Initial import

1 files changed, 2860 insertions, 0 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
new file mode 100644
index 000000000..b072e1747
--- /dev/null
+++ b/fs/btrfs/file.c
@@ -0,0 +1,2860 @@
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/time.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/backing-dev.h>
+#include <linux/mpage.h>
+#include <linux/falloc.h>
+#include <linux/swap.h>
+#include <linux/writeback.h>
+#include <linux/statfs.h>
+#include <linux/compat.h>
+#include <linux/slab.h>
+#include <linux/btrfs.h>
+#include <linux/uio.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "btrfs_inode.h"
+#include "print-tree.h"
+#include "tree-log.h"
+#include "locking.h"
+#include "volumes.h"
+#include "qgroup.h"
+
+static struct kmem_cache *btrfs_inode_defrag_cachep;
+/*
+ * when auto defrag is enabled we
+ * queue up these defrag structs to remember which
+ * inodes need defragging passes
+ */
+struct inode_defrag {
+	struct rb_node rb_node;
+	/* objectid */
+	u64 ino;
+	/*
+	 * transid where the defrag was added, we search for
+	 * extents newer than this
+	 */
+	u64 transid;
+
+	/* root objectid */
+	u64 root;
+
+	/* last offset we were able to defrag */
+	u64 last_offset;
+
+	/* if we've wrapped around back to zero once already */
+	int cycled;
+};
+
+static int __compare_inode_defrag(struct inode_defrag *defrag1,
+				  struct inode_defrag *defrag2)
+{
+	if (defrag1->root > defrag2->root)
+		return 1;
+	else if (defrag1->root < defrag2->root)
+		return -1;
+	else if (defrag1->ino > defrag2->ino)
+		return 1;
+	else if (defrag1->ino < defrag2->ino)
+		return -1;
+	else
+		return 0;
+}
+
+/* pop a record for an inode into the defrag tree.  The lock
+ * must be held already
+ *
+ * If you're inserting a record for an older transid than an
+ * existing record, the transid already in the tree is lowered
+ *
+ * If an existing record is found the defrag item you
+ * pass in is freed
+ */
+static int __btrfs_add_inode_defrag(struct inode *inode,
+				    struct inode_defrag *defrag)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct inode_defrag *entry;
+	struct rb_node **p;
+	struct rb_node *parent = NULL;
+	int ret;
+
+	p = &root->fs_info->defrag_inodes.rb_node;
+	while (*p) {
+		parent = *p;
+		entry = rb_entry(parent, struct inode_defrag, rb_node);
+
+		ret = __compare_inode_defrag(defrag, entry);
+		if (ret < 0)
+			p = &parent->rb_left;
+		else if (ret > 0)
+			p = &parent->rb_right;
+		else {
+			/* if we're reinserting an entry for
+			 * an old defrag run, make sure to
+			 * lower the transid of our existing record
+			 */
+			if (defrag->transid < entry->transid)
+				entry->transid = defrag->transid;
+			if (defrag->last_offset > entry->last_offset)
+				entry->last_offset = defrag->last_offset;
+			return -EEXIST;
+		}
+	}
+	set_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
+	rb_link_node(&defrag->rb_node, parent, p);
+	rb_insert_color(&defrag->rb_node, &root->fs_info->defrag_inodes);
+	return 0;
+}
+
+static inline int __need_auto_defrag(struct btrfs_root *root)
+{
+	if (!btrfs_test_opt(root, AUTO_DEFRAG))
+		return 0;
+
+	if (btrfs_fs_closing(root->fs_info))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * insert a defrag record for this inode if auto defrag is
+ * enabled
+ */
+int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
+			   struct inode *inode)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct inode_defrag *defrag;
+	u64 transid;
+	int ret;
+
+	if (!__need_auto_defrag(root))
+		return 0;
+
+	if (test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags))
+		return 0;
+
+	if (trans)
+		transid = trans->transid;
+	else
+		transid = BTRFS_I(inode)->root->last_trans;
+
+	defrag = kmem_cache_zalloc(btrfs_inode_defrag_cachep, GFP_NOFS);
+	if (!defrag)
+		return -ENOMEM;
+
+	defrag->ino = btrfs_ino(inode);
+	defrag->transid = transid;
+	defrag->root = root->root_key.objectid;
+
+	spin_lock(&root->fs_info->defrag_inodes_lock);
+	if (!test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags)) {
+		/*
+		 * If we set IN_DEFRAG flag and evict the inode from memory,
+		 * and then re-read this inode, this new inode doesn't have
+		 * IN_DEFRAG flag. At the case, we may find the existed defrag.
+		 */
+		ret = __btrfs_add_inode_defrag(inode, defrag);
+		if (ret)
+			kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	} else {
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	}
+	spin_unlock(&root->fs_info->defrag_inodes_lock);
+	return 0;
+}
+
+/*
+ * Requeue the defrag object. If there is a defrag object that points to
+ * the same inode in the tree, we will merge them together (by
+ * __btrfs_add_inode_defrag()) and free the one that we want to requeue.
+ */
+static void btrfs_requeue_inode_defrag(struct inode *inode,
+				       struct inode_defrag *defrag)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+
+	if (!__need_auto_defrag(root))
+		goto out;
+
+	/*
+	 * Here we don't check the IN_DEFRAG flag, because we need merge
+	 * them together.
+	 */
+	spin_lock(&root->fs_info->defrag_inodes_lock);
+	ret = __btrfs_add_inode_defrag(inode, defrag);
+	spin_unlock(&root->fs_info->defrag_inodes_lock);
+	if (ret)
+		goto out;
+	return;
+out:
+	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+}
+
+/*
+ * pick the defragable inode that we want, if it doesn't exist, we will get
+ * the next one.
+ */
+static struct inode_defrag *
+btrfs_pick_defrag_inode(struct btrfs_fs_info *fs_info, u64 root, u64 ino)
+{
+	struct inode_defrag *entry = NULL;
+	struct inode_defrag tmp;
+	struct rb_node *p;
+	struct rb_node *parent = NULL;
+	int ret;
+
+	tmp.ino = ino;
+	tmp.root = root;
+
+	spin_lock(&fs_info->defrag_inodes_lock);
+	p = fs_info->defrag_inodes.rb_node;
+	while (p) {
+		parent = p;
+		entry = rb_entry(parent, struct inode_defrag, rb_node);
+
+		ret = __compare_inode_defrag(&tmp, entry);
+		if (ret < 0)
+			p = parent->rb_left;
+		else if (ret > 0)
+			p = parent->rb_right;
+		else
+			goto out;
+	}
+
+	if (parent && __compare_inode_defrag(&tmp, entry) > 0) {
+		parent = rb_next(parent);
+		if (parent)
+			entry = rb_entry(parent, struct inode_defrag, rb_node);
+		else
+			entry = NULL;
+	}
+out:
+	if (entry)
+		rb_erase(parent, &fs_info->defrag_inodes);
+	spin_unlock(&fs_info->defrag_inodes_lock);
+	return entry;
+}
+
+void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info)
+{
+	struct inode_defrag *defrag;
+	struct rb_node *node;
+
+	spin_lock(&fs_info->defrag_inodes_lock);
+	node = rb_first(&fs_info->defrag_inodes);
+	while (node) {
+		rb_erase(node, &fs_info->defrag_inodes);
+		defrag = rb_entry(node, struct inode_defrag, rb_node);
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+
+		cond_resched_lock(&fs_info->defrag_inodes_lock);
+
+		node = rb_first(&fs_info->defrag_inodes);
+	}
+	spin_unlock(&fs_info->defrag_inodes_lock);
+}
+
+#define BTRFS_DEFRAG_BATCH	1024
+
+static int __btrfs_run_defrag_inode(struct btrfs_fs_info *fs_info,
+				    struct inode_defrag *defrag)
+{
+	struct btrfs_root *inode_root;
+	struct inode *inode;
+	struct btrfs_key key;
+	struct btrfs_ioctl_defrag_range_args range;
+	int num_defrag;
+	int index;
+	int ret;
+
+	/* get the inode */
+	key.objectid = defrag->root;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = (u64)-1;
+
+	index = srcu_read_lock(&fs_info->subvol_srcu);
+
+	inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
+	if (IS_ERR(inode_root)) {
+		ret = PTR_ERR(inode_root);
+		goto cleanup;
+	}
+
+	key.objectid = defrag->ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+	inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
+	if (IS_ERR(inode)) {
+		ret = PTR_ERR(inode);
+		goto cleanup;
+	}
+	srcu_read_unlock(&fs_info->subvol_srcu, index);
+
+	/* do a chunk of defrag */
+	clear_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
+	memset(&range, 0, sizeof(range));
+	range.len = (u64)-1;
+	range.start = defrag->last_offset;
+
+	sb_start_write(fs_info->sb);
+	num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
+				       BTRFS_DEFRAG_BATCH);
+	sb_end_write(fs_info->sb);
+	/*
+	 * if we filled the whole defrag batch, there
+	 * must be more work to do.  Queue this defrag
+	 * again
+	 */
+	if (num_defrag == BTRFS_DEFRAG_BATCH) {
+		defrag->last_offset = range.start;
+		btrfs_requeue_inode_defrag(inode, defrag);
+	} else if (defrag->last_offset && !defrag->cycled) {
+		/*
+		 * we didn't fill our defrag batch, but
+		 * we didn't start at zero.  Make sure we loop
+		 * around to the start of the file.
+		 */
+		defrag->last_offset = 0;
+		defrag->cycled = 1;
+		btrfs_requeue_inode_defrag(inode, defrag);
+	} else {
+		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	}
+
+	iput(inode);
+	return 0;
+cleanup:
+	srcu_read_unlock(&fs_info->subvol_srcu, index);
+	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
+	return ret;
+}
+
+/*
+ * run through the list of inodes in the FS that need
+ * defragging
+ */
+int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
+{
+	struct inode_defrag *defrag;
+	u64 first_ino = 0;
+	u64 root_objectid = 0;
+
+	atomic_inc(&fs_info->defrag_running);
+	while (1) {
+		/* Pause the auto defragger. */
+		if (test_bit(BTRFS_FS_STATE_REMOUNTING,
+			     &fs_info->fs_state))
+			break;
+
+		if (!__need_auto_defrag(fs_info->tree_root))
+			break;
+
+		/* find an inode to defrag */
+		defrag = btrfs_pick_defrag_inode(fs_info, root_objectid,
+						 first_ino);
+		if (!defrag) {
+			if (root_objectid || first_ino) {
+				root_objectid = 0;
+				first_ino = 0;
+				continue;
+			} else {
+				break;
+			}
+		}
+
+		first_ino = defrag->ino + 1;
+		root_objectid = defrag->root;
+
+		__btrfs_run_defrag_inode(fs_info, defrag);
+	}
+	atomic_dec(&fs_info->defrag_running);
+
+	/*
+	 * during unmount, we use the transaction_wait queue to
+	 * wait for the defragger to stop
+	 */
+	wake_up(&fs_info->transaction_wait);
+	return 0;
+}
+
+/* simple helper to fault in pages and copy.  This should go away
+ * and be replaced with calls into generic code.
