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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
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500107 unsigned minimum_buffers;
108
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000109 struct hlist_head *cache_hash;
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 hlist_node hash_list;
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;
Mikulas Patocka24809452013-07-10 23:41:18 +0100150 struct list_head write_list;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000151 struct bio bio;
152 struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
153};
154
155/*----------------------------------------------------------------*/
156
157static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT];
158static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT];
159
160static inline int dm_bufio_cache_index(struct dm_bufio_client *c)
161{
162 unsigned ret = c->blocks_per_page_bits - 1;
163
164 BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches));
165
166 return ret;
167}
168
169#define DM_BUFIO_CACHE(c) (dm_bufio_caches[dm_bufio_cache_index(c)])
170#define DM_BUFIO_CACHE_NAME(c) (dm_bufio_cache_names[dm_bufio_cache_index(c)])
171
172#define dm_bufio_in_request() (!!current->bio_list)
173
174static void dm_bufio_lock(struct dm_bufio_client *c)
175{
176 mutex_lock_nested(&c->lock, dm_bufio_in_request());
177}
178
179static int dm_bufio_trylock(struct dm_bufio_client *c)
180{
181 return mutex_trylock(&c->lock);
182}
183
184static void dm_bufio_unlock(struct dm_bufio_client *c)
185{
186 mutex_unlock(&c->lock);
187}
188
189/*
190 * FIXME Move to sched.h?
191 */
192#ifdef CONFIG_PREEMPT_VOLUNTARY
193# define dm_bufio_cond_resched() \
194do { \
195 if (unlikely(need_resched())) \
196 _cond_resched(); \
197} while (0)
198#else
199# define dm_bufio_cond_resched() do { } while (0)
200#endif
201
202/*----------------------------------------------------------------*/
203
204/*
205 * Default cache size: available memory divided by the ratio.
206 */
207static unsigned long dm_bufio_default_cache_size;
208
209/*
210 * Total cache size set by the user.
211 */
212static unsigned long dm_bufio_cache_size;
213
214/*
215 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
216 * at any time. If it disagrees, the user has changed cache size.
217 */
218static unsigned long dm_bufio_cache_size_latch;
219
220static DEFINE_SPINLOCK(param_spinlock);
221
222/*
223 * Buffers are freed after this timeout
224 */
225static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
226
227static unsigned long dm_bufio_peak_allocated;
228static unsigned long dm_bufio_allocated_kmem_cache;
229static unsigned long dm_bufio_allocated_get_free_pages;
230static unsigned long dm_bufio_allocated_vmalloc;
231static unsigned long dm_bufio_current_allocated;
232
233/*----------------------------------------------------------------*/
234
235/*
236 * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
237 */
238static unsigned long dm_bufio_cache_size_per_client;
239
240/*
241 * The current number of clients.
242 */
243static int dm_bufio_client_count;
244
245/*
246 * The list of all clients.
247 */
248static LIST_HEAD(dm_bufio_all_clients);
249
250/*
251 * This mutex protects dm_bufio_cache_size_latch,
252 * dm_bufio_cache_size_per_client and dm_bufio_client_count
253 */
254static DEFINE_MUTEX(dm_bufio_clients_lock);
255
256/*----------------------------------------------------------------*/
257
258static void adjust_total_allocated(enum data_mode data_mode, long diff)
259{
260 static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
261 &dm_bufio_allocated_kmem_cache,
262 &dm_bufio_allocated_get_free_pages,
263 &dm_bufio_allocated_vmalloc,
264 };
265
266 spin_lock(&param_spinlock);
267
268 *class_ptr[data_mode] += diff;
269
270 dm_bufio_current_allocated += diff;
271
272 if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
273 dm_bufio_peak_allocated = dm_bufio_current_allocated;
274
275 spin_unlock(&param_spinlock);
276}
277
278/*
279 * Change the number of clients and recalculate per-client limit.
280 */
281static void __cache_size_refresh(void)
282{
283 BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
284 BUG_ON(dm_bufio_client_count < 0);
285
Mikulas Patockafe5fe902012-10-12 16:59:46 +0100286 dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000287
288 /*
289 * Use default if set to 0 and report the actual cache size used.
290 */
291 if (!dm_bufio_cache_size_latch) {
292 (void)cmpxchg(&dm_bufio_cache_size, 0,
293 dm_bufio_default_cache_size);
294 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
295 }
296
297 dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
298 (dm_bufio_client_count ? : 1);
299}
300
301/*
302 * Allocating buffer data.
303 *
304 * Small buffers are allocated with kmem_cache, to use space optimally.
305 *
306 * For large buffers, we choose between get_free_pages and vmalloc.
307 * Each has advantages and disadvantages.
308 *
309 * __get_free_pages can randomly fail if the memory is fragmented.
310 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
311 * as low as 128M) so using it for caching is not appropriate.
312 *
313 * If the allocation may fail we use __get_free_pages. Memory fragmentation
314 * won't have a fatal effect here, but it just causes flushes of some other
315 * buffers and more I/O will be performed. Don't use __get_free_pages if it
316 * always fails (i.e. order >= MAX_ORDER).
317 *
318 * If the allocation shouldn't fail we use __vmalloc. This is only for the
319 * initial reserve allocation, so there's no risk of wasting all vmalloc
320 * space.
321 */
322static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
323 enum data_mode *data_mode)
324{
Mikulas Patocka502624b2013-05-10 14:37:15 +0100325 unsigned noio_flag;
326 void *ptr;
327
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000328 if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {
329 *data_mode = DATA_MODE_SLAB;
330 return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
331 }
332
333 if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT &&
334 gfp_mask & __GFP_NORETRY) {
335 *data_mode = DATA_MODE_GET_FREE_PAGES;
336 return (void *)__get_free_pages(gfp_mask,
337 c->pages_per_block_bits);
338 }
339
340 *data_mode = DATA_MODE_VMALLOC;
Mikulas Patocka502624b2013-05-10 14:37:15 +0100341
342 /*
343 * __vmalloc allocates the data pages and auxiliary structures with
344 * gfp_flags that were specified, but pagetables are always allocated
345 * with GFP_KERNEL, no matter what was specified as gfp_mask.
346 *
347 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
348 * all allocations done by this process (including pagetables) are done
349 * as if GFP_NOIO was specified.
350 */
351
352 if (gfp_mask & __GFP_NORETRY)
353 noio_flag = memalloc_noio_save();
354
Mikulas Patocka220cd052013-07-10 23:41:16 +0100355 ptr = __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL);
Mikulas Patocka502624b2013-05-10 14:37:15 +0100356
357 if (gfp_mask & __GFP_NORETRY)
358 memalloc_noio_restore(noio_flag);
359
360 return ptr;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000361}
362
363/*
364 * Free buffer's data.
