GNU Linux-libre 4.19.211-gnu1
[releases.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 <linux/slab.h>
18 #include <linux/prefetch.h>
19 #include "internal.h"
20
21 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
22 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
23 static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
24 static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
25 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
26 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
27 static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
28 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
29 static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
30 static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
31 static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
32 static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
33 static const struct fscache_state *fscache_object_dead(struct fscache_object *, int);
34
35 #define __STATE_NAME(n) fscache_osm_##n
36 #define STATE(n) (&__STATE_NAME(n))
37
38 /*
39  * Define a work state.  Work states are execution states.  No event processing
40  * is performed by them.  The function attached to a work state returns a
41  * pointer indicating the next state to which the state machine should
42  * transition.  Returning NO_TRANSIT repeats the current state, but goes back
43  * to the scheduler first.
44  */
45 #define WORK_STATE(n, sn, f) \
46         const struct fscache_state __STATE_NAME(n) = {                  \
47                 .name = #n,                                             \
48                 .short_name = sn,                                       \
49                 .work = f                                               \
50         }
51
52 /*
53  * Returns from work states.
54  */
55 #define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
56
57 #define NO_TRANSIT ((struct fscache_state *)NULL)
58
59 /*
60  * Define a wait state.  Wait states are event processing states.  No execution
61  * is performed by them.  Wait states are just tables of "if event X occurs,
62  * clear it and transition to state Y".  The dispatcher returns to the
63  * scheduler if none of the events in which the wait state has an interest are
64  * currently pending.
65  */
66 #define WAIT_STATE(n, sn, ...) \
67         const struct fscache_state __STATE_NAME(n) = {                  \
68                 .name = #n,                                             \
69                 .short_name = sn,                                       \
70                 .work = NULL,                                           \
71                 .transitions = { __VA_ARGS__, { 0, NULL } }             \
72         }
73
74 #define TRANSIT_TO(state, emask) \
75         { .events = (emask), .transit_to = STATE(state) }
76
77 /*
78  * The object state machine.
79  */
80 static WORK_STATE(INIT_OBJECT,          "INIT", fscache_initialise_object);
81 static WORK_STATE(PARENT_READY,         "PRDY", fscache_parent_ready);
82 static WORK_STATE(ABORT_INIT,           "ABRT", fscache_abort_initialisation);
83 static WORK_STATE(LOOK_UP_OBJECT,       "LOOK", fscache_look_up_object);
84 static WORK_STATE(CREATE_OBJECT,        "CRTO", fscache_look_up_object);
85 static WORK_STATE(OBJECT_AVAILABLE,     "AVBL", fscache_object_available);
86 static WORK_STATE(JUMPSTART_DEPS,       "JUMP", fscache_jumpstart_dependents);
87
88 static WORK_STATE(INVALIDATE_OBJECT,    "INVL", fscache_invalidate_object);
89 static WORK_STATE(UPDATE_OBJECT,        "UPDT", fscache_update_object);
90
91 static WORK_STATE(LOOKUP_FAILURE,       "LCFL", fscache_lookup_failure);
92 static WORK_STATE(KILL_OBJECT,          "KILL", fscache_kill_object);
93 static WORK_STATE(KILL_DEPENDENTS,      "KDEP", fscache_kill_dependents);
94 static WORK_STATE(DROP_OBJECT,          "DROP", fscache_drop_object);
95 static WORK_STATE(OBJECT_DEAD,          "DEAD", fscache_object_dead);
96
97 static WAIT_STATE(WAIT_FOR_INIT,        "?INI",
98                   TRANSIT_TO(INIT_OBJECT,       1 << FSCACHE_OBJECT_EV_NEW_CHILD));
99
100 static WAIT_STATE(WAIT_FOR_PARENT,      "?PRN",
101                   TRANSIT_TO(PARENT_READY,      1 << FSCACHE_OBJECT_EV_PARENT_READY));
102
103 static WAIT_STATE(WAIT_FOR_CMD,         "?CMD",
104                   TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
105                   TRANSIT_TO(UPDATE_OBJECT,     1 << FSCACHE_OBJECT_EV_UPDATE),
106                   TRANSIT_TO(JUMPSTART_DEPS,    1 << FSCACHE_OBJECT_EV_NEW_CHILD));
107
108 static WAIT_STATE(WAIT_FOR_CLEARANCE,   "?CLR",
109                   TRANSIT_TO(KILL_OBJECT,       1 << FSCACHE_OBJECT_EV_CLEARED));
110
111 /*
112  * Out-of-band event transition tables.  These are for handling unexpected
113  * events, such as an I/O error.  If an OOB event occurs, the state machine
114  * clears and disables the event and forces a transition to the nominated work
115  * state (acurrently executing work states will complete first).
