1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Primary bucket allocation code
4 *
5 * Copyright 2012 Google, Inc.
6 *
7 * Allocation in bcache is done in terms of buckets:
8 *
9 * Each bucket has associated an 8 bit gen; this gen corresponds to the gen in
10 * btree pointers - they must match for the pointer to be considered valid.
11 *
12 * Thus (assuming a bucket has no dirty data or metadata in it) we can reuse a
13 * bucket simply by incrementing its gen.
14 *
15 * The gens (along with the priorities; it's really the gens are important but
16 * the code is named as if it's the priorities) are written in an arbitrary list
17 * of buckets on disk, with a pointer to them in the journal header.
18 *
19 * When we invalidate a bucket, we have to write its new gen to disk and wait
20 * for that write to complete before we use it - otherwise after a crash we
21 * could have pointers that appeared to be good but pointed to data that had
22 * been overwritten.
23 *
24 * Since the gens and priorities are all stored contiguously on disk, we can
25 * batch this up: We fill up the free_inc list with freshly invalidated buckets,
26 * call prio_write(), and when prio_write() finishes we pull buckets off the
27 * free_inc list and optionally discard them.
28 *
29 * free_inc isn't the only freelist - if it was, we'd often to sleep while
30 * priorities and gens were being written before we could allocate. c->free is a
31 * smaller freelist, and buckets on that list are always ready to be used.
32 *
33 * If we've got discards enabled, that happens when a bucket moves from the
34 * free_inc list to the free list.
35 *
36 * There is another freelist, because sometimes we have buckets that we know
37 * have nothing pointing into them - these we can reuse without waiting for
38 * priorities to be rewritten. These come from freed btree nodes and buckets
39 * that garbage collection discovered no longer had valid keys pointing into
40 * them (because they were overwritten). That's the unused list - buckets on the
41 * unused list move to the free list, optionally being discarded in the process.
42 *
43 * It's also important to ensure that gens don't wrap around - with respect to
44 * either the oldest gen in the btree or the gen on disk. This is quite
45 * difficult to do in practice, but we explicitly guard against it anyways - if
46 * a bucket is in danger of wrapping around we simply skip invalidating it that
47 * time around, and we garbage collect or rewrite the priorities sooner than we
48 * would have otherwise.
49 *
50 * bch_bucket_alloc() allocates a single bucket from a specific cache.
51 *
52 * bch_bucket_alloc_set() allocates one bucket from different caches
53 * out of a cache set.
54 *
55 * free_some_buckets() drives all the processes described above. It's called
56 * from bch_bucket_alloc() and a few other places that need to make sure free
57 * buckets are ready.
58 *
59 * invalidate_buckets_(lru|fifo)() find buckets that are available to be
60 * invalidated, and then invalidate them and stick them on the free_inc list -
61 * in either lru or fifo order.
62 */
63
64#include "bcache.h"
65#include "btree.h"
66
67#include <linux/blkdev.h>
68#include <linux/kthread.h>
69#include <linux/random.h>
70#include <trace/events/bcache.h>
71
72#define MAX_OPEN_BUCKETS 128
73
74/* Bucket heap / gen */
75
76uint8_t bch_inc_gen(struct cache *ca, struct bucket *b)
77{
78 uint8_t ret = ++b->gen;
79
80 ca->set->need_gc = max(ca->set->need_gc, bucket_gc_gen(b));
81 WARN_ON_ONCE(ca->set->need_gc > BUCKET_GC_GEN_MAX);
82
83 return ret;
84}
85
86void bch_rescale_priorities(struct cache_set *c, int sectors)
87{
88 struct cache *ca;
89 struct bucket *b;
90 unsigned long next = c->nbuckets * c->cache->sb.bucket_size / 1024;
91 int r;
92
93 atomic_sub(i: sectors, v: &c->rescale);
94
95 do {
96 r = atomic_read(v: &c->rescale);
97
98 if (r >= 0)
99 return;
100 } while (atomic_cmpxchg(v: &c->rescale, old: r, new: r + next) != r);
101
102 mutex_lock(&c->bucket_lock);
103
104 c->min_prio = USHRT_MAX;
105
106 ca = c->cache;
107 for_each_bucket(b, ca)
108 if (b->prio &&
109 b->prio != BTREE_PRIO &&
110 !atomic_read(v: &b->pin)) {
111 b->prio--;
112 c->min_prio = min(c->min_prio, b->prio);
113 }
114
115 mutex_unlock(lock: &c->bucket_lock);
116}
117
118/*
119 * Background allocation thread: scans for buckets to be invalidated,
120 * invalidates them, rewrites prios/gens (marking them as invalidated on disk),
121 * then optionally issues discard commands to the newly free buckets, then puts
122 * them on the various freelists.
