1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* netfs cookie management
3 *
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * See Documentation/filesystems/caching/netfs-api.rst for more information on
8 * the netfs API.
9 */
10
11 #define FSCACHE_DEBUG_LEVEL COOKIE
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include "internal.h"
15
16 struct kmem_cache *fscache_cookie_jar;
17
18 static void fscache_cookie_lru_timed_out(struct timer_list *timer);
19 static void fscache_cookie_lru_worker(struct work_struct *work);
20 static void fscache_cookie_worker(struct work_struct *work);
21 static void fscache_unhash_cookie(struct fscache_cookie *cookie);
22 static void fscache_perform_invalidation(struct fscache_cookie *cookie);
23
24 #define fscache_cookie_hash_shift 15
25 static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift];
26 static LIST_HEAD(fscache_cookies);
27 static DEFINE_RWLOCK(fscache_cookies_lock);
28 static LIST_HEAD(fscache_cookie_lru);
29 static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
30 DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
31 static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
32 static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
33 static unsigned int fscache_lru_cookie_timeout = 10 * HZ;
34
35 void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
36 {
37 const u8 *k;
38
39 pr_err("%c-cookie c=%08x [fl=%lx na=%u nA=%u s=%c]\n",
40 prefix,
41 cookie->debug_id,
42 cookie->flags,
43 atomic_read(&cookie->n_active),
44 atomic_read(&cookie->n_accesses),
45 fscache_cookie_states[cookie->state]);
46 pr_err("%c-cookie V=%08x [%s]\n",
47 prefix,
48 cookie->volume->debug_id,
49 cookie->volume->key);
50
51 k = (cookie->key_len <= sizeof(cookie->inline_key)) ?
52 cookie->inline_key : cookie->key;
53 pr_err("%c-key=[%u] '%*phN'\n", prefix, cookie->key_len, cookie->key_len, k);
54 }
55
56 static void fscache_free_cookie(struct fscache_cookie *cookie)
57 {
58 if (WARN_ON_ONCE(!list_empty(&cookie->commit_link))) {
59 spin_lock(&fscache_cookie_lru_lock);
60 list_del_init(&cookie->commit_link);
61 spin_unlock(&fscache_cookie_lru_lock);
62 fscache_stat_d(&fscache_n_cookies_lru);
63 fscache_stat(&fscache_n_cookies_lru_removed);
64 }
65
66 if (WARN_ON_ONCE(test_bit(FSCACHE_COOKIE_IS_HASHED, &cookie->flags))) {
67 fscache_print_cookie(cookie, 'F');
68 return;
69 }
70
71 write_lock(&fscache_cookies_lock);
72 list_del(&cookie->proc_link);
73 write_unlock(&fscache_cookies_lock);
74 if (cookie->aux_len > sizeof(cookie->inline_aux))
75 kfree(cookie->aux);
76 if (cookie->key_len > sizeof(cookie->inline_key))
77 kfree(cookie->key);
78 fscache_stat_d(&fscache_n_cookies);
79 kmem_cache_free(fscache_cookie_jar, cookie);
80 }
81
82 static void __fscache_queue_cookie(struct fscache_cookie *cookie)
83 {
84 if (!queue_work(fscache_wq, &cookie->work))
85 fscache_put_cookie(cookie, fscache_cookie_put_over_queued);
86 }
87
88 static void fscache_queue_cookie(struct fscache_cookie *cookie,
89 enum fscache_cookie_trace where)
90 {
91 fscache_get_cookie(cookie, where);
92 __fscache_queue_cookie(cookie);
93 }
94
95 /*
96 * Initialise the access gate on a cookie by setting a flag to prevent the
97 * state machine from being queued when the access counter transitions to 0.
98 * We're only interested in this when we withdraw caching services from the
99 * cookie.
100 */
101 static void fscache_init_access_gate(struct fscache_cookie *cookie)
102 {
103 int n_accesses;
104
105 n_accesses = atomic_read(&cookie->n_accesses);
106 trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
107 n_accesses, fscache_access_cache_pin);
108 set_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags);
109 }
110
111 /**
112 * fscache_end_cookie_access - Unpin a cache at the end of an access.
113 * @cookie: A data file cookie
114 * @why: An indication of the circumstances of the access for tracing
115 *
116 * Unpin a cache cookie after we've accessed it and bring a deferred
117 * relinquishment or withdrawal state into effect.
118 *
119 * The @why indicator is provided for tracing purposes.
120 */
121 void fscache_end_cookie_access(struct fscache_cookie *cookie,
122 enum fscache_access_trace why)
123 {
124 int n_accesses;
125
126 smp_mb__before_atomic();
127 n_accesses = atomic_dec_return(&cookie->n_accesses);
128 trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
129 n_accesses, why);
130 if (n_accesses == 0 &&
131 !test_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags))
132 fscache_queue_cookie(cookie, fscache_cookie_get_end_access);
133 }
134 EXPORT_SYMBOL(fscache_end_cookie_access);
135
136 /*
137 * Pin the cache behind a cookie so that we can access it.
138 */
139 static void __fscache_begin_cookie_access(struct fscache_cookie *cookie,
140 enum fscache_access_trace why)
141 {
142 int n_accesses;
143
144 n_accesses = atomic_inc_return(&cookie->n_accesses);
145 smp_mb__after_atomic(); /* (Future) read state after is-caching.
