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Mikulas Patocka95d402f2011-10-31 20:19:09 +00001/*
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/vmalloc.h>
Mikulas Patocka95d402f2011-10-31 20:19:09 +000015#include <linux/shrinker.h>
Stephen Rothwell6f662632011-11-01 18:30:49 +110016#include <linux/module.h>
Mikulas Patocka95d402f2011-10-31 20:19:09 +000017
18#define DM_MSG_PREFIX "bufio"
19
20/*
21 * Memory management policy:
22 * Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
23 * or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
24 * Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
25 * Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
26 * dirty buffers.
27 */
28#define DM_BUFIO_MIN_BUFFERS 8
29
30#define DM_BUFIO_MEMORY_PERCENT 2
31#define DM_BUFIO_VMALLOC_PERCENT 25
32#define DM_BUFIO_WRITEBACK_PERCENT 75
33
34/*
35 * Check buffer ages in this interval (seconds)
36 */
37#define DM_BUFIO_WORK_TIMER_SECS 10
38
39/*
40 * Free buffers when they are older than this (seconds)
41 */
42#define DM_BUFIO_DEFAULT_AGE_SECS 60
43
44/*
45 * The number of bvec entries that are embedded directly in the buffer.
46 * If the chunk size is larger, dm-io is used to do the io.
47 */
48#define DM_BUFIO_INLINE_VECS 16
49
50/*
51 * Buffer hash
52 */
53#define DM_BUFIO_HASH_BITS 20
54#define DM_BUFIO_HASH(block) \
55 ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
56 ((1 << DM_BUFIO_HASH_BITS) - 1))
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 struct hlist_head *cache_hash;
108 wait_queue_head_t free_buffer_wait;
109
110 int async_write_error;
111
112 struct list_head client_list;
113 struct shrinker shrinker;
114};
115
116/*
117 * Buffer state bits.
118 */
119#define B_READING 0
120#define B_WRITING 1
121#define B_DIRTY 2
122
123/*
124 * Describes how the block was allocated:
125 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
126 * See the comment at alloc_buffer_data.
127 */
128enum data_mode {
129 DATA_MODE_SLAB = 0,
130 DATA_MODE_GET_FREE_PAGES = 1,
131 DATA_MODE_VMALLOC = 2,
132 DATA_MODE_LIMIT = 3
133};
134
135struct dm_buffer {
136 struct hlist_node hash_list;
137 struct list_head lru_list;
138 sector_t block;
139 void *data;
140 enum data_mode data_mode;
141 unsigned char list_mode; /* LIST_* */
142 unsigned hold_count;
143 int read_error;
144 int write_error;
145 unsigned long state;
146 unsigned long last_accessed;
147 struct dm_bufio_client *c;
148 struct bio bio;
149 struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
150};
151
152/*----------------------------------------------------------------*/
153
154static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT];
155static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT];
156
157static inline int dm_bufio_cache_index(struct dm_bufio_client *c)
158{
159 unsigned ret = c->blocks_per_page_bits - 1;
160
161 BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches));
162
163 return ret;
164}
165
166#define DM_BUFIO_CACHE(c) (dm_bufio_caches[dm_bufio_cache_index(c)])
167#define DM_BUFIO_CACHE_NAME(c) (dm_bufio_cache_names[dm_bufio_cache_index(c)])
168
169#define dm_bufio_in_request() (!!current->bio_list)
170
171static void dm_bufio_lock(struct dm_bufio_client *c)
172{
173 mutex_lock_nested(&c->lock, dm_bufio_in_request());
174}
175
176static int dm_bufio_trylock(struct dm_bufio_client *c)
177{
178 return mutex_trylock(&c->lock);
179}
180
181static void dm_bufio_unlock(struct dm_bufio_client *c)
182{
183 mutex_unlock(&c->lock);
184}
185
186/*
187 * FIXME Move to sched.h?
188 */
189#ifdef CONFIG_PREEMPT_VOLUNTARY
190# define dm_bufio_cond_resched() \
191do { \
192 if (unlikely(need_resched())) \
193 _cond_resched(); \
194} while (0)
195#else
196# define dm_bufio_cond_resched() do { } while (0)
197#endif
198
199/*----------------------------------------------------------------*/
200
201/*
202 * Default cache size: available memory divided by the ratio.
203 */
204static unsigned long dm_bufio_default_cache_size;
205
206/*
207 * Total cache size set by the user.
208 */
209static unsigned long dm_bufio_cache_size;
210
211/*
212 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
213 * at any time. If it disagrees, the user has changed cache size.
214 */
215static unsigned long dm_bufio_cache_size_latch;
216
217static DEFINE_SPINLOCK(param_spinlock);
218
219/*
220 * Buffers are freed after this timeout
221 */
222static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
223
224static unsigned long dm_bufio_peak_allocated;
225static unsigned long dm_bufio_allocated_kmem_cache;
226static unsigned long dm_bufio_allocated_get_free_pages;
227static unsigned long dm_bufio_allocated_vmalloc;
228static unsigned long dm_bufio_current_allocated;
229
230/*----------------------------------------------------------------*/
231
232/*
233 * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
234 */
235static unsigned long dm_bufio_cache_size_per_client;
236
237/*
238 * The current number of clients.
239 */
240static int dm_bufio_client_count;
241
242/*
243 * The list of all clients.
244 */
245static LIST_HEAD(dm_bufio_all_clients);
246
247/*
248 * This mutex protects dm_bufio_cache_size_latch,
249 * dm_bufio_cache_size_per_client and dm_bufio_client_count
250 */
251static DEFINE_MUTEX(dm_bufio_clients_lock);
252
253/*----------------------------------------------------------------*/
254
255static void adjust_total_allocated(enum data_mode data_mode, long diff)
256{
257 static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
258 &dm_bufio_allocated_kmem_cache,
259 &dm_bufio_allocated_get_free_pages,
260 &dm_bufio_allocated_vmalloc,
261 };
262
263 spin_lock(&param_spinlock);
264
265 *class_ptr[data_mode] += diff;
266
267 dm_bufio_current_allocated += diff;
268
269 if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
270 dm_bufio_peak_allocated = dm_bufio_current_allocated;
271
272 spin_unlock(&param_spinlock);
273}
274
275/*
276 * Change the number of clients and recalculate per-client limit.