116  *
117  * In such a situation, object->state remembers the state the machine should
118  * have been in/gone to and returning NO_TRANSIT returns to that.
119  */
120 static const struct fscache_transition fscache_osm_init_oob[] = {
121            TRANSIT_TO(ABORT_INIT,
122                       (1 << FSCACHE_OBJECT_EV_ERROR) |
123                       (1 << FSCACHE_OBJECT_EV_KILL)),
124            { 0, NULL }
125 };
126
127 static const struct fscache_transition fscache_osm_lookup_oob[] = {
128            TRANSIT_TO(LOOKUP_FAILURE,
129                       (1 << FSCACHE_OBJECT_EV_ERROR) |
130                       (1 << FSCACHE_OBJECT_EV_KILL)),
131            { 0, NULL }
132 };
133
134 static const struct fscache_transition fscache_osm_run_oob[] = {
135            TRANSIT_TO(KILL_OBJECT,
136                       (1 << FSCACHE_OBJECT_EV_ERROR) |
137                       (1 << FSCACHE_OBJECT_EV_KILL)),
138            { 0, NULL }
139 };
140
141 static int  fscache_get_object(struct fscache_object *,
142                                enum fscache_obj_ref_trace);
143 static void fscache_put_object(struct fscache_object *,
144                                enum fscache_obj_ref_trace);
145 static bool fscache_enqueue_dependents(struct fscache_object *, int);
146 static void fscache_dequeue_object(struct fscache_object *);
147 static void fscache_update_aux_data(struct fscache_object *);
148
149 /*
150  * we need to notify the parent when an op completes that we had outstanding
151  * upon it
152  */
153 static inline void fscache_done_parent_op(struct fscache_object *object)
154 {
155         struct fscache_object *parent = object->parent;
156
157         _enter("OBJ%x {OBJ%x,%x}",
158                object->debug_id, parent->debug_id, parent->n_ops);
159
160         spin_lock_nested(&parent->lock, 1);
161         parent->n_obj_ops--;
162         parent->n_ops--;
163         if (parent->n_ops == 0)
164                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
165         spin_unlock(&parent->lock);
166 }
167
168 /*
169  * Object state machine dispatcher.
170  */
171 static void fscache_object_sm_dispatcher(struct fscache_object *object)
172 {
173         const struct fscache_transition *t;
174         const struct fscache_state *state, *new_state;
175         unsigned long events, event_mask;
176         bool oob;
177         int event = -1;
178
179         ASSERT(object != NULL);
180
181         _enter("{OBJ%x,%s,%lx}",
182                object->debug_id, object->state->name, object->events);
183
184         event_mask = object->event_mask;
185 restart:
186         object->event_mask = 0; /* Mask normal event handling */
187         state = object->state;
188 restart_masked:
189         events = object->events;
190
191         /* Handle any out-of-band events (typically an error) */
192         if (events & object->oob_event_mask) {
193                 _debug("{OBJ%x} oob %lx",
194                        object->debug_id, events & object->oob_event_mask);
195                 oob = true;
196                 for (t = object->oob_table; t->events; t++) {
197                         if (events & t->events) {
198                                 state = t->transit_to;
199                                 ASSERT(state->work != NULL);
200                                 event = fls(events & t->events) - 1;
201                                 __clear_bit(event, &object->oob_event_mask);
202                                 clear_bit(event, &object->events);
203                                 goto execute_work_state;
204                         }
205                 }
206         }
207         oob = false;
208
209         /* Wait states are just transition tables */
210         if (!state->work) {
211                 if (events & event_mask) {
212                         for (t = state->transitions; t->events; t++) {
213                                 if (events & t->events) {
214                                         new_state = t->transit_to;
215                                         event = fls(events & t->events) - 1;
216                                         trace_fscache_osm(object, state,
217                                                           true, false, event);
218                                         clear_bit(event, &object->events);
219                                         _debug("{OBJ%x} ev %d: %s -> %s",
220                                                object->debug_id, event,
221                                                state->name, new_state->name);
222                                         object->state = state = new_state;
223                                         goto execute_work_state;
224                                 }
225                         }
226
