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-bio-record.h"
10 #include "dm-cache-metadata.h"
12 #include <linux/dm-io.h>
13 #include <linux/dm-kcopyd.h>
14 #include <linux/init.h>
15 #include <linux/mempool.h>
16 #include <linux/module.h>
17 #include <linux/slab.h>
18 #include <linux/vmalloc.h>
20 #define DM_MSG_PREFIX "cache"
22 DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle,
23 "A percentage of time allocated for copying to and/or from cache");
25 /*----------------------------------------------------------------*/
30 * oblock: index of an origin block
31 * cblock: index of a cache block
32 * promotion: movement of a block from origin to cache
33 * demotion: movement of a block from cache to origin
34 * migration: movement of a block between the origin and cache device,
38 /*----------------------------------------------------------------*/
40 static size_t bitset_size_in_bytes(unsigned nr_entries)
42 return sizeof(unsigned long) * dm_div_up(nr_entries, BITS_PER_LONG);
45 static unsigned long *alloc_bitset(unsigned nr_entries)
47 size_t s = bitset_size_in_bytes(nr_entries);
51 static void clear_bitset(void *bitset, unsigned nr_entries)
53 size_t s = bitset_size_in_bytes(nr_entries);
57 static void free_bitset(unsigned long *bits)
62 /*----------------------------------------------------------------*/
64 #define PRISON_CELLS 1024
65 #define MIGRATION_POOL_SIZE 128
66 #define COMMIT_PERIOD HZ
67 #define MIGRATION_COUNT_WINDOW 10
70 * The block size of the device holding cache data must be >= 32KB
72 #define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
75 * FIXME: the cache is read/write for the time being.
78 CM_WRITE, /* metadata may be changed */
79 CM_READ_ONLY, /* metadata may not be changed */
82 struct cache_features {
94 atomic_t copies_avoided;
95 atomic_t cache_cell_clash;
96 atomic_t commit_count;
97 atomic_t discard_count;
101 struct dm_target *ti;
102 struct dm_target_callbacks callbacks;
105 * Metadata is written to this device.
107 struct dm_dev *metadata_dev;
110 * The slower of the two data devices. Typically a spindle.
112 struct dm_dev *origin_dev;
115 * The faster of the two data devices. Typically an SSD.
117 struct dm_dev *cache_dev;
120 * Cache features such as write-through.
122 struct cache_features features;
125 * Size of the origin device in _complete_ blocks and native sectors.
127 dm_oblock_t origin_blocks;
128 sector_t origin_sectors;
131 * Size of the cache device in blocks.
133 dm_cblock_t cache_size;
136 * Fields for converting from sectors to blocks.
138 uint32_t sectors_per_block;
139 int sectors_per_block_shift;
141 struct dm_cache_metadata *cmd;
144 struct bio_list deferred_bios;
145 struct bio_list deferred_flush_bios;
146 struct bio_list deferred_writethrough_bios;
147 struct list_head quiesced_migrations;
148 struct list_head completed_migrations;
149 struct list_head need_commit_migrations;
150 sector_t migration_threshold;
151 atomic_t nr_migrations;
152 wait_queue_head_t migration_wait;
155 * cache_size entries, dirty if set
157 dm_cblock_t nr_dirty;
158 unsigned long *dirty_bitset;
161 * origin_blocks entries, discarded if set.
163 uint32_t discard_block_size; /* a power of 2 times sectors per block */
164 dm_dblock_t discard_nr_blocks;
165 unsigned long *discard_bitset;
167 struct dm_kcopyd_client *copier;
168 struct workqueue_struct *wq;
169 struct work_struct worker;
171 struct delayed_work waker;
172 unsigned long last_commit_jiffies;
174 struct dm_bio_prison *prison;
175 struct dm_deferred_set *all_io_ds;
177 mempool_t *migration_pool;
178 struct dm_cache_migration *next_migration;
180 struct dm_cache_policy *policy;
181 unsigned policy_nr_args;
183 bool need_tick_bio:1;
186 bool commit_requested:1;
187 bool loaded_mappings:1;
188 bool loaded_discards:1;
190 struct cache_stats stats;
193 * Rather than reconstructing the table line for the status we just
194 * save it and regurgitate.
196 unsigned nr_ctr_args;
197 const char **ctr_args;
200 struct per_bio_data {
203 struct dm_deferred_entry *all_io_entry;
206 * writethrough fields. These MUST remain at the end of this
207 * structure and the 'cache' member must be the first as it
208 * is used to determine the offsetof the writethrough fields.
212 bio_end_io_t *saved_bi_end_io;
213 struct dm_bio_details bio_details;
216 struct dm_cache_migration {
217 struct list_head list;
220 unsigned long start_jiffies;
221 dm_oblock_t old_oblock;
222 dm_oblock_t new_oblock;
230 struct dm_bio_prison_cell *old_ocell;
231 struct dm_bio_prison_cell *new_ocell;
235 * Processing a bio in the worker thread may require these memory
236 * allocations. We prealloc to avoid deadlocks (the same worker thread
237 * frees them back to the mempool).
240 struct dm_cache_migration *mg;
241 struct dm_bio_prison_cell *cell1;
242 struct dm_bio_prison_cell *cell2;
245 static void wake_worker(struct cache *cache)
247 queue_work(cache->wq, &cache->worker);
250 /*----------------------------------------------------------------*/
252 static struct dm_bio_prison_cell *alloc_prison_cell(struct cache *cache)
254 /* FIXME: change to use a local slab. */
255 return dm_bio_prison_alloc_cell(cache->prison, GFP_NOWAIT);
258 static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell *cell)
260 dm_bio_prison_free_cell(cache->prison, cell);
263 static int prealloc_data_structs(struct cache *cache, struct prealloc *p)
266 p->mg = mempool_alloc(cache->migration_pool, GFP_NOWAIT);
272 p->cell1 = alloc_prison_cell(cache);
278 p->cell2 = alloc_prison_cell(cache);
286 static void prealloc_free_structs(struct cache *cache, struct prealloc *p)
289 free_prison_cell(cache, p->cell2);
292 free_prison_cell(cache, p->cell1);
295 mempool_free(p->mg, cache->migration_pool);
298 static struct dm_cache_migration *prealloc_get_migration(struct prealloc *p)
300 struct dm_cache_migration *mg = p->mg;
309 * You must have a cell within the prealloc struct to return. If not this
310 * function will BUG() rather than returning NULL.