365 */
366static void free_buffer_data(struct dm_bufio_client *c,
367 void *data, enum data_mode data_mode)
368{
369 switch (data_mode) {
370 case DATA_MODE_SLAB:
371 kmem_cache_free(DM_BUFIO_CACHE(c), data);
372 break;
373
374 case DATA_MODE_GET_FREE_PAGES:
375 free_pages((unsigned long)data, c->pages_per_block_bits);
376 break;
377
378 case DATA_MODE_VMALLOC:
379 vfree(data);
380 break;
381
382 default:
383 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
384 data_mode);
385 BUG();
386 }
387}
388
389/*
390 * Allocate buffer and its data.
391 */
392static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
393{
394 struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size,
395 gfp_mask);
396
397 if (!b)
398 return NULL;
399
400 b->c = c;
401
402 b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
403 if (!b->data) {
404 kfree(b);
405 return NULL;
406 }
407
408 adjust_total_allocated(b->data_mode, (long)c->block_size);
409
410 return b;
411}
412
413/*
414 * Free buffer and its data.
415 */
416static void free_buffer(struct dm_buffer *b)
417{
418 struct dm_bufio_client *c = b->c;
419
420 adjust_total_allocated(b->data_mode, -(long)c->block_size);
421
422 free_buffer_data(c, b->data, b->data_mode);
423 kfree(b);
424}
425
426/*
427 * Link buffer to the hash list and clean or dirty queue.
428 */
429static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
430{
431 struct dm_bufio_client *c = b->c;
432
433 c->n_buffers[dirty]++;
434 b->block = block;
435 b->list_mode = dirty;
436 list_add(&b->lru_list, &c->lru[dirty]);
437 hlist_add_head(&b->hash_list, &c->cache_hash[DM_BUFIO_HASH(block)]);
438 b->last_accessed = jiffies;
439}
440
441/*
442 * Unlink buffer from the hash list and dirty or clean queue.
443 */
444static void __unlink_buffer(struct dm_buffer *b)
445{
446 struct dm_bufio_client *c = b->c;
447
448 BUG_ON(!c->n_buffers[b->list_mode]);
449
450 c->n_buffers[b->list_mode]--;
451 hlist_del(&b->hash_list);
452 list_del(&b->lru_list);
453}
454
455/*
456 * Place the buffer to the head of dirty or clean LRU queue.
457 */
458static void __relink_lru(struct dm_buffer *b, int dirty)
459{
460 struct dm_bufio_client *c = b->c;
461
462 BUG_ON(!c->n_buffers[b->list_mode]);
463
464 c->n_buffers[b->list_mode]--;
465 c->n_buffers[dirty]++;
466 b->list_mode = dirty;
Wei Yongjun54499af2012-10-12 16:59:44 +0100467 list_move(&b->lru_list, &c->lru[dirty]);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000468}
469
470/*----------------------------------------------------------------
471 * Submit I/O on the buffer.
472 *
473 * Bio interface is faster but it has some problems:
474 * the vector list is limited (increasing this limit increases
475 * memory-consumption per buffer, so it is not viable);
476 *
477 * the memory must be direct-mapped, not vmalloced;
478 *
479 * the I/O driver can reject requests spuriously if it thinks that
480 * the requests are too big for the device or if they cross a
481 * controller-defined memory boundary.
482 *
483 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
484 * it is not vmalloced, try using the bio interface.
485 *
486 * If the buffer is big, if it is vmalloced or if the underlying device
487 * rejects the bio because it is too large, use dm-io layer to do the I/O.
488 * The dm-io layer splits the I/O into multiple requests, avoiding the above
489 * shortcomings.
490 *--------------------------------------------------------------*/
491
492/*
493 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
494 * that the request was handled directly with bio interface.
495 */
496static void dmio_complete(unsigned long error, void *context)
497{
498 struct dm_buffer *b = context;
499
500 b->bio.bi_end_io(&b->bio, error ? -EIO : 0);
501}
502
503static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
504 bio_end_io_t *end_io)
505{
506 int r;
507 struct dm_io_request io_req = {
508 .bi_rw = rw,
509 .notify.fn = dmio_complete,
510 .notify.context = b,
511 .client = b->c->dm_io,
512 };
513 struct dm_io_region region = {
514 .bdev = b->c->bdev,
515 .sector = block << b->c->sectors_per_block_bits,
516 .count = b->c->block_size >> SECTOR_SHIFT,
517 };
518
519 if (b->data_mode != DATA_MODE_VMALLOC) {
520 io_req.mem.type = DM_IO_KMEM;
521 io_req.mem.ptr.addr = b->data;
522 } else {
523 io_req.mem.type = DM_IO_VMA;
524 io_req.mem.ptr.vma = b->data;
525 }
526
527 b->bio.bi_end_io = end_io;
528
529 r = dm_io(&io_req, 1, &region, NULL);
530 if (r)
531 end_io(&b->bio, r);
532}
533
534static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
535 bio_end_io_t *end_io)
536{
537 char *ptr;
538 int len;
539
540 bio_init(&b->bio);
541 b->bio.bi_io_vec = b->bio_vec;
542 b->bio.bi_max_vecs = DM_BUFIO_INLINE_VECS;
Kent Overstreet4f024f32013-10-11 15:44:27 -0700543 b->bio.bi_iter.bi_sector = block << b->c->sectors_per_block_bits;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000544 b->bio.bi_bdev = b->c->bdev;
545 b->bio.bi_end_io = end_io;
546
547 /*
548 * We assume that if len >= PAGE_SIZE ptr is page-aligned.
549 * If len < PAGE_SIZE the buffer doesn't cross page boundary.
550 */
551 ptr = b->data;
552 len = b->c->block_size;
553
554 if (len >= PAGE_SIZE)
555 BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1));
556 else
557 BUG_ON((unsigned long)ptr & (len - 1));
558
559 do {
560 if (!bio_add_page(&b->bio, virt_to_page(ptr),
561 len < PAGE_SIZE ? len : PAGE_SIZE,
562 virt_to_phys(ptr) & (PAGE_SIZE - 1))) {
563 BUG_ON(b->c->block_size <= PAGE_SIZE);
564 use_dmio(b, rw, block, end_io);
565 return;
566 }
567
568 len -= PAGE_SIZE;
569 ptr += PAGE_SIZE;
570 } while (len > 0);
571
572 submit_bio(rw, &b->bio);
573}
574
575static void submit_io(struct dm_buffer *b, int rw, sector_t block,
576 bio_end_io_t *end_io)
577{
578 if (rw == WRITE && b->c->write_callback)
579 b->c->write_callback(b);
580
581 if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE &&
582 b->data_mode != DATA_MODE_VMALLOC)
583 use_inline_bio(b, rw, block, end_io);
584 else
585 use_dmio(b, rw, block, end_io);
586}
587
588/*----------------------------------------------------------------
589 * Writing dirty buffers
590 *--------------------------------------------------------------*/
591
592/*
593 * The endio routine for write.
594 *
595 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
596 * it.