277 */
278static void __cache_size_refresh(void)
279{
280 BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
281 BUG_ON(dm_bufio_client_count < 0);
282
Mikulas Patockafe5fe902012-10-12 16:59:46 +0100283 dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000284
285 /*
286 * Use default if set to 0 and report the actual cache size used.
287 */
288 if (!dm_bufio_cache_size_latch) {
289 (void)cmpxchg(&dm_bufio_cache_size, 0,
290 dm_bufio_default_cache_size);
291 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
292 }
293
294 dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
295 (dm_bufio_client_count ? : 1);
296}
297
298/*
299 * Allocating buffer data.
300 *
301 * Small buffers are allocated with kmem_cache, to use space optimally.
302 *
303 * For large buffers, we choose between get_free_pages and vmalloc.
304 * Each has advantages and disadvantages.
305 *
306 * __get_free_pages can randomly fail if the memory is fragmented.
307 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
308 * as low as 128M) so using it for caching is not appropriate.
309 *
310 * If the allocation may fail we use __get_free_pages. Memory fragmentation
311 * won't have a fatal effect here, but it just causes flushes of some other
312 * buffers and more I/O will be performed. Don't use __get_free_pages if it
313 * always fails (i.e. order >= MAX_ORDER).
314 *
315 * If the allocation shouldn't fail we use __vmalloc. This is only for the
316 * initial reserve allocation, so there's no risk of wasting all vmalloc
317 * space.
318 */
319static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
320 enum data_mode *data_mode)
321{
322 if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {
323 *data_mode = DATA_MODE_SLAB;
324 return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
325 }
326
327 if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT &&
328 gfp_mask & __GFP_NORETRY) {
329 *data_mode = DATA_MODE_GET_FREE_PAGES;
330 return (void *)__get_free_pages(gfp_mask,
331 c->pages_per_block_bits);
332 }
333
334 *data_mode = DATA_MODE_VMALLOC;
335 return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
336}
337
338/*
339 * Free buffer's data.
340 */
341static void free_buffer_data(struct dm_bufio_client *c,
342 void *data, enum data_mode data_mode)
343{
344 switch (data_mode) {
345 case DATA_MODE_SLAB:
346 kmem_cache_free(DM_BUFIO_CACHE(c), data);
347 break;
348
349 case DATA_MODE_GET_FREE_PAGES:
350 free_pages((unsigned long)data, c->pages_per_block_bits);
351 break;
352
353 case DATA_MODE_VMALLOC:
354 vfree(data);
355 break;
356
357 default:
358 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
359 data_mode);
360 BUG();
361 }
362}
363
364/*
365 * Allocate buffer and its data.
366 */
367static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
368{
369 struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size,
370 gfp_mask);
371
372 if (!b)
373 return NULL;
374
375 b->c = c;
376
377 b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
378 if (!b->data) {
379 kfree(b);
380 return NULL;
381 }
382
383 adjust_total_allocated(b->data_mode, (long)c->block_size);
384
385 return b;
386}
387
388/*
389 * Free buffer and its data.
390 */
391static void free_buffer(struct dm_buffer *b)
392{
393 struct dm_bufio_client *c = b->c;
394
395 adjust_total_allocated(b->data_mode, -(long)c->block_size);
396
397 free_buffer_data(c, b->data, b->data_mode);
398 kfree(b);
399}
400
401/*
402 * Link buffer to the hash list and clean or dirty queue.
403 */
404static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
405{
406 struct dm_bufio_client *c = b->c;
407
408 c->n_buffers[dirty]++;
409 b->block = block;
410 b->list_mode = dirty;
411 list_add(&b->lru_list, &c->lru[dirty]);
412 hlist_add_head(&b->hash_list, &c->cache_hash[DM_BUFIO_HASH(block)]);
413 b->last_accessed = jiffies;
414}
415
416/*
417 * Unlink buffer from the hash list and dirty or clean queue.
418 */
419static void __unlink_buffer(struct dm_buffer *b)
420{
421 struct dm_bufio_client *c = b->c;
422
423 BUG_ON(!c->n_buffers[b->list_mode]);
424
425 c->n_buffers[b->list_mode]--;
426 hlist_del(&b->hash_list);
427 list_del(&b->lru_list);
428}
429
430/*
431 * Place the buffer to the head of dirty or clean LRU queue.
432 */
433static void __relink_lru(struct dm_buffer *b, int dirty)
434{
435 struct dm_bufio_client *c = b->c;
436
437 BUG_ON(!c->n_buffers[b->list_mode]);
438
439 c->n_buffers[b->list_mode]--;
440 c->n_buffers[dirty]++;
441 b->list_mode = dirty;
Wei Yongjun54499af2012-10-12 16:59:44 +0100442 list_move(&b->lru_list, &c->lru[dirty]);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000443}
444
445/*----------------------------------------------------------------
446 * Submit I/O on the buffer.
447 *
448 * Bio interface is faster but it has some problems:
449 * the vector list is limited (increasing this limit increases
450 * memory-consumption per buffer, so it is not viable);
451 *
452 * the memory must be direct-mapped, not vmalloced;
453 *
454 * the I/O driver can reject requests spuriously if it thinks that
455 * the requests are too big for the device or if they cross a
456 * controller-defined memory boundary.
457 *
458 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
459 * it is not vmalloced, try using the bio interface.
460 *
461 * If the buffer is big, if it is vmalloced or if the underlying device
462 * rejects the bio because it is too large, use dm-io layer to do the I/O.
463 * The dm-io layer splits the I/O into multiple requests, avoiding the above
464 * shortcomings.
465 *--------------------------------------------------------------*/
466
467/*
468 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
469 * that the request was handled directly with bio interface.