312 static struct dm_bio_prison_cell *prealloc_get_cell(struct prealloc *p)
314 struct dm_bio_prison_cell *r = NULL;
320 } else if (p->cell2) {
330 * You can't have more than two cells in a prealloc struct. BUG() will be
331 * called if you try and overfill.
333 static void prealloc_put_cell(struct prealloc *p, struct dm_bio_prison_cell *cell)
345 /*----------------------------------------------------------------*/
347 static void build_key(dm_oblock_t oblock, struct dm_cell_key *key)
351 key->block = from_oblock(oblock);
355 * The caller hands in a preallocated cell, and a free function for it.
356 * The cell will be freed if there's an error, or if it wasn't used because
357 * a cell with that key already exists.
359 typedef void (*cell_free_fn)(void *context, struct dm_bio_prison_cell *cell);
361 static int bio_detain(struct cache *cache, dm_oblock_t oblock,
362 struct bio *bio, struct dm_bio_prison_cell *cell_prealloc,
363 cell_free_fn free_fn, void *free_context,
364 struct dm_bio_prison_cell **cell_result)
367 struct dm_cell_key key;
369 build_key(oblock, &key);
370 r = dm_bio_detain(cache->prison, &key, bio, cell_prealloc, cell_result);
372 free_fn(free_context, cell_prealloc);
377 static int get_cell(struct cache *cache,
379 struct prealloc *structs,
380 struct dm_bio_prison_cell **cell_result)
383 struct dm_cell_key key;
384 struct dm_bio_prison_cell *cell_prealloc;
386 cell_prealloc = prealloc_get_cell(structs);
388 build_key(oblock, &key);
389 r = dm_get_cell(cache->prison, &key, cell_prealloc, cell_result);
391 prealloc_put_cell(structs, cell_prealloc);
396 /*----------------------------------------------------------------*/
398 static bool is_dirty(struct cache *cache, dm_cblock_t b)
400 return test_bit(from_cblock(b), cache->dirty_bitset);
403 static void set_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
405 if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) {
406 cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) + 1);
407 policy_set_dirty(cache->policy, oblock);
411 static void clear_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
413 if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) {
414 policy_clear_dirty(cache->policy, oblock);
415 cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) - 1);
416 if (!from_cblock(cache->nr_dirty))
417 dm_table_event(cache->ti->table);
421 /*----------------------------------------------------------------*/
422 static bool block_size_is_power_of_two(struct cache *cache)
424 return cache->sectors_per_block_shift >= 0;
427 static dm_block_t block_div(dm_block_t b, uint32_t n)
434 static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock)
436 uint32_t discard_blocks = cache->discard_block_size;
437 dm_block_t b = from_oblock(oblock);
439 if (!block_size_is_power_of_two(cache))
440 discard_blocks = discard_blocks / cache->sectors_per_block;
442 discard_blocks >>= cache->sectors_per_block_shift;
444 b = block_div(b, discard_blocks);
449 static void set_discard(struct cache *cache, dm_dblock_t b)
453 atomic_inc(&cache->stats.discard_count);
455 spin_lock_irqsave(&cache->lock, flags);
456 set_bit(from_dblock(b), cache->discard_bitset);
457 spin_unlock_irqrestore(&cache->lock, flags);
460 static void clear_discard(struct cache *cache, dm_dblock_t b)
464 spin_lock_irqsave(&cache->lock, flags);
465 clear_bit(from_dblock(b), cache->discard_bitset);
466 spin_unlock_irqrestore(&cache->lock, flags);
469 static bool is_discarded(struct cache *cache, dm_dblock_t b)
474 spin_lock_irqsave(&cache->lock, flags);
475 r = test_bit(from_dblock(b), cache->discard_bitset);
476 spin_unlock_irqrestore(&cache->lock, flags);
481 static bool is_discarded_oblock(struct cache *cache, dm_oblock_t b)
486 spin_lock_irqsave(&cache->lock, flags);
487 r = test_bit(from_dblock(oblock_to_dblock(cache, b)),
488 cache->discard_bitset);
489 spin_unlock_irqrestore(&cache->lock, flags);
494 /*----------------------------------------------------------------*/
496 static void load_stats(struct cache *cache)
498 struct dm_cache_statistics stats;
500 dm_cache_metadata_get_stats(cache->cmd, &stats);
501 atomic_set(&cache->stats.read_hit, stats.read_hits);
502 atomic_set(&cache->stats.read_miss, stats.read_misses);
503 atomic_set(&cache->stats.write_hit, stats.write_hits);
504 atomic_set(&cache->stats.write_miss, stats.write_misses);
507 static void save_stats(struct cache *cache)
509 struct dm_cache_statistics stats;
511 stats.read_hits = atomic_read(&cache->stats.read_hit);
512 stats.read_misses = atomic_read(&cache->stats.read_miss);
513 stats.write_hits = atomic_read(&cache->stats.write_hit);
514 stats.write_misses = atomic_read(&cache->stats.write_miss);
516 dm_cache_metadata_set_stats(cache->cmd, &stats);
519 /*----------------------------------------------------------------
521 *--------------------------------------------------------------*/
524 * If using writeback, leave out struct per_bio_data's writethrough fields.
