1 /* FS-Cache object state machine handler
2 *
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 * See Documentation/filesystems/caching/object.txt for a description of the
12 * object state machine and the in-kernel representations.
13 */
14
15 #define FSCACHE_DEBUG_LEVEL COOKIE
16 #include <linux/module.h>
17 #include "internal.h"
18
19 const char *fscache_object_states[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 };
34 EXPORT_SYMBOL(fscache_object_states);
35
36 const 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
52 static int fscache_get_object(struct fscache_object *);
53 static void fscache_put_object(struct fscache_object *);
54 static void fscache_initialise_object(struct fscache_object *);
55 static void fscache_lookup_object(struct fscache_object *);
56 static void fscache_object_available(struct fscache_object *);
57 static void fscache_release_object(struct fscache_object *);
58 static void fscache_withdraw_object(struct fscache_object *);
59 static void fscache_enqueue_dependents(struct fscache_object *);
60 static 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 */
fscache_done_parent_op(struct fscache_object * object)66 static 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 */
fscache_object_state_machine(struct fscache_object * object)89 static 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 */
253 lookup_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 */
270 active_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 */
289 terminal_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
312 change_state:
313 spin_lock(&object->lock);
314 object->state = new_state;
315 spin_unlock(&object->lock);
316
317 done:
318 _leave(" [->%s]", fscache_object_states[object->state]);
319 return;
320
321 unsupported_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 */
fscache_object_work_func(struct work_struct * work)332 void 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 }
348 EXPORT_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 */
fscache_initialise_object(struct fscache_object * object)359 static 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 */
fscache_lookup_object(struct fscache_object * object)436 static 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 */
fscache_object_lookup_negative(struct fscache_object * object)489 void 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 }
521 EXPORT_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 */
fscache_obtained_object(struct fscache_object * object)533 void 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 }
571 EXPORT_SYMBOL(fscache_obtained_object);
572
573 /*
574 * handle an object that has just become available
575 */
fscache_object_available(struct fscache_object * object)576 static 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 */
fscache_drop_object(struct fscache_object * object)613 static 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 */
fscache_release_object(struct fscache_object * object)652 static 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 */
fscache_withdraw_object(struct fscache_object * object)662 static 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 */
fscache_withdrawing_object(struct fscache_cache * cache,struct fscache_object * object)707 void 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 */
fscache_get_object(struct fscache_object * object)730 static 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 */
fscache_put_object(struct fscache_object * object)743 static 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 */
fscache_enqueue_object(struct fscache_object * object)753 void 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 */
fscache_object_sleep_till_congested(signed long * timeoutp)783 bool 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 }
798 EXPORT_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 */
fscache_enqueue_dependents(struct fscache_object * object)805 static 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 */
fscache_dequeue_object(struct fscache_object * object)837 void 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 */
fscache_check_aux(struct fscache_object * object,const void * data,uint16_t datalen)858 enum 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 }
892 EXPORT_SYMBOL(fscache_check_aux);
893