123 */
124
125static inline bool can_inc_bucket_gen(struct bucket *b)
126{
127 return bucket_gc_gen(b) < BUCKET_GC_GEN_MAX;
128}
129
130bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b)
131{
132 BUG_ON(!ca->set->gc_mark_valid);
133
134 return (!GC_MARK(k: b) ||
135 GC_MARK(k: b) == GC_MARK_RECLAIMABLE) &&
136 !atomic_read(v: &b->pin) &&
137 can_inc_bucket_gen(b);
138}
139
140void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
141{
142 lockdep_assert_held(&ca->set->bucket_lock);
143 BUG_ON(GC_MARK(b) && GC_MARK(b) != GC_MARK_RECLAIMABLE);
144
145 if (GC_SECTORS_USED(k: b))
146 trace_bcache_invalidate(ca, bucket: b - ca->buckets);
147
148 bch_inc_gen(ca, b);
149 b->prio = INITIAL_PRIO;
150 atomic_inc(v: &b->pin);
151}
152
153static void bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
154{
155 __bch_invalidate_one_bucket(ca, b);
156
157 fifo_push(&ca->free_inc, b - ca->buckets);
158}
159
160/*
161 * Determines what order we're going to reuse buckets, smallest bucket_prio()
162 * first: we also take into account the number of sectors of live data in that
163 * bucket, and in order for that multiply to make sense we have to scale bucket
164 *
165 * Thus, we scale the bucket priorities so that the bucket with the smallest
166 * prio is worth 1/8th of what INITIAL_PRIO is worth.
167 */
168
169#define bucket_prio(b) \
170({ \
171 unsigned int min_prio = (INITIAL_PRIO - ca->set->min_prio) / 8; \
172 \
173 (b->prio - ca->set->min_prio + min_prio) * GC_SECTORS_USED(b); \
174})
175
176#define bucket_max_cmp(l, r) (bucket_prio(l) < bucket_prio(r))
177#define bucket_min_cmp(l, r) (bucket_prio(l) > bucket_prio(r))
178
179static void invalidate_buckets_lru(struct cache *ca)
180{
181 struct bucket *b;
182 ssize_t i;
183
184 ca->heap.used = 0;
185
186 for_each_bucket(b, ca) {
187 if (!bch_can_invalidate_bucket(ca, b))
188 continue;
189
190 if (!heap_full(&ca->heap))
191 heap_add(&ca->heap, b, bucket_max_cmp);
192 else if (bucket_max_cmp(b, heap_peek(&ca->heap))) {
193 ca->heap.data[0] = b;
194 heap_sift(&ca->heap, 0, bucket_max_cmp);
195 }
196 }
197
198 for (i = ca->heap.used / 2 - 1; i >= 0; --i)
199 heap_sift(&ca->heap, i, bucket_min_cmp);
200
201 while (!fifo_full(&ca->free_inc)) {
202 if (!heap_pop(&ca->heap, b, bucket_min_cmp)) {
203 /*
204 * We don't want to be calling invalidate_buckets()
205 * multiple times when it can't do anything
206 */
207 ca->invalidate_needs_gc = 1;
208 wake_up_gc(c: ca->set);
209 return;
210 }
211
212 bch_invalidate_one_bucket(ca, b);
213 }
214}
215
216static void invalidate_buckets_fifo(struct cache *ca)
217{
218 struct bucket *b;
219 size_t checked = 0;
220
221 while (!fifo_full(&ca->free_inc)) {
222 if (ca->fifo_last_bucket < ca->sb.first_bucket ||
223 ca->fifo_last_bucket >= ca->sb.nbuckets)
224 ca->fifo_last_bucket = ca->sb.first_bucket;
225
226 b = ca->buckets + ca->fifo_last_bucket++;
227
228 if (bch_can_invalidate_bucket(ca, b))
229 bch_invalidate_one_bucket(ca, b);
230
231 if (++checked >= ca->sb.nbuckets) {
232 ca->invalidate_needs_gc = 1;
233 wake_up_gc(c: ca->set);
234 return;
235 }
236 }
237}
238
239static void invalidate_buckets_random(struct cache *ca)
240{
241 struct bucket *b;
242 size_t checked = 0;
243
244 while (!fifo_full(&ca->free_inc)) {