+ */
+static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
+					 size_t write_bytes,
+					 struct page **prepared_pages,
+					 struct iov_iter *i)
+{
+	size_t copied = 0;
+	size_t total_copied = 0;
+	int pg = 0;
+	int offset = pos & (PAGE_CACHE_SIZE - 1);
+
+	while (write_bytes > 0) {
+		size_t count = min_t(size_t,
+				     PAGE_CACHE_SIZE - offset, write_bytes);
+		struct page *page = prepared_pages[pg];
+		/*
+		 * Copy data from userspace to the current page
+		 */
+		copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
+
+		/* Flush processor's dcache for this page */
+		flush_dcache_page(page);
+
+		/*
+		 * if we get a partial write, we can end up with
+		 * partially up to date pages.  These add
+		 * a lot of complexity, so make sure they don't
+		 * happen by forcing this copy to be retried.
+		 *
+		 * The rest of the btrfs_file_write code will fall
+		 * back to page at a time copies after we return 0.
+		 */
+		if (!PageUptodate(page) && copied < count)
+			copied = 0;
+
+		iov_iter_advance(i, copied);
+		write_bytes -= copied;
+		total_copied += copied;
+
+		/* Return to btrfs_file_write_iter to fault page */
+		if (unlikely(copied == 0))
+			break;
+
+		if (copied < PAGE_CACHE_SIZE - offset) {
+			offset += copied;
+		} else {
+			pg++;
+			offset = 0;
+		}
+	}
+	return total_copied;
+}
+
+/*
+ * unlocks pages after btrfs_file_write is done with them
+ */
+static void btrfs_drop_pages(struct page **pages, size_t num_pages)
+{
+	size_t i;
+	for (i = 0; i < num_pages; i++) {
+		/* page checked is some magic around finding pages that
+		 * have been modified without going through btrfs_set_page_dirty
+		 * clear it here. There should be no need to mark the pages
+		 * accessed as prepare_pages should have marked them accessed
+		 * in prepare_pages via find_or_create_page()
+		 */
+		ClearPageChecked(pages[i]);
+		unlock_page(pages[i]);
+		page_cache_release(pages[i]);
+	}
+}
+
+/*
+ * after copy_from_user, pages need to be dirtied and we need to make
+ * sure holes are created between the current EOF and the start of
+ * any next extents (if required).
+ *
+ * this also makes the decision about creating an inline extent vs
+ * doing real data extents, marking pages dirty and delalloc as required.
+ */
+int btrfs_dirty_pages(struct btrfs_root *root, struct inode *inode,
+			     struct page **pages, size_t num_pages,
+			     loff_t pos, size_t write_bytes,
+			     struct extent_state **cached)
+{
+	int err = 0;
+	int i;
+	u64 num_bytes;
+	u64 start_pos;
+	u64 end_of_last_block;
+	u64 end_pos = pos + write_bytes;
+	loff_t isize = i_size_read(inode);
+
+	start_pos = pos & ~((u64)root->sectorsize - 1);
+	num_bytes = ALIGN(write_bytes + pos - start_pos, root->sectorsize);
+
+	end_of_last_block = start_pos + num_bytes - 1;
+	err = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block,
+					cached);
+	if (err)
+		return err;
+
+	for (i = 0; i < num_pages; i++) {
+		struct page *p = pages[i];
+		SetPageUptodate(p);
+		ClearPageChecked(p);
+		set_page_dirty(p);
+	}
+
+	/*
+	 * we've only changed i_size in ram, and we haven't updated
+	 * the disk i_size.  There is no need to log the inode
+	 * at this time.
+	 */
+	if (end_pos > isize)
+		i_size_write(inode, end_pos);
+	return 0;
+}
+
+/*
+ * this drops all the extents in the cache that intersect the range
+ * [start, end].  Existing extents are split as required.
+ */
+void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
+			     int skip_pinned)
+{
+	struct extent_map *em;
+	struct extent_map *split = NULL;
+	struct extent_map *split2 = NULL;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	u64 len = end - start + 1;
+	u64 gen;
+	int ret;
+	int testend = 1;
+	unsigned long flags;
+	int compressed = 0;
+	bool modified;
+
+	WARN_ON(end < start);
+	if (end == (u64)-1) {
+		len = (u64)-1;
+		testend = 0;
+	}
+	while (1) {
+		int no_splits = 0;
+
+		modified = false;
+		if (!split)
+			split = alloc_extent_map();
+		if (!split2)
+			split2 = alloc_extent_map();
+		if (!split || !split2)
+			no_splits = 1;
+
+		write_lock(&em_tree->lock);
+		em = lookup_extent_mapping(em_tree, start, len);
+		if (!em) {
+			write_unlock(&em_tree->lock);
+			break;
+		}
+		flags = em->flags;
+		gen = em->generation;
+		if (skip_pinned && test_bit(EXTENT_FLAG_PINNED, &em->flags)) {
+			if (testend && em->start + em->len >= start + len) {
+				free_extent_map(em);
+				write_unlock(&em_tree->lock);
+				break;
+			}
+			start = em->start + em->len;
+			if (testend)
+				len = start + len - (em->start + em->len);
+			free_extent_map(em);
+			write_unlock(&em_tree->lock);
+			continue;
+		}
+		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
+		clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+		clear_bit(EXTENT_FLAG_LOGGING, &flags);
+		modified = !list_empty(&em->list);
+		if (no_splits)
+			goto next;
+
+		if (em->start < start) {
+			split->start = em->start;
+			split->len = start - em->start;
+
+			if (em->block_start < EXTENT_MAP_LAST_BYTE) {
+				split->orig_start = em->orig_start;
+				split->block_start = em->block_start;
+
+				if (compressed)
+					split->block_len = em->block_len;
+				else
+					split->block_len = split->len;
+				split->orig_block_len = max(split->block_len,
+						em->orig_block_len);
+				split->ram_bytes = em->ram_bytes;
+			} else {
+				split->orig_start = split->start;
+				split->block_len = 0;
+				split->block_start = em->block_start;
+				split->orig_block_len = 0;
+				split->ram_bytes = split->len;
+			}
+
+			split->generation = gen;
+			split->bdev = em->bdev;
+			split->flags = flags;
+			split->compress_type = em->compress_type;
+			replace_extent_mapping(em_tree, em, split, modified);
+			free_extent_map(split);
+			split = split2;
+			split2 = NULL;
+		}
+		if (testend && em->start + em->len > start + len) {
+			u64 diff = start + len - em->start;
+
+			split->start = start + len;
+			split->len = em->start + em->len - (start + len);
+			split->bdev = em->bdev;
+			split->flags = flags;
+			split->compress_type = em->compress_type;
+			split->generation = gen;
+
+			if (em->block_start < EXTENT_MAP_LAST_BYTE) {
+				split->orig_block_len = max(em->block_len,
+						    em->orig_block_len);
+
+				split->ram_bytes = em->ram_bytes;
+				if (compressed) {
+					split->block_len = em->block_len;
+					split->block_start = em->block_start;
+					split->orig_start = em->orig_start;
+				} else {
+					split->block_len = split->len;
+					split->block_start = em->block_start
+						+ diff;
+					split->orig_start = em->orig_start;
+				}
+			} else {
+				split->ram_bytes = split->len;
+				split->orig_start = split->start;
+				split->block_len = 0;
+				split->block_start = em->block_start;
+				split->orig_block_len = 0;
+			}
+
+			if (extent_map_in_tree(em)) {
+				replace_extent_mapping(em_tree, em, split,
+						       modified);
+			} else {
+				ret = add_extent_mapping(em_tree, split,
+							 modified);
+				ASSERT(ret == 0); /* Logic error */
+			}
+			free_extent_map(split);
+			split = NULL;
+		}
+next:
+		if (extent_map_in_tree(em))
+			remove_extent_mapping(em_tree, em);
+		write_unlock(&em_tree->lock);
+
+		/* once for us */
+		free_extent_map(em);
+		/* once for the tree*/
+		free_extent_map(em);
+	}
+	if (split)
+		free_extent_map(split);
+	if (split2)
+		free_extent_map(split2);
+}
+
+/*
+ * this is very complex, but the basic idea is to drop all extents
+ * in the range start - end.  hint_block is filled in with a block number
+ * that would be a good hint to the block allocator for this file.
+ *
+ * If an extent intersects the range but is not entirely inside the range
+ * it is either truncated or split.  Anything entirely inside the range
+ * is deleted from the tree.
+ */
+int __btrfs_drop_extents(struct btrfs_trans_handle *trans,
+			 struct btrfs_root *root, struct inode *inode,
+			 struct btrfs_path *path, u64 start, u64 end,
+			 u64 *drop_end, int drop_cache,
+			 int replace_extent,
+			 u32 extent_item_size,
+			 int *key_inserted)
+{
+	struct extent_buffer *leaf;
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_key key;
+	struct btrfs_key new_key;
+	u64 ino = btrfs_ino(inode);
+	u64 search_start = start;
+	u64 disk_bytenr = 0;
+	u64 num_bytes = 0;
+	u64 extent_offset = 0;
+	u64 extent_end = 0;
+	int del_nr = 0;
+	int del_slot = 0;
+	int extent_type;
+	int recow;
+	int ret;
+	int modify_tree = -1;
+	int update_refs;
+	int found = 0;
+	int leafs_visited = 0;
+
+	if (drop_cache)
+		btrfs_drop_extent_cache(inode, start, end - 1, 0);
+
+	if (start >= BTRFS_I(inode)->disk_i_size && !replace_extent)
+		modify_tree = 0;
+
+	update_refs = (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
+		       root == root->fs_info->tree_root);
+	while (1) {
+		recow = 0;
+		ret = btrfs_lookup_file_extent(trans, root, path, ino,
+					       search_start, modify_tree);
+		if (ret < 0)
+			break;
+		if (ret > 0 && path->slots[0] > 0 && search_start == start) {
+			leaf = path->nodes[0];
+			btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
+			if (key.objectid == ino &&
+			    key.type == BTRFS_EXTENT_DATA_KEY)
+				path->slots[0]--;
+		}
+		ret = 0;
+		leafs_visited++;
+next_slot:
+		leaf = path->nodes[0];
+		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+			BUG_ON(del_nr > 0);
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				break;
+			if (ret > 0) {
+				ret = 0;
+				break;
+			}
+			leafs_visited++;
+			leaf = path->nodes[0];
+			recow = 1;
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+		if (key.objectid > ino ||
+		    key.type > BTRFS_EXTENT_DATA_KEY || key.offset >= end)
+			break;
+
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+		extent_type = btrfs_file_extent_type(leaf, fi);
+
+		if (extent_type == BTRFS_FILE_EXTENT_REG ||
+		    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
+			disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+			num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
+			extent_offset = btrfs_file_extent_offset(leaf, fi);
+			extent_end = key.offset +
+				btrfs_file_extent_num_bytes(leaf, fi);
+		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+			extent_end = key.offset +
+				btrfs_file_extent_inline_len(leaf,
+						     path->slots[0], fi);
+		} else {
+			WARN_ON(1);
+			extent_end = search_start;
+		}
+
+		/*
+		 * Don't skip extent items representing 0 byte lengths. They
+		 * used to be created (bug) if while punching holes we hit
+		 * -ENOSPC condition. So if we find one here, just ensure we
+		 * delete it, otherwise we would insert a new file extent item
+		 * with the same key (offset) as that 0 bytes length file
+		 * extent item in the call to setup_items_for_insert() later
+		 * in this function.
