Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 2212 insertions, 0 deletions

diff --git a/fs/locks.c b/fs/locks.c
new file mode 100644
index 000000000000..1792ce547af7
--- /dev/null
+++ b/fs/locks.c
@@ -0,0 +1,2212 @@
+/*
+ *  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/mandatory.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/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/security.h>
+#include <linux/slab.h>
+#include <linux/smp_lock.h>
+#include <linux/syscalls.h>
+#include <linux/time.h>
+
+#include <asm/semaphore.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)
+
+int leases_enable = 1;
+int lease_break_time = 45;
+
+#define for_each_lock(inode, lockp) \
+        for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
+
+LIST_HEAD(file_lock_list);
+
+EXPORT_SYMBOL(file_lock_list);
+
+static LIST_HEAD(blocked_list);
+
+static kmem_cache_t *filelock_cache;
+
+/* Allocate an empty lock structure. */
+static struct file_lock *locks_alloc_lock(void)
+{
+        return kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
+}
+
+/* Free a lock which is not in use. */
+static inline void locks_free_lock(struct file_lock *fl)
+{
+        if (fl == NULL) {
+                BUG();
+                return;
+        }
+        if (waitqueue_active(&fl->fl_wait))
+                panic("Attempting to free lock with active wait queue");
+
+        if (!list_empty(&fl->fl_block))
+                panic("Attempting to free lock with active block list");
+
+        if (!list_empty(&fl->fl_link))
+                panic("Attempting to free lock on active lock list");
+
+        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->fl_release_private)
+                        fl->fl_lmops->fl_release_private(fl);
+                fl->fl_lmops = NULL;
+        }
+
+        kmem_cache_free(filelock_cache, fl);
+}
+
+void locks_init_lock(struct file_lock *fl)
+{
+        INIT_LIST_HEAD(&fl->fl_link);
+        INIT_LIST_HEAD(&fl->fl_block);
+        init_waitqueue_head(&fl->fl_wait);
+        fl->fl_next = NULL;
+        fl->fl_fasync = NULL;
+        fl->fl_owner = NULL;
+        fl->fl_pid = 0;
+        fl->fl_file = NULL;
+        fl->fl_flags = 0;
+        fl->fl_type = 0;
+        fl->fl_start = fl->fl_end = 0;
+        fl->fl_ops = NULL;
+        fl->fl_lmops = NULL;
+}
+
+EXPORT_SYMBOL(locks_init_lock);
+
+/*
+ * Initialises the fields of the file lock which are invariant for
+ * free file_locks.
+ */
+static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags)
+{
+        struct file_lock *lock = (struct file_lock *) foo;
+
+        if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
+                                        SLAB_CTOR_CONSTRUCTOR)
+                return;
+
+        locks_init_lock(lock);
+}
+
+/*
+ * Initialize a new lock from an existing file_lock structure.
+ */
+void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
+{
+        new->fl_owner = fl->fl_owner;
+        new->fl_pid = fl->fl_pid;
+        new->fl_file = fl->fl_file;
+        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_ops = fl->fl_ops;
+        new->fl_lmops = fl->fl_lmops;
+        if (fl->fl_ops && fl->fl_ops->fl_copy_lock)
+                fl->fl_ops->fl_copy_lock(new, fl);
+        if (fl->fl_lmops && fl->fl_lmops->fl_copy_lock)
+                fl->fl_lmops->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 int flock_make_lock(struct file *filp, struct file_lock **lock,
+                unsigned int cmd)
+{
+        struct file_lock *fl;
+        int type = flock_translate_cmd(cmd);
+        if (type < 0)
+                return type;
+        
+        fl = locks_alloc_lock();
+        if (fl == NULL)
+                return -ENOMEM;
+
+        fl->fl_file = filp;
+        fl->fl_pid = current->tgid;
+        fl->fl_flags = FL_FLOCK;
+        fl->fl_type = type;
+        fl->fl_end = OFFSET_MAX;
+        
+        *lock = fl;
+        return 0;
+}
+
+static int assign_type(struct file_lock *fl, int type)
+{
+        switch (type) {
+        case F_RDLCK:
+        case F_WRLCK:
+        case F_UNLCK:
+                fl->fl_type = type;
+                break;
+        default:
+                return -EINVAL;
+        }
+        return 0;
+}
+
+/* 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)
+{
+        off_t start, end;
+
+        switch (l->l_whence) {
+        case 0: /*SEEK_SET*/
+                start = 0;
+                break;
+        case 1: /*SEEK_CUR*/
+                start = filp->f_pos;
+                break;
+        case 2: /*SEEK_END*/
+                start = i_size_read(filp->f_dentry->d_inode);
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        /* POSIX-1996 leaves the case l->l_len < 0 undefined;
+           POSIX-2001 defines it. */
+        start += l->l_start;
+        end = start + l->l_len - 1;
+        if (l->l_len < 0) {
+                end = start - 1;
+                start += l->l_len;
+        }
+
+        if (start < 0)
+                return -EINVAL;
+        if (l->l_len > 0 && end < 0)
+                return -EOVERFLOW;
+
+        fl->fl_start = start;   /* we record the absolute position */
+        fl->fl_end = end;
+        if (l->l_len == 0)
+                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);
+}
+
+#if BITS_PER_LONG == 32
+static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
+                                 struct flock64 *l)
+{
+        loff_t start;
+
+        switch (l->l_whence) {
+        case 0: /*SEEK_SET*/
+                start = 0;
+                break;
+        case 1: /*SEEK_CUR*/
+                start = filp->f_pos;
+                break;
+        case 2: /*SEEK_END*/
+                start = i_size_read(filp->f_dentry->d_inode);
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        if (((start += l->l_start) < 0) || (l->l_len < 0))
+                return -EINVAL;
+        fl->fl_end = start + l->l_len - 1;
+        if (l->l_len > 0 && fl->fl_end < 0)
+                return -EOVERFLOW;
+        fl->fl_start = start;   /* we record the absolute position */
+        if (l->l_len == 0)
+                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;
+
+        switch (l->l_type) {
+        case F_RDLCK:
+        case F_WRLCK:
+        case F_UNLCK:
+                fl->fl_type = l->l_type;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        return (0);
+}
+#endif
+
+/* default lease lock manager operations */
+static void lease_break_callback(struct file_lock *fl)
+{
