SLOW_WORK: Wait for outstanding work items belonging to a module to clear
[linux-2.6.git] / fs / fscache / object.c
1 /* FS-Cache object state machine handler
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  * See Documentation/filesystems/caching/object.txt for a description of the
12  * object state machine and the in-kernel representations.
13  */
14
15 #define FSCACHE_DEBUG_LEVEL COOKIE
16 #include <linux/module.h>
17 #include "internal.h"
18
19 const char *fscache_object_states[] = {
20         [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
21         [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
22         [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
23         [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
24         [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
25         [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
26         [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
27         [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
28         [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
29         [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
30         [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
31         [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
32         [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
33 };
34 EXPORT_SYMBOL(fscache_object_states);
35
36 static void fscache_object_slow_work_put_ref(struct slow_work *);
37 static int  fscache_object_slow_work_get_ref(struct slow_work *);
38 static void fscache_object_slow_work_execute(struct slow_work *);
39 static void fscache_initialise_object(struct fscache_object *);
40 static void fscache_lookup_object(struct fscache_object *);
41 static void fscache_object_available(struct fscache_object *);
42 static void fscache_release_object(struct fscache_object *);
43 static void fscache_withdraw_object(struct fscache_object *);
44 static void fscache_enqueue_dependents(struct fscache_object *);
45 static void fscache_dequeue_object(struct fscache_object *);
46
47 const struct slow_work_ops fscache_object_slow_work_ops = {
48         .owner          = THIS_MODULE,
49         .get_ref        = fscache_object_slow_work_get_ref,
50         .put_ref        = fscache_object_slow_work_put_ref,
51         .execute        = fscache_object_slow_work_execute,
52 };
53 EXPORT_SYMBOL(fscache_object_slow_work_ops);
54
55 /*
56  * we need to notify the parent when an op completes that we had outstanding
57  * upon it
58  */
59 static inline void fscache_done_parent_op(struct fscache_object *object)
60 {
61         struct fscache_object *parent = object->parent;
62
63         _enter("OBJ%x {OBJ%x,%x}",
64                object->debug_id, parent->debug_id, parent->n_ops);
65
66         spin_lock_nested(&parent->lock, 1);
67         parent->n_ops--;
68         parent->n_obj_ops--;
69         if (parent->n_ops == 0)
70                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
71         spin_unlock(&parent->lock);
72 }
73
74 /*
75  * process events that have been sent to an object's state machine
76  * - initiates parent lookup
77  * - does object lookup
78  * - does object creation
79  * - does object recycling and retirement
80  * - does object withdrawal
81  */
82 static void fscache_object_state_machine(struct fscache_object *object)
83 {
84         enum fscache_object_state new_state;
85
86         ASSERT(object != NULL);
87
88         _enter("{OBJ%x,%s,%lx}",
89                object->debug_id, fscache_object_states[object->state],
90                object->events);
91
92         switch (object->state) {
93                 /* wait for the parent object to become ready */
94         case FSCACHE_OBJECT_INIT:
95                 object->event_mask =
96                         ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
97                 fscache_initialise_object(object);
98                 goto done;
99
100                 /* look up the object metadata on disk */
101         case FSCACHE_OBJECT_LOOKING_UP:
102                 fscache_lookup_object(object);
103                 goto lookup_transit;
104
105                 /* create the object metadata on disk */
106         case FSCACHE_OBJECT_CREATING:
107                 fscache_lookup_object(object);
108                 goto lookup_transit;
109
110                 /* handle an object becoming available; start pending
111                  * operations and queue dependent operations for processing */
112         case FSCACHE_OBJECT_AVAILABLE:
113                 fscache_object_available(object);
114                 goto active_transit;
115
116                 /* normal running state */
117         case FSCACHE_OBJECT_ACTIVE:
118                 goto active_transit;
119
120                 /* update the object metadata on disk */
121         case FSCACHE_OBJECT_UPDATING:
122                 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
123                 fscache_stat(&fscache_n_updates_run);
124                 object->cache->ops->update_object(object);
125                 goto active_transit;
126
127                 /* handle an object dying during lookup or creation */
128         case FSCACHE_OBJECT_LC_DYING:
129                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
130                 object->cache->ops->lookup_complete(object);
