Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/linux...
[linux-btrfs-devel.git] / fs / afs / flock.c
blob757d664575dde8eff7659f471fce43692e992f06
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.
12 #include "internal.h"
14 #define AFS_LOCK_GRANTED 0
15 #define AFS_LOCK_PENDING 1
17 static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
18 static void afs_fl_release_private(struct file_lock *fl);
20 static struct workqueue_struct *afs_lock_manager;
21 static DEFINE_MUTEX(afs_lock_manager_mutex);
23 static const struct file_lock_operations afs_lock_ops = {
24 .fl_copy_lock = afs_fl_copy_lock,
25 .fl_release_private = afs_fl_release_private,
29 * initialise the lock manager thread if it isn't already running
31 static int afs_init_lock_manager(void)
33 int ret;
35 ret = 0;
36 if (!afs_lock_manager) {
37 mutex_lock(&afs_lock_manager_mutex);
38 if (!afs_lock_manager) {
39 afs_lock_manager =
40 create_singlethread_workqueue("kafs_lockd");
41 if (!afs_lock_manager)
42 ret = -ENOMEM;
44 mutex_unlock(&afs_lock_manager_mutex);
46 return ret;
50 * destroy the lock manager thread if it's running
52 void __exit afs_kill_lock_manager(void)
54 if (afs_lock_manager)
55 destroy_workqueue(afs_lock_manager);
59 * if the callback is broken on this vnode, then the lock may now be available
61 void afs_lock_may_be_available(struct afs_vnode *vnode)
63 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
65 queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
69 * the lock will time out in 5 minutes unless we extend it, so schedule
70 * extension in a bit less than that time
72 static void afs_schedule_lock_extension(struct afs_vnode *vnode)
74 queue_delayed_work(afs_lock_manager, &vnode->lock_work,
75 AFS_LOCKWAIT * HZ / 2);
79 * grant one or more locks (readlocks are allowed to jump the queue if the
80 * first lock in the queue is itself a readlock)
81 * - the caller must hold the vnode lock
83 static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
85 struct file_lock *p, *_p;
87 list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
88 if (fl->fl_type == F_RDLCK) {
89 list_for_each_entry_safe(p, _p, &vnode->pending_locks,
90 fl_u.afs.link) {
91 if (p->fl_type == F_RDLCK) {
92 p->fl_u.afs.state = AFS_LOCK_GRANTED;
93 list_move_tail(&p->fl_u.afs.link,
94 &vnode->granted_locks);
95 wake_up(&p->fl_wait);
102 * do work for a lock, including:
103 * - probing for a lock we're waiting on but didn't get immediately
104 * - extending a lock that's close to timing out
106 void afs_lock_work(struct work_struct *work)
108 struct afs_vnode *vnode =
109 container_of(work, struct afs_vnode, lock_work.work);
110 struct file_lock *fl;
111 afs_lock_type_t type;
112 struct key *key;
113 int ret;
115 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
117 spin_lock(&vnode->lock);
119 if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) {
120 _debug("unlock");
121 spin_unlock(&vnode->lock);
123 /* attempt to release the server lock; if it fails, we just
124 * wait 5 minutes and it'll time out anyway */
125 ret = afs_vnode_release_lock(vnode, vnode->unlock_key);
126 if (ret < 0)
127 printk(KERN_WARNING "AFS:"
128 " Failed to release lock on {%x:%x} error %d\n",
129 vnode->fid.vid, vnode->fid.vnode, ret);
131 spin_lock(&vnode->lock);
132 key_put(vnode->unlock_key);
133 vnode->unlock_key = NULL;
134 clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags);
137 /* if we've got a lock, then it must be time to extend that lock as AFS
138 * locks time out after 5 minutes */
139 if (!list_empty(&vnode->granted_locks)) {
140 _debug("extend");
142 if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
143 BUG();
144 fl = list_entry(vnode->granted_locks.next,
145 struct file_lock, fl_u.afs.link);
146 key = key_get(fl->fl_file->private_data);
147 spin_unlock(&vnode->lock);
149 ret = afs_vnode_extend_lock(vnode, key);
150 clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
151 key_put(key);
152 switch (ret) {
153 case 0:
154 afs_schedule_lock_extension(vnode);
155 break;
156 default:
157 /* ummm... we failed to extend the lock - retry
158 * extension shortly */
159 printk(KERN_WARNING "AFS:"
160 " Failed to extend lock on {%x:%x} error %d\n",
161 vnode->fid.vid, vnode->fid.vnode, ret);
162 queue_delayed_work(afs_lock_manager, &vnode->lock_work,
163 HZ * 10);
164 break;
166 _leave(" [extend]");
167 return;
170 /* if we don't have a granted lock, then we must've been called back by
171 * the server, and so if might be possible to get a lock we're
172 * currently waiting for */
173 if (!list_empty(&vnode->pending_locks)) {
174 _debug("get");
176 if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
177 BUG();
178 fl = list_entry(vnode->pending_locks.next,
179 struct file_lock, fl_u.afs.link);
180 key = key_get(fl->fl_file->private_data);
181 type = (fl->fl_type == F_RDLCK) ?
