1 #define MSNFS /* HACK HACK */
5 * Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
6 * Doug Evans (dje@spiff.uucp), August 07, 1992
8 * Deadlock detection added.
9 * FIXME: one thing isn't handled yet:
10 * - mandatory locks (requires lots of changes elsewhere)
11 * Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
13 * Miscellaneous edits, and a total rewrite of posix_lock_file() code.
14 * Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
16 * Converted file_lock_table to a linked list from an array, which eliminates
17 * the limits on how many active file locks are open.
18 * Chad Page (pageone@netcom.com), November 27, 1994
20 * Removed dependency on file descriptors. dup()'ed file descriptors now
21 * get the same locks as the original file descriptors, and a close() on
22 * any file descriptor removes ALL the locks on the file for the current
23 * process. Since locks still depend on the process id, locks are inherited
24 * after an exec() but not after a fork(). This agrees with POSIX, and both
25 * BSD and SVR4 practice.
26 * Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
28 * Scrapped free list which is redundant now that we allocate locks
29 * dynamically with kmalloc()/kfree().
30 * Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
32 * Implemented two lock personalities - FL_FLOCK and FL_POSIX.
34 * FL_POSIX locks are created with calls to fcntl() and lockf() through the
35 * fcntl() system call. They have the semantics described above.
37 * FL_FLOCK locks are created with calls to flock(), through the flock()
38 * system call, which is new. Old C libraries implement flock() via fcntl()
39 * and will continue to use the old, broken implementation.
41 * FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
42 * with a file pointer (filp). As a result they can be shared by a parent
43 * process and its children after a fork(). They are removed when the last
44 * file descriptor referring to the file pointer is closed (unless explicitly
47 * FL_FLOCK locks never deadlock, an existing lock is always removed before
48 * upgrading from shared to exclusive (or vice versa). When this happens
49 * any processes blocked by the current lock are woken up and allowed to
50 * run before the new lock is applied.
51 * Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
53 * Removed some race conditions in flock_lock_file(), marked other possible
54 * races. Just grep for FIXME to see them.
55 * Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
57 * Addressed Dmitry's concerns. Deadlock checking no longer recursive.
58 * Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
59 * once we've checked for blocking and deadlocking.
60 * Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
62 * Initial implementation of mandatory locks. SunOS turned out to be
63 * a rotten model, so I implemented the "obvious" semantics.
64 * See 'linux/Documentation/mandatory.txt' for details.
65 * Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
67 * Don't allow mandatory locks on mmap()'ed files. Added simple functions to
68 * check if a file has mandatory locks, used by mmap(), open() and creat() to
69 * see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
71 * Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
73 * Tidied up block list handling. Added '/proc/locks' interface.
74 * Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
76 * Fixed deadlock condition for pathological code that mixes calls to
77 * flock() and fcntl().
78 * Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
80 * Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
81 * for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
82 * guarantee sensible behaviour in the case where file system modules might
83 * be compiled with different options than the kernel itself.
84 * Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
86 * Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
87 * (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
88 * Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
90 * Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
91 * locks. Changed process synchronisation to avoid dereferencing locks that
92 * have already been freed.
93 * Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
95 * Made the block list a circular list to minimise searching in the list.
96 * Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
98 * Made mandatory locking a mount option. Default is not to allow mandatory
100 * Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
102 * Some adaptations for NFS support.
103 * Olaf Kirch (okir@monad.swb.de), Dec 1996,
105 * Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
106 * Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
108 * Use slab allocator instead of kmalloc/kfree.
109 * Use generic list implementation from <linux/list.h>.
110 * Sped up posix_locks_deadlock by only considering blocked locks.
111 * Matthew Wilcox <willy@thepuffingroup.com>, March, 2000.
113 * Leases and LOCK_MAND
114 * Matthew Wilcox <willy@linuxcare.com>, June, 2000.
115 * Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
118 #include <linux/slab.h>
119 #include <linux/file.h>
120 #include <linux/smp_lock.h>
121 #include <linux/init.h>
122 #include <linux/capability.h>
123 #include <linux/sched.h>
124 #include <linux/timer.h>
126 #include <asm/semaphore.h>
127 #include <asm/uaccess.h>
129 int leases_enable = 1;
130 int lease_break_time = 45;
132 LIST_HEAD(file_lock_list);
133 static LIST_HEAD(blocked_list);
135 static kmem_cache_t *filelock_cache;
137 /* Allocate an empty lock structure. */
138 static struct file_lock *locks_alloc_lock(int account)
140 struct file_lock *fl;
141 if (account && current->locks >= current->rlim[RLIMIT_LOCKS].rlim_cur)
143 fl = kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
149 /* Free a lock which is not in use. */
150 static inline void locks_free_lock(struct file_lock *fl)
157 if (waitqueue_active(&fl->fl_wait))
158 panic("Attempting to free lock with active wait queue");
160 if (!list_empty(&fl->fl_block))
161 panic("Attempting to free lock with active block list");
163 if (!list_empty(&fl->fl_link))
164 panic("Attempting to free lock on active lock list");
166 kmem_cache_free(filelock_cache, fl);
169 void locks_init_lock(struct file_lock *fl)
171 INIT_LIST_HEAD(&fl->fl_link);
172 INIT_LIST_HEAD(&fl->fl_block);
173 init_waitqueue_head(&fl->fl_wait);
175 fl->fl_fasync = NULL;
181 fl->fl_start = fl->fl_end = 0;
182 fl->fl_notify = NULL;
183 fl->fl_insert = NULL;
184 fl->fl_remove = NULL;
188 * Initialises the fields of the file lock which are invariant for
191 static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags)
193 struct file_lock *lock = (struct file_lock *) foo;
195 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
196 SLAB_CTOR_CONSTRUCTOR)
199 locks_init_lock(lock);
203 * Initialize a new lock from an existing file_lock structure.
