1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* FS-Cache object state machine handler
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * See Documentation/filesystems/caching/object.rst for a description of the
8 * object state machine and the in-kernel representations.
9 */
10
11 #define FSCACHE_DEBUG_LEVEL COOKIE
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/prefetch.h>
15 #include "internal.h"
16
17 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
18 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
19 static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
20 static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
21 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
22 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
23 static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
24 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
25 static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
26 static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
27 static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
28 static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
29 static const struct fscache_state *fscache_object_dead(struct fscache_object *, int);
30
31 #define __STATE_NAME(n) fscache_osm_##n
32 #define STATE(n) (&__STATE_NAME(n))
33
34 /*
35 * Define a work state. Work states are execution states. No event processing
36 * is performed by them. The function attached to a work state returns a
37 * pointer indicating the next state to which the state machine should
38 * transition. Returning NO_TRANSIT repeats the current state, but goes back
39 * to the scheduler first.
40 */
41 #define WORK_STATE(n, sn, f) \
42 const struct fscache_state __STATE_NAME(n) = { \
43 .name = #n, \
44 .short_name = sn, \
45 .work = f \
46 }
47
48 /*
49 * Returns from work states.
50 */
51 #define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
52
53 #define NO_TRANSIT ((struct fscache_state *)NULL)
54
55 /*
56 * Define a wait state. Wait states are event processing states. No execution
57 * is performed by them. Wait states are just tables of "if event X occurs,
58 * clear it and transition to state Y". The dispatcher returns to the
59 * scheduler if none of the events in which the wait state has an interest are
60 * currently pending.
61 */
62 #define WAIT_STATE(n, sn, ...) \
63 const struct fscache_state __STATE_NAME(n) = { \
64 .name = #n, \
65 .short_name = sn, \
66 .work = NULL, \
67 .transitions = { __VA_ARGS__, { 0, NULL } } \
68 }
69
70 #define TRANSIT_TO(state, emask) \
71 { .events = (emask), .transit_to = STATE(state) }
72
73 /*
74 * The object state machine.
75 */
76 static WORK_STATE(INIT_OBJECT, "INIT", fscache_initialise_object);
77 static WORK_STATE(PARENT_READY, "PRDY", fscache_parent_ready);
78 static WORK_STATE(ABORT_INIT, "ABRT", fscache_abort_initialisation);
79 static WORK_STATE(LOOK_UP_OBJECT, "LOOK", fscache_look_up_object);
80 static WORK_STATE(OBJECT_AVAILABLE, "AVBL", fscache_object_available);
81 static WORK_STATE(JUMPSTART_DEPS, "JUMP", fscache_jumpstart_dependents);
82
83 static WORK_STATE(INVALIDATE_OBJECT, "INVL", fscache_invalidate_object);
84 static WORK_STATE(UPDATE_OBJECT, "UPDT", fscache_update_object);
85
86 static WORK_STATE(LOOKUP_FAILURE, "LCFL", fscache_lookup_failure);
87 static WORK_STATE(KILL_OBJECT, "KILL", fscache_kill_object);
88 static WORK_STATE(KILL_DEPENDENTS, "KDEP", fscache_kill_dependents);
89 static WORK_STATE(DROP_OBJECT, "DROP", fscache_drop_object);
90 static WORK_STATE(OBJECT_DEAD, "DEAD", fscache_object_dead);
91
92 static WAIT_STATE(WAIT_FOR_INIT, "?INI",
93 TRANSIT_TO(INIT_OBJECT, 1 << FSCACHE_OBJECT_EV_NEW_CHILD));
94
95 static WAIT_STATE(WAIT_FOR_PARENT, "?PRN",
96 TRANSIT_TO(PARENT_READY, 1 << FSCACHE_OBJECT_EV_PARENT_READY));
97
98 static WAIT_STATE(WAIT_FOR_CMD, "?CMD",
99 TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
100 TRANSIT_TO(UPDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_UPDATE),
101 TRANSIT_TO(JUMPSTART_DEPS, 1 << FSCACHE_OBJECT_EV_NEW_CHILD));
102
103 static WAIT_STATE(WAIT_FOR_CLEARANCE, "?CLR",
104 TRANSIT_TO(KILL_OBJECT, 1 << FSCACHE_OBJECT_EV_CLEARED));
105
106 /*
107 * Out-of-band event transition tables. These are for handling unexpected
108 * events, such as an I/O error. If an OOB event occurs, the state machine
109 * clears and disables the event and forces a transition to the nominated work
110 * state (acurrently executing work states will complete first).
111 *
112 * In such a situation, object->state remembers the state the machine should
113 * have been in/gone to and returning NO_TRANSIT returns to that.
