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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 <linux/dm-bufio.h>
10
11#include <linux/device-mapper.h>
12#include <linux/dm-io.h>
13#include <linux/slab.h>
14#include <linux/sched/mm.h>
15#include <linux/jiffies.h>
16#include <linux/vmalloc.h>
17#include <linux/shrinker.h>
18#include <linux/module.h>
19#include <linux/rbtree.h>
20#include <linux/stacktrace.h>
21
22#define DM_MSG_PREFIX "bufio"
23
24/*
25 * Memory management policy:
26 * Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
27 * or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
28 * Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
29 * Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
30 * dirty buffers.
31 */
32#define DM_BUFIO_MIN_BUFFERS 8
33
34#define DM_BUFIO_MEMORY_PERCENT 2
35#define DM_BUFIO_VMALLOC_PERCENT 25
36#define DM_BUFIO_WRITEBACK_PERCENT 75
37
38/*
39 * Check buffer ages in this interval (seconds)
40 */
41#define DM_BUFIO_WORK_TIMER_SECS 30
42
43/*
44 * Free buffers when they are older than this (seconds)
45 */
46#define DM_BUFIO_DEFAULT_AGE_SECS 300
47
48/*
49 * The nr of bytes of cached data to keep around.
50 */
51#define DM_BUFIO_DEFAULT_RETAIN_BYTES (256 * 1024)
52
53/*
54 * Align buffer writes to this boundary.
55 * Tests show that SSDs have the highest IOPS when using 4k writes.
56 */
57#define DM_BUFIO_WRITE_ALIGN 4096
58
59/*
60 * dm_buffer->list_mode
61 */
62#define LIST_CLEAN 0
63#define LIST_DIRTY 1
64#define LIST_SIZE 2
65
66/*
67 * Linking of buffers:
68 * All buffers are linked to cache_hash with their hash_list field.
69 *
70 * Clean buffers that are not being written (B_WRITING not set)
71 * are linked to lru[LIST_CLEAN] with their lru_list field.
72 *
73 * Dirty and clean buffers that are being written are linked to
74 * lru[LIST_DIRTY] with their lru_list field. When the write
75 * finishes, the buffer cannot be relinked immediately (because we
76 * are in an interrupt context and relinking requires process
77 * context), so some clean-not-writing buffers can be held on
78 * dirty_lru too. They are later added to lru in the process
79 * context.
80 */
81struct dm_bufio_client {
82 struct mutex lock;
83
84 struct list_head lru[LIST_SIZE];
85 unsigned long n_buffers[LIST_SIZE];
86
87 struct block_device *bdev;
88 unsigned block_size;
89 s8 sectors_per_block_bits;
90 void (*alloc_callback)(struct dm_buffer *);
91 void (*write_callback)(struct dm_buffer *);
92
93 struct kmem_cache *slab_buffer;
94 struct kmem_cache *slab_cache;
95 struct dm_io_client *dm_io;
96
97 struct list_head reserved_buffers;
98 unsigned need_reserved_buffers;
99
100 unsigned minimum_buffers;
101
102 struct rb_root buffer_tree;
103 wait_queue_head_t free_buffer_wait;
104
105 sector_t start;
106
107 int async_write_error;
108
109 struct list_head client_list;
110 struct shrinker shrinker;
111};
112
113/*
114 * Buffer state bits.
115 */
116#define B_READING 0
117#define B_WRITING 1
118#define B_DIRTY 2
119
120/*
121 * Describes how the block was allocated:
122 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
123 * See the comment at alloc_buffer_data.
124 */
125enum data_mode {
126 DATA_MODE_SLAB = 0,
127 DATA_MODE_GET_FREE_PAGES = 1,
128 DATA_MODE_VMALLOC = 2,
129 DATA_MODE_LIMIT = 3
130};
131
132struct dm_buffer {
133 struct rb_node node;
134 struct list_head lru_list;
135 sector_t block;
136 void *data;
137 unsigned char data_mode; /* DATA_MODE_* */
138 unsigned char list_mode; /* LIST_* */
139 blk_status_t read_error;
140 blk_status_t write_error;
141 unsigned hold_count;
142 unsigned long state;
143 unsigned long last_accessed;
144 unsigned dirty_start;
145 unsigned dirty_end;
146 unsigned write_start;
147 unsigned write_end;
148 struct dm_bufio_client *c;
149 struct list_head write_list;
150 void (*end_io)(struct dm_buffer *, blk_status_t);
151#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
152#define MAX_STACK 10
153 struct stack_trace stack_trace;
154 unsigned long stack_entries[MAX_STACK];
155#endif
156};
157
158/*----------------------------------------------------------------*/
159
160#define dm_bufio_in_request() (!!current->bio_list)
161
162static void dm_bufio_lock(struct dm_bufio_client *c)
163{
164 mutex_lock_nested(&c->lock, dm_bufio_in_request());
165}
166
167static int dm_bufio_trylock(struct dm_bufio_client *c)
168{
169 return mutex_trylock(&c->lock);
170}
171
172static void dm_bufio_unlock(struct dm_bufio_client *c)
173{
174 mutex_unlock(&c->lock);
175}
176
177/*----------------------------------------------------------------*/
178
179/*
180 * Default cache size: available memory divided by the ratio.
181 */
182static unsigned long dm_bufio_default_cache_size;
183
184/*
185 * Total cache size set by the user.
186 */
187static unsigned long dm_bufio_cache_size;
188
189/*
190 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
191 * at any time. If it disagrees, the user has changed cache size.
192 */
193static unsigned long dm_bufio_cache_size_latch;
194
195static DEFINE_SPINLOCK(param_spinlock);
196
197/*
198 * Buffers are freed after this timeout
199 */
200static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
201static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
202
203static unsigned long dm_bufio_peak_allocated;
204static unsigned long dm_bufio_allocated_kmem_cache;
205static unsigned long dm_bufio_allocated_get_free_pages;
206static unsigned long dm_bufio_allocated_vmalloc;
207static unsigned long dm_bufio_current_allocated;
208
209/*----------------------------------------------------------------*/
210
211/*
212 * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
213 */
214static unsigned long dm_bufio_cache_size_per_client;
215
216/*
217 * The current number of clients.
218 */
219static int dm_bufio_client_count;
220
221/*
222 * The list of all clients.
223 */
224static LIST_HEAD(dm_bufio_all_clients);
225
226/*
227 * This mutex protects dm_bufio_cache_size_latch,
228 * dm_bufio_cache_size_per_client and dm_bufio_client_count
229 */
230static DEFINE_MUTEX(dm_bufio_clients_lock);
231
232#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
233static void buffer_record_stack(struct dm_buffer *b)
234{
235 b->stack_trace.nr_entries = 0;
236 b->stack_trace.max_entries = MAX_STACK;
237 b->stack_trace.entries = b->stack_entries;
238 b->stack_trace.skip = 2;
239 save_stack_trace(&b->stack_trace);
240}
241#endif
242
243/*----------------------------------------------------------------
244 * A red/black tree acts as an index for all the buffers.