146 * Reread n_accesses after is-caching
147 */
148 trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
149 n_accesses, why);
150 }
151
152 /**
153 * fscache_begin_cookie_access - Pin a cache so data can be accessed
154 * @cookie: A data file cookie
155 * @why: An indication of the circumstances of the access for tracing
156 *
157 * Attempt to pin the cache to prevent it from going away whilst we're
158 * accessing data and returns true if successful. This works as follows:
159 *
160 * (1) If the cookie is not being cached (ie. FSCACHE_COOKIE_IS_CACHING is not
161 * set), we return false to indicate access was not permitted.
162 *
163 * (2) If the cookie is being cached, we increment its n_accesses count and
164 * then recheck the IS_CACHING flag, ending the access if it got cleared.
165 *
166 * (3) When we end the access, we decrement the cookie's n_accesses and wake
167 * up the any waiters if it reaches 0.
168 *
169 * (4) Whilst the cookie is actively being cached, its n_accesses is kept
170 * artificially incremented to prevent wakeups from happening.
171 *
172 * (5) When the cache is taken offline or if the cookie is culled, the flag is
173 * cleared to prevent new accesses, the cookie's n_accesses is decremented
174 * and we wait for it to become 0.
175 *
176 * The @why indicator are merely provided for tracing purposes.
177 */
178 bool fscache_begin_cookie_access(struct fscache_cookie *cookie,
179 enum fscache_access_trace why)
180 {
181 if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags))
182 return false;
183 __fscache_begin_cookie_access(cookie, why);
184 if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags) ||
185 !fscache_cache_is_live(cookie->volume->cache)) {
186 fscache_end_cookie_access(cookie, fscache_access_unlive);
187 return false;
188 }
189 return true;
190 }
191
192 static inline void wake_up_cookie_state(struct fscache_cookie *cookie)
193 {
194 /* Use a barrier to ensure that waiters see the state variable
195 * change, as spin_unlock doesn't guarantee a barrier.
196 *
197 * See comments over wake_up_bit() and waitqueue_active().
198 */
199 smp_mb();
200 wake_up_var(&cookie->state);
201 }
202
203 /*
204 * Change the state a cookie is at and wake up anyone waiting for that. Impose
205 * an ordering between the stuff stored in the cookie and the state member.
206 * Paired with fscache_cookie_state().
207 */
208 static void __fscache_set_cookie_state(struct fscache_cookie *cookie,
209 enum fscache_cookie_state state)
210 {
211 smp_store_release(&cookie->state, state);
212 }
213
214 static void fscache_set_cookie_state(struct fscache_cookie *cookie,
215 enum fscache_cookie_state state)
216 {
217 spin_lock(&cookie->lock);
218 __fscache_set_cookie_state(cookie, state);
219 spin_unlock(&cookie->lock);
220 wake_up_cookie_state(cookie);
221 }
222
223 /**
224 * fscache_cookie_lookup_negative - Note negative lookup
225 * @cookie: The cookie that was being looked up
226 *
227 * Note that some part of the metadata path in the cache doesn't exist and so
228 * we can release any waiting readers in the certain knowledge that there's
229 * nothing for them to actually read.
230 *
231 * This function uses no locking and must only be called from the state machine.
232 */
233 void fscache_cookie_lookup_negative(struct fscache_cookie *cookie)
234 {
235 set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
236 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_CREATING);
237 }
238 EXPORT_SYMBOL(fscache_cookie_lookup_negative);
239
240 /**
241 * fscache_resume_after_invalidation - Allow I/O to resume after invalidation
242 * @cookie: The cookie that was invalidated
243 *
244 * Tell fscache that invalidation is sufficiently complete that I/O can be
245 * allowed again.
246 */
247 void fscache_resume_after_invalidation(struct fscache_cookie *cookie)
248 {
249 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
250 }
251 EXPORT_SYMBOL(fscache_resume_after_invalidation);
252
253 /**
254 * fscache_caching_failed - Report that a failure stopped caching on a cookie
255 * @cookie: The cookie that was affected
256 *
257 * Tell fscache that caching on a cookie needs to be stopped due to some sort
258 * of failure.
259 *
260 * This function uses no locking and must only be called from the state machine.
261 */
262 void fscache_caching_failed(struct fscache_cookie *cookie)
263 {
264 clear_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags);
265 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_FAILED);
266 trace_fscache_cookie(cookie->debug_id, refcount_read(&cookie->ref),
267 fscache_cookie_failed);
268 }
269 EXPORT_SYMBOL(fscache_caching_failed);
270
271 /*
272 * Set the index key in a cookie. The cookie struct has space for a 16-byte
273 * key plus length and hash, but if that's not big enough, it's instead a
274 * pointer to a buffer containing 3 bytes of hash, 1 byte of length and then
275 * the key data.