114 */
115 static const struct fscache_transition fscache_osm_init_oob[] = {
116 TRANSIT_TO(ABORT_INIT,
117 (1 << FSCACHE_OBJECT_EV_ERROR) |
118 (1 << FSCACHE_OBJECT_EV_KILL)),
119 { 0, NULL }
120 };
121
122 static const struct fscache_transition fscache_osm_lookup_oob[] = {
123 TRANSIT_TO(LOOKUP_FAILURE,
124 (1 << FSCACHE_OBJECT_EV_ERROR) |
125 (1 << FSCACHE_OBJECT_EV_KILL)),
126 { 0, NULL }
127 };
128
129 static const struct fscache_transition fscache_osm_run_oob[] = {
130 TRANSIT_TO(KILL_OBJECT,
131 (1 << FSCACHE_OBJECT_EV_ERROR) |
132 (1 << FSCACHE_OBJECT_EV_KILL)),
133 { 0, NULL }
134 };
135
136 static int fscache_get_object(struct fscache_object *,
137 enum fscache_obj_ref_trace);
138 static void fscache_put_object(struct fscache_object *,
139 enum fscache_obj_ref_trace);
140 static bool fscache_enqueue_dependents(struct fscache_object *, int);
141 static void fscache_dequeue_object(struct fscache_object *);
142 static void fscache_update_aux_data(struct fscache_object *);
143
144 /*
145 * we need to notify the parent when an op completes that we had outstanding
146 * upon it
147 */
fscache_done_parent_op(struct fscache_object * object)148 static inline void fscache_done_parent_op(struct fscache_object *object)
149 {
150 struct fscache_object *parent = object->parent;
151
152 _enter("OBJ%x {OBJ%x,%x}",
153 object->debug_id, parent->debug_id, parent->n_ops);
154
155 spin_lock_nested(&parent->lock, 1);
156 parent->n_obj_ops--;
157 parent->n_ops--;
158 if (parent->n_ops == 0)
159 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
160 spin_unlock(&parent->lock);
161 }
162
163 /*
164 * Object state machine dispatcher.
165 */
fscache_object_sm_dispatcher(struct fscache_object * object)166 static void fscache_object_sm_dispatcher(struct fscache_object *object)
167 {
168 const struct fscache_transition *t;
169 const struct fscache_state *state, *new_state;
170 unsigned long events, event_mask;
171 bool oob;
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;
180 restart:
181 object->event_mask = 0; /* Mask normal event handling */
182 state = object->state;
183 restart_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 oob = true;
191 for (t = object->oob_table; t->events; t++) {
192 if (events & t->events) {
193 state = t->transit_to;
194 ASSERT(state->work != NULL);
195 event = fls(events & t->events) - 1;
196 __clear_bit(event, &object->oob_event_mask);
197 clear_bit(event, &object->events);
198 goto execute_work_state;
199 }
200 }
201 }
202 oob = false;
203
204 /* Wait states are just transition tables */
205 if (!state->work) {
206 if (events & event_mask) {
207 for (t = state->transitions; t->events; t++) {
208 if (events & t->events) {
209 new_state = t->transit_to;
210 event = fls(events & t->events) - 1;
211 trace_fscache_osm(object, state,
212 true, false, event);
213 clear_bit(event, &object->events);
214 _debug("{OBJ%x} ev %d: %s -> %s",
215 object->debug_id, event,
216 state->name, new_state->name);
217 object->state = state = new_state;
218 goto execute_work_state;
219 }
220 }
221
222 /* The event mask didn't include all the tabled bits */
223 BUG();
224 }
225 /* Randomly woke up */
226 goto unmask_events;
227 }
228
229 execute_work_state:
230 _debug("{OBJ%x} exec %s", object->debug_id, state->name);
231
232 trace_fscache_osm(object, state, false, oob, event);
233 new_state = state->work(object, event);
234 event = -1;
235 if (new_state == NO_TRANSIT) {
236 _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
237 if (unlikely(state == STATE(OBJECT_DEAD))) {
238 _leave(" [dead]");
239 return;
240 }
241 fscache_enqueue_object(object);
242 event_mask = object->oob_event_mask;
243 goto unmask_events;
244 }
245
246 _debug("{OBJ%x} %s -> %s",
247 object->debug_id, state->name, new_state->name);
248 object->state = state = new_state;
249
250 if (state->work) {
251 if (unlikely(state == STATE(OBJECT_DEAD))) {
252 _leave(" [dead]");
253 return;
254 }
255 goto restart_masked;
256 }
257
258 /* Transited to wait state */
259 event_mask = object->oob_event_mask;
260 for (t = state->transitions; t->events; t++)
261 event_mask |= t->events;
262
263 unmask_events:
264 object->event_mask = event_mask;
265 smp_mb();
266 events = object->events;
267 if (events & event_mask)
268 goto restart;
269 _leave(" [msk %lx]", event_mask);
270 }
271
272 /*
273 * execute an object
274 */
fscache_object_work_func(struct work_struct * work)275 static void fscache_object_work_func(struct work_struct *work)
276 {
277 struct fscache_object *object =
278 container_of(work, struct fscache_object, work);
279
280 _enter("{OBJ%x}", object->debug_id);
281
282 fscache_object_sm_dispatcher(object);
283 fscache_put_object(object, fscache_obj_put_work);
284 }
285
286 /**
287 * fscache_object_init - Initialise a cache object description
288 * @object: Object description
289 * @cookie: Cookie object will be attached to
290 * @cache: Cache in which backing object will be found
291 *
292 * Initialise a cache object description to its basic values.