+        kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
+}
+
+static void lease_release_private_callback(struct file_lock *fl)
+{
+        if (!fl->fl_file)
+                return;
+
+        f_delown(fl->fl_file);
+        fl->fl_file->f_owner.signum = 0;
+}
+
+int lease_mylease_callback(struct file_lock *fl, struct file_lock *try)
+{
+        return fl->fl_file == try->fl_file;
+}
+
+struct lock_manager_operations lease_manager_ops = {
+        .fl_break = lease_break_callback,
+        .fl_release_private = lease_release_private_callback,
+        .fl_mylease = lease_mylease_callback,
+        .fl_change = lease_modify,
+};
+
+/*
+ * Initialize a lease, use the default lock manager operations
+ */
+static int lease_init(struct file *filp, int type, struct file_lock *fl)
+ {
+        fl->fl_owner = current->files;
+        fl->fl_pid = current->tgid;
+
+        fl->fl_file = filp;
+        fl->fl_flags = FL_LEASE;
+        if (assign_type(fl, type) != 0) {
+                locks_free_lock(fl);
+                return -EINVAL;
+        }
+        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 int lease_alloc(struct file *filp, int type, struct file_lock **flp)
+{
+        struct file_lock *fl = locks_alloc_lock();
+        int error;
+
+        if (fl == NULL)
+                return -ENOMEM;
+
+        error = lease_init(filp, type, fl);
+        if (error)
+                return error;
+        *flp = fl;
+        return 0;
+}
+
+/* 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 inline int
+posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
+{
+        if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner)
+                return fl2->fl_lmops == fl1->fl_lmops &&
+                        fl1->fl_lmops->fl_compare_owner(fl1, fl2);
+        return fl1->fl_owner == fl2->fl_owner;
+}
+
+/* Remove waiter from blocker's block list.
+ * When blocker ends up pointing to itself then the list is empty.
+ */
+static inline void __locks_delete_block(struct file_lock *waiter)
+{
+        list_del_init(&waiter->fl_block);
+        list_del_init(&waiter->fl_link);
+        waiter->fl_next = NULL;
+}
+
+/*
+ */
+static void locks_delete_block(struct file_lock *waiter)
+{
+        lock_kernel();
+        __locks_delete_block(waiter);
+        unlock_kernel();
+}
+
+/* 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.
+ */
+static void locks_insert_block(struct file_lock *blocker, 
+                               struct file_lock *waiter)
+{
+        if (!list_empty(&waiter->fl_block)) {
+                printk(KERN_ERR "locks_insert_block: removing duplicated lock "
+                        "(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid,
+                        waiter->fl_start, waiter->fl_end, waiter->fl_type);
+                __locks_delete_block(waiter);
+        }
+        list_add_tail(&waiter->fl_block, &blocker->fl_block);
+        waiter->fl_next = blocker;
+        if (IS_POSIX(blocker))
+                list_add(&waiter->fl_link, &blocked_list);
+}
+
+/* Wake up processes blocked waiting for blocker.
+ * If told to wait then schedule the processes until the block list
+ * is empty, otherwise empty the block list ourselves.
+ */
+static void locks_wake_up_blocks(struct file_lock *blocker)
+{
+        while (!list_empty(&blocker->fl_block)) {
+                struct file_lock *waiter = list_entry(blocker->fl_block.next,
+                                struct file_lock, fl_block);
+                __locks_delete_block(waiter);
+                if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
+                        waiter->fl_lmops->fl_notify(waiter);
+                else
+                        wake_up(&waiter->fl_wait);
+        }
+}
+
+/* Insert file lock fl into an inode's lock list at the position indicated
+ * by pos. At the same time add the lock to the global file lock list.
+ */
+static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
+{
+        list_add(&fl->fl_link, &file_lock_list);
+
+        /* insert into file's list */
+        fl->fl_next = *pos;
+        *pos = fl;
+
+        if (fl->fl_ops && fl->fl_ops->fl_insert)
+                fl->fl_ops->fl_insert(fl);
+}
+
+/*
+ * Delete a lock and then free it.
+ * Wake up processes that are blocked waiting for this lock,
+ * notify the FS that the lock has been cleared and
+ * finally free the lock.
+ */
+static void locks_delete_lock(struct file_lock **thisfl_p)
+{
+        struct file_lock *fl = *thisfl_p;
+
+        *thisfl_p = fl->fl_next;
+        fl->fl_next = NULL;
+        list_del_init(&fl->fl_link);
+
+        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;
+        }
+
+        if (fl->fl_ops && fl->fl_ops->fl_remove)
+                fl->fl_ops->fl_remove(fl);
+
+        locks_wake_up_blocks(fl);
+        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 (!IS_POSIX(sys_fl) || 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 (!IS_FLOCK(sys_fl) || (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));
+}
+
+static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
+{
+        int result = 0;
+        DECLARE_WAITQUEUE(wait, current);
+
+        __set_current_state(TASK_INTERRUPTIBLE);
+        add_wait_queue(fl_wait, &wait);
+        if (timeout == 0)
+                schedule();
+        else
+                result = schedule_timeout(timeout);
+        if (signal_pending(current))
+                result = -ERESTARTSYS;
+        remove_wait_queue(fl_wait, &wait);
+        __set_current_state(TASK_RUNNING);
+        return result;
+}
+
+static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
+{
+        int result;
+        locks_insert_block(blocker, waiter);
+        result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
+        __locks_delete_block(waiter);
+        return result;
+}
+
+struct file_lock *
+posix_test_lock(struct file *filp, struct file_lock *fl)
+{
+        struct file_lock *cfl;
+
+        lock_kernel();
+        for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
+                if (!IS_POSIX(cfl))
+                        continue;
+                if (posix_locks_conflict(cfl, fl))
+                        break;
+        }
+        unlock_kernel();
+
+        return (cfl);
+}
+
+EXPORT_SYMBOL(posix_test_lock);
+
+/* This function tests for deadlock condition before putting a process to
+ * sleep. The detection scheme is no longer recursive. Recursive was neat,
+ * but dangerous - we risked stack corruption if the lock data was bad, or
+ * if the recursion was too deep for any other reason.
