summaryrefslogtreecommitdiffstats
path: root/fs/fscache/object.c
blob: d236eb1d6f37345796b2dd31d0ec9c0848596f2f (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
/* FS-Cache object state machine handler
 *
 * 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.
 *
 * See Documentation/filesystems/caching/object.txt for a description of the
 * object state machine and the in-kernel representations.
 */

#define FSCACHE_DEBUG_LEVEL COOKIE
#include <linux/module.h>
#include "internal.h"

const char *fscache_object_states[] = {
	[FSCACHE_OBJECT_INIT]		= "OBJECT_INIT",
	[FSCACHE_OBJECT_LOOKING_UP]	= "OBJECT_LOOKING_UP",
	[FSCACHE_OBJECT_CREATING]	= "OBJECT_CREATING",
	[FSCACHE_OBJECT_AVAILABLE]	= "OBJECT_AVAILABLE",
	[FSCACHE_OBJECT_ACTIVE]		= "OBJECT_ACTIVE",
	[FSCACHE_OBJECT_UPDATING]	= "OBJECT_UPDATING",
	[FSCACHE_OBJECT_DYING]		= "OBJECT_DYING",
	[FSCACHE_OBJECT_LC_DYING]	= "OBJECT_LC_DYING",
	[FSCACHE_OBJECT_ABORT_INIT]	= "OBJECT_ABORT_INIT",
	[FSCACHE_OBJECT_RELEASING]	= "OBJECT_RELEASING",
	[FSCACHE_OBJECT_RECYCLING]	= "OBJECT_RECYCLING",
	[FSCACHE_OBJECT_WITHDRAWING]	= "OBJECT_WITHDRAWING",
	[FSCACHE_OBJECT_DEAD]		= "OBJECT_DEAD",
};
EXPORT_SYMBOL(fscache_object_states);

static void fscache_object_slow_work_put_ref(struct slow_work *);
static int  fscache_object_slow_work_get_ref(struct slow_work *);
static void fscache_object_slow_work_execute(struct slow_work *);
static void fscache_initialise_object(struct fscache_object *);
static void fscache_lookup_object(struct fscache_object *);
static void fscache_object_available(struct fscache_object *);
static void fscache_release_object(struct fscache_object *);
static void fscache_withdraw_object(struct fscache_object *);
static void fscache_enqueue_dependents(struct fscache_object *);
static void fscache_dequeue_object(struct fscache_object *);

const struct slow_work_ops fscache_object_slow_work_ops = {
	.owner		= THIS_MODULE,
	.get_ref	= fscache_object_slow_work_get_ref,
	.put_ref	= fscache_object_slow_work_put_ref,
	.execute	= fscache_object_slow_work_execute,
};
EXPORT_SYMBOL(fscache_object_slow_work_ops);

/*
 * we need to notify the parent when an op completes that we had outstanding
 * upon it
 */
static inline void fscache_done_parent_op(struct fscache_object *object)
{
	struct fscache_object *parent = object->parent;

	_enter("OBJ%x {OBJ%x,%x}",
	       object->debug_id, parent->debug_id, parent->n_ops);

	spin_lock_nested(&parent->lock, 1);
	parent->n_ops--;
	parent->n_obj_ops--;
	if (parent->n_ops == 0)
		fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
	spin_unlock(&parent->lock);
}

/*
 * process events that have been sent to an object's state machine
 * - initiates parent lookup
 * - does object lookup
 * - does object creation
 * - does object recycling and retirement
 * - does object withdrawal
 */
static void fscache_object_state_machine(struct fscache_object *object)
{
	enum fscache_object_state new_state;

	ASSERT(object != NULL);

	_enter("{OBJ%x,%s,%lx}",
	       object->debug_id, fscache_object_states[object->state],
	       object->events);

	switch (object->state) {
		/* wait for the parent object to become ready */
	case FSCACHE_OBJECT_INIT:
		object->event_mask =
			ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
		fscache_initialise_object(object);
		goto done;

		/* look up the object metadata on disk */
	case FSCACHE_OBJECT_LOOKING_UP:
		fscache_lookup_object(object);
		goto lookup_transit;