470 */
471static void dmio_complete(unsigned long error, void *context)
472{
473 struct dm_buffer *b = context;
474
475 b->bio.bi_end_io(&b->bio, error ? -EIO : 0);
476}
477
478static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
479 bio_end_io_t *end_io)
480{
481 int r;
482 struct dm_io_request io_req = {
483 .bi_rw = rw,
484 .notify.fn = dmio_complete,
485 .notify.context = b,
486 .client = b->c->dm_io,
487 };
488 struct dm_io_region region = {
489 .bdev = b->c->bdev,
490 .sector = block << b->c->sectors_per_block_bits,
491 .count = b->c->block_size >> SECTOR_SHIFT,
492 };
493
494 if (b->data_mode != DATA_MODE_VMALLOC) {
495 io_req.mem.type = DM_IO_KMEM;
496 io_req.mem.ptr.addr = b->data;
497 } else {
498 io_req.mem.type = DM_IO_VMA;
499 io_req.mem.ptr.vma = b->data;
500 }
501
502 b->bio.bi_end_io = end_io;
503
504 r = dm_io(&io_req, 1, &region, NULL);
505 if (r)
506 end_io(&b->bio, r);
507}
508
509static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
510 bio_end_io_t *end_io)
511{
512 char *ptr;
513 int len;
514
515 bio_init(&b->bio);
516 b->bio.bi_io_vec = b->bio_vec;
517 b->bio.bi_max_vecs = DM_BUFIO_INLINE_VECS;
518 b->bio.bi_sector = block << b->c->sectors_per_block_bits;
519 b->bio.bi_bdev = b->c->bdev;
520 b->bio.bi_end_io = end_io;
521
522 /*
523 * We assume that if len >= PAGE_SIZE ptr is page-aligned.
524 * If len < PAGE_SIZE the buffer doesn't cross page boundary.
525 */
526 ptr = b->data;
527 len = b->c->block_size;
528
529 if (len >= PAGE_SIZE)
530 BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1));
531 else
532 BUG_ON((unsigned long)ptr & (len - 1));
533
534 do {
535 if (!bio_add_page(&b->bio, virt_to_page(ptr),
536 len < PAGE_SIZE ? len : PAGE_SIZE,
537 virt_to_phys(ptr) & (PAGE_SIZE - 1))) {
538 BUG_ON(b->c->block_size <= PAGE_SIZE);
539 use_dmio(b, rw, block, end_io);
540 return;
541 }
542
543 len -= PAGE_SIZE;
544 ptr += PAGE_SIZE;
545 } while (len > 0);
546
547 submit_bio(rw, &b->bio);
548}
549
550static void submit_io(struct dm_buffer *b, int rw, sector_t block,
551 bio_end_io_t *end_io)
552{
553 if (rw == WRITE && b->c->write_callback)
554 b->c->write_callback(b);
555
556 if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE &&
557 b->data_mode != DATA_MODE_VMALLOC)
558 use_inline_bio(b, rw, block, end_io);
559 else
560 use_dmio(b, rw, block, end_io);
561}
562
563/*----------------------------------------------------------------
564 * Writing dirty buffers
565 *--------------------------------------------------------------*/
566
567/*
568 * The endio routine for write.
569 *
570 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
571 * it.
572 */
573static void write_endio(struct bio *bio, int error)
574{
575 struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
576
577 b->write_error = error;
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100578 if (unlikely(error)) {
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000579 struct dm_bufio_client *c = b->c;
580 (void)cmpxchg(&c->async_write_error, 0, error);
581 }
582
583 BUG_ON(!test_bit(B_WRITING, &b->state));
584
585 smp_mb__before_clear_bit();
586 clear_bit(B_WRITING, &b->state);
587 smp_mb__after_clear_bit();
588
589 wake_up_bit(&b->state, B_WRITING);
590}
591
592/*
593 * This function is called when wait_on_bit is actually waiting.
594 */
595static int do_io_schedule(void *word)
596{
597 io_schedule();
598
599 return 0;
600}
601
602/*
603 * Initiate a write on a dirty buffer, but don't wait for it.
604 *
605 * - If the buffer is not dirty, exit.
606 * - If there some previous write going on, wait for it to finish (we can't
607 * have two writes on the same buffer simultaneously).
608 * - Submit our write and don't wait on it. We set B_WRITING indicating
609 * that there is a write in progress.
610 */
611static void __write_dirty_buffer(struct dm_buffer *b)
612{
613 if (!test_bit(B_DIRTY, &b->state))
614 return;
615
616 clear_bit(B_DIRTY, &b->state);
617 wait_on_bit_lock(&b->state, B_WRITING,
618 do_io_schedule, TASK_UNINTERRUPTIBLE);
619
620 submit_io(b, WRITE, b->block, write_endio);
621}
622
623/*
624 * Wait until any activity on the buffer finishes. Possibly write the
625 * buffer if it is dirty. When this function finishes, there is no I/O
626 * running on the buffer and the buffer is not dirty.
627 */
628static void __make_buffer_clean(struct dm_buffer *b)
629{
630 BUG_ON(b->hold_count);
631
632 if (!b->state) /* fast case */
633 return;
634
635 wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
636 __write_dirty_buffer(b);
637 wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE);
638}
639
640/*
641 * Find some buffer that is not held by anybody, clean it, unlink it and
642 * return it.
643 */
644static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
645{
646 struct dm_buffer *b;
647
648 list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
649 BUG_ON(test_bit(B_WRITING, &b->state));
650 BUG_ON(test_bit(B_DIRTY, &b->state));
651
652 if (!b->hold_count) {
653 __make_buffer_clean(b);
654 __unlink_buffer(b);
655 return b;
656 }
657 dm_bufio_cond_resched();
658 }
659
660 list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
661 BUG_ON(test_bit(B_READING, &b->state));
662
663 if (!b->hold_count) {
664 __make_buffer_clean(b);
665 __unlink_buffer(b);
666 return b;
667 }
668 dm_bufio_cond_resched();
669 }
670
671 return NULL;
672}
673
674/*
675 * Wait until some other threads free some buffer or release hold count on
676 * some buffer.
677 *
678 * This function is entered with c->lock held, drops it and regains it
679 * before exiting.
680 */
681static void __wait_for_free_buffer(struct dm_bufio_client *c)
682{
683 DECLARE_WAITQUEUE(wait, current);
684
685 add_wait_queue(&c->free_buffer_wait, &wait);
686 set_task_state(current, TASK_UNINTERRUPTIBLE);
687 dm_bufio_unlock(c);
688
689 io_schedule();
690
691 set_task_state(current, TASK_RUNNING);
692 remove_wait_queue(&c->free_buffer_wait, &wait);
693
694 dm_bufio_lock(c);
695}
696
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100697enum new_flag {
698 NF_FRESH = 0,
699 NF_READ = 1,
700 NF_GET = 2,
701 NF_PREFETCH = 3
702};
703
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000704/*
705 * Allocate a new buffer. If the allocation is not possible, wait until
706 * some other thread frees a buffer.
