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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2009-2011 Red Hat, Inc.
4 *
5 * Author: Mikulas Patocka <mpatocka@redhat.com>
6 *
7 * This file is released under the GPL.
8 */
9
10#include <linux/dm-bufio.h>
11
12#include <linux/device-mapper.h>
13#include <linux/dm-io.h>
14#include <linux/slab.h>
15#include <linux/sched/mm.h>
16#include <linux/jiffies.h>
17#include <linux/vmalloc.h>
18#include <linux/shrinker.h>
19#include <linux/module.h>
20#include <linux/rbtree.h>
21#include <linux/stacktrace.h>
22#include <linux/jump_label.h>
23
24#include "dm.h"
25
26#define DM_MSG_PREFIX "bufio"
27
28/*
29 * Memory management policy:
30 * Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
31 * or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
32 * Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
33 * Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
34 * dirty buffers.
35 */
36#define DM_BUFIO_MIN_BUFFERS 8
37
38#define DM_BUFIO_MEMORY_PERCENT 2
39#define DM_BUFIO_VMALLOC_PERCENT 25
40#define DM_BUFIO_WRITEBACK_RATIO 3
41#define DM_BUFIO_LOW_WATERMARK_RATIO 16
42
43/*
44 * Check buffer ages in this interval (seconds)
45 */
46#define DM_BUFIO_WORK_TIMER_SECS 30
47
48/*
49 * Free buffers when they are older than this (seconds)
50 */
51#define DM_BUFIO_DEFAULT_AGE_SECS 300
52
53/*
54 * The nr of bytes of cached data to keep around.
55 */
56#define DM_BUFIO_DEFAULT_RETAIN_BYTES (256 * 1024)
57
58/*
59 * Align buffer writes to this boundary.
60 * Tests show that SSDs have the highest IOPS when using 4k writes.
61 */
62#define DM_BUFIO_WRITE_ALIGN 4096
63
64/*
65 * dm_buffer->list_mode
66 */
67#define LIST_CLEAN 0
68#define LIST_DIRTY 1
69#define LIST_SIZE 2
70
71/*--------------------------------------------------------------*/
72
73/*
74 * Rather than use an LRU list, we use a clock algorithm where entries
75 * are held in a circular list. When an entry is 'hit' a reference bit
76 * is set. The least recently used entry is approximated by running a
77 * cursor around the list selecting unreferenced entries. Referenced
78 * entries have their reference bit cleared as the cursor passes them.
79 */
80struct lru_entry {
81 struct list_head list;
82 atomic_t referenced;
83};
84
85struct lru_iter {
86 struct lru *lru;
87 struct list_head list;
88 struct lru_entry *stop;
89 struct lru_entry *e;
90};
91
92struct lru {
93 struct list_head *cursor;
94 unsigned long count;
95
96 struct list_head iterators;
97};
98
99/*--------------*/
100
101static void lru_init(struct lru *lru)
102{
103 lru->cursor = NULL;
104 lru->count = 0;
105 INIT_LIST_HEAD(&lru->iterators);
106}
107
108static void lru_destroy(struct lru *lru)
109{
110 WARN_ON_ONCE(lru->cursor);
111 WARN_ON_ONCE(!list_empty(&lru->iterators));
112}
113
114/*
115 * Insert a new entry into the lru.
116 */
117static void lru_insert(struct lru *lru, struct lru_entry *le)
118{
119 /*
120 * Don't be tempted to set to 1, makes the lru aspect
121 * perform poorly.
122 */
123 atomic_set(&le->referenced, 0);
124
125 if (lru->cursor) {
126 list_add_tail(&le->list, lru->cursor);
127 } else {
128 INIT_LIST_HEAD(&le->list);
129 lru->cursor = &le->list;
130 }
131 lru->count++;
132}
133
134/*--------------*/
135
136/*
137 * Convert a list_head pointer to an lru_entry pointer.
138 */
139static inline struct lru_entry *to_le(struct list_head *l)
140{
141 return container_of(l, struct lru_entry, list);
142}
143
144/*
145 * Initialize an lru_iter and add it to the list of cursors in the lru.
146 */
147static void lru_iter_begin(struct lru *lru, struct lru_iter *it)
148{
149 it->lru = lru;
150 it->stop = lru->cursor ? to_le(lru->cursor->prev) : NULL;
151 it->e = lru->cursor ? to_le(lru->cursor) : NULL;
152 list_add(&it->list, &lru->iterators);
153}
154
155/*
156 * Remove an lru_iter from the list of cursors in the lru.
157 */
158static inline void lru_iter_end(struct lru_iter *it)
159{
160 list_del(&it->list);
161}
162
163/* Predicate function type to be used with lru_iter_next */
164typedef bool (*iter_predicate)(struct lru_entry *le, void *context);
165
166/*
167 * Advance the cursor to the next entry that passes the
168 * predicate, and return that entry. Returns NULL if the
169 * iteration is complete.
170 */
171static struct lru_entry *lru_iter_next(struct lru_iter *it,
172 iter_predicate pred, void *context)
173{
174 struct lru_entry *e;
175
176 while (it->e) {
177 e = it->e;
178
179 /* advance the cursor */
180 if (it->e == it->stop)
181 it->e = NULL;
182 else
183 it->e = to_le(it->e->list.next);
184
185 if (pred(e, context))
186 return e;
187 }
188
189 return NULL;
190}
191
192/*
193 * Invalidate a specific lru_entry and update all cursors in
194 * the lru accordingly.
195 */
196static void lru_iter_invalidate(struct lru *lru, struct lru_entry *e)
197{
198 struct lru_iter *it;
199
200 list_for_each_entry(it, &lru->iterators, list) {
201 /* Move c->e forwards if necc. */
202 if (it->e == e) {
203 it->e = to_le(it->e->list.next);
204 if (it->e == e)
205 it->e = NULL;
206 }
207
208 /* Move it->stop backwards if necc. */
209 if (it->stop == e) {
210 it->stop = to_le(it->stop->list.prev);
211 if (it->stop == e)
212 it->stop = NULL;
213 }
214 }
215}
216
217/*--------------*/
218
219/*
220 * Remove a specific entry from the lru.
221 */
222static void lru_remove(struct lru *lru, struct lru_entry *le)
223{
224 lru_iter_invalidate(lru, le);
225 if (lru->count == 1) {
226 lru->cursor = NULL;
227 } else {
228 if (lru->cursor == &le->list)
229 lru->cursor = lru->cursor->next;
230 list_del(&le->list);
231 }
232 lru->count--;
233}
234
235/*
236 * Mark as referenced.
237 */
238static inline void lru_reference(struct lru_entry *le)
239{
240 atomic_set(&le->referenced, 1);
241}
242
243/*--------------*/
244
245/*
246 * Remove the least recently used entry (approx), that passes the predicate.
247 * Returns NULL on failure.
248 */
249enum evict_result {
250 ER_EVICT,
251 ER_DONT_EVICT,
252 ER_STOP, /* stop looking for something to evict */
253};
254
255typedef enum evict_result (*le_predicate)(struct lru_entry *le, void *context);
256
257static struct lru_entry *lru_evict(struct lru *lru, le_predicate pred, void *context, bool no_sleep)
258{
259 unsigned long tested = 0;
260 struct list_head *h = lru->cursor;
261 struct lru_entry *le;
262
263 if (!h)
264 return NULL;
265 /*
266 * In the worst case we have to loop around twice. Once to clear
267 * the reference flags, and then again to discover the predicate
268 * fails for all entries.
269 */
270 while (tested < lru->count) {
271 le = container_of(h, struct lru_entry, list);
272
273 if (atomic_read(&le->referenced)) {
274 atomic_set(&le->referenced, 0);
275 } else {
276 tested++;
277 switch (pred(le, context)) {
278 case ER_EVICT:
279 /*
280 * Adjust the cursor, so we start the next
281 * search from here.
282 */
283 lru->cursor = le->list.next;
284 lru_remove(lru, le);
285 return le;
286
287 case ER_DONT_EVICT:
288 break;
289
290 case ER_STOP:
291 lru->cursor = le->list.next;
292 return NULL;
293 }
294 }
295
296 h = h->next;
297
298 if (!no_sleep)
299 cond_resched();
300 }
301
302 return NULL;
303}
304
305/*--------------------------------------------------------------*/
306
307/*
308 * Buffer state bits.
309 */
310#define B_READING 0
311#define B_WRITING 1
312#define B_DIRTY 2
313
314/*
315 * Describes how the block was allocated:
316 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
317 * See the comment at alloc_buffer_data.
318 */
319enum data_mode {
320 DATA_MODE_SLAB = 0,
321 DATA_MODE_GET_FREE_PAGES = 1,
322 DATA_MODE_VMALLOC = 2,
323 DATA_MODE_LIMIT = 3
324};
325
326struct dm_buffer {
327 /* protected by the locks in dm_buffer_cache */
328 struct rb_node node;
329
330 /* immutable, so don't need protecting */
331 sector_t block;
332 void *data;
333 unsigned char data_mode; /* DATA_MODE_* */
334
335 /*
336 * These two fields are used in isolation, so do not need
337 * a surrounding lock.
338 */
339 atomic_t hold_count;
340 unsigned long last_accessed;
341
342 /*
343 * Everything else is protected by the mutex in
344 * dm_bufio_client
345 */
346 unsigned long state;
347 struct lru_entry lru;
348 unsigned char list_mode; /* LIST_* */
349 blk_status_t read_error;
350 blk_status_t write_error;
351 unsigned int dirty_start;
352 unsigned int dirty_end;
353 unsigned int write_start;
354 unsigned int write_end;
355 struct list_head write_list;
356 struct dm_bufio_client *c;
357 void (*end_io)(struct dm_buffer *b, blk_status_t bs);
358#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
359#define MAX_STACK 10
360 unsigned int stack_len;
361 unsigned long stack_entries[MAX_STACK];
362#endif
363};
364
365/*--------------------------------------------------------------*/
366
367/*
368 * The buffer cache manages buffers, particularly:
369 * - inc/dec of holder count
370 * - setting the last_accessed field
371 * - maintains clean/dirty state along with lru
372 * - selecting buffers that match predicates
373 *
374 * It does *not* handle:
375 * - allocation/freeing of buffers.
376 * - IO
377 * - Eviction or cache sizing.
378 *
379 * cache_get() and cache_put() are threadsafe, you do not need to
380 * protect these calls with a surrounding mutex. All the other
381 * methods are not threadsafe; they do use locking primitives, but
382 * only enough to ensure get/put are threadsafe.
383 */
384
385struct buffer_tree {
386 union {
387 struct rw_semaphore lock;
388 rwlock_t spinlock;
389 } u;
390 struct rb_root root;
391} ____cacheline_aligned_in_smp;
392
393struct dm_buffer_cache {
394 struct lru lru[LIST_SIZE];
395 /*
396 * We spread entries across multiple trees to reduce contention
397 * on the locks.
398 */
399 unsigned int num_locks;
400 bool no_sleep;
401 struct buffer_tree trees[];
402};
403
404static DEFINE_STATIC_KEY_FALSE(no_sleep_enabled);
405
406static inline unsigned int cache_index(sector_t block, unsigned int num_locks)
407{
408 return dm_hash_locks_index(block, num_locks);
409}
410
411static inline void cache_read_lock(struct dm_buffer_cache *bc, sector_t block)
412{
413 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
414 read_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
415 else
416 down_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
417}
418
419static inline void cache_read_unlock(struct dm_buffer_cache *bc, sector_t block)
420{
421 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
422 read_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
423 else
424 up_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
425}
426
427static inline void cache_write_lock(struct dm_buffer_cache *bc, sector_t block)
428{
429 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
430 write_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
431 else
432 down_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
433}
434
435static inline void cache_write_unlock(struct dm_buffer_cache *bc, sector_t block)
436{
437 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
438 write_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
439 else
440 up_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
441}
442
443/*
444 * Sometimes we want to repeatedly get and drop locks as part of an iteration.
445 * This struct helps avoid redundant drop and gets of the same lock.
446 */
447struct lock_history {
448 struct dm_buffer_cache *cache;
449 bool write;
450 unsigned int previous;
451 unsigned int no_previous;
452};
453
454static void lh_init(struct lock_history *lh, struct dm_buffer_cache *cache, bool write)
455{
456 lh->cache = cache;
457 lh->write = write;
458 lh->no_previous = cache->num_locks;
459 lh->previous = lh->no_previous;
460}
461
462static void __lh_lock(struct lock_history *lh, unsigned int index)
463{
464 if (lh->write) {
465 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
466 write_lock_bh(&lh->cache->trees[index].u.spinlock);
467 else
468 down_write(&lh->cache->trees[index].u.lock);
469 } else {
470 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
471 read_lock_bh(&lh->cache->trees[index].u.spinlock);
472 else
473 down_read(&lh->cache->trees[index].u.lock);
474 }
475}
476
477static void __lh_unlock(struct lock_history *lh, unsigned int index)
478{
479 if (lh->write) {
480 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
481 write_unlock_bh(&lh->cache->trees[index].u.spinlock);
482 else
483 up_write(&lh->cache->trees[index].u.lock);
484 } else {
485 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
486 read_unlock_bh(&lh->cache->trees[index].u.spinlock);
487 else
488 up_read(&lh->cache->trees[index].u.lock);
489 }
490}
491
492/*
493 * Make sure you call this since it will unlock the final lock.
494 */
495static void lh_exit(struct lock_history *lh)
496{
497 if (lh->previous != lh->no_previous) {
498 __lh_unlock(lh, lh->previous);
499 lh->previous = lh->no_previous;
500 }
501}
502
503/*
504 * Named 'next' because there is no corresponding
505 * 'up/unlock' call since it's done automatically.
506 */
507static void lh_next(struct lock_history *lh, sector_t b)
508{
509 unsigned int index = cache_index(b, lh->no_previous); /* no_previous is num_locks */
510
511 if (lh->previous != lh->no_previous) {
512 if (lh->previous != index) {
513 __lh_unlock(lh, lh->previous);
514 __lh_lock(lh, index);
515 lh->previous = index;
516 }
517 } else {
518 __lh_lock(lh, index);
519 lh->previous = index;
520 }
521}
522
523static inline struct dm_buffer *le_to_buffer(struct lru_entry *le)
524{
525 return container_of(le, struct dm_buffer, lru);
526}
527
528static struct dm_buffer *list_to_buffer(struct list_head *l)
529{
530 struct lru_entry *le = list_entry(l, struct lru_entry, list);
531
532 if (!le)
533 return NULL;
534
535 return le_to_buffer(le);
536}
537
538static void cache_init(struct dm_buffer_cache *bc, unsigned int num_locks, bool no_sleep)
539{
540 unsigned int i;
541
542 bc->num_locks = num_locks;
543 bc->no_sleep = no_sleep;
544
545 for (i = 0; i < bc->num_locks; i++) {
546 if (no_sleep)
547 rwlock_init(&bc->trees[i].u.spinlock);
548 else
549 init_rwsem(&bc->trees[i].u.lock);
550 bc->trees[i].root = RB_ROOT;
551 }
552
553 lru_init(&bc->lru[LIST_CLEAN]);
554 lru_init(&bc->lru[LIST_DIRTY]);
555}
556
557static void cache_destroy(struct dm_buffer_cache *bc)
558{
559 unsigned int i;
560
561 for (i = 0; i < bc->num_locks; i++)
562 WARN_ON_ONCE(!RB_EMPTY_ROOT(&bc->trees[i].root));
563
564 lru_destroy(&bc->lru[LIST_CLEAN]);
565 lru_destroy(&bc->lru[LIST_DIRTY]);
566}
567
568/*--------------*/
569
570/*
571 * not threadsafe, or racey depending how you look at it
572 */
573static inline unsigned long cache_count(struct dm_buffer_cache *bc, int list_mode)
574{
575 return bc->lru[list_mode].count;
576}
577
578static inline unsigned long cache_total(struct dm_buffer_cache *bc)
579{
580 return cache_count(bc, LIST_CLEAN) + cache_count(bc, LIST_DIRTY);
581}
582
583/*--------------*/
584
585/*
586 * Gets a specific buffer, indexed by block.
587 * If the buffer is found then its holder count will be incremented and
588 * lru_reference will be called.
589 *
590 * threadsafe
591 */
592static struct dm_buffer *__cache_get(const struct rb_root *root, sector_t block)
593{
594 struct rb_node *n = root->rb_node;
595 struct dm_buffer *b;
596
597 while (n) {
598 b = container_of(n, struct dm_buffer, node);
599
600 if (b->block == block)
601 return b;
602
603 n = block < b->block ? n->rb_left : n->rb_right;
604 }
605
606 return NULL;
607}
608
609static void __cache_inc_buffer(struct dm_buffer *b)
610{
611 atomic_inc(&b->hold_count);
612 WRITE_ONCE(b->last_accessed, jiffies);
613}
614
615static struct dm_buffer *cache_get(struct dm_buffer_cache *bc, sector_t block)
616{
617 struct dm_buffer *b;
618
619 cache_read_lock(bc, block);
620 b = __cache_get(&bc->trees[cache_index(block, bc->num_locks)].root, block);
621 if (b) {
622 lru_reference(&b->lru);
623 __cache_inc_buffer(b);
624 }
625 cache_read_unlock(bc, block);
626
627 return b;
628}
629
630/*--------------*/
631
632/*
633 * Returns true if the hold count hits zero.
634 * threadsafe
635 */
636static bool cache_put(struct dm_buffer_cache *bc, struct dm_buffer *b)
637{
638 bool r;
639
640 cache_read_lock(bc, b->block);
641 BUG_ON(!atomic_read(&b->hold_count));
642 r = atomic_dec_and_test(&b->hold_count);
643 cache_read_unlock(bc, b->block);
644
645 return r;
646}
647
648/*--------------*/
649
650typedef enum evict_result (*b_predicate)(struct dm_buffer *, void *);
651
652/*
653 * Evicts a buffer based on a predicate. The oldest buffer that
654 * matches the predicate will be selected. In addition to the
655 * predicate the hold_count of the selected buffer will be zero.
656 */
657struct evict_wrapper {
658 struct lock_history *lh;
659 b_predicate pred;
660 void *context;
661};
662
663/*
664 * Wraps the buffer predicate turning it into an lru predicate. Adds
665 * extra test for hold_count.
666 */
667static enum evict_result __evict_pred(struct lru_entry *le, void *context)
668{
669 struct evict_wrapper *w = context;
670 struct dm_buffer *b = le_to_buffer(le);
671
672 lh_next(w->lh, b->block);
673
674 if (atomic_read(&b->hold_count))
675 return ER_DONT_EVICT;
676
677 return w->pred(b, w->context);
678}
679
680static struct dm_buffer *__cache_evict(struct dm_buffer_cache *bc, int list_mode,
681 b_predicate pred, void *context,
682 struct lock_history *lh)
683{
684 struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
685 struct lru_entry *le;
686 struct dm_buffer *b;
687
688 le = lru_evict(&bc->lru[list_mode], __evict_pred, &w, bc->no_sleep);
689 if (!le)
690 return NULL;
691
692 b = le_to_buffer(le);
693 /* __evict_pred will have locked the appropriate tree. */
694 rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
695
696 return b;
697}
698
699static struct dm_buffer *cache_evict(struct dm_buffer_cache *bc, int list_mode,
700 b_predicate pred, void *context)
701{
702 struct dm_buffer *b;
703 struct lock_history lh;
704
705 lh_init(&lh, bc, true);
706 b = __cache_evict(bc, list_mode, pred, context, &lh);
707 lh_exit(&lh);
708
709 return b;
710}
711
712/*--------------*/
713
714/*
715 * Mark a buffer as clean or dirty. Not threadsafe.
716 */
717static void cache_mark(struct dm_buffer_cache *bc, struct dm_buffer *b, int list_mode)
718{
719 cache_write_lock(bc, b->block);
720 if (list_mode != b->list_mode) {
721 lru_remove(&bc->lru[b->list_mode], &b->lru);
722 b->list_mode = list_mode;
723 lru_insert(&bc->lru[b->list_mode], &b->lru);
724 }
725 cache_write_unlock(bc, b->block);
726}
727
728/*--------------*/
729
730/*
731 * Runs through the lru associated with 'old_mode', if the predicate matches then
732 * it moves them to 'new_mode'. Not threadsafe.
733 */
734static void __cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_mode,
735 b_predicate pred, void *context, struct lock_history *lh)
736{
737 struct lru_entry *le;
738 struct dm_buffer *b;
739 struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
740
741 while (true) {
742 le = lru_evict(&bc->lru[old_mode], __evict_pred, &w, bc->no_sleep);
743 if (!le)
744 break;
745
746 b = le_to_buffer(le);
747 b->list_mode = new_mode;
748 lru_insert(&bc->lru[b->list_mode], &b->lru);
749 }
750}
751
752static void cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_mode,
753 b_predicate pred, void *context)
754{
755 struct lock_history lh;
756
757 lh_init(&lh, bc, true);
758 __cache_mark_many(bc, old_mode, new_mode, pred, context, &lh);
759 lh_exit(&lh);
760}
761
762/*--------------*/
763
764/*
765 * Iterates through all clean or dirty entries calling a function for each
766 * entry. The callback may terminate the iteration early. Not threadsafe.
767 */
768
769/*
770 * Iterator functions should return one of these actions to indicate
771 * how the iteration should proceed.
772 */
773enum it_action {
774 IT_NEXT,
775 IT_COMPLETE,
776};
777
778typedef enum it_action (*iter_fn)(struct dm_buffer *b, void *context);
779
780static void __cache_iterate(struct dm_buffer_cache *bc, int list_mode,
781 iter_fn fn, void *context, struct lock_history *lh)
782{
783 struct lru *lru = &bc->lru[list_mode];
784 struct lru_entry *le, *first;
785
786 if (!lru->cursor)
787 return;
788
789 first = le = to_le(lru->cursor);
790 do {
791 struct dm_buffer *b = le_to_buffer(le);
792
793 lh_next(lh, b->block);
794
795 switch (fn(b, context)) {
796 case IT_NEXT:
797 break;
798
799 case IT_COMPLETE:
800 return;
801 }
802 cond_resched();
803
804 le = to_le(le->list.next);
805 } while (le != first);
806}
807
808static void cache_iterate(struct dm_buffer_cache *bc, int list_mode,
809 iter_fn fn, void *context)
810{
811 struct lock_history lh;
812
813 lh_init(&lh, bc, false);
814 __cache_iterate(bc, list_mode, fn, context, &lh);
815 lh_exit(&lh);
816}
817
818/*--------------*/
819
820/*
821 * Passes ownership of the buffer to the cache. Returns false if the
822 * buffer was already present (in which case ownership does not pass).
