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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
21static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
22static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
23static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
24static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
25static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
26static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
27static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
28static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
29static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
30static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
31static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
32static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
33
34#define __STATE_NAME(n) fscache_osm_##n
35#define STATE(n) (&__STATE_NAME(n))
36
37/*
38 * Define a work state. Work states are execution states. No event processing
39 * is performed by them. The function attached to a work state returns a
40 * pointer indicating the next state to which the state machine should
41 * transition. Returning NO_TRANSIT repeats the current state, but goes back
42 * to the scheduler first.
43 */
44#define WORK_STATE(n, sn, f) \
45 const struct fscache_state __STATE_NAME(n) = { \
46 .name = #n, \
47 .short_name = sn, \
48 .work = f \
49 }
50
51/*
52 * Returns from work states.
53 */
54#define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
55
56#define NO_TRANSIT ((struct fscache_state *)NULL)
57
58/*
59 * Define a wait state. Wait states are event processing states. No execution
60 * is performed by them. Wait states are just tables of "if event X occurs,
61 * clear it and transition to state Y". The dispatcher returns to the
62 * scheduler if none of the events in which the wait state has an interest are
63 * currently pending.
64 */
65#define WAIT_STATE(n, sn, ...) \
66 const struct fscache_state __STATE_NAME(n) = { \
67 .name = #n, \
68 .short_name = sn, \
69 .work = NULL, \
70 .transitions = { __VA_ARGS__, { 0, NULL } } \
71 }
72
73#define TRANSIT_TO(state, emask) \
74 { .events = (emask), .transit_to = STATE(state) }
75
76/*
77 * The object state machine.
78 */
79static WORK_STATE(INIT_OBJECT, "INIT", fscache_initialise_object);
80static WORK_STATE(PARENT_READY, "PRDY", fscache_parent_ready);
81static WORK_STATE(ABORT_INIT, "ABRT", fscache_abort_initialisation);
82static WORK_STATE(LOOK_UP_OBJECT, "LOOK", fscache_look_up_object);
83static WORK_STATE(CREATE_OBJECT, "CRTO", fscache_look_up_object);
84static WORK_STATE(OBJECT_AVAILABLE, "AVBL", fscache_object_available);
85static WORK_STATE(JUMPSTART_DEPS, "JUMP", fscache_jumpstart_dependents);
86
87static WORK_STATE(INVALIDATE_OBJECT, "INVL", fscache_invalidate_object);
88static WORK_STATE(UPDATE_OBJECT, "UPDT", fscache_update_object);
89
90static WORK_STATE(LOOKUP_FAILURE, "LCFL", fscache_lookup_failure);
91static WORK_STATE(KILL_OBJECT, "KILL", fscache_kill_object);
92static WORK_STATE(KILL_DEPENDENTS, "KDEP", fscache_kill_dependents);
93static WORK_STATE(DROP_OBJECT, "DROP", fscache_drop_object);
94static WORK_STATE(OBJECT_DEAD, "DEAD", (void*)2UL);
95
96static WAIT_STATE(WAIT_FOR_INIT, "?INI",
97 TRANSIT_TO(INIT_OBJECT, 1 << FSCACHE_OBJECT_EV_NEW_CHILD));
98
99static WAIT_STATE(WAIT_FOR_PARENT, "?PRN",
100 TRANSIT_TO(PARENT_READY, 1 << FSCACHE_OBJECT_EV_PARENT_READY));
101
102static WAIT_STATE(WAIT_FOR_CMD, "?CMD",
103 TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
104 TRANSIT_TO(UPDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_UPDATE),
105 TRANSIT_TO(JUMPSTART_DEPS, 1 << FSCACHE_OBJECT_EV_NEW_CHILD));
106
107static WAIT_STATE(WAIT_FOR_CLEARANCE, "?CLR",
108 TRANSIT_TO(KILL_OBJECT, 1 << FSCACHE_OBJECT_EV_CLEARED));
109
110/*
111 * Out-of-band event transition tables. These are for handling unexpected
112 * events, such as an I/O error. If an OOB event occurs, the state machine
113 * clears and disables the event and forces a transition to the nominated work
114 * state (acurrently executing work states will complete first).
115 *
116 * In such a situation, object->state remembers the state the machine should
117 * have been in/gone to and returning NO_TRANSIT returns to that.
118 */
119static const struct fscache_transition fscache_osm_init_oob[] = {
120 TRANSIT_TO(ABORT_INIT,
121 (1 << FSCACHE_OBJECT_EV_ERROR) |
122 (1 << FSCACHE_OBJECT_EV_KILL)),
123 { 0, NULL }
124};
125
126static const struct fscache_transition fscache_osm_lookup_oob[] = {
127 TRANSIT_TO(LOOKUP_FAILURE,
128 (1 << FSCACHE_OBJECT_EV_ERROR) |
129 (1 << FSCACHE_OBJECT_EV_KILL)),
130 { 0, NULL }
131};
132
133static const struct fscache_transition fscache_osm_run_oob[] = {
134 TRANSIT_TO(KILL_OBJECT,
135 (1 << FSCACHE_OBJECT_EV_ERROR) |
136 (1 << FSCACHE_OBJECT_EV_KILL)),
137 { 0, NULL }
138};
139
140static int fscache_get_object(struct fscache_object *);
141static void fscache_put_object(struct fscache_object *);
142static bool fscache_enqueue_dependents(struct fscache_object *, int);
143static void fscache_dequeue_object(struct fscache_object *);
144
145/*
146 * we need to notify the parent when an op completes that we had outstanding
147 * upon it
148 */
149static inline void fscache_done_parent_op(struct fscache_object *object)
150{
151 struct fscache_object *parent = object->parent;
152
153 _enter("OBJ%x {OBJ%x,%x}",
154 object->debug_id, parent->debug_id, parent->n_ops);
155
156 spin_lock_nested(&parent->lock, 1);
157 parent->n_obj_ops--;
158 parent->n_ops--;
159 if (parent->n_ops == 0)
160 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
161 spin_unlock(&parent->lock);
162}
163
164/*
165 * Object state machine dispatcher.