245 *--------------------------------------------------------------*/
246static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
247{
248 struct rb_node *n = c->buffer_tree.rb_node;
249 struct dm_buffer *b;
250
251 while (n) {
252 b = container_of(n, struct dm_buffer, node);
253
254 if (b->block == block)
255 return b;
256
257 n = (b->block < block) ? n->rb_left : n->rb_right;
258 }
259
260 return NULL;
261}
262
263static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
264{
265 struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
266 struct dm_buffer *found;
267
268 while (*new) {
269 found = container_of(*new, struct dm_buffer, node);
270
271 if (found->block == b->block) {
272 BUG_ON(found != b);
273 return;
274 }
275
276 parent = *new;
277 new = (found->block < b->block) ?
278 &((*new)->rb_left) : &((*new)->rb_right);
279 }
280
281 rb_link_node(&b->node, parent, new);
282 rb_insert_color(&b->node, &c->buffer_tree);
283}
284
285static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
286{
287 rb_erase(&b->node, &c->buffer_tree);
288}
289
290/*----------------------------------------------------------------*/
291
292static void adjust_total_allocated(unsigned char data_mode, long diff)
293{
294 static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
295 &dm_bufio_allocated_kmem_cache,
296 &dm_bufio_allocated_get_free_pages,
297 &dm_bufio_allocated_vmalloc,
298 };
299
300 spin_lock(¶m_spinlock);
301
302 *class_ptr[data_mode] += diff;
303
304 dm_bufio_current_allocated += diff;
305
306 if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
307 dm_bufio_peak_allocated = dm_bufio_current_allocated;
308
309 spin_unlock(¶m_spinlock);
310}
311
312/*
313 * Change the number of clients and recalculate per-client limit.
314 */
315static void __cache_size_refresh(void)
316{
317 BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
318 BUG_ON(dm_bufio_client_count < 0);
319
320 dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
321
322 /*
323 * Use default if set to 0 and report the actual cache size used.
324 */
325 if (!dm_bufio_cache_size_latch) {
326 (void)cmpxchg(&dm_bufio_cache_size, 0,
327 dm_bufio_default_cache_size);
328 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
329 }
330
331 dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
332 (dm_bufio_client_count ? : 1);
333}
334
335/*
336 * Allocating buffer data.
337 *
338 * Small buffers are allocated with kmem_cache, to use space optimally.
339 *
340 * For large buffers, we choose between get_free_pages and vmalloc.
341 * Each has advantages and disadvantages.
342 *
343 * __get_free_pages can randomly fail if the memory is fragmented.
344 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
345 * as low as 128M) so using it for caching is not appropriate.
346 *
347 * If the allocation may fail we use __get_free_pages. Memory fragmentation
348 * won't have a fatal effect here, but it just causes flushes of some other
349 * buffers and more I/O will be performed. Don't use __get_free_pages if it
350 * always fails (i.e. order >= MAX_ORDER).
351 *
352 * If the allocation shouldn't fail we use __vmalloc. This is only for the
353 * initial reserve allocation, so there's no risk of wasting all vmalloc
354 * space.
355 */
356static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
357 unsigned char *data_mode)
358{
359 if (unlikely(c->slab_cache != NULL)) {
360 *data_mode = DATA_MODE_SLAB;
361 return kmem_cache_alloc(c->slab_cache, gfp_mask);
362 }
363
364 if (c->block_size <= KMALLOC_MAX_SIZE &&
365 gfp_mask & __GFP_NORETRY) {
366 *data_mode = DATA_MODE_GET_FREE_PAGES;
367 return (void *)__get_free_pages(gfp_mask,
368 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
369 }
370
371 *data_mode = DATA_MODE_VMALLOC;
372
373 /*
374 * __vmalloc allocates the data pages and auxiliary structures with
375 * gfp_flags that were specified, but pagetables are always allocated
376 * with GFP_KERNEL, no matter what was specified as gfp_mask.
377 *
378 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
379 * all allocations done by this process (including pagetables) are done
380 * as if GFP_NOIO was specified.
381 */
382 if (gfp_mask & __GFP_NORETRY) {
383 unsigned noio_flag = memalloc_noio_save();
384 void *ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
385
386 memalloc_noio_restore(noio_flag);
387 return ptr;
388 }
389
390 return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
391}
392
393/*
394 * Free buffer's data.
395 */
396static void free_buffer_data(struct dm_bufio_client *c,
397 void *data, unsigned char data_mode)
398{
399 switch (data_mode) {
400 case DATA_MODE_SLAB:
401 kmem_cache_free(c->slab_cache, data);
402 break;
403
404 case DATA_MODE_GET_FREE_PAGES:
405 free_pages((unsigned long)data,
406 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
407 break;
408
409 case DATA_MODE_VMALLOC:
410 vfree(data);
411 break;
412
413 default:
414 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
415 data_mode);
416 BUG();
417 }
418}
419
420/*
421 * Allocate buffer and its data.
422 */
423static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
424{
425 struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
426
427 if (!b)
428 return NULL;
429
430 b->c = c;
431
432 b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
433 if (!b->data) {
434 kmem_cache_free(c->slab_buffer, b);
435 return NULL;
436 }
437
438 adjust_total_allocated(b->data_mode, (long)c->block_size);
439
440#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
441 memset(&b->stack_trace, 0, sizeof(b->stack_trace));
442#endif
443 return b;
444}
445
446/*
447 * Free buffer and its data.
448 */
449static void free_buffer(struct dm_buffer *b)
450{
451 struct dm_bufio_client *c = b->c;
452
453 adjust_total_allocated(b->data_mode, -(long)c->block_size);
454
455 free_buffer_data(c, b->data, b->data_mode);
456 kmem_cache_free(c->slab_buffer, b);
457}
458
459/*
460 * Link buffer to the hash list and clean or dirty queue.
461 */
462static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
463{
464 struct dm_bufio_client *c = b->c;
465
466 c->n_buffers[dirty]++;
467 b->block = block;
468 b->list_mode = dirty;
469 list_add(&b->lru_list, &c->lru[dirty]);
470 __insert(b->c, b);
471 b->last_accessed = jiffies;
472}
473
474/*
475 * Unlink buffer from the hash list and dirty or clean queue.
476 */
477static void __unlink_buffer(struct dm_buffer *b)
478{
479 struct dm_bufio_client *c = b->c;
480
481 BUG_ON(!c->n_buffers[b->list_mode]);
482
483 c->n_buffers[b->list_mode]--;
484 __remove(b->c, b);
485 list_del(&b->lru_list);
486}
487
488/*
489 * Place the buffer to the head of dirty or clean LRU queue.
490 */
491static void __relink_lru(struct dm_buffer *b, int dirty)
492{
493 struct dm_bufio_client *c = b->c;
494
495 BUG_ON(!c->n_buffers[b->list_mode]);
496
497 c->n_buffers[b->list_mode]--;
498 c->n_buffers[dirty]++;
499 b->list_mode = dirty;
500 list_move(&b->lru_list, &c->lru[dirty]);
501 b->last_accessed = jiffies;
502}
503
504/*----------------------------------------------------------------
505 * Submit I/O on the buffer.
506 *
507 * Bio interface is faster but it has some problems:
508 * the vector list is limited (increasing this limit increases
509 * memory-consumption per buffer, so it is not viable);
510 *
511 * the memory must be direct-mapped, not vmalloced;
512 *
513 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
514 * it is not vmalloced, try using the bio interface.