245 size_t n;
246
247 get_random_bytes(buf: &n, len: sizeof(n));
248
249 n %= (size_t) (ca->sb.nbuckets - ca->sb.first_bucket);
250 n += ca->sb.first_bucket;
251
252 b = ca->buckets + n;
253
254 if (bch_can_invalidate_bucket(ca, b))
255 bch_invalidate_one_bucket(ca, b);
256
257 if (++checked >= ca->sb.nbuckets / 2) {
258 ca->invalidate_needs_gc = 1;
259 wake_up_gc(c: ca->set);
260 return;
261 }
262 }
263}
264
265static void invalidate_buckets(struct cache *ca)
266{
267 BUG_ON(ca->invalidate_needs_gc);
268
269 switch (CACHE_REPLACEMENT(k: &ca->sb)) {
270 case CACHE_REPLACEMENT_LRU:
271 invalidate_buckets_lru(ca);
272 break;
273 case CACHE_REPLACEMENT_FIFO:
274 invalidate_buckets_fifo(ca);
275 break;
276 case CACHE_REPLACEMENT_RANDOM:
277 invalidate_buckets_random(ca);
278 break;
279 }
280}
281
282#define allocator_wait(ca, cond) \
283do { \
284 while (1) { \
285 set_current_state(TASK_INTERRUPTIBLE); \
286 if (cond) \
287 break; \
288 \
289 mutex_unlock(&(ca)->set->bucket_lock); \
290 if (kthread_should_stop() || \
291 test_bit(CACHE_SET_IO_DISABLE, &ca->set->flags)) { \
292 set_current_state(TASK_RUNNING); \
293 goto out; \
294 } \
295 \
296 schedule(); \
297 mutex_lock(&(ca)->set->bucket_lock); \
298 } \
299 __set_current_state(TASK_RUNNING); \
300} while (0)
301
302static int bch_allocator_push(struct cache *ca, long bucket)
303{
304 unsigned int i;
305
306 /* Prios/gens are actually the most important reserve */
307 if (fifo_push(&ca->free[RESERVE_PRIO], bucket))
308 return true;
309
310 for (i = 0; i < RESERVE_NR; i++)
311 if (fifo_push(&ca->free[i], bucket))
312 return true;
313
314 return false;
315}
316
317static int bch_allocator_thread(void *arg)
318{
319 struct cache *ca = arg;
320
321 mutex_lock(&ca->set->bucket_lock);
322
323 while (1) {
324 /*
325 * First, we pull buckets off of the unused and free_inc lists,
326 * possibly issue discards to them, then we add the bucket to
327 * the free list:
328 */
329 while (1) {
330 long bucket;
331
332 if (!fifo_pop(&ca->free_inc, bucket))
333 break;
334
335 if (ca->discard) {
336 mutex_unlock(lock: &ca->set->bucket_lock);
337 blkdev_issue_discard(bdev: ca->bdev,
338 sector: bucket_to_sector(c: ca->set, b: bucket),
339 nr_sects: ca->sb.bucket_size, GFP_KERNEL);
340 mutex_lock(&ca->set->bucket_lock);
341 }
342
343 allocator_wait(ca, bch_allocator_push(ca, bucket));
344 wake_up(&ca->set->btree_cache_wait);
345 wake_up(&ca->set->bucket_wait);
346 }
347
348 /*
349 * We've run out of free buckets, we need to find some buckets
350 * we can invalidate. First, invalidate them in memory and add
351 * them to the free_inc list:
352 */
353
354retry_invalidate:
355 allocator_wait(ca, ca->set->gc_mark_valid &&
356 !ca->invalidate_needs_gc);
357 invalidate_buckets(ca);
358
359 /*
360 * Now, we write their new gens to disk so we can start writing
361 * new stuff to them:
362 */
363 allocator_wait(ca, !atomic_read(&ca->set->prio_blocked));
364 if (CACHE_SYNC(k: &ca->sb)) {
365 /*
366 * This could deadlock if an allocation with a btree
367 * node locked ever blocked - having the btree node
368 * locked would block garbage collection, but here we're
369 * waiting on garbage collection before we invalidate
370 * and free anything.
