summaryrefslogtreecommitdiff
path: root/fs/afs/flock.c
blob: 0f2a94ba73cb9508560a8abba3556ddcbe1abf6d (plain)
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
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS file locking support
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include "internal.h"

#define AFS_LOCK_GRANTED	0
#define AFS_LOCK_PENDING	1
#define AFS_LOCK_YOUR_TRY	2

struct workqueue_struct *afs_lock_manager;

static void afs_next_locker(struct afs_vnode *vnode, int error);
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,
};

static inline void afs_set_lock_state(struct afs_vnode *vnode, enum afs_lock_state state)
{
	_debug("STATE %u -> %u", vnode->lock_state, state);
	vnode->lock_state = state;
}

static atomic_t afs_file_lock_debug_id;

/*
 * 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("{%llx:%llu}", vnode->fid.vid, vnode->fid.vnode);

	spin_lock(&vnode->lock);
	if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
		afs_next_locker(vnode, 0);
	trace_afs_flock_ev(vnode, NULL, afs_flock_callback_break, 0);
	spin_unlock(&vnode->lock);
}

/*
 * 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)
{
	ktime_t expires_at, now, duration;
	u64 duration_j;

	expires_at = ktime_add_ms(vnode->locked_at, AFS_LOCKWAIT * 1000 / 2);
	now = ktime_get_real();
	duration = ktime_sub(expires_at, now);
	if (duration <= 0)
		duration_j = 0;
	else
		duration_j = nsecs_to_jiffies(ktime_to_ns(duration));

	queue_delayed_work(afs_lock_manager, &vnode->lock_work, duration_j);
}

/*
 * In the case of successful completion of a lock operation, record the time
 * the reply appeared and start the lock extension timer.
 */
void afs_lock_op_done(struct afs_call *call)
{
	struct afs_vnode *vnode = call->lvnode;

	if (call->error == 0) {
		spin_lock(&vnode->lock);
		trace_afs_flock_ev(vnode, NULL, afs_flock_timestamp, 0);
		vnode->locked_at = call->reply_time;
		afs_schedule_lock_extension(vnode);
		spin_unlock(&vnode->lock);
	}
}

/*
 * 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 *p, *_p;
	bool exclusive = (vnode->lock_type == AFS_LOCK_WRITE);

	list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
		if (!exclusive && p->fl_type == F_WRLCK)
			continue;

		list_move_tail(&p->fl_u.afs.link, &vnode->granted_locks);
		p->fl_u.afs.state = AFS_LOCK_GRANTED;
		trace_afs_flock_op(vnode, p, afs_flock_op_grant);
		wake_up(&p->fl_wait);
	}
}

/*
 * If an error is specified, reject every pending lock that matches the
 * authentication and type of the lock we failed to get.  If there are any
 * remaining lockers, try to wake up one of them to have a go.
 */
static void afs_next_locker(struct afs_vnode *vnode, int error)
{
	struct file_lock *p, *_p, *next = NULL;
	struct key *key = vnode->lock_key;
	unsigned int fl_type = F_RDLCK;

	_enter("");

	if (vnode->lock_type == AFS_LOCK_WRITE)
		fl_type = F_WRLCK;

	list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
		if (error &&
		    p->fl_type == fl_type &&
		    afs_file_key(p->fl_file) == key) {
			list_del_init(&p->fl_u.afs.link);
			p->fl_u.afs.state = error;
			wake_up(&p->fl_wait);
		}

		/* Select the next locker to hand off to. */
		if (next &&
		    (next->fl_type == F_WRLCK || p->fl_type == F_RDLCK))
			continue;
		next = p;
	}

	vnode->lock_key = NULL;
	key_put(key);

	if (next) {
		afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
		next->fl_u.afs.state = AFS_LOCK_YOUR_TRY;
		trace_afs_flock_op(vnode, next, afs_flock_op_wake);
		wake_up(&next->fl_wait);
	} else {
		afs_set_lock_state(vnode, AFS_VNODE_LOCK_NONE);
		trace_afs_flock_ev(vnode, NULL, afs_flock_no_lockers, 0);
	}

