Initial import

1 files changed, 2703 insertions, 0 deletions

diff --git a/fs/locks.c b/fs/locks.c
new file mode 100644
index 000000000..653faabb0
--- /dev/null
+++ b/fs/locks.c
@@ -0,0 +1,2703 @@
+/*
+ *  linux/fs/locks.c
+ *
+ *  Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
+ *  Doug Evans (dje@spiff.uucp), August 07, 1992
+ *
+ *  Deadlock detection added.
+ *  FIXME: one thing isn't handled yet:
+ *	- mandatory locks (requires lots of changes elsewhere)
+ *  Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
+ *
+ *  Miscellaneous edits, and a total rewrite of posix_lock_file() code.
+ *  Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
+ *  
+ *  Converted file_lock_table to a linked list from an array, which eliminates
+ *  the limits on how many active file locks are open.
+ *  Chad Page (pageone@netcom.com), November 27, 1994
+ * 
+ *  Removed dependency on file descriptors. dup()'ed file descriptors now
+ *  get the same locks as the original file descriptors, and a close() on
+ *  any file descriptor removes ALL the locks on the file for the current
+ *  process. Since locks still depend on the process id, locks are inherited
+ *  after an exec() but not after a fork(). This agrees with POSIX, and both
+ *  BSD and SVR4 practice.
+ *  Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
+ *
+ *  Scrapped free list which is redundant now that we allocate locks
+ *  dynamically with kmalloc()/kfree().
+ *  Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
+ *
+ *  Implemented two lock personalities - FL_FLOCK and FL_POSIX.
+ *
+ *  FL_POSIX locks are created with calls to fcntl() and lockf() through the
+ *  fcntl() system call. They have the semantics described above.
+ *
+ *  FL_FLOCK locks are created with calls to flock(), through the flock()
+ *  system call, which is new. Old C libraries implement flock() via fcntl()
+ *  and will continue to use the old, broken implementation.
+ *
+ *  FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
+ *  with a file pointer (filp). As a result they can be shared by a parent
+ *  process and its children after a fork(). They are removed when the last
+ *  file descriptor referring to the file pointer is closed (unless explicitly
+ *  unlocked). 
+ *
+ *  FL_FLOCK locks never deadlock, an existing lock is always removed before
+ *  upgrading from shared to exclusive (or vice versa). When this happens
+ *  any processes blocked by the current lock are woken up and allowed to
+ *  run before the new lock is applied.
+ *  Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
+ *
+ *  Removed some race conditions in flock_lock_file(), marked other possible
+ *  races. Just grep for FIXME to see them. 
+ *  Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
+ *
+ *  Addressed Dmitry's concerns. Deadlock checking no longer recursive.
+ *  Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
+ *  once we've checked for blocking and deadlocking.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
+ *
+ *  Initial implementation of mandatory locks. SunOS turned out to be
+ *  a rotten model, so I implemented the "obvious" semantics.
+ *  See 'Documentation/filesystems/mandatory-locking.txt' for details.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
+ *
+ *  Don't allow mandatory locks on mmap()'ed files. Added simple functions to
+ *  check if a file has mandatory locks, used by mmap(), open() and creat() to
+ *  see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
+ *  Manual, Section 2.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
+ *
+ *  Tidied up block list handling. Added '/proc/locks' interface.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
+ *
+ *  Fixed deadlock condition for pathological code that mixes calls to
+ *  flock() and fcntl().
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
+ *
+ *  Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
+ *  for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
+ *  guarantee sensible behaviour in the case where file system modules might
+ *  be compiled with different options than the kernel itself.
+ *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
+ *
+ *  Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
+ *  (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
+ *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
+ *
+ *  Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
+ *  locks. Changed process synchronisation to avoid dereferencing locks that
+ *  have already been freed.
+ *  Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
+ *
+ *  Made the block list a circular list to minimise searching in the list.
+ *  Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
+ *
+ *  Made mandatory locking a mount option. Default is not to allow mandatory
+ *  locking.
+ *  Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
+ *
+ *  Some adaptations for NFS support.
+ *  Olaf Kirch (okir@monad.swb.de), Dec 1996,
+ *
+ *  Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
+ *  Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
+ *
+ *  Use slab allocator instead of kmalloc/kfree.
+ *  Use generic list implementation from <linux/list.h>.
+ *  Sped up posix_locks_deadlock by only considering blocked locks.
+ *  Matthew Wilcox <willy@debian.org>, March, 2000.
+ *
+ *  Leases and LOCK_MAND
+ *  Matthew Wilcox <willy@debian.org>, June, 2000.
+ *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
+ */
+
+#include <linux/capability.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/security.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/time.h>
+#include <linux/rcupdate.h>
+#include <linux/pid_namespace.h>
+#include <linux/hashtable.h>
+#include <linux/percpu.h>
+#include <linux/lglock.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/filelock.h>
+
+#include <asm/uaccess.h>
+
+#define IS_POSIX(fl)	(fl->fl_flags & FL_POSIX)
+#define IS_FLOCK(fl)	(fl->fl_flags & FL_FLOCK)
+#define IS_LEASE(fl)	(fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
+#define IS_OFDLCK(fl)	(fl->fl_flags & FL_OFDLCK)
+
+static bool lease_breaking(struct file_lock *fl)
+{
+	return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
+}
+
+static int target_leasetype(struct file_lock *fl)
+{
+	if (fl->fl_flags & FL_UNLOCK_PENDING)
+		return F_UNLCK;
+	if (fl->fl_flags & FL_DOWNGRADE_PENDING)
+		return F_RDLCK;
+	return fl->fl_type;
+}
+
+int leases_enable = 1;
+int lease_break_time = 45;
+
+/*
+ * The global file_lock_list is only used for displaying /proc/locks, so we
+ * keep a list on each CPU, with each list protected by its own spinlock via
+ * the file_lock_lglock. Note that alterations to the list also require that
+ * the relevant flc_lock is held.
+ */
+DEFINE_STATIC_LGLOCK(file_lock_lglock);
+static DEFINE_PER_CPU(struct hlist_head, file_lock_list);
+
+/*
+ * The blocked_hash is used to find POSIX lock loops for deadlock detection.
+ * It is protected by blocked_lock_lock.
+ *
+ * We hash locks by lockowner in order to optimize searching for the lock a
+ * particular lockowner is waiting on.
+ *
+ * FIXME: make this value scale via some heuristic? We generally will want more
+ * buckets when we have more lockowners holding locks, but that's a little
+ * difficult to determine without knowing what the workload will look like.
+ */
+#define BLOCKED_HASH_BITS	7
+static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
+
+/*
+ * This lock protects the blocked_hash. Generally, if you're accessing it, you
+ * want to be holding this lock.
+ *
+ * In addition, it also protects the fl->fl_block list, and the fl->fl_next
+ * pointer for file_lock structures that are acting as lock requests (in
+ * contrast to those that are acting as records of acquired locks).
+ *
+ * Note that when we acquire this lock in order to change the above fields,
+ * we often hold the flc_lock as well. In certain cases, when reading the fields
+ * protected by this lock, we can skip acquiring it iff we already hold the
+ * flc_lock.
+ *
+ * In particular, adding an entry to the fl_block list requires that you hold
+ * both the flc_lock and the blocked_lock_lock (acquired in that order).
+ * Deleting an entry from the list however only requires the file_lock_lock.
+ */
+static DEFINE_SPINLOCK(blocked_lock_lock);
+
+static struct kmem_cache *flctx_cache __read_mostly;
+static struct kmem_cache *filelock_cache __read_mostly;
+
+static struct file_lock_context *
+locks_get_lock_context(struct inode *inode, int type)
+{
+	struct file_lock_context *new;
+
+	if (likely(inode->i_flctx) || type == F_UNLCK)
+		goto out;
+
+	new = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
+	if (!new)
+		goto out;
+
+	spin_lock_init(&new->flc_lock);
+	INIT_LIST_HEAD(&new->flc_flock);
+	INIT_LIST_HEAD(&new->flc_posix);
+	INIT_LIST_HEAD(&new->flc_lease);
+
+	/*
+	 * Assign the pointer if it's not already assigned. If it is, then
+	 * free the context we just allocated.
+	 */
+	if (cmpxchg(&inode->i_flctx, NULL, new))
+		kmem_cache_free(flctx_cache, new);
+out:
+	return inode->i_flctx;
+}
+
+void
+locks_free_lock_context(struct file_lock_context *ctx)
+{
+	if (ctx) {
+		WARN_ON_ONCE(!list_empty(&ctx->flc_flock));
+		WARN_ON_ONCE(!list_empty(&ctx->flc_posix));
+		WARN_ON_ONCE(!list_empty(&ctx->flc_lease));
+		kmem_cache_free(flctx_cache, ctx);
+	}
+}
+
+static void locks_init_lock_heads(struct file_lock *fl)
+{
+	INIT_HLIST_NODE(&fl->fl_link);
+	INIT_LIST_HEAD(&fl->fl_list);
+	INIT_LIST_HEAD(&fl->fl_block);
+	init_waitqueue_head(&fl->fl_wait);
+}
+
+/* Allocate an empty lock structure. */
+struct file_lock *locks_alloc_lock(void)
+{
+	struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
+
+	if (fl)
+		locks_init_lock_heads(fl);
+
+	return fl;
+}
+EXPORT_SYMBOL_GPL(locks_alloc_lock);
+
+void locks_release_private(struct file_lock *fl)
+{
+	if (fl->fl_ops) {
+		if (fl->fl_ops->fl_release_private)
+			fl->fl_ops->fl_release_private(fl);
+		fl->fl_ops = NULL;
+	}
+
+	if (fl->fl_lmops) {
+		if (fl->fl_lmops->lm_put_owner) {
+			fl->fl_lmops->lm_put_owner(fl->fl_owner);
+			fl->fl_owner = NULL;
+		}
+		fl->fl_lmops = NULL;
+	}
+}
+EXPORT_SYMBOL_GPL(locks_release_private);
+
+/* Free a lock which is not in use. */
+void locks_free_lock(struct file_lock *fl)
+{
+	BUG_ON(waitqueue_active(&fl->fl_wait));
+	BUG_ON(!list_empty(&fl->fl_list));
+	BUG_ON(!list_empty(&fl->fl_block));
+	BUG_ON(!hlist_unhashed(&fl->fl_link));
+
+	locks_release_private(fl);
+	kmem_cache_free(filelock_cache, fl);
+}
+EXPORT_SYMBOL(locks_free_lock);
+
+static void
+locks_dispose_list(struct list_head *dispose)
+{
+	struct file_lock *fl;
+
+	while (!list_empty(dispose)) {
+		fl = list_first_entry(dispose, struct file_lock, fl_list);
+		list_del_init(&fl->fl_list);
+		locks_free_lock(fl);
+	}
+}
+
+void locks_init_lock(struct file_lock *fl)
+{
+	memset(fl, 0, sizeof(struct file_lock));
+	locks_init_lock_heads(fl);
+}
+
+EXPORT_SYMBOL(locks_init_lock);
+
+/*
+ * Initialize a new lock from an existing file_lock structure.