293 *
294 * See Documentation/filesystems/caching/backend-api.rst for a complete
295 * description.
296 */
fscache_object_init(struct fscache_object * object,struct fscache_cookie * cookie,struct fscache_cache * cache)297 void fscache_object_init(struct fscache_object *object,
298 struct fscache_cookie *cookie,
299 struct fscache_cache *cache)
300 {
301 const struct fscache_transition *t;
302
303 atomic_inc(&cache->object_count);
304
305 object->state = STATE(WAIT_FOR_INIT);
306 object->oob_table = fscache_osm_init_oob;
307 object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
308 spin_lock_init(&object->lock);
309 INIT_LIST_HEAD(&object->cache_link);
310 INIT_HLIST_NODE(&object->cookie_link);
311 INIT_WORK(&object->work, fscache_object_work_func);
312 INIT_LIST_HEAD(&object->dependents);
313 INIT_LIST_HEAD(&object->dep_link);
314 INIT_LIST_HEAD(&object->pending_ops);
315 object->n_children = 0;
316 object->n_ops = object->n_in_progress = object->n_exclusive = 0;
317 object->events = 0;
318 object->store_limit = 0;
319 object->store_limit_l = 0;
320 object->cache = cache;
321 object->cookie = cookie;
322 fscache_cookie_get(cookie, fscache_cookie_get_attach_object);
323 object->parent = NULL;
324 #ifdef CONFIG_FSCACHE_OBJECT_LIST
325 RB_CLEAR_NODE(&object->objlist_link);
326 #endif
327
328 object->oob_event_mask = 0;
329 for (t = object->oob_table; t->events; t++)
330 object->oob_event_mask |= t->events;
331 object->event_mask = object->oob_event_mask;
332 for (t = object->state->transitions; t->events; t++)
333 object->event_mask |= t->events;
334 }
335 EXPORT_SYMBOL(fscache_object_init);
336
337 /*
338 * Mark the object as no longer being live, making sure that we synchronise
339 * against op submission.
340 */
fscache_mark_object_dead(struct fscache_object * object)341 static inline void fscache_mark_object_dead(struct fscache_object *object)
342 {
343 spin_lock(&object->lock);
344 clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
345 spin_unlock(&object->lock);
346 }
347
348 /*
349 * Abort object initialisation before we start it.
350 */
fscache_abort_initialisation(struct fscache_object * object,int event)351 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
352 int event)
353 {
354 _enter("{OBJ%x},%d", object->debug_id, event);
355
356 object->oob_event_mask = 0;
357 fscache_dequeue_object(object);
358 return transit_to(KILL_OBJECT);
359 }
360
361 /*
362 * initialise an object
363 * - check the specified object's parent to see if we can make use of it
364 * immediately to do a creation
365 * - we may need to start the process of creating a parent and we need to wait
366 * for the parent's lookup and creation to complete if it's not there yet
367 */
fscache_initialise_object(struct fscache_object * object,int event)368 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
369 int event)
370 {
371 struct fscache_object *parent;
372 bool success;
373
374 _enter("{OBJ%x},%d", object->debug_id, event);
375
376 ASSERT(list_empty(&object->dep_link));
377
378 parent = object->parent;
379 if (!parent) {
380 _leave(" [no parent]");
381 return transit_to(DROP_OBJECT);
382 }
383
384 _debug("parent: %s of:%lx", parent->state->name, parent->flags);
385
386 if (fscache_object_is_dying(parent)) {
387 _leave(" [bad parent]");
388 return transit_to(DROP_OBJECT);
389 }
390
391 if (fscache_object_is_available(parent)) {
392 _leave(" [ready]");
393 return transit_to(PARENT_READY);
394 }
395
396 _debug("wait");
397
398 spin_lock(&parent->lock);
399 fscache_stat(&fscache_n_cop_grab_object);
400 success = false;
401 if (fscache_object_is_live(parent) &&
402 object->cache->ops->grab_object(object, fscache_obj_get_add_to_deps)) {
403 list_add(&object->dep_link, &parent->dependents);
404 success = true;
405 }
406 fscache_stat_d(&fscache_n_cop_grab_object);
407 spin_unlock(&parent->lock);
408 if (!success) {
409 _leave(" [grab failed]");
410 return transit_to(DROP_OBJECT);
411 }
412
413 /* fscache_acquire_non_index_cookie() uses this
414 * to wake the chain up */
415 fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
416 _leave(" [wait]");
417 return transit_to(WAIT_FOR_PARENT);
418 }
419
420 /*
421 * Once the parent object is ready, we should kick off our lookup op.
