2 * Copyright (C) 2012 Red Hat. All rights reserved.
4 * This file is released under the GPL.
8 #include "dm-bio-prison-v2.h"
9 #include "dm-bio-record.h"
10 #include "dm-cache-metadata.h"
12 #include <linux/dm-io.h>
13 #include <linux/dm-kcopyd.h>
14 #include <linux/jiffies.h>
15 #include <linux/init.h>
16 #include <linux/mempool.h>
17 #include <linux/module.h>
18 #include <linux/rwsem.h>
19 #include <linux/slab.h>
20 #include <linux/vmalloc.h>
22 #define DM_MSG_PREFIX "cache"
24 DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle
,
25 "A percentage of time allocated for copying to and/or from cache");
27 /*----------------------------------------------------------------*/
32 * oblock: index of an origin block
33 * cblock: index of a cache block
34 * promotion: movement of a block from origin to cache
35 * demotion: movement of a block from cache to origin
36 * migration: movement of a block between the origin and cache device,
40 /*----------------------------------------------------------------*/
46 * Sectors of in-flight IO.
51 * The time, in jiffies, when this device became idle (if it is
54 unsigned long idle_time
;
55 unsigned long last_update_time
;
58 static void iot_init(struct io_tracker
*iot
)
60 spin_lock_init(&iot
->lock
);
63 iot
->last_update_time
= jiffies
;
66 static bool __iot_idle_for(struct io_tracker
*iot
, unsigned long jifs
)
71 return time_after(jiffies
, iot
->idle_time
+ jifs
);
74 static bool iot_idle_for(struct io_tracker
*iot
, unsigned long jifs
)
79 spin_lock_irqsave(&iot
->lock
, flags
);
80 r
= __iot_idle_for(iot
, jifs
);
81 spin_unlock_irqrestore(&iot
->lock
, flags
);
86 static void iot_io_begin(struct io_tracker
*iot
, sector_t len
)
90 spin_lock_irqsave(&iot
->lock
, flags
);
91 iot
->in_flight
+= len
;
92 spin_unlock_irqrestore(&iot
->lock
, flags
);
95 static void __iot_io_end(struct io_tracker
*iot
, sector_t len
)
100 iot
->in_flight
-= len
;
102 iot
->idle_time
= jiffies
;
105 static void iot_io_end(struct io_tracker
*iot
, sector_t len
)
109 spin_lock_irqsave(&iot
->lock
, flags
);
110 __iot_io_end(iot
, len
);
111 spin_unlock_irqrestore(&iot
->lock
, flags
);
114 /*----------------------------------------------------------------*/
117 * Represents a chunk of future work. 'input' allows continuations to pass
118 * values between themselves, typically error values.
120 struct continuation
{
121 struct work_struct ws
;
125 static inline void init_continuation(struct continuation
*k
,
126 void (*fn
)(struct work_struct
*))
128 INIT_WORK(&k
->ws
, fn
);
132 static inline void queue_continuation(struct workqueue_struct
*wq
,
133 struct continuation
*k
)
135 queue_work(wq
, &k
->ws
);
138 /*----------------------------------------------------------------*/
141 * The batcher collects together pieces of work that need a particular
142 * operation to occur before they can proceed (typically a commit).
146 * The operation that everyone is waiting for.
148 int (*commit_op
)(void *context
);
149 void *commit_context
;
152 * This is how bios should be issued once the commit op is complete
153 * (accounted_request).
155 void (*issue_op
)(struct bio
*bio
, void *context
);
159 * Queued work gets put on here after commit.
161 struct workqueue_struct
*wq
;
164 struct list_head work_items
;
165 struct bio_list bios
;
166 struct work_struct commit_work
;
168 bool commit_scheduled
;
171 static void __commit(struct work_struct
*_ws
)
173 struct batcher
*b
= container_of(_ws
, struct batcher
, commit_work
);
177 struct list_head work_items
;
178 struct work_struct
*ws
, *tmp
;
179 struct continuation
*k
;
181 struct bio_list bios
;
183 INIT_LIST_HEAD(&work_items
);
184 bio_list_init(&bios
);
187 * We have to grab these before the commit_op to avoid a race
190 spin_lock_irqsave(&b
->lock
, flags
);
191 list_splice_init(&b
->work_items
, &work_items
);
192 bio_list_merge(&bios
, &b
->bios
);
193 bio_list_init(&b
->bios
);
194 b
->commit_scheduled
= false;
195 spin_unlock_irqrestore(&b
->lock
, flags
);
197 r
= b
->commit_op(b
->commit_context
);
199 list_for_each_entry_safe(ws
, tmp
, &work_items
, entry
) {
200 k
= container_of(ws
, struct continuation
, ws
);
202 INIT_LIST_HEAD(&ws
->entry
); /* to avoid a WARN_ON */
203 queue_work(b
->wq
, ws
);
206 while ((bio
= bio_list_pop(&bios
))) {
211 b
->issue_op(bio
, b
->issue_context
);
215 static void batcher_init(struct batcher
*b
,
216 int (*commit_op
)(void *),
217 void *commit_context
,
218 void (*issue_op
)(struct bio
*bio
, void *),
220 struct workqueue_struct
*wq
)
222 b
->commit_op
= commit_op
;
223 b
->commit_context
= commit_context
;
224 b
->issue_op
= issue_op
;
225 b
->issue_context
= issue_context
;
228 spin_lock_init(&b
->lock
);
229 INIT_LIST_HEAD(&b
->work_items
);
230 bio_list_init(&b
->bios
);
231 INIT_WORK(&b
->commit_work
, __commit
);
232 b
->commit_scheduled
= false;
235 static void async_commit(struct batcher
*b
)
237 queue_work(b
->wq
, &b
->commit_work
);
240 static void continue_after_commit(struct batcher
*b
, struct continuation
*k
)
243 bool commit_scheduled
;
245 spin_lock_irqsave(&b
->lock
, flags
);
246 commit_scheduled
= b
->commit_scheduled
;
247 list_add_tail(&k
->ws
.entry
, &b
->work_items
);
248 spin_unlock_irqrestore(&b
->lock
, flags
);
250 if (commit_scheduled
)
255 * Bios are errored if commit failed.
257 static void issue_after_commit(struct batcher
*b
, struct bio
*bio
)
260 bool commit_scheduled
;
262 spin_lock_irqsave(&b
->lock
, flags
);
263 commit_scheduled
= b
->commit_scheduled
;
264 bio_list_add(&b
->bios
, bio
);
265 spin_unlock_irqrestore(&b
->lock
, flags
);
267 if (commit_scheduled
)
272 * Call this if some urgent work is waiting for the commit to complete.
274 static void schedule_commit(struct batcher
*b
)
279 spin_lock_irqsave(&b
->lock
, flags
);
280 immediate
= !list_empty(&b
->work_items
) || !bio_list_empty(&b
->bios
);
281 b
->commit_scheduled
= true;
282 spin_unlock_irqrestore(&b
->lock
, flags
);
289 * There are a couple of places where we let a bio run, but want to do some
290 * work before calling its endio function. We do this by temporarily
291 * changing the endio fn.
293 struct dm_hook_info
{
294 bio_end_io_t
*bi_end_io
;
297 static void dm_hook_bio(struct dm_hook_info
*h
, struct bio
*bio
,
298 bio_end_io_t
*bi_end_io
, void *bi_private
)
300 h
->bi_end_io
= bio
->bi_end_io
;
302 bio
->bi_end_io
= bi_end_io
;
303 bio
->bi_private
= bi_private
;
306 static void dm_unhook_bio(struct dm_hook_info
*h
, struct bio
*bio
)
308 bio
->bi_end_io
= h
->bi_end_io
;
311 /*----------------------------------------------------------------*/
313 #define MIGRATION_POOL_SIZE 128
314 #define COMMIT_PERIOD HZ
315 #define MIGRATION_COUNT_WINDOW 10
318 * The block size of the device holding cache data must be
319 * between 32KB and 1GB.
321 #define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
322 #define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
324 enum cache_metadata_mode
{
325 CM_WRITE
, /* metadata may be changed */
326 CM_READ_ONLY
, /* metadata may not be changed */
332 * Data is written to cached blocks only. These blocks are marked
333 * dirty. If you lose the cache device you will lose data.
334 * Potential performance increase for both reads and writes.
339 * Data is written to both cache and origin. Blocks are never
340 * dirty. Potential performance benfit for reads only.
345 * A degraded mode useful for various cache coherency situations
346 * (eg, rolling back snapshots). Reads and writes always go to the
347 * origin. If a write goes to a cached oblock, then the cache
348 * block is invalidated.
353 struct cache_features
{
354 enum cache_metadata_mode mode
;
355 enum cache_io_mode io_mode
;
356 unsigned metadata_version
;
367 atomic_t copies_avoided
;
368 atomic_t cache_cell_clash
;
369 atomic_t commit_count
;
370 atomic_t discard_count
;
374 struct dm_target
*ti
;
375 struct dm_target_callbacks callbacks
;
377 struct dm_cache_metadata
*cmd
;
380 * Metadata is written to this device.
382 struct dm_dev
*metadata_dev
;
385 * The slower of the two data devices. Typically a spindle.
387 struct dm_dev
*origin_dev
;
390 * The faster of the two data devices. Typically an SSD.
392 struct dm_dev
*cache_dev
;
395 * Size of the origin device in _complete_ blocks and native sectors.
397 dm_oblock_t origin_blocks
;
398 sector_t origin_sectors
;
401 * Size of the cache device in blocks.
403 dm_cblock_t cache_size
;
406 * Fields for converting from sectors to blocks.
408 sector_t sectors_per_block
;
409 int sectors_per_block_shift
;
412 struct list_head deferred_cells
;
413 struct bio_list deferred_bios
;
414 struct bio_list deferred_writethrough_bios
;
415 sector_t migration_threshold
;
416 wait_queue_head_t migration_wait
;
417 atomic_t nr_allocated_migrations
;
420 * The number of in flight migrations that are performing
421 * background io. eg, promotion, writeback.
423 atomic_t nr_io_migrations
;
425 struct rw_semaphore quiesce_lock
;
428 * cache_size entries, dirty if set
431 unsigned long *dirty_bitset
;
434 * origin_blocks entries, discarded if set.
436 dm_dblock_t discard_nr_blocks
;
437 unsigned long *discard_bitset
;
438 uint32_t discard_block_size
; /* a power of 2 times sectors per block */
441 * Rather than reconstructing the table line for the status we just
442 * save it and regurgitate.
444 unsigned nr_ctr_args
;
445 const char **ctr_args
;
447 struct dm_kcopyd_client
*copier
;
448 struct workqueue_struct
*wq
;
449 struct work_struct deferred_bio_worker
;
450 struct work_struct deferred_writethrough_worker
;
451 struct work_struct migration_worker
;
452 struct delayed_work waker
;
453 struct dm_bio_prison_v2
*prison
;
455 mempool_t
*migration_pool
;
457 struct dm_cache_policy
*policy
;
458 unsigned policy_nr_args
;
460 bool need_tick_bio
:1;
463 bool commit_requested
:1;
464 bool loaded_mappings
:1;
465 bool loaded_discards
:1;
468 * Cache features such as write-through.
470 struct cache_features features
;
472 struct cache_stats stats
;
475 * Invalidation fields.
477 spinlock_t invalidation_lock
;
478 struct list_head invalidation_requests
;
480 struct io_tracker tracker
;
482 struct work_struct commit_ws
;
483 struct batcher committer
;
485 struct rw_semaphore background_work_lock
;
488 struct per_bio_data
{
491 struct dm_bio_prison_cell_v2
*cell
;
492 struct dm_hook_info hook_info
;
496 * writethrough fields. These MUST remain at the end of this
497 * structure and the 'cache' member must be the first as it
498 * is used to determine the offset of the writethrough fields.