276 */
277 static int fscache_set_key(struct fscache_cookie *cookie,
278 const void *index_key, size_t index_key_len)
279 {
280 void *buf;
281 size_t buf_size;
282
283 buf_size = round_up(index_key_len, sizeof(__le32));
284
285 if (index_key_len > sizeof(cookie->inline_key)) {
286 buf = kzalloc(buf_size, GFP_KERNEL);
287 if (!buf)
288 return -ENOMEM;
289 cookie->key = buf;
290 } else {
291 buf = cookie->inline_key;
292 }
293
294 memcpy(buf, index_key, index_key_len);
295 cookie->key_hash = fscache_hash(cookie->volume->key_hash,
296 buf, buf_size);
297 return 0;
298 }
299
300 static bool fscache_cookie_same(const struct fscache_cookie *a,
301 const struct fscache_cookie *b)
302 {
303 const void *ka, *kb;
304
305 if (a->key_hash != b->key_hash ||
306 a->volume != b->volume ||
307 a->key_len != b->key_len)
308 return false;
309
310 if (a->key_len <= sizeof(a->inline_key)) {
311 ka = &a->inline_key;
312 kb = &b->inline_key;
313 } else {
314 ka = a->key;
315 kb = b->key;
316 }
317 return memcmp(ka, kb, a->key_len) == 0;
318 }
319
320 static atomic_t fscache_cookie_debug_id = ATOMIC_INIT(1);
321
322 /*
323 * Allocate a cookie.
324 */
325 static struct fscache_cookie *fscache_alloc_cookie(
326 struct fscache_volume *volume,
327 u8 advice,
328 const void *index_key, size_t index_key_len,
329 const void *aux_data, size_t aux_data_len,
330 loff_t object_size)
331 {
332 struct fscache_cookie *cookie;
333
334 /* allocate and initialise a cookie */
335 cookie = kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
336 if (!cookie)
337 return NULL;
338 fscache_stat(&fscache_n_cookies);
339
340 cookie->volume = volume;
341 cookie->advice = advice;
342 cookie->key_len = index_key_len;
343 cookie->aux_len = aux_data_len;
344 cookie->object_size = object_size;
345 if (object_size == 0)
346 __set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
347
348 if (fscache_set_key(cookie, index_key, index_key_len) < 0)
349 goto nomem;
350
351 if (cookie->aux_len <= sizeof(cookie->inline_aux)) {
352 memcpy(cookie->inline_aux, aux_data, cookie->aux_len);
353 } else {
354 cookie->aux = kmemdup(aux_data, cookie->aux_len, GFP_KERNEL);
355 if (!cookie->aux)
356 goto nomem;
357 }
358
359 refcount_set(&cookie->ref, 1);
360 cookie->debug_id = atomic_inc_return(&fscache_cookie_debug_id);
361 spin_lock_init(&cookie->lock);
362 INIT_LIST_HEAD(&cookie->commit_link);
363 INIT_WORK(&cookie->work, fscache_cookie_worker);
364 __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
365
366 write_lock(&fscache_cookies_lock);
367 list_add_tail(&cookie->proc_link, &fscache_cookies);
368 write_unlock(&fscache_cookies_lock);
369 fscache_see_cookie(cookie, fscache_cookie_new_acquire);
370 return cookie;
371
372 nomem:
373 fscache_free_cookie(cookie);
374 return NULL;
375 }
376
377 static inline bool fscache_cookie_is_dropped(struct fscache_cookie *cookie)
378 {
379 return READ_ONCE(cookie->state) == FSCACHE_COOKIE_STATE_DROPPED;
380 }
381
382 static void fscache_wait_on_collision(struct fscache_cookie *candidate,
383 struct fscache_cookie *wait_for)
384 {
385 enum fscache_cookie_state *statep = &wait_for->state;
386
387 wait_var_event_timeout(statep, fscache_cookie_is_dropped(wait_for),
388 20 * HZ);
389 if (!fscache_cookie_is_dropped(wait_for)) {
390 pr_notice("Potential collision c=%08x old: c=%08x",
391 candidate->debug_id, wait_for->debug_id);
392 wait_var_event(statep, fscache_cookie_is_dropped(wait_for));
393 }
394 }
395
396 /*
397 * Attempt to insert the new cookie into the hash. If there's a collision, we
398 * wait for the old cookie to complete if it's being relinquished and an error
399 * otherwise.
400 */
401 static bool fscache_hash_cookie(struct fscache_cookie *candidate)
402 {
403 struct fscache_cookie *cursor, *wait_for = NULL;
404 struct hlist_bl_head *h;
405 struct hlist_bl_node *p;
406 unsigned int bucket;
407
408 bucket = candidate->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
409 h = &fscache_cookie_hash[bucket];
410
411 hlist_bl_lock(h);
412 hlist_bl_for_each_entry(cursor, p, h, hash_link) {
413 if (fscache_cookie_same(candidate, cursor)) {
414 if (!test_bit(FSCACHE_COOKIE_RELINQUISHED, &cursor->flags))
415 goto collision;
416 wait_for = fscache_get_cookie(cursor,
417 fscache_cookie_get_hash_collision);
418 break;
419 }
420 }
421
422 fscache_get_volume(candidate->volume, fscache_volume_get_cookie);
423 atomic_inc(&candidate->volume->n_cookies);
424 hlist_bl_add_head(&candidate->hash_link, h);
425 set_bit(FSCACHE_COOKIE_IS_HASHED, &candidate->flags);
426 hlist_bl_unlock(h);
427
428 if (wait_for) {
429 fscache_wait_on_collision(candidate, wait_for);
430 fscache_put_cookie(wait_for, fscache_cookie_put_hash_collision);
431 }
432 return true;
433
434 collision:
435 trace_fscache_cookie(cursor->debug_id, refcount_read(&cursor->ref),
436 fscache_cookie_collision);
437 pr_err("Duplicate cookie detected\n");
438 fscache_print_cookie(cursor, 'O');
439 fscache_print_cookie(candidate, 'N');
440 hlist_bl_unlock(h);
441 return false;
442 }
443
444 /*
445 * Request a cookie to represent a data storage object within a volume.