205 void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
207 new->fl_owner = fl->fl_owner;
208 new->fl_pid = fl->fl_pid;
209 new->fl_file = fl->fl_file;
210 new->fl_flags = fl->fl_flags;
211 new->fl_type = fl->fl_type;
212 new->fl_start = fl->fl_start;
213 new->fl_end = fl->fl_end;
214 new->fl_notify = fl->fl_notify;
215 new->fl_insert = fl->fl_insert;
216 new->fl_remove = fl->fl_remove;
217 new->fl_u = fl->fl_u;
220 /* Fill in a file_lock structure with an appropriate FLOCK lock. */
221 static struct file_lock *flock_make_lock(struct file *filp, unsigned int type)
223 struct file_lock *fl = locks_alloc_lock(1);
229 fl->fl_pid = current->pid;
230 fl->fl_flags = FL_FLOCK;
233 fl->fl_end = OFFSET_MAX;
234 fl->fl_notify = NULL;
235 fl->fl_insert = NULL;
236 fl->fl_remove = NULL;
241 static int assign_type(struct file_lock *fl, int type)
255 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
258 static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
263 switch (l->l_whence) {
271 start = filp->f_dentry->d_inode->i_size;
277 /* POSIX-1996 leaves the case l->l_len < 0 undefined;
278 POSIX-2001 defines it. */
284 end = start + l->l_len - 1;
289 if (l->l_len > 0 && end < 0)
291 fl->fl_start = start; /* we record the absolute position */
294 fl->fl_end = OFFSET_MAX;
296 fl->fl_owner = current->files;
297 fl->fl_pid = current->pid;
299 fl->fl_flags = FL_POSIX;
300 fl->fl_notify = NULL;
301 fl->fl_insert = NULL;
302 fl->fl_remove = NULL;
304 return assign_type(fl, l->l_type);
307 #if BITS_PER_LONG == 32
308 static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
313 switch (l->l_whence) {
321 start = filp->f_dentry->d_inode->i_size;
327 if (((start += l->l_start) < 0) || (l->l_len < 0))
329 fl->fl_end = start + l->l_len - 1;
330 if (l->l_len > 0 && fl->fl_end < 0)
332 fl->fl_start = start; /* we record the absolute position */
334 fl->fl_end = OFFSET_MAX;
336 fl->fl_owner = current->files;
337 fl->fl_pid = current->pid;
339 fl->fl_flags = FL_POSIX;
340 fl->fl_notify = NULL;
341 fl->fl_insert = NULL;
342 fl->fl_remove = NULL;
348 fl->fl_type = l->l_type;
358 /* Allocate a file_lock initialised to this type of lease */
359 static int lease_alloc(struct file *filp, int type, struct file_lock **flp)
361 struct file_lock *fl = locks_alloc_lock(1);
365 fl->fl_owner = current->files;
366 fl->fl_pid = current->pid;
369 fl->fl_flags = FL_LEASE;
370 if (assign_type(fl, type) != 0) {
375 fl->fl_end = OFFSET_MAX;
376 fl->fl_notify = NULL;
377 fl->fl_insert = NULL;
378 fl->fl_remove = NULL;
384 /* Check if two locks overlap each other.
386 static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
388 return ((fl1->fl_end >= fl2->fl_start) &&
389 (fl2->fl_end >= fl1->fl_start));
393 * Check whether two locks have the same owner
394 * N.B. Do we need the test on PID as well as owner?
395 * (Clone tasks should be considered as one "owner".)
398 locks_same_owner(struct file_lock *fl1, struct file_lock *fl2)
400 return (fl1->fl_owner == fl2->fl_owner) &&
401 (fl1->fl_pid == fl2->fl_pid);
404 /* Remove waiter from blocker's block list.
405 * When blocker ends up pointing to itself then the list is empty.
407 static void locks_delete_block(struct file_lock *waiter)
409 list_del(&waiter->fl_block);
410 INIT_LIST_HEAD(&waiter->fl_block);
411 list_del(&waiter->fl_link);
412 INIT_LIST_HEAD(&waiter->fl_link);
413 waiter->fl_next = NULL;
416 /* Insert waiter into blocker's block list.
417 * We use a circular list so that processes can be easily woken up in
418 * the order they blocked. The documentation doesn't require this but
419 * it seems like the reasonable thing to do.
421 static void locks_insert_block(struct file_lock *blocker,
422 struct file_lock *waiter)
424 if (!list_empty(&waiter->fl_block)) {
425 printk(KERN_ERR "locks_insert_block: removing duplicated lock "
426 "(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid,
427 waiter->fl_start, waiter->fl_end, waiter->fl_type);
428 locks_delete_block(waiter);
430 list_add_tail(&waiter->fl_block, &blocker->fl_block);
431 waiter->fl_next = blocker;
432 list_add(&waiter->fl_link, &blocked_list);
436 void locks_notify_blocked(struct file_lock *waiter)
438 if (waiter->fl_notify)
439 waiter->fl_notify(waiter);
441 wake_up(&waiter->fl_wait);
444 /* Wake up processes blocked waiting for blocker.
445 * If told to wait then schedule the processes until the block list
446 * is empty, otherwise empty the block list ourselves.
448 static void locks_wake_up_blocks(struct file_lock *blocker, unsigned int wait)
450 while (!list_empty(&blocker->fl_block)) {
451 struct file_lock *waiter = list_entry(blocker->fl_block.next, struct file_lock, fl_block);
454 locks_notify_blocked(waiter);
455 /* Let the blocked process remove waiter from the
456 * block list when it gets scheduled.
460 /* Remove waiter from the block list, because by the
461 * time it wakes up blocker won't exist any more.
463 locks_delete_block(waiter);
464 locks_notify_blocked(waiter);
469 /* Insert file lock fl into an inode's lock list at the position indicated
470 * by pos. At the same time add the lock to the global file lock list.
