ( $this->readOnly != '' );
+	}
+
+	/**
+	 * Get an explanatory message if this backend is read-only
+	 *
+	 * @return string|bool Returns false if the backend is not read-only
+	 */
+	final public function getReadOnlyReason() {
+		return ( $this->readOnly != '' ) ? $this->readOnly : false;
+	}
+
+	/**
+	 * This is the main entry point into the backend for write operations.
+	 * Callers supply an ordered list of operations to perform as a transaction.
+	 * Files will be locked, the stat cache cleared, and then the operations attempted.
+	 * If any serious errors occur, all attempted operations will be rolled back.
+	 *
+	 * $ops is an array of arrays. The outer array holds a list of operations.
+	 * Each inner array is a set of key value pairs that specify an operation.
+	 *
+	 * Supported operations and their parameters. The supported actions are:
+	 *  - create
+	 *  - store
+	 *  - copy
+	 *  - move
+	 *  - delete
+	 *  - null
+	 *
+	 * a) Create a new file in storage with the contents of a string
+	 * @code
+	 *     array(
+	 *         'op'                  => 'create',
+	 *         'dst'                 => <storage path>,
+	 *         'content'             => <string of new file contents>,
+	 *         'overwrite'           => <boolean>,
+	 *         'overwriteSame'       => <boolean>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     );
+	 * @endcode
+	 *
+	 * b) Copy a file system file into storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'store',
+	 *         'src'                 => <file system path>,
+	 *         'dst'                 => <storage path>,
+	 *         'overwrite'           => <boolean>,
+	 *         'overwriteSame'       => <boolean>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 *
+	 * c) Copy a file within storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'copy',
+	 *         'src'                 => <storage path>,
+	 *         'dst'                 => <storage path>,
+	 *         'overwrite'           => <boolean>,
+	 *         'overwriteSame'       => <boolean>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 *
+	 * d) Move a file within storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'move',
+	 *         'src'                 => <storage path>,
+	 *         'dst'                 => <storage path>,
+	 *         'overwrite'           => <boolean>,
+	 *         'overwriteSame'       => <boolean>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 *
+	 * e) Delete a file within storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'delete',
+	 *         'src'                 => <storage path>,
+	 *         'ignoreMissingSource' => <boolean>
+	 *     )
+	 * @endcode
+	 *
+	 * f) Do nothing (no-op)
+	 * @code
+	 *     array(
+	 *         'op'                  => 'null',
+	 *     )
+	 * @endcode
+	 *
+	 * Boolean flags for operations (operation-specific):
+	 *   - ignoreMissingSource : The operation will simply succeed and do
+	 *                           nothing if the source file does not exist.
+	 *   - overwrite           : Any destination file will be overwritten.
+	 *   - overwriteSame       : An error will not be given if a file already
+	 *                           exists at the destination that has the same
+	 *                           contents as the new contents to be written there.
+	 *   - disposition         : When supplied, the backend will add a Content-Disposition
+	 *                           header when GETs/HEADs of the destination file are made.
+	 *                           Backends that don't support file metadata will ignore this.
+	 *                           See http://tools.ietf.org/html/rfc6266 (since 1.20).
+	 *
+	 * $opts is an associative of boolean flags, including:
+	 *   - force               : Operation precondition errors no longer trigger an abort.
+	 *                           Any remaining operations are still attempted. Unexpected
+	 *                           failures may still cause remaning operations to be aborted.
+	 *   - nonLocking          : No locks are acquired for the operations.
+	 *                           This can increase performance for non-critical writes.
+	 *                           This has no effect unless the 'force' flag is set.
+	 *   - allowStale          : Don't require the latest available data.
+	 *                           This can increase performance for non-critical writes.
+	 *                           This has no effect unless the 'force' flag is set.
+	 *   - nonJournaled        : Don't log this operation batch in the file journal.
+	 *                           This limits the ability of recovery scripts.
+	 *   - parallelize         : Try to do operations in parallel when possible.
+	 *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20).
+	 *   - preserveCache       : Don't clear the process cache before checking files.
+	 *                           This should only be used if all entries in the process
+	 *                           cache were added after the files were already locked (since 1.20).
+	 *
+	 * @remarks Remarks on locking:
+	 * File system paths given to operations should refer to files that are
+	 * already locked or otherwise safe from modification from other processes.
+	 * Normally these files will be new temp files, which should be adequate.
+	 *
+	 * @par Return value:
+	 *
+	 * This returns a Status, which contains all warnings and fatals that occurred
+	 * during the operation. The 'failCount', 'successCount', and 'success' members
+	 * will reflect each operation attempted.
+	 *
+	 * The status will be "OK" unless:
+	 *   - a) unexpected operation errors occurred (network partitions, disk full...)
+	 *   - b) significant operation errors occurred and 'force' was not set
+	 *
+	 * @param $ops Array List of operations to execute in order
+	 * @param $opts Array Batch operation options
+	 * @return Status
+	 */
+	final public function doOperations( array $ops, array $opts = array() ) {
+		if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
+			return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
+		}
+		if ( empty( $opts['force'] ) ) { // sanity
+			unset( $opts['nonLocking'] );
+			unset( $opts['allowStale'] );
+		}
+		$opts['concurrency'] = 1; // off
+		if ( $this->parallelize === 'implicit' ) {
+			if ( !isset( $opts['parallelize'] ) || $opts['parallelize'] ) {
+				$opts['concurrency'] = $this->concurrency;
+			}
+		} elseif ( $this->parallelize === 'explicit' ) {
+			if ( !empty( $opts['parallelize'] ) ) {
+				$opts['concurrency'] = $this->concurrency;
+			}
+		}
+		return $this->doOperationsInternal( $ops, $opts );
+	}
+
+	/**
+	 * @see FileBackend::doOperations()
+	 */
+	abstract protected function doOperationsInternal( array $ops, array $opts );
+
+	/**
+	 * Same as doOperations() except it takes a single operation.
+	 * If you are doing a batch of operations that should either
+	 * all succeed or all fail, then use that function instead.
+	 *
+	 * @see FileBackend::doOperations()
+	 *
+	 * @param $op Array Operation
+	 * @param $opts Array Operation options
+	 * @return Status
+	 */
+	final public function doOperation( array $op, array $opts = array() ) {
+		return $this->doOperations( array( $op ), $opts );
+	}
+
+	/**
+	 * Performs a single create operation.
+	 * This sets $params['op'] to 'create' and passes it to doOperation().
+	 *
+	 * @see FileBackend::doOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @param $opts Array Operation options
+	 * @return Status
+	 */
+	final public function create( array $params, array $opts = array() ) {
+		return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
+	}
+
+	/**
+	 * Performs a single store operation.
+	 * This sets $params['op'] to 'store' and passes it to doOperation().
+	 *
+	 * @see FileBackend::doOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @param $opts Array Operation options
+	 * @return Status
+	 */
+	final public function store( array $params, array $opts = array() ) {
+		return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
+	}
+
+	/**
+	 * Performs a single copy operation.
+	 * This sets $params['op'] to 'copy' and passes it to doOperation().
+	 *
+	 * @see FileBackend::doOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @param $opts Array Operation options
+	 * @return Status
+	 */
+	final public function copy( array $params, array $opts = array() ) {
+		return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
+	}
+
+	/**
+	 * Performs a single move operation.
+	 * This sets $params['op'] to 'move' and passes it to doOperation().
+	 *
+	 * @see FileBackend::doOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @param $opts Array Operation options
+	 * @return Status
+	 */
+	final public function move( array $params, array $opts = array() ) {
+		return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
+	}
+
+	/**
+	 * Performs a single delete operation.
+	 * This sets $params['op'] to 'delete' and passes it to doOperation().
+	 *
+	 * @see FileBackend::doOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @param $opts Array Operation options
+	 * @return Status
+	 */
+	final public function delete( array $params, array $opts = array() ) {
+		return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
+	}
+
+	/**
+	 * Perform a set of independent file operations on some files.
+	 *
+	 * This does no locking, nor journaling, and possibly no stat calls.
+	 * Any destination files that already exist will be overwritten.
+	 * This should *only* be used on non-original files, like cache files.
+	 *
+	 * Supported operations and their parameters:
+	 *  - create
+	 *  - store
+	 *  - copy
+	 *  - move
+	 *  - delete
+	 *  - null
+	 *
+	 * a) Create a new file in storage with the contents of a string
+	 * @code
+	 *     array(
+	 *         'op'                  => 'create',
+	 *         'dst'                 => <storage path>,
+	 *         'content'             => <string of new file contents>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 * b) Copy a file system file into storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'store',
+	 *         'src'                 => <file system path>,
+	 *         'dst'                 => <storage path>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 * c) Copy a file within storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'copy',
+	 *         'src'                 => <storage path>,
+	 *         'dst'                 => <storage path>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 * d) Move a file within storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'move',
+	 *         'src'                 => <storage path>,
+	 *         'dst'                 => <storage path>,
+	 *         'disposition'         => <Content-Disposition header value>
+	 *     )
+	 * @endcode
+	 * e) Delete a file within storage
+	 * @code
+	 *     array(
+	 *         'op'                  => 'delete',
+	 *         'src'                 => <storage path>,
+	 *         'ignoreMissingSource' => <boolean>
+	 *     )
+	 * @endcode
+	 * f) Do nothing (no-op)
+	 * @code
+	 *     array(
+	 *         'op'                  => 'null',
+	 *     )
+	 * @endcode
+	 *
+	 * @par Boolean flags for operations (operation-specific):
+	 *   - ignoreMissingSource : The operation will simply succeed and do
+	 *                           nothing if the source file does not exist.
+	 *   - disposition         : When supplied, the backend will add a Content-Disposition
+	 *                           header when GETs/HEADs of the destination file are made.
+	 *                           Backends that don't support file metadata will ignore this.
+	 *                           See http://tools.ietf.org/html/rfc6266 (since 1.20).
+	 *
+	 * $opts is an associative of boolean flags, including:
+	 *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
+	 *
+	 * @par Return value:
+	 * This returns a Status, which contains all warnings and fatals that occurred
+	 * during the operation. The 'failCount', 'successCount', and 'success' members
+	 * will reflect each operation attempted for the given files. The status will be
+	 * considered "OK" as long as no fatal errors occurred.
+	 *
+	 * @param $ops Array Set of operations to execute
+	 * @param $opts Array Batch operation options
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function doQuickOperations( array $ops, array $opts = array() ) {
+		if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
+			return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
+		}
+		foreach ( $ops as &$op ) {
+			$op['overwrite'] = true; // avoids RTTs in key/value stores
+		}
+		return $this->doQuickOperationsInternal( $ops );
+	}
+
+	/**
+	 * @see FileBackend::doQuickOperations()
+	 * @since 1.20
+	 */
+	abstract protected function doQuickOperationsInternal( array $ops );
+
+	/**
+	 * Same as doQuickOperations() except it takes a single operation.
+	 * If you are doing a batch of operations, then use that function instead.
+	 *
+	 * @see FileBackend::doQuickOperations()
+	 *
+	 * @param $op Array Operation
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function doQuickOperation( array $op ) {
+		return $this->doQuickOperations( array( $op ) );
+	}
+
+	/**
+	 * Performs a single quick create operation.
+	 * This sets $params['op'] to 'create' and passes it to doQuickOperation().
+	 *
+	 * @see FileBackend::doQuickOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function quickCreate( array $params ) {
+		return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
+	}
+
+	/**
+	 * Performs a single quick store operation.
+	 * This sets $params['op'] to 'store' and passes it to doQuickOperation().
+	 *
+	 * @see FileBackend::doQuickOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function quickStore( array $params ) {
+		return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
+	}
+
+	/**
+	 * Performs a single quick copy operation.
+	 * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
+	 *
+	 * @see FileBackend::doQuickOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function quickCopy( array $params ) {
+		return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
+	}
+
+	/**
+	 * Performs a single quick move operation.
+	 * This sets $params['op'] to 'move' and passes it to doQuickOperation().
+	 *
+	 * @see FileBackend::doQuickOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function quickMove( array $params ) {
+		return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
+	}
+
+	/**
+	 * Performs a single quick delete operation.
+	 * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
+	 *
+	 * @see FileBackend::doQuickOperation()
+	 *
+	 * @param $params Array Operation parameters
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function quickDelete( array $params ) {
+		return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
+	}
+
+	/**
+	 * Concatenate a list of storage files into a single file system file.
+	 * The target path should refer to a file that is already locked or
+	 * otherwise safe from modification from other processes. Normally,
+	 * the file will be a new temp file, which should be adequate.
+	 *
+	 * @param $params Array Operation parameters
+	 * $params include:
+	 *   - srcs : ordered source storage paths (e.g. chunk1, chunk2, ...)
+	 *   - dst  : file system path to 0-byte temp file
+	 * @return Status
+	 */
+	abstract public function concatenate( array $params );
+
+	/**
+	 * Prepare a storage directory for usage.
+	 * This will create any required containers and parent directories.
+	 * Backends using key/value stores only need to create the container.
+	 *
+	 * The 'noAccess' and 'noListing' parameters works the same as in secure(),
+	 * except they are only applied *if* the directory/container had to be created.
+	 * These flags should always be set for directories that have private files.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - dir            : storage directory
+	 *   - noAccess       : try to deny file access (since 1.20)
+	 *   - noListing      : try to deny file listing (since 1.20)
+	 *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
+	 * @return Status
+	 */
+	final public function prepare( array $params ) {
+		if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
+			return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
+		}
+		return $this->doPrepare( $params );
+	}
+
+	/**
+	 * @see FileBackend::prepare()
+	 */
+	abstract protected function doPrepare( array $params );
+
+	/**
+	 * Take measures to block web access to a storage directory and
+	 * the container it belongs to. FS backends might add .htaccess
+	 * files whereas key/value store backends might revoke container
+	 * access to the storage user representing end-users in web requests.
+	 * This is not guaranteed to actually do anything.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - dir            : storage directory
+	 *   - noAccess       : try to deny file access
+	 *   - noListing      : try to deny file listing
+	 *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
+	 * @return Status
+	 */
+	final public function secure( array $params ) {
+		if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
+			return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
+		}
+		return $this->doSecure( $params );
+	}
+
+	/**
+	 * @see FileBackend::secure()
+	 */
+	abstract protected function doSecure( array $params );
+
+	/**
+	 * Remove measures to block web access to a storage directory and
+	 * the container it belongs to. FS backends might remove .htaccess
+	 * files whereas key/value store backends might grant container
+	 * access to the storage user representing end-users in web requests.
+	 * This essentially can undo the result of secure() calls.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - dir            : storage directory
+	 *   - access         : try to allow file access
+	 *   - listing        : try to allow file listing
+	 *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
+	 * @return Status
+	 * @since 1.20
+	 */
+	final public function publish( array $params ) {
+		if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
+			return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
+		}
+		return $this->doPublish( $params );
+	}
+
+	/**
+	 * @see FileBackend::publish()
+	 */
+	abstract protected function doPublish( array $params );
+
+	/**
+	 * Delete a storage directory if it is empty.
+	 * Backends using key/value stores may do nothing unless the directory
+	 * is that of an empty container, in which case it will be deleted.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - dir            : storage directory
+	 *   - recursive      : recursively delete empty subdirectories first (since 1.20)
+	 *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
+	 * @return Status
+	 */
+	final public function clean( array $params ) {
+		if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
+			return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
+		}
+		return $this->doClean( $params );
+	}
+
+	/**
+	 * @see FileBackend::clean()
+	 */
+	abstract protected function doClean( array $params );
+
+	/**
+	 * Check if a file exists at a storage path in the backend.
+	 * This returns false if only a directory exists at the path.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return bool|null Returns null on failure
+	 */
+	abstract public function fileExists( array $params );
+
+	/**
+	 * Get the last-modified timestamp of the file at a storage path.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return string|bool TS_MW timestamp or false on failure
+	 */
+	abstract public function getFileTimestamp( array $params );
+
+	/**
+	 * Get the contents of a file at a storage path in the backend.
+	 * This should be avoided for potentially large files.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return string|bool Returns false on failure
+	 */
+	abstract public function getFileContents( array $params );
+
+	/**
+	 * Get the size (bytes) of a file at a storage path in the backend.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return integer|bool Returns false on failure
+	 */
+	abstract public function getFileSize( array $params );
+
+	/**
+	 * Get quick information about a file at a storage path in the backend.
+	 * If the file does not exist, then this returns false.
+	 * Otherwise, the result is an associative array that includes:
+	 *   - mtime  : the last-modified timestamp (TS_MW)
+	 *   - size   : the file size (bytes)
+	 * Additional values may be included for internal use only.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return Array|bool|null Returns null on failure
+	 */
+	abstract public function getFileStat( array $params );
+
+	/**
+	 * Get a SHA-1 hash of the file at a storage path in the backend.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return string|bool Hash string or false on failure
+	 */
+	abstract public function getFileSha1Base36( array $params );
+
+	/**
+	 * Get the properties of the file at a storage path in the backend.
+	 * Returns FSFile::placeholderProps() on failure.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return Array
+	 */
+	abstract public function getFileProps( array $params );
+
+	/**
+	 * Stream the file at a storage path in the backend.
+	 * If the file does not exists, an HTTP 404 error will be given.
+	 * Appropriate HTTP headers (Status, Content-Type, Content-Length)
+	 * will be sent if streaming began, while none will be sent otherwise.
+	 * Implementations should flush the output buffer before sending data.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src     : source storage path
+	 *   - headers : list of additional HTTP headers to send on success
+	 *   - latest  : use the latest available data
+	 * @return Status
+	 */
+	abstract public function streamFile( array $params );
+
+	/**
+	 * Returns a file system file, identical to the file at a storage path.
+	 * The file returned is either:
+	 *   - a) A local copy of the file at a storage path in the backend.
+	 *        The temporary copy will have the same extension as the source.
+	 *   - b) An original of the file at a storage path in the backend.
+	 * Temporary files may be purged when the file object falls out of scope.
+	 *
+	 * Write operations should *never* be done on this file as some backends
+	 * may do internal tracking or may be instances of FileBackendMultiWrite.
+	 * In that later case, there are copies of the file that must stay in sync.
+	 * Additionally, further calls to this function may return the same file.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return FSFile|null Returns null on failure
+	 */
+	abstract public function getLocalReference( array $params );
+
+	/**
+	 * Get a local copy on disk of the file at a storage path in the backend.
+	 * The temporary copy will have the same file extension as the source.
+	 * Temporary files may be purged when the file object falls out of scope.
+	 *
+	 * @param $params Array
+	 * $params include:
+	 *   - src    : source storage path
+	 *   - latest : use the latest available data
+	 * @return TempFSFile|null Returns null on failure
+	 */
+	abstract public function getLocalCopy( array $params );
+
+	/**
+	 * Check if a directory exists at a given storage path.
+	 * Backends using key/value stores will check if the path is a
+	 * virtual directory, meaning there are files under the given directory.
+	 *
+	 * Storage backends with eventual consistency might return stale data.
+	 *
+	 * @param $params array
+	 * $params include:
+	 *   - dir : storage directory
+	 * @return bool|null Returns null on failure
+	 * @since 1.20
+	 */
+	abstract public function directoryExists( array $params );
+
+	/**
+	 * Get an iterator to list *all* directories under a storage directory.
+	 * If the directory is of the form "mwstore://backend/container",
+	 * then all directories in the container will be listed.
+	 * If the directory is of form "mwstore://backend/container/dir",
+	 * then all directories directly under that directory will be listed.
+	 * Results will be storage directories relative to the given directory.
+	 *
+	 * Storage backends with eventual consistency might return stale data.
+	 *
+	 * @param $params array
+	 * $params include:
+	 *   - dir     : storage directory
+	 *   - topOnly : only return direct child dirs of the directory
+	 * @return Traversable|Array|null Returns null on failure
+	 * @since 1.20
+	 */
+	abstract public function getDirectoryList( array $params );
+
+	/**
+	 * Same as FileBackend::getDirectoryList() except only lists
+	 * directories that are immediately under the given directory.
+	 *
+	 * Storage backends with eventual consistency might return stale data.
+	 *
+	 * @param $params array
+	 * $params include:
+	 *   - dir : storage directory
+	 * @return Traversable|Array|null Returns null on failure
+	 * @since 1.20
+	 */
+	final public function getTopDirectoryList( array $params ) {
+		return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
+	}
+
+	/**
+	 * Get an iterator to list *all* stored files under a storage directory.
+	 * If the directory is of the form "mwstore://backend/container",
+	 * then all files in the container will be listed.
+	 * If the directory is of form "mwstore://backend/container/dir",
+	 * then all files under that directory will be listed.
+	 * Results will be storage paths relative to the given directory.
+	 *
+	 * Storage backends with eventual consistency might return stale data.
+	 *
+	 * @param $params array
+	 * $params include:
+	 *   - dir     : storage directory
+	 *   - topOnly : only return direct child files of the directory (since 1.20)
+	 * @return Traversable|Array|null Returns null on failure
+	 */
+	abstract public function getFileList( array $params );
+
+	/**
+	 * Same as FileBackend::getFileList() except only lists
+	 * files that are immediately under the given directory.
+	 *
+	 * Storage backends with eventual consistency might return stale data.
+	 *
+	 * @param $params array
+	 * $params include:
+	 *   - dir : storage directory
+	 * @return Traversable|Array|null Returns null on failure
+	 * @since 1.20
+	 */
+	final public function getTopFileList( array $params ) {
+		return $this->getFileList( array( 'topOnly' => true ) + $params );
+	}
+
+	/**
+	 * Preload persistent file stat and property cache into in-process cache.
+	 * This should be used when stat calls will be made on a known list of a many files.
+	 *
+	 * @param $paths Array Storage paths
+	 * @return void
+	 */
+	public function preloadCache( array $paths ) {}
+
+	/**
+	 * Invalidate any in-process file stat and property cache.
+	 * If $paths is given, then only the cache for those files will be cleared.
+	 *
+	 * @param $paths Array Storage paths (optional)
+	 * @return void
+	 */
+	public function clearCache( array $paths = null ) {}
+
+	/**
+	 * Lock the files at the given storage paths in the backend.
+	 * This will either lock all the files or none (on failure).
+	 *
+	 * Callers should consider using getScopedFileLocks() instead.
+	 *
+	 * @param $paths Array Storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return Status
+	 */
+	final public function lockFiles( array $paths, $type ) {
+		return $this->lockManager->lock( $paths, $type );
+	}
+
+	/**
+	 * Unlock the files at the given storage paths in the backend.
+	 *
+	 * @param $paths Array Storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return Status
+	 */
+	final public function unlockFiles( array $paths, $type ) {
+		return $this->lockManager->unlock( $paths, $type );
+	}
+
+	/**
+	 * Lock the files at the given storage paths in the backend.
+	 * This will either lock all the files or none (on failure).
+	 * On failure, the status object will be updated with errors.
+	 *
+	 * Once the return value goes out scope, the locks will be released and
+	 * the status updated. Unlock fatals will not change the status "OK" value.
+	 *
+	 * @param $paths Array Storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @param $status Status Status to update on lock/unlock
+	 * @return ScopedLock|null Returns null on failure
+	 */
+	final public function getScopedFileLocks( array $paths, $type, Status $status ) {
+		return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
+	}
+
+	/**
+	 * Get an array of scoped locks needed for a batch of file operations.
+	 *
+	 * Normally, FileBackend::doOperations() handles locking, unless
+	 * the 'nonLocking' param is passed in. This function is useful if you
+	 * want the files to be locked for a broader scope than just when the
+	 * files are changing. For example, if you need to update DB metadata,
+	 * you may want to keep the files locked until finished.
+	 *
+	 * @see FileBackend::doOperations()
+	 *
+	 * @param $ops Array List of file operations to FileBackend::doOperations()
+	 * @param $status Status Status to update on lock/unlock
+	 * @return Array List of ScopedFileLocks or null values
+	 * @since 1.20
+	 */
+	abstract public function getScopedLocksForOps( array $ops, Status $status );
+
+	/**
+	 * Get the root storage path of this backend.
+	 * All container paths are "subdirectories" of this path.
+	 *
+	 * @return string Storage path
+	 * @since 1.20
+	 */
+	final public function getRootStoragePath() {
+		return "mwstore://{$this->name}";
+	}
+
+	/**
+	 * Get the file journal object for this backend
+	 *
+	 * @return FileJournal
+	 */
+	final public function getJournal() {
+		return $this->fileJournal;
+	}
+
+	/**
+	 * Check if a given path is a "mwstore://" path.
+	 * This does not do any further validation or any existence checks.
+	 *
+	 * @param $path string
+	 * @return bool
+	 */
+	final public static function isStoragePath( $path ) {
+		return ( strpos( $path, 'mwstore://' ) === 0 );
+	}
+
+	/**
+	 * Split a storage path into a backend name, a container name,
+	 * and a relative file path. The relative path may be the empty string.
+	 * This does not do any path normalization or traversal checks.
+	 *
+	 * @param $storagePath string
+	 * @return Array (backend, container, rel object) or (null, null, null)
+	 */
+	final public static function splitStoragePath( $storagePath ) {
+		if ( self::isStoragePath( $storagePath ) ) {
+			// Remove the "mwstore://" prefix and split the path
+			$parts = explode( '/', substr( $storagePath, 10 ), 3 );
+			if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
+				if ( count( $parts ) == 3 ) {
+					return $parts; // e.g. "backend/container/path"
+				} else {
+					return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
+				}
+			}
+		}
+		return array( null, null, null );
+	}
+
+	/**
+	 * Normalize a storage path by cleaning up directory separators.
+	 * Returns null if the path is not of the format of a valid storage path.
+	 *
+	 * @param $storagePath string
+	 * @return string|null
+	 */
+	final public static function normalizeStoragePath( $storagePath ) {
+		list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
+		if ( $relPath !== null ) { // must be for this backend
+			$relPath = self::normalizeContainerPath( $relPath );
+			if ( $relPath !== null ) {
+				return ( $relPath != '' )
+					? "mwstore://{$backend}/{$container}/{$relPath}"
+					: "mwstore://{$backend}/{$container}";
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * Get the parent storage directory of a storage path.
+	 * This returns a path like "mwstore://backend/container",
+	 * "mwstore://backend/container/...", or null if there is no parent.
+	 *
+	 * @param $storagePath string
+	 * @return string|null
+	 */
+	final public static function parentStoragePath( $storagePath ) {
+		$storagePath = dirname( $storagePath );
+		list( $b, $cont, $rel ) = self::splitStoragePath( $storagePath );
+		return ( $rel === null ) ? null : $storagePath;
+	}
+
+	/**
+	 * Get the final extension from a storage or FS path
+	 *
+	 * @param $path string
+	 * @return string
+	 */
+	final public static function extensionFromPath( $path ) {
+		$i = strrpos( $path, '.' );
+		return strtolower( $i ? substr( $path, $i + 1 ) : '' );
+	}
+
+	/**
+	 * Check if a relative path has no directory traversals
+	 *
+	 * @param $path string
+	 * @return bool
+	 * @since 1.20
+	 */
+	final public static function isPathTraversalFree( $path ) {
+		return ( self::normalizeContainerPath( $path ) !== null );
+	}
+
+	/**
+	 * Build a Content-Disposition header value per RFC 6266.
+	 *
+	 * @param $type string One of (attachment, inline)
+	 * @param $filename string Suggested file name (should not contain slashes)
+	 * @return string
+	 * @since 1.20
+	 */
+	final public static function makeContentDisposition( $type, $filename = '' ) {
+		$parts = array();
+
+		$type = strtolower( $type );
+		if ( !in_array( $type, array( 'inline', 'attachment' ) ) ) {
+			throw new MWException( "Invalid Content-Disposition type '$type'." );
+		}
+		$parts[] = $type;
+
+		if ( strlen( $filename ) ) {
+			$parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
+		}
+
+		return implode( ';', $parts );
+	}
+
+	/**
+	 * Validate and normalize a relative storage path.
+	 * Null is returned if the path involves directory traversal.
+	 * Traversal is insecure for FS backends and broken for others.
+	 *
+	 * This uses the same traversal protection as Title::secureAndSplit().
+	 *
+	 * @param $path string Storage path relative to a container
+	 * @return string|null
+	 */
+	final protected static function normalizeContainerPath( $path ) {
+		// Normalize directory separators
+		$path = strtr( $path, '\\', '/' );
+		// Collapse any consecutive directory separators
+		$path = preg_replace( '![/]{2,}!', '/', $path );
+		// Remove any leading directory separator
+		$path = ltrim( $path, '/' );
+		// Use the same traversal protection as Title::secureAndSplit()
+		if ( strpos( $path, '.' ) !== false ) {
+			if (
+				$path === '.' ||
+				$path === '..' ||
+				strpos( $path, './' ) === 0 ||
+				strpos( $path, '../' ) === 0 ||
+				strpos( $path, '/./' ) !== false ||
+				strpos( $path, '/../' ) !== false
+			) {
+				return null;
+			}
+		}
+		return $path;
+	}
+}
diff --git a/includes/filebackend/FileBackendGroup.php b/includes/filebackend/FileBackendGroup.php
new file mode 100644
index 00000000..8bbc96d0
--- /dev/null
+++ b/includes/filebackend/FileBackendGroup.php
@@ -0,0 +1,187 @@
+<?php
+/**
+ * File backend registration handling.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * Class to handle file backend registration
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+class FileBackendGroup {
+	/**
+	 * @var FileBackendGroup
+	 */
+	protected static $instance = null;
+
+	/** @var Array (name => ('class' => string, 'config' => array, 'instance' => object)) */
+	protected $backends = array();
+
+	protected function __construct() {}
+
+	/**
+	 * @return FileBackendGroup
+	 */
+	public static function singleton() {
+		if ( self::$instance == null ) {
+			self::$instance = new self();
+			self::$instance->initFromGlobals();
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Destroy the singleton instance
+	 *
+	 * @return void
+	 */
+	public static function destroySingleton() {
+		self::$instance = null;
+	}
+
+	/**
+	 * Register file backends from the global variables
+	 *
+	 * @return void
+	 */
+	protected function initFromGlobals() {
+		global $wgLocalFileRepo, $wgForeignFileRepos, $wgFileBackends;
+
+		// Register explicitly defined backends
+		$this->register( $wgFileBackends );
+
+		$autoBackends = array();
+		// Automatically create b/c backends for file repos...
+		$repos = array_merge( $wgForeignFileRepos, array( $wgLocalFileRepo ) );
+		foreach ( $repos as $info ) {
+			$backendName = $info['backend'];
+			if ( is_object( $backendName ) || isset( $this->backends[$backendName] ) ) {
+				continue; // already defined (or set to the object for some reason)
+			}
+			$repoName = $info['name'];
+			// Local vars that used to be FSRepo members...