446 *
447 * We never let on to the netfs about errors. We may set a negative cookie
448 * pointer, but that's okay
449 */
450 struct fscache_cookie *__fscache_acquire_cookie(
451 struct fscache_volume *volume,
452 u8 advice,
453 const void *index_key, size_t index_key_len,
454 const void *aux_data, size_t aux_data_len,
455 loff_t object_size)
456 {
457 struct fscache_cookie *cookie;
458
459 _enter("V=%x", volume->debug_id);
460
461 if (!index_key || !index_key_len || index_key_len > 255 || aux_data_len > 255)
462 return NULL;
463 if (!aux_data || !aux_data_len) {
464 aux_data = NULL;
465 aux_data_len = 0;
466 }
467
468 fscache_stat(&fscache_n_acquires);
469
470 cookie = fscache_alloc_cookie(volume, advice,
471 index_key, index_key_len,
472 aux_data, aux_data_len,
473 object_size);
474 if (!cookie) {
475 fscache_stat(&fscache_n_acquires_oom);
476 return NULL;
477 }
478
479 if (!fscache_hash_cookie(cookie)) {
480 fscache_see_cookie(cookie, fscache_cookie_discard);
481 fscache_free_cookie(cookie);
482 return NULL;
483 }
484
485 trace_fscache_acquire(cookie);
486 fscache_stat(&fscache_n_acquires_ok);
487 _leave(" = c=%08x", cookie->debug_id);
488 return cookie;
489 }
490 EXPORT_SYMBOL(__fscache_acquire_cookie);
491
492 /*
493 * Prepare a cache object to be written to.
494 */
495 static void fscache_prepare_to_write(struct fscache_cookie *cookie)
496 {
497 cookie->volume->cache->ops->prepare_to_write(cookie);
498 }
499
500 /*
501 * Look up a cookie in the cache.
502 */
503 static void fscache_perform_lookup(struct fscache_cookie *cookie)
504 {
505 enum fscache_access_trace trace = fscache_access_lookup_cookie_end_failed;
506 bool need_withdraw = false;
507
508 _enter("");
509
510 if (!cookie->volume->cache_priv) {
511 fscache_create_volume(cookie->volume, true);
512 if (!cookie->volume->cache_priv) {
513 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
514 goto out;
515 }
516 }
517
518 if (!cookie->volume->cache->ops->lookup_cookie(cookie)) {
519 if (cookie->state != FSCACHE_COOKIE_STATE_FAILED)
520 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
521 need_withdraw = true;
522 _leave(" [fail]");
523 goto out;
524 }
525
526 fscache_see_cookie(cookie, fscache_cookie_see_active);
527 spin_lock(&cookie->lock);
528 if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
529 __fscache_set_cookie_state(cookie,
530 FSCACHE_COOKIE_STATE_INVALIDATING);
531 else
532 __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
533 spin_unlock(&cookie->lock);
534 wake_up_cookie_state(cookie);
535 trace = fscache_access_lookup_cookie_end;
536
537 out:
538 fscache_end_cookie_access(cookie, trace);
539 if (need_withdraw)
540 fscache_withdraw_cookie(cookie);
541 fscache_end_volume_access(cookie->volume, cookie, trace);
542 }
543
544 /*
545 * Begin the process of looking up a cookie. We offload the actual process to
546 * a worker thread.
547 */
548 static bool fscache_begin_lookup(struct fscache_cookie *cookie, bool will_modify)
549 {
550 if (will_modify) {
551 set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
552 set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
553 }
554 if (!fscache_begin_volume_access(cookie->volume, cookie,
555 fscache_access_lookup_cookie))
556 return false;
557
558 __fscache_begin_cookie_access(cookie, fscache_access_lookup_cookie);
559 __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_LOOKING_UP);
560 set_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags);
561 set_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags);
562 return true;
563 }
564
565 /*
566 * Start using the cookie for I/O. This prevents the backing object from being
567 * reaped by VM pressure.
568 */
569 void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify)
570 {
571 enum fscache_cookie_state state;
572 bool queue = false;
573 int n_active;
574
575 _enter("c=%08x", cookie->debug_id);
576
577 if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
578 "Trying to use relinquished cookie\n"))
579 return;
580
581 spin_lock(&cookie->lock);
582
583 n_active = atomic_inc_return(&cookie->n_active);
584 trace_fscache_active(cookie->debug_id, refcount_read(&cookie->ref),
585 n_active, atomic_read(&cookie->n_accesses),
586 will_modify ?
587 fscache_active_use_modify : fscache_active_use);
588
589 again:
590 state = fscache_cookie_state(cookie);
591 switch (state) {
592 case FSCACHE_COOKIE_STATE_QUIESCENT:
593 queue = fscache_begin_lookup(cookie, will_modify);
594 break;
595
596 case FSCACHE_COOKIE_STATE_LOOKING_UP:
597 case FSCACHE_COOKIE_STATE_CREATING:
598 if (will_modify)
599 set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
600 break;
601 case FSCACHE_COOKIE_STATE_ACTIVE:
602 case FSCACHE_COOKIE_STATE_INVALIDATING:
603 if (will_modify &&
604 !test_and_set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags)) {
605 set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
606 queue = true;
607 }
608 /*
609 * We could race with cookie_lru which may set LRU_DISCARD bit
610 * but has yet to run the cookie state machine. If this happens
611 * and another thread tries to use the cookie, clear LRU_DISCARD
612 * so we don't end up withdrawing the cookie while in use.