823 * eg, a race with another thread.
824 *
825 * Holder count should be 1 on insertion.
826 *
827 * Not threadsafe.
828 */
829static bool __cache_insert(struct rb_root *root, struct dm_buffer *b)
830{
831 struct rb_node **new = &root->rb_node, *parent = NULL;
832 struct dm_buffer *found;
833
834 while (*new) {
835 found = container_of(*new, struct dm_buffer, node);
836
837 if (found->block == b->block)
838 return false;
839
840 parent = *new;
841 new = b->block < found->block ?
842 &found->node.rb_left : &found->node.rb_right;
843 }
844
845 rb_link_node(&b->node, parent, new);
846 rb_insert_color(&b->node, root);
847
848 return true;
849}
850
851static bool cache_insert(struct dm_buffer_cache *bc, struct dm_buffer *b)
852{
853 bool r;
854
855 if (WARN_ON_ONCE(b->list_mode >= LIST_SIZE))
856 return false;
857
858 cache_write_lock(bc, b->block);
859 BUG_ON(atomic_read(&b->hold_count) != 1);
860 r = __cache_insert(&bc->trees[cache_index(b->block, bc->num_locks)].root, b);
861 if (r)
862 lru_insert(&bc->lru[b->list_mode], &b->lru);
863 cache_write_unlock(bc, b->block);
864
865 return r;
866}
867
868/*--------------*/
869
870/*
871 * Removes buffer from cache, ownership of the buffer passes back to the caller.
872 * Fails if the hold_count is not one (ie. the caller holds the only reference).
873 *
874 * Not threadsafe.
875 */
876static bool cache_remove(struct dm_buffer_cache *bc, struct dm_buffer *b)
877{
878 bool r;
879
880 cache_write_lock(bc, b->block);
881
882 if (atomic_read(&b->hold_count) != 1) {
883 r = false;
884 } else {
885 r = true;
886 rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
887 lru_remove(&bc->lru[b->list_mode], &b->lru);
888 }
889
890 cache_write_unlock(bc, b->block);
891
892 return r;
893}
894
895/*--------------*/
896
897typedef void (*b_release)(struct dm_buffer *);
898
899static struct dm_buffer *__find_next(struct rb_root *root, sector_t block)
900{
901 struct rb_node *n = root->rb_node;
902 struct dm_buffer *b;
903 struct dm_buffer *best = NULL;
904
905 while (n) {
906 b = container_of(n, struct dm_buffer, node);
907
908 if (b->block == block)
909 return b;
910
911 if (block <= b->block) {
912 n = n->rb_left;
913 best = b;
914 } else {
915 n = n->rb_right;
916 }
917 }
918
919 return best;
920}
921
922static void __remove_range(struct dm_buffer_cache *bc,
923 struct rb_root *root,
924 sector_t begin, sector_t end,
925 b_predicate pred, b_release release)
926{
927 struct dm_buffer *b;
928
929 while (true) {
930 cond_resched();
931
932 b = __find_next(root, begin);
933 if (!b || (b->block >= end))
934 break;
935
936 begin = b->block + 1;
937
938 if (atomic_read(&b->hold_count))
939 continue;
940
941 if (pred(b, NULL) == ER_EVICT) {
942 rb_erase(&b->node, root);
943 lru_remove(&bc->lru[b->list_mode], &b->lru);
944 release(b);
945 }
946 }
947}
948
949static void cache_remove_range(struct dm_buffer_cache *bc,
950 sector_t begin, sector_t end,
951 b_predicate pred, b_release release)
952{
953 unsigned int i;
954
955 BUG_ON(bc->no_sleep);
956 for (i = 0; i < bc->num_locks; i++) {
957 down_write(&bc->trees[i].u.lock);
958 __remove_range(bc, &bc->trees[i].root, begin, end, pred, release);
959 up_write(&bc->trees[i].u.lock);
960 }
961}
962
963/*----------------------------------------------------------------*/
964
965/*
966 * Linking of buffers:
967 * All buffers are linked to buffer_cache with their node field.
968 *
969 * Clean buffers that are not being written (B_WRITING not set)
970 * are linked to lru[LIST_CLEAN] with their lru_list field.
971 *
972 * Dirty and clean buffers that are being written are linked to
973 * lru[LIST_DIRTY] with their lru_list field. When the write
974 * finishes, the buffer cannot be relinked immediately (because we
975 * are in an interrupt context and relinking requires process
976 * context), so some clean-not-writing buffers can be held on
977 * dirty_lru too. They are later added to lru in the process
978 * context.
979 */
980struct dm_bufio_client {
981 struct block_device *bdev;
982 unsigned int block_size;
983 s8 sectors_per_block_bits;
984
985 bool no_sleep;
986 struct mutex lock;
987 spinlock_t spinlock;
988
989 int async_write_error;
990
991 void (*alloc_callback)(struct dm_buffer *buf);
992 void (*write_callback)(struct dm_buffer *buf);
993 struct kmem_cache *slab_buffer;
994 struct kmem_cache *slab_cache;
995 struct dm_io_client *dm_io;
996
997 struct list_head reserved_buffers;
998 unsigned int need_reserved_buffers;
999
1000 unsigned int minimum_buffers;
1001
1002 sector_t start;
1003
1004 struct shrinker *shrinker;
1005 struct work_struct shrink_work;
1006 atomic_long_t need_shrink;
1007
1008 wait_queue_head_t free_buffer_wait;
1009
1010 struct list_head client_list;
1011
1012 /*
1013 * Used by global_cleanup to sort the clients list.
1014 */
1015 unsigned long oldest_buffer;
1016
1017 struct dm_buffer_cache cache; /* must be last member */
1018};
1019
1020/*----------------------------------------------------------------*/
1021
1022#define dm_bufio_in_request() (!!current->bio_list)
1023
1024static void dm_bufio_lock(struct dm_bufio_client *c)
1025{
1026 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
1027 spin_lock_bh(&c->spinlock);
1028 else
1029 mutex_lock_nested(&c->lock, dm_bufio_in_request());
1030}
1031
1032static void dm_bufio_unlock(struct dm_bufio_client *c)
1033{
1034 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
1035 spin_unlock_bh(&c->spinlock);
1036 else
1037 mutex_unlock(&c->lock);
1038}
1039
1040/*----------------------------------------------------------------*/
1041
1042/*
1043 * Default cache size: available memory divided by the ratio.
1044 */
1045static unsigned long dm_bufio_default_cache_size;
1046
1047/*
1048 * Total cache size set by the user.
1049 */
1050static unsigned long dm_bufio_cache_size;
1051
1052/*
1053 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
1054 * at any time. If it disagrees, the user has changed cache size.
1055 */
1056static unsigned long dm_bufio_cache_size_latch;
1057
1058static DEFINE_SPINLOCK(global_spinlock);
1059
1060/*
1061 * Buffers are freed after this timeout
1062 */
1063static unsigned int dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
1064static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
1065
1066static unsigned long dm_bufio_peak_allocated;
1067static unsigned long dm_bufio_allocated_kmem_cache;
1068static unsigned long dm_bufio_allocated_get_free_pages;
1069static unsigned long dm_bufio_allocated_vmalloc;
1070static unsigned long dm_bufio_current_allocated;
1071
1072/*----------------------------------------------------------------*/
1073
1074/*
1075 * The current number of clients.
1076 */
1077static int dm_bufio_client_count;
1078
1079/*
1080 * The list of all clients.
1081 */
1082static LIST_HEAD(dm_bufio_all_clients);
1083
1084/*
1085 * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
1086 */
1087static DEFINE_MUTEX(dm_bufio_clients_lock);
1088
1089static struct workqueue_struct *dm_bufio_wq;
1090static struct delayed_work dm_bufio_cleanup_old_work;
1091static struct work_struct dm_bufio_replacement_work;
1092
1093
1094#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1095static void buffer_record_stack(struct dm_buffer *b)
1096{
1097 b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
1098}
1099#endif
1100
1101/*----------------------------------------------------------------*/
1102
1103static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
1104{
1105 unsigned char data_mode;
1106 long diff;
1107
1108 static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
1109 &dm_bufio_allocated_kmem_cache,
1110 &dm_bufio_allocated_get_free_pages,
1111 &dm_bufio_allocated_vmalloc,
1112 };
1113
1114 data_mode = b->data_mode;
1115 diff = (long)b->c->block_size;
1116 if (unlink)
1117 diff = -diff;
1118
1119 spin_lock(&global_spinlock);
1120
1121 *class_ptr[data_mode] += diff;
1122
1123 dm_bufio_current_allocated += diff;
1124
1125 if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
1126 dm_bufio_peak_allocated = dm_bufio_current_allocated;
1127
1128 if (!unlink) {
1129 if (dm_bufio_current_allocated > dm_bufio_cache_size)
1130 queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
1131 }
1132
1133 spin_unlock(&global_spinlock);
1134}
1135
1136/*
1137 * Change the number of clients and recalculate per-client limit.
1138 */
1139static void __cache_size_refresh(void)
1140{
1141 if (WARN_ON(!mutex_is_locked(&dm_bufio_clients_lock)))
1142 return;
1143 if (WARN_ON(dm_bufio_client_count < 0))
1144 return;
1145
1146 dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
1147
1148 /*
1149 * Use default if set to 0 and report the actual cache size used.
1150 */
1151 if (!dm_bufio_cache_size_latch) {
1152 (void)cmpxchg(&dm_bufio_cache_size, 0,
1153 dm_bufio_default_cache_size);
1154 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
1155 }
1156}
1157
1158/*
1159 * Allocating buffer data.
1160 *
1161 * Small buffers are allocated with kmem_cache, to use space optimally.
1162 *
1163 * For large buffers, we choose between get_free_pages and vmalloc.
1164 * Each has advantages and disadvantages.
1165 *
1166 * __get_free_pages can randomly fail if the memory is fragmented.
1167 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
1168 * as low as 128M) so using it for caching is not appropriate.
1169 *
1170 * If the allocation may fail we use __get_free_pages. Memory fragmentation
1171 * won't have a fatal effect here, but it just causes flushes of some other
1172 * buffers and more I/O will be performed. Don't use __get_free_pages if it
1173 * always fails (i.e. order > MAX_PAGE_ORDER).
1174 *
1175 * If the allocation shouldn't fail we use __vmalloc. This is only for the
1176 * initial reserve allocation, so there's no risk of wasting all vmalloc
1177 * space.
1178 */
1179static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
1180 unsigned char *data_mode)
1181{
1182 if (unlikely(c->slab_cache != NULL)) {
1183 *data_mode = DATA_MODE_SLAB;
1184 return kmem_cache_alloc(c->slab_cache, gfp_mask);
1185 }
1186
1187 if (c->block_size <= KMALLOC_MAX_SIZE &&
1188 gfp_mask & __GFP_NORETRY) {
1189 *data_mode = DATA_MODE_GET_FREE_PAGES;
1190 return (void *)__get_free_pages(gfp_mask,
1191 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
1192 }
1193
1194 *data_mode = DATA_MODE_VMALLOC;
1195
1196 return __vmalloc(c->block_size, gfp_mask);
1197}
1198
1199/*
1200 * Free buffer's data.
1201 */
1202static void free_buffer_data(struct dm_bufio_client *c,
1203 void *data, unsigned char data_mode)
1204{
1205 switch (data_mode) {
1206 case DATA_MODE_SLAB:
1207 kmem_cache_free(c->slab_cache, data);
1208 break;
1209
1210 case DATA_MODE_GET_FREE_PAGES:
1211 free_pages((unsigned long)data,
1212 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
1213 break;
1214
1215 case DATA_MODE_VMALLOC:
1216 vfree(data);
1217 break;
1218
1219 default:
1220 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
1221 data_mode);
1222 BUG();
1223 }
1224}
1225
1226/*
1227 * Allocate buffer and its data.
1228 */
1229static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
1230{
1231 struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
1232
1233 if (!b)
1234 return NULL;
1235
1236 b->c = c;
1237
1238 b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
1239 if (!b->data) {
1240 kmem_cache_free(c->slab_buffer, b);
1241 return NULL;
1242 }
1243 adjust_total_allocated(b, false);
1244
1245#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1246 b->stack_len = 0;
1247#endif
1248 return b;
1249}
1250
1251/*
1252 * Free buffer and its data.
1253 */
1254static void free_buffer(struct dm_buffer *b)
1255{
1256 struct dm_bufio_client *c = b->c;
1257
1258 adjust_total_allocated(b, true);
1259 free_buffer_data(c, b->data, b->data_mode);
1260 kmem_cache_free(c->slab_buffer, b);
1261}
1262
1263/*
1264 *--------------------------------------------------------------------------
1265 * Submit I/O on the buffer.
1266 *
1267 * Bio interface is faster but it has some problems:
1268 * the vector list is limited (increasing this limit increases
1269 * memory-consumption per buffer, so it is not viable);
1270 *
1271 * the memory must be direct-mapped, not vmalloced;
1272 *
1273 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
1274 * it is not vmalloced, try using the bio interface.
1275 *
1276 * If the buffer is big, if it is vmalloced or if the underlying device
1277 * rejects the bio because it is too large, use dm-io layer to do the I/O.
1278 * The dm-io layer splits the I/O into multiple requests, avoiding the above
1279 * shortcomings.
1280 *--------------------------------------------------------------------------
1281 */
1282
1283/*
1284 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
1285 * that the request was handled directly with bio interface.
1286 */
1287static void dmio_complete(unsigned long error, void *context)
1288{
1289 struct dm_buffer *b = context;
1290
1291 b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
1292}
1293
1294static void use_dmio(struct dm_buffer *b, enum req_op op, sector_t sector,
1295 unsigned int n_sectors, unsigned int offset)
1296{
1297 int r;
1298 struct dm_io_request io_req = {
1299 .bi_opf = op,
1300 .notify.fn = dmio_complete,
1301 .notify.context = b,
1302 .client = b->c->dm_io,
1303 };
1304 struct dm_io_region region = {
1305 .bdev = b->c->bdev,
1306 .sector = sector,
1307 .count = n_sectors,
1308 };
1309
1310 if (b->data_mode != DATA_MODE_VMALLOC) {
1311 io_req.mem.type = DM_IO_KMEM;
1312 io_req.mem.ptr.addr = (char *)b->data + offset;
1313 } else {
1314 io_req.mem.type = DM_IO_VMA;
1315 io_req.mem.ptr.vma = (char *)b->data + offset;
1316 }
1317
1318 r = dm_io(&io_req, 1, ®ion, NULL);
1319 if (unlikely(r))
1320 b->end_io(b, errno_to_blk_status(r));
1321}
1322
1323static void bio_complete(struct bio *bio)
1324{
1325 struct dm_buffer *b = bio->bi_private;
1326 blk_status_t status = bio->bi_status;
1327
1328 bio_uninit(bio);
1329 kfree(bio);
1330 b->end_io(b, status);
1331}
1332
1333static void use_bio(struct dm_buffer *b, enum req_op op, sector_t sector,
1334 unsigned int n_sectors, unsigned int offset)
1335{
1336 struct bio *bio;
1337 char *ptr;
1338 unsigned int len;
1339
1340 bio = bio_kmalloc(1, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN);
1341 if (!bio) {
1342 use_dmio(b, op, sector, n_sectors, offset);
1343 return;
1344 }
1345 bio_init(bio, b->c->bdev, bio->bi_inline_vecs, 1, op);
1346 bio->bi_iter.bi_sector = sector;
1347 bio->bi_end_io = bio_complete;
1348 bio->bi_private = b;
1349
1350 ptr = (char *)b->data + offset;
1351 len = n_sectors << SECTOR_SHIFT;
1352
1353 __bio_add_page(bio, virt_to_page(ptr), len, offset_in_page(ptr));
1354
1355 submit_bio(bio);
1356}
1357
1358static inline sector_t block_to_sector(struct dm_bufio_client *c, sector_t block)
1359{
1360 sector_t sector;
1361
1362 if (likely(c->sectors_per_block_bits >= 0))
1363 sector = block << c->sectors_per_block_bits;
1364 else
1365 sector = block * (c->block_size >> SECTOR_SHIFT);
1366 sector += c->start;
1367
1368 return sector;
1369}
1370
1371static void submit_io(struct dm_buffer *b, enum req_op op,
1372 void (*end_io)(struct dm_buffer *, blk_status_t))
1373{
1374 unsigned int n_sectors;
1375 sector_t sector;
1376 unsigned int offset, end;
1377
1378 b->end_io = end_io;
1379
1380 sector = block_to_sector(b->c, b->block);
1381
1382 if (op != REQ_OP_WRITE) {
1383 n_sectors = b->c->block_size >> SECTOR_SHIFT;
1384 offset = 0;
1385 } else {
1386 if (b->c->write_callback)
1387 b->c->write_callback(b);
1388 offset = b->write_start;
1389 end = b->write_end;
1390 offset &= -DM_BUFIO_WRITE_ALIGN;
1391 end += DM_BUFIO_WRITE_ALIGN - 1;
1392 end &= -DM_BUFIO_WRITE_ALIGN;
1393 if (unlikely(end > b->c->block_size))
1394 end = b->c->block_size;
1395
1396 sector += offset >> SECTOR_SHIFT;
1397 n_sectors = (end - offset) >> SECTOR_SHIFT;
1398 }
1399
1400 if (b->data_mode != DATA_MODE_VMALLOC)
1401 use_bio(b, op, sector, n_sectors, offset);
1402 else
1403 use_dmio(b, op, sector, n_sectors, offset);
1404}
1405
1406/*
1407 *--------------------------------------------------------------
1408 * Writing dirty buffers
1409 *--------------------------------------------------------------
1410 */
1411
1412/*
1413 * The endio routine for write.
1414 *
1415 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
1416 * it.
1417 */
1418static void write_endio(struct dm_buffer *b, blk_status_t status)
1419{
1420 b->write_error = status;
1421 if (unlikely(status)) {
1422 struct dm_bufio_client *c = b->c;
1423
1424 (void)cmpxchg(&c->async_write_error, 0,
1425 blk_status_to_errno(status));
1426 }
1427
1428 BUG_ON(!test_bit(B_WRITING, &b->state));
1429
1430 smp_mb__before_atomic();
1431 clear_bit(B_WRITING, &b->state);
1432 smp_mb__after_atomic();
1433
1434 wake_up_bit(&b->state, B_WRITING);
1435}
1436
1437/*
1438 * Initiate a write on a dirty buffer, but don't wait for it.
1439 *
1440 * - If the buffer is not dirty, exit.
1441 * - If there some previous write going on, wait for it to finish (we can't
1442 * have two writes on the same buffer simultaneously).
1443 * - Submit our write and don't wait on it. We set B_WRITING indicating
1444 * that there is a write in progress.
1445 */
1446static void __write_dirty_buffer(struct dm_buffer *b,
1447 struct list_head *write_list)
1448{
1449 if (!test_bit(B_DIRTY, &b->state))
1450 return;
1451
1452 clear_bit(B_DIRTY, &b->state);
1453 wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
1454
1455 b->write_start = b->dirty_start;
1456 b->write_end = b->dirty_end;
1457
1458 if (!write_list)
1459 submit_io(b, REQ_OP_WRITE, write_endio);
1460 else
1461 list_add_tail(&b->write_list, write_list);
1462}
1463
1464static void __flush_write_list(struct list_head *write_list)
1465{
1466 struct blk_plug plug;
1467
1468 blk_start_plug(&plug);
1469 while (!list_empty(write_list)) {
1470 struct dm_buffer *b =
1471 list_entry(write_list->next, struct dm_buffer, write_list);
1472 list_del(&b->write_list);
1473 submit_io(b, REQ_OP_WRITE, write_endio);
1474 cond_resched();
1475 }
1476 blk_finish_plug(&plug);
1477}
1478
1479/*
1480 * Wait until any activity on the buffer finishes. Possibly write the
1481 * buffer if it is dirty. When this function finishes, there is no I/O
1482 * running on the buffer and the buffer is not dirty.
1483 */
1484static void __make_buffer_clean(struct dm_buffer *b)
1485{
1486 BUG_ON(atomic_read(&b->hold_count));
1487
1488 /* smp_load_acquire() pairs with read_endio()'s smp_mb__before_atomic() */
1489 if (!smp_load_acquire(&b->state)) /* fast case */
1490 return;
1491
1492 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1493 __write_dirty_buffer(b, NULL);
1494 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
1495}
1496
1497static enum evict_result is_clean(struct dm_buffer *b, void *context)
1498{
1499 struct dm_bufio_client *c = context;
1500
1501 /* These should never happen */
1502 if (WARN_ON_ONCE(test_bit(B_WRITING, &b->state)))
1503 return ER_DONT_EVICT;
1504 if (WARN_ON_ONCE(test_bit(B_DIRTY, &b->state)))
1505 return ER_DONT_EVICT;
1506 if (WARN_ON_ONCE(b->list_mode != LIST_CLEAN))
1507 return ER_DONT_EVICT;
1508
1509 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep &&
1510 unlikely(test_bit(B_READING, &b->state)))
1511 return ER_DONT_EVICT;
1512
1513 return ER_EVICT;
1514}
1515
1516static enum evict_result is_dirty(struct dm_buffer *b, void *context)
1517{
1518 /* These should never happen */
1519 if (WARN_ON_ONCE(test_bit(B_READING, &b->state)))
1520 return ER_DONT_EVICT;
1521 if (WARN_ON_ONCE(b->list_mode != LIST_DIRTY))
1522 return ER_DONT_EVICT;
1523
1524 return ER_EVICT;
1525}
1526
1527/*
1528 * Find some buffer that is not held by anybody, clean it, unlink it and
1529 * return it.
1530 */
1531static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
1532{
1533 struct dm_buffer *b;
1534
1535 b = cache_evict(&c->cache, LIST_CLEAN, is_clean, c);
1536 if (b) {
1537 /* this also waits for pending reads */
1538 __make_buffer_clean(b);
1539 return b;
1540 }
1541
1542 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
1543 return NULL;
1544
1545 b = cache_evict(&c->cache, LIST_DIRTY, is_dirty, NULL);
1546 if (b) {
1547 __make_buffer_clean(b);
1548 return b;
1549 }
1550
1551 return NULL;
1552}
1553
1554/*
1555 * Wait until some other threads free some buffer or release hold count on
1556 * some buffer.