422 */
fscache_parent_ready(struct fscache_object * object,int event)423 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
424 int event)
425 {
426 struct fscache_object *parent = object->parent;
427
428 _enter("{OBJ%x},%d", object->debug_id, event);
429
430 ASSERT(parent != NULL);
431
432 spin_lock(&parent->lock);
433 parent->n_ops++;
434 parent->n_obj_ops++;
435 spin_unlock(&parent->lock);
436
437 _leave("");
438 return transit_to(LOOK_UP_OBJECT);
439 }
440
441 /*
442 * look an object up in the cache from which it was allocated
443 * - we hold an "access lock" on the parent object, so the parent object cannot
444 * be withdrawn by either party till we've finished
445 */
fscache_look_up_object(struct fscache_object * object,int event)446 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
447 int event)
448 {
449 struct fscache_cookie *cookie = object->cookie;
450 struct fscache_object *parent = object->parent;
451 int ret;
452
453 _enter("{OBJ%x},%d", object->debug_id, event);
454
455 object->oob_table = fscache_osm_lookup_oob;
456
457 ASSERT(parent != NULL);
458 ASSERTCMP(parent->n_ops, >, 0);
459 ASSERTCMP(parent->n_obj_ops, >, 0);
460
461 /* make sure the parent is still available */
462 ASSERT(fscache_object_is_available(parent));
463
464 if (fscache_object_is_dying(parent) ||
465 test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
466 !fscache_use_cookie(object)) {
467 _leave(" [unavailable]");
468 return transit_to(LOOKUP_FAILURE);
469 }
470
471 _debug("LOOKUP \"%s\" in \"%s\"",
472 cookie->def->name, object->cache->tag->name);
473
474 fscache_stat(&fscache_n_object_lookups);
475 fscache_stat(&fscache_n_cop_lookup_object);
476 ret = object->cache->ops->lookup_object(object);
477 fscache_stat_d(&fscache_n_cop_lookup_object);
478
479 fscache_unuse_cookie(object);
480
481 if (ret == -ETIMEDOUT) {
482 /* probably stuck behind another object, so move this one to
483 * the back of the queue */
484 fscache_stat(&fscache_n_object_lookups_timed_out);
485 _leave(" [timeout]");
486 return NO_TRANSIT;
487 }
488
489 if (ret < 0) {
490 _leave(" [error]");
491 return transit_to(LOOKUP_FAILURE);
492 }
493
494 _leave(" [ok]");
495 return transit_to(OBJECT_AVAILABLE);
496 }
497
498 /**
499 * fscache_object_lookup_negative - Note negative cookie lookup
500 * @object: Object pointing to cookie to mark
501 *
502 * Note negative lookup, permitting those waiting to read data from an already
503 * existing backing object to continue as there's no data for them to read.
504 */
fscache_object_lookup_negative(struct fscache_object * object)505 void fscache_object_lookup_negative(struct fscache_object *object)
506 {
507 struct fscache_cookie *cookie = object->cookie;
508
509 _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
510
511 if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
512 fscache_stat(&fscache_n_object_lookups_negative);
513
514 /* Allow write requests to begin stacking up and read requests to begin
515 * returning ENODATA.
516 */
517 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
518 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
519
520 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
521 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
522 }
523 _leave("");
524 }
525 EXPORT_SYMBOL(fscache_object_lookup_negative);
526
527 /**
528 * fscache_obtained_object - Note successful object lookup or creation
529 * @object: Object pointing to cookie to mark
530 *
531 * Note successful lookup and/or creation, permitting those waiting to write
532 * data to a backing object to continue.
533 *
534 * Note that after calling this, an object's cookie may be relinquished by the
535 * netfs, and so must be accessed with object lock held.
536 */
fscache_obtained_object(struct fscache_object * object)537 void fscache_obtained_object(struct fscache_object *object)
538 {
539 struct fscache_cookie *cookie = object->cookie;
540
541 _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
542
543 /* if we were still looking up, then we must have a positive lookup
544 * result, in which case there may be data available */
545 if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
546 fscache_stat(&fscache_n_object_lookups_positive);
547
548 /* We do (presumably) have data */
549 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
550 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
551
552 /* Allow write requests to begin stacking up and read requests
553 * to begin shovelling data.