	_leave("");
}

/*
 * Kill off all waiters in the the pending lock queue due to the vnode being
 * deleted.
 */
static void afs_kill_lockers_enoent(struct afs_vnode *vnode)
{
	struct file_lock *p;

	afs_set_lock_state(vnode, AFS_VNODE_LOCK_DELETED);

	while (!list_empty(&vnode->pending_locks)) {
		p = list_entry(vnode->pending_locks.next,
			       struct file_lock, fl_u.afs.link);
		list_del_init(&p->fl_u.afs.link);
		p->fl_u.afs.state = -ENOENT;
		wake_up(&p->fl_wait);
	}

	key_put(vnode->lock_key);
	vnode->lock_key = NULL;
}

/*
 * Get a lock on a file
 */
static int afs_set_lock(struct afs_vnode *vnode, struct key *key,
			afs_lock_type_t type)
{
	struct afs_status_cb *scb;
	struct afs_fs_cursor fc;
	int ret;

	_enter("%s{%llx:%llu.%u},%x,%u",
	       vnode->volume->name,
	       vnode->fid.vid,
	       vnode->fid.vnode,
	       vnode->fid.unique,
	       key_serial(key), type);

	scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
	if (!scb)
		return -ENOMEM;

	ret = -ERESTARTSYS;
	if (afs_begin_vnode_operation(&fc, vnode, key, true)) {
		while (afs_select_fileserver(&fc)) {
			fc.cb_break = afs_calc_vnode_cb_break(vnode);
			afs_fs_set_lock(&fc, type, scb);
		}

		afs_check_for_remote_deletion(&fc, vnode);
		afs_vnode_commit_status(&fc, vnode, fc.cb_break, NULL, scb);
		ret = afs_end_vnode_operation(&fc);
	}

	kfree(scb);
	_leave(" = %d", ret);
	return ret;
}

/*
 * Extend a lock on a file
 */
static int afs_extend_lock(struct afs_vnode *vnode, struct key *key)
{
	struct afs_status_cb *scb;
	struct afs_fs_cursor fc;
	int ret;

	_enter("%s{%llx:%llu.%u},%x",
	       vnode->volume->name,
	       vnode->fid.vid,
	       vnode->fid.vnode,
	       vnode->fid.unique,
	       key_serial(key));

	scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
	if (!scb)
		return -ENOMEM;

	ret = -ERESTARTSYS;
	if (afs_begin_vnode_operation(&fc, vnode, key, false)) {
		while (afs_select_current_fileserver(&fc)) {
			fc.cb_break = afs_calc_vnode_cb_break(vnode);
			afs_fs_extend_lock(&fc, scb);
		}

		afs_check_for_remote_deletion(&fc, vnode);
		afs_vnode_commit_status(&fc, vnode, fc.cb_break, NULL, scb);
		ret = afs_end_vnode_operation(&fc);
	}

	kfree(scb);
	_leave(" = %d", ret);
	return ret;
}

/*
 * Release a lock on a file
 */
static int afs_release_lock(struct afs_vnode *vnode, struct key *key)
{
	struct afs_status_cb *scb;
	struct afs_fs_cursor fc;
	int ret;

	_enter("%s{%llx:%llu.%u},%x",
	       vnode->volume->name,
	       vnode->fid.vid,
	       vnode->fid.vnode,
	       vnode->fid.unique,
	       key_serial(key));

	scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
	if (!scb)
		return -ENOMEM;

	ret = -ERESTARTSYS;
	if (afs_begin_vnode_operation(&fc, vnode, key, false)) {
		while (afs_select_current_fileserver(&fc)) {
			fc.cb_break = afs_calc_vnode_cb_break(vnode);
			afs_fs_release_lock(&fc, scb);
		}

		afs_check_for_remote_deletion(&fc, vnode);
		afs_vnode_commit_status(&fc, vnode, fc.cb_break, NULL, scb);
		ret = afs_end_vnode_operation(&fc);
	}

	kfree(scb);
	_leave(" = %d", ret);
	return ret;
}

/*
 * 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 key *key;
	int ret;

	_enter("{%llx:%llu}", vnode->fid.vid, vnode->fid.vnode);

	spin_lock(&vnode->lock);

again:
	_debug("wstate %u for %p", vnode->lock_state, vnode);
	switch (vnode->lock_state) {
	case AFS_VNODE_LOCK_NEED_UNLOCK:
		afs_set_lock_state(vnode, AFS_VNODE_LOCK_UNLOCKING);
		trace_afs_flock_ev(vnode, NULL, afs_flock_work_unlocking, 0);
		spin_unlock(&vnode->lock);