1557 *
1558 * This function is entered with c->lock held, drops it and regains it
1559 * before exiting.
1560 */
1561static void __wait_for_free_buffer(struct dm_bufio_client *c)
1562{
1563 DECLARE_WAITQUEUE(wait, current);
1564
1565 add_wait_queue(&c->free_buffer_wait, &wait);
1566 set_current_state(TASK_UNINTERRUPTIBLE);
1567 dm_bufio_unlock(c);
1568
1569 /*
1570 * It's possible to miss a wake up event since we don't always
1571 * hold c->lock when wake_up is called. So we have a timeout here,
1572 * just in case.
1573 */
1574 io_schedule_timeout(5 * HZ);
1575
1576 remove_wait_queue(&c->free_buffer_wait, &wait);
1577
1578 dm_bufio_lock(c);
1579}
1580
1581enum new_flag {
1582 NF_FRESH = 0,
1583 NF_READ = 1,
1584 NF_GET = 2,
1585 NF_PREFETCH = 3
1586};
1587
1588/*
1589 * Allocate a new buffer. If the allocation is not possible, wait until
1590 * some other thread frees a buffer.
1591 *
1592 * May drop the lock and regain it.
1593 */
1594static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
1595{
1596 struct dm_buffer *b;
1597 bool tried_noio_alloc = false;
1598
1599 /*
1600 * dm-bufio is resistant to allocation failures (it just keeps
1601 * one buffer reserved in cases all the allocations fail).
1602 * So set flags to not try too hard:
1603 * GFP_NOWAIT: don't wait; if we need to sleep we'll release our
1604 * mutex and wait ourselves.
1605 * __GFP_NORETRY: don't retry and rather return failure
1606 * __GFP_NOMEMALLOC: don't use emergency reserves
1607 * __GFP_NOWARN: don't print a warning in case of failure
1608 *
1609 * For debugging, if we set the cache size to 1, no new buffers will
1610 * be allocated.
1611 */
1612 while (1) {
1613 if (dm_bufio_cache_size_latch != 1) {
1614 b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
1615 if (b)
1616 return b;
1617 }
1618
1619 if (nf == NF_PREFETCH)
1620 return NULL;
1621
1622 if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
1623 dm_bufio_unlock(c);
1624 b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
1625 dm_bufio_lock(c);
1626 if (b)
1627 return b;
1628 tried_noio_alloc = true;
1629 }
1630
1631 if (!list_empty(&c->reserved_buffers)) {
1632 b = list_to_buffer(c->reserved_buffers.next);
1633 list_del(&b->lru.list);
1634 c->need_reserved_buffers++;
1635
1636 return b;
1637 }
1638
1639 b = __get_unclaimed_buffer(c);
1640 if (b)
1641 return b;
1642
1643 __wait_for_free_buffer(c);
1644 }
1645}
1646
1647static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
1648{
1649 struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
1650
1651 if (!b)
1652 return NULL;
1653
1654 if (c->alloc_callback)
1655 c->alloc_callback(b);
1656
1657 return b;
1658}
1659
1660/*
1661 * Free a buffer and wake other threads waiting for free buffers.
1662 */
1663static void __free_buffer_wake(struct dm_buffer *b)
1664{
1665 struct dm_bufio_client *c = b->c;
1666
1667 b->block = -1;
1668 if (!c->need_reserved_buffers)
1669 free_buffer(b);
1670 else {
1671 list_add(&b->lru.list, &c->reserved_buffers);
1672 c->need_reserved_buffers--;
1673 }
1674
1675 /*
1676 * We hold the bufio lock here, so no one can add entries to the
1677 * wait queue anyway.
1678 */
1679 if (unlikely(waitqueue_active(&c->free_buffer_wait)))
1680 wake_up(&c->free_buffer_wait);
1681}
1682
1683static enum evict_result cleaned(struct dm_buffer *b, void *context)
1684{
1685 if (WARN_ON_ONCE(test_bit(B_READING, &b->state)))
1686 return ER_DONT_EVICT; /* should never happen */
1687
1688 if (test_bit(B_DIRTY, &b->state) || test_bit(B_WRITING, &b->state))
1689 return ER_DONT_EVICT;
1690 else
1691 return ER_EVICT;
1692}
1693
1694static void __move_clean_buffers(struct dm_bufio_client *c)
1695{
1696 cache_mark_many(&c->cache, LIST_DIRTY, LIST_CLEAN, cleaned, NULL);
1697}
1698
1699struct write_context {
1700 int no_wait;
1701 struct list_head *write_list;
1702};
1703
1704static enum it_action write_one(struct dm_buffer *b, void *context)
1705{
1706 struct write_context *wc = context;
1707
1708 if (wc->no_wait && test_bit(B_WRITING, &b->state))
1709 return IT_COMPLETE;
1710
1711 __write_dirty_buffer(b, wc->write_list);
1712 return IT_NEXT;
1713}
1714
1715static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
1716 struct list_head *write_list)
1717{
1718 struct write_context wc = {.no_wait = no_wait, .write_list = write_list};
1719
1720 __move_clean_buffers(c);
1721 cache_iterate(&c->cache, LIST_DIRTY, write_one, &wc);
1722}
1723
1724/*
1725 * Check if we're over watermark.
1726 * If we are over threshold_buffers, start freeing buffers.
1727 * If we're over "limit_buffers", block until we get under the limit.
1728 */
1729static void __check_watermark(struct dm_bufio_client *c,
1730 struct list_head *write_list)
1731{
1732 if (cache_count(&c->cache, LIST_DIRTY) >
1733 cache_count(&c->cache, LIST_CLEAN) * DM_BUFIO_WRITEBACK_RATIO)
1734 __write_dirty_buffers_async(c, 1, write_list);
1735}
1736
1737/*
1738 *--------------------------------------------------------------
1739 * Getting a buffer
1740 *--------------------------------------------------------------
1741 */
1742
1743static void cache_put_and_wake(struct dm_bufio_client *c, struct dm_buffer *b)
1744{
1745 /*
1746 * Relying on waitqueue_active() is racey, but we sleep
1747 * with schedule_timeout anyway.
1748 */
1749 if (cache_put(&c->cache, b) &&
1750 unlikely(waitqueue_active(&c->free_buffer_wait)))
1751 wake_up(&c->free_buffer_wait);
1752}
1753
1754/*
1755 * This assumes you have already checked the cache to see if the buffer
1756 * is already present (it will recheck after dropping the lock for allocation).
1757 */
1758static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
1759 enum new_flag nf, int *need_submit,
1760 struct list_head *write_list)
1761{
1762 struct dm_buffer *b, *new_b = NULL;
1763
1764 *need_submit = 0;
1765
1766 /* This can't be called with NF_GET */
1767 if (WARN_ON_ONCE(nf == NF_GET))
1768 return NULL;
1769
1770 new_b = __alloc_buffer_wait(c, nf);
1771 if (!new_b)
1772 return NULL;
1773
1774 /*
1775 * We've had a period where the mutex was unlocked, so need to
1776 * recheck the buffer tree.
1777 */
1778 b = cache_get(&c->cache, block);
1779 if (b) {
1780 __free_buffer_wake(new_b);
1781 goto found_buffer;
1782 }
1783
1784 __check_watermark(c, write_list);
1785
1786 b = new_b;
1787 atomic_set(&b->hold_count, 1);
1788 WRITE_ONCE(b->last_accessed, jiffies);
1789 b->block = block;
1790 b->read_error = 0;
1791 b->write_error = 0;
1792 b->list_mode = LIST_CLEAN;
1793
1794 if (nf == NF_FRESH)
1795 b->state = 0;
1796 else {
1797 b->state = 1 << B_READING;
1798 *need_submit = 1;
1799 }
1800
1801 /*
1802 * We mustn't insert into the cache until the B_READING state
1803 * is set. Otherwise another thread could get it and use
1804 * it before it had been read.
1805 */
1806 cache_insert(&c->cache, b);
1807
1808 return b;
1809
1810found_buffer:
1811 if (nf == NF_PREFETCH) {
1812 cache_put_and_wake(c, b);
1813 return NULL;
1814 }
1815
1816 /*
1817 * Note: it is essential that we don't wait for the buffer to be
1818 * read if dm_bufio_get function is used. Both dm_bufio_get and
1819 * dm_bufio_prefetch can be used in the driver request routine.
1820 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1821 * the same buffer, it would deadlock if we waited.
1822 */
1823 if (nf == NF_GET && unlikely(test_bit_acquire(B_READING, &b->state))) {
1824 cache_put_and_wake(c, b);
1825 return NULL;
1826 }
1827
1828 return b;
1829}
1830
1831/*
1832 * The endio routine for reading: set the error, clear the bit and wake up
1833 * anyone waiting on the buffer.
1834 */
1835static void read_endio(struct dm_buffer *b, blk_status_t status)
1836{
1837 b->read_error = status;
1838
1839 BUG_ON(!test_bit(B_READING, &b->state));
1840
1841 smp_mb__before_atomic();
1842 clear_bit(B_READING, &b->state);
1843 smp_mb__after_atomic();
1844
1845 wake_up_bit(&b->state, B_READING);
1846}
1847
1848/*
1849 * A common routine for dm_bufio_new and dm_bufio_read. Operation of these
1850 * functions is similar except that dm_bufio_new doesn't read the
1851 * buffer from the disk (assuming that the caller overwrites all the data
1852 * and uses dm_bufio_mark_buffer_dirty to write new data back).
1853 */
1854static void *new_read(struct dm_bufio_client *c, sector_t block,
1855 enum new_flag nf, struct dm_buffer **bp)
1856{
1857 int need_submit = 0;
1858 struct dm_buffer *b;
1859
1860 LIST_HEAD(write_list);
1861
1862 *bp = NULL;
1863
1864 /*
1865 * Fast path, hopefully the block is already in the cache. No need
1866 * to get the client lock for this.
1867 */
1868 b = cache_get(&c->cache, block);
1869 if (b) {
1870 if (nf == NF_PREFETCH) {
1871 cache_put_and_wake(c, b);
1872 return NULL;
1873 }
1874
1875 /*
1876 * Note: it is essential that we don't wait for the buffer to be
1877 * read if dm_bufio_get function is used. Both dm_bufio_get and
1878 * dm_bufio_prefetch can be used in the driver request routine.
1879 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1880 * the same buffer, it would deadlock if we waited.
1881 */
1882 if (nf == NF_GET && unlikely(test_bit_acquire(B_READING, &b->state))) {
1883 cache_put_and_wake(c, b);
1884 return NULL;
1885 }
1886 }
1887
1888 if (!b) {
1889 if (nf == NF_GET)
1890 return NULL;
1891
1892 dm_bufio_lock(c);
1893 b = __bufio_new(c, block, nf, &need_submit, &write_list);
1894 dm_bufio_unlock(c);
1895 }
1896
1897#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1898 if (b && (atomic_read(&b->hold_count) == 1))
1899 buffer_record_stack(b);
1900#endif
1901
1902 __flush_write_list(&write_list);
1903
1904 if (!b)
1905 return NULL;
1906
1907 if (need_submit)
1908 submit_io(b, REQ_OP_READ, read_endio);
1909
1910 if (nf != NF_GET) /* we already tested this condition above */
1911 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1912
1913 if (b->read_error) {
1914 int error = blk_status_to_errno(b->read_error);
1915
1916 dm_bufio_release(b);
1917
1918 return ERR_PTR(error);
1919 }
1920
1921 *bp = b;
1922
1923 return b->data;
1924}
1925
1926void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1927 struct dm_buffer **bp)
1928{
1929 return new_read(c, block, NF_GET, bp);
1930}
1931EXPORT_SYMBOL_GPL(dm_bufio_get);
1932
1933void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1934 struct dm_buffer **bp)
1935{
1936 if (WARN_ON_ONCE(dm_bufio_in_request()))
1937 return ERR_PTR(-EINVAL);
1938
1939 return new_read(c, block, NF_READ, bp);
1940}
1941EXPORT_SYMBOL_GPL(dm_bufio_read);
1942
1943void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1944 struct dm_buffer **bp)
1945{
1946 if (WARN_ON_ONCE(dm_bufio_in_request()))
1947 return ERR_PTR(-EINVAL);
1948
1949 return new_read(c, block, NF_FRESH, bp);
1950}
1951EXPORT_SYMBOL_GPL(dm_bufio_new);
1952
1953void dm_bufio_prefetch(struct dm_bufio_client *c,
1954 sector_t block, unsigned int n_blocks)
1955{
1956 struct blk_plug plug;
1957
1958 LIST_HEAD(write_list);
1959
1960 if (WARN_ON_ONCE(dm_bufio_in_request()))
1961 return; /* should never happen */
1962
1963 blk_start_plug(&plug);
1964
1965 for (; n_blocks--; block++) {
1966 int need_submit;
1967 struct dm_buffer *b;
1968
1969 b = cache_get(&c->cache, block);
1970 if (b) {
1971 /* already in cache */
1972 cache_put_and_wake(c, b);
1973 continue;
1974 }
1975
1976 dm_bufio_lock(c);
1977 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1978 &write_list);
1979 if (unlikely(!list_empty(&write_list))) {
1980 dm_bufio_unlock(c);
1981 blk_finish_plug(&plug);
1982 __flush_write_list(&write_list);
1983 blk_start_plug(&plug);
1984 dm_bufio_lock(c);
1985 }
1986 if (unlikely(b != NULL)) {
1987 dm_bufio_unlock(c);
1988
1989 if (need_submit)
1990 submit_io(b, REQ_OP_READ, read_endio);
1991 dm_bufio_release(b);
1992
1993 cond_resched();
1994
1995 if (!n_blocks)
1996 goto flush_plug;
1997 dm_bufio_lock(c);
1998 }
1999 dm_bufio_unlock(c);
2000 }
2001
2002flush_plug:
2003 blk_finish_plug(&plug);
2004}
2005EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
2006
2007void dm_bufio_release(struct dm_buffer *b)
2008{
2009 struct dm_bufio_client *c = b->c;
2010
2011 /*
2012 * If there were errors on the buffer, and the buffer is not
2013 * to be written, free the buffer. There is no point in caching
2014 * invalid buffer.
2015 */
2016 if ((b->read_error || b->write_error) &&
2017 !test_bit_acquire(B_READING, &b->state) &&
2018 !test_bit(B_WRITING, &b->state) &&
2019 !test_bit(B_DIRTY, &b->state)) {
2020 dm_bufio_lock(c);
2021
2022 /* cache remove can fail if there are other holders */
2023 if (cache_remove(&c->cache, b)) {
2024 __free_buffer_wake(b);
2025 dm_bufio_unlock(c);
2026 return;
2027 }
2028
2029 dm_bufio_unlock(c);
2030 }
2031
2032 cache_put_and_wake(c, b);
2033}
2034EXPORT_SYMBOL_GPL(dm_bufio_release);
2035
2036void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
2037 unsigned int start, unsigned int end)
2038{
2039 struct dm_bufio_client *c = b->c;
2040
2041 BUG_ON(start >= end);
2042 BUG_ON(end > b->c->block_size);
2043
2044 dm_bufio_lock(c);
2045
2046 BUG_ON(test_bit(B_READING, &b->state));
2047
2048 if (!test_and_set_bit(B_DIRTY, &b->state)) {
2049 b->dirty_start = start;
2050 b->dirty_end = end;
2051 cache_mark(&c->cache, b, LIST_DIRTY);
2052 } else {
2053 if (start < b->dirty_start)
2054 b->dirty_start = start;
2055 if (end > b->dirty_end)
2056 b->dirty_end = end;
2057 }
2058
2059 dm_bufio_unlock(c);
2060}
2061EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
2062
2063void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
2064{
2065 dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
2066}
2067EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
2068
2069void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
2070{
2071 LIST_HEAD(write_list);
2072
2073 if (WARN_ON_ONCE(dm_bufio_in_request()))
2074 return; /* should never happen */
2075
2076 dm_bufio_lock(c);
2077 __write_dirty_buffers_async(c, 0, &write_list);
2078 dm_bufio_unlock(c);
2079 __flush_write_list(&write_list);
2080}
2081EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
2082
2083/*
2084 * For performance, it is essential that the buffers are written asynchronously
2085 * and simultaneously (so that the block layer can merge the writes) and then
2086 * waited upon.
2087 *
2088 * Finally, we flush hardware disk cache.
2089 */
2090static bool is_writing(struct lru_entry *e, void *context)
2091{
2092 struct dm_buffer *b = le_to_buffer(e);
2093
2094 return test_bit(B_WRITING, &b->state);
2095}
2096
2097int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
2098{
2099 int a, f;
2100 unsigned long nr_buffers;
2101 struct lru_entry *e;
2102 struct lru_iter it;
2103
2104 LIST_HEAD(write_list);
2105
2106 dm_bufio_lock(c);
2107 __write_dirty_buffers_async(c, 0, &write_list);
2108 dm_bufio_unlock(c);
2109 __flush_write_list(&write_list);
2110 dm_bufio_lock(c);
2111
2112 nr_buffers = cache_count(&c->cache, LIST_DIRTY);
2113 lru_iter_begin(&c->cache.lru[LIST_DIRTY], &it);
2114 while ((e = lru_iter_next(&it, is_writing, c))) {
2115 struct dm_buffer *b = le_to_buffer(e);
2116 __cache_inc_buffer(b);
2117
2118 BUG_ON(test_bit(B_READING, &b->state));
2119
2120 if (nr_buffers) {
2121 nr_buffers--;
2122 dm_bufio_unlock(c);
2123 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
2124 dm_bufio_lock(c);
2125 } else {
2126 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
2127 }
2128
2129 if (!test_bit(B_DIRTY, &b->state) && !test_bit(B_WRITING, &b->state))
2130 cache_mark(&c->cache, b, LIST_CLEAN);
2131
2132 cache_put_and_wake(c, b);
2133
2134 cond_resched();
2135 }
2136 lru_iter_end(&it);
2137
2138 wake_up(&c->free_buffer_wait);
2139 dm_bufio_unlock(c);
2140
2141 a = xchg(&c->async_write_error, 0);
2142 f = dm_bufio_issue_flush(c);
2143 if (a)
2144 return a;
2145
2146 return f;
2147}
2148EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
2149
2150/*
2151 * Use dm-io to send an empty barrier to flush the device.
2152 */
2153int dm_bufio_issue_flush(struct dm_bufio_client *c)
2154{
2155 struct dm_io_request io_req = {
2156 .bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,
2157 .mem.type = DM_IO_KMEM,
2158 .mem.ptr.addr = NULL,
2159 .client = c->dm_io,
2160 };
2161 struct dm_io_region io_reg = {
2162 .bdev = c->bdev,
2163 .sector = 0,
2164 .count = 0,
2165 };
2166
2167 if (WARN_ON_ONCE(dm_bufio_in_request()))
2168 return -EINVAL;
2169
2170 return dm_io(&io_req, 1, &io_reg, NULL);
2171}
2172EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
2173
2174/*
2175 * Use dm-io to send a discard request to flush the device.
2176 */
2177int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t count)
2178{
2179 struct dm_io_request io_req = {
2180 .bi_opf = REQ_OP_DISCARD | REQ_SYNC,
2181 .mem.type = DM_IO_KMEM,
2182 .mem.ptr.addr = NULL,
2183 .client = c->dm_io,
2184 };
2185 struct dm_io_region io_reg = {
2186 .bdev = c->bdev,
2187 .sector = block_to_sector(c, block),
2188 .count = block_to_sector(c, count),
2189 };
2190
2191 if (WARN_ON_ONCE(dm_bufio_in_request()))
2192 return -EINVAL; /* discards are optional */
2193
2194 return dm_io(&io_req, 1, &io_reg, NULL);
2195}
2196EXPORT_SYMBOL_GPL(dm_bufio_issue_discard);
2197
2198static bool forget_buffer(struct dm_bufio_client *c, sector_t block)
2199{
2200 struct dm_buffer *b;
2201
2202 b = cache_get(&c->cache, block);
2203 if (b) {
2204 if (likely(!smp_load_acquire(&b->state))) {
2205 if (cache_remove(&c->cache, b))
2206 __free_buffer_wake(b);
2207 else
2208 cache_put_and_wake(c, b);
2209 } else {
2210 cache_put_and_wake(c, b);
2211 }
2212 }
2213
2214 return b ? true : false;
2215}
2216
2217/*
2218 * Free the given buffer.
2219 *
2220 * This is just a hint, if the buffer is in use or dirty, this function
2221 * does nothing.
2222 */
2223void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
2224{
2225 dm_bufio_lock(c);
2226 forget_buffer(c, block);
2227 dm_bufio_unlock(c);
2228}
2229EXPORT_SYMBOL_GPL(dm_bufio_forget);
2230
2231static enum evict_result idle(struct dm_buffer *b, void *context)
2232{
2233 return b->state ? ER_DONT_EVICT : ER_EVICT;
2234}
2235
2236void dm_bufio_forget_buffers(struct dm_bufio_client *c, sector_t block, sector_t n_blocks)
2237{
2238 dm_bufio_lock(c);
2239 cache_remove_range(&c->cache, block, block + n_blocks, idle, __free_buffer_wake);
2240 dm_bufio_unlock(c);
2241}
2242EXPORT_SYMBOL_GPL(dm_bufio_forget_buffers);
2243
2244void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned int n)
2245{
2246 c->minimum_buffers = n;
2247}
2248EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
2249
2250unsigned int dm_bufio_get_block_size(struct dm_bufio_client *c)
2251{
2252 return c->block_size;
2253}
2254EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
2255
2256sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
2257{
2258 sector_t s = bdev_nr_sectors(c->bdev);
2259
2260 if (s >= c->start)
2261 s -= c->start;
2262 else
2263 s = 0;
2264 if (likely(c->sectors_per_block_bits >= 0))
2265 s >>= c->sectors_per_block_bits;
2266 else
2267 sector_div(s, c->block_size >> SECTOR_SHIFT);
2268 return s;
2269}
2270EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
2271
2272struct dm_io_client *dm_bufio_get_dm_io_client(struct dm_bufio_client *c)
2273{
2274 return c->dm_io;
2275}
2276EXPORT_SYMBOL_GPL(dm_bufio_get_dm_io_client);
2277
2278sector_t dm_bufio_get_block_number(struct dm_buffer *b)
2279{
2280 return b->block;
2281}
2282EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
2283
2284void *dm_bufio_get_block_data(struct dm_buffer *b)
2285{
2286 return b->data;
2287}
2288EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
2289
2290void *dm_bufio_get_aux_data(struct dm_buffer *b)
2291{
2292 return b + 1;
2293}
2294EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
2295
2296struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
2297{
2298 return b->c;
2299}
2300EXPORT_SYMBOL_GPL(dm_bufio_get_client);
2301
2302static enum it_action warn_leak(struct dm_buffer *b, void *context)
2303{
2304 bool *warned = context;
2305
2306 WARN_ON(!(*warned));
2307 *warned = true;
2308 DMERR("leaked buffer %llx, hold count %u, list %d",
2309 (unsigned long long)b->block, atomic_read(&b->hold_count), b->list_mode);
2310#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
2311 stack_trace_print(b->stack_entries, b->stack_len, 1);
2312 /* mark unclaimed to avoid WARN_ON at end of drop_buffers() */
2313 atomic_set(&b->hold_count, 0);
2314#endif
2315 return IT_NEXT;
2316}
2317
2318static void drop_buffers(struct dm_bufio_client *c)
2319{
2320 int i;
2321 struct dm_buffer *b;
2322
2323 if (WARN_ON(dm_bufio_in_request()))
2324 return; /* should never happen */
2325
2326 /*
2327 * An optimization so that the buffers are not written one-by-one.