+			$directory = $info['directory'];
+			$deletedDir = isset( $info['deletedDir'] )
+				? $info['deletedDir']
+				: false; // deletion disabled
+			$thumbDir = isset( $info['thumbDir'] )
+				? $info['thumbDir']
+				: "{$directory}/thumb";
+			$fileMode = isset( $info['fileMode'] )
+				? $info['fileMode']
+				: 0644;
+			// Get the FS backend configuration
+			$autoBackends[] = array(
+				'name'           => $backendName,
+				'class'          => 'FSFileBackend',
+				'lockManager'    => 'fsLockManager',
+				'containerPaths' => array(
+					"{$repoName}-public"  => "{$directory}",
+					"{$repoName}-thumb"   => $thumbDir,
+					"{$repoName}-deleted" => $deletedDir,
+					"{$repoName}-temp"    => "{$directory}/temp"
+				),
+				'fileMode'       => $fileMode,
+			);
+		}
+
+		// Register implicitly defined backends
+		$this->register( $autoBackends );
+	}
+
+	/**
+	 * Register an array of file backend configurations
+	 *
+	 * @param $configs Array
+	 * @return void
+	 * @throws MWException
+	 */
+	protected function register( array $configs ) {
+		foreach ( $configs as $config ) {
+			if ( !isset( $config['name'] ) ) {
+				throw new MWException( "Cannot register a backend with no name." );
+			}
+			$name = $config['name'];
+			if ( !isset( $config['class'] ) ) {
+				throw new MWException( "Cannot register backend `{$name}` with no class." );
+			}
+			$class = $config['class'];
+
+			unset( $config['class'] ); // backend won't need this
+			$this->backends[$name] = array(
+				'class'    => $class,
+				'config'   => $config,
+				'instance' => null
+			);
+		}
+	}
+
+	/**
+	 * Get the backend object with a given name
+	 *
+	 * @param $name string
+	 * @return FileBackend
+	 * @throws MWException
+	 */
+	public function get( $name ) {
+		if ( !isset( $this->backends[$name] ) ) {
+			throw new MWException( "No backend defined with the name `$name`." );
+		}
+		// Lazy-load the actual backend instance
+		if ( !isset( $this->backends[$name]['instance'] ) ) {
+			$class = $this->backends[$name]['class'];
+			$config = $this->backends[$name]['config'];
+			$this->backends[$name]['instance'] = new $class( $config );
+		}
+		return $this->backends[$name]['instance'];
+	}
+
+	/**
+	 * Get the config array for a backend object with a given name
+	 *
+	 * @param $name string
+	 * @return Array
+	 * @throws MWException
+	 */
+	public function config( $name ) {
+		if ( !isset( $this->backends[$name] ) ) {
+			throw new MWException( "No backend defined with the name `$name`." );
+		}
+		$class = $this->backends[$name]['class'];
+		return array( 'class' => $class ) + $this->backends[$name]['config'];
+	}
+
+	/**
+	 * Get an appropriate backend object from a storage path
+	 *
+	 * @param $storagePath string
+	 * @return FileBackend|null Backend or null on failure
+	 */
+	public function backendFromPath( $storagePath ) {
+		list( $backend, $c, $p ) = FileBackend::splitStoragePath( $storagePath );
+		if ( $backend !== null && isset( $this->backends[$backend] ) ) {
+			return $this->get( $backend );
+		}
+		return null;
+	}
+}
diff --git a/includes/filebackend/FileBackendMultiWrite.php b/includes/filebackend/FileBackendMultiWrite.php
new file mode 100644
index 00000000..4be03231
--- /dev/null
+++ b/includes/filebackend/FileBackendMultiWrite.php
@@ -0,0 +1,689 @@
+<?php
+/**
+ * Proxy backend that mirrors writes to several internal backends.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Proxy backend that mirrors writes to several internal backends.
+ *
+ * This class defines a multi-write backend. Multiple backends can be
+ * registered to this proxy backend and it will act as a single backend.
+ * Use this when all access to those backends is through this proxy backend.
+ * At least one of the backends must be declared the "master" backend.
+ *
+ * Only use this class when transitioning from one storage system to another.
+ *
+ * Read operations are only done on the 'master' backend for consistency.
+ * Write operations are performed on all backends, in the order defined.
+ * If an operation fails on one backend it will be rolled back from the others.
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+class FileBackendMultiWrite extends FileBackend {
+	/** @var Array Prioritized list of FileBackendStore objects */
+	protected $backends = array(); // array of (backend index => backends)
+	protected $masterIndex = -1; // integer; index of master backend
+	protected $syncChecks = 0; // integer; bitfield
+	protected $autoResync = false; // boolean
+
+	/** @var Array */
+	protected $noPushDirConts = array();
+	protected $noPushQuickOps = false; // boolean
+
+	/* Possible internal backend consistency checks */
+	const CHECK_SIZE = 1;
+	const CHECK_TIME = 2;
+	const CHECK_SHA1 = 4;
+
+	/**
+	 * Construct a proxy backend that consists of several internal backends.
+	 * Locking, journaling, and read-only checks are handled by the proxy backend.
+	 *
+	 * Additional $config params include:
+	 *   - backends       : Array of backend config and multi-backend settings.
+	 *                      Each value is the config used in the constructor of a
+	 *                          FileBackendStore class, but with these additional settings:
+	 *                        - class         : The name of the backend class
+	 *                        - isMultiMaster : This must be set for one backend.
+	 *                        - template:     : If given a backend name, this will use
+	 *                                          the config of that backend as a template.
+	 *                                          Values specified here take precedence.
+	 *   - syncChecks     : Integer bitfield of internal backend sync checks to perform.
+	 *                      Possible bits include the FileBackendMultiWrite::CHECK_* constants.
+	 *                      There are constants for SIZE, TIME, and SHA1.
+	 *                      The checks are done before allowing any file operations.
+	 *   - autoResync     : Automatically resync the clone backends to the master backend
+	 *                      when pre-operation sync checks fail. This should only be used
+	 *                      if the master backend is stable and not missing any files.
+	 *   - noPushQuickOps : (hack) Only apply doQuickOperations() to the master backend.
+	 *   - noPushDirConts : (hack) Only apply directory functions to the master backend.
+	 *
+	 * @param $config Array
+	 * @throws MWException
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+		$this->syncChecks = isset( $config['syncChecks'] )
+			? $config['syncChecks']
+			: self::CHECK_SIZE;
+		$this->autoResync = !empty( $config['autoResync'] );
+		$this->noPushQuickOps = isset( $config['noPushQuickOps'] )
+			? $config['noPushQuickOps']
+			: false;
+		$this->noPushDirConts = isset( $config['noPushDirConts'] )
+			? $config['noPushDirConts']
+			: array();
+		// Construct backends here rather than via registration
+		// to keep these backends hidden from outside the proxy.
+		$namesUsed = array();
+		foreach ( $config['backends'] as $index => $config ) {
+			if ( isset( $config['template'] ) ) {
+				// Config is just a modified version of a registered backend's.
+				// This should only be used when that config is used only by this backend.
+				$config = $config + FileBackendGroup::singleton()->config( $config['template'] );
+			}
+			$name = $config['name'];
+			if ( isset( $namesUsed[$name] ) ) { // don't break FileOp predicates
+				throw new MWException( "Two or more backends defined with the name $name." );
+			}
+			$namesUsed[$name] = 1;
+			// Alter certain sub-backend settings for sanity
+			unset( $config['readOnly'] ); // use proxy backend setting
+			unset( $config['fileJournal'] ); // use proxy backend journal
+			$config['wikiId'] = $this->wikiId; // use the proxy backend wiki ID
+			$config['lockManager'] = 'nullLockManager'; // lock under proxy backend
+			if ( !empty( $config['isMultiMaster'] ) ) {
+				if ( $this->masterIndex >= 0 ) {
+					throw new MWException( 'More than one master backend defined.' );
+				}
+				$this->masterIndex = $index; // this is the "master"
+				$config['fileJournal'] = $this->fileJournal; // log under proxy backend
+			}
+			// Create sub-backend object
+			if ( !isset( $config['class'] ) ) {
+				throw new MWException( 'No class given for a backend config.' );
+			}
+			$class = $config['class'];
+			$this->backends[$index] = new $class( $config );
+		}
+		if ( $this->masterIndex < 0 ) { // need backends and must have a master
+			throw new MWException( 'No master backend defined.' );
+		}
+	}
+
+	/**
+	 * @see FileBackend::doOperationsInternal()
+	 * @return Status
+	 */
+	final protected function doOperationsInternal( array $ops, array $opts ) {
+		$status = Status::newGood();
+
+		$mbe = $this->backends[$this->masterIndex]; // convenience
+
+		// Get the paths to lock from the master backend
+		$realOps = $this->substOpBatchPaths( $ops, $mbe );
+		$paths = $mbe->getPathsToLockForOpsInternal( $mbe->getOperationsInternal( $realOps ) );
+		// Get the paths under the proxy backend's name
+		$paths['sh'] = $this->unsubstPaths( $paths['sh'] );
+		$paths['ex'] = $this->unsubstPaths( $paths['ex'] );
+		// Try to lock those files for the scope of this function...
+		if ( empty( $opts['nonLocking'] ) ) {
+			// Try to lock those files for the scope of this function...
+			$scopeLockS = $this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status );
+			$scopeLockE = $this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status );
+			if ( !$status->isOK() ) {
+				return $status; // abort
+			}
+		}
+		// Clear any cache entries (after locks acquired)
+		$this->clearCache();
+		$opts['preserveCache'] = true; // only locked files are cached
+		// Get the list of paths to read/write...
+		$relevantPaths = $this->fileStoragePathsForOps( $ops );
+		// Check if the paths are valid and accessible on all backends...
+		$status->merge( $this->accessibilityCheck( $relevantPaths ) );
+		if ( !$status->isOK() ) {
+			return $status; // abort
+		}
+		// Do a consistency check to see if the backends are consistent...
+		$syncStatus = $this->consistencyCheck( $relevantPaths );
+		if ( !$syncStatus->isOK() ) {
+			wfDebugLog( 'FileOperation', get_class( $this ) .
+				" failed sync check: " . FormatJson::encode( $relevantPaths ) );
+			// Try to resync the clone backends to the master on the spot...
+			if ( !$this->autoResync || !$this->resyncFiles( $relevantPaths )->isOK() ) {
+				$status->merge( $syncStatus );
+				return $status; // abort
+			}
+		}
+		// Actually attempt the operation batch on the master backend...
+		$masterStatus = $mbe->doOperations( $realOps, $opts );
+		$status->merge( $masterStatus );
+		// Propagate the operations to the clone backends if there were no fatal errors.
+		// If $ops only had one operation, this might avoid backend inconsistencies.
+		// This also avoids inconsistency for expected errors (like "file already exists").
+		if ( !count( $masterStatus->getErrorsArray() ) ) {
+			foreach ( $this->backends as $index => $backend ) {
+				if ( $index !== $this->masterIndex ) { // not done already
+					$realOps = $this->substOpBatchPaths( $ops, $backend );
+					$status->merge( $backend->doOperations( $realOps, $opts ) );
+				}
+			}
+		}
+		// Make 'success', 'successCount', and 'failCount' fields reflect
+		// the overall operation, rather than all the batches for each backend.
+		// Do this by only using success values from the master backend's batch.
+		$status->success = $masterStatus->success;
+		$status->successCount = $masterStatus->successCount;
+		$status->failCount = $masterStatus->failCount;
+
+		return $status;
+	}
+
+	/**
+	 * Check that a set of files are consistent across all internal backends
+	 *
+	 * @param $paths Array List of storage paths
+	 * @return Status
+	 */
+	public function consistencyCheck( array $paths ) {
+		$status = Status::newGood();
+		if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
+			return $status; // skip checks
+		}
+
+		$mBackend = $this->backends[$this->masterIndex];
+		foreach ( $paths as $path ) {
+			$params = array( 'src' => $path, 'latest' => true );
+			$mParams = $this->substOpPaths( $params, $mBackend );
+			// Stat the file on the 'master' backend
+			$mStat = $mBackend->getFileStat( $mParams );
+			if ( $this->syncChecks & self::CHECK_SHA1 ) {
+				$mSha1 = $mBackend->getFileSha1Base36( $mParams );
+			} else {
+				$mSha1 = false;
+			}
+			// Check if all clone backends agree with the master...
+			foreach ( $this->backends as $index => $cBackend ) {
+				if ( $index === $this->masterIndex ) {
+					continue; // master
+				}
+				$cParams = $this->substOpPaths( $params, $cBackend );
+				$cStat = $cBackend->getFileStat( $cParams );
+				if ( $mStat ) { // file is in master
+					if ( !$cStat ) { // file should exist
+						$status->fatal( 'backend-fail-synced', $path );
+						continue;
+					}
+					if ( $this->syncChecks & self::CHECK_SIZE ) {
+						if ( $cStat['size'] != $mStat['size'] ) { // wrong size
+							$status->fatal( 'backend-fail-synced', $path );
+							continue;
+						}
+					}
+					if ( $this->syncChecks & self::CHECK_TIME ) {
+						$mTs = wfTimestamp( TS_UNIX, $mStat['mtime'] );
+						$cTs = wfTimestamp( TS_UNIX, $cStat['mtime'] );
+						if ( abs( $mTs - $cTs ) > 30 ) { // outdated file somewhere
+							$status->fatal( 'backend-fail-synced', $path );
+							continue;
+						}
+					}
+					if ( $this->syncChecks & self::CHECK_SHA1 ) {
+						if ( $cBackend->getFileSha1Base36( $cParams ) !== $mSha1 ) { // wrong SHA1
+							$status->fatal( 'backend-fail-synced', $path );
+							continue;
+						}
+					}
+				} else { // file is not in master
+					if ( $cStat ) { // file should not exist
+						$status->fatal( 'backend-fail-synced', $path );
+					}
+				}
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Check that a set of file paths are usable across all internal backends
+	 *
+	 * @param $paths Array List of storage paths
+	 * @return Status
+	 */
+	public function accessibilityCheck( array $paths ) {
+		$status = Status::newGood();
+		if ( count( $this->backends ) <= 1 ) {
+			return $status; // skip checks
+		}
+
+		foreach ( $paths as $path ) {
+			foreach ( $this->backends as $backend ) {
+				$realPath = $this->substPaths( $path, $backend );
+				if ( !$backend->isPathUsableInternal( $realPath ) ) {
+					$status->fatal( 'backend-fail-usable', $path );
+				}
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Check that a set of files are consistent across all internal backends
+	 * and re-synchronize those files againt the "multi master" if needed.
+	 *
+	 * @param $paths Array List of storage paths
+	 * @return Status
+	 */
+	public function resyncFiles( array $paths ) {
+		$status = Status::newGood();
+
+		$mBackend = $this->backends[$this->masterIndex];
+		foreach ( $paths as $path ) {
+			$mPath  = $this->substPaths( $path, $mBackend );
+			$mSha1  = $mBackend->getFileSha1Base36( array( 'src' => $mPath ) );
+			$mExist = $mBackend->fileExists( array( 'src' => $mPath ) );
+			// Check if the master backend is available...
+			if ( $mExist === null ) {
+				$status->fatal( 'backend-fail-internal', $this->name );
+			}
+			// Check of all clone backends agree with the master...
+			foreach ( $this->backends as $index => $cBackend ) {
+				if ( $index === $this->masterIndex ) {
+					continue; // master
+				}
+				$cPath = $this->substPaths( $path, $cBackend );
+				$cSha1 = $cBackend->getFileSha1Base36( array( 'src' => $cPath ) );
+				if ( $mSha1 === $cSha1 ) {
+					// already synced; nothing to do
+				} elseif ( $mSha1 ) { // file is in master
+					$fsFile = $mBackend->getLocalReference( array( 'src' => $mPath ) );
+					$status->merge( $cBackend->quickStore(
+						array( 'src' => $fsFile->getPath(), 'dst' => $cPath )
+					) );
+				} elseif ( $mExist === false ) { // file is not in master
+					$status->merge( $cBackend->quickDelete( array( 'src' => $cPath ) ) );
+				}
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Get a list of file storage paths to read or write for a list of operations
+	 *
+	 * @param $ops Array Same format as doOperations()
+	 * @return Array List of storage paths to files (does not include directories)
+	 */
+	protected function fileStoragePathsForOps( array $ops ) {
+		$paths = array();
+		foreach ( $ops as $op ) {
+			if ( isset( $op['src'] ) ) {
+				$paths[] = $op['src'];
+			}
+			if ( isset( $op['srcs'] ) ) {
+				$paths = array_merge( $paths, $op['srcs'] );
+			}
+			if ( isset( $op['dst'] ) ) {
+				$paths[] = $op['dst'];
+			}
+		}
+		return array_unique( array_filter( $paths, 'FileBackend::isStoragePath' ) );
+	}
+
+	/**
+	 * Substitute the backend name in storage path parameters
+	 * for a set of operations with that of a given internal backend.
+	 *
+	 * @param $ops Array List of file operation arrays
+	 * @param $backend FileBackendStore
+	 * @return Array
+	 */
+	protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
+		$newOps = array(); // operations
+		foreach ( $ops as $op ) {
+			$newOp = $op; // operation
+			foreach ( array( 'src', 'srcs', 'dst', 'dir' ) as $par ) {
+				if ( isset( $newOp[$par] ) ) { // string or array
+					$newOp[$par] = $this->substPaths( $newOp[$par], $backend );
+				}
+			}
+			$newOps[] = $newOp;
+		}
+		return $newOps;
+	}
+
+	/**
+	 * Same as substOpBatchPaths() but for a single operation
+	 *
+	 * @param $ops array File operation array
+	 * @param $backend FileBackendStore
+	 * @return Array
+	 */
+	protected function substOpPaths( array $ops, FileBackendStore $backend ) {
+		$newOps = $this->substOpBatchPaths( array( $ops ), $backend );
+		return $newOps[0];
+	}
+
+	/**
+	 * Substitute the backend of storage paths with an internal backend's name
+	 *
+	 * @param $paths Array|string List of paths or single string path
+	 * @param $backend FileBackendStore
+	 * @return Array|string
+	 */
+	protected function substPaths( $paths, FileBackendStore $backend ) {
+		return preg_replace(
+			'!^mwstore://' . preg_quote( $this->name ) . '/!',
+			StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
+			$paths // string or array
+		);
+	}
+
+	/**
+	 * Substitute the backend of internal storage paths with the proxy backend's name
+	 *
+	 * @param $paths Array|string List of paths or single string path
+	 * @return Array|string
+	 */
+	protected function unsubstPaths( $paths ) {
+		return preg_replace(
+			'!^mwstore://([^/]+)!',
+			StringUtils::escapeRegexReplacement( "mwstore://{$this->name}" ),
+			$paths // string or array
+		);
+	}
+
+	/**
+	 * @see FileBackend::doQuickOperationsInternal()
+	 * @return Status
+	 */
+	protected function doQuickOperationsInternal( array $ops ) {
+		$status = Status::newGood();
+		// Do the operations on the master backend; setting Status fields...
+		$realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
+		$masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
+		$status->merge( $masterStatus );
+		// Propagate the operations to the clone backends...
+		if ( !$this->noPushQuickOps ) {
+			foreach ( $this->backends as $index => $backend ) {
+				if ( $index !== $this->masterIndex ) { // not done already
+					$realOps = $this->substOpBatchPaths( $ops, $backend );
+					$status->merge( $backend->doQuickOperations( $realOps ) );
+				}
+			}
+		}
+		// Make 'success', 'successCount', and 'failCount' fields reflect
+		// the overall operation, rather than all the batches for each backend.
+		// Do this by only using success values from the master backend's batch.
+		$status->success = $masterStatus->success;
+		$status->successCount = $masterStatus->successCount;
+		$status->failCount = $masterStatus->failCount;
+		return $status;
+	}
+
+	/**
+	 * @param $path string Storage path
+	 * @return bool Path container should have dir changes pushed to all backends
+	 */
+	protected function replicateContainerDirChanges( $path ) {
+		list( $b, $shortCont, $r ) = self::splitStoragePath( $path );
+		return !in_array( $shortCont, $this->noPushDirConts );
+	}
+
+	/**
+	 * @see FileBackend::doPrepare()
+	 * @return Status
+	 */
+	protected function doPrepare( array $params ) {
+		$status = Status::newGood();
+		$replicate = $this->replicateContainerDirChanges( $params['dir'] );
+		foreach ( $this->backends as $index => $backend ) {
+			if ( $replicate || $index == $this->masterIndex ) {
+				$realParams = $this->substOpPaths( $params, $backend );
+				$status->merge( $backend->doPrepare( $realParams ) );
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::doSecure()
+	 * @param $params array
+	 * @return Status
+	 */
+	protected function doSecure( array $params ) {
+		$status = Status::newGood();
+		$replicate = $this->replicateContainerDirChanges( $params['dir'] );
+		foreach ( $this->backends as $index => $backend ) {
+			if ( $replicate || $index == $this->masterIndex ) {
+				$realParams = $this->substOpPaths( $params, $backend );
+				$status->merge( $backend->doSecure( $realParams ) );
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::doPublish()
+	 * @param $params array
+	 * @return Status
+	 */
+	protected function doPublish( array $params ) {
+		$status = Status::newGood();
+		$replicate = $this->replicateContainerDirChanges( $params['dir'] );
+		foreach ( $this->backends as $index => $backend ) {
+			if ( $replicate || $index == $this->masterIndex ) {
+				$realParams = $this->substOpPaths( $params, $backend );
+				$status->merge( $backend->doPublish( $realParams ) );
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::doClean()
+	 * @param $params array
+	 * @return Status
+	 */
+	protected function doClean( array $params ) {
+		$status = Status::newGood();
+		$replicate = $this->replicateContainerDirChanges( $params['dir'] );
+		foreach ( $this->backends as $index => $backend ) {
+			if ( $replicate || $index == $this->masterIndex ) {
+				$realParams = $this->substOpPaths( $params, $backend );
+				$status->merge( $backend->doClean( $realParams ) );
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::concatenate()
+	 * @param $params array
+	 * @return Status
+	 */
+	public function concatenate( array $params ) {
+		// We are writing to an FS file, so we don't need to do this per-backend
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->concatenate( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::fileExists()
+	 * @param $params array
+	 */
+	public function fileExists( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->fileExists( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileTimestamp()
+	 * @param $params array
+	 * @return bool|string
+	 */
+	public function getFileTimestamp( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileTimestamp( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileSize()
+	 * @param $params array
+	 * @return bool|int
+	 */
+	public function getFileSize( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileSize( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileStat()
+	 * @param $params array
+	 * @return Array|bool|null
+	 */
+	public function getFileStat( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileStat( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileContents()
+	 * @param $params array
+	 * @return bool|string
+	 */
+	public function getFileContents( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileContents( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileSha1Base36()
+	 * @param $params array
+	 * @return bool|string
+	 */
+	public function getFileSha1Base36( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileSha1Base36( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileProps()
+	 * @param $params array
+	 * @return Array
+	 */
+	public function getFileProps( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileProps( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::streamFile()
+	 * @param $params array
+	 * @return \Status
+	 */
+	public function streamFile( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->streamFile( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getLocalReference()
+	 * @param $params array
+	 * @return FSFile|null
+	 */
+	public function getLocalReference( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getLocalReference( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getLocalCopy()
+	 * @param $params array
+	 * @return null|TempFSFile
+	 */
+	public function getLocalCopy( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getLocalCopy( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::directoryExists()
+	 * @param $params array
+	 * @return bool|null
+	 */
+	public function directoryExists( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->directoryExists( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getSubdirectoryList()
+	 * @param $params array
+	 * @return Array|null|Traversable
+	 */
+	public function getDirectoryList( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::getFileList()
+	 * @param $params array
+	 * @return Array|null|\Traversable
+	 */
+	public function getFileList( array $params ) {
+		$realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
+		return $this->backends[$this->masterIndex]->getFileList( $realParams );
+	}
+
+	/**
+	 * @see FileBackend::clearCache()
+	 */
+	public function clearCache( array $paths = null ) {
+		foreach ( $this->backends as $backend ) {
+			$realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
+			$backend->clearCache( $realPaths );
+		}
+	}
+
+	/**
+	 * @see FileBackend::getScopedLocksForOps()
+	 */
+	public function getScopedLocksForOps( array $ops, Status $status ) {
+		$fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $ops );
+		// Get the paths to lock from the master backend
+		$paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
+		// Get the paths under the proxy backend's name
+		$paths['sh'] = $this->unsubstPaths( $paths['sh'] );
+		$paths['ex'] = $this->unsubstPaths( $paths['ex'] );
+		return array(
+			$this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status ),
+			$this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status )
+		);
+	}
+}
diff --git a/includes/filebackend/FileBackendStore.php b/includes/filebackend/FileBackendStore.php
new file mode 100644
index 00000000..083dfea9
--- /dev/null
+++ b/includes/filebackend/FileBackendStore.php
@@ -0,0 +1,1766 @@
+<?php
+/**
+ * Base class for all backends using particular storage medium.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Base class for all backends using particular storage medium.
+ *
+ * This class defines the methods as abstract that subclasses must implement.
+ * Outside callers should *not* use functions with "Internal" in the name.
+ *
+ * The FileBackend operations are implemented using basic functions
+ * such as storeInternal(), copyInternal(), deleteInternal() and the like.
+ * This class is also responsible for path resolution and sanitization.
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+abstract class FileBackendStore extends FileBackend {
+	/** @var BagOStuff */
+	protected $memCache;
+	/** @var ProcessCacheLRU */
+	protected $cheapCache; // Map of paths to small (RAM/disk) cache items
+	/** @var ProcessCacheLRU */
+	protected $expensiveCache; // Map of paths to large (RAM/disk) cache items
+
+	/** @var Array Map of container names to sharding settings */
+	protected $shardViaHashLevels = array(); // (container name => config array)
+
+	protected $maxFileSize = 4294967296; // integer bytes (4GiB)
+
+	/**
+	 * @see FileBackend::__construct()
+	 *
+	 * @param $config Array
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+		$this->memCache       = new EmptyBagOStuff(); // disabled by default
+		$this->cheapCache     = new ProcessCacheLRU( 300 );
+		$this->expensiveCache = new ProcessCacheLRU( 5 );
+	}
+
+	/**
+	 * Get the maximum allowable file size given backend
+	 * medium restrictions and basic performance constraints.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * @return integer Bytes
+	 */
+	final public function maxFileSizeInternal() {
+		return $this->maxFileSize;
+	}
+
+	/**
+	 * Check if a file can be created at a given storage path.
+	 * FS backends should check if the parent directory exists and the file is writable.
+	 * Backends using key/value stores should check if the container exists.
+	 *
+	 * @param $storagePath string
+	 * @return bool
+	 */
+	abstract public function isPathUsableInternal( $storagePath );
+
+	/**
+	 * Create a file in the backend with the given contents.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * $params include:
+	 *   - content       : the raw file contents
+	 *   - dst           : destination storage path
+	 *   - overwrite     : overwrite any file that exists at the destination
+	 *   - disposition   : Content-Disposition header value for the destination
+	 *   - async         : Status will be returned immediately if supported.
+	 *                     If the status is OK, then its value field will be
+	 *                     set to a FileBackendStoreOpHandle object.
+	 *
+	 * @param $params Array
+	 * @return Status
+	 */
+	final public function createInternal( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		if ( strlen( $params['content'] ) > $this->maxFileSizeInternal() ) {
+			$status = Status::newFatal( 'backend-fail-maxsize',
+				$params['dst'], $this->maxFileSizeInternal() );
+		} else {
+			$status = $this->doCreateInternal( $params );
+			$this->clearCache( array( $params['dst'] ) );
+			if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+				$this->deleteFileCache( $params['dst'] ); // persistent cache
+			}
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::createInternal()
+	 */
+	abstract protected function doCreateInternal( array $params );
+
+	/**
+	 * Store a file into the backend from a file on disk.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * $params include:
+	 *   - src           : source path on disk
+	 *   - dst           : destination storage path
+	 *   - overwrite     : overwrite any file that exists at the destination
+	 *   - disposition   : Content-Disposition header value for the destination
+	 *   - async         : Status will be returned immediately if supported.
+	 *                     If the status is OK, then its value field will be
+	 *                     set to a FileBackendStoreOpHandle object.
+	 *
+	 * @param $params Array
+	 * @return Status
+	 */
+	final public function storeInternal( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		if ( filesize( $params['src'] ) > $this->maxFileSizeInternal() ) {
+			$status = Status::newFatal( 'backend-fail-maxsize',
+				$params['dst'], $this->maxFileSizeInternal() );
+		} else {
+			$status = $this->doStoreInternal( $params );
+			$this->clearCache( array( $params['dst'] ) );
+			if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+				$this->deleteFileCache( $params['dst'] ); // persistent cache
+			}
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::storeInternal()
+	 */
+	abstract protected function doStoreInternal( array $params );
+
+	/**
+	 * Copy a file from one storage path to another in the backend.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * $params include:
+	 *   - src           : source storage path
+	 *   - dst           : destination storage path
+	 *   - overwrite     : overwrite any file that exists at the destination
+	 *   - disposition   : Content-Disposition header value for the destination
+	 *   - async         : Status will be returned immediately if supported.
+	 *                     If the status is OK, then its value field will be
+	 *                     set to a FileBackendStoreOpHandle object.
+	 *
+	 * @param $params Array
+	 * @return Status
+	 */
+	final public function copyInternal( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = $this->doCopyInternal( $params );
+		$this->clearCache( array( $params['dst'] ) );
+		if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+			$this->deleteFileCache( $params['dst'] ); // persistent cache
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::copyInternal()
+	 */
+	abstract protected function doCopyInternal( array $params );
+
+	/**
+	 * Delete a file at the storage path.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * $params include:
+	 *   - src                 : source storage path
+	 *   - ignoreMissingSource : do nothing if the source file does not exist
+	 *   - async               : Status will be returned immediately if supported.
+	 *                           If the status is OK, then its value field will be
+	 *                           set to a FileBackendStoreOpHandle object.
+	 *
+	 * @param $params Array
+	 * @return Status
+	 */
+	final public function deleteInternal( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = $this->doDeleteInternal( $params );
+		$this->clearCache( array( $params['src'] ) );
+		$this->deleteFileCache( $params['src'] ); // persistent cache
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::deleteInternal()
+	 */
+	abstract protected function doDeleteInternal( array $params );
+
+	/**
+	 * Move a file from one storage path to another in the backend.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * $params include:
+	 *   - src           : source storage path
+	 *   - dst           : destination storage path
+	 *   - overwrite     : overwrite any file that exists at the destination
+	 *   - disposition   : Content-Disposition header value for the destination
+	 *   - async         : Status will be returned immediately if supported.
+	 *                     If the status is OK, then its value field will be
+	 *                     set to a FileBackendStoreOpHandle object.
+	 *
+	 * @param $params Array
+	 * @return Status
+	 */
+	final public function moveInternal( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = $this->doMoveInternal( $params );
+		$this->clearCache( array( $params['src'], $params['dst'] ) );
+		$this->deleteFileCache( $params['src'] ); // persistent cache
+		if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+			$this->deleteFileCache( $params['dst'] ); // persistent cache
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::moveInternal()
+	 * @return Status
+	 */
+	protected function doMoveInternal( array $params ) {
+		unset( $params['async'] ); // two steps, won't work here :)
+		// Copy source to dest
+		$status = $this->copyInternal( $params );
+		if ( $status->isOK() ) {
+			// Delete source (only fails due to races or medium going down)
+			$status->merge( $this->deleteInternal( array( 'src' => $params['src'] ) ) );
+			$status->setResult( true, $status->value ); // ignore delete() errors
+		}
+		return $status;
+	}
+
+	/**
+	 * No-op file operation that does nothing.
+	 * Do not call this function from places outside FileBackend and FileOp.
+	 *
+	 * @param $params Array
+	 * @return Status
+	 */
+	final public function nullInternal( array $params ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see FileBackend::concatenate()
+	 * @return Status
+	 */
+	final public function concatenate( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		// Try to lock the source files for the scope of this function
+		$scopeLockS = $this->getScopedFileLocks( $params['srcs'], LockManager::LOCK_UW, $status );
+		if ( $status->isOK() ) {
+			// Actually do the file concatenation...
+			$start_time = microtime( true );
+			$status->merge( $this->doConcatenate( $params ) );
+			$sec = microtime( true ) - $start_time;
+			if ( !$status->isOK() ) {
+				wfDebugLog( 'FileOperation', get_class( $this ) . " failed to concatenate " .
+					count( $params['srcs'] ) . " file(s) [$sec sec]" );
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::concatenate()
+	 * @return Status
+	 */
+	protected function doConcatenate( array $params ) {
+		$status = Status::newGood();
+		$tmpPath = $params['dst']; // convenience
+
+		// Check that the specified temp file is valid...