707 *
708 * May drop the lock and regain it.
709 */
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100710static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000711{
712 struct dm_buffer *b;
713
714 /*
715 * dm-bufio is resistant to allocation failures (it just keeps
716 * one buffer reserved in cases all the allocations fail).
717 * So set flags to not try too hard:
718 * GFP_NOIO: don't recurse into the I/O layer
719 * __GFP_NORETRY: don't retry and rather return failure
720 * __GFP_NOMEMALLOC: don't use emergency reserves
721 * __GFP_NOWARN: don't print a warning in case of failure
722 *
723 * For debugging, if we set the cache size to 1, no new buffers will
724 * be allocated.
725 */
726 while (1) {
727 if (dm_bufio_cache_size_latch != 1) {
728 b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
729 if (b)
730 return b;
731 }
732
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100733 if (nf == NF_PREFETCH)
734 return NULL;
735
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000736 if (!list_empty(&c->reserved_buffers)) {
737 b = list_entry(c->reserved_buffers.next,
738 struct dm_buffer, lru_list);
739 list_del(&b->lru_list);
740 c->need_reserved_buffers++;
741
742 return b;
743 }
744
745 b = __get_unclaimed_buffer(c);
746 if (b)
747 return b;
748
749 __wait_for_free_buffer(c);
750 }
751}
752
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100753static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000754{
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100755 struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
756
757 if (!b)
758 return NULL;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000759
760 if (c->alloc_callback)
761 c->alloc_callback(b);
762
763 return b;
764}
765
766/*
767 * Free a buffer and wake other threads waiting for free buffers.
768 */
769static void __free_buffer_wake(struct dm_buffer *b)
770{
771 struct dm_bufio_client *c = b->c;
772
773 if (!c->need_reserved_buffers)
774 free_buffer(b);
775 else {
776 list_add(&b->lru_list, &c->reserved_buffers);
777 c->need_reserved_buffers--;
778 }
779
780 wake_up(&c->free_buffer_wait);
781}
782
783static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait)
784{
785 struct dm_buffer *b, *tmp;
786
787 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
788 BUG_ON(test_bit(B_READING, &b->state));
789
790 if (!test_bit(B_DIRTY, &b->state) &&
791 !test_bit(B_WRITING, &b->state)) {
792 __relink_lru(b, LIST_CLEAN);
793 continue;
794 }
795
796 if (no_wait && test_bit(B_WRITING, &b->state))
797 return;
798
799 __write_dirty_buffer(b);
800 dm_bufio_cond_resched();
801 }
802}
803
804/*
805 * Get writeback threshold and buffer limit for a given client.
806 */
807static void __get_memory_limit(struct dm_bufio_client *c,
808 unsigned long *threshold_buffers,
809 unsigned long *limit_buffers)
810{
811 unsigned long buffers;
812
Mikulas Patockafe5fe902012-10-12 16:59:46 +0100813 if (ACCESS_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch) {
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000814 mutex_lock(&dm_bufio_clients_lock);
815 __cache_size_refresh();
816 mutex_unlock(&dm_bufio_clients_lock);
817 }
818
819 buffers = dm_bufio_cache_size_per_client >>
820 (c->sectors_per_block_bits + SECTOR_SHIFT);
821
822 if (buffers < DM_BUFIO_MIN_BUFFERS)
823 buffers = DM_BUFIO_MIN_BUFFERS;
824
825 *limit_buffers = buffers;
826 *threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100;
827}
828
829/*
830 * Check if we're over watermark.
831 * If we are over threshold_buffers, start freeing buffers.
832 * If we're over "limit_buffers", block until we get under the limit.
833 */
834static void __check_watermark(struct dm_bufio_client *c)
835{
836 unsigned long threshold_buffers, limit_buffers;
837
838 __get_memory_limit(c, &threshold_buffers, &limit_buffers);
839
840 while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
841 limit_buffers) {
842
843 struct dm_buffer *b = __get_unclaimed_buffer(c);
844
845 if (!b)
846 return;
847
848 __free_buffer_wake(b);
849 dm_bufio_cond_resched();
850 }
851
852 if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
853 __write_dirty_buffers_async(c, 1);
854}
855
856/*
857 * Find a buffer in the hash.
858 */
859static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
860{
861 struct dm_buffer *b;
862 struct hlist_node *hn;
863
864 hlist_for_each_entry(b, hn, &c->cache_hash[DM_BUFIO_HASH(block)],
865 hash_list) {
866 dm_bufio_cond_resched();
867 if (b->block == block)
868 return b;
869 }
870
871 return NULL;
872}
873
874/*----------------------------------------------------------------
875 * Getting a buffer
876 *--------------------------------------------------------------*/
877
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000878static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100879 enum new_flag nf, int *need_submit)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000880{
881 struct dm_buffer *b, *new_b = NULL;
882
883 *need_submit = 0;
884
885 b = __find(c, block);
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100886 if (b)
887 goto found_buffer;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000888
889 if (nf == NF_GET)
890 return NULL;
891
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100892 new_b = __alloc_buffer_wait(c, nf);
893 if (!new_b)
894 return NULL;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000895
896 /*
897 * We've had a period where the mutex was unlocked, so need to
898 * recheck the hash table.
899 */
900 b = __find(c, block);
901 if (b) {
902 __free_buffer_wake(new_b);
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100903 goto found_buffer;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000904 }
905
906 __check_watermark(c);
907
908 b = new_b;
909 b->hold_count = 1;
910 b->read_error = 0;
911 b->write_error = 0;
912 __link_buffer(b, block, LIST_CLEAN);
913
914 if (nf == NF_FRESH) {
915 b->state = 0;
916 return b;
917 }
918
919 b->state = 1 << B_READING;
920 *need_submit = 1;
921
922 return b;
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100923
924found_buffer:
925 if (nf == NF_PREFETCH)
926 return NULL;
927 /*
928 * Note: it is essential that we don't wait for the buffer to be
929 * read if dm_bufio_get function is used. Both dm_bufio_get and
930 * dm_bufio_prefetch can be used in the driver request routine.
931 * If the user called both dm_bufio_prefetch and dm_bufio_get on
932 * the same buffer, it would deadlock if we waited.