+ *
+ * We rely on the fact that a task can only be on one lock's wait queue
+ * at a time. When we find blocked_task on a wait queue we can re-search
+ * with blocked_task equal to that queue's owner, until either blocked_task
+ * isn't found, or blocked_task is found on a queue owned by my_task.
+ *
+ * Note: the above assumption may not be true when handling lock requests
+ * from a broken NFS client. But broken NFS clients have a lot more to
+ * worry about than proper deadlock detection anyway... --okir
+ */
+int posix_locks_deadlock(struct file_lock *caller_fl,
+                                struct file_lock *block_fl)
+{
+        struct list_head *tmp;
+
+next_task:
+        if (posix_same_owner(caller_fl, block_fl))
+                return 1;
+        list_for_each(tmp, &blocked_list) {
+                struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
+                if (posix_same_owner(fl, block_fl)) {
+                        fl = fl->fl_next;
+                        block_fl = fl;
+                        goto next_task;
+                }
+        }
+        return 0;
+}
+
+EXPORT_SYMBOL(posix_locks_deadlock);
+
+/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
+ * at the head of the list, but that's secret knowledge known only to
+ * flock_lock_file and posix_lock_file.
+ */
+static int flock_lock_file(struct file *filp, struct file_lock *new_fl)
+{
+        struct file_lock **before;
+        struct inode * inode = filp->f_dentry->d_inode;
+        int error = 0;
+        int found = 0;
+
+        lock_kernel();
+        for_each_lock(inode, before) {
+                struct file_lock *fl = *before;
+                if (IS_POSIX(fl))
+                        break;
+                if (IS_LEASE(fl))
+                        continue;
+                if (filp != fl->fl_file)
+                        continue;
+                if (new_fl->fl_type == fl->fl_type)
+                        goto out;
+                found = 1;
+                locks_delete_lock(before);
+                break;
+        }
+        unlock_kernel();
+
+        if (new_fl->fl_type == F_UNLCK)
+                return 0;
+
+        /*
+         * If a higher-priority process was blocked on the old file lock,
+         * give it the opportunity to lock the file.
+         */
+        if (found)
+                cond_resched();
+
+        lock_kernel();
+        for_each_lock(inode, before) {
+                struct file_lock *fl = *before;
+                if (IS_POSIX(fl))
+                        break;
+                if (IS_LEASE(fl))
+                        continue;
+                if (!flock_locks_conflict(new_fl, fl))
+                        continue;
+                error = -EAGAIN;
+                if (new_fl->fl_flags & FL_SLEEP) {
+                        locks_insert_block(fl, new_fl);
+                }
+                goto out;
+        }
+        locks_insert_lock(&inode->i_flock, new_fl);
+        error = 0;
+
+out:
+        unlock_kernel();
+        return error;
+}
+
+EXPORT_SYMBOL(posix_lock_file);
+
+static int __posix_lock_file(struct inode *inode, struct file_lock *request)
+{
+        struct file_lock *fl;
+        struct file_lock *new_fl, *new_fl2;
+        struct file_lock *left = NULL;
+        struct file_lock *right = NULL;
+        struct file_lock **before;
+        int error, added = 0;
+
+        /*
+         * We may need two file_lock structures for this operation,
+         * so we get them in advance to avoid races.
+         */
+        new_fl = locks_alloc_lock();
+        new_fl2 = locks_alloc_lock();
+
+        lock_kernel();
+        if (request->fl_type != F_UNLCK) {
+                for_each_lock(inode, before) {
+                        struct file_lock *fl = *before;
+                        if (!IS_POSIX(fl))
+                                continue;
+                        if (!posix_locks_conflict(request, fl))
+                                continue;
+                        error = -EAGAIN;
+                        if (!(request->fl_flags & FL_SLEEP))
+                                goto out;
+                        error = -EDEADLK;
+                        if (posix_locks_deadlock(request, fl))
+                                goto out;
+                        error = -EAGAIN;
+                        locks_insert_block(fl, request);
+                        goto out;
+                }
+        }
+
+        /* If we're just looking for a conflict, we're done. */
+        error = 0;
+        if (request->fl_flags & FL_ACCESS)
+                goto out;
+
+        error = -ENOLCK; /* "no luck" */
+        if (!(new_fl && new_fl2))
+                goto out;
+
+        /*
+         * We've allocated the new locks in advance, so there are no
+         * errors possible (and no blocking operations) from here on.
+         * 
+         * Find the first old lock with the same owner as the new lock.
+         */
+        
+        before = &inode->i_flock;
+
+        /* First skip locks owned by other processes.  */
+        while ((fl = *before) && (!IS_POSIX(fl) ||
+                                  !posix_same_owner(request, fl))) {
+                before = &fl->fl_next;
+        }
+
+        /* Process locks with this owner.  */
+        while ((fl = *before) && posix_same_owner(request, fl)) {
+                /* Detect adjacent or overlapping regions (if same lock type)
+                 */
+                if (request->fl_type == fl->fl_type) {
+                        if (fl->fl_end < request->fl_start - 1)
+                                goto next_lock;
+                        /* If the next lock in the list has entirely bigger
+                         * addresses than the new one, insert the lock here.
+                         */
+                        if (fl->fl_start > request->fl_end + 1)
+                                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(before);
+                                continue;
+                        }
+                        request = fl;
+                        added = 1;
+                }
+                else {
+                        /* Processing for different lock types is a bit
+                         * more complex.
