1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
|
/* AFS file locking support
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include "internal.h"
#define AFS_LOCK_GRANTED 0
#define AFS_LOCK_PENDING 1
struct workqueue_struct *afs_lock_manager;
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
static void afs_fl_release_private(struct file_lock *fl);
static const struct file_lock_operations afs_lock_ops = {
.fl_copy_lock = afs_fl_copy_lock,
.fl_release_private = afs_fl_release_private,
};
/*
* if the callback is broken on this vnode, then the lock may now be available
*/
void afs_lock_may_be_available(struct afs_vnode *vnode)
{
_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
}
/*
* the lock will time out in 5 minutes unless we extend it, so schedule
* extension in a bit less than that time
*/
static void afs_schedule_lock_extension(struct afs_vnode *vnode)
{
queue_delayed_work(afs_lock_manager, &vnode->lock_work,
AFS_LOCKWAIT * HZ / 2);
}
/*
* grant one or more locks (readlocks are allowed to jump the queue if the
* first lock in the queue is itself a readlock)
* - the caller must hold the vnode lock
*/
static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
{
struct file_lock *p, *_p;
list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
if (fl->fl_type == F_RDLCK) {
list_for_each_entry_safe(p, _p, &vnode->pending_locks,
fl_u.afs.link) {
if (p->fl_type == F_RDLCK) {
p->fl_u.afs.state = AFS_LOCK_GRANTED;
list_move_tail(&p->fl_u.afs.link,
&vnode->granted_locks);
wake_up(&p->fl_wait);
}
}
}
}
/*
* do work for a lock, including:
* - probing for a lock we're waiting on but didn't get immediately
* - extending a lock that's close to timing out
*/
void afs_lock_work(struct work_struct *work)
{
struct afs_vnode *vnode =
container_of(work, struct afs_vnode, lock_work.work);
struct file_lock *fl;
afs_lock_type_t type;
struct key *key;
int ret;
_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
spin_lock(&vnode->lock);
if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) {
_debug("unlock");
spin_unlock(&vnode->lock);
/* attempt to release the server lock; if it fails, we just
* wait 5 minutes and it'll time out anyway */
ret = afs_vnode_release_lock(vnode, vnode->unlock_key);
if (ret < 0)
printk(KERN_WARNING "AFS:"
" Failed to release lock on {%x:%x} error %d\n",
vnode->fid.vid, vnode->fid.vnode, ret);
spin_lock(&vnode->lock);
key_put(vnode->unlock_key);
vnode->unlock_key = NULL;
clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags);
}
/* if we've got a lock, then it must be time to extend that lock as AFS
* locks time out after 5 minutes */
if (!list_empty(&vnode->granted_locks)) {
_debug("extend");
if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
BUG();
fl = list_entry(vnode->granted_locks.next,
struct file_lock, fl_u.afs.link);
key = key_get(fl->fl_file->private_data);
spin_unlock(&vnode->lock);
ret = afs_vnode_extend_lock(vnode, key);
clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
key_put(key);
switch (ret) {
case 0:
afs_schedule_lock_extension(vnode);
break;
default:
/* ummm... we failed to extend the lock - retry
* extension shortly */
printk(KERN_WARNING "AFS:"
" Failed to extend lock on {%x:%x} error %d\n",
vnode->fid.vid, vnode->fid.vnode, ret);
queue_delayed_work(afs_lock_manager, &vnode->lock_work,
HZ * 10);
break;
}
_leave(" [extend]");
return;
}
/* if we don't have a granted lock, then we must've been called back by
* the server, and so if might be possible to get a lock we're
* currently waiting for */
if (!list_empty(&vnode->pending_locks)) {
_debug("get");
if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
BUG();
fl = list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link);
key = key_get(fl->fl_file->private_data);
type = (fl->fl_type == F_RDLCK) ?
