2 * Copyright (C) 2012 Red Hat. All rights reserved.
4 * This file is released under the GPL.
8 #include "dm-bio-prison.h"
9 #include "dm-cache-metadata.h"
11 #include <linux/dm-io.h>
12 #include <linux/dm-kcopyd.h>
13 #include <linux/init.h>
14 #include <linux/mempool.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/vmalloc.h>
19 #define DM_MSG_PREFIX "cache"
21 DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle
,
22 "A percentage of time allocated for copying to and/or from cache");
24 /*----------------------------------------------------------------*/
29 * oblock: index of an origin block
30 * cblock: index of a cache block
31 * promotion: movement of a block from origin to cache
32 * demotion: movement of a block from cache to origin
33 * migration: movement of a block between the origin and cache device,
37 /*----------------------------------------------------------------*/
39 static size_t bitset_size_in_bytes(unsigned nr_entries
)
41 return sizeof(unsigned long) * dm_div_up(nr_entries
, BITS_PER_LONG
);
44 static unsigned long *alloc_bitset(unsigned nr_entries
)
46 size_t s
= bitset_size_in_bytes(nr_entries
);
50 static void clear_bitset(void *bitset
, unsigned nr_entries
)
52 size_t s
= bitset_size_in_bytes(nr_entries
);
56 static void free_bitset(unsigned long *bits
)
61 /*----------------------------------------------------------------*/
63 #define PRISON_CELLS 1024
64 #define MIGRATION_POOL_SIZE 128
65 #define COMMIT_PERIOD HZ
66 #define MIGRATION_COUNT_WINDOW 10
69 * The block size of the device holding cache data must be >= 32KB
71 #define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
74 * FIXME: the cache is read/write for the time being.
77 CM_WRITE
, /* metadata may be changed */
78 CM_READ_ONLY
, /* metadata may not be changed */
81 struct cache_features
{
93 atomic_t copies_avoided
;
94 atomic_t cache_cell_clash
;
95 atomic_t commit_count
;
96 atomic_t discard_count
;
100 struct dm_target
*ti
;
101 struct dm_target_callbacks callbacks
;
104 * Metadata is written to this device.
106 struct dm_dev
*metadata_dev
;
109 * The slower of the two data devices. Typically a spindle.
111 struct dm_dev
*origin_dev
;
114 * The faster of the two data devices. Typically an SSD.
116 struct dm_dev
*cache_dev
;
119 * Cache features such as write-through.
121 struct cache_features features
;
124 * Size of the origin device in _complete_ blocks and native sectors.
126 dm_oblock_t origin_blocks
;
127 sector_t origin_sectors
;
130 * Size of the cache device in blocks.
132 dm_cblock_t cache_size
;
135 * Fields for converting from sectors to blocks.
137 uint32_t sectors_per_block
;
138 int sectors_per_block_shift
;
140 struct dm_cache_metadata
*cmd
;
143 struct bio_list deferred_bios
;
144 struct bio_list deferred_flush_bios
;
145 struct list_head quiesced_migrations
;
146 struct list_head completed_migrations
;
147 struct list_head need_commit_migrations
;
148 sector_t migration_threshold
;
149 atomic_t nr_migrations
;
150 wait_queue_head_t migration_wait
;
153 * cache_size entries, dirty if set
155 dm_cblock_t nr_dirty
;
156 unsigned long *dirty_bitset
;
159 * origin_blocks entries, discarded if set.
161 sector_t discard_block_size
; /* a power of 2 times sectors per block */
162 dm_dblock_t discard_nr_blocks
;
163 unsigned long *discard_bitset
;
165 struct dm_kcopyd_client
*copier
;
166 struct workqueue_struct
*wq
;
167 struct work_struct worker
;
169 struct delayed_work waker
;
170 unsigned long last_commit_jiffies
;
172 struct dm_bio_prison
*prison
;
173 struct dm_deferred_set
*all_io_ds
;
175 mempool_t
*migration_pool
;
176 struct dm_cache_migration
*next_migration
;
178 struct dm_cache_policy
*policy
;
179 unsigned policy_nr_args
;
181 bool need_tick_bio
:1;
184 bool commit_requested
:1;
185 bool loaded_mappings
:1;
186 bool loaded_discards
:1;
188 struct cache_stats stats
;
191 * Rather than reconstructing the table line for the status we just
192 * save it and regurgitate.
194 unsigned nr_ctr_args
;
195 const char **ctr_args
;
198 struct per_bio_data
{
201 struct dm_deferred_entry
*all_io_entry
;
204 struct dm_cache_migration
{
205 struct list_head list
;
208 unsigned long start_jiffies
;
209 dm_oblock_t old_oblock
;
210 dm_oblock_t new_oblock
;
218 struct dm_bio_prison_cell
*old_ocell
;
219 struct dm_bio_prison_cell
*new_ocell
;
223 * Processing a bio in the worker thread may require these memory
224 * allocations. We prealloc to avoid deadlocks (the same worker thread
225 * frees them back to the mempool).
228 struct dm_cache_migration
*mg
;
229 struct dm_bio_prison_cell
*cell1
;
230 struct dm_bio_prison_cell
*cell2
;
233 static void wake_worker(struct cache
*cache
)
235 queue_work(cache
->wq
, &cache
->worker
);
238 /*----------------------------------------------------------------*/
240 static struct dm_bio_prison_cell
*alloc_prison_cell(struct cache
*cache
)
242 /* FIXME: change to use a local slab. */
243 return dm_bio_prison_alloc_cell(cache
->prison
, GFP_NOWAIT
);
246 static void free_prison_cell(struct cache
*cache
, struct dm_bio_prison_cell
*cell
)
248 dm_bio_prison_free_cell(cache
->prison
, cell
);
251 static int prealloc_data_structs(struct cache
*cache
, struct prealloc
*p
)
254 p
->mg
= mempool_alloc(cache
->migration_pool
, GFP_NOWAIT
);
260 p
->cell1
= alloc_prison_cell(cache
);
266 p
->cell2
= alloc_prison_cell(cache
);
274 static void prealloc_free_structs(struct cache
*cache
, struct prealloc
*p
)
277 free_prison_cell(cache
, p
->cell2
);
280 free_prison_cell(cache
, p
->cell1
);
283 mempool_free(p
->mg
, cache
->migration_pool
);
286 static struct dm_cache_migration
*prealloc_get_migration(struct prealloc
*p
)
288 struct dm_cache_migration
*mg
= p
->mg
;
297 * You must have a cell within the prealloc struct to return. If not this
298 * function will BUG() rather than returning NULL.
300 static struct dm_bio_prison_cell
*prealloc_get_cell(struct prealloc
*p
)
302 struct dm_bio_prison_cell
*r
= NULL
;
308 } else if (p
->cell2
) {
318 * You can't have more than two cells in a prealloc struct. BUG() will be
319 * called if you try and overfill.
321 static void prealloc_put_cell(struct prealloc
*p
, struct dm_bio_prison_cell
*cell
)
333 /*----------------------------------------------------------------*/
335 static void build_key(dm_oblock_t oblock
, struct dm_cell_key
*key
)
339 key
->block
= from_oblock(oblock
);
343 * The caller hands in a preallocated cell, and a free function for it.
344 * The cell will be freed if there's an error, or if it wasn't used because
345 * a cell with that key already exists.
