1 /* AFS file locking support
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
14 #define AFS_LOCK_GRANTED 0
15 #define AFS_LOCK_PENDING 1
16 #define AFS_LOCK_YOUR_TRY 2
18 struct workqueue_struct *afs_lock_manager;
20 static void afs_next_locker(struct afs_vnode *vnode, int error);
21 static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
22 static void afs_fl_release_private(struct file_lock *fl);
24 static const struct file_lock_operations afs_lock_ops = {
25 .fl_copy_lock = afs_fl_copy_lock,
26 .fl_release_private = afs_fl_release_private,
29 static inline void afs_set_lock_state(struct afs_vnode *vnode, enum afs_lock_state state)
31 _debug("STATE %u -> %u", vnode->lock_state, state);
32 vnode->lock_state = state;
36 * if the callback is broken on this vnode, then the lock may now be available
38 void afs_lock_may_be_available(struct afs_vnode *vnode)
40 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
42 spin_lock(&vnode->lock);
43 if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
44 afs_next_locker(vnode, 0);
45 spin_unlock(&vnode->lock);
49 * the lock will time out in 5 minutes unless we extend it, so schedule
50 * extension in a bit less than that time
52 static void __maybe_unused afs_schedule_lock_extension(struct afs_vnode *vnode)
54 queue_delayed_work(afs_lock_manager, &vnode->lock_work,
55 AFS_LOCKWAIT * HZ / 2);
59 * grant one or more locks (readlocks are allowed to jump the queue if the
60 * first lock in the queue is itself a readlock)
61 * - the caller must hold the vnode lock
63 static void afs_grant_locks(struct afs_vnode *vnode)
65 struct file_lock *p, *_p;
66 bool exclusive = (vnode->lock_type == AFS_LOCK_WRITE);
68 list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
69 if (!exclusive && p->fl_type == F_WRLCK)
72 list_move_tail(&p->fl_u.afs.link, &vnode->granted_locks);
73 p->fl_u.afs.state = AFS_LOCK_GRANTED;
79 * If an error is specified, reject every pending lock that matches the
80 * authentication and type of the lock we failed to get. If there are any
81 * remaining lockers, try to wake up one of them to have a go.
83 static void afs_next_locker(struct afs_vnode *vnode, int error)
85 struct file_lock *p, *_p, *next = NULL;
86 struct key *key = vnode->lock_key;
87 unsigned int fl_type = F_RDLCK;
91 if (vnode->lock_type == AFS_LOCK_WRITE)
94 list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
96 p->fl_type == fl_type &&
97 afs_file_key(p->fl_file) == key) {
98 list_del_init(&p->fl_u.afs.link);
99 p->fl_u.afs.state = error;
100 wake_up(&p->fl_wait);
103 /* Select the next locker to hand off to. */
105 (next->fl_type == F_WRLCK || p->fl_type == F_RDLCK))
110 vnode->lock_key = NULL;
114 afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
115 next->fl_u.afs.state = AFS_LOCK_YOUR_TRY;
116 wake_up(&next->fl_wait);
118 afs_set_lock_state(vnode, AFS_VNODE_LOCK_NONE);
125 * Get a lock on a file
127 static int afs_set_lock(struct afs_vnode *vnode, struct key *key,
128 afs_lock_type_t type)
130 struct afs_fs_cursor fc;
133 _enter("%s{%x:%u.%u},%x,%u",
138 key_serial(key), type);
141 if (afs_begin_vnode_operation(&fc, vnode, key)) {
142 while (afs_select_fileserver(&fc)) {
143 fc.cb_break = afs_calc_vnode_cb_break(vnode);
144 afs_fs_set_lock(&fc, type);
147 afs_check_for_remote_deletion(&fc, fc.vnode);
148 afs_vnode_commit_status(&fc, vnode, fc.cb_break);
149 ret = afs_end_vnode_operation(&fc);
152 _leave(" = %d", ret);
157 * Extend a lock on a file
159 static int afs_extend_lock(struct afs_vnode *vnode, struct key *key)
161 struct afs_fs_cursor fc;
164 _enter("%s{%x:%u.%u},%x",
172 if (afs_begin_vnode_operation(&fc, vnode, key)) {
173 while (afs_select_current_fileserver(&fc)) {
174 fc.cb_break = afs_calc_vnode_cb_break(vnode);
175 afs_fs_extend_lock(&fc);
178 afs_check_for_remote_deletion(&fc, fc.vnode);
179 afs_vnode_commit_status(&fc, vnode, fc.cb_break);
180 ret = afs_end_vnode_operation(&fc);
183 _leave(" = %d", ret);
188 * Release a lock on a file
190 static int afs_release_lock(struct afs_vnode *vnode, struct key *key)