		/* create the object metadata on disk */
	case FSCACHE_OBJECT_CREATING:
		fscache_lookup_object(object);
		goto lookup_transit;

		/* handle an object becoming available; start pending
		 * operations and queue dependent operations for processing */
	case FSCACHE_OBJECT_AVAILABLE:
		fscache_object_available(object);
		goto active_transit;

		/* normal running state */
	case FSCACHE_OBJECT_ACTIVE:
		goto active_transit;

		/* update the object metadata on disk */
	case FSCACHE_OBJECT_UPDATING:
		clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
		fscache_stat(&fscache_n_updates_run);
		object->cache->ops->update_object(object);
		goto active_transit;

		/* handle an object dying during lookup or creation */
	case FSCACHE_OBJECT_LC_DYING:
		object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
		object->cache->ops->lookup_complete(object);

		spin_lock(&object->lock);
		object->state = FSCACHE_OBJECT_DYING;
		if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
				       &object->cookie->flags))
			wake_up_bit(&object->cookie->flags,
				    FSCACHE_COOKIE_CREATING);
		spin_unlock(&object->lock);

		fscache_done_parent_op(object);

		/* wait for completion of all active operations on this object
		 * and the death of all child objects of this object */
	case FSCACHE_OBJECT_DYING:
	dying:
		clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
		spin_lock(&object->lock);
		_debug("dying OBJ%x {%d,%d}",
		       object->debug_id, object->n_ops, object->n_children);
		if (object->n_ops == 0 && object->n_children == 0) {
			object->event_mask &=
				~(1 << FSCACHE_OBJECT_EV_CLEARED);
			object->event_mask |=
				(1 << FSCACHE_OBJECT_EV_WITHDRAW) |
				(1 << FSCACHE_OBJECT_EV_RETIRE) |
				(1 << FSCACHE_OBJECT_EV_RELEASE) |
				(1 << FSCACHE_OBJECT_EV_ERROR);
		} else {
			object->event_mask &=
				~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
				  (1 << FSCACHE_OBJECT_EV_RETIRE) |
				  (1 << FSCACHE_OBJECT_EV_RELEASE) |
				  (1 << FSCACHE_OBJECT_EV_ERROR));
			object->event_mask |=
				1 << FSCACHE_OBJECT_EV_CLEARED;
		}
		spin_unlock(&object->lock);
		fscache_enqueue_dependents(object);
		goto terminal_transit;

		/* handle an abort during initialisation */
	case FSCACHE_OBJECT_ABORT_INIT:
		_debug("handle abort init %lx", object->events);
		object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);

		spin_lock(&object->lock);
		fscache_dequeue_object(object);

		object->state = FSCACHE_OBJECT_DYING;
		if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
				       &object->cookie->flags))
			wake_up_bit(&object->cookie->flags,
				    FSCACHE_COOKIE_CREATING);
		spin_unlock(&object->lock);
		goto dying;

		/* handle the netfs releasing an object and possibly marking it
		 * obsolete too */
	case FSCACHE_OBJECT_RELEASING:
	case FSCACHE_OBJECT_RECYCLING:
		object->event_mask &=
			~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
			  (1 << FSCACHE_OBJECT_EV_RETIRE) |
			  (1 << FSCACHE_OBJECT_EV_RELEASE) |
			  (1 << FSCACHE_OBJECT_EV_ERROR));
		fscache_release_object(object);
		spin_lock(&object->lock);
		object->state = FSCACHE_OBJECT_DEAD;
		spin_unlock(&object->lock);
		fscache_stat(&fscache_n_object_dead);
		goto terminal_transit;

		/* handle the parent cache of this object being withdrawn from
		 * active service */
	case FSCACHE_OBJECT_WITHDRAWING:
		object->event_mask &=
			~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
			  (1 << FSCACHE_OBJECT_EV_RETIRE) |
			  (1 << FSCACHE_OBJECT_EV_RELEASE) |
			  (1 << FSCACHE_OBJECT_EV_ERROR));
		fscache_withdraw_object(object);
		spin_lock(&object->lock);
		object->state = FSCACHE_OBJECT_DEAD;
		spin_unlock(&object->lock);
		fscache_stat(&fscache_n_object_dead);
		goto terminal_transit;

