1 /* AFS file locking support
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
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.
10 */
11
12 #include "internal.h"
13
14 #define AFS_LOCK_GRANTED 0
15 #define AFS_LOCK_PENDING 1
16
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);
19
20 static struct workqueue_struct *afs_lock_manager;
21 static DEFINE_MUTEX(afs_lock_manager_mutex);
22
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,
26 };
27
28 /*
29 * initialise the lock manager thread if it isn't already running
30 */
afs_init_lock_manager(void)31 static int afs_init_lock_manager(void)
32 {
33 int ret;
34
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;
43 }
44 mutex_unlock(&afs_lock_manager_mutex);
45 }
46 return ret;
47 }
48
49 /*
50 * destroy the lock manager thread if it's running
51 */
afs_kill_lock_manager(void)52 void __exit afs_kill_lock_manager(void)
53 {
54 if (afs_lock_manager)
55 destroy_workqueue(afs_lock_manager);
56 }
57
58 /*
59 * if the callback is broken on this vnode, then the lock may now be available
60 */
afs_lock_may_be_available(struct afs_vnode * vnode)61 void afs_lock_may_be_available(struct afs_vnode *vnode)
62 {
63 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
64
65 queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
66 }
67
68 /*
69 * the lock will time out in 5 minutes unless we extend it, so schedule
70 * extension in a bit less than that time
71 */
afs_schedule_lock_extension(struct afs_vnode * vnode)72 static void afs_schedule_lock_extension(struct afs_vnode *vnode)
73 {
74 queue_delayed_work(afs_lock_manager, &vnode->lock_work,
75 AFS_LOCKWAIT * HZ / 2);
76 }
77
78 /*
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
82 */
afs_grant_locks(struct afs_vnode * vnode,struct file_lock * fl)83 static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
84 {
85 struct file_lock *p, *_p;
86
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);
96 }
97 }
98 }
99 }
100
101 /*
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
105 */
afs_lock_work(struct work_struct * work)106 void afs_lock_work(struct work_struct *work)
107 {
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;
114
115 _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
116
117 spin_lock(&vnode->lock);
118
119 if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) {
120 _debug("unlock");
121 spin_unlock(&vnode->lock);
122
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);
130
131 spin_lock(&vnode->lock);
132 key_put(vnode->unlock_key);
133 vnode->unlock_key = NULL;
134 clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags);
135 }
136
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");
141
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);
148
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;
165 }
166 _leave(" [extend]");
167 return;
168 }
169
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");
175
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);
184
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);
219 }
220 break;
221 }
222 key_put(key);
223 _leave(" [pend]");
224 return;
225 }
226
227 /* looks like the lock request was withdrawn on a signal */
228 spin_unlock(&vnode->lock);
229 _leave(" [no locks]");
230 }
231
232 /*
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
237 */
afs_defer_unlock(struct afs_vnode * vnode,struct key * key)238 static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key)
239 {
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);
248 }
249
250 /*
251 * request a lock on a file on the server
252 */
afs_do_setlk(struct file * file,struct file_lock * fl)253 static int afs_do_setlk(struct file *file, struct file_lock *fl)
254 {
255 struct inode *inode = file_inode(file);
256 struct afs_vnode *vnode = AFS_FS_I(inode);
257 afs_lock_type_t type;
258 struct key *key = file->private_data;
259 int ret;
260
261 _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
262
263 /* only whole-file locks are supported */
264 if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
265 return -EINVAL;
266
267 ret = afs_init_lock_manager();
268 if (ret < 0)
269 return ret;
270
271 fl->fl_ops = &afs_lock_ops;
272 INIT_LIST_HEAD(&fl->fl_u.afs.link);
273 fl->fl_u.afs.state = AFS_LOCK_PENDING;
274
275 type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
276
277 spin_lock(&inode->i_lock);
278
279 /* make sure we've got a callback on this file and that our view of the
280 * data version is up to date */
281 ret = afs_vnode_fetch_status(vnode, NULL, key);
282 if (ret < 0)
283 goto error;
284
285 if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) {
286 ret = -EAGAIN;