526 #define PB_DATA_SIZE_WB (offsetof(struct per_bio_data, cache))
527 #define PB_DATA_SIZE_WT (sizeof(struct per_bio_data))
529 static size_t get_per_bio_data_size(struct cache *cache)
531 return cache->features.write_through ? PB_DATA_SIZE_WT : PB_DATA_SIZE_WB;
534 static struct per_bio_data *get_per_bio_data(struct bio *bio, size_t data_size)
536 struct per_bio_data *pb = dm_per_bio_data(bio, data_size);
541 static struct per_bio_data *init_per_bio_data(struct bio *bio, size_t data_size)
543 struct per_bio_data *pb = get_per_bio_data(bio, data_size);
546 pb->req_nr = dm_bio_get_target_bio_nr(bio);
547 pb->all_io_entry = NULL;
552 /*----------------------------------------------------------------
554 *--------------------------------------------------------------*/
555 static void remap_to_origin(struct cache *cache, struct bio *bio)
557 bio->bi_bdev = cache->origin_dev->bdev;
560 static void remap_to_cache(struct cache *cache, struct bio *bio,
563 sector_t bi_sector = bio->bi_sector;
565 bio->bi_bdev = cache->cache_dev->bdev;
566 if (!block_size_is_power_of_two(cache))
567 bio->bi_sector = (from_cblock(cblock) * cache->sectors_per_block) +
568 sector_div(bi_sector, cache->sectors_per_block);
570 bio->bi_sector = (from_cblock(cblock) << cache->sectors_per_block_shift) |
571 (bi_sector & (cache->sectors_per_block - 1));
574 static void check_if_tick_bio_needed(struct cache *cache, struct bio *bio)
577 size_t pb_data_size = get_per_bio_data_size(cache);
578 struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
580 spin_lock_irqsave(&cache->lock, flags);
581 if (cache->need_tick_bio &&
582 !(bio->bi_rw & (REQ_FUA | REQ_FLUSH | REQ_DISCARD))) {
584 cache->need_tick_bio = false;
586 spin_unlock_irqrestore(&cache->lock, flags);
589 static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio,
592 check_if_tick_bio_needed(cache, bio);
593 remap_to_origin(cache, bio);
594 if (bio_data_dir(bio) == WRITE)
595 clear_discard(cache, oblock_to_dblock(cache, oblock));
598 static void remap_to_cache_dirty(struct cache *cache, struct bio *bio,
599 dm_oblock_t oblock, dm_cblock_t cblock)
601 remap_to_cache(cache, bio, cblock);
602 if (bio_data_dir(bio) == WRITE) {
603 set_dirty(cache, oblock, cblock);
604 clear_discard(cache, oblock_to_dblock(cache, oblock));
608 static dm_oblock_t get_bio_block(struct cache *cache, struct bio *bio)
610 sector_t block_nr = bio->bi_sector;
612 if (!block_size_is_power_of_two(cache))
613 (void) sector_div(block_nr, cache->sectors_per_block);
615 block_nr >>= cache->sectors_per_block_shift;
617 return to_oblock(block_nr);
620 static int bio_triggers_commit(struct cache *cache, struct bio *bio)
622 return bio->bi_rw & (REQ_FLUSH | REQ_FUA);
625 static void issue(struct cache *cache, struct bio *bio)
629 if (!bio_triggers_commit(cache, bio)) {
630 generic_make_request(bio);
635 * Batch together any bios that trigger commits and then issue a
636 * single commit for them in do_worker().
638 spin_lock_irqsave(&cache->lock, flags);
639 cache->commit_requested = true;
640 bio_list_add(&cache->deferred_flush_bios, bio);
641 spin_unlock_irqrestore(&cache->lock, flags);
644 static void defer_writethrough_bio(struct cache *cache, struct bio *bio)
648 spin_lock_irqsave(&cache->lock, flags);
649 bio_list_add(&cache->deferred_writethrough_bios, bio);
650 spin_unlock_irqrestore(&cache->lock, flags);
655 static void writethrough_endio(struct bio *bio, int err)
657 struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
658 bio->bi_end_io = pb->saved_bi_end_io;
665 dm_bio_restore(&pb->bio_details, bio);
666 remap_to_cache(pb->cache, bio, pb->cblock);
669 * We can't issue this bio directly, since we're in interrupt
670 * context. So it get's put on a bio list for processing by the
673 defer_writethrough_bio(pb->cache, bio);
677 * When running in writethrough mode we need to send writes to clean blocks
678 * to both the cache and origin devices. In future we'd like to clone the
679 * bio and send them in parallel, but for now we're doing them in
680 * series as this is easier.
682 static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio,
683 dm_oblock_t oblock, dm_cblock_t cblock)
685 struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
689 pb->saved_bi_end_io = bio->bi_end_io;
690 dm_bio_record(&pb->bio_details, bio);
691 bio->bi_end_io = writethrough_endio;
693 remap_to_origin_clear_discard(pb->cache, bio, oblock);
696 /*----------------------------------------------------------------
697 * Migration processing
699 * Migration covers moving data from the origin device to the cache, or
701 *--------------------------------------------------------------*/
702 static void free_migration(struct dm_cache_migration *mg)
704 mempool_free(mg, mg->cache->migration_pool);
707 static void inc_nr_migrations(struct cache *cache)
709 atomic_inc(&cache->nr_migrations);
712 static void dec_nr_migrations(struct cache *cache)
714 atomic_dec(&cache->nr_migrations);
717 * Wake the worker in case we're suspending the target.