+ */
+void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
+{
+	new->fl_owner = fl->fl_owner;
+	new->fl_pid = fl->fl_pid;
+	new->fl_file = NULL;
+	new->fl_flags = fl->fl_flags;
+	new->fl_type = fl->fl_type;
+	new->fl_start = fl->fl_start;
+	new->fl_end = fl->fl_end;
+	new->fl_lmops = fl->fl_lmops;
+	new->fl_ops = NULL;
+
+	if (fl->fl_lmops) {
+		if (fl->fl_lmops->lm_get_owner)
+			fl->fl_lmops->lm_get_owner(fl->fl_owner);
+	}
+}
+EXPORT_SYMBOL(locks_copy_conflock);
+
+void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
+{
+	/* "new" must be a freshly-initialized lock */
+	WARN_ON_ONCE(new->fl_ops);
+
+	locks_copy_conflock(new, fl);
+
+	new->fl_file = fl->fl_file;
+	new->fl_ops = fl->fl_ops;
+
+	if (fl->fl_ops) {
+		if (fl->fl_ops->fl_copy_lock)
+			fl->fl_ops->fl_copy_lock(new, fl);
+	}
+}
+
+EXPORT_SYMBOL(locks_copy_lock);
+
+static inline int flock_translate_cmd(int cmd) {
+	if (cmd & LOCK_MAND)
+		return cmd & (LOCK_MAND | LOCK_RW);
+	switch (cmd) {
+	case LOCK_SH:
+		return F_RDLCK;
+	case LOCK_EX:
+		return F_WRLCK;
+	case LOCK_UN:
+		return F_UNLCK;
+	}
+	return -EINVAL;
+}
+
+/* Fill in a file_lock structure with an appropriate FLOCK lock. */
+static struct file_lock *
+flock_make_lock(struct file *filp, unsigned int cmd)
+{
+	struct file_lock *fl;
+	int type = flock_translate_cmd(cmd);
+
+	if (type < 0)
+		return ERR_PTR(type);
+	
+	fl = locks_alloc_lock();
+	if (fl == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	fl->fl_file = filp;
+	fl->fl_owner = filp;
+	fl->fl_pid = current->tgid;
+	fl->fl_flags = FL_FLOCK;
+	fl->fl_type = type;
+	fl->fl_end = OFFSET_MAX;
+	
+	return fl;
+}
+
+static int assign_type(struct file_lock *fl, long type)
+{
+	switch (type) {
+	case F_RDLCK:
+	case F_WRLCK:
+	case F_UNLCK:
+		fl->fl_type = type;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
+				 struct flock64 *l)
+{
+	switch (l->l_whence) {
+	case SEEK_SET:
+		fl->fl_start = 0;
+		break;
+	case SEEK_CUR:
+		fl->fl_start = filp->f_pos;
+		break;
+	case SEEK_END:
+		fl->fl_start = i_size_read(file_inode(filp));
+		break;
+	default:
+		return -EINVAL;
+	}
+	if (l->l_start > OFFSET_MAX - fl->fl_start)
+		return -EOVERFLOW;
+	fl->fl_start += l->l_start;
+	if (fl->fl_start < 0)
+		return -EINVAL;
+
+	/* POSIX-1996 leaves the case l->l_len < 0 undefined;
+	   POSIX-2001 defines it. */
+	if (l->l_len > 0) {
+		if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
+			return -EOVERFLOW;
+		fl->fl_end = fl->fl_start + l->l_len - 1;
+
+	} else if (l->l_len < 0) {
+		if (fl->fl_start + l->l_len < 0)
+			return -EINVAL;
+		fl->fl_end = fl->fl_start - 1;
+		fl->fl_start += l->l_len;
+	} else
+		fl->fl_end = OFFSET_MAX;
+
+	fl->fl_owner = current->files;
+	fl->fl_pid = current->tgid;
+	fl->fl_file = filp;
+	fl->fl_flags = FL_POSIX;
+	fl->fl_ops = NULL;
+	fl->fl_lmops = NULL;
+
+	return assign_type(fl, l->l_type);
+}
+
+/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
+ * style lock.
+ */
+static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
+			       struct flock *l)
+{
+	struct flock64 ll = {
+		.l_type = l->l_type,
+		.l_whence = l->l_whence,
+		.l_start = l->l_start,
+		.l_len = l->l_len,
+	};
+
+	return flock64_to_posix_lock(filp, fl, &ll);
+}
+
+/* default lease lock manager operations */
+static bool
+lease_break_callback(struct file_lock *fl)
+{
+	kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
+	return false;
+}
+
+static void
+lease_setup(struct file_lock *fl, void **priv)
+{
+	struct file *filp = fl->fl_file;
+	struct fasync_struct *fa = *priv;
+
+	/*
+	 * fasync_insert_entry() returns the old entry if any. If there was no
+	 * old entry, then it used "priv" and inserted it into the fasync list.
+	 * Clear the pointer to indicate that it shouldn't be freed.
+	 */
+	if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa))
+		*priv = NULL;
+
+	__f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
+}
+
+static const struct lock_manager_operations lease_manager_ops = {
+	.lm_break = lease_break_callback,
+	.lm_change = lease_modify,
+	.lm_setup = lease_setup,
+};
+
+/*
+ * Initialize a lease, use the default lock manager operations
+ */
+static int lease_init(struct file *filp, long type, struct file_lock *fl)
+ {
+	if (assign_type(fl, type) != 0)
+		return -EINVAL;
+
+	fl->fl_owner = filp;
+	fl->fl_pid = current->tgid;
+
+	fl->fl_file = filp;
+	fl->fl_flags = FL_LEASE;
+	fl->fl_start = 0;
+	fl->fl_end = OFFSET_MAX;
+	fl->fl_ops = NULL;
+	fl->fl_lmops = &lease_manager_ops;
+	return 0;
+}
+
+/* Allocate a file_lock initialised to this type of lease */
+static struct file_lock *lease_alloc(struct file *filp, long type)
+{
+	struct file_lock *fl = locks_alloc_lock();
+	int error = -ENOMEM;
+
+	if (fl == NULL)
+		return ERR_PTR(error);
+
+	error = lease_init(filp, type, fl);
+	if (error) {
+		locks_free_lock(fl);
+		return ERR_PTR(error);
+	}
+	return fl;
+}
+
+/* Check if two locks overlap each other.
+ */
+static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
+{
+	return ((fl1->fl_end >= fl2->fl_start) &&
+		(fl2->fl_end >= fl1->fl_start));
+}
+
+/*
+ * Check whether two locks have the same owner.
+ */
+static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
+{
+	if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner)
+		return fl2->fl_lmops == fl1->fl_lmops &&
+			fl1->fl_lmops->lm_compare_owner(fl1, fl2);
+	return fl1->fl_owner == fl2->fl_owner;
+}
+
+/* Must be called with the flc_lock held! */
+static void locks_insert_global_locks(struct file_lock *fl)
+{
+	lg_local_lock(&file_lock_lglock);
+	fl->fl_link_cpu = smp_processor_id();
+	hlist_add_head(&fl->fl_link, this_cpu_ptr(&file_lock_list));
+	lg_local_unlock(&file_lock_lglock);
+}
+
+/* Must be called with the flc_lock held! */
+static void locks_delete_global_locks(struct file_lock *fl)
+{
+	/*
+	 * Avoid taking lock if already unhashed. This is safe since this check
+	 * is done while holding the flc_lock, and new insertions into the list
+	 * also require that it be held.
+	 */
+	if (hlist_unhashed(&fl->fl_link))
+		return;
+	lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu);
+	hlist_del_init(&fl->fl_link);
+	lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu);
+}
+
+static unsigned long
+posix_owner_key(struct file_lock *fl)
+{
+	if (fl->fl_lmops && fl->fl_lmops->lm_owner_key)
+		return fl->fl_lmops->lm_owner_key(fl);
+	return (unsigned long)fl->fl_owner;
+}
+
+static void locks_insert_global_blocked(struct file_lock *waiter)
+{
+	lockdep_assert_held(&blocked_lock_lock);
+
+	hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter));
+}
+
+static void locks_delete_global_blocked(struct file_lock *waiter)
+{
+	lockdep_assert_held(&blocked_lock_lock);
+
+	hash_del(&waiter->fl_link);
+}
+
+/* Remove waiter from blocker's block list.
+ * When blocker ends up pointing to itself then the list is empty.
+ *
+ * Must be called with blocked_lock_lock held.
+ */
+static void __locks_delete_block(struct file_lock *waiter)
+{
+	locks_delete_global_blocked(waiter);
+	list_del_init(&waiter->fl_block);
+	waiter->fl_next = NULL;
+}
+
+static void locks_delete_block(struct file_lock *waiter)
+{
+	spin_lock(&blocked_lock_lock);
+	__locks_delete_block(waiter);
+	spin_unlock(&blocked_lock_lock);
+}
+
+/* Insert waiter into blocker's block list.
+ * We use a circular list so that processes can be easily woken up in
+ * the order they blocked. The documentation doesn't require this but
+ * it seems like the reasonable thing to do.
+ *
+ * Must be called with both the flc_lock and blocked_lock_lock held. The
+ * fl_block list itself is protected by the blocked_lock_lock, but by ensuring
+ * that the flc_lock is also held on insertions we can avoid taking the
+ * blocked_lock_lock in some cases when we see that the fl_block list is empty.