		/* complain about the object being woken up once it is
		 * deceased */
	case FSCACHE_OBJECT_DEAD:
		printk(KERN_ERR "FS-Cache:"
		       " Unexpected event in dead state %lx\n",
		       object->events & object->event_mask);
		BUG();

	default:
		printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
		       object->state);
		BUG();
	}

	/* determine the transition from a lookup state */
lookup_transit:
	switch (fls(object->events & object->event_mask) - 1) {
	case FSCACHE_OBJECT_EV_WITHDRAW:
	case FSCACHE_OBJECT_EV_RETIRE:
	case FSCACHE_OBJECT_EV_RELEASE:
	case FSCACHE_OBJECT_EV_ERROR:
		new_state = FSCACHE_OBJECT_LC_DYING;
		goto change_state;
	case FSCACHE_OBJECT_EV_REQUEUE:
		goto done;
	case -1:
		goto done; /* sleep until event */
	default:
		goto unsupported_event;
	}

	/* determine the transition from an active state */
active_transit:
	switch (fls(object->events & object->event_mask) - 1) {
	case FSCACHE_OBJECT_EV_WITHDRAW:
	case FSCACHE_OBJECT_EV_RETIRE:
	case FSCACHE_OBJECT_EV_RELEASE:
	case FSCACHE_OBJECT_EV_ERROR:
		new_state = FSCACHE_OBJECT_DYING;
		goto change_state;
	case FSCACHE_OBJECT_EV_UPDATE:
		new_state = FSCACHE_OBJECT_UPDATING;
		goto change_state;
	case -1:
		new_state = FSCACHE_OBJECT_ACTIVE;
		goto change_state; /* sleep until event */
	default:
		goto unsupported_event;
	}

	/* determine the transition from a terminal state */
terminal_transit:
	switch (fls(object->events & object->event_mask) - 1) {
	case FSCACHE_OBJECT_EV_WITHDRAW:
		new_state = FSCACHE_OBJECT_WITHDRAWING;
		goto change_state;
	case FSCACHE_OBJECT_EV_RETIRE:
		new_state = FSCACHE_OBJECT_RECYCLING;
		goto change_state;
	case FSCACHE_OBJECT_EV_RELEASE:
		new_state = FSCACHE_OBJECT_RELEASING;
		goto change_state;
	case FSCACHE_OBJECT_EV_ERROR:
		new_state = FSCACHE_OBJECT_WITHDRAWING;
		goto change_state;
	case FSCACHE_OBJECT_EV_CLEARED:
		new_state = FSCACHE_OBJECT_DYING;
		goto change_state;
	case -1:
		goto done; /* sleep until event */
	default:
		goto unsupported_event;
	}

change_state:
	spin_lock(&object->lock);
	object->state = new_state;
	spin_unlock(&object->lock);

done:
	_leave(" [->%s]", fscache_object_states[object->state]);
	return;

unsupported_event:
	printk(KERN_ERR "FS-Cache:"
	       " Unsupported event %lx [mask %lx] in state %s\n",
	       object->events, object->event_mask,
	       fscache_object_states[object->state]);
	BUG();
}

/*
 * execute an object
 */
static void fscache_object_slow_work_execute(struct slow_work *work)
{
	struct fscache_object *object =
		container_of(work, struct fscache_object, work);
	unsigned long start;

	_enter("{OBJ%x}", object->debug_id);

	clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);

	start = jiffies;
	fscache_object_state_machine(object);
	fscache_hist(fscache_objs_histogram, start);
	if (object->events & object->event_mask)
		fscache_enqueue_object(object);
}

/*
 * initialise an object
 * - check the specified object's parent to see if we can make use of it
 *   immediately to do a creation
 * - we may need to start the process of creating a parent and we need to wait
 *   for the parent's lookup and creation to complete if it's not there yet
 * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 *   leaf-most cookies of the object and all its children
 */
static void fscache_initialise_object(struct fscache_object *object)
{
	struct fscache_object *parent;