192 struct afs_fs_cursor fc;
195 _enter("%s{%x:%u.%u},%x",
203 if (afs_begin_vnode_operation(&fc, vnode, key)) {
204 while (afs_select_current_fileserver(&fc)) {
205 fc.cb_break = afs_calc_vnode_cb_break(vnode);
206 afs_fs_release_lock(&fc);
209 afs_check_for_remote_deletion(&fc, fc.vnode);
210 afs_vnode_commit_status(&fc, vnode, fc.cb_break);
211 ret = afs_end_vnode_operation(&fc);
214 _leave(" = %d", ret);
219 * do work for a lock, including:
220 * - probing for a lock we're waiting on but didn't get immediately
221 * - extending a lock that's close to timing out
223 void afs_lock_work(struct work_struct *work)
225 struct afs_vnode *vnode =
226 container_of(work, struct afs_vnode, lock_work.work);
230 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
232 spin_lock(&vnode->lock);
235 _debug("wstate %u for %p", vnode->lock_state, vnode);
236 switch (vnode->lock_state) {
237 case AFS_VNODE_LOCK_NEED_UNLOCK:
239 afs_set_lock_state(vnode, AFS_VNODE_LOCK_UNLOCKING);
240 spin_unlock(&vnode->lock);
242 /* attempt to release the server lock; if it fails, we just
243 * wait 5 minutes and it'll expire anyway */
244 ret = afs_release_lock(vnode, vnode->lock_key);
246 printk(KERN_WARNING "AFS:"
247 " Failed to release lock on {%x:%x} error %d\n",
248 vnode->fid.vid, vnode->fid.vnode, ret);
250 spin_lock(&vnode->lock);
251 afs_next_locker(vnode, 0);
252 spin_unlock(&vnode->lock);
255 /* If we've already got a lock, then it must be time to extend that
256 * lock as AFS locks time out after 5 minutes.
258 case AFS_VNODE_LOCK_GRANTED:
261 ASSERT(!list_empty(&vnode->granted_locks));
263 key = key_get(vnode->lock_key);
264 afs_set_lock_state(vnode, AFS_VNODE_LOCK_EXTENDING);
265 spin_unlock(&vnode->lock);
267 ret = afs_extend_lock(vnode, key); /* RPC */
271 pr_warning("AFS: Failed to extend lock on {%x:%x} error %d\n",
272 vnode->fid.vid, vnode->fid.vnode, ret);
274 spin_lock(&vnode->lock);
276 if (vnode->lock_state != AFS_VNODE_LOCK_EXTENDING)
278 afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
281 queue_delayed_work(afs_lock_manager, &vnode->lock_work,
283 spin_unlock(&vnode->lock);
287 /* If we're waiting for a callback to indicate lock release, we can't
288 * actually rely on this, so need to recheck at regular intervals. The
289 * problem is that the server might not notify us if the lock just
290 * expires (say because a client died) rather than being explicitly
293 case AFS_VNODE_LOCK_WAITING_FOR_CB:
295 afs_next_locker(vnode, 0);
296 spin_unlock(&vnode->lock);
300 /* Looks like a lock request was withdrawn. */
301 spin_unlock(&vnode->lock);
308 * pass responsibility for the unlocking of a vnode on the server to the
309 * manager thread, lest a pending signal in the calling thread interrupt
311 * - the caller must hold the vnode lock
313 static void afs_defer_unlock(struct afs_vnode *vnode)
315 _enter("%u", vnode->lock_state);
317 if (list_empty(&vnode->granted_locks) &&
318 (vnode->lock_state == AFS_VNODE_LOCK_GRANTED ||
319 vnode->lock_state == AFS_VNODE_LOCK_EXTENDING)) {
320 cancel_delayed_work(&vnode->lock_work);
322 afs_set_lock_state(vnode, AFS_VNODE_LOCK_NEED_UNLOCK);
323 queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
328 * Check that our view of the file metadata is up to date and check to see
329 * whether we think that we have a locking permit.
331 static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key,
332 afs_lock_type_t type, bool can_sleep)
337 /* Make sure we've got a callback on this file and that our view of the
338 * data version is up to date.
340 ret = afs_validate(vnode, key);
344 /* Check the permission set to see if we're actually going to be
345 * allowed to get a lock on this file.
347 ret = afs_check_permit(vnode, key, &access);
351 /* At a rough estimation, you need LOCK, WRITE or INSERT perm to
352 * read-lock a file and WRITE or INSERT perm to write-lock a file.
354 * We can't rely on the server to do this for us since if we want to
355 * share a read lock that we already have, we won't go the server.