+ */
+static void __locks_insert_block(struct file_lock *blocker,
+					struct file_lock *waiter)
+{
+	BUG_ON(!list_empty(&waiter->fl_block));
+	waiter->fl_next = blocker;
+	list_add_tail(&waiter->fl_block, &blocker->fl_block);
+	if (IS_POSIX(blocker) && !IS_OFDLCK(blocker))
+		locks_insert_global_blocked(waiter);
+}
+
+/* Must be called with flc_lock held. */
+static void locks_insert_block(struct file_lock *blocker,
+					struct file_lock *waiter)
+{
+	spin_lock(&blocked_lock_lock);
+	__locks_insert_block(blocker, waiter);
+	spin_unlock(&blocked_lock_lock);
+}
+
+/*
+ * Wake up processes blocked waiting for blocker.
+ *
+ * Must be called with the inode->flc_lock held!
+ */
+static void locks_wake_up_blocks(struct file_lock *blocker)
+{
+	/*
+	 * Avoid taking global lock if list is empty. This is safe since new
+	 * blocked requests are only added to the list under the flc_lock, and
+	 * the flc_lock is always held here. Note that removal from the fl_block
+	 * list does not require the flc_lock, so we must recheck list_empty()
+	 * after acquiring the blocked_lock_lock.
+	 */
+	if (list_empty(&blocker->fl_block))
+		return;
+
+	spin_lock(&blocked_lock_lock);
+	while (!list_empty(&blocker->fl_block)) {
+		struct file_lock *waiter;
+
+		waiter = list_first_entry(&blocker->fl_block,
+				struct file_lock, fl_block);
+		__locks_delete_block(waiter);
+		if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
+			waiter->fl_lmops->lm_notify(waiter);
+		else
+			wake_up(&waiter->fl_wait);
+	}
+	spin_unlock(&blocked_lock_lock);
+}
+
+static void
+locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before)
+{
+	fl->fl_nspid = get_pid(task_tgid(current));
+	list_add_tail(&fl->fl_list, before);
+	locks_insert_global_locks(fl);
+}
+
+static void
+locks_unlink_lock_ctx(struct file_lock *fl)
+{
+	locks_delete_global_locks(fl);
+	list_del_init(&fl->fl_list);
+	if (fl->fl_nspid) {
+		put_pid(fl->fl_nspid);
+		fl->fl_nspid = NULL;
+	}
+	locks_wake_up_blocks(fl);
+}
+
+static void
+locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose)
+{
+	locks_unlink_lock_ctx(fl);
+	if (dispose)
+		list_add(&fl->fl_list, dispose);
+	else
+		locks_free_lock(fl);
+}
+
+/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
+ * checks for shared/exclusive status of overlapping locks.
+ */
+static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+{
+	if (sys_fl->fl_type == F_WRLCK)
+		return 1;
+	if (caller_fl->fl_type == F_WRLCK)
+		return 1;
+	return 0;
+}
+
+/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
+ * checking before calling the locks_conflict().
+ */
+static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+{
+	/* POSIX locks owned by the same process do not conflict with
+	 * each other.
+	 */
+	if (posix_same_owner(caller_fl, sys_fl))
+		return (0);
+
+	/* Check whether they overlap */
+	if (!locks_overlap(caller_fl, sys_fl))
+		return 0;
+
+	return (locks_conflict(caller_fl, sys_fl));
+}
+
+/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
+ * checking before calling the locks_conflict().
+ */
+static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+{
+	/* FLOCK locks referring to the same filp do not conflict with
+	 * each other.
+	 */
+	if (caller_fl->fl_file == sys_fl->fl_file)
+		return (0);
+	if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
+		return 0;
+
+	return (locks_conflict(caller_fl, sys_fl));
+}
+
+void
+posix_test_lock(struct file *filp, struct file_lock *fl)
+{
+	struct file_lock *cfl;
+	struct file_lock_context *ctx;
+	struct inode *inode = file_inode(filp);
+
+	ctx = inode->i_flctx;
+	if (!ctx || list_empty_careful(&ctx->flc_posix)) {
+		fl->fl_type = F_UNLCK;
+		return;
+	}
+
+	spin_lock(&ctx->flc_lock);
+	list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
+		if (posix_locks_conflict(fl, cfl)) {
+			locks_copy_conflock(fl, cfl);
+			if (cfl->fl_nspid)
+				fl->fl_pid = pid_vnr(cfl->fl_nspid);
+			goto out;
+		}
+	}
+	fl->fl_type = F_UNLCK;
+out:
+	spin_unlock(&ctx->flc_lock);
+	return;
+}
+EXPORT_SYMBOL(posix_test_lock);
+
+/*
+ * Deadlock detection:
+ *
+ * We attempt to detect deadlocks that are due purely to posix file
+ * locks.
+ *
+ * We assume that a task can be waiting for at most one lock at a time.
+ * So for any acquired lock, the process holding that lock may be
+ * waiting on at most one other lock.  That lock in turns may be held by
+ * someone waiting for at most one other lock.  Given a requested lock
+ * caller_fl which is about to wait for a conflicting lock block_fl, we
+ * follow this chain of waiters to ensure we are not about to create a
+ * cycle.
+ *
+ * Since we do this before we ever put a process to sleep on a lock, we
+ * are ensured that there is never a cycle; that is what guarantees that
+ * the while() loop in posix_locks_deadlock() eventually completes.
+ *
+ * Note: the above assumption may not be true when handling lock
+ * requests from a broken NFS client. It may also fail in the presence
+ * of tasks (such as posix threads) sharing the same open file table.
+ * To handle those cases, we just bail out after a few iterations.
+ *
+ * For FL_OFDLCK locks, the owner is the filp, not the files_struct.
+ * Because the owner is not even nominally tied to a thread of
+ * execution, the deadlock detection below can't reasonably work well. Just
+ * skip it for those.
+ *
+ * In principle, we could do a more limited deadlock detection on FL_OFDLCK
+ * locks that just checks for the case where two tasks are attempting to
+ * upgrade from read to write locks on the same inode.
+ */
+
+#define MAX_DEADLK_ITERATIONS 10
+
+/* Find a lock that the owner of the given block_fl is blocking on. */
+static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
+{
+	struct file_lock *fl;
+
+	hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) {
+		if (posix_same_owner(fl, block_fl))
+			return fl->fl_next;
+	}
+	return NULL;
+}
+
+/* Must be called with the blocked_lock_lock held! */
+static int posix_locks_deadlock(struct file_lock *caller_fl,
+				struct file_lock *block_fl)
+{
+	int i = 0;
+
+	lockdep_assert_held(&blocked_lock_lock);
+
+	/*
+	 * This deadlock detector can't reasonably detect deadlocks with
+	 * FL_OFDLCK locks, since they aren't owned by a process, per-se.
+	 */
+	if (IS_OFDLCK(caller_fl))
+		return 0;
+
+	while ((block_fl = what_owner_is_waiting_for(block_fl))) {
+		if (i++ > MAX_DEADLK_ITERATIONS)
+			return 0;
+		if (posix_same_owner(caller_fl, block_fl))
+			return 1;
+	}
+	return 0;
+}
+
+/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
+ * after any leases, but before any posix locks.
+ *
+ * Note that if called with an FL_EXISTS argument, the caller may determine
+ * whether or not a lock was successfully freed by testing the return
+ * value for -ENOENT.
+ */
+static int flock_lock_file(struct file *filp, struct file_lock *request)
+{
+	struct file_lock *new_fl = NULL;
+	struct file_lock *fl;
+	struct file_lock_context *ctx;
+	struct inode *inode = file_inode(filp);
+	int error = 0;
+	bool found = false;
+	LIST_HEAD(dispose);
+
+	ctx = locks_get_lock_context(inode, request->fl_type);
+	if (!ctx) {
+		if (request->fl_type != F_UNLCK)
+			return -ENOMEM;
+		return (request->fl_flags & FL_EXISTS) ? -ENOENT : 0;
+	}
+
+	if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
+		new_fl = locks_alloc_lock();
+		if (!new_fl)
+			return -ENOMEM;
+	}
+
+	spin_lock(&ctx->flc_lock);
+	if (request->fl_flags & FL_ACCESS)
+		goto find_conflict;
+
+	list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
+		if (filp != fl->fl_file)
+			continue;
+		if (request->fl_type == fl->fl_type)
+			goto out;
+		found = true;
+		locks_delete_lock_ctx(fl, &dispose);
+		break;
+	}
+
+	if (request->fl_type == F_UNLCK) {
+		if ((request->fl_flags & FL_EXISTS) && !found)
+			error = -ENOENT;
+		goto out;
+	}
+
+find_conflict:
+	list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
+		if (!flock_locks_conflict(request, fl))
+			continue;
+		error = -EAGAIN;
+		if (!(request->fl_flags & FL_SLEEP))
+			goto out;
+		error = FILE_LOCK_DEFERRED;
+		locks_insert_block(fl, request);
+		goto out;
+	}
+	if (request->fl_flags & FL_ACCESS)
+		goto out;
+	locks_copy_lock(new_fl, request);
+	locks_insert_lock_ctx(new_fl, &ctx->flc_flock);
+	new_fl = NULL;
+	error = 0;
+
+out:
+	spin_unlock(&ctx->flc_lock);
+	if (new_fl)
+		locks_free_lock(new_fl);
+	locks_dispose_list(&dispose);
+	return error;
+}
+
+static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
+{
+	struct file_lock *fl, *tmp;
+	struct file_lock *new_fl = NULL;
+	struct file_lock *new_fl2 = NULL;
+	struct file_lock *left = NULL;
+	struct file_lock *right = NULL;
+	struct file_lock_context *ctx;
+	int error;
+	bool added = false;
+	LIST_HEAD(dispose);
+
+	ctx = locks_get_lock_context(inode, request->fl_type);
+	if (!ctx)
+		return (request->fl_type == F_UNLCK) ? 0 : -ENOMEM;
+
+	/*
+	 * We may need two file_lock structures for this operation,
+	 * so we get them in advance to avoid races.
+	 *
+	 * In some cases we can be sure, that no new locks will be needed
+	 */
+	if (!(request->fl_flags & FL_ACCESS) &&
+	    (request->fl_type != F_UNLCK ||
+	     request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
+		new_fl = locks_alloc_lock();
+		new_fl2 = locks_alloc_lock();
+	}
+
+	spin_lock(&ctx->flc_lock);
+	/*
+	 * New lock request. Walk all POSIX locks and look for conflicts. If
+	 * there are any, either return error or put the request on the
+	 * blocker's list of waiters and the global blocked_hash.