371 *
372 * But this should be safe since the btree code always
373 * uses btree_check_reserve() before allocating now, and
374 * if it fails it blocks without btree nodes locked.
375 */
376 if (!fifo_full(&ca->free_inc))
377 goto retry_invalidate;
378
379 if (bch_prio_write(ca, wait: false) < 0) {
380 ca->invalidate_needs_gc = 1;
381 wake_up_gc(c: ca->set);
382 }
383 }
384 }
385out:
386 wait_for_kthread_stop();
387 return 0;
388}
389
390/* Allocation */
391
392long bch_bucket_alloc(struct cache *ca, unsigned int reserve, bool wait)
393{
394 DEFINE_WAIT(w);
395 struct bucket *b;
396 long r;
397
398
399 /* No allocation if CACHE_SET_IO_DISABLE bit is set */
400 if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &ca->set->flags)))
401 return -1;
402
403 /* fastpath */
404 if (fifo_pop(&ca->free[RESERVE_NONE], r) ||
405 fifo_pop(&ca->free[reserve], r))
406 goto out;
407
408 if (!wait) {
409 trace_bcache_alloc_fail(ca, reserve);
410 return -1;
411 }
412
413 do {
414 prepare_to_wait(wq_head: &ca->set->bucket_wait, wq_entry: &w,
415 TASK_UNINTERRUPTIBLE);
416
417 mutex_unlock(lock: &ca->set->bucket_lock);
418 schedule();
419 mutex_lock(&ca->set->bucket_lock);
420 } while (!fifo_pop(&ca->free[RESERVE_NONE], r) &&
421 !fifo_pop(&ca->free[reserve], r));
422
423 finish_wait(wq_head: &ca->set->bucket_wait, wq_entry: &w);
424out:
425 if (ca->alloc_thread)
426 wake_up_process(tsk: ca->alloc_thread);
427
428 trace_bcache_alloc(ca, bucket: reserve);
429
430 if (expensive_debug_checks(ca->set)) {
431 size_t iter;
432 long i;
433 unsigned int j;
434
435 for (iter = 0; iter < prio_buckets(ca) * 2; iter++)
436 BUG_ON(ca->prio_buckets[iter] == (uint64_t) r);
437
438 for (j = 0; j < RESERVE_NR; j++)
439 fifo_for_each(i, &ca->free[j], iter)
440 BUG_ON(i == r);
441 fifo_for_each(i, &ca->free_inc, iter)
442 BUG_ON(i == r);
443 }
444
445 b = ca->buckets + r;
446
447 BUG_ON(atomic_read(&b->pin) != 1);
448
449 SET_GC_SECTORS_USED(k: b, v: ca->sb.bucket_size);
450
451 if (reserve <= RESERVE_PRIO) {
452 SET_GC_MARK(k: b, GC_MARK_METADATA);
453 SET_GC_MOVE(k: b, v: 0);
454 b->prio = BTREE_PRIO;
455 } else {
456 SET_GC_MARK(k: b, GC_MARK_RECLAIMABLE);
457 SET_GC_MOVE(k: b, v: 0);
458 b->prio = INITIAL_PRIO;
459 }
460
461 if (ca->set->avail_nbuckets > 0) {
462 ca->set->avail_nbuckets--;
463 bch_update_bucket_in_use(c: ca->set, stats: &ca->set->gc_stats);
464 }
465
466 return r;
467}
468
469void __bch_bucket_free(struct cache *ca, struct bucket *b)
470{
471 SET_GC_MARK(k: b, v: 0);
472 SET_GC_SECTORS_USED(k: b, v: 0);
473
474 if (ca->set->avail_nbuckets < ca->set->nbuckets) {
475 ca->set->avail_nbuckets++;
476 bch_update_bucket_in_use(c: ca->set, stats: &ca->set->gc_stats);
477 }
478}
479
480void bch_bucket_free(struct cache_set *c, struct bkey *k)
481{
482 unsigned int i;
483
484 for (i = 0; i < KEY_PTRS(k); i++)
485 __bch_bucket_free(ca: c->cache, b: PTR_BUCKET(c, k, ptr: i));
486}
487
488int __bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
489 struct bkey *k, bool wait)
490{
491 struct cache *ca;
492 long b;
493
494 /* No allocation if CACHE_SET_IO_DISABLE bit is set */
495 if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &c->flags)))
496 return -1;
497
498 lockdep_assert_held(&c->bucket_lock);
499
500 bkey_init(k);
501
502 ca = c->cache;
503 b = bch_bucket_alloc(ca, reserve, wait);
504 if (b == -1)
505 goto err;
506
507 k->ptr[0] = MAKE_PTR(ca->buckets[b].gen,
508 bucket_to_sector(c, b),
509 ca->sb.nr_this_dev);
510
511 SET_KEY_PTRS(k, v: 1);
512
513 return 0;
514err:
515 bch_bucket_free(c, k);
516 bkey_put(c, k);
517 return -1;
518}
519
520int bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