347 typedef void (*cell_free_fn
)(void *context
, struct dm_bio_prison_cell
*cell
);
349 static int bio_detain(struct cache
*cache
, dm_oblock_t oblock
,
350 struct bio
*bio
, struct dm_bio_prison_cell
*cell_prealloc
,
351 cell_free_fn free_fn
, void *free_context
,
352 struct dm_bio_prison_cell
**cell_result
)
355 struct dm_cell_key key
;
357 build_key(oblock
, &key
);
358 r
= dm_bio_detain(cache
->prison
, &key
, bio
, cell_prealloc
, cell_result
);
360 free_fn(free_context
, cell_prealloc
);
365 static int get_cell(struct cache
*cache
,
367 struct prealloc
*structs
,
368 struct dm_bio_prison_cell
**cell_result
)
371 struct dm_cell_key key
;
372 struct dm_bio_prison_cell
*cell_prealloc
;
374 cell_prealloc
= prealloc_get_cell(structs
);
376 build_key(oblock
, &key
);
377 r
= dm_get_cell(cache
->prison
, &key
, cell_prealloc
, cell_result
);
379 prealloc_put_cell(structs
, cell_prealloc
);
384 /*----------------------------------------------------------------*/
386 static bool is_dirty(struct cache
*cache
, dm_cblock_t b
)
388 return test_bit(from_cblock(b
), cache
->dirty_bitset
);
391 static void set_dirty(struct cache
*cache
, dm_oblock_t oblock
, dm_cblock_t cblock
)
393 if (!test_and_set_bit(from_cblock(cblock
), cache
->dirty_bitset
)) {
394 cache
->nr_dirty
= to_cblock(from_cblock(cache
->nr_dirty
) + 1);
395 policy_set_dirty(cache
->policy
, oblock
);
399 static void clear_dirty(struct cache
*cache
, dm_oblock_t oblock
, dm_cblock_t cblock
)
401 if (test_and_clear_bit(from_cblock(cblock
), cache
->dirty_bitset
)) {
402 policy_clear_dirty(cache
->policy
, oblock
);
403 cache
->nr_dirty
= to_cblock(from_cblock(cache
->nr_dirty
) - 1);
404 if (!from_cblock(cache
->nr_dirty
))
405 dm_table_event(cache
->ti
->table
);
409 /*----------------------------------------------------------------*/
410 static bool block_size_is_power_of_two(struct cache
*cache
)
412 return cache
->sectors_per_block_shift
>= 0;
415 static dm_dblock_t
oblock_to_dblock(struct cache
*cache
, dm_oblock_t oblock
)
417 sector_t discard_blocks
= cache
->discard_block_size
;
418 dm_block_t b
= from_oblock(oblock
);
420 if (!block_size_is_power_of_two(cache
))
421 (void) sector_div(discard_blocks
, cache
->sectors_per_block
);
423 discard_blocks
>>= cache
->sectors_per_block_shift
;
425 (void) sector_div(b
, discard_blocks
);
430 static void set_discard(struct cache
*cache
, dm_dblock_t b
)
434 atomic_inc(&cache
->stats
.discard_count
);
436 spin_lock_irqsave(&cache
->lock
, flags
);
437 set_bit(from_dblock(b
), cache
->discard_bitset
);
438 spin_unlock_irqrestore(&cache
->lock
, flags
);
441 static void clear_discard(struct cache
*cache
, dm_dblock_t b
)
445 spin_lock_irqsave(&cache
->lock
, flags
);
446 clear_bit(from_dblock(b
), cache
->discard_bitset
);
447 spin_unlock_irqrestore(&cache
->lock
, flags
);
450 static bool is_discarded(struct cache
*cache
, dm_dblock_t b
)
455 spin_lock_irqsave(&cache
->lock
, flags
);
456 r
= test_bit(from_dblock(b
), cache
->discard_bitset
);
457 spin_unlock_irqrestore(&cache
->lock
, flags
);
462 static bool is_discarded_oblock(struct cache
*cache
, dm_oblock_t b
)
467 spin_lock_irqsave(&cache
->lock
, flags
);
468 r
= test_bit(from_dblock(oblock_to_dblock(cache
, b
)),
469 cache
->discard_bitset
);
470 spin_unlock_irqrestore(&cache
->lock
, flags
);
475 /*----------------------------------------------------------------*/
477 static void load_stats(struct cache
*cache
)
479 struct dm_cache_statistics stats
;
481 dm_cache_metadata_get_stats(cache
->cmd
, &stats
);
482 atomic_set(&cache
->stats
.read_hit
, stats
.read_hits
);
483 atomic_set(&cache
->stats
.read_miss
, stats
.read_misses
);
484 atomic_set(&cache
->stats
.write_hit
, stats
.write_hits
);
485 atomic_set(&cache
->stats
.write_miss
, stats
.write_misses
);
488 static void save_stats(struct cache
*cache
)
490 struct dm_cache_statistics stats
;
492 stats
.read_hits
= atomic_read(&cache
->stats
.read_hit
);
493 stats
.read_misses
= atomic_read(&cache
->stats
.read_miss
);
494 stats
.write_hits
= atomic_read(&cache
->stats
.write_hit
);
495 stats
.write_misses
= atomic_read(&cache
->stats
.write_miss
);
497 dm_cache_metadata_set_stats(cache
->cmd
, &stats
);
500 /*----------------------------------------------------------------
502 *--------------------------------------------------------------*/
503 static struct per_bio_data
*get_per_bio_data(struct bio
*bio
)
505 struct per_bio_data
*pb
= dm_per_bio_data(bio
, sizeof(struct per_bio_data
));
510 static struct per_bio_data
*init_per_bio_data(struct bio
*bio
)
512 struct per_bio_data
*pb
= get_per_bio_data(bio
);
515 pb
->req_nr
= dm_bio_get_target_bio_nr(bio
);
516 pb
->all_io_entry
= NULL
;
521 /*----------------------------------------------------------------
523 *--------------------------------------------------------------*/
524 static void remap_to_origin(struct cache
*cache
, struct bio
*bio
)
526 bio
->bi_bdev
= cache
->origin_dev
->bdev
;
529 static void remap_to_cache(struct cache
*cache
, struct bio
*bio
,
532 sector_t bi_sector
= bio
->bi_sector
;
534 bio
->bi_bdev
= cache
->cache_dev
->bdev
;
535 if (!block_size_is_power_of_two(cache
))
536 bio
->bi_sector
= (from_cblock(cblock
) * cache
->sectors_per_block
) +
537 sector_div(bi_sector
, cache
->sectors_per_block
);
539 bio
->bi_sector
= (from_cblock(cblock
) << cache
->sectors_per_block_shift
) |
540 (bi_sector
& (cache
->sectors_per_block
- 1));
543 static void check_if_tick_bio_needed(struct cache
*cache
, struct bio
*bio
)
546 struct per_bio_data
*pb
= get_per_bio_data(bio
);
548 spin_lock_irqsave(&cache
->lock
, flags
);
549 if (cache
->need_tick_bio
&&
550 !(bio
->bi_rw
& (REQ_FUA
| REQ_FLUSH
| REQ_DISCARD
))) {
552 cache
->need_tick_bio
= false;
554 spin_unlock_irqrestore(&cache
->lock
, flags
);
557 static void remap_to_origin_clear_discard(struct cache
*cache
, struct bio
*bio
,
560 check_if_tick_bio_needed(cache
, bio
);
561 remap_to_origin(cache
, bio
);
562 if (bio_data_dir(bio
) == WRITE
)
563 clear_discard(cache
, oblock_to_dblock(cache
, oblock
));
566 static void remap_to_cache_dirty(struct cache
*cache
, struct bio
*bio
,
567 dm_oblock_t oblock
, dm_cblock_t cblock
)
569 remap_to_cache(cache
, bio
, cblock
);
570 if (bio_data_dir(bio
) == WRITE
) {
571 set_dirty(cache
, oblock
, cblock
);
572 clear_discard(cache
, oblock_to_dblock(cache
, oblock
));
576 static dm_oblock_t
get_bio_block(struct cache
*cache
, struct bio
*bio
)
578 sector_t block_nr
= bio
->bi_sector
;
580 if (!block_size_is_power_of_two(cache
))
581 (void) sector_div(block_nr
, cache
->sectors_per_block
);
583 block_nr
>>= cache
->sectors_per_block_shift
;
585 return to_oblock(block_nr
);
588 static int bio_triggers_commit(struct cache
*cache
, struct bio
*bio
)
590 return bio
->bi_rw
& (REQ_FLUSH
| REQ_FUA
);
593 static void issue(struct cache
*cache
, struct bio
*bio
)
597 if (!bio_triggers_commit(cache
, bio
)) {
598 generic_make_request(bio
);
603 * Batch together any bios that trigger commits and then issue a
604 * single commit for them in do_worker().
606 spin_lock_irqsave(&cache
->lock
, flags
);
607 cache
->commit_requested
= true;
608 bio_list_add(&cache
->deferred_flush_bios
, bio
);
609 spin_unlock_irqrestore(&cache
->lock
, flags
);
612 /*----------------------------------------------------------------
613 * Migration processing
615 * Migration covers moving data from the origin device to the cache, or
617 *--------------------------------------------------------------*/
618 static void free_migration(struct dm_cache_migration
*mg
)
620 mempool_free(mg
, mg
->cache
->migration_pool
);
623 static void inc_nr_migrations(struct cache
*cache
)
625 atomic_inc(&cache
->nr_migrations
);
628 static void dec_nr_migrations(struct cache
*cache
)
630 atomic_dec(&cache
->nr_migrations
);
633 * Wake the worker in case we're suspending the target.