357 if (type == AFS_LOCK_READ) {
358 if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE | AFS_ACE_LOCK)))
360 if (vnode->status.lock_count == -1 && !can_sleep)
361 return -EAGAIN; /* Write locked */
363 if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE)))
365 if (vnode->status.lock_count != 0 && !can_sleep)
366 return -EAGAIN; /* Locked */
373 * request a lock on a file on the server
375 static int afs_do_setlk(struct file *file, struct file_lock *fl)
377 struct inode *inode = locks_inode(file);
378 struct afs_vnode *vnode = AFS_FS_I(inode);
379 afs_lock_type_t type;
380 struct key *key = afs_file_key(file);
383 _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
385 fl->fl_ops = &afs_lock_ops;
386 INIT_LIST_HEAD(&fl->fl_u.afs.link);
387 fl->fl_u.afs.state = AFS_LOCK_PENDING;
389 type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
391 ret = afs_do_setlk_check(vnode, key, type, fl->fl_flags & FL_SLEEP);
395 spin_lock(&vnode->lock);
396 list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
398 /* If we've already got a lock on the server then try to move to having
399 * the VFS grant the requested lock. Note that this means that other
400 * clients may get starved out.
402 _debug("try %u", vnode->lock_state);
403 if (vnode->lock_state == AFS_VNODE_LOCK_GRANTED) {
404 if (type == AFS_LOCK_READ) {
405 _debug("instant readlock");
406 list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
407 fl->fl_u.afs.state = AFS_LOCK_GRANTED;
408 goto vnode_is_locked_u;
411 if (vnode->lock_type == AFS_LOCK_WRITE) {
412 _debug("instant writelock");
413 list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
414 fl->fl_u.afs.state = AFS_LOCK_GRANTED;
415 goto vnode_is_locked_u;
419 if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
423 /* We don't have a lock on this vnode and we aren't currently waiting
424 * for one either, so ask the server for a lock.
426 * Note that we need to be careful if we get interrupted by a signal
427 * after dispatching the request as we may still get the lock, even
428 * though we don't wait for the reply (it's not too bad a problem - the
429 * lock will expire in 5 mins anyway).
431 _debug("not locked");
432 vnode->lock_key = key_get(key);
433 vnode->lock_type = type;
434 afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
435 spin_unlock(&vnode->lock);
437 ret = afs_set_lock(vnode, key, type); /* RPC */
439 spin_lock(&vnode->lock);
446 fl->fl_u.afs.state = ret;
447 list_del_init(&fl->fl_u.afs.link);
448 afs_next_locker(vnode, ret);
452 fl->fl_u.afs.state = ret;
453 list_del_init(&fl->fl_u.afs.link);
454 afs_next_locker(vnode, 0);
458 /* The server doesn't have a lock-waiting queue, so the client
459 * will have to retry. The server will break the outstanding
460 * callbacks on a file when a lock is released.
462 _debug("would block");
463 ASSERT(list_empty(&vnode->granted_locks));
464 ASSERTCMP(vnode->pending_locks.next, ==, &fl->fl_u.afs.link);
465 goto lock_is_contended;
469 afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
470 afs_grant_locks(vnode);
471 goto vnode_is_locked_u;
475 spin_unlock(&vnode->lock);
477 /* the lock has been granted by the server... */
478 ASSERTCMP(fl->fl_u.afs.state, ==, AFS_LOCK_GRANTED);
480 /* ... but the VFS still needs to distribute access on this client. */
481 ret = locks_lock_file_wait(file, fl);
483 goto vfs_rejected_lock;
485 /* Again, make sure we've got a callback on this file and, again, make
486 * sure that our view of the data version is up to date (we ignore
487 * errors incurred here and deal with the consequences elsewhere).
489 afs_validate(vnode, key);
494 if (!(fl->fl_flags & FL_SLEEP)) {
495 list_del_init(&fl->fl_u.afs.link);
496 afs_next_locker(vnode, 0);
501 afs_set_lock_state(vnode, AFS_VNODE_LOCK_WAITING_FOR_CB);
502 queue_delayed_work(afs_lock_manager, &vnode->lock_work, HZ * 5);
505 /* We're going to have to wait. Either this client doesn't have a lock
506 * on the server yet and we need to wait for a callback to occur, or
507 * the client does have a lock on the server, but it's shared and we
508 * need an exclusive lock.