287 goto error;
288 }
289
290 spin_lock(&vnode->lock);
291
292 /* if we've already got a readlock on the server then we can instantly
293 * grant another readlock, irrespective of whether there are any
294 * pending writelocks */
295 if (type == AFS_LOCK_READ &&
296 vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
297 _debug("instant readlock");
298 ASSERTCMP(vnode->flags &
299 ((1 << AFS_VNODE_LOCKING) |
300 (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
301 ASSERT(!list_empty(&vnode->granted_locks));
302 goto sharing_existing_lock;
303 }
304
305 /* if there's no-one else with a lock on this vnode, then we need to
306 * ask the server for a lock */
307 if (list_empty(&vnode->pending_locks) &&
308 list_empty(&vnode->granted_locks)) {
309 _debug("not locked");
310 ASSERTCMP(vnode->flags &
311 ((1 << AFS_VNODE_LOCKING) |
312 (1 << AFS_VNODE_READLOCKED) |
313 (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
314 list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
315 set_bit(AFS_VNODE_LOCKING, &vnode->flags);
316 spin_unlock(&vnode->lock);
317
318 ret = afs_vnode_set_lock(vnode, key, type);
319 clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
320 switch (ret) {
321 case 0:
322 _debug("acquired");
323 goto acquired_server_lock;
324 case -EWOULDBLOCK:
325 _debug("would block");
326 spin_lock(&vnode->lock);
327 ASSERT(list_empty(&vnode->granted_locks));
328 ASSERTCMP(vnode->pending_locks.next, ==,
329 &fl->fl_u.afs.link);
330 goto wait;
331 default:
332 spin_lock(&vnode->lock);
333 list_del_init(&fl->fl_u.afs.link);
334 spin_unlock(&vnode->lock);
335 goto error;
336 }
337 }
338
339 /* otherwise, we need to wait for a local lock to become available */
340 _debug("wait local");
341 list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
342 wait:
343 if (!(fl->fl_flags & FL_SLEEP)) {
344 _debug("noblock");
345 ret = -EAGAIN;
346 goto abort_attempt;
347 }
348 spin_unlock(&vnode->lock);
349
350 /* now we need to sleep and wait for the lock manager thread to get the
351 * lock from the server */
352 _debug("sleep");
353 ret = wait_event_interruptible(fl->fl_wait,
354 fl->fl_u.afs.state <= AFS_LOCK_GRANTED);
355 if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
356 ret = fl->fl_u.afs.state;
357 if (ret < 0)
358 goto error;
359 spin_lock(&vnode->lock);
360 goto given_lock;
361 }
362
363 /* we were interrupted, but someone may still be in the throes of
364 * giving us the lock */
365 _debug("intr");
366 ASSERTCMP(ret, ==, -ERESTARTSYS);
367
368 spin_lock(&vnode->lock);
369 if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
370 ret = fl->fl_u.afs.state;
371 if (ret < 0) {
372 spin_unlock(&vnode->lock);
373 goto error;
374 }
375 goto given_lock;
376 }
377
378 abort_attempt:
379 /* we aren't going to get the lock, either because we're unwilling to
380 * wait, or because some signal happened */
381 _debug("abort");
382 if (list_empty(&vnode->granted_locks) &&
383 vnode->pending_locks.next == &fl->fl_u.afs.link) {
384 if (vnode->pending_locks.prev != &fl->fl_u.afs.link) {
385 /* kick the next pending lock into having a go */
386 list_del_init(&fl->fl_u.afs.link);
387 afs_lock_may_be_available(vnode);
388 }
389 } else {
390 list_del_init(&fl->fl_u.afs.link);
391 }
392 spin_unlock(&vnode->lock);
393 goto error;
394
395 acquired_server_lock:
396 /* we've acquired a server lock, but it needs to be renewed after 5
397 * mins */
398 spin_lock(&vnode->lock);
399 afs_schedule_lock_extension(vnode);
400 if (type == AFS_LOCK_READ)
401 set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
402 else
403 set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
404 sharing_existing_lock:
405 /* the lock has been granted as far as we're concerned... */
406 fl->fl_u.afs.state = AFS_LOCK_GRANTED;
407 list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
408 given_lock:
409 /* ... but we do still need to get the VFS's blessing */
410 ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING)));
411 ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) |
412 (1 << AFS_VNODE_WRITELOCKED))) != 0);
413 ret = posix_lock_file(file, fl, NULL);
414 if (ret < 0)
415 goto vfs_rejected_lock;
416 spin_unlock(&vnode->lock);
417
418 /* again, make sure we've got a callback on this file and, again, make
419 * sure that our view of the data version is up to date (we ignore
420 * errors incurred here and deal with the consequences elsewhere) */
421 afs_vnode_fetch_status(vnode, NULL, key);
422
423 error:
424 spin_unlock(&inode->i_lock);
425 _leave(" = %d", ret);
426 return ret;
427
428 vfs_rejected_lock:
429 /* the VFS rejected the lock we just obtained, so we have to discard
430 * what we just got */