227                         /* The event mask didn't include all the tabled bits */
228                         BUG();
229                 }
230                 /* Randomly woke up */
231                 goto unmask_events;
232         }
233
234 execute_work_state:
235         _debug("{OBJ%x} exec %s", object->debug_id, state->name);
236
237         trace_fscache_osm(object, state, false, oob, event);
238         new_state = state->work(object, event);
239         event = -1;
240         if (new_state == NO_TRANSIT) {
241                 _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
242                 if (unlikely(state == STATE(OBJECT_DEAD))) {
243                         _leave(" [dead]");
244                         return;
245                 }
246                 fscache_enqueue_object(object);
247                 event_mask = object->oob_event_mask;
248                 goto unmask_events;
249         }
250
251         _debug("{OBJ%x} %s -> %s",
252                object->debug_id, state->name, new_state->name);
253         object->state = state = new_state;
254
255         if (state->work) {
256                 if (unlikely(state == STATE(OBJECT_DEAD))) {
257                         _leave(" [dead]");
258                         return;
259                 }
260                 goto restart_masked;
261         }
262
263         /* Transited to wait state */
264         event_mask = object->oob_event_mask;
265         for (t = state->transitions; t->events; t++)
266                 event_mask |= t->events;
267
268 unmask_events:
269         object->event_mask = event_mask;
270         smp_mb();
271         events = object->events;
272         if (events & event_mask)
273                 goto restart;
274         _leave(" [msk %lx]", event_mask);
275 }
276
277 /*
278  * execute an object
279  */
280 static void fscache_object_work_func(struct work_struct *work)
281 {
282         struct fscache_object *object =
283                 container_of(work, struct fscache_object, work);
284         unsigned long start;
285
286         _enter("{OBJ%x}", object->debug_id);
287
288         start = jiffies;
289         fscache_object_sm_dispatcher(object);
290         fscache_hist(fscache_objs_histogram, start);
291         fscache_put_object(object, fscache_obj_put_work);
292 }
293
294 /**
295  * fscache_object_init - Initialise a cache object description
296  * @object: Object description
297  * @cookie: Cookie object will be attached to
298  * @cache: Cache in which backing object will be found
299  *
300  * Initialise a cache object description to its basic values.
301  *
302  * See Documentation/filesystems/caching/backend-api.txt for a complete
303  * description.
304  */
305 void fscache_object_init(struct fscache_object *object,
306                          struct fscache_cookie *cookie,
307                          struct fscache_cache *cache)
308 {
309         const struct fscache_transition *t;
310
311         atomic_inc(&cache->object_count);
312
313         object->state = STATE(WAIT_FOR_INIT);
314         object->oob_table = fscache_osm_init_oob;
315         object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
316         spin_lock_init(&object->lock);
317         INIT_LIST_HEAD(&object->cache_link);
318         INIT_HLIST_NODE(&object->cookie_link);
319         INIT_WORK(&object->work, fscache_object_work_func);
320         INIT_LIST_HEAD(&object->dependents);
321         INIT_LIST_HEAD(&object->dep_link);
322         INIT_LIST_HEAD(&object->pending_ops);
323         object->n_children = 0;
324         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
325         object->events = 0;
326         object->store_limit = 0;
327         object->store_limit_l = 0;
328         object->cache = cache;
329         object->cookie = cookie;
330         fscache_cookie_get(cookie, fscache_cookie_get_attach_object);
331         object->parent = NULL;
332 #ifdef CONFIG_FSCACHE_OBJECT_LIST
333         RB_CLEAR_NODE(&object->objlist_link);
334 #endif
335
336         object->oob_event_mask = 0;
337         for (t = object->oob_table; t->events; t++)
338                 object->oob_event_mask |= t->events;
339         object->event_mask = object->oob_event_mask;
340         for (t = object->state->transitions; t->events; t++)
341                 object->event_mask |= t->events;
342 }
343 EXPORT_SYMBOL(fscache_object_init);
344
345 /*
346  * Mark the object as no longer being live, making sure that we synchronise
347  * against op submission.
348  */
349 static inline void fscache_mark_object_dead(struct fscache_object *object)
350 {
351         spin_lock(&object->lock);
352         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
353         spin_unlock(&object->lock);
354 }
355
356 /*
357  * Abort object initialisation before we start it.