+		 */
+		if (extent_end == key.offset && extent_end >= search_start)
+			goto delete_extent_item;
+
+		if (extent_end <= search_start) {
+			path->slots[0]++;
+			goto next_slot;
+		}
+
+		found = 1;
+		search_start = max(key.offset, start);
+		if (recow || !modify_tree) {
+			modify_tree = -1;
+			btrfs_release_path(path);
+			continue;
+		}
+
+		/*
+		 *     | - range to drop - |
+		 *  | -------- extent -------- |
+		 */
+		if (start > key.offset && end < extent_end) {
+			BUG_ON(del_nr > 0);
+			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+				ret = -EOPNOTSUPP;
+				break;
+			}
+
+			memcpy(&new_key, &key, sizeof(new_key));
+			new_key.offset = start;
+			ret = btrfs_duplicate_item(trans, root, path,
+						   &new_key);
+			if (ret == -EAGAIN) {
+				btrfs_release_path(path);
+				continue;
+			}
+			if (ret < 0)
+				break;
+
+			leaf = path->nodes[0];
+			fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
+					    struct btrfs_file_extent_item);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							start - key.offset);
+
+			fi = btrfs_item_ptr(leaf, path->slots[0],
+					    struct btrfs_file_extent_item);
+
+			extent_offset += start - key.offset;
+			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							extent_end - start);
+			btrfs_mark_buffer_dirty(leaf);
+
+			if (update_refs && disk_bytenr > 0) {
+				ret = btrfs_inc_extent_ref(trans, root,
+						disk_bytenr, num_bytes, 0,
+						root->root_key.objectid,
+						new_key.objectid,
+						start - extent_offset, 1);
+				BUG_ON(ret); /* -ENOMEM */
+			}
+			key.offset = start;
+		}
+		/*
+		 *  | ---- range to drop ----- |
+		 *      | -------- extent -------- |
+		 */
+		if (start <= key.offset && end < extent_end) {
+			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+				ret = -EOPNOTSUPP;
+				break;
+			}
+
+			memcpy(&new_key, &key, sizeof(new_key));
+			new_key.offset = end;
+			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
+
+			extent_offset += end - key.offset;
+			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							extent_end - end);
+			btrfs_mark_buffer_dirty(leaf);
+			if (update_refs && disk_bytenr > 0)
+				inode_sub_bytes(inode, end - key.offset);
+			break;
+		}
+
+		search_start = extent_end;
+		/*
+		 *       | ---- range to drop ----- |
+		 *  | -------- extent -------- |
+		 */
+		if (start > key.offset && end >= extent_end) {
+			BUG_ON(del_nr > 0);
+			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+				ret = -EOPNOTSUPP;
+				break;
+			}
+
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							start - key.offset);
+			btrfs_mark_buffer_dirty(leaf);
+			if (update_refs && disk_bytenr > 0)
+				inode_sub_bytes(inode, extent_end - start);
+			if (end == extent_end)
+				break;
+
+			path->slots[0]++;
+			goto next_slot;
+		}
+
+		/*
+		 *  | ---- range to drop ----- |
+		 *    | ------ extent ------ |
+		 */
+		if (start <= key.offset && end >= extent_end) {
+delete_extent_item:
+			if (del_nr == 0) {
+				del_slot = path->slots[0];
+				del_nr = 1;
+			} else {
+				BUG_ON(del_slot + del_nr != path->slots[0]);
+				del_nr++;
+			}
+
+			if (update_refs &&
+			    extent_type == BTRFS_FILE_EXTENT_INLINE) {
+				inode_sub_bytes(inode,
+						extent_end - key.offset);
+				extent_end = ALIGN(extent_end,
+						   root->sectorsize);
+			} else if (update_refs && disk_bytenr > 0) {
+				ret = btrfs_free_extent(trans, root,
+						disk_bytenr, num_bytes, 0,
+						root->root_key.objectid,
+						key.objectid, key.offset -
+						extent_offset, 0);
+				BUG_ON(ret); /* -ENOMEM */
+				inode_sub_bytes(inode,
+						extent_end - key.offset);
+			}
+
+			if (end == extent_end)
+				break;
+
+			if (path->slots[0] + 1 < btrfs_header_nritems(leaf)) {
+				path->slots[0]++;
+				goto next_slot;
+			}
+
+			ret = btrfs_del_items(trans, root, path, del_slot,
+					      del_nr);
+			if (ret) {
+				btrfs_abort_transaction(trans, root, ret);
+				break;
+			}
+
+			del_nr = 0;
+			del_slot = 0;
+
+			btrfs_release_path(path);
+			continue;
+		}
+
+		BUG_ON(1);
+	}
+
+	if (!ret && del_nr > 0) {
+		/*
+		 * Set path->slots[0] to first slot, so that after the delete
+		 * if items are move off from our leaf to its immediate left or
+		 * right neighbor leafs, we end up with a correct and adjusted
+		 * path->slots[0] for our insertion (if replace_extent != 0).
+		 */
+		path->slots[0] = del_slot;
+		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
+		if (ret)
+			btrfs_abort_transaction(trans, root, ret);
+	}
+
+	leaf = path->nodes[0];
+	/*
+	 * If btrfs_del_items() was called, it might have deleted a leaf, in
+	 * which case it unlocked our path, so check path->locks[0] matches a
+	 * write lock.
+	 */
+	if (!ret && replace_extent && leafs_visited == 1 &&
+	    (path->locks[0] == BTRFS_WRITE_LOCK_BLOCKING ||
+	     path->locks[0] == BTRFS_WRITE_LOCK) &&
+	    btrfs_leaf_free_space(root, leaf) >=
+	    sizeof(struct btrfs_item) + extent_item_size) {
+
+		key.objectid = ino;
+		key.type = BTRFS_EXTENT_DATA_KEY;
+		key.offset = start;
+		if (!del_nr && path->slots[0] < btrfs_header_nritems(leaf)) {
+			struct btrfs_key slot_key;
+
+			btrfs_item_key_to_cpu(leaf, &slot_key, path->slots[0]);
+			if (btrfs_comp_cpu_keys(&key, &slot_key) > 0)
+				path->slots[0]++;
+		}
+		setup_items_for_insert(root, path, &key,
+				       &extent_item_size,
+				       extent_item_size,
+				       sizeof(struct btrfs_item) +
+				       extent_item_size, 1);
+		*key_inserted = 1;
+	}
+
+	if (!replace_extent || !(*key_inserted))
+		btrfs_release_path(path);
+	if (drop_end)
+		*drop_end = found ? min(end, extent_end) : end;
+	return ret;
+}
+
+int btrfs_drop_extents(struct btrfs_trans_handle *trans,
+		       struct btrfs_root *root, struct inode *inode, u64 start,
+		       u64 end, int drop_cache)
+{
+	struct btrfs_path *path;
+	int ret;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+	ret = __btrfs_drop_extents(trans, root, inode, path, start, end, NULL,
+				   drop_cache, 0, 0, NULL);
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int extent_mergeable(struct extent_buffer *leaf, int slot,
+			    u64 objectid, u64 bytenr, u64 orig_offset,
+			    u64 *start, u64 *end)
+{
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_key key;
+	u64 extent_end;
+
+	if (slot < 0 || slot >= btrfs_header_nritems(leaf))
+		return 0;
+
+	btrfs_item_key_to_cpu(leaf, &key, slot);
+	if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
+		return 0;
+
+	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG ||
+	    btrfs_file_extent_disk_bytenr(leaf, fi) != bytenr ||
+	    btrfs_file_extent_offset(leaf, fi) != key.offset - orig_offset ||
+	    btrfs_file_extent_compression(leaf, fi) ||
+	    btrfs_file_extent_encryption(leaf, fi) ||
+	    btrfs_file_extent_other_encoding(leaf, fi))
+		return 0;
+
+	extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
+	if ((*start && *start != key.offset) || (*end && *end != extent_end))
+		return 0;
+
+	*start = key.offset;
+	*end = extent_end;
+	return 1;
+}
+
+/*
+ * Mark extent in the range start - end as written.
+ *
+ * This changes extent type from 'pre-allocated' to 'regular'. If only
+ * part of extent is marked as written, the extent will be split into
+ * two or three.