166 */
167static void fscache_object_sm_dispatcher(struct fscache_object *object)
168{
169 const struct fscache_transition *t;
170 const struct fscache_state *state, *new_state;
171 unsigned long events, event_mask;
172 int event = -1;
173
174 ASSERT(object != NULL);
175
176 _enter("{OBJ%x,%s,%lx}",
177 object->debug_id, object->state->name, object->events);
178
179 event_mask = object->event_mask;
180restart:
181 object->event_mask = 0; /* Mask normal event handling */
182 state = object->state;
183restart_masked:
184 events = object->events;
185
186 /* Handle any out-of-band events (typically an error) */
187 if (events & object->oob_event_mask) {
188 _debug("{OBJ%x} oob %lx",
189 object->debug_id, events & object->oob_event_mask);
190 for (t = object->oob_table; t->events; t++) {
191 if (events & t->events) {
192 state = t->transit_to;
193 ASSERT(state->work != NULL);
194 event = fls(events & t->events) - 1;
195 __clear_bit(event, &object->oob_event_mask);
196 clear_bit(event, &object->events);
197 goto execute_work_state;
198 }
199 }
200 }
201
202 /* Wait states are just transition tables */
203 if (!state->work) {
204 if (events & event_mask) {
205 for (t = state->transitions; t->events; t++) {
206 if (events & t->events) {
207 new_state = t->transit_to;
208 event = fls(events & t->events) - 1;
209 clear_bit(event, &object->events);
210 _debug("{OBJ%x} ev %d: %s -> %s",
211 object->debug_id, event,
212 state->name, new_state->name);
213 object->state = state = new_state;
214 goto execute_work_state;
215 }
216 }
217
218 /* The event mask didn't include all the tabled bits */
219 BUG();
220 }
221 /* Randomly woke up */
222 goto unmask_events;
223 }
224
225execute_work_state:
226 _debug("{OBJ%x} exec %s", object->debug_id, state->name);
227
228 new_state = state->work(object, event);
229 event = -1;
230 if (new_state == NO_TRANSIT) {
231 _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
232 fscache_enqueue_object(object);
233 event_mask = object->oob_event_mask;
234 goto unmask_events;
235 }
236
237 _debug("{OBJ%x} %s -> %s",
238 object->debug_id, state->name, new_state->name);
239 object->state = state = new_state;
240
241 if (state->work) {
242 if (unlikely(state->work == ((void *)2UL))) {
243 _leave(" [dead]");
244 return;
245 }
246 goto restart_masked;
247 }
248
249 /* Transited to wait state */
250 event_mask = object->oob_event_mask;
251 for (t = state->transitions; t->events; t++)
252 event_mask |= t->events;
253
254unmask_events:
255 object->event_mask = event_mask;
256 smp_mb();
257 events = object->events;
258 if (events & event_mask)
259 goto restart;
260 _leave(" [msk %lx]", event_mask);
261}
262
263/*
264 * execute an object
265 */
266static void fscache_object_work_func(struct work_struct *work)
267{
268 struct fscache_object *object =
269 container_of(work, struct fscache_object, work);
270 unsigned long start;
271
272 _enter("{OBJ%x}", object->debug_id);
273
274 start = jiffies;
275 fscache_object_sm_dispatcher(object);
276 fscache_hist(fscache_objs_histogram, start);
277 fscache_put_object(object);
278}
279
280/**
281 * fscache_object_init - Initialise a cache object description
282 * @object: Object description
283 * @cookie: Cookie object will be attached to
284 * @cache: Cache in which backing object will be found
285 *
286 * Initialise a cache object description to its basic values.
287 *
288 * See Documentation/filesystems/caching/backend-api.txt for a complete
289 * description.
290 */
291void fscache_object_init(struct fscache_object *object,
292 struct fscache_cookie *cookie,
293 struct fscache_cache *cache)
294{
295 const struct fscache_transition *t;
296
297 atomic_inc(&cache->object_count);
298
299 object->state = STATE(WAIT_FOR_INIT);
300 object->oob_table = fscache_osm_init_oob;
301 object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
302 spin_lock_init(&object->lock);
303 INIT_LIST_HEAD(&object->cache_link);
304 INIT_HLIST_NODE(&object->cookie_link);
305 INIT_WORK(&object->work, fscache_object_work_func);
306 INIT_LIST_HEAD(&object->dependents);
307 INIT_LIST_HEAD(&object->dep_link);
308 INIT_LIST_HEAD(&object->pending_ops);
309 object->n_children = 0;
310 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
311 object->events = 0;
312 object->store_limit = 0;
313 object->store_limit_l = 0;
314 object->cache = cache;
315 object->cookie = cookie;
316 object->parent = NULL;
317#ifdef CONFIG_FSCACHE_OBJECT_LIST
318 RB_CLEAR_NODE(&object->objlist_link);
319#endif
320
321 object->oob_event_mask = 0;
322 for (t = object->oob_table; t->events; t++)
323 object->oob_event_mask |= t->events;
324 object->event_mask = object->oob_event_mask;
325 for (t = object->state->transitions; t->events; t++)
326 object->event_mask |= t->events;
327}
328EXPORT_SYMBOL(fscache_object_init);
329
330/*
331 * Mark the object as no longer being live, making sure that we synchronise
332 * against op submission.
333 */
334static inline void fscache_mark_object_dead(struct fscache_object *object)
335{
336 spin_lock(&object->lock);
337 clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
338 spin_unlock(&object->lock);
339}
340
341/*
342 * Abort object initialisation before we start it.
343 */
344static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
345 int event)
346{
347 _enter("{OBJ%x},%d", object->debug_id, event);
348
349 object->oob_event_mask = 0;
350 fscache_dequeue_object(object);
351 return transit_to(KILL_OBJECT);
352}
353
354/*
355 * initialise an object
356 * - check the specified object's parent to see if we can make use of it
357 * immediately to do a creation
358 * - we may need to start the process of creating a parent and we need to wait
359 * for the parent's lookup and creation to complete if it's not there yet
360 */
361static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
362 int event)
363{
364 struct fscache_object *parent;
365 bool success;
366
367 _enter("{OBJ%x},%d", object->debug_id, event);
368
369 ASSERT(list_empty(&object->dep_link));
370
371 parent = object->parent;
372 if (!parent) {
373 _leave(" [no parent]");
374 return transit_to(DROP_OBJECT);
375 }
376
377 _debug("parent: %s of:%lx", parent->state->name, parent->flags);
378
379 if (fscache_object_is_dying(parent)) {
380 _leave(" [bad parent]");
381 return transit_to(DROP_OBJECT);
382 }
383
384 if (fscache_object_is_available(parent)) {
385 _leave(" [ready]");
386 return transit_to(PARENT_READY);
387 }
388
389 _debug("wait");
390
391 spin_lock(&parent->lock);
392 fscache_stat(&fscache_n_cop_grab_object);
393 success = false;
394 if (fscache_object_is_live(parent) &&
395 object->cache->ops->grab_object(object)) {
396 list_add(&object->dep_link, &parent->dependents);
397 success = true;
398 }
399 fscache_stat_d(&fscache_n_cop_grab_object);
400 spin_unlock(&parent->lock);
401 if (!success) {
402 _leave(" [grab failed]");
403 return transit_to(DROP_OBJECT);
404 }
405
406 /* fscache_acquire_non_index_cookie() uses this
407 * to wake the chain up */
408 fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
409 _leave(" [wait]");
410 return transit_to(WAIT_FOR_PARENT);
411}
412
413/*
414 * Once the parent object is ready, we should kick off our lookup op.
415 */
416static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
417 int event)
418{
419 struct fscache_object *parent = object->parent;
420
421 _enter("{OBJ%x},%d", object->debug_id, event);
422
423 ASSERT(parent != NULL);
424
425 spin_lock(&parent->lock);
426 parent->n_ops++;
427 parent->n_obj_ops++;
428 object->lookup_jif = jiffies;
429 spin_unlock(&parent->lock);
430
431 _leave("");
432 return transit_to(LOOK_UP_OBJECT);
433}
434
435/*
436 * look an object up in the cache from which it was allocated
437 * - we hold an "access lock" on the parent object, so the parent object cannot
438 * be withdrawn by either party till we've finished
439 */
440static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
441 int event)
442{
443 struct fscache_cookie *cookie = object->cookie;
444 struct fscache_object *parent = object->parent;
445 int ret;
446
447 _enter("{OBJ%x},%d", object->debug_id, event);
448
449 object->oob_table = fscache_osm_lookup_oob;
450
451 ASSERT(parent != NULL);
452 ASSERTCMP(parent->n_ops, >, 0);
453 ASSERTCMP(parent->n_obj_ops, >, 0);
454
455 /* make sure the parent is still available */
456 ASSERT(fscache_object_is_available(parent));
457
458 if (fscache_object_is_dying(parent) ||
459 test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
460 !fscache_use_cookie(object)) {
461 _leave(" [unavailable]");
462 return transit_to(LOOKUP_FAILURE);
463 }
464
465 _debug("LOOKUP \"%s\" in \"%s\"",
466 cookie->def->name, object->cache->tag->name);
467
468 fscache_stat(&fscache_n_object_lookups);
469 fscache_stat(&fscache_n_cop_lookup_object);
470 ret = object->cache->ops->lookup_object(object);
471 fscache_stat_d(&fscache_n_cop_lookup_object);
472
473 fscache_unuse_cookie(object);
474
475 if (ret == -ETIMEDOUT) {
476 /* probably stuck behind another object, so move this one to
477 * the back of the queue */
478 fscache_stat(&fscache_n_object_lookups_timed_out);
479 _leave(" [timeout]");
480 return NO_TRANSIT;
481 }
482
483 if (ret < 0) {
484 _leave(" [error]");
485 return transit_to(LOOKUP_FAILURE);
486 }
487
488 _leave(" [ok]");
489 return transit_to(OBJECT_AVAILABLE);
490}
491
492/**
493 * fscache_object_lookup_negative - Note negative cookie lookup
494 * @object: Object pointing to cookie to mark
495 *
496 * Note negative lookup, permitting those waiting to read data from an already
497 * existing backing object to continue as there's no data for them to read.
