FreeBSD/Linux Kernel Cross Reference
sys/fs/locks.c

     #define MSNFS   /* HACK HACK */
     /*
      *  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 'linux/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@thepuffingroup.com>, March, 2000.
    *
    *  Leases and LOCK_MAND
    *  Matthew Wilcox <willy@linuxcare.com>, June, 2000.
    *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
    */
   
   #include <linux/slab.h>
   #include <linux/file.h>
   #include <linux/smp_lock.h>
   #include <linux/init.h>
   #include <linux/capability.h>
   #include <linux/sched.h>
   #include <linux/timer.h>
   
   #include <asm/semaphore.h>
   #include <asm/uaccess.h>
   
   int leases_enable = 1;
   int lease_break_time = 45;
   
   LIST_HEAD(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(int account)
   {
           struct file_lock *fl;
           if (account && current->locks >= current->rlim[RLIMIT_LOCKS].rlim_cur)
                   return NULL;
           fl = kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
           if (fl)
                   current->locks++;
           return fl;
   }
   
   /* Free a lock which is not in use. */
   static inline void locks_free_lock(struct file_lock *fl)
   {
           if (fl == NULL) {
                   BUG();
                   return;
           }
           current->locks--;
           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");
   
           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 = 0;
           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_notify = NULL;
           fl->fl_insert = NULL;
           fl->fl_remove = NULL;
   }
   
   /*
    * 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_notify = fl->fl_notify;
           new->fl_insert = fl->fl_insert;
           new->fl_remove = fl->fl_remove;
           new->fl_u = fl->fl_u;
   }
   
   /* Fill in a file_lock structure with an appropriate FLOCK lock. */
   static struct file_lock *flock_make_lock(struct file *filp, unsigned int type)
   {
           struct file_lock *fl = locks_alloc_lock(1);
           if (fl == NULL)
                   return NULL;
   
           fl->fl_owner = NULL;
           fl->fl_file = filp;
           fl->fl_pid = current->pid;
           fl->fl_flags = FL_FLOCK;
           fl->fl_type = type;
           fl->fl_start = 0;
           fl->fl_end = OFFSET_MAX;
           fl->fl_notify = NULL;
           fl->fl_insert = NULL;
           fl->fl_remove = NULL;
           
           return fl;
   }
   
   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 = filp->f_dentry->d_inode->i_size;
                   break;
           default:
                   return -EINVAL;
           }
   
           /* POSIX-1996 leaves the case l->l_len < 0 undefined;
              POSIX-2001 defines it. */
           start += l->l_start;
           if (l->l_len < 0) {
                   end = start - 1;
                   start += l->l_len;
           } else {
                   end = start + l->l_len - 1;
           }
   
           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->pid;
           fl->fl_file = filp;
           fl->fl_flags = FL_POSIX;
           fl->fl_notify = NULL;
           fl->fl_insert = NULL;
           fl->fl_remove = 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 = filp->f_dentry->d_inode->i_size;
                   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->pid;
           fl->fl_file = filp;
           fl->fl_flags = FL_POSIX;
           fl->fl_notify = NULL;
           fl->fl_insert = NULL;
           fl->fl_remove = 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
   
   /* 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(1);
           if (fl == NULL)
                   return -ENOMEM;
   
           fl->fl_owner = current->files;
           fl->fl_pid = current->pid;
   
           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_notify = NULL;
           fl->fl_insert = NULL;
           fl->fl_remove = NULL;
   
           *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
    * N.B. Do we need the test on PID as well as owner?
    * (Clone tasks should be considered as one "owner".)
    */
   static inline int
   locks_same_owner(struct file_lock *fl1, struct file_lock *fl2)
   {
           return (fl1->fl_owner == fl2->fl_owner) &&
                  (fl1->fl_pid   == fl2->fl_pid);
   }
   