515 *
516 * If the buffer is big, if it is vmalloced or if the underlying device
517 * rejects the bio because it is too large, use dm-io layer to do the I/O.
518 * The dm-io layer splits the I/O into multiple requests, avoiding the above
519 * shortcomings.
520 *--------------------------------------------------------------*/
521
522/*
523 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
524 * that the request was handled directly with bio interface.
525 */
526static void dmio_complete(unsigned long error, void *context)
527{
528 struct dm_buffer *b = context;
529
530 b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
531}
532
533static void use_dmio(struct dm_buffer *b, int rw, sector_t sector,
534 unsigned n_sectors, unsigned offset)
535{
536 int r;
537 struct dm_io_request io_req = {
538 .bi_op = rw,
539 .bi_op_flags = 0,
540 .notify.fn = dmio_complete,
541 .notify.context = b,
542 .client = b->c->dm_io,
543 };
544 struct dm_io_region region = {
545 .bdev = b->c->bdev,
546 .sector = sector,
547 .count = n_sectors,
548 };
549
550 if (b->data_mode != DATA_MODE_VMALLOC) {
551 io_req.mem.type = DM_IO_KMEM;
552 io_req.mem.ptr.addr = (char *)b->data + offset;
553 } else {
554 io_req.mem.type = DM_IO_VMA;
555 io_req.mem.ptr.vma = (char *)b->data + offset;
556 }
557
558 r = dm_io(&io_req, 1, ®ion, NULL);
559 if (unlikely(r))
560 b->end_io(b, errno_to_blk_status(r));
561}
562
563static void bio_complete(struct bio *bio)
564{
565 struct dm_buffer *b = bio->bi_private;
566 blk_status_t status = bio->bi_status;
567 bio_put(bio);
568 b->end_io(b, status);
569}
570
571static void use_bio(struct dm_buffer *b, int rw, sector_t sector,
572 unsigned n_sectors, unsigned offset)
573{
574 struct bio *bio;
575 char *ptr;
576 unsigned vec_size, len;
577
578 vec_size = b->c->block_size >> PAGE_SHIFT;
579 if (unlikely(b->c->sectors_per_block_bits < PAGE_SHIFT - SECTOR_SHIFT))
580 vec_size += 2;
581
582 bio = bio_kmalloc(GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN, vec_size);
583 if (!bio) {
584dmio:
585 use_dmio(b, rw, sector, n_sectors, offset);
586 return;
587 }
588
589 bio->bi_iter.bi_sector = sector;
590 bio_set_dev(bio, b->c->bdev);
591 bio_set_op_attrs(bio, rw, 0);
592 bio->bi_end_io = bio_complete;
593 bio->bi_private = b;
594
595 ptr = (char *)b->data + offset;
596 len = n_sectors << SECTOR_SHIFT;
597
598 do {
599 unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len);
600 if (!bio_add_page(bio, virt_to_page(ptr), this_step,
601 offset_in_page(ptr))) {
602 bio_put(bio);
603 goto dmio;
604 }
605
606 len -= this_step;
607 ptr += this_step;
608 } while (len > 0);
609
610 submit_bio(bio);
611}
612
613static void submit_io(struct dm_buffer *b, int rw, void (*end_io)(struct dm_buffer *, blk_status_t))
614{
615 unsigned n_sectors;
616 sector_t sector;
617 unsigned offset, end;
618
619 b->end_io = end_io;
620
621 if (likely(b->c->sectors_per_block_bits >= 0))
622 sector = b->block << b->c->sectors_per_block_bits;
623 else
624 sector = b->block * (b->c->block_size >> SECTOR_SHIFT);
625 sector += b->c->start;
626
627 if (rw != REQ_OP_WRITE) {
628 n_sectors = b->c->block_size >> SECTOR_SHIFT;
629 offset = 0;
630 } else {
631 if (b->c->write_callback)
632 b->c->write_callback(b);
633 offset = b->write_start;
634 end = b->write_end;
635 offset &= -DM_BUFIO_WRITE_ALIGN;
636 end += DM_BUFIO_WRITE_ALIGN - 1;
637 end &= -DM_BUFIO_WRITE_ALIGN;
638 if (unlikely(end > b->c->block_size))
639 end = b->c->block_size;
640
641 sector += offset >> SECTOR_SHIFT;
642 n_sectors = (end - offset) >> SECTOR_SHIFT;
643 }
644
645 if (b->data_mode != DATA_MODE_VMALLOC)
646 use_bio(b, rw, sector, n_sectors, offset);
647 else
648 use_dmio(b, rw, sector, n_sectors, offset);
649}
650
651/*----------------------------------------------------------------
652 * Writing dirty buffers
653 *--------------------------------------------------------------*/
654
655/*
656 * The endio routine for write.
657 *
658 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
659 * it.
660 */
661static void write_endio(struct dm_buffer *b, blk_status_t status)
662{
663 b->write_error = status;
664 if (unlikely(status)) {
665 struct dm_bufio_client *c = b->c;
666
667 (void)cmpxchg(&c->async_write_error, 0,
668 blk_status_to_errno(status));
669 }
670
671 BUG_ON(!test_bit(B_WRITING, &b->state));
672
673 smp_mb__before_atomic();
674 clear_bit(B_WRITING, &b->state);
675 smp_mb__after_atomic();
676
677 wake_up_bit(&b->state, B_WRITING);
678}
679
680/*
681 * Initiate a write on a dirty buffer, but don't wait for it.
682 *
683 * - If the buffer is not dirty, exit.
684 * - If there some previous write going on, wait for it to finish (we can't
685 * have two writes on the same buffer simultaneously).
686 * - Submit our write and don't wait on it. We set B_WRITING indicating
687 * that there is a write in progress.
688 */
689static void __write_dirty_buffer(struct dm_buffer *b,
690 struct list_head *write_list)
691{
692 if (!test_bit(B_DIRTY, &b->state))
693 return;
694
695 clear_bit(B_DIRTY, &b->state);
696 wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
697
698 b->write_start = b->dirty_start;
699 b->write_end = b->dirty_end;
700
701 if (!write_list)
702 submit_io(b, REQ_OP_WRITE, write_endio);
703 else
704 list_add_tail(&b->write_list, write_list);
705}
706
707static void __flush_write_list(struct list_head *write_list)
708{
709 struct blk_plug plug;
710 blk_start_plug(&plug);
711 while (!list_empty(write_list)) {
712 struct dm_buffer *b =
713 list_entry(write_list->next, struct dm_buffer, write_list);
714 list_del(&b->write_list);
715 submit_io(b, REQ_OP_WRITE, write_endio);
716 cond_resched();
717 }
718 blk_finish_plug(&plug);
719}
720
721/*
722 * Wait until any activity on the buffer finishes. Possibly write the
723 * buffer if it is dirty. When this function finishes, there is no I/O
724 * running on the buffer and the buffer is not dirty.
725 */
726static void __make_buffer_clean(struct dm_buffer *b)
727{
728 BUG_ON(b->hold_count);
729
730 if (!b->state) /* fast case */
731 return;
732
733 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
734 __write_dirty_buffer(b, NULL);
735 wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
736}
737
738/*
739 * Find some buffer that is not held by anybody, clean it, unlink it and
740 * return it.