502 struct dm_bio_details bio_details
;
505 struct dm_cache_migration
{
506 struct continuation k
;
509 struct policy_work
*op
;
510 struct bio
*overwrite_bio
;
511 struct dm_bio_prison_cell_v2
*cell
;
513 dm_cblock_t invalidate_cblock
;
514 dm_oblock_t invalidate_oblock
;
517 /*----------------------------------------------------------------*/
519 static bool writethrough_mode(struct cache_features
*f
)
521 return f
->io_mode
== CM_IO_WRITETHROUGH
;
524 static bool writeback_mode(struct cache_features
*f
)
526 return f
->io_mode
== CM_IO_WRITEBACK
;
529 static inline bool passthrough_mode(struct cache_features
*f
)
531 return unlikely(f
->io_mode
== CM_IO_PASSTHROUGH
);
534 /*----------------------------------------------------------------*/
536 static void wake_deferred_bio_worker(struct cache
*cache
)
538 queue_work(cache
->wq
, &cache
->deferred_bio_worker
);
541 static void wake_deferred_writethrough_worker(struct cache
*cache
)
543 queue_work(cache
->wq
, &cache
->deferred_writethrough_worker
);
546 static void wake_migration_worker(struct cache
*cache
)
548 if (passthrough_mode(&cache
->features
))
551 queue_work(cache
->wq
, &cache
->migration_worker
);
554 /*----------------------------------------------------------------*/
556 static struct dm_bio_prison_cell_v2
*alloc_prison_cell(struct cache
*cache
)
558 return dm_bio_prison_alloc_cell_v2(cache
->prison
, GFP_NOWAIT
);
561 static void free_prison_cell(struct cache
*cache
, struct dm_bio_prison_cell_v2
*cell
)
563 dm_bio_prison_free_cell_v2(cache
->prison
, cell
);
566 static struct dm_cache_migration
*alloc_migration(struct cache
*cache
)
568 struct dm_cache_migration
*mg
;
570 mg
= mempool_alloc(cache
->migration_pool
, GFP_NOWAIT
);
573 atomic_inc(&mg
->cache
->nr_allocated_migrations
);
579 static void free_migration(struct dm_cache_migration
*mg
)
581 struct cache
*cache
= mg
->cache
;
583 if (atomic_dec_and_test(&cache
->nr_allocated_migrations
))
584 wake_up(&cache
->migration_wait
);
586 mempool_free(mg
, cache
->migration_pool
);
589 /*----------------------------------------------------------------*/
591 static inline dm_oblock_t
oblock_succ(dm_oblock_t b
)
593 return to_oblock(from_oblock(b
) + 1ull);
596 static void build_key(dm_oblock_t begin
, dm_oblock_t end
, struct dm_cell_key_v2
*key
)
600 key
->block_begin
= from_oblock(begin
);
601 key
->block_end
= from_oblock(end
);
605 * We have two lock levels. Level 0, which is used to prevent WRITEs, and
606 * level 1 which prevents *both* READs and WRITEs.
608 #define WRITE_LOCK_LEVEL 0
609 #define READ_WRITE_LOCK_LEVEL 1
611 static unsigned lock_level(struct bio
*bio
)
613 return bio_data_dir(bio
) == WRITE
?
615 READ_WRITE_LOCK_LEVEL
;
618 /*----------------------------------------------------------------
620 *--------------------------------------------------------------*/
623 * If using writeback, leave out struct per_bio_data's writethrough fields.
625 #define PB_DATA_SIZE_WB (offsetof(struct per_bio_data, cache))
626 #define PB_DATA_SIZE_WT (sizeof(struct per_bio_data))
628 static size_t get_per_bio_data_size(struct cache
*cache
)
630 return writethrough_mode(&cache
->features
) ? PB_DATA_SIZE_WT
: PB_DATA_SIZE_WB
;
633 static struct per_bio_data
*get_per_bio_data(struct bio
*bio
, size_t data_size
)
635 struct per_bio_data
*pb
= dm_per_bio_data(bio
, data_size
);
640 static struct per_bio_data
*init_per_bio_data(struct bio
*bio
, size_t data_size
)
642 struct per_bio_data
*pb
= get_per_bio_data(bio
, data_size
);
645 pb
->req_nr
= dm_bio_get_target_bio_nr(bio
);
652 /*----------------------------------------------------------------*/
654 static void defer_bio(struct cache
*cache
, struct bio
*bio
)
658 spin_lock_irqsave(&cache
->lock
, flags
);
659 bio_list_add(&cache
->deferred_bios
, bio
);
660 spin_unlock_irqrestore(&cache
->lock
, flags
);
662 wake_deferred_bio_worker(cache
);
665 static void defer_bios(struct cache
*cache
, struct bio_list
*bios
)
669 spin_lock_irqsave(&cache
->lock
, flags
);
670 bio_list_merge(&cache
->deferred_bios
, bios
);
672 spin_unlock_irqrestore(&cache
->lock
, flags
);
674 wake_deferred_bio_worker(cache
);
677 /*----------------------------------------------------------------*/
679 static bool bio_detain_shared(struct cache
*cache
, dm_oblock_t oblock
, struct bio
*bio
)
683 struct per_bio_data
*pb
;
684 struct dm_cell_key_v2 key
;
685 dm_oblock_t end
= to_oblock(from_oblock(oblock
) + 1ULL);
686 struct dm_bio_prison_cell_v2
*cell_prealloc
, *cell
;
688 cell_prealloc
= alloc_prison_cell(cache
); /* FIXME: allow wait if calling from worker */
689 if (!cell_prealloc
) {
690 defer_bio(cache
, bio
);
694 build_key(oblock
, end
, &key
);
695 r
= dm_cell_get_v2(cache
->prison
, &key
, lock_level(bio
), bio
, cell_prealloc
, &cell
);
698 * Failed to get the lock.
700 free_prison_cell(cache
, cell_prealloc
);
704 if (cell
!= cell_prealloc
)
705 free_prison_cell(cache
, cell_prealloc
);
707 pb_size
= get_per_bio_data_size(cache
);
708 pb
= get_per_bio_data(bio
, pb_size
);
714 /*----------------------------------------------------------------*/
716 static bool is_dirty(struct cache
*cache
, dm_cblock_t b
)
718 return test_bit(from_cblock(b
), cache
->dirty_bitset
);
721 static void set_dirty(struct cache
*cache
, dm_cblock_t cblock
)
723 if (!test_and_set_bit(from_cblock(cblock
), cache
->dirty_bitset
)) {
724 atomic_inc(&cache
->nr_dirty
);
725 policy_set_dirty(cache
->policy
, cblock
);
730 * These two are called when setting after migrations to force the policy
731 * and dirty bitset to be in sync.
733 static void force_set_dirty(struct cache
*cache
, dm_cblock_t cblock
)
735 if (!test_and_set_bit(from_cblock(cblock
), cache
->dirty_bitset
))
736 atomic_inc(&cache
->nr_dirty
);
737 policy_set_dirty(cache
->policy
, cblock
);
740 static void force_clear_dirty(struct cache
*cache
, dm_cblock_t cblock
)
742 if (test_and_clear_bit(from_cblock(cblock
), cache
->dirty_bitset
)) {
743 if (atomic_dec_return(&cache
->nr_dirty
) == 0)
744 dm_table_event(cache
->ti
->table
);
747 policy_clear_dirty(cache
->policy
, cblock
);
750 /*----------------------------------------------------------------*/
752 static bool block_size_is_power_of_two(struct cache
*cache
)
754 return cache
->sectors_per_block_shift
>= 0;
757 /* gcc on ARM generates spurious references to __udivdi3 and __umoddi3 */
758 #if defined(CONFIG_ARM) && __GNUC__ == 4 && __GNUC_MINOR__ <= 6
761 static dm_block_t
block_div(dm_block_t b
, uint32_t n
)
768 static dm_block_t
oblocks_per_dblock(struct cache
*cache
)
770 dm_block_t oblocks
= cache
->discard_block_size
;
772 if (block_size_is_power_of_two(cache
))
773 oblocks
>>= cache
->sectors_per_block_shift
;
775 oblocks
= block_div(oblocks
, cache
->sectors_per_block
);
780 static dm_dblock_t
oblock_to_dblock(struct cache
*cache
, dm_oblock_t oblock
)
782 return to_dblock(block_div(from_oblock(oblock
),
783 oblocks_per_dblock(cache
)));
786 static void set_discard(struct cache
*cache
, dm_dblock_t b
)
790 BUG_ON(from_dblock(b
) >= from_dblock(cache
->discard_nr_blocks
));
791 atomic_inc(&cache
->stats
.discard_count
);
793 spin_lock_irqsave(&cache
->lock
, flags
);
794 set_bit(from_dblock(b
), cache
->discard_bitset
);
795 spin_unlock_irqrestore(&cache
->lock
, flags
);
798 static void clear_discard(struct cache
*cache
, dm_dblock_t b
)
802 spin_lock_irqsave(&cache
->lock
, flags
);
803 clear_bit(from_dblock(b
), cache
->discard_bitset
);
804 spin_unlock_irqrestore(&cache
->lock
, flags
);
807 static bool is_discarded(struct cache
*cache
, dm_dblock_t b
)
812 spin_lock_irqsave(&cache
->lock
, flags
);
813 r
= test_bit(from_dblock(b
), cache
->discard_bitset
);
814 spin_unlock_irqrestore(&cache
->lock
, flags
);
819 static bool is_discarded_oblock(struct cache
*cache
, dm_oblock_t b
)
824 spin_lock_irqsave(&cache
->lock
, flags
);
825 r
= test_bit(from_dblock(oblock_to_dblock(cache
, b
)),
826 cache
->discard_bitset
);
827 spin_unlock_irqrestore(&cache
->lock
, flags
);
832 /*----------------------------------------------------------------
834 *--------------------------------------------------------------*/
835 static void remap_to_origin(struct cache
*cache
, struct bio
*bio
)
837 bio
->bi_bdev
= cache
->origin_dev
->bdev
;
840 static void remap_to_cache(struct cache
*cache
, struct bio
*bio
,
843 sector_t bi_sector
= bio
->bi_iter
.bi_sector
;
844 sector_t block
= from_cblock(cblock
);
846 bio
->bi_bdev
= cache
->cache_dev
->bdev
;
847 if (!block_size_is_power_of_two(cache
))
848 bio
->bi_iter
.bi_sector
=
849 (block
* cache
->sectors_per_block
) +
850 sector_div(bi_sector
, cache
->sectors_per_block
);
852 bio
->bi_iter
.bi_sector
=
853 (block
<< cache
->sectors_per_block_shift
) |
854 (bi_sector
& (cache
->sectors_per_block
- 1));
857 static void check_if_tick_bio_needed(struct cache
*cache
, struct bio
*bio
)
860 size_t pb_data_size
= get_per_bio_data_size(cache
);
861 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
863 spin_lock_irqsave(&cache
->lock
, flags
);
864 if (cache
->need_tick_bio
&& !op_is_flush(bio
->bi_opf
) &&
865 bio_op(bio
) != REQ_OP_DISCARD
) {
867 cache
->need_tick_bio
= false;
869 spin_unlock_irqrestore(&cache
->lock
, flags
);
872 static void remap_to_origin_clear_discard(struct cache
*cache
, struct bio
*bio
,
875 // FIXME: this is called way too much.
876 check_if_tick_bio_needed(cache
, bio
);
877 remap_to_origin(cache
, bio
);
878 if (bio_data_dir(bio
) == WRITE
)
879 clear_discard(cache
, oblock_to_dblock(cache
, oblock
));
882 static void remap_to_cache_dirty(struct cache
*cache
, struct bio
*bio
,
883 dm_oblock_t oblock
, dm_cblock_t cblock
)
885 check_if_tick_bio_needed(cache
, bio
);
886 remap_to_cache(cache
, bio
, cblock
);
887 if (bio_data_dir(bio
) == WRITE
) {
888 set_dirty(cache
, cblock
);
889 clear_discard(cache
, oblock_to_dblock(cache
, oblock
));
893 static dm_oblock_t
get_bio_block(struct cache
*cache
, struct bio
*bio
)
895 sector_t block_nr
= bio
->bi_iter
.bi_sector
;
897 if (!block_size_is_power_of_two(cache
))
898 (void) sector_div(block_nr
, cache
->sectors_per_block
);
900 block_nr
>>= cache
->sectors_per_block_shift
;
902 return to_oblock(block_nr
);
905 static bool accountable_bio(struct cache
*cache
, struct bio
*bio
)
907 return bio_op(bio
) != REQ_OP_DISCARD
;
910 static void accounted_begin(struct cache
*cache
, struct bio
*bio
)
912 size_t pb_data_size
= get_per_bio_data_size(cache
);
913 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
915 if (accountable_bio(cache
, bio
)) {
916 pb
->len
= bio_sectors(bio
);
917 iot_io_begin(&cache
->tracker
, pb
->len
);
921 static void accounted_complete(struct cache
*cache
, struct bio
*bio
)
923 size_t pb_data_size
= get_per_bio_data_size(cache
);
924 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
926 iot_io_end(&cache
->tracker
, pb
->len
);
929 static void accounted_request(struct cache
*cache
, struct bio
*bio
)
931 accounted_begin(cache
, bio
);
932 generic_make_request(bio
);
935 static void issue_op(struct bio
*bio
, void *context
)
937 struct cache
*cache
= context
;
938 accounted_request(cache
, bio
);
941 static void defer_writethrough_bio(struct cache
*cache
, struct bio
*bio
)
945 spin_lock_irqsave(&cache
->lock
, flags
);
946 bio_list_add(&cache
->deferred_writethrough_bios
, bio
);
947 spin_unlock_irqrestore(&cache
->lock
, flags
);
949 wake_deferred_writethrough_worker(cache
);
952 static void writethrough_endio(struct bio
*bio
)
954 struct per_bio_data
*pb
= get_per_bio_data(bio
, PB_DATA_SIZE_WT
);
956 dm_unhook_bio(&pb
->hook_info
, bio
);
963 dm_bio_restore(&pb
->bio_details
, bio
);
964 remap_to_cache(pb
->cache
, bio
, pb
->cblock
);
967 * We can't issue this bio directly, since we're in interrupt
968 * context. So it gets put on a bio list for processing by the
971 defer_writethrough_bio(pb
->cache
, bio
);
975 * FIXME: send in parallel, huge latency as is.