+	 */
+	if (request->fl_type != F_UNLCK) {
+		list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
+			if (!posix_locks_conflict(request, fl))
+				continue;
+			if (conflock)
+				locks_copy_conflock(conflock, fl);
+			error = -EAGAIN;
+			if (!(request->fl_flags & FL_SLEEP))
+				goto out;
+			/*
+			 * Deadlock detection and insertion into the blocked
+			 * locks list must be done while holding the same lock!
+			 */
+			error = -EDEADLK;
+			spin_lock(&blocked_lock_lock);
+			if (likely(!posix_locks_deadlock(request, fl))) {
+				error = FILE_LOCK_DEFERRED;
+				__locks_insert_block(fl, request);
+			}
+			spin_unlock(&blocked_lock_lock);
+			goto out;
+  		}
+  	}
+
+	/* If we're just looking for a conflict, we're done. */
+	error = 0;
+	if (request->fl_flags & FL_ACCESS)
+		goto out;
+
+	/* Find the first old lock with the same owner as the new lock */
+	list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
+		if (posix_same_owner(request, fl))
+			break;
+	}
+
+	/* Process locks with this owner. */
+	list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, fl_list) {
+		if (!posix_same_owner(request, fl))
+			break;
+
+		/* Detect adjacent or overlapping regions (if same lock type) */
+		if (request->fl_type == fl->fl_type) {
+			/* In all comparisons of start vs end, use
+			 * "start - 1" rather than "end + 1". If end
+			 * is OFFSET_MAX, end + 1 will become negative.
+			 */
+			if (fl->fl_end < request->fl_start - 1)
+				continue;
+			/* If the next lock in the list has entirely bigger
+			 * addresses than the new one, insert the lock here.
+			 */
+			if (fl->fl_start - 1 > request->fl_end)
+				break;
+
+			/* If we come here, the new and old lock are of the
+			 * same type and adjacent or overlapping. Make one
+			 * lock yielding from the lower start address of both
+			 * locks to the higher end address.
+			 */
+			if (fl->fl_start > request->fl_start)
+				fl->fl_start = request->fl_start;
+			else
+				request->fl_start = fl->fl_start;
+			if (fl->fl_end < request->fl_end)
+				fl->fl_end = request->fl_end;
+			else
+				request->fl_end = fl->fl_end;
+			if (added) {
+				locks_delete_lock_ctx(fl, &dispose);
+				continue;
+			}
+			request = fl;
+			added = true;
+		} else {
+			/* Processing for different lock types is a bit
+			 * more complex.
+			 */
+			if (fl->fl_end < request->fl_start)
+				continue;
+			if (fl->fl_start > request->fl_end)
+				break;
+			if (request->fl_type == F_UNLCK)
+				added = true;
+			if (fl->fl_start < request->fl_start)
+				left = fl;
+			/* If the next lock in the list has a higher end
+			 * address than the new one, insert the new one here.
+			 */
+			if (fl->fl_end > request->fl_end) {
+				right = fl;
+				break;
+			}
+			if (fl->fl_start >= request->fl_start) {
+				/* The new lock completely replaces an old
+				 * one (This may happen several times).
+				 */
+				if (added) {
+					locks_delete_lock_ctx(fl, &dispose);
+					continue;
+				}
+				/*
+				 * Replace the old lock with new_fl, and
+				 * remove the old one. It's safe to do the
+				 * insert here since we know that we won't be
+				 * using new_fl later, and that the lock is
+				 * just replacing an existing lock.
+				 */
+				error = -ENOLCK;
+				if (!new_fl)
+					goto out;
+				locks_copy_lock(new_fl, request);
+				request = new_fl;
+				new_fl = NULL;
+				locks_insert_lock_ctx(request, &fl->fl_list);
+				locks_delete_lock_ctx(fl, &dispose);
+				added = true;
+			}
+		}
+	}
+
+	/*
+	 * The above code only modifies existing locks in case of merging or
+	 * replacing. If new lock(s) need to be inserted all modifications are
+	 * done below this, so it's safe yet to bail out.
+	 */
+	error = -ENOLCK; /* "no luck" */
+	if (right && left == right && !new_fl2)
+		goto out;
+
+	error = 0;
+	if (!added) {
+		if (request->fl_type == F_UNLCK) {
+			if (request->fl_flags & FL_EXISTS)
+				error = -ENOENT;
+			goto out;
+		}
+
+		if (!new_fl) {
+			error = -ENOLCK;
+			goto out;
+		}
+		locks_copy_lock(new_fl, request);
+		locks_insert_lock_ctx(new_fl, &fl->fl_list);
+		fl = new_fl;
+		new_fl = NULL;
+	}
+	if (right) {
+		if (left == right) {
+			/* The new lock breaks the old one in two pieces,
+			 * so we have to use the second new lock.
+			 */
+			left = new_fl2;
+			new_fl2 = NULL;
+			locks_copy_lock(left, right);
+			locks_insert_lock_ctx(left, &fl->fl_list);
+		}
+		right->fl_start = request->fl_end + 1;
+		locks_wake_up_blocks(right);
+	}
+	if (left) {
+		left->fl_end = request->fl_start - 1;
+		locks_wake_up_blocks(left);
+	}
+ out:
+	spin_unlock(&ctx->flc_lock);
+	/*
+	 * Free any unused locks.
+	 */
+	if (new_fl)
+		locks_free_lock(new_fl);
+	if (new_fl2)
+		locks_free_lock(new_fl2);
+	locks_dispose_list(&dispose);
+	return error;
+}
+
+/**
+ * posix_lock_file - Apply a POSIX-style lock to a file
+ * @filp: The file to apply the lock to
+ * @fl: The lock to be applied
+ * @conflock: Place to return a copy of the conflicting lock, if found.
+ *
+ * Add a POSIX style lock to a file.
+ * We merge adjacent & overlapping locks whenever possible.
+ * POSIX locks are sorted by owner task, then by starting address
+ *
+ * Note that if called with an FL_EXISTS argument, the caller may determine
+ * whether or not a lock was successfully freed by testing the return
+ * value for -ENOENT.
+ */
+int posix_lock_file(struct file *filp, struct file_lock *fl,
+			struct file_lock *conflock)
+{
+	return __posix_lock_file(file_inode(filp), fl, conflock);
+}
+EXPORT_SYMBOL(posix_lock_file);
+
+/**
+ * posix_lock_file_wait - Apply a POSIX-style lock to a file
+ * @filp: The file to apply the lock to
+ * @fl: The lock to be applied
+ *
+ * Add a POSIX style lock to a file.
+ * We merge adjacent & overlapping locks whenever possible.
+ * POSIX locks are sorted by owner task, then by starting address
+ */
+int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
+{
+	int error;
+	might_sleep ();
+	for (;;) {
+		error = posix_lock_file(filp, fl, NULL);
+		if (error != FILE_LOCK_DEFERRED)
+			break;
+		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+		if (!error)
+			continue;
+
+		locks_delete_block(fl);
+		break;
+	}
+	return error;
+}
+EXPORT_SYMBOL(posix_lock_file_wait);
+
+/**
+ * locks_mandatory_locked - Check for an active lock
+ * @file: the file to check
+ *
+ * Searches the inode's list of locks to find any POSIX locks which conflict.
+ * This function is called from locks_verify_locked() only.
+ */
+int locks_mandatory_locked(struct file *file)
+{
+	int ret;
+	struct inode *inode = file_inode(file);
+	struct file_lock_context *ctx;
+	struct file_lock *fl;
+
+	ctx = inode->i_flctx;
+	if (!ctx || list_empty_careful(&ctx->flc_posix))
+		return 0;
+
+	/*
+	 * Search the lock list for this inode for any POSIX locks.
+	 */
+	spin_lock(&ctx->flc_lock);
+	ret = 0;
+	list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
+		if (fl->fl_owner != current->files &&
+		    fl->fl_owner != file) {
+			ret = -EAGAIN;
+			break;
+		}
+	}
+	spin_unlock(&ctx->flc_lock);
+	return ret;
+}
+
+/**
+ * locks_mandatory_area - Check for a conflicting lock
+ * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
+ *		for shared
+ * @inode:      the file to check
+ * @filp:       how the file was opened (if it was)
+ * @offset:     start of area to check
+ * @count:      length of area to check
+ *
+ * Searches the inode's list of locks to find any POSIX locks which conflict.
+ * This function is called from rw_verify_area() and
+ * locks_verify_truncate().
+ */
+int locks_mandatory_area(int read_write, struct inode *inode,
+			 struct file *filp, loff_t offset,
+			 size_t count)
+{
+	struct file_lock fl;
+	int error;
+	bool sleep = false;
+
+	locks_init_lock(&fl);
+	fl.fl_pid = current->tgid;
+	fl.fl_file = filp;
+	fl.fl_flags = FL_POSIX | FL_ACCESS;
+	if (filp && !(filp->f_flags & O_NONBLOCK))
+		sleep = true;
+	fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
+	fl.fl_start = offset;
+	fl.fl_end = offset + count - 1;
+
+	for (;;) {
+		if (filp) {
+			fl.fl_owner = filp;
+			fl.fl_flags &= ~FL_SLEEP;
+			error = __posix_lock_file(inode, &fl, NULL);
+			if (!error)
+				break;
+		}
+
+		if (sleep)
+			fl.fl_flags |= FL_SLEEP;
+		fl.fl_owner = current->files;
+		error = __posix_lock_file(inode, &fl, NULL);
+		if (error != FILE_LOCK_DEFERRED)
+			break;
+		error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
+		if (!error) {
+			/*
+			 * If we've been sleeping someone might have
+			 * changed the permissions behind our back.