597 */
598static void write_endio(struct bio *bio, int error)
599{
600 struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
601
602 b->write_error = error;
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100603 if (unlikely(error)) {
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000604 struct dm_bufio_client *c = b->c;
605 (void)cmpxchg(&c->async_write_error, 0, error);
606 }
607
608 BUG_ON(!test_bit(B_WRITING, &b->state));
609
610 smp_mb__before_clear_bit();
611 clear_bit(B_WRITING, &b->state);
612 smp_mb__after_clear_bit();
613
614 wake_up_bit(&b->state, B_WRITING);
615}
616
617/*
618 * This function is called when wait_on_bit is actually waiting.
619 */
620static int do_io_schedule(void *word)
621{
622 io_schedule();
623
624 return 0;
625}
626
627/*
628 * Initiate a write on a dirty buffer, but don't wait for it.
629 *
630 * - If the buffer is not dirty, exit.
631 * - If there some previous write going on, wait for it to finish (we can't
632 * have two writes on the same buffer simultaneously).
633 * - Submit our write and don't wait on it. We set B_WRITING indicating
634 * that there is a write in progress.
635 */
Mikulas Patocka24809452013-07-10 23:41:18 +0100636static void __write_dirty_buffer(struct dm_buffer *b,
637 struct list_head *write_list)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000638{
639 if (!test_bit(B_DIRTY, &b->state))
640 return;
641
642 clear_bit(B_DIRTY, &b->state);
643 wait_on_bit_lock(&b->state, B_WRITING,
644 do_io_schedule, TASK_UNINTERRUPTIBLE);
645
Mikulas Patocka24809452013-07-10 23:41:18 +0100646 if (!write_list)
647 submit_io(b, WRITE, b->block, write_endio);
648 else
649 list_add_tail(&b->write_list, write_list);
650}
651
652static void __flush_write_list(struct list_head *write_list)
653{
654 struct blk_plug plug;
655 blk_start_plug(&plug);
656 while (!list_empty(write_list)) {
657 struct dm_buffer *b =
658 list_entry(write_list->next, struct dm_buffer, write_list);
659 list_del(&b->write_list);
660 submit_io(b, WRITE, b->block, write_endio);
661 dm_bufio_cond_resched();
662 }
663 blk_finish_plug(&plug);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000664}
665
666/*
667 * Wait until any activity on the buffer finishes. Possibly write the
668 * buffer if it is dirty. When this function finishes, there is no I/O
669 * running on the buffer and the buffer is not dirty.
670 */
671static void __make_buffer_clean(struct dm_buffer *b)
672{
673 BUG_ON(b->hold_count);
674
675 if (!b->state) /* fast case */
676 return;
677
678 wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
Mikulas Patocka24809452013-07-10 23:41:18 +0100679 __write_dirty_buffer(b, NULL);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000680 wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE);
681}
682
683/*
684 * Find some buffer that is not held by anybody, clean it, unlink it and
685 * return it.
686 */
687static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
688{
689 struct dm_buffer *b;
690
691 list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
692 BUG_ON(test_bit(B_WRITING, &b->state));
693 BUG_ON(test_bit(B_DIRTY, &b->state));
694
695 if (!b->hold_count) {
696 __make_buffer_clean(b);
697 __unlink_buffer(b);
698 return b;
699 }
700 dm_bufio_cond_resched();
701 }
702
703 list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
704 BUG_ON(test_bit(B_READING, &b->state));
705
706 if (!b->hold_count) {
707 __make_buffer_clean(b);
708 __unlink_buffer(b);
709 return b;
710 }
711 dm_bufio_cond_resched();
712 }
713
714 return NULL;
715}
716
717/*
718 * Wait until some other threads free some buffer or release hold count on
719 * some buffer.
720 *
721 * This function is entered with c->lock held, drops it and regains it
722 * before exiting.
723 */
724static void __wait_for_free_buffer(struct dm_bufio_client *c)
725{
726 DECLARE_WAITQUEUE(wait, current);
727
728 add_wait_queue(&c->free_buffer_wait, &wait);
729 set_task_state(current, TASK_UNINTERRUPTIBLE);
730 dm_bufio_unlock(c);
731
732 io_schedule();
733
734 set_task_state(current, TASK_RUNNING);
735 remove_wait_queue(&c->free_buffer_wait, &wait);
736
737 dm_bufio_lock(c);
738}
739
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100740enum new_flag {
741 NF_FRESH = 0,
742 NF_READ = 1,
743 NF_GET = 2,
744 NF_PREFETCH = 3
745};
746
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000747/*
748 * Allocate a new buffer. If the allocation is not possible, wait until
749 * some other thread frees a buffer.
750 *
751 * May drop the lock and regain it.
752 */
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100753static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000754{
755 struct dm_buffer *b;
756
757 /*
758 * dm-bufio is resistant to allocation failures (it just keeps
759 * one buffer reserved in cases all the allocations fail).
760 * So set flags to not try too hard:
761 * GFP_NOIO: don't recurse into the I/O layer
762 * __GFP_NORETRY: don't retry and rather return failure
763 * __GFP_NOMEMALLOC: don't use emergency reserves
764 * __GFP_NOWARN: don't print a warning in case of failure
765 *
766 * For debugging, if we set the cache size to 1, no new buffers will
767 * be allocated.
768 */
769 while (1) {
770 if (dm_bufio_cache_size_latch != 1) {
771 b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
772 if (b)
773 return b;
774 }
775
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100776 if (nf == NF_PREFETCH)
777 return NULL;
778
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000779 if (!list_empty(&c->reserved_buffers)) {
780 b = list_entry(c->reserved_buffers.next,
781 struct dm_buffer, lru_list);
782 list_del(&b->lru_list);
783 c->need_reserved_buffers++;
784
785 return b;
786 }
787
788 b = __get_unclaimed_buffer(c);
789 if (b)
790 return b;
791
792 __wait_for_free_buffer(c);
793 }
794}
795
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100796static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000797{
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100798 struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
799
800 if (!b)
801 return NULL;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000802
803 if (c->alloc_callback)
804 c->alloc_callback(b);
805
806 return b;
807}
808
809/*
810 * Free a buffer and wake other threads waiting for free buffers.
811 */
812static void __free_buffer_wake(struct dm_buffer *b)
813{
814 struct dm_bufio_client *c = b->c;
815
816 if (!c->need_reserved_buffers)
817 free_buffer(b);
818 else {
819 list_add(&b->lru_list, &c->reserved_buffers);
820 c->need_reserved_buffers--;
821 }
822
823 wake_up(&c->free_buffer_wait);
824}
825
Mikulas Patocka24809452013-07-10 23:41:18 +0100826static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
827 struct list_head *write_list)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000828{
829 struct dm_buffer *b, *tmp;
830
831 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
832 BUG_ON(test_bit(B_READING, &b->state));
833
834 if (!test_bit(B_DIRTY, &b->state) &&
835 !test_bit(B_WRITING, &b->state)) {
836 __relink_lru(b, LIST_CLEAN);
837 continue;
838 }
839
840 if (no_wait && test_bit(B_WRITING, &b->state))
841 return;
842
Mikulas Patocka24809452013-07-10 23:41:18 +0100843 __write_dirty_buffer(b, write_list);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000844 dm_bufio_cond_resched();
845 }
846}
847
848/*
849 * Get writeback threshold and buffer limit for a given client.