554 */
555 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
556 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
557 } else {
558 fscache_stat(&fscache_n_object_created);
559 }
560
561 set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
562 _leave("");
563 }
564 EXPORT_SYMBOL(fscache_obtained_object);
565
566 /*
567 * handle an object that has just become available
568 */
fscache_object_available(struct fscache_object * object,int event)569 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
570 int event)
571 {
572 _enter("{OBJ%x},%d", object->debug_id, event);
573
574 object->oob_table = fscache_osm_run_oob;
575
576 spin_lock(&object->lock);
577
578 fscache_done_parent_op(object);
579 if (object->n_in_progress == 0) {
580 if (object->n_ops > 0) {
581 ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
582 fscache_start_operations(object);
583 } else {
584 ASSERT(list_empty(&object->pending_ops));
585 }
586 }
587 spin_unlock(&object->lock);
588
589 fscache_stat(&fscache_n_cop_lookup_complete);
590 object->cache->ops->lookup_complete(object);
591 fscache_stat_d(&fscache_n_cop_lookup_complete);
592
593 fscache_stat(&fscache_n_object_avail);
594
595 _leave("");
596 return transit_to(JUMPSTART_DEPS);
597 }
598
599 /*
600 * Wake up this object's dependent objects now that we've become available.
601 */
fscache_jumpstart_dependents(struct fscache_object * object,int event)602 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
603 int event)
604 {
605 _enter("{OBJ%x},%d", object->debug_id, event);
606
607 if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
608 return NO_TRANSIT; /* Not finished; requeue */
609 return transit_to(WAIT_FOR_CMD);
610 }
611
612 /*
613 * Handle lookup or creation failute.
614 */
fscache_lookup_failure(struct fscache_object * object,int event)615 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
616 int event)
617 {
618 struct fscache_cookie *cookie;
619
620 _enter("{OBJ%x},%d", object->debug_id, event);
621
622 object->oob_event_mask = 0;
623
624 fscache_stat(&fscache_n_cop_lookup_complete);
625 object->cache->ops->lookup_complete(object);
626 fscache_stat_d(&fscache_n_cop_lookup_complete);
627
628 set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
629
630 cookie = object->cookie;
631 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
632 if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
633 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
634
635 fscache_done_parent_op(object);
636 return transit_to(KILL_OBJECT);
637 }
638
639 /*
640 * Wait for completion of all active operations on this object and the death of
641 * all child objects of this object.
642 */
fscache_kill_object(struct fscache_object * object,int event)643 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
644 int event)
645 {
646 _enter("{OBJ%x,%d,%d},%d",
647 object->debug_id, object->n_ops, object->n_children, event);
648
649 fscache_mark_object_dead(object);
650 object->oob_event_mask = 0;
651
652 if (test_bit(FSCACHE_OBJECT_RETIRED, &object->flags)) {
653 /* Reject any new read/write ops and abort any that are pending. */
654 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
655 fscache_cancel_all_ops(object);
656 }
657
658 if (list_empty(&object->dependents) &&
659 object->n_ops == 0 &&
660 object->n_children == 0)
661 return transit_to(DROP_OBJECT);
662
663 if (object->n_in_progress == 0) {
664 spin_lock(&object->lock);
665 if (object->n_ops > 0 && object->n_in_progress == 0)
666 fscache_start_operations(object);
667 spin_unlock(&object->lock);
668 }
669
670 if (!list_empty(&object->dependents))
671 return transit_to(KILL_DEPENDENTS);
672
673 return transit_to(WAIT_FOR_CLEARANCE);
674 }
675
676 /*
677 * Kill dependent objects.
678 */
fscache_kill_dependents(struct fscache_object * object,int event)679 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
680 int event)
681 {
682 _enter("{OBJ%x},%d", object->debug_id, event);
683
684 if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
685 return NO_TRANSIT; /* Not finished */
686 return transit_to(WAIT_FOR_CLEARANCE);
687 }
688
689 /*
690 * Drop an object's attachments
691 */
fscache_drop_object(struct fscache_object * object,int event)692 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
693 int event)
694 {
695 struct fscache_object *parent = object->parent;
696 struct fscache_cookie *cookie = object->cookie;
697 struct fscache_cache *cache = object->cache;
698 bool awaken = false;
699
700 _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
701
702 ASSERT(cookie != NULL);
703 ASSERT(!hlist_unhashed(&object->cookie_link));
704
705 if (test_bit(FSCACHE_COOKIE_AUX_UPDATED, &cookie->flags)) {
706 _debug("final update");
707 fscache_update_aux_data(object);
708 }
709
710 /* Make sure the cookie no longer points here and that the netfs isn't
711 * waiting for us.