+                         */
+                        if (fl->fl_end < request->fl_start)
+                                goto next_lock;
+                        if (fl->fl_start > request->fl_end)
+                                break;
+                        if (request->fl_type == F_UNLCK)
+                                added = 1;
+                        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(before);
+                                        continue;
+                                }
+                                /* Replace the old lock with the new one.
+                                 * Wake up anybody waiting for the old one,
+                                 * as the change in lock type might satisfy
+                                 * their needs.
+                                 */
+                                locks_wake_up_blocks(fl);
+                                fl->fl_start = request->fl_start;
+                                fl->fl_end = request->fl_end;
+                                fl->fl_type = request->fl_type;
+                                fl->fl_u = request->fl_u;
+                                request = fl;
+                                added = 1;
+                        }
+                }
+                /* Go on to next lock.
+                 */
+        next_lock:
+                before = &fl->fl_next;
+        }
+
+        error = 0;
+        if (!added) {
+                if (request->fl_type == F_UNLCK)
+                        goto out;
+                locks_copy_lock(new_fl, request);
+                locks_insert_lock(before, 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(before, left);
+                }
+                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:
+        unlock_kernel();
+        /*
+         * Free any unused locks.
+         */
+        if (new_fl)
+                locks_free_lock(new_fl);
+        if (new_fl2)
+                locks_free_lock(new_fl2);
+        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
+ *
+ * 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(struct file *filp, struct file_lock *fl)
+{
+        return __posix_lock_file(filp->f_dentry->d_inode, fl);
+}
+
+/**
+ * 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->f_dentry->d_inode, fl);
+                if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
+                        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
+ * @inode: 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 inode *inode)
+{
+        fl_owner_t owner = current->files;
+        struct file_lock *fl;
+
+        /*
+         * Search the lock list for this inode for any POSIX locks.
+         */
+        lock_kernel();
+        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
+                if (!IS_POSIX(fl))
+                        continue;
+                if (fl->fl_owner != owner)
+                        break;
+        }
+        unlock_kernel();
+        return fl ? -EAGAIN : 0;
+}
+
+/**
+ * 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;
+
+        locks_init_lock(&fl);
+        fl.fl_owner = current->files;
+        fl.fl_pid = current->tgid;
+        fl.fl_file = filp;
+        fl.fl_flags = FL_POSIX | FL_ACCESS;
+        if (filp && !(filp->f_flags & O_NONBLOCK))
+                fl.fl_flags |= FL_SLEEP;
+        fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
+        fl.fl_start = offset;
+        fl.fl_end = offset + count - 1;
+
+        for (;;) {
+                error = __posix_lock_file(inode, &fl);
+                if (error != -EAGAIN)
+                        break;
+                if (!(fl.fl_flags & FL_SLEEP))
+                        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 ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+                                continue;
+                }
+
+                locks_delete_block(&fl);
+                break;
+        }
+
+        return error;
+}
+
+EXPORT_SYMBOL(locks_mandatory_area);
+
+/* We already had a lease on this file; just change its type */
+int lease_modify(struct file_lock **before, int arg)
+{
+        struct file_lock *fl = *before;
+        int error = assign_type(fl, arg);
+
+        if (error)
+                return error;
+        locks_wake_up_blocks(fl);
+        if (arg == F_UNLCK)
+                locks_delete_lock(before);
+        return 0;
+}
+
+EXPORT_SYMBOL(lease_modify);
+
+static void time_out_leases(struct inode *inode)
+{
+        struct file_lock **before;
+        struct file_lock *fl;
+
+        before = &inode->i_flock;
+        while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) {
+                if ((fl->fl_break_time == 0)
+                                || time_before(jiffies, fl->fl_break_time)) {
+                        before = &fl->fl_next;
+                        continue;
+                }
+                printk(KERN_INFO "lease broken - owner pid = %d\n", fl->fl_pid);
+                lease_modify(before, fl->fl_type & ~F_INPROGRESS);
+                if (fl == *before)      /* lease_modify may have freed fl */
+                        before = &fl->fl_next;
+        }
+}
+
+/**
+ *      __break_lease   -       revoke all outstanding leases on file
+ *      @inode: the inode of the file to return
+ *      @mode: the open mode (read or write)
+ *
+ *      break_lease (inlined for speed) has checked there already
+ *      is 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)
+{
+        int error = 0, future;
+        struct file_lock *new_fl, *flock;
+        struct file_lock *fl;
+        int alloc_err;
+        unsigned long break_time;
+        int i_have_this_lease = 0;
+
+        alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK,
+                        &new_fl);
+
+        lock_kernel();
+
+        time_out_leases(inode);
+
+        flock = inode->i_flock;
+        if ((flock == NULL) || !IS_LEASE(flock))
+                goto out;
+
+        for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
+                if (fl->fl_owner == current->files)
+                        i_have_this_lease = 1;
+
+        if (mode & FMODE_WRITE) {
+                /* If we want write access, we have to revoke any lease. */
+                future = F_UNLCK | F_INPROGRESS;
+        } else if (flock->fl_type & F_INPROGRESS) {
+                /* If the lease is already being broken, we just leave it */
+                future = flock->fl_type;
+        } else if (flock->fl_type & F_WRLCK) {
+                /* Downgrade the exclusive lease to a read-only lease. */
+                future = F_RDLCK | F_INPROGRESS;
+        } else {
+                /* the existing lease was read-only, so we can read too. */
+                goto out;
+        }
+
+        if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) {
+                error = alloc_err;
+                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 */
+        }
+
+        for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
+                if (fl->fl_type != future) {
+                        fl->fl_type = future;
+                        fl->fl_break_time = break_time;
+                        /* lease must have lmops break callback */
+                        fl->fl_lmops->fl_break(fl);
+                }
+        }
+
+        if (i_have_this_lease || (mode & O_NONBLOCK)) {
+                error = -EWOULDBLOCK;
+                goto out;
+        }
+
+restart:
+        break_time = flock->fl_break_time;
+        if (break_time != 0) {
+                break_time -= jiffies;
+                if (break_time == 0)
+                        break_time++;
+        }
+        error = locks_block_on_timeout(flock, new_fl, break_time);
+        if (error >= 0) {
+                if (error == 0)
+                        time_out_leases(inode);
+                /* Wait for the next lease that has not been broken yet */
+                for (flock = inode->i_flock; flock && IS_LEASE(flock);
+                                flock = flock->fl_next) {
+                        if (flock->fl_type & F_INPROGRESS)
+                                goto restart;
+                }
+                error = 0;
+        }
+
+out:
+        unlock_kernel();
+        if (!alloc_err)
+                locks_free_lock(new_fl);
+        return error;
+}
+
+EXPORT_SYMBOL(__break_lease);
+
+/**
+ *      lease_get_mtime
+ *      @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 modifiying it.