472 static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
474 list_add(&fl->fl_link, &file_lock_list);
476 /* insert into file's list */
485 * Remove lock from the lock lists
487 static inline void _unhash_lock(struct file_lock **thisfl_p)
489 struct file_lock *fl = *thisfl_p;
491 *thisfl_p = fl->fl_next;
494 list_del_init(&fl->fl_link);
498 * Wake up processes that are blocked waiting for this lock,
499 * notify the FS that the lock has been cleared and
500 * finally free the lock.
502 static inline void _delete_lock(struct file_lock *fl, unsigned int wait)
504 fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
505 if (fl->fl_fasync != NULL){
506 printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
507 fl->fl_fasync = NULL;
513 locks_wake_up_blocks(fl, wait);
518 * Delete a lock and then free it.
520 static void locks_delete_lock(struct file_lock **thisfl_p, unsigned int wait)
522 struct file_lock *fl = *thisfl_p;
524 _unhash_lock(thisfl_p);
525 _delete_lock(fl, wait);
529 * Call back client filesystem in order to get it to unregister a lock,
530 * then delete lock. Essentially useful only in locks_remove_*().
531 * Note: this must be called with the semaphore already held!
533 static inline void locks_unlock_delete(struct file_lock **thisfl_p)
535 struct file_lock *fl = *thisfl_p;
536 int (*lock)(struct file *, int, struct file_lock *);
538 _unhash_lock(thisfl_p);
539 if (fl->fl_file->f_op &&
540 (lock = fl->fl_file->f_op->lock) != NULL) {
541 fl->fl_type = F_UNLCK;
542 lock(fl->fl_file, F_SETLK, fl);
547 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality
548 * checks for shared/exclusive status of overlapping locks.
550 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
552 switch (caller_fl->fl_type) {
554 return (sys_fl->fl_type == F_WRLCK);
560 printk(KERN_ERR "locks_conflict(): impossible lock type - %d\n",
564 return (0); /* This should never happen */
567 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
568 * checking before calling the locks_conflict().
570 static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
572 /* POSIX locks owned by the same process do not conflict with
575 if (!(sys_fl->fl_flags & FL_POSIX) ||
576 locks_same_owner(caller_fl, sys_fl))
579 /* Check whether they overlap */
580 if (!locks_overlap(caller_fl, sys_fl))
583 return (locks_conflict(caller_fl, sys_fl));
586 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
587 * checking before calling the locks_conflict().
589 static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
591 /* FLOCK locks referring to the same filp do not conflict with
594 if (!(sys_fl->fl_flags & FL_FLOCK) ||
595 (caller_fl->fl_file == sys_fl->fl_file))
598 if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
602 return (locks_conflict(caller_fl, sys_fl));
605 static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
608 DECLARE_WAITQUEUE(wait, current);
610 current->state = TASK_INTERRUPTIBLE;
611 add_wait_queue(fl_wait, &wait);
615 result = schedule_timeout(timeout);
616 if (signal_pending(current))
617 result = -ERESTARTSYS;
618 remove_wait_queue(fl_wait, &wait);
619 current->state = TASK_RUNNING;
623 static int locks_block_on(struct file_lock *blocker, struct file_lock *waiter)
626 locks_insert_block(blocker, waiter);
627 result = interruptible_sleep_on_locked(&waiter->fl_wait, 0);
628 locks_delete_block(waiter);
632 static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
635 locks_insert_block(blocker, waiter);
636 result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
637 locks_delete_block(waiter);
642 posix_test_lock(struct file *filp, struct file_lock *fl)
644 struct file_lock *cfl;
647 for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
648 if (!(cfl->fl_flags & FL_POSIX))
650 if (posix_locks_conflict(cfl, fl))
658 /* This function tests for deadlock condition before putting a process to
659 * sleep. The detection scheme is no longer recursive. Recursive was neat,
660 * but dangerous - we risked stack corruption if the lock data was bad, or
661 * if the recursion was too deep for any other reason.
663 * We rely on the fact that a task can only be on one lock's wait queue
664 * at a time. When we find blocked_task on a wait queue we can re-search
665 * with blocked_task equal to that queue's owner, until either blocked_task
666 * isn't found, or blocked_task is found on a queue owned by my_task.
668 * Note: the above assumption may not be true when handling lock requests
669 * from a broken NFS client. But broken NFS clients have a lot more to
670 * worry about than proper deadlock detection anyway... --okir
672 int posix_locks_deadlock(struct file_lock *caller_fl,
673 struct file_lock *block_fl)
675 struct list_head *tmp;
676 fl_owner_t caller_owner, blocked_owner;
677 unsigned int caller_pid, blocked_pid;
679 caller_owner = caller_fl->fl_owner;
680 caller_pid = caller_fl->fl_pid;
681 blocked_owner = block_fl->fl_owner;
682 blocked_pid = block_fl->fl_pid;
685 if (caller_owner == blocked_owner && caller_pid == blocked_pid)
687 list_for_each(tmp, &blocked_list) {
688 struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
689 if ((fl->fl_owner == blocked_owner)
690 && (fl->fl_pid == blocked_pid)) {
692 blocked_owner = fl->fl_owner;
693 blocked_pid = fl->fl_pid;
700 int locks_mandatory_locked(struct inode *inode)
702 fl_owner_t owner = current->files;
703 struct file_lock *fl;
706 * Search the lock list for this inode for any POSIX locks.