+ */
+int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
+			      struct inode *inode, u64 start, u64 end)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct extent_buffer *leaf;
+	struct btrfs_path *path;
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_key key;
+	struct btrfs_key new_key;
+	u64 bytenr;
+	u64 num_bytes;
+	u64 extent_end;
+	u64 orig_offset;
+	u64 other_start;
+	u64 other_end;
+	u64 split;
+	int del_nr = 0;
+	int del_slot = 0;
+	int recow;
+	int ret;
+	u64 ino = btrfs_ino(inode);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+again:
+	recow = 0;
+	split = start;
+	key.objectid = ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = split;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret < 0)
+		goto out;
+	if (ret > 0 && path->slots[0] > 0)
+		path->slots[0]--;
+
+	leaf = path->nodes[0];
+	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+	BUG_ON(key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY);
+	fi = btrfs_item_ptr(leaf, path->slots[0],
+			    struct btrfs_file_extent_item);
+	BUG_ON(btrfs_file_extent_type(leaf, fi) !=
+	       BTRFS_FILE_EXTENT_PREALLOC);
+	extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
+	BUG_ON(key.offset > start || extent_end < end);
+
+	bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+	num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
+	orig_offset = key.offset - btrfs_file_extent_offset(leaf, fi);
+	memcpy(&new_key, &key, sizeof(new_key));
+
+	if (start == key.offset && end < extent_end) {
+		other_start = 0;
+		other_end = start;
+		if (extent_mergeable(leaf, path->slots[0] - 1,
+				     ino, bytenr, orig_offset,
+				     &other_start, &other_end)) {
+			new_key.offset = end;
+			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
+			fi = btrfs_item_ptr(leaf, path->slots[0],
+					    struct btrfs_file_extent_item);
+			btrfs_set_file_extent_generation(leaf, fi,
+							 trans->transid);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							extent_end - end);
+			btrfs_set_file_extent_offset(leaf, fi,
+						     end - orig_offset);
+			fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
+					    struct btrfs_file_extent_item);
+			btrfs_set_file_extent_generation(leaf, fi,
+							 trans->transid);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							end - other_start);
+			btrfs_mark_buffer_dirty(leaf);
+			goto out;
+		}
+	}
+
+	if (start > key.offset && end == extent_end) {
+		other_start = end;
+		other_end = 0;
+		if (extent_mergeable(leaf, path->slots[0] + 1,
+				     ino, bytenr, orig_offset,
+				     &other_start, &other_end)) {
+			fi = btrfs_item_ptr(leaf, path->slots[0],
+					    struct btrfs_file_extent_item);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							start - key.offset);
+			btrfs_set_file_extent_generation(leaf, fi,
+							 trans->transid);
+			path->slots[0]++;
+			new_key.offset = start;
+			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
+
+			fi = btrfs_item_ptr(leaf, path->slots[0],
+					    struct btrfs_file_extent_item);
+			btrfs_set_file_extent_generation(leaf, fi,
+							 trans->transid);
+			btrfs_set_file_extent_num_bytes(leaf, fi,
+							other_end - start);
+			btrfs_set_file_extent_offset(leaf, fi,
+						     start - orig_offset);
+			btrfs_mark_buffer_dirty(leaf);
+			goto out;
+		}
+	}
+
+	while (start > key.offset || end < extent_end) {
+		if (key.offset == start)
+			split = end;
+
+		new_key.offset = split;
+		ret = btrfs_duplicate_item(trans, root, path, &new_key);
+		if (ret == -EAGAIN) {
+			btrfs_release_path(path);
+			goto again;
+		}
+		if (ret < 0) {
+			btrfs_abort_transaction(trans, root, ret);
+			goto out;
+		}
+
+		leaf = path->nodes[0];
+		fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
+				    struct btrfs_file_extent_item);
+		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
+		btrfs_set_file_extent_num_bytes(leaf, fi,
+						split - key.offset);
+
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+
+		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
+		btrfs_set_file_extent_offset(leaf, fi, split - orig_offset);
+		btrfs_set_file_extent_num_bytes(leaf, fi,
+						extent_end - split);
+		btrfs_mark_buffer_dirty(leaf);
+
+		ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0,
+					   root->root_key.objectid,
+					   ino, orig_offset, 1);
+		BUG_ON(ret); /* -ENOMEM */
+
+		if (split == start) {
+			key.offset = start;
+		} else {
+			BUG_ON(start != key.offset);
+			path->slots[0]--;
+			extent_end = end;
+		}
+		recow = 1;
+	}
+
+	other_start = end;
+	other_end = 0;
+	if (extent_mergeable(leaf, path->slots[0] + 1,
+			     ino, bytenr, orig_offset,
+			     &other_start, &other_end)) {
+		if (recow) {
+			btrfs_release_path(path);
+			goto again;
+		}
+		extent_end = other_end;
+		del_slot = path->slots[0] + 1;
+		del_nr++;
+		ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
+					0, root->root_key.objectid,
+					ino, orig_offset, 0);
+		BUG_ON(ret); /* -ENOMEM */
+	}
+	other_start = 0;
+	other_end = start;
+	if (extent_mergeable(leaf, path->slots[0] - 1,
+			     ino, bytenr, orig_offset,
+			     &other_start, &other_end)) {
+		if (recow) {
+			btrfs_release_path(path);
+			goto again;
+		}
+		key.offset = other_start;
+		del_slot = path->slots[0];
+		del_nr++;
+		ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
+					0, root->root_key.objectid,
+					ino, orig_offset, 0);
+		BUG_ON(ret); /* -ENOMEM */
+	}
+	if (del_nr == 0) {
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+			   struct btrfs_file_extent_item);
+		btrfs_set_file_extent_type(leaf, fi,
+					   BTRFS_FILE_EXTENT_REG);
+		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
+		btrfs_mark_buffer_dirty(leaf);
+	} else {
+		fi = btrfs_item_ptr(leaf, del_slot - 1,
+			   struct btrfs_file_extent_item);
+		btrfs_set_file_extent_type(leaf, fi,
+					   BTRFS_FILE_EXTENT_REG);
+		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
+		btrfs_set_file_extent_num_bytes(leaf, fi,
+						extent_end - key.offset);
+		btrfs_mark_buffer_dirty(leaf);
+
+		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
+		if (ret < 0) {
+			btrfs_abort_transaction(trans, root, ret);
+			goto out;
+		}
+	}
+out:
+	btrfs_free_path(path);
+	return 0;
+}
+
+/*
+ * on error we return an unlocked page and the error value
+ * on success we return a locked page and 0
+ */
+static int prepare_uptodate_page(struct page *page, u64 pos,
+				 bool force_uptodate)
+{
+	int ret = 0;
+
+	if (((pos & (PAGE_CACHE_SIZE - 1)) || force_uptodate) &&
+	    !PageUptodate(page)) {
+		ret = btrfs_readpage(NULL, page);
+		if (ret)
+			return ret;
+		lock_page(page);
+		if (!PageUptodate(page)) {
+			unlock_page(page);
+			return -EIO;
+		}
+	}
+	return 0;
+}
+
+/*
+ * this just gets pages into the page cache and locks them down.
+ */
+static noinline int prepare_pages(struct inode *inode, struct page **pages,
+				  size_t num_pages, loff_t pos,
+				  size_t write_bytes, bool force_uptodate)
+{
+	int i;
+	unsigned long index = pos >> PAGE_CACHE_SHIFT;
+	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
+	int err = 0;
+	int faili;
+
+	for (i = 0; i < num_pages; i++) {
+		pages[i] = find_or_create_page(inode->i_mapping, index + i,
+					       mask | __GFP_WRITE);
+		if (!pages[i]) {
+			faili = i - 1;
+			err = -ENOMEM;
+			goto fail;
+		}
+
+		if (i == 0)
+			err = prepare_uptodate_page(pages[i], pos,
+						    force_uptodate);
+		if (i == num_pages - 1)
+			err = prepare_uptodate_page(pages[i],
+						    pos + write_bytes, false);
+		if (err) {
+			page_cache_release(pages[i]);
+			faili = i - 1;
+			goto fail;
+		}
+		wait_on_page_writeback(pages[i]);
+	}
+
+	return 0;
+fail:
+	while (faili >= 0) {
+		unlock_page(pages[faili]);
+		page_cache_release(pages[faili]);
+		faili--;
+	}
+	return err;
+
+}
+
+/*
+ * This function locks the extent and properly waits for data=ordered extents
+ * to finish before allowing the pages to be modified if need.
+ *
+ * The return value:
+ * 1 - the extent is locked
+ * 0 - the extent is not locked, and everything is OK
+ * -EAGAIN - need re-prepare the pages
+ * the other < 0 number - Something wrong happens
+ */
+static noinline int
+lock_and_cleanup_extent_if_need(struct inode *inode, struct page **pages,
+				size_t num_pages, loff_t pos,
+				u64 *lockstart, u64 *lockend,
+				struct extent_state **cached_state)
+{
+	u64 start_pos;
+	u64 last_pos;
+	int i;
+	int ret = 0;
+
+	start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
+	last_pos = start_pos + ((u64)num_pages << PAGE_CACHE_SHIFT) - 1;
+
+	if (start_pos < inode->i_size) {
+		struct btrfs_ordered_extent *ordered;
+		lock_extent_bits(&BTRFS_I(inode)->io_tree,
+				 start_pos, last_pos, 0, cached_state);
+		ordered = btrfs_lookup_ordered_range(inode, start_pos,
+						     last_pos - start_pos + 1);
+		if (ordered &&
+		    ordered->file_offset + ordered->len > start_pos &&
+		    ordered->file_offset <= last_pos) {
+			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+					     start_pos, last_pos,
+					     cached_state, GFP_NOFS);
+			for (i = 0; i < num_pages; i++) {
+				unlock_page(pages[i]);
+				page_cache_release(pages[i]);
+			}
+			btrfs_start_ordered_extent(inode, ordered, 1);
+			btrfs_put_ordered_extent(ordered);
+			return -EAGAIN;
+		}
+		if (ordered)
+			btrfs_put_ordered_extent(ordered);
+
+		clear_extent_bit(&BTRFS_I(inode)->io_tree, start_pos,
+				  last_pos, EXTENT_DIRTY | EXTENT_DELALLOC |
+				  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
+				  0, 0, cached_state, GFP_NOFS);
+		*lockstart = start_pos;
+		*lockend = last_pos;
+		ret = 1;
+	}
+
+	for (i = 0; i < num_pages; i++) {
+		if (clear_page_dirty_for_io(pages[i]))
+			account_page_redirty(pages[i]);
+		set_page_extent_mapped(pages[i]);
+		WARN_ON(!PageLocked(pages[i]));
+	}
+
+	return ret;
+}
+
+static noinline int check_can_nocow(struct inode *inode, loff_t pos,
+				    size_t *write_bytes)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_ordered_extent *ordered;
+	u64 lockstart, lockend;
+	u64 num_bytes;
+	int ret;
+
+	ret = btrfs_start_write_no_snapshoting(root);
+	if (!ret)
+		return -ENOSPC;
+
+	lockstart = round_down(pos, root->sectorsize);
+	lockend = round_up(pos + *write_bytes, root->sectorsize) - 1;
+
+	while (1) {
+		lock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
+		ordered = btrfs_lookup_ordered_range(inode, lockstart,
+						     lockend - lockstart + 1);
+		if (!ordered) {
+			break;
+		}
+		unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
+		btrfs_start_ordered_extent(inode, ordered, 1);
+		btrfs_put_ordered_extent(ordered);
+	}
+
+	num_bytes = lockend - lockstart + 1;
+	ret = can_nocow_extent(inode, lockstart, &num_bytes, NULL, NULL, NULL);
+	if (ret <= 0) {
+		ret = 0;
+		btrfs_end_write_no_snapshoting(root);
+	} else {
+		*write_bytes = min_t(size_t, *write_bytes ,
+				     num_bytes - pos + lockstart);
+	}
+
+	unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
+
+	return ret;
+}
+
+static noinline ssize_t __btrfs_buffered_write(struct file *file,
+					       struct iov_iter *i,
+					       loff_t pos)
+{
+	struct inode *inode = file_inode(file);
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct page **pages = NULL;
+	struct extent_state *cached_state = NULL;
+	u64 release_bytes = 0;
+	u64 lockstart;
+	u64 lockend;
+	unsigned long first_index;
+	size_t num_written = 0;
+	int nrptrs;
+	int ret = 0;
+	bool only_release_metadata = false;
+	bool force_page_uptodate = false;
+	bool need_unlock;
+
+	nrptrs = min(DIV_ROUND_UP(iov_iter_count(i), PAGE_CACHE_SIZE),
+			PAGE_CACHE_SIZE / (sizeof(struct page *)));
+	nrptrs = min(nrptrs, current->nr_dirtied_pause - current->nr_dirtied);
+	nrptrs = max(nrptrs, 8);
+	pages = kmalloc_array(nrptrs, sizeof(struct page *), GFP_KERNEL);
+	if (!pages)
+		return -ENOMEM;
+
+	first_index = pos >> PAGE_CACHE_SHIFT;
+
+	while (iov_iter_count(i) > 0) {
+		size_t offset = pos & (PAGE_CACHE_SIZE - 1);
+		size_t write_bytes = min(iov_iter_count(i),
+					 nrptrs * (size_t)PAGE_CACHE_SIZE -
+					 offset);
+		size_t num_pages = DIV_ROUND_UP(write_bytes + offset,
+						PAGE_CACHE_SIZE);
+		size_t reserve_bytes;
+		size_t dirty_pages;
+		size_t copied;
+
+		WARN_ON(num_pages > nrptrs);
+
+		/*
+		 * Fault pages before locking them in prepare_pages
+		 * to avoid recursive lock
+		 */
+		if (unlikely(iov_iter_fault_in_readable(i, write_bytes))) {
+			ret = -EFAULT;
+			break;
+		}
+
+		reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
+		ret = btrfs_check_data_free_space(inode, reserve_bytes, write_bytes);
+		if (ret == -ENOSPC &&
+		    (BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
+					      BTRFS_INODE_PREALLOC))) {
+			ret = check_can_nocow(inode, pos, &write_bytes);
+			if (ret > 0) {
+				only_release_metadata = true;
+				/*
+				 * our prealloc extent may be smaller than
+				 * write_bytes, so scale down.