2328 */
2329 dm_bufio_write_dirty_buffers_async(c);
2330
2331 dm_bufio_lock(c);
2332
2333 while ((b = __get_unclaimed_buffer(c)))
2334 __free_buffer_wake(b);
2335
2336 for (i = 0; i < LIST_SIZE; i++) {
2337 bool warned = false;
2338
2339 cache_iterate(&c->cache, i, warn_leak, &warned);
2340 }
2341
2342#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
2343 while ((b = __get_unclaimed_buffer(c)))
2344 __free_buffer_wake(b);
2345#endif
2346
2347 for (i = 0; i < LIST_SIZE; i++)
2348 WARN_ON(cache_count(&c->cache, i));
2349
2350 dm_bufio_unlock(c);
2351}
2352
2353static unsigned long get_retain_buffers(struct dm_bufio_client *c)
2354{
2355 unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
2356
2357 if (likely(c->sectors_per_block_bits >= 0))
2358 retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
2359 else
2360 retain_bytes /= c->block_size;
2361
2362 return retain_bytes;
2363}
2364
2365static void __scan(struct dm_bufio_client *c)
2366{
2367 int l;
2368 struct dm_buffer *b;
2369 unsigned long freed = 0;
2370 unsigned long retain_target = get_retain_buffers(c);
2371 unsigned long count = cache_total(&c->cache);
2372
2373 for (l = 0; l < LIST_SIZE; l++) {
2374 while (true) {
2375 if (count - freed <= retain_target)
2376 atomic_long_set(&c->need_shrink, 0);
2377 if (!atomic_long_read(&c->need_shrink))
2378 break;
2379
2380 b = cache_evict(&c->cache, l,
2381 l == LIST_CLEAN ? is_clean : is_dirty, c);
2382 if (!b)
2383 break;
2384
2385 __make_buffer_clean(b);
2386 __free_buffer_wake(b);
2387
2388 atomic_long_dec(&c->need_shrink);
2389 freed++;
2390 cond_resched();
2391 }
2392 }
2393}
2394
2395static void shrink_work(struct work_struct *w)
2396{
2397 struct dm_bufio_client *c = container_of(w, struct dm_bufio_client, shrink_work);
2398
2399 dm_bufio_lock(c);
2400 __scan(c);
2401 dm_bufio_unlock(c);
2402}
2403
2404static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
2405{
2406 struct dm_bufio_client *c;
2407
2408 c = shrink->private_data;
2409 atomic_long_add(sc->nr_to_scan, &c->need_shrink);
2410 queue_work(dm_bufio_wq, &c->shrink_work);
2411
2412 return sc->nr_to_scan;
2413}
2414
2415static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
2416{
2417 struct dm_bufio_client *c = shrink->private_data;
2418 unsigned long count = cache_total(&c->cache);
2419 unsigned long retain_target = get_retain_buffers(c);
2420 unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
2421
2422 if (unlikely(count < retain_target))
2423 count = 0;
2424 else
2425 count -= retain_target;
2426
2427 if (unlikely(count < queued_for_cleanup))
2428 count = 0;
2429 else
2430 count -= queued_for_cleanup;
2431
2432 return count;
2433}
2434
2435/*
2436 * Create the buffering interface
2437 */
2438struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned int block_size,
2439 unsigned int reserved_buffers, unsigned int aux_size,
2440 void (*alloc_callback)(struct dm_buffer *),
2441 void (*write_callback)(struct dm_buffer *),
2442 unsigned int flags)
2443{
2444 int r;
2445 unsigned int num_locks;
2446 struct dm_bufio_client *c;
2447 char slab_name[27];
2448
2449 if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
2450 DMERR("%s: block size not specified or is not multiple of 512b", __func__);
2451 r = -EINVAL;
2452 goto bad_client;
2453 }
2454
2455 num_locks = dm_num_hash_locks();
2456 c = kzalloc(sizeof(*c) + (num_locks * sizeof(struct buffer_tree)), GFP_KERNEL);
2457 if (!c) {
2458 r = -ENOMEM;
2459 goto bad_client;
2460 }
2461 cache_init(&c->cache, num_locks, (flags & DM_BUFIO_CLIENT_NO_SLEEP) != 0);
2462
2463 c->bdev = bdev;
2464 c->block_size = block_size;
2465 if (is_power_of_2(block_size))
2466 c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
2467 else
2468 c->sectors_per_block_bits = -1;
2469
2470 c->alloc_callback = alloc_callback;
2471 c->write_callback = write_callback;
2472
2473 if (flags & DM_BUFIO_CLIENT_NO_SLEEP) {
2474 c->no_sleep = true;
2475 static_branch_inc(&no_sleep_enabled);
2476 }
2477
2478 mutex_init(&c->lock);
2479 spin_lock_init(&c->spinlock);
2480 INIT_LIST_HEAD(&c->reserved_buffers);
2481 c->need_reserved_buffers = reserved_buffers;
2482
2483 dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
2484
2485 init_waitqueue_head(&c->free_buffer_wait);
2486 c->async_write_error = 0;
2487
2488 c->dm_io = dm_io_client_create();
2489 if (IS_ERR(c->dm_io)) {
2490 r = PTR_ERR(c->dm_io);
2491 goto bad_dm_io;
2492 }
2493
2494 if (block_size <= KMALLOC_MAX_SIZE &&
2495 (block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
2496 unsigned int align = min(1U << __ffs(block_size), (unsigned int)PAGE_SIZE);
2497
2498 snprintf(slab_name, sizeof(slab_name), "dm_bufio_cache-%u", block_size);
2499 c->slab_cache = kmem_cache_create(slab_name, block_size, align,
2500 SLAB_RECLAIM_ACCOUNT, NULL);
2501 if (!c->slab_cache) {
2502 r = -ENOMEM;
2503 goto bad;
2504 }
2505 }
2506 if (aux_size)
2507 snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u", aux_size);
2508 else
2509 snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer");
2510 c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
2511 0, SLAB_RECLAIM_ACCOUNT, NULL);
2512 if (!c->slab_buffer) {
2513 r = -ENOMEM;
2514 goto bad;
2515 }
2516
2517 while (c->need_reserved_buffers) {
2518 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
2519
2520 if (!b) {
2521 r = -ENOMEM;
2522 goto bad;
2523 }
2524 __free_buffer_wake(b);
2525 }
2526
2527 INIT_WORK(&c->shrink_work, shrink_work);
2528 atomic_long_set(&c->need_shrink, 0);
2529
2530 c->shrinker = shrinker_alloc(0, "dm-bufio:(%u:%u)",
2531 MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
2532 if (!c->shrinker) {
2533 r = -ENOMEM;
2534 goto bad;
2535 }
2536
2537 c->shrinker->count_objects = dm_bufio_shrink_count;
2538 c->shrinker->scan_objects = dm_bufio_shrink_scan;
2539 c->shrinker->seeks = 1;
2540 c->shrinker->batch = 0;
2541 c->shrinker->private_data = c;
2542
2543 shrinker_register(c->shrinker);
2544
2545 mutex_lock(&dm_bufio_clients_lock);
2546 dm_bufio_client_count++;
2547 list_add(&c->client_list, &dm_bufio_all_clients);
2548 __cache_size_refresh();
2549 mutex_unlock(&dm_bufio_clients_lock);
2550
2551 return c;
2552
2553bad:
2554 while (!list_empty(&c->reserved_buffers)) {
2555 struct dm_buffer *b = list_to_buffer(c->reserved_buffers.next);
2556
2557 list_del(&b->lru.list);
2558 free_buffer(b);
2559 }
2560 kmem_cache_destroy(c->slab_cache);
2561 kmem_cache_destroy(c->slab_buffer);
2562 dm_io_client_destroy(c->dm_io);
2563bad_dm_io:
2564 mutex_destroy(&c->lock);
2565 if (c->no_sleep)
2566 static_branch_dec(&no_sleep_enabled);
2567 kfree(c);
2568bad_client:
2569 return ERR_PTR(r);
2570}
2571EXPORT_SYMBOL_GPL(dm_bufio_client_create);
2572
2573/*
2574 * Free the buffering interface.
2575 * It is required that there are no references on any buffers.
2576 */
2577void dm_bufio_client_destroy(struct dm_bufio_client *c)
2578{
2579 unsigned int i;
2580
2581 drop_buffers(c);
2582
2583 shrinker_free(c->shrinker);
2584 flush_work(&c->shrink_work);
2585
2586 mutex_lock(&dm_bufio_clients_lock);
2587
2588 list_del(&c->client_list);
2589 dm_bufio_client_count--;
2590 __cache_size_refresh();
2591
2592 mutex_unlock(&dm_bufio_clients_lock);
2593
2594 WARN_ON(c->need_reserved_buffers);
2595
2596 while (!list_empty(&c->reserved_buffers)) {
2597 struct dm_buffer *b = list_to_buffer(c->reserved_buffers.next);
2598
2599 list_del(&b->lru.list);
2600 free_buffer(b);
2601 }
2602
2603 for (i = 0; i < LIST_SIZE; i++)
2604 if (cache_count(&c->cache, i))
2605 DMERR("leaked buffer count %d: %lu", i, cache_count(&c->cache, i));
2606
2607 for (i = 0; i < LIST_SIZE; i++)
2608 WARN_ON(cache_count(&c->cache, i));
2609
2610 cache_destroy(&c->cache);
2611 kmem_cache_destroy(c->slab_cache);
2612 kmem_cache_destroy(c->slab_buffer);
2613 dm_io_client_destroy(c->dm_io);
2614 mutex_destroy(&c->lock);
2615 if (c->no_sleep)
2616 static_branch_dec(&no_sleep_enabled);
2617 kfree(c);
2618}
2619EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
2620
2621void dm_bufio_client_reset(struct dm_bufio_client *c)
2622{
2623 drop_buffers(c);
2624 flush_work(&c->shrink_work);
2625}
2626EXPORT_SYMBOL_GPL(dm_bufio_client_reset);
2627
2628void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
2629{
2630 c->start = start;
2631}
2632EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
2633
2634/*--------------------------------------------------------------*/
2635
2636static unsigned int get_max_age_hz(void)
2637{
2638 unsigned int max_age = READ_ONCE(dm_bufio_max_age);
2639
2640 if (max_age > UINT_MAX / HZ)
2641 max_age = UINT_MAX / HZ;
2642
2643 return max_age * HZ;
2644}
2645
2646static bool older_than(struct dm_buffer *b, unsigned long age_hz)
2647{
2648 return time_after_eq(jiffies, READ_ONCE(b->last_accessed) + age_hz);
2649}
2650
2651struct evict_params {
2652 gfp_t gfp;
2653 unsigned long age_hz;
2654
2655 /*
2656 * This gets updated with the largest last_accessed (ie. most
2657 * recently used) of the evicted buffers. It will not be reinitialised
2658 * by __evict_many(), so you can use it across multiple invocations.
2659 */
2660 unsigned long last_accessed;
2661};
2662
2663/*
2664 * We may not be able to evict this buffer if IO pending or the client
2665 * is still using it.
2666 *
2667 * And if GFP_NOFS is used, we must not do any I/O because we hold
2668 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
2669 * rerouted to different bufio client.
2670 */
2671static enum evict_result select_for_evict(struct dm_buffer *b, void *context)
2672{
2673 struct evict_params *params = context;
2674
2675 if (!(params->gfp & __GFP_FS) ||
2676 (static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {
2677 if (test_bit_acquire(B_READING, &b->state) ||
2678 test_bit(B_WRITING, &b->state) ||
2679 test_bit(B_DIRTY, &b->state))
2680 return ER_DONT_EVICT;
2681 }
2682
2683 return older_than(b, params->age_hz) ? ER_EVICT : ER_STOP;
2684}
2685
2686static unsigned long __evict_many(struct dm_bufio_client *c,
2687 struct evict_params *params,
2688 int list_mode, unsigned long max_count)
2689{
2690 unsigned long count;
2691 unsigned long last_accessed;
2692 struct dm_buffer *b;
2693
2694 for (count = 0; count < max_count; count++) {
2695 b = cache_evict(&c->cache, list_mode, select_for_evict, params);
2696 if (!b)
2697 break;
2698
2699 last_accessed = READ_ONCE(b->last_accessed);
2700 if (time_after_eq(params->last_accessed, last_accessed))
2701 params->last_accessed = last_accessed;
2702
2703 __make_buffer_clean(b);
2704 __free_buffer_wake(b);
2705
2706 cond_resched();
2707 }
2708
2709 return count;
2710}
2711
2712static void evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
2713{
2714 struct evict_params params = {.gfp = 0, .age_hz = age_hz, .last_accessed = 0};
2715 unsigned long retain = get_retain_buffers(c);
2716 unsigned long count;
2717 LIST_HEAD(write_list);
2718
2719 dm_bufio_lock(c);
2720
2721 __check_watermark(c, &write_list);
2722 if (unlikely(!list_empty(&write_list))) {
2723 dm_bufio_unlock(c);
2724 __flush_write_list(&write_list);
2725 dm_bufio_lock(c);
2726 }
2727
2728 count = cache_total(&c->cache);
2729 if (count > retain)
2730 __evict_many(c, ¶ms, LIST_CLEAN, count - retain);
2731
2732 dm_bufio_unlock(c);
2733}
2734
2735static void cleanup_old_buffers(void)
2736{
2737 unsigned long max_age_hz = get_max_age_hz();
2738 struct dm_bufio_client *c;
2739
2740 mutex_lock(&dm_bufio_clients_lock);
2741
2742 __cache_size_refresh();
2743
2744 list_for_each_entry(c, &dm_bufio_all_clients, client_list)
2745 evict_old_buffers(c, max_age_hz);
2746
2747 mutex_unlock(&dm_bufio_clients_lock);
2748}
2749
2750static void work_fn(struct work_struct *w)
2751{
2752 cleanup_old_buffers();
2753
2754 queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2755 DM_BUFIO_WORK_TIMER_SECS * HZ);
2756}
2757
2758/*--------------------------------------------------------------*/
2759
2760/*
2761 * Global cleanup tries to evict the oldest buffers from across _all_
2762 * the clients. It does this by repeatedly evicting a few buffers from
2763 * the client that holds the oldest buffer. It's approximate, but hopefully
2764 * good enough.
2765 */
2766static struct dm_bufio_client *__pop_client(void)
2767{
2768 struct list_head *h;
2769
2770 if (list_empty(&dm_bufio_all_clients))
2771 return NULL;
2772
2773 h = dm_bufio_all_clients.next;
2774 list_del(h);
2775 return container_of(h, struct dm_bufio_client, client_list);
2776}
2777
2778/*
2779 * Inserts the client in the global client list based on its
2780 * 'oldest_buffer' field.
2781 */
2782static void __insert_client(struct dm_bufio_client *new_client)
2783{
2784 struct dm_bufio_client *c;
2785 struct list_head *h = dm_bufio_all_clients.next;
2786
2787 while (h != &dm_bufio_all_clients) {
2788 c = container_of(h, struct dm_bufio_client, client_list);
2789 if (time_after_eq(c->oldest_buffer, new_client->oldest_buffer))
2790 break;
2791 h = h->next;
2792 }
2793
2794 list_add_tail(&new_client->client_list, h);
2795}
2796
2797static unsigned long __evict_a_few(unsigned long nr_buffers)
2798{
2799 unsigned long count;
2800 struct dm_bufio_client *c;
2801 struct evict_params params = {
2802 .gfp = GFP_KERNEL,
2803 .age_hz = 0,
2804 /* set to jiffies in case there are no buffers in this client */
2805 .last_accessed = jiffies
2806 };
2807
2808 c = __pop_client();
2809 if (!c)
2810 return 0;
2811
2812 dm_bufio_lock(c);
2813 count = __evict_many(c, ¶ms, LIST_CLEAN, nr_buffers);
2814 dm_bufio_unlock(c);
2815
2816 if (count)
2817 c->oldest_buffer = params.last_accessed;
2818 __insert_client(c);
2819
2820 return count;
2821}
2822
2823static void check_watermarks(void)
2824{
2825 LIST_HEAD(write_list);
2826 struct dm_bufio_client *c;
2827
2828 mutex_lock(&dm_bufio_clients_lock);
2829 list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
2830 dm_bufio_lock(c);
2831 __check_watermark(c, &write_list);
2832 dm_bufio_unlock(c);
2833 }
2834 mutex_unlock(&dm_bufio_clients_lock);
2835
2836 __flush_write_list(&write_list);
2837}
2838
2839static void evict_old(void)
2840{
2841 unsigned long threshold = dm_bufio_cache_size -
2842 dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
2843
2844 mutex_lock(&dm_bufio_clients_lock);
2845 while (dm_bufio_current_allocated > threshold) {
2846 if (!__evict_a_few(64))
2847 break;
2848 cond_resched();
2849 }
2850 mutex_unlock(&dm_bufio_clients_lock);
2851}
2852
2853static void do_global_cleanup(struct work_struct *w)
2854{
2855 check_watermarks();
2856 evict_old();
2857}
2858
2859/*
2860 *--------------------------------------------------------------
2861 * Module setup
2862 *--------------------------------------------------------------
2863 */
2864
2865/*
2866 * This is called only once for the whole dm_bufio module.
2867 * It initializes memory limit.
2868 */
2869static int __init dm_bufio_init(void)
2870{
2871 __u64 mem;
2872
2873 dm_bufio_allocated_kmem_cache = 0;
2874 dm_bufio_allocated_get_free_pages = 0;
2875 dm_bufio_allocated_vmalloc = 0;
2876 dm_bufio_current_allocated = 0;
2877
2878 mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(),
2879 DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
2880
2881 if (mem > ULONG_MAX)
2882 mem = ULONG_MAX;
2883
2884#ifdef CONFIG_MMU
2885 if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
2886 mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
2887#endif
2888
2889 dm_bufio_default_cache_size = mem;
2890
2891 mutex_lock(&dm_bufio_clients_lock);
2892 __cache_size_refresh();
2893 mutex_unlock(&dm_bufio_clients_lock);
2894
2895 dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
2896 if (!dm_bufio_wq)
2897 return -ENOMEM;
2898
2899 INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
2900 INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
2901 queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2902 DM_BUFIO_WORK_TIMER_SECS * HZ);
2903
2904 return 0;
2905}
2906
2907/*
2908 * This is called once when unloading the dm_bufio module.
2909 */
2910static void __exit dm_bufio_exit(void)
2911{
2912 int bug = 0;
2913
2914 cancel_delayed_work_sync(&dm_bufio_cleanup_old_work);
2915 destroy_workqueue(dm_bufio_wq);
2916
2917 if (dm_bufio_client_count) {
2918 DMCRIT("%s: dm_bufio_client_count leaked: %d",
2919 __func__, dm_bufio_client_count);
2920 bug = 1;
2921 }
2922
2923 if (dm_bufio_current_allocated) {
2924 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
2925 __func__, dm_bufio_current_allocated);
2926 bug = 1;
2927 }
2928
2929 if (dm_bufio_allocated_get_free_pages) {
2930 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
2931 __func__, dm_bufio_allocated_get_free_pages);
2932 bug = 1;
2933 }
2934
2935 if (dm_bufio_allocated_vmalloc) {
2936 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
2937 __func__, dm_bufio_allocated_vmalloc);
2938 bug = 1;
2939 }
2940
2941 WARN_ON(bug); /* leaks are not worth crashing the system */
2942}
2943
2944module_init(dm_bufio_init)
2945module_exit(dm_bufio_exit)
2946
2947module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, 0644);
2948MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
2949
2950module_param_named(max_age_seconds, dm_bufio_max_age, uint, 0644);
2951MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
2952
2953module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, 0644);
2954MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
2955
2956module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, 0644);
2957MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
2958
2959module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, 0444);
2960MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
2961
2962module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, 0444);
2963MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
2964
2965module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, 0444);
2966MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
2967
2968module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, 0444);
2969MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
2970
2971MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
2972MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
2973MODULE_LICENSE("GPL");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2009-2011 Red Hat, Inc.
4 *
5 * Author: Mikulas Patocka <mpatocka@redhat.com>
6 *
7 * This file is released under the GPL.
8 */
9
10#include <linux/dm-bufio.h>
11
12#include <linux/device-mapper.h>
13#include <linux/dm-io.h>
14#include <linux/slab.h>
15#include <linux/sched/mm.h>
16#include <linux/jiffies.h>
17#include <linux/vmalloc.h>
18#include <linux/shrinker.h>
19#include <linux/module.h>
20#include <linux/rbtree.h>
21#include <linux/stacktrace.h>
22#include <linux/jump_label.h>
23
24#include "dm.h"
25
26#define DM_MSG_PREFIX "bufio"
27
28/*
29 * Memory management policy:
30 * Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
31 * or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
32 * Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
33 * Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
34 * dirty buffers.
35 */
36#define DM_BUFIO_MIN_BUFFERS 8
37
38#define DM_BUFIO_MEMORY_PERCENT 2
39#define DM_BUFIO_VMALLOC_PERCENT 25
40#define DM_BUFIO_WRITEBACK_RATIO 3
41#define DM_BUFIO_LOW_WATERMARK_RATIO 16
42
43/*
44 * Check buffer ages in this interval (seconds)
45 */
46#define DM_BUFIO_WORK_TIMER_SECS 30
47
48/*
49 * Free buffers when they are older than this (seconds)
50 */
51#define DM_BUFIO_DEFAULT_AGE_SECS 300
52
53/*
54 * The nr of bytes of cached data to keep around.