719 wake_up(&cache->migration_wait);
722 static void __cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
725 (holder ? dm_cell_release : dm_cell_release_no_holder)
726 (cache->prison, cell, &cache->deferred_bios);
727 free_prison_cell(cache, cell);
730 static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
735 spin_lock_irqsave(&cache->lock, flags);
736 __cell_defer(cache, cell, holder);
737 spin_unlock_irqrestore(&cache->lock, flags);
742 static void cleanup_migration(struct dm_cache_migration *mg)
744 dec_nr_migrations(mg->cache);
748 static void migration_failure(struct dm_cache_migration *mg)
750 struct cache *cache = mg->cache;
753 DMWARN_LIMIT("writeback failed; couldn't copy block");
754 set_dirty(cache, mg->old_oblock, mg->cblock);
755 cell_defer(cache, mg->old_ocell, false);
757 } else if (mg->demote) {
758 DMWARN_LIMIT("demotion failed; couldn't copy block");
759 policy_force_mapping(cache->policy, mg->new_oblock, mg->old_oblock);
761 cell_defer(cache, mg->old_ocell, mg->promote ? 0 : 1);
763 cell_defer(cache, mg->new_ocell, 1);
765 DMWARN_LIMIT("promotion failed; couldn't copy block");
766 policy_remove_mapping(cache->policy, mg->new_oblock);
767 cell_defer(cache, mg->new_ocell, 1);
770 cleanup_migration(mg);
773 static void migration_success_pre_commit(struct dm_cache_migration *mg)
776 struct cache *cache = mg->cache;
779 cell_defer(cache, mg->old_ocell, false);
780 clear_dirty(cache, mg->old_oblock, mg->cblock);
781 cleanup_migration(mg);
784 } else if (mg->demote) {
785 if (dm_cache_remove_mapping(cache->cmd, mg->cblock)) {
786 DMWARN_LIMIT("demotion failed; couldn't update on disk metadata");
787 policy_force_mapping(cache->policy, mg->new_oblock,
790 cell_defer(cache, mg->new_ocell, true);
791 cleanup_migration(mg);
795 if (dm_cache_insert_mapping(cache->cmd, mg->cblock, mg->new_oblock)) {
796 DMWARN_LIMIT("promotion failed; couldn't update on disk metadata");
797 policy_remove_mapping(cache->policy, mg->new_oblock);
798 cleanup_migration(mg);
803 spin_lock_irqsave(&cache->lock, flags);
804 list_add_tail(&mg->list, &cache->need_commit_migrations);
805 cache->commit_requested = true;
806 spin_unlock_irqrestore(&cache->lock, flags);
809 static void migration_success_post_commit(struct dm_cache_migration *mg)
812 struct cache *cache = mg->cache;
815 DMWARN("writeback unexpectedly triggered commit");
818 } else if (mg->demote) {
819 cell_defer(cache, mg->old_ocell, mg->promote ? 0 : 1);
824 spin_lock_irqsave(&cache->lock, flags);
825 list_add_tail(&mg->list, &cache->quiesced_migrations);
826 spin_unlock_irqrestore(&cache->lock, flags);
829 cleanup_migration(mg);
832 cell_defer(cache, mg->new_ocell, true);
833 clear_dirty(cache, mg->new_oblock, mg->cblock);
834 cleanup_migration(mg);
838 static void copy_complete(int read_err, unsigned long write_err, void *context)
841 struct dm_cache_migration *mg = (struct dm_cache_migration *) context;
842 struct cache *cache = mg->cache;
844 if (read_err || write_err)
847 spin_lock_irqsave(&cache->lock, flags);
848 list_add_tail(&mg->list, &cache->completed_migrations);
849 spin_unlock_irqrestore(&cache->lock, flags);
854 static void issue_copy_real(struct dm_cache_migration *mg)
857 struct dm_io_region o_region, c_region;
858 struct cache *cache = mg->cache;
860 o_region.bdev = cache->origin_dev->bdev;
861 o_region.count = cache->sectors_per_block;
863 c_region.bdev = cache->cache_dev->bdev;
864 c_region.sector = from_cblock(mg->cblock) * cache->sectors_per_block;
865 c_region.count = cache->sectors_per_block;
867 if (mg->writeback || mg->demote) {
869 o_region.sector = from_oblock(mg->old_oblock) * cache->sectors_per_block;
870 r = dm_kcopyd_copy(cache->copier, &c_region, 1, &o_region, 0, copy_complete, mg);
873 o_region.sector = from_oblock(mg->new_oblock) * cache->sectors_per_block;
874 r = dm_kcopyd_copy(cache->copier, &o_region, 1, &c_region, 0, copy_complete, mg);
878 migration_failure(mg);
881 static void avoid_copy(struct dm_cache_migration *mg)
883 atomic_inc(&mg->cache->stats.copies_avoided);
884 migration_success_pre_commit(mg);
887 static void issue_copy(struct dm_cache_migration *mg)
890 struct cache *cache = mg->cache;
892 if (mg->writeback || mg->demote)
893 avoid = !is_dirty(cache, mg->cblock) ||
894 is_discarded_oblock(cache, mg->old_oblock);
896 avoid = is_discarded_oblock(cache, mg->new_oblock);
898 avoid ? avoid_copy(mg) : issue_copy_real(mg);
901 static void complete_migration(struct dm_cache_migration *mg)
904 migration_failure(mg);
906 migration_success_pre_commit(mg);
909 static void process_migrations(struct cache *cache, struct list_head *head,
910 void (*fn)(struct dm_cache_migration *))
913 struct list_head list;
914 struct dm_cache_migration *mg, *tmp;
916 INIT_LIST_HEAD(&list);
917 spin_lock_irqsave(&cache->lock, flags);
918 list_splice_init(head, &list);
919 spin_unlock_irqrestore(&cache->lock, flags);
921 list_for_each_entry_safe(mg, tmp, &list, list)
925 static void __queue_quiesced_migration(struct dm_cache_migration *mg)
927 list_add_tail(&mg->list, &mg->cache->quiesced_migrations);
930 static void queue_quiesced_migration(struct dm_cache_migration *mg)
933 struct cache *cache = mg->cache;
935 spin_lock_irqsave(&cache->lock, flags);
936 __queue_quiesced_migration(mg);
937 spin_unlock_irqrestore(&cache->lock, flags);
942 static void queue_quiesced_migrations(struct cache *cache, struct list_head *work)
945 struct dm_cache_migration *mg, *tmp;
947 spin_lock_irqsave(&cache->lock, flags);
948 list_for_each_entry_safe(mg, tmp, work, list)
949 __queue_quiesced_migration(mg);
950 spin_unlock_irqrestore(&cache->lock, flags);
955 static void check_for_quiesced_migrations(struct cache *cache,
956 struct per_bio_data *pb)
958 struct list_head work;
960 if (!pb->all_io_entry)
963 INIT_LIST_HEAD(&work);
964 if (pb->all_io_entry)
965 dm_deferred_entry_dec(pb->all_io_entry, &work);
967 if (!list_empty(&work))