850 */
851static void __get_memory_limit(struct dm_bufio_client *c,
852 unsigned long *threshold_buffers,
853 unsigned long *limit_buffers)
854{
855 unsigned long buffers;
856
Mikulas Patockafe5fe902012-10-12 16:59:46 +0100857 if (ACCESS_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch) {
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000858 mutex_lock(&dm_bufio_clients_lock);
859 __cache_size_refresh();
860 mutex_unlock(&dm_bufio_clients_lock);
861 }
862
863 buffers = dm_bufio_cache_size_per_client >>
864 (c->sectors_per_block_bits + SECTOR_SHIFT);
865
Mikulas Patocka55b082e2014-01-13 19:13:05 -0500866 if (buffers < c->minimum_buffers)
867 buffers = c->minimum_buffers;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000868
869 *limit_buffers = buffers;
870 *threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100;
871}
872
873/*
874 * Check if we're over watermark.
875 * If we are over threshold_buffers, start freeing buffers.
876 * If we're over "limit_buffers", block until we get under the limit.
877 */
Mikulas Patocka24809452013-07-10 23:41:18 +0100878static void __check_watermark(struct dm_bufio_client *c,
879 struct list_head *write_list)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000880{
881 unsigned long threshold_buffers, limit_buffers;
882
883 __get_memory_limit(c, &threshold_buffers, &limit_buffers);
884
885 while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
886 limit_buffers) {
887
888 struct dm_buffer *b = __get_unclaimed_buffer(c);
889
890 if (!b)
891 return;
892
893 __free_buffer_wake(b);
894 dm_bufio_cond_resched();
895 }
896
897 if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
Mikulas Patocka24809452013-07-10 23:41:18 +0100898 __write_dirty_buffers_async(c, 1, write_list);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000899}
900
901/*
902 * Find a buffer in the hash.
903 */
904static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
905{
906 struct dm_buffer *b;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000907
Sasha Levinb67bfe02013-02-27 17:06:00 -0800908 hlist_for_each_entry(b, &c->cache_hash[DM_BUFIO_HASH(block)],
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000909 hash_list) {
910 dm_bufio_cond_resched();
911 if (b->block == block)
912 return b;
913 }
914
915 return NULL;
916}
917
918/*----------------------------------------------------------------
919 * Getting a buffer
920 *--------------------------------------------------------------*/
921
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000922static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
Mikulas Patocka24809452013-07-10 23:41:18 +0100923 enum new_flag nf, int *need_submit,
924 struct list_head *write_list)
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000925{
926 struct dm_buffer *b, *new_b = NULL;
927
928 *need_submit = 0;
929
930 b = __find(c, block);
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100931 if (b)
932 goto found_buffer;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000933
934 if (nf == NF_GET)
935 return NULL;
936
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100937 new_b = __alloc_buffer_wait(c, nf);
938 if (!new_b)
939 return NULL;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000940
941 /*
942 * We've had a period where the mutex was unlocked, so need to
943 * recheck the hash table.
944 */
945 b = __find(c, block);
946 if (b) {
947 __free_buffer_wake(new_b);
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100948 goto found_buffer;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000949 }
950
Mikulas Patocka24809452013-07-10 23:41:18 +0100951 __check_watermark(c, write_list);
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000952
953 b = new_b;
954 b->hold_count = 1;
955 b->read_error = 0;
956 b->write_error = 0;
957 __link_buffer(b, block, LIST_CLEAN);
958
959 if (nf == NF_FRESH) {
960 b->state = 0;
961 return b;
962 }
963
964 b->state = 1 << B_READING;
965 *need_submit = 1;
966
967 return b;
Mikulas Patockaa66cc282012-03-28 18:41:29 +0100968
969found_buffer:
970 if (nf == NF_PREFETCH)
971 return NULL;
972 /*
973 * Note: it is essential that we don't wait for the buffer to be
974 * read if dm_bufio_get function is used. Both dm_bufio_get and
975 * dm_bufio_prefetch can be used in the driver request routine.
976 * If the user called both dm_bufio_prefetch and dm_bufio_get on
977 * the same buffer, it would deadlock if we waited.
978 */
979 if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
980 return NULL;
981
982 b->hold_count++;
983 __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
984 test_bit(B_WRITING, &b->state));
985 return b;
Mikulas Patocka95d402f2011-10-31 20:19:09 +0000986}
987
988/*
989 * The endio routine for reading: set the error, clear the bit and wake up
990 * anyone waiting on the buffer.
991 */
992static void read_endio(struct bio *bio, int error)
993{
994 struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
995
996 b->read_error = error;
997
998 BUG_ON(!test_bit(B_READING, &b->state));
999
1000 smp_mb__before_clear_bit();
1001 clear_bit(B_READING, &b->state);
1002 smp_mb__after_clear_bit();
1003
1004 wake_up_bit(&b->state, B_READING);
1005}
1006
1007/*
1008 * A common routine for dm_bufio_new and dm_bufio_read. Operation of these
1009 * functions is similar except that dm_bufio_new doesn't read the
1010 * buffer from the disk (assuming that the caller overwrites all the data
1011 * and uses dm_bufio_mark_buffer_dirty to write new data back).