521 struct bkey *k, bool wait)
522{
523 int ret;
524
525 mutex_lock(&c->bucket_lock);
526 ret = __bch_bucket_alloc_set(c, reserve, k, wait);
527 mutex_unlock(lock: &c->bucket_lock);
528 return ret;
529}
530
531/* Sector allocator */
532
533struct open_bucket {
534 struct list_head list;
535 unsigned int last_write_point;
536 unsigned int sectors_free;
537 BKEY_PADDED(key);
538};
539
540/*
541 * We keep multiple buckets open for writes, and try to segregate different
542 * write streams for better cache utilization: first we try to segregate flash
543 * only volume write streams from cached devices, secondly we look for a bucket
544 * where the last write to it was sequential with the current write, and
545 * failing that we look for a bucket that was last used by the same task.
546 *
547 * The ideas is if you've got multiple tasks pulling data into the cache at the
548 * same time, you'll get better cache utilization if you try to segregate their
549 * data and preserve locality.
550 *
551 * For example, dirty sectors of flash only volume is not reclaimable, if their
552 * dirty sectors mixed with dirty sectors of cached device, such buckets will
553 * be marked as dirty and won't be reclaimed, though the dirty data of cached
554 * device have been written back to backend device.
555 *
556 * And say you've starting Firefox at the same time you're copying a
557 * bunch of files. Firefox will likely end up being fairly hot and stay in the
558 * cache awhile, but the data you copied might not be; if you wrote all that
559 * data to the same buckets it'd get invalidated at the same time.
560 *
561 * Both of those tasks will be doing fairly random IO so we can't rely on
562 * detecting sequential IO to segregate their data, but going off of the task
563 * should be a sane heuristic.
564 */
565static struct open_bucket *pick_data_bucket(struct cache_set *c,
566 const struct bkey *search,
567 unsigned int write_point,
568 struct bkey *alloc)
569{
570 struct open_bucket *ret, *ret_task = NULL;
571
572 list_for_each_entry_reverse(ret, &c->data_buckets, list)
573 if (UUID_FLASH_ONLY(k: &c->uuids[KEY_INODE(k: &ret->key)]) !=
574 UUID_FLASH_ONLY(k: &c->uuids[KEY_INODE(k: search)]))
575 continue;
576 else if (!bkey_cmp(l: &ret->key, r: search))
577 goto found;
578 else if (ret->last_write_point == write_point)
579 ret_task = ret;
580
581 ret = ret_task ?: list_first_entry(&c->data_buckets,
582 struct open_bucket, list);
583found:
584 if (!ret->sectors_free && KEY_PTRS(k: alloc)) {
585 ret->sectors_free = c->cache->sb.bucket_size;
586 bkey_copy(&ret->key, alloc);
587 bkey_init(k: alloc);
588 }
589
590 if (!ret->sectors_free)
591 ret = NULL;
592
593 return ret;
594}
595
596/*
597 * Allocates some space in the cache to write to, and k to point to the newly
598 * allocated space, and updates KEY_SIZE(k) and KEY_OFFSET(k) (to point to the
599 * end of the newly allocated space).
600 *
601 * May allocate fewer sectors than @sectors, KEY_SIZE(k) indicates how many
602 * sectors were actually allocated.
603 *
604 * If s->writeback is true, will not fail.
605 */
606bool bch_alloc_sectors(struct cache_set *c,
607 struct bkey *k,
608 unsigned int sectors,
609 unsigned int write_point,
610 unsigned int write_prio,
611 bool wait)
612{
613 struct open_bucket *b;
614 BKEY_PADDED(key) alloc;
615 unsigned int i;
616
617 /*
618 * We might have to allocate a new bucket, which we can't do with a
619 * spinlock held. So if we have to allocate, we drop the lock, allocate
620 * and then retry. KEY_PTRS() indicates whether alloc points to
621 * allocated bucket(s).