		/* attempt to release the server lock; if it fails, we just
		 * wait 5 minutes and it'll expire anyway */
		ret = afs_release_lock(vnode, vnode->lock_key);
		if (ret < 0 && vnode->lock_state != AFS_VNODE_LOCK_DELETED) {
			trace_afs_flock_ev(vnode, NULL, afs_flock_release_fail,
					   ret);
			printk(KERN_WARNING "AFS:"
			       " Failed to release lock on {%llx:%llx} error %d\n",
			       vnode->fid.vid, vnode->fid.vnode, ret);
		}

		spin_lock(&vnode->lock);
		if (ret == -ENOENT)
			afs_kill_lockers_enoent(vnode);
		else
			afs_next_locker(vnode, 0);
		spin_unlock(&vnode->lock);
		return;

	/* If we've already got a lock, then it must be time to extend that
	 * lock as AFS locks time out after 5 minutes.
	 */
	case AFS_VNODE_LOCK_GRANTED:
		_debug("extend");

		ASSERT(!list_empty(&vnode->granted_locks));

		key = key_get(vnode->lock_key);
		afs_set_lock_state(vnode, AFS_VNODE_LOCK_EXTENDING);
		trace_afs_flock_ev(vnode, NULL, afs_flock_work_extending, 0);
		spin_unlock(&vnode->lock);

		ret = afs_extend_lock(vnode, key); /* RPC */
		key_put(key);

		if (ret < 0) {
			trace_afs_flock_ev(vnode, NULL, afs_flock_extend_fail,
					   ret);
			pr_warn("AFS: Failed to extend lock on {%llx:%llx} error %d\n",
				vnode->fid.vid, vnode->fid.vnode, ret);
		}

		spin_lock(&vnode->lock);

		if (ret == -ENOENT) {
			afs_kill_lockers_enoent(vnode);
			spin_unlock(&vnode->lock);
			return;
		}

		if (vnode->lock_state != AFS_VNODE_LOCK_EXTENDING)
			goto again;
		afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);

		if (ret != 0)
			queue_delayed_work(afs_lock_manager, &vnode->lock_work,
					   HZ * 10);
		spin_unlock(&vnode->lock);
		_leave(" [ext]");
		return;

	/* If we're waiting for a callback to indicate lock release, we can't
	 * actually rely on this, so need to recheck at regular intervals.  The
	 * problem is that the server might not notify us if the lock just
	 * expires (say because a client died) rather than being explicitly
	 * released.
	 */
	case AFS_VNODE_LOCK_WAITING_FOR_CB:
		_debug("retry");
		afs_next_locker(vnode, 0);
		spin_unlock(&vnode->lock);
		return;

	case AFS_VNODE_LOCK_DELETED:
		afs_kill_lockers_enoent(vnode);
		spin_unlock(&vnode->lock);
		return;

		/* Fall through */
	default:
		/* Looks like a lock request was withdrawn. */
		spin_unlock(&vnode->lock);
		_leave(" [no]");
		return;
	}
}

/*
 * 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)
{
	_enter("%u", vnode->lock_state);

	if (list_empty(&vnode->granted_locks) &&
	    (vnode->lock_state == AFS_VNODE_LOCK_GRANTED ||
	     vnode->lock_state == AFS_VNODE_LOCK_EXTENDING)) {
		cancel_delayed_work(&vnode->lock_work);

		afs_set_lock_state(vnode, AFS_VNODE_LOCK_NEED_UNLOCK);
		trace_afs_flock_ev(vnode, NULL, afs_flock_defer_unlock, 0);
		queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
	}
}

/*
 * Check that our view of the file metadata is up to date and check to see
 * whether we think that we have a locking permit.
 */
static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key,
			      enum afs_flock_mode mode, afs_lock_type_t type)
{
	afs_access_t access;
	int ret;

	/* 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)
		return ret;

	/* Check the permission set to see if we're actually going to be
	 * allowed to get a lock on this file.
	 */
	ret = afs_check_permit(vnode, key, &access);
	if (ret < 0)
		return ret;