741 */
742static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
743{
744 struct dm_buffer *b;
745
746 list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
747 BUG_ON(test_bit(B_WRITING, &b->state));
748 BUG_ON(test_bit(B_DIRTY, &b->state));
749
750 if (!b->hold_count) {
751 __make_buffer_clean(b);
752 __unlink_buffer(b);
753 return b;
754 }
755 cond_resched();
756 }
757
758 list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
759 BUG_ON(test_bit(B_READING, &b->state));
760
761 if (!b->hold_count) {
762 __make_buffer_clean(b);
763 __unlink_buffer(b);
764 return b;
765 }
766 cond_resched();
767 }
768
769 return NULL;
770}
771
772/*
773 * Wait until some other threads free some buffer or release hold count on
774 * some buffer.
775 *
776 * This function is entered with c->lock held, drops it and regains it
777 * before exiting.
778 */
779static void __wait_for_free_buffer(struct dm_bufio_client *c)
780{
781 DECLARE_WAITQUEUE(wait, current);
782
783 add_wait_queue(&c->free_buffer_wait, &wait);
784 set_current_state(TASK_UNINTERRUPTIBLE);
785 dm_bufio_unlock(c);
786
787 io_schedule();
788
789 remove_wait_queue(&c->free_buffer_wait, &wait);
790
791 dm_bufio_lock(c);
792}
793
794enum new_flag {
795 NF_FRESH = 0,
796 NF_READ = 1,
797 NF_GET = 2,
798 NF_PREFETCH = 3
799};
800
801/*
802 * Allocate a new buffer. If the allocation is not possible, wait until
803 * some other thread frees a buffer.
804 *
805 * May drop the lock and regain it.
806 */
807static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
808{
809 struct dm_buffer *b;
810 bool tried_noio_alloc = false;
811
812 /*
813 * dm-bufio is resistant to allocation failures (it just keeps
814 * one buffer reserved in cases all the allocations fail).
815 * So set flags to not try too hard:
816 * GFP_NOWAIT: don't wait; if we need to sleep we'll release our
817 * mutex and wait ourselves.
818 * __GFP_NORETRY: don't retry and rather return failure
819 * __GFP_NOMEMALLOC: don't use emergency reserves
820 * __GFP_NOWARN: don't print a warning in case of failure
821 *
822 * For debugging, if we set the cache size to 1, no new buffers will
823 * be allocated.
824 */
825 while (1) {
826 if (dm_bufio_cache_size_latch != 1) {
827 b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
828 if (b)
829 return b;
830 }
831
832 if (nf == NF_PREFETCH)
833 return NULL;
834
835 if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
836 dm_bufio_unlock(c);
837 b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
838 dm_bufio_lock(c);
839 if (b)
840 return b;
841 tried_noio_alloc = true;
842 }
843
844 if (!list_empty(&c->reserved_buffers)) {
845 b = list_entry(c->reserved_buffers.next,
846 struct dm_buffer, lru_list);
847 list_del(&b->lru_list);
848 c->need_reserved_buffers++;
849
850 return b;
851 }
852
853 b = __get_unclaimed_buffer(c);
854 if (b)
855 return b;
856
857 __wait_for_free_buffer(c);
858 }
859}
860
861static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
862{
863 struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
864
865 if (!b)
866 return NULL;
867
868 if (c->alloc_callback)
869 c->alloc_callback(b);
870
871 return b;
872}
873
874/*
875 * Free a buffer and wake other threads waiting for free buffers.
876 */
877static void __free_buffer_wake(struct dm_buffer *b)
878{
879 struct dm_bufio_client *c = b->c;
880
881 if (!c->need_reserved_buffers)
882 free_buffer(b);
883 else {
884 list_add(&b->lru_list, &c->reserved_buffers);
885 c->need_reserved_buffers--;
886 }
887
888 wake_up(&c->free_buffer_wait);
889}
890
891static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
892 struct list_head *write_list)
893{
894 struct dm_buffer *b, *tmp;
895
896 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
897 BUG_ON(test_bit(B_READING, &b->state));
898
899 if (!test_bit(B_DIRTY, &b->state) &&
900 !test_bit(B_WRITING, &b->state)) {
901 __relink_lru(b, LIST_CLEAN);
902 continue;
903 }
904
905 if (no_wait && test_bit(B_WRITING, &b->state))
906 return;
907
908 __write_dirty_buffer(b, write_list);
909 cond_resched();
910 }
911}
912
913/*
914 * Get writeback threshold and buffer limit for a given client.
915 */
916static void __get_memory_limit(struct dm_bufio_client *c,
917 unsigned long *threshold_buffers,
918 unsigned long *limit_buffers)
919{
920 unsigned long buffers;
921
922 if (unlikely(READ_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) {
923 if (mutex_trylock(&dm_bufio_clients_lock)) {
924 __cache_size_refresh();
925 mutex_unlock(&dm_bufio_clients_lock);
926 }
927 }
928
929 buffers = dm_bufio_cache_size_per_client;
930 if (likely(c->sectors_per_block_bits >= 0))
931 buffers >>= c->sectors_per_block_bits + SECTOR_SHIFT;
932 else
933 buffers /= c->block_size;
934
935 if (buffers < c->minimum_buffers)
936 buffers = c->minimum_buffers;
937
938 *limit_buffers = buffers;
939 *threshold_buffers = mult_frac(buffers,
940 DM_BUFIO_WRITEBACK_PERCENT, 100);
941}
942
943/*
944 * Check if we're over watermark.
945 * If we are over threshold_buffers, start freeing buffers.
946 * If we're over "limit_buffers", block until we get under the limit.
947 */
948static void __check_watermark(struct dm_bufio_client *c,
949 struct list_head *write_list)
950{
951 unsigned long threshold_buffers, limit_buffers;
952
953 __get_memory_limit(c, &threshold_buffers, &limit_buffers);
954
955 while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
956 limit_buffers) {
957
958 struct dm_buffer *b = __get_unclaimed_buffer(c);
959
960 if (!b)
961 return;
962
963 __free_buffer_wake(b);
964 cond_resched();
965 }
966
967 if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
968 __write_dirty_buffers_async(c, 1, write_list);
969}
970
971/*----------------------------------------------------------------
972 * Getting a buffer
973 *--------------------------------------------------------------*/
974
975static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
976 enum new_flag nf, int *need_submit,
977 struct list_head *write_list)
978{
979 struct dm_buffer *b, *new_b = NULL;
980
981 *need_submit = 0;
982
983 b = __find(c, block);
984 if (b)
985 goto found_buffer;
986
987 if (nf == NF_GET)
988 return NULL;
989
990 new_b = __alloc_buffer_wait(c, nf);
991 if (!new_b)
992 return NULL;
993
994 /*
995 * We've had a period where the mutex was unlocked, so need to
996 * recheck the hash table.