622 */
623
624 bkey_init(k: &alloc.key);
625 spin_lock(lock: &c->data_bucket_lock);
626
627 while (!(b = pick_data_bucket(c, search: k, write_point, alloc: &alloc.key))) {
628 unsigned int watermark = write_prio
629 ? RESERVE_MOVINGGC
630 : RESERVE_NONE;
631
632 spin_unlock(lock: &c->data_bucket_lock);
633
634 if (bch_bucket_alloc_set(c, reserve: watermark, k: &alloc.key, wait))
635 return false;
636
637 spin_lock(lock: &c->data_bucket_lock);
638 }
639
640 /*
641 * If we had to allocate, we might race and not need to allocate the
642 * second time we call pick_data_bucket(). If we allocated a bucket but
643 * didn't use it, drop the refcount bch_bucket_alloc_set() took:
644 */
645 if (KEY_PTRS(k: &alloc.key))
646 bkey_put(c, k: &alloc.key);
647
648 for (i = 0; i < KEY_PTRS(k: &b->key); i++)
649 EBUG_ON(ptr_stale(c, &b->key, i));
650
651 /* Set up the pointer to the space we're allocating: */
652
653 for (i = 0; i < KEY_PTRS(k: &b->key); i++)
654 k->ptr[i] = b->key.ptr[i];
655
656 sectors = min(sectors, b->sectors_free);
657
658 SET_KEY_OFFSET(k, v: KEY_OFFSET(k) + sectors);
659 SET_KEY_SIZE(k, v: sectors);
660 SET_KEY_PTRS(k, v: KEY_PTRS(k: &b->key));
661
662 /*
663 * Move b to the end of the lru, and keep track of what this bucket was
664 * last used for:
665 */
666 list_move_tail(list: &b->list, head: &c->data_buckets);
667 bkey_copy_key(dest: &b->key, src: k);
668 b->last_write_point = write_point;
669
670 b->sectors_free -= sectors;
671
672 for (i = 0; i < KEY_PTRS(k: &b->key); i++) {
673 SET_PTR_OFFSET(k: &b->key, i, v: PTR_OFFSET(k: &b->key, i) + sectors);
674
675 atomic_long_add(i: sectors,
676 v: &c->cache->sectors_written);
677 }
678
679 if (b->sectors_free < c->cache->sb.block_size)
680 b->sectors_free = 0;
681
682 /*
683 * k takes refcounts on the buckets it points to until it's inserted
684 * into the btree, but if we're done with this bucket we just transfer
685 * get_data_bucket()'s refcount.
686 */
687 if (b->sectors_free)
688 for (i = 0; i < KEY_PTRS(k: &b->key); i++)
689 atomic_inc(v: &PTR_BUCKET(c, k: &b->key, ptr: i)->pin);
690
691 spin_unlock(lock: &c->data_bucket_lock);
692 return true;
693}
694
695/* Init */
696
697void bch_open_buckets_free(struct cache_set *c)
698{
699 struct open_bucket *b;
700
701 while (!list_empty(head: &c->data_buckets)) {
702 b = list_first_entry(&c->data_buckets,
703 struct open_bucket, list);
704 list_del(entry: &b->list);
705 kfree(objp: b);
706 }
707}
708
709int bch_open_buckets_alloc(struct cache_set *c)
710{
711 int i;
712
713 spin_lock_init(&c->data_bucket_lock);
714
715 for (i = 0; i < MAX_OPEN_BUCKETS; i++) {
716 struct open_bucket *b = kzalloc(size: sizeof(*b), GFP_KERNEL);
717
718 if (!b)
719 return -ENOMEM;
720
721 list_add(new: &b->list, head: &c->data_buckets);
722 }
723
724 return 0;
725}
726
727int bch_cache_allocator_start(struct cache *ca)
728{
729 struct task_struct *k = kthread_run(bch_allocator_thread,
730 ca, "bcache_allocator");
731 if (IS_ERR(ptr: k))
732 return PTR_ERR(ptr: k);
733
734 ca->alloc_thread = k;
735 return 0;
736}
737

source code of linux/drivers/md/bcache/alloc.c