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