498 */
499void fscache_object_lookup_negative(struct fscache_object *object)
500{
501 struct fscache_cookie *cookie = object->cookie;
502
503 _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
504
505 if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
506 fscache_stat(&fscache_n_object_lookups_negative);
507
508 /* Allow write requests to begin stacking up and read requests to begin
509 * returning ENODATA.
510 */
511 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
512 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
513
514 _debug("wake up lookup %p", &cookie->flags);
515 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
516 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
517 }
518 _leave("");
519}
520EXPORT_SYMBOL(fscache_object_lookup_negative);
521
522/**
523 * fscache_obtained_object - Note successful object lookup or creation
524 * @object: Object pointing to cookie to mark
525 *
526 * Note successful lookup and/or creation, permitting those waiting to write
527 * data to a backing object to continue.
528 *
529 * Note that after calling this, an object's cookie may be relinquished by the
530 * netfs, and so must be accessed with object lock held.
531 */
532void fscache_obtained_object(struct fscache_object *object)
533{
534 struct fscache_cookie *cookie = object->cookie;
535
536 _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
537
538 /* if we were still looking up, then we must have a positive lookup
539 * result, in which case there may be data available */
540 if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
541 fscache_stat(&fscache_n_object_lookups_positive);
542
543 /* We do (presumably) have data */
544 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
545 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
546
547 /* Allow write requests to begin stacking up and read requests
548 * to begin shovelling data.
549 */
550 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
551 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
552 } else {
553 fscache_stat(&fscache_n_object_created);
554 }
555
556 set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
557 _leave("");
558}
559EXPORT_SYMBOL(fscache_obtained_object);
560
561/*
562 * handle an object that has just become available
563 */
564static const struct fscache_state *fscache_object_available(struct fscache_object *object,
565 int event)
566{
567 _enter("{OBJ%x},%d", object->debug_id, event);
568
569 object->oob_table = fscache_osm_run_oob;
570
571 spin_lock(&object->lock);
572
573 fscache_done_parent_op(object);
574 if (object->n_in_progress == 0) {
575 if (object->n_ops > 0) {
576 ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
577 fscache_start_operations(object);
578 } else {
579 ASSERT(list_empty(&object->pending_ops));
580 }
581 }
582 spin_unlock(&object->lock);
583
584 fscache_stat(&fscache_n_cop_lookup_complete);
585 object->cache->ops->lookup_complete(object);
586 fscache_stat_d(&fscache_n_cop_lookup_complete);
587
588 fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
589 fscache_stat(&fscache_n_object_avail);
590
591 _leave("");
592 return transit_to(JUMPSTART_DEPS);
593}
594
595/*
596 * Wake up this object's dependent objects now that we've become available.
597 */
598static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
599 int event)
600{
601 _enter("{OBJ%x},%d", object->debug_id, event);
602
603 if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
604 return NO_TRANSIT; /* Not finished; requeue */
605 return transit_to(WAIT_FOR_CMD);
606}
607
608/*
609 * Handle lookup or creation failute.
610 */
611static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
612 int event)
613{
614 struct fscache_cookie *cookie;
615
616 _enter("{OBJ%x},%d", object->debug_id, event);
617
618 object->oob_event_mask = 0;
619
620 fscache_stat(&fscache_n_cop_lookup_complete);
621 object->cache->ops->lookup_complete(object);
622 fscache_stat_d(&fscache_n_cop_lookup_complete);
623
624 set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
625
626 cookie = object->cookie;
627 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
628 if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
629 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
630
631 fscache_done_parent_op(object);
632 return transit_to(KILL_OBJECT);
633}
634
635/*
636 * Wait for completion of all active operations on this object and the death of
637 * all child objects of this object.
638 */
639static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
640 int event)
641{
642 _enter("{OBJ%x,%d,%d},%d",
643 object->debug_id, object->n_ops, object->n_children, event);
644
645 fscache_mark_object_dead(object);
646 object->oob_event_mask = 0;
647
648 if (list_empty(&object->dependents) &&
649 object->n_ops == 0 &&
650 object->n_children == 0)
651 return transit_to(DROP_OBJECT);
652
653 if (object->n_in_progress == 0) {
654 spin_lock(&object->lock);
655 if (object->n_ops > 0 && object->n_in_progress == 0)
656 fscache_start_operations(object);
657 spin_unlock(&object->lock);
658 }
659
660 if (!list_empty(&object->dependents))
661 return transit_to(KILL_DEPENDENTS);
662
663 return transit_to(WAIT_FOR_CLEARANCE);
664}
665
666/*
667 * Kill dependent objects.
668 */
669static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
670 int event)
671{
672 _enter("{OBJ%x},%d", object->debug_id, event);
673
674 if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
675 return NO_TRANSIT; /* Not finished */
676 return transit_to(WAIT_FOR_CLEARANCE);
677}
678
679/*
680 * Drop an object's attachments
681 */
682static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
683 int event)
684{
685 struct fscache_object *parent = object->parent;
686 struct fscache_cookie *cookie = object->cookie;
687 struct fscache_cache *cache = object->cache;
688 bool awaken = false;
689
690 _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
691
692 ASSERT(cookie != NULL);
693 ASSERT(!hlist_unhashed(&object->cookie_link));
694
695 /* Make sure the cookie no longer points here and that the netfs isn't
696 * waiting for us.
697 */
698 spin_lock(&cookie->lock);
699 hlist_del_init(&object->cookie_link);
700 if (hlist_empty(&cookie->backing_objects) &&
701 test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
702 awaken = true;
703 spin_unlock(&cookie->lock);
704
705 if (awaken)
706 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
707
708 /* Prevent a race with our last child, which has to signal EV_CLEARED
709 * before dropping our spinlock.