933 */
934 if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
935 return NULL;
936
937 b->hold_count++;
938 __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
939 test_bit(B_WRITING, &b->state));
940 return b;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000941}
942
943/*
944 * The endio routine for reading: set the error, clear the bit and wake up
945 * anyone waiting on the buffer.
946 */
947static void read_endio(struct bio *bio, int error)
948{
949 struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
950
951 b->read_error = error;
952
953 BUG_ON(!test_bit(B_READING, &b->state));
954
955 smp_mb__before_clear_bit();
956 clear_bit(B_READING, &b->state);
957 smp_mb__after_clear_bit();
958
959 wake_up_bit(&b->state, B_READING);
960}
961
962/*
963 * A common routine for dm_bufio_new and dm_bufio_read. Operation of these
964 * functions is similar except that dm_bufio_new doesn't read the
965 * buffer from the disk (assuming that the caller overwrites all the data
966 * and uses dm_bufio_mark_buffer_dirty to write new data back).
967 */
968static void *new_read(struct dm_bufio_client *c, sector_t block,
969 enum new_flag nf, struct dm_buffer **bp)
970{
971 int need_submit;
972 struct dm_buffer *b;
973
974 dm_bufio_lock(c);
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100975 b = __bufio_new(c, block, nf, &need_submit);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000976 dm_bufio_unlock(c);
977
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100978 if (!b)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000979 return b;
980
981 if (need_submit)
982 submit_io(b, READ, b->block, read_endio);
983
984 wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
985
986 if (b->read_error) {
987 int error = b->read_error;
988
989 dm_bufio_release(b);
990
991 return ERR_PTR(error);
992 }
993
994 *bp = b;
995
996 return b->data;
997}
998
999void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1000 struct dm_buffer **bp)
1001{
1002 return new_read(c, block, NF_GET, bp);
1003}
1004EXPORT_SYMBOL_GPL(dm_bufio_get);
1005
1006void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1007 struct dm_buffer **bp)
1008{
1009 BUG_ON(dm_bufio_in_request());
1010
1011 return new_read(c, block, NF_READ, bp);
1012}
1013EXPORT_SYMBOL_GPL(dm_bufio_read);
1014
1015void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1016 struct dm_buffer **bp)
1017{
1018 BUG_ON(dm_bufio_in_request());
1019
1020 return new_read(c, block, NF_FRESH, bp);
1021}
1022EXPORT_SYMBOL_GPL(dm_bufio_new);
1023
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001024void dm_bufio_prefetch(struct dm_bufio_client *c,
1025 sector_t block, unsigned n_blocks)
1026{
1027 struct blk_plug plug;
1028
1029 blk_start_plug(&plug);
1030 dm_bufio_lock(c);
1031
1032 for (; n_blocks--; block++) {
1033 int need_submit;
1034 struct dm_buffer *b;
1035 b = __bufio_new(c, block, NF_PREFETCH, &need_submit);
1036 if (unlikely(b != NULL)) {
1037 dm_bufio_unlock(c);
1038
1039 if (need_submit)
1040 submit_io(b, READ, b->block, read_endio);
1041 dm_bufio_release(b);
1042
1043 dm_bufio_cond_resched();
1044
1045 if (!n_blocks)
1046 goto flush_plug;
1047 dm_bufio_lock(c);
1048 }
1049
1050 }
1051
1052 dm_bufio_unlock(c);
1053
1054flush_plug:
1055 blk_finish_plug(&plug);
1056}
1057EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1058
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001059void dm_bufio_release(struct dm_buffer *b)
1060{
1061 struct dm_bufio_client *c = b->c;
1062
1063 dm_bufio_lock(c);
1064
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001065 BUG_ON(!b->hold_count);
1066
1067 b->hold_count--;
1068 if (!b->hold_count) {
1069 wake_up(&c->free_buffer_wait);
1070
1071 /*
1072 * If there were errors on the buffer, and the buffer is not
1073 * to be written, free the buffer. There is no point in caching
1074 * invalid buffer.
1075 */
1076 if ((b->read_error || b->write_error) &&
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001077 !test_bit(B_READING, &b->state) &&
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001078 !test_bit(B_WRITING, &b->state) &&
1079 !test_bit(B_DIRTY, &b->state)) {
1080 __unlink_buffer(b);
1081 __free_buffer_wake(b);
1082 }
1083 }
1084
1085 dm_bufio_unlock(c);
1086}
1087EXPORT_SYMBOL_GPL(dm_bufio_release);
1088
1089void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1090{
1091 struct dm_bufio_client *c = b->c;
1092
1093 dm_bufio_lock(c);
1094
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001095 BUG_ON(test_bit(B_READING, &b->state));
1096
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001097 if (!test_and_set_bit(B_DIRTY, &b->state))
1098 __relink_lru(b, LIST_DIRTY);
1099
1100 dm_bufio_unlock(c);
1101}
1102EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1103
1104void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1105{
1106 BUG_ON(dm_bufio_in_request());
1107
1108 dm_bufio_lock(c);
1109 __write_dirty_buffers_async(c, 0);
1110 dm_bufio_unlock(c);
1111}
1112EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1113
1114/*
1115 * For performance, it is essential that the buffers are written asynchronously
1116 * and simultaneously (so that the block layer can merge the writes) and then
1117 * waited upon.
1118 *
1119 * Finally, we flush hardware disk cache.
1120 */
1121int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1122{
1123 int a, f;
1124 unsigned long buffers_processed = 0;
1125 struct dm_buffer *b, *tmp;
1126
1127 dm_bufio_lock(c);
1128 __write_dirty_buffers_async(c, 0);
1129
1130again:
1131 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1132 int dropped_lock = 0;
1133
1134 if (buffers_processed < c->n_buffers[LIST_DIRTY])
1135 buffers_processed++;
1136
1137 BUG_ON(test_bit(B_READING, &b->state));
1138
1139 if (test_bit(B_WRITING, &b->state)) {
1140 if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1141 dropped_lock = 1;
1142 b->hold_count++;
1143 dm_bufio_unlock(c);
1144 wait_on_bit(&b->state, B_WRITING,
1145 do_io_schedule,
1146 TASK_UNINTERRUPTIBLE);
1147 dm_bufio_lock(c);
1148 b->hold_count--;
1149 } else
1150 wait_on_bit(&b->state, B_WRITING,
1151 do_io_schedule,
1152 TASK_UNINTERRUPTIBLE);
1153 }
1154
1155 if (!test_bit(B_DIRTY, &b->state) &&
1156 !test_bit(B_WRITING, &b->state))
1157 __relink_lru(b, LIST_CLEAN);
1158
1159 dm_bufio_cond_resched();
1160
1161 /*
1162 * If we dropped the lock, the list is no longer consistent,
1163 * so we must restart the search.