976 * When running in writethrough mode we need to send writes to clean blocks
977 * to both the cache and origin devices. In future we'd like to clone the
978 * bio and send them in parallel, but for now we're doing them in
979 * series as this is easier.
981 static void remap_to_origin_then_cache(struct cache
*cache
, struct bio
*bio
,
982 dm_oblock_t oblock
, dm_cblock_t cblock
)
984 struct per_bio_data
*pb
= get_per_bio_data(bio
, PB_DATA_SIZE_WT
);
988 dm_hook_bio(&pb
->hook_info
, bio
, writethrough_endio
, NULL
);
989 dm_bio_record(&pb
->bio_details
, bio
);
991 remap_to_origin_clear_discard(pb
->cache
, bio
, oblock
);
994 /*----------------------------------------------------------------
996 *--------------------------------------------------------------*/
997 static enum cache_metadata_mode
get_cache_mode(struct cache
*cache
)
999 return cache
->features
.mode
;
1002 static const char *cache_device_name(struct cache
*cache
)
1004 return dm_device_name(dm_table_get_md(cache
->ti
->table
));
1007 static void notify_mode_switch(struct cache
*cache
, enum cache_metadata_mode mode
)
1009 const char *descs
[] = {
1015 dm_table_event(cache
->ti
->table
);
1016 DMINFO("%s: switching cache to %s mode",
1017 cache_device_name(cache
), descs
[(int)mode
]);
1020 static void set_cache_mode(struct cache
*cache
, enum cache_metadata_mode new_mode
)
1023 enum cache_metadata_mode old_mode
= get_cache_mode(cache
);
1025 if (dm_cache_metadata_needs_check(cache
->cmd
, &needs_check
)) {
1026 DMERR("%s: unable to read needs_check flag, setting failure mode.",
1027 cache_device_name(cache
));
1031 if (new_mode
== CM_WRITE
&& needs_check
) {
1032 DMERR("%s: unable to switch cache to write mode until repaired.",
1033 cache_device_name(cache
));
1034 if (old_mode
!= new_mode
)
1035 new_mode
= old_mode
;
1037 new_mode
= CM_READ_ONLY
;
1040 /* Never move out of fail mode */
1041 if (old_mode
== CM_FAIL
)
1047 dm_cache_metadata_set_read_only(cache
->cmd
);
1051 dm_cache_metadata_set_read_write(cache
->cmd
);
1055 cache
->features
.mode
= new_mode
;
1057 if (new_mode
!= old_mode
)
1058 notify_mode_switch(cache
, new_mode
);
1061 static void abort_transaction(struct cache
*cache
)
1063 const char *dev_name
= cache_device_name(cache
);
1065 if (get_cache_mode(cache
) >= CM_READ_ONLY
)
1068 if (dm_cache_metadata_set_needs_check(cache
->cmd
)) {
1069 DMERR("%s: failed to set 'needs_check' flag in metadata", dev_name
);
1070 set_cache_mode(cache
, CM_FAIL
);
1073 DMERR_LIMIT("%s: aborting current metadata transaction", dev_name
);
1074 if (dm_cache_metadata_abort(cache
->cmd
)) {
1075 DMERR("%s: failed to abort metadata transaction", dev_name
);
1076 set_cache_mode(cache
, CM_FAIL
);
1080 static void metadata_operation_failed(struct cache
*cache
, const char *op
, int r
)
1082 DMERR_LIMIT("%s: metadata operation '%s' failed: error = %d",
1083 cache_device_name(cache
), op
, r
);
1084 abort_transaction(cache
);
1085 set_cache_mode(cache
, CM_READ_ONLY
);
1088 /*----------------------------------------------------------------*/
1090 static void load_stats(struct cache
*cache
)
1092 struct dm_cache_statistics stats
;
1094 dm_cache_metadata_get_stats(cache
->cmd
, &stats
);
1095 atomic_set(&cache
->stats
.read_hit
, stats
.read_hits
);
1096 atomic_set(&cache
->stats
.read_miss
, stats
.read_misses
);
1097 atomic_set(&cache
->stats
.write_hit
, stats
.write_hits
);
1098 atomic_set(&cache
->stats
.write_miss
, stats
.write_misses
);
1101 static void save_stats(struct cache
*cache
)
1103 struct dm_cache_statistics stats
;
1105 if (get_cache_mode(cache
) >= CM_READ_ONLY
)
1108 stats
.read_hits
= atomic_read(&cache
->stats
.read_hit
);
1109 stats
.read_misses
= atomic_read(&cache
->stats
.read_miss
);
1110 stats
.write_hits
= atomic_read(&cache
->stats
.write_hit
);
1111 stats
.write_misses
= atomic_read(&cache
->stats
.write_miss
);
1113 dm_cache_metadata_set_stats(cache
->cmd
, &stats
);
1116 static void update_stats(struct cache_stats
*stats
, enum policy_operation op
)
1119 case POLICY_PROMOTE
:
1120 atomic_inc(&stats
->promotion
);
1124 atomic_inc(&stats
->demotion
);
1127 case POLICY_WRITEBACK
:
1128 atomic_inc(&stats
->writeback
);
1133 /*----------------------------------------------------------------
1134 * Migration processing
1136 * Migration covers moving data from the origin device to the cache, or
1138 *--------------------------------------------------------------*/
1140 static void inc_io_migrations(struct cache
*cache
)
1142 atomic_inc(&cache
->nr_io_migrations
);
1145 static void dec_io_migrations(struct cache
*cache
)
1147 atomic_dec(&cache
->nr_io_migrations
);
1150 static bool discard_or_flush(struct bio
*bio
)
1152 return bio_op(bio
) == REQ_OP_DISCARD
|| op_is_flush(bio
->bi_opf
);
1155 static void calc_discard_block_range(struct cache
*cache
, struct bio
*bio
,
1156 dm_dblock_t
*b
, dm_dblock_t
*e
)
1158 sector_t sb
= bio
->bi_iter
.bi_sector
;
1159 sector_t se
= bio_end_sector(bio
);
1161 *b
= to_dblock(dm_sector_div_up(sb
, cache
->discard_block_size
));
1163 if (se
- sb
< cache
->discard_block_size
)
1166 *e
= to_dblock(block_div(se
, cache
->discard_block_size
));
1169 /*----------------------------------------------------------------*/
1171 static void prevent_background_work(struct cache
*cache
)
1174 down_write(&cache
->background_work_lock
);
1178 static void allow_background_work(struct cache
*cache
)
1181 up_write(&cache
->background_work_lock
);
1185 static bool background_work_begin(struct cache
*cache
)
1190 r
= down_read_trylock(&cache
->background_work_lock
);
1196 static void background_work_end(struct cache
*cache
)
1199 up_read(&cache
->background_work_lock
);
1203 /*----------------------------------------------------------------*/
1205 static void quiesce(struct dm_cache_migration
*mg
,
1206 void (*continuation
)(struct work_struct
*))
1208 init_continuation(&mg
->k
, continuation
);
1209 dm_cell_quiesce_v2(mg
->cache
->prison
, mg
->cell
, &mg
->k
.ws
);
1212 static struct dm_cache_migration
*ws_to_mg(struct work_struct
*ws
)
1214 struct continuation
*k
= container_of(ws
, struct continuation
, ws
);
1215 return container_of(k
, struct dm_cache_migration
, k
);
1218 static void copy_complete(int read_err
, unsigned long write_err
, void *context
)
1220 struct dm_cache_migration
*mg
= container_of(context
, struct dm_cache_migration
, k
);
1222 if (read_err
|| write_err
)
1225 queue_continuation(mg
->cache
->wq
, &mg
->k
);
1228 static int copy(struct dm_cache_migration
*mg
, bool promote
)
1231 struct dm_io_region o_region
, c_region
;
1232 struct cache
*cache
= mg
->cache
;
1234 o_region
.bdev
= cache
->origin_dev
->bdev
;
1235 o_region
.sector
= from_oblock(mg
->op
->oblock
) * cache
->sectors_per_block
;
1236 o_region
.count
= cache
->sectors_per_block
;
1238 c_region
.bdev
= cache
->cache_dev
->bdev
;
1239 c_region
.sector
= from_cblock(mg
->op
->cblock
) * cache
->sectors_per_block
;
1240 c_region
.count
= cache
->sectors_per_block
;
1243 r
= dm_kcopyd_copy(cache
->copier
, &o_region
, 1, &c_region
, 0, copy_complete
, &mg
->k
);
1245 r
= dm_kcopyd_copy(cache
->copier
, &c_region
, 1, &o_region
, 0, copy_complete
, &mg
->k
);
1250 static void bio_drop_shared_lock(struct cache
*cache
, struct bio
*bio
)
1252 size_t pb_data_size
= get_per_bio_data_size(cache
);
1253 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
1255 if (pb
->cell
&& dm_cell_put_v2(cache
->prison
, pb
->cell
))
1256 free_prison_cell(cache
, pb
->cell
);
1260 static void overwrite_endio(struct bio
*bio
)
1262 struct dm_cache_migration
*mg
= bio
->bi_private
;
1263 struct cache
*cache
= mg
->cache
;
1264 size_t pb_data_size
= get_per_bio_data_size(cache
);
1265 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
1267 dm_unhook_bio(&pb
->hook_info
, bio
);
1270 mg
->k
.input
= bio
->bi_error
;
1272 queue_continuation(mg
->cache
->wq
, &mg
->k
);
1275 static void overwrite(struct dm_cache_migration
*mg
,
1276 void (*continuation
)(struct work_struct
*))
1278 struct bio
*bio
= mg
->overwrite_bio
;
1279 size_t pb_data_size
= get_per_bio_data_size(mg
->cache
);
1280 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
1282 dm_hook_bio(&pb
->hook_info
, bio
, overwrite_endio
, mg
);
1285 * The overwrite bio is part of the copy operation, as such it does
1286 * not set/clear discard or dirty flags.
1288 if (mg
->op
->op
== POLICY_PROMOTE
)
1289 remap_to_cache(mg
->cache
, bio
, mg
->op
->cblock
);
1291 remap_to_origin(mg
->cache
, bio
);
1293 init_continuation(&mg
->k
, continuation
);
1294 accounted_request(mg
->cache
, bio
);
1300 * 1) exclusive lock preventing WRITEs
1302 * 3) copy or issue overwrite bio
1303 * 4) upgrade to exclusive lock preventing READs and WRITEs
1305 * 6) update metadata and commit
1308 static void mg_complete(struct dm_cache_migration
*mg
, bool success
)
1310 struct bio_list bios
;
1311 struct cache
*cache
= mg
->cache
;
1312 struct policy_work
*op
= mg
->op
;
1313 dm_cblock_t cblock
= op
->cblock
;
1316 update_stats(&cache
->stats
, op
->op
);
1319 case POLICY_PROMOTE
:
1320 clear_discard(cache
, oblock_to_dblock(cache
, op
->oblock
));
1321 policy_complete_background_work(cache
->policy
, op
, success
);
1323 if (mg
->overwrite_bio
) {
1325 force_set_dirty(cache
, cblock
);
1327 mg
->overwrite_bio
->bi_error
= (mg
->k
.input
? : -EIO
);
1328 bio_endio(mg
->overwrite_bio
);
1331 force_clear_dirty(cache
, cblock
);
1332 dec_io_migrations(cache
);
1338 * We clear dirty here to update the nr_dirty counter.