   /* Remove waiter from blocker's block list.
    * When blocker ends up pointing to itself then the list is empty.
    */
   static void locks_delete_block(struct file_lock *waiter)
   {
           list_del(&waiter->fl_block);
           INIT_LIST_HEAD(&waiter->fl_block);
           list_del(&waiter->fl_link);
           INIT_LIST_HEAD(&waiter->fl_link);
           waiter->fl_next = NULL;
   }
   
   /* 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;
           list_add(&waiter->fl_link, &blocked_list);
   }
   
   static inline
   void locks_notify_blocked(struct file_lock *waiter)
   {
           if (waiter->fl_notify)
                   waiter->fl_notify(waiter);
           else
                   wake_up(&waiter->fl_wait);
   }
   
   /* 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, unsigned int wait)
   {
           while (!list_empty(&blocker->fl_block)) {
                   struct file_lock *waiter = list_entry(blocker->fl_block.next, struct file_lock, fl_block);
   
                   if (wait) {
                           locks_notify_blocked(waiter);
                           /* Let the blocked process remove waiter from the
                            * block list when it gets scheduled.
                            */
                           yield();
                   } else {
                           /* Remove waiter from the block list, because by the
                            * time it wakes up blocker won't exist any more.
                            */
                           locks_delete_block(waiter);
                           locks_notify_blocked(waiter);
                   }
           }
   }
   
   /* 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_insert)
                   fl->fl_insert(fl);
   }
   
   /*
    * Remove lock from the lock lists
    */
   static inline void _unhash_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);
   }
   
   /*
    * 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 inline void _delete_lock(struct file_lock *fl, unsigned int wait)
   {
           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_remove)
                   fl->fl_remove(fl);
   
           locks_wake_up_blocks(fl, wait);
           locks_free_lock(fl);
   }
   
   /*
    * Delete a lock and then free it.
    */
   static void locks_delete_lock(struct file_lock **thisfl_p, unsigned int wait)
   {
           struct file_lock *fl = *thisfl_p;
   
           _unhash_lock(thisfl_p);
           _delete_lock(fl, wait);
   }
   
   /*
    * Call back client filesystem in order to get it to unregister a lock,
    * then delete lock. Essentially useful only in locks_remove_*().
    * Note: this must be called with the semaphore already held!
    */
   static inline void locks_unlock_delete(struct file_lock **thisfl_p)
   {
           struct file_lock *fl = *thisfl_p;
           int (*lock)(struct file *, int, struct file_lock *);
   
           _unhash_lock(thisfl_p);
           if (fl->fl_file->f_op &&
               (lock = fl->fl_file->f_op->lock) != NULL) {
                   fl->fl_type = F_UNLCK;
                   lock(fl->fl_file, F_SETLK, fl);
           }
           _delete_lock(fl, 0);
   }
   
   /* 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)
   {
           switch (caller_fl->fl_type) {
           case F_RDLCK:
                   return (sys_fl->fl_type == F_WRLCK);
   
           case F_WRLCK:
                   return (1);
   
           default:
                   printk(KERN_ERR "locks_conflict(): impossible lock type - %d\n",
                          caller_fl->fl_type);
                   break;
           }
           return (0);     /* This should never happen */
   }
   
   /* 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 (!(sys_fl->fl_flags & FL_POSIX) ||
               locks_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 (!(sys_fl->fl_flags & FL_FLOCK) ||
               (caller_fl->fl_file == sys_fl->fl_file))
                   return (0);
   #ifdef MSNFS
           if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
                   return 0;
   #endif
   
           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);
   