	_enter("");
	ASSERT(object->cookie != NULL);
	ASSERT(object->cookie->parent != NULL);
	ASSERT(list_empty(&object->work.link));

	if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
			      (1 << FSCACHE_OBJECT_EV_RELEASE) |
			      (1 << FSCACHE_OBJECT_EV_RETIRE) |
			      (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
		_debug("abort init %lx", object->events);
		spin_lock(&object->lock);
		object->state = FSCACHE_OBJECT_ABORT_INIT;
		spin_unlock(&object->lock);
		return;
	}

	spin_lock(&object->cookie->lock);
	spin_lock_nested(&object->cookie->parent->lock, 1);

	parent = object->parent;
	if (!parent) {
		_debug("no parent");
		set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
	} else {
		spin_lock(&object->lock);
		spin_lock_nested(&parent->lock, 1);
		_debug("parent %s", fscache_object_states[parent->state]);

		if (parent->state >= FSCACHE_OBJECT_DYING) {
			_debug("bad parent");
			set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
		} else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
			_debug("wait");

			/* we may get woken up in this state by child objects
			 * binding on to us, so we need to make sure we don't
			 * add ourself to the list multiple times */
			if (list_empty(&object->dep_link)) {
				object->cache->ops->grab_object(object);
				list_add(&object->dep_link,
					 &parent->dependents);

				/* fscache_acquire_non_index_cookie() uses this
				 * to wake the chain up */
				if (parent->state == FSCACHE_OBJECT_INIT)
					fscache_enqueue_object(parent);
			}
		} else {
			_debug("go");
			parent->n_ops++;
			parent->n_obj_ops++;
			object->lookup_jif = jiffies;
			object->state = FSCACHE_OBJECT_LOOKING_UP;
			set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
		}

		spin_unlock(&parent->lock);
		spin_unlock(&object->lock);
	}

	spin_unlock(&object->cookie->parent->lock);
	spin_unlock(&object->cookie->lock);
	_leave("");
}

/*
 * look an object up in the cache from which it was allocated
 * - we hold an "access lock" on the parent object, so the parent object cannot
 *   be withdrawn by either party till we've finished
 * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 *   leaf-most cookies of the object and all its children
 */
static void fscache_lookup_object(struct fscache_object *object)
{
	struct fscache_cookie *cookie = object->cookie;
	struct fscache_object *parent;

	_enter("");

	parent = object->parent;
	ASSERT(parent != NULL);
	ASSERTCMP(parent->n_ops, >, 0);
	ASSERTCMP(parent->n_obj_ops, >, 0);

	/* make sure the parent is still available */
	ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);

	if (parent->state >= FSCACHE_OBJECT_DYING ||
	    test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
		_debug("unavailable");
		set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
		_leave("");
		return;
	}

	_debug("LOOKUP \"%s/%s\" in \"%s\"",
	       parent->cookie->def->name, cookie->def->name,
	       object->cache->tag->name);

	fscache_stat(&fscache_n_object_lookups);
	object->cache->ops->lookup_object(object);

	if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
		set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);

	_leave("");
}

/**
 * fscache_object_lookup_negative - Note negative cookie lookup
 * @object: Object pointing to cookie to mark
 *
 * Note negative lookup, permitting those waiting to read data from an already
 * existing backing object to continue as there's no data for them to read.
 */
void fscache_object_lookup_negative(struct fscache_object *object)
{
	struct fscache_cookie *cookie = object->cookie;

	_enter("{OBJ%x,%s}",
	       object->debug_id, fscache_object_states[object->state]);

	spin_lock(&object->lock);
	if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
		fscache_stat(&fscache_n_object_lookups_negative);

		/* transit here to allow write requests to begin stacking up
		 * and read requests to begin returning ENODATA */
		object->state = FSCACHE_OBJECT_CREATING;
		spin_unlock(&object->lock);

		set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
		set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);

		_debug("wake up lookup %p", &cookie->flags);
		smp_mb__before_clear_bit();
		clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
		smp_mb__after_clear_bit();
		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
	} else {
		ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
		spin_unlock(&object->lock);
	}