997 */
998 b = __find(c, block);
999 if (b) {
1000 __free_buffer_wake(new_b);
1001 goto found_buffer;
1002 }
1003
1004 __check_watermark(c, write_list);
1005
1006 b = new_b;
1007 b->hold_count = 1;
1008 b->read_error = 0;
1009 b->write_error = 0;
1010 __link_buffer(b, block, LIST_CLEAN);
1011
1012 if (nf == NF_FRESH) {
1013 b->state = 0;
1014 return b;
1015 }
1016
1017 b->state = 1 << B_READING;
1018 *need_submit = 1;
1019
1020 return b;
1021
1022found_buffer:
1023 if (nf == NF_PREFETCH)
1024 return NULL;
1025 /*
1026 * Note: it is essential that we don't wait for the buffer to be
1027 * read if dm_bufio_get function is used. Both dm_bufio_get and
1028 * dm_bufio_prefetch can be used in the driver request routine.
1029 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1030 * the same buffer, it would deadlock if we waited.
1031 */
1032 if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
1033 return NULL;
1034
1035 b->hold_count++;
1036 __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1037 test_bit(B_WRITING, &b->state));
1038 return b;
1039}
1040
1041/*
1042 * The endio routine for reading: set the error, clear the bit and wake up
1043 * anyone waiting on the buffer.
1044 */
1045static void read_endio(struct dm_buffer *b, blk_status_t status)
1046{
1047 b->read_error = status;
1048
1049 BUG_ON(!test_bit(B_READING, &b->state));
1050
1051 smp_mb__before_atomic();
1052 clear_bit(B_READING, &b->state);
1053 smp_mb__after_atomic();
1054
1055 wake_up_bit(&b->state, B_READING);
1056}
1057
1058/*
1059 * A common routine for dm_bufio_new and dm_bufio_read. Operation of these
1060 * functions is similar except that dm_bufio_new doesn't read the
1061 * buffer from the disk (assuming that the caller overwrites all the data
1062 * and uses dm_bufio_mark_buffer_dirty to write new data back).
1063 */
1064static void *new_read(struct dm_bufio_client *c, sector_t block,
1065 enum new_flag nf, struct dm_buffer **bp)
1066{
1067 int need_submit;
1068 struct dm_buffer *b;
1069
1070 LIST_HEAD(write_list);
1071
1072 dm_bufio_lock(c);
1073 b = __bufio_new(c, block, nf, &need_submit, &write_list);
1074#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1075 if (b && b->hold_count == 1)
1076 buffer_record_stack(b);
1077#endif
1078 dm_bufio_unlock(c);
1079
1080 __flush_write_list(&write_list);
1081
1082 if (!b)
1083 return NULL;
1084
1085 if (need_submit)
1086 submit_io(b, REQ_OP_READ, read_endio);
1087
1088 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1089
1090 if (b->read_error) {
1091 int error = blk_status_to_errno(b->read_error);
1092
1093 dm_bufio_release(b);
1094
1095 return ERR_PTR(error);
1096 }
1097
1098 *bp = b;
1099
1100 return b->data;
1101}
1102
1103void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1104 struct dm_buffer **bp)
1105{
1106 return new_read(c, block, NF_GET, bp);
1107}
1108EXPORT_SYMBOL_GPL(dm_bufio_get);
1109
1110void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1111 struct dm_buffer **bp)
1112{
1113 BUG_ON(dm_bufio_in_request());
1114
1115 return new_read(c, block, NF_READ, bp);
1116}
1117EXPORT_SYMBOL_GPL(dm_bufio_read);
1118
1119void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1120 struct dm_buffer **bp)
1121{
1122 BUG_ON(dm_bufio_in_request());
1123
1124 return new_read(c, block, NF_FRESH, bp);
1125}
1126EXPORT_SYMBOL_GPL(dm_bufio_new);
1127
1128void dm_bufio_prefetch(struct dm_bufio_client *c,
1129 sector_t block, unsigned n_blocks)
1130{
1131 struct blk_plug plug;
1132
1133 LIST_HEAD(write_list);
1134
1135 BUG_ON(dm_bufio_in_request());
1136
1137 blk_start_plug(&plug);
1138 dm_bufio_lock(c);
1139
1140 for (; n_blocks--; block++) {
1141 int need_submit;
1142 struct dm_buffer *b;
1143 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1144 &write_list);
1145 if (unlikely(!list_empty(&write_list))) {
1146 dm_bufio_unlock(c);
1147 blk_finish_plug(&plug);
1148 __flush_write_list(&write_list);
1149 blk_start_plug(&plug);
1150 dm_bufio_lock(c);
1151 }
1152 if (unlikely(b != NULL)) {
1153 dm_bufio_unlock(c);
1154
1155 if (need_submit)
1156 submit_io(b, REQ_OP_READ, read_endio);
1157 dm_bufio_release(b);
1158
1159 cond_resched();
1160
1161 if (!n_blocks)
1162 goto flush_plug;
1163 dm_bufio_lock(c);
1164 }
1165 }
1166
1167 dm_bufio_unlock(c);
1168
1169flush_plug:
1170 blk_finish_plug(&plug);
1171}
1172EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1173
1174void dm_bufio_release(struct dm_buffer *b)
1175{
1176 struct dm_bufio_client *c = b->c;
1177
1178 dm_bufio_lock(c);
1179
1180 BUG_ON(!b->hold_count);
1181
1182 b->hold_count--;
1183 if (!b->hold_count) {
1184 wake_up(&c->free_buffer_wait);
1185
1186 /*
1187 * If there were errors on the buffer, and the buffer is not
1188 * to be written, free the buffer. There is no point in caching
1189 * invalid buffer.
1190 */
1191 if ((b->read_error || b->write_error) &&
1192 !test_bit(B_READING, &b->state) &&
1193 !test_bit(B_WRITING, &b->state) &&
1194 !test_bit(B_DIRTY, &b->state)) {
1195 __unlink_buffer(b);
1196 __free_buffer_wake(b);
1197 }
1198 }
1199
1200 dm_bufio_unlock(c);
1201}
1202EXPORT_SYMBOL_GPL(dm_bufio_release);
1203
1204void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
1205 unsigned start, unsigned end)
1206{
1207 struct dm_bufio_client *c = b->c;
1208
1209 BUG_ON(start >= end);
1210 BUG_ON(end > b->c->block_size);
1211
1212 dm_bufio_lock(c);
1213
1214 BUG_ON(test_bit(B_READING, &b->state));
1215
1216 if (!test_and_set_bit(B_DIRTY, &b->state)) {
1217 b->dirty_start = start;
1218 b->dirty_end = end;
1219 __relink_lru(b, LIST_DIRTY);
1220 } else {
1221 if (start < b->dirty_start)
1222 b->dirty_start = start;
1223 if (end > b->dirty_end)
1224 b->dirty_end = end;
1225 }
1226
1227 dm_bufio_unlock(c);
1228}
1229EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
1230
1231void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1232{
1233 dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
1234}
1235EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1236
1237void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1238{
1239 LIST_HEAD(write_list);
1240
1241 BUG_ON(dm_bufio_in_request());
1242
1243 dm_bufio_lock(c);
1244 __write_dirty_buffers_async(c, 0, &write_list);
1245 dm_bufio_unlock(c);
1246 __flush_write_list(&write_list);
1247}
1248EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1249
1250/*
1251 * For performance, it is essential that the buffers are written asynchronously
1252 * and simultaneously (so that the block layer can merge the writes) and then
1253 * waited upon.
1254 *
1255 * Finally, we flush hardware disk cache.