709 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
710 if (!(fl->fl_flags & FL_POSIX))
712 if (fl->fl_owner != owner)
716 return fl ? -EAGAIN : 0;
719 int locks_mandatory_area(int read_write, struct inode *inode,
720 struct file *filp, loff_t offset,
723 struct file_lock *fl;
724 struct file_lock *new_fl = locks_alloc_lock(0);
730 new_fl->fl_owner = current->files;
731 new_fl->fl_pid = current->pid;
732 new_fl->fl_file = filp;
733 new_fl->fl_flags = FL_POSIX | FL_ACCESS;
734 new_fl->fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
735 new_fl->fl_start = offset;
736 new_fl->fl_end = offset + count - 1;
742 /* Search the lock list for this inode for locks that conflict with
743 * the proposed read/write.
745 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
746 if (!(fl->fl_flags & FL_POSIX))
748 if (fl->fl_start > new_fl->fl_end)
750 if (posix_locks_conflict(new_fl, fl)) {
752 if (filp && (filp->f_flags & O_NONBLOCK))
755 if (posix_locks_deadlock(new_fl, fl))
758 error = locks_block_on(fl, new_fl);
763 * If we've been sleeping someone might have
764 * changed the permissions behind our back.
766 if ((inode->i_mode & (S_ISGID | S_IXGRP)) != S_ISGID)
771 locks_free_lock(new_fl);
776 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
777 * at the head of the list, but that's secret knowledge known only to
778 * flock_lock_file and posix_lock_file.
780 static int flock_lock_file(struct file *filp, unsigned int lock_type,
783 struct file_lock *fl;
784 struct file_lock *new_fl = NULL;
785 struct file_lock **before;
786 struct inode * inode = filp->f_dentry->d_inode;
788 int unlock = (lock_type == F_UNLCK);
791 * If we need a new lock, get it in advance to avoid races.
795 new_fl = flock_make_lock(filp, lock_type);
803 before = &inode->i_flock;
804 while (((fl = *before) != NULL) && (fl->fl_flags & FL_FLOCK)) {
805 if (filp == fl->fl_file) {
806 if (lock_type == fl->fl_type)
811 before = &fl->fl_next;
813 /* change means that we are changing the type of an existing lock,
814 * or else unlocking it.
817 /* N.B. What if the wait argument is false? */
818 locks_delete_lock(before, !unlock);
820 * If we waited, another lock may have been added ...
829 for (fl = inode->i_flock; (fl != NULL) && (fl->fl_flags & FL_FLOCK);
831 if (!flock_locks_conflict(new_fl, fl))
836 error = locks_block_on(fl, new_fl);
841 locks_insert_lock(&inode->i_flock, new_fl);
847 locks_free_lock(new_fl);
853 * @filp: The file to apply the lock to
854 * @caller: The lock to be applied
855 * @wait: 1 to retry automatically, 0 to return -EAGAIN
857 * Add a POSIX style lock to a file.
858 * We merge adjacent locks whenever possible. POSIX locks are sorted by owner
859 * task, then by starting address
862 * To make freeing a lock much faster, we keep a pointer to the lock before the
863 * actual one. But the real gain of the new coding was, that lock_it() and
864 * unlock_it() became one function.
866 * To all purists: Yes, I use a few goto's. Just pass on to the next function.
869 int posix_lock_file(struct file *filp, struct file_lock *caller,
872 struct file_lock *fl;
873 struct file_lock *new_fl, *new_fl2;
874 struct file_lock *left = NULL;
875 struct file_lock *right = NULL;
876 struct file_lock **before;
877 struct inode * inode = filp->f_dentry->d_inode;
878 int error, added = 0;
881 * We may need two file_lock structures for this operation,
882 * so we get them in advance to avoid races.
884 new_fl = locks_alloc_lock(0);
885 new_fl2 = locks_alloc_lock(0);
886 error = -ENOLCK; /* "no luck" */
887 if (!(new_fl && new_fl2))
891 if (caller->fl_type != F_UNLCK) {
893 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
894 if (!(fl->fl_flags & FL_POSIX))
896 if (!posix_locks_conflict(caller, fl))
902 if (posix_locks_deadlock(caller, fl))
905 error = locks_block_on(fl, caller);
913 * We've allocated the new locks in advance, so there are no
914 * errors possible (and no blocking operations) from here on.
916 * Find the first old lock with the same owner as the new lock.
919 before = &inode->i_flock;
921 /* First skip locks owned by other processes.
923 while ((fl = *before) && (!(fl->fl_flags & FL_POSIX) ||
924 !locks_same_owner(caller, fl))) {
925 before = &fl->fl_next;
928 /* Process locks with this owner.
930 while ((fl = *before) && locks_same_owner(caller, fl)) {
931 /* Detect adjacent or overlapping regions (if same lock type)
933 if (caller->fl_type == fl->fl_type) {
934 if (fl->fl_end < caller->fl_start - 1)
936 /* If the next lock in the list has entirely bigger
937 * addresses than the new one, insert the lock here.
939 if (fl->fl_start > caller->fl_end + 1)
942 /* If we come here, the new and old lock are of the
943 * same type and adjacent or overlapping. Make one
944 * lock yielding from the lower start address of both
945 * locks to the higher end address.
947 if (fl->fl_start > caller->fl_start)
948 fl->fl_start = caller->fl_start;
950 caller->fl_start = fl->fl_start;
951 if (fl->fl_end < caller->fl_end)
952 fl->fl_end = caller->fl_end;
954 caller->fl_end = fl->fl_end;
956 locks_delete_lock(before, 0);
963 /* Processing for different lock types is a bit
966 if (fl->fl_end < caller->fl_start)
968 if (fl->fl_start > caller->fl_end)
970 if (caller->fl_type == F_UNLCK)
972 if (fl->fl_start < caller->fl_start)
974 /* If the next lock in the list has a higher end
975 * address than the new one, insert the new one here.
977 if (fl->fl_end > caller->fl_end) {
981 if (fl->fl_start >= caller->fl_start) {
982 /* The new lock completely replaces an old
983 * one (This may happen several times).