635 wake_up(&cache
->migration_wait
);
638 static void __cell_defer(struct cache
*cache
, struct dm_bio_prison_cell
*cell
,
641 (holder
? dm_cell_release
: dm_cell_release_no_holder
)
642 (cache
->prison
, cell
, &cache
->deferred_bios
);
643 free_prison_cell(cache
, cell
);
646 static void cell_defer(struct cache
*cache
, struct dm_bio_prison_cell
*cell
,
651 spin_lock_irqsave(&cache
->lock
, flags
);
652 __cell_defer(cache
, cell
, holder
);
653 spin_unlock_irqrestore(&cache
->lock
, flags
);
658 static void cleanup_migration(struct dm_cache_migration
*mg
)
660 dec_nr_migrations(mg
->cache
);
664 static void migration_failure(struct dm_cache_migration
*mg
)
666 struct cache
*cache
= mg
->cache
;
669 DMWARN_LIMIT("writeback failed; couldn't copy block");
670 set_dirty(cache
, mg
->old_oblock
, mg
->cblock
);
671 cell_defer(cache
, mg
->old_ocell
, false);
673 } else if (mg
->demote
) {
674 DMWARN_LIMIT("demotion failed; couldn't copy block");
675 policy_force_mapping(cache
->policy
, mg
->new_oblock
, mg
->old_oblock
);
677 cell_defer(cache
, mg
->old_ocell
, mg
->promote
? 0 : 1);
679 cell_defer(cache
, mg
->new_ocell
, 1);
681 DMWARN_LIMIT("promotion failed; couldn't copy block");
682 policy_remove_mapping(cache
->policy
, mg
->new_oblock
);
683 cell_defer(cache
, mg
->new_ocell
, 1);
686 cleanup_migration(mg
);
689 static void migration_success_pre_commit(struct dm_cache_migration
*mg
)
692 struct cache
*cache
= mg
->cache
;
695 cell_defer(cache
, mg
->old_ocell
, false);
696 clear_dirty(cache
, mg
->old_oblock
, mg
->cblock
);
697 cleanup_migration(mg
);
700 } else if (mg
->demote
) {
701 if (dm_cache_remove_mapping(cache
->cmd
, mg
->cblock
)) {
702 DMWARN_LIMIT("demotion failed; couldn't update on disk metadata");
703 policy_force_mapping(cache
->policy
, mg
->new_oblock
,
706 cell_defer(cache
, mg
->new_ocell
, true);
707 cleanup_migration(mg
);
711 if (dm_cache_insert_mapping(cache
->cmd
, mg
->cblock
, mg
->new_oblock
)) {
712 DMWARN_LIMIT("promotion failed; couldn't update on disk metadata");
713 policy_remove_mapping(cache
->policy
, mg
->new_oblock
);
714 cleanup_migration(mg
);
719 spin_lock_irqsave(&cache
->lock
, flags
);
720 list_add_tail(&mg
->list
, &cache
->need_commit_migrations
);
721 cache
->commit_requested
= true;
722 spin_unlock_irqrestore(&cache
->lock
, flags
);
725 static void migration_success_post_commit(struct dm_cache_migration
*mg
)
728 struct cache
*cache
= mg
->cache
;
731 DMWARN("writeback unexpectedly triggered commit");
734 } else if (mg
->demote
) {
735 cell_defer(cache
, mg
->old_ocell
, mg
->promote
? 0 : 1);
740 spin_lock_irqsave(&cache
->lock
, flags
);
741 list_add_tail(&mg
->list
, &cache
->quiesced_migrations
);
742 spin_unlock_irqrestore(&cache
->lock
, flags
);
745 cleanup_migration(mg
);
748 cell_defer(cache
, mg
->new_ocell
, true);
749 clear_dirty(cache
, mg
->new_oblock
, mg
->cblock
);
750 cleanup_migration(mg
);
754 static void copy_complete(int read_err
, unsigned long write_err
, void *context
)
757 struct dm_cache_migration
*mg
= (struct dm_cache_migration
*) context
;
758 struct cache
*cache
= mg
->cache
;
760 if (read_err
|| write_err
)
763 spin_lock_irqsave(&cache
->lock
, flags
);
764 list_add_tail(&mg
->list
, &cache
->completed_migrations
);
765 spin_unlock_irqrestore(&cache
->lock
, flags
);
770 static void issue_copy_real(struct dm_cache_migration
*mg
)
773 struct dm_io_region o_region
, c_region
;
774 struct cache
*cache
= mg
->cache
;
776 o_region
.bdev
= cache
->origin_dev
->bdev
;
777 o_region
.count
= cache
->sectors_per_block
;
779 c_region
.bdev
= cache
->cache_dev
->bdev
;
780 c_region
.sector
= from_cblock(mg
->cblock
) * cache
->sectors_per_block
;
781 c_region
.count
= cache
->sectors_per_block
;
783 if (mg
->writeback
|| mg
->demote
) {
785 o_region
.sector
= from_oblock(mg
->old_oblock
) * cache
->sectors_per_block
;
786 r
= dm_kcopyd_copy(cache
->copier
, &c_region
, 1, &o_region
, 0, copy_complete
, mg
);
789 o_region
.sector
= from_oblock(mg
->new_oblock
) * cache
->sectors_per_block
;
790 r
= dm_kcopyd_copy(cache
->copier
, &o_region
, 1, &c_region
, 0, copy_complete
, mg
);
794 migration_failure(mg
);
797 static void avoid_copy(struct dm_cache_migration
*mg
)
799 atomic_inc(&mg
->cache
->stats
.copies_avoided
);
800 migration_success_pre_commit(mg
);
803 static void issue_copy(struct dm_cache_migration
*mg
)
806 struct cache
*cache
= mg
->cache
;
808 if (mg
->writeback
|| mg
->demote
)
809 avoid
= !is_dirty(cache
, mg
->cblock
) ||
810 is_discarded_oblock(cache
, mg
->old_oblock
);
812 avoid
= is_discarded_oblock(cache
, mg
->new_oblock
);
814 avoid
? avoid_copy(mg
) : issue_copy_real(mg
);
817 static void complete_migration(struct dm_cache_migration
*mg
)
820 migration_failure(mg
);
822 migration_success_pre_commit(mg
);
825 static void process_migrations(struct cache
*cache
, struct list_head
*head
,
826 void (*fn
)(struct dm_cache_migration
*))
829 struct list_head list
;
830 struct dm_cache_migration
*mg
, *tmp
;
832 INIT_LIST_HEAD(&list
);
833 spin_lock_irqsave(&cache
->lock
, flags
);
834 list_splice_init(head
, &list
);
835 spin_unlock_irqrestore(&cache
->lock
, flags
);
837 list_for_each_entry_safe(mg
, tmp
, &list
, list
)
841 static void __queue_quiesced_migration(struct dm_cache_migration
*mg
)
843 list_add_tail(&mg
->list
, &mg
->cache
->quiesced_migrations
);
846 static void queue_quiesced_migration(struct dm_cache_migration
*mg
)
849 struct cache
*cache
= mg
->cache
;
851 spin_lock_irqsave(&cache
->lock
, flags
);
852 __queue_quiesced_migration(mg
);
853 spin_unlock_irqrestore(&cache
->lock
, flags
);
858 static void queue_quiesced_migrations(struct cache
*cache
, struct list_head
*work
)
861 struct dm_cache_migration
*mg
, *tmp
;
863 spin_lock_irqsave(&cache
->lock
, flags
);
864 list_for_each_entry_safe(mg
, tmp
, work
, list
)
865 __queue_quiesced_migration(mg
);
866 spin_unlock_irqrestore(&cache
->lock
, flags
);
871 static void check_for_quiesced_migrations(struct cache
*cache
,
872 struct per_bio_data
*pb
)
874 struct list_head work
;
876 if (!pb
->all_io_entry
)
879 INIT_LIST_HEAD(&work
);
880 if (pb
->all_io_entry
)
881 dm_deferred_entry_dec(pb
->all_io_entry
, &work
);
883 if (!list_empty(&work
))
884 queue_quiesced_migrations(cache
, &work
);
887 static void quiesce_migration(struct dm_cache_migration
*mg
)
889 if (!dm_deferred_set_add_work(mg
->cache
->all_io_ds
, &mg
->list
))
890 queue_quiesced_migration(mg
);
893 static void promote(struct cache
*cache
, struct prealloc
*structs
,
894 dm_oblock_t oblock
, dm_cblock_t cblock
,
895 struct dm_bio_prison_cell
*cell
)
897 struct dm_cache_migration
*mg
= prealloc_get_migration(structs
);
900 mg
->writeback
= false;
904 mg
->new_oblock
= oblock
;
906 mg
->old_ocell
= NULL
;
907 mg
->new_ocell
= cell
;
908 mg
->start_jiffies
= jiffies
;
910 inc_nr_migrations(cache
);
911 quiesce_migration(mg
);
914 static void writeback(struct cache
*cache
, struct prealloc
*structs
,
915 dm_oblock_t oblock
, dm_cblock_t cblock
,
916 struct dm_bio_prison_cell
*cell
)
918 struct dm_cache_migration
*mg
= prealloc_get_migration(structs
);
921 mg
->writeback
= true;
925 mg
->old_oblock
= oblock
;
927 mg
->old_ocell
= cell
;
928 mg
->new_ocell
= NULL
;
929 mg
->start_jiffies
= jiffies
;
931 inc_nr_migrations(cache
);
932 quiesce_migration(mg
);
935 static void demote_then_promote(struct cache
*cache
, struct prealloc
*structs
,
936 dm_oblock_t old_oblock
, dm_oblock_t new_oblock
,
938 struct dm_bio_prison_cell
*old_ocell
,
939 struct dm_bio_prison_cell
*new_ocell
)
941 struct dm_cache_migration
*mg
= prealloc_get_migration(structs
);
944 mg
->writeback
= false;
948 mg
->old_oblock
= old_oblock
;
949 mg
->new_oblock
= new_oblock
;
951 mg
->old_ocell
= old_ocell
;
952 mg
->new_ocell
= new_ocell
;
953 mg
->start_jiffies
= jiffies
;
955 inc_nr_migrations(cache
);
956 quiesce_migration(mg
);
959 /*----------------------------------------------------------------
961 *--------------------------------------------------------------*/
962 static void defer_bio(struct cache
*cache
, struct bio
*bio
)
966 spin_lock_irqsave(&cache
->lock
, flags
);
967 bio_list_add(&cache
->deferred_bios
, bio
);
968 spin_unlock_irqrestore(&cache
->lock
, flags
);
973 static void process_flush_bio(struct cache
*cache
, struct bio
*bio
)
975 struct per_bio_data
*pb
= get_per_bio_data(bio
);
977 BUG_ON(bio
->bi_size
);
979 remap_to_origin(cache
, bio
);
981 remap_to_cache(cache
, bio
, 0);
987 * People generally discard large parts of a device, eg, the whole device
988 * when formatting. Splitting these large discards up into cache block
989 * sized ios and then quiescing (always neccessary for discard) takes too
992 * We keep it simple, and allow any size of discard to come in, and just
993 * mark off blocks on the discard bitset. No passdown occurs!