	/* At a rough estimation, you need LOCK, WRITE or INSERT perm to
	 * read-lock a file and WRITE or INSERT perm to write-lock a file.
	 *
	 * We can't rely on the server to do this for us since if we want to
	 * share a read lock that we already have, we won't go the server.
	 */
	if (type == AFS_LOCK_READ) {
		if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE | AFS_ACE_LOCK)))
			return -EACCES;
	} else {
		if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE)))
			return -EACCES;
	}

	return 0;
}

/*
 * request a lock on a file on the server
 */
static int afs_do_setlk(struct file *file, struct file_lock *fl)
{
	struct inode *inode = locks_inode(file);
	struct afs_vnode *vnode = AFS_FS_I(inode);
	enum afs_flock_mode mode = AFS_FS_S(inode->i_sb)->flock_mode;
	afs_lock_type_t type;
	struct key *key = afs_file_key(file);
	bool partial, no_server_lock = false;
	int ret;

	if (mode == afs_flock_mode_unset)
		mode = afs_flock_mode_openafs;

	_enter("{%llx:%llu},%llu-%llu,%u,%u",
	       vnode->fid.vid, vnode->fid.vnode,
	       fl->fl_start, fl->fl_end, fl->fl_type, mode);

	fl->fl_ops = &afs_lock_ops;
	INIT_LIST_HEAD(&fl->fl_u.afs.link);
	fl->fl_u.afs.state = AFS_LOCK_PENDING;

	partial = (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX);
	type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
	if (mode == afs_flock_mode_write && partial)
		type = AFS_LOCK_WRITE;

	ret = afs_do_setlk_check(vnode, key, mode, type);
	if (ret < 0)
		return ret;

	trace_afs_flock_op(vnode, fl, afs_flock_op_set_lock);

	/* AFS3 protocol only supports full-file locks and doesn't provide any
	 * method of upgrade/downgrade, so we need to emulate for partial-file
	 * locks.
	 *
	 * The OpenAFS client only gets a server lock for a full-file lock and
	 * keeps partial-file locks local.  Allow this behaviour to be emulated
	 * (as the default).
	 */
	if (mode == afs_flock_mode_local ||
	    (partial && mode == afs_flock_mode_openafs)) {
		no_server_lock = true;
		goto skip_server_lock;
	}

	spin_lock(&vnode->lock);
	list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);

	ret = -ENOENT;
	if (vnode->lock_state == AFS_VNODE_LOCK_DELETED)
		goto error_unlock;

	/* If we've already got a lock on the server then try to move to having
	 * the VFS grant the requested lock.  Note that this means that other
	 * clients may get starved out.
	 */
	_debug("try %u", vnode->lock_state);
	if (vnode->lock_state == AFS_VNODE_LOCK_GRANTED) {
		if (type == AFS_LOCK_READ) {
			_debug("instant readlock");
			list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
			fl->fl_u.afs.state = AFS_LOCK_GRANTED;
			goto vnode_is_locked_u;
		}

		if (vnode->lock_type == AFS_LOCK_WRITE) {
			_debug("instant writelock");
			list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
			fl->fl_u.afs.state = AFS_LOCK_GRANTED;
			goto vnode_is_locked_u;
		}
	}

	if (vnode->lock_state == AFS_VNODE_LOCK_NONE &&
	    !(fl->fl_flags & FL_SLEEP)) {
		ret = -EAGAIN;
		if (type == AFS_LOCK_READ) {
			if (vnode->status.lock_count == -1)
				goto lock_is_contended; /* Write locked */
		} else {
			if (vnode->status.lock_count != 0)
				goto lock_is_contended; /* Locked */
		}
	}

	if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
		goto need_to_wait;

try_to_lock:
	/* We don't have a lock on this vnode and we aren't currently waiting
	 * for one either, so ask the server for a lock.
	 *
	 * Note that we need to be careful if we get interrupted by a signal
	 * after dispatching the request as we may still get the lock, even
	 * though we don't wait for the reply (it's not too bad a problem - the
	 * lock will expire in 5 mins anyway).
	 */
	trace_afs_flock_ev(vnode, fl, afs_flock_try_to_lock, 0);
	vnode->lock_key = key_get(key);
	vnode->lock_type = type;
	afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
	spin_unlock(&vnode->lock);

	ret = afs_set_lock(vnode, key, type); /* RPC */

	spin_lock(&vnode->lock);
	switch (ret) {
	case -EKEYREJECTED:
	case -EKEYEXPIRED:
	case -EKEYREVOKED:
	case -EPERM:
	case -EACCES:
		fl->fl_u.afs.state = ret;
		trace_afs_flock_ev(vnode, fl, afs_flock_fail_perm, ret);
		list_del_init(&fl->fl_u.afs.link);
		afs_next_locker(vnode, ret);
		goto error_unlock;