986 locks_delete_lock(before, 0);
989 /* Replace the old lock with the new one.
990 * Wake up anybody waiting for the old one,
991 * as the change in lock type might satisfy
994 locks_wake_up_blocks(fl, 0); /* This cannot schedule()! */
995 fl->fl_start = caller->fl_start;
996 fl->fl_end = caller->fl_end;
997 fl->fl_type = caller->fl_type;
998 fl->fl_u = caller->fl_u;
1003 /* Go on to next lock.
1006 before = &fl->fl_next;
1011 if (caller->fl_type == F_UNLCK)
1013 locks_copy_lock(new_fl, caller);
1014 locks_insert_lock(before, new_fl);
1018 if (left == right) {
1019 /* The new lock breaks the old one in two pieces,
1020 * so we have to use the second new lock.
1024 locks_copy_lock(left, right);
1025 locks_insert_lock(before, left);
1027 right->fl_start = caller->fl_end + 1;
1028 locks_wake_up_blocks(right, 0);
1031 left->fl_end = caller->fl_start - 1;
1032 locks_wake_up_blocks(left, 0);
1038 * Free any unused locks.
1041 locks_free_lock(new_fl);
1043 locks_free_lock(new_fl2);
1047 static inline int flock_translate_cmd(int cmd) {
1049 if (cmd & LOCK_MAND)
1050 return cmd & (LOCK_MAND | LOCK_RW);
1052 switch (cmd &~ LOCK_NB) {
1063 /* We already had a lease on this file; just change its type */
1064 static int lease_modify(struct file_lock **before, int arg)
1066 struct file_lock *fl = *before;
1067 int error = assign_type(fl, arg);
1071 locks_wake_up_blocks(fl, 0);
1072 if (arg == F_UNLCK) {
1073 struct file *filp = fl->fl_file;
1075 filp->f_owner.pid = 0;
1076 filp->f_owner.uid = 0;
1077 filp->f_owner.euid = 0;
1078 filp->f_owner.signum = 0;
1079 locks_delete_lock(before, 0);
1084 static void time_out_leases(struct inode *inode)
1086 struct file_lock **before;
1087 struct file_lock *fl;
1089 before = &inode->i_flock;
1090 while ((fl = *before) && (fl->fl_flags & FL_LEASE)
1091 && (fl->fl_type & F_INPROGRESS)) {
1092 if ((fl->fl_break_time == 0)
1093 || time_before(jiffies, fl->fl_break_time)) {
1094 before = &fl->fl_next;
1097 printk(KERN_INFO "lease broken - owner pid = %d\n", fl->fl_pid);
1098 lease_modify(before, fl->fl_type & ~F_INPROGRESS);
1099 if (fl == *before) /* lease_modify may have freed fl */
1100 before = &fl->fl_next;
1105 * __get_lease - revoke all outstanding leases on file
1106 * @inode: the inode of the file to return
1107 * @mode: the open mode (read or write)
1109 * get_lease (inlined for speed) has checked there already
1110 * is a lease on this file. Leases are broken on a call to open()
1111 * or truncate(). This function can sleep unless you
1112 * specified %O_NONBLOCK to your open().
1114 int __get_lease(struct inode *inode, unsigned int mode)
1116 int error = 0, future;
1117 struct file_lock *new_fl, *flock;
1118 struct file_lock *fl;
1120 unsigned long break_time;
1121 int i_have_this_lease = 0;
1123 alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK,
1128 time_out_leases(inode);
1130 flock = inode->i_flock;
1131 if ((flock == NULL) || (flock->fl_flags & FL_LEASE) == 0)
1134 for (fl = flock; fl && (fl->fl_flags & FL_LEASE); fl = fl->fl_next)
1135 if (fl->fl_owner == current->files)
1136 i_have_this_lease = 1;
1138 if (mode & FMODE_WRITE) {
1139 /* If we want write access, we have to revoke any lease. */
1140 future = F_UNLCK | F_INPROGRESS;
1141 } else if (flock->fl_type & F_INPROGRESS) {
1142 /* If the lease is already being broken, we just leave it */
1143 future = flock->fl_type;
1144 } else if (flock->fl_type & F_WRLCK) {
1145 /* Downgrade the exclusive lease to a read-only lease. */
1146 future = F_RDLCK | F_INPROGRESS;
1148 /* the existing lease was read-only, so we can read too. */
1152 if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) {
1158 if (lease_break_time > 0) {
1159 break_time = jiffies + lease_break_time * HZ;
1160 if (break_time == 0)
1161 break_time++; /* so that 0 means no break time */
1164 for (fl = flock; fl && (fl->fl_flags & FL_LEASE); fl = fl->fl_next) {
1165 if (fl->fl_type != future) {
1166 fl->fl_type = future;
1167 fl->fl_break_time = break_time;
1168 kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
1172 if (i_have_this_lease || (mode & O_NONBLOCK)) {
1173 error = -EWOULDBLOCK;
1178 break_time = flock->fl_break_time;
1179 if (break_time != 0) {
1180 break_time -= jiffies;
1181 if (break_time == 0)
1184 error = locks_block_on_timeout(flock, new_fl, break_time);
1187 time_out_leases(inode);
1188 /* Wait for the next lease that has not been broken yet */
1189 for (flock = inode->i_flock;
1190 flock && (flock->fl_flags & FL_LEASE);
1191 flock = flock->fl_next) {
1192 if (flock->fl_type & F_INPROGRESS)
1201 locks_free_lock(new_fl);
1209 * This is to force NFS clients to flush their caches for files with
1210 * exclusive leases. The justification is that if someone has an
1211 * exclusive lease, then they could be modifiying it.