358  */
359 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
360                                                                 int event)
361 {
362         _enter("{OBJ%x},%d", object->debug_id, event);
363
364         object->oob_event_mask = 0;
365         fscache_dequeue_object(object);
366         return transit_to(KILL_OBJECT);
367 }
368
369 /*
370  * initialise an object
371  * - check the specified object's parent to see if we can make use of it
372  *   immediately to do a creation
373  * - we may need to start the process of creating a parent and we need to wait
374  *   for the parent's lookup and creation to complete if it's not there yet
375  */
376 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
377                                                              int event)
378 {
379         struct fscache_object *parent;
380         bool success;
381
382         _enter("{OBJ%x},%d", object->debug_id, event);
383
384         ASSERT(list_empty(&object->dep_link));
385
386         parent = object->parent;
387         if (!parent) {
388                 _leave(" [no parent]");
389                 return transit_to(DROP_OBJECT);
390         }
391
392         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
393
394         if (fscache_object_is_dying(parent)) {
395                 _leave(" [bad parent]");
396                 return transit_to(DROP_OBJECT);
397         }
398
399         if (fscache_object_is_available(parent)) {
400                 _leave(" [ready]");
401                 return transit_to(PARENT_READY);
402         }
403
404         _debug("wait");
405
406         spin_lock(&parent->lock);
407         fscache_stat(&fscache_n_cop_grab_object);
408         success = false;
409         if (fscache_object_is_live(parent) &&
410             object->cache->ops->grab_object(object, fscache_obj_get_add_to_deps)) {
411                 list_add(&object->dep_link, &parent->dependents);
412                 success = true;
413         }
414         fscache_stat_d(&fscache_n_cop_grab_object);
415         spin_unlock(&parent->lock);
416         if (!success) {
417                 _leave(" [grab failed]");
418                 return transit_to(DROP_OBJECT);
419         }
420
421         /* fscache_acquire_non_index_cookie() uses this
422          * to wake the chain up */
423         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
424         _leave(" [wait]");
425         return transit_to(WAIT_FOR_PARENT);
426 }
427
428 /*
429  * Once the parent object is ready, we should kick off our lookup op.
430  */
431 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
432                                                         int event)
433 {
434         struct fscache_object *parent = object->parent;
435
436         _enter("{OBJ%x},%d", object->debug_id, event);
437
438         ASSERT(parent != NULL);
439
440         spin_lock(&parent->lock);
441         parent->n_ops++;
442         parent->n_obj_ops++;
443         object->lookup_jif = jiffies;
444         spin_unlock(&parent->lock);
445
446         _leave("");
447         return transit_to(LOOK_UP_OBJECT);
448 }
449
450 /*
451  * look an object up in the cache from which it was allocated
452  * - we hold an "access lock" on the parent object, so the parent object cannot
453  *   be withdrawn by either party till we've finished
454  */
455 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
456                                                           int event)
457 {
458         struct fscache_cookie *cookie = object->cookie;
459         struct fscache_object *parent = object->parent;
460         int ret;
461
462         _enter("{OBJ%x},%d", object->debug_id, event);
463
464         object->oob_table = fscache_osm_lookup_oob;
465
466         ASSERT(parent != NULL);
467         ASSERTCMP(parent->n_ops, >, 0);
468         ASSERTCMP(parent->n_obj_ops, >, 0);
469
470         /* make sure the parent is still available */
471         ASSERT(fscache_object_is_available(parent));
472
473         if (fscache_object_is_dying(parent) ||
474             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
475             !fscache_use_cookie(object)) {
476                 _leave(" [unavailable]");
477                 return transit_to(LOOKUP_FAILURE);
478         }
479
480         _debug("LOOKUP \"%s\" in \"%s\"",
481                cookie->def->name, object->cache->tag->name);
482
483         fscache_stat(&fscache_n_object_lookups);
484         fscache_stat(&fscache_n_cop_lookup_object);
485         ret = object->cache->ops->lookup_object(object);
486         fscache_stat_d(&fscache_n_cop_lookup_object);
487
488         fscache_unuse_cookie(object);
489
490         if (ret == -ETIMEDOUT) {
491                 /* probably stuck behind another object, so move this one to
492                  * the back of the queue */
493                 fscache_stat(&fscache_n_object_lookups_timed_out);
494                 _leave(" [timeout]");
495                 return NO_TRANSIT;
496         }
497
498         if (ret < 0) {
499                 _leave(" [error]");
500                 return transit_to(LOOKUP_FAILURE);
501         }
502
503         _leave(" [ok]");
504         return transit_to(OBJECT_AVAILABLE);
505 }
506
507 /**
508  * fscache_object_lookup_negative - Note negative cookie lookup
509  * @object: Object pointing to cookie to mark
510  *
511  * Note negative lookup, permitting those waiting to read data from an already
512  * existing backing object to continue as there's no data for them to read.
513  */
514 void fscache_object_lookup_negative(struct fscache_object *object)
515 {
516         struct fscache_cookie *cookie = object->cookie;
517
518         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
519
520         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
521                 fscache_stat(&fscache_n_object_lookups_negative);
522
523                 /* Allow write requests to begin stacking up and read requests to begin
524                  * returning ENODATA.
525                  */
526                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
527                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
528
529                 _debug("wake up lookup %p", &cookie->flags);
530                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
531                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
532         }
533         _leave("");
534 }
535 EXPORT_SYMBOL(fscache_object_lookup_negative);
536
537 /**
538  * fscache_obtained_object - Note successful object lookup or creation
539  * @object: Object pointing to cookie to mark
540  *
541  * Note successful lookup and/or creation, permitting those waiting to write
542  * data to a backing object to continue.