710 */
711 spin_lock(&object->lock);
712 spin_unlock(&object->lock);
713
714 /* Discard from the cache's collection of objects */
715 spin_lock(&cache->object_list_lock);
716 list_del_init(&object->cache_link);
717 spin_unlock(&cache->object_list_lock);
718
719 fscache_stat(&fscache_n_cop_drop_object);
720 cache->ops->drop_object(object);
721 fscache_stat_d(&fscache_n_cop_drop_object);
722
723 /* The parent object wants to know when all it dependents have gone */
724 if (parent) {
725 _debug("release parent OBJ%x {%d}",
726 parent->debug_id, parent->n_children);
727
728 spin_lock(&parent->lock);
729 parent->n_children--;
730 if (parent->n_children == 0)
731 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
732 spin_unlock(&parent->lock);
733 object->parent = NULL;
734 }
735
736 /* this just shifts the object release to the work processor */
737 fscache_put_object(object);
738 fscache_stat(&fscache_n_object_dead);
739
740 _leave("");
741 return transit_to(OBJECT_DEAD);
742}
743
744/*
745 * get a ref on an object
746 */
747static int fscache_get_object(struct fscache_object *object)
748{
749 int ret;
750
751 fscache_stat(&fscache_n_cop_grab_object);
752 ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
753 fscache_stat_d(&fscache_n_cop_grab_object);
754 return ret;
755}
756
757/*
758 * Discard a ref on an object
759 */
760static void fscache_put_object(struct fscache_object *object)
761{
762 fscache_stat(&fscache_n_cop_put_object);
763 object->cache->ops->put_object(object);
764 fscache_stat_d(&fscache_n_cop_put_object);
765}
766
767/**
768 * fscache_object_destroy - Note that a cache object is about to be destroyed
769 * @object: The object to be destroyed
770 *
771 * Note the imminent destruction and deallocation of a cache object record.
772 */
773void fscache_object_destroy(struct fscache_object *object)
774{
775 fscache_objlist_remove(object);
776
777 /* We can get rid of the cookie now */
778 fscache_cookie_put(object->cookie);
779 object->cookie = NULL;
780}
781EXPORT_SYMBOL(fscache_object_destroy);
782
783/*
784 * enqueue an object for metadata-type processing
785 */
786void fscache_enqueue_object(struct fscache_object *object)
787{
788 _enter("{OBJ%x}", object->debug_id);
789
790 if (fscache_get_object(object) >= 0) {
791 wait_queue_head_t *cong_wq =
792 &get_cpu_var(fscache_object_cong_wait);
793
794 if (queue_work(fscache_object_wq, &object->work)) {
795 if (fscache_object_congested())
796 wake_up(cong_wq);
797 } else
798 fscache_put_object(object);
799
800 put_cpu_var(fscache_object_cong_wait);
801 }
802}
803
804/**
805 * fscache_object_sleep_till_congested - Sleep until object wq is congested
806 * @timeoutp: Scheduler sleep timeout
807 *
808 * Allow an object handler to sleep until the object workqueue is congested.
809 *
810 * The caller must set up a wake up event before calling this and must have set
811 * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
812 * condition before calling this function as no test is made here.
813 *
814 * %true is returned if the object wq is congested, %false otherwise.
815 */
816bool fscache_object_sleep_till_congested(signed long *timeoutp)
817{
818 wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
819 DEFINE_WAIT(wait);
820
821 if (fscache_object_congested())
822 return true;
823
824 add_wait_queue_exclusive(cong_wq, &wait);
825 if (!fscache_object_congested())
826 *timeoutp = schedule_timeout(*timeoutp);
827 finish_wait(cong_wq, &wait);
828
829 return fscache_object_congested();
830}
831EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
832
833/*
834 * Enqueue the dependents of an object for metadata-type processing.
835 *
836 * If we don't manage to finish the list before the scheduler wants to run
837 * again then return false immediately. We return true if the list was
838 * cleared.
839 */
840static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
841{
842 struct fscache_object *dep;
843 bool ret = true;
844
845 _enter("{OBJ%x}", object->debug_id);
846
847 if (list_empty(&object->dependents))
848 return true;
849
850 spin_lock(&object->lock);
851
852 while (!list_empty(&object->dependents)) {
853 dep = list_entry(object->dependents.next,
854 struct fscache_object, dep_link);
855 list_del_init(&dep->dep_link);
856
857 fscache_raise_event(dep, event);
858 fscache_put_object(dep);
859
860 if (!list_empty(&object->dependents) && need_resched()) {
861 ret = false;
862 break;
863 }
864 }
865
866 spin_unlock(&object->lock);
867 return ret;
868}
869
870/*
871 * remove an object from whatever queue it's waiting on
872 */
873static void fscache_dequeue_object(struct fscache_object *object)
874{
875 _enter("{OBJ%x}", object->debug_id);
876
877 if (!list_empty(&object->dep_link)) {
878 spin_lock(&object->parent->lock);
879 list_del_init(&object->dep_link);
880 spin_unlock(&object->parent->lock);
881 }
882
883 _leave("");
884}
885
886/**
887 * fscache_check_aux - Ask the netfs whether an object on disk is still valid
888 * @object: The object to ask about
889 * @data: The auxiliary data for the object
890 * @datalen: The size of the auxiliary data
891 *
892 * This function consults the netfs about the coherency state of an object.
893 * The caller must be holding a ref on cookie->n_active (held by
894 * fscache_look_up_object() on behalf of the cache backend during object lookup
895 * and creation).
896 */
897enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
898 const void *data, uint16_t datalen)
899{
900 enum fscache_checkaux result;
901
902 if (!object->cookie->def->check_aux) {
903 fscache_stat(&fscache_n_checkaux_none);
904 return FSCACHE_CHECKAUX_OKAY;
905 }
906
907 result = object->cookie->def->check_aux(object->cookie->netfs_data,
908 data, datalen);
909 switch (result) {
910 /* entry okay as is */
911 case FSCACHE_CHECKAUX_OKAY:
912 fscache_stat(&fscache_n_checkaux_okay);
913 break;
914
915 /* entry requires update */
916 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
917 fscache_stat(&fscache_n_checkaux_update);
918 break;
919
920 /* entry requires deletion */
921 case FSCACHE_CHECKAUX_OBSOLETE:
922 fscache_stat(&fscache_n_checkaux_obsolete);
923 break;
924
925 default:
926 BUG();
927 }
928
929 return result;
930}
931EXPORT_SYMBOL(fscache_check_aux);
932
933/*
934 * Asynchronously invalidate an object.
935 */
936static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
937 int event)
938{
939 struct fscache_operation *op;
940 struct fscache_cookie *cookie = object->cookie;
941
942 _enter("{OBJ%x},%d", object->debug_id, event);
943
944 /* We're going to need the cookie. If the cookie is not available then
945 * retire the object instead.
946 */
947 if (!fscache_use_cookie(object)) {
948 ASSERT(object->cookie->stores.rnode == NULL);
949 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
950 _leave(" [no cookie]");
951 return transit_to(KILL_OBJECT);
952 }
953
954 /* Reject any new read/write ops and abort any that are pending. */
955 fscache_invalidate_writes(cookie);
956 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
957 fscache_cancel_all_ops(object);
958
959 /* Now we have to wait for in-progress reads and writes */
960 op = kzalloc(sizeof(*op), GFP_KERNEL);
961 if (!op)
962 goto nomem;
963
964 fscache_operation_init(op, object->cache->ops->invalidate_object,
965 NULL, NULL);
966 op->flags = FSCACHE_OP_ASYNC |
967 (1 << FSCACHE_OP_EXCLUSIVE) |
968 (1 << FSCACHE_OP_UNUSE_COOKIE);
969
970 spin_lock(&cookie->lock);
971 if (fscache_submit_exclusive_op(object, op) < 0)
972 goto submit_op_failed;
973 spin_unlock(&cookie->lock);
974 fscache_put_operation(op);
975
976 /* Once we've completed the invalidation, we know there will be no data
977 * stored in the cache and thus we can reinstate the data-check-skip
978 * optimisation.
979 */
980 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
981
982 /* We can allow read and write requests to come in once again. They'll
983 * queue up behind our exclusive invalidation operation.