1213 time_t lease_get_mtime(struct inode *inode)
1215 struct file_lock *flock = inode->i_flock;
1216 if (flock && (flock->fl_flags & FL_LEASE) && (flock->fl_type & F_WRLCK))
1217 return CURRENT_TIME;
1218 return inode->i_mtime;
1222 * fcntl_getlease - Enquire what lease is currently active
1225 * The value returned by this function will be one of
1226 * (if no lease break is pending):
1228 * %F_RDLCK to indicate a shared lease is held.
1230 * %F_WRLCK to indicate an exclusive lease is held.
1232 * %F_UNLCK to indicate no lease is held.
1234 * (if a lease break is pending):
1236 * %F_RDLCK to indicate an exclusive lease needs to be
1237 * changed to a shared lease (or removed).
1239 * %F_UNLCK to indicate the lease needs to be removed.
1241 * XXX: sfr & willy disagree over whether F_INPROGRESS
1242 * should be returned to userspace.
1244 int fcntl_getlease(struct file *filp)
1246 struct file_lock *fl;
1250 time_out_leases(filp->f_dentry->d_inode);
1251 for (fl = filp->f_dentry->d_inode->i_flock;
1252 fl && (fl->fl_flags & FL_LEASE);
1254 if (fl->fl_file == filp) {
1255 type = fl->fl_type & ~F_INPROGRESS;
1264 * fcntl_setlease - sets a lease on an open file
1265 * @fd: open file descriptor
1266 * @filp: file pointer
1267 * @arg: type of lease to obtain
1269 * Call this fcntl to establish a lease on the file.
1270 * Note that you also need to call %F_SETSIG to
1271 * receive a signal when the lease is broken.
1273 int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1275 struct file_lock *fl, **before, **my_before = NULL;
1276 struct dentry *dentry;
1277 struct inode *inode;
1278 int error, rdlease_count = 0, wrlease_count = 0;
1280 dentry = filp->f_dentry;
1281 inode = dentry->d_inode;
1283 if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
1285 if (!S_ISREG(inode->i_mode))
1290 time_out_leases(inode);
1293 * FIXME: What about F_RDLCK and files open for writing?
1296 if ((arg == F_WRLCK)
1297 && ((atomic_read(&dentry->d_count) > 1)
1298 || (atomic_read(&inode->i_count) > 1)))
1302 * At this point, we know that if there is an exclusive
1303 * lease on this file, then we hold it on this filp
1304 * (otherwise our open of this file would have blocked).
1305 * And if we are trying to acquire an exclusive lease,
1306 * then the file is not open by anyone (including us)
1307 * except for this filp.
1309 for (before = &inode->i_flock;
1310 ((fl = *before) != NULL) && (fl->fl_flags & FL_LEASE);
1311 before = &fl->fl_next) {
1312 if (fl->fl_file == filp)
1314 else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
1316 * Someone is in the process of opening this
1317 * file for writing so we may not take an
1318 * exclusive lease on it.
1325 if ((arg == F_RDLCK && (wrlease_count > 0)) ||
1326 (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
1329 if (my_before != NULL) {
1330 error = lease_modify(my_before, arg);
1342 error = lease_alloc(filp, arg, &fl);
1346 error = fasync_helper(fd, filp, 1, &fl->fl_fasync);
1348 locks_free_lock(fl);
1351 fl->fl_next = *before;
1353 list_add(&fl->fl_link, &file_lock_list);
1354 filp->f_owner.pid = current->pid;
1355 filp->f_owner.uid = current->uid;
1356 filp->f_owner.euid = current->euid;
1363 * sys_flock: - flock() system call.
1364 * @fd: the file descriptor to lock.
1365 * @cmd: the type of lock to apply.
1367 * Apply a %FL_FLOCK style lock to an open file descriptor.
1368 * The @cmd can be one of
1370 * %LOCK_SH -- a shared lock.
1372 * %LOCK_EX -- an exclusive lock.
1374 * %LOCK_UN -- remove an existing lock.
1376 * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
1378 * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1379 * processes read and write access respectively.
1381 asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
1391 error = flock_translate_cmd(cmd);
1397 if ((type != F_UNLCK)
1399 && !(type & LOCK_MAND)
1401 && !(filp->f_mode & 3))
1405 error = flock_lock_file(filp, type,
1406 (cmd & (LOCK_UN | LOCK_NB)) ? 0 : 1);
1415 /* Report the first existing lock that would conflict with l.
1416 * This implements the F_GETLK command of fcntl().
1418 int fcntl_getlk(unsigned int fd, struct flock *l)
1421 struct file_lock *fl, file_lock;
1426 if (copy_from_user(&flock, l, sizeof(flock)))
1429 if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1437 error = flock_to_posix_lock(filp, &file_lock, &flock);
1441 if (filp->f_op && filp->f_op->lock) {
1442 error = filp->f_op->lock(filp, F_GETLK, &file_lock);
1445 else if (error == LOCK_USE_CLNT)
1446 /* Bypass for NFS with no locking - 2.0.36 compat */
1447 fl = posix_test_lock(filp, &file_lock);
1449 fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
1451 fl = posix_test_lock(filp, &file_lock);
1454 flock.l_type = F_UNLCK;
1456 flock.l_pid = fl->fl_pid;
1457 #if BITS_PER_LONG == 32
1459 * Make sure we can represent the posix lock via
1460 * legacy 32bit flock.
1463 if (fl->fl_start > OFFT_OFFSET_MAX)
1465 if ((fl->fl_end != OFFSET_MAX)
1466 && (fl->fl_end > OFFT_OFFSET_MAX))
1469 flock.l_start = fl->fl_start;
1470 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
1471 fl->fl_end - fl->fl_start + 1;
1473 flock.l_type = fl->fl_type;
1476 if (!copy_to_user(l, &flock, sizeof(flock)))
1485 /* Apply the lock described by l to an open file descriptor.