182 AFS_LOCK_READ : AFS_LOCK_WRITE;
183 spin_unlock(&vnode->lock);
185 ret = afs_vnode_set_lock(vnode, key, type);
186 clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
187 switch (ret) {
188 case -EWOULDBLOCK:
189 _debug("blocked");
190 break;
191 case 0:
192 _debug("acquired");
193 if (type == AFS_LOCK_READ)
194 set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
195 else
196 set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
197 ret = AFS_LOCK_GRANTED;
198 default:
199 spin_lock(&vnode->lock);
200 /* the pending lock may have been withdrawn due to a
201 * signal */
202 if (list_entry(vnode->pending_locks.next,
203 struct file_lock, fl_u.afs.link) == fl) {
204 fl->fl_u.afs.state = ret;
205 if (ret == AFS_LOCK_GRANTED)
206 afs_grant_locks(vnode, fl);
207 else
208 list_del_init(&fl->fl_u.afs.link);
209 wake_up(&fl->fl_wait);
210 spin_unlock(&vnode->lock);
211 } else {
212 _debug("withdrawn");
213 clear_bit(AFS_VNODE_READLOCKED, &vnode->flags);
214 clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
215 spin_unlock(&vnode->lock);
216 afs_vnode_release_lock(vnode, key);
217 if (!list_empty(&vnode->pending_locks))
218 afs_lock_may_be_available(vnode);
220 break;
222 key_put(key);
223 _leave(" [pend]");
224 return;
227 /* looks like the lock request was withdrawn on a signal */
228 spin_unlock(&vnode->lock);
229 _leave(" [no locks]");
233 * pass responsibility for the unlocking of a vnode on the server to the
234 * manager thread, lest a pending signal in the calling thread interrupt
235 * AF_RXRPC
236 * - the caller must hold the vnode lock
238 static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key)
240 cancel_delayed_work(&vnode->lock_work);
241 if (!test_and_clear_bit(AFS_VNODE_READLOCKED, &vnode->flags) &&
242 !test_and_clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags))
243 BUG();
244 if (test_and_set_bit(AFS_VNODE_UNLOCKING, &vnode->flags))
245 BUG();
246 vnode->unlock_key = key_get(key);
247 afs_lock_may_be_available(vnode);
251 * request a lock on a file on the server
253 static int afs_do_setlk(struct file *file, struct file_lock *fl)
255 struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
256 afs_lock_type_t type;
257 struct key *key = file->private_data;
258 int ret;
260 _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
262 /* only whole-file locks are supported */
263 if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
264 return -EINVAL;
266 ret = afs_init_lock_manager();
267 if (ret < 0)
268 return ret;
270 fl->fl_ops = &afs_lock_ops;
271 INIT_LIST_HEAD(&fl->fl_u.afs.link);
272 fl->fl_u.afs.state = AFS_LOCK_PENDING;
274 type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
276 lock_flocks();
278 /* make sure we've got a callback on this file and that our view of the
279 * data version is up to date */
280 ret = afs_vnode_fetch_status(vnode, NULL, key);
281 if (ret < 0)
282 goto error;
284 if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) {
285 ret = -EAGAIN;
286 goto error;
289 spin_lock(&vnode->lock);
291 /* if we've already got a readlock on the server then we can instantly
292 * grant another readlock, irrespective of whether there are any
293 * pending writelocks */
294 if (type == AFS_LOCK_READ &&
295 vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
296 _debug("instant readlock");
297 ASSERTCMP(vnode->flags &
298 ((1 << AFS_VNODE_LOCKING) |
299 (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
300 ASSERT(!list_empty(&vnode->granted_locks));
301 goto sharing_existing_lock;
304 /* if there's no-one else with a lock on this vnode, then we need to
305 * ask the server for a lock */
306 if (list_empty(&vnode->pending_locks) &&
307 list_empty(&vnode->granted_locks)) {
308 _debug("not locked");
309 ASSERTCMP(vnode->flags &
310 ((1 << AFS_VNODE_LOCKING) |
311 (1 << AFS_VNODE_READLOCKED) |
312 (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