55 */
56#define DM_BUFIO_DEFAULT_RETAIN_BYTES (256 * 1024)
57
58/*
59 * Align buffer writes to this boundary.
60 * Tests show that SSDs have the highest IOPS when using 4k writes.
61 */
62#define DM_BUFIO_WRITE_ALIGN 4096
63
64/*
65 * dm_buffer->list_mode
66 */
67#define LIST_CLEAN 0
68#define LIST_DIRTY 1
69#define LIST_SIZE 2
70
71/*--------------------------------------------------------------*/
72
73/*
74 * Rather than use an LRU list, we use a clock algorithm where entries
75 * are held in a circular list. When an entry is 'hit' a reference bit
76 * is set. The least recently used entry is approximated by running a
77 * cursor around the list selecting unreferenced entries. Referenced
78 * entries have their reference bit cleared as the cursor passes them.
79 */
80struct lru_entry {
81 struct list_head list;
82 atomic_t referenced;
83};
84
85struct lru_iter {
86 struct lru *lru;
87 struct list_head list;
88 struct lru_entry *stop;
89 struct lru_entry *e;
90};
91
92struct lru {
93 struct list_head *cursor;
94 unsigned long count;
95
96 struct list_head iterators;
97};
98
99/*--------------*/
100
101static void lru_init(struct lru *lru)
102{
103 lru->cursor = NULL;
104 lru->count = 0;
105 INIT_LIST_HEAD(&lru->iterators);
106}
107
108static void lru_destroy(struct lru *lru)
109{
110 WARN_ON_ONCE(lru->cursor);
111 WARN_ON_ONCE(!list_empty(&lru->iterators));
112}
113
114/*
115 * Insert a new entry into the lru.
116 */
117static void lru_insert(struct lru *lru, struct lru_entry *le)
118{
119 /*
120 * Don't be tempted to set to 1, makes the lru aspect
121 * perform poorly.
122 */
123 atomic_set(&le->referenced, 0);
124
125 if (lru->cursor) {
126 list_add_tail(&le->list, lru->cursor);
127 } else {
128 INIT_LIST_HEAD(&le->list);
129 lru->cursor = &le->list;
130 }
131 lru->count++;
132}
133
134/*--------------*/
135
136/*
137 * Convert a list_head pointer to an lru_entry pointer.
138 */
139static inline struct lru_entry *to_le(struct list_head *l)
140{
141 return container_of(l, struct lru_entry, list);
142}
143
144/*
145 * Initialize an lru_iter and add it to the list of cursors in the lru.
146 */
147static void lru_iter_begin(struct lru *lru, struct lru_iter *it)
148{
149 it->lru = lru;
150 it->stop = lru->cursor ? to_le(lru->cursor->prev) : NULL;
151 it->e = lru->cursor ? to_le(lru->cursor) : NULL;
152 list_add(&it->list, &lru->iterators);
153}
154
155/*
156 * Remove an lru_iter from the list of cursors in the lru.
157 */
158static inline void lru_iter_end(struct lru_iter *it)
159{
160 list_del(&it->list);
161}
162
163/* Predicate function type to be used with lru_iter_next */
164typedef bool (*iter_predicate)(struct lru_entry *le, void *context);
165
166/*
167 * Advance the cursor to the next entry that passes the
168 * predicate, and return that entry. Returns NULL if the
169 * iteration is complete.
170 */
171static struct lru_entry *lru_iter_next(struct lru_iter *it,
172 iter_predicate pred, void *context)
173{
174 struct lru_entry *e;
175
176 while (it->e) {
177 e = it->e;
178
179 /* advance the cursor */
180 if (it->e == it->stop)
181 it->e = NULL;
182 else
183 it->e = to_le(it->e->list.next);
184
185 if (pred(e, context))
186 return e;
187 }
188
189 return NULL;
190}
191
192/*
193 * Invalidate a specific lru_entry and update all cursors in
194 * the lru accordingly.
195 */
196static void lru_iter_invalidate(struct lru *lru, struct lru_entry *e)
197{
198 struct lru_iter *it;
199
200 list_for_each_entry(it, &lru->iterators, list) {
201 /* Move c->e forwards if necc. */
202 if (it->e == e) {
203 it->e = to_le(it->e->list.next);
204 if (it->e == e)
205 it->e = NULL;
206 }
207
208 /* Move it->stop backwards if necc. */
209 if (it->stop == e) {
210 it->stop = to_le(it->stop->list.prev);
211 if (it->stop == e)
212 it->stop = NULL;
213 }
214 }
215}
216
217/*--------------*/
218
219/*
220 * Remove a specific entry from the lru.
221 */
222static void lru_remove(struct lru *lru, struct lru_entry *le)
223{
224 lru_iter_invalidate(lru, le);
225 if (lru->count == 1) {
226 lru->cursor = NULL;
227 } else {
228 if (lru->cursor == &le->list)
229 lru->cursor = lru->cursor->next;
230 list_del(&le->list);
231 }
232 lru->count--;
233}
234
235/*
236 * Mark as referenced.
237 */
238static inline void lru_reference(struct lru_entry *le)
239{
240 atomic_set(&le->referenced, 1);
241}
242
243/*--------------*/
244
245/*
246 * Remove the least recently used entry (approx), that passes the predicate.
247 * Returns NULL on failure.
248 */
249enum evict_result {
250 ER_EVICT,
251 ER_DONT_EVICT,
252 ER_STOP, /* stop looking for something to evict */
253};
254
255typedef enum evict_result (*le_predicate)(struct lru_entry *le, void *context);
256
257static struct lru_entry *lru_evict(struct lru *lru, le_predicate pred, void *context, bool no_sleep)
258{
259 unsigned long tested = 0;
260 struct list_head *h = lru->cursor;
261 struct lru_entry *le;
262
263 if (!h)
264 return NULL;
265 /*
266 * In the worst case we have to loop around twice. Once to clear
267 * the reference flags, and then again to discover the predicate
268 * fails for all entries.
269 */
270 while (tested < lru->count) {
271 le = container_of(h, struct lru_entry, list);
272
273 if (atomic_read(&le->referenced)) {
274 atomic_set(&le->referenced, 0);
275 } else {
276 tested++;
277 switch (pred(le, context)) {
278 case ER_EVICT:
279 /*
280 * Adjust the cursor, so we start the next
281 * search from here.
282 */
283 lru->cursor = le->list.next;
284 lru_remove(lru, le);
285 return le;
286
287 case ER_DONT_EVICT:
288 break;
289
290 case ER_STOP:
291 lru->cursor = le->list.next;
292 return NULL;
293 }
294 }
295
296 h = h->next;
297
298 if (!no_sleep)
299 cond_resched();
300 }
301
302 return NULL;
303}
304
305/*--------------------------------------------------------------*/
306
307/*
308 * Buffer state bits.
309 */
310#define B_READING 0
311#define B_WRITING 1
312#define B_DIRTY 2
313
314/*
315 * Describes how the block was allocated:
316 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
317 * See the comment at alloc_buffer_data.
318 */
319enum data_mode {
320 DATA_MODE_SLAB = 0,
321 DATA_MODE_KMALLOC = 1,
322 DATA_MODE_GET_FREE_PAGES = 2,
323 DATA_MODE_VMALLOC = 3,
324 DATA_MODE_LIMIT = 4
325};
326
327struct dm_buffer {
328 /* protected by the locks in dm_buffer_cache */
329 struct rb_node node;
330
331 /* immutable, so don't need protecting */
332 sector_t block;
333 void *data;
334 unsigned char data_mode; /* DATA_MODE_* */
335
336 /*
337 * These two fields are used in isolation, so do not need
338 * a surrounding lock.
339 */
340 atomic_t hold_count;
341 unsigned long last_accessed;
342
343 /*
344 * Everything else is protected by the mutex in
345 * dm_bufio_client
346 */
347 unsigned long state;
348 struct lru_entry lru;
349 unsigned char list_mode; /* LIST_* */
350 blk_status_t read_error;
351 blk_status_t write_error;
352 unsigned int dirty_start;
353 unsigned int dirty_end;
354 unsigned int write_start;
355 unsigned int write_end;
356 struct list_head write_list;
357 struct dm_bufio_client *c;
358 void (*end_io)(struct dm_buffer *b, blk_status_t bs);
359#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
360#define MAX_STACK 10
361 unsigned int stack_len;
362 unsigned long stack_entries[MAX_STACK];
363#endif
364};
365
366/*--------------------------------------------------------------*/
367
368/*
369 * The buffer cache manages buffers, particularly:
370 * - inc/dec of holder count
371 * - setting the last_accessed field
372 * - maintains clean/dirty state along with lru
373 * - selecting buffers that match predicates
374 *
375 * It does *not* handle:
376 * - allocation/freeing of buffers.
377 * - IO
378 * - Eviction or cache sizing.
379 *
380 * cache_get() and cache_put() are threadsafe, you do not need to
381 * protect these calls with a surrounding mutex. All the other
382 * methods are not threadsafe; they do use locking primitives, but
383 * only enough to ensure get/put are threadsafe.
384 */
385
386struct buffer_tree {
387 union {
388 struct rw_semaphore lock;
389 rwlock_t spinlock;
390 } u;
391 struct rb_root root;
392} ____cacheline_aligned_in_smp;
393
394struct dm_buffer_cache {
395 struct lru lru[LIST_SIZE];
396 /*
397 * We spread entries across multiple trees to reduce contention
398 * on the locks.
399 */
400 unsigned int num_locks;
401 bool no_sleep;
402 struct buffer_tree trees[];
403};
404
405static DEFINE_STATIC_KEY_FALSE(no_sleep_enabled);
406
407static inline unsigned int cache_index(sector_t block, unsigned int num_locks)
408{
409 return dm_hash_locks_index(block, num_locks);
410}
411
412static inline void cache_read_lock(struct dm_buffer_cache *bc, sector_t block)
413{
414 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
415 read_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
416 else
417 down_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
418}
419
420static inline void cache_read_unlock(struct dm_buffer_cache *bc, sector_t block)
421{
422 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
423 read_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
424 else
425 up_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
426}
427
428static inline void cache_write_lock(struct dm_buffer_cache *bc, sector_t block)
429{
430 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
431 write_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
432 else
433 down_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
434}
435
436static inline void cache_write_unlock(struct dm_buffer_cache *bc, sector_t block)
437{
438 if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
439 write_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
440 else
441 up_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
442}
443
444/*
445 * Sometimes we want to repeatedly get and drop locks as part of an iteration.
446 * This struct helps avoid redundant drop and gets of the same lock.
447 */
448struct lock_history {
449 struct dm_buffer_cache *cache;
450 bool write;
451 unsigned int previous;
452 unsigned int no_previous;
453};
454
455static void lh_init(struct lock_history *lh, struct dm_buffer_cache *cache, bool write)
456{
457 lh->cache = cache;
458 lh->write = write;
459 lh->no_previous = cache->num_locks;
460 lh->previous = lh->no_previous;
461}
462
463static void __lh_lock(struct lock_history *lh, unsigned int index)
464{
465 if (lh->write) {
466 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
467 write_lock_bh(&lh->cache->trees[index].u.spinlock);
468 else
469 down_write(&lh->cache->trees[index].u.lock);
470 } else {
471 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
472 read_lock_bh(&lh->cache->trees[index].u.spinlock);
473 else
474 down_read(&lh->cache->trees[index].u.lock);
475 }
476}
477
478static void __lh_unlock(struct lock_history *lh, unsigned int index)
479{
480 if (lh->write) {
481 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
482 write_unlock_bh(&lh->cache->trees[index].u.spinlock);
483 else
484 up_write(&lh->cache->trees[index].u.lock);
485 } else {
486 if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
487 read_unlock_bh(&lh->cache->trees[index].u.spinlock);
488 else
489 up_read(&lh->cache->trees[index].u.lock);
490 }
491}
492
493/*
494 * Make sure you call this since it will unlock the final lock.
495 */
496static void lh_exit(struct lock_history *lh)
497{
498 if (lh->previous != lh->no_previous) {
499 __lh_unlock(lh, lh->previous);
500 lh->previous = lh->no_previous;
501 }
502}
503
504/*
505 * Named 'next' because there is no corresponding
506 * 'up/unlock' call since it's done automatically.
507 */
508static void lh_next(struct lock_history *lh, sector_t b)
509{
510 unsigned int index = cache_index(b, lh->no_previous); /* no_previous is num_locks */
511
512 if (lh->previous != lh->no_previous) {
513 if (lh->previous != index) {
514 __lh_unlock(lh, lh->previous);
515 __lh_lock(lh, index);
516 lh->previous = index;
517 }
518 } else {
519 __lh_lock(lh, index);
520 lh->previous = index;
521 }
522}
523
524static inline struct dm_buffer *le_to_buffer(struct lru_entry *le)
525{
526 return container_of(le, struct dm_buffer, lru);
527}
528
529static struct dm_buffer *list_to_buffer(struct list_head *l)
530{
531 struct lru_entry *le = list_entry(l, struct lru_entry, list);
532
533 return le_to_buffer(le);
534}
535
536static void cache_init(struct dm_buffer_cache *bc, unsigned int num_locks, bool no_sleep)
537{
538 unsigned int i;
539
540 bc->num_locks = num_locks;
541 bc->no_sleep = no_sleep;
542
543 for (i = 0; i < bc->num_locks; i++) {
544 if (no_sleep)
545 rwlock_init(&bc->trees[i].u.spinlock);
546 else
547 init_rwsem(&bc->trees[i].u.lock);
548 bc->trees[i].root = RB_ROOT;
549 }
550
551 lru_init(&bc->lru[LIST_CLEAN]);
552 lru_init(&bc->lru[LIST_DIRTY]);
553}
554
555static void cache_destroy(struct dm_buffer_cache *bc)
556{
557 unsigned int i;
558
559 for (i = 0; i < bc->num_locks; i++)
560 WARN_ON_ONCE(!RB_EMPTY_ROOT(&bc->trees[i].root));
561
562 lru_destroy(&bc->lru[LIST_CLEAN]);
563 lru_destroy(&bc->lru[LIST_DIRTY]);
564}
565
566/*--------------*/
567
568/*
569 * not threadsafe, or racey depending how you look at it
570 */
571static inline unsigned long cache_count(struct dm_buffer_cache *bc, int list_mode)
572{
573 return bc->lru[list_mode].count;
574}
575
576static inline unsigned long cache_total(struct dm_buffer_cache *bc)
577{
578 return cache_count(bc, LIST_CLEAN) + cache_count(bc, LIST_DIRTY);
579}
580
581/*--------------*/
582
583/*
584 * Gets a specific buffer, indexed by block.
585 * If the buffer is found then its holder count will be incremented and
586 * lru_reference will be called.
587 *
588 * threadsafe
589 */
590static struct dm_buffer *__cache_get(const struct rb_root *root, sector_t block)
591{
592 struct rb_node *n = root->rb_node;
593 struct dm_buffer *b;
594
595 while (n) {
596 b = container_of(n, struct dm_buffer, node);
597
598 if (b->block == block)
599 return b;
600
601 n = block < b->block ? n->rb_left : n->rb_right;
602 }
603
604 return NULL;
605}
606
607static void __cache_inc_buffer(struct dm_buffer *b)
608{
609 atomic_inc(&b->hold_count);
610 WRITE_ONCE(b->last_accessed, jiffies);
611}
612
613static struct dm_buffer *cache_get(struct dm_buffer_cache *bc, sector_t block)
614{
615 struct dm_buffer *b;
616
617 cache_read_lock(bc, block);
618 b = __cache_get(&bc->trees[cache_index(block, bc->num_locks)].root, block);
619 if (b) {
620 lru_reference(&b->lru);
621 __cache_inc_buffer(b);
622 }
623 cache_read_unlock(bc, block);
624
625 return b;
626}
627
628/*--------------*/
629
630/*
631 * Returns true if the hold count hits zero.
632 * threadsafe
633 */
634static bool cache_put(struct dm_buffer_cache *bc, struct dm_buffer *b)
635{
636 bool r;
637
638 cache_read_lock(bc, b->block);
639 BUG_ON(!atomic_read(&b->hold_count));
640 r = atomic_dec_and_test(&b->hold_count);
641 cache_read_unlock(bc, b->block);
642
643 return r;
644}
645
646/*--------------*/
647
648typedef enum evict_result (*b_predicate)(struct dm_buffer *, void *);
649
650/*
651 * Evicts a buffer based on a predicate. The oldest buffer that
652 * matches the predicate will be selected. In addition to the
653 * predicate the hold_count of the selected buffer will be zero.
654 */
655struct evict_wrapper {
656 struct lock_history *lh;
657 b_predicate pred;
658 void *context;
659};
660
661/*
662 * Wraps the buffer predicate turning it into an lru predicate. Adds
663 * extra test for hold_count.
664 */
665static enum evict_result __evict_pred(struct lru_entry *le, void *context)
666{
667 struct evict_wrapper *w = context;
668 struct dm_buffer *b = le_to_buffer(le);
669
670 lh_next(w->lh, b->block);
671
672 if (atomic_read(&b->hold_count))
673 return ER_DONT_EVICT;
674
675 return w->pred(b, w->context);
676}
677
678static struct dm_buffer *__cache_evict(struct dm_buffer_cache *bc, int list_mode,
679 b_predicate pred, void *context,
680 struct lock_history *lh)
681{
682 struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
683 struct lru_entry *le;
684 struct dm_buffer *b;
685
686 le = lru_evict(&bc->lru[list_mode], __evict_pred, &w, bc->no_sleep);
687 if (!le)
688 return NULL;
689
690 b = le_to_buffer(le);
691 /* __evict_pred will have locked the appropriate tree. */
692 rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
693
694 return b;
695}
696
697static struct dm_buffer *cache_evict(struct dm_buffer_cache *bc, int list_mode,
698 b_predicate pred, void *context)
699{
700 struct dm_buffer *b;
701 struct lock_history lh;
702
703 lh_init(&lh, bc, true);
704 b = __cache_evict(bc, list_mode, pred, context, &lh);
705 lh_exit(&lh);
706
707 return b;
708}
709
710/*--------------*/
711
712/*
713 * Mark a buffer as clean or dirty. Not threadsafe.
714 */
715static void cache_mark(struct dm_buffer_cache *bc, struct dm_buffer *b, int list_mode)
716{
717 cache_write_lock(bc, b->block);
718 if (list_mode != b->list_mode) {
719 lru_remove(&bc->lru[b->list_mode], &b->lru);
720 b->list_mode = list_mode;
721 lru_insert(&bc->lru[b->list_mode], &b->lru);
722 }
723 cache_write_unlock(bc, b->block);
724}
725
726/*--------------*/
727
728/*
729 * Runs through the lru associated with 'old_mode', if the predicate matches then
730 * it moves them to 'new_mode'. Not threadsafe.
731 */
732static void __cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_mode,
733 b_predicate pred, void *context, struct lock_history *lh)
734{
735 struct lru_entry *le;
736 struct dm_buffer *b;
737 struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
738
739 while (true) {
740 le = lru_evict(&bc->lru[old_mode], __evict_pred, &w, bc->no_sleep);
741 if (!le)
742 break;
743
744 b = le_to_buffer(le);
745 b->list_mode = new_mode;
746 lru_insert(&bc->lru[b->list_mode], &b->lru);
747 }
748}
749
750static void cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_mode,
751 b_predicate pred, void *context)
752{
753 struct lock_history lh;
754
755 lh_init(&lh, bc, true);
756 __cache_mark_many(bc, old_mode, new_mode, pred, context, &lh);
757 lh_exit(&lh);
758}
759
760/*--------------*/
761
762/*
763 * Iterates through all clean or dirty entries calling a function for each
764 * entry. The callback may terminate the iteration early. Not threadsafe.
765 */
766
767/*
768 * Iterator functions should return one of these actions to indicate
769 * how the iteration should proceed.
770 */
771enum it_action {
772 IT_NEXT,
773 IT_COMPLETE,
774};
775
776typedef enum it_action (*iter_fn)(struct dm_buffer *b, void *context);
777
778static void __cache_iterate(struct dm_buffer_cache *bc, int list_mode,
779 iter_fn fn, void *context, struct lock_history *lh)
780{
781 struct lru *lru = &bc->lru[list_mode];
782 struct lru_entry *le, *first;
783
784 if (!lru->cursor)
785 return;
786
787 first = le = to_le(lru->cursor);
788 do {
789 struct dm_buffer *b = le_to_buffer(le);
790
791 lh_next(lh, b->block);
792
793 switch (fn(b, context)) {
794 case IT_NEXT:
795 break;
796
797 case IT_COMPLETE:
798 return;
799 }
800 cond_resched();
801
802 le = to_le(le->list.next);
803 } while (le != first);
804}
805
806static void cache_iterate(struct dm_buffer_cache *bc, int list_mode,
807 iter_fn fn, void *context)
808{
809 struct lock_history lh;
810
811 lh_init(&lh, bc, false);
812 __cache_iterate(bc, list_mode, fn, context, &lh);
813 lh_exit(&lh);
814}
815
816/*--------------*/
817
818/*
819 * Passes ownership of the buffer to the cache. Returns false if the
820 * buffer was already present (in which case ownership does not pass).
821 * eg, a race with another thread.
822 *
823 * Holder count should be 1 on insertion.
824 *
825 * Not threadsafe.
826 */
827static bool __cache_insert(struct rb_root *root, struct dm_buffer *b)
828{
829 struct rb_node **new = &root->rb_node, *parent = NULL;
830 struct dm_buffer *found;
831
832 while (*new) {
833 found = container_of(*new, struct dm_buffer, node);
834
835 if (found->block == b->block)
836 return false;
837
838 parent = *new;
839 new = b->block < found->block ?
840 &found->node.rb_left : &found->node.rb_right;
841 }
842
843 rb_link_node(&b->node, parent, new);
844 rb_insert_color(&b->node, root);
845
846 return true;
847}
848
849static bool cache_insert(struct dm_buffer_cache *bc, struct dm_buffer *b)
850{
851 bool r;
852
853 if (WARN_ON_ONCE(b->list_mode >= LIST_SIZE))
854 return false;
855
856 cache_write_lock(bc, b->block);
857 BUG_ON(atomic_read(&b->hold_count) != 1);
858 r = __cache_insert(&bc->trees[cache_index(b->block, bc->num_locks)].root, b);
859 if (r)
860 lru_insert(&bc->lru[b->list_mode], &b->lru);
861 cache_write_unlock(bc, b->block);
862
863 return r;
864}
865
866/*--------------*/
867
868/*
869 * Removes buffer from cache, ownership of the buffer passes back to the caller.