	case -ENOENT:
		fl->fl_u.afs.state = ret;
		trace_afs_flock_ev(vnode, fl, afs_flock_fail_other, ret);
		list_del_init(&fl->fl_u.afs.link);
		afs_kill_lockers_enoent(vnode);
		goto error_unlock;

	default:
		fl->fl_u.afs.state = ret;
		trace_afs_flock_ev(vnode, fl, afs_flock_fail_other, ret);
		list_del_init(&fl->fl_u.afs.link);
		afs_next_locker(vnode, 0);
		goto error_unlock;

	case -EWOULDBLOCK:
		/* The server doesn't have a lock-waiting queue, so the client
		 * will have to retry.  The server will break the outstanding
		 * callbacks on a file when a lock is released.
		 */
		ASSERT(list_empty(&vnode->granted_locks));
		ASSERTCMP(vnode->pending_locks.next, ==, &fl->fl_u.afs.link);
		goto lock_is_contended;

	case 0:
		afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
		trace_afs_flock_ev(vnode, fl, afs_flock_acquired, type);
		afs_grant_locks(vnode);
		goto vnode_is_locked_u;
	}

vnode_is_locked_u:
	spin_unlock(&vnode->lock);
vnode_is_locked:
	/* the lock has been granted by the server... */
	ASSERTCMP(fl->fl_u.afs.state, ==, AFS_LOCK_GRANTED);

skip_server_lock:
	/* ... but the VFS still needs to distribute access on this client. */
	trace_afs_flock_ev(vnode, fl, afs_flock_vfs_locking, 0);
	ret = locks_lock_file_wait(file, fl);
	trace_afs_flock_ev(vnode, fl, afs_flock_vfs_lock, ret);
	if (ret < 0)
		goto vfs_rejected_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_validate(vnode, key);
	_leave(" = 0");
	return 0;

lock_is_contended:
	if (!(fl->fl_flags & FL_SLEEP)) {
		list_del_init(&fl->fl_u.afs.link);
		afs_next_locker(vnode, 0);
		ret = -EAGAIN;
		goto error_unlock;
	}

	afs_set_lock_state(vnode, AFS_VNODE_LOCK_WAITING_FOR_CB);
	trace_afs_flock_ev(vnode, fl, afs_flock_would_block, ret);
	queue_delayed_work(afs_lock_manager, &vnode->lock_work, HZ * 5);

need_to_wait:
	/* We're going to have to wait.  Either this client doesn't have a lock
	 * on the server yet and we need to wait for a callback to occur, or
	 * the client does have a lock on the server, but it's shared and we
	 * need an exclusive lock.
	 */
	spin_unlock(&vnode->lock);

	trace_afs_flock_ev(vnode, fl, afs_flock_waiting, 0);
	ret = wait_event_interruptible(fl->fl_wait,
				       fl->fl_u.afs.state != AFS_LOCK_PENDING);
	trace_afs_flock_ev(vnode, fl, afs_flock_waited, ret);

	if (fl->fl_u.afs.state >= 0 && fl->fl_u.afs.state != AFS_LOCK_GRANTED) {
		spin_lock(&vnode->lock);

		switch (fl->fl_u.afs.state) {
		case AFS_LOCK_YOUR_TRY:
			fl->fl_u.afs.state = AFS_LOCK_PENDING;
			goto try_to_lock;
		case AFS_LOCK_PENDING:
			if (ret > 0) {
				/* We need to retry the lock.  We may not be
				 * notified by the server if it just expired
				 * rather than being released.
				 */
				ASSERTCMP(vnode->lock_state, ==, AFS_VNODE_LOCK_WAITING_FOR_CB);
				afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
				fl->fl_u.afs.state = AFS_LOCK_PENDING;
				goto try_to_lock;
			}
			goto error_unlock;
		case AFS_LOCK_GRANTED:
		default:
			break;
		}

		spin_unlock(&vnode->lock);
	}

	if (fl->fl_u.afs.state == AFS_LOCK_GRANTED)
		goto vnode_is_locked;
	ret = fl->fl_u.afs.state;
	goto error;

vfs_rejected_lock:
	/* The VFS rejected the lock we just obtained, so we have to discard
	 * what we just got.  We defer this to the lock manager work item to
	 * deal with.
	 */
	_debug("vfs refused %d", ret);
	if (no_server_lock)
		goto error;
	spin_lock(&vnode->lock);
	list_del_init(&fl->fl_u.afs.link);
	afs_defer_unlock(vnode);

error_unlock:
	spin_unlock(&vnode->lock);
error:
	_leave(" = %d", ret);
	return ret;
}