543  *
544  * Note that after calling this, an object's cookie may be relinquished by the
545  * netfs, and so must be accessed with object lock held.
546  */
547 void fscache_obtained_object(struct fscache_object *object)
548 {
549         struct fscache_cookie *cookie = object->cookie;
550
551         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
552
553         /* if we were still looking up, then we must have a positive lookup
554          * result, in which case there may be data available */
555         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
556                 fscache_stat(&fscache_n_object_lookups_positive);
557
558                 /* We do (presumably) have data */
559                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
560                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
561
562                 /* Allow write requests to begin stacking up and read requests
563                  * to begin shovelling data.
564                  */
565                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
566                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
567         } else {
568                 fscache_stat(&fscache_n_object_created);
569         }
570
571         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
572         _leave("");
573 }
574 EXPORT_SYMBOL(fscache_obtained_object);
575
576 /*
577  * handle an object that has just become available
578  */
579 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
580                                                             int event)
581 {
582         _enter("{OBJ%x},%d", object->debug_id, event);
583
584         object->oob_table = fscache_osm_run_oob;
585
586         spin_lock(&object->lock);
587
588         fscache_done_parent_op(object);
589         if (object->n_in_progress == 0) {
590                 if (object->n_ops > 0) {
591                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
592                         fscache_start_operations(object);
593                 } else {
594                         ASSERT(list_empty(&object->pending_ops));
595                 }
596         }
597         spin_unlock(&object->lock);
598
599         fscache_stat(&fscache_n_cop_lookup_complete);
600         object->cache->ops->lookup_complete(object);
601         fscache_stat_d(&fscache_n_cop_lookup_complete);
602
603         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
604         fscache_stat(&fscache_n_object_avail);
605
606         _leave("");
607         return transit_to(JUMPSTART_DEPS);
608 }
609
610 /*
611  * Wake up this object's dependent objects now that we've become available.
612  */
613 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
614                                                                 int event)
615 {
616         _enter("{OBJ%x},%d", object->debug_id, event);
617
618         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
619                 return NO_TRANSIT; /* Not finished; requeue */
620         return transit_to(WAIT_FOR_CMD);
621 }
622
623 /*
624  * Handle lookup or creation failute.
625  */
626 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
627                                                           int event)
628 {
629         struct fscache_cookie *cookie;
630
631         _enter("{OBJ%x},%d", object->debug_id, event);
632
633         object->oob_event_mask = 0;
634
635         fscache_stat(&fscache_n_cop_lookup_complete);
636         object->cache->ops->lookup_complete(object);
637         fscache_stat_d(&fscache_n_cop_lookup_complete);
638
639         set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
640
641         cookie = object->cookie;
642         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
643         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
644                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
645
646         fscache_done_parent_op(object);
647         return transit_to(KILL_OBJECT);
648 }
649
650 /*
651  * Wait for completion of all active operations on this object and the death of
652  * all child objects of this object.
653  */
654 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
655                                                        int event)
656 {
657         _enter("{OBJ%x,%d,%d},%d",
658                object->debug_id, object->n_ops, object->n_children, event);
659
660         fscache_mark_object_dead(object);
661         object->oob_event_mask = 0;
662
663         if (test_bit(FSCACHE_OBJECT_RETIRED, &object->flags)) {
664                 /* Reject any new read/write ops and abort any that are pending. */
665                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
666                 fscache_cancel_all_ops(object);
667         }
668
669         if (list_empty(&object->dependents) &&
670             object->n_ops == 0 &&
671             object->n_children == 0)
672                 return transit_to(DROP_OBJECT);
673
674         if (object->n_in_progress == 0) {
675                 spin_lock(&object->lock);
676                 if (object->n_ops > 0 && object->n_in_progress == 0)
677                         fscache_start_operations(object);
678                 spin_unlock(&object->lock);
679         }
680
681         if (!list_empty(&object->dependents))
682                 return transit_to(KILL_DEPENDENTS);
683
684         return transit_to(WAIT_FOR_CLEARANCE);
685 }
686
687 /*
688  * Kill dependent objects.
689  */
690 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
691                                                            int event)
692 {
693         _enter("{OBJ%x},%d", object->debug_id, event);
694
695         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
696                 return NO_TRANSIT; /* Not finished */
697         return transit_to(WAIT_FOR_CLEARANCE);
698 }
699
700 /*
701  * Drop an object's attachments
702  */
703 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
704                                                        int event)
705 {
706         struct fscache_object *parent = object->parent;
707         struct fscache_cookie *cookie = object->cookie;
708         struct fscache_cache *cache = object->cache;
709         bool awaken = false;
710
711         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
712
713         ASSERT(cookie != NULL);
714         ASSERT(!hlist_unhashed(&object->cookie_link));
715
716         if (test_bit(FSCACHE_COOKIE_AUX_UPDATED, &cookie->flags)) {
717                 _debug("final update");
718                 fscache_update_aux_data(object);
719         }
720
721         /* Make sure the cookie no longer points here and that the netfs isn't
722          * waiting for us.