1486 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1488 int fcntl_setlk(unsigned int fd, unsigned int cmd, struct flock *l)
1491 struct file_lock *file_lock = locks_alloc_lock(0);
1493 struct inode *inode;
1496 if (file_lock == NULL)
1500 * This might block, so we do it before checking the inode.
1503 if (copy_from_user(&flock, l, sizeof(flock)))
1506 /* Get arguments and validate them ...
1515 inode = filp->f_dentry->d_inode;
1517 /* Don't allow mandatory locks on files that may be memory mapped
1520 if (IS_MANDLOCK(inode) &&
1521 (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) {
1522 struct address_space *mapping = inode->i_mapping;
1524 if (mapping->i_mmap_shared != NULL) {
1530 error = flock_to_posix_lock(filp, file_lock, &flock);
1535 switch (flock.l_type) {
1537 if (!(filp->f_mode & FMODE_READ))
1541 if (!(filp->f_mode & FMODE_WRITE))
1549 /* warn a bit for now, but don't overdo it */
1551 static int count = 0;
1555 "fcntl_setlk() called by process %d (%s) with broken flock() emulation\n",
1556 current->pid, current->comm);
1559 if (!(filp->f_mode & 3))
1568 if (filp->f_op && filp->f_op->lock != NULL) {
1569 error = filp->f_op->lock(filp, cmd, file_lock);
1573 error = posix_lock_file(filp, file_lock, cmd == F_SETLKW);
1578 locks_free_lock(file_lock);
1582 #if BITS_PER_LONG == 32
1583 /* Report the first existing lock that would conflict with l.
1584 * This implements the F_GETLK command of fcntl().
1586 int fcntl_getlk64(unsigned int fd, struct flock64 *l)
1589 struct file_lock *fl, file_lock;
1590 struct flock64 flock;
1594 if (copy_from_user(&flock, l, sizeof(flock)))
1597 if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1605 error = flock64_to_posix_lock(filp, &file_lock, &flock);
1609 if (filp->f_op && filp->f_op->lock) {
1610 error = filp->f_op->lock(filp, F_GETLK, &file_lock);
1613 else if (error == LOCK_USE_CLNT)
1614 /* Bypass for NFS with no locking - 2.0.36 compat */
1615 fl = posix_test_lock(filp, &file_lock);
1617 fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
1619 fl = posix_test_lock(filp, &file_lock);
1622 flock.l_type = F_UNLCK;
1624 flock.l_pid = fl->fl_pid;
1625 flock.l_start = fl->fl_start;
1626 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
1627 fl->fl_end - fl->fl_start + 1;
1629 flock.l_type = fl->fl_type;
1632 if (!copy_to_user(l, &flock, sizeof(flock)))
1641 /* Apply the lock described by l to an open file descriptor.
1642 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1644 int fcntl_setlk64(unsigned int fd, unsigned int cmd, struct flock64 *l)
1647 struct file_lock *file_lock = locks_alloc_lock(0);
1648 struct flock64 flock;
1649 struct inode *inode;
1652 if (file_lock == NULL)
1656 * This might block, so we do it before checking the inode.
1659 if (copy_from_user(&flock, l, sizeof(flock)))
1662 /* Get arguments and validate them ...
1671 inode = filp->f_dentry->d_inode;
1673 /* Don't allow mandatory locks on files that may be memory mapped
1676 if (IS_MANDLOCK(inode) &&
1677 (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) {
1678 struct address_space *mapping = inode->i_mapping;
1680 if (mapping->i_mmap_shared != NULL) {
1686 error = flock64_to_posix_lock(filp, file_lock, &flock);
1691 switch (flock.l_type) {
1693 if (!(filp->f_mode & FMODE_READ))
1697 if (!(filp->f_mode & FMODE_WRITE))
1709 if (filp->f_op && filp->f_op->lock != NULL) {
1710 error = filp->f_op->lock(filp, cmd, file_lock);
1714 error = posix_lock_file(filp, file_lock, cmd == F_SETLKW64);
1719 locks_free_lock(file_lock);
1722 #endif /* BITS_PER_LONG == 32 */
1725 * This function is called when the file is being removed
1726 * from the task's fd array.
1728 void locks_remove_posix(struct file *filp, fl_owner_t owner)
1730 struct inode * inode = filp->f_dentry->d_inode;
1731 struct file_lock *fl;
1732 struct file_lock **before;
1735 * For POSIX locks we free all locks on this file for the given task.
1737 if (!inode->i_flock) {
1739 * Notice that something might be grabbing a lock right now.
1740 * Consider it as a race won by us - event is async, so even if
1741 * we miss the lock added we can trivially consider it as added
1742 * after we went through this call.
1747 before = &inode->i_flock;
1748 while ((fl = *before) != NULL) {
1749 if ((fl->fl_flags & FL_POSIX) && fl->fl_owner == owner) {
1750 locks_unlock_delete(before);
1751 before = &inode->i_flock;
1754 before = &fl->fl_next;
1760 * This function is called on the last close of an open file.
1762 void locks_remove_flock(struct file *filp)
1764 struct inode * inode = filp->f_dentry->d_inode;
1765 struct file_lock *fl;
1766 struct file_lock **before;
1768 if (!inode->i_flock)
1772 before = &inode->i_flock;
1774 while ((fl = *before) != NULL) {
1775 if (fl->fl_file == filp) {
1776 if (fl->fl_flags & FL_FLOCK) {
1777 locks_delete_lock(before, 0);
1780 if (fl->fl_flags & FL_LEASE) {
1781 lease_modify(before, F_UNLCK);
1785 before = &fl->fl_next;
1791 * posix_block_lock - blocks waiting for a file lock
1792 * @blocker: the lock which is blocking
1793 * @waiter: the lock which conflicts and has to wait
1795 * lockd needs to block waiting for locks.