1256 */
1257int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1258{
1259 int a, f;
1260 unsigned long buffers_processed = 0;
1261 struct dm_buffer *b, *tmp;
1262
1263 LIST_HEAD(write_list);
1264
1265 dm_bufio_lock(c);
1266 __write_dirty_buffers_async(c, 0, &write_list);
1267 dm_bufio_unlock(c);
1268 __flush_write_list(&write_list);
1269 dm_bufio_lock(c);
1270
1271again:
1272 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1273 int dropped_lock = 0;
1274
1275 if (buffers_processed < c->n_buffers[LIST_DIRTY])
1276 buffers_processed++;
1277
1278 BUG_ON(test_bit(B_READING, &b->state));
1279
1280 if (test_bit(B_WRITING, &b->state)) {
1281 if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1282 dropped_lock = 1;
1283 b->hold_count++;
1284 dm_bufio_unlock(c);
1285 wait_on_bit_io(&b->state, B_WRITING,
1286 TASK_UNINTERRUPTIBLE);
1287 dm_bufio_lock(c);
1288 b->hold_count--;
1289 } else
1290 wait_on_bit_io(&b->state, B_WRITING,
1291 TASK_UNINTERRUPTIBLE);
1292 }
1293
1294 if (!test_bit(B_DIRTY, &b->state) &&
1295 !test_bit(B_WRITING, &b->state))
1296 __relink_lru(b, LIST_CLEAN);
1297
1298 cond_resched();
1299
1300 /*
1301 * If we dropped the lock, the list is no longer consistent,
1302 * so we must restart the search.
1303 *
1304 * In the most common case, the buffer just processed is
1305 * relinked to the clean list, so we won't loop scanning the
1306 * same buffer again and again.
1307 *
1308 * This may livelock if there is another thread simultaneously
1309 * dirtying buffers, so we count the number of buffers walked
1310 * and if it exceeds the total number of buffers, it means that
1311 * someone is doing some writes simultaneously with us. In
1312 * this case, stop, dropping the lock.
1313 */
1314 if (dropped_lock)
1315 goto again;
1316 }
1317 wake_up(&c->free_buffer_wait);
1318 dm_bufio_unlock(c);
1319
1320 a = xchg(&c->async_write_error, 0);
1321 f = dm_bufio_issue_flush(c);
1322 if (a)
1323 return a;
1324
1325 return f;
1326}
1327EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1328
1329/*
1330 * Use dm-io to send and empty barrier flush the device.
1331 */
1332int dm_bufio_issue_flush(struct dm_bufio_client *c)
1333{
1334 struct dm_io_request io_req = {
1335 .bi_op = REQ_OP_WRITE,
1336 .bi_op_flags = REQ_PREFLUSH | REQ_SYNC,
1337 .mem.type = DM_IO_KMEM,
1338 .mem.ptr.addr = NULL,
1339 .client = c->dm_io,
1340 };
1341 struct dm_io_region io_reg = {
1342 .bdev = c->bdev,
1343 .sector = 0,
1344 .count = 0,
1345 };
1346
1347 BUG_ON(dm_bufio_in_request());
1348
1349 return dm_io(&io_req, 1, &io_reg, NULL);
1350}
1351EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1352
1353/*
1354 * We first delete any other buffer that may be at that new location.
1355 *
1356 * Then, we write the buffer to the original location if it was dirty.
1357 *
1358 * Then, if we are the only one who is holding the buffer, relink the buffer
1359 * in the hash queue for the new location.
1360 *
1361 * If there was someone else holding the buffer, we write it to the new
1362 * location but not relink it, because that other user needs to have the buffer
1363 * at the same place.
1364 */
1365void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1366{
1367 struct dm_bufio_client *c = b->c;
1368 struct dm_buffer *new;
1369
1370 BUG_ON(dm_bufio_in_request());
1371
1372 dm_bufio_lock(c);
1373
1374retry:
1375 new = __find(c, new_block);
1376 if (new) {
1377 if (new->hold_count) {
1378 __wait_for_free_buffer(c);
1379 goto retry;
1380 }
1381
1382 /*
1383 * FIXME: Is there any point waiting for a write that's going
1384 * to be overwritten in a bit?
1385 */
1386 __make_buffer_clean(new);
1387 __unlink_buffer(new);
1388 __free_buffer_wake(new);
1389 }
1390
1391 BUG_ON(!b->hold_count);
1392 BUG_ON(test_bit(B_READING, &b->state));
1393
1394 __write_dirty_buffer(b, NULL);
1395 if (b->hold_count == 1) {
1396 wait_on_bit_io(&b->state, B_WRITING,
1397 TASK_UNINTERRUPTIBLE);
1398 set_bit(B_DIRTY, &b->state);
1399 b->dirty_start = 0;
1400 b->dirty_end = c->block_size;
1401 __unlink_buffer(b);
1402 __link_buffer(b, new_block, LIST_DIRTY);
1403 } else {
1404 sector_t old_block;
1405 wait_on_bit_lock_io(&b->state, B_WRITING,
1406 TASK_UNINTERRUPTIBLE);
1407 /*
1408 * Relink buffer to "new_block" so that write_callback
1409 * sees "new_block" as a block number.
1410 * After the write, link the buffer back to old_block.
1411 * All this must be done in bufio lock, so that block number
1412 * change isn't visible to other threads.
1413 */
1414 old_block = b->block;
1415 __unlink_buffer(b);
1416 __link_buffer(b, new_block, b->list_mode);
1417 submit_io(b, REQ_OP_WRITE, write_endio);
1418 wait_on_bit_io(&b->state, B_WRITING,
1419 TASK_UNINTERRUPTIBLE);
1420 __unlink_buffer(b);
1421 __link_buffer(b, old_block, b->list_mode);
1422 }
1423
1424 dm_bufio_unlock(c);
1425 dm_bufio_release(b);
1426}
1427EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1428
1429/*
1430 * Free the given buffer.
1431 *
1432 * This is just a hint, if the buffer is in use or dirty, this function
1433 * does nothing.
1434 */
1435void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1436{
1437 struct dm_buffer *b;
1438
1439 dm_bufio_lock(c);
1440
1441 b = __find(c, block);
1442 if (b && likely(!b->hold_count) && likely(!b->state)) {
1443 __unlink_buffer(b);
1444 __free_buffer_wake(b);
1445 }
1446
1447 dm_bufio_unlock(c);
1448}
1449EXPORT_SYMBOL_GPL(dm_bufio_forget);
1450
1451void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1452{
1453 c->minimum_buffers = n;
1454}
1455EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
1456
1457unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1458{
1459 return c->block_size;
1460}
1461EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1462
1463sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1464{
1465 sector_t s = i_size_read(c->bdev->bd_inode) >> SECTOR_SHIFT;
1466 if (likely(c->sectors_per_block_bits >= 0))
1467 s >>= c->sectors_per_block_bits;
1468 else
1469 sector_div(s, c->block_size >> SECTOR_SHIFT);
1470 return s;
1471}
1472EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1473
1474sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1475{
1476 return b->block;
1477}
1478EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1479
1480void *dm_bufio_get_block_data(struct dm_buffer *b)
1481{
1482 return b->data;
1483}
1484EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1485
1486void *dm_bufio_get_aux_data(struct dm_buffer *b)
1487{
1488 return b + 1;
1489}
1490EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1491
1492struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1493{
1494 return b->c;
1495}
1496EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1497
1498static void drop_buffers(struct dm_bufio_client *c)
1499{
1500 struct dm_buffer *b;
1501 int i;
1502 bool warned = false;
1503
1504 BUG_ON(dm_bufio_in_request());
1505
1506 /*
1507 * An optimization so that the buffers are not written one-by-one.