870 * Fails if the hold_count is not one (ie. the caller holds the only reference).
871 *
872 * Not threadsafe.
873 */
874static bool cache_remove(struct dm_buffer_cache *bc, struct dm_buffer *b)
875{
876 bool r;
877
878 cache_write_lock(bc, b->block);
879
880 if (atomic_read(&b->hold_count) != 1) {
881 r = false;
882 } else {
883 r = true;
884 rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
885 lru_remove(&bc->lru[b->list_mode], &b->lru);
886 }
887
888 cache_write_unlock(bc, b->block);
889
890 return r;
891}
892
893/*--------------*/
894
895typedef void (*b_release)(struct dm_buffer *);
896
897static struct dm_buffer *__find_next(struct rb_root *root, sector_t block)
898{
899 struct rb_node *n = root->rb_node;
900 struct dm_buffer *b;
901 struct dm_buffer *best = NULL;
902
903 while (n) {
904 b = container_of(n, struct dm_buffer, node);
905
906 if (b->block == block)
907 return b;
908
909 if (block <= b->block) {
910 n = n->rb_left;
911 best = b;
912 } else {
913 n = n->rb_right;
914 }
915 }
916
917 return best;
918}
919
920static void __remove_range(struct dm_buffer_cache *bc,
921 struct rb_root *root,
922 sector_t begin, sector_t end,
923 b_predicate pred, b_release release)
924{
925 struct dm_buffer *b;
926
927 while (true) {
928 cond_resched();
929
930 b = __find_next(root, begin);
931 if (!b || (b->block >= end))
932 break;
933
934 begin = b->block + 1;
935
936 if (atomic_read(&b->hold_count))
937 continue;
938
939 if (pred(b, NULL) == ER_EVICT) {
940 rb_erase(&b->node, root);
941 lru_remove(&bc->lru[b->list_mode], &b->lru);
942 release(b);
943 }
944 }
945}
946
947static void cache_remove_range(struct dm_buffer_cache *bc,
948 sector_t begin, sector_t end,
949 b_predicate pred, b_release release)
950{
951 unsigned int i;
952
953 BUG_ON(bc->no_sleep);
954 for (i = 0; i < bc->num_locks; i++) {
955 down_write(&bc->trees[i].u.lock);
956 __remove_range(bc, &bc->trees[i].root, begin, end, pred, release);
957 up_write(&bc->trees[i].u.lock);
958 }
959}
960
961/*----------------------------------------------------------------*/
962
963/*
964 * Linking of buffers:
965 * All buffers are linked to buffer_cache with their node field.
966 *
967 * Clean buffers that are not being written (B_WRITING not set)
968 * are linked to lru[LIST_CLEAN] with their lru_list field.
969 *
970 * Dirty and clean buffers that are being written are linked to
971 * lru[LIST_DIRTY] with their lru_list field. When the write
972 * finishes, the buffer cannot be relinked immediately (because we
973 * are in an interrupt context and relinking requires process
974 * context), so some clean-not-writing buffers can be held on
975 * dirty_lru too. They are later added to lru in the process
976 * context.
977 */
978struct dm_bufio_client {
979 struct block_device *bdev;
980 unsigned int block_size;
981 s8 sectors_per_block_bits;
982
983 bool no_sleep;
984 struct mutex lock;
985 spinlock_t spinlock;
986
987 int async_write_error;
988
989 void (*alloc_callback)(struct dm_buffer *buf);
990 void (*write_callback)(struct dm_buffer *buf);
991 struct kmem_cache *slab_buffer;
992 struct kmem_cache *slab_cache;
993 struct dm_io_client *dm_io;
994
995 struct list_head reserved_buffers;
996 unsigned int need_reserved_buffers;
997
998 unsigned int minimum_buffers;
999
1000 sector_t start;
1001
1002 struct shrinker *shrinker;
1003 struct work_struct shrink_work;
1004 atomic_long_t need_shrink;
1005
1006 wait_queue_head_t free_buffer_wait;
1007
1008 struct list_head client_list;
1009
1010 /*
1011 * Used by global_cleanup to sort the clients list.
1012 */
1013 unsigned long oldest_buffer;
1014
1015 struct dm_buffer_cache cache; /* must be last member */
1016};
1017
1018/*----------------------------------------------------------------*/
1019
1020#define dm_bufio_in_request() (!!current->bio_list)
1021
1022static void dm_bufio_lock(struct dm_bufio_client *c)
1023{
1024 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
1025 spin_lock_bh(&c->spinlock);
1026 else
1027 mutex_lock_nested(&c->lock, dm_bufio_in_request());
1028}
1029
1030static void dm_bufio_unlock(struct dm_bufio_client *c)
1031{
1032 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
1033 spin_unlock_bh(&c->spinlock);
1034 else
1035 mutex_unlock(&c->lock);
1036}
1037
1038/*----------------------------------------------------------------*/
1039
1040/*
1041 * Default cache size: available memory divided by the ratio.
1042 */
1043static unsigned long dm_bufio_default_cache_size;
1044
1045/*
1046 * Total cache size set by the user.
1047 */
1048static unsigned long dm_bufio_cache_size;
1049
1050/*
1051 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
1052 * at any time. If it disagrees, the user has changed cache size.
1053 */
1054static unsigned long dm_bufio_cache_size_latch;
1055
1056static DEFINE_SPINLOCK(global_spinlock);
1057
1058/*
1059 * Buffers are freed after this timeout
1060 */
1061static unsigned int dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
1062static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
1063
1064static unsigned long dm_bufio_peak_allocated;
1065static unsigned long dm_bufio_allocated_kmem_cache;
1066static unsigned long dm_bufio_allocated_kmalloc;
1067static unsigned long dm_bufio_allocated_get_free_pages;
1068static unsigned long dm_bufio_allocated_vmalloc;
1069static unsigned long dm_bufio_current_allocated;
1070
1071/*----------------------------------------------------------------*/
1072
1073/*
1074 * The current number of clients.
1075 */
1076static int dm_bufio_client_count;
1077
1078/*
1079 * The list of all clients.
1080 */
1081static LIST_HEAD(dm_bufio_all_clients);
1082
1083/*
1084 * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
1085 */
1086static DEFINE_MUTEX(dm_bufio_clients_lock);
1087
1088static struct workqueue_struct *dm_bufio_wq;
1089static struct delayed_work dm_bufio_cleanup_old_work;
1090static struct work_struct dm_bufio_replacement_work;
1091
1092
1093#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1094static void buffer_record_stack(struct dm_buffer *b)
1095{
1096 b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
1097}
1098#endif
1099
1100/*----------------------------------------------------------------*/
1101
1102static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
1103{
1104 unsigned char data_mode;
1105 long diff;
1106
1107 static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
1108 &dm_bufio_allocated_kmem_cache,
1109 &dm_bufio_allocated_kmalloc,
1110 &dm_bufio_allocated_get_free_pages,
1111 &dm_bufio_allocated_vmalloc,
1112 };
1113
1114 data_mode = b->data_mode;
1115 diff = (long)b->c->block_size;
1116 if (unlink)
1117 diff = -diff;
1118
1119 spin_lock(&global_spinlock);
1120
1121 *class_ptr[data_mode] += diff;
1122
1123 dm_bufio_current_allocated += diff;
1124
1125 if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
1126 dm_bufio_peak_allocated = dm_bufio_current_allocated;
1127
1128 if (!unlink) {
1129 if (dm_bufio_current_allocated > dm_bufio_cache_size)
1130 queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
1131 }
1132
1133 spin_unlock(&global_spinlock);
1134}
1135
1136/*
1137 * Change the number of clients and recalculate per-client limit.
1138 */
1139static void __cache_size_refresh(void)
1140{
1141 if (WARN_ON(!mutex_is_locked(&dm_bufio_clients_lock)))
1142 return;
1143 if (WARN_ON(dm_bufio_client_count < 0))
1144 return;
1145
1146 dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
1147
1148 /*
1149 * Use default if set to 0 and report the actual cache size used.
1150 */
1151 if (!dm_bufio_cache_size_latch) {
1152 (void)cmpxchg(&dm_bufio_cache_size, 0,
1153 dm_bufio_default_cache_size);
1154 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
1155 }
1156}
1157
1158/*
1159 * Allocating buffer data.
1160 *
1161 * Small buffers are allocated with kmem_cache, to use space optimally.
1162 *
1163 * For large buffers, we choose between get_free_pages and vmalloc.
1164 * Each has advantages and disadvantages.
1165 *
1166 * __get_free_pages can randomly fail if the memory is fragmented.
1167 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
1168 * as low as 128M) so using it for caching is not appropriate.
1169 *
1170 * If the allocation may fail we use __get_free_pages. Memory fragmentation
1171 * won't have a fatal effect here, but it just causes flushes of some other
1172 * buffers and more I/O will be performed. Don't use __get_free_pages if it
1173 * always fails (i.e. order > MAX_PAGE_ORDER).
1174 *
1175 * If the allocation shouldn't fail we use __vmalloc. This is only for the
1176 * initial reserve allocation, so there's no risk of wasting all vmalloc
1177 * space.
1178 */
1179static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
1180 unsigned char *data_mode)
1181{
1182 if (unlikely(c->slab_cache != NULL)) {
1183 *data_mode = DATA_MODE_SLAB;
1184 return kmem_cache_alloc(c->slab_cache, gfp_mask);
1185 }
1186
1187 if (unlikely(c->block_size < PAGE_SIZE)) {
1188 *data_mode = DATA_MODE_KMALLOC;
1189 return kmalloc(c->block_size, gfp_mask | __GFP_RECLAIMABLE);
1190 }
1191
1192 if (c->block_size <= KMALLOC_MAX_SIZE &&
1193 gfp_mask & __GFP_NORETRY) {
1194 *data_mode = DATA_MODE_GET_FREE_PAGES;
1195 return (void *)__get_free_pages(gfp_mask,
1196 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
1197 }
1198
1199 *data_mode = DATA_MODE_VMALLOC;
1200
1201 return __vmalloc(c->block_size, gfp_mask);
1202}
1203
1204/*
1205 * Free buffer's data.
1206 */
1207static void free_buffer_data(struct dm_bufio_client *c,
1208 void *data, unsigned char data_mode)
1209{
1210 switch (data_mode) {
1211 case DATA_MODE_SLAB:
1212 kmem_cache_free(c->slab_cache, data);
1213 break;
1214
1215 case DATA_MODE_KMALLOC:
1216 kfree(data);
1217 break;
1218
1219 case DATA_MODE_GET_FREE_PAGES:
1220 free_pages((unsigned long)data,
1221 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
1222 break;
1223
1224 case DATA_MODE_VMALLOC:
1225 vfree(data);
1226 break;
1227
1228 default:
1229 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
1230 data_mode);
1231 BUG();
1232 }
1233}
1234
1235/*
1236 * Allocate buffer and its data.
1237 */
1238static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
1239{
1240 struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
1241
1242 if (!b)
1243 return NULL;
1244
1245 b->c = c;
1246
1247 b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
1248 if (!b->data) {
1249 kmem_cache_free(c->slab_buffer, b);
1250 return NULL;
1251 }
1252 adjust_total_allocated(b, false);
1253
1254#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1255 b->stack_len = 0;
1256#endif
1257 return b;
1258}
1259
1260/*
1261 * Free buffer and its data.
1262 */
1263static void free_buffer(struct dm_buffer *b)
1264{
1265 struct dm_bufio_client *c = b->c;
1266
1267 adjust_total_allocated(b, true);
1268 free_buffer_data(c, b->data, b->data_mode);
1269 kmem_cache_free(c->slab_buffer, b);
1270}
1271
1272/*
1273 *--------------------------------------------------------------------------
1274 * Submit I/O on the buffer.
1275 *
1276 * Bio interface is faster but it has some problems:
1277 * the vector list is limited (increasing this limit increases
1278 * memory-consumption per buffer, so it is not viable);
1279 *
1280 * the memory must be direct-mapped, not vmalloced;
1281 *
1282 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
1283 * it is not vmalloced, try using the bio interface.
1284 *
1285 * If the buffer is big, if it is vmalloced or if the underlying device
1286 * rejects the bio because it is too large, use dm-io layer to do the I/O.
1287 * The dm-io layer splits the I/O into multiple requests, avoiding the above
1288 * shortcomings.
1289 *--------------------------------------------------------------------------
1290 */
1291
1292/*
1293 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
1294 * that the request was handled directly with bio interface.
1295 */
1296static void dmio_complete(unsigned long error, void *context)
1297{
1298 struct dm_buffer *b = context;
1299
1300 b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
1301}
1302
1303static void use_dmio(struct dm_buffer *b, enum req_op op, sector_t sector,
1304 unsigned int n_sectors, unsigned int offset,
1305 unsigned short ioprio)
1306{
1307 int r;
1308 struct dm_io_request io_req = {
1309 .bi_opf = op,
1310 .notify.fn = dmio_complete,
1311 .notify.context = b,
1312 .client = b->c->dm_io,
1313 };
1314 struct dm_io_region region = {
1315 .bdev = b->c->bdev,
1316 .sector = sector,
1317 .count = n_sectors,
1318 };
1319
1320 if (b->data_mode != DATA_MODE_VMALLOC) {
1321 io_req.mem.type = DM_IO_KMEM;
1322 io_req.mem.ptr.addr = (char *)b->data + offset;
1323 } else {
1324 io_req.mem.type = DM_IO_VMA;
1325 io_req.mem.ptr.vma = (char *)b->data + offset;
1326 }
1327
1328 r = dm_io(&io_req, 1, ®ion, NULL, ioprio);
1329 if (unlikely(r))
1330 b->end_io(b, errno_to_blk_status(r));
1331}
1332
1333static void bio_complete(struct bio *bio)
1334{
1335 struct dm_buffer *b = bio->bi_private;
1336 blk_status_t status = bio->bi_status;
1337
1338 bio_uninit(bio);
1339 kfree(bio);
1340 b->end_io(b, status);
1341}
1342
1343static void use_bio(struct dm_buffer *b, enum req_op op, sector_t sector,
1344 unsigned int n_sectors, unsigned int offset,
1345 unsigned short ioprio)
1346{
1347 struct bio *bio;
1348 char *ptr;
1349 unsigned int len;
1350
1351 bio = bio_kmalloc(1, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN);
1352 if (!bio) {
1353 use_dmio(b, op, sector, n_sectors, offset, ioprio);
1354 return;
1355 }
1356 bio_init(bio, b->c->bdev, bio->bi_inline_vecs, 1, op);
1357 bio->bi_iter.bi_sector = sector;
1358 bio->bi_end_io = bio_complete;
1359 bio->bi_private = b;
1360 bio->bi_ioprio = ioprio;
1361
1362 ptr = (char *)b->data + offset;
1363 len = n_sectors << SECTOR_SHIFT;
1364
1365 __bio_add_page(bio, virt_to_page(ptr), len, offset_in_page(ptr));
1366
1367 submit_bio(bio);
1368}
1369
1370static inline sector_t block_to_sector(struct dm_bufio_client *c, sector_t block)
1371{
1372 sector_t sector;
1373
1374 if (likely(c->sectors_per_block_bits >= 0))
1375 sector = block << c->sectors_per_block_bits;
1376 else
1377 sector = block * (c->block_size >> SECTOR_SHIFT);
1378 sector += c->start;
1379
1380 return sector;
1381}
1382
1383static void submit_io(struct dm_buffer *b, enum req_op op, unsigned short ioprio,
1384 void (*end_io)(struct dm_buffer *, blk_status_t))
1385{
1386 unsigned int n_sectors;
1387 sector_t sector;
1388 unsigned int offset, end;
1389
1390 b->end_io = end_io;
1391
1392 sector = block_to_sector(b->c, b->block);
1393
1394 if (op != REQ_OP_WRITE) {
1395 n_sectors = b->c->block_size >> SECTOR_SHIFT;
1396 offset = 0;
1397 } else {
1398 if (b->c->write_callback)
1399 b->c->write_callback(b);
1400 offset = b->write_start;
1401 end = b->write_end;
1402 offset &= -DM_BUFIO_WRITE_ALIGN;
1403 end += DM_BUFIO_WRITE_ALIGN - 1;
1404 end &= -DM_BUFIO_WRITE_ALIGN;
1405 if (unlikely(end > b->c->block_size))
1406 end = b->c->block_size;
1407
1408 sector += offset >> SECTOR_SHIFT;
1409 n_sectors = (end - offset) >> SECTOR_SHIFT;
1410 }
1411
1412 if (b->data_mode != DATA_MODE_VMALLOC)
1413 use_bio(b, op, sector, n_sectors, offset, ioprio);
1414 else
1415 use_dmio(b, op, sector, n_sectors, offset, ioprio);
1416}
1417
1418/*
1419 *--------------------------------------------------------------
1420 * Writing dirty buffers
1421 *--------------------------------------------------------------
1422 */
1423
1424/*
1425 * The endio routine for write.
1426 *
1427 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
1428 * it.
1429 */
1430static void write_endio(struct dm_buffer *b, blk_status_t status)
1431{
1432 b->write_error = status;
1433 if (unlikely(status)) {
1434 struct dm_bufio_client *c = b->c;
1435
1436 (void)cmpxchg(&c->async_write_error, 0,
1437 blk_status_to_errno(status));
1438 }
1439
1440 BUG_ON(!test_bit(B_WRITING, &b->state));
1441
1442 smp_mb__before_atomic();
1443 clear_bit(B_WRITING, &b->state);
1444 smp_mb__after_atomic();
1445
1446 wake_up_bit(&b->state, B_WRITING);
1447}
1448
1449/*
1450 * Initiate a write on a dirty buffer, but don't wait for it.
1451 *
1452 * - If the buffer is not dirty, exit.
1453 * - If there some previous write going on, wait for it to finish (we can't
1454 * have two writes on the same buffer simultaneously).
1455 * - Submit our write and don't wait on it. We set B_WRITING indicating
1456 * that there is a write in progress.
1457 */
1458static void __write_dirty_buffer(struct dm_buffer *b,
1459 struct list_head *write_list)
1460{
1461 if (!test_bit(B_DIRTY, &b->state))
1462 return;
1463
1464 clear_bit(B_DIRTY, &b->state);
1465 wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
1466
1467 b->write_start = b->dirty_start;
1468 b->write_end = b->dirty_end;
1469
1470 if (!write_list)
1471 submit_io(b, REQ_OP_WRITE, IOPRIO_DEFAULT, write_endio);
1472 else
1473 list_add_tail(&b->write_list, write_list);
1474}
1475
1476static void __flush_write_list(struct list_head *write_list)
1477{
1478 struct blk_plug plug;
1479
1480 blk_start_plug(&plug);
1481 while (!list_empty(write_list)) {
1482 struct dm_buffer *b =
1483 list_entry(write_list->next, struct dm_buffer, write_list);
1484 list_del(&b->write_list);
1485 submit_io(b, REQ_OP_WRITE, IOPRIO_DEFAULT, write_endio);
1486 cond_resched();
1487 }
1488 blk_finish_plug(&plug);
1489}
1490
1491/*
1492 * Wait until any activity on the buffer finishes. Possibly write the
1493 * buffer if it is dirty. When this function finishes, there is no I/O
1494 * running on the buffer and the buffer is not dirty.
1495 */
1496static void __make_buffer_clean(struct dm_buffer *b)
1497{
1498 BUG_ON(atomic_read(&b->hold_count));
1499
1500 /* smp_load_acquire() pairs with read_endio()'s smp_mb__before_atomic() */
1501 if (!smp_load_acquire(&b->state)) /* fast case */
1502 return;
1503
1504 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1505 __write_dirty_buffer(b, NULL);
1506 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
1507}
1508
1509static enum evict_result is_clean(struct dm_buffer *b, void *context)
1510{
1511 struct dm_bufio_client *c = context;
1512
1513 /* These should never happen */
1514 if (WARN_ON_ONCE(test_bit(B_WRITING, &b->state)))
1515 return ER_DONT_EVICT;
1516 if (WARN_ON_ONCE(test_bit(B_DIRTY, &b->state)))
1517 return ER_DONT_EVICT;
1518 if (WARN_ON_ONCE(b->list_mode != LIST_CLEAN))
1519 return ER_DONT_EVICT;
1520
1521 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep &&
1522 unlikely(test_bit(B_READING, &b->state)))
1523 return ER_DONT_EVICT;
1524
1525 return ER_EVICT;
1526}
1527
1528static enum evict_result is_dirty(struct dm_buffer *b, void *context)
1529{
1530 /* These should never happen */
1531 if (WARN_ON_ONCE(test_bit(B_READING, &b->state)))
1532 return ER_DONT_EVICT;
1533 if (WARN_ON_ONCE(b->list_mode != LIST_DIRTY))
1534 return ER_DONT_EVICT;
1535
1536 return ER_EVICT;
1537}
1538
1539/*
1540 * Find some buffer that is not held by anybody, clean it, unlink it and
1541 * return it.
1542 */
1543static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
1544{
1545 struct dm_buffer *b;
1546
1547 b = cache_evict(&c->cache, LIST_CLEAN, is_clean, c);
1548 if (b) {
1549 /* this also waits for pending reads */
1550 __make_buffer_clean(b);
1551 return b;
1552 }
1553
1554 if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
1555 return NULL;
1556
1557 b = cache_evict(&c->cache, LIST_DIRTY, is_dirty, NULL);
1558 if (b) {
1559 __make_buffer_clean(b);
1560 return b;
1561 }
1562
1563 return NULL;
1564}
1565
1566/*
1567 * Wait until some other threads free some buffer or release hold count on
1568 * some buffer.
1569 *
1570 * This function is entered with c->lock held, drops it and regains it
1571 * before exiting.
1572 */
1573static void __wait_for_free_buffer(struct dm_bufio_client *c)
1574{
1575 DECLARE_WAITQUEUE(wait, current);
1576
1577 add_wait_queue(&c->free_buffer_wait, &wait);
1578 set_current_state(TASK_UNINTERRUPTIBLE);
1579 dm_bufio_unlock(c);
1580
1581 /*
1582 * It's possible to miss a wake up event since we don't always
1583 * hold c->lock when wake_up is called. So we have a timeout here,
1584 * just in case.