+		wfSuppressWarnings();
+		$ok = ( is_file( $tmpPath ) && !filesize( $tmpPath ) );
+		wfRestoreWarnings();
+		if ( !$ok ) { // not present or not empty
+			$status->fatal( 'backend-fail-opentemp', $tmpPath );
+			return $status;
+		}
+
+		// Build up the temp file using the source chunks (in order)...
+		$tmpHandle = fopen( $tmpPath, 'ab' );
+		if ( $tmpHandle === false ) {
+			$status->fatal( 'backend-fail-opentemp', $tmpPath );
+			return $status;
+		}
+		foreach ( $params['srcs'] as $virtualSource ) {
+			// Get a local FS version of the chunk
+			$tmpFile = $this->getLocalReference( array( 'src' => $virtualSource ) );
+			if ( !$tmpFile ) {
+				$status->fatal( 'backend-fail-read', $virtualSource );
+				return $status;
+			}
+			// Get a handle to the local FS version
+			$sourceHandle = fopen( $tmpFile->getPath(), 'r' );
+			if ( $sourceHandle === false ) {
+				fclose( $tmpHandle );
+				$status->fatal( 'backend-fail-read', $virtualSource );
+				return $status;
+			}
+			// Append chunk to file (pass chunk size to avoid magic quotes)
+			if ( !stream_copy_to_stream( $sourceHandle, $tmpHandle ) ) {
+				fclose( $sourceHandle );
+				fclose( $tmpHandle );
+				$status->fatal( 'backend-fail-writetemp', $tmpPath );
+				return $status;
+			}
+			fclose( $sourceHandle );
+		}
+		if ( !fclose( $tmpHandle ) ) {
+			$status->fatal( 'backend-fail-closetemp', $tmpPath );
+			return $status;
+		}
+
+		clearstatcache(); // temp file changed
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::doPrepare()
+	 * @return Status
+	 */
+	final protected function doPrepare( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+
+		$status = Status::newGood();
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dir'] );
+			wfProfileOut( __METHOD__ . '-' . $this->name );
+			wfProfileOut( __METHOD__ );
+			return $status; // invalid storage path
+		}
+
+		if ( $shard !== null ) { // confined to a single container/shard
+			$status->merge( $this->doPrepareInternal( $fullCont, $dir, $params ) );
+		} else { // directory is on several shards
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
+				$status->merge( $this->doPrepareInternal( "{$fullCont}{$suffix}", $dir, $params ) );
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doPrepare()
+	 * @return Status
+	 */
+	protected function doPrepareInternal( $container, $dir, array $params ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see FileBackend::doSecure()
+	 * @return Status
+	 */
+	final protected function doSecure( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dir'] );
+			wfProfileOut( __METHOD__ . '-' . $this->name );
+			wfProfileOut( __METHOD__ );
+			return $status; // invalid storage path
+		}
+
+		if ( $shard !== null ) { // confined to a single container/shard
+			$status->merge( $this->doSecureInternal( $fullCont, $dir, $params ) );
+		} else { // directory is on several shards
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
+				$status->merge( $this->doSecureInternal( "{$fullCont}{$suffix}", $dir, $params ) );
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doSecure()
+	 * @return Status
+	 */
+	protected function doSecureInternal( $container, $dir, array $params ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see FileBackend::doPublish()
+	 * @return Status
+	 */
+	final protected function doPublish( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dir'] );
+			wfProfileOut( __METHOD__ . '-' . $this->name );
+			wfProfileOut( __METHOD__ );
+			return $status; // invalid storage path
+		}
+
+		if ( $shard !== null ) { // confined to a single container/shard
+			$status->merge( $this->doPublishInternal( $fullCont, $dir, $params ) );
+		} else { // directory is on several shards
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
+				$status->merge( $this->doPublishInternal( "{$fullCont}{$suffix}", $dir, $params ) );
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doPublish()
+	 * @return Status
+	 */
+	protected function doPublishInternal( $container, $dir, array $params ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see FileBackend::doClean()
+	 * @return Status
+	 */
+	final protected function doClean( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		// Recursive: first delete all empty subdirs recursively
+		if ( !empty( $params['recursive'] ) && !$this->directoriesAreVirtual() ) {
+			$subDirsRel = $this->getTopDirectoryList( array( 'dir' => $params['dir'] ) );
+			if ( $subDirsRel !== null ) { // no errors
+				foreach ( $subDirsRel as $subDirRel ) {
+					$subDir = $params['dir'] . "/{$subDirRel}"; // full path
+					$status->merge( $this->doClean( array( 'dir' => $subDir ) + $params ) );
+				}
+			}
+		}
+
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dir'] );
+			wfProfileOut( __METHOD__ . '-' . $this->name );
+			wfProfileOut( __METHOD__ );
+			return $status; // invalid storage path
+		}
+
+		// Attempt to lock this directory...
+		$filesLockEx = array( $params['dir'] );
+		$scopedLockE = $this->getScopedFileLocks( $filesLockEx, LockManager::LOCK_EX, $status );
+		if ( !$status->isOK() ) {
+			wfProfileOut( __METHOD__ . '-' . $this->name );
+			wfProfileOut( __METHOD__ );
+			return $status; // abort
+		}
+
+		if ( $shard !== null ) { // confined to a single container/shard
+			$status->merge( $this->doCleanInternal( $fullCont, $dir, $params ) );
+			$this->deleteContainerCache( $fullCont ); // purge cache
+		} else { // directory is on several shards
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
+				$status->merge( $this->doCleanInternal( "{$fullCont}{$suffix}", $dir, $params ) );
+				$this->deleteContainerCache( "{$fullCont}{$suffix}" ); // purge cache
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doClean()
+	 * @return Status
+	 */
+	protected function doCleanInternal( $container, $dir, array $params ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see FileBackend::fileExists()
+	 * @return bool|null
+	 */
+	final public function fileExists( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$stat = $this->getFileStat( $params );
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return ( $stat === null ) ? null : (bool)$stat; // null => failure
+	}
+
+	/**
+	 * @see FileBackend::getFileTimestamp()
+	 * @return bool
+	 */
+	final public function getFileTimestamp( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$stat = $this->getFileStat( $params );
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $stat ? $stat['mtime'] : false;
+	}
+
+	/**
+	 * @see FileBackend::getFileSize()
+	 * @return bool
+	 */
+	final public function getFileSize( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$stat = $this->getFileStat( $params );
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $stat ? $stat['size'] : false;
+	}
+
+	/**
+	 * @see FileBackend::getFileStat()
+	 * @return bool
+	 */
+	final public function getFileStat( array $params ) {
+		$path = self::normalizeStoragePath( $params['src'] );
+		if ( $path === null ) {
+			return false; // invalid storage path
+		}
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$latest = !empty( $params['latest'] ); // use latest data?
+		if ( !$this->cheapCache->has( $path, 'stat' ) ) {
+			$this->primeFileCache( array( $path ) ); // check persistent cache
+		}
+		if ( $this->cheapCache->has( $path, 'stat' ) ) {
+			$stat = $this->cheapCache->get( $path, 'stat' );
+			// If we want the latest data, check that this cached
+			// value was in fact fetched with the latest available data.
+			if ( !$latest || $stat['latest'] ) {
+				wfProfileOut( __METHOD__ . '-' . $this->name );
+				wfProfileOut( __METHOD__ );
+				return $stat;
+			}
+		}
+		wfProfileIn( __METHOD__ . '-miss' );
+		wfProfileIn( __METHOD__ . '-miss-' . $this->name );
+		$stat = $this->doGetFileStat( $params );
+		wfProfileOut( __METHOD__ . '-miss-' . $this->name );
+		wfProfileOut( __METHOD__ . '-miss' );
+		if ( is_array( $stat ) ) { // don't cache negatives
+			$stat['latest'] = $latest;
+			$this->cheapCache->set( $path, 'stat', $stat );
+			$this->setFileCache( $path, $stat ); // update persistent cache
+			if ( isset( $stat['sha1'] ) ) { // some backends store SHA-1 as metadata
+				$this->cheapCache->set( $path, 'sha1',
+					array( 'hash' => $stat['sha1'], 'latest' => $latest ) );
+			}
+		} else {
+			wfDebug( __METHOD__ . ": File $path does not exist.\n" );
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $stat;
+	}
+
+	/**
+	 * @see FileBackendStore::getFileStat()
+	 */
+	abstract protected function doGetFileStat( array $params );
+
+	/**
+	 * @see FileBackend::getFileContents()
+	 * @return bool|string
+	 */
+	public function getFileContents( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$tmpFile = $this->getLocalReference( $params );
+		if ( !$tmpFile ) {
+			wfProfileOut( __METHOD__ . '-' . $this->name );
+			wfProfileOut( __METHOD__ );
+			return false;
+		}
+		wfSuppressWarnings();
+		$data = file_get_contents( $tmpFile->getPath() );
+		wfRestoreWarnings();
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $data;
+	}
+
+	/**
+	 * @see FileBackend::getFileSha1Base36()
+	 * @return bool|string
+	 */
+	final public function getFileSha1Base36( array $params ) {
+		$path = self::normalizeStoragePath( $params['src'] );
+		if ( $path === null ) {
+			return false; // invalid storage path
+		}
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$latest = !empty( $params['latest'] ); // use latest data?
+		if ( $this->cheapCache->has( $path, 'sha1' ) ) {
+			$stat = $this->cheapCache->get( $path, 'sha1' );
+			// If we want the latest data, check that this cached
+			// value was in fact fetched with the latest available data.
+			if ( !$latest || $stat['latest'] ) {
+				wfProfileOut( __METHOD__ . '-' . $this->name );
+				wfProfileOut( __METHOD__ );
+				return $stat['hash'];
+			}
+		}
+		wfProfileIn( __METHOD__ . '-miss' );
+		wfProfileIn( __METHOD__ . '-miss-' . $this->name );
+		$hash = $this->doGetFileSha1Base36( $params );
+		wfProfileOut( __METHOD__ . '-miss-' . $this->name );
+		wfProfileOut( __METHOD__ . '-miss' );
+		if ( $hash ) { // don't cache negatives
+			$this->cheapCache->set( $path, 'sha1',
+				array( 'hash' => $hash, 'latest' => $latest ) );
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $hash;
+	}
+
+	/**
+	 * @see FileBackendStore::getFileSha1Base36()
+	 * @return bool|string
+	 */
+	protected function doGetFileSha1Base36( array $params ) {
+		$fsFile = $this->getLocalReference( $params );
+		if ( !$fsFile ) {
+			return false;
+		} else {
+			return $fsFile->getSha1Base36();
+		}
+	}
+
+	/**
+	 * @see FileBackend::getFileProps()
+	 * @return Array
+	 */
+	final public function getFileProps( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$fsFile = $this->getLocalReference( $params );
+		$props = $fsFile ? $fsFile->getProps() : FSFile::placeholderProps();
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $props;
+	}
+
+	/**
+	 * @see FileBackend::getLocalReference()
+	 * @return TempFSFile|null
+	 */
+	public function getLocalReference( array $params ) {
+		$path = self::normalizeStoragePath( $params['src'] );
+		if ( $path === null ) {
+			return null; // invalid storage path
+		}
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$latest = !empty( $params['latest'] ); // use latest data?
+		if ( $this->expensiveCache->has( $path, 'localRef' ) ) {
+			$val = $this->expensiveCache->get( $path, 'localRef' );
+			// If we want the latest data, check that this cached
+			// value was in fact fetched with the latest available data.
+			if ( !$latest || $val['latest'] ) {
+				wfProfileOut( __METHOD__ . '-' . $this->name );
+				wfProfileOut( __METHOD__ );
+				return $val['object'];
+			}
+		}
+		$tmpFile = $this->getLocalCopy( $params );
+		if ( $tmpFile ) { // don't cache negatives
+			$this->expensiveCache->set( $path, 'localRef',
+				array( 'object' => $tmpFile, 'latest' => $latest ) );
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $tmpFile;
+	}
+
+	/**
+	 * @see FileBackend::streamFile()
+	 * @return Status
+	 */
+	final public function streamFile( array $params ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		$info = $this->getFileStat( $params );
+		if ( !$info ) { // let StreamFile handle the 404
+			$status->fatal( 'backend-fail-notexists', $params['src'] );
+		}
+
+		// Set output buffer and HTTP headers for stream
+		$extraHeaders = isset( $params['headers'] ) ? $params['headers'] : array();
+		$res = StreamFile::prepareForStream( $params['src'], $info, $extraHeaders );
+		if ( $res == StreamFile::NOT_MODIFIED ) {
+			// do nothing; client cache is up to date
+		} elseif ( $res == StreamFile::READY_STREAM ) {
+			wfProfileIn( __METHOD__ . '-send' );
+			wfProfileIn( __METHOD__ . '-send-' . $this->name );
+			$status = $this->doStreamFile( $params );
+			wfProfileOut( __METHOD__ . '-send-' . $this->name );
+			wfProfileOut( __METHOD__ . '-send' );
+		} else {
+			$status->fatal( 'backend-fail-stream', $params['src'] );
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::streamFile()
+	 * @return Status
+	 */
+	protected function doStreamFile( array $params ) {
+		$status = Status::newGood();
+
+		$fsFile = $this->getLocalReference( $params );
+		if ( !$fsFile ) {
+			$status->fatal( 'backend-fail-stream', $params['src'] );
+		} elseif ( !readfile( $fsFile->getPath() ) ) {
+			$status->fatal( 'backend-fail-stream', $params['src'] );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::directoryExists()
+	 * @return bool|null
+	 */
+	final public function directoryExists( array $params ) {
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) {
+			return false; // invalid storage path
+		}
+		if ( $shard !== null ) { // confined to a single container/shard
+			return $this->doDirectoryExists( $fullCont, $dir, $params );
+		} else { // directory is on several shards
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			$res = false; // response
+			foreach ( $this->getContainerSuffixes( $shortCont ) as $suffix ) {
+				$exists = $this->doDirectoryExists( "{$fullCont}{$suffix}", $dir, $params );
+				if ( $exists ) {
+					$res = true;
+					break; // found one!
+				} elseif ( $exists === null ) { // error?
+					$res = null; // if we don't find anything, it is indeterminate
+				}
+			}
+			return $res;
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::directoryExists()
+	 *
+	 * @param $container string Resolved container name
+	 * @param $dir string Resolved path relative to container
+	 * @param $params Array
+	 * @return bool|null
+	 */
+	abstract protected function doDirectoryExists( $container, $dir, array $params );
+
+	/**
+	 * @see FileBackend::getDirectoryList()
+	 * @return Traversable|Array|null Returns null on failure
+	 */
+	final public function getDirectoryList( array $params ) {
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) { // invalid storage path
+			return null;
+		}
+		if ( $shard !== null ) {
+			// File listing is confined to a single container/shard
+			return $this->getDirectoryListInternal( $fullCont, $dir, $params );
+		} else {
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			// File listing spans multiple containers/shards
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			return new FileBackendStoreShardDirIterator( $this,
+				$fullCont, $dir, $this->getContainerSuffixes( $shortCont ), $params );
+		}
+	}
+
+	/**
+	 * Do not call this function from places outside FileBackend
+	 *
+	 * @see FileBackendStore::getDirectoryList()
+	 *
+	 * @param $container string Resolved container name
+	 * @param $dir string Resolved path relative to container
+	 * @param $params Array
+	 * @return Traversable|Array|null Returns null on failure
+	 */
+	abstract public function getDirectoryListInternal( $container, $dir, array $params );
+
+	/**
+	 * @see FileBackend::getFileList()
+	 * @return Traversable|Array|null Returns null on failure
+	 */
+	final public function getFileList( array $params ) {
+		list( $fullCont, $dir, $shard ) = $this->resolveStoragePath( $params['dir'] );
+		if ( $dir === null ) { // invalid storage path
+			return null;
+		}
+		if ( $shard !== null ) {
+			// File listing is confined to a single container/shard
+			return $this->getFileListInternal( $fullCont, $dir, $params );
+		} else {
+			wfDebug( __METHOD__ . ": iterating over all container shards.\n" );
+			// File listing spans multiple containers/shards
+			list( $b, $shortCont, $r ) = self::splitStoragePath( $params['dir'] );
+			return new FileBackendStoreShardFileIterator( $this,
+				$fullCont, $dir, $this->getContainerSuffixes( $shortCont ), $params );
+		}
+	}
+
+	/**
+	 * Do not call this function from places outside FileBackend
+	 *
+	 * @see FileBackendStore::getFileList()
+	 *
+	 * @param $container string Resolved container name
+	 * @param $dir string Resolved path relative to container
+	 * @param $params Array
+	 * @return Traversable|Array|null Returns null on failure
+	 */
+	abstract public function getFileListInternal( $container, $dir, array $params );
+
+	/**
+	 * Return a list of FileOp objects from a list of operations.
+	 * Do not call this function from places outside FileBackend.
+	 *
+	 * The result must have the same number of items as the input.
+	 * An exception is thrown if an unsupported operation is requested.
+	 *
+	 * @param $ops Array Same format as doOperations()
+	 * @return Array List of FileOp objects
+	 * @throws MWException
+	 */
+	final public function getOperationsInternal( array $ops ) {
+		$supportedOps = array(
+			'store'       => 'StoreFileOp',
+			'copy'        => 'CopyFileOp',
+			'move'        => 'MoveFileOp',
+			'delete'      => 'DeleteFileOp',
+			'create'      => 'CreateFileOp',
+			'null'        => 'NullFileOp'
+		);
+
+		$performOps = array(); // array of FileOp objects
+		// Build up ordered array of FileOps...
+		foreach ( $ops as $operation ) {
+			$opName = $operation['op'];
+			if ( isset( $supportedOps[$opName] ) ) {
+				$class = $supportedOps[$opName];
+				// Get params for this operation
+				$params = $operation;
+				// Append the FileOp class
+				$performOps[] = new $class( $this, $params );
+			} else {
+				throw new MWException( "Operation '$opName' is not supported." );
+			}
+		}
+
+		return $performOps;
+	}
+
+	/**
+	 * Get a list of storage paths to lock for a list of operations
+	 * Returns an array with 'sh' (shared) and 'ex' (exclusive) keys,
+	 * each corresponding to a list of storage paths to be locked.
+	 *
+	 * @param $performOps Array List of FileOp objects
+	 * @return Array ('sh' => list of paths, 'ex' => list of paths)
+	 */
+	final public function getPathsToLockForOpsInternal( array $performOps ) {
+		// Build up a list of files to lock...
+		$paths = array( 'sh' => array(), 'ex' => array() );
+		foreach ( $performOps as $fileOp ) {
+			$paths['sh'] = array_merge( $paths['sh'], $fileOp->storagePathsRead() );
+			$paths['ex'] = array_merge( $paths['ex'], $fileOp->storagePathsChanged() );
+		}
+		// Optimization: if doing an EX lock anyway, don't also set an SH one
+		$paths['sh'] = array_diff( $paths['sh'], $paths['ex'] );
+		// Get a shared lock on the parent directory of each path changed
+		$paths['sh'] = array_merge( $paths['sh'], array_map( 'dirname', $paths['ex'] ) );
+
+		return $paths;
+	}
+
+	/**
+	 * @see FileBackend::getScopedLocksForOps()
+	 * @return Array
+	 */
+	public function getScopedLocksForOps( array $ops, Status $status ) {
+		$paths = $this->getPathsToLockForOpsInternal( $this->getOperationsInternal( $ops ) );
+		return array(
+			$this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status ),
+			$this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status )
+		);
+	}
+
+	/**
+	 * @see FileBackend::doOperationsInternal()
+	 * @return Status
+	 */
+	final protected function doOperationsInternal( array $ops, array $opts ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		// Build up a list of FileOps...
+		$performOps = $this->getOperationsInternal( $ops );
+
+		// Acquire any locks as needed...
+		if ( empty( $opts['nonLocking'] ) ) {
+			// Build up a list of files to lock...
+			$paths = $this->getPathsToLockForOpsInternal( $performOps );
+			// Try to lock those files for the scope of this function...
+			$scopeLockS = $this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status );
+			$scopeLockE = $this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status );
+			if ( !$status->isOK() ) {
+				wfProfileOut( __METHOD__ . '-' . $this->name );
+				wfProfileOut( __METHOD__ );
+				return $status; // abort
+			}
+		}
+
+		// Clear any file cache entries (after locks acquired)
+		if ( empty( $opts['preserveCache'] ) ) {
+			$this->clearCache();
+		}
+
+		// Load from the persistent file and container caches
+		$this->primeFileCache( $performOps );
+		$this->primeContainerCache( $performOps );
+
+		// Actually attempt the operation batch...
+		$subStatus = FileOpBatch::attempt( $performOps, $opts, $this->fileJournal );
+
+		// Merge errors into status fields
+		$status->merge( $subStatus );
+		$status->success = $subStatus->success; // not done in merge()
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * @see FileBackend::doQuickOperationsInternal()
+	 * @return Status
+	 * @throws MWException
+	 */
+	final protected function doQuickOperationsInternal( array $ops ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		$status = Status::newGood();
+
+		$supportedOps = array( 'create', 'store', 'copy', 'move', 'delete', 'null' );
+		$async = ( $this->parallelize === 'implicit' );
+		$maxConcurrency = $this->concurrency; // throttle
+
+		$statuses = array(); // array of (index => Status)
+		$fileOpHandles = array(); // list of (index => handle) arrays
+		$curFileOpHandles = array(); // current handle batch
+		// Perform the sync-only ops and build up op handles for the async ops...
+		foreach ( $ops as $index => $params ) {
+			if ( !in_array( $params['op'], $supportedOps ) ) {
+				wfProfileOut( __METHOD__ . '-' . $this->name );
+				wfProfileOut( __METHOD__ );
+				throw new MWException( "Operation '{$params['op']}' is not supported." );
+			}
+			$method = $params['op'] . 'Internal'; // e.g. "storeInternal"
+			$subStatus = $this->$method( array( 'async' => $async ) + $params );
+			if ( $subStatus->value instanceof FileBackendStoreOpHandle ) { // async
+				if ( count( $curFileOpHandles ) >= $maxConcurrency ) {
+					$fileOpHandles[] = $curFileOpHandles; // push this batch
+					$curFileOpHandles = array();
+				}
+				$curFileOpHandles[$index] = $subStatus->value; // keep index
+			} else { // error or completed
+				$statuses[$index] = $subStatus; // keep index
+			}
+		}
+		if ( count( $curFileOpHandles ) ) {
+			$fileOpHandles[] = $curFileOpHandles; // last batch
+		}
+		// Do all the async ops that can be done concurrently...
+		foreach ( $fileOpHandles as $fileHandleBatch ) {
+			$statuses = $statuses + $this->executeOpHandlesInternal( $fileHandleBatch );
+		}
+		// Marshall and merge all the responses...
+		foreach ( $statuses as $index => $subStatus ) {
+			$status->merge( $subStatus );
+			if ( $subStatus->isOK() ) {
+				$status->success[$index] = true;
+				++$status->successCount;
+			} else {
+				$status->success[$index] = false;
+				++$status->failCount;
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * Execute a list of FileBackendStoreOpHandle handles in parallel.
+	 * The resulting Status object fields will correspond
+	 * to the order in which the handles where given.
+	 *
+	 * @param $handles Array List of FileBackendStoreOpHandle objects
+	 * @return Array Map of Status objects
+	 * @throws MWException
+	 */
+	final public function executeOpHandlesInternal( array $fileOpHandles ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+		foreach ( $fileOpHandles as $fileOpHandle ) {
+			if ( !( $fileOpHandle instanceof FileBackendStoreOpHandle ) ) {
+				throw new MWException( "Given a non-FileBackendStoreOpHandle object." );
+			} elseif ( $fileOpHandle->backend->getName() !== $this->getName() ) {
+				throw new MWException( "Given a FileBackendStoreOpHandle for the wrong backend." );
+			}
+		}
+		$res = $this->doExecuteOpHandlesInternal( $fileOpHandles );
+		foreach ( $fileOpHandles as $fileOpHandle ) {
+			$fileOpHandle->closeResources();
+		}
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+		return $res;
+	}
+
+	/**
+	 * @see FileBackendStore::executeOpHandlesInternal()
+	 * @return Array List of corresponding Status objects
+	 */
+	protected function doExecuteOpHandlesInternal( array $fileOpHandles ) {
+		foreach ( $fileOpHandles as $fileOpHandle ) { // OK if empty
+			throw new MWException( "This backend supports no asynchronous operations." );
+		}
+		return array();
+	}
+
+	/**
+	 * @see FileBackend::preloadCache()
+	 */
+	final public function preloadCache( array $paths ) {
+		$fullConts = array(); // full container names
+		foreach ( $paths as $path ) {
+			list( $fullCont, $r, $s ) = $this->resolveStoragePath( $path );
+			$fullConts[] = $fullCont;
+		}
+		// Load from the persistent file and container caches
+		$this->primeContainerCache( $fullConts );
+		$this->primeFileCache( $paths );
+	}
+
+	/**
+	 * @see FileBackend::clearCache()
+	 */
+	final public function clearCache( array $paths = null ) {
+		if ( is_array( $paths ) ) {
+			$paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
+			$paths = array_filter( $paths, 'strlen' ); // remove nulls
+		}
+		if ( $paths === null ) {
+			$this->cheapCache->clear();
+			$this->expensiveCache->clear();
+		} else {
+			foreach ( $paths as $path ) {
+				$this->cheapCache->clear( $path );
+				$this->expensiveCache->clear( $path );
+			}
+		}
+		$this->doClearCache( $paths );
+	}
+
+	/**
+	 * Clears any additional stat caches for storage paths
+	 *
+	 * @see FileBackend::clearCache()
+	 *
+	 * @param $paths Array Storage paths (optional)
+	 * @return void
+	 */
+	protected function doClearCache( array $paths = null ) {}
+
+	/**
+	 * Is this a key/value store where directories are just virtual?
+	 * Virtual directories exists in so much as files exists that are
+	 * prefixed with the directory path followed by a forward slash.
+	 *
+	 * @return bool
+	 */
+	abstract protected function directoriesAreVirtual();
+
+	/**
+	 * Check if a container name is valid.
+	 * This checks for for length and illegal characters.
+	 *
+	 * @param $container string
+	 * @return bool
+	 */
+	final protected static function isValidContainerName( $container ) {
+		// This accounts for Swift and S3 restrictions while leaving room
+		// for things like '.xxx' (hex shard chars) or '.seg' (segments).
+		// This disallows directory separators or traversal characters.
+		// Note that matching strings URL encode to the same string;
+		// in Swift, the length restriction is *after* URL encoding.
+		return preg_match( '/^[a-z0-9][a-z0-9-_]{0,199}$/i', $container );
+	}
+
+	/**
+	 * Splits a storage path into an internal container name,
+	 * an internal relative file name, and a container shard suffix.
+	 * Any shard suffix is already appended to the internal container name.
+	 * This also checks that the storage path is valid and within this backend.
+	 *
+	 * If the container is sharded but a suffix could not be determined,
+	 * this means that the path can only refer to a directory and can only
+	 * be scanned by looking in all the container shards.
+	 *
+	 * @param $storagePath string
+	 * @return Array (container, path, container suffix) or (null, null, null) if invalid
+	 */
+	final protected function resolveStoragePath( $storagePath ) {
+		list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
+		if ( $backend === $this->name ) { // must be for this backend
+			$relPath = self::normalizeContainerPath( $relPath );
+			if ( $relPath !== null ) {
+				// Get shard for the normalized path if this container is sharded
+				$cShard = $this->getContainerShard( $container, $relPath );
+				// Validate and sanitize the relative path (backend-specific)
+				$relPath = $this->resolveContainerPath( $container, $relPath );
+				if ( $relPath !== null ) {
+					// Prepend any wiki ID prefix to the container name
+					$container = $this->fullContainerName( $container );
+					if ( self::isValidContainerName( $container ) ) {
+						// Validate and sanitize the container name (backend-specific)
+						$container = $this->resolveContainerName( "{$container}{$cShard}" );
+						if ( $container !== null ) {
+							return array( $container, $relPath, $cShard );
+						}
+					}
+				}
+			}
+		}
+		return array( null, null, null );
+	}
+
+	/**
+	 * Like resolveStoragePath() except null values are returned if
+	 * the container is sharded and the shard could not be determined.
+	 *
+	 * @see FileBackendStore::resolveStoragePath()
+	 *
+	 * @param $storagePath string
+	 * @return Array (container, path) or (null, null) if invalid
+	 */
+	final protected function resolveStoragePathReal( $storagePath ) {
+		list( $container, $relPath, $cShard ) = $this->resolveStoragePath( $storagePath );
+		if ( $cShard !== null ) {
+			return array( $container, $relPath );
+		}
+		return array( null, null );
+	}
+
+	/**
+	 * Get the container name shard suffix for a given path.
+	 * Any empty suffix means the container is not sharded.
+	 *
+	 * @param $container string Container name
+	 * @param $relPath string Storage path relative to the container
+	 * @return string|null Returns null if shard could not be determined
+	 */
+	final protected function getContainerShard( $container, $relPath ) {
+		list( $levels, $base, $repeat ) = $this->getContainerHashLevels( $container );
+		if ( $levels == 1 || $levels == 2 ) {
+			// Hash characters are either base 16 or 36
+			$char = ( $base == 36 ) ? '[0-9a-z]' : '[0-9a-f]';
+			// Get a regex that represents the shard portion of paths.
+			// The concatenation of the captures gives us the shard.
+			if ( $levels === 1 ) { // 16 or 36 shards per container
+				$hashDirRegex = '(' . $char . ')';
+			} else { // 256 or 1296 shards per container
+				if ( $repeat ) { // verbose hash dir format (e.g. "a/ab/abc")
+					$hashDirRegex = $char . '/(' . $char . '{2})';
+				} else { // short hash dir format (e.g. "a/b/c")
+					$hashDirRegex = '(' . $char . ')/(' . $char . ')';
+				}
+			}
+			// Allow certain directories to be above the hash dirs so as
+			// to work with FileRepo (e.g. "archive/a/ab" or "temp/a/ab").
+			// They must be 2+ chars to avoid any hash directory ambiguity.
+			$m = array();
+			if ( preg_match( "!^(?:[^/]{2,}/)*$hashDirRegex(?:/|$)!", $relPath, $m ) ) {
+				return '.' . implode( '', array_slice( $m, 1 ) );
+			}
+			return null; // failed to match
+		}
+		return ''; // no sharding
+	}
+
+	/**
+	 * Check if a storage path maps to a single shard.
+	 * Container dirs like "a", where the container shards on "x/xy",
+	 * can reside on several shards. Such paths are tricky to handle.
+	 *
+	 * @param $storagePath string Storage path
+	 * @return bool
+	 */
+	final public function isSingleShardPathInternal( $storagePath ) {
+		list( $c, $r, $shard ) = $this->resolveStoragePath( $storagePath );
+		return ( $shard !== null );
+	}
+
+	/**
+	 * Get the sharding config for a container.
+	 * If greater than 0, then all file storage paths within
+	 * the container are required to be hashed accordingly.