1341 force_clear_dirty(cache
, cblock
);
1342 policy_complete_background_work(cache
->policy
, op
, success
);
1343 dec_io_migrations(cache
);
1346 case POLICY_WRITEBACK
:
1348 force_clear_dirty(cache
, cblock
);
1349 policy_complete_background_work(cache
->policy
, op
, success
);
1350 dec_io_migrations(cache
);
1354 bio_list_init(&bios
);
1356 if (dm_cell_unlock_v2(cache
->prison
, mg
->cell
, &bios
))
1357 free_prison_cell(cache
, mg
->cell
);
1361 defer_bios(cache
, &bios
);
1362 wake_migration_worker(cache
);
1364 background_work_end(cache
);
1367 static void mg_success(struct work_struct
*ws
)
1369 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1370 mg_complete(mg
, mg
->k
.input
== 0);
1373 static void mg_update_metadata(struct work_struct
*ws
)
1376 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1377 struct cache
*cache
= mg
->cache
;
1378 struct policy_work
*op
= mg
->op
;
1381 case POLICY_PROMOTE
:
1382 r
= dm_cache_insert_mapping(cache
->cmd
, op
->cblock
, op
->oblock
);
1384 DMERR_LIMIT("%s: migration failed; couldn't insert mapping",
1385 cache_device_name(cache
));
1386 metadata_operation_failed(cache
, "dm_cache_insert_mapping", r
);
1388 mg_complete(mg
, false);
1391 mg_complete(mg
, true);
1395 r
= dm_cache_remove_mapping(cache
->cmd
, op
->cblock
);
1397 DMERR_LIMIT("%s: migration failed; couldn't update on disk metadata",
1398 cache_device_name(cache
));
1399 metadata_operation_failed(cache
, "dm_cache_remove_mapping", r
);
1401 mg_complete(mg
, false);
1406 * It would be nice if we only had to commit when a REQ_FLUSH
1407 * comes through. But there's one scenario that we have to
1410 * - vblock x in a cache block
1412 * - cache block gets reallocated and over written
1415 * When we recover, because there was no commit the cache will
1416 * rollback to having the data for vblock x in the cache block.
1417 * But the cache block has since been overwritten, so it'll end
1418 * up pointing to data that was never in 'x' during the history
1421 * To avoid this issue we require a commit as part of the
1422 * demotion operation.
1424 init_continuation(&mg
->k
, mg_success
);
1425 continue_after_commit(&cache
->committer
, &mg
->k
);
1426 schedule_commit(&cache
->committer
);
1429 case POLICY_WRITEBACK
:
1430 mg_complete(mg
, true);
1435 static void mg_update_metadata_after_copy(struct work_struct
*ws
)
1437 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1440 * Did the copy succeed?
1443 mg_complete(mg
, false);
1445 mg_update_metadata(ws
);
1448 static void mg_upgrade_lock(struct work_struct
*ws
)
1451 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1454 * Did the copy succeed?
1457 mg_complete(mg
, false);
1461 * Now we want the lock to prevent both reads and writes.
1463 r
= dm_cell_lock_promote_v2(mg
->cache
->prison
, mg
->cell
,
1464 READ_WRITE_LOCK_LEVEL
);
1466 mg_complete(mg
, false);
1469 quiesce(mg
, mg_update_metadata
);
1472 mg_update_metadata(ws
);
1476 static void mg_copy(struct work_struct
*ws
)
1479 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1481 if (mg
->overwrite_bio
) {
1483 * It's safe to do this here, even though it's new data
1484 * because all IO has been locked out of the block.
1486 * mg_lock_writes() already took READ_WRITE_LOCK_LEVEL
1487 * so _not_ using mg_upgrade_lock() as continutation.
1489 overwrite(mg
, mg_update_metadata_after_copy
);
1492 struct cache
*cache
= mg
->cache
;
1493 struct policy_work
*op
= mg
->op
;
1494 bool is_policy_promote
= (op
->op
== POLICY_PROMOTE
);
1496 if ((!is_policy_promote
&& !is_dirty(cache
, op
->cblock
)) ||
1497 is_discarded_oblock(cache
, op
->oblock
)) {
1498 mg_upgrade_lock(ws
);
1502 init_continuation(&mg
->k
, mg_upgrade_lock
);
1504 r
= copy(mg
, is_policy_promote
);
1506 DMERR_LIMIT("%s: migration copy failed", cache_device_name(cache
));
1508 mg_complete(mg
, false);
1513 static int mg_lock_writes(struct dm_cache_migration
*mg
)
1516 struct dm_cell_key_v2 key
;
1517 struct cache
*cache
= mg
->cache
;
1518 struct dm_bio_prison_cell_v2
*prealloc
;
1520 prealloc
= alloc_prison_cell(cache
);
1522 DMERR_LIMIT("%s: alloc_prison_cell failed", cache_device_name(cache
));
1523 mg_complete(mg
, false);
1528 * Prevent writes to the block, but allow reads to continue.
1529 * Unless we're using an overwrite bio, in which case we lock
1532 build_key(mg
->op
->oblock
, oblock_succ(mg
->op
->oblock
), &key
);
1533 r
= dm_cell_lock_v2(cache
->prison
, &key
,
1534 mg
->overwrite_bio
? READ_WRITE_LOCK_LEVEL
: WRITE_LOCK_LEVEL
,
1535 prealloc
, &mg
->cell
);
1537 free_prison_cell(cache
, prealloc
);
1538 mg_complete(mg
, false);
1542 if (mg
->cell
!= prealloc
)
1543 free_prison_cell(cache
, prealloc
);
1548 quiesce(mg
, mg_copy
);
1553 static int mg_start(struct cache
*cache
, struct policy_work
*op
, struct bio
*bio
)
1555 struct dm_cache_migration
*mg
;
1557 if (!background_work_begin(cache
)) {
1558 policy_complete_background_work(cache
->policy
, op
, false);
1562 mg
= alloc_migration(cache
);
1564 policy_complete_background_work(cache
->policy
, op
, false);
1565 background_work_end(cache
);
1569 memset(mg
, 0, sizeof(*mg
));
1573 mg
->overwrite_bio
= bio
;
1576 inc_io_migrations(cache
);
1578 return mg_lock_writes(mg
);
1581 /*----------------------------------------------------------------
1582 * invalidation processing
1583 *--------------------------------------------------------------*/
1585 static void invalidate_complete(struct dm_cache_migration
*mg
, bool success
)
1587 struct bio_list bios
;
1588 struct cache
*cache
= mg
->cache
;
1590 bio_list_init(&bios
);
1591 if (dm_cell_unlock_v2(cache
->prison
, mg
->cell
, &bios
))
1592 free_prison_cell(cache
, mg
->cell
);
1594 if (!success
&& mg
->overwrite_bio
)
1595 bio_io_error(mg
->overwrite_bio
);
1598 defer_bios(cache
, &bios
);
1600 background_work_end(cache
);
1603 static void invalidate_completed(struct work_struct
*ws
)
1605 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1606 invalidate_complete(mg
, !mg
->k
.input
);
1609 static int invalidate_cblock(struct cache
*cache
, dm_cblock_t cblock
)
1611 int r
= policy_invalidate_mapping(cache
->policy
, cblock
);
1613 r
= dm_cache_remove_mapping(cache
->cmd
, cblock
);
1615 DMERR_LIMIT("%s: invalidation failed; couldn't update on disk metadata",
1616 cache_device_name(cache
));
1617 metadata_operation_failed(cache
, "dm_cache_remove_mapping", r
);
1620 } else if (r
== -ENODATA
) {
1622 * Harmless, already unmapped.
1627 DMERR("%s: policy_invalidate_mapping failed", cache_device_name(cache
));
1632 static void invalidate_remove(struct work_struct
*ws
)
1635 struct dm_cache_migration
*mg
= ws_to_mg(ws
);
1636 struct cache
*cache
= mg
->cache
;
1638 r
= invalidate_cblock(cache
, mg
->invalidate_cblock
);
1640 invalidate_complete(mg
, false);
1644 init_continuation(&mg
->k
, invalidate_completed
);
1645 continue_after_commit(&cache
->committer
, &mg
->k
);
1646 remap_to_origin_clear_discard(cache
, mg
->overwrite_bio
, mg
->invalidate_oblock
);
1647 mg
->overwrite_bio
= NULL
;
1648 schedule_commit(&cache
->committer
);
1651 static int invalidate_lock(struct dm_cache_migration
*mg
)
1654 struct dm_cell_key_v2 key
;
1655 struct cache
*cache
= mg
->cache
;
1656 struct dm_bio_prison_cell_v2
*prealloc
;
1658 prealloc
= alloc_prison_cell(cache
);
1660 invalidate_complete(mg
, false);
1664 build_key(mg
->invalidate_oblock
, oblock_succ(mg
->invalidate_oblock
), &key
);
1665 r
= dm_cell_lock_v2(cache
->prison
, &key
,
1666 READ_WRITE_LOCK_LEVEL
, prealloc
, &mg
->cell
);
1668 free_prison_cell(cache
, prealloc
);
1669 invalidate_complete(mg
, false);
1673 if (mg
->cell
!= prealloc
)
1674 free_prison_cell(cache
, prealloc
);
1677 quiesce(mg
, invalidate_remove
);
1681 * We can't call invalidate_remove() directly here because we
1682 * might still be in request context.
1684 init_continuation(&mg
->k
, invalidate_remove
);
1685 queue_work(cache
->wq
, &mg
->k
.ws
);
1691 static int invalidate_start(struct cache
*cache
, dm_cblock_t cblock
,
1692 dm_oblock_t oblock
, struct bio
*bio
)
1694 struct dm_cache_migration
*mg
;
1696 if (!background_work_begin(cache
))
1699 mg
= alloc_migration(cache
);
1701 background_work_end(cache
);
1705 memset(mg
, 0, sizeof(*mg
));
1708 mg
->overwrite_bio
= bio
;
1709 mg
->invalidate_cblock
= cblock
;
1710 mg
->invalidate_oblock
= oblock
;
1712 return invalidate_lock(mg
);
1715 /*----------------------------------------------------------------
1717 *--------------------------------------------------------------*/
1724 static enum busy
spare_migration_bandwidth(struct cache
*cache
)
1726 bool idle
= iot_idle_for(&cache
->tracker
, HZ
);
1727 sector_t current_volume
= (atomic_read(&cache
->nr_io_migrations
) + 1) *
1728 cache
->sectors_per_block
;
1730 if (idle
&& current_volume
<= cache
->migration_threshold
)
1736 static void inc_hit_counter(struct cache
*cache
, struct bio
*bio
)
1738 atomic_inc(bio_data_dir(bio
) == READ
?
1739 &cache
->stats
.read_hit
: &cache
->stats
.write_hit
);
1742 static void inc_miss_counter(struct cache
*cache
, struct bio
*bio
)
1744 atomic_inc(bio_data_dir(bio
) == READ
?