           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);
           current->state = TASK_RUNNING;
           return result;
   }
   
   static int locks_block_on(struct file_lock *blocker, struct file_lock *waiter)
   {
           int result;
           locks_insert_block(blocker, waiter);
           result = interruptible_sleep_on_locked(&waiter->fl_wait, 0);
           locks_delete_block(waiter);
           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 (!(cfl->fl_flags & FL_POSIX))
                           continue;
                   if (posix_locks_conflict(cfl, fl))
                           break;
           }
           unlock_kernel();
   
           return (cfl);
   }
   
   /* 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;
           fl_owner_t caller_owner, blocked_owner;
           unsigned int     caller_pid, blocked_pid;
   
           caller_owner = caller_fl->fl_owner;
           caller_pid = caller_fl->fl_pid;
           blocked_owner = block_fl->fl_owner;
           blocked_pid = block_fl->fl_pid;
   
   next_task:
           if (caller_owner == blocked_owner && caller_pid == blocked_pid)
                   return 1;
           list_for_each(tmp, &blocked_list) {
                   struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
                   if ((fl->fl_owner == blocked_owner)
                       && (fl->fl_pid == blocked_pid)) {
                           fl = fl->fl_next;
                           blocked_owner = fl->fl_owner;
                           blocked_pid = fl->fl_pid;
                           goto next_task;
                   }
           }
           return 0;
   }
   
   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 (!(fl->fl_flags & FL_POSIX))
                           continue;
                   if (fl->fl_owner != owner)
                           break;
           }
           unlock_kernel();
           return fl ? -EAGAIN : 0;
   }
   
   int locks_mandatory_area(int read_write, struct inode *inode,
                            struct file *filp, loff_t offset,
                            size_t count)
   {
           struct file_lock *fl;
           struct file_lock *new_fl = locks_alloc_lock(0);
           int error;
   
           if (new_fl == NULL)
                   return -ENOMEM;
   
           new_fl->fl_owner = current->files;
           new_fl->fl_pid = current->pid;
           new_fl->fl_file = filp;
           new_fl->fl_flags = FL_POSIX | FL_ACCESS;
           new_fl->fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
           new_fl->fl_start = offset;
           new_fl->fl_end = offset + count - 1;
   
           error = 0;
           lock_kernel();
   
   repeat:
           /* Search the lock list for this inode for locks that conflict with
            * the proposed read/write.
            */
           for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
                   if (!(fl->fl_flags & FL_POSIX))
                           continue;
                   if (fl->fl_start > new_fl->fl_end)
                           break;
                   if (posix_locks_conflict(new_fl, fl)) {
                           error = -EAGAIN;
                           if (filp && (filp->f_flags & O_NONBLOCK))
                                   break;
                           error = -EDEADLK;
                           if (posix_locks_deadlock(new_fl, fl))
                                   break;
           
                           error = locks_block_on(fl, new_fl);
                           if (error != 0)
                                   break;
           
                           /*
                            * If we've been sleeping someone might have
                            * changed the permissions behind our back.
                            */
                           if ((inode->i_mode & (S_ISGID | S_IXGRP)) != S_ISGID)
                                   break;
                           goto repeat;
                   }
           }
           locks_free_lock(new_fl);
           unlock_kernel();
           return error;
   }
   
   /* 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, unsigned int lock_type,
                              unsigned int wait)
   {
           struct file_lock *fl;
           struct file_lock *new_fl = NULL;
           struct file_lock **before;
           struct inode * inode = filp->f_dentry->d_inode;
           int error, change;
           int unlock = (lock_type == F_UNLCK);
   
           /*
            * If we need a new lock, get it in advance to avoid races.
            */
           if (!unlock) {
                   error = -ENOLCK;
                   new_fl = flock_make_lock(filp, lock_type);
                   if (!new_fl)
                           return error;
           }
   
           error = 0;
   search:
           change = 0;
           before = &inode->i_flock;
           while (((fl = *before) != NULL) && (fl->fl_flags & FL_FLOCK)) {
                   if (filp == fl->fl_file) {
                           if (lock_type == fl->fl_type)
                                   goto out;
                           change = 1;
                           break;
                   }
                   before = &fl->fl_next;
           }
           /* change means that we are changing the type of an existing lock,
            * or else unlocking it.
            */
           if (change) {
                   /* N.B. What if the wait argument is false? */
                   locks_delete_lock(before, !unlock);
                   /*
                    * If we waited, another lock may have been added ...
                    */
                   if (!unlock)
                           goto search;
           }
           if (unlock)
                   goto out;
   