+	 *
+	 * @param $container string
+	 * @return Array (integer levels, integer base, repeat flag) or (0, 0, false)
+	 */
+	final protected function getContainerHashLevels( $container ) {
+		if ( isset( $this->shardViaHashLevels[$container] ) ) {
+			$config = $this->shardViaHashLevels[$container];
+			$hashLevels = (int)$config['levels'];
+			if ( $hashLevels == 1 || $hashLevels == 2 ) {
+				$hashBase = (int)$config['base'];
+				if ( $hashBase == 16 || $hashBase == 36 ) {
+					return array( $hashLevels, $hashBase, $config['repeat'] );
+				}
+			}
+		}
+		return array( 0, 0, false ); // no sharding
+	}
+
+	/**
+	 * Get a list of full container shard suffixes for a container
+	 *
+	 * @param $container string
+	 * @return Array
+	 */
+	final protected function getContainerSuffixes( $container ) {
+		$shards = array();
+		list( $digits, $base ) = $this->getContainerHashLevels( $container );
+		if ( $digits > 0 ) {
+			$numShards = pow( $base, $digits );
+			for ( $index = 0; $index < $numShards; $index++ ) {
+				$shards[] = '.' . wfBaseConvert( $index, 10, $base, $digits );
+			}
+		}
+		return $shards;
+	}
+
+	/**
+	 * Get the full container name, including the wiki ID prefix
+	 *
+	 * @param $container string
+	 * @return string
+	 */
+	final protected function fullContainerName( $container ) {
+		if ( $this->wikiId != '' ) {
+			return "{$this->wikiId}-$container";
+		} else {
+			return $container;
+		}
+	}
+
+	/**
+	 * Resolve a container name, checking if it's allowed by the backend.
+	 * This is intended for internal use, such as encoding illegal chars.
+	 * Subclasses can override this to be more restrictive.
+	 *
+	 * @param $container string
+	 * @return string|null
+	 */
+	protected function resolveContainerName( $container ) {
+		return $container;
+	}
+
+	/**
+	 * Resolve a relative storage path, checking if it's allowed by the backend.
+	 * This is intended for internal use, such as encoding illegal chars or perhaps
+	 * getting absolute paths (e.g. FS based backends). Note that the relative path
+	 * may be the empty string (e.g. the path is simply to the container).
+	 *
+	 * @param $container string Container name
+	 * @param $relStoragePath string Storage path relative to the container
+	 * @return string|null Path or null if not valid
+	 */
+	protected function resolveContainerPath( $container, $relStoragePath ) {
+		return $relStoragePath;
+	}
+
+	/**
+	 * Get the cache key for a container
+	 *
+	 * @param $container string Resolved container name
+	 * @return string
+	 */
+	private function containerCacheKey( $container ) {
+		return wfMemcKey( 'backend', $this->getName(), 'container', $container );
+	}
+
+	/**
+	 * Set the cached info for a container
+	 *
+	 * @param $container string Resolved container name
+	 * @param $val mixed Information to cache
+	 */
+	final protected function setContainerCache( $container, $val ) {
+		$this->memCache->add( $this->containerCacheKey( $container ), $val, 14*86400 );
+	}
+
+	/**
+	 * Delete the cached info for a container.
+	 * The cache key is salted for a while to prevent race conditions.
+	 *
+	 * @param $container string Resolved container name
+	 */
+	final protected function deleteContainerCache( $container ) {
+		if ( !$this->memCache->set( $this->containerCacheKey( $container ), 'PURGED', 300 ) ) {
+			trigger_error( "Unable to delete stat cache for container $container." );
+		}
+	}
+
+	/**
+	 * Do a batch lookup from cache for container stats for all containers
+	 * used in a list of container names, storage paths, or FileOp objects.
+	 *
+	 * @param $items Array
+	 * @return void
+	 */
+	final protected function primeContainerCache( array $items ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+
+		$paths = array(); // list of storage paths
+		$contNames = array(); // (cache key => resolved container name)
+		// Get all the paths/containers from the items...
+		foreach ( $items as $item ) {
+			if ( $item instanceof FileOp ) {
+				$paths = array_merge( $paths, $item->storagePathsRead() );
+				$paths = array_merge( $paths, $item->storagePathsChanged() );
+			} elseif ( self::isStoragePath( $item ) ) {
+				$paths[] = $item;
+			} elseif ( is_string( $item ) ) { // full container name
+				$contNames[$this->containerCacheKey( $item )] = $item;
+			}
+		}
+		// Get all the corresponding cache keys for paths...
+		foreach ( $paths as $path ) {
+			list( $fullCont, $r, $s ) = $this->resolveStoragePath( $path );
+			if ( $fullCont !== null ) { // valid path for this backend
+				$contNames[$this->containerCacheKey( $fullCont )] = $fullCont;
+			}
+		}
+
+		$contInfo = array(); // (resolved container name => cache value)
+		// Get all cache entries for these container cache keys...
+		$values = $this->memCache->getMulti( array_keys( $contNames ) );
+		foreach ( $values as $cacheKey => $val ) {
+			$contInfo[$contNames[$cacheKey]] = $val;
+		}
+
+		// Populate the container process cache for the backend...
+		$this->doPrimeContainerCache( array_filter( $contInfo, 'is_array' ) );
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+	}
+
+	/**
+	 * Fill the backend-specific process cache given an array of
+	 * resolved container names and their corresponding cached info.
+	 * Only containers that actually exist should appear in the map.
+	 *
+	 * @param $containerInfo Array Map of resolved container names to cached info
+	 * @return void
+	 */
+	protected function doPrimeContainerCache( array $containerInfo ) {}
+
+	/**
+	 * Get the cache key for a file path
+	 *
+	 * @param $path string Storage path
+	 * @return string
+	 */
+	private function fileCacheKey( $path ) {
+		return wfMemcKey( 'backend', $this->getName(), 'file', sha1( $path ) );
+	}
+
+	/**
+	 * Set the cached stat info for a file path.
+	 * Negatives (404s) are not cached. By not caching negatives, we can skip cache
+	 * salting for the case when a file is created at a path were there was none before.
+	 *
+	 * @param $path string Storage path
+	 * @param $val mixed Information to cache
+	 */
+	final protected function setFileCache( $path, $val ) {
+		$this->memCache->add( $this->fileCacheKey( $path ), $val, 7*86400 );
+	}
+
+	/**
+	 * Delete the cached stat info for a file path.
+	 * The cache key is salted for a while to prevent race conditions.
+	 *
+	 * @param $path string Storage path
+	 */
+	final protected function deleteFileCache( $path ) {
+		if ( !$this->memCache->set( $this->fileCacheKey( $path ), 'PURGED', 300 ) ) {
+			trigger_error( "Unable to delete stat cache for file $path." );
+		}
+	}
+
+	/**
+	 * Do a batch lookup from cache for file stats for all paths
+	 * used in a list of storage paths or FileOp objects.
+	 *
+	 * @param $items Array List of storage paths or FileOps
+	 * @return void
+	 */
+	final protected function primeFileCache( array $items ) {
+		wfProfileIn( __METHOD__ );
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+
+		$paths = array(); // list of storage paths
+		$pathNames = array(); // (cache key => storage path)
+		// Get all the paths/containers from the items...
+		foreach ( $items as $item ) {
+			if ( $item instanceof FileOp ) {
+				$paths = array_merge( $paths, $item->storagePathsRead() );
+				$paths = array_merge( $paths, $item->storagePathsChanged() );
+			} elseif ( self::isStoragePath( $item ) ) {
+				$paths[] = $item;
+			}
+		}
+		// Get all the corresponding cache keys for paths...
+		foreach ( $paths as $path ) {
+			list( $cont, $rel, $s ) = $this->resolveStoragePath( $path );
+			if ( $rel !== null ) { // valid path for this backend
+				$pathNames[$this->fileCacheKey( $path )] = $path;
+			}
+		}
+		// Get all cache entries for these container cache keys...
+		$values = $this->memCache->getMulti( array_keys( $pathNames ) );
+		foreach ( $values as $cacheKey => $val ) {
+			if ( is_array( $val ) ) {
+				$path = $pathNames[$cacheKey];
+				$this->cheapCache->set( $path, 'stat', $val );
+				if ( isset( $val['sha1'] ) ) { // some backends store SHA-1 as metadata
+					$this->cheapCache->set( $path, 'sha1',
+						array( 'hash' => $val['sha1'], 'latest' => $val['latest'] ) );
+				}
+			}
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		wfProfileOut( __METHOD__ );
+	}
+}
+
+/**
+ * FileBackendStore helper class for performing asynchronous file operations.
+ *
+ * For example, calling FileBackendStore::createInternal() with the "async"
+ * param flag may result in a Status that contains this object as a value.
+ * This class is largely backend-specific and is mostly just "magic" to be
+ * passed to FileBackendStore::executeOpHandlesInternal().
+ */
+abstract class FileBackendStoreOpHandle {
+	/** @var Array */
+	public $params = array(); // params to caller functions
+	/** @var FileBackendStore */
+	public $backend;
+	/** @var Array */
+	public $resourcesToClose = array();
+
+	public $call; // string; name that identifies the function called
+
+	/**
+	 * Close all open file handles
+	 *
+	 * @return void
+	 */
+	public function closeResources() {
+		array_map( 'fclose', $this->resourcesToClose );
+	}
+}
+
+/**
+ * FileBackendStore helper function to handle listings that span container shards.
+ * Do not use this class from places outside of FileBackendStore.
+ *
+ * @ingroup FileBackend
+ */
+abstract class FileBackendStoreShardListIterator implements Iterator {
+	/** @var FileBackendStore */
+	protected $backend;
+	/** @var Array */
+	protected $params;
+	/** @var Array */
+	protected $shardSuffixes;
+	protected $container; // string; full container name
+	protected $directory; // string; resolved relative path
+
+	/** @var Traversable */
+	protected $iter;
+	protected $curShard = 0; // integer
+	protected $pos = 0; // integer
+
+	/** @var Array */
+	protected $multiShardPaths = array(); // (rel path => 1)
+
+	/**
+	 * @param $backend FileBackendStore
+	 * @param $container string Full storage container name
+	 * @param $dir string Storage directory relative to container
+	 * @param $suffixes Array List of container shard suffixes
+	 * @param $params Array
+	 */
+	public function __construct(
+		FileBackendStore $backend, $container, $dir, array $suffixes, array $params
+	) {
+		$this->backend = $backend;
+		$this->container = $container;
+		$this->directory = $dir;
+		$this->shardSuffixes = $suffixes;
+		$this->params = $params;
+	}
+
+	/**
+	 * @see Iterator::key()
+	 * @return integer
+	 */
+	public function key() {
+		return $this->pos;
+	}
+
+	/**
+	 * @see Iterator::valid()
+	 * @return bool
+	 */
+	public function valid() {
+		if ( $this->iter instanceof Iterator ) {
+			return $this->iter->valid();
+		} elseif ( is_array( $this->iter ) ) {
+			return ( current( $this->iter ) !== false ); // no paths can have this value
+		}
+		return false; // some failure?
+	}
+
+	/**
+	 * @see Iterator::current()
+	 * @return string|bool String or false
+	 */
+	public function current() {
+		return ( $this->iter instanceof Iterator )
+			? $this->iter->current()
+			: current( $this->iter );
+	}
+
+	/**
+	 * @see Iterator::next()
+	 * @return void
+	 */
+	public function next() {
+		++$this->pos;
+		( $this->iter instanceof Iterator ) ? $this->iter->next() : next( $this->iter );
+		do {
+			$continue = false; // keep scanning shards?
+			$this->filterViaNext(); // filter out duplicates
+			// Find the next non-empty shard if no elements are left
+			if ( !$this->valid() ) {
+				$this->nextShardIteratorIfNotValid();
+				$continue = $this->valid(); // re-filter unless we ran out of shards
+			}
+		} while ( $continue );
+	}
+
+	/**
+	 * @see Iterator::rewind()
+	 * @return void
+	 */
+	public function rewind() {
+		$this->pos = 0;
+		$this->curShard = 0;
+		$this->setIteratorFromCurrentShard();
+		do {
+			$continue = false; // keep scanning shards?
+			$this->filterViaNext(); // filter out duplicates
+			// Find the next non-empty shard if no elements are left
+			if ( !$this->valid() ) {
+				$this->nextShardIteratorIfNotValid();
+				$continue = $this->valid(); // re-filter unless we ran out of shards
+			}
+		} while ( $continue );
+	}
+
+	/**
+	 * Filter out duplicate items by advancing to the next ones
+	 */
+	protected function filterViaNext() {
+		while ( $this->valid() ) {
+			$rel = $this->iter->current(); // path relative to given directory
+			$path = $this->params['dir'] . "/{$rel}"; // full storage path
+			if ( $this->backend->isSingleShardPathInternal( $path ) ) {
+				break; // path is only on one shard; no issue with duplicates
+			} elseif ( isset( $this->multiShardPaths[$rel] ) ) {
+				// Don't keep listing paths that are on multiple shards
+				( $this->iter instanceof Iterator ) ? $this->iter->next() : next( $this->iter );
+			} else {
+				$this->multiShardPaths[$rel] = 1;
+				break;
+			}
+		}
+	}
+
+	/**
+	 * If the list iterator for this container shard is out of items,
+	 * then move on to the next container that has items.
+	 * If there are none, then it advances to the last container.
+	 */
+	protected function nextShardIteratorIfNotValid() {
+		while ( !$this->valid() && ++$this->curShard < count( $this->shardSuffixes ) ) {
+			$this->setIteratorFromCurrentShard();
+		}
+	}
+
+	/**
+	 * Set the list iterator to that of the current container shard
+	 */
+	protected function setIteratorFromCurrentShard() {
+		$this->iter = $this->listFromShard(
+			$this->container . $this->shardSuffixes[$this->curShard],
+			$this->directory, $this->params );
+		// Start loading results so that current() works
+		if ( $this->iter ) {
+			( $this->iter instanceof Iterator ) ? $this->iter->rewind() : reset( $this->iter );
+		}
+	}
+
+	/**
+	 * Get the list for a given container shard
+	 *
+	 * @param $container string Resolved container name
+	 * @param $dir string Resolved path relative to container
+	 * @param $params Array
+	 * @return Traversable|Array|null
+	 */
+	abstract protected function listFromShard( $container, $dir, array $params );
+}
+
+/**
+ * Iterator for listing directories
+ */
+class FileBackendStoreShardDirIterator extends FileBackendStoreShardListIterator {
+	/**
+	 * @see FileBackendStoreShardListIterator::listFromShard()
+	 * @return Array|null|Traversable
+	 */
+	protected function listFromShard( $container, $dir, array $params ) {
+		return $this->backend->getDirectoryListInternal( $container, $dir, $params );
+	}
+}
+
+/**
+ * Iterator for listing regular files
+ */
+class FileBackendStoreShardFileIterator extends FileBackendStoreShardListIterator {
+	/**
+	 * @see FileBackendStoreShardListIterator::listFromShard()
+	 * @return Array|null|Traversable
+	 */
+	protected function listFromShard( $container, $dir, array $params ) {
+		return $this->backend->getFileListInternal( $container, $dir, $params );
+	}
+}
diff --git a/includes/filebackend/FileOp.php b/includes/filebackend/FileOp.php
new file mode 100644
index 00000000..7c43c489
--- /dev/null
+++ b/includes/filebackend/FileOp.php
@@ -0,0 +1,764 @@
+<?php
+/**
+ * Helper class for representing operations with transaction support.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * FileBackend helper class for representing operations.
+ * Do not use this class from places outside FileBackend.
+ *
+ * Methods called from FileOpBatch::attempt() should avoid throwing
+ * exceptions at all costs. FileOp objects should be lightweight in order
+ * to support large arrays in memory and serialization.
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+abstract class FileOp {
+	/** @var Array */
+	protected $params = array();
+	/** @var FileBackendStore */
+	protected $backend;
+
+	protected $state = self::STATE_NEW; // integer
+	protected $failed = false; // boolean
+	protected $async = false; // boolean
+	protected $useLatest = true; // boolean
+	protected $batchId; // string
+
+	protected $sourceSha1; // string
+	protected $destSameAsSource; // boolean
+
+	/* Object life-cycle */
+	const STATE_NEW = 1;
+	const STATE_CHECKED = 2;
+	const STATE_ATTEMPTED = 3;
+
+	/**
+	 * Build a new file operation transaction
+	 *
+	 * @param $backend FileBackendStore
+	 * @param $params Array
+	 * @throws MWException
+	 */
+	final public function __construct( FileBackendStore $backend, array $params ) {
+		$this->backend = $backend;
+		list( $required, $optional ) = $this->allowedParams();
+		foreach ( $required as $name ) {
+			if ( isset( $params[$name] ) ) {
+				$this->params[$name] = $params[$name];
+			} else {
+				throw new MWException( "File operation missing parameter '$name'." );
+			}
+		}
+		foreach ( $optional as $name ) {
+			if ( isset( $params[$name] ) ) {
+				$this->params[$name] = $params[$name];
+			}
+		}
+		$this->params = $params;
+	}
+
+	/**
+	 * Set the batch UUID this operation belongs to
+	 *
+	 * @param $batchId string
+	 * @return void
+	 */
+	final public function setBatchId( $batchId ) {
+		$this->batchId = $batchId;
+	}
+
+	/**
+	 * Whether to allow stale data for file reads and stat checks
+	 *
+	 * @param $allowStale bool
+	 * @return void
+	 */
+	final public function allowStaleReads( $allowStale ) {
+		$this->useLatest = !$allowStale;
+	}
+
+	/**
+	 * Get the value of the parameter with the given name
+	 *
+	 * @param $name string
+	 * @return mixed Returns null if the parameter is not set
+	 */
+	final public function getParam( $name ) {
+		return isset( $this->params[$name] ) ? $this->params[$name] : null;
+	}
+
+	/**
+	 * Check if this operation failed precheck() or attempt()
+	 *
+	 * @return bool
+	 */
+	final public function failed() {
+		return $this->failed;
+	}
+
+	/**
+	 * Get a new empty predicates array for precheck()
+	 *
+	 * @return Array
+	 */
+	final public static function newPredicates() {
+		return array( 'exists' => array(), 'sha1' => array() );
+	}
+
+	/**
+	 * Get a new empty dependency tracking array for paths read/written to
+	 *
+	 * @return Array
+	 */
+	final public static function newDependencies() {
+		return array( 'read' => array(), 'write' => array() );
+	}
+
+	/**
+	 * Update a dependency tracking array to account for this operation
+	 *
+	 * @param $deps Array Prior path reads/writes; format of FileOp::newPredicates()
+	 * @return Array
+	 */
+	final public function applyDependencies( array $deps ) {
+		$deps['read']  += array_fill_keys( $this->storagePathsRead(), 1 );
+		$deps['write'] += array_fill_keys( $this->storagePathsChanged(), 1 );
+		return $deps;
+	}
+
+	/**
+	 * Check if this operation changes files listed in $paths
+	 *
+	 * @param $paths Array Prior path reads/writes; format of FileOp::newPredicates()
+	 * @return boolean
+	 */
+	final public function dependsOn( array $deps ) {
+		foreach ( $this->storagePathsChanged() as $path ) {
+			if ( isset( $deps['read'][$path] ) || isset( $deps['write'][$path] ) ) {
+				return true; // "output" or "anti" dependency
+			}
+		}
+		foreach ( $this->storagePathsRead() as $path ) {
+			if ( isset( $deps['write'][$path] ) ) {
+				return true; // "flow" dependency
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Get the file journal entries for this file operation
+	 *
+	 * @param $oPredicates Array Pre-op info about files (format of FileOp::newPredicates)
+	 * @param $nPredicates Array Post-op info about files (format of FileOp::newPredicates)
+	 * @return Array
+	 */
+	final public function getJournalEntries( array $oPredicates, array $nPredicates ) {
+		$nullEntries = array();
+		$updateEntries = array();
+		$deleteEntries = array();
+		$pathsUsed = array_merge( $this->storagePathsRead(), $this->storagePathsChanged() );
+		foreach ( $pathsUsed as $path ) {
+			$nullEntries[] = array( // assertion for recovery
+				'op'      => 'null',
+				'path'    => $path,
+				'newSha1' => $this->fileSha1( $path, $oPredicates )
+			);
+		}
+		foreach ( $this->storagePathsChanged() as $path ) {
+			if ( $nPredicates['sha1'][$path] === false ) { // deleted
+				$deleteEntries[] = array(
+					'op'      => 'delete',
+					'path'    => $path,
+					'newSha1' => ''
+				);
+			} else { // created/updated
+				$updateEntries[] = array(
+					'op'      => $this->fileExists( $path, $oPredicates ) ? 'update' : 'create',
+					'path'    => $path,
+					'newSha1' => $nPredicates['sha1'][$path]
+				);
+			}
+		}
+		return array_merge( $nullEntries, $updateEntries, $deleteEntries );
+	}
+
+	/**
+	 * Check preconditions of the operation without writing anything
+	 *
+	 * @param $predicates Array
+	 * @return Status
+	 */
+	final public function precheck( array &$predicates ) {
+		if ( $this->state !== self::STATE_NEW ) {
+			return Status::newFatal( 'fileop-fail-state', self::STATE_NEW, $this->state );
+		}
+		$this->state = self::STATE_CHECKED;
+		$status = $this->doPrecheck( $predicates );
+		if ( !$status->isOK() ) {
+			$this->failed = true;
+		}
+		return $status;
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doPrecheck( array &$predicates ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * Attempt the operation
+	 *
+	 * @return Status
+	 */
+	final public function attempt() {
+		if ( $this->state !== self::STATE_CHECKED ) {
+			return Status::newFatal( 'fileop-fail-state', self::STATE_CHECKED, $this->state );
+		} elseif ( $this->failed ) { // failed precheck
+			return Status::newFatal( 'fileop-fail-attempt-precheck' );
+		}
+		$this->state = self::STATE_ATTEMPTED;
+		$status = $this->doAttempt();
+		if ( !$status->isOK() ) {
+			$this->failed = true;
+			$this->logFailure( 'attempt' );
+		}
+		return $status;
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doAttempt() {
+		return Status::newGood();
+	}
+
+	/**
+	 * Attempt the operation in the background
+	 *
+	 * @return Status
+	 */
+	final public function attemptAsync() {
+		$this->async = true;
+		$result = $this->attempt();
+		$this->async = false;
+		return $result;
+	}
+
+	/**
+	 * Get the file operation parameters
+	 *
+	 * @return Array (required params list, optional params list)
+	 */
+	protected function allowedParams() {
+		return array( array(), array() );
+	}
+
+	/**
+	 * Adjust params to FileBackendStore internal file calls
+	 *
+	 * @param $params Array
+	 * @return Array (required params list, optional params list)
+	 */
+	protected function setFlags( array $params ) {
+		return array( 'async' => $this->async ) + $params;
+	}
+
+	/**
+	 * Get a list of storage paths read from for this operation
+	 *
+	 * @return Array
+	 */
+	final public function storagePathsRead() {
+		return array_map( 'FileBackend::normalizeStoragePath', $this->doStoragePathsRead() );
+	}
+
+	/**
+	 * @see FileOp::storagePathsRead()
+	 * @return Array
+	 */
+	protected function doStoragePathsRead() {
+		return array();
+	}
+
+	/**
+	 * Get a list of storage paths written to for this operation
+	 *
+	 * @return Array
+	 */
+	final public function storagePathsChanged() {
+		return array_map( 'FileBackend::normalizeStoragePath', $this->doStoragePathsChanged() );
+	}
+
+	/**
+	 * @see FileOp::storagePathsChanged()
+	 * @return Array
+	 */
+	protected function doStoragePathsChanged() {
+		return array();
+	}
+
+	/**
+	 * Check for errors with regards to the destination file already existing.
+	 * This also updates the destSameAsSource and sourceSha1 member variables.
+	 * A bad status will be returned if there is no chance it can be overwritten.
+	 *
+	 * @param $predicates Array
+	 * @return Status
+	 */
+	protected function precheckDestExistence( array $predicates ) {
+		$status = Status::newGood();
+		// Get hash of source file/string and the destination file
+		$this->sourceSha1 = $this->getSourceSha1Base36(); // FS file or data string
+		if ( $this->sourceSha1 === null ) { // file in storage?
+			$this->sourceSha1 = $this->fileSha1( $this->params['src'], $predicates );
+		}
+		$this->destSameAsSource = false;
+		if ( $this->fileExists( $this->params['dst'], $predicates ) ) {
+			if ( $this->getParam( 'overwrite' ) ) {
+				return $status; // OK
+			} elseif ( $this->getParam( 'overwriteSame' ) ) {
+				$dhash = $this->fileSha1( $this->params['dst'], $predicates );
+				// Check if hashes are valid and match each other...
+				if ( !strlen( $this->sourceSha1 ) || !strlen( $dhash ) ) {
+					$status->fatal( 'backend-fail-hashes' );
+				} elseif ( $this->sourceSha1 !== $dhash ) {
+					// Give an error if the files are not identical
+					$status->fatal( 'backend-fail-notsame', $this->params['dst'] );
+				} else {
+					$this->destSameAsSource = true; // OK
+				}
+				return $status; // do nothing; either OK or bad status
+			} else {
+				$status->fatal( 'backend-fail-alreadyexists', $this->params['dst'] );
+				return $status;
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * precheckDestExistence() helper function to get the source file SHA-1.
+	 * Subclasses should overwride this iff the source is not in storage.
+	 *
+	 * @return string|bool Returns false on failure
+	 */
+	protected function getSourceSha1Base36() {
+		return null; // N/A
+	}
+
+	/**
+	 * Check if a file will exist in storage when this operation is attempted
+	 *
+	 * @param $source string Storage path
+	 * @param $predicates Array
+	 * @return bool
+	 */
+	final protected function fileExists( $source, array $predicates ) {
+		if ( isset( $predicates['exists'][$source] ) ) {
+			return $predicates['exists'][$source]; // previous op assures this
+		} else {
+			$params = array( 'src' => $source, 'latest' => $this->useLatest );
+			return $this->backend->fileExists( $params );
+		}
+	}
+
+	/**
+	 * Get the SHA-1 of a file in storage when this operation is attempted
+	 *
+	 * @param $source string Storage path
+	 * @param $predicates Array
+	 * @return string|bool False on failure
+	 */
+	final protected function fileSha1( $source, array $predicates ) {
+		if ( isset( $predicates['sha1'][$source] ) ) {
+			return $predicates['sha1'][$source]; // previous op assures this
+		} else {
+			$params = array( 'src' => $source, 'latest' => $this->useLatest );
+			return $this->backend->getFileSha1Base36( $params );
+		}
+	}
+
+	/**
+	 * Get the backend this operation is for
+	 *
+	 * @return FileBackendStore
+	 */
+	public function getBackend() {
+		return $this->backend;
+	}
+
+	/**
+	 * Log a file operation failure and preserve any temp files
+	 *
+	 * @param $action string
+	 * @return void
+	 */
+	final public function logFailure( $action ) {
+		$params = $this->params;
+		$params['failedAction'] = $action;
+		try {
+			wfDebugLog( 'FileOperation', get_class( $this ) .
+				" failed (batch #{$this->batchId}): " . FormatJson::encode( $params ) );
+		} catch ( Exception $e ) {
+			// bad config? debug log error?
+		}
+	}
+}
+
+/**
+ * Store a file into the backend from a file on the file system.
+ * Parameters for this operation are outlined in FileBackend::doOperations().
+ */
+class StoreFileOp extends FileOp {
+	/**
+	 * @return array
+	 */
+	protected function allowedParams() {
+		return array( array( 'src', 'dst' ),
+			array( 'overwrite', 'overwriteSame', 'disposition' ) );
+	}
+
+	/**
+	 * @param $predicates array
+	 * @return Status
+	 */
+	protected function doPrecheck( array &$predicates ) {
+		$status = Status::newGood();
+		// Check if the source file exists on the file system
+		if ( !is_file( $this->params['src'] ) ) {
+			$status->fatal( 'backend-fail-notexists', $this->params['src'] );
+			return $status;
+		// Check if the source file is too big
+		} elseif ( filesize( $this->params['src'] ) > $this->backend->maxFileSizeInternal() ) {
+			$status->fatal( 'backend-fail-maxsize',
+				$this->params['dst'], $this->backend->maxFileSizeInternal() );
+			$status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
+			return $status;
+		// Check if a file can be placed at the destination
+		} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
+			$status->fatal( 'backend-fail-usable', $this->params['dst'] );
+			$status->fatal( 'backend-fail-store', $this->params['src'], $this->params['dst'] );
+			return $status;
+		}
+		// Check if destination file exists
+		$status->merge( $this->precheckDestExistence( $predicates ) );
+		if ( $status->isOK() ) {
+			// Update file existence predicates
+			$predicates['exists'][$this->params['dst']] = true;
+			$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
+		}
+		return $status; // safe to call attempt()
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doAttempt() {
+		// Store the file at the destination
+		if ( !$this->destSameAsSource ) {
+			return $this->backend->storeInternal( $this->setFlags( $this->params ) );
+		}
+		return Status::newGood();
+	}
+
+	/**
+	 * @return bool|string
+	 */
+	protected function getSourceSha1Base36() {
+		wfSuppressWarnings();
+		$hash = sha1_file( $this->params['src'] );
+		wfRestoreWarnings();
+		if ( $hash !== false ) {
+			$hash = wfBaseConvert( $hash, 16, 36, 31 );
+		}
+		return $hash;
+	}
+
+	protected function doStoragePathsChanged() {
+		return array( $this->params['dst'] );
+	}
+}
+
+/**
+ * Create a file in the backend with the given content.
+ * Parameters for this operation are outlined in FileBackend::doOperations().
+ */
+class CreateFileOp extends FileOp {
+	protected function allowedParams() {
+		return array( array( 'content', 'dst' ),
+			array( 'overwrite', 'overwriteSame', 'disposition' ) );
+	}
+
+	protected function doPrecheck( array &$predicates ) {
+		$status = Status::newGood();
+		// Check if the source data is too big
+		if ( strlen( $this->getParam( 'content' ) ) > $this->backend->maxFileSizeInternal() ) {
+			$status->fatal( 'backend-fail-maxsize',
+				$this->params['dst'], $this->backend->maxFileSizeInternal() );
+			$status->fatal( 'backend-fail-create', $this->params['dst'] );
+			return $status;
+		// Check if a file can be placed at the destination
+		} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
+			$status->fatal( 'backend-fail-usable', $this->params['dst'] );
+			$status->fatal( 'backend-fail-create', $this->params['dst'] );
+			return $status;
+		}
+		// Check if destination file exists
+		$status->merge( $this->precheckDestExistence( $predicates ) );
+		if ( $status->isOK() ) {
+			// Update file existence predicates
+			$predicates['exists'][$this->params['dst']] = true;
+			$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
+		}
+		return $status; // safe to call attempt()
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doAttempt() {
+		if ( !$this->destSameAsSource ) {
+			// Create the file at the destination
+			return $this->backend->createInternal( $this->setFlags( $this->params ) );
+		}
+		return Status::newGood();
+	}
+
+	/**
+	 * @return bool|String
+	 */
+	protected function getSourceSha1Base36() {
+		return wfBaseConvert( sha1( $this->params['content'] ), 16, 36, 31 );
+	}
+
+	/**
+	 * @return array
+	 */
+	protected function doStoragePathsChanged() {
+		return array( $this->params['dst'] );
+	}
+}
+
+/**
+ * Copy a file from one storage path to another in the backend.
+ * Parameters for this operation are outlined in FileBackend::doOperations().