+ */
+void lease_get_mtime(struct inode *inode, struct timespec *time)
+{
+        struct file_lock *flock = inode->i_flock;
+        if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
+                *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;
+        int type = F_UNLCK;
+
+        lock_kernel();
+        time_out_leases(filp->f_dentry->d_inode);
+        for (fl = filp->f_dentry->d_inode->i_flock; fl && IS_LEASE(fl);
+                        fl = fl->fl_next) {
+                if (fl->fl_file == filp) {
+                        type = fl->fl_type & ~F_INPROGRESS;
+                        break;
+                }
+        }
+        unlock_kernel();
+        return type;
+}
+
+/**
+ *      __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
+ *
+ *      The (input) flp->fl_lmops->fl_break function is required
+ *      by break_lease().
+ *
+ *      Called with kernel lock held.
+ */
+int __setlease(struct file *filp, long arg, struct file_lock **flp)
+{
+        struct file_lock *fl, **before, **my_before = NULL, *lease = *flp;
+        struct dentry *dentry = filp->f_dentry;
+        struct inode *inode = dentry->d_inode;
+        int error, rdlease_count = 0, wrlease_count = 0;
+
+        time_out_leases(inode);
+
+        error = -EINVAL;
+        if (!flp || !(*flp) || !(*flp)->fl_lmops || !(*flp)->fl_lmops->fl_break)
+                goto out;
+
+        error = -EAGAIN;
+        if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
+                goto out;
+        if ((arg == F_WRLCK)
+            && ((atomic_read(&dentry->d_count) > 1)
+                || (atomic_read(&inode->i_count) > 1)))
+                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.
+         */
+        for (before = &inode->i_flock;
+                        ((fl = *before) != NULL) && IS_LEASE(fl);
+                        before = &fl->fl_next) {
+                if (lease->fl_lmops->fl_mylease(fl, lease))
+                        my_before = before;
+                else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
+                        /*
+                         * Someone is in the process of opening this
+                         * file for writing so we may not take an
+                         * exclusive lease on it.
+                         */
+                        wrlease_count++;
+                else
+                        rdlease_count++;
+        }
+
+        if ((arg == F_RDLCK && (wrlease_count > 0)) ||
+            (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
+                goto out;
+
+        if (my_before != NULL) {
+                error = lease->fl_lmops->fl_change(my_before, arg);
+                goto out;
+        }
+
+        error = 0;
+        if (arg == F_UNLCK)
+                goto out;
+
+        error = -EINVAL;
+        if (!leases_enable)
+                goto out;
+
+        error = lease_alloc(filp, arg, &fl);
+        if (error)
+                goto out;
+
+        locks_copy_lock(fl, lease);
+
+        locks_insert_lock(before, fl);
+
+        *flp = fl;
+out:
+        return error;
+}
+
+ /**
+ *      setlease        -       sets a lease on an open file
+ *      @filp: file pointer
+ *      @arg: type of lease to obtain
+ *      @lease: file_lock to use
+ *
+ *      Call this to establish a lease on the file.
+ *      The fl_lmops fl_break function is required by break_lease
+ */
+
+int setlease(struct file *filp, long arg, struct file_lock **lease)
+{
+        struct dentry *dentry = filp->f_dentry;
+        struct inode *inode = dentry->d_inode;
+        int error;
+
+        if ((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;
+
+        lock_kernel();
+        error = __setlease(filp, arg, lease);
+        unlock_kernel();
+
+        return error;
+}
+
+EXPORT_SYMBOL(setlease);
+
+/**
+ *      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)
+{
+        struct file_lock fl, *flp = &fl;
+        struct dentry *dentry = filp->f_dentry;
+        struct inode *inode = dentry->d_inode;
+        int error;
+
+        if ((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;
+
+        locks_init_lock(&fl);
+        error = lease_init(filp, arg, &fl);
+        if (error)
+                return error;
+
+        lock_kernel();
+
+        error = __setlease(filp, arg, &flp);
+        if (error)
+                goto out_unlock;
+
+        error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
+        if (error < 0) {
+                /* remove lease just inserted by __setlease */
+                flp->fl_type = F_UNLCK | F_INPROGRESS;
+                flp->fl_break_time = jiffies- 10;
+                time_out_leases(inode);
+                goto out_unlock;
+        }
+
+        error = f_setown(filp, current->pid, 0);
+out_unlock:
+        unlock_kernel();
+        return error;
+}
+
+/**
+ * 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 != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
+                        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.
+ */
+asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
+{
+        struct file *filp;
+        struct file_lock *lock;
+        int can_sleep, unlock;
+        int error;
+
+        error = -EBADF;
+        filp = fget(fd);
+        if (!filp)
+                goto out;
+
+        can_sleep = !(cmd & LOCK_NB);
+        cmd &= ~LOCK_NB;
+        unlock = (cmd == LOCK_UN);
+
+        if (!unlock && !(cmd & LOCK_MAND) && !(filp->f_mode & 3))
+                goto out_putf;
+
+        error = flock_make_lock(filp, &lock, cmd);
+        if (error)
+                goto out_putf;
+        if (can_sleep)
+                lock->fl_flags |= FL_SLEEP;
+
+        error = security_file_lock(filp, cmd);
+        if (error)
+                goto out_free;
+
+        if (filp->f_op && filp->f_op->flock)
+                error = filp->f_op->flock(filp,
+                                          (can_sleep) ? F_SETLKW : F_SETLK,
+                                          lock);
+        else
+                error = flock_lock_file_wait(filp, lock);
+
+ out_free:
+        if (list_empty(&lock->fl_link)) {
+                locks_free_lock(lock);
+        }
+
+ out_putf:
+        fput(filp);
+ out:
+        return error;
+}
+
+/* Report the first existing lock that would conflict with l.