1745 &cache
->stats
.read_miss
: &cache
->stats
.write_miss
);
1748 /*----------------------------------------------------------------*/
1750 static bool bio_writes_complete_block(struct cache
*cache
, struct bio
*bio
)
1752 return (bio_data_dir(bio
) == WRITE
) &&
1753 (bio
->bi_iter
.bi_size
== (cache
->sectors_per_block
<< SECTOR_SHIFT
));
1756 static bool optimisable_bio(struct cache
*cache
, struct bio
*bio
, dm_oblock_t block
)
1758 return writeback_mode(&cache
->features
) &&
1759 (is_discarded_oblock(cache
, block
) || bio_writes_complete_block(cache
, bio
));
1762 static int map_bio(struct cache
*cache
, struct bio
*bio
, dm_oblock_t block
,
1763 bool *commit_needed
)
1766 bool rb
, background_queued
;
1768 size_t pb_data_size
= get_per_bio_data_size(cache
);
1769 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
1771 *commit_needed
= false;
1773 rb
= bio_detain_shared(cache
, block
, bio
);
1776 * An exclusive lock is held for this block, so we have to
1777 * wait. We set the commit_needed flag so the current
1778 * transaction will be committed asap, allowing this lock
1781 *commit_needed
= true;
1782 return DM_MAPIO_SUBMITTED
;
1785 data_dir
= bio_data_dir(bio
);
1787 if (optimisable_bio(cache
, bio
, block
)) {
1788 struct policy_work
*op
= NULL
;
1790 r
= policy_lookup_with_work(cache
->policy
, block
, &cblock
, data_dir
, true, &op
);
1791 if (unlikely(r
&& r
!= -ENOENT
)) {
1792 DMERR_LIMIT("%s: policy_lookup_with_work() failed with r = %d",
1793 cache_device_name(cache
), r
);
1795 return DM_MAPIO_SUBMITTED
;
1798 if (r
== -ENOENT
&& op
) {
1799 bio_drop_shared_lock(cache
, bio
);
1800 BUG_ON(op
->op
!= POLICY_PROMOTE
);
1801 mg_start(cache
, op
, bio
);
1802 return DM_MAPIO_SUBMITTED
;
1805 r
= policy_lookup(cache
->policy
, block
, &cblock
, data_dir
, false, &background_queued
);
1806 if (unlikely(r
&& r
!= -ENOENT
)) {
1807 DMERR_LIMIT("%s: policy_lookup() failed with r = %d",
1808 cache_device_name(cache
), r
);
1810 return DM_MAPIO_SUBMITTED
;
1813 if (background_queued
)
1814 wake_migration_worker(cache
);
1821 inc_miss_counter(cache
, bio
);
1822 if (pb
->req_nr
== 0) {
1823 accounted_begin(cache
, bio
);
1824 remap_to_origin_clear_discard(cache
, bio
, block
);
1828 * This is a duplicate writethrough io that is no
1829 * longer needed because the block has been demoted.
1832 return DM_MAPIO_SUBMITTED
;
1838 inc_hit_counter(cache
, bio
);
1841 * Passthrough always maps to the origin, invalidating any
1842 * cache blocks that are written to.
1844 if (passthrough_mode(&cache
->features
)) {
1845 if (bio_data_dir(bio
) == WRITE
) {
1846 bio_drop_shared_lock(cache
, bio
);
1847 atomic_inc(&cache
->stats
.demotion
);
1848 invalidate_start(cache
, cblock
, block
, bio
);
1850 remap_to_origin_clear_discard(cache
, bio
, block
);
1853 if (bio_data_dir(bio
) == WRITE
&& writethrough_mode(&cache
->features
) &&
1854 !is_dirty(cache
, cblock
)) {
1855 remap_to_origin_then_cache(cache
, bio
, block
, cblock
);
1856 accounted_begin(cache
, bio
);
1858 remap_to_cache_dirty(cache
, bio
, block
, cblock
);
1863 * dm core turns FUA requests into a separate payload and FLUSH req.
1865 if (bio
->bi_opf
& REQ_FUA
) {
1867 * issue_after_commit will call accounted_begin a second time. So
1868 * we call accounted_complete() to avoid double accounting.
1870 accounted_complete(cache
, bio
);
1871 issue_after_commit(&cache
->committer
, bio
);
1872 *commit_needed
= true;
1873 return DM_MAPIO_SUBMITTED
;
1876 return DM_MAPIO_REMAPPED
;
1879 static bool process_bio(struct cache
*cache
, struct bio
*bio
)
1883 if (map_bio(cache
, bio
, get_bio_block(cache
, bio
), &commit_needed
) == DM_MAPIO_REMAPPED
)
1884 generic_make_request(bio
);
1886 return commit_needed
;
1890 * A non-zero return indicates read_only or fail_io mode.
1892 static int commit(struct cache
*cache
, bool clean_shutdown
)
1896 if (get_cache_mode(cache
) >= CM_READ_ONLY
)
1899 atomic_inc(&cache
->stats
.commit_count
);
1900 r
= dm_cache_commit(cache
->cmd
, clean_shutdown
);
1902 metadata_operation_failed(cache
, "dm_cache_commit", r
);
1908 * Used by the batcher.
1910 static int commit_op(void *context
)
1912 struct cache
*cache
= context
;
1914 if (dm_cache_changed_this_transaction(cache
->cmd
))
1915 return commit(cache
, false);
1920 /*----------------------------------------------------------------*/
1922 static bool process_flush_bio(struct cache
*cache
, struct bio
*bio
)
1924 size_t pb_data_size
= get_per_bio_data_size(cache
);
1925 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
1928 remap_to_origin(cache
, bio
);
1930 remap_to_cache(cache
, bio
, 0);
1932 issue_after_commit(&cache
->committer
, bio
);
1936 static bool process_discard_bio(struct cache
*cache
, struct bio
*bio
)
1940 // FIXME: do we need to lock the region? Or can we just assume the
1941 // user wont be so foolish as to issue discard concurrently with
1943 calc_discard_block_range(cache
, bio
, &b
, &e
);
1945 set_discard(cache
, b
);
1946 b
= to_dblock(from_dblock(b
) + 1);
1954 static void process_deferred_bios(struct work_struct
*ws
)
1956 struct cache
*cache
= container_of(ws
, struct cache
, deferred_bio_worker
);
1958 unsigned long flags
;
1959 bool commit_needed
= false;
1960 struct bio_list bios
;
1963 bio_list_init(&bios
);
1965 spin_lock_irqsave(&cache
->lock
, flags
);
1966 bio_list_merge(&bios
, &cache
->deferred_bios
);
1967 bio_list_init(&cache
->deferred_bios
);
1968 spin_unlock_irqrestore(&cache
->lock
, flags
);
1970 while ((bio
= bio_list_pop(&bios
))) {
1971 if (bio
->bi_opf
& REQ_PREFLUSH
)
1972 commit_needed
= process_flush_bio(cache
, bio
) || commit_needed
;
1974 else if (bio_op(bio
) == REQ_OP_DISCARD
)
1975 commit_needed
= process_discard_bio(cache
, bio
) || commit_needed
;
1978 commit_needed
= process_bio(cache
, bio
) || commit_needed
;
1982 schedule_commit(&cache
->committer
);
1985 static void process_deferred_writethrough_bios(struct work_struct
*ws
)
1987 struct cache
*cache
= container_of(ws
, struct cache
, deferred_writethrough_worker
);
1989 unsigned long flags
;
1990 struct bio_list bios
;
1993 bio_list_init(&bios
);
1995 spin_lock_irqsave(&cache
->lock
, flags
);
1996 bio_list_merge(&bios
, &cache
->deferred_writethrough_bios
);
1997 bio_list_init(&cache
->deferred_writethrough_bios
);
1998 spin_unlock_irqrestore(&cache
->lock
, flags
);
2001 * These bios have already been through accounted_begin()
2003 while ((bio
= bio_list_pop(&bios
)))
2004 generic_make_request(bio
);
2007 /*----------------------------------------------------------------
2009 *--------------------------------------------------------------*/
2011 static void requeue_deferred_bios(struct cache
*cache
)
2014 struct bio_list bios
;
2016 bio_list_init(&bios
);
2017 bio_list_merge(&bios
, &cache
->deferred_bios
);
2018 bio_list_init(&cache
->deferred_bios
);
2020 while ((bio
= bio_list_pop(&bios
))) {
2021 bio
->bi_error
= DM_ENDIO_REQUEUE
;
2027 * We want to commit periodically so that not too much
2028 * unwritten metadata builds up.
2030 static void do_waker(struct work_struct
*ws
)
2032 struct cache
*cache
= container_of(to_delayed_work(ws
), struct cache
, waker
);
2034 policy_tick(cache
->policy
, true);
2035 wake_migration_worker(cache
);
2036 schedule_commit(&cache
->committer
);
2037 queue_delayed_work(cache
->wq
, &cache
->waker
, COMMIT_PERIOD
);
2040 static void check_migrations(struct work_struct
*ws
)
2043 struct policy_work
*op
;
2044 struct cache
*cache
= container_of(ws
, struct cache
, migration_worker
);
2048 b
= spare_migration_bandwidth(cache
);
2050 r
= policy_get_background_work(cache
->policy
, b
== IDLE
, &op
);
2055 DMERR_LIMIT("%s: policy_background_work failed",
2056 cache_device_name(cache
));
2060 r
= mg_start(cache
, op
, NULL
);
2066 /*----------------------------------------------------------------
2068 *--------------------------------------------------------------*/
2071 * This function gets called on the error paths of the constructor, so we
2072 * have to cope with a partially initialised struct.
2074 static void destroy(struct cache
*cache
)
2078 mempool_destroy(cache
->migration_pool
);
2081 dm_bio_prison_destroy_v2(cache
->prison
);
2084 destroy_workqueue(cache
->wq
);
2086 if (cache
->dirty_bitset
)
2087 free_bitset(cache
->dirty_bitset
);
2089 if (cache
->discard_bitset
)
2090 free_bitset(cache
->discard_bitset
);
2093 dm_kcopyd_client_destroy(cache
->copier
);
2096 dm_cache_metadata_close(cache
->cmd
);
2098 if (cache
->metadata_dev
)
2099 dm_put_device(cache
->ti
, cache
->metadata_dev
);
2101 if (cache
->origin_dev
)
2102 dm_put_device(cache
->ti
, cache
->origin_dev
);
2104 if (cache
->cache_dev
)
2105 dm_put_device(cache
->ti
, cache
->cache_dev
);
2108 dm_cache_policy_destroy(cache
->policy
);
2110 for (i
= 0; i
< cache
->nr_ctr_args
; i
++)
2111 kfree(cache
->ctr_args
[i
]);
2112 kfree(cache
->ctr_args
);
2117 static void cache_dtr(struct dm_target
*ti
)
2119 struct cache
*cache
= ti
->private;
2124 static sector_t
get_dev_size(struct dm_dev
*dev
)
2126 return i_size_read(dev
->bdev
->bd_inode
) >> SECTOR_SHIFT
;
2129 /*----------------------------------------------------------------*/
2132 * Construct a cache device mapping.
2134 * cache <metadata dev> <cache dev> <origin dev> <block size>
2135 * <#feature args> [<feature arg>]*
2136 * <policy> <#policy args> [<policy arg>]*
2138 * metadata dev : fast device holding the persistent metadata
2139 * cache dev : fast device holding cached data blocks
2140 * origin dev : slow device holding original data blocks
2141 * block size : cache unit size in sectors
2143 * #feature args : number of feature arguments passed
2144 * feature args : writethrough. (The default is writeback.)
2146 * policy : the replacement policy to use
2147 * #policy args : an even number of policy arguments corresponding
2148 * to key/value pairs passed to the policy
2149 * policy args : key/value pairs passed to the policy
2150 * E.g. 'sequential_threshold 1024'
2151 * See cache-policies.txt for details.
2153 * Optional feature arguments are:
2154 * writethrough : write through caching that prohibits cache block
2155 * content from being different from origin block content.
2156 * Without this argument, the default behaviour is to write
2157 * back cache block contents later for performance reasons,
2158 * so they may differ from the corresponding origin blocks.