995 * To implement passdown we need to change the bio_prison such that a cell
996 * can have a key that spans many blocks.
998 static void process_discard_bio(struct cache
*cache
, struct bio
*bio
)
1000 dm_block_t start_block
= dm_sector_div_up(bio
->bi_sector
,
1001 cache
->discard_block_size
);
1002 dm_block_t end_block
= bio
->bi_sector
+ bio_sectors(bio
);
1005 (void) sector_div(end_block
, cache
->discard_block_size
);
1007 for (b
= start_block
; b
< end_block
; b
++)
1008 set_discard(cache
, to_dblock(b
));
1013 static bool spare_migration_bandwidth(struct cache
*cache
)
1015 sector_t current_volume
= (atomic_read(&cache
->nr_migrations
) + 1) *
1016 cache
->sectors_per_block
;
1017 return current_volume
< cache
->migration_threshold
;
1020 static bool is_writethrough_io(struct cache
*cache
, struct bio
*bio
,
1023 return bio_data_dir(bio
) == WRITE
&&
1024 cache
->features
.write_through
&& !is_dirty(cache
, cblock
);
1027 static void inc_hit_counter(struct cache
*cache
, struct bio
*bio
)
1029 atomic_inc(bio_data_dir(bio
) == READ
?
1030 &cache
->stats
.read_hit
: &cache
->stats
.write_hit
);
1033 static void inc_miss_counter(struct cache
*cache
, struct bio
*bio
)
1035 atomic_inc(bio_data_dir(bio
) == READ
?
1036 &cache
->stats
.read_miss
: &cache
->stats
.write_miss
);
1039 static void process_bio(struct cache
*cache
, struct prealloc
*structs
,
1043 bool release_cell
= true;
1044 dm_oblock_t block
= get_bio_block(cache
, bio
);
1045 struct dm_bio_prison_cell
*cell_prealloc
, *old_ocell
, *new_ocell
;
1046 struct policy_result lookup_result
;
1047 struct per_bio_data
*pb
= get_per_bio_data(bio
);
1048 bool discarded_block
= is_discarded_oblock(cache
, block
);
1049 bool can_migrate
= discarded_block
|| spare_migration_bandwidth(cache
);
1052 * Check to see if that block is currently migrating.
1054 cell_prealloc
= prealloc_get_cell(structs
);
1055 r
= bio_detain(cache
, block
, bio
, cell_prealloc
,
1056 (cell_free_fn
) prealloc_put_cell
,
1057 structs
, &new_ocell
);
1061 r
= policy_map(cache
->policy
, block
, true, can_migrate
, discarded_block
,
1062 bio
, &lookup_result
);
1064 if (r
== -EWOULDBLOCK
)
1065 /* migration has been denied */
1066 lookup_result
.op
= POLICY_MISS
;
1068 switch (lookup_result
.op
) {
1070 inc_hit_counter(cache
, bio
);
1071 pb
->all_io_entry
= dm_deferred_entry_inc(cache
->all_io_ds
);
1073 if (is_writethrough_io(cache
, bio
, lookup_result
.cblock
)) {
1075 * No need to mark anything dirty in write through mode.
1078 remap_to_cache(cache
, bio
, lookup_result
.cblock
) :
1079 remap_to_origin_clear_discard(cache
, bio
, block
);
1081 remap_to_cache_dirty(cache
, bio
, block
, lookup_result
.cblock
);
1087 inc_miss_counter(cache
, bio
);
1088 pb
->all_io_entry
= dm_deferred_entry_inc(cache
->all_io_ds
);
1090 if (pb
->req_nr
!= 0) {
1092 * This is a duplicate writethrough io that is no
1093 * longer needed because the block has been demoted.
1097 remap_to_origin_clear_discard(cache
, bio
, block
);
1103 atomic_inc(&cache
->stats
.promotion
);
1104 promote(cache
, structs
, block
, lookup_result
.cblock
, new_ocell
);
1105 release_cell
= false;
1108 case POLICY_REPLACE
:
1109 cell_prealloc
= prealloc_get_cell(structs
);
1110 r
= bio_detain(cache
, lookup_result
.old_oblock
, bio
, cell_prealloc
,
1111 (cell_free_fn
) prealloc_put_cell
,
1112 structs
, &old_ocell
);
1115 * We have to be careful to avoid lock inversion of
1116 * the cells. So we back off, and wait for the
1117 * old_ocell to become free.
1119 policy_force_mapping(cache
->policy
, block
,
1120 lookup_result
.old_oblock
);
1121 atomic_inc(&cache
->stats
.cache_cell_clash
);
1124 atomic_inc(&cache
->stats
.demotion
);
1125 atomic_inc(&cache
->stats
.promotion
);
1127 demote_then_promote(cache
, structs
, lookup_result
.old_oblock
,
1128 block
, lookup_result
.cblock
,
1129 old_ocell
, new_ocell
);
1130 release_cell
= false;
1134 DMERR_LIMIT("%s: erroring bio, unknown policy op: %u", __func__
,
1135 (unsigned) lookup_result
.op
);
1140 cell_defer(cache
, new_ocell
, false);
1143 static int need_commit_due_to_time(struct cache
*cache
)
1145 return jiffies
< cache
->last_commit_jiffies
||
1146 jiffies
> cache
->last_commit_jiffies
+ COMMIT_PERIOD
;
1149 static int commit_if_needed(struct cache
*cache
)
1151 if (dm_cache_changed_this_transaction(cache
->cmd
) &&
1152 (cache
->commit_requested
|| need_commit_due_to_time(cache
))) {
1153 atomic_inc(&cache
->stats
.commit_count
);
1154 cache
->last_commit_jiffies
= jiffies
;
1155 cache
->commit_requested
= false;
1156 return dm_cache_commit(cache
->cmd
, false);
1162 static void process_deferred_bios(struct cache
*cache
)
1164 unsigned long flags
;
1165 struct bio_list bios
;
1167 struct prealloc structs
;
1169 memset(&structs
, 0, sizeof(structs
));
1170 bio_list_init(&bios
);
1172 spin_lock_irqsave(&cache
->lock
, flags
);
1173 bio_list_merge(&bios
, &cache
->deferred_bios
);
1174 bio_list_init(&cache
->deferred_bios
);
1175 spin_unlock_irqrestore(&cache
->lock
, flags
);
1177 while (!bio_list_empty(&bios
)) {
1179 * If we've got no free migration structs, and processing
1180 * this bio might require one, we pause until there are some
1181 * prepared mappings to process.
1183 if (prealloc_data_structs(cache
, &structs
)) {
1184 spin_lock_irqsave(&cache
->lock
, flags
);
1185 bio_list_merge(&cache
->deferred_bios
, &bios
);
1186 spin_unlock_irqrestore(&cache
->lock
, flags
);
1190 bio
= bio_list_pop(&bios
);
1192 if (bio
->bi_rw
& REQ_FLUSH
)
1193 process_flush_bio(cache
, bio
);
1194 else if (bio
->bi_rw
& REQ_DISCARD
)
1195 process_discard_bio(cache
, bio
);
1197 process_bio(cache
, &structs
, bio
);
1200 prealloc_free_structs(cache
, &structs
);
1203 static void process_deferred_flush_bios(struct cache
*cache
, bool submit_bios
)
1205 unsigned long flags
;
1206 struct bio_list bios
;
1209 bio_list_init(&bios
);
1211 spin_lock_irqsave(&cache
->lock
, flags
);
1212 bio_list_merge(&bios
, &cache
->deferred_flush_bios
);
1213 bio_list_init(&cache
->deferred_flush_bios
);
1214 spin_unlock_irqrestore(&cache
->lock
, flags
);
1216 while ((bio
= bio_list_pop(&bios
)))
1217 submit_bios
? generic_make_request(bio
) : bio_io_error(bio
);
1220 static void writeback_some_dirty_blocks(struct cache
*cache
)
1225 struct prealloc structs
;
1226 struct dm_bio_prison_cell
*old_ocell
;
1228 memset(&structs
, 0, sizeof(structs
));
1230 while (spare_migration_bandwidth(cache
)) {
1231 if (prealloc_data_structs(cache
, &structs
))
1234 r
= policy_writeback_work(cache
->policy
, &oblock
, &cblock
);
1238 r
= get_cell(cache
, oblock
, &structs
, &old_ocell
);
1240 policy_set_dirty(cache
->policy
, oblock
);
1244 writeback(cache
, &structs
, oblock
, cblock
, old_ocell
);
1247 prealloc_free_structs(cache
, &structs
);
1250 /*----------------------------------------------------------------
1252 *--------------------------------------------------------------*/
1253 static void start_quiescing(struct cache
*cache
)
1255 unsigned long flags
;
1257 spin_lock_irqsave(&cache
->lock
, flags
);
1258 cache
->quiescing
= 1;
1259 spin_unlock_irqrestore(&cache
->lock
, flags
);
1262 static void stop_quiescing(struct cache
*cache
)
1264 unsigned long flags
;
1266 spin_lock_irqsave(&cache
->lock
, flags
);
1267 cache
->quiescing
= 0;
1268 spin_unlock_irqrestore(&cache
->lock
, flags
);
1271 static bool is_quiescing(struct cache
*cache
)
1274 unsigned long flags
;
1276 spin_lock_irqsave(&cache
->lock
, flags
);
1277 r
= cache
->quiescing
;
1278 spin_unlock_irqrestore(&cache
->lock
, flags
);
1283 static void wait_for_migrations(struct cache
*cache
)
1285 wait_event(cache
->migration_wait
, !atomic_read(&cache
->nr_migrations
));
1288 static void stop_worker(struct cache
*cache
)
1290 cancel_delayed_work(&cache
->waker
);
1291 flush_workqueue(cache
->wq
);
1294 static void requeue_deferred_io(struct cache
*cache
)
1297 struct bio_list bios
;
1299 bio_list_init(&bios
);
1300 bio_list_merge(&bios
, &cache
->deferred_bios
);
1301 bio_list_init(&cache
->deferred_bios
);
1303 while ((bio
= bio_list_pop(&bios
)))
1304 bio_endio(bio
, DM_ENDIO_REQUEUE
);
1307 static int more_work(struct cache
*cache
)
1309 if (is_quiescing(cache
))
1310 return !list_empty(&cache
->quiesced_migrations
) ||
1311 !list_empty(&cache
->completed_migrations
) ||
1312 !list_empty(&cache
->need_commit_migrations
);
1314 return !bio_list_empty(&cache
->deferred_bios
) ||
1315 !bio_list_empty(&cache
->deferred_flush_bios
) ||
1316 !list_empty(&cache
->quiesced_migrations
) ||
1317 !list_empty(&cache
->completed_migrations
) ||
1318 !list_empty(&cache
->need_commit_migrations
);
1321 static void do_worker(struct work_struct
*ws
)
1323 struct cache
*cache
= container_of(ws
, struct cache
, worker
);
1326 if (!is_quiescing(cache
))
1327 process_deferred_bios(cache
);
1329 process_migrations(cache
, &cache
->quiesced_migrations
, issue_copy
);
1330 process_migrations(cache
, &cache
->completed_migrations
, complete_migration
);
1332 writeback_some_dirty_blocks(cache
);
1334 if (commit_if_needed(cache
)) {
1335 process_deferred_flush_bios(cache
, false);
1338 * FIXME: rollback metadata or just go into a
1339 * failure mode and error everything
1342 process_deferred_flush_bios(cache
, true);
1343 process_migrations(cache
, &cache
->need_commit_migrations
,
1344 migration_success_post_commit
);
1346 } while (more_work(cache
));
1350 * We want to commit periodically so that not too much
1351 * unwritten metadata builds up.