+ */
+class CopyFileOp extends FileOp {
+	/**
+	 * @return array
+	 */
+	protected function allowedParams() {
+		return array( array( 'src', 'dst' ),
+			array( 'overwrite', 'overwriteSame', 'disposition' ) );
+	}
+
+	/**
+	 * @param $predicates array
+	 * @return Status
+	 */
+	protected function doPrecheck( array &$predicates ) {
+		$status = Status::newGood();
+		// Check if the source file exists
+		if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
+			$status->fatal( 'backend-fail-notexists', $this->params['src'] );
+			return $status;
+		// Check if a file can be placed at the destination
+		} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
+			$status->fatal( 'backend-fail-usable', $this->params['dst'] );
+			$status->fatal( 'backend-fail-copy', $this->params['src'], $this->params['dst'] );
+			return $status;
+		}
+		// Check if destination file exists
+		$status->merge( $this->precheckDestExistence( $predicates ) );
+		if ( $status->isOK() ) {
+			// Update file existence predicates
+			$predicates['exists'][$this->params['dst']] = true;
+			$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
+		}
+		return $status; // safe to call attempt()
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doAttempt() {
+		// Do nothing if the src/dst paths are the same
+		if ( $this->params['src'] !== $this->params['dst'] ) {
+			// Copy the file into the destination
+			if ( !$this->destSameAsSource ) {
+				return $this->backend->copyInternal( $this->setFlags( $this->params ) );
+			}
+		}
+		return Status::newGood();
+	}
+
+	/**
+	 * @return array
+	 */
+	protected function doStoragePathsRead() {
+		return array( $this->params['src'] );
+	}
+
+	/**
+	 * @return array
+	 */
+	protected function doStoragePathsChanged() {
+		return array( $this->params['dst'] );
+	}
+}
+
+/**
+ * Move a file from one storage path to another in the backend.
+ * Parameters for this operation are outlined in FileBackend::doOperations().
+ */
+class MoveFileOp extends FileOp {
+	/**
+	 * @return array
+	 */
+	protected function allowedParams() {
+		return array( array( 'src', 'dst' ),
+			array( 'overwrite', 'overwriteSame', 'disposition' ) );
+	}
+
+	/**
+	 * @param $predicates array
+	 * @return Status
+	 */
+	protected function doPrecheck( array &$predicates ) {
+		$status = Status::newGood();
+		// Check if the source file exists
+		if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
+			$status->fatal( 'backend-fail-notexists', $this->params['src'] );
+			return $status;
+		// Check if a file can be placed at the destination
+		} elseif ( !$this->backend->isPathUsableInternal( $this->params['dst'] ) ) {
+			$status->fatal( 'backend-fail-usable', $this->params['dst'] );
+			$status->fatal( 'backend-fail-move', $this->params['src'], $this->params['dst'] );
+			return $status;
+		}
+		// Check if destination file exists
+		$status->merge( $this->precheckDestExistence( $predicates ) );
+		if ( $status->isOK() ) {
+			// Update file existence predicates
+			$predicates['exists'][$this->params['src']] = false;
+			$predicates['sha1'][$this->params['src']] = false;
+			$predicates['exists'][$this->params['dst']] = true;
+			$predicates['sha1'][$this->params['dst']] = $this->sourceSha1;
+		}
+		return $status; // safe to call attempt()
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doAttempt() {
+		// Do nothing if the src/dst paths are the same
+		if ( $this->params['src'] !== $this->params['dst'] ) {
+			if ( !$this->destSameAsSource ) {
+				// Move the file into the destination
+				return $this->backend->moveInternal( $this->setFlags( $this->params ) );
+			} else {
+				// Just delete source as the destination needs no changes
+				$params = array( 'src' => $this->params['src'] );
+				return $this->backend->deleteInternal( $this->setFlags( $params ) );
+			}
+		}
+		return Status::newGood();
+	}
+
+	/**
+	 * @return array
+	 */
+	protected function doStoragePathsRead() {
+		return array( $this->params['src'] );
+	}
+
+	/**
+	 * @return array
+	 */
+	protected function doStoragePathsChanged() {
+		return array( $this->params['src'], $this->params['dst'] );
+	}
+}
+
+/**
+ * Delete a file at the given storage path from the backend.
+ * Parameters for this operation are outlined in FileBackend::doOperations().
+ */
+class DeleteFileOp extends FileOp {
+	/**
+	 * @return array
+	 */
+	protected function allowedParams() {
+		return array( array( 'src' ), array( 'ignoreMissingSource' ) );
+	}
+
+	protected $needsDelete = true;
+
+	/**
+	 * @param array $predicates
+	 * @return Status
+	 */
+	protected function doPrecheck( array &$predicates ) {
+		$status = Status::newGood();
+		// Check if the source file exists
+		if ( !$this->fileExists( $this->params['src'], $predicates ) ) {
+			if ( !$this->getParam( 'ignoreMissingSource' ) ) {
+				$status->fatal( 'backend-fail-notexists', $this->params['src'] );
+				return $status;
+			}
+			$this->needsDelete = false;
+		}
+		// Update file existence predicates
+		$predicates['exists'][$this->params['src']] = false;
+		$predicates['sha1'][$this->params['src']] = false;
+		return $status; // safe to call attempt()
+	}
+
+	/**
+	 * @return Status
+	 */
+	protected function doAttempt() {
+		if ( $this->needsDelete ) {
+			// Delete the source file
+			return $this->backend->deleteInternal( $this->setFlags( $this->params ) );
+		}
+		return Status::newGood();
+	}
+
+	/**
+	 * @return array
+	 */
+	protected function doStoragePathsChanged() {
+		return array( $this->params['src'] );
+	}
+}
+
+/**
+ * Placeholder operation that has no params and does nothing
+ */
+class NullFileOp extends FileOp {}
diff --git a/includes/filebackend/FileOpBatch.php b/includes/filebackend/FileOpBatch.php
new file mode 100644
index 00000000..33558725
--- /dev/null
+++ b/includes/filebackend/FileOpBatch.php
@@ -0,0 +1,240 @@
+<?php
+/**
+ * Helper class for representing batch file operations.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Aaron Schulz
+ */
+
+/**
+ * Helper class for representing batch file operations.
+ * Do not use this class from places outside FileBackend.
+ *
+ * Methods should avoid throwing exceptions at all costs.
+ *
+ * @ingroup FileBackend
+ * @since 1.20
+ */
+class FileOpBatch {
+	/* Timeout related parameters */
+	const MAX_BATCH_SIZE = 1000; // integer
+
+	/**
+	 * Attempt to perform a series of file operations.
+	 * Callers are responsible for handling file locking.
+	 *
+	 * $opts is an array of options, including:
+	 *   - force        : Errors that would normally cause a rollback do not.
+	 *                    The remaining operations are still attempted if any fail.
+	 *   - allowStale   : Don't require the latest available data.
+	 *                    This can increase performance for non-critical writes.
+	 *                    This has no effect unless the 'force' flag is set.
+	 *   - nonJournaled : Don't log this operation batch in the file journal.
+	 *   - concurrency  : Try to do this many operations in parallel when possible.
+	 *
+	 * The resulting Status will be "OK" unless:
+	 *   - a) unexpected operation errors occurred (network partitions, disk full...)
+	 *   - b) significant operation errors occurred and 'force' was not set
+	 *
+	 * @param $performOps Array List of FileOp operations
+	 * @param $opts Array Batch operation options
+	 * @param $journal FileJournal Journal to log operations to
+	 * @return Status
+	 */
+	public static function attempt( array $performOps, array $opts, FileJournal $journal ) {
+		wfProfileIn( __METHOD__ );
+		$status = Status::newGood();
+
+		$n = count( $performOps );
+		if ( $n > self::MAX_BATCH_SIZE ) {
+			$status->fatal( 'backend-fail-batchsize', $n, self::MAX_BATCH_SIZE );
+			wfProfileOut( __METHOD__ );
+			return $status;
+		}
+
+		$batchId = $journal->getTimestampedUUID();
+		$allowStale = !empty( $opts['allowStale'] );
+		$ignoreErrors = !empty( $opts['force'] );
+		$journaled = empty( $opts['nonJournaled'] );
+		$maxConcurrency = isset( $opts['concurrency'] ) ? $opts['concurrency'] : 1;
+
+		$entries = array(); // file journal entry list
+		$predicates = FileOp::newPredicates(); // account for previous ops in prechecks
+		$curBatch = array(); // concurrent FileOp sub-batch accumulation
+		$curBatchDeps = FileOp::newDependencies(); // paths used in FileOp sub-batch
+		$pPerformOps = array(); // ordered list of concurrent FileOp sub-batches
+		$lastBackend = null; // last op backend name
+		// Do pre-checks for each operation; abort on failure...
+		foreach ( $performOps as $index => $fileOp ) {
+			$backendName = $fileOp->getBackend()->getName();
+			$fileOp->setBatchId( $batchId ); // transaction ID
+			$fileOp->allowStaleReads( $allowStale ); // consistency level
+			// Decide if this op can be done concurrently within this sub-batch
+			// or if a new concurrent sub-batch must be started after this one...
+			if ( $fileOp->dependsOn( $curBatchDeps )
+				|| count( $curBatch ) >= $maxConcurrency
+				|| ( $backendName !== $lastBackend && count( $curBatch ) )
+			) {
+				$pPerformOps[] = $curBatch; // push this batch
+				$curBatch = array(); // start a new sub-batch
+				$curBatchDeps = FileOp::newDependencies();
+			}
+			$lastBackend = $backendName;
+			$curBatch[$index] = $fileOp; // keep index
+			// Update list of affected paths in this batch
+			$curBatchDeps = $fileOp->applyDependencies( $curBatchDeps );
+			// Simulate performing the operation...
+			$oldPredicates = $predicates;
+			$subStatus = $fileOp->precheck( $predicates ); // updates $predicates
+			$status->merge( $subStatus );
+			if ( $subStatus->isOK() ) {
+				if ( $journaled ) { // journal log entries
+					$entries = array_merge( $entries,
+						$fileOp->getJournalEntries( $oldPredicates, $predicates ) );
+				}
+			} else { // operation failed?
+				$status->success[$index] = false;
+				++$status->failCount;
+				if ( !$ignoreErrors ) {
+					wfProfileOut( __METHOD__ );
+					return $status; // abort
+				}
+			}
+		}
+		// Push the last sub-batch
+		if ( count( $curBatch ) ) {
+			$pPerformOps[] = $curBatch;
+		}
+
+		// Log the operations in the file journal...
+		if ( count( $entries ) ) {
+			$subStatus = $journal->logChangeBatch( $entries, $batchId );
+			if ( !$subStatus->isOK() ) {
+				wfProfileOut( __METHOD__ );
+				return $subStatus; // abort
+			}
+		}
+
+		if ( $ignoreErrors ) { // treat precheck() fatals as mere warnings
+			$status->setResult( true, $status->value );
+		}
+
+		// Attempt each operation (in parallel if allowed and possible)...
+		if ( count( $pPerformOps ) < count( $performOps ) ) {
+			self::runBatchParallel( $pPerformOps, $status );
+		} else {
+			self::runBatchSeries( $performOps, $status );
+		}
+
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * Attempt a list of file operations in series.
+	 * This will abort remaining ops on failure.
+	 *
+	 * @param $performOps Array
+	 * @param $status Status
+	 * @return bool Success
+	 */
+	protected static function runBatchSeries( array $performOps, Status $status ) {
+		foreach ( $performOps as $index => $fileOp ) {
+			if ( $fileOp->failed() ) {
+				continue; // nothing to do
+			}
+			$subStatus = $fileOp->attempt();
+			$status->merge( $subStatus );
+			if ( $subStatus->isOK() ) {
+				$status->success[$index] = true;
+				++$status->successCount;
+			} else {
+				$status->success[$index] = false;
+				++$status->failCount;
+				// We can't continue (even with $ignoreErrors) as $predicates is wrong.
+				// Log the remaining ops as failed for recovery...
+				for ( $i = ($index + 1); $i < count( $performOps ); $i++ ) {
+					$performOps[$i]->logFailure( 'attempt_aborted' );
+				}
+				return false; // bail out
+			}
+		}
+		return true;
+	}
+
+	/**
+	 * Attempt a list of file operations sub-batches in series.
+	 *
+	 * The operations *in* each sub-batch will be done in parallel.
+	 * The caller is responsible for making sure the operations
+	 * within any given sub-batch do not depend on each other.
+	 * This will abort remaining ops on failure.
+	 *
+	 * @param $pPerformOps Array
+	 * @param $status Status
+	 * @return bool Success
+	 */
+	protected static function runBatchParallel( array $pPerformOps, Status $status ) {
+		$aborted = false;
+		foreach ( $pPerformOps as $performOpsBatch ) {
+			if ( $aborted ) { // check batch op abort flag...
+				// We can't continue (even with $ignoreErrors) as $predicates is wrong.
+				// Log the remaining ops as failed for recovery...
+				foreach ( $performOpsBatch as $i => $fileOp ) {
+					$performOpsBatch[$i]->logFailure( 'attempt_aborted' );
+				}
+				continue;
+			}
+			$statuses = array();
+			$opHandles = array();
+			// Get the backend; all sub-batch ops belong to a single backend
+			$backend = reset( $performOpsBatch )->getBackend();
+			// If attemptAsync() returns synchronously, it was either an
+			// error Status or the backend just doesn't support async ops.
+			foreach ( $performOpsBatch as $i => $fileOp ) {
+				if ( !$fileOp->failed() ) { // failed => already has Status
+					$subStatus = $fileOp->attemptAsync();
+					if ( $subStatus->value instanceof FileBackendStoreOpHandle ) {
+						$opHandles[$i] = $subStatus->value; // deferred
+					} else {
+						$statuses[$i] = $subStatus; // done already
+					}
+				}
+			}
+			// Try to do all the operations concurrently...
+			$statuses = $statuses + $backend->executeOpHandlesInternal( $opHandles );
+			// Marshall and merge all the responses (blocking)...
+			foreach ( $performOpsBatch as $i => $fileOp ) {
+				if ( !$fileOp->failed() ) { // failed => already has Status
+					$subStatus = $statuses[$i];
+					$status->merge( $subStatus );
+					if ( $subStatus->isOK() ) {
+						$status->success[$i] = true;
+						++$status->successCount;
+					} else {
+						$status->success[$i] = false;
+						++$status->failCount;
+						$aborted = true; // set abort flag; we can't continue
+					}
+				}
+			}
+		}
+		return $status;
+	}
+}
diff --git a/includes/filebackend/SwiftFileBackend.php b/includes/filebackend/SwiftFileBackend.php
new file mode 100644
index 00000000..b6f0aa60
--- /dev/null
+++ b/includes/filebackend/SwiftFileBackend.php
@@ -0,0 +1,1544 @@
+<?php
+/**
+ * OpenStack Swift based file backend.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ * @author Russ Nelson
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Class for an OpenStack Swift based file backend.
+ *
+ * This requires the SwiftCloudFiles MediaWiki extension, which includes
+ * the php-cloudfiles library (https://github.com/rackspace/php-cloudfiles).
+ * php-cloudfiles requires the curl, fileinfo, and mb_string PHP extensions.
+ *
+ * Status messages should avoid mentioning the Swift account name.
+ * Likewise, error suppression should be used to avoid path disclosure.
+ *
+ * @ingroup FileBackend
+ * @since 1.19
+ */
+class SwiftFileBackend extends FileBackendStore {
+	/** @var CF_Authentication */
+	protected $auth; // Swift authentication handler
+	protected $authTTL; // integer seconds
+	protected $swiftAnonUser; // string; username to handle unauthenticated requests
+	protected $swiftUseCDN; // boolean; whether CloudFiles CDN is enabled
+	protected $swiftCDNExpiry; // integer; how long to cache things in the CDN
+	protected $swiftCDNPurgable; // boolean; whether object CDN purging is enabled
+
+	/** @var CF_Connection */
+	protected $conn; // Swift connection handle
+	protected $sessionStarted = 0; // integer UNIX timestamp
+
+	/** @var CloudFilesException */
+	protected $connException;
+	protected $connErrorTime = 0; // UNIX timestamp
+
+	/** @var BagOStuff */
+	protected $srvCache;
+
+	/** @var ProcessCacheLRU */
+	protected $connContainerCache; // container object cache
+
+	/**
+	 * @see FileBackendStore::__construct()
+	 * Additional $config params include:
+	 *   - swiftAuthUrl       : Swift authentication server URL
+	 *   - swiftUser          : Swift user used by MediaWiki (account:username)
+	 *   - swiftKey           : Swift authentication key for the above user
+	 *   - swiftAuthTTL       : Swift authentication TTL (seconds)
+	 *   - swiftAnonUser      : Swift user used for end-user requests (account:username).
+	 *                          If set, then views of public containers are assumed to go
+	 *                          through this user. If not set, then public containers are
+	 *                          accessible to unauthenticated requests via ".r:*" in the ACL.
+	 *   - swiftUseCDN        : Whether a Cloud Files Content Delivery Network is set up
+	 *   - swiftCDNExpiry     : How long (in seconds) to store content in the CDN.
+	 *                          If files may likely change, this should probably not exceed
+	 *                          a few days. For example, deletions may take this long to apply.
+	 *                          If object purging is enabled, however, this is not an issue.
+	 *   - swiftCDNPurgable   : Whether object purge requests are allowed by the CDN.
+	 *   - shardViaHashLevels : Map of container names to sharding config with:
+	 *                             - base   : base of hash characters, 16 or 36
+	 *                             - levels : the number of hash levels (and digits)
+	 *                             - repeat : hash subdirectories are prefixed with all the
+	 *                                        parent hash directory names (e.g. "a/ab/abc")
+	 *   - cacheAuthInfo      : Whether to cache authentication tokens in APC, XCache, ect.
+	 *                          If those are not available, then the main cache will be used.
+	 *                          This is probably insecure in shared hosting environments.
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+		if ( !MWInit::classExists( 'CF_Constants' ) ) {
+			throw new MWException( 'SwiftCloudFiles extension not installed.' );
+		}
+		// Required settings
+		$this->auth = new CF_Authentication(
+			$config['swiftUser'],
+			$config['swiftKey'],
+			null, // account; unused
+			$config['swiftAuthUrl']
+		);
+		// Optional settings
+		$this->authTTL = isset( $config['swiftAuthTTL'] )
+			? $config['swiftAuthTTL']
+			: 5 * 60; // some sane number
+		$this->swiftAnonUser = isset( $config['swiftAnonUser'] )
+			? $config['swiftAnonUser']
+			: '';
+		$this->shardViaHashLevels = isset( $config['shardViaHashLevels'] )
+			? $config['shardViaHashLevels']
+			: '';
+		$this->swiftUseCDN = isset( $config['swiftUseCDN'] )
+			? $config['swiftUseCDN']
+			: false;
+		$this->swiftCDNExpiry = isset( $config['swiftCDNExpiry'] )
+			? $config['swiftCDNExpiry']
+			: 12*3600; // 12 hours is safe (tokens last 24 hours per http://docs.openstack.org)
+		$this->swiftCDNPurgable = isset( $config['swiftCDNPurgable'] )
+			? $config['swiftCDNPurgable']
+			: true;
+		// Cache container information to mask latency
+		$this->memCache = wfGetMainCache();
+		// Process cache for container info
+		$this->connContainerCache = new ProcessCacheLRU( 300 );
+		// Cache auth token information to avoid RTTs
+		if ( !empty( $config['cacheAuthInfo'] ) ) {
+			if ( php_sapi_name() === 'cli' ) {
+				$this->srvCache = wfGetMainCache(); // preferrably memcached
+			} else {
+				try { // look for APC, XCache, WinCache, ect...
+					$this->srvCache = ObjectCache::newAccelerator( array() );
+				} catch ( Exception $e ) {}
+			}
+		}
+		$this->srvCache = $this->srvCache ? $this->srvCache : new EmptyBagOStuff();
+	}
+
+	/**
+	 * @see FileBackendStore::resolveContainerPath()
+	 * @return null
+	 */
+	protected function resolveContainerPath( $container, $relStoragePath ) {
+		if ( !mb_check_encoding( $relStoragePath, 'UTF-8' ) ) { // mb_string required by CF
+			return null; // not UTF-8, makes it hard to use CF and the swift HTTP API
+		} elseif ( strlen( urlencode( $relStoragePath ) ) > 1024 ) {
+			return null; // too long for Swift
+		}
+		return $relStoragePath;
+	}
+
+	/**
+	 * @see FileBackendStore::isPathUsableInternal()
+	 * @return bool
+	 */
+	public function isPathUsableInternal( $storagePath ) {
+		list( $container, $rel ) = $this->resolveStoragePathReal( $storagePath );
+		if ( $rel === null ) {
+			return false; // invalid
+		}
+
+		try {
+			$this->getContainer( $container );
+			return true; // container exists
+		} catch ( NoSuchContainerException $e ) {
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, null, __METHOD__, array( 'path' => $storagePath ) );
+		}
+
+		return false;
+	}
+
+	/**
+	 * @param $disposition string Content-Disposition header value
+	 * @return string Truncated Content-Disposition header value to meet Swift limits
+	 */
+	protected function truncDisp( $disposition ) {
+		$res = '';
+		foreach ( explode( ';', $disposition ) as $part ) {
+			$part = trim( $part );
+			$new  = ( $res === '' ) ? $part : "{$res};{$part}";
+			if ( strlen( $new ) <= 255 ) {
+				$res = $new;
+			} else {
+				break; // too long; sigh
+			}
+		}
+		return $res;
+	}
+
+	/**
+	 * @see FileBackendStore::doCreateInternal()
+	 * @return Status
+	 */
+	protected function doCreateInternal( array $params ) {
+		$status = Status::newGood();
+
+		list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
+		if ( $dstRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		// (a) Check the destination container and object
+		try {
+			$dContObj = $this->getContainer( $dstCont );
+			if ( empty( $params['overwrite'] ) &&
+				$this->fileExists( array( 'src' => $params['dst'], 'latest' => 1 ) ) )
+			{
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-create', $params['dst'] );
+			return $status;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		// (b) Get a SHA-1 hash of the object
+		$sha1Hash = wfBaseConvert( sha1( $params['content'] ), 16, 36, 31 );
+
+		// (c) Actually create the object
+		try {
+			// Create a fresh CF_Object with no fields preloaded.
+			// We don't want to preserve headers, metadata, and such.
+			$obj = new CF_Object( $dContObj, $dstRel, false, false ); // skip HEAD
+			// Note: metadata keys stored as [Upper case char][[Lower case char]...]
+			$obj->metadata = array( 'Sha1base36' => $sha1Hash );
+			// Manually set the ETag (https://github.com/rackspace/php-cloudfiles/issues/59).
+			// The MD5 here will be checked within Swift against its own MD5.
+			$obj->set_etag( md5( $params['content'] ) );
+			// Use the same content type as StreamFile for security
+			$obj->content_type = StreamFile::contentTypeFromPath( $params['dst'] );
+			if ( !strlen( $obj->content_type ) ) { // special case
+				$obj->content_type = 'unknown/unknown';
+			}
+			// Set the Content-Disposition header if requested
+			if ( isset( $params['disposition'] ) ) {
+				$obj->headers['Content-Disposition'] = $this->truncDisp( $params['disposition'] );
+			}
+			if ( !empty( $params['async'] ) ) { // deferred
+				$op = $obj->write_async( $params['content'] );
+				$status->value = new SwiftFileOpHandle( $this, $params, 'Create', $op );
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$status->value->affectedObjects[] = $obj;
+				}
+			} else { // actually write the object in Swift
+				$obj->write( $params['content'] );
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$this->purgeCDNCache( array( $obj ) );
+				}
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( BadContentTypeException $e ) {
+			$status->fatal( 'backend-fail-contenttype', $params['dst'] );
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see SwiftFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseCreate( CF_Async_Op $cfOp, Status $status, array $params ) {
+		try {
+			$cfOp->getLastResponse();
+		} catch ( BadContentTypeException $e ) {
+			$status->fatal( 'backend-fail-contenttype', $params['dst'] );
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doStoreInternal()
+	 * @return Status
+	 */
+	protected function doStoreInternal( array $params ) {
+		$status = Status::newGood();
+
+		list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
+		if ( $dstRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		// (a) Check the destination container and object
+		try {
+			$dContObj = $this->getContainer( $dstCont );
+			if ( empty( $params['overwrite'] ) &&
+				$this->fileExists( array( 'src' => $params['dst'], 'latest' => 1 ) ) )
+			{
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+			return $status;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		// (b) Get a SHA-1 hash of the object
+		$sha1Hash = sha1_file( $params['src'] );
+		if ( $sha1Hash === false ) { // source doesn't exist?
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+			return $status;
+		}
+		$sha1Hash = wfBaseConvert( $sha1Hash, 16, 36, 31 );
+
+		// (c) Actually store the object
+		try {
+			// Create a fresh CF_Object with no fields preloaded.
+			// We don't want to preserve headers, metadata, and such.
+			$obj = new CF_Object( $dContObj, $dstRel, false, false ); // skip HEAD
+			// Note: metadata keys stored as [Upper case char][[Lower case char]...]
+			$obj->metadata = array( 'Sha1base36' => $sha1Hash );
+			// The MD5 here will be checked within Swift against its own MD5.
+			$obj->set_etag( md5_file( $params['src'] ) );
+			// Use the same content type as StreamFile for security
+			$obj->content_type = StreamFile::contentTypeFromPath( $params['dst'] );
+			if ( !strlen( $obj->content_type ) ) { // special case
+				$obj->content_type = 'unknown/unknown';
+			}
+			// Set the Content-Disposition header if requested
+			if ( isset( $params['disposition'] ) ) {
+				$obj->headers['Content-Disposition'] = $this->truncDisp( $params['disposition'] );
+			}
+			if ( !empty( $params['async'] ) ) { // deferred
+				wfSuppressWarnings();
+				$fp = fopen( $params['src'], 'rb' );
+				wfRestoreWarnings();
+				if ( !$fp ) {
+					$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+				} else {
+					$op = $obj->write_async( $fp, filesize( $params['src'] ), true );
+					$status->value = new SwiftFileOpHandle( $this, $params, 'Store', $op );
+					$status->value->resourcesToClose[] = $fp;
+					if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+						$status->value->affectedObjects[] = $obj;
+					}
+				}
+			} else { // actually write the object in Swift
+				$obj->load_from_filename( $params['src'], true ); // calls $obj->write()
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$this->purgeCDNCache( array( $obj ) );
+				}
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( BadContentTypeException $e ) {
+			$status->fatal( 'backend-fail-contenttype', $params['dst'] );
+		} catch ( IOException $e ) {
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see SwiftFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseStore( CF_Async_Op $cfOp, Status $status, array $params ) {
+		try {
+			$cfOp->getLastResponse();
+		} catch ( BadContentTypeException $e ) {
+			$status->fatal( 'backend-fail-contenttype', $params['dst'] );
+		} catch ( IOException $e ) {
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doCopyInternal()
+	 * @return Status
+	 */
+	protected function doCopyInternal( array $params ) {
+		$status = Status::newGood();
+
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+			return $status;
+		}
+
+		list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
+		if ( $dstRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		// (a) Check the source/destination containers and destination object
+		try {
+			$sContObj = $this->getContainer( $srcCont );
+			$dContObj = $this->getContainer( $dstCont );
+			if ( empty( $params['overwrite'] ) &&
+				$this->fileExists( array( 'src' => $params['dst'], 'latest' => 1 ) ) )
+			{
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+			return $status;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		// (b) Actually copy the file to the destination
+		try {
+			$dstObj = new CF_Object( $dContObj, $dstRel, false, false ); // skip HEAD
+			$hdrs = array(); // source file headers to override with new values
+			if ( isset( $params['disposition'] ) ) {
+				$hdrs['Content-Disposition'] = $this->truncDisp( $params['disposition'] );
+			}
+			if ( !empty( $params['async'] ) ) { // deferred
+				$op = $sContObj->copy_object_to_async( $srcRel, $dContObj, $dstRel, null, $hdrs );
+				$status->value = new SwiftFileOpHandle( $this, $params, 'Copy', $op );
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$status->value->affectedObjects[] = $dstObj;
+				}
+			} else { // actually write the object in Swift
+				$sContObj->copy_object_to( $srcRel, $dContObj, $dstRel, null, $hdrs );
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$this->purgeCDNCache( array( $dstObj ) );
+				}
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( NoSuchObjectException $e ) { // source object does not exist
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see SwiftFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseCopy( CF_Async_Op $cfOp, Status $status, array $params ) {
+		try {
+			$cfOp->getLastResponse();
+		} catch ( NoSuchObjectException $e ) { // source object does not exist
+			$status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doMoveInternal()
+	 * @return Status
+	 */
+	protected function doMoveInternal( array $params ) {
+		$status = Status::newGood();
+
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+			return $status;
+		}
+
+		list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
+		if ( $dstRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['dst'] );
+			return $status;
+		}
+
+		// (a) Check the source/destination containers and destination object
+		try {
+			$sContObj = $this->getContainer( $srcCont );
+			$dContObj = $this->getContainer( $dstCont );
+			if ( empty( $params['overwrite'] ) &&
+				$this->fileExists( array( 'src' => $params['dst'], 'latest' => 1 ) ) )
+			{
+				$status->fatal( 'backend-fail-alreadyexists', $params['dst'] );
+				return $status;
+			}
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
+			return $status;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		// (b) Actually move the file to the destination
+		try {
+			$srcObj = new CF_Object( $sContObj, $srcRel, false, false ); // skip HEAD
+			$dstObj = new CF_Object( $dContObj, $dstRel, false, false ); // skip HEAD
+			$hdrs = array(); // source file headers to override with new values
+			if ( isset( $params['disposition'] ) ) {
+				$hdrs['Content-Disposition'] = $this->truncDisp( $params['disposition'] );
+			}
+			if ( !empty( $params['async'] ) ) { // deferred
+				$op = $sContObj->move_object_to_async( $srcRel, $dContObj, $dstRel, null, $hdrs );
+				$status->value = new SwiftFileOpHandle( $this, $params, 'Move', $op );
+				$status->value->affectedObjects[] = $srcObj;
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$status->value->affectedObjects[] = $dstObj;
+				}
+			} else { // actually write the object in Swift
+				$sContObj->move_object_to( $srcRel, $dContObj, $dstRel, null, $hdrs );
+				$this->purgeCDNCache( array( $srcObj ) );
+				if ( !empty( $params['overwrite'] ) ) { // file possibly mutated
+					$this->purgeCDNCache( array( $dstObj ) );
+				}
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( NoSuchObjectException $e ) { // source object does not exist
+			$status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see SwiftFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseMove( CF_Async_Op $cfOp, Status $status, array $params ) {
+		try {
+			$cfOp->getLastResponse();
+		} catch ( NoSuchObjectException $e ) { // source object does not exist
+			$status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doDeleteInternal()
+	 * @return Status
+	 */
+	protected function doDeleteInternal( array $params ) {
+		$status = Status::newGood();
+
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+			return $status;
+		}
+
+		try {
+			$sContObj = $this->getContainer( $srcCont );
+			$srcObj = new CF_Object( $sContObj, $srcRel, false, false ); // skip HEAD
+			if ( !empty( $params['async'] ) ) { // deferred
+				$op = $sContObj->delete_object_async( $srcRel );
+				$status->value = new SwiftFileOpHandle( $this, $params, 'Delete', $op );
+				$status->value->affectedObjects[] = $srcObj;
+			} else { // actually write the object in Swift
+				$sContObj->delete_object( $srcRel );
+				$this->purgeCDNCache( array( $srcObj ) );
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-delete', $params['src'] );
+		} catch ( NoSuchObjectException $e ) {
+			if ( empty( $params['ignoreMissingSource'] ) ) {
+				$status->fatal( 'backend-fail-delete', $params['src'] );
+			}
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see SwiftFileBackend::doExecuteOpHandlesInternal()
+	 */
+	protected function _getResponseDelete( CF_Async_Op $cfOp, Status $status, array $params ) {
+		try {
+			$cfOp->getLastResponse();
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-delete', $params['src'] );
+		} catch ( NoSuchObjectException $e ) {
+			if ( empty( $params['ignoreMissingSource'] ) ) {
+				$status->fatal( 'backend-fail-delete', $params['src'] );
+			}
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doPrepareInternal()
+	 * @return Status
+	 */
+	protected function doPrepareInternal( $fullCont, $dir, array $params ) {
+		$status = Status::newGood();
+
+		// (a) Check if container already exists
+		try {
+			$contObj = $this->getContainer( $fullCont );
+			// NoSuchContainerException not thrown: container must exist
+			return $status; // already exists
+		} catch ( NoSuchContainerException $e ) {
+			// NoSuchContainerException thrown: container does not exist
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		// (b) Create container as needed
+		try {
+			$contObj = $this->createContainer( $fullCont );
+			if ( !empty( $params['noAccess'] ) ) {
+				// Make container private to end-users...