+				 */
+				num_pages = DIV_ROUND_UP(write_bytes + offset,
+							 PAGE_CACHE_SIZE);
+				reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
+				ret = 0;
+			} else {
+				ret = -ENOSPC;
+			}
+		}
+
+		if (ret)
+			break;
+
+		ret = btrfs_delalloc_reserve_metadata(inode, reserve_bytes);
+		if (ret) {
+			if (!only_release_metadata)
+				btrfs_free_reserved_data_space(inode,
+							       reserve_bytes);
+			else
+				btrfs_end_write_no_snapshoting(root);
+			break;
+		}
+
+		release_bytes = reserve_bytes;
+		need_unlock = false;
+again:
+		/*
+		 * This is going to setup the pages array with the number of
+		 * pages we want, so we don't really need to worry about the
+		 * contents of pages from loop to loop
+		 */
+		ret = prepare_pages(inode, pages, num_pages,
+				    pos, write_bytes,
+				    force_page_uptodate);
+		if (ret)
+			break;
+
+		ret = lock_and_cleanup_extent_if_need(inode, pages, num_pages,
+						      pos, &lockstart, &lockend,
+						      &cached_state);
+		if (ret < 0) {
+			if (ret == -EAGAIN)
+				goto again;
+			break;
+		} else if (ret > 0) {
+			need_unlock = true;
+			ret = 0;
+		}
+
+		copied = btrfs_copy_from_user(pos, num_pages,
+					   write_bytes, pages, i);
+
+		/*
+		 * if we have trouble faulting in the pages, fall
+		 * back to one page at a time
+		 */
+		if (copied < write_bytes)
+			nrptrs = 1;
+
+		if (copied == 0) {
+			force_page_uptodate = true;
+			dirty_pages = 0;
+		} else {
+			force_page_uptodate = false;
+			dirty_pages = DIV_ROUND_UP(copied + offset,
+						   PAGE_CACHE_SIZE);
+		}
+
+		/*
+		 * If we had a short copy we need to release the excess delaloc
+		 * bytes we reserved.  We need to increment outstanding_extents
+		 * because btrfs_delalloc_release_space will decrement it, but
+		 * we still have an outstanding extent for the chunk we actually
+		 * managed to copy.
+		 */
+		if (num_pages > dirty_pages) {
+			release_bytes = (num_pages - dirty_pages) <<
+				PAGE_CACHE_SHIFT;
+			if (copied > 0) {
+				spin_lock(&BTRFS_I(inode)->lock);
+				BTRFS_I(inode)->outstanding_extents++;
+				spin_unlock(&BTRFS_I(inode)->lock);
+			}
+			if (only_release_metadata)
+				btrfs_delalloc_release_metadata(inode,
+								release_bytes);
+			else
+				btrfs_delalloc_release_space(inode,
+							     release_bytes);
+		}
+
+		release_bytes = dirty_pages << PAGE_CACHE_SHIFT;
+
+		if (copied > 0)
+			ret = btrfs_dirty_pages(root, inode, pages,
+						dirty_pages, pos, copied,
+						NULL);
+		if (need_unlock)
+			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+					     lockstart, lockend, &cached_state,
+					     GFP_NOFS);
+		if (ret) {
+			btrfs_drop_pages(pages, num_pages);
+			break;
+		}
+
+		release_bytes = 0;
+		if (only_release_metadata)
+			btrfs_end_write_no_snapshoting(root);
+
+		if (only_release_metadata && copied > 0) {
+			lockstart = round_down(pos, root->sectorsize);
+			lockend = lockstart +
+				(dirty_pages << PAGE_CACHE_SHIFT) - 1;
+
+			set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
+				       lockend, EXTENT_NORESERVE, NULL,
+				       NULL, GFP_NOFS);
+			only_release_metadata = false;
+		}
+
+		btrfs_drop_pages(pages, num_pages);
+
+		cond_resched();
+
+		balance_dirty_pages_ratelimited(inode->i_mapping);
+		if (dirty_pages < (root->nodesize >> PAGE_CACHE_SHIFT) + 1)
+			btrfs_btree_balance_dirty(root);
+
+		pos += copied;
+		num_written += copied;
+	}
+
+	kfree(pages);
+
+	if (release_bytes) {
+		if (only_release_metadata) {
+			btrfs_end_write_no_snapshoting(root);
+			btrfs_delalloc_release_metadata(inode, release_bytes);
+		} else {
+			btrfs_delalloc_release_space(inode, release_bytes);
+		}
+	}
+
+	return num_written ? num_written : ret;
+}
+
+static ssize_t __btrfs_direct_write(struct kiocb *iocb,
+				    struct iov_iter *from,
+				    loff_t pos)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	ssize_t written;
+	ssize_t written_buffered;
+	loff_t endbyte;
+	int err;
+
+	written = generic_file_direct_write(iocb, from, pos);
+
+	if (written < 0 || !iov_iter_count(from))
+		return written;
+
+	pos += written;
+	written_buffered = __btrfs_buffered_write(file, from, pos);
+	if (written_buffered < 0) {
+		err = written_buffered;
+		goto out;
+	}
+	/*
+	 * Ensure all data is persisted. We want the next direct IO read to be
+	 * able to read what was just written.
+	 */
+	endbyte = pos + written_buffered - 1;
+	err = btrfs_fdatawrite_range(inode, pos, endbyte);
+	if (err)
+		goto out;
+	err = filemap_fdatawait_range(inode->i_mapping, pos, endbyte);
+	if (err)
+		goto out;
+	written += written_buffered;
+	iocb->ki_pos = pos + written_buffered;
+	invalidate_mapping_pages(file->f_mapping, pos >> PAGE_CACHE_SHIFT,
+				 endbyte >> PAGE_CACHE_SHIFT);
+out:
+	return written ? written : err;
+}
+
+static void update_time_for_write(struct inode *inode)
+{
+	struct timespec now;
+
+	if (IS_NOCMTIME(inode))
+		return;
+
+	now = current_fs_time(inode->i_sb);
+	if (!timespec_equal(&inode->i_mtime, &now))
+		inode->i_mtime = now;
+
+	if (!timespec_equal(&inode->i_ctime, &now))
+		inode->i_ctime = now;
+
+	if (IS_I_VERSION(inode))
+		inode_inc_iversion(inode);
+}
+
+static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
+				    struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	u64 start_pos;
+	u64 end_pos;
+	ssize_t num_written = 0;
+	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
+	ssize_t err;
+	loff_t pos;
+	size_t count;
+
+	mutex_lock(&inode->i_mutex);
+	err = generic_write_checks(iocb, from);
+	if (err <= 0) {
+		mutex_unlock(&inode->i_mutex);
+		return err;
+	}
+
+	current->backing_dev_info = inode_to_bdi(inode);
+	err = file_remove_suid(file);
+	if (err) {
+		mutex_unlock(&inode->i_mutex);
+		goto out;
+	}
+
+	/*
+	 * If BTRFS flips readonly due to some impossible error
+	 * (fs_info->fs_state now has BTRFS_SUPER_FLAG_ERROR),
+	 * although we have opened a file as writable, we have
+	 * to stop this write operation to ensure FS consistency.
+	 */
+	if (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state)) {
+		mutex_unlock(&inode->i_mutex);
+		err = -EROFS;
+		goto out;
+	}
+
+	/*
+	 * We reserve space for updating the inode when we reserve space for the
+	 * extent we are going to write, so we will enospc out there.  We don't
+	 * need to start yet another transaction to update the inode as we will
+	 * update the inode when we finish writing whatever data we write.
+	 */
+	update_time_for_write(inode);
+
+	pos = iocb->ki_pos;
+	count = iov_iter_count(from);
+	start_pos = round_down(pos, root->sectorsize);
+	if (start_pos > i_size_read(inode)) {
+		/* Expand hole size to cover write data, preventing empty gap */
+		end_pos = round_up(pos + count, root->sectorsize);
+		err = btrfs_cont_expand(inode, i_size_read(inode), end_pos);
+		if (err) {
+			mutex_unlock(&inode->i_mutex);
+			goto out;
+		}
+	}
+
+	if (sync)
+		atomic_inc(&BTRFS_I(inode)->sync_writers);
+
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		num_written = __btrfs_direct_write(iocb, from, pos);
+	} else {
+		num_written = __btrfs_buffered_write(file, from, pos);
+		if (num_written > 0)
+			iocb->ki_pos = pos + num_written;
+	}
+
+	mutex_unlock(&inode->i_mutex);
+
+	/*
+	 * We also have to set last_sub_trans to the current log transid,
+	 * otherwise subsequent syncs to a file that's been synced in this
+	 * transaction will appear to have already occured.
+	 */
+	spin_lock(&BTRFS_I(inode)->lock);
+	BTRFS_I(inode)->last_sub_trans = root->log_transid;
+	spin_unlock(&BTRFS_I(inode)->lock);
+	if (num_written > 0) {
+		err = generic_write_sync(file, pos, num_written);
+		if (err < 0)
+			num_written = err;
+	}
+
+	if (sync)
+		atomic_dec(&BTRFS_I(inode)->sync_writers);
+out:
+	current->backing_dev_info = NULL;
+	return num_written ? num_written : err;
+}
+
+int btrfs_release_file(struct inode *inode, struct file *filp)
+{
+	if (filp->private_data)
+		btrfs_ioctl_trans_end(filp);
+	/*
+	 * ordered_data_close is set by settattr when we are about to truncate
+	 * a file from a non-zero size to a zero size.  This tries to
+	 * flush down new bytes that may have been written if the
+	 * application were using truncate to replace a file in place.
+	 */
+	if (test_and_clear_bit(BTRFS_INODE_ORDERED_DATA_CLOSE,
+			       &BTRFS_I(inode)->runtime_flags))
+			filemap_flush(inode->i_mapping);
+	return 0;
+}
+
+static int start_ordered_ops(struct inode *inode, loff_t start, loff_t end)
+{
+	int ret;
+
+	atomic_inc(&BTRFS_I(inode)->sync_writers);
+	ret = btrfs_fdatawrite_range(inode, start, end);
+	atomic_dec(&BTRFS_I(inode)->sync_writers);
+
+	return ret;
+}
+
+/*
+ * fsync call for both files and directories.  This logs the inode into
+ * the tree log instead of forcing full commits whenever possible.