AFS_LOCK_READ : AFS_LOCK_WRITE;
spin_unlock(&vnode->lock);
ret = afs_vnode_set_lock(vnode, key, type);
clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
switch (ret) {
case -EWOULDBLOCK:
_debug("blocked");
break;
case 0:
_debug("acquired");
if (type == AFS_LOCK_READ)
set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
else
set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
ret = AFS_LOCK_GRANTED;
default:
spin_lock(&vnode->lock);
/* the pending lock may have been withdrawn due to a
* signal */
if (list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link) == fl) {
fl->fl_u.afs.state = ret;
if (ret == AFS_LOCK_GRANTED)
afs_grant_locks(vnode, fl);
else
list_del_init(&fl->fl_u.afs.link);
wake_up(&fl->fl_wait);
spin_unlock(&vnode->lock);
} else {
_debug("withdrawn");
clear_bit(AFS_VNODE_READLOCKED, &vnode->flags);
clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
spin_unlock(&vnode->lock);
afs_vnode_release_lock(vnode, key);
if (!list_empty(&vnode->pending_locks))
afs_lock_may_be_available(vnode);
}
break;
}
key_put(key);
_leave(" [pend]");
return;
}
/* looks like the lock request was withdrawn on a signal */
spin_unlock(&vnode->lock);
_leave(" [no locks]");
}
/*
* pass responsibility for the unlocking of a vnode on the server to the
* manager thread, lest a pending signal in the calling thread interrupt
* AF_RXRPC
* - the caller must hold the vnode lock
*/
static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key)
{
cancel_delayed_work(&vnode->lock_work);
if (!test_and_clear_bit(AFS_VNODE_READLOCKED, &vnode->flags) &&
!test_and_clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags))
BUG();
if (test_and_set_bit(AFS_VNODE_UNLOCKING, &vnode->flags))
BUG();
vnode->unlock_key = key_get(key);
afs_lock_may_be_available(vnode);
}
/*
* request a lock on a file on the server
*/
static int afs_do_setlk(struct file *file, struct file_lock *fl)
{
struct inode *inode = file_inode(file);
struct afs_vnode *vnode = AFS_FS_I(inode);
afs_lock_type_t type;
struct key *key = file->private_data;
int ret;
_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
/* only whole-file locks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
fl->fl_ops = &afs_lock_ops;
INIT_LIST_HEAD(&fl->fl_u.afs.link);
fl->fl_u.afs.state = AFS_LOCK_PENDING;
type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
spin_lock(&inode->i_lock);
/* make sure we've got a callback on this file and that our view of the
* data version is up to date */
ret = afs_validate(vnode, key);
if (ret < 0)
goto error;
if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) {
ret = -EAGAIN;
goto error;
}
spin_lock(&vnode->lock);
/* if we've already got a readlock on the server then we can instantly
* grant another readlock, irrespective of whether there are any
* pending writelocks */
if (type == AFS_LOCK_READ &&
vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
_debug("instant readlock");
ASSERTCMP(vnode->flags &
((1 << AFS_VNODE_LOCKING) |
(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
ASSERT(!list_empty(&vnode->granted_locks));
goto sharing_existing_lock;
}
/* if there's no-one else with a lock on this vnode, then we need to
* ask the server for a lock */
if (list_empty(&vnode->pending_locks) &&
list_empty(&vnode->granted_locks)) {
_debug("not locked");
ASSERTCMP(vnode->flags &
((1 << AFS_VNODE_LOCKING) |
(1 << AFS_VNODE_READLOCKED) |
(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
set_bit(AFS_VNODE_LOCKING, &vnode->flags);
spin_unlock(&vnode->lock);
ret = afs_vnode_set_lock(vnode, key, type);
clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
switch (ret) {
case 0:
_debug("acquired");
goto acquired_server_lock;
case -EWOULDBLOCK:
_debug("would block");
spin_lock(&vnode->lock);
ASSERT(list_empty(&vnode->granted_locks));
ASSERTCMP(vnode->pending_locks.next, ==,
&fl->fl_u.afs.link);
goto wait;
default:
spin_lock(&vnode->lock);
list_del_init(&fl->fl_u.afs.link);
spin_unlock(&vnode->lock);
goto error;
}
}
/* otherwise, we need to wait for a local lock to become available */
_debug("wait local");
list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
wait:
if (!(fl->fl_flags & FL_SLEEP)) {
_debug("noblock");
ret = -EAGAIN;
goto abort_attempt;
}
spin_unlock(&vnode->lock);
/* now we need to sleep and wait for the lock manager thread to get the
* lock from the server */
_debug("sleep");
ret = wait_event_interruptible(fl->fl_wait,
fl->fl_u.afs.state <= AFS_LOCK_GRANTED);
if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
ret = fl->fl_u.afs.state;
if (ret < 0)
goto error;
spin_lock(&vnode->lock);
goto given_lock;
}
/* we were interrupted, but someone may still be in the throes of
* giving us the lock */
_debug("intr");
ASSERTCMP(ret, ==, -ERESTARTSYS);
spin_lock(&vnode->lock);
if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
ret = fl->fl_u.afs.state;
if (ret < 0) {
spin_unlock(&vnode->lock);
goto error;
}
goto given_lock;
}
abort_attempt:
/* we aren't going to get the lock, either because we're unwilling to
* wait, or because some signal happened */
_debug("abort");
if (list_empty(&vnode->granted_locks) &&