+ * This implements the F_GETLK command of fcntl().
+ */
+int fcntl_getlk(struct file *filp, struct flock __user *l)
+{
+        struct file_lock *fl, 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 (filp->f_op && filp->f_op->lock) {
+                error = filp->f_op->lock(filp, F_GETLK, &file_lock);
+                if (error < 0)
+                        goto out;
+                else
+                  fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
+        } else {
+                fl = posix_test_lock(filp, &file_lock);
+        }
+ 
+        flock.l_type = F_UNLCK;
+        if (fl != NULL) {
+                flock.l_pid = fl->fl_pid;
+#if BITS_PER_LONG == 32
+                /*
+                 * Make sure we can represent the posix lock via
+                 * legacy 32bit flock.
+                 */
+                error = -EOVERFLOW;
+                if (fl->fl_start > OFFT_OFFSET_MAX)
+                        goto out;
+                if ((fl->fl_end != OFFSET_MAX)
+                    && (fl->fl_end > OFFT_OFFSET_MAX))
+                        goto out;
+#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;
+        }
+        error = -EFAULT;
+        if (!copy_to_user(l, &flock, sizeof(flock)))
+                error = 0;
+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_setlk(struct file *filp, unsigned int cmd, struct flock __user *l)
+{
+        struct file_lock *file_lock = locks_alloc_lock();
+        struct flock flock;
+        struct inode *inode;
+        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 = filp->f_dentry->d_inode;
+
+        /* Don't allow mandatory locks on files that may be memory mapped
+         * and shared.
+         */
+        if (IS_MANDLOCK(inode) &&
+            (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
+            mapping_writably_mapped(filp->f_mapping)) {
+                error = -EAGAIN;
+                goto out;
+        }
+
+        error = flock_to_posix_lock(filp, file_lock, &flock);
+        if (error)
+                goto out;
+        if (cmd == F_SETLKW) {
+                file_lock->fl_flags |= FL_SLEEP;
+        }
+        
+        error = -EBADF;
+        switch (flock.l_type) {
+        case F_RDLCK:
+                if (!(filp->f_mode & FMODE_READ))
+                        goto out;
+                break;
+        case F_WRLCK:
+                if (!(filp->f_mode & FMODE_WRITE))
+                        goto out;
+                break;
+        case F_UNLCK:
+                break;
+        default:
+                error = -EINVAL;
+                goto out;
+        }
+
+        error = security_file_lock(filp, file_lock->fl_type);
+        if (error)
+                goto out;
+
+        if (filp->f_op && filp->f_op->lock != NULL) {
+                error = filp->f_op->lock(filp, cmd, file_lock);
+                goto out;
+        }
+
+        for (;;) {
+                error = __posix_lock_file(inode, file_lock);
+                if ((error != -EAGAIN) || (cmd == F_SETLK))
+                        break;
+                error = wait_event_interruptible(file_lock->fl_wait,
+                                !file_lock->fl_next);
+                if (!error)
+                        continue;
+
+                locks_delete_block(file_lock);
+                break;
+        }
+
+ 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, struct flock64 __user *l)
+{
+        struct file_lock *fl, 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 (filp->f_op && filp->f_op->lock) {
+                error = filp->f_op->lock(filp, F_GETLK, &file_lock);
+                if (error < 0)
+                        goto out;
+                else
+                  fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
+        } else {
+                fl = posix_test_lock(filp, &file_lock);
+        }
+ 
+        flock.l_type = F_UNLCK;
+        if (fl != NULL) {
+                flock.l_pid = 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;
+        }
+        error = -EFAULT;
+        if (!copy_to_user(l, &flock, sizeof(flock)))
+                error = 0;
+  
+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(struct file *filp, unsigned int cmd, struct flock64 __user *l)
+{
+        struct file_lock *file_lock = locks_alloc_lock();
+        struct flock64 flock;
+        struct inode *inode;
+        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 = filp->f_dentry->d_inode;
+
+        /* Don't allow mandatory locks on files that may be memory mapped
+         * and shared.
+         */
+        if (IS_MANDLOCK(inode) &&
+            (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
+            mapping_writably_mapped(filp->f_mapping)) {
+                error = -EAGAIN;
+                goto out;
+        }
+
+        error = flock64_to_posix_lock(filp, file_lock, &flock);
+        if (error)
+                goto out;
+        if (cmd == F_SETLKW64) {
+                file_lock->fl_flags |= FL_SLEEP;
+        }
+        
+        error = -EBADF;
+        switch (flock.l_type) {
+        case F_RDLCK:
+                if (!(filp->f_mode & FMODE_READ))
+                        goto out;
+                break;
+        case F_WRLCK:
+                if (!(filp->f_mode & FMODE_WRITE))
+                        goto out;
+                break;
+        case F_UNLCK:
+                break;
+        default:
+                error = -EINVAL;
+                goto out;
+        }
+
+        error = security_file_lock(filp, file_lock->fl_type);
+        if (error)
+                goto out;
+
+        if (filp->f_op && filp->f_op->lock != NULL) {
+                error = filp->f_op->lock(filp, cmd, file_lock);
+                goto out;
+        }
+
+        for (;;) {
+                error = __posix_lock_file(inode, file_lock);
+                if ((error != -EAGAIN) || (cmd == F_SETLK64))
+                        break;
+                error = wait_event_interruptible(file_lock->fl_wait,
+                                !file_lock->fl_next);
+                if (!error)
+                        continue;
+
+                locks_delete_block(file_lock);
+                break;
+        }
+
+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, **before;
+
+        /*
+         * 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.