984 */
985 if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
986 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
987 _leave(" [ok]");
988 return transit_to(UPDATE_OBJECT);
989
990nomem:
991 fscache_mark_object_dead(object);
992 fscache_unuse_cookie(object);
993 _leave(" [ENOMEM]");
994 return transit_to(KILL_OBJECT);
995
996submit_op_failed:
997 fscache_mark_object_dead(object);
998 spin_unlock(&cookie->lock);
999 fscache_unuse_cookie(object);
1000 kfree(op);
1001 _leave(" [EIO]");
1002 return transit_to(KILL_OBJECT);
1003}
1004
1005static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1006 int event)
1007{
1008 const struct fscache_state *s;
1009
1010 fscache_stat(&fscache_n_invalidates_run);
1011 fscache_stat(&fscache_n_cop_invalidate_object);
1012 s = _fscache_invalidate_object(object, event);
1013 fscache_stat_d(&fscache_n_cop_invalidate_object);
1014 return s;
1015}
1016
1017/*
1018 * Asynchronously update an object.
1019 */
1020static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1021 int event)
1022{
1023 _enter("{OBJ%x},%d", object->debug_id, event);
1024
1025 fscache_stat(&fscache_n_updates_run);
1026 fscache_stat(&fscache_n_cop_update_object);
1027 object->cache->ops->update_object(object);
1028 fscache_stat_d(&fscache_n_cop_update_object);
1029
1030 _leave("");
1031 return transit_to(WAIT_FOR_CMD);
1032}
1033
1034/**
1035 * fscache_object_retrying_stale - Note retrying stale object
1036 * @object: The object that will be retried
1037 *
1038 * Note that an object lookup found an on-disk object that was adjudged to be
1039 * stale and has been deleted. The lookup will be retried.
1040 */
1041void fscache_object_retrying_stale(struct fscache_object *object)
1042{
1043 fscache_stat(&fscache_n_cache_no_space_reject);
1044}
1045EXPORT_SYMBOL(fscache_object_retrying_stale);
1046
1047/**
1048 * fscache_object_mark_killed - Note that an object was killed
1049 * @object: The object that was culled
1050 * @why: The reason the object was killed.
1051 *
1052 * Note that an object was killed. Returns true if the object was
1053 * already marked killed, false if it wasn't.
1054 */
1055void fscache_object_mark_killed(struct fscache_object *object,
1056 enum fscache_why_object_killed why)
1057{
1058 if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1059 pr_err("Error: Object already killed by cache [%s]\n",
1060 object->cache->identifier);
1061 return;
1062 }
1063
1064 switch (why) {
1065 case FSCACHE_OBJECT_NO_SPACE:
1066 fscache_stat(&fscache_n_cache_no_space_reject);
1067 break;
1068 case FSCACHE_OBJECT_IS_STALE:
1069 fscache_stat(&fscache_n_cache_stale_objects);
1070 break;
1071 case FSCACHE_OBJECT_WAS_RETIRED:
1072 fscache_stat(&fscache_n_cache_retired_objects);
1073 break;
1074 case FSCACHE_OBJECT_WAS_CULLED:
1075 fscache_stat(&fscache_n_cache_culled_objects);
1076 break;
1077 }
1078}
1079EXPORT_SYMBOL(fscache_object_mark_killed);
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
19const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
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};
34EXPORT_SYMBOL(fscache_object_states);
35
36const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
37 [FSCACHE_OBJECT_INIT] = "INIT",
38 [FSCACHE_OBJECT_LOOKING_UP] = "LOOK",
39 [FSCACHE_OBJECT_CREATING] = "CRTN",
40 [FSCACHE_OBJECT_AVAILABLE] = "AVBL",
41 [FSCACHE_OBJECT_ACTIVE] = "ACTV",
42 [FSCACHE_OBJECT_UPDATING] = "UPDT",
43 [FSCACHE_OBJECT_DYING] = "DYNG",
44 [FSCACHE_OBJECT_LC_DYING] = "LCDY",
45 [FSCACHE_OBJECT_ABORT_INIT] = "ABTI",
46 [FSCACHE_OBJECT_RELEASING] = "RELS",
47 [FSCACHE_OBJECT_RECYCLING] = "RCYC",
48 [FSCACHE_OBJECT_WITHDRAWING] = "WTHD",
49 [FSCACHE_OBJECT_DEAD] = "DEAD",
50};
51
52static int fscache_get_object(struct fscache_object *);
53static void fscache_put_object(struct fscache_object *);
54static void fscache_initialise_object(struct fscache_object *);
55static void fscache_lookup_object(struct fscache_object *);
56static void fscache_object_available(struct fscache_object *);
57static void fscache_release_object(struct fscache_object *);
58static void fscache_withdraw_object(struct fscache_object *);
59static void fscache_enqueue_dependents(struct fscache_object *);
60static void fscache_dequeue_object(struct fscache_object *);
61
62/*
63 * we need to notify the parent when an op completes that we had outstanding
64 * upon it
65 */
66static inline void fscache_done_parent_op(struct fscache_object *object)
67{
68 struct fscache_object *parent = object->parent;
69
70 _enter("OBJ%x {OBJ%x,%x}",
71 object->debug_id, parent->debug_id, parent->n_ops);
72
73 spin_lock_nested(&parent->lock, 1);
74 parent->n_ops--;
75 parent->n_obj_ops--;
76 if (parent->n_ops == 0)
77 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
78 spin_unlock(&parent->lock);
79}
80
81/*
82 * process events that have been sent to an object's state machine
83 * - initiates parent lookup
84 * - does object lookup
85 * - does object creation
86 * - does object recycling and retirement
87 * - does object withdrawal
88 */
89static void fscache_object_state_machine(struct fscache_object *object)
90{
91 enum fscache_object_state new_state;
92 struct fscache_cookie *cookie;
93
94 ASSERT(object != NULL);
95
96 _enter("{OBJ%x,%s,%lx}",
97 object->debug_id, fscache_object_states[object->state],
98 object->events);
99
100 switch (object->state) {
101 /* wait for the parent object to become ready */
102 case FSCACHE_OBJECT_INIT:
103 object->event_mask =
104 ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
105 fscache_initialise_object(object);
106 goto done;
107
108 /* look up the object metadata on disk */
109 case FSCACHE_OBJECT_LOOKING_UP:
110 fscache_lookup_object(object);
111 goto lookup_transit;
112
113 /* create the object metadata on disk */
114 case FSCACHE_OBJECT_CREATING:
115 fscache_lookup_object(object);
116 goto lookup_transit;
117
118 /* handle an object becoming available; start pending
119 * operations and queue dependent operations for processing */
120 case FSCACHE_OBJECT_AVAILABLE:
121 fscache_object_available(object);
122 goto active_transit;
123
124 /* normal running state */
125 case FSCACHE_OBJECT_ACTIVE:
126 goto active_transit;
127
128 /* update the object metadata on disk */
129 case FSCACHE_OBJECT_UPDATING:
130 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
131 fscache_stat(&fscache_n_updates_run);
132 fscache_stat(&fscache_n_cop_update_object);
133 object->cache->ops->update_object(object);