1585 */
1586 io_schedule_timeout(5 * HZ);
1587
1588 remove_wait_queue(&c->free_buffer_wait, &wait);
1589
1590 dm_bufio_lock(c);
1591}
1592
1593enum new_flag {
1594 NF_FRESH = 0,
1595 NF_READ = 1,
1596 NF_GET = 2,
1597 NF_PREFETCH = 3
1598};
1599
1600/*
1601 * Allocate a new buffer. If the allocation is not possible, wait until
1602 * some other thread frees a buffer.
1603 *
1604 * May drop the lock and regain it.
1605 */
1606static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
1607{
1608 struct dm_buffer *b;
1609 bool tried_noio_alloc = false;
1610
1611 /*
1612 * dm-bufio is resistant to allocation failures (it just keeps
1613 * one buffer reserved in cases all the allocations fail).
1614 * So set flags to not try too hard:
1615 * GFP_NOWAIT: don't wait; if we need to sleep we'll release our
1616 * mutex and wait ourselves.
1617 * __GFP_NORETRY: don't retry and rather return failure
1618 * __GFP_NOMEMALLOC: don't use emergency reserves
1619 * __GFP_NOWARN: don't print a warning in case of failure
1620 *
1621 * For debugging, if we set the cache size to 1, no new buffers will
1622 * be allocated.
1623 */
1624 while (1) {
1625 if (dm_bufio_cache_size_latch != 1) {
1626 b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
1627 if (b)
1628 return b;
1629 }
1630
1631 if (nf == NF_PREFETCH)
1632 return NULL;
1633
1634 if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
1635 dm_bufio_unlock(c);
1636 b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
1637 dm_bufio_lock(c);
1638 if (b)
1639 return b;
1640 tried_noio_alloc = true;
1641 }
1642
1643 if (!list_empty(&c->reserved_buffers)) {
1644 b = list_to_buffer(c->reserved_buffers.next);
1645 list_del(&b->lru.list);
1646 c->need_reserved_buffers++;
1647
1648 return b;
1649 }
1650
1651 b = __get_unclaimed_buffer(c);
1652 if (b)
1653 return b;
1654
1655 __wait_for_free_buffer(c);
1656 }
1657}
1658
1659static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
1660{
1661 struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
1662
1663 if (!b)
1664 return NULL;
1665
1666 if (c->alloc_callback)
1667 c->alloc_callback(b);
1668
1669 return b;
1670}
1671
1672/*
1673 * Free a buffer and wake other threads waiting for free buffers.
1674 */
1675static void __free_buffer_wake(struct dm_buffer *b)
1676{
1677 struct dm_bufio_client *c = b->c;
1678
1679 b->block = -1;
1680 if (!c->need_reserved_buffers)
1681 free_buffer(b);
1682 else {
1683 list_add(&b->lru.list, &c->reserved_buffers);
1684 c->need_reserved_buffers--;
1685 }
1686
1687 /*
1688 * We hold the bufio lock here, so no one can add entries to the
1689 * wait queue anyway.
1690 */
1691 if (unlikely(waitqueue_active(&c->free_buffer_wait)))
1692 wake_up(&c->free_buffer_wait);
1693}
1694
1695static enum evict_result cleaned(struct dm_buffer *b, void *context)
1696{
1697 if (WARN_ON_ONCE(test_bit(B_READING, &b->state)))
1698 return ER_DONT_EVICT; /* should never happen */
1699
1700 if (test_bit(B_DIRTY, &b->state) || test_bit(B_WRITING, &b->state))
1701 return ER_DONT_EVICT;
1702 else
1703 return ER_EVICT;
1704}
1705
1706static void __move_clean_buffers(struct dm_bufio_client *c)
1707{
1708 cache_mark_many(&c->cache, LIST_DIRTY, LIST_CLEAN, cleaned, NULL);
1709}
1710
1711struct write_context {
1712 int no_wait;
1713 struct list_head *write_list;
1714};
1715
1716static enum it_action write_one(struct dm_buffer *b, void *context)
1717{
1718 struct write_context *wc = context;
1719
1720 if (wc->no_wait && test_bit(B_WRITING, &b->state))
1721 return IT_COMPLETE;
1722
1723 __write_dirty_buffer(b, wc->write_list);
1724 return IT_NEXT;
1725}
1726
1727static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
1728 struct list_head *write_list)
1729{
1730 struct write_context wc = {.no_wait = no_wait, .write_list = write_list};
1731
1732 __move_clean_buffers(c);
1733 cache_iterate(&c->cache, LIST_DIRTY, write_one, &wc);
1734}
1735
1736/*
1737 * Check if we're over watermark.
1738 * If we are over threshold_buffers, start freeing buffers.
1739 * If we're over "limit_buffers", block until we get under the limit.
1740 */
1741static void __check_watermark(struct dm_bufio_client *c,
1742 struct list_head *write_list)
1743{
1744 if (cache_count(&c->cache, LIST_DIRTY) >
1745 cache_count(&c->cache, LIST_CLEAN) * DM_BUFIO_WRITEBACK_RATIO)
1746 __write_dirty_buffers_async(c, 1, write_list);
1747}
1748
1749/*
1750 *--------------------------------------------------------------
1751 * Getting a buffer
1752 *--------------------------------------------------------------
1753 */
1754
1755static void cache_put_and_wake(struct dm_bufio_client *c, struct dm_buffer *b)
1756{
1757 /*
1758 * Relying on waitqueue_active() is racey, but we sleep
1759 * with schedule_timeout anyway.
1760 */
1761 if (cache_put(&c->cache, b) &&
1762 unlikely(waitqueue_active(&c->free_buffer_wait)))
1763 wake_up(&c->free_buffer_wait);
1764}
1765
1766/*
1767 * This assumes you have already checked the cache to see if the buffer
1768 * is already present (it will recheck after dropping the lock for allocation).
1769 */
1770static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
1771 enum new_flag nf, int *need_submit,
1772 struct list_head *write_list)
1773{
1774 struct dm_buffer *b, *new_b = NULL;
1775
1776 *need_submit = 0;
1777
1778 /* This can't be called with NF_GET */
1779 if (WARN_ON_ONCE(nf == NF_GET))
1780 return NULL;
1781
1782 new_b = __alloc_buffer_wait(c, nf);
1783 if (!new_b)
1784 return NULL;
1785
1786 /*
1787 * We've had a period where the mutex was unlocked, so need to
1788 * recheck the buffer tree.
1789 */
1790 b = cache_get(&c->cache, block);
1791 if (b) {
1792 __free_buffer_wake(new_b);
1793 goto found_buffer;
1794 }
1795
1796 __check_watermark(c, write_list);
1797
1798 b = new_b;
1799 atomic_set(&b->hold_count, 1);
1800 WRITE_ONCE(b->last_accessed, jiffies);
1801 b->block = block;
1802 b->read_error = 0;
1803 b->write_error = 0;
1804 b->list_mode = LIST_CLEAN;
1805
1806 if (nf == NF_FRESH)
1807 b->state = 0;
1808 else {
1809 b->state = 1 << B_READING;
1810 *need_submit = 1;
1811 }
1812
1813 /*
1814 * We mustn't insert into the cache until the B_READING state
1815 * is set. Otherwise another thread could get it and use
1816 * it before it had been read.
1817 */
1818 cache_insert(&c->cache, b);
1819
1820 return b;
1821
1822found_buffer:
1823 if (nf == NF_PREFETCH) {
1824 cache_put_and_wake(c, b);
1825 return NULL;
1826 }
1827
1828 /*
1829 * Note: it is essential that we don't wait for the buffer to be
1830 * read if dm_bufio_get function is used. Both dm_bufio_get and
1831 * dm_bufio_prefetch can be used in the driver request routine.
1832 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1833 * the same buffer, it would deadlock if we waited.
1834 */
1835 if (nf == NF_GET && unlikely(test_bit_acquire(B_READING, &b->state))) {
1836 cache_put_and_wake(c, b);
1837 return NULL;
1838 }
1839
1840 return b;
1841}
1842
1843/*
1844 * The endio routine for reading: set the error, clear the bit and wake up
1845 * anyone waiting on the buffer.
1846 */
1847static void read_endio(struct dm_buffer *b, blk_status_t status)
1848{
1849 b->read_error = status;
1850
1851 BUG_ON(!test_bit(B_READING, &b->state));
1852
1853 smp_mb__before_atomic();
1854 clear_bit(B_READING, &b->state);
1855 smp_mb__after_atomic();
1856
1857 wake_up_bit(&b->state, B_READING);
1858}
1859
1860/*
1861 * A common routine for dm_bufio_new and dm_bufio_read. Operation of these
1862 * functions is similar except that dm_bufio_new doesn't read the
1863 * buffer from the disk (assuming that the caller overwrites all the data
1864 * and uses dm_bufio_mark_buffer_dirty to write new data back).
1865 */
1866static void *new_read(struct dm_bufio_client *c, sector_t block,
1867 enum new_flag nf, struct dm_buffer **bp,
1868 unsigned short ioprio)
1869{
1870 int need_submit = 0;
1871 struct dm_buffer *b;
1872
1873 LIST_HEAD(write_list);
1874
1875 *bp = NULL;
1876
1877 /*
1878 * Fast path, hopefully the block is already in the cache. No need
1879 * to get the client lock for this.
1880 */
1881 b = cache_get(&c->cache, block);
1882 if (b) {
1883 if (nf == NF_PREFETCH) {
1884 cache_put_and_wake(c, b);
1885 return NULL;
1886 }
1887
1888 /*
1889 * Note: it is essential that we don't wait for the buffer to be
1890 * read if dm_bufio_get function is used. Both dm_bufio_get and
1891 * dm_bufio_prefetch can be used in the driver request routine.
1892 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1893 * the same buffer, it would deadlock if we waited.
1894 */
1895 if (nf == NF_GET && unlikely(test_bit_acquire(B_READING, &b->state))) {
1896 cache_put_and_wake(c, b);
1897 return NULL;
1898 }
1899 }
1900
1901 if (!b) {
1902 if (nf == NF_GET)
1903 return NULL;
1904
1905 dm_bufio_lock(c);
1906 b = __bufio_new(c, block, nf, &need_submit, &write_list);
1907 dm_bufio_unlock(c);
1908 }
1909
1910#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1911 if (b && (atomic_read(&b->hold_count) == 1))
1912 buffer_record_stack(b);
1913#endif
1914
1915 __flush_write_list(&write_list);
1916
1917 if (!b)
1918 return NULL;
1919
1920 if (need_submit)
1921 submit_io(b, REQ_OP_READ, ioprio, read_endio);
1922
1923 if (nf != NF_GET) /* we already tested this condition above */
1924 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1925
1926 if (b->read_error) {
1927 int error = blk_status_to_errno(b->read_error);
1928
1929 dm_bufio_release(b);
1930
1931 return ERR_PTR(error);
1932 }
1933
1934 *bp = b;
1935
1936 return b->data;
1937}
1938
1939void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1940 struct dm_buffer **bp)
1941{
1942 return new_read(c, block, NF_GET, bp, IOPRIO_DEFAULT);
1943}
1944EXPORT_SYMBOL_GPL(dm_bufio_get);
1945
1946static void *__dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1947 struct dm_buffer **bp, unsigned short ioprio)
1948{
1949 if (WARN_ON_ONCE(dm_bufio_in_request()))
1950 return ERR_PTR(-EINVAL);
1951
1952 return new_read(c, block, NF_READ, bp, ioprio);
1953}
1954
1955void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1956 struct dm_buffer **bp)
1957{
1958 return __dm_bufio_read(c, block, bp, IOPRIO_DEFAULT);
1959}
1960EXPORT_SYMBOL_GPL(dm_bufio_read);
1961
1962void *dm_bufio_read_with_ioprio(struct dm_bufio_client *c, sector_t block,
1963 struct dm_buffer **bp, unsigned short ioprio)
1964{
1965 return __dm_bufio_read(c, block, bp, ioprio);
1966}
1967EXPORT_SYMBOL_GPL(dm_bufio_read_with_ioprio);
1968
1969void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1970 struct dm_buffer **bp)
1971{
1972 if (WARN_ON_ONCE(dm_bufio_in_request()))
1973 return ERR_PTR(-EINVAL);
1974
1975 return new_read(c, block, NF_FRESH, bp, IOPRIO_DEFAULT);
1976}
1977EXPORT_SYMBOL_GPL(dm_bufio_new);
1978
1979static void __dm_bufio_prefetch(struct dm_bufio_client *c,
1980 sector_t block, unsigned int n_blocks,
1981 unsigned short ioprio)
1982{
1983 struct blk_plug plug;
1984
1985 LIST_HEAD(write_list);
1986
1987 if (WARN_ON_ONCE(dm_bufio_in_request()))
1988 return; /* should never happen */
1989
1990 blk_start_plug(&plug);
1991
1992 for (; n_blocks--; block++) {
1993 int need_submit;
1994 struct dm_buffer *b;
1995
1996 b = cache_get(&c->cache, block);
1997 if (b) {
1998 /* already in cache */
1999 cache_put_and_wake(c, b);
2000 continue;
2001 }
2002
2003 dm_bufio_lock(c);
2004 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
2005 &write_list);
2006 if (unlikely(!list_empty(&write_list))) {
2007 dm_bufio_unlock(c);
2008 blk_finish_plug(&plug);
2009 __flush_write_list(&write_list);
2010 blk_start_plug(&plug);
2011 dm_bufio_lock(c);
2012 }
2013 if (unlikely(b != NULL)) {
2014 dm_bufio_unlock(c);
2015
2016 if (need_submit)
2017 submit_io(b, REQ_OP_READ, ioprio, read_endio);
2018 dm_bufio_release(b);
2019
2020 cond_resched();
2021
2022 if (!n_blocks)
2023 goto flush_plug;
2024 dm_bufio_lock(c);
2025 }
2026 dm_bufio_unlock(c);
2027 }
2028
2029flush_plug:
2030 blk_finish_plug(&plug);
2031}
2032
2033void dm_bufio_prefetch(struct dm_bufio_client *c, sector_t block, unsigned int n_blocks)
2034{
2035 return __dm_bufio_prefetch(c, block, n_blocks, IOPRIO_DEFAULT);
2036}
2037EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
2038
2039void dm_bufio_prefetch_with_ioprio(struct dm_bufio_client *c, sector_t block,
2040 unsigned int n_blocks, unsigned short ioprio)
2041{
2042 return __dm_bufio_prefetch(c, block, n_blocks, ioprio);
2043}
2044EXPORT_SYMBOL_GPL(dm_bufio_prefetch_with_ioprio);
2045
2046void dm_bufio_release(struct dm_buffer *b)
2047{
2048 struct dm_bufio_client *c = b->c;
2049
2050 /*
2051 * If there were errors on the buffer, and the buffer is not
2052 * to be written, free the buffer. There is no point in caching
2053 * invalid buffer.
2054 */
2055 if ((b->read_error || b->write_error) &&
2056 !test_bit_acquire(B_READING, &b->state) &&
2057 !test_bit(B_WRITING, &b->state) &&
2058 !test_bit(B_DIRTY, &b->state)) {
2059 dm_bufio_lock(c);
2060
2061 /* cache remove can fail if there are other holders */
2062 if (cache_remove(&c->cache, b)) {
2063 __free_buffer_wake(b);
2064 dm_bufio_unlock(c);
2065 return;
2066 }
2067
2068 dm_bufio_unlock(c);
2069 }
2070
2071 cache_put_and_wake(c, b);
2072}
2073EXPORT_SYMBOL_GPL(dm_bufio_release);
2074
2075void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
2076 unsigned int start, unsigned int end)
2077{
2078 struct dm_bufio_client *c = b->c;
2079
2080 BUG_ON(start >= end);
2081 BUG_ON(end > b->c->block_size);
2082
2083 dm_bufio_lock(c);
2084
2085 BUG_ON(test_bit(B_READING, &b->state));
2086
2087 if (!test_and_set_bit(B_DIRTY, &b->state)) {
2088 b->dirty_start = start;
2089 b->dirty_end = end;
2090 cache_mark(&c->cache, b, LIST_DIRTY);
2091 } else {
2092 if (start < b->dirty_start)
2093 b->dirty_start = start;
2094 if (end > b->dirty_end)
2095 b->dirty_end = end;
2096 }
2097
2098 dm_bufio_unlock(c);
2099}
2100EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
2101
2102void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
2103{
2104 dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
2105}
2106EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
2107
2108void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
2109{
2110 LIST_HEAD(write_list);
2111
2112 if (WARN_ON_ONCE(dm_bufio_in_request()))
2113 return; /* should never happen */
2114
2115 dm_bufio_lock(c);
2116 __write_dirty_buffers_async(c, 0, &write_list);
2117 dm_bufio_unlock(c);
2118 __flush_write_list(&write_list);
2119}
2120EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
2121
2122/*
2123 * For performance, it is essential that the buffers are written asynchronously
2124 * and simultaneously (so that the block layer can merge the writes) and then
2125 * waited upon.
2126 *
2127 * Finally, we flush hardware disk cache.
2128 */
2129static bool is_writing(struct lru_entry *e, void *context)
2130{
2131 struct dm_buffer *b = le_to_buffer(e);
2132
2133 return test_bit(B_WRITING, &b->state);
2134}
2135
2136int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
2137{
2138 int a, f;
2139 unsigned long nr_buffers;
2140 struct lru_entry *e;
2141 struct lru_iter it;
2142
2143 LIST_HEAD(write_list);
2144
2145 dm_bufio_lock(c);
2146 __write_dirty_buffers_async(c, 0, &write_list);
2147 dm_bufio_unlock(c);
2148 __flush_write_list(&write_list);
2149 dm_bufio_lock(c);
2150
2151 nr_buffers = cache_count(&c->cache, LIST_DIRTY);
2152 lru_iter_begin(&c->cache.lru[LIST_DIRTY], &it);
2153 while ((e = lru_iter_next(&it, is_writing, c))) {
2154 struct dm_buffer *b = le_to_buffer(e);
2155 __cache_inc_buffer(b);
2156
2157 BUG_ON(test_bit(B_READING, &b->state));
2158
2159 if (nr_buffers) {
2160 nr_buffers--;
2161 dm_bufio_unlock(c);
2162 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
2163 dm_bufio_lock(c);
2164 } else {
2165 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
2166 }
2167
2168 if (!test_bit(B_DIRTY, &b->state) && !test_bit(B_WRITING, &b->state))
2169 cache_mark(&c->cache, b, LIST_CLEAN);
2170
2171 cache_put_and_wake(c, b);
2172
2173 cond_resched();
2174 }
2175 lru_iter_end(&it);
2176
2177 wake_up(&c->free_buffer_wait);
2178 dm_bufio_unlock(c);
2179
2180 a = xchg(&c->async_write_error, 0);
2181 f = dm_bufio_issue_flush(c);
2182 if (a)
2183 return a;
2184
2185 return f;
2186}
2187EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
2188
2189/*
2190 * Use dm-io to send an empty barrier to flush the device.
2191 */
2192int dm_bufio_issue_flush(struct dm_bufio_client *c)
2193{
2194 struct dm_io_request io_req = {
2195 .bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,
2196 .mem.type = DM_IO_KMEM,
2197 .mem.ptr.addr = NULL,
2198 .client = c->dm_io,
2199 };
2200 struct dm_io_region io_reg = {
2201 .bdev = c->bdev,
2202 .sector = 0,
2203 .count = 0,
2204 };
2205
2206 if (WARN_ON_ONCE(dm_bufio_in_request()))
2207 return -EINVAL;
2208
2209 return dm_io(&io_req, 1, &io_reg, NULL, IOPRIO_DEFAULT);
2210}
2211EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
2212
2213/*
2214 * Use dm-io to send a discard request to flush the device.
2215 */
2216int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t count)
2217{
2218 struct dm_io_request io_req = {
2219 .bi_opf = REQ_OP_DISCARD | REQ_SYNC,
2220 .mem.type = DM_IO_KMEM,
2221 .mem.ptr.addr = NULL,
2222 .client = c->dm_io,
2223 };
2224 struct dm_io_region io_reg = {
2225 .bdev = c->bdev,
2226 .sector = block_to_sector(c, block),
2227 .count = block_to_sector(c, count),
2228 };
2229
2230 if (WARN_ON_ONCE(dm_bufio_in_request()))
2231 return -EINVAL; /* discards are optional */
2232
2233 return dm_io(&io_req, 1, &io_reg, NULL, IOPRIO_DEFAULT);
2234}
2235EXPORT_SYMBOL_GPL(dm_bufio_issue_discard);
2236
2237static bool forget_buffer(struct dm_bufio_client *c, sector_t block)
2238{
2239 struct dm_buffer *b;
2240
2241 b = cache_get(&c->cache, block);
2242 if (b) {
2243 if (likely(!smp_load_acquire(&b->state))) {
2244 if (cache_remove(&c->cache, b))
2245 __free_buffer_wake(b);
2246 else
2247 cache_put_and_wake(c, b);
2248 } else {
2249 cache_put_and_wake(c, b);
2250 }
2251 }
2252
2253 return b ? true : false;
2254}
2255
2256/*
2257 * Free the given buffer.
2258 *
2259 * This is just a hint, if the buffer is in use or dirty, this function
2260 * does nothing.