+			 */
+			if (__mandatory_lock(inode))
+				continue;
+		}
+
+		locks_delete_block(&fl);
+		break;
+	}
+
+	return error;
+}
+
+EXPORT_SYMBOL(locks_mandatory_area);
+
+static void lease_clear_pending(struct file_lock *fl, int arg)
+{
+	switch (arg) {
+	case F_UNLCK:
+		fl->fl_flags &= ~FL_UNLOCK_PENDING;
+		/* fall through: */
+	case F_RDLCK:
+		fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
+	}
+}
+
+/* We already had a lease on this file; just change its type */
+int lease_modify(struct file_lock *fl, int arg, struct list_head *dispose)
+{
+	int error = assign_type(fl, arg);
+
+	if (error)
+		return error;
+	lease_clear_pending(fl, arg);
+	locks_wake_up_blocks(fl);
+	if (arg == F_UNLCK) {
+		struct file *filp = fl->fl_file;
+
+		f_delown(filp);
+		filp->f_owner.signum = 0;
+		fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
+		if (fl->fl_fasync != NULL) {
+			printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
+			fl->fl_fasync = NULL;
+		}
+		locks_delete_lock_ctx(fl, dispose);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(lease_modify);
+
+static bool past_time(unsigned long then)
+{
+	if (!then)
+		/* 0 is a special value meaning "this never expires": */
+		return false;
+	return time_after(jiffies, then);
+}
+
+static void time_out_leases(struct inode *inode, struct list_head *dispose)
+{
+	struct file_lock_context *ctx = inode->i_flctx;
+	struct file_lock *fl, *tmp;
+
+	lockdep_assert_held(&ctx->flc_lock);
+
+	list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
+		trace_time_out_leases(inode, fl);
+		if (past_time(fl->fl_downgrade_time))
+			lease_modify(fl, F_RDLCK, dispose);
+		if (past_time(fl->fl_break_time))
+			lease_modify(fl, F_UNLCK, dispose);
+	}
+}
+
+static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
+{
+	if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT))
+		return false;
+	if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
+		return false;
+	return locks_conflict(breaker, lease);
+}
+
+static bool
+any_leases_conflict(struct inode *inode, struct file_lock *breaker)
+{
+	struct file_lock_context *ctx = inode->i_flctx;
+	struct file_lock *fl;
+
+	lockdep_assert_held(&ctx->flc_lock);
+
+	list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
+		if (leases_conflict(fl, breaker))
+			return true;
+	}
+	return false;
+}
+
+/**
+ *	__break_lease	-	revoke all outstanding leases on file
+ *	@inode: the inode of the file to return
+ *	@mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
+ *	    break all leases
+ *	@type: FL_LEASE: break leases and delegations; FL_DELEG: break
+ *	    only delegations
+ *
+ *	break_lease (inlined for speed) has checked there already is at least
+ *	some kind of lock (maybe a lease) on this file.  Leases are broken on
+ *	a call to open() or truncate().  This function can sleep unless you
+ *	specified %O_NONBLOCK to your open().
+ */
+int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
+{
+	int error = 0;
+	struct file_lock_context *ctx = inode->i_flctx;
+	struct file_lock *new_fl, *fl, *tmp;
+	unsigned long break_time;
+	int want_write = (mode & O_ACCMODE) != O_RDONLY;
+	LIST_HEAD(dispose);
+
+	new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
+	if (IS_ERR(new_fl))
+		return PTR_ERR(new_fl);
+	new_fl->fl_flags = type;
+
+	/* typically we will check that ctx is non-NULL before calling */
+	if (!ctx) {
+		WARN_ON_ONCE(1);
+		return error;
+	}
+
+	spin_lock(&ctx->flc_lock);
+
+	time_out_leases(inode, &dispose);
+
+	if (!any_leases_conflict(inode, new_fl))
+		goto out;
+
+	break_time = 0;
+	if (lease_break_time > 0) {
+		break_time = jiffies + lease_break_time * HZ;
+		if (break_time == 0)
+			break_time++;	/* so that 0 means no break time */
+	}
+
+	list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
+		if (!leases_conflict(fl, new_fl))
+			continue;
+		if (want_write) {
+			if (fl->fl_flags & FL_UNLOCK_PENDING)
+				continue;
+			fl->fl_flags |= FL_UNLOCK_PENDING;
+			fl->fl_break_time = break_time;
+		} else {
+			if (lease_breaking(fl))
+				continue;
+			fl->fl_flags |= FL_DOWNGRADE_PENDING;
+			fl->fl_downgrade_time = break_time;
+		}
+		if (fl->fl_lmops->lm_break(fl))
+			locks_delete_lock_ctx(fl, &dispose);
+	}
+
+	if (list_empty(&ctx->flc_lease))
+		goto out;
+
+	if (mode & O_NONBLOCK) {
+		trace_break_lease_noblock(inode, new_fl);
+		error = -EWOULDBLOCK;
+		goto out;
+	}
+
+restart:
+	fl = list_first_entry(&ctx->flc_lease, struct file_lock, fl_list);
+	break_time = fl->fl_break_time;
+	if (break_time != 0)
+		break_time -= jiffies;
+	if (break_time == 0)
+		break_time++;
+	locks_insert_block(fl, new_fl);
+	trace_break_lease_block(inode, new_fl);
+	spin_unlock(&ctx->flc_lock);
+	locks_dispose_list(&dispose);
+	error = wait_event_interruptible_timeout(new_fl->fl_wait,
+						!new_fl->fl_next, break_time);
+	spin_lock(&ctx->flc_lock);
+	trace_break_lease_unblock(inode, new_fl);
+	locks_delete_block(new_fl);
+	if (error >= 0) {
+		/*
+		 * Wait for the next conflicting lease that has not been
+		 * broken yet
+		 */
+		if (error == 0)
+			time_out_leases(inode, &dispose);
+		if (any_leases_conflict(inode, new_fl))
+			goto restart;
+		error = 0;
+	}
+out:
+	spin_unlock(&ctx->flc_lock);
+	locks_dispose_list(&dispose);
+	locks_free_lock(new_fl);
+	return error;
+}
+
+EXPORT_SYMBOL(__break_lease);
+
+/**
+ *	lease_get_mtime - get the last modified time of an inode
+ *	@inode: the inode
+ *      @time:  pointer to a timespec which will contain the last modified time
+ *
+ * This is to force NFS clients to flush their caches for files with
+ * exclusive leases.  The justification is that if someone has an
+ * exclusive lease, then they could be modifying it.
+ */
+void lease_get_mtime(struct inode *inode, struct timespec *time)
+{
+	bool has_lease = false;
+	struct file_lock_context *ctx = inode->i_flctx;
+	struct file_lock *fl;
+
+	if (ctx && !list_empty_careful(&ctx->flc_lease)) {
+		spin_lock(&ctx->flc_lock);
+		if (!list_empty(&ctx->flc_lease)) {
+			fl = list_first_entry(&ctx->flc_lease,
+						struct file_lock, fl_list);
+			if (fl->fl_type == F_WRLCK)
+				has_lease = true;
+		}
+		spin_unlock(&ctx->flc_lock);
+	}
+
+	if (has_lease)
+		*time = current_fs_time(inode->i_sb);
+	else
+		*time = inode->i_mtime;
+}
+
+EXPORT_SYMBOL(lease_get_mtime);
+
+/**
+ *	fcntl_getlease - Enquire what lease is currently active
+ *	@filp: the file
+ *
+ *	The value returned by this function will be one of
+ *	(if no lease break is pending):
+ *
+ *	%F_RDLCK to indicate a shared lease is held.
+ *
+ *	%F_WRLCK to indicate an exclusive lease is held.
+ *
+ *	%F_UNLCK to indicate no lease is held.
+ *
+ *	(if a lease break is pending):
+ *
+ *	%F_RDLCK to indicate an exclusive lease needs to be
+ *		changed to a shared lease (or removed).
+ *
+ *	%F_UNLCK to indicate the lease needs to be removed.
+ *
+ *	XXX: sfr & willy disagree over whether F_INPROGRESS
+ *	should be returned to userspace.
+ */
+int fcntl_getlease(struct file *filp)
+{
+	struct file_lock *fl;
+	struct inode *inode = file_inode(filp);
+	struct file_lock_context *ctx = inode->i_flctx;
+	int type = F_UNLCK;
+	LIST_HEAD(dispose);
+
+	if (ctx && !list_empty_careful(&ctx->flc_lease)) {
+		spin_lock(&ctx->flc_lock);
+		time_out_leases(file_inode(filp), &dispose);
+		list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
+			if (fl->fl_file != filp)
+				continue;
+			type = target_leasetype(fl);
+			break;
+		}
+		spin_unlock(&ctx->flc_lock);
+		locks_dispose_list(&dispose);
+	}
+	return type;
+}
+
+/**
+ * check_conflicting_open - see if the given dentry points to a file that has
+ * 			    an existing open that would conflict with the
+ * 			    desired lease.
+ * @dentry:	dentry to check
+ * @arg:	type of lease that we're trying to acquire
+ *
+ * Check to see if there's an existing open fd on this file that would
+ * conflict with the lease we're trying to set.
+ */
+static int
+check_conflicting_open(const struct dentry *dentry, const long arg, int flags)
+{
+	int ret = 0;
+	struct inode *inode = dentry->d_inode;
+
+	if (flags & FL_LAYOUT)
+		return 0;
+
+	if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
+		return -EAGAIN;
+
+	if ((arg == F_WRLCK) && ((d_count(dentry) > 1) ||
+	    (atomic_read(&inode->i_count) > 1)))
+		ret = -EAGAIN;
+
+	return ret;
+}
+
+static int
+generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **priv)
+{
+	struct file_lock *fl, *my_fl = NULL, *lease;
+	struct dentry *dentry = filp->f_path.dentry;
+	struct inode *inode = dentry->d_inode;
+	struct file_lock_context *ctx;
+	bool is_deleg = (*flp)->fl_flags & FL_DELEG;
+	int error;
+	LIST_HEAD(dispose);
+
+	lease = *flp;
+	trace_generic_add_lease(inode, lease);
+
+	/* Note that arg is never F_UNLCK here */
+	ctx = locks_get_lock_context(inode, arg);
+	if (!ctx)
+		return -ENOMEM;
+
+	/*
+	 * In the delegation case we need mutual exclusion with
+	 * a number of operations that take the i_mutex.  We trylock
+	 * because delegations are an optional optimization, and if
+	 * there's some chance of a conflict--we'd rather not
+	 * bother, maybe that's a sign this just isn't a good file to
+	 * hand out a delegation on.
+	 */
+	if (is_deleg && !mutex_trylock(&inode->i_mutex))
+		return -EAGAIN;
+
+	if (is_deleg && arg == F_WRLCK) {
+		/* Write delegations are not currently supported: */
+		mutex_unlock(&inode->i_mutex);
+		WARN_ON_ONCE(1);
+		return -EINVAL;
+	}
+
+	spin_lock(&ctx->flc_lock);
+	time_out_leases(inode, &dispose);
+	error = check_conflicting_open(dentry, arg, lease->fl_flags);
+	if (error)
+		goto out;
+
+	/*
+	 * At this point, we know that if there is an exclusive
+	 * lease on this file, then we hold it on this filp
+	 * (otherwise our open of this file would have blocked).