313 list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
314 set_bit(AFS_VNODE_LOCKING, &vnode->flags);
315 spin_unlock(&vnode->lock);
317 ret = afs_vnode_set_lock(vnode, key, type);
318 clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
319 switch (ret) {
320 case 0:
321 _debug("acquired");
322 goto acquired_server_lock;
323 case -EWOULDBLOCK:
324 _debug("would block");
325 spin_lock(&vnode->lock);
326 ASSERT(list_empty(&vnode->granted_locks));
327 ASSERTCMP(vnode->pending_locks.next, ==,
328 &fl->fl_u.afs.link);
329 goto wait;
330 default:
331 spin_lock(&vnode->lock);
332 list_del_init(&fl->fl_u.afs.link);
333 spin_unlock(&vnode->lock);
334 goto error;
338 /* otherwise, we need to wait for a local lock to become available */
339 _debug("wait local");
340 list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
341 wait:
342 if (!(fl->fl_flags & FL_SLEEP)) {
343 _debug("noblock");
344 ret = -EAGAIN;
345 goto abort_attempt;
347 spin_unlock(&vnode->lock);
349 /* now we need to sleep and wait for the lock manager thread to get the
350 * lock from the server */
351 _debug("sleep");
352 ret = wait_event_interruptible(fl->fl_wait,
353 fl->fl_u.afs.state <= AFS_LOCK_GRANTED);
354 if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
355 ret = fl->fl_u.afs.state;
356 if (ret < 0)
357 goto error;
358 spin_lock(&vnode->lock);
359 goto given_lock;
362 /* we were interrupted, but someone may still be in the throes of
363 * giving us the lock */
364 _debug("intr");
365 ASSERTCMP(ret, ==, -ERESTARTSYS);
367 spin_lock(&vnode->lock);
368 if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
369 ret = fl->fl_u.afs.state;
370 if (ret < 0) {
371 spin_unlock(&vnode->lock);
372 goto error;
374 goto given_lock;
377 abort_attempt:
378 /* we aren't going to get the lock, either because we're unwilling to
379 * wait, or because some signal happened */
380 _debug("abort");
381 if (list_empty(&vnode->granted_locks) &&
382 vnode->pending_locks.next == &fl->fl_u.afs.link) {
383 if (vnode->pending_locks.prev != &fl->fl_u.afs.link) {
384 /* kick the next pending lock into having a go */
385 list_del_init(&fl->fl_u.afs.link);
386 afs_lock_may_be_available(vnode);
388 } else {
389 list_del_init(&fl->fl_u.afs.link);
391 spin_unlock(&vnode->lock);
392 goto error;
394 acquired_server_lock:
395 /* we've acquired a server lock, but it needs to be renewed after 5
396 * mins */
397 spin_lock(&vnode->lock);
398 afs_schedule_lock_extension(vnode);
399 if (type == AFS_LOCK_READ)
400 set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
401 else
402 set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
403 sharing_existing_lock:
404 /* the lock has been granted as far as we're concerned... */
405 fl->fl_u.afs.state = AFS_LOCK_GRANTED;
406 list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
407 given_lock:
408 /* ... but we do still need to get the VFS's blessing */
409 ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING)));
410 ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) |
411 (1 << AFS_VNODE_WRITELOCKED))) != 0);
412 ret = posix_lock_file(file, fl, NULL);
413 if (ret < 0)
414 goto vfs_rejected_lock;
415 spin_unlock(&vnode->lock);
417 /* again, make sure we've got a callback on this file and, again, make
418 * sure that our view of the data version is up to date (we ignore
419 * errors incurred here and deal with the consequences elsewhere) */
420 afs_vnode_fetch_status(vnode, NULL, key);
422 error:
423 unlock_flocks();
424 _leave(" = %d", ret);
425 return ret;
427 vfs_rejected_lock:
428 /* the VFS rejected the lock we just obtained, so we have to discard
429 * what we just got */
430 _debug("vfs refused %d", ret);
431 list_del_init(&fl->fl_u.afs.link);
432 if (list_empty(&vnode->granted_locks))
433 afs_defer_unlock(vnode, key);
434 goto abort_attempt;
438 * unlock on a file on the server