613 */
614 if (test_and_clear_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags))
615 fscache_see_cookie(cookie, fscache_cookie_see_lru_discard_clear);
616 break;
617
618 case FSCACHE_COOKIE_STATE_FAILED:
619 case FSCACHE_COOKIE_STATE_WITHDRAWING:
620 break;
621
622 case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
623 spin_unlock(&cookie->lock);
624 wait_var_event(&cookie->state,
625 fscache_cookie_state(cookie) !=
626 FSCACHE_COOKIE_STATE_LRU_DISCARDING);
627 spin_lock(&cookie->lock);
628 goto again;
629
630 case FSCACHE_COOKIE_STATE_DROPPED:
631 case FSCACHE_COOKIE_STATE_RELINQUISHING:
632 WARN(1, "Can't use cookie in state %u\n", state);
633 break;
634 }
635
636 spin_unlock(&cookie->lock);
637 if (queue)
638 fscache_queue_cookie(cookie, fscache_cookie_get_use_work);
639 _leave("");
640 }
641 EXPORT_SYMBOL(__fscache_use_cookie);
642
643 static void fscache_unuse_cookie_locked(struct fscache_cookie *cookie)
644 {
645 clear_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags);
646 if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags))
647 return;
648
649 cookie->unused_at = jiffies;
650 spin_lock(&fscache_cookie_lru_lock);
651 if (list_empty(&cookie->commit_link)) {
652 fscache_get_cookie(cookie, fscache_cookie_get_lru);
653 fscache_stat(&fscache_n_cookies_lru);
654 }
655 list_move_tail(&cookie->commit_link, &fscache_cookie_lru);
656
657 spin_unlock(&fscache_cookie_lru_lock);
658 timer_reduce(&fscache_cookie_lru_timer,
659 jiffies + fscache_lru_cookie_timeout);
660 }
661
662 /*
663 * Stop using the cookie for I/O.
664 */
665 void __fscache_unuse_cookie(struct fscache_cookie *cookie,
666 const void *aux_data, const loff_t *object_size)
667 {
668 unsigned int debug_id = cookie->debug_id;
669 unsigned int r = refcount_read(&cookie->ref);
670 unsigned int a = atomic_read(&cookie->n_accesses);
671 unsigned int c;
672
673 if (aux_data || object_size)
674 __fscache_update_cookie(cookie, aux_data, object_size);
675
676 /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
677 c = atomic_fetch_add_unless(&cookie->n_active, -1, 1);
678 if (c != 1) {
679 trace_fscache_active(debug_id, r, c - 1, a, fscache_active_unuse);
680 return;
681 }
682
683 spin_lock(&cookie->lock);
684 r = refcount_read(&cookie->ref);
685 a = atomic_read(&cookie->n_accesses);
686 c = atomic_dec_return(&cookie->n_active);
687 trace_fscache_active(debug_id, r, c, a, fscache_active_unuse);
688 if (c == 0)
689 fscache_unuse_cookie_locked(cookie);
690 spin_unlock(&cookie->lock);
691 }
692 EXPORT_SYMBOL(__fscache_unuse_cookie);
693
694 /*
695 * Perform work upon the cookie, such as committing its cache state,
696 * relinquishing it or withdrawing the backing cache. We're protected from the
697 * cache going away under us as object withdrawal must come through this
698 * non-reentrant work item.
699 */
700 static void fscache_cookie_state_machine(struct fscache_cookie *cookie)
701 {
702 enum fscache_cookie_state state;
703 bool wake = false;
704
705 _enter("c=%x", cookie->debug_id);
706
707 again:
708 spin_lock(&cookie->lock);
709 again_locked:
710 state = cookie->state;
711 switch (state) {
712 case FSCACHE_COOKIE_STATE_QUIESCENT:
713 /* The QUIESCENT state is jumped to the LOOKING_UP state by
714 * fscache_use_cookie().