1012 */
1013static void *new_read(struct dm_bufio_client *c, sector_t block,
1014 enum new_flag nf, struct dm_buffer **bp)
1015{
1016 int need_submit;
1017 struct dm_buffer *b;
1018
Mikulas Patocka24809452013-07-10 23:41:18 +01001019 LIST_HEAD(write_list);
1020
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001021 dm_bufio_lock(c);
Mikulas Patocka24809452013-07-10 23:41:18 +01001022 b = __bufio_new(c, block, nf, &need_submit, &write_list);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001023 dm_bufio_unlock(c);
1024
Mikulas Patocka24809452013-07-10 23:41:18 +01001025 __flush_write_list(&write_list);
1026
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001027 if (!b)
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001028 return b;
1029
1030 if (need_submit)
1031 submit_io(b, READ, b->block, read_endio);
1032
1033 wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
1034
1035 if (b->read_error) {
1036 int error = b->read_error;
1037
1038 dm_bufio_release(b);
1039
1040 return ERR_PTR(error);
1041 }
1042
1043 *bp = b;
1044
1045 return b->data;
1046}
1047
1048void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1049 struct dm_buffer **bp)
1050{
1051 return new_read(c, block, NF_GET, bp);
1052}
1053EXPORT_SYMBOL_GPL(dm_bufio_get);
1054
1055void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1056 struct dm_buffer **bp)
1057{
1058 BUG_ON(dm_bufio_in_request());
1059
1060 return new_read(c, block, NF_READ, bp);
1061}
1062EXPORT_SYMBOL_GPL(dm_bufio_read);
1063
1064void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1065 struct dm_buffer **bp)
1066{
1067 BUG_ON(dm_bufio_in_request());
1068
1069 return new_read(c, block, NF_FRESH, bp);
1070}
1071EXPORT_SYMBOL_GPL(dm_bufio_new);
1072
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001073void dm_bufio_prefetch(struct dm_bufio_client *c,
1074 sector_t block, unsigned n_blocks)
1075{
1076 struct blk_plug plug;
1077
Mikulas Patocka24809452013-07-10 23:41:18 +01001078 LIST_HEAD(write_list);
1079
Mikulas Patocka3b6b7812013-03-20 17:21:25 +00001080 BUG_ON(dm_bufio_in_request());
1081
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001082 blk_start_plug(&plug);
1083 dm_bufio_lock(c);
1084
1085 for (; n_blocks--; block++) {
1086 int need_submit;
1087 struct dm_buffer *b;
Mikulas Patocka24809452013-07-10 23:41:18 +01001088 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1089 &write_list);
1090 if (unlikely(!list_empty(&write_list))) {
1091 dm_bufio_unlock(c);
1092 blk_finish_plug(&plug);
1093 __flush_write_list(&write_list);
1094 blk_start_plug(&plug);
1095 dm_bufio_lock(c);
1096 }
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001097 if (unlikely(b != NULL)) {
1098 dm_bufio_unlock(c);
1099
1100 if (need_submit)
1101 submit_io(b, READ, b->block, read_endio);
1102 dm_bufio_release(b);
1103
1104 dm_bufio_cond_resched();
1105
1106 if (!n_blocks)
1107 goto flush_plug;
1108 dm_bufio_lock(c);
1109 }
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001110 }
1111
1112 dm_bufio_unlock(c);
1113
1114flush_plug:
1115 blk_finish_plug(&plug);
1116}
1117EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1118
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001119void dm_bufio_release(struct dm_buffer *b)
1120{
1121 struct dm_bufio_client *c = b->c;
1122
1123 dm_bufio_lock(c);
1124
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001125 BUG_ON(!b->hold_count);
1126
1127 b->hold_count--;
1128 if (!b->hold_count) {
1129 wake_up(&c->free_buffer_wait);
1130
1131 /*
1132 * If there were errors on the buffer, and the buffer is not
1133 * to be written, free the buffer. There is no point in caching
1134 * invalid buffer.
1135 */
1136 if ((b->read_error || b->write_error) &&
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001137 !test_bit(B_READING, &b->state) &&
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001138 !test_bit(B_WRITING, &b->state) &&
1139 !test_bit(B_DIRTY, &b->state)) {
1140 __unlink_buffer(b);
1141 __free_buffer_wake(b);
1142 }
1143 }
1144
1145 dm_bufio_unlock(c);
1146}
1147EXPORT_SYMBOL_GPL(dm_bufio_release);
1148
1149void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1150{
1151 struct dm_bufio_client *c = b->c;
1152
1153 dm_bufio_lock(c);
1154
Mikulas Patockaa66cc282012-03-28 18:41:29 +01001155 BUG_ON(test_bit(B_READING, &b->state));
1156
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001157 if (!test_and_set_bit(B_DIRTY, &b->state))
1158 __relink_lru(b, LIST_DIRTY);
1159
1160 dm_bufio_unlock(c);
1161}
1162EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1163
1164void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1165{
Mikulas Patocka24809452013-07-10 23:41:18 +01001166 LIST_HEAD(write_list);
1167
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001168 BUG_ON(dm_bufio_in_request());
1169
1170 dm_bufio_lock(c);
Mikulas Patocka24809452013-07-10 23:41:18 +01001171 __write_dirty_buffers_async(c, 0, &write_list);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001172 dm_bufio_unlock(c);
Mikulas Patocka24809452013-07-10 23:41:18 +01001173 __flush_write_list(&write_list);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001174}
1175EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1176
1177/*
1178 * For performance, it is essential that the buffers are written asynchronously
1179 * and simultaneously (so that the block layer can merge the writes) and then
1180 * waited upon.
1181 *
1182 * Finally, we flush hardware disk cache.
1183 */
1184int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1185{
1186 int a, f;
1187 unsigned long buffers_processed = 0;
1188 struct dm_buffer *b, *tmp;
1189
Mikulas Patocka24809452013-07-10 23:41:18 +01001190 LIST_HEAD(write_list);
1191
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001192 dm_bufio_lock(c);
Mikulas Patocka24809452013-07-10 23:41:18 +01001193 __write_dirty_buffers_async(c, 0, &write_list);
1194 dm_bufio_unlock(c);
1195 __flush_write_list(&write_list);
1196 dm_bufio_lock(c);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001197
1198again:
1199 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1200 int dropped_lock = 0;
1201
1202 if (buffers_processed < c->n_buffers[LIST_DIRTY])
1203 buffers_processed++;
1204
1205 BUG_ON(test_bit(B_READING, &b->state));
1206
1207 if (test_bit(B_WRITING, &b->state)) {
1208 if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1209 dropped_lock = 1;
1210 b->hold_count++;
1211 dm_bufio_unlock(c);
1212 wait_on_bit(&b->state, B_WRITING,
1213 do_io_schedule,
1214 TASK_UNINTERRUPTIBLE);
1215 dm_bufio_lock(c);
1216 b->hold_count--;
1217 } else
1218 wait_on_bit(&b->state, B_WRITING,
1219 do_io_schedule,
1220 TASK_UNINTERRUPTIBLE);
1221 }
1222
1223 if (!test_bit(B_DIRTY, &b->state) &&
1224 !test_bit(B_WRITING, &b->state))
1225 __relink_lru(b, LIST_CLEAN);
1226
1227 dm_bufio_cond_resched();
1228
1229 /*
1230 * If we dropped the lock, the list is no longer consistent,
1231 * so we must restart the search.
1232 *
1233 * In the most common case, the buffer just processed is
1234 * relinked to the clean list, so we won't loop scanning the
1235 * same buffer again and again.
1236 *
1237 * This may livelock if there is another thread simultaneously
1238 * dirtying buffers, so we count the number of buffers walked
1239 * and if it exceeds the total number of buffers, it means that
1240 * someone is doing some writes simultaneously with us. In
1241 * this case, stop, dropping the lock.
1242 */
1243 if (dropped_lock)
1244 goto again;
1245 }
1246 wake_up(&c->free_buffer_wait);
1247 dm_bufio_unlock(c);
1248
1249 a = xchg(&c->async_write_error, 0);
1250 f = dm_bufio_issue_flush(c);
1251 if (a)
1252 return a;
1253
1254 return f;
1255}
1256EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1257
1258/*
1259 * Use dm-io to send and empty barrier flush the device.