   repeat:
           for (fl = inode->i_flock; (fl != NULL) && (fl->fl_flags & FL_FLOCK);
                fl = fl->fl_next) {
                   if (!flock_locks_conflict(new_fl, fl))
                           continue;
                   error = -EAGAIN;
                   if (!wait)
                           goto out;
                   error = locks_block_on(fl, new_fl);
                   if (error != 0)
                           goto out;
                   goto repeat;
           }
           locks_insert_lock(&inode->i_flock, new_fl);
           new_fl = NULL;
           error = 0;
   
   out:
           if (new_fl)
                   locks_free_lock(new_fl);
           return error;
   }
   
   /**
    *      posix_lock_file:
    *      @filp: The file to apply the lock to
    *      @caller: The lock to be applied
    *      @wait: 1 to retry automatically, 0 to return -EAGAIN
    *
    * Add a POSIX style lock to a file.
    * We merge adjacent locks whenever possible. POSIX locks are sorted by owner
    * task, then by starting address
    *
    * Kai Petzke writes:
    * To make freeing a lock much faster, we keep a pointer to the lock before the
    * actual one. But the real gain of the new coding was, that lock_it() and
    * unlock_it() became one function.
    *
    * To all purists: Yes, I use a few goto's. Just pass on to the next function.
    */
   
   int posix_lock_file(struct file *filp, struct file_lock *caller,
                              unsigned int wait)
   {
           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;
           struct inode * inode = filp->f_dentry->d_inode;
           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(0);
           new_fl2 = locks_alloc_lock(0);
           error = -ENOLCK; /* "no luck" */
           if (!(new_fl && new_fl2))
                   goto out_nolock;
   
           lock_kernel();
           if (caller->fl_type != F_UNLCK) {
     repeat:
                   for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
                           if (!(fl->fl_flags & FL_POSIX))
                                   continue;
                           if (!posix_locks_conflict(caller, fl))
                                   continue;
                           error = -EAGAIN;
                           if (!wait)
                                   goto out;
                           error = -EDEADLK;
                           if (posix_locks_deadlock(caller, fl))
                                   goto out;
   
                           error = locks_block_on(fl, caller);
                           if (error != 0)
                                   goto out;
                           goto repeat;
                   }
           }
   
           /*
            * 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) && (!(fl->fl_flags & FL_POSIX) ||
                                     !locks_same_owner(caller, fl))) {
                   before = &fl->fl_next;
           }
   
           /* Process locks with this owner.
            */
           while ((fl = *before) && locks_same_owner(caller, fl)) {
                   /* Detect adjacent or overlapping regions (if same lock type)
                    */
                   if (caller->fl_type == fl->fl_type) {
                           if (fl->fl_end < caller->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 > caller->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 > caller->fl_start)
                                   fl->fl_start = caller->fl_start;
                           else
                                   caller->fl_start = fl->fl_start;
                           if (fl->fl_end < caller->fl_end)
                                   fl->fl_end = caller->fl_end;
                           else
                                   caller->fl_end = fl->fl_end;
                           if (added) {
                                   locks_delete_lock(before, 0);
                                   continue;
                           }
                           caller = fl;
                           added = 1;
                   }
                   else {
                           /* Processing for different lock types is a bit
                            * more complex.
                            */
                           if (fl->fl_end < caller->fl_start)
                                   goto next_lock;
                           if (fl->fl_start > caller->fl_end)
                                   break;
                           if (caller->fl_type == F_UNLCK)
                                   added = 1;
                           if (fl->fl_start < caller->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 > caller->fl_end) {
                                   right = fl;
                                   break;
                           }
                           if (fl->fl_start >= caller->fl_start) {
                                   /* The new lock completely replaces an old
                                    * one (This may happen several times).
                                    */
                                   if (added) {
                                           locks_delete_lock(before, 0);
                                           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, 0);    /* This cannot schedule()! */
                                   fl->fl_start = caller->fl_start;
                                   fl->fl_end = caller->fl_end;
                                   fl->fl_type = caller->fl_type;
                                   fl->fl_u = caller->fl_u;
                                   caller = fl;
                                  added = 1;
                          }
                  }
                  /* Go on to next lock.
                   */
          next_lock:
                  before = &fl->fl_next;
          }
  