968 queue_quiesced_migrations(cache, &work);
971 static void quiesce_migration(struct dm_cache_migration *mg)
973 if (!dm_deferred_set_add_work(mg->cache->all_io_ds, &mg->list))
974 queue_quiesced_migration(mg);
977 static void promote(struct cache *cache, struct prealloc *structs,
978 dm_oblock_t oblock, dm_cblock_t cblock,
979 struct dm_bio_prison_cell *cell)
981 struct dm_cache_migration *mg = prealloc_get_migration(structs);
984 mg->writeback = false;
988 mg->new_oblock = oblock;
990 mg->old_ocell = NULL;
991 mg->new_ocell = cell;
992 mg->start_jiffies = jiffies;
994 inc_nr_migrations(cache);
995 quiesce_migration(mg);
998 static void writeback(struct cache *cache, struct prealloc *structs,
999 dm_oblock_t oblock, dm_cblock_t cblock,
1000 struct dm_bio_prison_cell *cell)
1002 struct dm_cache_migration *mg = prealloc_get_migration(structs);
1005 mg->writeback = true;
1007 mg->promote = false;
1009 mg->old_oblock = oblock;
1010 mg->cblock = cblock;
1011 mg->old_ocell = cell;
1012 mg->new_ocell = NULL;
1013 mg->start_jiffies = jiffies;
1015 inc_nr_migrations(cache);
1016 quiesce_migration(mg);
1019 static void demote_then_promote(struct cache *cache, struct prealloc *structs,
1020 dm_oblock_t old_oblock, dm_oblock_t new_oblock,
1022 struct dm_bio_prison_cell *old_ocell,
1023 struct dm_bio_prison_cell *new_ocell)
1025 struct dm_cache_migration *mg = prealloc_get_migration(structs);
1028 mg->writeback = false;
1032 mg->old_oblock = old_oblock;
1033 mg->new_oblock = new_oblock;
1034 mg->cblock = cblock;
1035 mg->old_ocell = old_ocell;
1036 mg->new_ocell = new_ocell;
1037 mg->start_jiffies = jiffies;
1039 inc_nr_migrations(cache);
1040 quiesce_migration(mg);
1043 /*----------------------------------------------------------------
1045 *--------------------------------------------------------------*/
1046 static void defer_bio(struct cache *cache, struct bio *bio)
1048 unsigned long flags;
1050 spin_lock_irqsave(&cache->lock, flags);
1051 bio_list_add(&cache->deferred_bios, bio);
1052 spin_unlock_irqrestore(&cache->lock, flags);
1057 static void process_flush_bio(struct cache *cache, struct bio *bio)
1059 size_t pb_data_size = get_per_bio_data_size(cache);
1060 struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1062 BUG_ON(bio->bi_size);
1064 remap_to_origin(cache, bio);
1066 remap_to_cache(cache, bio, 0);
1072 * People generally discard large parts of a device, eg, the whole device
1073 * when formatting. Splitting these large discards up into cache block
1074 * sized ios and then quiescing (always neccessary for discard) takes too
1077 * We keep it simple, and allow any size of discard to come in, and just
1078 * mark off blocks on the discard bitset. No passdown occurs!
1080 * To implement passdown we need to change the bio_prison such that a cell
1081 * can have a key that spans many blocks.
1083 static void process_discard_bio(struct cache *cache, struct bio *bio)
1085 dm_block_t start_block = dm_sector_div_up(bio->bi_sector,
1086 cache->discard_block_size);
1087 dm_block_t end_block = bio->bi_sector + bio_sectors(bio);
1090 end_block = block_div(end_block, cache->discard_block_size);
1092 for (b = start_block; b < end_block; b++)
1093 set_discard(cache, to_dblock(b));
1098 static bool spare_migration_bandwidth(struct cache *cache)
1100 sector_t current_volume = (atomic_read(&cache->nr_migrations) + 1) *
1101 cache->sectors_per_block;
1102 return current_volume < cache->migration_threshold;
1105 static bool is_writethrough_io(struct cache *cache, struct bio *bio,
1108 return bio_data_dir(bio) == WRITE &&
1109 cache->features.write_through && !is_dirty(cache, cblock);
1112 static void inc_hit_counter(struct cache *cache, struct bio *bio)
1114 atomic_inc(bio_data_dir(bio) == READ ?
1115 &cache->stats.read_hit : &cache->stats.write_hit);
1118 static void inc_miss_counter(struct cache *cache, struct bio *bio)
1120 atomic_inc(bio_data_dir(bio) == READ ?
1121 &cache->stats.read_miss : &cache->stats.write_miss);
1124 static void process_bio(struct cache *cache, struct prealloc *structs,
1128 bool release_cell = true;
1129 dm_oblock_t block = get_bio_block(cache, bio);
1130 struct dm_bio_prison_cell *cell_prealloc, *old_ocell, *new_ocell;
1131 struct policy_result lookup_result;
1132 size_t pb_data_size = get_per_bio_data_size(cache);
1133 struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1134 bool discarded_block = is_discarded_oblock(cache, block);
1135 bool can_migrate = discarded_block || spare_migration_bandwidth(cache);
1138 * Check to see if that block is currently migrating.
1140 cell_prealloc = prealloc_get_cell(structs);
1141 r = bio_detain(cache, block, bio, cell_prealloc,
1142 (cell_free_fn) prealloc_put_cell,
1143 structs, &new_ocell);
1147 r = policy_map(cache->policy, block, true, can_migrate, discarded_block,
1148 bio, &lookup_result);
1150 if (r == -EWOULDBLOCK)
1151 /* migration has been denied */
1152 lookup_result.op = POLICY_MISS;
1154 switch (lookup_result.op) {
1156 inc_hit_counter(cache, bio);
1157 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1159 if (is_writethrough_io(cache, bio, lookup_result.cblock))
1160 remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
1162 remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
1168 inc_miss_counter(cache, bio);
1169 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1170 remap_to_origin_clear_discard(cache, bio, block);
1175 atomic_inc(&cache->stats.promotion);
1176 promote(cache, structs, block, lookup_result.cblock, new_ocell);
1177 release_cell = false;
1180 case POLICY_REPLACE:
1181 cell_prealloc = prealloc_get_cell(structs);
1182 r = bio_detain(cache, lookup_result.old_oblock, bio, cell_prealloc,
1183 (cell_free_fn) prealloc_put_cell,
1184 structs, &old_ocell);
1187 * We have to be careful to avoid lock inversion of
1188 * the cells. So we back off, and wait for the
1189 * old_ocell to become free.