+	 * And if we are trying to acquire an exclusive lease,
+	 * then the file is not open by anyone (including us)
+	 * except for this filp.
+	 */
+	error = -EAGAIN;
+	list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
+		if (fl->fl_file == filp &&
+		    fl->fl_owner == lease->fl_owner) {
+			my_fl = fl;
+			continue;
+		}
+
+		/*
+		 * No exclusive leases if someone else has a lease on
+		 * this file:
+		 */
+		if (arg == F_WRLCK)
+			goto out;
+		/*
+		 * Modifying our existing lease is OK, but no getting a
+		 * new lease if someone else is opening for write:
+		 */
+		if (fl->fl_flags & FL_UNLOCK_PENDING)
+			goto out;
+	}
+
+	if (my_fl != NULL) {
+		lease = my_fl;
+		error = lease->fl_lmops->lm_change(lease, arg, &dispose);
+		if (error)
+			goto out;
+		goto out_setup;
+	}
+
+	error = -EINVAL;
+	if (!leases_enable)
+		goto out;
+
+	locks_insert_lock_ctx(lease, &ctx->flc_lease);
+	/*
+	 * The check in break_lease() is lockless. It's possible for another
+	 * open to race in after we did the earlier check for a conflicting
+	 * open but before the lease was inserted. Check again for a
+	 * conflicting open and cancel the lease if there is one.
+	 *
+	 * We also add a barrier here to ensure that the insertion of the lock
+	 * precedes these checks.
+	 */
+	smp_mb();
+	error = check_conflicting_open(dentry, arg, lease->fl_flags);
+	if (error) {
+		locks_unlink_lock_ctx(lease);
+		goto out;
+	}
+
+out_setup:
+	if (lease->fl_lmops->lm_setup)
+		lease->fl_lmops->lm_setup(lease, priv);
+out:
+	spin_unlock(&ctx->flc_lock);
+	locks_dispose_list(&dispose);
+	if (is_deleg)
+		mutex_unlock(&inode->i_mutex);
+	if (!error && !my_fl)
+		*flp = NULL;
+	return error;
+}
+
+static int generic_delete_lease(struct file *filp, void *owner)
+{
+	int error = -EAGAIN;
+	struct file_lock *fl, *victim = NULL;
+	struct dentry *dentry = filp->f_path.dentry;
+	struct inode *inode = dentry->d_inode;
+	struct file_lock_context *ctx = inode->i_flctx;
+	LIST_HEAD(dispose);
+
+	if (!ctx) {
+		trace_generic_delete_lease(inode, NULL);
+		return error;
+	}
+
+	spin_lock(&ctx->flc_lock);
+	list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
+		if (fl->fl_file == filp &&
+		    fl->fl_owner == owner) {
+			victim = fl;
+			break;
+		}
+	}
+	trace_generic_delete_lease(inode, victim);
+	if (victim)
+		error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
+	spin_unlock(&ctx->flc_lock);
+	locks_dispose_list(&dispose);
+	return error;
+}
+
+/**
+ *	generic_setlease	-	sets a lease on an open file
+ *	@filp:	file pointer
+ *	@arg:	type of lease to obtain
+ *	@flp:	input - file_lock to use, output - file_lock inserted
+ *	@priv:	private data for lm_setup (may be NULL if lm_setup
+ *		doesn't require it)
+ *
+ *	The (input) flp->fl_lmops->lm_break function is required
+ *	by break_lease().
+ */
+int generic_setlease(struct file *filp, long arg, struct file_lock **flp,
+			void **priv)
+{
+	struct dentry *dentry = filp->f_path.dentry;
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
+		return -EACCES;
+	if (!S_ISREG(inode->i_mode))
+		return -EINVAL;
+	error = security_file_lock(filp, arg);
+	if (error)
+		return error;
+
+	switch (arg) {
+	case F_UNLCK:
+		return generic_delete_lease(filp, *priv);
+	case F_RDLCK:
+	case F_WRLCK:
+		if (!(*flp)->fl_lmops->lm_break) {
+			WARN_ON_ONCE(1);
+			return -ENOLCK;
+		}
+
+		return generic_add_lease(filp, arg, flp, priv);
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(generic_setlease);
+
+/**
+ * vfs_setlease        -       sets a lease on an open file
+ * @filp:	file pointer
+ * @arg:	type of lease to obtain
+ * @lease:	file_lock to use when adding a lease
+ * @priv:	private info for lm_setup when adding a lease (may be
+ * 		NULL if lm_setup doesn't require it)
+ *
+ * Call this to establish a lease on the file. The "lease" argument is not
+ * used for F_UNLCK requests and may be NULL. For commands that set or alter
+ * an existing lease, the (*lease)->fl_lmops->lm_break operation must be set;
+ * if not, this function will return -ENOLCK (and generate a scary-looking
+ * stack trace).
+ *
+ * The "priv" pointer is passed directly to the lm_setup function as-is. It
+ * may be NULL if the lm_setup operation doesn't require it.
+ */
+int
+vfs_setlease(struct file *filp, long arg, struct file_lock **lease, void **priv)
+{
+	if (filp->f_op->setlease)
+		return filp->f_op->setlease(filp, arg, lease, priv);
+	else
+		return generic_setlease(filp, arg, lease, priv);
+}
+EXPORT_SYMBOL_GPL(vfs_setlease);
+
+static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
+{
+	struct file_lock *fl;
+	struct fasync_struct *new;
+	int error;
+
+	fl = lease_alloc(filp, arg);
+	if (IS_ERR(fl))
+		return PTR_ERR(fl);
+
+	new = fasync_alloc();
+	if (!new) {
+		locks_free_lock(fl);
+		return -ENOMEM;
+	}
+	new->fa_fd = fd;
+
+	error = vfs_setlease(filp, arg, &fl, (void **)&new);
+	if (fl)
+		locks_free_lock(fl);
+	if (new)
+		fasync_free(new);
+	return error;
+}
+
+/**
+ *	fcntl_setlease	-	sets a lease on an open file
+ *	@fd: open file descriptor
+ *	@filp: file pointer
+ *	@arg: type of lease to obtain
+ *
+ *	Call this fcntl to establish a lease on the file.
+ *	Note that you also need to call %F_SETSIG to
+ *	receive a signal when the lease is broken.
+ */
+int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
+{
+	if (arg == F_UNLCK)
+		return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
+	return do_fcntl_add_lease(fd, filp, arg);
+}
+
+/**
+ * flock_lock_file_wait - Apply a FLOCK-style lock to a file
+ * @filp: The file to apply the lock to
+ * @fl: The lock to be applied
+ *
+ * Add a FLOCK style lock to a file.
+ */
+int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
+{
+	int error;
+	might_sleep();
+	for (;;) {
+		error = flock_lock_file(filp, fl);
+		if (error != FILE_LOCK_DEFERRED)
+			break;
+		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+		if (!error)
+			continue;
+
+		locks_delete_block(fl);
+		break;
+	}
+	return error;
+}
+
+EXPORT_SYMBOL(flock_lock_file_wait);
+
+/**
+ *	sys_flock: - flock() system call.
+ *	@fd: the file descriptor to lock.
+ *	@cmd: the type of lock to apply.
+ *
+ *	Apply a %FL_FLOCK style lock to an open file descriptor.
+ *	The @cmd can be one of
+ *
+ *	%LOCK_SH -- a shared lock.
+ *
+ *	%LOCK_EX -- an exclusive lock.
+ *
+ *	%LOCK_UN -- remove an existing lock.
+ *
+ *	%LOCK_MAND -- a `mandatory' flock.  This exists to emulate Windows Share Modes.
+ *
+ *	%LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
+ *	processes read and write access respectively.
+ */
+SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
+{
+	struct fd f = fdget(fd);
+	struct file_lock *lock;
+	int can_sleep, unlock;
+	int error;
+
+	error = -EBADF;
+	if (!f.file)
+		goto out;
+
+	can_sleep = !(cmd & LOCK_NB);
+	cmd &= ~LOCK_NB;
+	unlock = (cmd == LOCK_UN);
+
+	if (!unlock && !(cmd & LOCK_MAND) &&
+	    !(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
+		goto out_putf;
+
+	lock = flock_make_lock(f.file, cmd);
+	if (IS_ERR(lock)) {
+		error = PTR_ERR(lock);
+		goto out_putf;
+	}
+
+	if (can_sleep)
+		lock->fl_flags |= FL_SLEEP;
+
+	error = security_file_lock(f.file, lock->fl_type);
+	if (error)
+		goto out_free;
+
+	if (f.file->f_op->flock)
+		error = f.file->f_op->flock(f.file,
+					  (can_sleep) ? F_SETLKW : F_SETLK,
+					  lock);
+	else
+		error = flock_lock_file_wait(f.file, lock);
+
+ out_free:
+	locks_free_lock(lock);
+
+ out_putf:
+	fdput(f);
+ out:
+	return error;
+}
+
+/**
+ * vfs_test_lock - test file byte range lock
+ * @filp: The file to test lock for
+ * @fl: The lock to test; also used to hold result
+ *
+ * Returns -ERRNO on failure.  Indicates presence of conflicting lock by
+ * setting conf->fl_type to something other than F_UNLCK.
+ */
+int vfs_test_lock(struct file *filp, struct file_lock *fl)
+{
+	if (filp->f_op->lock)
+		return filp->f_op->lock(filp, F_GETLK, fl);
+	posix_test_lock(filp, fl);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vfs_test_lock);
+
+static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
+{
+	flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
+#if BITS_PER_LONG == 32
+	/*
+	 * Make sure we can represent the posix lock via
+	 * legacy 32bit flock.
+	 */
+	if (fl->fl_start > OFFT_OFFSET_MAX)
+		return -EOVERFLOW;
+	if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
+		return -EOVERFLOW;
+#endif
+	flock->l_start = fl->fl_start;
+	flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
+		fl->fl_end - fl->fl_start + 1;
+	flock->l_whence = 0;
+	flock->l_type = fl->fl_type;
+	return 0;
+}
+
+#if BITS_PER_LONG == 32
+static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
+{
+	flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
+	flock->l_start = fl->fl_start;
+	flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
+		fl->fl_end - fl->fl_start + 1;
+	flock->l_whence = 0;
+	flock->l_type = fl->fl_type;
+}
+#endif
+
+/* Report the first existing lock that would conflict with l.
+ * This implements the F_GETLK command of fcntl().