131
132                 spin_lock(&object->lock);
133                 object->state = FSCACHE_OBJECT_DYING;
134                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
135                                        &object->cookie->flags))
136                         wake_up_bit(&object->cookie->flags,
137                                     FSCACHE_COOKIE_CREATING);
138                 spin_unlock(&object->lock);
139
140                 fscache_done_parent_op(object);
141
142                 /* wait for completion of all active operations on this object
143                  * and the death of all child objects of this object */
144         case FSCACHE_OBJECT_DYING:
145         dying:
146                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
147                 spin_lock(&object->lock);
148                 _debug("dying OBJ%x {%d,%d}",
149                        object->debug_id, object->n_ops, object->n_children);
150                 if (object->n_ops == 0 && object->n_children == 0) {
151                         object->event_mask &=
152                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
153                         object->event_mask |=
154                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
155                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
156                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
157                                 (1 << FSCACHE_OBJECT_EV_ERROR);
158                 } else {
159                         object->event_mask &=
160                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
161                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
162                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
163                                   (1 << FSCACHE_OBJECT_EV_ERROR));
164                         object->event_mask |=
165                                 1 << FSCACHE_OBJECT_EV_CLEARED;
166                 }
167                 spin_unlock(&object->lock);
168                 fscache_enqueue_dependents(object);
169                 goto terminal_transit;
170
171                 /* handle an abort during initialisation */
172         case FSCACHE_OBJECT_ABORT_INIT:
173                 _debug("handle abort init %lx", object->events);
174                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
175
176                 spin_lock(&object->lock);
177                 fscache_dequeue_object(object);
178
179                 object->state = FSCACHE_OBJECT_DYING;
180                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
181                                        &object->cookie->flags))
182                         wake_up_bit(&object->cookie->flags,
183                                     FSCACHE_COOKIE_CREATING);
184                 spin_unlock(&object->lock);
185                 goto dying;
186
187                 /* handle the netfs releasing an object and possibly marking it
188                  * obsolete too */
189         case FSCACHE_OBJECT_RELEASING:
190         case FSCACHE_OBJECT_RECYCLING:
191                 object->event_mask &=
192                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
193                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
194                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
195                           (1 << FSCACHE_OBJECT_EV_ERROR));
196                 fscache_release_object(object);
197                 spin_lock(&object->lock);
198                 object->state = FSCACHE_OBJECT_DEAD;
199                 spin_unlock(&object->lock);
200                 fscache_stat(&fscache_n_object_dead);
201                 goto terminal_transit;
202
203                 /* handle the parent cache of this object being withdrawn from
204                  * active service */
205         case FSCACHE_OBJECT_WITHDRAWING:
206                 object->event_mask &=
207                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
208                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
209                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
210                           (1 << FSCACHE_OBJECT_EV_ERROR));
211                 fscache_withdraw_object(object);
212                 spin_lock(&object->lock);
213                 object->state = FSCACHE_OBJECT_DEAD;
214                 spin_unlock(&object->lock);
215                 fscache_stat(&fscache_n_object_dead);
216                 goto terminal_transit;
217
218                 /* complain about the object being woken up once it is
219                  * deceased */
220         case FSCACHE_OBJECT_DEAD:
221                 printk(KERN_ERR "FS-Cache:"
222                        " Unexpected event in dead state %lx\n",
223                        object->events & object->event_mask);
224                 BUG();
225
226         default:
227                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
228                        object->state);
229                 BUG();
230         }
231
232         /* determine the transition from a lookup state */
233 lookup_transit:
234         switch (fls(object->events & object->event_mask) - 1) {
235         case FSCACHE_OBJECT_EV_WITHDRAW:
236         case FSCACHE_OBJECT_EV_RETIRE:
237         case FSCACHE_OBJECT_EV_RELEASE:
238         case FSCACHE_OBJECT_EV_ERROR:
239                 new_state = FSCACHE_OBJECT_LC_DYING;
240                 goto change_state;
241         case FSCACHE_OBJECT_EV_REQUEUE:
242                 goto done;
243         case -1:
244                 goto done; /* sleep until event */
245         default:
246                 goto unsupported_event;
247         }
248
249         /* determine the transition from an active state */
250 active_transit:
251         switch (fls(object->events & object->event_mask) - 1) {
252         case FSCACHE_OBJECT_EV_WITHDRAW:
253         case FSCACHE_OBJECT_EV_RETIRE:
254         case FSCACHE_OBJECT_EV_RELEASE:
255         case FSCACHE_OBJECT_EV_ERROR:
256                 new_state = FSCACHE_OBJECT_DYING;
257                 goto change_state;
258         case FSCACHE_OBJECT_EV_UPDATE:
259                 new_state = FSCACHE_OBJECT_UPDATING;
260                 goto change_state;
261         case -1:
262                 new_state = FSCACHE_OBJECT_ACTIVE;
263                 goto change_state; /* sleep until event */
264         default:
265                 goto unsupported_event;
266         }
267
268         /* determine the transition from a terminal state */
269 terminal_transit:
270         switch (fls(object->events & object->event_mask) - 1) {
271         case FSCACHE_OBJECT_EV_WITHDRAW:
272                 new_state = FSCACHE_OBJECT_WITHDRAWING;
273                 goto change_state;
274         case FSCACHE_OBJECT_EV_RETIRE:
275                 new_state = FSCACHE_OBJECT_RECYCLING;
276                 goto change_state;
277         case FSCACHE_OBJECT_EV_RELEASE:
278                 new_state = FSCACHE_OBJECT_RELEASING;
279                 goto change_state;
280         case FSCACHE_OBJECT_EV_ERROR:
281                 new_state = FSCACHE_OBJECT_WITHDRAWING;
282                 goto change_state;
283         case FSCACHE_OBJECT_EV_CLEARED:
284                 new_state = FSCACHE_OBJECT_DYING;
285                 goto change_state;
286         case -1:
287                 goto done; /* sleep until event */
288         default:
289                 goto unsupported_event;
290         }
291
292 change_state:
293         spin_lock(&object->lock);
294         object->state = new_state;
295         spin_unlock(&object->lock);
296
297 done:
298         _leave(" [->%s]", fscache_object_states[object->state]);
299         return;
300
301 unsupported_event:
302         printk(KERN_ERR "FS-Cache:"
303                " Unsupported event %lx [mask %lx] in state %s\n",
304                object->events, object->event_mask,
305                fscache_object_states[object->state]);
306         BUG();
307 }
308
309 /*
310  * execute an object
311  */
312 static void fscache_object_slow_work_execute(struct slow_work *work)
313 {
314         struct fscache_object *object =
315                 container_of(work, struct fscache_object, work);
316         unsigned long start;
317
318         _enter("{OBJ%x}", object->debug_id);
319
320         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
321
322         start = jiffies;
323         fscache_object_state_machine(object);
324         fscache_hist(fscache_objs_histogram, start);
325         if (object->events & object->event_mask)
326                 fscache_enqueue_object(object);
327 }
328
329 /*
330  * initialise an object
331  * - check the specified object's parent to see if we can make use of it
332  *   immediately to do a creation
333  * - we may need to start the process of creating a parent and we need to wait
334  *   for the parent's lookup and creation to complete if it's not there yet
335  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
336  *   leaf-most cookies of the object and all its children
337  */
338 static void fscache_initialise_object(struct fscache_object *object)
339 {
340         struct fscache_object *parent;
341
342         _enter("");
343         ASSERT(object->cookie != NULL);
344         ASSERT(object->cookie->parent != NULL);
345         ASSERT(list_empty(&object->work.link));
346
347         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
348                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
349                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
350                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
351                 _debug("abort init %lx", object->events);
352                 spin_lock(&object->lock);
353                 object->state = FSCACHE_OBJECT_ABORT_INIT;
354                 spin_unlock(&object->lock);
355                 return;
356         }
357
358         spin_lock(&object->cookie->lock);
359         spin_lock_nested(&object->cookie->parent->lock, 1);
360
361         parent = object->parent;
362         if (!parent) {
363                 _debug("no parent");
364                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
365         } else {
366                 spin_lock(&object->lock);
367                 spin_lock_nested(&parent->lock, 1);
368                 _debug("parent %s", fscache_object_states[parent->state]);
369
370                 if (parent->state >= FSCACHE_OBJECT_DYING) {
371                         _debug("bad parent");
372                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
373                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