1798 posix_block_lock(struct file_lock *blocker, struct file_lock *waiter)
1800 locks_insert_block(blocker, waiter);
1804 * posix_unblock_lock - stop waiting for a file lock
1805 * @waiter: the lock which was waiting
1807 * lockd needs to block waiting for locks.
1810 posix_unblock_lock(struct file_lock *waiter)
1812 if (!list_empty(&waiter->fl_block))
1813 locks_delete_block(waiter);
1816 static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
1818 struct inode *inode = NULL;
1820 if (fl->fl_file != NULL)
1821 inode = fl->fl_file->f_dentry->d_inode;
1823 out += sprintf(out, "%d:%s ", id, pfx);
1824 if (fl->fl_flags & FL_POSIX) {
1825 out += sprintf(out, "%6s %s ",
1826 (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
1827 (inode == NULL) ? "*NOINODE*" :
1828 (IS_MANDLOCK(inode) &&
1829 (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ?
1830 "MANDATORY" : "ADVISORY ");
1831 } else if (fl->fl_flags & FL_FLOCK) {
1833 if (fl->fl_type & LOCK_MAND) {
1834 out += sprintf(out, "FLOCK MSNFS ");
1837 out += sprintf(out, "FLOCK ADVISORY ");
1838 } else if (fl->fl_flags & FL_LEASE) {
1839 out += sprintf(out, "LEASE ");
1840 if (fl->fl_type & F_INPROGRESS)
1841 out += sprintf(out, "BREAKING ");
1842 else if (fl->fl_file)
1843 out += sprintf(out, "ACTIVE ");
1845 out += sprintf(out, "BREAKER ");
1847 out += sprintf(out, "UNKNOWN UNKNOWN ");
1850 if (fl->fl_type & LOCK_MAND) {
1851 out += sprintf(out, "%s ",
1852 (fl->fl_type & LOCK_READ)
1853 ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
1854 : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
1857 out += sprintf(out, "%s ",
1858 (fl->fl_type & F_INPROGRESS)
1859 ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
1860 : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
1861 out += sprintf(out, "%d %s:%ld ",
1863 inode ? kdevname(inode->i_dev) : "<none>",
1864 inode ? inode->i_ino : 0);
1865 out += sprintf(out, "%Ld ", fl->fl_start);
1866 if (fl->fl_end == OFFSET_MAX)
1867 out += sprintf(out, "EOF ");
1869 out += sprintf(out, "%Ld ", fl->fl_end);
1870 sprintf(out, "%08lx %08lx %08lx %08lx %08lx\n",
1871 (long)fl, (long)fl->fl_link.prev, (long)fl->fl_link.next,
1872 (long)fl->fl_next, (long)fl->fl_block.next);
1875 static void move_lock_status(char **p, off_t* pos, off_t offset)
1879 if(*pos >= offset) {
1880 /* the complete line is valid */
1885 if(*pos+len > offset) {
1886 /* use the second part of the line */
1887 int i = offset-*pos;
1888 memmove(*p,*p+i,len-i);
1893 /* discard the complete line */
1898 * get_locks_status - reports lock usage in /proc/locks
1899 * @buffer: address in userspace to write into
1901 * @offset: how far we are through the buffer
1902 * @length: how much to read
1905 int get_locks_status(char *buffer, char **start, off_t offset, int length)
1907 struct list_head *tmp;
1913 list_for_each(tmp, &file_lock_list) {
1914 struct list_head *btmp;
1915 struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
1916 lock_get_status(q, fl, ++i, "");
1917 move_lock_status(&q, &pos, offset);
1919 if(pos >= offset+length)
1922 list_for_each(btmp, &fl->fl_block) {
1923 struct file_lock *bfl = list_entry(btmp,
1924 struct file_lock, fl_block);
1925 lock_get_status(q, bfl, i, " ->");
1926 move_lock_status(&q, &pos, offset);
1928 if(pos >= offset+length)
1935 if(q-buffer < length)
1942 * lock_may_read - checks that the region is free of locks
1943 * @inode: the inode that is being read
1944 * @start: the first byte to read
1945 * @len: the number of bytes to read
1947 * Emulates Windows locking requirements. Whole-file
1948 * mandatory locks (share modes) can prohibit a read and
1949 * byte-range POSIX locks can prohibit a read if they overlap.
1951 * N.B. this function is only ever called
1952 * from knfsd and ownership of locks is never checked.
1954 int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
1956 struct file_lock *fl;
1959 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1960 if (fl->fl_flags == FL_POSIX) {
1961 if (fl->fl_type == F_RDLCK)
1963 if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
1965 } else if (fl->fl_flags == FL_FLOCK) {
1966 if (!(fl->fl_type & LOCK_MAND))
1968 if (fl->fl_type & LOCK_READ)
1980 * lock_may_write - checks that the region is free of locks
1981 * @inode: the inode that is being written
1982 * @start: the first byte to write
1983 * @len: the number of bytes to write
1985 * Emulates Windows locking requirements. Whole-file
1986 * mandatory locks (share modes) can prohibit a write and
1987 * byte-range POSIX locks can prohibit a write if they overlap.
1989 * N.B. this function is only ever called
1990 * from knfsd and ownership of locks is never checked.
1992 int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
1994 struct file_lock *fl;
1997 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1998 if (fl->fl_flags == FL_POSIX) {
1999 if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2001 } else if (fl->fl_flags == FL_FLOCK) {
2002 if (!(fl->fl_type & LOCK_MAND))
2004 if (fl->fl_type & LOCK_WRITE)
2016 static int __init filelock_init(void)
2018 filelock_cache = kmem_cache_create("file_lock_cache",
2019 sizeof(struct file_lock), 0, 0, init_once, NULL);
2020 if (!filelock_cache)
2021 panic("cannot create file lock slab cache");
2025 module_init(filelock_init)