1353 static void do_waker(struct work_struct
*ws
)
1355 struct cache
*cache
= container_of(to_delayed_work(ws
), struct cache
, waker
);
1357 queue_delayed_work(cache
->wq
, &cache
->waker
, COMMIT_PERIOD
);
1360 /*----------------------------------------------------------------*/
1362 static int is_congested(struct dm_dev
*dev
, int bdi_bits
)
1364 struct request_queue
*q
= bdev_get_queue(dev
->bdev
);
1365 return bdi_congested(&q
->backing_dev_info
, bdi_bits
);
1368 static int cache_is_congested(struct dm_target_callbacks
*cb
, int bdi_bits
)
1370 struct cache
*cache
= container_of(cb
, struct cache
, callbacks
);
1372 return is_congested(cache
->origin_dev
, bdi_bits
) ||
1373 is_congested(cache
->cache_dev
, bdi_bits
);
1376 /*----------------------------------------------------------------
1378 *--------------------------------------------------------------*/
1381 * This function gets called on the error paths of the constructor, so we
1382 * have to cope with a partially initialised struct.
1384 static void destroy(struct cache
*cache
)
1388 if (cache
->next_migration
)
1389 mempool_free(cache
->next_migration
, cache
->migration_pool
);
1391 if (cache
->migration_pool
)
1392 mempool_destroy(cache
->migration_pool
);
1394 if (cache
->all_io_ds
)
1395 dm_deferred_set_destroy(cache
->all_io_ds
);
1398 dm_bio_prison_destroy(cache
->prison
);
1401 destroy_workqueue(cache
->wq
);
1403 if (cache
->dirty_bitset
)
1404 free_bitset(cache
->dirty_bitset
);
1406 if (cache
->discard_bitset
)
1407 free_bitset(cache
->discard_bitset
);
1410 dm_kcopyd_client_destroy(cache
->copier
);
1413 dm_cache_metadata_close(cache
->cmd
);
1415 if (cache
->metadata_dev
)
1416 dm_put_device(cache
->ti
, cache
->metadata_dev
);
1418 if (cache
->origin_dev
)
1419 dm_put_device(cache
->ti
, cache
->origin_dev
);
1421 if (cache
->cache_dev
)
1422 dm_put_device(cache
->ti
, cache
->cache_dev
);
1425 dm_cache_policy_destroy(cache
->policy
);
1427 for (i
= 0; i
< cache
->nr_ctr_args
; i
++)
1428 kfree(cache
->ctr_args
[i
]);
1429 kfree(cache
->ctr_args
);
1434 static void cache_dtr(struct dm_target
*ti
)
1436 struct cache
*cache
= ti
->private;
1441 static sector_t
get_dev_size(struct dm_dev
*dev
)
1443 return i_size_read(dev
->bdev
->bd_inode
) >> SECTOR_SHIFT
;
1446 /*----------------------------------------------------------------*/
1449 * Construct a cache device mapping.
1451 * cache <metadata dev> <cache dev> <origin dev> <block size>
1452 * <#feature args> [<feature arg>]*
1453 * <policy> <#policy args> [<policy arg>]*
1455 * metadata dev : fast device holding the persistent metadata
1456 * cache dev : fast device holding cached data blocks
1457 * origin dev : slow device holding original data blocks
1458 * block size : cache unit size in sectors
1460 * #feature args : number of feature arguments passed
1461 * feature args : writethrough. (The default is writeback.)
1463 * policy : the replacement policy to use
1464 * #policy args : an even number of policy arguments corresponding
1465 * to key/value pairs passed to the policy
1466 * policy args : key/value pairs passed to the policy
1467 * E.g. 'sequential_threshold 1024'
1468 * See cache-policies.txt for details.
1470 * Optional feature arguments are:
1471 * writethrough : write through caching that prohibits cache block
1472 * content from being different from origin block content.
1473 * Without this argument, the default behaviour is to write
1474 * back cache block contents later for performance reasons,
1475 * so they may differ from the corresponding origin blocks.