+ */
+int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l)
+{
+	struct file_lock file_lock;
+	struct flock flock;
+	int error;
+
+	error = -EFAULT;
+	if (copy_from_user(&flock, l, sizeof(flock)))
+		goto out;
+	error = -EINVAL;
+	if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
+		goto out;
+
+	error = flock_to_posix_lock(filp, &file_lock, &flock);
+	if (error)
+		goto out;
+
+	if (cmd == F_OFD_GETLK) {
+		error = -EINVAL;
+		if (flock.l_pid != 0)
+			goto out;
+
+		cmd = F_GETLK;
+		file_lock.fl_flags |= FL_OFDLCK;
+		file_lock.fl_owner = filp;
+	}
+
+	error = vfs_test_lock(filp, &file_lock);
+	if (error)
+		goto out;
+ 
+	flock.l_type = file_lock.fl_type;
+	if (file_lock.fl_type != F_UNLCK) {
+		error = posix_lock_to_flock(&flock, &file_lock);
+		if (error)
+			goto rel_priv;
+	}
+	error = -EFAULT;
+	if (!copy_to_user(l, &flock, sizeof(flock)))
+		error = 0;
+rel_priv:
+	locks_release_private(&file_lock);
+out:
+	return error;
+}
+
+/**
+ * vfs_lock_file - file byte range lock
+ * @filp: The file to apply the lock to
+ * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
+ * @fl: The lock to be applied
+ * @conf: Place to return a copy of the conflicting lock, if found.
+ *
+ * A caller that doesn't care about the conflicting lock may pass NULL
+ * as the final argument.
+ *
+ * If the filesystem defines a private ->lock() method, then @conf will
+ * be left unchanged; so a caller that cares should initialize it to
+ * some acceptable default.
+ *
+ * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
+ * locks, the ->lock() interface may return asynchronously, before the lock has
+ * been granted or denied by the underlying filesystem, if (and only if)
+ * lm_grant is set. Callers expecting ->lock() to return asynchronously
+ * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
+ * the request is for a blocking lock. When ->lock() does return asynchronously,
+ * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock
+ * request completes.
+ * If the request is for non-blocking lock the file system should return
+ * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
+ * with the result. If the request timed out the callback routine will return a
+ * nonzero return code and the file system should release the lock. The file
+ * system is also responsible to keep a corresponding posix lock when it
+ * grants a lock so the VFS can find out which locks are locally held and do
+ * the correct lock cleanup when required.
+ * The underlying filesystem must not drop the kernel lock or call
+ * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
+ * return code.
+ */
+int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
+{
+	if (filp->f_op->lock)
+		return filp->f_op->lock(filp, cmd, fl);
+	else
+		return posix_lock_file(filp, fl, conf);
+}
+EXPORT_SYMBOL_GPL(vfs_lock_file);
+
+static int do_lock_file_wait(struct file *filp, unsigned int cmd,
+			     struct file_lock *fl)
+{
+	int error;
+
+	error = security_file_lock(filp, fl->fl_type);
+	if (error)
+		return error;
+
+	for (;;) {
+		error = vfs_lock_file(filp, cmd, fl, NULL);
+		if (error != FILE_LOCK_DEFERRED)
+			break;
+		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+		if (!error)
+			continue;
+
+		locks_delete_block(fl);
+		break;
+	}
+
+	return error;
+}
+
+/* Ensure that fl->fl_filp has compatible f_mode for F_SETLK calls */
+static int
+check_fmode_for_setlk(struct file_lock *fl)
+{
+	switch (fl->fl_type) {
+	case F_RDLCK:
+		if (!(fl->fl_file->f_mode & FMODE_READ))
+			return -EBADF;
+		break;
+	case F_WRLCK:
+		if (!(fl->fl_file->f_mode & FMODE_WRITE))
+			return -EBADF;
+	}
+	return 0;
+}
+
+/* Apply the lock described by l to an open file descriptor.
+ * This implements both the F_SETLK and F_SETLKW commands of fcntl().
+ */
+int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
+		struct flock __user *l)
+{
+	struct file_lock *file_lock = locks_alloc_lock();
+	struct flock flock;
+	struct inode *inode;
+	struct file *f;
+	int error;
+
+	if (file_lock == NULL)
+		return -ENOLCK;
+
+	/*
+	 * This might block, so we do it before checking the inode.
+	 */
+	error = -EFAULT;
+	if (copy_from_user(&flock, l, sizeof(flock)))
+		goto out;
+
+	inode = file_inode(filp);
+
+	/* Don't allow mandatory locks on files that may be memory mapped
+	 * and shared.
+	 */
+	if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
+		error = -EAGAIN;
+		goto out;
+	}
+
+again:
+	error = flock_to_posix_lock(filp, file_lock, &flock);
+	if (error)
+		goto out;
+
+	error = check_fmode_for_setlk(file_lock);
+	if (error)
+		goto out;
+
+	/*
+	 * If the cmd is requesting file-private locks, then set the
+	 * FL_OFDLCK flag and override the owner.
+	 */
+	switch (cmd) {
+	case F_OFD_SETLK:
+		error = -EINVAL;
+		if (flock.l_pid != 0)
+			goto out;
+
+		cmd = F_SETLK;
+		file_lock->fl_flags |= FL_OFDLCK;
+		file_lock->fl_owner = filp;
+		break;
+	case F_OFD_SETLKW:
+		error = -EINVAL;
+		if (flock.l_pid != 0)
+			goto out;
+
+		cmd = F_SETLKW;
+		file_lock->fl_flags |= FL_OFDLCK;
+		file_lock->fl_owner = filp;
+		/* Fallthrough */
+	case F_SETLKW:
+		file_lock->fl_flags |= FL_SLEEP;
+	}
+
+	error = do_lock_file_wait(filp, cmd, file_lock);
+
+	/*
+	 * Attempt to detect a close/fcntl race and recover by
+	 * releasing the lock that was just acquired.
+	 */
+	/*
+	 * we need that spin_lock here - it prevents reordering between
+	 * update of i_flctx->flc_posix and check for it done in close().
+	 * rcu_read_lock() wouldn't do.
+	 */
+	spin_lock(&current->files->file_lock);
+	f = fcheck(fd);
+	spin_unlock(&current->files->file_lock);
+	if (!error && f != filp && flock.l_type != F_UNLCK) {
+		flock.l_type = F_UNLCK;
+		goto again;
+	}
+
+out:
+	locks_free_lock(file_lock);
+	return error;
+}
+
+#if BITS_PER_LONG == 32
+/* Report the first existing lock that would conflict with l.
+ * This implements the F_GETLK command of fcntl().
+ */
+int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
+{
+	struct file_lock file_lock;
+	struct flock64 flock;
+	int error;
+
+	error = -EFAULT;
+	if (copy_from_user(&flock, l, sizeof(flock)))
+		goto out;
+	error = -EINVAL;
+	if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
+		goto out;
+
+	error = flock64_to_posix_lock(filp, &file_lock, &flock);
+	if (error)
+		goto out;
+
+	if (cmd == F_OFD_GETLK) {
+		error = -EINVAL;
+		if (flock.l_pid != 0)
+			goto out;
+
+		cmd = F_GETLK64;
+		file_lock.fl_flags |= FL_OFDLCK;
+		file_lock.fl_owner = filp;
+	}
+
+	error = vfs_test_lock(filp, &file_lock);
+	if (error)
+		goto out;
+
+	flock.l_type = file_lock.fl_type;
+	if (file_lock.fl_type != F_UNLCK)
+		posix_lock_to_flock64(&flock, &file_lock);
+
+	error = -EFAULT;
+	if (!copy_to_user(l, &flock, sizeof(flock)))
+		error = 0;
+
+	locks_release_private(&file_lock);
+out:
+	return error;
+}
+
+/* Apply the lock described by l to an open file descriptor.
+ * This implements both the F_SETLK and F_SETLKW commands of fcntl().
+ */
+int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
+		struct flock64 __user *l)
+{
+	struct file_lock *file_lock = locks_alloc_lock();
+	struct flock64 flock;
+	struct inode *inode;
+	struct file *f;
+	int error;
+
+	if (file_lock == NULL)
+		return -ENOLCK;
+
+	/*
+	 * This might block, so we do it before checking the inode.
+	 */
+	error = -EFAULT;
+	if (copy_from_user(&flock, l, sizeof(flock)))
+		goto out;
+
+	inode = file_inode(filp);
+
+	/* Don't allow mandatory locks on files that may be memory mapped
+	 * and shared.
+	 */
+	if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
+		error = -EAGAIN;
+		goto out;
+	}
+
+again:
+	error = flock64_to_posix_lock(filp, file_lock, &flock);
+	if (error)
+		goto out;
+
+	error = check_fmode_for_setlk(file_lock);
+	if (error)
+		goto out;
+
+	/*
+	 * If the cmd is requesting file-private locks, then set the
+	 * FL_OFDLCK flag and override the owner.
+	 */
+	switch (cmd) {
+	case F_OFD_SETLK:
+		error = -EINVAL;
+		if (flock.l_pid != 0)
+			goto out;
+
+		cmd = F_SETLK64;
+		file_lock->fl_flags |= FL_OFDLCK;
+		file_lock->fl_owner = filp;
+		break;
+	case F_OFD_SETLKW:
+		error = -EINVAL;
+		if (flock.l_pid != 0)
+			goto out;
+
+		cmd = F_SETLKW64;
+		file_lock->fl_flags |= FL_OFDLCK;
+		file_lock->fl_owner = filp;
+		/* Fallthrough */
+	case F_SETLKW64:
+		file_lock->fl_flags |= FL_SLEEP;
+	}
+
+	error = do_lock_file_wait(filp, cmd, file_lock);
+
+	/*
+	 * Attempt to detect a close/fcntl race and recover by
+	 * releasing the lock that was just acquired.
+	 */
+	spin_lock(&current->files->file_lock);
+	f = fcheck(fd);
+	spin_unlock(&current->files->file_lock);
+	if (!error && f != filp && flock.l_type != F_UNLCK) {
+		flock.l_type = F_UNLCK;
+		goto again;
+	}
+
+out:
+	locks_free_lock(file_lock);
+	return error;
+}
+#endif /* BITS_PER_LONG == 32 */
+
+/*
+ * This function is called when the file is being removed
+ * from the task's fd array.  POSIX locks belonging to this task
+ * are deleted at this time.
