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