1191 policy_force_mapping(cache->policy, block,
1192 lookup_result.old_oblock);
1193 atomic_inc(&cache->stats.cache_cell_clash);
1196 atomic_inc(&cache->stats.demotion);
1197 atomic_inc(&cache->stats.promotion);
1199 demote_then_promote(cache, structs, lookup_result.old_oblock,
1200 block, lookup_result.cblock,
1201 old_ocell, new_ocell);
1202 release_cell = false;
1206 DMERR_LIMIT("%s: erroring bio, unknown policy op: %u", __func__,
1207 (unsigned) lookup_result.op);
1212 cell_defer(cache, new_ocell, false);
1215 static int need_commit_due_to_time(struct cache *cache)
1217 return jiffies < cache->last_commit_jiffies ||
1218 jiffies > cache->last_commit_jiffies + COMMIT_PERIOD;
1221 static int commit_if_needed(struct cache *cache)
1223 if (dm_cache_changed_this_transaction(cache->cmd) &&
1224 (cache->commit_requested || need_commit_due_to_time(cache))) {
1225 atomic_inc(&cache->stats.commit_count);
1226 cache->last_commit_jiffies = jiffies;
1227 cache->commit_requested = false;
1228 return dm_cache_commit(cache->cmd, false);
1234 static void process_deferred_bios(struct cache *cache)
1236 unsigned long flags;
1237 struct bio_list bios;
1239 struct prealloc structs;
1241 memset(&structs, 0, sizeof(structs));
1242 bio_list_init(&bios);
1244 spin_lock_irqsave(&cache->lock, flags);
1245 bio_list_merge(&bios, &cache->deferred_bios);
1246 bio_list_init(&cache->deferred_bios);
1247 spin_unlock_irqrestore(&cache->lock, flags);
1249 while (!bio_list_empty(&bios)) {
1251 * If we've got no free migration structs, and processing
1252 * this bio might require one, we pause until there are some
1253 * prepared mappings to process.
1255 if (prealloc_data_structs(cache, &structs)) {
1256 spin_lock_irqsave(&cache->lock, flags);
1257 bio_list_merge(&cache->deferred_bios, &bios);
1258 spin_unlock_irqrestore(&cache->lock, flags);
1262 bio = bio_list_pop(&bios);
1264 if (bio->bi_rw & REQ_FLUSH)
1265 process_flush_bio(cache, bio);
1266 else if (bio->bi_rw & REQ_DISCARD)
1267 process_discard_bio(cache, bio);
1269 process_bio(cache, &structs, bio);
1272 prealloc_free_structs(cache, &structs);
1275 static void process_deferred_flush_bios(struct cache *cache, bool submit_bios)
1277 unsigned long flags;
1278 struct bio_list bios;
1281 bio_list_init(&bios);
1283 spin_lock_irqsave(&cache->lock, flags);
1284 bio_list_merge(&bios, &cache->deferred_flush_bios);
1285 bio_list_init(&cache->deferred_flush_bios);
1286 spin_unlock_irqrestore(&cache->lock, flags);
1288 while ((bio = bio_list_pop(&bios)))
1289 submit_bios ? generic_make_request(bio) : bio_io_error(bio);
1292 static void process_deferred_writethrough_bios(struct cache *cache)
1294 unsigned long flags;
1295 struct bio_list bios;
1298 bio_list_init(&bios);
1300 spin_lock_irqsave(&cache->lock, flags);
1301 bio_list_merge(&bios, &cache->deferred_writethrough_bios);
1302 bio_list_init(&cache->deferred_writethrough_bios);
1303 spin_unlock_irqrestore(&cache->lock, flags);
1305 while ((bio = bio_list_pop(&bios)))
1306 generic_make_request(bio);
1309 static void writeback_some_dirty_blocks(struct cache *cache)
1314 struct prealloc structs;
1315 struct dm_bio_prison_cell *old_ocell;
1317 memset(&structs, 0, sizeof(structs));
1319 while (spare_migration_bandwidth(cache)) {
1320 if (prealloc_data_structs(cache, &structs))
1323 r = policy_writeback_work(cache->policy, &oblock, &cblock);
1327 r = get_cell(cache, oblock, &structs, &old_ocell);
1329 policy_set_dirty(cache->policy, oblock);
1333 writeback(cache, &structs, oblock, cblock, old_ocell);
1336 prealloc_free_structs(cache, &structs);
1339 /*----------------------------------------------------------------
1341 *--------------------------------------------------------------*/
1342 static void start_quiescing(struct cache *cache)
1344 unsigned long flags;
1346 spin_lock_irqsave(&cache->lock, flags);
1347 cache->quiescing = 1;
1348 spin_unlock_irqrestore(&cache->lock, flags);
1351 static void stop_quiescing(struct cache *cache)
1353 unsigned long flags;
1355 spin_lock_irqsave(&cache->lock, flags);
1356 cache->quiescing = 0;
1357 spin_unlock_irqrestore(&cache->lock, flags);
1360 static bool is_quiescing(struct cache *cache)
1363 unsigned long flags;
1365 spin_lock_irqsave(&cache->lock, flags);
1366 r = cache->quiescing;
1367 spin_unlock_irqrestore(&cache->lock, flags);
1372 static void wait_for_migrations(struct cache *cache)
1374 wait_event(cache->migration_wait, !atomic_read(&cache->nr_migrations));
1377 static void stop_worker(struct cache *cache)
1379 cancel_delayed_work(&cache->waker);
1380 flush_workqueue(cache->wq);
1383 static void requeue_deferred_io(struct cache *cache)
1386 struct bio_list bios;
1388 bio_list_init(&bios);
1389 bio_list_merge(&bios, &cache->deferred_bios);
1390 bio_list_init(&cache->deferred_bios);
1392 while ((bio = bio_list_pop(&bios)))
1393 bio_endio(bio, DM_ENDIO_REQUEUE);
1396 static int more_work(struct cache *cache)
1398 if (is_quiescing(cache))
1399 return !list_empty(&cache->quiesced_migrations) ||
1400 !list_empty(&cache->completed_migrations) ||
1401 !list_empty(&cache->need_commit_migrations);
1403 return !bio_list_empty(&cache->deferred_bios) ||
1404 !bio_list_empty(&cache->deferred_flush_bios) ||
1405 !bio_list_empty(&cache->deferred_writethrough_bios) ||
1406 !list_empty(&cache->quiesced_migrations) ||
1407 !list_empty(&cache->completed_migrations) ||
1408 !list_empty(&cache->need_commit_migrations);
1411 static void do_worker(struct work_struct *ws)
1413 struct cache *cache = container_of(ws, struct cache, worker);
1416 if (!is_quiescing(cache))
1417 process_deferred_bios(cache);
1419 process_migrations(cache, &cache->quiesced_migrations, issue_copy);
1420 process_migrations(cache, &cache->completed_migrations, complete_migration);
1422 writeback_some_dirty_blocks(cache);
1424 process_deferred_writethrough_bios(cache);
1426 if (commit_if_needed(cache)) {
1427 process_deferred_flush_bios(cache, false);
1430 * FIXME: rollback metadata or just go into a
1431 * failure mode and error everything
1434 process_deferred_flush_bios(cache, true);
1435 process_migrations(cache, &cache->need_commit_migrations,
1436 migration_success_post_commit);
1438 } while (more_work(cache));
1442 * We want to commit periodically so that not too much
1443 * unwritten metadata builds up.