723          */
724         spin_lock(&cookie->lock);
725         hlist_del_init(&object->cookie_link);
726         if (hlist_empty(&cookie->backing_objects) &&
727             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
728                 awaken = true;
729         spin_unlock(&cookie->lock);
730
731         if (awaken)
732                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
733         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
734                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
735
736
737         /* Prevent a race with our last child, which has to signal EV_CLEARED
738          * before dropping our spinlock.
739          */
740         spin_lock(&object->lock);
741         spin_unlock(&object->lock);
742
743         /* Discard from the cache's collection of objects */
744         spin_lock(&cache->object_list_lock);
745         list_del_init(&object->cache_link);
746         spin_unlock(&cache->object_list_lock);
747
748         fscache_stat(&fscache_n_cop_drop_object);
749         cache->ops->drop_object(object);
750         fscache_stat_d(&fscache_n_cop_drop_object);
751
752         /* The parent object wants to know when all it dependents have gone */
753         if (parent) {
754                 _debug("release parent OBJ%x {%d}",
755                        parent->debug_id, parent->n_children);
756
757                 spin_lock(&parent->lock);
758                 parent->n_children--;
759                 if (parent->n_children == 0)
760                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
761                 spin_unlock(&parent->lock);
762                 object->parent = NULL;
763         }
764
765         /* this just shifts the object release to the work processor */
766         fscache_put_object(object, fscache_obj_put_drop_obj);
767         fscache_stat(&fscache_n_object_dead);
768
769         _leave("");
770         return transit_to(OBJECT_DEAD);
771 }
772
773 /*
774  * get a ref on an object
775  */
776 static int fscache_get_object(struct fscache_object *object,
777                               enum fscache_obj_ref_trace why)
778 {
779         int ret;
780
781         fscache_stat(&fscache_n_cop_grab_object);
782         ret = object->cache->ops->grab_object(object, why) ? 0 : -EAGAIN;
783         fscache_stat_d(&fscache_n_cop_grab_object);
784         return ret;
785 }
786
787 /*
788  * Discard a ref on an object
789  */
790 static void fscache_put_object(struct fscache_object *object,
791                                enum fscache_obj_ref_trace why)
792 {
793         fscache_stat(&fscache_n_cop_put_object);
794         object->cache->ops->put_object(object, why);
795         fscache_stat_d(&fscache_n_cop_put_object);
796 }
797
798 /**
799  * fscache_object_destroy - Note that a cache object is about to be destroyed
800  * @object: The object to be destroyed
801  *
802  * Note the imminent destruction and deallocation of a cache object record.
803  */
804 void fscache_object_destroy(struct fscache_object *object)
805 {
806         fscache_objlist_remove(object);
807
808         /* We can get rid of the cookie now */
809         fscache_cookie_put(object->cookie, fscache_cookie_put_object);
810         object->cookie = NULL;
811 }
812 EXPORT_SYMBOL(fscache_object_destroy);
813
814 /*
815  * enqueue an object for metadata-type processing
816  */
817 void fscache_enqueue_object(struct fscache_object *object)
818 {
819         _enter("{OBJ%x}", object->debug_id);
820
821         if (fscache_get_object(object, fscache_obj_get_queue) >= 0) {
822                 wait_queue_head_t *cong_wq =
823                         &get_cpu_var(fscache_object_cong_wait);
824
825                 if (queue_work(fscache_object_wq, &object->work)) {
826                         if (fscache_object_congested())
827                                 wake_up(cong_wq);
828                 } else
829                         fscache_put_object(object, fscache_obj_put_queue);
830
831                 put_cpu_var(fscache_object_cong_wait);
832         }
833 }
834
835 /**
836  * fscache_object_sleep_till_congested - Sleep until object wq is congested
837  * @timeoutp: Scheduler sleep timeout
838  *
839  * Allow an object handler to sleep until the object workqueue is congested.
840  *
841  * The caller must set up a wake up event before calling this and must have set
842  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
843  * condition before calling this function as no test is made here.
844  *
845  * %true is returned if the object wq is congested, %false otherwise.
846  */
847 bool fscache_object_sleep_till_congested(signed long *timeoutp)
848 {
849         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
850         DEFINE_WAIT(wait);
851
852         if (fscache_object_congested())
853                 return true;
854
855         add_wait_queue_exclusive(cong_wq, &wait);
856         if (!fscache_object_congested())
857                 *timeoutp = schedule_timeout(*timeoutp);
858         finish_wait(cong_wq, &wait);
859
860         return fscache_object_congested();
861 }
862 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
863
864 /*
865  * Enqueue the dependents of an object for metadata-type processing.