374                         _debug("wait");
375
376                         /* we may get woken up in this state by child objects
377                          * binding on to us, so we need to make sure we don't
378                          * add ourself to the list multiple times */
379                         if (list_empty(&object->dep_link)) {
380                                 object->cache->ops->grab_object(object);
381                                 list_add(&object->dep_link,
382                                          &parent->dependents);
383
384                                 /* fscache_acquire_non_index_cookie() uses this
385                                  * to wake the chain up */
386                                 if (parent->state == FSCACHE_OBJECT_INIT)
387                                         fscache_enqueue_object(parent);
388                         }
389                 } else {
390                         _debug("go");
391                         parent->n_ops++;
392                         parent->n_obj_ops++;
393                         object->lookup_jif = jiffies;
394                         object->state = FSCACHE_OBJECT_LOOKING_UP;
395                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
396                 }
397
398                 spin_unlock(&parent->lock);
399                 spin_unlock(&object->lock);
400         }
401
402         spin_unlock(&object->cookie->parent->lock);
403         spin_unlock(&object->cookie->lock);
404         _leave("");
405 }
406
407 /*
408  * look an object up in the cache from which it was allocated
409  * - we hold an "access lock" on the parent object, so the parent object cannot
410  *   be withdrawn by either party till we've finished
411  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
412  *   leaf-most cookies of the object and all its children
413  */
414 static void fscache_lookup_object(struct fscache_object *object)
415 {
416         struct fscache_cookie *cookie = object->cookie;
417         struct fscache_object *parent;
418
419         _enter("");
420
421         parent = object->parent;
422         ASSERT(parent != NULL);
423         ASSERTCMP(parent->n_ops, >, 0);
424         ASSERTCMP(parent->n_obj_ops, >, 0);
425
426         /* make sure the parent is still available */
427         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
428
429         if (parent->state >= FSCACHE_OBJECT_DYING ||
430             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
431                 _debug("unavailable");
432                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
433                 _leave("");
434                 return;
435         }
436
437         _debug("LOOKUP \"%s/%s\" in \"%s\"",
438                parent->cookie->def->name, cookie->def->name,
439                object->cache->tag->name);
440
441         fscache_stat(&fscache_n_object_lookups);
442         object->cache->ops->lookup_object(object);
443
444         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
445                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
446
447         _leave("");
448 }
449
450 /**
451  * fscache_object_lookup_negative - Note negative cookie lookup
452  * @object: Object pointing to cookie to mark
453  *
454  * Note negative lookup, permitting those waiting to read data from an already
455  * existing backing object to continue as there's no data for them to read.
456  */
457 void fscache_object_lookup_negative(struct fscache_object *object)
458 {
459         struct fscache_cookie *cookie = object->cookie;
460
461         _enter("{OBJ%x,%s}",
462                object->debug_id, fscache_object_states[object->state]);
463
464         spin_lock(&object->lock);
465         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
466                 fscache_stat(&fscache_n_object_lookups_negative);
467
468                 /* transit here to allow write requests to begin stacking up
469                  * and read requests to begin returning ENODATA */
470                 object->state = FSCACHE_OBJECT_CREATING;
471                 spin_unlock(&object->lock);
472
473                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
474                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
475
476                 _debug("wake up lookup %p", &cookie->flags);
477                 smp_mb__before_clear_bit();
478                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
479                 smp_mb__after_clear_bit();
480                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
481                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
482         } else {
483                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
484                 spin_unlock(&object->lock);
485         }
486
487         _leave("");
488 }
489 EXPORT_SYMBOL(fscache_object_lookup_negative);
490
491 /**
492  * fscache_obtained_object - Note successful object lookup or creation
493  * @object: Object pointing to cookie to mark
494  *
495  * Note successful lookup and/or creation, permitting those waiting to write
496  * data to a backing object to continue.
497  *
498  * Note that after calling this, an object's cookie may be relinquished by the
499  * netfs, and so must be accessed with object lock held.