134 fscache_stat_d(&fscache_n_cop_update_object);
135 goto active_transit;
136
137 /* handle an object dying during lookup or creation */
138 case FSCACHE_OBJECT_LC_DYING:
139 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
140 fscache_stat(&fscache_n_cop_lookup_complete);
141 object->cache->ops->lookup_complete(object);
142 fscache_stat_d(&fscache_n_cop_lookup_complete);
143
144 spin_lock(&object->lock);
145 object->state = FSCACHE_OBJECT_DYING;
146 cookie = object->cookie;
147 if (cookie) {
148 if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
149 &cookie->flags))
150 wake_up_bit(&cookie->flags,
151 FSCACHE_COOKIE_LOOKING_UP);
152 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
153 &cookie->flags))
154 wake_up_bit(&cookie->flags,
155 FSCACHE_COOKIE_CREATING);
156 }
157 spin_unlock(&object->lock);
158
159 fscache_done_parent_op(object);
160
161 /* wait for completion of all active operations on this object
162 * and the death of all child objects of this object */
163 case FSCACHE_OBJECT_DYING:
164 dying:
165 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
166 spin_lock(&object->lock);
167 _debug("dying OBJ%x {%d,%d}",
168 object->debug_id, object->n_ops, object->n_children);
169 if (object->n_ops == 0 && object->n_children == 0) {
170 object->event_mask &=
171 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
172 object->event_mask |=
173 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
174 (1 << FSCACHE_OBJECT_EV_RETIRE) |
175 (1 << FSCACHE_OBJECT_EV_RELEASE) |
176 (1 << FSCACHE_OBJECT_EV_ERROR);
177 } else {
178 object->event_mask &=
179 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
180 (1 << FSCACHE_OBJECT_EV_RETIRE) |
181 (1 << FSCACHE_OBJECT_EV_RELEASE) |
182 (1 << FSCACHE_OBJECT_EV_ERROR));
183 object->event_mask |=
184 1 << FSCACHE_OBJECT_EV_CLEARED;
185 }
186 spin_unlock(&object->lock);
187 fscache_enqueue_dependents(object);
188 fscache_start_operations(object);
189 goto terminal_transit;
190
191 /* handle an abort during initialisation */
192 case FSCACHE_OBJECT_ABORT_INIT:
193 _debug("handle abort init %lx", object->events);
194 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
195
196 spin_lock(&object->lock);
197 fscache_dequeue_object(object);
198
199 object->state = FSCACHE_OBJECT_DYING;
200 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
201 &object->cookie->flags))
202 wake_up_bit(&object->cookie->flags,
203 FSCACHE_COOKIE_CREATING);
204 spin_unlock(&object->lock);
205 goto dying;
206
207 /* handle the netfs releasing an object and possibly marking it
208 * obsolete too */
209 case FSCACHE_OBJECT_RELEASING:
210 case FSCACHE_OBJECT_RECYCLING:
211 object->event_mask &=
212 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
213 (1 << FSCACHE_OBJECT_EV_RETIRE) |
214 (1 << FSCACHE_OBJECT_EV_RELEASE) |
215 (1 << FSCACHE_OBJECT_EV_ERROR));
216 fscache_release_object(object);
217 spin_lock(&object->lock);
218 object->state = FSCACHE_OBJECT_DEAD;
219 spin_unlock(&object->lock);
220 fscache_stat(&fscache_n_object_dead);
221 goto terminal_transit;
222
223 /* handle the parent cache of this object being withdrawn from
224 * active service */
225 case FSCACHE_OBJECT_WITHDRAWING:
226 object->event_mask &=
227 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
228 (1 << FSCACHE_OBJECT_EV_RETIRE) |
229 (1 << FSCACHE_OBJECT_EV_RELEASE) |
230 (1 << FSCACHE_OBJECT_EV_ERROR));
231 fscache_withdraw_object(object);
232 spin_lock(&object->lock);
233 object->state = FSCACHE_OBJECT_DEAD;
234 spin_unlock(&object->lock);
235 fscache_stat(&fscache_n_object_dead);
236 goto terminal_transit;
237
238 /* complain about the object being woken up once it is
239 * deceased */
240 case FSCACHE_OBJECT_DEAD:
241 printk(KERN_ERR "FS-Cache:"
242 " Unexpected event in dead state %lx\n",
243 object->events & object->event_mask);
244 BUG();
245
246 default:
247 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
248 object->state);
249 BUG();
250 }
251
252 /* determine the transition from a lookup state */
253lookup_transit:
254 switch (fls(object->events & object->event_mask) - 1) {
255 case FSCACHE_OBJECT_EV_WITHDRAW:
256 case FSCACHE_OBJECT_EV_RETIRE:
257 case FSCACHE_OBJECT_EV_RELEASE:
258 case FSCACHE_OBJECT_EV_ERROR:
259 new_state = FSCACHE_OBJECT_LC_DYING;
260 goto change_state;
261 case FSCACHE_OBJECT_EV_REQUEUE:
262 goto done;
263 case -1:
264 goto done; /* sleep until event */
265 default:
266 goto unsupported_event;
267 }
268
269 /* determine the transition from an active state */
270active_transit:
271 switch (fls(object->events & object->event_mask) - 1) {
272 case FSCACHE_OBJECT_EV_WITHDRAW:
273 case FSCACHE_OBJECT_EV_RETIRE:
274 case FSCACHE_OBJECT_EV_RELEASE:
275 case FSCACHE_OBJECT_EV_ERROR:
276 new_state = FSCACHE_OBJECT_DYING;
277 goto change_state;
278 case FSCACHE_OBJECT_EV_UPDATE:
279 new_state = FSCACHE_OBJECT_UPDATING;
280 goto change_state;
281 case -1:
282 new_state = FSCACHE_OBJECT_ACTIVE;
283 goto change_state; /* sleep until event */
284 default:
285 goto unsupported_event;
286 }
287
288 /* determine the transition from a terminal state */
289terminal_transit:
290 switch (fls(object->events & object->event_mask) - 1) {
291 case FSCACHE_OBJECT_EV_WITHDRAW:
292 new_state = FSCACHE_OBJECT_WITHDRAWING;
293 goto change_state;
294 case FSCACHE_OBJECT_EV_RETIRE:
295 new_state = FSCACHE_OBJECT_RECYCLING;
296 goto change_state;
297 case FSCACHE_OBJECT_EV_RELEASE:
298 new_state = FSCACHE_OBJECT_RELEASING;
299 goto change_state;
300 case FSCACHE_OBJECT_EV_ERROR:
301 new_state = FSCACHE_OBJECT_WITHDRAWING;
302 goto change_state;
303 case FSCACHE_OBJECT_EV_CLEARED:
304 new_state = FSCACHE_OBJECT_DYING;
305 goto change_state;
306 case -1:
307 goto done; /* sleep until event */
308 default:
309 goto unsupported_event;
310 }
311
312change_state:
313 spin_lock(&object->lock);
314 object->state = new_state;
315 spin_unlock(&object->lock);
316
317done:
318 _leave(" [->%s]", fscache_object_states[object->state]);
319 return;
320
321unsupported_event:
322 printk(KERN_ERR "FS-Cache:"
323 " Unsupported event %lx [mask %lx] in state %s\n",
324 object->events, object->event_mask,
325 fscache_object_states[object->state]);
326 BUG();
327}
328
329/*
330 * execute an object
331 */
332void fscache_object_work_func(struct work_struct *work)
333{
334 struct fscache_object *object =
335 container_of(work, struct fscache_object, work);
336 unsigned long start;
337
338 _enter("{OBJ%x}", object->debug_id);
339
340 start = jiffies;
341 fscache_object_state_machine(object);