866  *
867  * If we don't manage to finish the list before the scheduler wants to run
868  * again then return false immediately.  We return true if the list was
869  * cleared.
870  */
871 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
872 {
873         struct fscache_object *dep;
874         bool ret = true;
875
876         _enter("{OBJ%x}", object->debug_id);
877
878         if (list_empty(&object->dependents))
879                 return true;
880
881         spin_lock(&object->lock);
882
883         while (!list_empty(&object->dependents)) {
884                 dep = list_entry(object->dependents.next,
885                                  struct fscache_object, dep_link);
886                 list_del_init(&dep->dep_link);
887
888                 fscache_raise_event(dep, event);
889                 fscache_put_object(dep, fscache_obj_put_enq_dep);
890
891                 if (!list_empty(&object->dependents) && need_resched()) {
892                         ret = false;
893                         break;
894                 }
895         }
896
897         spin_unlock(&object->lock);
898         return ret;
899 }
900
901 /*
902  * remove an object from whatever queue it's waiting on
903  */
904 static void fscache_dequeue_object(struct fscache_object *object)
905 {
906         _enter("{OBJ%x}", object->debug_id);
907
908         if (!list_empty(&object->dep_link)) {
909                 spin_lock(&object->parent->lock);
910                 list_del_init(&object->dep_link);
911                 spin_unlock(&object->parent->lock);
912         }
913
914         _leave("");
915 }
916
917 /**
918  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
919  * @object: The object to ask about
920  * @data: The auxiliary data for the object
921  * @datalen: The size of the auxiliary data
922  *
923  * This function consults the netfs about the coherency state of an object.
924  * The caller must be holding a ref on cookie->n_active (held by
925  * fscache_look_up_object() on behalf of the cache backend during object lookup
926  * and creation).
927  */
928 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
929                                         const void *data, uint16_t datalen,
930                                         loff_t object_size)
931 {
932         enum fscache_checkaux result;
933
934         if (!object->cookie->def->check_aux) {
935                 fscache_stat(&fscache_n_checkaux_none);
936                 return FSCACHE_CHECKAUX_OKAY;
937         }
938
939         result = object->cookie->def->check_aux(object->cookie->netfs_data,
940                                                 data, datalen, object_size);
941         switch (result) {
942                 /* entry okay as is */
943         case FSCACHE_CHECKAUX_OKAY:
944                 fscache_stat(&fscache_n_checkaux_okay);
945                 break;
946
947                 /* entry requires update */
948         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
949                 fscache_stat(&fscache_n_checkaux_update);
950                 break;
951
952                 /* entry requires deletion */
953         case FSCACHE_CHECKAUX_OBSOLETE:
954                 fscache_stat(&fscache_n_checkaux_obsolete);
955                 break;
956
957         default:
958                 BUG();
959         }
960
961         return result;
962 }
963 EXPORT_SYMBOL(fscache_check_aux);
964
965 /*
966  * Asynchronously invalidate an object.
967  */
968 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
969                                                               int event)
970 {
971         struct fscache_operation *op;
972         struct fscache_cookie *cookie = object->cookie;
973
974         _enter("{OBJ%x},%d", object->debug_id, event);
975
976         /* We're going to need the cookie.  If the cookie is not available then
977          * retire the object instead.
978          */
979         if (!fscache_use_cookie(object)) {
980                 ASSERT(radix_tree_empty(&object->cookie->stores));
981                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
982                 _leave(" [no cookie]");
983                 return transit_to(KILL_OBJECT);
984         }
985
986         /* Reject any new read/write ops and abort any that are pending. */
987         fscache_invalidate_writes(cookie);
988         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
989         fscache_cancel_all_ops(object);
990
991         /* Now we have to wait for in-progress reads and writes */
992         op = kzalloc(sizeof(*op), GFP_KERNEL);
993         if (!op)
994                 goto nomem;
995
996         fscache_operation_init(cookie, op, object->cache->ops->invalidate_object,
997                                NULL, NULL);
998         op->flags = FSCACHE_OP_ASYNC |
999                 (1 << FSCACHE_OP_EXCLUSIVE) |
1000                 (1 << FSCACHE_OP_UNUSE_COOKIE);
1001         trace_fscache_page_op(cookie, NULL, op, fscache_page_op_invalidate);
1002
1003         spin_lock(&cookie->lock);
1004         if (fscache_submit_exclusive_op(object, op) < 0)
1005                 goto submit_op_failed;
1006         spin_unlock(&cookie->lock);
1007         fscache_put_operation(op);
1008
1009         /* Once we've completed the invalidation, we know there will be no data
1010          * stored in the cache and thus we can reinstate the data-check-skip
1011          * optimisation.