+         */
+        before = &filp->f_dentry->d_inode->i_flock;
+        if (*before == NULL)
+                return;
+
+        lock.fl_type = F_UNLCK;
+        lock.fl_flags = FL_POSIX;
+        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;
+
+        if (filp->f_op && filp->f_op->lock != NULL) {
+                filp->f_op->lock(filp, F_SETLK, &lock);
+                goto out;
+        }
+
+        /* Can't use posix_lock_file here; we need to remove it no matter
+         * which pid we have.
+         */
+        lock_kernel();
+        while (*before != NULL) {
+                struct file_lock *fl = *before;
+                if (IS_POSIX(fl) && posix_same_owner(fl, &lock)) {
+                        locks_delete_lock(before);
+                        continue;
+                }
+                before = &fl->fl_next;
+        }
+        unlock_kernel();
+out:
+        if (lock.fl_ops && lock.fl_ops->fl_release_private)
+                lock.fl_ops->fl_release_private(&lock);
+}
+
+EXPORT_SYMBOL(locks_remove_posix);
+
+/*
+ * This function is called on the last close of an open file.
+ */
+void locks_remove_flock(struct file *filp)
+{
+        struct inode * inode = filp->f_dentry->d_inode; 
+        struct file_lock *fl;
+        struct file_lock **before;
+
+        if (!inode->i_flock)
+                return;
+
+        if (filp->f_op && filp->f_op->flock) {
+                struct file_lock fl = {
+                        .fl_pid = current->tgid,
+                        .fl_file = filp,
+                        .fl_flags = FL_FLOCK,
+                        .fl_type = F_UNLCK,
+                        .fl_end = OFFSET_MAX,
+                };
+                filp->f_op->flock(filp, F_SETLKW, &fl);
+        }
+
+        lock_kernel();
+        before = &inode->i_flock;
+
+        while ((fl = *before) != NULL) {
+                if (fl->fl_file == filp) {
+                        /*
+                         * We might have a POSIX lock that was created at the same time
+                         * the filp was closed for the last time. Just remove that too,
+                         * regardless of ownership, since nobody can own it.
+                         */
+                        if (IS_FLOCK(fl) || IS_POSIX(fl)) {
+                                locks_delete_lock(before);
+                                continue;
+                        }
+                        if (IS_LEASE(fl)) {
+                                lease_modify(before, F_UNLCK);
+                                continue;
+                        }
+                        /* What? */
+                        BUG();
+                }
+                before = &fl->fl_next;
+        }
+        unlock_kernel();
+}
+
+/**
+ *      posix_block_lock - blocks waiting for a file lock
+ *      @blocker: the lock which is blocking
+ *      @waiter: the lock which conflicts and has to wait
+ *
+ * lockd needs to block waiting for locks.
+ */
+void
+posix_block_lock(struct file_lock *blocker, struct file_lock *waiter)
+{
+        locks_insert_block(blocker, waiter);
+}
+
+EXPORT_SYMBOL(posix_block_lock);
+
+/**
+ *      posix_unblock_lock - stop waiting for a file lock
+ *      @filp:   how the file was opened
+ *      @waiter: the lock which was waiting
+ *
+ *      lockd needs to block waiting for locks.
+ */
+void
+posix_unblock_lock(struct file *filp, struct file_lock *waiter)
+{
+        /* 
+         * A remote machine may cancel the lock request after it's been
+         * granted locally.  If that happens, we need to delete the lock.
+         */
+        lock_kernel();
+        if (waiter->fl_next) {
+                __locks_delete_block(waiter);
+                unlock_kernel();
+        } else {
+                unlock_kernel();
+                waiter->fl_type = F_UNLCK;
+                posix_lock_file(filp, waiter);
+        }
+}
+
+EXPORT_SYMBOL(posix_unblock_lock);
+
+static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
+{
+        struct inode *inode = NULL;
+
+        if (fl->fl_file != NULL)
+                inode = fl->fl_file->f_dentry->d_inode;
+
+        out += sprintf(out, "%d:%s ", id, pfx);
+        if (IS_POSIX(fl)) {
+                out += sprintf(out, "%6s %s ",
+                             (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
+                             (inode == NULL) ? "*NOINODE*" :
+                             (IS_MANDLOCK(inode) &&
+                              (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ?
+                             "MANDATORY" : "ADVISORY ");
+        } else if (IS_FLOCK(fl)) {
+                if (fl->fl_type & LOCK_MAND) {
+                        out += sprintf(out, "FLOCK  MSNFS     ");
+                } else {
+                        out += sprintf(out, "FLOCK  ADVISORY  ");
+                }
+        } else if (IS_LEASE(fl)) {
+                out += sprintf(out, "LEASE  ");
+                if (fl->fl_type & F_INPROGRESS)
+                        out += sprintf(out, "BREAKING  ");
+                else if (fl->fl_file)
+                        out += sprintf(out, "ACTIVE    ");
+                else
+                        out += sprintf(out, "BREAKER   ");
+        } else {
+                out += sprintf(out, "UNKNOWN UNKNOWN  ");
+        }
+        if (fl->fl_type & LOCK_MAND) {
+                out += sprintf(out, "%s ",
+                               (fl->fl_type & LOCK_READ)
+                               ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
+                               : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
+        } else {
+                out += sprintf(out, "%s ",
+                               (fl->fl_type & F_INPROGRESS)
+                               ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
+                               : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
+        }
+        if (inode) {
+#ifdef WE_CAN_BREAK_LSLK_NOW
+                out += sprintf(out, "%d %s:%ld ", fl->fl_pid,
+                                inode->i_sb->s_id, inode->i_ino);
+#else
+                /* userspace relies on this representation of dev_t ;-( */
+                out += sprintf(out, "%d %02x:%02x:%ld ", fl->fl_pid,
+                                MAJOR(inode->i_sb->s_dev),
+                                MINOR(inode->i_sb->s_dev), inode->i_ino);
+#endif
+        } else {
+                out += sprintf(out, "%d <none>:0 ", fl->fl_pid);
+        }
+        if (IS_POSIX(fl)) {
+                if (fl->fl_end == OFFSET_MAX)
+                        out += sprintf(out, "%Ld EOF\n", fl->fl_start);
+                else
+                        out += sprintf(out, "%Ld %Ld\n", fl->fl_start,
+                                        fl->fl_end);
+        } else {
+                out += sprintf(out, "0 EOF\n");
+        }
+}
+
+static void move_lock_status(char **p, off_t* pos, off_t offset)
+{
+        int len;
+        len = strlen(*p);
+        if(*pos >= offset) {
+                /* the complete line is valid */
+                *p += len;
+                *pos += len;
+                return;
+        }
+        if(*pos+len > offset) {
+                /* use the second part of the line */
+                int i = offset-*pos;
+                memmove(*p,*p+i,len-i);
+                *p += len-i;
+                *pos += len;
+                return;
+        }
+        /* discard the complete line */
+        *pos += len;
+}
+
+/**
+ *      get_locks_status        -       reports lock usage in /proc/locks
+ *      @buffer: address in userspace to write into
+ *      @start: ?