	_leave("");
}
EXPORT_SYMBOL(fscache_object_lookup_negative);

/**
 * fscache_obtained_object - Note successful object lookup or creation
 * @object: Object pointing to cookie to mark
 *
 * Note successful lookup and/or creation, permitting those waiting to write
 * data to a backing object to continue.
 *
 * Note that after calling this, an object's cookie may be relinquished by the
 * netfs, and so must be accessed with object lock held.
 */
void fscache_obtained_object(struct fscache_object *object)
{
	struct fscache_cookie *cookie = object->cookie;

	_enter("{OBJ%x,%s}",
	       object->debug_id, fscache_object_states[object->state]);

	/* if we were still looking up, then we must have a positive lookup
	 * result, in which case there may be data available */
	spin_lock(&object->lock);
	if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
		fscache_stat(&fscache_n_object_lookups_positive);

		clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);

		object->state = FSCACHE_OBJECT_AVAILABLE;
		spin_unlock(&object->lock);

		smp_mb__before_clear_bit();
		clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
		smp_mb__after_clear_bit();
		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
	} else {
		ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
		fscache_stat(&fscache_n_object_created);

		object->state = FSCACHE_OBJECT_AVAILABLE;
		spin_unlock(&object->lock);
		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
		smp_wmb();
	}

	if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);

	_leave("");
}
EXPORT_SYMBOL(fscache_obtained_object);

/*
 * handle an object that has just become available
 */
static void fscache_object_available(struct fscache_object *object)
{
	_enter("{OBJ%x}", object->debug_id);

	spin_lock(&object->lock);

	if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
		wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);

	fscache_done_parent_op(object);
	if (object->n_in_progress == 0) {
		if (object->n_ops > 0) {
			ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
			ASSERTIF(object->n_ops > object->n_obj_ops,
				 !list_empty(&object->pending_ops));
			fscache_start_operations(object);
		} else {
			ASSERT(list_empty(&object->pending_ops));
		}
	}
	spin_unlock(&object->lock);

	object->cache->ops->lookup_complete(object);
	fscache_enqueue_dependents(object);

	fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
	fscache_stat(&fscache_n_object_avail);

	_leave("");
}

/*
 * drop an object's attachments
 */
static void fscache_drop_object(struct fscache_object *object)
{
	struct fscache_object *parent = object->parent;
	struct fscache_cache *cache = object->cache;

	_enter("{OBJ%x,%d}", object->debug_id, object->n_children);

	spin_lock(&cache->object_list_lock);
	list_del_init(&object->cache_link);
	spin_unlock(&cache->object_list_lock);

	cache->ops->drop_object(object);

	if (parent) {
		_debug("release parent OBJ%x {%d}",
		       parent->debug_id, parent->n_children);

		spin_lock(&parent->lock);
		parent->n_children--;
		if (parent->n_children == 0)
			fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
		spin_unlock(&parent->lock);
		object->parent = NULL;
	}

	/* this just shifts the object release to the slow work processor */
	object->cache->ops->put_object(object);

	_leave("");
}

/*
 * release or recycle an object that the netfs has discarded
 */
static void fscache_release_object(struct fscache_object *object)
{
	_enter("");

	fscache_drop_object(object);
}

/*
 * withdraw an object from active service
 */
static void fscache_withdraw_object(struct fscache_object *object)
{
	struct fscache_cookie *cookie;
	bool detached;

	_enter("");

	spin_lock(&object->lock);
	cookie = object->cookie;
	if (cookie) {
		/* need to get the cookie lock before the object lock, starting
		 * from the object pointer */
		atomic_inc(&cookie->usage);
		spin_unlock(&object->lock);

		detached = false;
		spin_lock(&cookie->lock);
		spin_lock(&object->lock);

		if (object->cookie == cookie) {
			hlist_del_init(&object->cookie_link);
			object->cookie = NULL;
			detached = true;
		}
		spin_unlock(&cookie->lock);
		fscache_cookie_put(cookie);
		if (detached)
			fscache_cookie_put(cookie);
	}

	spin_unlock(&object->lock);

	fscache_drop_object(object);
}

/*
 * withdraw an object from active service at the behest of the cache
 * - need break the links to a cached object cookie
 * - called under two situations:
 *   (1) recycler decides to reclaim an in-use object
 *   (2) a cache is unmounted
 * - have to take care as the cookie can be being relinquished by the netfs
 *   simultaneously
 * - the object is pinned by the caller holding a refcount on it
 */
void fscache_withdrawing_object(struct fscache_cache *cache,
				struct fscache_object *object)
{
	bool enqueue = false;