1508 */
1509 dm_bufio_write_dirty_buffers_async(c);
1510
1511 dm_bufio_lock(c);
1512
1513 while ((b = __get_unclaimed_buffer(c)))
1514 __free_buffer_wake(b);
1515
1516 for (i = 0; i < LIST_SIZE; i++)
1517 list_for_each_entry(b, &c->lru[i], lru_list) {
1518 WARN_ON(!warned);
1519 warned = true;
1520 DMERR("leaked buffer %llx, hold count %u, list %d",
1521 (unsigned long long)b->block, b->hold_count, i);
1522#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1523 print_stack_trace(&b->stack_trace, 1);
1524 b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */
1525#endif
1526 }
1527
1528#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1529 while ((b = __get_unclaimed_buffer(c)))
1530 __free_buffer_wake(b);
1531#endif
1532
1533 for (i = 0; i < LIST_SIZE; i++)
1534 BUG_ON(!list_empty(&c->lru[i]));
1535
1536 dm_bufio_unlock(c);
1537}
1538
1539/*
1540 * We may not be able to evict this buffer if IO pending or the client
1541 * is still using it. Caller is expected to know buffer is too old.
1542 *
1543 * And if GFP_NOFS is used, we must not do any I/O because we hold
1544 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1545 * rerouted to different bufio client.
1546 */
1547static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1548{
1549 if (!(gfp & __GFP_FS)) {
1550 if (test_bit(B_READING, &b->state) ||
1551 test_bit(B_WRITING, &b->state) ||
1552 test_bit(B_DIRTY, &b->state))
1553 return false;
1554 }
1555
1556 if (b->hold_count)
1557 return false;
1558
1559 __make_buffer_clean(b);
1560 __unlink_buffer(b);
1561 __free_buffer_wake(b);
1562
1563 return true;
1564}
1565
1566static unsigned long get_retain_buffers(struct dm_bufio_client *c)
1567{
1568 unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
1569 if (likely(c->sectors_per_block_bits >= 0))
1570 retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
1571 else
1572 retain_bytes /= c->block_size;
1573 return retain_bytes;
1574}
1575
1576static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1577 gfp_t gfp_mask)
1578{
1579 int l;
1580 struct dm_buffer *b, *tmp;
1581 unsigned long freed = 0;
1582 unsigned long count = c->n_buffers[LIST_CLEAN] +
1583 c->n_buffers[LIST_DIRTY];
1584 unsigned long retain_target = get_retain_buffers(c);
1585
1586 for (l = 0; l < LIST_SIZE; l++) {
1587 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1588 if (__try_evict_buffer(b, gfp_mask))
1589 freed++;
1590 if (!--nr_to_scan || ((count - freed) <= retain_target))
1591 return freed;
1592 cond_resched();
1593 }
1594 }
1595 return freed;
1596}
1597
1598static unsigned long
1599dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1600{
1601 struct dm_bufio_client *c;
1602 unsigned long freed;
1603
1604 c = container_of(shrink, struct dm_bufio_client, shrinker);
1605 if (sc->gfp_mask & __GFP_FS)
1606 dm_bufio_lock(c);
1607 else if (!dm_bufio_trylock(c))
1608 return SHRINK_STOP;
1609
1610 freed = __scan(c, sc->nr_to_scan, sc->gfp_mask);
1611 dm_bufio_unlock(c);
1612 return freed;
1613}
1614
1615static unsigned long
1616dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1617{
1618 struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
1619 unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) +
1620 READ_ONCE(c->n_buffers[LIST_DIRTY]);
1621 unsigned long retain_target = get_retain_buffers(c);
1622
1623 return (count < retain_target) ? 0 : (count - retain_target);
1624}
1625
1626/*
1627 * Create the buffering interface
1628 */
1629struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1630 unsigned reserved_buffers, unsigned aux_size,
1631 void (*alloc_callback)(struct dm_buffer *),
1632 void (*write_callback)(struct dm_buffer *))
1633{
1634 int r;
1635 struct dm_bufio_client *c;
1636 unsigned i;
1637 char slab_name[27];
1638
1639 if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
1640 DMERR("%s: block size not specified or is not multiple of 512b", __func__);
1641 r = -EINVAL;
1642 goto bad_client;
1643 }
1644
1645 c = kzalloc(sizeof(*c), GFP_KERNEL);
1646 if (!c) {
1647 r = -ENOMEM;
1648 goto bad_client;
1649 }
1650 c->buffer_tree = RB_ROOT;
1651
1652 c->bdev = bdev;
1653 c->block_size = block_size;
1654 if (is_power_of_2(block_size))
1655 c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1656 else
1657 c->sectors_per_block_bits = -1;
1658
1659 c->alloc_callback = alloc_callback;
1660 c->write_callback = write_callback;
1661
1662 for (i = 0; i < LIST_SIZE; i++) {
1663 INIT_LIST_HEAD(&c->lru[i]);
1664 c->n_buffers[i] = 0;
1665 }
1666
1667 mutex_init(&c->lock);
1668 INIT_LIST_HEAD(&c->reserved_buffers);
1669 c->need_reserved_buffers = reserved_buffers;
1670
1671 dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
1672
1673 init_waitqueue_head(&c->free_buffer_wait);
1674 c->async_write_error = 0;
1675
1676 c->dm_io = dm_io_client_create();
1677 if (IS_ERR(c->dm_io)) {
1678 r = PTR_ERR(c->dm_io);
1679 goto bad_dm_io;
1680 }
1681
1682 if (block_size <= KMALLOC_MAX_SIZE &&
1683 (block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
1684 unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE);
1685 snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size);
1686 c->slab_cache = kmem_cache_create(slab_name, block_size, align,
1687 SLAB_RECLAIM_ACCOUNT, NULL);
1688 if (!c->slab_cache) {
1689 r = -ENOMEM;
1690 goto bad;
1691 }
1692 }
1693 if (aux_size)
1694 snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer-%u", aux_size);
1695 else
1696 snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer");
1697 c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
1698 0, SLAB_RECLAIM_ACCOUNT, NULL);
1699 if (!c->slab_buffer) {
1700 r = -ENOMEM;
1701 goto bad;
1702 }
1703
1704 while (c->need_reserved_buffers) {
1705 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1706
1707 if (!b) {
1708 r = -ENOMEM;
1709 goto bad;
1710 }
1711 __free_buffer_wake(b);
1712 }
1713
1714 c->shrinker.count_objects = dm_bufio_shrink_count;
1715 c->shrinker.scan_objects = dm_bufio_shrink_scan;
1716 c->shrinker.seeks = 1;
1717 c->shrinker.batch = 0;
1718 r = register_shrinker(&c->shrinker);
1719 if (r)
1720 goto bad;
1721
1722 mutex_lock(&dm_bufio_clients_lock);
1723 dm_bufio_client_count++;
1724 list_add(&c->client_list, &dm_bufio_all_clients);
1725 __cache_size_refresh();
1726 mutex_unlock(&dm_bufio_clients_lock);
1727
1728 return c;
1729
1730bad:
1731 while (!list_empty(&c->reserved_buffers)) {
1732 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1733 struct dm_buffer, lru_list);
1734 list_del(&b->lru_list);
1735 free_buffer(b);
1736 }
1737 kmem_cache_destroy(c->slab_cache);
1738 kmem_cache_destroy(c->slab_buffer);
1739 dm_io_client_destroy(c->dm_io);
1740bad_dm_io:
1741 mutex_destroy(&c->lock);
1742 kfree(c);
1743bad_client:
1744 return ERR_PTR(r);
1745}
1746EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1747
1748/*
1749 * Free the buffering interface.