1445 static void do_waker(struct work_struct *ws)
1447 struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker);
1449 queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);
1452 /*----------------------------------------------------------------*/
1454 static int is_congested(struct dm_dev *dev, int bdi_bits)
1456 struct request_queue *q = bdev_get_queue(dev->bdev);
1457 return bdi_congested(&q->backing_dev_info, bdi_bits);
1460 static int cache_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
1462 struct cache *cache = container_of(cb, struct cache, callbacks);
1464 return is_congested(cache->origin_dev, bdi_bits) ||
1465 is_congested(cache->cache_dev, bdi_bits);
1468 /*----------------------------------------------------------------
1470 *--------------------------------------------------------------*/
1473 * This function gets called on the error paths of the constructor, so we
1474 * have to cope with a partially initialised struct.
1476 static void destroy(struct cache *cache)
1480 if (cache->next_migration)
1481 mempool_free(cache->next_migration, cache->migration_pool);
1483 if (cache->migration_pool)
1484 mempool_destroy(cache->migration_pool);
1486 if (cache->all_io_ds)
1487 dm_deferred_set_destroy(cache->all_io_ds);
1490 dm_bio_prison_destroy(cache->prison);
1493 destroy_workqueue(cache->wq);
1495 if (cache->dirty_bitset)
1496 free_bitset(cache->dirty_bitset);
1498 if (cache->discard_bitset)
1499 free_bitset(cache->discard_bitset);
1502 dm_kcopyd_client_destroy(cache->copier);
1505 dm_cache_metadata_close(cache->cmd);
1507 if (cache->metadata_dev)
1508 dm_put_device(cache->ti, cache->metadata_dev);
1510 if (cache->origin_dev)
1511 dm_put_device(cache->ti, cache->origin_dev);
1513 if (cache->cache_dev)
1514 dm_put_device(cache->ti, cache->cache_dev);
1517 dm_cache_policy_destroy(cache->policy);
1519 for (i = 0; i < cache->nr_ctr_args ; i++)
1520 kfree(cache->ctr_args[i]);
1521 kfree(cache->ctr_args);
1526 static void cache_dtr(struct dm_target *ti)
1528 struct cache *cache = ti->private;
1533 static sector_t get_dev_size(struct dm_dev *dev)
1535 return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
1538 /*----------------------------------------------------------------*/
1541 * Construct a cache device mapping.
1543 * cache <metadata dev> <cache dev> <origin dev> <block size>
1544 * <#feature args> [<feature arg>]*
1545 * <policy> <#policy args> [<policy arg>]*
1547 * metadata dev : fast device holding the persistent metadata
1548 * cache dev : fast device holding cached data blocks
1549 * origin dev : slow device holding original data blocks
1550 * block size : cache unit size in sectors
1552 * #feature args : number of feature arguments passed
1553 * feature args : writethrough. (The default is writeback.)
1555 * policy : the replacement policy to use
1556 * #policy args : an even number of policy arguments corresponding
1557 * to key/value pairs passed to the policy
1558 * policy args : key/value pairs passed to the policy
1559 * E.g. 'sequential_threshold 1024'
1560 * See cache-policies.txt for details.
1562 * Optional feature arguments are:
1563 * writethrough : write through caching that prohibits cache block
1564 * content from being different from origin block content.
1565 * Without this argument, the default behaviour is to write
1566 * back cache block contents later for performance reasons,
1567 * so they may differ from the corresponding origin blocks.