+ *
+ * It needs to call filemap_fdatawait so that all ordered extent updates are
+ * in the metadata btree are up to date for copying to the log.
+ *
+ * It drops the inode mutex before doing the tree log commit.  This is an
+ * important optimization for directories because holding the mutex prevents
+ * new operations on the dir while we write to disk.
+ */
+int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct inode *inode = d_inode(dentry);
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_log_ctx ctx;
+	int ret = 0;
+	bool full_sync = 0;
+
+	trace_btrfs_sync_file(file, datasync);
+
+	/*
+	 * We write the dirty pages in the range and wait until they complete
+	 * out of the ->i_mutex. If so, we can flush the dirty pages by
+	 * multi-task, and make the performance up.  See
+	 * btrfs_wait_ordered_range for an explanation of the ASYNC check.
+	 */
+	ret = start_ordered_ops(inode, start, end);
+	if (ret)
+		return ret;
+
+	mutex_lock(&inode->i_mutex);
+	atomic_inc(&root->log_batch);
+	full_sync = test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+			     &BTRFS_I(inode)->runtime_flags);
+	/*
+	 * We might have have had more pages made dirty after calling
+	 * start_ordered_ops and before acquiring the inode's i_mutex.
+	 */
+	if (full_sync) {
+		/*
+		 * For a full sync, we need to make sure any ordered operations
+		 * start and finish before we start logging the inode, so that
+		 * all extents are persisted and the respective file extent
+		 * items are in the fs/subvol btree.
+		 */
+		ret = btrfs_wait_ordered_range(inode, start, end - start + 1);
+	} else {
+		/*
+		 * Start any new ordered operations before starting to log the
+		 * inode. We will wait for them to finish in btrfs_sync_log().
+		 *
+		 * Right before acquiring the inode's mutex, we might have new
+		 * writes dirtying pages, which won't immediately start the
+		 * respective ordered operations - that is done through the
+		 * fill_delalloc callbacks invoked from the writepage and
+		 * writepages address space operations. So make sure we start
+		 * all ordered operations before starting to log our inode. Not
+		 * doing this means that while logging the inode, writeback
+		 * could start and invoke writepage/writepages, which would call
+		 * the fill_delalloc callbacks (cow_file_range,
+		 * submit_compressed_extents). These callbacks add first an
+		 * extent map to the modified list of extents and then create
+		 * the respective ordered operation, which means in
+		 * tree-log.c:btrfs_log_inode() we might capture all existing
+		 * ordered operations (with btrfs_get_logged_extents()) before
+		 * the fill_delalloc callback adds its ordered operation, and by
+		 * the time we visit the modified list of extent maps (with
+		 * btrfs_log_changed_extents()), we see and process the extent
+		 * map they created. We then use the extent map to construct a
+		 * file extent item for logging without waiting for the
+		 * respective ordered operation to finish - this file extent
+		 * item points to a disk location that might not have yet been
+		 * written to, containing random data - so after a crash a log
+		 * replay will make our inode have file extent items that point
+		 * to disk locations containing invalid data, as we returned
+		 * success to userspace without waiting for the respective
+		 * ordered operation to finish, because it wasn't captured by
+		 * btrfs_get_logged_extents().
+		 */
+		ret = start_ordered_ops(inode, start, end);
+	}
+	if (ret) {
+		mutex_unlock(&inode->i_mutex);
+		goto out;
+	}
+	atomic_inc(&root->log_batch);
+
+	/*
+	 * If the last transaction that changed this file was before the current
+	 * transaction and we have the full sync flag set in our inode, we can
+	 * bail out now without any syncing.
+	 *
+	 * Note that we can't bail out if the full sync flag isn't set. This is
+	 * because when the full sync flag is set we start all ordered extents
+	 * and wait for them to fully complete - when they complete they update
+	 * the inode's last_trans field through:
+	 *
+	 *     btrfs_finish_ordered_io() ->
+	 *         btrfs_update_inode_fallback() ->
+	 *             btrfs_update_inode() ->
+	 *                 btrfs_set_inode_last_trans()
+	 *
+	 * So we are sure that last_trans is up to date and can do this check to
+	 * bail out safely. For the fast path, when the full sync flag is not
+	 * set in our inode, we can not do it because we start only our ordered
+	 * extents and don't wait for them to complete (that is when
+	 * btrfs_finish_ordered_io runs), so here at this point their last_trans
+	 * value might be less than or equals to fs_info->last_trans_committed,
+	 * and setting a speculative last_trans for an inode when a buffered
+	 * write is made (such as fs_info->generation + 1 for example) would not
+	 * be reliable since after setting the value and before fsync is called
+	 * any number of transactions can start and commit (transaction kthread
+	 * commits the current transaction periodically), and a transaction
+	 * commit does not start nor waits for ordered extents to complete.
+	 */
+	smp_mb();
+	if (btrfs_inode_in_log(inode, root->fs_info->generation) ||
+	    (full_sync && BTRFS_I(inode)->last_trans <=
+	     root->fs_info->last_trans_committed)) {
+		/*
+		 * We'v had everything committed since the last time we were
+		 * modified so clear this flag in case it was set for whatever
+		 * reason, it's no longer relevant.
+		 */
+		clear_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+			  &BTRFS_I(inode)->runtime_flags);
+		mutex_unlock(&inode->i_mutex);
+		goto out;
+	}
+
+	/*
+	 * ok we haven't committed the transaction yet, lets do a commit
+	 */
+	if (file->private_data)
+		btrfs_ioctl_trans_end(file);
+
+	/*
+	 * We use start here because we will need to wait on the IO to complete
+	 * in btrfs_sync_log, which could require joining a transaction (for
+	 * example checking cross references in the nocow path).  If we use join
+	 * here we could get into a situation where we're waiting on IO to
+	 * happen that is blocked on a transaction trying to commit.  With start
+	 * we inc the extwriter counter, so we wait for all extwriters to exit
+	 * before we start blocking join'ers.  This comment is to keep somebody
+	 * from thinking they are super smart and changing this to
+	 * btrfs_join_transaction *cough*Josef*cough*.
+	 */
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		mutex_unlock(&inode->i_mutex);
+		goto out;
+	}
+	trans->sync = true;
+
+	btrfs_init_log_ctx(&ctx);
+
+	ret = btrfs_log_dentry_safe(trans, root, dentry, start, end, &ctx);
+	if (ret < 0) {
+		/* Fallthrough and commit/free transaction. */
+		ret = 1;
+	}
+
+	/* we've logged all the items and now have a consistent
+	 * version of the file in the log.  It is possible that
+	 * someone will come in and modify the file, but that's
+	 * fine because the log is consistent on disk, and we
+	 * have references to all of the file's extents
+	 *
+	 * It is possible that someone will come in and log the
+	 * file again, but that will end up using the synchronization
+	 * inside btrfs_sync_log to keep things safe.
+	 */
+	mutex_unlock(&inode->i_mutex);
+
+	/*
+	 * If any of the ordered extents had an error, just return it to user
+	 * space, so that the application knows some writes didn't succeed and
+	 * can take proper action (retry for e.g.). Blindly committing the
+	 * transaction in this case, would fool userspace that everything was
+	 * successful. And we also want to make sure our log doesn't contain
+	 * file extent items pointing to extents that weren't fully written to -
+	 * just like in the non fast fsync path, where we check for the ordered
+	 * operation's error flag before writing to the log tree and return -EIO
+	 * if any of them had this flag set (btrfs_wait_ordered_range) -
+	 * therefore we need to check for errors in the ordered operations,
+	 * which are indicated by ctx.io_err.
+	 */
+	if (ctx.io_err) {
+		btrfs_end_transaction(trans, root);
+		ret = ctx.io_err;
+		goto out;
+	}
+
+	if (ret != BTRFS_NO_LOG_SYNC) {
+		if (!ret) {
+			ret = btrfs_sync_log(trans, root, &ctx);
+			if (!ret) {
+				ret = btrfs_end_transaction(trans, root);
+				goto out;
+			}
+		}
+		if (!full_sync) {
+			ret = btrfs_wait_ordered_range(inode, start,
+						       end - start + 1);
+			if (ret) {
+				btrfs_end_transaction(trans, root);
+				goto out;
+			}
+		}
+		ret = btrfs_commit_transaction(trans, root);
+	} else {
+		ret = btrfs_end_transaction(trans, root);
+	}
+out:
+	return ret > 0 ? -EIO : ret;
+}
+
+static const struct vm_operations_struct btrfs_file_vm_ops = {
+	.fault		= filemap_fault,
+	.map_pages	= filemap_map_pages,
+	.page_mkwrite	= btrfs_page_mkwrite,
+};
+
+static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
+{
+	struct address_space *mapping = filp->f_mapping;
+
+	if (!mapping->a_ops->readpage)
+		return -ENOEXEC;
+
+	file_accessed(filp);
+	vma->vm_ops = &btrfs_file_vm_ops;
+
+	return 0;
+}
+
+static int hole_mergeable(struct inode *inode, struct extent_buffer *leaf,
+			  int slot, u64 start, u64 end)
+{
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_key key;
+
+	if (slot < 0 || slot >= btrfs_header_nritems(leaf))
+		return 0;
+
+	btrfs_item_key_to_cpu(leaf, &key, slot);
+	if (key.objectid != btrfs_ino(inode) ||
+	    key.type != BTRFS_EXTENT_DATA_KEY)
+		return 0;
+
+	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+
+	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG)
+		return 0;
+
+	if (btrfs_file_extent_disk_bytenr(leaf, fi))
+		return 0;
+
+	if (key.offset == end)
+		return 1;
+	if (key.offset + btrfs_file_extent_num_bytes(leaf, fi) == start)
+		return 1;
+	return 0;
+}
+
+static int fill_holes(struct btrfs_trans_handle *trans, struct inode *inode,
+		      struct btrfs_path *path, u64 offset, u64 end)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct extent_buffer *leaf;
+	struct btrfs_file_extent_item *fi;
+	struct extent_map *hole_em;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	struct btrfs_key key;
+	int ret;
+
+	if (btrfs_fs_incompat(root->fs_info, NO_HOLES))
+		goto out;
+
+	key.objectid = btrfs_ino(inode);
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = offset;
+
+	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+	if (ret < 0)
+		return ret;
+	BUG_ON(!ret);
+
+	leaf = path->nodes[0];
+	if (hole_mergeable(inode, leaf, path->slots[0]-1, offset, end)) {
+		u64 num_bytes;
+
+		path->slots[0]--;
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) +
+			end - offset;
+		btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
+		btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
+		btrfs_set_file_extent_offset(leaf, fi, 0);
+		btrfs_mark_buffer_dirty(leaf);
+		goto out;
+	}
+
+	if (hole_mergeable(inode, leaf, path->slots[0], offset, end)) {
+		u64 num_bytes;
+
+		key.offset = offset;
+		btrfs_set_item_key_safe(root->fs_info, path, &key);
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) + end -
+			offset;
+		btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
+		btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
+		btrfs_set_file_extent_offset(leaf, fi, 0);
+		btrfs_mark_buffer_dirty(leaf);
+		goto out;
+	}
+	btrfs_release_path(path);
+
+	ret = btrfs_insert_file_extent(trans, root, btrfs_ino(inode), offset,
+				       0, 0, end - offset, 0, end - offset,
+				       0, 0, 0);
+	if (ret)
+		return ret;
+
+out:
+	btrfs_release_path(path);
+
+	hole_em = alloc_extent_map();
+	if (!hole_em) {
+		btrfs_drop_extent_cache(inode, offset, end - 1, 0);
+		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+			&BTRFS_I(inode)->runtime_flags);
+	} else {
+		hole_em->start = offset;
+		hole_em->len = end - offset;
+		hole_em->ram_bytes = hole_em->len;
+		hole_em->orig_start = offset;
+
+		hole_em->block_start = EXTENT_MAP_HOLE;
+		hole_em->block_len = 0;
+		hole_em->orig_block_len = 0;
+		hole_em->bdev = root->fs_info->fs_devices->latest_bdev;
+		hole_em->compress_type = BTRFS_COMPRESS_NONE;
+		hole_em->generation = trans->transid;
+
+		do {
+			btrfs_drop_extent_cache(inode, offset, end - 1, 0);
+			write_lock(&em_tree->lock);
+			ret = add_extent_mapping(em_tree, hole_em, 1);
+			write_unlock(&em_tree->lock);
+		} while (ret == -EEXIST);
+		free_extent_map(hole_em);
+		if (ret)
+			set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+				&BTRFS_I(inode)->runtime_flags);
+	}
+
+	return 0;
+}
+
+/*
+ * Find a hole extent on given inode and change start/len to the end of hole
+ * extent.(hole/vacuum extent whose em->start <= start &&
+ *	   em->start + em->len > start)
+ * When a hole extent is found, return 1 and modify start/len.