vnode->pending_locks.next == &fl->fl_u.afs.link) {
if (vnode->pending_locks.prev != &fl->fl_u.afs.link) {
/* kick the next pending lock into having a go */
list_del_init(&fl->fl_u.afs.link);
afs_lock_may_be_available(vnode);
}
} else {
list_del_init(&fl->fl_u.afs.link);
}
spin_unlock(&vnode->lock);
goto error;
acquired_server_lock:
/* we've acquired a server lock, but it needs to be renewed after 5
* mins */
spin_lock(&vnode->lock);
afs_schedule_lock_extension(vnode);
if (type == AFS_LOCK_READ)
set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
else
set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
sharing_existing_lock:
/* the lock has been granted as far as we're concerned... */
fl->fl_u.afs.state = AFS_LOCK_GRANTED;
list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
given_lock:
/* ... but we do still need to get the VFS's blessing */
ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING)));
ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) |
(1 << AFS_VNODE_WRITELOCKED))) != 0);
ret = posix_lock_file(file, fl, NULL);
if (ret < 0)
goto vfs_rejected_lock;
spin_unlock(&vnode->lock);
/* again, make sure we've got a callback on this file and, again, make
* sure that our view of the data version is up to date (we ignore
* errors incurred here and deal with the consequences elsewhere) */
afs_vnode_fetch_status(vnode, NULL, key, false);
error:
spin_unlock(&inode->i_lock);
_leave(" = %d", ret);
return ret;
vfs_rejected_lock:
/* the VFS rejected the lock we just obtained, so we have to discard
* what we just got */
_debug("vfs refused %d", ret);
list_del_init(&fl->fl_u.afs.link);
if (list_empty(&vnode->granted_locks))
afs_defer_unlock(vnode, key);
goto abort_attempt;
}
/*
* unlock on a file on the server
*/
static int afs_do_unlk(struct file *file, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
struct key *key = file->private_data;
int ret;
_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
/* only whole-file unlocks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
fl->fl_ops = &afs_lock_ops;
INIT_LIST_HEAD(&fl->fl_u.afs.link);
fl->fl_u.afs.state = AFS_LOCK_PENDING;
spin_lock(&vnode->lock);
ret = posix_lock_file(file, fl, NULL);
if (ret < 0) {
spin_unlock(&vnode->lock);
_leave(" = %d [vfs]", ret);
return ret;
}
/* discard the server lock only if all granted locks are gone */
if (list_empty(&vnode->granted_locks))
afs_defer_unlock(vnode, key);
spin_unlock(&vnode->lock);
_leave(" = 0");
return 0;
}
/*
* return information about a lock we currently hold, if indeed we hold one
*/
static int afs_do_getlk(struct file *file, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
struct key *key = file->private_data;
int ret, lock_count;
_enter("");
fl->fl_type = F_UNLCK;
inode_lock(&vnode->vfs_inode);
/* check local lock records first */
ret = 0;
posix_test_lock(file, fl);
if (fl->fl_type == F_UNLCK) {
/* no local locks; consult the server */
ret = afs_vnode_fetch_status(vnode, NULL, key, true);
if (ret < 0)
goto error;
lock_count = vnode->status.lock_count;
if (lock_count) {
if (lock_count > 0)
fl->fl_type = F_RDLCK;
else
fl->fl_type = F_WRLCK;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
}
}
error:
inode_unlock(&vnode->vfs_inode);
_leave(" = %d [%hd]", ret, fl->fl_type);
return ret;
}
/*
* manage POSIX locks on a file
*/
int afs_lock(struct file *file, int cmd, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
_enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
vnode->fid.vid, vnode->fid.vnode, cmd,
fl->fl_type, fl->fl_flags,
(long long) fl->fl_start, (long long) fl->fl_end);
/* AFS doesn't support mandatory locks */
if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
return -ENOLCK;
if (IS_GETLK(cmd))
return afs_do_getlk(file, fl);
if (fl->fl_type == F_UNLCK)
return afs_do_unlk(file, fl);
return afs_do_setlk(file, fl);
}
/*
* manage FLOCK locks on a file
*/
int afs_flock(struct file *file, int cmd, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
_enter("{%x:%u},%d,{t=%x,fl=%x}",
vnode->fid.vid, vnode->fid.vnode, cmd,
fl->fl_type, fl->fl_flags);
/*
* No BSD flocks over NFS allowed.
* Note: we could try to fake a POSIX lock request here by
* using ((u32) filp | 0x80000000) or some such as the pid.
* Not sure whether that would be unique, though, or whether
* that would break in other places.
*/
if (!(fl->fl_flags & FL_FLOCK))
return -ENOLCK;
/* we're simulating flock() locks using posix locks on the server */
if (fl->fl_type == F_UNLCK)
return afs_do_unlk(file, fl);
return afs_do_setlk(file, fl);
}
/*
* the POSIX lock management core VFS code copies the lock record and adds the
* copy into its own list, so we need to add that copy to the vnode's lock
* queue in the same place as the original (which will be deleted shortly
* after)
*/
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
{
_enter("");
list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
}
/*
* need to remove this lock from the vnode queue when it's removed from the
* VFS's list
*/
static void afs_fl_release_private(struct file_lock *fl)
{
_enter("");
list_del_init(&fl->fl_u.afs.link);
}
|