+ *      @offset: how far we are through the buffer
+ *      @length: how much to read
+ */
+
+int get_locks_status(char *buffer, char **start, off_t offset, int length)
+{
+        struct list_head *tmp;
+        char *q = buffer;
+        off_t pos = 0;
+        int i = 0;
+
+        lock_kernel();
+        list_for_each(tmp, &file_lock_list) {
+                struct list_head *btmp;
+                struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
+                lock_get_status(q, fl, ++i, "");
+                move_lock_status(&q, &pos, offset);
+
+                if(pos >= offset+length)
+                        goto done;
+
+                list_for_each(btmp, &fl->fl_block) {
+                        struct file_lock *bfl = list_entry(btmp,
+                                        struct file_lock, fl_block);
+                        lock_get_status(q, bfl, i, " ->");
+                        move_lock_status(&q, &pos, offset);
+
+                        if(pos >= offset+length)
+                                goto done;
+                }
+        }
+done:
+        unlock_kernel();
+        *start = buffer;
+        if(q-buffer < length)
+                return (q-buffer);
+        return length;
+}
+
+/**
+ *      lock_may_read - checks that the region is free of locks
+ *      @inode: the inode that is being read
+ *      @start: the first byte to read
+ *      @len: the number of bytes to read
+ *
+ *      Emulates Windows locking requirements.  Whole-file
+ *      mandatory locks (share modes) can prohibit a read and
+ *      byte-range POSIX locks can prohibit a read if they overlap.
+ *
+ *      N.B. this function is only ever called
+ *      from knfsd and ownership of locks is never checked.
+ */
+int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
+{
+        struct file_lock *fl;
+        int result = 1;
+        lock_kernel();
+        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
+                if (IS_POSIX(fl)) {
+                        if (fl->fl_type == F_RDLCK)
+                                continue;
+                        if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
+                                continue;
+                } else if (IS_FLOCK(fl)) {
+                        if (!(fl->fl_type & LOCK_MAND))
+                                continue;
+                        if (fl->fl_type & LOCK_READ)
+                                continue;
+                } else
+                        continue;
+                result = 0;
+                break;
+        }
+        unlock_kernel();
+        return result;
+}
+
+EXPORT_SYMBOL(lock_may_read);
+
+/**
+ *      lock_may_write - checks that the region is free of locks
+ *      @inode: the inode that is being written
+ *      @start: the first byte to write
+ *      @len: the number of bytes to write
+ *
+ *      Emulates Windows locking requirements.  Whole-file
+ *      mandatory locks (share modes) can prohibit a write and
+ *      byte-range POSIX locks can prohibit a write if they overlap.
+ *
+ *      N.B. this function is only ever called
+ *      from knfsd and ownership of locks is never checked.
+ */
+int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
+{
+        struct file_lock *fl;
+        int result = 1;
+        lock_kernel();
+        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
+                if (IS_POSIX(fl)) {
+                        if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
+                                continue;
+                } else if (IS_FLOCK(fl)) {
+                        if (!(fl->fl_type & LOCK_MAND))
+                                continue;
+                        if (fl->fl_type & LOCK_WRITE)
+                                continue;
+                } else
+                        continue;
+                result = 0;
+                break;
+        }
+        unlock_kernel();
+        return result;
+}
+
+EXPORT_SYMBOL(lock_may_write);
+
+static inline void __steal_locks(struct file *file, fl_owner_t from)
+{
+        struct inode *inode = file->f_dentry->d_inode;
+        struct file_lock *fl = inode->i_flock;
+
+        while (fl) {
+                if (fl->fl_file == file && fl->fl_owner == from)
+                        fl->fl_owner = current->files;
+                fl = fl->fl_next;
+        }
+}
+
+/* When getting ready for executing a binary, we make sure that current
+ * has a files_struct on its own. Before dropping the old files_struct,
+ * we take over ownership of all locks for all file descriptors we own.
+ * Note that we may accidentally steal a lock for a file that a sibling
+ * has created since the unshare_files() call.
+ */
+void steal_locks(fl_owner_t from)
+{
+        struct files_struct *files = current->files;
+        int i, j;
+
+        if (from == files)
+                return;
+
+        lock_kernel();
+        j = 0;
+        for (;;) {
+                unsigned long set;
+                i = j * __NFDBITS;
+                if (i >= files->max_fdset || i >= files->max_fds)
+                        break;
+                set = files->open_fds->fds_bits[j++];
+                while (set) {
+                        if (set & 1) {
+                                struct file *file = files->fd[i];
+                                if (file)
+                                        __steal_locks(file, from);
+                        }
+                        i++;
+                        set >>= 1;
+                }
+        }
+        unlock_kernel();
+}
+EXPORT_SYMBOL(steal_locks);
+
+static int __init filelock_init(void)
+{
+        filelock_cache = kmem_cache_create("file_lock_cache",
+                        sizeof(struct file_lock), 0, SLAB_PANIC,
+                        init_once, NULL);
+        return 0;
+}
+
+core_initcall(filelock_init);