          error = 0;
          if (!added) {
                  if (caller->fl_type == F_UNLCK)
                          goto out;
                  locks_copy_lock(new_fl, caller);
                  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 = caller->fl_end + 1;
                  locks_wake_up_blocks(right, 0);
          }
          if (left) {
                  left->fl_end = caller->fl_start - 1;
                  locks_wake_up_blocks(left, 0);
          }
  out:
          unlock_kernel();
  out_nolock:
          /*
           * Free any unused locks.
           */
          if (new_fl)
                  locks_free_lock(new_fl);
          if (new_fl2)
                  locks_free_lock(new_fl2);
          return error;
  }
  
  static inline int flock_translate_cmd(int cmd) {
  #ifdef MSNFS
          if (cmd & LOCK_MAND)
                  return cmd & (LOCK_MAND | LOCK_RW);
  #endif
          switch (cmd &~ LOCK_NB) {
          case LOCK_SH:
                  return F_RDLCK;
          case LOCK_EX:
                  return F_WRLCK;
          case LOCK_UN:
                  return F_UNLCK;
          }
          return -EINVAL;
  }
  
  /* We already had a lease on this file; just change its type */
  static 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, 0);
          if (arg == F_UNLCK) {
                  struct file *filp = fl->fl_file;
  
                  filp->f_owner.pid = 0;
                  filp->f_owner.uid = 0;
                  filp->f_owner.euid = 0;
                  filp->f_owner.signum = 0;
                  locks_delete_lock(before, 0);
          }
          return 0;
  }
  
  static void time_out_leases(struct inode *inode)
  {
          struct file_lock **before;
          struct file_lock *fl;
  
          before = &inode->i_flock;
          while ((fl = *before) && (fl->fl_flags & FL_LEASE)
                          && (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;
          }
  }
  
  /**
   *      __get_lease     -       revoke all outstanding leases on file
   *      @inode: the inode of the file to return
   *      @mode: the open mode (read or write)
   *
   *      get_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 __get_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) || (flock->fl_flags & FL_LEASE) == 0)
                  goto out;
  
          for (fl = flock; fl && (fl->fl_flags & FL_LEASE); 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 && (fl->fl_flags & FL_LEASE); fl = fl->fl_next) {
                  if (fl->fl_type != future) {
                          fl->fl_type = future;
                          fl->fl_break_time = break_time;
                          kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
                  }
          }
  
          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 && (flock->fl_flags & FL_LEASE);
                                  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;
  }
  
  /**
   *      lease_get_mtime
   *      @inode: the inode
   *
   * 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.
   */
  time_t lease_get_mtime(struct inode *inode)
  {
          struct file_lock *flock = inode->i_flock;
          if (flock && (flock->fl_flags & FL_LEASE) && (flock->fl_type & F_WRLCK))
                  return CURRENT_TIME;
          return inode->i_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 && (fl->fl_flags & FL_LEASE);
                          fl = fl->fl_next) {
                  if (fl->fl_file == filp) {
                          type = fl->fl_type & ~F_INPROGRESS;
                          break;
                  }
          }
          unlock_kernel();
          return type;
  }
  
  /**
   *      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, **before, **my_before = NULL;
          struct dentry *dentry;
          struct inode *inode;
          int error, rdlease_count = 0, wrlease_count = 0;
  
          dentry = filp->f_dentry;
          inode = dentry->d_inode;
  
          if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
                  return -EACCES;
          if (!S_ISREG(inode->i_mode))
                  return -EINVAL;
  
          lock_kernel();
  
          time_out_leases(inode);
  