1164 *
1165 * In the most common case, the buffer just processed is
1166 * relinked to the clean list, so we won't loop scanning the
1167 * same buffer again and again.
1168 *
1169 * This may livelock if there is another thread simultaneously
1170 * dirtying buffers, so we count the number of buffers walked
1171 * and if it exceeds the total number of buffers, it means that
1172 * someone is doing some writes simultaneously with us. In
1173 * this case, stop, dropping the lock.
1174 */
1175 if (dropped_lock)
1176 goto again;
1177 }
1178 wake_up(&c->free_buffer_wait);
1179 dm_bufio_unlock(c);
1180
1181 a = xchg(&c->async_write_error, 0);
1182 f = dm_bufio_issue_flush(c);
1183 if (a)
1184 return a;
1185
1186 return f;
1187}
1188EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1189
1190/*
1191 * Use dm-io to send and empty barrier flush the device.
1192 */
1193int dm_bufio_issue_flush(struct dm_bufio_client *c)
1194{
1195 struct dm_io_request io_req = {
1196 .bi_rw = REQ_FLUSH,
1197 .mem.type = DM_IO_KMEM,
1198 .mem.ptr.addr = NULL,
1199 .client = c->dm_io,
1200 };
1201 struct dm_io_region io_reg = {
1202 .bdev = c->bdev,
1203 .sector = 0,
1204 .count = 0,
1205 };
1206
1207 BUG_ON(dm_bufio_in_request());
1208
1209 return dm_io(&io_req, 1, &io_reg, NULL);
1210}
1211EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1212
1213/*
1214 * We first delete any other buffer that may be at that new location.
1215 *
1216 * Then, we write the buffer to the original location if it was dirty.
1217 *
1218 * Then, if we are the only one who is holding the buffer, relink the buffer
1219 * in the hash queue for the new location.
1220 *
1221 * If there was someone else holding the buffer, we write it to the new
1222 * location but not relink it, because that other user needs to have the buffer
1223 * at the same place.
1224 */
1225void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1226{
1227 struct dm_bufio_client *c = b->c;
1228 struct dm_buffer *new;
1229
1230 BUG_ON(dm_bufio_in_request());
1231
1232 dm_bufio_lock(c);
1233
1234retry:
1235 new = __find(c, new_block);
1236 if (new) {
1237 if (new->hold_count) {
1238 __wait_for_free_buffer(c);
1239 goto retry;
1240 }
1241
1242 /*
1243 * FIXME: Is there any point waiting for a write that's going
1244 * to be overwritten in a bit?
1245 */
1246 __make_buffer_clean(new);
1247 __unlink_buffer(new);
1248 __free_buffer_wake(new);
1249 }
1250
1251 BUG_ON(!b->hold_count);
1252 BUG_ON(test_bit(B_READING, &b->state));
1253
1254 __write_dirty_buffer(b);
1255 if (b->hold_count == 1) {
1256 wait_on_bit(&b->state, B_WRITING,
1257 do_io_schedule, TASK_UNINTERRUPTIBLE);
1258 set_bit(B_DIRTY, &b->state);
1259 __unlink_buffer(b);
1260 __link_buffer(b, new_block, LIST_DIRTY);
1261 } else {
1262 sector_t old_block;
1263 wait_on_bit_lock(&b->state, B_WRITING,
1264 do_io_schedule, TASK_UNINTERRUPTIBLE);
1265 /*
1266 * Relink buffer to "new_block" so that write_callback
1267 * sees "new_block" as a block number.
1268 * After the write, link the buffer back to old_block.
1269 * All this must be done in bufio lock, so that block number
1270 * change isn't visible to other threads.
1271 */
1272 old_block = b->block;
1273 __unlink_buffer(b);
1274 __link_buffer(b, new_block, b->list_mode);
1275 submit_io(b, WRITE, new_block, write_endio);
1276 wait_on_bit(&b->state, B_WRITING,
1277 do_io_schedule, TASK_UNINTERRUPTIBLE);
1278 __unlink_buffer(b);
1279 __link_buffer(b, old_block, b->list_mode);
1280 }
1281
1282 dm_bufio_unlock(c);
1283 dm_bufio_release(b);
1284}
1285EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1286
1287unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1288{
1289 return c->block_size;
1290}
1291EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1292
1293sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1294{
1295 return i_size_read(c->bdev->bd_inode) >>
1296 (SECTOR_SHIFT + c->sectors_per_block_bits);
1297}
1298EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1299
1300sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1301{
1302 return b->block;
1303}
1304EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1305
1306void *dm_bufio_get_block_data(struct dm_buffer *b)
1307{
1308 return b->data;
1309}
1310EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1311
1312void *dm_bufio_get_aux_data(struct dm_buffer *b)
1313{
1314 return b + 1;
1315}
1316EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1317
1318struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1319{
1320 return b->c;
1321}
1322EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1323
1324static void drop_buffers(struct dm_bufio_client *c)
1325{
1326 struct dm_buffer *b;
1327 int i;
1328
1329 BUG_ON(dm_bufio_in_request());
1330
1331 /*
1332 * An optimization so that the buffers are not written one-by-one.
1333 */
1334 dm_bufio_write_dirty_buffers_async(c);
1335
1336 dm_bufio_lock(c);
1337
1338 while ((b = __get_unclaimed_buffer(c)))
1339 __free_buffer_wake(b);
1340
1341 for (i = 0; i < LIST_SIZE; i++)
1342 list_for_each_entry(b, &c->lru[i], lru_list)
1343 DMERR("leaked buffer %llx, hold count %u, list %d",
1344 (unsigned long long)b->block, b->hold_count, i);
1345
1346 for (i = 0; i < LIST_SIZE; i++)
1347 BUG_ON(!list_empty(&c->lru[i]));
1348
1349 dm_bufio_unlock(c);
1350}
1351
1352/*
1353 * Test if the buffer is unused and too old, and commit it.