1478 struct dm_target
*ti
;
1480 struct dm_dev
*metadata_dev
;
1482 struct dm_dev
*cache_dev
;
1483 sector_t cache_sectors
;
1485 struct dm_dev
*origin_dev
;
1486 sector_t origin_sectors
;
1488 uint32_t block_size
;
1490 const char *policy_name
;
1492 const char **policy_argv
;
1494 struct cache_features features
;
1497 static void destroy_cache_args(struct cache_args
*ca
)
1499 if (ca
->metadata_dev
)
1500 dm_put_device(ca
->ti
, ca
->metadata_dev
);
1503 dm_put_device(ca
->ti
, ca
->cache_dev
);
1506 dm_put_device(ca
->ti
, ca
->origin_dev
);
1511 static bool at_least_one_arg(struct dm_arg_set
*as
, char **error
)
1514 *error
= "Insufficient args";
1521 static int parse_metadata_dev(struct cache_args
*ca
, struct dm_arg_set
*as
,
1525 sector_t metadata_dev_size
;
1526 char b
[BDEVNAME_SIZE
];
1528 if (!at_least_one_arg(as
, error
))
1531 r
= dm_get_device(ca
->ti
, dm_shift_arg(as
), FMODE_READ
| FMODE_WRITE
,
1534 *error
= "Error opening metadata device";
1538 metadata_dev_size
= get_dev_size(ca
->metadata_dev
);
1539 if (metadata_dev_size
> DM_CACHE_METADATA_MAX_SECTORS_WARNING
)
1540 DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
1541 bdevname(ca
->metadata_dev
->bdev
, b
), THIN_METADATA_MAX_SECTORS
);
1546 static int parse_cache_dev(struct cache_args
*ca
, struct dm_arg_set
*as
,
1551 if (!at_least_one_arg(as
, error
))
1554 r
= dm_get_device(ca
->ti
, dm_shift_arg(as
), FMODE_READ
| FMODE_WRITE
,
1557 *error
= "Error opening cache device";
1560 ca
->cache_sectors
= get_dev_size(ca
->cache_dev
);
1565 static int parse_origin_dev(struct cache_args
*ca
, struct dm_arg_set
*as
,
1570 if (!at_least_one_arg(as
, error
))
1573 r
= dm_get_device(ca
->ti
, dm_shift_arg(as
), FMODE_READ
| FMODE_WRITE
,
1576 *error
= "Error opening origin device";
1580 ca
->origin_sectors
= get_dev_size(ca
->origin_dev
);
1581 if (ca
->ti
->len
> ca
->origin_sectors
) {
1582 *error
= "Device size larger than cached device";
1589 static int parse_block_size(struct cache_args
*ca
, struct dm_arg_set
*as
,
1594 if (!at_least_one_arg(as
, error
))
1597 if (kstrtoul(dm_shift_arg(as
), 10, &tmp
) || !tmp
||
1598 tmp
< DATA_DEV_BLOCK_SIZE_MIN_SECTORS
||
1599 tmp
& (DATA_DEV_BLOCK_SIZE_MIN_SECTORS
- 1)) {
1600 *error
= "Invalid data block size";
1604 if (tmp
> ca
->cache_sectors
) {
1605 *error
= "Data block size is larger than the cache device";
1609 ca
->block_size
= tmp
;
1614 static void init_features(struct cache_features
*cf
)
1616 cf
->mode
= CM_WRITE
;
1617 cf
->write_through
= false;
1620 static int parse_features(struct cache_args
*ca
, struct dm_arg_set
*as
,
1623 static struct dm_arg _args
[] = {
1624 {0, 1, "Invalid number of cache feature arguments"},
1630 struct cache_features
*cf
= &ca
->features
;
1634 r
= dm_read_arg_group(_args
, as
, &argc
, error
);
1639 arg
= dm_shift_arg(as
);
1641 if (!strcasecmp(arg
, "writeback"))
1642 cf
->write_through
= false;
1644 else if (!strcasecmp(arg
, "writethrough"))
1645 cf
->write_through
= true;
1648 *error
= "Unrecognised cache feature requested";
1656 static int parse_policy(struct cache_args
*ca
, struct dm_arg_set
*as
,
1659 static struct dm_arg _args
[] = {
1660 {0, 1024, "Invalid number of policy arguments"},
1665 if (!at_least_one_arg(as
, error
))
1668 ca
->policy_name
= dm_shift_arg(as
);
1670 r
= dm_read_arg_group(_args
, as
, &ca
->policy_argc
, error
);
1674 ca
->policy_argv
= (const char **)as
->argv
;
1675 dm_consume_args(as
, ca
->policy_argc
);
1680 static int parse_cache_args(struct cache_args
*ca
, int argc
, char **argv
,
1684 struct dm_arg_set as
;
1689 r
= parse_metadata_dev(ca
, &as
, error
);
1693 r
= parse_cache_dev(ca
, &as
, error
);
1697 r
= parse_origin_dev(ca
, &as
, error
);
1701 r
= parse_block_size(ca
, &as
, error
);
1705 r
= parse_features(ca
, &as
, error
);
1709 r
= parse_policy(ca
, &as
, error
);
1716 /*----------------------------------------------------------------*/
1718 static struct kmem_cache
*migration_cache
;
1720 static int set_config_values(struct dm_cache_policy
*p
, int argc
, const char **argv
)
1725 DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs.");
1730 r
= policy_set_config_value(p
, argv
[0], argv
[1]);
1732 DMWARN("policy_set_config_value failed: key = '%s', value = '%s'",
1744 static int create_cache_policy(struct cache
*cache
, struct cache_args
*ca
,
1749 cache
->policy
= dm_cache_policy_create(ca
->policy_name
,
1751 cache
->origin_sectors
,
1752 cache
->sectors_per_block
);
1753 if (!cache
->policy
) {
1754 *error
= "Error creating cache's policy";
1758 r
= set_config_values(cache
->policy
, ca
->policy_argc
, ca
->policy_argv
);
1760 dm_cache_policy_destroy(cache
->policy
);
1766 * We want the discard block size to be a power of two, at least the size
1767 * of the cache block size, and have no more than 2^14 discard blocks
1768 * across the origin.
1770 #define MAX_DISCARD_BLOCKS (1 << 14)
1772 static bool too_many_discard_blocks(sector_t discard_block_size
,
1773 sector_t origin_size
)
1775 (void) sector_div(origin_size
, discard_block_size
);
1777 return origin_size
> MAX_DISCARD_BLOCKS
;
1780 static sector_t
calculate_discard_block_size(sector_t cache_block_size
,
1781 sector_t origin_size
)
1783 sector_t discard_block_size
;
1785 discard_block_size
= roundup_pow_of_two(cache_block_size
);
1788 while (too_many_discard_blocks(discard_block_size
, origin_size
))
1789 discard_block_size
*= 2;
1791 return discard_block_size
;
1794 #define DEFAULT_MIGRATION_THRESHOLD (2048 * 100)
1796 static unsigned cache_num_write_bios(struct dm_target
*ti
, struct bio
*bio
);
1798 static int cache_create(struct cache_args
*ca
, struct cache
**result
)
1801 char **error
= &ca
->ti
->error
;
1802 struct cache
*cache
;
1803 struct dm_target
*ti
= ca
->ti
;
1804 dm_block_t origin_blocks
;
1805 struct dm_cache_metadata
*cmd
;
1806 bool may_format
= ca
->features
.mode
== CM_WRITE
;
1808 cache
= kzalloc(sizeof(*cache
), GFP_KERNEL
);
1813 ti
->private = cache
;
1814 ti
->per_bio_data_size
= sizeof(struct per_bio_data
);
1815 ti
->num_flush_bios
= 2;
1816 ti
->flush_supported
= true;
1818 ti
->num_discard_bios
= 1;
1819 ti
->discards_supported
= true;
1820 ti
->discard_zeroes_data_unsupported
= true;
1822 memcpy(&cache
->features
, &ca
->features
, sizeof(cache
->features
));
1824 if (cache
->features
.write_through
)
1825 ti
->num_write_bios
= cache_num_write_bios
;
1827 cache
->callbacks
.congested_fn
= cache_is_congested
;
1828 dm_table_add_target_callbacks(ti
->table
, &cache
->callbacks
);
1830 cache
->metadata_dev
= ca
->metadata_dev
;
1831 cache
->origin_dev
= ca
->origin_dev
;
1832 cache
->cache_dev
= ca
->cache_dev
;
1834 ca
->metadata_dev
= ca
->origin_dev
= ca
->cache_dev
= NULL
;
1836 /* FIXME: factor out this whole section */
1837 origin_blocks
= cache
->origin_sectors
= ca
->origin_sectors
;
1838 (void) sector_div(origin_blocks
, ca
->block_size
);
1839 cache
->origin_blocks
= to_oblock(origin_blocks
);
1841 cache
->sectors_per_block
= ca
->block_size
;
1842 if (dm_set_target_max_io_len(ti
, cache
->sectors_per_block
)) {
1847 if (ca
->block_size
& (ca
->block_size
- 1)) {
1848 dm_block_t cache_size
= ca
->cache_sectors
;
1850 cache
->sectors_per_block_shift
= -1;
1851 (void) sector_div(cache_size
, ca
->block_size
);
1852 cache
->cache_size
= to_cblock(cache_size
);
1854 cache
->sectors_per_block_shift
= __ffs(ca
->block_size
);
1855 cache
->cache_size
= to_cblock(ca
->cache_sectors
>> cache
->sectors_per_block_shift
);
1858 r
= create_cache_policy(cache
, ca
, error
);
1861 cache
->policy_nr_args
= ca
->policy_argc
;
1863 cmd
= dm_cache_metadata_open(cache
->metadata_dev
->bdev
,
1864 ca
->block_size
, may_format
,
1865 dm_cache_policy_get_hint_size(cache
->policy
));
1867 *error
= "Error creating metadata object";
1873 spin_lock_init(&cache
->lock
);
1874 bio_list_init(&cache
->deferred_bios
);
1875 bio_list_init(&cache
->deferred_flush_bios
);
1876 INIT_LIST_HEAD(&cache
->quiesced_migrations
);
1877 INIT_LIST_HEAD(&cache
->completed_migrations
);
1878 INIT_LIST_HEAD(&cache
->need_commit_migrations
);
1879 cache