1750 * It is required that there are no references on any buffers.
1751 */
1752void dm_bufio_client_destroy(struct dm_bufio_client *c)
1753{
1754 unsigned i;
1755
1756 drop_buffers(c);
1757
1758 unregister_shrinker(&c->shrinker);
1759
1760 mutex_lock(&dm_bufio_clients_lock);
1761
1762 list_del(&c->client_list);
1763 dm_bufio_client_count--;
1764 __cache_size_refresh();
1765
1766 mutex_unlock(&dm_bufio_clients_lock);
1767
1768 BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1769 BUG_ON(c->need_reserved_buffers);
1770
1771 while (!list_empty(&c->reserved_buffers)) {
1772 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1773 struct dm_buffer, lru_list);
1774 list_del(&b->lru_list);
1775 free_buffer(b);
1776 }
1777
1778 for (i = 0; i < LIST_SIZE; i++)
1779 if (c->n_buffers[i])
1780 DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1781
1782 for (i = 0; i < LIST_SIZE; i++)
1783 BUG_ON(c->n_buffers[i]);
1784
1785 kmem_cache_destroy(c->slab_cache);
1786 kmem_cache_destroy(c->slab_buffer);
1787 dm_io_client_destroy(c->dm_io);
1788 mutex_destroy(&c->lock);
1789 kfree(c);
1790}
1791EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1792
1793void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
1794{
1795 c->start = start;
1796}
1797EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
1798
1799static unsigned get_max_age_hz(void)
1800{
1801 unsigned max_age = READ_ONCE(dm_bufio_max_age);
1802
1803 if (max_age > UINT_MAX / HZ)
1804 max_age = UINT_MAX / HZ;
1805
1806 return max_age * HZ;
1807}
1808
1809static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1810{
1811 return time_after_eq(jiffies, b->last_accessed + age_hz);
1812}
1813
1814static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1815{
1816 struct dm_buffer *b, *tmp;
1817 unsigned long retain_target = get_retain_buffers(c);
1818 unsigned long count;
1819 LIST_HEAD(write_list);
1820
1821 dm_bufio_lock(c);
1822
1823 __check_watermark(c, &write_list);
1824 if (unlikely(!list_empty(&write_list))) {
1825 dm_bufio_unlock(c);
1826 __flush_write_list(&write_list);
1827 dm_bufio_lock(c);
1828 }
1829
1830 count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1831 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1832 if (count <= retain_target)
1833 break;
1834
1835 if (!older_than(b, age_hz))
1836 break;
1837
1838 if (__try_evict_buffer(b, 0))
1839 count--;
1840
1841 cond_resched();
1842 }
1843
1844 dm_bufio_unlock(c);
1845}
1846
1847static void cleanup_old_buffers(void)
1848{
1849 unsigned long max_age_hz = get_max_age_hz();
1850 struct dm_bufio_client *c;
1851
1852 mutex_lock(&dm_bufio_clients_lock);
1853
1854 __cache_size_refresh();
1855
1856 list_for_each_entry(c, &dm_bufio_all_clients, client_list)
1857 __evict_old_buffers(c, max_age_hz);
1858
1859 mutex_unlock(&dm_bufio_clients_lock);
1860}
1861
1862static struct workqueue_struct *dm_bufio_wq;
1863static struct delayed_work dm_bufio_work;
1864
1865static void work_fn(struct work_struct *w)
1866{
1867 cleanup_old_buffers();
1868
1869 queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1870 DM_BUFIO_WORK_TIMER_SECS * HZ);
1871}
1872
1873/*----------------------------------------------------------------
1874 * Module setup
1875 *--------------------------------------------------------------*/
1876
1877/*
1878 * This is called only once for the whole dm_bufio module.
1879 * It initializes memory limit.
1880 */
1881static int __init dm_bufio_init(void)
1882{
1883 __u64 mem;
1884
1885 dm_bufio_allocated_kmem_cache = 0;
1886 dm_bufio_allocated_get_free_pages = 0;
1887 dm_bufio_allocated_vmalloc = 0;
1888 dm_bufio_current_allocated = 0;
1889
1890 mem = (__u64)mult_frac(totalram_pages - totalhigh_pages,
1891 DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
1892
1893 if (mem > ULONG_MAX)
1894 mem = ULONG_MAX;
1895
1896#ifdef CONFIG_MMU
1897 if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
1898 mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
1899#endif
1900
1901 dm_bufio_default_cache_size = mem;
1902
1903 mutex_lock(&dm_bufio_clients_lock);
1904 __cache_size_refresh();
1905 mutex_unlock(&dm_bufio_clients_lock);
1906
1907 dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
1908 if (!dm_bufio_wq)
1909 return -ENOMEM;
1910
1911 INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1912 queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1913 DM_BUFIO_WORK_TIMER_SECS * HZ);
1914
1915 return 0;
1916}
1917
1918/*
1919 * This is called once when unloading the dm_bufio module.
1920 */
1921static void __exit dm_bufio_exit(void)
1922{
1923 int bug = 0;
1924
1925 cancel_delayed_work_sync(&dm_bufio_work);
1926 destroy_workqueue(dm_bufio_wq);
1927
1928 if (dm_bufio_client_count) {
1929 DMCRIT("%s: dm_bufio_client_count leaked: %d",
1930 __func__, dm_bufio_client_count);
1931 bug = 1;
1932 }
1933
1934 if (dm_bufio_current_allocated) {
1935 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1936 __func__, dm_bufio_current_allocated);
1937 bug = 1;
1938 }
1939
1940 if (dm_bufio_allocated_get_free_pages) {
1941 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1942 __func__, dm_bufio_allocated_get_free_pages);
1943 bug = 1;
1944 }
1945
1946 if (dm_bufio_allocated_vmalloc) {
1947 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1948 __func__, dm_bufio_allocated_vmalloc);
1949 bug = 1;
1950 }
1951
1952 BUG_ON(bug);
1953}
1954
1955module_init(dm_bufio_init)
1956module_exit(dm_bufio_exit)
1957
1958module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1959MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1960
1961module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1962MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1963
1964module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
1965MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
1966
1967module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
1968MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
1969
1970module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
1971MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
1972
1973module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
1974MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
1975
1976module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
1977MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
1978
1979module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
1980MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
1981
1982MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
1983MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
1984MODULE_LICENSE("GPL");