500  */
501 void fscache_obtained_object(struct fscache_object *object)
502 {
503         struct fscache_cookie *cookie = object->cookie;
504
505         _enter("{OBJ%x,%s}",
506                object->debug_id, fscache_object_states[object->state]);
507
508         /* if we were still looking up, then we must have a positive lookup
509          * result, in which case there may be data available */
510         spin_lock(&object->lock);
511         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
512                 fscache_stat(&fscache_n_object_lookups_positive);
513
514                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
515
516                 object->state = FSCACHE_OBJECT_AVAILABLE;
517                 spin_unlock(&object->lock);
518
519                 smp_mb__before_clear_bit();
520                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
521                 smp_mb__after_clear_bit();
522                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
523                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
524         } else {
525                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
526                 fscache_stat(&fscache_n_object_created);
527
528                 object->state = FSCACHE_OBJECT_AVAILABLE;
529                 spin_unlock(&object->lock);
530                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
531                 smp_wmb();
532         }
533
534         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
535                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
536
537         _leave("");
538 }
539 EXPORT_SYMBOL(fscache_obtained_object);
540
541 /*
542  * handle an object that has just become available
543  */
544 static void fscache_object_available(struct fscache_object *object)
545 {
546         _enter("{OBJ%x}", object->debug_id);
547
548         spin_lock(&object->lock);
549
550         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
551                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
552
553         fscache_done_parent_op(object);
554         if (object->n_in_progress == 0) {
555                 if (object->n_ops > 0) {
556                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
557                         ASSERTIF(object->n_ops > object->n_obj_ops,
558                                  !list_empty(&object->pending_ops));
559                         fscache_start_operations(object);
560                 } else {
561                         ASSERT(list_empty(&object->pending_ops));
562                 }
563         }
564         spin_unlock(&object->lock);
565
566         object->cache->ops->lookup_complete(object);
567         fscache_enqueue_dependents(object);
568
569         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
570         fscache_stat(&fscache_n_object_avail);
571
572         _leave("");
573 }
574
575 /*
576  * drop an object's attachments
577  */
578 static void fscache_drop_object(struct fscache_object *object)
579 {
580         struct fscache_object *parent = object->parent;
581         struct fscache_cache *cache = object->cache;
582
583         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
584
585         spin_lock(&cache->object_list_lock);
586         list_del_init(&object->cache_link);
587         spin_unlock(&cache->object_list_lock);
588
589         cache->ops->drop_object(object);
590
591         if (parent) {
592                 _debug("release parent OBJ%x {%d}",
593                        parent->debug_id, parent->n_children);
594
595                 spin_lock(&parent->lock);
596                 parent->n_children--;
597                 if (parent->n_children == 0)
598                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
599                 spin_unlock(&parent->lock);
600                 object->parent = NULL;
601         }
602
603         /* this just shifts the object release to the slow work processor */
604         object->cache->ops->put_object(object);
605
606         _leave("");
607 }
608
609 /*
610  * release or recycle an object that the netfs has discarded
611  */
612 static void fscache_release_object(struct fscache_object *object)
613 {
614         _enter("");
615
616         fscache_drop_object(object);
617 }
618
619 /*
620  * withdraw an object from active service
621  */
622 static void fscache_withdraw_object(struct fscache_object *object)
623 {
624         struct fscache_cookie *cookie;
625         bool detached;
626
627         _enter("");
628
629         spin_lock(&object->lock);
630         cookie = object->cookie;
631         if (cookie) {
632                 /* need to get the cookie lock before the object lock, starting
633                  * from the object pointer */
634                 atomic_inc(&cookie->usage);
635                 spin_unlock(&object->lock);
636
637                 detached = false;
638                 spin_lock(&cookie->lock);
639                 spin_lock(&object->lock);
640
641                 if (object->cookie == cookie) {
642                         hlist_del_init(&object->cookie_link);
643                         object->cookie = NULL;
644                         detached = true;
645                 }
646                 spin_unlock(&cookie->lock);
647                 fscache_cookie_put(cookie);