2161 struct dm_target
*ti
;
2163 struct dm_dev
*metadata_dev
;
2165 struct dm_dev
*cache_dev
;
2166 sector_t cache_sectors
;
2168 struct dm_dev
*origin_dev
;
2169 sector_t origin_sectors
;
2171 uint32_t block_size
;
2173 const char *policy_name
;
2175 const char **policy_argv
;
2177 struct cache_features features
;
2180 static void destroy_cache_args(struct cache_args
*ca
)
2182 if (ca
->metadata_dev
)
2183 dm_put_device(ca
->ti
, ca
->metadata_dev
);
2186 dm_put_device(ca
->ti
, ca
->cache_dev
);
2189 dm_put_device(ca
->ti
, ca
->origin_dev
);
2194 static bool at_least_one_arg(struct dm_arg_set
*as
, char **error
)
2197 *error
= "Insufficient args";
2204 static int parse_metadata_dev(struct cache_args
*ca
, struct dm_arg_set
*as
,
2208 sector_t metadata_dev_size
;
2209 char b
[BDEVNAME_SIZE
];
2211 if (!at_least_one_arg(as
, error
))
2214 r
= dm_get_device(ca
->ti
, dm_shift_arg(as
), FMODE_READ
| FMODE_WRITE
,
2217 *error
= "Error opening metadata device";
2221 metadata_dev_size
= get_dev_size(ca
->metadata_dev
);
2222 if (metadata_dev_size
> DM_CACHE_METADATA_MAX_SECTORS_WARNING
)
2223 DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
2224 bdevname(ca
->metadata_dev
->bdev
, b
), THIN_METADATA_MAX_SECTORS
);
2229 static int parse_cache_dev(struct cache_args
*ca
, struct dm_arg_set
*as
,
2234 if (!at_least_one_arg(as
, error
))
2237 r
= dm_get_device(ca
->ti
, dm_shift_arg(as
), FMODE_READ
| FMODE_WRITE
,
2240 *error
= "Error opening cache device";
2243 ca
->cache_sectors
= get_dev_size(ca
->cache_dev
);
2248 static int parse_origin_dev(struct cache_args
*ca
, struct dm_arg_set
*as
,
2253 if (!at_least_one_arg(as
, error
))
2256 r
= dm_get_device(ca
->ti
, dm_shift_arg(as
), FMODE_READ
| FMODE_WRITE
,
2259 *error
= "Error opening origin device";
2263 ca
->origin_sectors
= get_dev_size(ca
->origin_dev
);
2264 if (ca
->ti
->len
> ca
->origin_sectors
) {
2265 *error
= "Device size larger than cached device";
2272 static int parse_block_size(struct cache_args
*ca
, struct dm_arg_set
*as
,
2275 unsigned long block_size
;
2277 if (!at_least_one_arg(as
, error
))
2280 if (kstrtoul(dm_shift_arg(as
), 10, &block_size
) || !block_size
||
2281 block_size
< DATA_DEV_BLOCK_SIZE_MIN_SECTORS
||
2282 block_size
> DATA_DEV_BLOCK_SIZE_MAX_SECTORS
||
2283 block_size
& (DATA_DEV_BLOCK_SIZE_MIN_SECTORS
- 1)) {
2284 *error
= "Invalid data block size";
2288 if (block_size
> ca
->cache_sectors
) {
2289 *error
= "Data block size is larger than the cache device";
2293 ca
->block_size
= block_size
;
2298 static void init_features(struct cache_features
*cf
)
2300 cf
->mode
= CM_WRITE
;
2301 cf
->io_mode
= CM_IO_WRITEBACK
;
2302 cf
->metadata_version
= 1;
2305 static int parse_features(struct cache_args
*ca
, struct dm_arg_set
*as
,
2308 static struct dm_arg _args
[] = {
2309 {0, 2, "Invalid number of cache feature arguments"},
2315 struct cache_features
*cf
= &ca
->features
;
2319 r
= dm_read_arg_group(_args
, as
, &argc
, error
);
2324 arg
= dm_shift_arg(as
);
2326 if (!strcasecmp(arg
, "writeback"))
2327 cf
->io_mode
= CM_IO_WRITEBACK
;
2329 else if (!strcasecmp(arg
, "writethrough"))
2330 cf
->io_mode
= CM_IO_WRITETHROUGH
;
2332 else if (!strcasecmp(arg
, "passthrough"))
2333 cf
->io_mode
= CM_IO_PASSTHROUGH
;
2335 else if (!strcasecmp(arg
, "metadata2"))
2336 cf
->metadata_version
= 2;
2339 *error
= "Unrecognised cache feature requested";
2347 static int parse_policy(struct cache_args
*ca
, struct dm_arg_set
*as
,
2350 static struct dm_arg _args
[] = {
2351 {0, 1024, "Invalid number of policy arguments"},
2356 if (!at_least_one_arg(as
, error
))
2359 ca
->policy_name
= dm_shift_arg(as
);
2361 r
= dm_read_arg_group(_args
, as
, &ca
->policy_argc
, error
);
2365 ca
->policy_argv
= (const char **)as
->argv
;
2366 dm_consume_args(as
, ca
->policy_argc
);
2371 static int parse_cache_args(struct cache_args
*ca
, int argc
, char **argv
,
2375 struct dm_arg_set as
;
2380 r
= parse_metadata_dev(ca
, &as
, error
);
2384 r
= parse_cache_dev(ca
, &as
, error
);
2388 r
= parse_origin_dev(ca
, &as
, error
);
2392 r
= parse_block_size(ca
, &as
, error
);
2396 r
= parse_features(ca
, &as
, error
);
2400 r
= parse_policy(ca
, &as
, error
);
2407 /*----------------------------------------------------------------*/
2409 static struct kmem_cache
*migration_cache
;
2411 #define NOT_CORE_OPTION 1
2413 static int process_config_option(struct cache
*cache
, const char *key
, const char *value
)
2417 if (!strcasecmp(key
, "migration_threshold")) {
2418 if (kstrtoul(value
, 10, &tmp
))
2421 cache
->migration_threshold
= tmp
;
2425 return NOT_CORE_OPTION
;
2428 static int set_config_value(struct cache
*cache
, const char *key
, const char *value
)
2430 int r
= process_config_option(cache
, key
, value
);
2432 if (r
== NOT_CORE_OPTION
)
2433 r
= policy_set_config_value(cache
->policy
, key
, value
);
2436 DMWARN("bad config value for %s: %s", key
, value
);
2441 static int set_config_values(struct cache
*cache
, int argc
, const char **argv
)
2446 DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs.");
2451 r
= set_config_value(cache
, argv
[0], argv
[1]);
2462 static int create_cache_policy(struct cache
*cache
, struct cache_args
*ca
,
2465 struct dm_cache_policy
*p
= dm_cache_policy_create(ca
->policy_name
,
2467 cache
->origin_sectors
,
2468 cache
->sectors_per_block
);
2470 *error
= "Error creating cache's policy";
2474 BUG_ON(!cache
->policy
);
2480 * We want the discard block size to be at least the size of the cache
2481 * block size and have no more than 2^14 discard blocks across the origin.
2483 #define MAX_DISCARD_BLOCKS (1 << 14)
2485 static bool too_many_discard_blocks(sector_t discard_block_size
,
2486 sector_t origin_size
)
2488 (void) sector_div(origin_size
, discard_block_size
);
2490 return origin_size
> MAX_DISCARD_BLOCKS
;
2493 static sector_t
calculate_discard_block_size(sector_t cache_block_size
,
2494 sector_t origin_size
)
2496 sector_t discard_block_size
= cache_block_size
;
2499 while (too_many_discard_blocks(discard_block_size
, origin_size
))
2500 discard_block_size
*= 2;
2502 return discard_block_size
;
2505 static void set_cache_size(struct cache
*cache
, dm_cblock_t size
)
2507 dm_block_t nr_blocks
= from_cblock(size
);
2509 if (nr_blocks
> (1 << 20) && cache
->cache_size
!= size
)
2510 DMWARN_LIMIT("You have created a cache device with a lot of individual cache blocks (%llu)\n"
2511 "All these mappings can consume a lot of kernel memory, and take some time to read/write.\n"
2512 "Please consider increasing the cache block size to reduce the overall cache block count.",
2513 (unsigned long long) nr_blocks
);
2515 cache
->cache_size
= size
;
2518 static int is_congested(struct dm_dev
*dev
, int bdi_bits
)
2520 struct request_queue
*q
= bdev_get_queue(dev
->bdev
);
2521 return bdi_congested(q
->backing_dev_info
, bdi_bits
);
2524 static int cache_is_congested(struct dm_target_callbacks
*cb
, int bdi_bits
)
2526 struct cache
*cache
= container_of(cb
, struct cache
, callbacks
);
2528 return is_congested(cache
->origin_dev
, bdi_bits
) ||
2529 is_congested(cache
->cache_dev
, bdi_bits
);
2532 #define DEFAULT_MIGRATION_THRESHOLD 2048
2534 static int cache_create(struct cache_args
*ca
, struct cache
**result
)
2537 char **error
= &ca
->ti
->error
;
2538 struct cache
*cache
;
2539 struct dm_target
*ti
= ca
->ti
;
2540 dm_block_t origin_blocks
;
2541 struct dm_cache_metadata
*cmd
;
2542 bool may_format
= ca
->features
.mode
== CM_WRITE
;
2544 cache
= kzalloc(sizeof(*cache
), GFP_KERNEL
);
2549 ti
->private = cache
;
2550 ti
->num_flush_bios
= 2;
2551 ti
->flush_supported
= true;
2553 ti
->num_discard_bios
= 1;
2554 ti
->discards_supported
= true;
2555 ti
->split_discard_bios
= false;
2557 cache
->features
= ca
->features
;
2558 ti
->per_io_data_size
= get_per_bio_data_size(cache
);
2560 cache
->callbacks
.congested_fn
= cache_is_congested
;
2561 dm_table_add_target_callbacks(ti
->table
, &cache
->callbacks
);
2563 cache
->metadata_dev
= ca
->metadata_dev
;
2564 cache
->origin_dev
= ca
->origin_dev
;
2565 cache
->cache_dev
= ca
->cache_dev
;
2567 ca
->metadata_dev
= ca
->origin_dev
= ca
->cache_dev
= NULL
;
2569 origin_blocks
= cache
->origin_sectors
= ca
->origin_sectors
;
2570 origin_blocks
= block_div(origin_blocks
, ca
->block_size
);
2571 cache
->origin_blocks
= to_oblock(origin_blocks
);
2573 cache
->sectors_per_block
= ca
->block_size
;
2574 if (dm_set_target_max_io_len(ti
, cache
->sectors_per_block
)) {
2579 if (ca
->block_size
& (ca
->block_size
- 1)) {
2580 dm_block_t cache_size
= ca
->cache_sectors
;
2582 cache
->sectors_per_block_shift
= -1;
2583 cache_size
= block_div(cache_size
, ca
->block_size
);
2584 set_cache_size(cache
, to_cblock(cache_size
));
2586 cache
->sectors_per_block_shift
= __ffs(ca
->block_size
);
2587 set_cache_size(cache
, to_cblock(ca
->cache_sectors
>> cache
->sectors_per_block_shift
));
2590 r
= create_cache_policy(cache
, ca
, error
);
2594 cache
->policy_nr_args
= ca
->policy_argc
;
2595 cache
->migration_threshold
= DEFAULT_MIGRATION_THRESHOLD
;
2597 r
= set_config_values(cache
, ca
->policy_argc
, ca
->policy_argv
);
2599 *error
= "Error setting cache policy's config values";
2603 cmd
= dm_cache_metadata_open(cache
->metadata_dev
->bdev
,
2604 ca
->block_size
, may_format
,
2605 dm_cache_policy_get_hint_size(cache
->policy
),
2606 ca
->features
.metadata_version
);
2608 *error
= "Error creating metadata object";
2613 set_cache_mode(cache
, CM_WRITE
);
2614 if (get_cache_mode(cache
) != CM_WRITE
) {
2615 *error
= "Unable to get write access to metadata, please check/repair metadata.";
2620 if (passthrough_mode(&cache
->features
)) {
2623 r
= dm_cache_metadata_all_clean(cache
->cmd
, &all_clean
);
2625 *error
= "dm_cache_metadata_all_clean() failed";
2630 *error
= "Cannot enter passthrough mode unless all blocks are clean";
2635 policy_allow_migrations(cache
->policy
, false);
2638 spin_lock_init(&cache
->lock
);
2639 INIT_LIST_HEAD(&cache
->deferred_cells
);
2640 bio_list_init(&cache
->deferred_bios
);
2641 bio_list_init(&cache
->deferred_writethrough_bios
);
2642 atomic_set(&cache
->nr_allocated_migrations
, 0);
2643 atomic_set(&cache
->nr_io_migrations
, 0);
2644 init_waitqueue_head(&cache
->migration_wait
);
2647 atomic_set(&cache
->nr_dirty
, 0);
2648 cache
->dirty_bitset
= alloc_bitset(from_cblock(cache
->cache_size
));
2649 if (!cache
->dirty_bitset
) {
2650 *error
= "could not allocate dirty bitset";
2653 clear_bitset(cache