/*
 * 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(locks_inode(file));
	int ret;

	_enter("{%llx:%llu},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);

	trace_afs_flock_op(vnode, fl, afs_flock_op_unlock);

	/* Flush all pending writes before doing anything with locks. */
	vfs_fsync(file, 0);

	ret = locks_lock_file_wait(file, fl);
	_leave(" = %d [%u]", ret, vnode->lock_state);
	return ret;
}

/*
 * 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(locks_inode(file));
	struct key *key = afs_file_key(file);
	int ret, lock_count;

	_enter("");

	if (vnode->lock_state == AFS_VNODE_LOCK_DELETED)
		return -ENOENT;

	fl->fl_type = F_UNLCK;

	/* check local lock records first */
	posix_test_lock(file, fl);
	if (fl->fl_type == F_UNLCK) {
		/* no local locks; consult the server */
		ret = afs_fetch_status(vnode, key, false, NULL);
		if (ret < 0)
			goto error;

		lock_count = READ_ONCE(vnode->status.lock_count);
		if (lock_count != 0) {
			if (lock_count > 0)
				fl->fl_type = F_RDLCK;
			else
				fl->fl_type = F_WRLCK;
			fl->fl_start = 0;
			fl->fl_end = OFFSET_MAX;
			fl->fl_pid = 0;
		}
	}

	ret = 0;
error:
	_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(locks_inode(file));
	enum afs_flock_operation op;
	int ret;

	_enter("{%llx:%llu},%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);

	fl->fl_u.afs.debug_id = atomic_inc_return(&afs_file_lock_debug_id);
	trace_afs_flock_op(vnode, fl, afs_flock_op_lock);

	if (fl->fl_type == F_UNLCK)
		ret = afs_do_unlk(file, fl);
	else
		ret = afs_do_setlk(file, fl);

	switch (ret) {
	case 0:		op = afs_flock_op_return_ok; break;
	case -EAGAIN:	op = afs_flock_op_return_eagain; break;
	case -EDEADLK:	op = afs_flock_op_return_edeadlk; break;
	default:	op = afs_flock_op_return_error; break;
	}
	trace_afs_flock_op(vnode, fl, op);
	return ret;
}

/*
 * 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(locks_inode(file));
	enum afs_flock_operation op;
	int ret;

	_enter("{%llx:%llu},%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;

	fl->fl_u.afs.debug_id = atomic_inc_return(&afs_file_lock_debug_id);
	trace_afs_flock_op(vnode, fl, afs_flock_op_flock);

	/* we're simulating flock() locks using posix locks on the server */
	if (fl->fl_type == F_UNLCK)
		ret = afs_do_unlk(file, fl);
	else
		ret = afs_do_setlk(file, fl);

	switch (ret) {
	case 0:		op = afs_flock_op_return_ok; break;
	case -EAGAIN:	op = afs_flock_op_return_eagain; break;
	case -EDEADLK:	op = afs_flock_op_return_edeadlk; break;
	default:	op = afs_flock_op_return_error; break;
	}
	trace_afs_flock_op(vnode, fl, op);
	return ret;
}

/*
 * 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)
{
	struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));

	_enter("");

	new->fl_u.afs.debug_id = atomic_inc_return(&afs_file_lock_debug_id);

	spin_lock(&vnode->lock);
	trace_afs_flock_op(vnode, new, afs_flock_op_copy_lock);
	list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
	spin_unlock(&vnode->lock);
}

/*
 * 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)
{
	struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));

	_enter("");

	spin_lock(&vnode->lock);

	trace_afs_flock_op(vnode, fl, afs_flock_op_release_lock);
	list_del_init(&fl->fl_u.afs.link);
	if (list_empty(&vnode->granted_locks))
		afs_defer_unlock(vnode);

	_debug("state %u for %p", vnode->lock_state, vnode);
	spin_unlock(&vnode->lock);
}