648                 if (detached)
649                         fscache_cookie_put(cookie);
650         }
651
652         spin_unlock(&object->lock);
653
654         fscache_drop_object(object);
655 }
656
657 /*
658  * withdraw an object from active service at the behest of the cache
659  * - need break the links to a cached object cookie
660  * - called under two situations:
661  *   (1) recycler decides to reclaim an in-use object
662  *   (2) a cache is unmounted
663  * - have to take care as the cookie can be being relinquished by the netfs
664  *   simultaneously
665  * - the object is pinned by the caller holding a refcount on it
666  */
667 void fscache_withdrawing_object(struct fscache_cache *cache,
668                                 struct fscache_object *object)
669 {
670         bool enqueue = false;
671
672         _enter(",OBJ%x", object->debug_id);
673
674         spin_lock(&object->lock);
675         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
676                 object->state = FSCACHE_OBJECT_WITHDRAWING;
677                 enqueue = true;
678         }
679         spin_unlock(&object->lock);
680
681         if (enqueue)
682                 fscache_enqueue_object(object);
683
684         _leave("");
685 }
686
687 /*
688  * allow the slow work item processor to get a ref on an object
689  */
690 static int fscache_object_slow_work_get_ref(struct slow_work *work)
691 {
692         struct fscache_object *object =
693                 container_of(work, struct fscache_object, work);
694
695         return object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
696 }
697
698 /*
699  * allow the slow work item processor to discard a ref on a work item
700  */
701 static void fscache_object_slow_work_put_ref(struct slow_work *work)
702 {
703         struct fscache_object *object =
704                 container_of(work, struct fscache_object, work);
705
706         return object->cache->ops->put_object(object);
707 }
708
709 /*
710  * enqueue an object for metadata-type processing
711  */
712 void fscache_enqueue_object(struct fscache_object *object)
713 {
714         _enter("{OBJ%x}", object->debug_id);
715
716         slow_work_enqueue(&object->work);
717 }
718
719 /*
720  * enqueue the dependents of an object for metadata-type processing
721  * - the caller must hold the object's lock
722  * - this may cause an already locked object to wind up being processed again
723  */
724 static void fscache_enqueue_dependents(struct fscache_object *object)
725 {
726         struct fscache_object *dep;
727
728         _enter("{OBJ%x}", object->debug_id);
729
730         if (list_empty(&object->dependents))
731                 return;
732
733         spin_lock(&object->lock);
734
735         while (!list_empty(&object->dependents)) {
736                 dep = list_entry(object->dependents.next,
737                                  struct fscache_object, dep_link);
738                 list_del_init(&dep->dep_link);
739
740
741                 /* sort onto appropriate lists */
742                 fscache_enqueue_object(dep);
743                 dep->cache->ops->put_object(dep);
744
745                 if (!list_empty(&object->dependents))
746                         cond_resched_lock(&object->lock);
747         }
748
749         spin_unlock(&object->lock);
750 }
751
752 /*
753  * remove an object from whatever queue it's waiting on
754  * - the caller must hold object->lock
755  */
756 void fscache_dequeue_object(struct fscache_object *object)
757 {
758         _enter("{OBJ%x}", object->debug_id);
759
760         if (!list_empty(&object->dep_link)) {
761                 spin_lock(&object->parent->lock);
762                 list_del_init(&object->dep_link);
763                 spin_unlock(&object->parent->lock);
764         }
765
766         _leave("");
767 }
768
769 /**
770  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
771  * @object: The object to ask about
772  * @data: The auxiliary data for the object
773  * @datalen: The size of the auxiliary data
774  *
775  * This function consults the netfs about the coherency state of an object
776  */
777 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
778                                         const void *data, uint16_t datalen)
779 {
780         enum fscache_checkaux result;
781
782         if (!object->cookie->def->check_aux) {
783                 fscache_stat(&fscache_n_checkaux_none);
784                 return FSCACHE_CHECKAUX_OKAY;
785         }
786
787         result = object->cookie->def->check_aux(object->cookie->netfs_data,
788                                                 data, datalen);
789         switch (result) {
790                 /* entry okay as is */
791         case FSCACHE_CHECKAUX_OKAY:
792                 fscache_stat(&fscache_n_checkaux_okay);
793                 break;
794
795                 /* entry requires update */
796         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
797                 fscache_stat(&fscache_n_checkaux_update);
798                 break;
799
800                 /* entry requires deletion */
801         case FSCACHE_CHECKAUX_OBSOLETE:
802                 fscache_stat(&fscache_n_checkaux_obsolete);
803                 break;
804
805         default:
806                 BUG();
807         }
808
809         return result;
810 }
811 EXPORT_SYMBOL(fscache_check_aux);