          /*
           * FIXME: What about F_RDLCK and files open for writing?
           */
          error = -EAGAIN;
          if ((arg == F_WRLCK)
              && ((atomic_read(&dentry->d_count) > 1)
                  || (atomic_read(&inode->i_count) > 1)))
                  goto out_unlock;
  
          /*
           * 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) && (fl->fl_flags & FL_LEASE);
                          before = &fl->fl_next) {
                  if (fl->fl_file == filp)
                          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_unlock;
  
          if (my_before != NULL) {
                  error = lease_modify(my_before, arg);
                  goto out_unlock;
          }
  
          error = 0;
          if (arg == F_UNLCK)
                  goto out_unlock;
  
          error = -EINVAL;
          if (!leases_enable)
                  goto out_unlock;
  
          error = lease_alloc(filp, arg, &fl);
          if (error)
                  goto out_unlock;
  
          error = fasync_helper(fd, filp, 1, &fl->fl_fasync);
          if (error < 0) {
                  locks_free_lock(fl);
                  goto out_unlock;
          }
          fl->fl_next = *before;
          *before = fl;
          list_add(&fl->fl_link, &file_lock_list);
          filp->f_owner.pid = current->pid;
          filp->f_owner.uid = current->uid;
          filp->f_owner.euid = current->euid;
  out_unlock:
          unlock_kernel();
          return error;
  }
  
  /**
   *      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;
          int error, type;
  
          error = -EBADF;
          filp = fget(fd);
          if (!filp)
                  goto out;
  
          error = flock_translate_cmd(cmd);
          if (error < 0)
                  goto out_putf;
          type = error;
  
          error = -EBADF;
          if ((type != F_UNLCK)
  #ifdef MSNFS
                  && !(type & LOCK_MAND)
  #endif
                  && !(filp->f_mode & 3))
                  goto out_putf;
  
          lock_kernel();
          error = flock_lock_file(filp, type,
                                  (cmd & (LOCK_UN | LOCK_NB)) ? 0 : 1);
          unlock_kernel();
  
  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(unsigned int fd, struct flock *l)
  {
          struct file *filp;
          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 = -EBADF;
          filp = fget(fd);
          if (!filp)
                  goto out;
  
          error = flock_to_posix_lock(filp, &file_lock, &flock);
          if (error)
                  goto out_putf;
  
          if (filp->f_op && filp->f_op->lock) {
                  error = filp->f_op->lock(filp, F_GETLK, &file_lock);
                  if (error < 0)
                          goto out_putf;
                  else if (error == LOCK_USE_CLNT)
                    /* Bypass for NFS with no locking - 2.0.36 compat */
                    fl = posix_test_lock(filp, &file_lock);
                  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_putf;
                  if ((fl->fl_end != OFFSET_MAX)
                      && (fl->fl_end > OFFT_OFFSET_MAX))
                          goto out_putf;
  #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_putf:
          fput(filp);
  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(unsigned int fd, unsigned int cmd, struct flock *l)
  {
          struct file *filp;
          struct file_lock *file_lock = locks_alloc_lock(0);
          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;
  
          /* Get arguments and validate them ...
           */
  
          error = -EBADF;
          filp = fget(fd);
          if (!filp)
                  goto out;
  
          error = -EINVAL;
          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) {
                  struct address_space *mapping = inode->i_mapping;
  
                  if (mapping->i_mmap_shared != NULL) {
                          error = -EAGAIN;
                          goto out_putf;
                  }
          }
  
          error = flock_to_posix_lock(filp, file_lock, &flock);
          if (error)
                  goto out_putf;
          