342 fscache_hist(fscache_objs_histogram, start);
343 if (object->events & object->event_mask)
344 fscache_enqueue_object(object);
345 clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
346 fscache_put_object(object);
347}
348EXPORT_SYMBOL(fscache_object_work_func);
349
350/*
351 * initialise an object
352 * - check the specified object's parent to see if we can make use of it
353 * immediately to do a creation
354 * - we may need to start the process of creating a parent and we need to wait
355 * for the parent's lookup and creation to complete if it's not there yet
356 * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
357 * leaf-most cookies of the object and all its children
358 */
359static void fscache_initialise_object(struct fscache_object *object)
360{
361 struct fscache_object *parent;
362
363 _enter("");
364 ASSERT(object->cookie != NULL);
365 ASSERT(object->cookie->parent != NULL);
366
367 if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
368 (1 << FSCACHE_OBJECT_EV_RELEASE) |
369 (1 << FSCACHE_OBJECT_EV_RETIRE) |
370 (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
371 _debug("abort init %lx", object->events);
372 spin_lock(&object->lock);
373 object->state = FSCACHE_OBJECT_ABORT_INIT;
374 spin_unlock(&object->lock);
375 return;
376 }
377
378 spin_lock(&object->cookie->lock);
379 spin_lock_nested(&object->cookie->parent->lock, 1);
380
381 parent = object->parent;
382 if (!parent) {
383 _debug("no parent");
384 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
385 } else {
386 spin_lock(&object->lock);
387 spin_lock_nested(&parent->lock, 1);
388 _debug("parent %s", fscache_object_states[parent->state]);
389
390 if (parent->state >= FSCACHE_OBJECT_DYING) {
391 _debug("bad parent");
392 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
393 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
394 _debug("wait");
395
396 /* we may get woken up in this state by child objects
397 * binding on to us, so we need to make sure we don't
398 * add ourself to the list multiple times */
399 if (list_empty(&object->dep_link)) {
400 fscache_stat(&fscache_n_cop_grab_object);
401 object->cache->ops->grab_object(object);
402 fscache_stat_d(&fscache_n_cop_grab_object);
403 list_add(&object->dep_link,
404 &parent->dependents);
405
406 /* fscache_acquire_non_index_cookie() uses this
407 * to wake the chain up */
408 if (parent->state == FSCACHE_OBJECT_INIT)
409 fscache_enqueue_object(parent);
410 }
411 } else {
412 _debug("go");
413 parent->n_ops++;
414 parent->n_obj_ops++;
415 object->lookup_jif = jiffies;
416 object->state = FSCACHE_OBJECT_LOOKING_UP;
417 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
418 }
419
420 spin_unlock(&parent->lock);
421 spin_unlock(&object->lock);
422 }
423
424 spin_unlock(&object->cookie->parent->lock);
425 spin_unlock(&object->cookie->lock);
426 _leave("");
427}
428
429/*
430 * look an object up in the cache from which it was allocated
431 * - we hold an "access lock" on the parent object, so the parent object cannot
432 * be withdrawn by either party till we've finished
433 * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
434 * leaf-most cookies of the object and all its children
435 */
436static void fscache_lookup_object(struct fscache_object *object)
437{
438 struct fscache_cookie *cookie = object->cookie;
439 struct fscache_object *parent;
440 int ret;
441
442 _enter("");
443
444 parent = object->parent;
445 ASSERT(parent != NULL);
446 ASSERTCMP(parent->n_ops, >, 0);
447 ASSERTCMP(parent->n_obj_ops, >, 0);
448
449 /* make sure the parent is still available */
450 ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
451
452 if (parent->state >= FSCACHE_OBJECT_DYING ||
453 test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
454 _debug("unavailable");
455 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
456 _leave("");
457 return;
458 }
459
460 _debug("LOOKUP \"%s/%s\" in \"%s\"",
461 parent->cookie->def->name, cookie->def->name,
462 object->cache->tag->name);
463
464 fscache_stat(&fscache_n_object_lookups);
465 fscache_stat(&fscache_n_cop_lookup_object);
466 ret = object->cache->ops->lookup_object(object);
467 fscache_stat_d(&fscache_n_cop_lookup_object);
468
469 if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
470 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
471
472 if (ret == -ETIMEDOUT) {
473 /* probably stuck behind another object, so move this one to
474 * the back of the queue */
475 fscache_stat(&fscache_n_object_lookups_timed_out);
476 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
477 }
478
479 _leave("");
480}
481
482/**
483 * fscache_object_lookup_negative - Note negative cookie lookup
484 * @object: Object pointing to cookie to mark
485 *
486 * Note negative lookup, permitting those waiting to read data from an already
487 * existing backing object to continue as there's no data for them to read.
488 */
489void fscache_object_lookup_negative(struct fscache_object *object)
490{
491 struct fscache_cookie *cookie = object->cookie;
492
493 _enter("{OBJ%x,%s}",
494 object->debug_id, fscache_object_states[object->state]);
495
496 spin_lock(&object->lock);
497 if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
498 fscache_stat(&fscache_n_object_lookups_negative);
499
500 /* transit here to allow write requests to begin stacking up
501 * and read requests to begin returning ENODATA */
502 object->state = FSCACHE_OBJECT_CREATING;
503 spin_unlock(&object->lock);
504
505 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
506 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
507
508 _debug("wake up lookup %p", &cookie->flags);
509 smp_mb__before_clear_bit();
510 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
511 smp_mb__after_clear_bit();
512 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
513 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
514 } else {
515 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
516 spin_unlock(&object->lock);
517 }
518
519 _leave("");
520}
521EXPORT_SYMBOL(fscache_object_lookup_negative);
522
523/**
524 * fscache_obtained_object - Note successful object lookup or creation
525 * @object: Object pointing to cookie to mark
526 *
527 * Note successful lookup and/or creation, permitting those waiting to write
528 * data to a backing object to continue.
529 *
530 * Note that after calling this, an object's cookie may be relinquished by the
531 * netfs, and so must be accessed with object lock held.