712 */
713 spin_lock(&cookie->lock);
714 hlist_del_init(&object->cookie_link);
715 if (hlist_empty(&cookie->backing_objects) &&
716 test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
717 awaken = true;
718 spin_unlock(&cookie->lock);
719
720 if (awaken)
721 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
722 if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
723 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
724
725
726 /* Prevent a race with our last child, which has to signal EV_CLEARED
727 * before dropping our spinlock.
728 */
729 spin_lock(&object->lock);
730 spin_unlock(&object->lock);
731
732 /* Discard from the cache's collection of objects */
733 spin_lock(&cache->object_list_lock);
734 list_del_init(&object->cache_link);
735 spin_unlock(&cache->object_list_lock);
736
737 fscache_stat(&fscache_n_cop_drop_object);
738 cache->ops->drop_object(object);
739 fscache_stat_d(&fscache_n_cop_drop_object);
740
741 /* The parent object wants to know when all it dependents have gone */
742 if (parent) {
743 _debug("release parent OBJ%x {%d}",
744 parent->debug_id, parent->n_children);
745
746 spin_lock(&parent->lock);
747 parent->n_children--;
748 if (parent->n_children == 0)
749 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
750 spin_unlock(&parent->lock);
751 object->parent = NULL;
752 }
753
754 /* this just shifts the object release to the work processor */
755 fscache_put_object(object, fscache_obj_put_drop_obj);
756 fscache_stat(&fscache_n_object_dead);
757
758 _leave("");
759 return transit_to(OBJECT_DEAD);
760 }
761
762 /*
763 * get a ref on an object
764 */
fscache_get_object(struct fscache_object * object,enum fscache_obj_ref_trace why)765 static int fscache_get_object(struct fscache_object *object,
766 enum fscache_obj_ref_trace why)
767 {
768 int ret;
769
770 fscache_stat(&fscache_n_cop_grab_object);
771 ret = object->cache->ops->grab_object(object, why) ? 0 : -EAGAIN;
772 fscache_stat_d(&fscache_n_cop_grab_object);
773 return ret;
774 }
775
776 /*
777 * Discard a ref on an object
778 */
fscache_put_object(struct fscache_object * object,enum fscache_obj_ref_trace why)779 static void fscache_put_object(struct fscache_object *object,
780 enum fscache_obj_ref_trace why)
781 {
782 fscache_stat(&fscache_n_cop_put_object);
783 object->cache->ops->put_object(object, why);
784 fscache_stat_d(&fscache_n_cop_put_object);
785 }
786
787 /**
788 * fscache_object_destroy - Note that a cache object is about to be destroyed
789 * @object: The object to be destroyed
790 *
791 * Note the imminent destruction and deallocation of a cache object record.
792 */
fscache_object_destroy(struct fscache_object * object)793 void fscache_object_destroy(struct fscache_object *object)
794 {
795 /* We can get rid of the cookie now */
796 fscache_cookie_put(object->cookie, fscache_cookie_put_object);
797 object->cookie = NULL;
798 }
799 EXPORT_SYMBOL(fscache_object_destroy);
800
801 /*
802 * enqueue an object for metadata-type processing
803 */
fscache_enqueue_object(struct fscache_object * object)804 void fscache_enqueue_object(struct fscache_object *object)
805 {
806 _enter("{OBJ%x}", object->debug_id);
807
808 if (fscache_get_object(object, fscache_obj_get_queue) >= 0) {
809 wait_queue_head_t *cong_wq =
810 &get_cpu_var(fscache_object_cong_wait);
811
812 if (queue_work(fscache_object_wq, &object->work)) {
813 if (fscache_object_congested())
814 wake_up(cong_wq);
815 } else
816 fscache_put_object(object, fscache_obj_put_queue);
817
818 put_cpu_var(fscache_object_cong_wait);
819 }
820 }
821
822 /**
823 * fscache_object_sleep_till_congested - Sleep until object wq is congested
824 * @timeoutp: Scheduler sleep timeout
825 *
826 * Allow an object handler to sleep until the object workqueue is congested.
827 *
828 * The caller must set up a wake up event before calling this and must have set
829 * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
830 * condition before calling this function as no test is made here.
831 *
832 * %true is returned if the object wq is congested, %false otherwise.
833 */
fscache_object_sleep_till_congested(signed long * timeoutp)834 bool fscache_object_sleep_till_congested(signed long *timeoutp)
835 {
836 wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
837 DEFINE_WAIT(wait);
838
839 if (fscache_object_congested())
840 return true;
841
842 add_wait_queue_exclusive(cong_wq, &wait);
843 if (!fscache_object_congested())
844 *timeoutp = schedule_timeout(*timeoutp);
845 finish_wait(cong_wq, &wait);
846
847 return fscache_object_congested();
848 }
849 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
850
851 /*
852 * Enqueue the dependents of an object for metadata-type processing.
853 *
854 * If we don't manage to finish the list before the scheduler wants to run
855 * again then return false immediately. We return true if the list was
856 * cleared.