1260 */
1261int dm_bufio_issue_flush(struct dm_bufio_client *c)
1262{
1263 struct dm_io_request io_req = {
Mikulas Patocka3daec3b2013-03-01 22:45:45 +00001264 .bi_rw = WRITE_FLUSH,
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001265 .mem.type = DM_IO_KMEM,
1266 .mem.ptr.addr = NULL,
1267 .client = c->dm_io,
1268 };
1269 struct dm_io_region io_reg = {
1270 .bdev = c->bdev,
1271 .sector = 0,
1272 .count = 0,
1273 };
1274
1275 BUG_ON(dm_bufio_in_request());
1276
1277 return dm_io(&io_req, 1, &io_reg, NULL);
1278}
1279EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1280
1281/*
1282 * We first delete any other buffer that may be at that new location.
1283 *
1284 * Then, we write the buffer to the original location if it was dirty.
1285 *
1286 * Then, if we are the only one who is holding the buffer, relink the buffer
1287 * in the hash queue for the new location.
1288 *
1289 * If there was someone else holding the buffer, we write it to the new
1290 * location but not relink it, because that other user needs to have the buffer
1291 * at the same place.
1292 */
1293void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1294{
1295 struct dm_bufio_client *c = b->c;
1296 struct dm_buffer *new;
1297
1298 BUG_ON(dm_bufio_in_request());
1299
1300 dm_bufio_lock(c);
1301
1302retry:
1303 new = __find(c, new_block);
1304 if (new) {
1305 if (new->hold_count) {
1306 __wait_for_free_buffer(c);
1307 goto retry;
1308 }
1309
1310 /*
1311 * FIXME: Is there any point waiting for a write that's going
1312 * to be overwritten in a bit?
1313 */
1314 __make_buffer_clean(new);
1315 __unlink_buffer(new);
1316 __free_buffer_wake(new);
1317 }
1318
1319 BUG_ON(!b->hold_count);
1320 BUG_ON(test_bit(B_READING, &b->state));
1321
Mikulas Patocka24809452013-07-10 23:41:18 +01001322 __write_dirty_buffer(b, NULL);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001323 if (b->hold_count == 1) {
1324 wait_on_bit(&b->state, B_WRITING,
1325 do_io_schedule, TASK_UNINTERRUPTIBLE);
1326 set_bit(B_DIRTY, &b->state);
1327 __unlink_buffer(b);
1328 __link_buffer(b, new_block, LIST_DIRTY);
1329 } else {
1330 sector_t old_block;
1331 wait_on_bit_lock(&b->state, B_WRITING,
1332 do_io_schedule, TASK_UNINTERRUPTIBLE);
1333 /*
1334 * Relink buffer to "new_block" so that write_callback
1335 * sees "new_block" as a block number.
1336 * After the write, link the buffer back to old_block.
1337 * All this must be done in bufio lock, so that block number
1338 * change isn't visible to other threads.
1339 */
1340 old_block = b->block;
1341 __unlink_buffer(b);
1342 __link_buffer(b, new_block, b->list_mode);
1343 submit_io(b, WRITE, new_block, write_endio);
1344 wait_on_bit(&b->state, B_WRITING,
1345 do_io_schedule, TASK_UNINTERRUPTIBLE);
1346 __unlink_buffer(b);
1347 __link_buffer(b, old_block, b->list_mode);
1348 }
1349
1350 dm_bufio_unlock(c);
1351 dm_bufio_release(b);
1352}
1353EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1354
Mikulas Patocka55494bf2014-01-13 19:12:36 -05001355/*
1356 * Free the given buffer.
1357 *
1358 * This is just a hint, if the buffer is in use or dirty, this function
1359 * does nothing.
1360 */
1361void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1362{
1363 struct dm_buffer *b;
1364
1365 dm_bufio_lock(c);
1366
1367 b = __find(c, block);
1368 if (b && likely(!b->hold_count) && likely(!b->state)) {
1369 __unlink_buffer(b);
1370 __free_buffer_wake(b);
1371 }
1372
1373 dm_bufio_unlock(c);
1374}
1375EXPORT_SYMBOL(dm_bufio_forget);
1376
Mikulas Patocka55b082e2014-01-13 19:13:05 -05001377void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1378{
1379 c->minimum_buffers = n;
1380}
1381EXPORT_SYMBOL(dm_bufio_set_minimum_buffers);
1382
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001383unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1384{
1385 return c->block_size;
1386}
1387EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1388
1389sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1390{
1391 return i_size_read(c->bdev->bd_inode) >>
1392 (SECTOR_SHIFT + c->sectors_per_block_bits);
1393}
1394EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1395
1396sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1397{
1398 return b->block;
1399}
1400EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1401
1402void *dm_bufio_get_block_data(struct dm_buffer *b)
1403{
1404 return b->data;
1405}
1406EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1407
1408void *dm_bufio_get_aux_data(struct dm_buffer *b)
1409{
1410 return b + 1;
1411}
1412EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1413
1414struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1415{
1416 return b->c;
1417}
1418EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1419
1420static void drop_buffers(struct dm_bufio_client *c)
1421{
1422 struct dm_buffer *b;
1423 int i;
1424
1425 BUG_ON(dm_bufio_in_request());
1426
1427 /*
1428 * An optimization so that the buffers are not written one-by-one.
1429 */
1430 dm_bufio_write_dirty_buffers_async(c);
1431
1432 dm_bufio_lock(c);
1433
1434 while ((b = __get_unclaimed_buffer(c)))
1435 __free_buffer_wake(b);
1436
1437 for (i = 0; i < LIST_SIZE; i++)
1438 list_for_each_entry(b, &c->lru[i], lru_list)
1439 DMERR("leaked buffer %llx, hold count %u, list %d",
1440 (unsigned long long)b->block, b->hold_count, i);
1441
1442 for (i = 0; i < LIST_SIZE; i++)
1443 BUG_ON(!list_empty(&c->lru[i]));
1444
1445 dm_bufio_unlock(c);
1446}
1447
1448/*
1449 * Test if the buffer is unused and too old, and commit it.
1450 * At if noio is set, we must not do any I/O because we hold
1451 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets rerouted to
1452 * different bufio client.