532 */
533void fscache_obtained_object(struct fscache_object *object)
534{
535 struct fscache_cookie *cookie = object->cookie;
536
537 _enter("{OBJ%x,%s}",
538 object->debug_id, fscache_object_states[object->state]);
539
540 /* if we were still looking up, then we must have a positive lookup
541 * result, in which case there may be data available */
542 spin_lock(&object->lock);
543 if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
544 fscache_stat(&fscache_n_object_lookups_positive);
545
546 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
547
548 object->state = FSCACHE_OBJECT_AVAILABLE;
549 spin_unlock(&object->lock);
550
551 smp_mb__before_clear_bit();
552 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
553 smp_mb__after_clear_bit();
554 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
555 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
556 } else {
557 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
558 fscache_stat(&fscache_n_object_created);
559
560 object->state = FSCACHE_OBJECT_AVAILABLE;
561 spin_unlock(&object->lock);
562 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
563 smp_wmb();
564 }
565
566 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
567 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
568
569 _leave("");
570}
571EXPORT_SYMBOL(fscache_obtained_object);
572
573/*
574 * handle an object that has just become available
575 */
576static void fscache_object_available(struct fscache_object *object)
577{
578 _enter("{OBJ%x}", object->debug_id);
579
580 spin_lock(&object->lock);
581
582 if (object->cookie &&
583 test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
584 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
585
586 fscache_done_parent_op(object);
587 if (object->n_in_progress == 0) {
588 if (object->n_ops > 0) {
589 ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
590 ASSERTIF(object->n_ops > object->n_obj_ops,
591 !list_empty(&object->pending_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 fscache_enqueue_dependents(object);
603
604 fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
605 fscache_stat(&fscache_n_object_avail);
606
607 _leave("");
608}
609
610/*
611 * drop an object's attachments
612 */
613static void fscache_drop_object(struct fscache_object *object)
614{
615 struct fscache_object *parent = object->parent;
616 struct fscache_cache *cache = object->cache;
617
618 _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
619
620 ASSERTCMP(object->cookie, ==, NULL);
621 ASSERT(hlist_unhashed(&object->cookie_link));
622
623 spin_lock(&cache->object_list_lock);
624 list_del_init(&object->cache_link);
625 spin_unlock(&cache->object_list_lock);
626
627 fscache_stat(&fscache_n_cop_drop_object);
628 cache->ops->drop_object(object);
629 fscache_stat_d(&fscache_n_cop_drop_object);
630
631 if (parent) {
632 _debug("release parent OBJ%x {%d}",
633 parent->debug_id, parent->n_children);
634
635 spin_lock(&parent->lock);
636 parent->n_children--;
637 if (parent->n_children == 0)
638 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
639 spin_unlock(&parent->lock);
640 object->parent = NULL;
641 }
642
643 /* this just shifts the object release to the work processor */
644 fscache_put_object(object);
645
646 _leave("");
647}
648
649/*
650 * release or recycle an object that the netfs has discarded
651 */
652static void fscache_release_object(struct fscache_object *object)
653{
654 _enter("");
655
656 fscache_drop_object(object);
657}
658
659/*
660 * withdraw an object from active service
661 */
662static void fscache_withdraw_object(struct fscache_object *object)
663{
664 struct fscache_cookie *cookie;
665 bool detached;
666
667 _enter("");
668
669 spin_lock(&object->lock);
670 cookie = object->cookie;
671 if (cookie) {
672 /* need to get the cookie lock before the object lock, starting
673 * from the object pointer */
674 atomic_inc(&cookie->usage);
675 spin_unlock(&object->lock);
676
677 detached = false;
678 spin_lock(&cookie->lock);
679 spin_lock(&object->lock);
680
681 if (object->cookie == cookie) {
682 hlist_del_init(&object->cookie_link);
683 object->cookie = NULL;
684 detached = true;
685 }
686 spin_unlock(&cookie->lock);
687 fscache_cookie_put(cookie);
688 if (detached)
689 fscache_cookie_put(cookie);
690 }
691
692 spin_unlock(&object->lock);
693
694 fscache_drop_object(object);
695}
696
697/*
698 * withdraw an object from active service at the behest of the cache
699 * - need break the links to a cached object cookie
700 * - called under two situations:
701 * (1) recycler decides to reclaim an in-use object
702 * (2) a cache is unmounted
703 * - have to take care as the cookie can be being relinquished by the netfs
704 * simultaneously
705 * - the object is pinned by the caller holding a refcount on it
706 */
707void fscache_withdrawing_object(struct fscache_cache *cache,
708 struct fscache_object *object)
709{
710 bool enqueue = false;
711
712 _enter(",OBJ%x", object->debug_id);
713
714 spin_lock(&object->lock);
715 if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
716 object->state = FSCACHE_OBJECT_WITHDRAWING;
717 enqueue = true;
718 }
719 spin_unlock(&object->lock);
720
721 if (enqueue)
722 fscache_enqueue_object(object);
723
724 _leave("");
725}
726
727/*
728 * get a ref on an object
729 */
730static int fscache_get_object(struct fscache_object *object)
731{
732 int ret;
733
734 fscache_stat(&fscache_n_cop_grab_object);
735 ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
736 fscache_stat_d(&fscache_n_cop_grab_object);
737 return ret;
738}
739
740/*
741 * discard a ref on a work item
742 */
743static void fscache_put_object(struct fscache_object *object)
744{
745 fscache_stat(&fscache_n_cop_put_object);
746 object->cache->ops->put_object(object);
747 fscache_stat_d(&fscache_n_cop_put_object);
748}
749
750/*
751 * enqueue an object for metadata-type processing
752 */
753void fscache_enqueue_object(struct fscache_object *object)
754{
755 _enter("{OBJ%x}", object->debug_id);
756
757 if (fscache_get_object(object) >= 0) {
758 wait_queue_head_t *cong_wq =
759 &get_cpu_var(fscache_object_cong_wait);
760
761 if (queue_work(fscache_object_wq, &object->work)) {
762 if (fscache_object_congested())
763 wake_up(cong_wq);
764 } else
765 fscache_put_object(object);
766
767 put_cpu_var(fscache_object_cong_wait);
768 }
769}
770
771/**
772 * fscache_object_sleep_till_congested - Sleep until object wq is congested
773 * @timoutp: Scheduler sleep timeout
774 *
775 * Allow an object handler to sleep until the object workqueue is congested.
776 *
777 * The caller must set up a wake up event before calling this and must have set
778 * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
779 * condition before calling this function as no test is made here.
780 *
781 * %true is returned if the object wq is congested, %false otherwise.
782 */
783bool fscache_object_sleep_till_congested(signed long *timeoutp)
784{
785 wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
786 DEFINE_WAIT(wait);
787
788 if (fscache_object_congested())
789 return true;
790
791 add_wait_queue_exclusive(cong_wq, &wait);
792 if (!fscache_object_congested())
793 *timeoutp = schedule_timeout(*timeoutp);
794 finish_wait(cong_wq, &wait);
795
796 return fscache_object_congested();
797}
798EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
799
800/*
801 * enqueue the dependents of an object for metadata-type processing
802 * - the caller must hold the object's lock
803 * - this may cause an already locked object to wind up being processed again
804 */
805static void fscache_enqueue_dependents(struct fscache_object *object)
806{
807 struct fscache_object *dep;
808
809 _enter("{OBJ%x}", object->debug_id);
810
811 if (list_empty(&object->dependents))
812 return;
813
814 spin_lock(&object->lock);
815
816 while (!list_empty(&object->dependents)) {
817 dep = list_entry(object->dependents.next,
818 struct fscache_object, dep_link);
819 list_del_init(&dep->dep_link);
820
821
822 /* sort onto appropriate lists */
823 fscache_enqueue_object(dep);
824 fscache_put_object(dep);
825
826 if (!list_empty(&object->dependents))
827 cond_resched_lock(&object->lock);
828 }
829
830 spin_unlock(&object->lock);
831}
832
833/*
834 * remove an object from whatever queue it's waiting on
835 * - the caller must hold object->lock
836 */
837void fscache_dequeue_object(struct fscache_object *object)
838{
839 _enter("{OBJ%x}", object->debug_id);
840
841 if (!list_empty(&object->dep_link)) {
842 spin_lock(&object->parent->lock);
843 list_del_init(&object->dep_link);
844 spin_unlock(&object->parent->lock);
845 }
846
847 _leave("");
848}
849
850/**
851 * fscache_check_aux - Ask the netfs whether an object on disk is still valid
852 * @object: The object to ask about
853 * @data: The auxiliary data for the object
854 * @datalen: The size of the auxiliary data
855 *
856 * This function consults the netfs about the coherency state of an object
857 */
858enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
859 const void *data, uint16_t datalen)
860{
861 enum fscache_checkaux result;
862
863 if (!object->cookie->def->check_aux) {
864 fscache_stat(&fscache_n_checkaux_none);
865 return FSCACHE_CHECKAUX_OKAY;
866 }
867
868 result = object->cookie->def->check_aux(object->cookie->netfs_data,
869 data, datalen);
870 switch (result) {
871 /* entry okay as is */
872 case FSCACHE_CHECKAUX_OKAY:
873 fscache_stat(&fscache_n_checkaux_okay);
874 break;
875
876 /* entry requires update */
877 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
878 fscache_stat(&fscache_n_checkaux_update);
879 break;
880
881 /* entry requires deletion */
882 case FSCACHE_CHECKAUX_OBSOLETE:
883 fscache_stat(&fscache_n_checkaux_obsolete);
884 break;
885
886 default:
887 BUG();
888 }
889
890 return result;
891}
892EXPORT_SYMBOL(fscache_check_aux);