857 */
fscache_enqueue_dependents(struct fscache_object * object,int event)858 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
859 {
860 struct fscache_object *dep;
861 bool ret = true;
862
863 _enter("{OBJ%x}", object->debug_id);
864
865 if (list_empty(&object->dependents))
866 return true;
867
868 spin_lock(&object->lock);
869
870 while (!list_empty(&object->dependents)) {
871 dep = list_entry(object->dependents.next,
872 struct fscache_object, dep_link);
873 list_del_init(&dep->dep_link);
874
875 fscache_raise_event(dep, event);
876 fscache_put_object(dep, fscache_obj_put_enq_dep);
877
878 if (!list_empty(&object->dependents) && need_resched()) {
879 ret = false;
880 break;
881 }
882 }
883
884 spin_unlock(&object->lock);
885 return ret;
886 }
887
888 /*
889 * remove an object from whatever queue it's waiting on
890 */
fscache_dequeue_object(struct fscache_object * object)891 static void fscache_dequeue_object(struct fscache_object *object)
892 {
893 _enter("{OBJ%x}", object->debug_id);
894
895 if (!list_empty(&object->dep_link)) {
896 spin_lock(&object->parent->lock);
897 list_del_init(&object->dep_link);
898 spin_unlock(&object->parent->lock);
899 }
900
901 _leave("");
902 }
903
904 /**
905 * fscache_check_aux - Ask the netfs whether an object on disk is still valid
906 * @object: The object to ask about
907 * @data: The auxiliary data for the object
908 * @datalen: The size of the auxiliary data
909 * @object_size: The size of the object according to the server.
910 *
911 * This function consults the netfs about the coherency state of an object.
912 * The caller must be holding a ref on cookie->n_active (held by
913 * fscache_look_up_object() on behalf of the cache backend during object lookup
914 * and creation).
915 */
fscache_check_aux(struct fscache_object * object,const void * data,uint16_t datalen,loff_t object_size)916 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
917 const void *data, uint16_t datalen,
918 loff_t object_size)
919 {
920 enum fscache_checkaux result;
921
922 if (!object->cookie->def->check_aux) {
923 fscache_stat(&fscache_n_checkaux_none);
924 return FSCACHE_CHECKAUX_OKAY;
925 }
926
927 result = object->cookie->def->check_aux(object->cookie->netfs_data,
928 data, datalen, object_size);
929 switch (result) {
930 /* entry okay as is */
931 case FSCACHE_CHECKAUX_OKAY:
932 fscache_stat(&fscache_n_checkaux_okay);
933 break;
934
935 /* entry requires update */
936 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
937 fscache_stat(&fscache_n_checkaux_update);
938 break;
939
940 /* entry requires deletion */
941 case FSCACHE_CHECKAUX_OBSOLETE:
942 fscache_stat(&fscache_n_checkaux_obsolete);
943 break;
944
945 default:
946 BUG();
947 }
948
949 return result;
950 }
951 EXPORT_SYMBOL(fscache_check_aux);
952
953 /*
954 * Asynchronously invalidate an object.
955 */
_fscache_invalidate_object(struct fscache_object * object,int event)956 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
957 int event)
958 {
959 struct fscache_operation *op;
960 struct fscache_cookie *cookie = object->cookie;
961
962 _enter("{OBJ%x},%d", object->debug_id, event);
963
964 /* We're going to need the cookie. If the cookie is not available then
965 * retire the object instead.
966 */
967 if (!fscache_use_cookie(object)) {
968 ASSERT(radix_tree_empty(&object->cookie->stores));
969 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
970 _leave(" [no cookie]");
971 return transit_to(KILL_OBJECT);
972 }
973
974 /* Reject any new read/write ops and abort any that are pending. */
975 fscache_invalidate_writes(cookie);
976 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
977 fscache_cancel_all_ops(object);
978
979 /* Now we have to wait for in-progress reads and writes */
980 op = kzalloc(sizeof(*op), GFP_KERNEL);
981 if (!op)
982 goto nomem;
983
984 fscache_operation_init(cookie, op, object->cache->ops->invalidate_object,
985 NULL, NULL);
986 op->flags = FSCACHE_OP_ASYNC |
987 (1 << FSCACHE_OP_EXCLUSIVE) |
988 (1 << FSCACHE_OP_UNUSE_COOKIE);
989 trace_fscache_page_op(cookie, NULL, op, fscache_page_op_invalidate);
990
991 spin_lock(&cookie->lock);
992 if (fscache_submit_exclusive_op(object, op) < 0)
993 goto submit_op_failed;
994 spin_unlock(&cookie->lock);
995 fscache_put_operation(op);
996
997 /* Once we've completed the invalidation, we know there will be no data
998 * stored in the cache and thus we can reinstate the data-check-skip
999 * optimisation.