->migration_threshold
= DEFAULT_MIGRATION_THRESHOLD
;
1880 atomic_set(&cache
->nr_migrations
, 0);
1881 init_waitqueue_head(&cache
->migration_wait
);
1883 cache
->nr_dirty
= 0;
1884 cache
->dirty_bitset
= alloc_bitset(from_cblock(cache
->cache_size
));
1885 if (!cache
->dirty_bitset
) {
1886 *error
= "could not allocate dirty bitset";
1889 clear_bitset(cache
->dirty_bitset
, from_cblock(cache
->cache_size
));
1891 cache
->discard_block_size
=
1892 calculate_discard_block_size(cache
->sectors_per_block
,
1893 cache
->origin_sectors
);
1894 cache
->discard_nr_blocks
= oblock_to_dblock(cache
, cache
->origin_blocks
);
1895 cache
->discard_bitset
= alloc_bitset(from_dblock(cache
->discard_nr_blocks
));
1896 if (!cache
->discard_bitset
) {
1897 *error
= "could not allocate discard bitset";
1900 clear_bitset(cache
->discard_bitset
, from_dblock(cache
->discard_nr_blocks
));
1902 cache
->copier
= dm_kcopyd_client_create(&dm_kcopyd_throttle
);
1903 if (IS_ERR(cache
->copier
)) {
1904 *error
= "could not create kcopyd client";
1905 r
= PTR_ERR(cache
->copier
);
1909 cache
->wq
= alloc_ordered_workqueue("dm-" DM_MSG_PREFIX
, WQ_MEM_RECLAIM
);
1911 *error
= "could not create workqueue for metadata object";
1914 INIT_WORK(&cache
->worker
, do_worker
);
1915 INIT_DELAYED_WORK(&cache
->waker
, do_waker
);
1916 cache
->last_commit_jiffies
= jiffies
;
1918 cache
->prison
= dm_bio_prison_create(PRISON_CELLS
);
1919 if (!cache
->prison
) {
1920 *error
= "could not create bio prison";
1924 cache
->all_io_ds
= dm_deferred_set_create();
1925 if (!cache
->all_io_ds
) {
1926 *error
= "could not create all_io deferred set";
1930 cache
->migration_pool
= mempool_create_slab_pool(MIGRATION_POOL_SIZE
,
1932 if (!cache
->migration_pool
) {
1933 *error
= "Error creating cache's migration mempool";
1937 cache
->next_migration
= NULL
;
1939 cache
->need_tick_bio
= true;
1940 cache
->sized
= false;
1941 cache
->quiescing
= false;
1942 cache
->commit_requested
= false;
1943 cache
->loaded_mappings
= false;
1944 cache
->loaded_discards
= false;
1948 atomic_set(&cache
->stats
.demotion
, 0);
1949 atomic_set(&cache
->stats
.promotion
, 0);
1950 atomic_set(&cache
->stats
.copies_avoided
, 0);
1951 atomic_set(&cache
->stats
.cache_cell_clash
, 0);
1952 atomic_set(&cache
->stats
.commit_count
, 0);
1953 atomic_set(&cache
->stats
.discard_count
, 0);
1963 static int copy_ctr_args(struct cache
*cache
, int argc
, const char **argv
)
1968 copy
= kcalloc(argc
, sizeof(*copy
), GFP_KERNEL
);
1971 for (i
= 0; i
< argc
; i
++) {
1972 copy
[i
] = kstrdup(argv
[i
], GFP_KERNEL
);
1981 cache
->nr_ctr_args
= argc
;
1982 cache
->ctr_args
= copy
;
1987 static int cache_ctr(struct dm_target
*ti
, unsigned argc
, char **argv
)
1990 struct cache_args
*ca
;
1991 struct cache
*cache
= NULL
;
1993 ca
= kzalloc(sizeof(*ca
), GFP_KERNEL
);
1995 ti
->error
= "Error allocating memory for cache";
2000 r
= parse_cache_args(ca
, argc
, argv
, &ti
->error
);
2004 r
= cache_create(ca
, &cache
);
2006 r
= copy_ctr_args(cache
, argc
- 3, (const char **)argv
+ 3);
2012 ti
->private = cache
;
2015 destroy_cache_args(ca
);
2019 static unsigned cache_num_write_bios(struct dm_target
*ti
, struct bio
*bio
)
2022 struct cache
*cache
= ti
->private;
2023 dm_oblock_t block
= get_bio_block(cache
, bio
);
2026 r
= policy_lookup(cache
->policy
, block
, &cblock
);
2028 return 2; /* assume the worst */
2030 return (!r
&& !is_dirty(cache
, cblock
)) ? 2 : 1;
2033 static int cache_map(struct dm_target
*ti
, struct bio
*bio
)
2035 struct cache
*cache
= ti
->private;
2038 dm_oblock_t block
= get_bio_block(cache
, bio
);
2039 bool can_migrate
= false;
2040 bool discarded_block
;
2041 struct dm_bio_prison_cell
*cell
;
2042 struct policy_result lookup_result
;
2043 struct per_bio_data
*pb
;
2045 if (from_oblock(block
) > from_oblock(cache
->origin_blocks
)) {
2047 * This can only occur if the io goes to a partial block at
2048 * the end of the origin device. We don't cache these.
2049 * Just remap to the origin and carry on.
2051 remap_to_origin_clear_discard(cache
, bio
, block
);
2052 return DM_MAPIO_REMAPPED
;
2055 pb
= init_per_bio_data(bio
);
2057 if (bio
->bi_rw
& (REQ_FLUSH
| REQ_FUA
| REQ_DISCARD
)) {
2058 defer_bio(cache
, bio
);
2059 return DM_MAPIO_SUBMITTED
;
2063 * Check to see if that block is currently migrating.
2065 cell
= alloc_prison_cell(cache
);
2067 defer_bio(cache
, bio
);
2068 return DM_MAPIO_SUBMITTED
;
2071 r
= bio_detain(cache
, block
, bio
, cell
,
2072 (cell_free_fn
) free_prison_cell
,
2076 defer_bio(cache
, bio
);
2078 return DM_MAPIO_SUBMITTED
;
2081 discarded_block
= is_discarded_oblock(cache
, block
);
2083 r
= policy_map(cache
->policy
, block
, false, can_migrate
, discarded_block
,
2084 bio
, &lookup_result
);
2085 if (r
== -EWOULDBLOCK
) {
2086 cell_defer(cache
, cell
, true);
2087 return DM_MAPIO_SUBMITTED
;
2090 DMERR_LIMIT("Unexpected return from cache replacement policy: %d", r
);
2092 return DM_MAPIO_SUBMITTED
;
2095 switch (lookup_result
.op
) {
2097 inc_hit_counter(cache
, bio
);
2098 pb
->all_io_entry
= dm_deferred_entry_inc(cache
->all_io_ds
);
2100 if (is_writethrough_io(cache
, bio
, lookup_result
.cblock
)) {
2102 * No need to mark anything dirty in write through mode.
2105 remap_to_cache(cache
, bio
, lookup_result
.cblock
) :
2106 remap_to_origin_clear_discard(cache
, bio
, block
);
2107 cell_defer(cache
, cell
, false);
2109 remap_to_cache_dirty(cache
, bio
, block
, lookup_result
.cblock
);
2110 cell_defer(cache
, cell
, false);
2115 inc_miss_counter(cache
, bio
);
2116 pb
->all_io_entry
= dm_deferred_entry_inc(cache
->all_io_ds
);
2118 if (pb
->req_nr
!= 0) {
2120 * This is a duplicate writethrough io that is no
2121 * longer needed because the block has been demoted.
2124 cell_defer(cache
, cell
, false);
2125 return DM_MAPIO_SUBMITTED
;
2127 remap_to_origin_clear_discard(cache
, bio
, block
);
2128 cell_defer(cache
, cell
, false);
2133 DMERR_LIMIT("%s: erroring bio: unknown policy op: %u", __func__
,
2134 (unsigned) lookup_result
.op
);
2136 return DM_MAPIO_SUBMITTED
;
2139 return DM_MAPIO_REMAPPED
;
2142 static int cache_end_io(struct dm_target
*ti
, struct bio
*bio
, int error
)
2144 struct cache
*cache
= ti
->private;
2145 unsigned long flags
;
2146 struct per_bio_data
*pb
= get_per_bio_data(bio
);
2149 policy_tick(cache
->policy
);
2151 spin_lock_irqsave(&cache
->lock
, flags
);
2152 cache
->need_tick_bio
= true;
2153 spin_unlock_irqrestore(&cache
->lock
, flags
);
2156 check_for_quiesced_migrations(cache
, pb
);
2161 static int write_dirty_bitset(struct cache
*cache
)
2165 for (i
= 0; i
< from_cblock(cache
->cache_size
); i
++) {
2166 r
= dm_cache_set_dirty(cache
->cmd
, to_cblock(i
),
2167 is_dirty(cache
, to_cblock(i
)));
2175 static int write_discard_bitset(struct cache
*cache
)
2179 r
= dm_cache_discard_bitset_resize(cache
->cmd
, cache
->discard_block_size
,
2180 cache
->discard_nr_blocks
);
2182 DMERR("could not resize on-disk discard bitset");
2186 for (i
= 0; i
< from_dblock(cache
->discard_nr_blocks
); i
++) {
2187 r
= dm_cache_set_discard(cache
->cmd
, to_dblock(i
),
2188 is_discarded(cache
, to_dblock(i
)));
2196 static int save_hint(void *context
, dm_cblock_t cblock
, dm_oblock_t oblock
,
2199 struct cache
*cache
= context
;
2200 return dm_cache_save_hint(cache
->cmd
, cblock
, hint
);
2203 static int write_hints(struct cache
*cache
)
2207 r
= dm_cache_begin_hints(cache
->cmd
, cache
->policy
);
2209 DMERR("dm_cache_begin_hints failed");
2213 r
= policy_walk_mappings(cache
->policy
, save_hint
, cache
);
2215 DMERR("policy_walk_mappings failed");
2221 * returns true on success
2223 static bool sync_metadata(struct cache
*cache
)
2227 r1
= write_dirty_bitset(cache
);
2229 DMERR("could not write dirty bitset");
2231 r2
= write_discard_bitset(cache
);
2233 DMERR("could not write discard bitset");
2237 r3
= write_hints(cache
);
2239 DMERR("could not write hints");
2242 * If writing the above metadata failed, we still commit, but don't
2243 * set the clean shutdown flag. This will effectively force every
2244 * dirty bit to be set on reload.