->dirty_bitset
, from_cblock(cache
->cache_size
));
2655 cache
->discard_block_size
=
2656 calculate_discard_block_size(cache
->sectors_per_block
,
2657 cache
->origin_sectors
);
2658 cache
->discard_nr_blocks
= to_dblock(dm_sector_div_up(cache
->origin_sectors
,
2659 cache
->discard_block_size
));
2660 cache
->discard_bitset
= alloc_bitset(from_dblock(cache
->discard_nr_blocks
));
2661 if (!cache
->discard_bitset
) {
2662 *error
= "could not allocate discard bitset";
2665 clear_bitset(cache
->discard_bitset
, from_dblock(cache
->discard_nr_blocks
));
2667 cache
->copier
= dm_kcopyd_client_create(&dm_kcopyd_throttle
);
2668 if (IS_ERR(cache
->copier
)) {
2669 *error
= "could not create kcopyd client";
2670 r
= PTR_ERR(cache
->copier
);
2674 cache
->wq
= alloc_workqueue("dm-" DM_MSG_PREFIX
, WQ_MEM_RECLAIM
, 0);
2676 *error
= "could not create workqueue for metadata object";
2679 INIT_WORK(&cache
->deferred_bio_worker
, process_deferred_bios
);
2680 INIT_WORK(&cache
->deferred_writethrough_worker
,
2681 process_deferred_writethrough_bios
);
2682 INIT_WORK(&cache
->migration_worker
, check_migrations
);
2683 INIT_DELAYED_WORK(&cache
->waker
, do_waker
);
2685 cache
->prison
= dm_bio_prison_create_v2(cache
->wq
);
2686 if (!cache
->prison
) {
2687 *error
= "could not create bio prison";
2691 cache
->migration_pool
= mempool_create_slab_pool(MIGRATION_POOL_SIZE
,
2693 if (!cache
->migration_pool
) {
2694 *error
= "Error creating cache's migration mempool";
2698 cache
->need_tick_bio
= true;
2699 cache
->sized
= false;
2700 cache
->invalidate
= false;
2701 cache
->commit_requested
= false;
2702 cache
->loaded_mappings
= false;
2703 cache
->loaded_discards
= false;
2707 atomic_set(&cache
->stats
.demotion
, 0);
2708 atomic_set(&cache
->stats
.promotion
, 0);
2709 atomic_set(&cache
->stats
.copies_avoided
, 0);
2710 atomic_set(&cache
->stats
.cache_cell_clash
, 0);
2711 atomic_set(&cache
->stats
.commit_count
, 0);
2712 atomic_set(&cache
->stats
.discard_count
, 0);
2714 spin_lock_init(&cache
->invalidation_lock
);
2715 INIT_LIST_HEAD(&cache
->invalidation_requests
);
2717 batcher_init(&cache
->committer
, commit_op
, cache
,
2718 issue_op
, cache
, cache
->wq
);
2719 iot_init(&cache
->tracker
);
2721 init_rwsem(&cache
->background_work_lock
);
2722 prevent_background_work(cache
);
2731 static int copy_ctr_args(struct cache
*cache
, int argc
, const char **argv
)
2736 copy
= kcalloc(argc
, sizeof(*copy
), GFP_KERNEL
);
2739 for (i
= 0; i
< argc
; i
++) {
2740 copy
[i
] = kstrdup(argv
[i
], GFP_KERNEL
);
2749 cache
->nr_ctr_args
= argc
;
2750 cache
->ctr_args
= copy
;
2755 static int cache_ctr(struct dm_target
*ti
, unsigned argc
, char **argv
)
2758 struct cache_args
*ca
;
2759 struct cache
*cache
= NULL
;
2761 ca
= kzalloc(sizeof(*ca
), GFP_KERNEL
);
2763 ti
->error
= "Error allocating memory for cache";
2768 r
= parse_cache_args(ca
, argc
, argv
, &ti
->error
);
2772 r
= cache_create(ca
, &cache
);
2776 r
= copy_ctr_args(cache
, argc
- 3, (const char **)argv
+ 3);
2782 ti
->private = cache
;
2784 destroy_cache_args(ca
);
2788 /*----------------------------------------------------------------*/
2790 static int cache_map(struct dm_target
*ti
, struct bio
*bio
)
2792 struct cache
*cache
= ti
->private;
2796 dm_oblock_t block
= get_bio_block(cache
, bio
);
2797 size_t pb_data_size
= get_per_bio_data_size(cache
);
2799 init_per_bio_data(bio
, pb_data_size
);
2800 if (unlikely(from_oblock(block
) >= from_oblock(cache
->origin_blocks
))) {
2802 * This can only occur if the io goes to a partial block at
2803 * the end of the origin device. We don't cache these.
2804 * Just remap to the origin and carry on.
2806 remap_to_origin(cache
, bio
);
2807 accounted_begin(cache
, bio
);
2808 return DM_MAPIO_REMAPPED
;
2811 if (discard_or_flush(bio
)) {
2812 defer_bio(cache
, bio
);
2813 return DM_MAPIO_SUBMITTED
;
2816 r
= map_bio(cache
, bio
, block
, &commit_needed
);
2818 schedule_commit(&cache
->committer
);
2823 static int cache_end_io(struct dm_target
*ti
, struct bio
*bio
, int error
)
2825 struct cache
*cache
= ti
->private;
2826 unsigned long flags
;
2827 size_t pb_data_size
= get_per_bio_data_size(cache
);
2828 struct per_bio_data
*pb
= get_per_bio_data(bio
, pb_data_size
);
2831 policy_tick(cache
->policy
, false);
2833 spin_lock_irqsave(&cache
->lock
, flags
);
2834 cache
->need_tick_bio
= true;
2835 spin_unlock_irqrestore(&cache
->lock
, flags
);
2838 bio_drop_shared_lock(cache
, bio
);
2839 accounted_complete(cache
, bio
);
2844 static int write_dirty_bitset(struct cache
*cache
)
2848 if (get_cache_mode(cache
) >= CM_READ_ONLY
)
2851 r
= dm_cache_set_dirty_bits(cache
->cmd
, from_cblock(cache
->cache_size
), cache
->dirty_bitset
);
2853 metadata_operation_failed(cache
, "dm_cache_set_dirty_bits", r
);
2858 static int write_discard_bitset(struct cache
*cache
)
2862 if (get_cache_mode(cache
) >= CM_READ_ONLY
)
2865 r
= dm_cache_discard_bitset_resize(cache
->cmd
, cache
->discard_block_size
,
2866 cache
->discard_nr_blocks
);
2868 DMERR("%s: could not resize on-disk discard bitset", cache_device_name(cache
));
2869 metadata_operation_failed(cache
, "dm_cache_discard_bitset_resize", r
);
2873 for (i
= 0; i
< from_dblock(cache
->discard_nr_blocks
); i
++) {
2874 r
= dm_cache_set_discard(cache
->cmd
, to_dblock(i
),
2875 is_discarded(cache
, to_dblock(i
)));
2877 metadata_operation_failed(cache
, "dm_cache_set_discard", r
);
2885 static int write_hints(struct cache
*cache
)
2889 if (get_cache_mode(cache
) >= CM_READ_ONLY
)
2892 r
= dm_cache_write_hints(cache
->cmd
, cache
->policy
);
2894 metadata_operation_failed(cache
, "dm_cache_write_hints", r
);
2902 * returns true on success
2904 static bool sync_metadata(struct cache
*cache
)
2908 r1
= write_dirty_bitset(cache
);
2910 DMERR("%s: could not write dirty bitset", cache_device_name(cache
));
2912 r2
= write_discard_bitset(cache
);
2914 DMERR("%s: could not write discard bitset", cache_device_name(cache
));
2918 r3
= write_hints(cache
);
2920 DMERR("%s: could not write hints", cache_device_name(cache
));
2923 * If writing the above metadata failed, we still commit, but don't
2924 * set the clean shutdown flag. This will effectively force every
2925 * dirty bit to be set on reload.
2927 r4
= commit(cache
, !r1
&& !r2
&& !r3
);
2929 DMERR("%s: could not write cache metadata", cache_device_name(cache
));
2931 return !r1
&& !r2
&& !r3
&& !r4
;
2934 static void cache_postsuspend(struct dm_target
*ti
)
2936 struct cache
*cache
= ti
->private;
2938 prevent_background_work(cache
);
2939 BUG_ON(atomic_read(&cache
->nr_io_migrations
));
2941 cancel_delayed_work(&cache
->waker
);
2942 flush_workqueue(cache
->wq
);
2943 WARN_ON(cache
->tracker
.in_flight
);
2946 * If it's a flush suspend there won't be any deferred bios, so this
2949 requeue_deferred_bios(cache
);
2951 if (get_cache_mode(cache
) == CM_WRITE
)
2952 (void) sync_metadata(cache
);
2955 static int load_mapping(void *context
, dm_oblock_t oblock
, dm_cblock_t cblock
,
2956 bool dirty
, uint32_t hint
, bool hint_valid
)
2959 struct cache
*cache
= context
;
2962 set_bit(from_cblock(cblock
), cache
->dirty_bitset
);
2963 atomic_inc(&cache
->nr_dirty
);
2965 clear_bit(from_cblock(cblock
), cache
->dirty_bitset
);
2967 r
= policy_load_mapping(cache
->policy
, oblock
, cblock
, dirty
, hint
, hint_valid
);
2975 * The discard block size in the on disk metadata is not
2976 * neccessarily the same as we're currently using. So we have to
2977 * be careful to only set the discarded attribute if we know it
2978 * covers a complete block of the new size.
2980 struct discard_load_info
{
2981 struct cache
*cache
;
2984 * These blocks are sized using the on disk dblock size, rather
2985 * than the current one.
2987 dm_block_t block_size
;
2988 dm_block_t discard_begin
, discard_end
;
2991 static void discard_load_info_init(struct cache
*cache
,
2992 struct discard_load_info
*li
)
2995 li
->discard_begin
= li
->discard_end
= 0;
2998 static void set_discard_range(struct discard_load_info
*li
)
3002 if (li
->discard_begin
== li
->discard_end
)
3006 * Convert to sectors.
3008 b
= li
->discard_begin
* li
->block_size
;
3009 e
= li
->discard_end
* li
->block_size
;
3012 * Then convert back to the current dblock size.
3014 b
= dm_sector_div_up(b
, li
->cache
->discard_block_size
);
3015 sector_div(e
, li
->cache
->discard_block_size
);
3018 * The origin may have shrunk, so we need to check we're still in
3021 if (e
> from_dblock(li
->cache
->discard_nr_blocks
))
3022 e
= from_dblock(li
->cache
->discard_nr_blocks
);
3025 set_discard(li
->cache
, to_dblock(b
));
3028 static int load_discard(void *context
, sector_t discard_block_size
,
3029 dm_dblock_t dblock
, bool discard
)
3031 struct discard_load_info
*li
= context
;
3033 li
->block_size
= discard_block_size
;
3036 if (from_dblock(dblock
) == li
->discard_end
)
3038 * We're already in a discard range, just extend it.
3040 li
->discard_end
= li
->discard_end
+ 1ULL;
3044 * Emit the old range and start a new one.
3046 set_discard_range(li
);
3047 li
->discard_begin
= from_dblock(dblock
);
3048 li
->discard_end
= li
->discard_begin
+ 1ULL;
3051 set_discard_range(li
);
3052 li
->discard_begin
= li
->discard_end
= 0;
3058 static dm_cblock_t
get_cache_dev_size(struct cache
*cache
)
3060 sector_t size
= get_dev_size(cache
->cache_dev
);
3061 (void) sector_div(size
, cache
->sectors_per_block
);
3062 return to_cblock(size
);
3065 static bool can_resize(struct cache
*cache
, dm_cblock_t new_size
)
3067 if (from_cblock(new_size
) > from_cblock(cache
->cache_size
))
3071 * We can't drop a dirty block when shrinking the cache.
3073 while (from_cblock(new_size
) < from_cblock(cache
->cache_size
)) {
3074 new_size
= to_cblock(from_cblock(new_size
) + 1);
3075 if (is_dirty(cache
, new_size
)) {
3076 DMERR("%s: unable to shrink cache; cache block %llu is dirty",
3077 cache_device_name(cache
),
3078 (unsigned long long) from_cblock(new_size
));
3086 static int resize_cache_dev(struct cache
*cache
, dm_cblock_t new_size
)
3090 r
= dm_cache_resize(cache
->cmd
, new_size
);
3092 DMERR("%s: could not resize cache metadata", cache_device_name(cache
));
3093 metadata_operation_failed(cache
, "dm_cache_resize", r
);
3097 set_cache_size(cache
, new_size
);
3102 static int cache_preresume(struct dm_target
*ti
)
3105 struct cache
*cache
= ti
->private;
3106 dm_cblock_t csize
= get_cache_dev_size(cache
);
3109 * Check to see if the cache has resized.