715 */
716
717 if (atomic_read(&cookie->n_accesses) == 0 &&
718 test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
719 __fscache_set_cookie_state(cookie,
720 FSCACHE_COOKIE_STATE_RELINQUISHING);
721 wake = true;
722 goto again_locked;
723 }
724 break;
725
726 case FSCACHE_COOKIE_STATE_LOOKING_UP:
727 spin_unlock(&cookie->lock);
728 fscache_init_access_gate(cookie);
729 fscache_perform_lookup(cookie);
730 goto again;
731
732 case FSCACHE_COOKIE_STATE_INVALIDATING:
733 spin_unlock(&cookie->lock);
734 fscache_perform_invalidation(cookie);
735 goto again;
736
737 case FSCACHE_COOKIE_STATE_ACTIVE:
738 if (test_and_clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags)) {
739 spin_unlock(&cookie->lock);
740 fscache_prepare_to_write(cookie);
741 spin_lock(&cookie->lock);
742 }
743 if (test_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags)) {
744 if (atomic_read(&cookie->n_accesses) != 0)
745 /* still being accessed: postpone it */
746 break;
747
748 __fscache_set_cookie_state(cookie,
749 FSCACHE_COOKIE_STATE_LRU_DISCARDING);
750 wake = true;
751 goto again_locked;
752 }
753 fallthrough;
754
755 case FSCACHE_COOKIE_STATE_FAILED:
756 if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
757 fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
758
759 if (atomic_read(&cookie->n_accesses) != 0)
760 break;
761 if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
762 __fscache_set_cookie_state(cookie,
763 FSCACHE_COOKIE_STATE_RELINQUISHING);
764 wake = true;
765 goto again_locked;
766 }
767 if (test_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags)) {
768 __fscache_set_cookie_state(cookie,
769 FSCACHE_COOKIE_STATE_WITHDRAWING);
770 wake = true;
771 goto again_locked;
772 }
773 break;
774
775 case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
776 case FSCACHE_COOKIE_STATE_RELINQUISHING:
777 case FSCACHE_COOKIE_STATE_WITHDRAWING:
778 if (cookie->cache_priv) {
779 spin_unlock(&cookie->lock);
780 cookie->volume->cache->ops->withdraw_cookie(cookie);
781 spin_lock(&cookie->lock);
782 }
783
784 if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
785 fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
786
787 switch (state) {
788 case FSCACHE_COOKIE_STATE_RELINQUISHING:
789 fscache_see_cookie(cookie, fscache_cookie_see_relinquish);
790 fscache_unhash_cookie(cookie);
791 __fscache_set_cookie_state(cookie,
792 FSCACHE_COOKIE_STATE_DROPPED);
793 wake = true;
794 goto out;
795 case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
796 fscache_see_cookie(cookie, fscache_cookie_see_lru_discard);
797 break;
798 case FSCACHE_COOKIE_STATE_WITHDRAWING:
799 fscache_see_cookie(cookie, fscache_cookie_see_withdraw);
800 break;
801 default:
802 BUG();
803 }
804
805 clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
806 clear_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags);
807 clear_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags);
808 clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
809 set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
810 __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
811 wake = true;
812 goto again_locked;
813
814 case FSCACHE_COOKIE_STATE_DROPPED:
815 break;
816
817 default:
818 WARN_ONCE(1, "Cookie %x in unexpected state %u\n",
819 cookie->debug_id, state);
820 break;
821 }
822
823 out:
824 spin_unlock(&cookie->lock);
825 if (wake)
826 wake_up_cookie_state(cookie);
827 _leave("");
828 }
829
830 static void fscache_cookie_worker(struct work_struct *work)
831 {
832 struct fscache_cookie *cookie = container_of(work, struct fscache_cookie, work);
833
834 fscache_see_cookie(cookie, fscache_cookie_see_work);
835 fscache_cookie_state_machine(cookie);
836 fscache_put_cookie(cookie, fscache_cookie_put_work);
837 }
838
839 /*
840 * Wait for the object to become inactive. The cookie's work item will be
841 * scheduled when someone transitions n_accesses to 0 - but if someone's
842 * already done that, schedule it anyway.
843 */
844 static void __fscache_withdraw_cookie(struct fscache_cookie *cookie)
845 {
846 int n_accesses;
847 bool unpinned;
848
849 unpinned = test_and_clear_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags);
850
851 /* Need to read the access count after unpinning */
852 n_accesses = atomic_read(&cookie->n_accesses);
853 if (unpinned)
854 trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
855 n_accesses, fscache_access_cache_unpin);
856 if (n_accesses == 0)
857 fscache_queue_cookie(cookie, fscache_cookie_get_end_access);
858 }
859
860 static void fscache_cookie_lru_do_one(struct fscache_cookie *cookie)
861 {
862 fscache_see_cookie(cookie, fscache_cookie_see_lru_do_one);
863
864 spin_lock(&cookie->lock);
865 if (cookie->state != FSCACHE_COOKIE_STATE_ACTIVE ||
866 time_before(jiffies, cookie->unused_at + fscache_lru_cookie_timeout) ||
867 atomic_read(&cookie->n_active) > 0) {
868 spin_unlock(&cookie->lock);
869 fscache_stat(&fscache_n_cookies_lru_removed);
870 } else {
871 set_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags);
872 spin_unlock(&cookie->lock);
873 fscache_stat(&fscache_n_cookies_lru_expired);
874 _debug("lru c=%x", cookie->debug_id);
875 __fscache_withdraw_cookie(cookie);
876 }
877
878 fscache_put_cookie(cookie, fscache_cookie_put_lru);
879 }
880
881 static void fscache_cookie_lru_worker(struct work_struct *work)
882 {
883 struct fscache_cookie *cookie;
884 unsigned long unused_at;
885
886 spin_lock(&fscache_cookie_lru_lock);
887
888 while (!list_empty(&fscache_cookie_lru)) {
889 cookie = list_first_entry(&fscache_cookie_lru,
890 struct fscache_cookie, commit_link);
891 unused_at = cookie->unused_at + fscache_lru_cookie_timeout;
892 if (time_before(jiffies, unused_at)) {
893 timer_reduce(&fscache_cookie_lru_timer, unused_at);
894 break;
895 }
896
897 list_del_init(&cookie->commit_link);
898 fscache_stat_d(&fscache_n_cookies_lru);
899 spin_unlock(&fscache_cookie_lru_lock);
900 fscache_cookie_lru_do_one(cookie);
901 spin_lock(&fscache_cookie_lru_lock);
902 }
903
904 spin_unlock(&fscache_cookie_lru_lock);
905 }
906
907 static void fscache_cookie_lru_timed_out(struct timer_list *timer)
908 {
909 queue_work(fscache_wq, &fscache_cookie_lru_work);
910 }
911
912 static void fscache_cookie_drop_from_lru(struct fscache_cookie *cookie)
913 {
914 bool need_put = false;
915
916 if (!list_empty(&cookie->commit_link)) {
917 spin_lock(&fscache_cookie_lru_lock);
918 if (!list_empty(&cookie->commit_link)) {
919 list_del_init(&cookie->commit_link);
920 fscache_stat_d(&fscache_n_cookies_lru);
921 fscache_stat(&fscache_n_cookies_lru_dropped);
922 need_put = true;
923 }
924 spin_unlock(&fscache_cookie_lru_lock);
925 if (need_put)
926 fscache_put_cookie(cookie, fscache_cookie_put_lru);
927 }
928 }
929
930 /*
931 * Remove a cookie from the hash table.