+				$status->merge( $this->doSecureInternal( $fullCont, $dir, $params ) );
+			} else {
+				// Make container public to end-users...
+				$status->merge( $this->doPublishInternal( $fullCont, $dir, $params ) );
+			}
+			if ( $this->swiftUseCDN ) { // Rackspace style CDN
+				$contObj->make_public( $this->swiftCDNExpiry );
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doSecureInternal()
+	 * @return Status
+	 */
+	protected function doSecureInternal( $fullCont, $dir, array $params ) {
+		$status = Status::newGood();
+		if ( empty( $params['noAccess'] ) ) {
+			return $status; // nothing to do
+		}
+
+		// Restrict container from end-users...
+		try {
+			// doPrepareInternal() should have been called,
+			// so the Swift container should already exist...
+			$contObj = $this->getContainer( $fullCont ); // normally a cache hit
+			// NoSuchContainerException not thrown: container must exist
+
+			// Make container private to end-users...
+			$status->merge( $this->setContainerAccess(
+				$contObj,
+				array( $this->auth->username ), // read
+				array( $this->auth->username ) // write
+			) );
+			if ( $this->swiftUseCDN && $contObj->is_public() ) { // Rackspace style CDN
+				$contObj->make_private();
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doPublishInternal()
+	 * @return Status
+	 */
+	protected function doPublishInternal( $fullCont, $dir, array $params ) {
+		$status = Status::newGood();
+
+		// Unrestrict container from end-users...
+		try {
+			// doPrepareInternal() should have been called,
+			// so the Swift container should already exist...
+			$contObj = $this->getContainer( $fullCont ); // normally a cache hit
+			// NoSuchContainerException not thrown: container must exist
+
+			// Make container public to end-users...
+			if ( $this->swiftAnonUser != '' ) {
+				$status->merge( $this->setContainerAccess(
+					$contObj,
+					array( $this->auth->username, $this->swiftAnonUser ), // read
+					array( $this->auth->username, $this->swiftAnonUser ) // write
+				) );
+			} else {
+				$status->merge( $this->setContainerAccess(
+					$contObj,
+					array( $this->auth->username, '.r:*' ), // read
+					array( $this->auth->username ) // write
+				) );
+			}
+			if ( $this->swiftUseCDN && !$contObj->is_public() ) { // Rackspace style CDN
+				$contObj->make_public();
+			}
+		} catch ( CDNNotEnabledException $e ) {
+			// CDN not enabled; nothing to see here
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doCleanInternal()
+	 * @return Status
+	 */
+	protected function doCleanInternal( $fullCont, $dir, array $params ) {
+		$status = Status::newGood();
+
+		// Only containers themselves can be removed, all else is virtual
+		if ( $dir != '' ) {
+			return $status; // nothing to do
+		}
+
+		// (a) Check the container
+		try {
+			$contObj = $this->getContainer( $fullCont, true );
+		} catch ( NoSuchContainerException $e ) {
+			return $status; // ok, nothing to do
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		// (b) Delete the container if empty
+		if ( $contObj->object_count == 0 ) {
+			try {
+				$this->deleteContainer( $fullCont );
+			} catch ( NoSuchContainerException $e ) {
+				return $status; // race?
+			} catch ( NonEmptyContainerException $e ) {
+				return $status; // race? consistency delay?
+			} catch ( CloudFilesException $e ) { // some other exception?
+				$this->handleException( $e, $status, __METHOD__, $params );
+				return $status;
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::doFileExists()
+	 * @return array|bool|null
+	 */
+	protected function doGetFileStat( array $params ) {
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			return false; // invalid storage path
+		}
+
+		$stat = false;
+		try {
+			$contObj = $this->getContainer( $srcCont );
+			$srcObj = $contObj->get_object( $srcRel, $this->headersFromParams( $params ) );
+			$this->addMissingMetadata( $srcObj, $params['src'] );
+			$stat = array(
+				// Convert dates like "Tue, 03 Jan 2012 22:01:04 GMT" to TS_MW
+				'mtime' => wfTimestamp( TS_MW, $srcObj->last_modified ),
+				'size'  => (int)$srcObj->content_length,
+				'sha1'  => $srcObj->metadata['Sha1base36']
+			);
+		} catch ( NoSuchContainerException $e ) {
+		} catch ( NoSuchObjectException $e ) {
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$stat = null;
+			$this->handleException( $e, null, __METHOD__, $params );
+		}
+
+		return $stat;
+	}
+
+	/**
+	 * Fill in any missing object metadata and save it to Swift
+	 *
+	 * @param $obj CF_Object
+	 * @param $path string Storage path to object
+	 * @return bool Success
+	 * @throws Exception cloudfiles exceptions
+	 */
+	protected function addMissingMetadata( CF_Object $obj, $path ) {
+		if ( isset( $obj->metadata['Sha1base36'] ) ) {
+			return true; // nothing to do
+		}
+		wfProfileIn( __METHOD__ );
+		$status = Status::newGood();
+		$scopeLockS = $this->getScopedFileLocks( array( $path ), LockManager::LOCK_UW, $status );
+		if ( $status->isOK() ) {
+			# Do not stat the file in getLocalCopy() to avoid infinite loops
+			$tmpFile = $this->getLocalCopy( array( 'src' => $path, 'latest' => 1, 'nostat' => 1 ) );
+			if ( $tmpFile ) {
+				$hash = $tmpFile->getSha1Base36();
+				if ( $hash !== false ) {
+					$obj->metadata['Sha1base36'] = $hash;
+					$obj->sync_metadata(); // save to Swift
+					wfProfileOut( __METHOD__ );
+					return true; // success
+				}
+			}
+		}
+		$obj->metadata['Sha1base36'] = false;
+		wfProfileOut( __METHOD__ );
+		return false; // failed
+	}
+
+	/**
+	 * @see FileBackend::getFileContents()
+	 * @return bool|null|string
+	 */
+	public function getFileContents( array $params ) {
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			return false; // invalid storage path
+		}
+
+		if ( !$this->fileExists( $params ) ) {
+			return null;
+		}
+
+		$data = false;
+		try {
+			$sContObj = $this->getContainer( $srcCont );
+			$obj = new CF_Object( $sContObj, $srcRel, false, false ); // skip HEAD
+			$data = $obj->read( $this->headersFromParams( $params ) );
+		} catch ( NoSuchContainerException $e ) {
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, null, __METHOD__, $params );
+		}
+
+		return $data;
+	}
+
+	/**
+	 * @see FileBackendStore::doDirectoryExists()
+	 * @return bool|null
+	 */
+	protected function doDirectoryExists( $fullCont, $dir, array $params ) {
+		try {
+			$container = $this->getContainer( $fullCont );
+			$prefix = ( $dir == '' ) ? null : "{$dir}/";
+			return ( count( $container->list_objects( 1, null, $prefix ) ) > 0 );
+		} catch ( NoSuchContainerException $e ) {
+			return false;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, null, __METHOD__,
+				array( 'cont' => $fullCont, 'dir' => $dir ) );
+		}
+
+		return null; // error
+	}
+
+	/**
+	 * @see FileBackendStore::getDirectoryListInternal()
+	 * @return SwiftFileBackendDirList
+	 */
+	public function getDirectoryListInternal( $fullCont, $dir, array $params ) {
+		return new SwiftFileBackendDirList( $this, $fullCont, $dir, $params );
+	}
+
+	/**
+	 * @see FileBackendStore::getFileListInternal()
+	 * @return SwiftFileBackendFileList
+	 */
+	public function getFileListInternal( $fullCont, $dir, array $params ) {
+		return new SwiftFileBackendFileList( $this, $fullCont, $dir, $params );
+	}
+
+	/**
+	 * Do not call this function outside of SwiftFileBackendFileList
+	 *
+	 * @param $fullCont string Resolved container name
+	 * @param $dir string Resolved storage directory with no trailing slash
+	 * @param $after string|null Storage path of file to list items after
+	 * @param $limit integer Max number of items to list
+	 * @param $params Array Includes flag for 'topOnly'
+	 * @return Array List of relative paths of dirs directly under $dir
+	 */
+	public function getDirListPageInternal( $fullCont, $dir, &$after, $limit, array $params ) {
+		$dirs = array();
+		if ( $after === INF ) {
+			return $dirs; // nothing more
+		}
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+
+		try {
+			$container = $this->getContainer( $fullCont );
+			$prefix = ( $dir == '' ) ? null : "{$dir}/";
+			// Non-recursive: only list dirs right under $dir
+			if ( !empty( $params['topOnly'] ) ) {
+				$objects = $container->list_objects( $limit, $after, $prefix, null, '/' );
+				foreach ( $objects as $object ) { // files and dirs
+					if ( substr( $object, -1 ) === '/' ) {
+						$dirs[] = $object; // directories end in '/'
+					}
+				}
+			// Recursive: list all dirs under $dir and its subdirs
+			} else {
+				// Get directory from last item of prior page
+				$lastDir = $this->getParentDir( $after ); // must be first page
+				$objects = $container->list_objects( $limit, $after, $prefix );
+				foreach ( $objects as $object ) { // files
+					$objectDir = $this->getParentDir( $object ); // directory of object
+					if ( $objectDir !== false ) { // file has a parent dir
+						// Swift stores paths in UTF-8, using binary sorting.
+						// See function "create_container_table" in common/db.py.
+						// If a directory is not "greater" than the last one,
+						// then it was already listed by the calling iterator.
+						if ( strcmp( $objectDir, $lastDir ) > 0 ) {
+							$pDir = $objectDir;
+							do { // add dir and all its parent dirs
+								$dirs[] = "{$pDir}/";
+								$pDir = $this->getParentDir( $pDir );
+							} while ( $pDir !== false // sanity
+								&& strcmp( $pDir, $lastDir ) > 0 // not done already
+								&& strlen( $pDir ) > strlen( $dir ) // within $dir
+							);
+						}
+						$lastDir = $objectDir;
+					}
+				}
+			}
+			if ( count( $objects ) < $limit ) {
+				$after = INF; // avoid a second RTT
+			} else {
+				$after = end( $objects ); // update last item
+			}
+		} catch ( NoSuchContainerException $e ) {
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, null, __METHOD__,
+				array( 'cont' => $fullCont, 'dir' => $dir ) );
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		return $dirs;
+	}
+
+	protected function getParentDir( $path ) {
+		return ( strpos( $path, '/' ) !== false ) ? dirname( $path ) : false;
+	}
+
+	/**
+	 * Do not call this function outside of SwiftFileBackendFileList
+	 *
+	 * @param $fullCont string Resolved container name
+	 * @param $dir string Resolved storage directory with no trailing slash
+	 * @param $after string|null Storage path of file to list items after
+	 * @param $limit integer Max number of items to list
+	 * @param $params Array Includes flag for 'topOnly'
+	 * @return Array List of relative paths of files under $dir
+	 */
+	public function getFileListPageInternal( $fullCont, $dir, &$after, $limit, array $params ) {
+		$files = array();
+		if ( $after === INF ) {
+			return $files; // nothing more
+		}
+		wfProfileIn( __METHOD__ . '-' . $this->name );
+
+		try {
+			$container = $this->getContainer( $fullCont );
+			$prefix = ( $dir == '' ) ? null : "{$dir}/";
+			// Non-recursive: only list files right under $dir
+			if ( !empty( $params['topOnly'] ) ) { // files and dirs
+				$objects = $container->list_objects( $limit, $after, $prefix, null, '/' );
+				foreach ( $objects as $object ) {
+					if ( substr( $object, -1 ) !== '/' ) {
+						$files[] = $object; // directories end in '/'
+					}
+				}
+			// Recursive: list all files under $dir and its subdirs
+			} else { // files
+				$objects = $container->list_objects( $limit, $after, $prefix );
+				$files = $objects;
+			}
+			if ( count( $objects ) < $limit ) {
+				$after = INF; // avoid a second RTT
+			} else {
+				$after = end( $objects ); // update last item
+			}
+		} catch ( NoSuchContainerException $e ) {
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, null, __METHOD__,
+				array( 'cont' => $fullCont, 'dir' => $dir ) );
+		}
+
+		wfProfileOut( __METHOD__ . '-' . $this->name );
+		return $files;
+	}
+
+	/**
+	 * @see FileBackendStore::doGetFileSha1base36()
+	 * @return bool
+	 */
+	protected function doGetFileSha1base36( array $params ) {
+		$stat = $this->getFileStat( $params );
+		if ( $stat ) {
+			return $stat['sha1'];
+		} else {
+			return false;
+		}
+	}
+
+	/**
+	 * @see FileBackendStore::doStreamFile()
+	 * @return Status
+	 */
+	protected function doStreamFile( array $params ) {
+		$status = Status::newGood();
+
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			$status->fatal( 'backend-fail-invalidpath', $params['src'] );
+		}
+
+		try {
+			$cont = $this->getContainer( $srcCont );
+		} catch ( NoSuchContainerException $e ) {
+			$status->fatal( 'backend-fail-stream', $params['src'] );
+			return $status;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+			return $status;
+		}
+
+		try {
+			$output = fopen( 'php://output', 'wb' );
+			$obj = new CF_Object( $cont, $srcRel, false, false ); // skip HEAD
+			$obj->stream( $output, $this->headersFromParams( $params ) );
+		} catch ( NoSuchObjectException $e ) {
+			$status->fatal( 'backend-fail-stream', $params['src'] );
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, $status, __METHOD__, $params );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileBackendStore::getLocalCopy()
+	 * @return null|TempFSFile
+	 */
+	public function getLocalCopy( array $params ) {
+		list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
+		if ( $srcRel === null ) {
+			return null;
+		}
+
+		// Blindly create a tmp file and stream to it, catching any exception if the file does
+		// not exist. Also, doing a stat here will cause infinite loops when filling metadata.
+		$tmpFile = null;
+		try {
+			$sContObj = $this->getContainer( $srcCont );
+			$obj = new CF_Object( $sContObj, $srcRel, false, false ); // skip HEAD
+			// Get source file extension
+			$ext = FileBackend::extensionFromPath( $srcRel );
+			// Create a new temporary file...
+			$tmpFile = TempFSFile::factory( 'localcopy_', $ext );
+			if ( $tmpFile ) {
+				$handle = fopen( $tmpFile->getPath(), 'wb' );
+				if ( $handle ) {
+					$obj->stream( $handle, $this->headersFromParams( $params ) );
+					fclose( $handle );
+				} else {
+					$tmpFile = null; // couldn't open temp file
+				}
+			}
+		} catch ( NoSuchContainerException $e ) {
+			$tmpFile = null;
+		} catch ( NoSuchObjectException $e ) {
+			$tmpFile = null;
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$tmpFile = null;
+			$this->handleException( $e, null, __METHOD__, $params );
+		}
+
+		return $tmpFile;
+	}
+
+	/**
+	 * @see FileBackendStore::directoriesAreVirtual()
+	 * @return bool
+	 */
+	protected function directoriesAreVirtual() {
+		return true;
+	}
+
+	/**
+	 * Get headers to send to Swift when reading a file based
+	 * on a FileBackend params array, e.g. that of getLocalCopy().
+	 * $params is currently only checked for a 'latest' flag.
+	 *
+	 * @param $params Array
+	 * @return Array
+	 */
+	protected function headersFromParams( array $params ) {
+		$hdrs = array();
+		if ( !empty( $params['latest'] ) ) {
+			$hdrs[] = 'X-Newest: true';
+		}
+		return $hdrs;
+	}
+
+	/**
+	 * @see FileBackendStore::doExecuteOpHandlesInternal()
+	 * @return Array List of corresponding Status objects
+	 */
+	protected function doExecuteOpHandlesInternal( array $fileOpHandles ) {
+		$statuses = array();
+
+		$cfOps = array(); // list of CF_Async_Op objects
+		foreach ( $fileOpHandles as $index => $fileOpHandle ) {
+			$cfOps[$index] = $fileOpHandle->cfOp;
+		}
+		$batch = new CF_Async_Op_Batch( $cfOps );
+
+		$cfOps = $batch->execute();
+		foreach ( $cfOps as $index => $cfOp ) {
+			$status = Status::newGood();
+			try { // catch exceptions; update status
+				$function = '_getResponse' . $fileOpHandles[$index]->call;
+				$this->$function( $cfOp, $status, $fileOpHandles[$index]->params );
+				$this->purgeCDNCache( $fileOpHandles[$index]->affectedObjects );
+			} catch ( CloudFilesException $e ) { // some other exception?
+				$this->handleException( $e, $status,
+					__CLASS__ . ":$function", $fileOpHandles[$index]->params );
+			}
+			$statuses[$index] = $status;
+		}
+
+		return $statuses;
+	}
+
+	/**
+	 * Set read/write permissions for a Swift container.
+	 *
+	 * $readGrps is a list of the possible criteria for a request to have
+	 * access to read a container. Each item is one of the following formats:
+	 *   - account:user       : Grants access if the request is by the given user
+	 *   - .r:<regex>         : Grants access if the request is from a referrer host that
+	 *                          matches the expression and the request is not for a listing.
+	 *                          Setting this to '*' effectively makes a container public.
+	 *   - .rlistings:<regex> : Grants access if the request is from a referrer host that
+	 *                          matches the expression and the request for a listing.
+	 *
+	 * $writeGrps is a list of the possible criteria for a request to have
+	 * access to write to a container. Each item is of the following format:
+	 *   - account:user       : Grants access if the request is by the given user
+	 *
+	 * @see http://swift.openstack.org/misc.html#acls
+	 *
+	 * In general, we don't allow listings to end-users. It's not useful, isn't well-defined
+	 * (lists are truncated to 10000 item with no way to page), and is just a performance risk.
+	 *
+	 * @param $contObj CF_Container Swift container
+	 * @param $readGrps Array List of read access routes
+	 * @param $writeGrps Array List of write access routes
+	 * @return Status
+	 */
+	protected function setContainerAccess(
+		CF_Container $contObj, array $readGrps, array $writeGrps
+	) {
+		$creds = $contObj->cfs_auth->export_credentials();
+
+		$url = $creds['storage_url'] . '/' . rawurlencode( $contObj->name );
+
+		// Note: 10 second timeout consistent with php-cloudfiles
+		$req = MWHttpRequest::factory( $url, array( 'method' => 'POST', 'timeout' => 10 ) );
+		$req->setHeader( 'X-Auth-Token', $creds['auth_token'] );
+		$req->setHeader( 'X-Container-Read', implode( ',', $readGrps ) );
+		$req->setHeader( 'X-Container-Write', implode( ',', $writeGrps ) );
+
+		return $req->execute(); // should return 204
+	}
+
+	/**
+	 * Purge the CDN cache of affected objects if CDN caching is enabled.
+	 * This is for Rackspace/Akamai CDNs.
+	 *
+	 * @param $objects Array List of CF_Object items
+	 * @return void
+	 */
+	public function purgeCDNCache( array $objects ) {
+		if ( $this->swiftUseCDN && $this->swiftCDNPurgable ) {
+			foreach ( $objects as $object ) {
+				try {
+					$object->purge_from_cdn();
+				} catch ( CDNNotEnabledException $e ) {
+					// CDN not enabled; nothing to see here
+				} catch ( CloudFilesException $e ) {
+					$this->handleException( $e, null, __METHOD__,
+						array( 'cont' => $object->container->name, 'obj' => $object->name ) );
+				}
+			}
+		}
+	}
+
+	/**
+	 * Get an authenticated connection handle to the Swift proxy
+	 *
+	 * @return CF_Connection|bool False on failure
+	 * @throws CloudFilesException
+	 */
+	protected function getConnection() {
+		if ( $this->connException instanceof CloudFilesException ) {
+			if ( ( time() - $this->connErrorTime ) < 60 ) {
+				throw $this->connException; // failed last attempt; don't bother
+			} else { // actually retry this time
+				$this->connException = null;
+				$this->connErrorTime = 0;
+			}
+		}
+		// Session keys expire after a while, so we renew them periodically
+		$reAuth = ( ( time() - $this->sessionStarted ) > $this->authTTL );
+		// Authenticate with proxy and get a session key...
+		if ( !$this->conn || $reAuth ) {
+			$this->sessionStarted = 0;
+			$this->connContainerCache->clear();
+			$cacheKey = $this->getCredsCacheKey( $this->auth->username );
+			$creds = $this->srvCache->get( $cacheKey ); // credentials
+			if ( is_array( $creds ) ) { // cache hit
+				$this->auth->load_cached_credentials(
+					$creds['auth_token'], $creds['storage_url'], $creds['cdnm_url'] );
+				$this->sessionStarted = time() - ceil( $this->authTTL/2 ); // skew for worst case
+			} else { // cache miss
+				try {
+					$this->auth->authenticate();
+					$creds = $this->auth->export_credentials();
+					$this->srvCache->add( $cacheKey, $creds, ceil( $this->authTTL/2 ) ); // cache
+					$this->sessionStarted = time();
+				} catch ( CloudFilesException $e ) {
+					$this->connException = $e; // don't keep re-trying
+					$this->connErrorTime = time();
+					throw $e; // throw it back
+				}
+			}
+			if ( $this->conn ) { // re-authorizing?
+				$this->conn->close(); // close active cURL handles in CF_Http object
+			}
+			$this->conn = new CF_Connection( $this->auth );
+		}
+		return $this->conn;
+	}
+
+	/**
+	 * Close the connection to the Swift proxy
+	 *
+	 * @return void
+	 */
+	protected function closeConnection() {
+		if ( $this->conn ) {
+			$this->conn->close(); // close active cURL handles in CF_Http object
+			$this->sessionStarted = 0;
+			$this->connContainerCache->clear();
+		}
+	}
+
+	/**
+	 * Get the cache key for a container
+	 *
+	 * @param $username string
+	 * @return string
+	 */
+	private function getCredsCacheKey( $username ) {
+		return wfMemcKey( 'backend', $this->getName(), 'usercreds', $username );
+	}
+
+	/**
+	 * @see FileBackendStore::doClearCache()
+	 */
+	protected function doClearCache( array $paths = null ) {
+		$this->connContainerCache->clear(); // clear container object cache
+	}
+
+	/**
+	 * Get a Swift container object, possibly from process cache.
+	 * Use $reCache if the file count or byte count is needed.
+	 *
+	 * @param $container string Container name
+	 * @param $bypassCache bool Bypass all caches and load from Swift
+	 * @return CF_Container
+	 * @throws CloudFilesException
+	 */
+	protected function getContainer( $container, $bypassCache = false ) {
+		$conn = $this->getConnection(); // Swift proxy connection
+		if ( $bypassCache ) { // purge cache
+			$this->connContainerCache->clear( $container );
+		} elseif ( !$this->connContainerCache->has( $container, 'obj' ) ) {
+			$this->primeContainerCache( array( $container ) ); // check persistent cache
+		}
+		if ( !$this->connContainerCache->has( $container, 'obj' ) ) {
+			$contObj = $conn->get_container( $container );
+			// NoSuchContainerException not thrown: container must exist
+			$this->connContainerCache->set( $container, 'obj', $contObj ); // cache it
+			if ( !$bypassCache ) {
+				$this->setContainerCache( $container, // update persistent cache
+					array( 'bytes' => $contObj->bytes_used, 'count' => $contObj->object_count )
+				);
+			}
+		}
+		return $this->connContainerCache->get( $container, 'obj' );
+	}
+
+	/**
+	 * Create a Swift container
+	 *
+	 * @param $container string Container name
+	 * @return CF_Container
+	 * @throws CloudFilesException
+	 */
+	protected function createContainer( $container ) {
+		$conn = $this->getConnection(); // Swift proxy connection
+		$contObj = $conn->create_container( $container );
+		$this->connContainerCache->set( $container, 'obj', $contObj ); // cache
+		return $contObj;
+	}
+
+	/**
+	 * Delete a Swift container
+	 *
+	 * @param $container string Container name
+	 * @return void
+	 * @throws CloudFilesException
+	 */
+	protected function deleteContainer( $container ) {
+		$conn = $this->getConnection(); // Swift proxy connection
+		$this->connContainerCache->clear( $container ); // purge
+		$conn->delete_container( $container );
+	}
+
+	/**
+	 * @see FileBackendStore::doPrimeContainerCache()
+	 * @return void
+	 */
+	protected function doPrimeContainerCache( array $containerInfo ) {
+		try {
+			$conn = $this->getConnection(); // Swift proxy connection
+			foreach ( $containerInfo as $container => $info ) {
+				$contObj = new CF_Container( $conn->cfs_auth, $conn->cfs_http,
+					$container, $info['count'], $info['bytes'] );
+				$this->connContainerCache->set( $container, 'obj', $contObj );
+			}
+		} catch ( CloudFilesException $e ) { // some other exception?
+			$this->handleException( $e, null, __METHOD__, array() );
+		}
+	}
+
+	/**
+	 * Log an unexpected exception for this backend.
+	 * This also sets the Status object to have a fatal error.
+	 *
+	 * @param $e Exception
+	 * @param $status Status|null
+	 * @param $func string
+	 * @param $params Array
+	 * @return void
+	 */
+	protected function handleException( Exception $e, $status, $func, array $params ) {
+		if ( $status instanceof Status ) {
+			if ( $e instanceof AuthenticationException ) {
+				$status->fatal( 'backend-fail-connect', $this->name );
+			} else {
+				$status->fatal( 'backend-fail-internal', $this->name );
+			}
+		}
+		if ( $e->getMessage() ) {
+			trigger_error( "$func: " . $e->getMessage(), E_USER_WARNING );
+		}
+		if ( $e instanceof InvalidResponseException ) { // possibly a stale token
+			$this->srvCache->delete( $this->getCredsCacheKey( $this->auth->username ) );
+			$this->closeConnection(); // force a re-connect and re-auth next time
+		}
+		wfDebugLog( 'SwiftBackend',
+			get_class( $e ) . " in '{$func}' (given '" . FormatJson::encode( $params ) . "')" .
+			( $e->getMessage() ? ": {$e->getMessage()}" : "" )
+		);
+	}
+}
+
+/**
+ * @see FileBackendStoreOpHandle
+ */
+class SwiftFileOpHandle extends FileBackendStoreOpHandle {
+	/** @var CF_Async_Op */
+	public $cfOp;
+	/** @var Array */
+	public $affectedObjects = array();
+
+	public function __construct( $backend, array $params, $call, CF_Async_Op $cfOp ) {
+		$this->backend = $backend;
+		$this->params = $params;
+		$this->call = $call;
+		$this->cfOp = $cfOp;
+	}
+}
+
+/**
+ * SwiftFileBackend helper class to page through listings.
+ * Swift also has a listing limit of 10,000 objects for sanity.
+ * Do not use this class from places outside SwiftFileBackend.
+ *
+ * @ingroup FileBackend
+ */
+abstract class SwiftFileBackendList implements Iterator {
+	/** @var Array */
+	protected $bufferIter = array();
+	protected $bufferAfter = null; // string; list items *after* this path
+	protected $pos = 0; // integer
+	/** @var Array */
+	protected $params = array();
+
+	/** @var SwiftFileBackend */
+	protected $backend;
+	protected $container; // string; container name
+	protected $dir; // string; storage directory
+	protected $suffixStart; // integer
+
+	const PAGE_SIZE = 9000; // file listing buffer size
+
+	/**
+	 * @param $backend SwiftFileBackend
+	 * @param $fullCont string Resolved container name
+	 * @param $dir string Resolved directory relative to container
+	 * @param $params Array
+	 */
+	public function __construct( SwiftFileBackend $backend, $fullCont, $dir, array $params ) {
+		$this->backend = $backend;
+		$this->container = $fullCont;
+		$this->dir = $dir;
+		if ( substr( $this->dir, -1 ) === '/' ) {
+			$this->dir = substr( $this->dir, 0, -1 ); // remove trailing slash
+		}
+		if ( $this->dir == '' ) { // whole container
+			$this->suffixStart = 0;
+		} else { // dir within container
+			$this->suffixStart = strlen( $this->dir ) + 1; // size of "path/to/dir/"
+		}
+		$this->params = $params;
+	}
+
+	/**
+	 * @see Iterator::key()
+	 * @return integer
+	 */
+	public function key() {
+		return $this->pos;
+	}
+
+	/**
+	 * @see Iterator::next()
+	 * @return void
+	 */
+	public function next() {
+		// Advance to the next file in the page
+		next( $this->bufferIter );
+		++$this->pos;
+		// Check if there are no files left in this page and
+		// advance to the next page if this page was not empty.
+		if ( !$this->valid() && count( $this->bufferIter ) ) {
+			$this->bufferIter = $this->pageFromList(
+				$this->container, $this->dir, $this->bufferAfter, self::PAGE_SIZE, $this->params
+			); // updates $this->bufferAfter
+		}
+	}
+
+	/**
+	 * @see Iterator::rewind()
+	 * @return void
+	 */
+	public function rewind() {
+		$this->pos = 0;
+		$this->bufferAfter = null;
+		$this->bufferIter = $this->pageFromList(
+			$this->container, $this->dir, $this->bufferAfter, self::PAGE_SIZE, $this->params
+		); // updates $this->bufferAfter
+	}
+
+	/**
+	 * @see Iterator::valid()
+	 * @return bool
+	 */
+	public function valid() {
+		if ( $this->bufferIter === null ) {
+			return false; // some failure?
+		} else {
+			return ( current( $this->bufferIter ) !== false ); // no paths can have this value
+		}
+	}
+
+	/**
+	 * Get the given list portion (page)
+	 *
+	 * @param $container string Resolved container name
+	 * @param $dir string Resolved path relative to container
+	 * @param $after string|null
+	 * @param $limit integer
+	 * @param $params Array
+	 * @return Traversable|Array|null Returns null on failure
+	 */
+	abstract protected function pageFromList( $container, $dir, &$after, $limit, array $params );
+}
+
+/**
+ * Iterator for listing directories
+ */
+class SwiftFileBackendDirList extends SwiftFileBackendList {
+	/**
+	 * @see Iterator::current()
+	 * @return string|bool String (relative path) or false
+	 */
+	public function current() {
+		return substr( current( $this->bufferIter ), $this->suffixStart, -1 );
+	}
+
+	/**
+	 * @see SwiftFileBackendList::pageFromList()
+	 * @return Array|null
+	 */
+	protected function pageFromList( $container, $dir, &$after, $limit, array $params ) {
+		return $this->backend->getDirListPageInternal( $container, $dir, $after, $limit, $params );
+	}
+}
+
+/**
+ * Iterator for listing regular files
+ */
+class SwiftFileBackendFileList extends SwiftFileBackendList {
+	/**
+	 * @see Iterator::current()
+	 * @return string|bool String (relative path) or false
+	 */
+	public function current() {
+		return substr( current( $this->bufferIter ), $this->suffixStart );
+	}
+
+	/**
+	 * @see SwiftFileBackendList::pageFromList()
+	 * @return Array|null
+	 */
+	protected function pageFromList( $container, $dir, &$after, $limit, array $params ) {
+		return $this->backend->getFileListPageInternal( $container, $dir, $after, $limit, $params );
+	}
+}
diff --git a/includes/filebackend/TempFSFile.php b/includes/filebackend/TempFSFile.php
new file mode 100644
index 00000000..5032bf68
--- /dev/null
+++ b/includes/filebackend/TempFSFile.php
@@ -0,0 +1,121 @@
+<?php
+/**
+ * Location holder of files stored temporarily
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileBackend
+ */
+
+/**
+ * This class is used to hold the location and do limited manipulation
+ * of files stored temporarily (this will be whatever wfTempDir() returns)
+ *
+ * @ingroup FileBackend
+ */
+class TempFSFile extends FSFile {
+	protected $canDelete = false; // bool; garbage collect the temp file
+
+	/** @var Array of active temp files to purge on shutdown */
+	protected static $instances = array();
+
+	/**
+	 * Make a new temporary file on the file system.