510 spin_unlock(&vnode->lock);
513 ret = wait_event_interruptible(fl->fl_wait,
514 fl->fl_u.afs.state != AFS_LOCK_PENDING);
515 _debug("wait = %d", ret);
517 if (fl->fl_u.afs.state >= 0 && fl->fl_u.afs.state != AFS_LOCK_GRANTED) {
518 spin_lock(&vnode->lock);
520 switch (fl->fl_u.afs.state) {
521 case AFS_LOCK_YOUR_TRY:
522 fl->fl_u.afs.state = AFS_LOCK_PENDING;
524 case AFS_LOCK_PENDING:
526 /* We need to retry the lock. We may not be
527 * notified by the server if it just expired
528 * rather than being released.
530 ASSERTCMP(vnode->lock_state, ==, AFS_VNODE_LOCK_WAITING_FOR_CB);
531 afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
532 fl->fl_u.afs.state = AFS_LOCK_PENDING;
536 case AFS_LOCK_GRANTED:
541 spin_unlock(&vnode->lock);
544 if (fl->fl_u.afs.state == AFS_LOCK_GRANTED)
545 goto vnode_is_locked;
546 ret = fl->fl_u.afs.state;
550 /* The VFS rejected the lock we just obtained, so we have to discard
551 * what we just got. We defer this to the lock manager work item to
554 _debug("vfs refused %d", ret);
555 spin_lock(&vnode->lock);
556 list_del_init(&fl->fl_u.afs.link);
557 afs_defer_unlock(vnode);
560 spin_unlock(&vnode->lock);
562 _leave(" = %d", ret);
567 * unlock on a file on the server
569 static int afs_do_unlk(struct file *file, struct file_lock *fl)
571 struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
574 _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
576 /* Flush all pending writes before doing anything with locks. */
579 ret = locks_lock_file_wait(file, fl);
580 _leave(" = %d [%u]", ret, vnode->lock_state);
585 * return information about a lock we currently hold, if indeed we hold one
587 static int afs_do_getlk(struct file *file, struct file_lock *fl)
589 struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
590 struct key *key = afs_file_key(file);
595 fl->fl_type = F_UNLCK;
597 /* check local lock records first */
598 posix_test_lock(file, fl);
599 if (fl->fl_type == F_UNLCK) {
600 /* no local locks; consult the server */
601 ret = afs_fetch_status(vnode, key, false);
605 lock_count = READ_ONCE(vnode->status.lock_count);
606 if (lock_count != 0) {
608 fl->fl_type = F_RDLCK;
610 fl->fl_type = F_WRLCK;
612 fl->fl_end = OFFSET_MAX;
619 _leave(" = %d [%hd]", ret, fl->fl_type);
624 * manage POSIX locks on a file
626 int afs_lock(struct file *file, int cmd, struct file_lock *fl)
628 struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
630 _enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
631 vnode->fid.vid, vnode->fid.vnode, cmd,
632 fl->fl_type, fl->fl_flags,
633 (long long) fl->fl_start, (long long) fl->fl_end);
635 /* AFS doesn't support mandatory locks */
636 if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
640 return afs_do_getlk(file, fl);
641 if (fl->fl_type == F_UNLCK)
642 return afs_do_unlk(file, fl);
643 return afs_do_setlk(file, fl);
647 * manage FLOCK locks on a file
649 int afs_flock(struct file *file, int cmd, struct file_lock *fl)
651 struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
653 _enter("{%x:%u},%d,{t=%x,fl=%x}",
654 vnode->fid.vid, vnode->fid.vnode, cmd,
655 fl->fl_type, fl->fl_flags);
658 * No BSD flocks over NFS allowed.
659 * Note: we could try to fake a POSIX lock request here by
660 * using ((u32) filp | 0x80000000) or some such as the pid.
661 * Not sure whether that would be unique, though, or whether
662 * that would break in other places.
664 if (!(fl->fl_flags & FL_FLOCK))
667 /* we're simulating flock() locks using posix locks on the server */
668 if (fl->fl_type == F_UNLCK)
669 return afs_do_unlk(file, fl);
670 return afs_do_setlk(file, fl);
674 * the POSIX lock management core VFS code copies the lock record and adds the
675 * copy into its own list, so we need to add that copy to the vnode's lock
676 * queue in the same place as the original (which will be deleted shortly
679 static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
681 struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));
685 spin_lock(&vnode->lock);
686 list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
687 spin_unlock(&vnode->lock);
691 * need to remove this lock from the vnode queue when it's removed from the
694 static void afs_fl_release_private(struct file_lock *fl)
696 struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));
700 spin_lock(&vnode->lock);
702 list_del_init(&fl->fl_u.afs.link);
703 if (list_empty(&vnode->granted_locks))
704 afs_defer_unlock(vnode);
706 _debug("state %u for %p", vnode->lock_state, vnode);
707 spin_unlock(&vnode->lock);