+ */
+void locks_remove_posix(struct file *filp, fl_owner_t owner)
+{
+	struct file_lock lock;
+	struct file_lock_context *ctx = file_inode(filp)->i_flctx;
+
+	/*
+	 * If there are no locks held on this file, we don't need to call
+	 * posix_lock_file().  Another process could be setting a lock on this
+	 * file at the same time, but we wouldn't remove that lock anyway.
+	 */
+	if (!ctx || list_empty(&ctx->flc_posix))
+		return;
+
+	lock.fl_type = F_UNLCK;
+	lock.fl_flags = FL_POSIX | FL_CLOSE;
+	lock.fl_start = 0;
+	lock.fl_end = OFFSET_MAX;
+	lock.fl_owner = owner;
+	lock.fl_pid = current->tgid;
+	lock.fl_file = filp;
+	lock.fl_ops = NULL;
+	lock.fl_lmops = NULL;
+
+	vfs_lock_file(filp, F_SETLK, &lock, NULL);
+
+	if (lock.fl_ops && lock.fl_ops->fl_release_private)
+		lock.fl_ops->fl_release_private(&lock);
+}
+
+EXPORT_SYMBOL(locks_remove_posix);
+
+/* The i_flctx must be valid when calling into here */
+static void
+locks_remove_flock(struct file *filp)
+{
+	struct file_lock fl = {
+		.fl_owner = filp,
+		.fl_pid = current->tgid,
+		.fl_file = filp,
+		.fl_flags = FL_FLOCK,
+		.fl_type = F_UNLCK,
+		.fl_end = OFFSET_MAX,
+	};
+	struct file_lock_context *flctx = file_inode(filp)->i_flctx;
+
+	if (list_empty(&flctx->flc_flock))
+		return;
+
+	if (filp->f_op->flock)
+		filp->f_op->flock(filp, F_SETLKW, &fl);
+	else
+		flock_lock_file(filp, &fl);
+
+	if (fl.fl_ops && fl.fl_ops->fl_release_private)
+		fl.fl_ops->fl_release_private(&fl);
+}
+
+/* The i_flctx must be valid when calling into here */
+static void
+locks_remove_lease(struct file *filp)
+{
+	struct inode *inode = file_inode(filp);
+	struct file_lock_context *ctx = inode->i_flctx;
+	struct file_lock *fl, *tmp;
+	LIST_HEAD(dispose);
+
+	if (list_empty(&ctx->flc_lease))
+		return;
+
+	spin_lock(&ctx->flc_lock);
+	list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list)
+		if (filp == fl->fl_file)
+			lease_modify(fl, F_UNLCK, &dispose);
+	spin_unlock(&ctx->flc_lock);
+	locks_dispose_list(&dispose);
+}
+
+/*
+ * This function is called on the last close of an open file.
+ */
+void locks_remove_file(struct file *filp)
+{
+	if (!file_inode(filp)->i_flctx)
+		return;
+
+	/* remove any OFD locks */
+	locks_remove_posix(filp, filp);
+
+	/* remove flock locks */
+	locks_remove_flock(filp);
+
+	/* remove any leases */
+	locks_remove_lease(filp);
+}
+
+/**
+ *	posix_unblock_lock - stop waiting for a file lock
+ *	@waiter: the lock which was waiting
+ *
+ *	lockd needs to block waiting for locks.
+ */
+int
+posix_unblock_lock(struct file_lock *waiter)
+{
+	int status = 0;
+
+	spin_lock(&blocked_lock_lock);
+	if (waiter->fl_next)
+		__locks_delete_block(waiter);
+	else
+		status = -ENOENT;
+	spin_unlock(&blocked_lock_lock);
+	return status;
+}
+EXPORT_SYMBOL(posix_unblock_lock);
+
+/**
+ * vfs_cancel_lock - file byte range unblock lock
+ * @filp: The file to apply the unblock to
+ * @fl: The lock to be unblocked
+ *
+ * Used by lock managers to cancel blocked requests
+ */
+int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
+{
+	if (filp->f_op->lock)
+		return filp->f_op->lock(filp, F_CANCELLK, fl);
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(vfs_cancel_lock);
+
+#ifdef CONFIG_PROC_FS
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+
+struct locks_iterator {
+	int	li_cpu;
+	loff_t	li_pos;
+};
+
+static void lock_get_status(struct seq_file *f, struct file_lock *fl,
+			    loff_t id, char *pfx)
+{
+	struct inode *inode = NULL;
+	unsigned int fl_pid;
+
+	if (fl->fl_nspid)
+		fl_pid = pid_vnr(fl->fl_nspid);
+	else
+		fl_pid = fl->fl_pid;
+
+	if (fl->fl_file != NULL)
+		inode = file_inode(fl->fl_file);
+
+	seq_printf(f, "%lld:%s ", id, pfx);
+	if (IS_POSIX(fl)) {
+		if (fl->fl_flags & FL_ACCESS)
+			seq_puts(f, "ACCESS");
+		else if (IS_OFDLCK(fl))
+			seq_puts(f, "OFDLCK");
+		else
+			seq_puts(f, "POSIX ");
+
+		seq_printf(f, " %s ",
+			     (inode == NULL) ? "*NOINODE*" :
+			     mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
+	} else if (IS_FLOCK(fl)) {
+		if (fl->fl_type & LOCK_MAND) {
+			seq_puts(f, "FLOCK  MSNFS     ");
+		} else {
+			seq_puts(f, "FLOCK  ADVISORY  ");
+		}
+	} else if (IS_LEASE(fl)) {
+		if (fl->fl_flags & FL_DELEG)
+			seq_puts(f, "DELEG  ");
+		else
+			seq_puts(f, "LEASE  ");
+
+		if (lease_breaking(fl))
+			seq_puts(f, "BREAKING  ");
+		else if (fl->fl_file)
+			seq_puts(f, "ACTIVE    ");
+		else
+			seq_puts(f, "BREAKER   ");
+	} else {
+		seq_puts(f, "UNKNOWN UNKNOWN  ");
+	}
+	if (fl->fl_type & LOCK_MAND) {
+		seq_printf(f, "%s ",
+			       (fl->fl_type & LOCK_READ)
+			       ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
+			       : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
+	} else {
+		seq_printf(f, "%s ",
+			       (lease_breaking(fl))
+			       ? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ "
+			       : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
+	}
+	if (inode) {
+		/* userspace relies on this representation of dev_t */
+		seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
+				MAJOR(inode->i_sb->s_dev),
+				MINOR(inode->i_sb->s_dev), inode->i_ino);
+	} else {
+		seq_printf(f, "%d <none>:0 ", fl_pid);
+	}
+	if (IS_POSIX(fl)) {
+		if (fl->fl_end == OFFSET_MAX)
+			seq_printf(f, "%Ld EOF\n", fl->fl_start);
+		else
+			seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
+	} else {
+		seq_puts(f, "0 EOF\n");
+	}
+}
+
+static int locks_show(struct seq_file *f, void *v)
+{
+	struct locks_iterator *iter = f->private;
+	struct file_lock *fl, *bfl;
+
+	fl = hlist_entry(v, struct file_lock, fl_link);
+
+	lock_get_status(f, fl, iter->li_pos, "");
+
+	list_for_each_entry(bfl, &fl->fl_block, fl_block)
+		lock_get_status(f, bfl, iter->li_pos, " ->");
+
+	return 0;
+}
+
+static void __show_fd_locks(struct seq_file *f,
+			struct list_head *head, int *id,
+			struct file *filp, struct files_struct *files)
+{
+	struct file_lock *fl;
+
+	list_for_each_entry(fl, head, fl_list) {
+
+		if (filp != fl->fl_file)
+			continue;
+		if (fl->fl_owner != files &&
+		    fl->fl_owner != filp)
+			continue;
+
+		(*id)++;
+		seq_puts(f, "lock:\t");
+		lock_get_status(f, fl, *id, "");
+	}
+}
+
+void show_fd_locks(struct seq_file *f,
+		  struct file *filp, struct files_struct *files)
+{
+	struct inode *inode = file_inode(filp);
+	struct file_lock_context *ctx;
+	int id = 0;
+
+	ctx = inode->i_flctx;
+	if (!ctx)
+		return;
+
+	spin_lock(&ctx->flc_lock);
+	__show_fd_locks(f, &ctx->flc_flock, &id, filp, files);
+	__show_fd_locks(f, &ctx->flc_posix, &id, filp, files);
+	__show_fd_locks(f, &ctx->flc_lease, &id, filp, files);
+	spin_unlock(&ctx->flc_lock);
+}
+
+static void *locks_start(struct seq_file *f, loff_t *pos)
+	__acquires(&blocked_lock_lock)
+{
+	struct locks_iterator *iter = f->private;
+
+	iter->li_pos = *pos + 1;
+	lg_global_lock(&file_lock_lglock);
+	spin_lock(&blocked_lock_lock);
+	return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos);
+}
+
+static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
+{
+	struct locks_iterator *iter = f->private;
+
+	++iter->li_pos;
+	return seq_hlist_next_percpu(v, &file_lock_list, &iter->li_cpu, pos);
+}
+
+static void locks_stop(struct seq_file *f, void *v)
+	__releases(&blocked_lock_lock)
+{
+	spin_unlock(&blocked_lock_lock);
+	lg_global_unlock(&file_lock_lglock);
+}
+
+static const struct seq_operations locks_seq_operations = {
+	.start	= locks_start,
+	.next	= locks_next,
+	.stop	= locks_stop,
+	.show	= locks_show,
+};
+
+static int locks_open(struct inode *inode, struct file *filp)
+{
+	return seq_open_private(filp, &locks_seq_operations,
+					sizeof(struct locks_iterator));
+}
+
+static const struct file_operations proc_locks_operations = {
+	.open		= locks_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release_private,
+};
+
+static int __init proc_locks_init(void)
+{
+	proc_create("locks", 0, NULL, &proc_locks_operations);
+	return 0;
+}
+module_init(proc_locks_init);
+#endif
+
+static int __init filelock_init(void)
+{
+	int i;
+
+	flctx_cache = kmem_cache_create("file_lock_ctx",
+			sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL);
+
+	filelock_cache = kmem_cache_create("file_lock_cache",
+			sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
+
+	lg_lock_init(&file_lock_lglock, "file_lock_lglock");
+
+	for_each_possible_cpu(i)
+		INIT_HLIST_HEAD(per_cpu_ptr(&file_lock_list, i));
+
+	return 0;
+}
+
+core_initcall(filelock_init);