+ */
+static int find_first_non_hole(struct inode *inode, u64 *start, u64 *len)
+{
+	struct extent_map *em;
+	int ret = 0;
+
+	em = btrfs_get_extent(inode, NULL, 0, *start, *len, 0);
+	if (IS_ERR_OR_NULL(em)) {
+		if (!em)
+			ret = -ENOMEM;
+		else
+			ret = PTR_ERR(em);
+		return ret;
+	}
+
+	/* Hole or vacuum extent(only exists in no-hole mode) */
+	if (em->block_start == EXTENT_MAP_HOLE) {
+		ret = 1;
+		*len = em->start + em->len > *start + *len ?
+		       0 : *start + *len - em->start - em->len;
+		*start = em->start + em->len;
+	}
+	free_extent_map(em);
+	return ret;
+}
+
+static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct extent_state *cached_state = NULL;
+	struct btrfs_path *path;
+	struct btrfs_block_rsv *rsv;
+	struct btrfs_trans_handle *trans;
+	u64 lockstart;
+	u64 lockend;
+	u64 tail_start;
+	u64 tail_len;
+	u64 orig_start = offset;
+	u64 cur_offset;
+	u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
+	u64 drop_end;
+	int ret = 0;
+	int err = 0;
+	int rsv_count;
+	bool same_page;
+	bool no_holes = btrfs_fs_incompat(root->fs_info, NO_HOLES);
+	u64 ino_size;
+	bool truncated_page = false;
+	bool updated_inode = false;
+
+	ret = btrfs_wait_ordered_range(inode, offset, len);
+	if (ret)
+		return ret;
+
+	mutex_lock(&inode->i_mutex);
+	ino_size = round_up(inode->i_size, PAGE_CACHE_SIZE);
+	ret = find_first_non_hole(inode, &offset, &len);
+	if (ret < 0)
+		goto out_only_mutex;
+	if (ret && !len) {
+		/* Already in a large hole */
+		ret = 0;
+		goto out_only_mutex;
+	}
+
+	lockstart = round_up(offset, BTRFS_I(inode)->root->sectorsize);
+	lockend = round_down(offset + len,
+			     BTRFS_I(inode)->root->sectorsize) - 1;
+	same_page = ((offset >> PAGE_CACHE_SHIFT) ==
+		    ((offset + len - 1) >> PAGE_CACHE_SHIFT));
+
+	/*
+	 * We needn't truncate any page which is beyond the end of the file
+	 * because we are sure there is no data there.
+	 */
+	/*
+	 * Only do this if we are in the same page and we aren't doing the
+	 * entire page.
+	 */
+	if (same_page && len < PAGE_CACHE_SIZE) {
+		if (offset < ino_size) {
+			truncated_page = true;
+			ret = btrfs_truncate_page(inode, offset, len, 0);
+		} else {
+			ret = 0;
+		}
+		goto out_only_mutex;
+	}
+
+	/* zero back part of the first page */
+	if (offset < ino_size) {
+		truncated_page = true;
+		ret = btrfs_truncate_page(inode, offset, 0, 0);
+		if (ret) {
+			mutex_unlock(&inode->i_mutex);
+			return ret;
+		}
+	}
+
+	/* Check the aligned pages after the first unaligned page,
+	 * if offset != orig_start, which means the first unaligned page
+	 * including serveral following pages are already in holes,
+	 * the extra check can be skipped */
+	if (offset == orig_start) {
+		/* after truncate page, check hole again */
+		len = offset + len - lockstart;
+		offset = lockstart;
+		ret = find_first_non_hole(inode, &offset, &len);
+		if (ret < 0)
+			goto out_only_mutex;
+		if (ret && !len) {
+			ret = 0;
+			goto out_only_mutex;
+		}
+		lockstart = offset;
+	}
+
+	/* Check the tail unaligned part is in a hole */
+	tail_start = lockend + 1;
+	tail_len = offset + len - tail_start;
+	if (tail_len) {
+		ret = find_first_non_hole(inode, &tail_start, &tail_len);
+		if (unlikely(ret < 0))
+			goto out_only_mutex;
+		if (!ret) {
+			/* zero the front end of the last page */
+			if (tail_start + tail_len < ino_size) {
+				truncated_page = true;
+				ret = btrfs_truncate_page(inode,
+						tail_start + tail_len, 0, 1);
+				if (ret)
+					goto out_only_mutex;
+			}
+		}
+	}
+
+	if (lockend < lockstart) {
+		ret = 0;
+		goto out_only_mutex;
+	}
+
+	while (1) {
+		struct btrfs_ordered_extent *ordered;
+
+		truncate_pagecache_range(inode, lockstart, lockend);
+
+		lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+				 0, &cached_state);
+		ordered = btrfs_lookup_first_ordered_extent(inode, lockend);
+
+		/*
+		 * We need to make sure we have no ordered extents in this range
+		 * and nobody raced in and read a page in this range, if we did
+		 * we need to try again.
+		 */
+		if ((!ordered ||
+		    (ordered->file_offset + ordered->len <= lockstart ||
+		     ordered->file_offset > lockend)) &&
+		     !btrfs_page_exists_in_range(inode, lockstart, lockend)) {
+			if (ordered)
+				btrfs_put_ordered_extent(ordered);
+			break;
+		}
+		if (ordered)
+			btrfs_put_ordered_extent(ordered);
+		unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart,
+				     lockend, &cached_state, GFP_NOFS);
+		ret = btrfs_wait_ordered_range(inode, lockstart,
+					       lockend - lockstart + 1);
+		if (ret) {
+			mutex_unlock(&inode->i_mutex);
+			return ret;
+		}
+	}
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	rsv = btrfs_alloc_block_rsv(root, BTRFS_BLOCK_RSV_TEMP);
+	if (!rsv) {
+		ret = -ENOMEM;
+		goto out_free;
+	}
+	rsv->size = btrfs_calc_trunc_metadata_size(root, 1);
+	rsv->failfast = 1;
+
+	/*
+	 * 1 - update the inode
+	 * 1 - removing the extents in the range
+	 * 1 - adding the hole extent if no_holes isn't set
+	 */
+	rsv_count = no_holes ? 2 : 3;
+	trans = btrfs_start_transaction(root, rsv_count);
+	if (IS_ERR(trans)) {
+		err = PTR_ERR(trans);
+		goto out_free;
+	}
+
+	ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv, rsv,
+				      min_size);
+	BUG_ON(ret);
+	trans->block_rsv = rsv;
+
+	cur_offset = lockstart;
+	len = lockend - cur_offset;
+	while (cur_offset < lockend) {
+		ret = __btrfs_drop_extents(trans, root, inode, path,
+					   cur_offset, lockend + 1,
+					   &drop_end, 1, 0, 0, NULL);
+		if (ret != -ENOSPC)
+			break;
+
+		trans->block_rsv = &root->fs_info->trans_block_rsv;
+
+		if (cur_offset < ino_size) {
+			ret = fill_holes(trans, inode, path, cur_offset,
+					 drop_end);
+			if (ret) {
+				err = ret;
+				break;
+			}
+		}
+
+		cur_offset = drop_end;
+
+		ret = btrfs_update_inode(trans, root, inode);
+		if (ret) {
+			err = ret;
+			break;
+		}
+
+		btrfs_end_transaction(trans, root);
+		btrfs_btree_balance_dirty(root);
+
+		trans = btrfs_start_transaction(root, rsv_count);
+		if (IS_ERR(trans)) {
+			ret = PTR_ERR(trans);
+			trans = NULL;
+			break;
+		}
+
+		ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv,
+					      rsv, min_size);
+		BUG_ON(ret);	/* shouldn't happen */
+		trans->block_rsv = rsv;
+
+		ret = find_first_non_hole(inode, &cur_offset, &len);
+		if (unlikely(ret < 0))
+			break;
+		if (ret && !len) {
+			ret = 0;
+			break;
+		}
+	}
+
+	if (ret) {
+		err = ret;
+		goto out_trans;
+	}
+
+	trans->block_rsv = &root->fs_info->trans_block_rsv;
+	/*
+	 * Don't insert file hole extent item if it's for a range beyond eof
+	 * (because it's useless) or if it represents a 0 bytes range (when
+	 * cur_offset == drop_end).
+	 */
+	if (cur_offset < ino_size && cur_offset < drop_end) {
+		ret = fill_holes(trans, inode, path, cur_offset, drop_end);
+		if (ret) {
+			err = ret;
+			goto out_trans;
+		}
+	}
+
+out_trans:
+	if (!trans)
+		goto out_free;
+
+	inode_inc_iversion(inode);
+	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+
+	trans->block_rsv = &root->fs_info->trans_block_rsv;
+	ret = btrfs_update_inode(trans, root, inode);
+	updated_inode = true;
+	btrfs_end_transaction(trans, root);
+	btrfs_btree_balance_dirty(root);
+out_free:
+	btrfs_free_path(path);
+	btrfs_free_block_rsv(root, rsv);
+out:
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+			     &cached_state, GFP_NOFS);
+out_only_mutex:
+	if (!updated_inode && truncated_page && !ret && !err) {
+		/*
+		 * If we only end up zeroing part of a page, we still need to
+		 * update the inode item, so that all the time fields are
+		 * updated as well as the necessary btrfs inode in memory fields
+		 * for detecting, at fsync time, if the inode isn't yet in the
+		 * log tree or it's there but not up to date.