2246 r4
= dm_cache_commit(cache
->cmd
, !r1
&& !r2
&& !r3
);
2248 DMERR("could not write cache metadata. Data loss may occur.");
2250 return !r1
&& !r2
&& !r3
&& !r4
;
2253 static void cache_postsuspend(struct dm_target
*ti
)
2255 struct cache
*cache
= ti
->private;
2257 start_quiescing(cache
);
2258 wait_for_migrations(cache
);
2260 requeue_deferred_io(cache
);
2261 stop_quiescing(cache
);
2263 (void) sync_metadata(cache
);
2266 static int load_mapping(void *context
, dm_oblock_t oblock
, dm_cblock_t cblock
,
2267 bool dirty
, uint32_t hint
, bool hint_valid
)
2270 struct cache
*cache
= context
;
2272 r
= policy_load_mapping(cache
->policy
, oblock
, cblock
, hint
, hint_valid
);
2277 set_dirty(cache
, oblock
, cblock
);
2279 clear_dirty(cache
, oblock
, cblock
);
2284 static int load_discard(void *context
, sector_t discard_block_size
,
2285 dm_dblock_t dblock
, bool discard
)
2287 struct cache
*cache
= context
;
2289 /* FIXME: handle mis-matched block size */
2292 set_discard(cache
, dblock
);
2294 clear_discard(cache
, dblock
);
2299 static int cache_preresume(struct dm_target
*ti
)
2302 struct cache
*cache
= ti
->private;
2303 sector_t actual_cache_size
= get_dev_size(cache
->cache_dev
);
2304 (void) sector_div(actual_cache_size
, cache
->sectors_per_block
);
2307 * Check to see if the cache has resized.
2309 if (from_cblock(cache
->cache_size
) != actual_cache_size
|| !cache
->sized
) {
2310 cache
->cache_size
= to_cblock(actual_cache_size
);
2312 r
= dm_cache_resize(cache
->cmd
, cache
->cache_size
);
2314 DMERR("could not resize cache metadata");
2318 cache
->sized
= true;
2321 if (!cache
->loaded_mappings
) {
2322 r
= dm_cache_load_mappings(cache
->cmd
,
2323 dm_cache_policy_get_name(cache
->policy
),
2324 load_mapping
, cache
);
2326 DMERR("could not load cache mappings");
2330 cache
->loaded_mappings
= true;
2333 if (!cache
->loaded_discards
) {
2334 r
= dm_cache_load_discards(cache
->cmd
, load_discard
, cache
);
2336 DMERR("could not load origin discards");
2340 cache
->loaded_discards
= true;
2346 static void cache_resume(struct dm_target
*ti
)
2348 struct cache
*cache
= ti
->private;
2350 cache
->need_tick_bio
= true;
2351 do_waker(&cache
->waker
.work
);
2357 * <#used metadata blocks>/<#total metadata blocks>
2358 * <#read hits> <#read misses> <#write hits> <#write misses>
2359 * <#demotions> <#promotions> <#blocks in cache> <#dirty>
2360 * <#features> <features>*
2361 * <#core args> <core args>
2362 * <#policy args> <policy args>*
2364 static void cache_status(struct dm_target
*ti
, status_type_t type
,
2365 unsigned status_flags
, char *result
, unsigned maxlen
)
2370 dm_block_t nr_free_blocks_metadata
= 0;
2371 dm_block_t nr_blocks_metadata
= 0;
2372 char buf
[BDEVNAME_SIZE
];
2373 struct cache
*cache
= ti
->private;
2374 dm_cblock_t residency
;
2377 case STATUSTYPE_INFO
:
2378 /* Commit to ensure statistics aren't out-of-date */
2379 if (!(status_flags
& DM_STATUS_NOFLUSH_FLAG
) && !dm_suspended(ti
)) {
2380 r
= dm_cache_commit(cache
->cmd
, false);
2382 DMERR("could not commit metadata for accurate status");
2385 r
= dm_cache_get_free_metadata_block_count(cache
->cmd
,
2386 &nr_free_blocks_metadata
);
2388 DMERR("could not get metadata free block count");
2392 r
= dm_cache_get_metadata_dev_size(cache
->cmd
, &nr_blocks_metadata
);
2394 DMERR("could not get metadata device size");
2398 residency
= policy_residency(cache
->policy
);
2400 DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
2401 (unsigned long long)(nr_blocks_metadata
- nr_free_blocks_metadata
),
2402 (unsigned long long)nr_blocks_metadata
,
2403 (unsigned) atomic_read(&cache
->stats
.read_hit
),
2404 (unsigned) atomic_read(&cache
->stats
.read_miss
),
2405 (unsigned) atomic_read(&cache
->stats
.write_hit
),
2406 (unsigned) atomic_read(&cache
->stats
.write_miss
),
2407 (unsigned) atomic_read(&cache
->stats
.demotion
),
2408 (unsigned) atomic_read(&cache
->stats
.promotion
),
2409 (unsigned long long) from_cblock(residency
),
2412 if (cache
->features
.write_through
)
2413 DMEMIT("1 writethrough ");
2417 DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache
->migration_threshold
);
2419 r
= policy_emit_config_values(cache
->policy
, result
+ sz
, maxlen
- sz
);
2421 DMERR("policy_emit_config_values returned %d", r
);
2426 case STATUSTYPE_TABLE
:
2427 format_dev_t(buf
, cache
->metadata_dev
->bdev
->bd_dev
);
2429 format_dev_t(buf
, cache
->cache_dev
->bdev
->bd_dev
);
2431 format_dev_t(buf
, cache
->origin_dev
->bdev
->bd_dev
);
2434 for (i
= 0; i
< cache
->nr_ctr_args
- 1; i
++)
2435 DMEMIT(" %s", cache
->ctr_args
[i
]);
2436 if (cache
->nr_ctr_args
)
2437 DMEMIT(" %s", cache
->ctr_args
[cache
->nr_ctr_args
- 1]);
2446 #define NOT_CORE_OPTION 1
2448 static int process_config_option(struct cache
*cache
, char **argv
)
2452 if (!strcasecmp(argv
[0], "migration_threshold")) {
2453 if (kstrtoul(argv
[1], 10, &tmp
))
2456 cache
->migration_threshold
= tmp
;
2460 return NOT_CORE_OPTION
;
2464 * Supports <key> <value>.
2466 * The key migration_threshold is supported by the cache target core.
2468 static int cache_message(struct dm_target
*ti
, unsigned argc
, char **argv
)
2471 struct cache
*cache
= ti
->private;
2476 r
= process_config_option(cache
, argv
);
2477 if (r
== NOT_CORE_OPTION
)
2478 return policy_set_config_value(cache
->policy
, argv
[0], argv
[1]);
2483 static int cache_iterate_devices(struct dm_target
*ti
,
2484 iterate_devices_callout_fn fn
, void *data
)
2487 struct cache
*cache
= ti
->private;
2489 r
= fn(ti
, cache
->cache_dev
, 0, get_dev_size(cache
->cache_dev
), data
);
2491 r
= fn(ti
, cache
->origin_dev
, 0, ti
->len
, data
);
2497 * We assume I/O is going to the origin (which is the volume
2498 * more likely to have restrictions e.g. by being striped).
2499 * (Looking up the exact location of the data would be expensive
2500 * and could always be out of date by the time the bio is submitted.)
2502 static int cache_bvec_merge(struct dm_target
*ti
,
2503 struct bvec_merge_data
*bvm
,
2504 struct bio_vec
*biovec
, int max_size
)
2506 struct cache
*cache
= ti
->private;
2507 struct request_queue
*q
= bdev_get_queue(cache
->origin_dev
->bdev
);
2509 if (!q
->merge_bvec_fn
)
2512 bvm
->bi_bdev
= cache
->origin_dev
->bdev
;
2513 return min(max_size
, q
->merge_bvec_fn(q
, bvm
, biovec
));
2516 static void set_discard_limits(struct cache
*cache
, struct queue_limits
*limits
)
2519 * FIXME: these limits may be incompatible with the cache device
2521 limits
->max_discard_sectors
= cache
->discard_block_size
* 1024;
2522 limits
->discard_granularity
= cache
->discard_block_size
<< SECTOR_SHIFT
;
2525 static void cache_io_hints(struct dm_target
*ti
, struct queue_limits
*limits
)
2527 struct cache
*cache
= ti
->private;
2529 blk_limits_io_min(limits
, 0);
2530 blk_limits_io_opt(limits
, cache
->sectors_per_block
<< SECTOR_SHIFT
);
2531 set_discard_limits(cache
, limits
);
2534 /*----------------------------------------------------------------*/
2536 static struct target_type cache_target
= {
2538 .version
= {1, 0, 0},
2539 .module
= THIS_MODULE
,
2543 .end_io
= cache_end_io
,
2544 .postsuspend
= cache_postsuspend
,
2545 .preresume
= cache_preresume
,
2546 .resume
= cache_resume
,
2547 .status
= cache_status
,
2548 .message
= cache_message
,
2549 .iterate_devices
= cache_iterate_devices
,
2550 .merge
= cache_bvec_merge
,
2551 .io_hints
= cache_io_hints
,
2554 static int __init
dm_cache_init(void)
2558 r
= dm_register_target(&cache_target
);
2560 DMERR("cache target registration failed: %d", r
);
2564 migration_cache
= KMEM_CACHE(dm_cache_migration
, 0);
2565 if (!migration_cache
) {
2566 dm_unregister_target(&cache_target
);
2573 static void __exit
dm_cache_exit(void)
2575 dm_unregister_target(&cache_target
);
2576 kmem_cache_destroy(migration_cache
);
2579 module_init(dm_cache_init
);
2580 module_exit(dm_cache_exit
);
2582 MODULE_DESCRIPTION(DM_NAME
" cache target");
2583 MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
2584 MODULE_LICENSE("GPL");