	_enter(",OBJ%x", object->debug_id);

	spin_lock(&object->lock);
	if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
		object->state = FSCACHE_OBJECT_WITHDRAWING;
		enqueue = true;
	}
	spin_unlock(&object->lock);

	if (enqueue)
		fscache_enqueue_object(object);

	_leave("");
}

/*
 * allow the slow work item processor to get a ref on an object
 */
static int fscache_object_slow_work_get_ref(struct slow_work *work)
{
	struct fscache_object *object =
		container_of(work, struct fscache_object, work);

	return object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
}

/*
 * allow the slow work item processor to discard a ref on a work item
 */
static void fscache_object_slow_work_put_ref(struct slow_work *work)
{
	struct fscache_object *object =
		container_of(work, struct fscache_object, work);

	return object->cache->ops->put_object(object);
}

/*
 * enqueue an object for metadata-type processing
 */
void fscache_enqueue_object(struct fscache_object *object)
{
	_enter("{OBJ%x}", object->debug_id);

	slow_work_enqueue(&object->work);
}

/*
 * enqueue the dependents of an object for metadata-type processing
 * - the caller must hold the object's lock
 * - this may cause an already locked object to wind up being processed again
 */
static void fscache_enqueue_dependents(struct fscache_object *object)
{
	struct fscache_object *dep;

	_enter("{OBJ%x}", object->debug_id);

	if (list_empty(&object->dependents))
		return;

	spin_lock(&object->lock);

	while (!list_empty(&object->dependents)) {
		dep = list_entry(object->dependents.next,
				 struct fscache_object, dep_link);
		list_del_init(&dep->dep_link);


		/* sort onto appropriate lists */
		fscache_enqueue_object(dep);
		dep->cache->ops->put_object(dep);

		if (!list_empty(&object->dependents))
			cond_resched_lock(&object->lock);
	}

	spin_unlock(&object->lock);
}

/*
 * remove an object from whatever queue it's waiting on
 * - the caller must hold object->lock
 */
void fscache_dequeue_object(struct fscache_object *object)
{
	_enter("{OBJ%x}", object->debug_id);

	if (!list_empty(&object->dep_link)) {
		spin_lock(&object->parent->lock);
		list_del_init(&object->dep_link);
		spin_unlock(&object->parent->lock);
	}

	_leave("");
}

/**
 * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 * @object: The object to ask about
 * @data: The auxiliary data for the object
 * @datalen: The size of the auxiliary data
 *
 * This function consults the netfs about the coherency state of an object
 */
enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
					const void *data, uint16_t datalen)
{
	enum fscache_checkaux result;

	if (!object->cookie->def->check_aux) {
		fscache_stat(&fscache_n_checkaux_none);
		return FSCACHE_CHECKAUX_OKAY;
	}

	result = object->cookie->def->check_aux(object->cookie->netfs_data,
						data, datalen);
	switch (result) {
		/* entry okay as is */
	case FSCACHE_CHECKAUX_OKAY:
		fscache_stat(&fscache_n_checkaux_okay);
		break;

		/* entry requires update */
	case FSCACHE_CHECKAUX_NEEDS_UPDATE:
		fscache_stat(&fscache_n_checkaux_update);
		break;

		/* entry requires deletion */
	case FSCACHE_CHECKAUX_OBSOLETE:
		fscache_stat(&fscache_n_checkaux_obsolete);
		break;

	default:
		BUG();
	}

	return result;
}
EXPORT_SYMBOL(fscache_check_aux);