932 */
933 static void fscache_unhash_cookie(struct fscache_cookie *cookie)
934 {
935 struct hlist_bl_head *h;
936 unsigned int bucket;
937
938 bucket = cookie->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
939 h = &fscache_cookie_hash[bucket];
940
941 hlist_bl_lock(h);
942 hlist_bl_del(&cookie->hash_link);
943 clear_bit(FSCACHE_COOKIE_IS_HASHED, &cookie->flags);
944 hlist_bl_unlock(h);
945 fscache_stat(&fscache_n_relinquishes_dropped);
946 }
947
948 static void fscache_drop_withdraw_cookie(struct fscache_cookie *cookie)
949 {
950 fscache_cookie_drop_from_lru(cookie);
951 __fscache_withdraw_cookie(cookie);
952 }
953
954 /**
955 * fscache_withdraw_cookie - Mark a cookie for withdrawal
956 * @cookie: The cookie to be withdrawn.
957 *
958 * Allow the cache backend to withdraw the backing for a cookie for its own
959 * reasons, even if that cookie is in active use.
960 */
961 void fscache_withdraw_cookie(struct fscache_cookie *cookie)
962 {
963 set_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags);
964 fscache_drop_withdraw_cookie(cookie);
965 }
966 EXPORT_SYMBOL(fscache_withdraw_cookie);
967
968 /*
969 * Allow the netfs to release a cookie back to the cache.
970 * - the object will be marked as recyclable on disk if retire is true
971 */
972 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
973 {
974 fscache_stat(&fscache_n_relinquishes);
975 if (retire)
976 fscache_stat(&fscache_n_relinquishes_retire);
977
978 _enter("c=%08x{%d},%d",
979 cookie->debug_id, atomic_read(&cookie->n_active), retire);
980
981 if (WARN(test_and_set_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
982 "Cookie c=%x already relinquished\n", cookie->debug_id))
983 return;
984
985 if (retire)
986 set_bit(FSCACHE_COOKIE_RETIRED, &cookie->flags);
987 trace_fscache_relinquish(cookie, retire);
988
989 ASSERTCMP(atomic_read(&cookie->n_active), ==, 0);
990 ASSERTCMP(atomic_read(&cookie->volume->n_cookies), >, 0);
991 atomic_dec(&cookie->volume->n_cookies);
992
993 if (test_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags)) {
994 set_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags);
995 fscache_drop_withdraw_cookie(cookie);
996 } else {
997 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_DROPPED);
998 fscache_unhash_cookie(cookie);
999 }
1000 fscache_put_cookie(cookie, fscache_cookie_put_relinquish);
1001 }
1002 EXPORT_SYMBOL(__fscache_relinquish_cookie);
1003
1004 /*
1005 * Drop a reference to a cookie.
1006 */
1007 void fscache_put_cookie(struct fscache_cookie *cookie,
1008 enum fscache_cookie_trace where)
1009 {
1010 struct fscache_volume *volume = cookie->volume;
1011 unsigned int cookie_debug_id = cookie->debug_id;
1012 bool zero;
1013 int ref;
1014
1015 zero = __refcount_dec_and_test(&cookie->ref, &ref);
1016 trace_fscache_cookie(cookie_debug_id, ref - 1, where);
1017 if (zero) {
1018 fscache_free_cookie(cookie);
1019 fscache_put_volume(volume, fscache_volume_put_cookie);
1020 }
1021 }
1022 EXPORT_SYMBOL(fscache_put_cookie);
1023
1024 /*
1025 * Get a reference to a cookie.
1026 */
1027 struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
1028 enum fscache_cookie_trace where)
1029 {
1030 int ref;
1031
1032 __refcount_inc(&cookie->ref, &ref);
1033 trace_fscache_cookie(cookie->debug_id, ref + 1, where);
1034 return cookie;
1035 }
1036 EXPORT_SYMBOL(fscache_get_cookie);
1037
1038 /*
1039 * Ask the cache to effect invalidation of a cookie.