+	 * Temporary files may be purged when the file object falls out of scope.
+	 *
+	 * @param $prefix string
+	 * @param $extension string
+	 * @return TempFSFile|null
+	 */
+	public static function factory( $prefix, $extension = '' ) {
+		wfProfileIn( __METHOD__ );
+		$base = wfTempDir() . '/' . $prefix . wfRandomString( 12 );
+		$ext = ( $extension != '' ) ? ".{$extension}" : "";
+		for ( $attempt = 1; true; $attempt++ ) {
+			$path = "{$base}-{$attempt}{$ext}";
+			wfSuppressWarnings();
+			$newFileHandle = fopen( $path, 'x' );
+			wfRestoreWarnings();
+			if ( $newFileHandle ) {
+				fclose( $newFileHandle );
+				break; // got it
+			}
+			if ( $attempt >= 5 ) {
+				wfProfileOut( __METHOD__ );
+				return null; // give up
+			}
+		}
+		$tmpFile = new self( $path );
+		$tmpFile->canDelete = true; // safely instantiated
+		wfProfileOut( __METHOD__ );
+		return $tmpFile;
+	}
+
+	/**
+	 * Purge this file off the file system
+	 *
+	 * @return bool Success
+	 */
+	public function purge() {
+		$this->canDelete = false; // done
+		wfSuppressWarnings();
+		$ok = unlink( $this->path );
+		wfRestoreWarnings();
+		return $ok;
+	}
+
+	/**
+	 * Clean up the temporary file only after an object goes out of scope
+	 *
+	 * @param $object Object
+	 * @return void
+	 */
+	public function bind( $object ) {
+		if ( is_object( $object ) ) {
+			$object->tempFSFileReferences[] = $this;
+		}
+	}
+
+	/**
+	 * Set flag to not clean up after the temporary file
+	 *
+	 * @return void
+	 */
+	public function preserve() {
+		$this->canDelete = false;
+	}
+
+	/**
+	 * Set flag clean up after the temporary file
+	 *
+	 * @return void
+	 */
+	public function autocollect() {
+		$this->canDelete = true;
+	}
+
+	/**
+	 * Cleans up after the temporary file by deleting it
+	 */
+	function __destruct() {
+		if ( $this->canDelete ) {
+			wfSuppressWarnings();
+			unlink( $this->path );
+			wfRestoreWarnings();
+		}
+	}
+}
diff --git a/includes/filebackend/filejournal/DBFileJournal.php b/includes/filebackend/filejournal/DBFileJournal.php
new file mode 100644
index 00000000..f6268c25
--- /dev/null
+++ b/includes/filebackend/filejournal/DBFileJournal.php
@@ -0,0 +1,152 @@
+<?php
+/**
+ * Version of FileJournal that logs to a DB table.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileJournal
+ * @author Aaron Schulz
+ */
+
+/**
+ * Version of FileJournal that logs to a DB table
+ * @since 1.20
+ */
+class DBFileJournal extends FileJournal {
+	/** @var DatabaseBase */
+	protected $dbw;
+
+	protected $wiki = false; // string; wiki DB name
+
+	/**
+	 * Construct a new instance from configuration.
+	 * $config includes:
+	 *     'wiki' : wiki name to use for LoadBalancer
+	 *
+	 * @param $config Array
+	 */
+	protected function __construct( array $config ) {
+		parent::__construct( $config );
+
+		$this->wiki = $config['wiki'];
+	}
+
+	/**
+	 * @see FileJournal::logChangeBatch()
+	 * @return Status
+	 */
+	protected function doLogChangeBatch( array $entries, $batchId ) {
+		$status = Status::newGood();
+
+		try {
+			$dbw = $this->getMasterDB();
+		} catch ( DBError $e ) {
+			$status->fatal( 'filejournal-fail-dbconnect', $this->backend );
+			return $status;
+		}
+
+		$now = wfTimestamp( TS_UNIX );
+
+		$data = array();
+		foreach ( $entries as $entry ) {
+			$data[] = array(
+				'fj_batch_uuid' => $batchId,
+				'fj_backend'    => $this->backend,
+				'fj_op'         => $entry['op'],
+				'fj_path'       => $entry['path'],
+				'fj_new_sha1'   => $entry['newSha1'],
+				'fj_timestamp'  => $dbw->timestamp( $now )
+			);
+		}
+
+		try {
+			$dbw->insert( 'filejournal', $data, __METHOD__ );
+		} catch ( DBError $e ) {
+			$status->fatal( 'filejournal-fail-dbquery', $this->backend );
+			return $status;
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see FileJournal::doGetChangeEntries()
+	 * @return Array
+	 * @throws DBError
+	 */
+	protected function doGetChangeEntries( $start, $limit ) {
+		$dbw = $this->getMasterDB();
+
+		$res = $dbw->select( 'filejournal', '*',
+			array(
+				'fj_backend' => $this->backend,
+				'fj_id >= ' . $dbw->addQuotes( (int)$start ) ), // $start may be 0
+			__METHOD__,
+			array_merge( array( 'ORDER BY' => 'fj_id ASC' ),
+				$limit ? array( 'LIMIT' => $limit ) : array() )
+		);
+
+		$entries = array();
+		foreach ( $res as $row ) {
+			$item = array();
+			foreach ( (array)$row as $key => $value ) {
+				$item[substr( $key, 3 )] = $value; // "fj_op" => "op"
+			}
+			$entries[] = $item;
+		}
+
+		return $entries;
+	}
+
+	/**
+	 * @see FileJournal::purgeOldLogs()
+	 * @return Status
+	 * @throws DBError
+	 */
+	protected function doPurgeOldLogs() {
+		$status = Status::newGood();
+		if ( $this->ttlDays <= 0 ) {
+			return $status; // nothing to do
+		}
+
+		$dbw = $this->getMasterDB();
+		$dbCutoff = $dbw->timestamp( time() - 86400 * $this->ttlDays );
+
+		$dbw->delete( 'filejournal',
+			array( 'fj_timestamp < ' . $dbw->addQuotes( $dbCutoff ) ),
+			__METHOD__
+		);
+
+		return $status;
+	}
+
+	/**
+	 * Get a master connection to the logging DB
+	 *
+	 * @return DatabaseBase
+	 * @throws DBError
+	 */
+	protected function getMasterDB() {
+		if ( !$this->dbw ) {
+			// Get a separate connection in autocommit mode
+			$lb = wfGetLBFactory()->newMainLB();
+			$this->dbw = $lb->getConnection( DB_MASTER, array(), $this->wiki );
+			$this->dbw->clearFlag( DBO_TRX );
+		}
+		return $this->dbw;
+	}
+}
diff --git a/includes/filebackend/filejournal/FileJournal.php b/includes/filebackend/filejournal/FileJournal.php
new file mode 100644
index 00000000..ce029bbe
--- /dev/null
+++ b/includes/filebackend/filejournal/FileJournal.php
@@ -0,0 +1,196 @@
+<?php
+/**
+ * @defgroup FileJournal File journal
+ * @ingroup FileBackend
+ */
+
+/**
+ * File operation journaling.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup FileJournal
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Class for handling file operation journaling.
+ *
+ * Subclasses should avoid throwing exceptions at all costs.
+ *
+ * @ingroup FileJournal
+ * @since 1.20
+ */
+abstract class FileJournal {
+	protected $backend; // string
+	protected $ttlDays; // integer
+
+	/**
+	 * Construct a new instance from configuration.
+	 * $config includes:
+	 *     'ttlDays' : days to keep log entries around (false means "forever")
+	 *
+	 * @param $config Array
+	 */
+	protected function __construct( array $config ) {
+		$this->ttlDays = isset( $config['ttlDays'] ) ? $config['ttlDays'] : false;
+	}
+
+	/**
+	 * Create an appropriate FileJournal object from config
+	 *
+	 * @param $config Array
+	 * @param $backend string A registered file backend name
+	 * @throws MWException
+	 * @return FileJournal
+	 */
+	final public static function factory( array $config, $backend ) {
+		$class = $config['class'];
+		$jrn = new $class( $config );
+		if ( !$jrn instanceof self ) {
+			throw new MWException( "Class given is not an instance of FileJournal." );
+		}
+		$jrn->backend = $backend;
+		return $jrn;
+	}
+
+	/**
+	 * Get a statistically unique ID string
+	 *
+	 * @return string <9 char TS_MW timestamp in base 36><22 random base 36 chars>
+	 */
+	final public function getTimestampedUUID() {
+		$s = '';
+		for ( $i = 0; $i < 5; $i++ ) {
+			$s .= mt_rand( 0, 2147483647 );
+		}
+		$s = wfBaseConvert( sha1( $s ), 16, 36, 31 );
+		return substr( wfBaseConvert( wfTimestamp( TS_MW ), 10, 36, 9 ) . $s, 0, 31 );
+	}
+
+	/**
+	 * Log changes made by a batch file operation.
+	 * $entries is an array of log entries, each of which contains:
+	 *     op      : Basic operation name (create, store, copy, delete)
+	 *     path    : The storage path of the file
+	 *     newSha1 : The final base 36 SHA-1 of the file
+	 * Note that 'false' should be used as the SHA-1 for non-existing files.
+	 *
+	 * @param $entries Array List of file operations (each an array of parameters)
+	 * @param $batchId string UUID string that identifies the operation batch
+	 * @return Status
+	 */
+	final public function logChangeBatch( array $entries, $batchId ) {
+		if ( !count( $entries ) ) {
+			return Status::newGood();
+		}
+		return $this->doLogChangeBatch( $entries, $batchId );
+	}
+
+	/**
+	 * @see FileJournal::logChangeBatch()
+	 *
+	 * @param $entries Array List of file operations (each an array of parameters)
+	 * @param $batchId string UUID string that identifies the operation batch
+	 * @return Status
+	 */
+	abstract protected function doLogChangeBatch( array $entries, $batchId );
+
+	/**
+	 * Get an array of file change log entries.
+	 * A starting change ID and/or limit can be specified.
+	 *
+	 * The result as a list of associative arrays, each having:
+	 *     id         : unique, monotonic, ID for this change
+	 *     batch_uuid : UUID for an operation batch
+	 *     backend    : the backend name
+	 *     op         : primitive operation (create,update,delete,null)
+	 *     path       : affected storage path
+	 *     new_sha1   : base 36 sha1 of the new file had the operation succeeded
+	 *     timestamp  : TS_MW timestamp of the batch change
+
+	 * Also, $next is updated to the ID of the next entry.
+	 *
+	 * @param $start integer Starting change ID or null
+	 * @param $limit integer Maximum number of items to return
+	 * @param &$next string
+	 * @return Array
+	 */
+	final public function getChangeEntries( $start = null, $limit = 0, &$next = null ) {
+		$entries = $this->doGetChangeEntries( $start, $limit ? $limit + 1 : 0 );
+		if ( $limit && count( $entries ) > $limit ) {
+			$last = array_pop( $entries ); // remove the extra entry
+			$next = $last['id']; // update for next call
+		} else {
+			$next = null; // end of list
+		}
+		return $entries;
+	}
+
+	/**
+	 * @see FileJournal::getChangeEntries()
+	 * @return Array
+	 */
+	abstract protected function doGetChangeEntries( $start, $limit );
+
+	/**
+	 * Purge any old log entries
+	 *
+	 * @return Status
+	 */
+	final public function purgeOldLogs() {
+		return $this->doPurgeOldLogs();
+	}
+
+	/**
+	 * @see FileJournal::purgeOldLogs()
+	 * @return Status
+	 */
+	abstract protected function doPurgeOldLogs();
+}
+
+/**
+ * Simple version of FileJournal that does nothing
+ * @since 1.20
+ */
+class NullFileJournal extends FileJournal {
+	/**
+	 * @see FileJournal::logChangeBatch()
+	 * @param $entries array
+	 * @param $batchId string
+	 * @return Status
+	 */
+	protected function doLogChangeBatch( array $entries, $batchId ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see FileJournal::doGetChangeEntries()
+	 * @return Array
+	 */
+	protected function doGetChangeEntries( $start, $limit ) {
+		return array();
+	}
+
+	/**
+	 * @see FileJournal::purgeOldLogs()
+	 * @return Status
+	 */
+	protected function doPurgeOldLogs() {
+		return Status::newGood();
+	}
+}
diff --git a/includes/filebackend/lockmanager/DBLockManager.php b/includes/filebackend/lockmanager/DBLockManager.php
new file mode 100644
index 00000000..a8fe258b
--- /dev/null
+++ b/includes/filebackend/lockmanager/DBLockManager.php
@@ -0,0 +1,374 @@
+<?php
+/**
+ * Version of LockManager based on using DB table locks.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup LockManager
+ */
+
+/**
+ * Version of LockManager based on using DB table locks.
+ * This is meant for multi-wiki systems that may share files.
+ * All locks are blocking, so it might be useful to set a small
+ * lock-wait timeout via server config to curtail deadlocks.
+ *
+ * All lock requests for a resource, identified by a hash string, will map
+ * to one bucket. Each bucket maps to one or several peer DBs, each on their
+ * own server, all having the filelocks.sql tables (with row-level locking).
+ * A majority of peer DBs must agree for a lock to be acquired.
+ *
+ * Caching is used to avoid hitting servers that are down.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class DBLockManager extends QuorumLockManager {
+	/** @var Array Map of DB names to server config */
+	protected $dbServers; // (DB name => server config array)
+	/** @var BagOStuff */
+	protected $statusCache;
+
+	protected $lockExpiry; // integer number of seconds
+	protected $safeDelay; // integer number of seconds
+
+	protected $session = 0; // random integer
+	/** @var Array Map Database connections (DB name => Database) */
+	protected $conns = array();
+
+	/**
+	 * Construct a new instance from configuration.
+	 *
+	 * $config paramaters include:
+	 *   - dbServers   : Associative array of DB names to server configuration.
+	 *                   Configuration is an associative array that includes:
+	 *                     - host        : DB server name
+	 *                     - dbname      : DB name
+	 *                     - type        : DB type (mysql,postgres,...)
+	 *                     - user        : DB user
+	 *                     - password    : DB user password
+	 *                     - tablePrefix : DB table prefix
+	 *                     - flags       : DB flags (see DatabaseBase)
+	 *   - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
+	 *                   each having an odd-numbered list of DB names (peers) as values.
+	 *                   Any DB named 'localDBMaster' will automatically use the DB master
+	 *                   settings for this wiki (without the need for a dbServers entry).
+	 *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
+	 *                   This tells the DB server how long to wait before assuming
+	 *                   connection failure and releasing all the locks for a session.
+	 *
+	 * @param Array $config
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+
+		$this->dbServers = isset( $config['dbServers'] )
+			? $config['dbServers']
+			: array(); // likely just using 'localDBMaster'
+		// Sanitize srvsByBucket config to prevent PHP errors
+		$this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
+		$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
+
+		if ( isset( $config['lockExpiry'] ) ) {
+			$this->lockExpiry = $config['lockExpiry'];
+		} else {
+			$met = ini_get( 'max_execution_time' );
+			$this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
+		}
+		$this->safeDelay = ( $this->lockExpiry <= 0 )
+			? 60 // pick a safe-ish number to match DB timeout default
+			: $this->lockExpiry; // cover worst case
+
+		foreach ( $this->srvsByBucket as $bucket ) {
+			if ( count( $bucket ) > 1 ) { // multiple peers
+				// Tracks peers that couldn't be queried recently to avoid lengthy
+				// connection timeouts. This is useless if each bucket has one peer.
+				try {
+					$this->statusCache = ObjectCache::newAccelerator( array() );
+				} catch ( MWException $e ) {
+					trigger_error( __CLASS__ .
+						" using multiple DB peers without apc, xcache, or wincache." );
+				}
+				break;
+			}
+		}
+
+		$this->session = wfRandomString( 31 );
+	}
+
+	/**
+	 * Get a connection to a lock DB and acquire locks on $paths.
+	 * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
+	 *
+	 * @see QuorumLockManager::getLocksOnServer()
+	 * @return Status
+	 */
+	protected function getLocksOnServer( $lockSrv, array $paths, $type ) {
+		$status = Status::newGood();
+
+		if ( $type == self::LOCK_EX ) { // writer locks
+			try {
+				$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+				# Build up values for INSERT clause
+				$data = array();
+				foreach ( $keys as $key ) {
+					$data[] = array( 'fle_key' => $key );
+				}
+				# Wait on any existing writers and block new ones if we get in
+				$db = $this->getConnection( $lockSrv ); // checked in isServerUp()
+				$db->insert( 'filelocks_exclusive', $data, __METHOD__ );
+			} catch ( DBError $e ) {
+				foreach ( $paths as $path ) {
+					$status->fatal( 'lockmanager-fail-acquirelock', $path );
+				}
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::freeLocksOnServer()
+	 * @return Status
+	 */
+	protected function freeLocksOnServer( $lockSrv, array $paths, $type ) {
+		return Status::newGood(); // not supported
+	}
+
+	/**
+	 * @see QuorumLockManager::releaseAllLocks()
+	 * @return Status
+	 */
+	protected function releaseAllLocks() {
+		$status = Status::newGood();
+
+		foreach ( $this->conns as $lockDb => $db ) {
+			if ( $db->trxLevel() ) { // in transaction
+				try {
+					$db->rollback( __METHOD__ ); // finish transaction and kill any rows
+				} catch ( DBError $e ) {
+					$status->fatal( 'lockmanager-fail-db-release', $lockDb );
+				}
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::isServerUp()
+	 * @return bool
+	 */
+	protected function isServerUp( $lockSrv ) {
+		if ( !$this->cacheCheckFailures( $lockSrv ) ) {
+			return false; // recent failure to connect
+		}
+		try {
+			$this->getConnection( $lockSrv );
+		} catch ( DBError $e ) {
+			$this->cacheRecordFailure( $lockSrv );
+			return false; // failed to connect
+		}
+		return true;
+	}
+
+	/**
+	 * Get (or reuse) a connection to a lock DB
+	 *
+	 * @param $lockDb string
+	 * @return DatabaseBase
+	 * @throws DBError
+	 */
+	protected function getConnection( $lockDb ) {
+		if ( !isset( $this->conns[$lockDb] ) ) {
+			$db = null;
+			if ( $lockDb === 'localDBMaster' ) {
+				$lb = wfGetLBFactory()->newMainLB();
+				$db = $lb->getConnection( DB_MASTER );
+			} elseif ( isset( $this->dbServers[$lockDb] ) ) {
+				$config = $this->dbServers[$lockDb];
+				$db = DatabaseBase::factory( $config['type'], $config );
+			}
+			if ( !$db ) {
+				return null; // config error?
+			}
+			$this->conns[$lockDb] = $db;
+			$this->conns[$lockDb]->clearFlag( DBO_TRX );
+			# If the connection drops, try to avoid letting the DB rollback
+			# and release the locks before the file operations are finished.
+			# This won't handle the case of DB server restarts however.
+			$options = array();
+			if ( $this->lockExpiry > 0 ) {
+				$options['connTimeout'] = $this->lockExpiry;
+			}
+			$this->conns[$lockDb]->setSessionOptions( $options );
+			$this->initConnection( $lockDb, $this->conns[$lockDb] );
+		}
+		if ( !$this->conns[$lockDb]->trxLevel() ) {
+			$this->conns[$lockDb]->begin( __METHOD__ ); // start transaction
+		}
+		return $this->conns[$lockDb];
+	}
+
+	/**
+	 * Do additional initialization for new lock DB connection
+	 *
+	 * @param $lockDb string
+	 * @param $db DatabaseBase
+	 * @return void
+	 * @throws DBError
+	 */
+	protected function initConnection( $lockDb, DatabaseBase $db ) {}
+
+	/**
+	 * Checks if the DB has not recently had connection/query errors.
+	 * This just avoids wasting time on doomed connection attempts.
+	 *
+	 * @param $lockDb string
+	 * @return bool
+	 */
+	protected function cacheCheckFailures( $lockDb ) {
+		return ( $this->statusCache && $this->safeDelay > 0 )
+			? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
+			: true;
+	}
+
+	/**
+	 * Log a lock request failure to the cache
+	 *
+	 * @param $lockDb string
+	 * @return bool Success
+	 */
+	protected function cacheRecordFailure( $lockDb ) {
+		return ( $this->statusCache && $this->safeDelay > 0 )
+			? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
+			: true;
+	}
+
+	/**
+	 * Get a cache key for recent query misses for a DB
+	 *
+	 * @param $lockDb string
+	 * @return string
+	 */
+	protected function getMissKey( $lockDb ) {
+		$lockDb = ( $lockDb === 'localDBMaster' ) ? wfWikiID() : $lockDb; // non-relative
+		return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
+	}
+
+	/**
+	 * Make sure remaining locks get cleared for sanity
+	 */
+	function __destruct() {
+		foreach ( $this->conns as $db ) {
+			if ( $db->trxLevel() ) { // in transaction
+				try {
+					$db->rollback( __METHOD__ ); // finish transaction and kill any rows
+				} catch ( DBError $e ) {
+					// oh well
+				}
+			}
+			$db->close();
+		}
+	}
+}
+
+/**
+ * MySQL version of DBLockManager that supports shared locks.
+ * All locks are non-blocking, which avoids deadlocks.
+ *
+ * @ingroup LockManager
+ */
+class MySqlLockManager extends DBLockManager {
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_SH,
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	/**
+	 * @param $lockDb string
+	 * @param $db DatabaseBase
+	 */
+	protected function initConnection( $lockDb, DatabaseBase $db ) {
+		# Let this transaction see lock rows from other transactions
+		$db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
+	}
+
+	/**
+	 * Get a connection to a lock DB and acquire locks on $paths.
+	 * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
+	 *
+	 * @see DBLockManager::getLocksOnServer()
+	 * @return Status
+	 */
+	protected function getLocksOnServer( $lockSrv, array $paths, $type ) {
+		$status = Status::newGood();
+
+		$db = $this->getConnection( $lockSrv ); // checked in isServerUp()
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		# Build up values for INSERT clause
+		$data = array();
+		foreach ( $keys as $key ) {
+			$data[] = array( 'fls_key' => $key, 'fls_session' => $this->session );
+		}
+		# Block new writers...
+		$db->insert( 'filelocks_shared', $data, __METHOD__, array( 'IGNORE' ) );
+		# Actually do the locking queries...
+		if ( $type == self::LOCK_SH ) { // reader locks
+			# Bail if there are any existing writers...
+			$blocked = $db->selectField( 'filelocks_exclusive', '1',
+				array( 'fle_key' => $keys ),
+				__METHOD__
+			);
+			# Prospective writers that haven't yet updated filelocks_exclusive
+			# will recheck filelocks_shared after doing so and bail due to our entry.
+		} else { // writer locks
+			$encSession = $db->addQuotes( $this->session );
+			# Bail if there are any existing writers...
+			# The may detect readers, but the safe check for them is below.
+			# Note: if two writers come at the same time, both bail :)
+			$blocked = $db->selectField( 'filelocks_shared', '1',
+				array( 'fls_key' => $keys, "fls_session != $encSession" ),
+				__METHOD__
+			);
+			if ( !$blocked ) {
+				# Build up values for INSERT clause
+				$data = array();
+				foreach ( $keys as $key ) {
+					$data[] = array( 'fle_key' => $key );
+				}
+				# Block new readers/writers...
+				$db->insert( 'filelocks_exclusive', $data, __METHOD__ );
+				# Bail if there are any existing readers...
+				$blocked = $db->selectField( 'filelocks_shared', '1',
+					array( 'fls_key' => $keys, "fls_session != $encSession" ),
+					__METHOD__
+				);
+			}
+		}
+
+		if ( $blocked ) {
+			foreach ( $paths as $path ) {
+				$status->fatal( 'lockmanager-fail-acquirelock', $path );
+			}
+		}
+
+		return $status;
+	}
+}
diff --git a/includes/filebackend/lockmanager/FSLockManager.php b/includes/filebackend/lockmanager/FSLockManager.php
new file mode 100644
index 00000000..9a6206fd
--- /dev/null
+++ b/includes/filebackend/lockmanager/FSLockManager.php
@@ -0,0 +1,255 @@
+<?php
+/**
+ * Simple version of LockManager based on using FS lock files.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup LockManager
+ */
+
+/**
+ * Simple version of LockManager based on using FS lock files.
+ * All locks are non-blocking, which avoids deadlocks.
+ *
+ * This should work fine for small sites running off one server.
+ * Do not use this with 'lockDirectory' set to an NFS mount unless the
+ * NFS client is at least version 2.6.12. Otherwise, the BSD flock()
+ * locks will be ignored; see http://nfs.sourceforge.net/#section_d.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class FSLockManager extends LockManager {
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_SH,
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	protected $lockDir; // global dir for all servers
+
+	/** @var Array Map of (locked key => lock type => lock file handle) */
+	protected $handles = array();
+
+	/**
+	 * Construct a new instance from configuration.
+	 *
+	 * $config includes:
+	 *   - lockDirectory : Directory containing the lock files
+	 *
+	 * @param array $config
+	 */
+	function __construct( array $config ) {
+		parent::__construct( $config );
+
+		$this->lockDir = $config['lockDirectory'];
+	}
+
+	/**
+	 * @see LockManager::doLock()
+	 * @param $paths array
+	 * @param $type int
+	 * @return Status
+	 */
+	protected function doLock( array $paths, $type ) {
+		$status = Status::newGood();
+
+		$lockedPaths = array(); // files locked in this attempt
+		foreach ( $paths as $path ) {
+			$status->merge( $this->doSingleLock( $path, $type ) );
+			if ( $status->isOK() ) {
+				$lockedPaths[] = $path;
+			} else {
+				// Abort and unlock everything
+				$status->merge( $this->doUnlock( $lockedPaths, $type ) );
+				return $status;
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see LockManager::doUnlock()
+	 * @param $paths array
+	 * @param $type int
+	 * @return Status
+	 */
+	protected function doUnlock( array $paths, $type ) {
+		$status = Status::newGood();
+
+		foreach ( $paths as $path ) {
+			$status->merge( $this->doSingleUnlock( $path, $type ) );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Lock a single resource key
+	 *
+	 * @param $path string
+	 * @param $type integer
+	 * @return Status
+	 */
+	protected function doSingleLock( $path, $type ) {
+		$status = Status::newGood();
+
+		if ( isset( $this->locksHeld[$path][$type] ) ) {
+			++$this->locksHeld[$path][$type];
+		} elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
+			$this->locksHeld[$path][$type] = 1;
+		} else {
+			wfSuppressWarnings();
+			$handle = fopen( $this->getLockPath( $path ), 'a+' );
+			wfRestoreWarnings();
+			if ( !$handle ) { // lock dir missing?
+				wfMkdirParents( $this->lockDir );
+				$handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
+			}
+			if ( $handle ) {
+				// Either a shared or exclusive lock
+				$lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
+				if ( flock( $handle, $lock | LOCK_NB ) ) {
+					// Record this lock as active
+					$this->locksHeld[$path][$type] = 1;
+					$this->handles[$path][$type] = $handle;
+				} else {
+					fclose( $handle );
+					$status->fatal( 'lockmanager-fail-acquirelock', $path );
+				}
+			} else {
+				$status->fatal( 'lockmanager-fail-openlock', $path );
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Unlock a single resource key
+	 *
+	 * @param $path string
+	 * @param $type integer
+	 * @return Status
+	 */
+	protected function doSingleUnlock( $path, $type ) {
+		$status = Status::newGood();
+
+		if ( !isset( $this->locksHeld[$path] ) ) {
+			$status->warning( 'lockmanager-notlocked', $path );
+		} elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
+			$status->warning( 'lockmanager-notlocked', $path );
+		} else {
+			$handlesToClose = array();
+			--$this->locksHeld[$path][$type];
+			if ( $this->locksHeld[$path][$type] <= 0 ) {
+				unset( $this->locksHeld[$path][$type] );
+				// If a LOCK_SH comes in while we have a LOCK_EX, we don't
+				// actually add a handler, so check for handler existence.
+				if ( isset( $this->handles[$path][$type] ) ) {
+					if ( $type === self::LOCK_EX
+						&& isset( $this->locksHeld[$path][self::LOCK_SH] )
+						&& !isset( $this->handles[$path][self::LOCK_SH] ) )
+					{
+						// EX lock came first: move this handle to the SH one
+						$this->handles[$path][self::LOCK_SH] = $this->handles[$path][$type];
+					} else {
+						// Mark this handle to be unlocked and closed
+						$handlesToClose[] = $this->handles[$path][$type];
+					}
+					unset( $this->handles[$path][$type] );
+				}
+			}
+			if ( !count( $this->locksHeld[$path] ) ) {
+				unset( $this->locksHeld[$path] ); // no locks on this path
+			}
+			// Unlock handles to release locks and delete
+			// any lock files that end up with no locks on them...
+			if ( wfIsWindows() ) {
+				// Windows: for any process, including this one,
+				// calling unlink() on a locked file will fail
+				$status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
+				$status->merge( $this->pruneKeyLockFiles( $path ) );
+			} else {
+				// Unix: unlink() can be used on files currently open by this
+				// process and we must do so in order to avoid race conditions
+				$status->merge( $this->pruneKeyLockFiles( $path ) );
+				$status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @param $path string
+	 * @param $handlesToClose array
+	 * @return Status
+	 */
+	private function closeLockHandles( $path, array $handlesToClose ) {
+		$status = Status::newGood();
+		foreach ( $handlesToClose as $handle ) {
+			if ( !flock( $handle, LOCK_UN ) ) {
+				$status->fatal( 'lockmanager-fail-releaselock', $path );
+			}
+			if ( !fclose( $handle ) ) {
+				$status->warning( 'lockmanager-fail-closelock', $path );
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * @param $path string
+	 * @return Status
+	 */
+	private function pruneKeyLockFiles( $path ) {
+		$status = Status::newGood();
+		if ( !isset( $this->locksHeld[$path] ) ) {
+			# No locks are held for the lock file anymore
+			if ( !unlink( $this->getLockPath( $path ) ) ) {
+				$status->warning( 'lockmanager-fail-deletelock', $path );
+			}
+			unset( $this->handles[$path] );
+		}
+		return $status;
+	}
+
+	/**
+	 * Get the path to the lock file for a key
+	 * @param $path string
+	 * @return string
+	 */
+	protected function getLockPath( $path ) {
+		$hash = self::sha1Base36( $path );
+		return "{$this->lockDir}/{$hash}.lock";
+	}
+
+	/**
+	 * Make sure remaining locks get cleared for sanity
+	 */
+	function __destruct() {
+		while ( count( $this->locksHeld ) ) {
+			foreach ( $this->locksHeld as $path => $locks ) {
+				$this->doSingleUnlock( $path, self::LOCK_EX );
+				$this->doSingleUnlock( $path, self::LOCK_SH );
+			}
+		}
+	}
+}
diff --git a/includes/filebackend/lockmanager/LSLockManager.php b/includes/filebackend/lockmanager/LSLockManager.php
new file mode 100644
index 00000000..89428182
--- /dev/null
+++ b/includes/filebackend/lockmanager/LSLockManager.php
@@ -0,0 +1,218 @@
+<?php
+/**
+ * Version of LockManager based on using lock daemon servers.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup LockManager
+ */
+
+/**
+ * Manage locks using a lock daemon server.
+ *
+ * Version of LockManager based on using lock daemon servers.