          error = -EBADF;
          switch (flock.l_type) {
          case F_RDLCK:
                  if (!(filp->f_mode & FMODE_READ))
                          goto out_putf;
                  break;
          case F_WRLCK:
                  if (!(filp->f_mode & FMODE_WRITE))
                          goto out_putf;
                  break;
          case F_UNLCK:
                  break;
          case F_SHLCK:
          case F_EXLCK:
  #ifdef __sparc__
  /* warn a bit for now, but don't overdo it */
  {
          static int count = 0;
          if (!count) {
                  count=1;
                  printk(KERN_WARNING
                         "fcntl_setlk() called by process %d (%s) with broken flock() emulation\n",
                         current->pid, current->comm);
          }
  }
                  if (!(filp->f_mode & 3))
                          goto out_putf;
                  break;
  #endif
          default:
                  error = -EINVAL;
                  goto out_putf;
          }
  
          if (filp->f_op && filp->f_op->lock != NULL) {
                  error = filp->f_op->lock(filp, cmd, file_lock);
                  if (error < 0)
                          goto out_putf;
          }
          error = posix_lock_file(filp, file_lock, cmd == F_SETLKW);
  
  out_putf:
          fput(filp);
  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(unsigned int fd, struct flock64 *l)
  {
          struct file *filp;
          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 = -EBADF;
          filp = fget(fd);
          if (!filp)
                  goto out;
  
          error = flock64_to_posix_lock(filp, &file_lock, &flock);
          if (error)
                  goto out_putf;
  
          if (filp->f_op && filp->f_op->lock) {
                  error = filp->f_op->lock(filp, F_GETLK, &file_lock);
                  if (error < 0)
                          goto out_putf;
                  else if (error == LOCK_USE_CLNT)
                    /* Bypass for NFS with no locking - 2.0.36 compat */
                    fl = posix_test_lock(filp, &file_lock);
                  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_putf:
          fput(filp);
  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, unsigned int cmd, struct flock64 *l)
  {
          struct file *filp;
          struct file_lock *file_lock = locks_alloc_lock(0);
          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;
  
          /* Get arguments and validate them ...
           */
  
          error = -EBADF;
          filp = fget(fd);
          if (!filp)
                  goto out;
  
          error = -EINVAL;
          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) {
                  struct address_space *mapping = inode->i_mapping;
  
                  if (mapping->i_mmap_shared != NULL) {
                          error = -EAGAIN;
                          goto out_putf;
                  }
          }
  
          error = flock64_to_posix_lock(filp, file_lock, &flock);
          if (error)
                  goto out_putf;
          
          error = -EBADF;
          switch (flock.l_type) {
          case F_RDLCK:
                  if (!(filp->f_mode & FMODE_READ))
                          goto out_putf;
                  break;
          case F_WRLCK:
                  if (!(filp->f_mode & FMODE_WRITE))
                          goto out_putf;
                  break;
          case F_UNLCK:
                  break;
          case F_SHLCK:
          case F_EXLCK:
          default:
                  error = -EINVAL;
                  goto out_putf;
          }
  
          if (filp->f_op && filp->f_op->lock != NULL) {
                  error = filp->f_op->lock(filp, cmd, file_lock);
                  if (error < 0)
                          goto out_putf;
          }
          error = posix_lock_file(filp, file_lock, cmd == F_SETLKW64);
  
  out_putf:
          fput(filp);
  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.
   */
  void locks_remove_posix(struct file *filp, fl_owner_t owner)
  {
          struct inode * inode = filp->f_dentry->d_inode;
          struct file_lock *fl;
          struct file_lock **before;
  
          /*
           * For POSIX locks we free all locks on this file for the given task.
           */
          if (!inode->i_flock) {
                  /*
                   * Notice that something might be grabbing a lock right now.
                   * Consider it as a race won by us - event is async, so even if
                   * we miss the lock added we can trivially consider it as added
                   * after we went through this call.
                   */
                  return;
          }
          lock_kernel();
          before = &inode->i_flock;
          while ((fl = *before) != NULL) {
                  if ((fl->fl_flags & FL_POSIX) && fl->fl_owner == owner) {
                          locks_unlock_delete(before);
                          before = &inode->i_flock;
                          continue;
                  }
                  before = &fl->fl_next;
          }
          unlock_kernel();
  }
  