1040 */
1041 static void fscache_perform_invalidation(struct fscache_cookie *cookie)
1042 {
1043 if (!cookie->volume->cache->ops->invalidate_cookie(cookie))
1044 fscache_caching_failed(cookie);
1045 fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
1046 }
1047
1048 /*
1049 * Invalidate an object.
1050 */
1051 void __fscache_invalidate(struct fscache_cookie *cookie,
1052 const void *aux_data, loff_t new_size,
1053 unsigned int flags)
1054 {
1055 bool is_caching;
1056
1057 _enter("c=%x", cookie->debug_id);
1058
1059 fscache_stat(&fscache_n_invalidates);
1060
1061 if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
1062 "Trying to invalidate relinquished cookie\n"))
1063 return;
1064
1065 if ((flags & FSCACHE_INVAL_DIO_WRITE) &&
1066 test_and_set_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
1067 return;
1068
1069 spin_lock(&cookie->lock);
1070 set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
1071 fscache_update_aux(cookie, aux_data, &new_size);
1072 cookie->inval_counter++;
1073 trace_fscache_invalidate(cookie, new_size);
1074
1075 switch (cookie->state) {
1076 case FSCACHE_COOKIE_STATE_INVALIDATING: /* is_still_valid will catch it */
1077 default:
1078 spin_unlock(&cookie->lock);
1079 _leave(" [no %u]", cookie->state);
1080 return;
1081
1082 case FSCACHE_COOKIE_STATE_LOOKING_UP:
1083 if (!test_and_set_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
1084 __fscache_begin_cookie_access(cookie, fscache_access_invalidate_cookie);
1085 fallthrough;
1086 case FSCACHE_COOKIE_STATE_CREATING:
1087 spin_unlock(&cookie->lock);
1088 _leave(" [look %x]", cookie->inval_counter);
1089 return;
1090
1091 case FSCACHE_COOKIE_STATE_ACTIVE:
1092 is_caching = fscache_begin_cookie_access(
1093 cookie, fscache_access_invalidate_cookie);
1094 if (is_caching)
1095 __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_INVALIDATING);
1096 spin_unlock(&cookie->lock);
1097 wake_up_cookie_state(cookie);
1098
1099 if (is_caching)
1100 fscache_queue_cookie(cookie, fscache_cookie_get_inval_work);
1101 _leave(" [inv]");
1102 return;
1103 }
1104 }
1105 EXPORT_SYMBOL(__fscache_invalidate);
1106
1107 #ifdef CONFIG_PROC_FS
1108 /*
1109 * Generate a list of extant cookies in /proc/fs/fscache/cookies
1110 */
1111 static int fscache_cookies_seq_show(struct seq_file *m, void *v)
1112 {
1113 struct fscache_cookie *cookie;
1114 unsigned int keylen = 0, auxlen = 0;
1115 u8 *p;
1116
1117 if (v == &fscache_cookies) {
1118 seq_puts(m,
1119 "COOKIE VOLUME REF ACT ACC S FL DEF \n"
1120 "======== ======== === === === = == ================\n"
1121 );
1122 return 0;
1123 }
1124
1125 cookie = list_entry(v, struct fscache_cookie, proc_link);
1126
1127 seq_printf(m,
1128 "%08x %08x %3d %3d %3d %c %02lx",
1129 cookie->debug_id,
1130 cookie->volume->debug_id,
1131 refcount_read(&cookie->ref),
1132 atomic_read(&cookie->n_active),
1133 atomic_read(&cookie->n_accesses),
1134 fscache_cookie_states[cookie->state],
1135 cookie->flags);
1136
1137 keylen = cookie->key_len;
1138 auxlen = cookie->aux_len;
1139
1140 if (keylen > 0 || auxlen > 0) {
1141 seq_puts(m, " ");
1142 p = keylen <= sizeof(cookie->inline_key) ?
1143 cookie->inline_key : cookie->key;
1144 for (; keylen > 0; keylen--)
1145 seq_printf(m, "%02x", *p++);
1146 if (auxlen > 0) {
1147 seq_puts(m, ", ");
1148 p = auxlen <= sizeof(cookie->inline_aux) ?
1149 cookie->inline_aux : cookie->aux;
1150 for (; auxlen > 0; auxlen--)
1151 seq_printf(m, "%02x", *p++);
1152 }
1153 }
1154
1155 seq_puts(m, "\n");
1156 return 0;
1157 }
1158
1159 static void *fscache_cookies_seq_start(struct seq_file *m, loff_t *_pos)
1160 __acquires(fscache_cookies_lock)
1161 {
1162 read_lock(&fscache_cookies_lock);
1163 return seq_list_start_head(&fscache_cookies, *_pos);
1164 }
1165
1166 static void *fscache_cookies_seq_next(struct seq_file *m, void *v, loff_t *_pos)
1167 {
1168 return seq_list_next(v, &fscache_cookies, _pos);
1169 }
1170
1171 static void fscache_cookies_seq_stop(struct seq_file *m, void *v)
1172 __releases(rcu)
1173 {
1174 read_unlock(&fscache_cookies_lock);
1175 }
1176
1177
1178 const struct seq_operations fscache_cookies_seq_ops = {
1179 .start = fscache_cookies_seq_start,
1180 .next = fscache_cookies_seq_next,
1181 .stop = fscache_cookies_seq_stop,
1182 .show = fscache_cookies_seq_show,
1183 };
1184 #endif
1185
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