440 static int afs_do_unlk(struct file *file, struct file_lock *fl)
442 struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
443 struct key *key = file->private_data;
444 int ret;
446 _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
448 /* only whole-file unlocks are supported */
449 if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
450 return -EINVAL;
452 fl->fl_ops = &afs_lock_ops;
453 INIT_LIST_HEAD(&fl->fl_u.afs.link);
454 fl->fl_u.afs.state = AFS_LOCK_PENDING;
456 spin_lock(&vnode->lock);
457 ret = posix_lock_file(file, fl, NULL);
458 if (ret < 0) {
459 spin_unlock(&vnode->lock);
460 _leave(" = %d [vfs]", ret);
461 return ret;
464 /* discard the server lock only if all granted locks are gone */
465 if (list_empty(&vnode->granted_locks))
466 afs_defer_unlock(vnode, key);
467 spin_unlock(&vnode->lock);
468 _leave(" = 0");
469 return 0;
473 * return information about a lock we currently hold, if indeed we hold one
475 static int afs_do_getlk(struct file *file, struct file_lock *fl)
477 struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
478 struct key *key = file->private_data;
479 int ret, lock_count;
481 _enter("");
483 fl->fl_type = F_UNLCK;
485 mutex_lock(&vnode->vfs_inode.i_mutex);
487 /* check local lock records first */
488 ret = 0;
489 posix_test_lock(file, fl);
490 if (fl->fl_type == F_UNLCK) {
491 /* no local locks; consult the server */
492 ret = afs_vnode_fetch_status(vnode, NULL, key);
493 if (ret < 0)
494 goto error;
495 lock_count = vnode->status.lock_count;
496 if (lock_count) {
497 if (lock_count > 0)
498 fl->fl_type = F_RDLCK;
499 else
500 fl->fl_type = F_WRLCK;
501 fl->fl_start = 0;
502 fl->fl_end = OFFSET_MAX;
506 error:
507 mutex_unlock(&vnode->vfs_inode.i_mutex);
508 _leave(" = %d [%hd]", ret, fl->fl_type);
509 return ret;
513 * manage POSIX locks on a file
515 int afs_lock(struct file *file, int cmd, struct file_lock *fl)
517 struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
519 _enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
520 vnode->fid.vid, vnode->fid.vnode, cmd,
521 fl->fl_type, fl->fl_flags,
522 (long long) fl->fl_start, (long long) fl->fl_end);
524 /* AFS doesn't support mandatory locks */
525 if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
526 return -ENOLCK;
528 if (IS_GETLK(cmd))
529 return afs_do_getlk(file, fl);
530 if (fl->fl_type == F_UNLCK)
531 return afs_do_unlk(file, fl);
532 return afs_do_setlk(file, fl);
536 * manage FLOCK locks on a file
538 int afs_flock(struct file *file, int cmd, struct file_lock *fl)
540 struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
542 _enter("{%x:%u},%d,{t=%x,fl=%x}",
543 vnode->fid.vid, vnode->fid.vnode, cmd,
544 fl->fl_type, fl->fl_flags);
547 * No BSD flocks over NFS allowed.
548 * Note: we could try to fake a POSIX lock request here by
549 * using ((u32) filp | 0x80000000) or some such as the pid.
550 * Not sure whether that would be unique, though, or whether
551 * that would break in other places.
553 if (!(fl->fl_flags & FL_FLOCK))
554 return -ENOLCK;
556 /* we're simulating flock() locks using posix locks on the server */
557 fl->fl_owner = (fl_owner_t) file;
558 fl->fl_start = 0;
559 fl->fl_end = OFFSET_MAX;
561 if (fl->fl_type == F_UNLCK)
562 return afs_do_unlk(file, fl);
563 return afs_do_setlk(file, fl);
567 * the POSIX lock management core VFS code copies the lock record and adds the
568 * copy into its own list, so we need to add that copy to the vnode's lock
569 * queue in the same place as the original (which will be deleted shortly
570 * after)
572 static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
574 _enter("");
576 list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
580 * need to remove this lock from the vnode queue when it's removed from the
581 * VFS's list
583 static void afs_fl_release_private(struct file_lock *fl)
585 _enter("");
587 list_del_init(&fl->fl_u.afs.link);