1354 * At if noio is set, we must not do any I/O because we hold
1355 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets rerouted to
1356 * different bufio client.
1357 */
1358static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp,
1359 unsigned long max_jiffies)
1360{
1361 if (jiffies - b->last_accessed < max_jiffies)
1362 return 1;
1363
1364 if (!(gfp & __GFP_IO)) {
1365 if (test_bit(B_READING, &b->state) ||
1366 test_bit(B_WRITING, &b->state) ||
1367 test_bit(B_DIRTY, &b->state))
1368 return 1;
1369 }
1370
1371 if (b->hold_count)
1372 return 1;
1373
1374 __make_buffer_clean(b);
1375 __unlink_buffer(b);
1376 __free_buffer_wake(b);
1377
1378 return 0;
1379}
1380
1381static void __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1382 struct shrink_control *sc)
1383{
1384 int l;
1385 struct dm_buffer *b, *tmp;
1386
1387 for (l = 0; l < LIST_SIZE; l++) {
1388 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list)
1389 if (!__cleanup_old_buffer(b, sc->gfp_mask, 0) &&
1390 !--nr_to_scan)
1391 return;
1392 dm_bufio_cond_resched();
1393 }
1394}
1395
1396static int shrink(struct shrinker *shrinker, struct shrink_control *sc)
1397{
1398 struct dm_bufio_client *c =
1399 container_of(shrinker, struct dm_bufio_client, shrinker);
1400 unsigned long r;
1401 unsigned long nr_to_scan = sc->nr_to_scan;
1402
1403 if (sc->gfp_mask & __GFP_IO)
1404 dm_bufio_lock(c);
1405 else if (!dm_bufio_trylock(c))
1406 return !nr_to_scan ? 0 : -1;
1407
1408 if (nr_to_scan)
1409 __scan(c, nr_to_scan, sc);
1410
1411 r = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1412 if (r > INT_MAX)
1413 r = INT_MAX;
1414
1415 dm_bufio_unlock(c);
1416
1417 return r;
1418}
1419
1420/*
1421 * Create the buffering interface
1422 */
1423struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1424 unsigned reserved_buffers, unsigned aux_size,
1425 void (*alloc_callback)(struct dm_buffer *),
1426 void (*write_callback)(struct dm_buffer *))
1427{
1428 int r;
1429 struct dm_bufio_client *c;
1430 unsigned i;
1431
1432 BUG_ON(block_size < 1 << SECTOR_SHIFT ||
1433 (block_size & (block_size - 1)));
1434
1435 c = kmalloc(sizeof(*c), GFP_KERNEL);
1436 if (!c) {
1437 r = -ENOMEM;
1438 goto bad_client;
1439 }
1440 c->cache_hash = vmalloc(sizeof(struct hlist_head) << DM_BUFIO_HASH_BITS);
1441 if (!c->cache_hash) {
1442 r = -ENOMEM;
1443 goto bad_hash;
1444 }
1445
1446 c->bdev = bdev;
1447 c->block_size = block_size;
1448 c->sectors_per_block_bits = ffs(block_size) - 1 - SECTOR_SHIFT;
1449 c->pages_per_block_bits = (ffs(block_size) - 1 >= PAGE_SHIFT) ?
1450 ffs(block_size) - 1 - PAGE_SHIFT : 0;
1451 c->blocks_per_page_bits = (ffs(block_size) - 1 < PAGE_SHIFT ?
1452 PAGE_SHIFT - (ffs(block_size) - 1) : 0);
1453
1454 c->aux_size = aux_size;
1455 c->alloc_callback = alloc_callback;
1456 c->write_callback = write_callback;
1457
1458 for (i = 0; i < LIST_SIZE; i++) {
1459 INIT_LIST_HEAD(&c->lru[i]);
1460 c->n_buffers[i] = 0;
1461 }
1462
1463 for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
1464 INIT_HLIST_HEAD(&c->cache_hash[i]);
1465
1466 mutex_init(&c->lock);
1467 INIT_LIST_HEAD(&c->reserved_buffers);
1468 c->need_reserved_buffers = reserved_buffers;
1469
1470 init_waitqueue_head(&c->free_buffer_wait);
1471 c->async_write_error = 0;
1472
1473 c->dm_io = dm_io_client_create();
1474 if (IS_ERR(c->dm_io)) {
1475 r = PTR_ERR(c->dm_io);
1476 goto bad_dm_io;
1477 }
1478
1479 mutex_lock(&dm_bufio_clients_lock);
1480 if (c->blocks_per_page_bits) {
1481 if (!DM_BUFIO_CACHE_NAME(c)) {
1482 DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size);
1483 if (!DM_BUFIO_CACHE_NAME(c)) {
1484 r = -ENOMEM;
1485 mutex_unlock(&dm_bufio_clients_lock);
1486 goto bad_cache;
1487 }
1488 }
1489
1490 if (!DM_BUFIO_CACHE(c)) {
1491 DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c),
1492 c->block_size,
1493 c->block_size, 0, NULL);
1494 if (!DM_BUFIO_CACHE(c)) {
1495 r = -ENOMEM;
1496 mutex_unlock(&dm_bufio_clients_lock);
1497 goto bad_cache;
1498 }
1499 }
1500 }
1501 mutex_unlock(&dm_bufio_clients_lock);
1502
1503 while (c->need_reserved_buffers) {
1504 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1505
1506 if (!b) {
1507 r = -ENOMEM;
1508 goto bad_buffer;
1509 }
1510 __free_buffer_wake(b);
1511 }
1512
1513 mutex_lock(&dm_bufio_clients_lock);
1514 dm_bufio_client_count++;
1515 list_add(&c->client_list, &dm_bufio_all_clients);
1516 __cache_size_refresh();
1517 mutex_unlock(&dm_bufio_clients_lock);
1518
1519 c->shrinker.shrink = shrink;
1520 c->shrinker.seeks = 1;
1521 c->shrinker.batch = 0;
1522 register_shrinker(&c->shrinker);
1523
1524 return c;
1525
1526bad_buffer:
1527bad_cache:
1528 while (!list_empty(&c->reserved_buffers)) {
1529 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1530 struct dm_buffer, lru_list);
1531 list_del(&b->lru_list);
1532 free_buffer(b);
1533 }
1534 dm_io_client_destroy(c->dm_io);
1535bad_dm_io:
1536 vfree(c->cache_hash);
1537bad_hash:
1538 kfree(c);
1539bad_client:
1540 return ERR_PTR(r);
1541}
1542EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1543
1544/*
1545 * Free the buffering interface.