1453 */
1454static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp,
1455 unsigned long max_jiffies)
1456{
1457 if (jiffies - b->last_accessed < max_jiffies)
Dave Chinner7dc19d52013-08-28 10:18:11 +10001458 return 0;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001459
1460 if (!(gfp & __GFP_IO)) {
1461 if (test_bit(B_READING, &b->state) ||
1462 test_bit(B_WRITING, &b->state) ||
1463 test_bit(B_DIRTY, &b->state))
Dave Chinner7dc19d52013-08-28 10:18:11 +10001464 return 0;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001465 }
1466
1467 if (b->hold_count)
Dave Chinner7dc19d52013-08-28 10:18:11 +10001468 return 0;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001469
1470 __make_buffer_clean(b);
1471 __unlink_buffer(b);
1472 __free_buffer_wake(b);
1473
Dave Chinner7dc19d52013-08-28 10:18:11 +10001474 return 1;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001475}
1476
Dave Chinner7dc19d52013-08-28 10:18:11 +10001477static long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1478 gfp_t gfp_mask)
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001479{
1480 int l;
1481 struct dm_buffer *b, *tmp;
Dave Chinner7dc19d52013-08-28 10:18:11 +10001482 long freed = 0;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001483
1484 for (l = 0; l < LIST_SIZE; l++) {
Dave Chinner7dc19d52013-08-28 10:18:11 +10001485 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1486 freed += __cleanup_old_buffer(b, gfp_mask, 0);
1487 if (!--nr_to_scan)
1488 break;
1489 }
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001490 dm_bufio_cond_resched();
1491 }
Dave Chinner7dc19d52013-08-28 10:18:11 +10001492 return freed;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001493}
1494
Dave Chinner7dc19d52013-08-28 10:18:11 +10001495static unsigned long
1496dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001497{
Dave Chinner7dc19d52013-08-28 10:18:11 +10001498 struct dm_bufio_client *c;
1499 unsigned long freed;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001500
Dave Chinner7dc19d52013-08-28 10:18:11 +10001501 c = container_of(shrink, struct dm_bufio_client, shrinker);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001502 if (sc->gfp_mask & __GFP_IO)
1503 dm_bufio_lock(c);
1504 else if (!dm_bufio_trylock(c))
Dave Chinner7dc19d52013-08-28 10:18:11 +10001505 return SHRINK_STOP;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001506
Dave Chinner7dc19d52013-08-28 10:18:11 +10001507 freed = __scan(c, sc->nr_to_scan, sc->gfp_mask);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001508 dm_bufio_unlock(c);
Dave Chinner7dc19d52013-08-28 10:18:11 +10001509 return freed;
1510}
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001511
Dave Chinner7dc19d52013-08-28 10:18:11 +10001512static unsigned long
1513dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1514{
1515 struct dm_bufio_client *c;
1516 unsigned long count;
1517
1518 c = container_of(shrink, struct dm_bufio_client, shrinker);
1519 if (sc->gfp_mask & __GFP_IO)
1520 dm_bufio_lock(c);
1521 else if (!dm_bufio_trylock(c))
1522 return 0;
1523
1524 count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1525 dm_bufio_unlock(c);
1526 return count;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001527}
1528
1529/*
1530 * Create the buffering interface
1531 */
1532struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1533 unsigned reserved_buffers, unsigned aux_size,
1534 void (*alloc_callback)(struct dm_buffer *),
1535 void (*write_callback)(struct dm_buffer *))
1536{
1537 int r;
1538 struct dm_bufio_client *c;
1539 unsigned i;
1540
1541 BUG_ON(block_size < 1 << SECTOR_SHIFT ||
1542 (block_size & (block_size - 1)));
1543
1544 c = kmalloc(sizeof(*c), GFP_KERNEL);
1545 if (!c) {
1546 r = -ENOMEM;
1547 goto bad_client;
1548 }
1549 c->cache_hash = vmalloc(sizeof(struct hlist_head) << DM_BUFIO_HASH_BITS);
1550 if (!c->cache_hash) {
1551 r = -ENOMEM;
1552 goto bad_hash;
1553 }
1554
1555 c->bdev = bdev;
1556 c->block_size = block_size;
1557 c->sectors_per_block_bits = ffs(block_size) - 1 - SECTOR_SHIFT;
1558 c->pages_per_block_bits = (ffs(block_size) - 1 >= PAGE_SHIFT) ?
1559 ffs(block_size) - 1 - PAGE_SHIFT : 0;
1560 c->blocks_per_page_bits = (ffs(block_size) - 1 < PAGE_SHIFT ?
1561 PAGE_SHIFT - (ffs(block_size) - 1) : 0);
1562
1563 c->aux_size = aux_size;
1564 c->alloc_callback = alloc_callback;
1565 c->write_callback = write_callback;
1566
1567 for (i = 0; i < LIST_SIZE; i++) {
1568 INIT_LIST_HEAD(&c->lru[i]);
1569 c->n_buffers[i] = 0;
1570 }
1571
1572 for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
1573 INIT_HLIST_HEAD(&c->cache_hash[i]);
1574
1575 mutex_init(&c->lock);
1576 INIT_LIST_HEAD(&c->reserved_buffers);
1577 c->need_reserved_buffers = reserved_buffers;
1578
Mikulas Patocka55b082e2014-01-13 19:13:05 -05001579 c->minimum_buffers = DM_BUFIO_MIN_BUFFERS;
1580
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001581 init_waitqueue_head(&c->free_buffer_wait);
1582 c->async_write_error = 0;
1583
1584 c->dm_io = dm_io_client_create();
1585 if (IS_ERR(c->dm_io)) {
1586 r = PTR_ERR(c->dm_io);
1587 goto bad_dm_io;
1588 }
1589
1590 mutex_lock(&dm_bufio_clients_lock);
1591 if (c->blocks_per_page_bits) {
1592 if (!DM_BUFIO_CACHE_NAME(c)) {
1593 DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size);
1594 if (!DM_BUFIO_CACHE_NAME(c)) {
1595 r = -ENOMEM;
1596 mutex_unlock(&dm_bufio_clients_lock);
1597 goto bad_cache;
1598 }
1599 }
1600
1601 if (!DM_BUFIO_CACHE(c)) {
1602 DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c),
1603 c->block_size,
1604 c->block_size, 0, NULL);
1605 if (!DM_BUFIO_CACHE(c)) {
1606 r = -ENOMEM;
1607 mutex_unlock(&dm_bufio_clients_lock);
1608 goto bad_cache;
1609 }
1610 }
1611 }
1612 mutex_unlock(&dm_bufio_clients_lock);
1613
1614 while (c->need_reserved_buffers) {
1615 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1616
1617 if (!b) {
1618 r = -ENOMEM;
1619 goto bad_buffer;
1620 }
1621 __free_buffer_wake(b);
1622 }
1623
1624 mutex_lock(&dm_bufio_clients_lock);
1625 dm_bufio_client_count++;
1626 list_add(&c->client_list, &dm_bufio_all_clients);
1627 __cache_size_refresh();
1628 mutex_unlock(&dm_bufio_clients_lock);
1629
Dave Chinner7dc19d52013-08-28 10:18:11 +10001630 c->shrinker.count_objects = dm_bufio_shrink_count;
1631 c->shrinker.scan_objects = dm_bufio_shrink_scan;
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001632 c->shrinker.seeks = 1;
1633 c->shrinker.batch = 0;
1634 register_shrinker(&c->shrinker);
1635
1636 return c;
1637
1638bad_buffer:
1639bad_cache:
1640 while (!list_empty(&c->reserved_buffers)) {
1641 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1642 struct dm_buffer, lru_list);
1643 list_del(&b->lru_list);
1644 free_buffer(b);
1645 }
1646 dm_io_client_destroy(c->dm_io);
1647bad_dm_io:
1648 vfree(c->cache_hash);
1649bad_hash:
1650 kfree(c);
1651bad_client:
1652 return ERR_PTR(r);
1653}
1654EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1655
1656/*
1657 * Free the buffering interface.