  /*
   * 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;
  
          lock_kernel();
          before = &inode->i_flock;
  
          while ((fl = *before) != NULL) {
                  if (fl->fl_file == filp) {
                          if (fl->fl_flags & FL_FLOCK) {
                                  locks_delete_lock(before, 0);
                                  continue;
                          }
                          if (fl->fl_flags & FL_LEASE) {
                                  lease_modify(before, F_UNLCK);
                                  continue;
                          }
                  }
                  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);
  }
  
  /**
   *      posix_unblock_lock - stop waiting for a file lock
   *      @waiter: the lock which was waiting
   *
   *      lockd needs to block waiting for locks.
   */
  void
  posix_unblock_lock(struct file_lock *waiter)
  {
          if (!list_empty(&waiter->fl_block))
                  locks_delete_block(waiter);
  }
  
  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 (fl->fl_flags & FL_POSIX) {
                  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 (fl->fl_flags & FL_FLOCK) {
  #ifdef MSNFS
                  if (fl->fl_type & LOCK_MAND) {
                          out += sprintf(out, "FLOCK  MSNFS     ");
                  } else
  #endif
                          out += sprintf(out, "FLOCK  ADVISORY  ");
          } else if (fl->fl_flags & FL_LEASE) {
                  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  ");
          }
  #ifdef MSNFS
          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
  #endif
                  out += sprintf(out, "%s ",
                                 (fl->fl_type & F_INPROGRESS)
                                 ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
                                 : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
          out += sprintf(out, "%d %s:%ld ",
                       fl->fl_pid,
                       inode ? kdevname(inode->i_dev) : "<none>",
                       inode ? inode->i_ino : 0);
          out += sprintf(out, "%Ld ", fl->fl_start);
          if (fl->fl_end == OFFSET_MAX)
                  out += sprintf(out, "EOF ");
          else
                  out += sprintf(out, "%Ld ", fl->fl_end);
          sprintf(out, "%08lx %08lx %08lx %08lx %08lx\n",
                  (long)fl, (long)fl->fl_link.prev, (long)fl->fl_link.next,
                  (long)fl->fl_next, (long)fl->fl_block.next);
  }
  
  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;
  }
  
  void steal_locks(fl_owner_t from)
  {
          struct list_head *tmp;
  
          if (from == current->files)
                  return;
  
          lock_kernel();
          list_for_each(tmp, &file_lock_list) {
                  struct file_lock *fl = list_entry(tmp, struct file_lock,
                                                    fl_link);
                  if (fl->fl_owner == from)
                          fl->fl_owner = current->files;
          }
          unlock_kernel();
  }
  
  #ifdef MSNFS
  /**
   *      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 (fl->fl_flags == FL_POSIX) {
                          if (fl->fl_type == F_RDLCK)
                                  continue;
                          if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
                                  continue;
                  } else if (fl->fl_flags == FL_FLOCK) {
                          if (!(fl->fl_type & LOCK_MAND))
                                  continue;
                          if (fl->fl_type & LOCK_READ)
                                  continue;
                  } else
                          continue;
                  result = 0;
                  break;
          }
          unlock_kernel();
          return result;
  }
  
  /**
   *      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 (fl->fl_flags == FL_POSIX) {
                          if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
                                  continue;
                  } else if (fl->fl_flags == FL_FLOCK) {
                          if (!(fl->fl_type & LOCK_MAND))
                                  continue;
                          if (fl->fl_type & LOCK_WRITE)
                                  continue;
                  } else
                          continue;
                  result = 0;
                  break;
          }
          unlock_kernel();
          return result;
  }
  #endif
  
  static int __init filelock_init(void)
  {
          filelock_cache = kmem_cache_create("file_lock_cache",
                          sizeof(struct file_lock), 0, 0, init_once, NULL);
          if (!filelock_cache)
                  panic("cannot create file lock slab cache");
          return 0;
  }
  
  module_init(filelock_init)

Cache object: 270c696c9f9ccb3494129890345c8033