1546 * It is required that there are no references on any buffers.
1547 */
1548void dm_bufio_client_destroy(struct dm_bufio_client *c)
1549{
1550 unsigned i;
1551
1552 drop_buffers(c);
1553
1554 unregister_shrinker(&c->shrinker);
1555
1556 mutex_lock(&dm_bufio_clients_lock);
1557
1558 list_del(&c->client_list);
1559 dm_bufio_client_count--;
1560 __cache_size_refresh();
1561
1562 mutex_unlock(&dm_bufio_clients_lock);
1563
1564 for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
1565 BUG_ON(!hlist_empty(&c->cache_hash[i]));
1566
1567 BUG_ON(c->need_reserved_buffers);
1568
1569 while (!list_empty(&c->reserved_buffers)) {
1570 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1571 struct dm_buffer, lru_list);
1572 list_del(&b->lru_list);
1573 free_buffer(b);
1574 }
1575
1576 for (i = 0; i < LIST_SIZE; i++)
1577 if (c->n_buffers[i])
1578 DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1579
1580 for (i = 0; i < LIST_SIZE; i++)
1581 BUG_ON(c->n_buffers[i]);
1582
1583 dm_io_client_destroy(c->dm_io);
1584 vfree(c->cache_hash);
1585 kfree(c);
1586}
1587EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1588
1589static void cleanup_old_buffers(void)
1590{
Mikulas Patockafe5fe902012-10-12 16:59:46 +01001591 unsigned long max_age = ACCESS_ONCE(dm_bufio_max_age);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001592 struct dm_bufio_client *c;
1593
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001594 if (max_age > ULONG_MAX / HZ)
1595 max_age = ULONG_MAX / HZ;
1596
1597 mutex_lock(&dm_bufio_clients_lock);
1598 list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
1599 if (!dm_bufio_trylock(c))
1600 continue;
1601
1602 while (!list_empty(&c->lru[LIST_CLEAN])) {
1603 struct dm_buffer *b;
1604 b = list_entry(c->lru[LIST_CLEAN].prev,
1605 struct dm_buffer, lru_list);
1606 if (__cleanup_old_buffer(b, 0, max_age * HZ))
1607 break;
1608 dm_bufio_cond_resched();
1609 }
1610
1611 dm_bufio_unlock(c);
1612 dm_bufio_cond_resched();
1613 }
1614 mutex_unlock(&dm_bufio_clients_lock);
1615}
1616
1617static struct workqueue_struct *dm_bufio_wq;
1618static struct delayed_work dm_bufio_work;
1619
1620static void work_fn(struct work_struct *w)
1621{
1622 cleanup_old_buffers();
1623
1624 queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1625 DM_BUFIO_WORK_TIMER_SECS * HZ);
1626}
1627
1628/*----------------------------------------------------------------
1629 * Module setup
1630 *--------------------------------------------------------------*/
1631
1632/*
1633 * This is called only once for the whole dm_bufio module.
1634 * It initializes memory limit.
1635 */
1636static int __init dm_bufio_init(void)
1637{
1638 __u64 mem;
1639
1640 memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
1641 memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
1642
1643 mem = (__u64)((totalram_pages - totalhigh_pages) *
1644 DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT;
1645
1646 if (mem > ULONG_MAX)
1647 mem = ULONG_MAX;
1648
1649#ifdef CONFIG_MMU
1650 /*
1651 * Get the size of vmalloc space the same way as VMALLOC_TOTAL
1652 * in fs/proc/internal.h
1653 */
1654 if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100)
1655 mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100;
1656#endif
1657
1658 dm_bufio_default_cache_size = mem;
1659
1660 mutex_lock(&dm_bufio_clients_lock);
1661 __cache_size_refresh();
1662 mutex_unlock(&dm_bufio_clients_lock);
1663
1664 dm_bufio_wq = create_singlethread_workqueue("dm_bufio_cache");
1665 if (!dm_bufio_wq)
1666 return -ENOMEM;
1667
1668 INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1669 queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1670 DM_BUFIO_WORK_TIMER_SECS * HZ);
1671
1672 return 0;
1673}
1674
1675/*
1676 * This is called once when unloading the dm_bufio module.
1677 */
1678static void __exit dm_bufio_exit(void)
1679{
1680 int bug = 0;
1681 int i;
1682
1683 cancel_delayed_work_sync(&dm_bufio_work);
1684 destroy_workqueue(dm_bufio_wq);
1685
1686 for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) {
1687 struct kmem_cache *kc = dm_bufio_caches[i];
1688
1689 if (kc)
1690 kmem_cache_destroy(kc);
1691 }
1692
1693 for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++)
1694 kfree(dm_bufio_cache_names[i]);
1695
1696 if (dm_bufio_client_count) {
1697 DMCRIT("%s: dm_bufio_client_count leaked: %d",
1698 __func__, dm_bufio_client_count);
1699 bug = 1;
1700 }
1701
1702 if (dm_bufio_current_allocated) {
1703 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1704 __func__, dm_bufio_current_allocated);
1705 bug = 1;
1706 }
1707
1708 if (dm_bufio_allocated_get_free_pages) {
1709 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1710 __func__, dm_bufio_allocated_get_free_pages);
1711 bug = 1;
1712 }
1713
1714 if (dm_bufio_allocated_vmalloc) {
1715 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1716 __func__, dm_bufio_allocated_vmalloc);
1717 bug = 1;
1718 }
1719
1720 if (bug)
1721 BUG();
1722}
1723
1724module_init(dm_bufio_init)
1725module_exit(dm_bufio_exit)
1726
1727module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1728MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1729
1730module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1731MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1732
1733module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
1734MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
1735
1736module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
1737MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
1738
1739module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
1740MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
1741
1742module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
1743MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
1744
1745module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
1746MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
1747
1748MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
1749MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
1750MODULE_LICENSE("GPL");