3111 if (!cache
->sized
) {
3112 r
= resize_cache_dev(cache
, csize
);
3116 cache
->sized
= true;
3118 } else if (csize
!= cache
->cache_size
) {
3119 if (!can_resize(cache
, csize
))
3122 r
= resize_cache_dev(cache
, csize
);
3127 if (!cache
->loaded_mappings
) {
3128 r
= dm_cache_load_mappings(cache
->cmd
, cache
->policy
,
3129 load_mapping
, cache
);
3131 DMERR("%s: could not load cache mappings", cache_device_name(cache
));
3132 metadata_operation_failed(cache
, "dm_cache_load_mappings", r
);
3136 cache
->loaded_mappings
= true;
3139 if (!cache
->loaded_discards
) {
3140 struct discard_load_info li
;
3143 * The discard bitset could have been resized, or the
3144 * discard block size changed. To be safe we start by
3145 * setting every dblock to not discarded.
3147 clear_bitset(cache
->discard_bitset
, from_dblock(cache
->discard_nr_blocks
));
3149 discard_load_info_init(cache
, &li
);
3150 r
= dm_cache_load_discards(cache
->cmd
, load_discard
, &li
);
3152 DMERR("%s: could not load origin discards", cache_device_name(cache
));
3153 metadata_operation_failed(cache
, "dm_cache_load_discards", r
);
3156 set_discard_range(&li
);
3158 cache
->loaded_discards
= true;
3164 static void cache_resume(struct dm_target
*ti
)
3166 struct cache
*cache
= ti
->private;
3168 cache
->need_tick_bio
= true;
3169 allow_background_work(cache
);
3170 do_waker(&cache
->waker
.work
);
3176 * <metadata block size> <#used metadata blocks>/<#total metadata blocks>
3177 * <cache block size> <#used cache blocks>/<#total cache blocks>
3178 * <#read hits> <#read misses> <#write hits> <#write misses>
3179 * <#demotions> <#promotions> <#dirty>
3180 * <#features> <features>*
3181 * <#core args> <core args>
3182 * <policy name> <#policy args> <policy args>* <cache metadata mode> <needs_check>
3184 static void cache_status(struct dm_target
*ti
, status_type_t type
,
3185 unsigned status_flags
, char *result
, unsigned maxlen
)
3190 dm_block_t nr_free_blocks_metadata
= 0;
3191 dm_block_t nr_blocks_metadata
= 0;
3192 char buf
[BDEVNAME_SIZE
];
3193 struct cache
*cache
= ti
->private;
3194 dm_cblock_t residency
;
3198 case STATUSTYPE_INFO
:
3199 if (get_cache_mode(cache
) == CM_FAIL
) {
3204 /* Commit to ensure statistics aren't out-of-date */
3205 if (!(status_flags
& DM_STATUS_NOFLUSH_FLAG
) && !dm_suspended(ti
))
3206 (void) commit(cache
, false);
3208 r
= dm_cache_get_free_metadata_block_count(cache
->cmd
, &nr_free_blocks_metadata
);
3210 DMERR("%s: dm_cache_get_free_metadata_block_count returned %d",
3211 cache_device_name(cache
), r
);
3215 r
= dm_cache_get_metadata_dev_size(cache
->cmd
, &nr_blocks_metadata
);
3217 DMERR("%s: dm_cache_get_metadata_dev_size returned %d",
3218 cache_device_name(cache
), r
);
3222 residency
= policy_residency(cache
->policy
);
3224 DMEMIT("%u %llu/%llu %llu %llu/%llu %u %u %u %u %u %u %lu ",
3225 (unsigned)DM_CACHE_METADATA_BLOCK_SIZE
,
3226 (unsigned long long)(nr_blocks_metadata
- nr_free_blocks_metadata
),
3227 (unsigned long long)nr_blocks_metadata
,
3228 (unsigned long long)cache
->sectors_per_block
,
3229 (unsigned long long) from_cblock(residency
),
3230 (unsigned long long) from_cblock(cache
->cache_size
),
3231 (unsigned) atomic_read(&cache
->stats
.read_hit
),
3232 (unsigned) atomic_read(&cache
->stats
.read_miss
),
3233 (unsigned) atomic_read(&cache
->stats
.write_hit
),
3234 (unsigned) atomic_read(&cache
->stats
.write_miss
),
3235 (unsigned) atomic_read(&cache
->stats
.demotion
),
3236 (unsigned) atomic_read(&cache
->stats
.promotion
),
3237 (unsigned long) atomic_read(&cache
->nr_dirty
));
3239 if (cache
->features
.metadata_version
== 2)
3240 DMEMIT("2 metadata2 ");
3244 if (writethrough_mode(&cache
->features
))
3245 DMEMIT("writethrough ");
3247 else if (passthrough_mode(&cache
->features
))
3248 DMEMIT("passthrough ");
3250 else if (writeback_mode(&cache
->features
))
3251 DMEMIT("writeback ");
3254 DMERR("%s: internal error: unknown io mode: %d",
3255 cache_device_name(cache
), (int) cache
->features
.io_mode
);
3259 DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache
->migration_threshold
);
3261 DMEMIT("%s ", dm_cache_policy_get_name(cache
->policy
));
3263 r
= policy_emit_config_values(cache
->policy
, result
, maxlen
, &sz
);
3265 DMERR("%s: policy_emit_config_values returned %d",
3266 cache_device_name(cache
), r
);
3269 if (get_cache_mode(cache
) == CM_READ_ONLY
)
3274 r
= dm_cache_metadata_needs_check(cache
->cmd
, &needs_check
);
3276 if (r
|| needs_check
)
3277 DMEMIT("needs_check ");
3283 case STATUSTYPE_TABLE
:
3284 format_dev_t(buf
, cache
->metadata_dev
->bdev
->bd_dev
);
3286 format_dev_t(buf
, cache
->cache_dev
->bdev
->bd_dev
);
3288 format_dev_t(buf
, cache
->origin_dev
->bdev
->bd_dev
);
3291 for (i
= 0; i
< cache
->nr_ctr_args
- 1; i
++)
3292 DMEMIT(" %s", cache
->ctr_args
[i
]);
3293 if (cache
->nr_ctr_args
)
3294 DMEMIT(" %s", cache
->ctr_args
[cache
->nr_ctr_args
- 1]);
3304 * Defines a range of cblocks, begin to (end - 1) are in the range. end is
3305 * the one-past-the-end value.
3307 struct cblock_range
{
3313 * A cache block range can take two forms:
3315 * i) A single cblock, eg. '3456'
3316 * ii) A begin and end cblock with a dash between, eg. 123-234
3318 static int parse_cblock_range(struct cache
*cache
, const char *str
,
3319 struct cblock_range
*result
)
3326 * Try and parse form (ii) first.
3328 r
= sscanf(str
, "%llu-%llu%c", &b
, &e
, &dummy
);
3333 result
->begin
= to_cblock(b
);
3334 result
->end
= to_cblock(e
);
3339 * That didn't work, try form (i).
3341 r
= sscanf(str
, "%llu%c", &b
, &dummy
);
3346 result
->begin
= to_cblock(b
);
3347 result
->end
= to_cblock(from_cblock(result
->begin
) + 1u);
3351 DMERR("%s: invalid cblock range '%s'", cache_device_name(cache
), str
);
3355 static int validate_cblock_range(struct cache
*cache
, struct cblock_range
*range
)
3357 uint64_t b
= from_cblock(range
->begin
);
3358 uint64_t e
= from_cblock(range
->end
);
3359 uint64_t n
= from_cblock(cache
->cache_size
);
3362 DMERR("%s: begin cblock out of range: %llu >= %llu",
3363 cache_device_name(cache
), b
, n
);
3368 DMERR("%s: end cblock out of range: %llu > %llu",
3369 cache_device_name(cache
), e
, n
);
3374 DMERR("%s: invalid cblock range: %llu >= %llu",
3375 cache_device_name(cache
), b
, e
);
3382 static inline dm_cblock_t
cblock_succ(dm_cblock_t b
)
3384 return to_cblock(from_cblock(b
) + 1);
3387 static int request_invalidation(struct cache
*cache
, struct cblock_range
*range
)
3392 * We don't need to do any locking here because we know we're in
3393 * passthrough mode. There's is potential for a race between an
3394 * invalidation triggered by an io and an invalidation message. This
3395 * is harmless, we must not worry if the policy call fails.
3397 while (range
->begin
!= range
->end
) {
3398 r
= invalidate_cblock(cache
, range
->begin
);
3402 range
->begin
= cblock_succ(range
->begin
);
3405 cache
->commit_requested
= true;
3409 static int process_invalidate_cblocks_message(struct cache
*cache
, unsigned count
,
3410 const char **cblock_ranges
)
3414 struct cblock_range range
;
3416 if (!passthrough_mode(&cache
->features
)) {
3417 DMERR("%s: cache has to be in passthrough mode for invalidation",
3418 cache_device_name(cache
));
3422 for (i
= 0; i
< count
; i
++) {
3423 r
= parse_cblock_range(cache
, cblock_ranges
[i
], &range
);
3427 r
= validate_cblock_range(cache
, &range
);
3432 * Pass begin and end origin blocks to the worker and wake it.
3434 r
= request_invalidation(cache
, &range
);
3446 * "invalidate_cblocks [(<begin>)|(<begin>-<end>)]*
3448 * The key migration_threshold is supported by the cache target core.
3450 static int cache_message(struct dm_target
*ti
, unsigned argc
, char **argv
)
3452 struct cache
*cache
= ti
->private;
3457 if (get_cache_mode(cache
) >= CM_READ_ONLY
) {
3458 DMERR("%s: unable to service cache target messages in READ_ONLY or FAIL mode",
3459 cache_device_name(cache
));
3463 if (!strcasecmp(argv
[0], "invalidate_cblocks"))
3464 return process_invalidate_cblocks_message(cache
, argc
- 1, (const char **) argv
+ 1);
3469 return set_config_value(cache
, argv
[0], argv
[1]);
3472 static int cache_iterate_devices(struct dm_target
*ti
,
3473 iterate_devices_callout_fn fn
, void *data
)
3476 struct cache
*cache
= ti
->private;
3478 r
= fn(ti
, cache
->cache_dev
, 0, get_dev_size(cache
->cache_dev
), data
);
3480 r
= fn(ti
, cache
->origin_dev
, 0, ti
->len
, data
);
3485 static void set_discard_limits(struct cache
*cache
, struct queue_limits
*limits
)
3488 * FIXME: these limits may be incompatible with the cache device
3490 limits
->max_discard_sectors
= min_t(sector_t
, cache
->discard_block_size
* 1024,
3491 cache
->origin_sectors
);
3492 limits
->discard_granularity
= cache
->discard_block_size
<< SECTOR_SHIFT
;
3495 static void cache_io_hints(struct dm_target
*ti
, struct queue_limits
*limits
)
3497 struct cache
*cache
= ti
->private;
3498 uint64_t io_opt_sectors
= limits
->io_opt
>> SECTOR_SHIFT
;
3501 * If the system-determined stacked limits are compatible with the
3502 * cache's blocksize (io_opt is a factor) do not override them.
3504 if (io_opt_sectors
< cache
->sectors_per_block
||
3505 do_div(io_opt_sectors
, cache
->sectors_per_block
)) {
3506 blk_limits_io_min(limits
, cache
->sectors_per_block
<< SECTOR_SHIFT
);
3507 blk_limits_io_opt(limits
, cache
->sectors_per_block
<< SECTOR_SHIFT
);
3509 set_discard_limits(cache
, limits
);
3512 /*----------------------------------------------------------------*/
3514 static struct target_type cache_target
= {
3516 .version
= {2, 0, 0},
3517 .module
= THIS_MODULE
,
3521 .end_io
= cache_end_io
,
3522 .postsuspend
= cache_postsuspend
,
3523 .preresume
= cache_preresume
,
3524 .resume
= cache_resume
,
3525 .status
= cache_status
,
3526 .message
= cache_message
,
3527 .iterate_devices
= cache_iterate_devices
,
3528 .io_hints
= cache_io_hints
,
3531 static int __init
dm_cache_init(void)
3535 r
= dm_register_target(&cache_target
);
3537 DMERR("cache target registration failed: %d", r
);
3541 migration_cache
= KMEM_CACHE(dm_cache_migration
, 0);
3542 if (!migration_cache
) {
3543 dm_unregister_target(&cache_target
);
3550 static void __exit
dm_cache_exit(void)
3552 dm_unregister_target(&cache_target
);
3553 kmem_cache_destroy(migration_cache
);
3556 module_init(dm_cache_init
);
3557 module_exit(dm_cache_exit
);
3559 MODULE_DESCRIPTION(DM_NAME
" cache target");
3560 MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
3561 MODULE_LICENSE("GPL");