1658 * It is required that there are no references on any buffers.
1659 */
1660void dm_bufio_client_destroy(struct dm_bufio_client *c)
1661{
1662 unsigned i;
1663
1664 drop_buffers(c);
1665
1666 unregister_shrinker(&c->shrinker);
1667
1668 mutex_lock(&dm_bufio_clients_lock);
1669
1670 list_del(&c->client_list);
1671 dm_bufio_client_count--;
1672 __cache_size_refresh();
1673
1674 mutex_unlock(&dm_bufio_clients_lock);
1675
1676 for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
1677 BUG_ON(!hlist_empty(&c->cache_hash[i]));
1678
1679 BUG_ON(c->need_reserved_buffers);
1680
1681 while (!list_empty(&c->reserved_buffers)) {
1682 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1683 struct dm_buffer, lru_list);
1684 list_del(&b->lru_list);
1685 free_buffer(b);
1686 }
1687
1688 for (i = 0; i < LIST_SIZE; i++)
1689 if (c->n_buffers[i])
1690 DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1691
1692 for (i = 0; i < LIST_SIZE; i++)
1693 BUG_ON(c->n_buffers[i]);
1694
1695 dm_io_client_destroy(c->dm_io);
1696 vfree(c->cache_hash);
1697 kfree(c);
1698}
1699EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1700
1701static void cleanup_old_buffers(void)
1702{
Mikulas Patockafe5fe902012-10-12 16:59:46 +01001703 unsigned long max_age = ACCESS_ONCE(dm_bufio_max_age);
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001704 struct dm_bufio_client *c;
1705
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001706 if (max_age > ULONG_MAX / HZ)
1707 max_age = ULONG_MAX / HZ;
1708
1709 mutex_lock(&dm_bufio_clients_lock);
1710 list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
1711 if (!dm_bufio_trylock(c))
1712 continue;
1713
1714 while (!list_empty(&c->lru[LIST_CLEAN])) {
1715 struct dm_buffer *b;
1716 b = list_entry(c->lru[LIST_CLEAN].prev,
1717 struct dm_buffer, lru_list);
Dave Chinner7dc19d52013-08-28 10:18:11 +10001718 if (!__cleanup_old_buffer(b, 0, max_age * HZ))
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001719 break;
1720 dm_bufio_cond_resched();
1721 }
1722
1723 dm_bufio_unlock(c);
1724 dm_bufio_cond_resched();
1725 }
1726 mutex_unlock(&dm_bufio_clients_lock);
1727}
1728
1729static struct workqueue_struct *dm_bufio_wq;
1730static struct delayed_work dm_bufio_work;
1731
1732static void work_fn(struct work_struct *w)
1733{
1734 cleanup_old_buffers();
1735
1736 queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1737 DM_BUFIO_WORK_TIMER_SECS * HZ);
1738}
1739
1740/*----------------------------------------------------------------
1741 * Module setup
1742 *--------------------------------------------------------------*/
1743
1744/*
1745 * This is called only once for the whole dm_bufio module.
1746 * It initializes memory limit.
1747 */
1748static int __init dm_bufio_init(void)
1749{
1750 __u64 mem;
1751
Mikulas Patocka4cb57ab2013-12-05 17:33:29 -05001752 dm_bufio_allocated_kmem_cache = 0;
1753 dm_bufio_allocated_get_free_pages = 0;
1754 dm_bufio_allocated_vmalloc = 0;
1755 dm_bufio_current_allocated = 0;
1756
Mikulas Patocka95d402f2011-10-31 20:19:09 +00001757 memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
1758 memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
1759
1760 mem = (__u64)((totalram_pages - totalhigh_pages) *
1761 DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT;
1762
1763 if (mem > ULONG_MAX)
1764 mem = ULONG_MAX;
1765
1766#ifdef CONFIG_MMU
1767 /*
1768 * Get the size of vmalloc space the same way as VMALLOC_TOTAL
1769 * in fs/proc/internal.h
1770 */
1771 if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100)
1772 mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100;
1773#endif
1774
1775 dm_bufio_default_cache_size = mem;
1776
1777 mutex_lock(&dm_bufio_clients_lock);
1778 __cache_size_refresh();
1779 mutex_unlock(&dm_bufio_clients_lock);
1780
1781 dm_bufio_wq = create_singlethread_workqueue("dm_bufio_cache");
1782 if (!dm_bufio_wq)
1783 return -ENOMEM;
1784
1785 INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1786 queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1787 DM_BUFIO_WORK_TIMER_SECS * HZ);
1788
1789 return 0;
1790}
1791
1792/*
1793 * This is called once when unloading the dm_bufio module.
1794 */
1795static void __exit dm_bufio_exit(void)
1796{
1797 int bug = 0;
1798 int i;
1799
1800 cancel_delayed_work_sync(&dm_bufio_work);
1801 destroy_workqueue(dm_bufio_wq);
1802
1803 for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) {
1804 struct kmem_cache *kc = dm_bufio_caches[i];
1805
1806 if (kc)
1807 kmem_cache_destroy(kc);
1808 }
1809
1810 for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++)
1811 kfree(dm_bufio_cache_names[i]);
1812
1813 if (dm_bufio_client_count) {
1814 DMCRIT("%s: dm_bufio_client_count leaked: %d",
1815 __func__, dm_bufio_client_count);
1816 bug = 1;
1817 }
1818
1819 if (dm_bufio_current_allocated) {
1820 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1821 __func__, dm_bufio_current_allocated);
1822 bug = 1;
1823 }
1824
1825 if (dm_bufio_allocated_get_free_pages) {
1826 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1827 __func__, dm_bufio_allocated_get_free_pages);
1828 bug = 1;
1829 }
1830
1831 if (dm_bufio_allocated_vmalloc) {
1832 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1833 __func__, dm_bufio_allocated_vmalloc);
1834 bug = 1;
1835 }
1836
1837 if (bug)
1838 BUG();
1839}
1840
1841module_init(dm_bufio_init)
1842module_exit(dm_bufio_exit)
1843
1844module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1845MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1846
1847module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1848MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1849
1850module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
1851MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
1852
1853module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
1854MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
1855
1856module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
1857MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
1858
1859module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
1860MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
1861
1862module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
1863MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
1864
1865MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
1866MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
1867MODULE_LICENSE("GPL");