+ * This is meant for multi-wiki systems that may share files.
+ * All locks are non-blocking, which avoids deadlocks.
+ *
+ * All lock requests for a resource, identified by a hash string, will map
+ * to one bucket. Each bucket maps to one or several peer servers, each
+ * running LockServerDaemon.php, listening on a designated TCP port.
+ * A majority of peers must agree for a lock to be acquired.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class LSLockManager extends QuorumLockManager {
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_SH,
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	/** @var Array Map of server names to server config */
+	protected $lockServers; // (server name => server config array)
+
+	/** @var Array Map Server connections (server name => resource) */
+	protected $conns = array();
+
+	protected $connTimeout; // float number of seconds
+	protected $session = ''; // random SHA-1 string
+
+	/**
+	 * Construct a new instance from configuration.
+	 *
+	 * $config paramaters include:
+	 *   - lockServers  : Associative array of server names to configuration.
+	 *                    Configuration is an associative array that includes:
+	 *                      - host    : IP address/hostname
+	 *                      - port    : TCP port
+	 *                      - authKey : Secret string the lock server uses
+	 *   - srvsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
+	 *                    each having an odd-numbered list of server names (peers) as values.
+	 *   - connTimeout  : Lock server connection attempt timeout. [optional]
+	 *
+	 * @param Array $config
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+
+		$this->lockServers = $config['lockServers'];
+		// Sanitize srvsByBucket config to prevent PHP errors
+		$this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
+		$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
+
+		if ( isset( $config['connTimeout'] ) ) {
+			$this->connTimeout = $config['connTimeout'];
+		} else {
+			$this->connTimeout = 3; // use some sane amount
+		}
+
+		$this->session = wfRandomString( 32 ); // 128 bits
+	}
+
+	/**
+	 * @see QuorumLockManager::getLocksOnServer()
+	 * @return Status
+	 */
+	protected function getLocksOnServer( $lockSrv, array $paths, $type ) {
+		$status = Status::newGood();
+
+		// Send out the command and get the response...
+		$type = ( $type == self::LOCK_SH ) ? 'SH' : 'EX';
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		$response = $this->sendCommand( $lockSrv, 'ACQUIRE', $type, $keys );
+
+		if ( $response !== 'ACQUIRED' ) {
+			foreach ( $paths as $path ) {
+				$status->fatal( 'lockmanager-fail-acquirelock', $path );
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::freeLocksOnServer()
+	 * @return Status
+	 */
+	protected function freeLocksOnServer( $lockSrv, array $paths, $type ) {
+		$status = Status::newGood();
+
+		// Send out the command and get the response...
+		$type = ( $type == self::LOCK_SH ) ? 'SH' : 'EX';
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		$response = $this->sendCommand( $lockSrv, 'RELEASE', $type, $keys );
+
+		if ( $response !== 'RELEASED' ) {
+			foreach ( $paths as $path ) {
+				$status->fatal( 'lockmanager-fail-releaselock', $path );
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::releaseAllLocks()
+	 * @return Status
+	 */
+	protected function releaseAllLocks() {
+		$status = Status::newGood();
+
+		foreach ( $this->conns as $lockSrv => $conn ) {
+			$response = $this->sendCommand( $lockSrv, 'RELEASE_ALL', '', array() );
+			if ( $response !== 'RELEASED_ALL' ) {
+				$status->fatal( 'lockmanager-fail-svr-release', $lockSrv );
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::isServerUp()
+	 * @return bool
+	 */
+	protected function isServerUp( $lockSrv ) {
+		return (bool)$this->getConnection( $lockSrv );
+	}
+
+	/**
+	 * Send a command and get back the response
+	 *
+	 * @param $lockSrv string
+	 * @param $action string
+	 * @param $type string
+	 * @param $values Array
+	 * @return string|bool
+	 */
+	protected function sendCommand( $lockSrv, $action, $type, $values ) {
+		$conn = $this->getConnection( $lockSrv );
+		if ( !$conn ) {
+			return false; // no connection
+		}
+		$authKey = $this->lockServers[$lockSrv]['authKey'];
+		// Build of the command as a flat string...
+		$values = implode( '|', $values );
+		$key = sha1( $this->session . $action . $type . $values . $authKey );
+		// Send out the command...
+		if ( fwrite( $conn, "{$this->session}:$key:$action:$type:$values\n" ) === false ) {
+			return false;
+		}
+		// Get the response...
+		$response = fgets( $conn );
+		if ( $response === false ) {
+			return false;
+		}
+		return trim( $response );
+	}
+
+	/**
+	 * Get (or reuse) a connection to a lock server
+	 *
+	 * @param $lockSrv string
+	 * @return resource
+	 */
+	protected function getConnection( $lockSrv ) {
+		if ( !isset( $this->conns[$lockSrv] ) ) {
+			$cfg = $this->lockServers[$lockSrv];
+			wfSuppressWarnings();
+			$errno = $errstr = '';
+			$conn = fsockopen( $cfg['host'], $cfg['port'], $errno, $errstr, $this->connTimeout );
+			wfRestoreWarnings();
+			if ( $conn === false ) {
+				return null;
+			}
+			$sec = floor( $this->connTimeout );
+			$usec = floor( ( $this->connTimeout - floor( $this->connTimeout ) ) * 1e6 );
+			stream_set_timeout( $conn, $sec, $usec );
+			$this->conns[$lockSrv] = $conn;
+		}
+		return $this->conns[$lockSrv];
+	}
+
+	/**
+	 * Make sure remaining locks get cleared for sanity
+	 */
+	function __destruct() {
+		$this->releaseAllLocks();
+		foreach ( $this->conns as $conn ) {
+			fclose( $conn );
+		}
+	}
+}
diff --git a/includes/filebackend/lockmanager/LockManager.php b/includes/filebackend/lockmanager/LockManager.php
new file mode 100644
index 00000000..07853f87
--- /dev/null
+++ b/includes/filebackend/lockmanager/LockManager.php
@@ -0,0 +1,425 @@
+<?php
+/**
+ * @defgroup LockManager Lock management
+ * @ingroup FileBackend
+ */
+
+/**
+ * Resource locking handling.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup LockManager
+ * @author Aaron Schulz
+ */
+
+/**
+ * @brief Class for handling resource locking.
+ *
+ * Locks on resource keys can either be shared or exclusive.
+ *
+ * Implementations must keep track of what is locked by this proccess
+ * in-memory and support nested locking calls (using reference counting).
+ * At least LOCK_UW and LOCK_EX must be implemented. LOCK_SH can be a no-op.
+ * Locks should either be non-blocking or have low wait timeouts.
+ *
+ * Subclasses should avoid throwing exceptions at all costs.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+abstract class LockManager {
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_EX, // subclasses may use self::LOCK_SH
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	/** @var Array Map of (resource path => lock type => count) */
+	protected $locksHeld = array();
+
+	/* Lock types; stronger locks have higher values */
+	const LOCK_SH = 1; // shared lock (for reads)
+	const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
+	const LOCK_EX = 3; // exclusive lock (for writes)
+
+	/**
+	 * Construct a new instance from configuration
+	 *
+	 * @param $config Array
+	 */
+	public function __construct( array $config ) {}
+
+	/**
+	 * Lock the resources at the given abstract paths
+	 *
+	 * @param $paths Array List of resource names
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return Status
+	 */
+	final public function lock( array $paths, $type = self::LOCK_EX ) {
+		wfProfileIn( __METHOD__ );
+		$status = $this->doLock( array_unique( $paths ), $this->lockTypeMap[$type] );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * Unlock the resources at the given abstract paths
+	 *
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return Status
+	 */
+	final public function unlock( array $paths, $type = self::LOCK_EX ) {
+		wfProfileIn( __METHOD__ );
+		$status = $this->doUnlock( array_unique( $paths ), $this->lockTypeMap[$type] );
+		wfProfileOut( __METHOD__ );
+		return $status;
+	}
+
+	/**
+	 * Get the base 36 SHA-1 of a string, padded to 31 digits
+	 *
+	 * @param $path string
+	 * @return string
+	 */
+	final protected static function sha1Base36( $path ) {
+		return wfBaseConvert( sha1( $path ), 16, 36, 31 );
+	}
+
+	/**
+	 * Lock resources with the given keys and lock type
+	 *
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return string
+	 */
+	abstract protected function doLock( array $paths, $type );
+
+	/**
+	 * Unlock resources with the given keys and lock type
+	 *
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return string
+	 */
+	abstract protected function doUnlock( array $paths, $type );
+}
+
+/**
+ * Self-releasing locks
+ *
+ * LockManager helper class to handle scoped locks, which
+ * release when an object is destroyed or goes out of scope.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class ScopedLock {
+	/** @var LockManager */
+	protected $manager;
+	/** @var Status */
+	protected $status;
+	/** @var Array List of resource paths*/
+	protected $paths;
+
+	protected $type; // integer lock type
+
+	/**
+	 * @param $manager LockManager
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @param $status Status
+	 */
+	protected function __construct(
+		LockManager $manager, array $paths, $type, Status $status
+	) {
+		$this->manager = $manager;
+		$this->paths = $paths;
+		$this->status = $status;
+		$this->type = $type;
+	}
+
+	/**
+	 * Get a ScopedLock object representing a lock on resource paths.
+	 * Any locks are released once this object goes out of scope.
+	 * The status object is updated with any errors or warnings.
+	 *
+	 * @param $manager LockManager
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @param $status Status
+	 * @return ScopedLock|null Returns null on failure
+	 */
+	public static function factory(
+		LockManager $manager, array $paths, $type, Status $status
+	) {
+		$lockStatus = $manager->lock( $paths, $type );
+		$status->merge( $lockStatus );
+		if ( $lockStatus->isOK() ) {
+			return new self( $manager, $paths, $type, $status );
+		}
+		return null;
+	}
+
+	function __destruct() {
+		$wasOk = $this->status->isOK();
+		$this->status->merge( $this->manager->unlock( $this->paths, $this->type ) );
+		if ( $wasOk ) {
+			// Make sure status is OK, despite any unlockFiles() fatals
+			$this->status->setResult( true, $this->status->value );
+		}
+	}
+}
+
+/**
+ * Version of LockManager that uses a quorum from peer servers for locks.
+ * The resource space can also be sharded into separate peer groups.
+ *
+ * @ingroup LockManager
+ * @since 1.20
+ */
+abstract class QuorumLockManager extends LockManager {
+	/** @var Array Map of bucket indexes to peer server lists */
+	protected $srvsByBucket = array(); // (bucket index => (lsrv1, lsrv2, ...))
+
+	/**
+	 * @see LockManager::doLock()
+	 * @param $paths array
+	 * @param $type int
+	 * @return Status
+	 */
+	final protected function doLock( array $paths, $type ) {
+		$status = Status::newGood();
+
+		$pathsToLock = array(); // (bucket => paths)
+		// Get locks that need to be acquired (buckets => locks)...
+		foreach ( $paths as $path ) {
+			if ( isset( $this->locksHeld[$path][$type] ) ) {
+				++$this->locksHeld[$path][$type];
+			} elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
+				$this->locksHeld[$path][$type] = 1;
+			} else {
+				$bucket = $this->getBucketFromKey( $path );
+				$pathsToLock[$bucket][] = $path;
+			}
+		}
+
+		$lockedPaths = array(); // files locked in this attempt
+		// Attempt to acquire these locks...
+		foreach ( $pathsToLock as $bucket => $paths ) {
+			// Try to acquire the locks for this bucket
+			$status->merge( $this->doLockingRequestBucket( $bucket, $paths, $type ) );
+			if ( !$status->isOK() ) {
+				$status->merge( $this->doUnlock( $lockedPaths, $type ) );
+				return $status;
+			}
+			// Record these locks as active
+			foreach ( $paths as $path ) {
+				$this->locksHeld[$path][$type] = 1; // locked
+			}
+			// Keep track of what locks were made in this attempt
+			$lockedPaths = array_merge( $lockedPaths, $paths );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * @see LockManager::doUnlock()
+	 * @param $paths array
+	 * @param $type int
+	 * @return Status
+	 */
+	final protected function doUnlock( array $paths, $type ) {
+		$status = Status::newGood();
+
+		$pathsToUnlock = array();
+		foreach ( $paths as $path ) {
+			if ( !isset( $this->locksHeld[$path][$type] ) ) {
+				$status->warning( 'lockmanager-notlocked', $path );
+			} else {
+				--$this->locksHeld[$path][$type];
+				// Reference count the locks held and release locks when zero
+				if ( $this->locksHeld[$path][$type] <= 0 ) {
+					unset( $this->locksHeld[$path][$type] );
+					$bucket = $this->getBucketFromKey( $path );
+					$pathsToUnlock[$bucket][] = $path;
+				}
+				if ( !count( $this->locksHeld[$path] ) ) {
+					unset( $this->locksHeld[$path] ); // no SH or EX locks left for key
+				}
+			}
+		}
+
+		// Remove these specific locks if possible, or at least release
+		// all locks once this process is currently not holding any locks.
+		foreach ( $pathsToUnlock as $bucket => $paths ) {
+			$status->merge( $this->doUnlockingRequestBucket( $bucket, $paths, $type ) );
+		}
+		if ( !count( $this->locksHeld ) ) {
+			$status->merge( $this->releaseAllLocks() );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Attempt to acquire locks with the peers for a bucket.
+	 * This is all or nothing; if any key is locked then this totally fails.
+	 *
+	 * @param $bucket integer
+	 * @param $paths Array List of resource keys to lock
+	 * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
+	 * @return Status
+	 */
+	final protected function doLockingRequestBucket( $bucket, array $paths, $type ) {
+		$status = Status::newGood();
+
+		$yesVotes = 0; // locks made on trustable servers
+		$votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
+		$quorum = floor( $votesLeft/2 + 1 ); // simple majority
+		// Get votes for each peer, in order, until we have enough...
+		foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
+			if ( !$this->isServerUp( $lockSrv ) ) {
+				--$votesLeft;
+				$status->warning( 'lockmanager-fail-svr-acquire', $lockSrv );
+				continue; // server down?
+			}
+			// Attempt to acquire the lock on this peer
+			$status->merge( $this->getLocksOnServer( $lockSrv, $paths, $type ) );
+			if ( !$status->isOK() ) {
+				return $status; // vetoed; resource locked
+			}
+			++$yesVotes; // success for this peer
+			if ( $yesVotes >= $quorum ) {
+				return $status; // lock obtained
+			}
+			--$votesLeft;
+			$votesNeeded = $quorum - $yesVotes;
+			if ( $votesNeeded > $votesLeft ) {
+				break; // short-circuit
+			}
+		}
+		// At this point, we must not have met the quorum
+		$status->setResult( false );
+
+		return $status;
+	}
+
+	/**
+	 * Attempt to release locks with the peers for a bucket
+	 *
+	 * @param $bucket integer
+	 * @param $paths Array List of resource keys to lock
+	 * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
+	 * @return Status
+	 */
+	final protected function doUnlockingRequestBucket( $bucket, array $paths, $type ) {
+		$status = Status::newGood();
+
+		foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
+			if ( !$this->isServerUp( $lockSrv ) ) {
+				$status->fatal( 'lockmanager-fail-svr-release', $lockSrv );
+			// Attempt to release the lock on this peer
+			} else {
+				$status->merge( $this->freeLocksOnServer( $lockSrv, $paths, $type ) );
+			}
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Get the bucket for resource path.
+	 * This should avoid throwing any exceptions.
+	 *
+	 * @param $path string
+	 * @return integer
+	 */
+	protected function getBucketFromKey( $path ) {
+		$prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
+		return (int)base_convert( $prefix, 16, 10 ) % count( $this->srvsByBucket );
+	}
+
+	/**
+	 * Check if a lock server is up
+	 *
+	 * @param $lockSrv string
+	 * @return bool
+	 */
+	abstract protected function isServerUp( $lockSrv );
+
+	/**
+	 * Get a connection to a lock server and acquire locks on $paths
+	 *
+	 * @param $lockSrv string
+	 * @param $paths array
+	 * @param $type integer
+	 * @return Status
+	 */
+	abstract protected function getLocksOnServer( $lockSrv, array $paths, $type );
+
+	/**
+	 * Get a connection to a lock server and release locks on $paths.
+	 *
+	 * Subclasses must effectively implement this or releaseAllLocks().
+	 *
+	 * @param $lockSrv string
+	 * @param $paths array
+	 * @param $type integer
+	 * @return Status
+	 */
+	abstract protected function freeLocksOnServer( $lockSrv, array $paths, $type );
+
+	/**
+	 * Release all locks that this session is holding.
+	 *
+	 * Subclasses must effectively implement this or freeLocksOnServer().
+	 *
+	 * @return Status
+	 */
+	abstract protected function releaseAllLocks();
+}
+
+/**
+ * Simple version of LockManager that does nothing
+ * @since 1.19
+ */
+class NullLockManager extends LockManager {
+	/**
+	 * @see LockManager::doLock()
+	 * @param $paths array
+	 * @param $type int
+	 * @return Status
+	 */
+	protected function doLock( array $paths, $type ) {
+		return Status::newGood();
+	}
+
+	/**
+	 * @see LockManager::doUnlock()
+	 * @param $paths array
+	 * @param $type int
+	 * @return Status
+	 */
+	protected function doUnlock( array $paths, $type ) {
+		return Status::newGood();
+	}
+}
diff --git a/includes/filebackend/lockmanager/LockManagerGroup.php b/includes/filebackend/lockmanager/LockManagerGroup.php
new file mode 100644
index 00000000..8c8c940a
--- /dev/null
+++ b/includes/filebackend/lockmanager/LockManagerGroup.php
@@ -0,0 +1,143 @@
+<?php
+/**
+ * Lock manager registration handling.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup LockManager
+ */
+
+/**
+ * Class to handle file lock manager registration
+ *
+ * @ingroup LockManager
+ * @author Aaron Schulz
+ * @since 1.19
+ */
+class LockManagerGroup {
+	/**
+	 * @var LockManagerGroup
+	 */
+	protected static $instance = null;
+
+	/** @var Array of (name => ('class' =>, 'config' =>, 'instance' =>)) */
+	protected $managers = array();
+
+	protected function __construct() {}
+
+	/**
+	 * @return LockManagerGroup
+	 */
+	public static function singleton() {
+		if ( self::$instance == null ) {
+			self::$instance = new self();
+			self::$instance->initFromGlobals();
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Destroy the singleton instance, so that a new one will be created next
+	 * time singleton() is called.
+	 */
+	public static function destroySingleton() {
+		self::$instance = null;
+	}
+
+	/**
+	 * Register lock managers from the global variables
+	 *
+	 * @return void
+	 */
+	protected function initFromGlobals() {
+		global $wgLockManagers;
+
+		$this->register( $wgLockManagers );
+	}
+
+	/**
+	 * Register an array of file lock manager configurations
+	 *
+	 * @param $configs Array
+	 * @return void
+	 * @throws MWException
+	 */
+	protected function register( array $configs ) {
+		foreach ( $configs as $config ) {
+			if ( !isset( $config['name'] ) ) {
+				throw new MWException( "Cannot register a lock manager with no name." );
+			}
+			$name = $config['name'];
+			if ( !isset( $config['class'] ) ) {
+				throw new MWException( "Cannot register lock manager `{$name}` with no class." );
+			}
+			$class = $config['class'];
+			unset( $config['class'] ); // lock manager won't need this
+			$this->managers[$name] = array(
+				'class'    => $class,
+				'config'   => $config,
+				'instance' => null
+			);
+		}
+	}
+
+	/**
+	 * Get the lock manager object with a given name
+	 *
+	 * @param $name string
+	 * @return LockManager
+	 * @throws MWException
+	 */
+	public function get( $name ) {
+		if ( !isset( $this->managers[$name] ) ) {
+			throw new MWException( "No lock manager defined with the name `$name`." );
+		}
+		// Lazy-load the actual lock manager instance
+		if ( !isset( $this->managers[$name]['instance'] ) ) {
+			$class = $this->managers[$name]['class'];
+			$config = $this->managers[$name]['config'];
+			$this->managers[$name]['instance'] = new $class( $config );
+		}
+		return $this->managers[$name]['instance'];
+	}
+
+	/**
+	 * Get the default lock manager configured for the site.
+	 * Returns NullLockManager if no lock manager could be found.
+	 *
+	 * @return LockManager
+	 */
+	public function getDefault() {
+		return isset( $this->managers['default'] )
+			? $this->get( 'default' )
+			: new NullLockManager( array() );
+	}
+
+	/**
+	 * Get the default lock manager configured for the site
+	 * or at least some other effective configured lock manager.
+	 * Throws an exception if no lock manager could be found.
+	 *
+	 * @return LockManager
+	 * @throws MWException
+	 */
+	public function getAny() {
+		return isset( $this->managers['default'] )
+			? $this->get( 'default' )
+			: $this->get( 'fsLockManager' );
+	}
+}
diff --git a/includes/filebackend/lockmanager/MemcLockManager.php b/includes/filebackend/lockmanager/MemcLockManager.php
new file mode 100644
index 00000000..57c0463d
--- /dev/null
+++ b/includes/filebackend/lockmanager/MemcLockManager.php
@@ -0,0 +1,319 @@
+<?php
+/**
+ * Version of LockManager based on using memcached servers.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup LockManager
+ */
+
+/**
+ * Manage locks using memcached servers.
+ *
+ * Version of LockManager based on using memcached servers.
+ * This is meant for multi-wiki systems that may share files.
+ * All locks are non-blocking, which avoids deadlocks.
+ *
+ * All lock requests for a resource, identified by a hash string, will map
+ * to one bucket. Each bucket maps to one or several peer servers, each running memcached.
+ * A majority of peers must agree for a lock to be acquired.
+ *
+ * @ingroup LockManager
+ * @since 1.20
+ */
+class MemcLockManager extends QuorumLockManager {
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_SH,
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	/** @var Array Map server names to MemcachedBagOStuff objects */
+	protected $bagOStuffs = array();
+	/** @var Array */
+	protected $serversUp = array(); // (server name => bool)
+
+	protected $lockExpiry; // integer; maximum time locks can be held
+	protected $session = ''; // string; random SHA-1 UUID
+	protected $wikiId = ''; // string
+
+	/**
+	 * Construct a new instance from configuration.
+	 *
+	 * $config paramaters include:
+	 *   - lockServers  : Associative array of server names to "<IP>:<port>" strings.
+	 *   - srvsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
+	 *                    each having an odd-numbered list of server names (peers) as values.
+	 *   - memcConfig   : Configuration array for ObjectCache::newFromParams. [optional]
+	 *                    If set, this must use one of the memcached classes.
+	 *   - wikiId       : Wiki ID string that all resources are relative to. [optional]
+	 *
+	 * @param Array $config
+	 */
+	public function __construct( array $config ) {
+		parent::__construct( $config );
+
+		// Sanitize srvsByBucket config to prevent PHP errors
+		$this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
+		$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
+
+		$memcConfig = isset( $config['memcConfig'] )
+			? $config['memcConfig']
+			: array( 'class' => 'MemcachedPhpBagOStuff' );
+
+		foreach ( $config['lockServers'] as $name => $address ) {
+			$params = array( 'servers' => array( $address ) ) + $memcConfig;
+			$cache = ObjectCache::newFromParams( $params );
+			if ( $cache instanceof MemcachedBagOStuff ) {
+				$this->bagOStuffs[$name] = $cache;
+			} else {
+				throw new MWException(
+					'Only MemcachedBagOStuff classes are supported by MemcLockManager.' );
+			}
+		}
+
+		$this->wikiId = isset( $config['wikiId'] ) ? $config['wikiId'] : wfWikiID();
+
+		$met = ini_get( 'max_execution_time' ); // this is 0 in CLI mode
+		$this->lockExpiry = $met ? 2*(int)$met : 2*3600;
+
+		$this->session = wfRandomString( 32 );
+	}
+
+	/**
+	 * @see QuorumLockManager::getLocksOnServer()
+	 * @return Status
+	 */
+	protected function getLocksOnServer( $lockSrv, array $paths, $type ) {
+		$status = Status::newGood();
+
+		$memc = $this->getCache( $lockSrv );
+		$keys = array_map( array( $this, 'recordKeyForPath' ), $paths ); // lock records
+
+		// Lock all of the active lock record keys...
+		if ( !$this->acquireMutexes( $memc, $keys ) ) {
+			foreach ( $paths as $path ) {
+				$status->fatal( 'lockmanager-fail-acquirelock', $path );
+			}
+			return;
+		}
+
+		// Fetch all the existing lock records...
+		$lockRecords = $memc->getMulti( $keys );
+
+		$now = time();
+		// Check if the requested locks conflict with existing ones...
+		foreach ( $paths as $path ) {
+			$locksKey = $this->recordKeyForPath( $path );
+			$locksHeld = isset( $lockRecords[$locksKey] )
+				? $lockRecords[$locksKey]
+				: array( self::LOCK_SH => array(), self::LOCK_EX => array() ); // init
+			foreach ( $locksHeld[self::LOCK_EX] as $session => $expiry ) {
+				if ( $expiry < $now ) { // stale?
+					unset( $locksHeld[self::LOCK_EX][$session] );
+				} elseif ( $session !== $this->session ) {
+					$status->fatal( 'lockmanager-fail-acquirelock', $path );
+				}
+			}
+			if ( $type === self::LOCK_EX ) {
+				foreach ( $locksHeld[self::LOCK_SH] as $session => $expiry ) {
+					if ( $expiry < $now ) { // stale?
+						unset( $locksHeld[self::LOCK_SH][$session] );
+					} elseif ( $session !== $this->session ) {
+						$status->fatal( 'lockmanager-fail-acquirelock', $path );
+					}
+				}
+			}
+			if ( $status->isOK() ) {
+				// Register the session in the lock record array
+				$locksHeld[$type][$this->session] = $now + $this->lockExpiry;
+				// We will update this record if none of the other locks conflict
+				$lockRecords[$locksKey] = $locksHeld;
+			}
+		}
+
+		// If there were no lock conflicts, update all the lock records...
+		if ( $status->isOK() ) {
+			foreach ( $lockRecords as $locksKey => $locksHeld ) {
+				$memc->set( $locksKey, $locksHeld );
+				wfDebug( __METHOD__ . ": acquired lock on key $locksKey.\n" );
+			}
+		}
+
+		// Unlock all of the active lock record keys...
+		$this->releaseMutexes( $memc, $keys );
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::freeLocksOnServer()
+	 * @return Status
+	 */
+	protected function freeLocksOnServer( $lockSrv, array $paths, $type ) {
+		$status = Status::newGood();
+
+		$memc = $this->getCache( $lockSrv );
+		$keys = array_map( array( $this, 'recordKeyForPath' ), $paths ); // lock records
+
+		// Lock all of the active lock record keys...
+		if ( !$this->acquireMutexes( $memc, $keys ) ) {
+			foreach ( $paths as $path ) {
+				$status->fatal( 'lockmanager-fail-releaselock', $path );
+			}
+			return;
+		}
+
+		// Fetch all the existing lock records...
+		$lockRecords = $memc->getMulti( $keys );
+
+		// Remove the requested locks from all records...
+		foreach ( $paths as $path ) {
+			$locksKey = $this->recordKeyForPath( $path ); // lock record
+			if ( !isset( $lockRecords[$locksKey] ) ) {
+				continue; // nothing to do
+			}
+			$locksHeld = $lockRecords[$locksKey];
+			if ( is_array( $locksHeld ) && isset( $locksHeld[$type] ) ) {
+				unset( $locksHeld[$type][$this->session] );
+				$ok = $memc->set( $locksKey, $locksHeld );
+			} else {
+				$ok = true;
+			}
+			if ( !$ok ) {
+				$status->fatal( 'lockmanager-fail-releaselock', $path );
+			}
+			wfDebug( __METHOD__ . ": released lock on key $locksKey.\n" );
+		}
+
+		// Unlock all of the active lock record keys...
+		$this->releaseMutexes( $memc, $keys );
+
+		return $status;
+	}
+
+	/**
+	 * @see QuorumLockManager::releaseAllLocks()
+	 * @return Status
+	 */
+	protected function releaseAllLocks() {
+		return Status::newGood(); // not supported
+	}
+
+	/**
+	 * @see QuorumLockManager::isServerUp()
+	 * @return bool
+	 */
+	protected function isServerUp( $lockSrv ) {
+		return (bool)$this->getCache( $lockSrv );
+	}
+
+	/**
+	 * Get the MemcachedBagOStuff object for a $lockSrv
+	 *
+	 * @param $lockSrv string Server name
+	 * @return MemcachedBagOStuff|null
+	 */
+	protected function getCache( $lockSrv ) {
+		$memc = null;
+		if ( isset( $this->bagOStuffs[$lockSrv] ) ) {
+			$memc = $this->bagOStuffs[$lockSrv];
+			if ( !isset( $this->serversUp[$lockSrv] ) ) {
+				$this->serversUp[$lockSrv] = $memc->set( 'MemcLockManager:ping', 1, 1 );
+				if ( !$this->serversUp[$lockSrv] ) {
+					trigger_error( __METHOD__ . ": Could not contact $lockSrv.", E_USER_WARNING );
+				}
+			}
+			if ( !$this->serversUp[$lockSrv] ) {
+				return null; // server appears to be down
+			}
+		}
+		return $memc;
+	}
+
+	/**
+	 * @param $path string
+	 * @return string
+	 */
+	protected function recordKeyForPath( $path ) {
+		$hash = LockManager::sha1Base36( $path );
+		list( $db, $prefix ) = wfSplitWikiID( $this->wikiId );
+		return wfForeignMemcKey( $db, $prefix, __CLASS__, 'locks', $hash );
+	}
+
+	/**
+	 * @param $memc MemcachedBagOStuff
+	 * @param $keys Array List of keys to acquire
+	 * @return bool
+	 */
+	protected function acquireMutexes( MemcachedBagOStuff $memc, array $keys ) {
+		$lockedKeys = array();
+
+		// Acquire the keys in lexicographical order, to avoid deadlock problems.
+		// If P1 is waiting to acquire a key P2 has, P2 can't also be waiting for a key P1 has.
+		sort( $keys );
+
+		// Try to quickly loop to acquire the keys, but back off after a few rounds.
+		// This reduces memcached spam, especially in the rare case where a server acquires
+		// some lock keys and dies without releasing them. Lock keys expire after a few minutes.
+		$rounds = 0;
+		$start = microtime( true );
+		do {
+			if ( ( ++$rounds % 4 ) == 0 ) {
+				usleep( 1000*50 ); // 50 ms
+			}
+			foreach ( array_diff( $keys, $lockedKeys ) as $key ) {
+				if ( $memc->add( "$key:mutex", 1, 180 ) ) { // lock record
+					$lockedKeys[] = $key;
+				} else {
+					continue; // acquire in order
+				}
+			}
+		} while ( count( $lockedKeys ) < count( $keys ) && ( microtime( true ) - $start ) <= 6 );
+
+		if ( count( $lockedKeys ) != count( $keys ) ) {
+			$this->releaseMutexes( $lockedKeys ); // failed; release what was locked
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * @param $memc MemcachedBagOStuff
+	 * @param $keys Array List of acquired keys
+	 * @return void
+	 */
+	protected function releaseMutexes( MemcachedBagOStuff $memc, array $keys ) {
+		foreach ( $keys as $key ) {
+			$memc->delete( "$key:mutex" );
+		}
+	}
+
+	/**
+	 * Make sure remaining locks get cleared for sanity
+	 */
+	function __destruct() {
+		while ( count( $this->locksHeld ) ) {
+			foreach ( $this->locksHeld as $path => $locks ) {
+				$this->doUnlock( array( $path ), self::LOCK_EX );
+				$this->doUnlock( array( $path ), self::LOCK_SH );
+			}
+		}
+	}
+}