2261 */
2262void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
2263{
2264 dm_bufio_lock(c);
2265 forget_buffer(c, block);
2266 dm_bufio_unlock(c);
2267}
2268EXPORT_SYMBOL_GPL(dm_bufio_forget);
2269
2270static enum evict_result idle(struct dm_buffer *b, void *context)
2271{
2272 return b->state ? ER_DONT_EVICT : ER_EVICT;
2273}
2274
2275void dm_bufio_forget_buffers(struct dm_bufio_client *c, sector_t block, sector_t n_blocks)
2276{
2277 dm_bufio_lock(c);
2278 cache_remove_range(&c->cache, block, block + n_blocks, idle, __free_buffer_wake);
2279 dm_bufio_unlock(c);
2280}
2281EXPORT_SYMBOL_GPL(dm_bufio_forget_buffers);
2282
2283void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned int n)
2284{
2285 c->minimum_buffers = n;
2286}
2287EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
2288
2289unsigned int dm_bufio_get_block_size(struct dm_bufio_client *c)
2290{
2291 return c->block_size;
2292}
2293EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
2294
2295sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
2296{
2297 sector_t s = bdev_nr_sectors(c->bdev);
2298
2299 if (s >= c->start)
2300 s -= c->start;
2301 else
2302 s = 0;
2303 if (likely(c->sectors_per_block_bits >= 0))
2304 s >>= c->sectors_per_block_bits;
2305 else
2306 sector_div(s, c->block_size >> SECTOR_SHIFT);
2307 return s;
2308}
2309EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
2310
2311struct dm_io_client *dm_bufio_get_dm_io_client(struct dm_bufio_client *c)
2312{
2313 return c->dm_io;
2314}
2315EXPORT_SYMBOL_GPL(dm_bufio_get_dm_io_client);
2316
2317sector_t dm_bufio_get_block_number(struct dm_buffer *b)
2318{
2319 return b->block;
2320}
2321EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
2322
2323void *dm_bufio_get_block_data(struct dm_buffer *b)
2324{
2325 return b->data;
2326}
2327EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
2328
2329void *dm_bufio_get_aux_data(struct dm_buffer *b)
2330{
2331 return b + 1;
2332}
2333EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
2334
2335struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
2336{
2337 return b->c;
2338}
2339EXPORT_SYMBOL_GPL(dm_bufio_get_client);
2340
2341static enum it_action warn_leak(struct dm_buffer *b, void *context)
2342{
2343 bool *warned = context;
2344
2345 WARN_ON(!(*warned));
2346 *warned = true;
2347 DMERR("leaked buffer %llx, hold count %u, list %d",
2348 (unsigned long long)b->block, atomic_read(&b->hold_count), b->list_mode);
2349#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
2350 stack_trace_print(b->stack_entries, b->stack_len, 1);
2351 /* mark unclaimed to avoid WARN_ON at end of drop_buffers() */
2352 atomic_set(&b->hold_count, 0);
2353#endif
2354 return IT_NEXT;
2355}
2356
2357static void drop_buffers(struct dm_bufio_client *c)
2358{
2359 int i;
2360 struct dm_buffer *b;
2361
2362 if (WARN_ON(dm_bufio_in_request()))
2363 return; /* should never happen */
2364
2365 /*
2366 * An optimization so that the buffers are not written one-by-one.
2367 */
2368 dm_bufio_write_dirty_buffers_async(c);
2369
2370 dm_bufio_lock(c);
2371
2372 while ((b = __get_unclaimed_buffer(c)))
2373 __free_buffer_wake(b);
2374
2375 for (i = 0; i < LIST_SIZE; i++) {
2376 bool warned = false;
2377
2378 cache_iterate(&c->cache, i, warn_leak, &warned);
2379 }
2380
2381#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
2382 while ((b = __get_unclaimed_buffer(c)))
2383 __free_buffer_wake(b);
2384#endif
2385
2386 for (i = 0; i < LIST_SIZE; i++)
2387 WARN_ON(cache_count(&c->cache, i));
2388
2389 dm_bufio_unlock(c);
2390}
2391
2392static unsigned long get_retain_buffers(struct dm_bufio_client *c)
2393{
2394 unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
2395
2396 if (likely(c->sectors_per_block_bits >= 0))
2397 retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
2398 else
2399 retain_bytes /= c->block_size;
2400
2401 return retain_bytes;
2402}
2403
2404static void __scan(struct dm_bufio_client *c)
2405{
2406 int l;
2407 struct dm_buffer *b;
2408 unsigned long freed = 0;
2409 unsigned long retain_target = get_retain_buffers(c);
2410 unsigned long count = cache_total(&c->cache);
2411
2412 for (l = 0; l < LIST_SIZE; l++) {
2413 while (true) {
2414 if (count - freed <= retain_target)
2415 atomic_long_set(&c->need_shrink, 0);
2416 if (!atomic_long_read(&c->need_shrink))
2417 break;
2418
2419 b = cache_evict(&c->cache, l,
2420 l == LIST_CLEAN ? is_clean : is_dirty, c);
2421 if (!b)
2422 break;
2423
2424 __make_buffer_clean(b);
2425 __free_buffer_wake(b);
2426
2427 atomic_long_dec(&c->need_shrink);
2428 freed++;
2429 cond_resched();
2430 }
2431 }
2432}
2433
2434static void shrink_work(struct work_struct *w)
2435{
2436 struct dm_bufio_client *c = container_of(w, struct dm_bufio_client, shrink_work);
2437
2438 dm_bufio_lock(c);
2439 __scan(c);
2440 dm_bufio_unlock(c);
2441}
2442
2443static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
2444{
2445 struct dm_bufio_client *c;
2446
2447 c = shrink->private_data;
2448 atomic_long_add(sc->nr_to_scan, &c->need_shrink);
2449 queue_work(dm_bufio_wq, &c->shrink_work);
2450
2451 return sc->nr_to_scan;
2452}
2453
2454static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
2455{
2456 struct dm_bufio_client *c = shrink->private_data;
2457 unsigned long count = cache_total(&c->cache);
2458 unsigned long retain_target = get_retain_buffers(c);
2459 unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
2460
2461 if (unlikely(count < retain_target))
2462 count = 0;
2463 else
2464 count -= retain_target;
2465
2466 if (unlikely(count < queued_for_cleanup))
2467 count = 0;
2468 else
2469 count -= queued_for_cleanup;
2470
2471 return count;
2472}
2473
2474/*
2475 * Create the buffering interface
2476 */
2477struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned int block_size,
2478 unsigned int reserved_buffers, unsigned int aux_size,
2479 void (*alloc_callback)(struct dm_buffer *),
2480 void (*write_callback)(struct dm_buffer *),
2481 unsigned int flags)
2482{
2483 int r;
2484 unsigned int num_locks;
2485 struct dm_bufio_client *c;
2486 char slab_name[64];
2487 static atomic_t seqno = ATOMIC_INIT(0);
2488
2489 if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
2490 DMERR("%s: block size not specified or is not multiple of 512b", __func__);
2491 r = -EINVAL;
2492 goto bad_client;
2493 }
2494
2495 num_locks = dm_num_hash_locks();
2496 c = kzalloc(sizeof(*c) + (num_locks * sizeof(struct buffer_tree)), GFP_KERNEL);
2497 if (!c) {
2498 r = -ENOMEM;
2499 goto bad_client;
2500 }
2501 cache_init(&c->cache, num_locks, (flags & DM_BUFIO_CLIENT_NO_SLEEP) != 0);
2502
2503 c->bdev = bdev;
2504 c->block_size = block_size;
2505 if (is_power_of_2(block_size))
2506 c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
2507 else
2508 c->sectors_per_block_bits = -1;
2509
2510 c->alloc_callback = alloc_callback;
2511 c->write_callback = write_callback;
2512
2513 if (flags & DM_BUFIO_CLIENT_NO_SLEEP) {
2514 c->no_sleep = true;
2515 static_branch_inc(&no_sleep_enabled);
2516 }
2517
2518 mutex_init(&c->lock);
2519 spin_lock_init(&c->spinlock);
2520 INIT_LIST_HEAD(&c->reserved_buffers);
2521 c->need_reserved_buffers = reserved_buffers;
2522
2523 dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
2524
2525 init_waitqueue_head(&c->free_buffer_wait);
2526 c->async_write_error = 0;
2527
2528 c->dm_io = dm_io_client_create();
2529 if (IS_ERR(c->dm_io)) {
2530 r = PTR_ERR(c->dm_io);
2531 goto bad_dm_io;
2532 }
2533
2534 if (block_size <= KMALLOC_MAX_SIZE && !is_power_of_2(block_size)) {
2535 unsigned int align = min(1U << __ffs(block_size), (unsigned int)PAGE_SIZE);
2536
2537 snprintf(slab_name, sizeof(slab_name), "dm_bufio_cache-%u-%u",
2538 block_size, atomic_inc_return(&seqno));
2539 c->slab_cache = kmem_cache_create(slab_name, block_size, align,
2540 SLAB_RECLAIM_ACCOUNT, NULL);
2541 if (!c->slab_cache) {
2542 r = -ENOMEM;
2543 goto bad;
2544 }
2545 }
2546 if (aux_size)
2547 snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u-%u",
2548 aux_size, atomic_inc_return(&seqno));
2549 else
2550 snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u",
2551 atomic_inc_return(&seqno));
2552 c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
2553 0, SLAB_RECLAIM_ACCOUNT, NULL);
2554 if (!c->slab_buffer) {
2555 r = -ENOMEM;
2556 goto bad;
2557 }
2558
2559 while (c->need_reserved_buffers) {
2560 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
2561
2562 if (!b) {
2563 r = -ENOMEM;
2564 goto bad;
2565 }
2566 __free_buffer_wake(b);
2567 }
2568
2569 INIT_WORK(&c->shrink_work, shrink_work);
2570 atomic_long_set(&c->need_shrink, 0);
2571
2572 c->shrinker = shrinker_alloc(0, "dm-bufio:(%u:%u)",
2573 MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
2574 if (!c->shrinker) {
2575 r = -ENOMEM;
2576 goto bad;
2577 }
2578
2579 c->shrinker->count_objects = dm_bufio_shrink_count;
2580 c->shrinker->scan_objects = dm_bufio_shrink_scan;
2581 c->shrinker->seeks = 1;
2582 c->shrinker->batch = 0;
2583 c->shrinker->private_data = c;
2584
2585 shrinker_register(c->shrinker);
2586
2587 mutex_lock(&dm_bufio_clients_lock);
2588 dm_bufio_client_count++;
2589 list_add(&c->client_list, &dm_bufio_all_clients);
2590 __cache_size_refresh();
2591 mutex_unlock(&dm_bufio_clients_lock);
2592
2593 return c;
2594
2595bad:
2596 while (!list_empty(&c->reserved_buffers)) {
2597 struct dm_buffer *b = list_to_buffer(c->reserved_buffers.next);
2598
2599 list_del(&b->lru.list);
2600 free_buffer(b);
2601 }
2602 kmem_cache_destroy(c->slab_cache);
2603 kmem_cache_destroy(c->slab_buffer);
2604 dm_io_client_destroy(c->dm_io);
2605bad_dm_io:
2606 mutex_destroy(&c->lock);
2607 if (c->no_sleep)
2608 static_branch_dec(&no_sleep_enabled);
2609 kfree(c);
2610bad_client:
2611 return ERR_PTR(r);
2612}
2613EXPORT_SYMBOL_GPL(dm_bufio_client_create);
2614
2615/*
2616 * Free the buffering interface.
2617 * It is required that there are no references on any buffers.
2618 */
2619void dm_bufio_client_destroy(struct dm_bufio_client *c)
2620{
2621 unsigned int i;
2622
2623 drop_buffers(c);
2624
2625 shrinker_free(c->shrinker);
2626 flush_work(&c->shrink_work);
2627
2628 mutex_lock(&dm_bufio_clients_lock);
2629
2630 list_del(&c->client_list);
2631 dm_bufio_client_count--;
2632 __cache_size_refresh();
2633
2634 mutex_unlock(&dm_bufio_clients_lock);
2635
2636 WARN_ON(c->need_reserved_buffers);
2637
2638 while (!list_empty(&c->reserved_buffers)) {
2639 struct dm_buffer *b = list_to_buffer(c->reserved_buffers.next);
2640
2641 list_del(&b->lru.list);
2642 free_buffer(b);
2643 }
2644
2645 for (i = 0; i < LIST_SIZE; i++)
2646 if (cache_count(&c->cache, i))
2647 DMERR("leaked buffer count %d: %lu", i, cache_count(&c->cache, i));
2648
2649 for (i = 0; i < LIST_SIZE; i++)
2650 WARN_ON(cache_count(&c->cache, i));
2651
2652 cache_destroy(&c->cache);
2653 kmem_cache_destroy(c->slab_cache);
2654 kmem_cache_destroy(c->slab_buffer);
2655 dm_io_client_destroy(c->dm_io);
2656 mutex_destroy(&c->lock);
2657 if (c->no_sleep)
2658 static_branch_dec(&no_sleep_enabled);
2659 kfree(c);
2660}
2661EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
2662
2663void dm_bufio_client_reset(struct dm_bufio_client *c)
2664{
2665 drop_buffers(c);
2666 flush_work(&c->shrink_work);
2667}
2668EXPORT_SYMBOL_GPL(dm_bufio_client_reset);
2669
2670void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
2671{
2672 c->start = start;
2673}
2674EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
2675
2676/*--------------------------------------------------------------*/
2677
2678static unsigned int get_max_age_hz(void)
2679{
2680 unsigned int max_age = READ_ONCE(dm_bufio_max_age);
2681
2682 if (max_age > UINT_MAX / HZ)
2683 max_age = UINT_MAX / HZ;
2684
2685 return max_age * HZ;
2686}
2687
2688static bool older_than(struct dm_buffer *b, unsigned long age_hz)
2689{
2690 return time_after_eq(jiffies, READ_ONCE(b->last_accessed) + age_hz);
2691}
2692
2693struct evict_params {
2694 gfp_t gfp;
2695 unsigned long age_hz;
2696
2697 /*
2698 * This gets updated with the largest last_accessed (ie. most
2699 * recently used) of the evicted buffers. It will not be reinitialised
2700 * by __evict_many(), so you can use it across multiple invocations.
2701 */
2702 unsigned long last_accessed;
2703};
2704
2705/*
2706 * We may not be able to evict this buffer if IO pending or the client
2707 * is still using it.
2708 *
2709 * And if GFP_NOFS is used, we must not do any I/O because we hold
2710 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
2711 * rerouted to different bufio client.
2712 */
2713static enum evict_result select_for_evict(struct dm_buffer *b, void *context)
2714{
2715 struct evict_params *params = context;
2716
2717 if (!(params->gfp & __GFP_FS) ||
2718 (static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {
2719 if (test_bit_acquire(B_READING, &b->state) ||
2720 test_bit(B_WRITING, &b->state) ||
2721 test_bit(B_DIRTY, &b->state))
2722 return ER_DONT_EVICT;
2723 }
2724
2725 return older_than(b, params->age_hz) ? ER_EVICT : ER_STOP;
2726}
2727
2728static unsigned long __evict_many(struct dm_bufio_client *c,
2729 struct evict_params *params,
2730 int list_mode, unsigned long max_count)
2731{
2732 unsigned long count;
2733 unsigned long last_accessed;
2734 struct dm_buffer *b;
2735
2736 for (count = 0; count < max_count; count++) {
2737 b = cache_evict(&c->cache, list_mode, select_for_evict, params);
2738 if (!b)
2739 break;
2740
2741 last_accessed = READ_ONCE(b->last_accessed);
2742 if (time_after_eq(params->last_accessed, last_accessed))
2743 params->last_accessed = last_accessed;
2744
2745 __make_buffer_clean(b);
2746 __free_buffer_wake(b);
2747
2748 cond_resched();
2749 }
2750
2751 return count;
2752}
2753
2754static void evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
2755{
2756 struct evict_params params = {.gfp = 0, .age_hz = age_hz, .last_accessed = 0};
2757 unsigned long retain = get_retain_buffers(c);
2758 unsigned long count;
2759 LIST_HEAD(write_list);
2760
2761 dm_bufio_lock(c);
2762
2763 __check_watermark(c, &write_list);
2764 if (unlikely(!list_empty(&write_list))) {
2765 dm_bufio_unlock(c);
2766 __flush_write_list(&write_list);
2767 dm_bufio_lock(c);
2768 }
2769
2770 count = cache_total(&c->cache);
2771 if (count > retain)
2772 __evict_many(c, ¶ms, LIST_CLEAN, count - retain);
2773
2774 dm_bufio_unlock(c);
2775}
2776
2777static void cleanup_old_buffers(void)
2778{
2779 unsigned long max_age_hz = get_max_age_hz();
2780 struct dm_bufio_client *c;
2781
2782 mutex_lock(&dm_bufio_clients_lock);
2783
2784 __cache_size_refresh();
2785
2786 list_for_each_entry(c, &dm_bufio_all_clients, client_list)
2787 evict_old_buffers(c, max_age_hz);
2788
2789 mutex_unlock(&dm_bufio_clients_lock);
2790}
2791
2792static void work_fn(struct work_struct *w)
2793{
2794 cleanup_old_buffers();
2795
2796 queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2797 DM_BUFIO_WORK_TIMER_SECS * HZ);
2798}
2799
2800/*--------------------------------------------------------------*/
2801
2802/*
2803 * Global cleanup tries to evict the oldest buffers from across _all_
2804 * the clients. It does this by repeatedly evicting a few buffers from
2805 * the client that holds the oldest buffer. It's approximate, but hopefully
2806 * good enough.
2807 */
2808static struct dm_bufio_client *__pop_client(void)
2809{
2810 struct list_head *h;
2811
2812 if (list_empty(&dm_bufio_all_clients))
2813 return NULL;
2814
2815 h = dm_bufio_all_clients.next;
2816 list_del(h);
2817 return container_of(h, struct dm_bufio_client, client_list);
2818}
2819
2820/*
2821 * Inserts the client in the global client list based on its
2822 * 'oldest_buffer' field.
2823 */
2824static void __insert_client(struct dm_bufio_client *new_client)
2825{
2826 struct dm_bufio_client *c;
2827 struct list_head *h = dm_bufio_all_clients.next;
2828
2829 while (h != &dm_bufio_all_clients) {
2830 c = container_of(h, struct dm_bufio_client, client_list);
2831 if (time_after_eq(c->oldest_buffer, new_client->oldest_buffer))
2832 break;
2833 h = h->next;
2834 }
2835
2836 list_add_tail(&new_client->client_list, h);
2837}
2838
2839static unsigned long __evict_a_few(unsigned long nr_buffers)
2840{
2841 unsigned long count;
2842 struct dm_bufio_client *c;
2843 struct evict_params params = {
2844 .gfp = GFP_KERNEL,
2845 .age_hz = 0,
2846 /* set to jiffies in case there are no buffers in this client */
2847 .last_accessed = jiffies
2848 };
2849
2850 c = __pop_client();
2851 if (!c)
2852 return 0;
2853
2854 dm_bufio_lock(c);
2855 count = __evict_many(c, ¶ms, LIST_CLEAN, nr_buffers);
2856 dm_bufio_unlock(c);
2857
2858 if (count)
2859 c->oldest_buffer = params.last_accessed;
2860 __insert_client(c);
2861
2862 return count;
2863}
2864
2865static void check_watermarks(void)
2866{
2867 LIST_HEAD(write_list);
2868 struct dm_bufio_client *c;
2869
2870 mutex_lock(&dm_bufio_clients_lock);
2871 list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
2872 dm_bufio_lock(c);
2873 __check_watermark(c, &write_list);
2874 dm_bufio_unlock(c);
2875 }
2876 mutex_unlock(&dm_bufio_clients_lock);
2877
2878 __flush_write_list(&write_list);
2879}
2880
2881static void evict_old(void)
2882{
2883 unsigned long threshold = dm_bufio_cache_size -
2884 dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
2885
2886 mutex_lock(&dm_bufio_clients_lock);
2887 while (dm_bufio_current_allocated > threshold) {
2888 if (!__evict_a_few(64))
2889 break;
2890 cond_resched();
2891 }
2892 mutex_unlock(&dm_bufio_clients_lock);
2893}
2894
2895static void do_global_cleanup(struct work_struct *w)
2896{
2897 check_watermarks();
2898 evict_old();
2899}
2900
2901/*
2902 *--------------------------------------------------------------
2903 * Module setup
2904 *--------------------------------------------------------------
2905 */
2906
2907/*
2908 * This is called only once for the whole dm_bufio module.
2909 * It initializes memory limit.
2910 */
2911static int __init dm_bufio_init(void)
2912{
2913 __u64 mem;
2914
2915 dm_bufio_allocated_kmem_cache = 0;
2916 dm_bufio_allocated_kmalloc = 0;
2917 dm_bufio_allocated_get_free_pages = 0;
2918 dm_bufio_allocated_vmalloc = 0;
2919 dm_bufio_current_allocated = 0;
2920
2921 mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(),
2922 DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
2923
2924 if (mem > ULONG_MAX)
2925 mem = ULONG_MAX;
2926
2927#ifdef CONFIG_MMU
2928 if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
2929 mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
2930#endif
2931
2932 dm_bufio_default_cache_size = mem;
2933
2934 mutex_lock(&dm_bufio_clients_lock);
2935 __cache_size_refresh();
2936 mutex_unlock(&dm_bufio_clients_lock);
2937
2938 dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
2939 if (!dm_bufio_wq)
2940 return -ENOMEM;
2941
2942 INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
2943 INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
2944 queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2945 DM_BUFIO_WORK_TIMER_SECS * HZ);
2946
2947 return 0;
2948}
2949
2950/*
2951 * This is called once when unloading the dm_bufio module.
2952 */
2953static void __exit dm_bufio_exit(void)
2954{
2955 int bug = 0;
2956
2957 cancel_delayed_work_sync(&dm_bufio_cleanup_old_work);
2958 destroy_workqueue(dm_bufio_wq);
2959
2960 if (dm_bufio_client_count) {
2961 DMCRIT("%s: dm_bufio_client_count leaked: %d",
2962 __func__, dm_bufio_client_count);
2963 bug = 1;
2964 }
2965
2966 if (dm_bufio_current_allocated) {
2967 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
2968 __func__, dm_bufio_current_allocated);
2969 bug = 1;
2970 }
2971
2972 if (dm_bufio_allocated_get_free_pages) {
2973 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
2974 __func__, dm_bufio_allocated_get_free_pages);
2975 bug = 1;
2976 }
2977
2978 if (dm_bufio_allocated_vmalloc) {
2979 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
2980 __func__, dm_bufio_allocated_vmalloc);
2981 bug = 1;
2982 }
2983
2984 WARN_ON(bug); /* leaks are not worth crashing the system */
2985}
2986
2987module_init(dm_bufio_init)
2988module_exit(dm_bufio_exit)
2989
2990module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, 0644);
2991MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
2992
2993module_param_named(max_age_seconds, dm_bufio_max_age, uint, 0644);
2994MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
2995
2996module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, 0644);
2997MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
2998
2999module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, 0644);
3000MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
3001
3002module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, 0444);
3003MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
3004
3005module_param_named(allocated_kmalloc_bytes, dm_bufio_allocated_kmalloc, ulong, 0444);
3006MODULE_PARM_DESC(allocated_kmalloc_bytes, "Memory allocated with kmalloc_alloc");
3007
3008module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, 0444);
3009MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
3010
3011module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, 0444);
3012MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
3013
3014module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, 0444);
3015MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
3016
3017MODULE_AUTHOR("Mikulas Patocka <dm-devel@lists.linux.dev>");
3018MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
3019MODULE_LICENSE("GPL");