431 _debug("vfs refused %d", ret);
432 list_del_init(&fl->fl_u.afs.link);
433 if (list_empty(&vnode->granted_locks))
434 afs_defer_unlock(vnode, key);
435 goto abort_attempt;
436 }
437
438 /*
439 * unlock on a file on the server
440 */
afs_do_unlk(struct file * file,struct file_lock * fl)441 static int afs_do_unlk(struct file *file, struct file_lock *fl)
442 {
443 struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
444 struct key *key = file->private_data;
445 int ret;
446
447 _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
448
449 /* only whole-file unlocks are supported */
450 if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
451 return -EINVAL;
452
453 fl->fl_ops = &afs_lock_ops;
454 INIT_LIST_HEAD(&fl->fl_u.afs.link);
455 fl->fl_u.afs.state = AFS_LOCK_PENDING;
456
457 spin_lock(&vnode->lock);
458 ret = posix_lock_file(file, fl, NULL);
459 if (ret < 0) {
460 spin_unlock(&vnode->lock);
461 _leave(" = %d [vfs]", ret);
462 return ret;
463 }
464
465 /* discard the server lock only if all granted locks are gone */
466 if (list_empty(&vnode->granted_locks))
467 afs_defer_unlock(vnode, key);
468 spin_unlock(&vnode->lock);
469 _leave(" = 0");
470 return 0;
471 }
472
473 /*
474 * return information about a lock we currently hold, if indeed we hold one
475 */
afs_do_getlk(struct file * file,struct file_lock * fl)476 static int afs_do_getlk(struct file *file, struct file_lock *fl)
477 {
478 struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
479 struct key *key = file->private_data;
480 int ret, lock_count;
481
482 _enter("");
483
484 fl->fl_type = F_UNLCK;
485
486 mutex_lock(&vnode->vfs_inode.i_mutex);
487
488 /* check local lock records first */
489 ret = 0;
490 posix_test_lock(file, fl);
491 if (fl->fl_type == F_UNLCK) {
492 /* no local locks; consult the server */
493 ret = afs_vnode_fetch_status(vnode, NULL, key);
494 if (ret < 0)
495 goto error;
496 lock_count = vnode->status.lock_count;
497 if (lock_count) {
498 if (lock_count > 0)
499 fl->fl_type = F_RDLCK;
500 else
501 fl->fl_type = F_WRLCK;
502 fl->fl_start = 0;
503 fl->fl_end = OFFSET_MAX;
504 }
505 }
506
507 error:
508 mutex_unlock(&vnode->vfs_inode.i_mutex);
509 _leave(" = %d [%hd]", ret, fl->fl_type);
510 return ret;
511 }
512
513 /*
514 * manage POSIX locks on a file
515 */
afs_lock(struct file * file,int cmd,struct file_lock * fl)516 int afs_lock(struct file *file, int cmd, struct file_lock *fl)
517 {
518 struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
519
520 _enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
521 vnode->fid.vid, vnode->fid.vnode, cmd,
522 fl->fl_type, fl->fl_flags,
523 (long long) fl->fl_start, (long long) fl->fl_end);
524
525 /* AFS doesn't support mandatory locks */
526 if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
527 return -ENOLCK;
528
529 if (IS_GETLK(cmd))
530 return afs_do_getlk(file, fl);
531 if (fl->fl_type == F_UNLCK)
532 return afs_do_unlk(file, fl);
533 return afs_do_setlk(file, fl);
534 }
535
536 /*
537 * manage FLOCK locks on a file
538 */
afs_flock(struct file * file,int cmd,struct file_lock * fl)539 int afs_flock(struct file *file, int cmd, struct file_lock *fl)
540 {
541 struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
542
543 _enter("{%x:%u},%d,{t=%x,fl=%x}",
544 vnode->fid.vid, vnode->fid.vnode, cmd,
545 fl->fl_type, fl->fl_flags);
546
547 /*
548 * No BSD flocks over NFS allowed.
549 * Note: we could try to fake a POSIX lock request here by
550 * using ((u32) filp | 0x80000000) or some such as the pid.
551 * Not sure whether that would be unique, though, or whether
552 * that would break in other places.
553 */
554 if (!(fl->fl_flags & FL_FLOCK))
555 return -ENOLCK;
556
557 /* we're simulating flock() locks using posix locks on the server */
558 if (fl->fl_type == F_UNLCK)
559 return afs_do_unlk(file, fl);
560 return afs_do_setlk(file, fl);
561 }
562
563 /*
564 * the POSIX lock management core VFS code copies the lock record and adds the
565 * copy into its own list, so we need to add that copy to the vnode's lock
566 * queue in the same place as the original (which will be deleted shortly
567 * after)
568 */
afs_fl_copy_lock(struct file_lock * new,struct file_lock * fl)569 static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
570 {
571 _enter("");
572
573 list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
574 }
575
576 /*
577 * need to remove this lock from the vnode queue when it's removed from the
578 * VFS's list
579 */
afs_fl_release_private(struct file_lock * fl)580 static void afs_fl_release_private(struct file_lock *fl)
581 {
582 _enter("");
583
584 list_del_init(&fl->fl_u.afs.link);
585 }
586