+		 */
+		trans = btrfs_start_transaction(root, 1);
+		if (IS_ERR(trans)) {
+			err = PTR_ERR(trans);
+		} else {
+			err = btrfs_update_inode(trans, root, inode);
+			ret = btrfs_end_transaction(trans, root);
+		}
+	}
+	mutex_unlock(&inode->i_mutex);
+	if (ret && !err)
+		err = ret;
+	return err;
+}
+
+static long btrfs_fallocate(struct file *file, int mode,
+			    loff_t offset, loff_t len)
+{
+	struct inode *inode = file_inode(file);
+	struct extent_state *cached_state = NULL;
+	u64 cur_offset;
+	u64 last_byte;
+	u64 alloc_start;
+	u64 alloc_end;
+	u64 alloc_hint = 0;
+	u64 locked_end;
+	struct extent_map *em;
+	int blocksize = BTRFS_I(inode)->root->sectorsize;
+	int ret;
+
+	alloc_start = round_down(offset, blocksize);
+	alloc_end = round_up(offset + len, blocksize);
+
+	/* Make sure we aren't being give some crap mode */
+	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
+		return -EOPNOTSUPP;
+
+	if (mode & FALLOC_FL_PUNCH_HOLE)
+		return btrfs_punch_hole(inode, offset, len);
+
+	/*
+	 * Make sure we have enough space before we do the
+	 * allocation.
+	 */
+	ret = btrfs_check_data_free_space(inode, alloc_end - alloc_start, alloc_end - alloc_start);
+	if (ret)
+		return ret;
+
+	mutex_lock(&inode->i_mutex);
+	ret = inode_newsize_ok(inode, alloc_end);
+	if (ret)
+		goto out;
+
+	if (alloc_start > inode->i_size) {
+		ret = btrfs_cont_expand(inode, i_size_read(inode),
+					alloc_start);
+		if (ret)
+			goto out;
+	} else {
+		/*
+		 * If we are fallocating from the end of the file onward we
+		 * need to zero out the end of the page if i_size lands in the
+		 * middle of a page.
+		 */
+		ret = btrfs_truncate_page(inode, inode->i_size, 0, 0);
+		if (ret)
+			goto out;
+	}
+
+	/*
+	 * wait for ordered IO before we have any locks.  We'll loop again
+	 * below with the locks held.
+	 */
+	ret = btrfs_wait_ordered_range(inode, alloc_start,
+				       alloc_end - alloc_start);
+	if (ret)
+		goto out;
+
+	locked_end = alloc_end - 1;
+	while (1) {
+		struct btrfs_ordered_extent *ordered;
+
+		/* the extent lock is ordered inside the running
+		 * transaction
+		 */
+		lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
+				 locked_end, 0, &cached_state);
+		ordered = btrfs_lookup_first_ordered_extent(inode,
+							    alloc_end - 1);
+		if (ordered &&
+		    ordered->file_offset + ordered->len > alloc_start &&
+		    ordered->file_offset < alloc_end) {
+			btrfs_put_ordered_extent(ordered);
+			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
+					     alloc_start, locked_end,
+					     &cached_state, GFP_NOFS);
+			/*
+			 * we can't wait on the range with the transaction
+			 * running or with the extent lock held
+			 */
+			ret = btrfs_wait_ordered_range(inode, alloc_start,
+						       alloc_end - alloc_start);
+			if (ret)
+				goto out;
+		} else {
+			if (ordered)
+				btrfs_put_ordered_extent(ordered);
+			break;
+		}
+	}
+
+	cur_offset = alloc_start;
+	while (1) {
+		u64 actual_end;
+
+		em = btrfs_get_extent(inode, NULL, 0, cur_offset,
+				      alloc_end - cur_offset, 0);
+		if (IS_ERR_OR_NULL(em)) {
+			if (!em)
+				ret = -ENOMEM;
+			else
+				ret = PTR_ERR(em);
+			break;
+		}
+		last_byte = min(extent_map_end(em), alloc_end);
+		actual_end = min_t(u64, extent_map_end(em), offset + len);
+		last_byte = ALIGN(last_byte, blocksize);
+
+		if (em->block_start == EXTENT_MAP_HOLE ||
+		    (cur_offset >= inode->i_size &&
+		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
+			ret = btrfs_prealloc_file_range(inode, mode, cur_offset,
+							last_byte - cur_offset,
+							1 << inode->i_blkbits,
+							offset + len,
+							&alloc_hint);
+		} else if (actual_end > inode->i_size &&
+			   !(mode & FALLOC_FL_KEEP_SIZE)) {
+			struct btrfs_trans_handle *trans;
+			struct btrfs_root *root = BTRFS_I(inode)->root;
+
+			/*
+			 * We didn't need to allocate any more space, but we
+			 * still extended the size of the file so we need to
+			 * update i_size and the inode item.
+			 */
+			trans = btrfs_start_transaction(root, 1);
+			if (IS_ERR(trans)) {
+				ret = PTR_ERR(trans);
+			} else {
+				inode->i_ctime = CURRENT_TIME;
+				i_size_write(inode, actual_end);
+				btrfs_ordered_update_i_size(inode, actual_end,
+							    NULL);
+				ret = btrfs_update_inode(trans, root, inode);
+				if (ret)
+					btrfs_end_transaction(trans, root);
+				else
+					ret = btrfs_end_transaction(trans,
+								    root);
+			}
+		}
+		free_extent_map(em);
+		if (ret < 0)
+			break;
+
+		cur_offset = last_byte;
+		if (cur_offset >= alloc_end) {
+			ret = 0;
+			break;
+		}
+	}
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
+			     &cached_state, GFP_NOFS);
+out:
+	mutex_unlock(&inode->i_mutex);
+	/* Let go of our reservation. */
+	btrfs_free_reserved_data_space(inode, alloc_end - alloc_start);
+	return ret;
+}
+
+static int find_desired_extent(struct inode *inode, loff_t *offset, int whence)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct extent_map *em = NULL;
+	struct extent_state *cached_state = NULL;
+	u64 lockstart;
+	u64 lockend;
+	u64 start;
+	u64 len;
+	int ret = 0;
+
+	if (inode->i_size == 0)
+		return -ENXIO;
+
+	/*
+	 * *offset can be negative, in this case we start finding DATA/HOLE from
+	 * the very start of the file.
+	 */
+	start = max_t(loff_t, 0, *offset);
+
+	lockstart = round_down(start, root->sectorsize);
+	lockend = round_up(i_size_read(inode), root->sectorsize);
+	if (lockend <= lockstart)
+		lockend = lockstart + root->sectorsize;
+	lockend--;
+	len = lockend - lockstart + 1;
+
+	lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend, 0,
+			 &cached_state);
+
+	while (start < inode->i_size) {
+		em = btrfs_get_extent_fiemap(inode, NULL, 0, start, len, 0);
+		if (IS_ERR(em)) {
+			ret = PTR_ERR(em);
+			em = NULL;
+			break;
+		}
+
+		if (whence == SEEK_HOLE &&
+		    (em->block_start == EXTENT_MAP_HOLE ||
+		     test_bit(EXTENT_FLAG_PREALLOC, &em->flags)))
+			break;
+		else if (whence == SEEK_DATA &&
+			   (em->block_start != EXTENT_MAP_HOLE &&
+			    !test_bit(EXTENT_FLAG_PREALLOC, &em->flags)))
+			break;
+
+		start = em->start + em->len;
+		free_extent_map(em);
+		em = NULL;
+		cond_resched();
+	}
+	free_extent_map(em);
+	if (!ret) {
+		if (whence == SEEK_DATA && start >= inode->i_size)
+			ret = -ENXIO;
+		else
+			*offset = min_t(loff_t, start, inode->i_size);
+	}
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
+			     &cached_state, GFP_NOFS);
+	return ret;
+}
+
+static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *inode = file->f_mapping->host;
+	int ret;
+
+	mutex_lock(&inode->i_mutex);
+	switch (whence) {
+	case SEEK_END:
+	case SEEK_CUR:
+		offset = generic_file_llseek(file, offset, whence);
+		goto out;
+	case SEEK_DATA:
+	case SEEK_HOLE:
+		if (offset >= i_size_read(inode)) {
+			mutex_unlock(&inode->i_mutex);
+			return -ENXIO;
+		}
+
+		ret = find_desired_extent(inode, &offset, whence);
+		if (ret) {
+			mutex_unlock(&inode->i_mutex);
+			return ret;
+		}
+	}
+
+	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
+out:
+	mutex_unlock(&inode->i_mutex);
+	return offset;
+}
+
+const struct file_operations btrfs_file_operations = {
+	.llseek		= btrfs_file_llseek,
+	.read_iter      = generic_file_read_iter,
+	.splice_read	= generic_file_splice_read,
+	.write_iter	= btrfs_file_write_iter,
+	.mmap		= btrfs_file_mmap,
+	.open		= generic_file_open,
+	.release	= btrfs_release_file,
+	.fsync		= btrfs_sync_file,
+	.fallocate	= btrfs_fallocate,
+	.unlocked_ioctl	= btrfs_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= btrfs_ioctl,
+#endif
+};
+
+void btrfs_auto_defrag_exit(void)
+{
+	if (btrfs_inode_defrag_cachep)
+		kmem_cache_destroy(btrfs_inode_defrag_cachep);
+}
+
+int btrfs_auto_defrag_init(void)
+{
+	btrfs_inode_defrag_cachep = kmem_cache_create("btrfs_inode_defrag",
+					sizeof(struct inode_defrag), 0,
+					SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+					NULL);
+	if (!btrfs_inode_defrag_cachep)
+		return -ENOMEM;
+
+	return 0;
+}
+
+int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end)
+{
+	int ret;
+
+	/*
+	 * So with compression we will find and lock a dirty page and clear the
+	 * first one as dirty, setup an async extent, and immediately return
+	 * with the entire range locked but with nobody actually marked with
+	 * writeback.  So we can't just filemap_write_and_wait_range() and
+	 * expect it to work since it will just kick off a thread to do the
+	 * actual work.  So we need to call filemap_fdatawrite_range _again_
+	 * since it will wait on the page lock, which won't be unlocked until
+	 * after the pages have been marked as writeback and so we're good to go
+	 * from there.  We have to do this otherwise we'll miss the ordered
+	 * extents and that results in badness.  Please Josef, do not think you
+	 * know better and pull this out at some point in the future, it is
+	 * right and you are wrong.
+	 */
+	ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
+	if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
+			     &BTRFS_I(inode)->runtime_flags))
+		ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
+
+	return ret;
+}