1012          */
1013         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1014
1015         /* We can allow read and write requests to come in once again.  They'll
1016          * queue up behind our exclusive invalidation operation.
1017          */
1018         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
1019                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
1020         _leave(" [ok]");
1021         return transit_to(UPDATE_OBJECT);
1022
1023 nomem:
1024         fscache_mark_object_dead(object);
1025         fscache_unuse_cookie(object);
1026         _leave(" [ENOMEM]");
1027         return transit_to(KILL_OBJECT);
1028
1029 submit_op_failed:
1030         fscache_mark_object_dead(object);
1031         spin_unlock(&cookie->lock);
1032         fscache_unuse_cookie(object);
1033         kfree(op);
1034         _leave(" [EIO]");
1035         return transit_to(KILL_OBJECT);
1036 }
1037
1038 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1039                                                              int event)
1040 {
1041         const struct fscache_state *s;
1042
1043         fscache_stat(&fscache_n_invalidates_run);
1044         fscache_stat(&fscache_n_cop_invalidate_object);
1045         s = _fscache_invalidate_object(object, event);
1046         fscache_stat_d(&fscache_n_cop_invalidate_object);
1047         return s;
1048 }
1049
1050 /*
1051  * Update auxiliary data.
1052  */
1053 static void fscache_update_aux_data(struct fscache_object *object)
1054 {
1055         fscache_stat(&fscache_n_updates_run);
1056         fscache_stat(&fscache_n_cop_update_object);
1057         object->cache->ops->update_object(object);
1058         fscache_stat_d(&fscache_n_cop_update_object);
1059 }
1060
1061 /*
1062  * Asynchronously update an object.
1063  */
1064 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1065                                                          int event)
1066 {
1067         _enter("{OBJ%x},%d", object->debug_id, event);
1068
1069         fscache_update_aux_data(object);
1070
1071         _leave("");
1072         return transit_to(WAIT_FOR_CMD);
1073 }
1074
1075 /**
1076  * fscache_object_retrying_stale - Note retrying stale object
1077  * @object: The object that will be retried
1078  *
1079  * Note that an object lookup found an on-disk object that was adjudged to be
1080  * stale and has been deleted.  The lookup will be retried.
1081  */
1082 void fscache_object_retrying_stale(struct fscache_object *object)
1083 {
1084         fscache_stat(&fscache_n_cache_no_space_reject);
1085 }
1086 EXPORT_SYMBOL(fscache_object_retrying_stale);
1087
1088 /**
1089  * fscache_object_mark_killed - Note that an object was killed
1090  * @object: The object that was culled
1091  * @why: The reason the object was killed.
1092  *
1093  * Note that an object was killed.  Returns true if the object was
1094  * already marked killed, false if it wasn't.
1095  */
1096 void fscache_object_mark_killed(struct fscache_object *object,
1097                                 enum fscache_why_object_killed why)
1098 {
1099         if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1100                 pr_err("Error: Object already killed by cache [%s]\n",
1101                        object->cache->identifier);
1102                 return;
1103         }
1104
1105         switch (why) {
1106         case FSCACHE_OBJECT_NO_SPACE:
1107                 fscache_stat(&fscache_n_cache_no_space_reject);
1108                 break;
1109         case FSCACHE_OBJECT_IS_STALE:
1110                 fscache_stat(&fscache_n_cache_stale_objects);
1111                 break;
1112         case FSCACHE_OBJECT_WAS_RETIRED:
1113                 fscache_stat(&fscache_n_cache_retired_objects);
1114                 break;
1115         case FSCACHE_OBJECT_WAS_CULLED:
1116                 fscache_stat(&fscache_n_cache_culled_objects);
1117                 break;
1118         }
1119 }
1120 EXPORT_SYMBOL(fscache_object_mark_killed);
1121
1122 /*
1123  * The object is dead.  We can get here if an object gets queued by an event
1124  * that would lead to its death (such as EV_KILL) when the dispatcher is
1125  * already running (and so can be requeued) but hasn't yet cleared the event
1126  * mask.
1127  */
1128 static const struct fscache_state *fscache_object_dead(struct fscache_object *object,
1129                                                        int event)
1130 {
1131         if (!test_and_set_bit(FSCACHE_OBJECT_RUN_AFTER_DEAD,
1132                               &object->flags))
1133                 return NO_TRANSIT;
1134
1135         WARN(true, "FS-Cache object redispatched after death");
1136         return NO_TRANSIT;
1137 }