1000 */
1001 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1002
1003 /* We can allow read and write requests to come in once again. They'll
1004 * queue up behind our exclusive invalidation operation.
1005 */
1006 if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
1007 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
1008 _leave(" [ok]");
1009 return transit_to(UPDATE_OBJECT);
1010
1011 nomem:
1012 fscache_mark_object_dead(object);
1013 fscache_unuse_cookie(object);
1014 _leave(" [ENOMEM]");
1015 return transit_to(KILL_OBJECT);
1016
1017 submit_op_failed:
1018 fscache_mark_object_dead(object);
1019 spin_unlock(&cookie->lock);
1020 fscache_unuse_cookie(object);
1021 kfree(op);
1022 _leave(" [EIO]");
1023 return transit_to(KILL_OBJECT);
1024 }
1025
fscache_invalidate_object(struct fscache_object * object,int event)1026 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1027 int event)
1028 {
1029 const struct fscache_state *s;
1030
1031 fscache_stat(&fscache_n_invalidates_run);
1032 fscache_stat(&fscache_n_cop_invalidate_object);
1033 s = _fscache_invalidate_object(object, event);
1034 fscache_stat_d(&fscache_n_cop_invalidate_object);
1035 return s;
1036 }
1037
1038 /*
1039 * Update auxiliary data.
1040 */
fscache_update_aux_data(struct fscache_object * object)1041 static void fscache_update_aux_data(struct fscache_object *object)
1042 {
1043 fscache_stat(&fscache_n_updates_run);
1044 fscache_stat(&fscache_n_cop_update_object);
1045 object->cache->ops->update_object(object);
1046 fscache_stat_d(&fscache_n_cop_update_object);
1047 }
1048
1049 /*
1050 * Asynchronously update an object.
1051 */
fscache_update_object(struct fscache_object * object,int event)1052 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1053 int event)
1054 {
1055 _enter("{OBJ%x},%d", object->debug_id, event);
1056
1057 fscache_update_aux_data(object);
1058
1059 _leave("");
1060 return transit_to(WAIT_FOR_CMD);
1061 }
1062
1063 /**
1064 * fscache_object_retrying_stale - Note retrying stale object
1065 * @object: The object that will be retried
1066 *
1067 * Note that an object lookup found an on-disk object that was adjudged to be
1068 * stale and has been deleted. The lookup will be retried.
1069 */
fscache_object_retrying_stale(struct fscache_object * object)1070 void fscache_object_retrying_stale(struct fscache_object *object)
1071 {
1072 fscache_stat(&fscache_n_cache_no_space_reject);
1073 }
1074 EXPORT_SYMBOL(fscache_object_retrying_stale);
1075
1076 /**
1077 * fscache_object_mark_killed - Note that an object was killed
1078 * @object: The object that was culled
1079 * @why: The reason the object was killed.
1080 *
1081 * Note that an object was killed. Returns true if the object was
1082 * already marked killed, false if it wasn't.
1083 */
fscache_object_mark_killed(struct fscache_object * object,enum fscache_why_object_killed why)1084 void fscache_object_mark_killed(struct fscache_object *object,
1085 enum fscache_why_object_killed why)
1086 {
1087 if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1088 pr_err("Error: Object already killed by cache [%s]\n",
1089 object->cache->identifier);
1090 return;
1091 }
1092
1093 switch (why) {
1094 case FSCACHE_OBJECT_NO_SPACE:
1095 fscache_stat(&fscache_n_cache_no_space_reject);
1096 break;
1097 case FSCACHE_OBJECT_IS_STALE:
1098 fscache_stat(&fscache_n_cache_stale_objects);
1099 break;
1100 case FSCACHE_OBJECT_WAS_RETIRED:
1101 fscache_stat(&fscache_n_cache_retired_objects);
1102 break;
1103 case FSCACHE_OBJECT_WAS_CULLED:
1104 fscache_stat(&fscache_n_cache_culled_objects);
1105 break;
1106 }
1107 }
1108 EXPORT_SYMBOL(fscache_object_mark_killed);
1109
1110 /*
1111 * The object is dead. We can get here if an object gets queued by an event
1112 * that would lead to its death (such as EV_KILL) when the dispatcher is
1113 * already running (and so can be requeued) but hasn't yet cleared the event
1114 * mask.
1115 */
fscache_object_dead(struct fscache_object * object,int event)1116 static const struct fscache_state *fscache_object_dead(struct fscache_object *object,
1117 int event)
1118 {
1119 if (!test_and_set_bit(FSCACHE_OBJECT_RUN_AFTER_DEAD,
1120 &object->flags))
1121 return NO_TRANSIT;
1122
1123 WARN(true, "FS-Cache object redispatched after death");
1124 return NO_TRANSIT;
1125 }
1126