1570 struct dm_target *ti;
1572 struct dm_dev *metadata_dev;
1574 struct dm_dev *cache_dev;
1575 sector_t cache_sectors;
1577 struct dm_dev *origin_dev;
1578 sector_t origin_sectors;
1580 uint32_t block_size;
1582 const char *policy_name;
1584 const char **policy_argv;
1586 struct cache_features features;
1589 static void destroy_cache_args(struct cache_args *ca)
1591 if (ca->metadata_dev)
1592 dm_put_device(ca->ti, ca->metadata_dev);
1595 dm_put_device(ca->ti, ca->cache_dev);
1598 dm_put_device(ca->ti, ca->origin_dev);
1603 static bool at_least_one_arg(struct dm_arg_set *as, char **error)
1606 *error = "Insufficient args";
1613 static int parse_metadata_dev(struct cache_args *ca, struct dm_arg_set *as,
1617 sector_t metadata_dev_size;
1618 char b[BDEVNAME_SIZE];
1620 if (!at_least_one_arg(as, error))
1623 r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1626 *error = "Error opening metadata device";
1630 metadata_dev_size = get_dev_size(ca->metadata_dev);
1631 if (metadata_dev_size > DM_CACHE_METADATA_MAX_SECTORS_WARNING)
1632 DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
1633 bdevname(ca->metadata_dev->bdev, b), THIN_METADATA_MAX_SECTORS);
1638 static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as,
1643 if (!at_least_one_arg(as, error))
1646 r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1649 *error = "Error opening cache device";
1652 ca->cache_sectors = get_dev_size(ca->cache_dev);
1657 static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as,
1662 if (!at_least_one_arg(as, error))
1665 r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1668 *error = "Error opening origin device";
1672 ca->origin_sectors = get_dev_size(ca->origin_dev);
1673 if (ca->ti->len > ca->origin_sectors) {
1674 *error = "Device size larger than cached device";
1681 static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as,
1686 if (!at_least_one_arg(as, error))
1689 if (kstrtoul(dm_shift_arg(as), 10, &tmp) || !tmp ||
1690 tmp < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
1691 tmp & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
1692 *error = "Invalid data block size";
1696 if (tmp > ca->cache_sectors) {
1697 *error = "Data block size is larger than the cache device";
1701 ca->block_size = tmp;
1706 static void init_features(struct cache_features *cf)
1708 cf->mode = CM_WRITE;
1709 cf->write_through = false;
1712 static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
1715 static struct dm_arg _args[] = {
1716 {0, 1, "Invalid number of cache feature arguments"},
1722 struct cache_features *cf = &ca->features;
1726 r = dm_read_arg_group(_args, as, &argc, error);
1731 arg = dm_shift_arg(as);
1733 if (!strcasecmp(arg, "writeback"))
1734 cf->write_through = false;
1736 else if (!strcasecmp(arg, "writethrough"))
1737 cf->write_through = true;
1740 *error = "Unrecognised cache feature requested";
1748 static int parse_policy(struct cache_args *ca, struct dm_arg_set *as,
1751 static struct dm_arg _args[] = {
1752 {0, 1024, "Invalid number of policy arguments"},
1757 if (!at_least_one_arg(as, error))
1760 ca->policy_name = dm_shift_arg(as);
1762 r = dm_read_arg_group(_args, as, &ca->policy_argc, error);
1766 ca->policy_argv = (const char **)as->argv;
1767 dm_consume_args(as, ca->policy_argc);
1772 static int parse_cache_args(struct cache_args *ca, int argc, char **argv,
1776 struct dm_arg_set as;
1781 r = parse_metadata_dev(ca, &as, error);
1785 r = parse_cache_dev(ca, &as, error);
1789 r = parse_origin_dev(ca, &as, error);
1793 r = parse_block_size(ca, &as, error);
1797 r = parse_features(ca, &as, error);
1801 r = parse_policy(ca, &as, error);
1808 /*----------------------------------------------------------------*/
1810 static struct kmem_cache *migration_cache;
1812 static int set_config_values(struct dm_cache_policy *p, int argc, const char **argv)
1817 DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs.");
1822 r = policy_set_config_value(p, argv[0], argv[1]);
1824 DMWARN("policy_set_config_value failed: key = '%s', value = '%s'",
1836 static int create_cache_policy(struct cache *cache, struct cache_args *ca,
1841 cache->policy = dm_cache_policy_create(ca->policy_name,
1843 cache->origin_sectors,
1844 cache->sectors_per_block);
1845 if (!cache->policy) {
1846 *error = "Error creating cache's policy";
1850 r = set_config_values(cache->policy, ca->policy_argc, ca->policy_argv);
1852 *error = "Error setting cache policy's config values";
1853 dm_cache_policy_destroy(cache->policy);
1854 cache->policy = NULL;
1861 * We want the discard block size to be a power of two, at least the size
1862 * of the cache block size, and have no more than 2^14 discard blocks
1863 * across the origin.
1865 #define MAX_DISCARD_BLOCKS (1 << 14)
1867 static bool too_many_discard_blocks(sector_t discard_block_size,
1868 sector_t origin_size)
1870 (void) sector_div(origin_size, discard_block_size);
1872 return origin_size > MAX_DISCARD_BLOCKS;
1875 static sector_t calculate_discard_block_size(sector_t cache_block_size,
1876 sector_t origin_size)
1878 sector_t discard_block_size;
1880 discard_block_size = roundup_pow_of_two(cache_block_size);
1883 while (too_many_discard_blocks(discard_block_size, origin_size))
1884 discard_block_size *= 2;
1886 return discard_block_size;
1889 #define DEFAULT_MIGRATION_THRESHOLD (2048 * 100)
1891 static int cache_create(struct cache_args *ca, struct cache **result)
1894 char **error = &ca->ti->error;
1895 struct cache *cache;
1896 struct dm_target *ti = ca->ti;
1897 dm_block_t origin_blocks;
1898 struct dm_cache_metadata *cmd;
1899 bool may_format = ca->features.mode == CM_WRITE;
1901 cache = kzalloc(sizeof(*cache), GFP_KERNEL);
1906 ti->private = cache;
1907 ti->num_flush_bios = 2;
1908 ti->flush_supported = true;
1910 ti->num_discard_bios = 1;
1911 ti->discards_supported = true;
1912 ti->discard_zeroes_data_unsupported = true;
1914 memcpy(&cache->features, &ca->features, sizeof(cache->features));
1915 ti->per_bio_data_size = get_per_bio_data_size(cache);
1917 cache->callbacks.congested_fn = cache_is_congested;
1918 dm_table_add_target_callbacks(ti->table, &cache->callbacks);
1920 cache->metadata_dev = ca->metadata_dev;
1921 cache->origin_dev = ca->origin_dev;
1922 cache->cache_dev = ca->cache_dev;
1924 ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL;
1926 /* FIXME: factor out this whole section */
1927 origin_blocks = cache->origin_sectors = ca->origin_sectors;
1928 origin_blocks = block_div(origin_blocks, ca->block_size);
1929 cache->origin_blocks = to_oblock(origin_blocks);
1931 cache->sectors_per_block = ca->block_size;
1932 if (dm_set_target_max_io_len(ti, cache->sectors_per_block)) {
1937 if (ca->block_size & (ca->block_size - 1)) {
1938 dm_block_t cache_size = ca->cache_sectors;
1940 cache->sectors_per_block_shift = -1;
1941 cache_size = block_div(cache_size, ca->block_size);
1942 cache->cache_size = to_cblock(cache_size);
1944 cache->sectors_per_block_shift = __ffs(ca->block_size);
1945 cache->cache_size = to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift);
1948 r = create_cache_policy(cache, ca, error);
1951 cache->policy_nr_args = ca->policy_argc;
1953 cmd = dm_cache_metadata_open(cache->metadata_dev->bdev,
1954 ca->block_size, may_format,
1955 dm_cache_policy_get_hint_size(cache->policy));
1957 *error = "Error creating metadata object";
1963 spin_lock_init(&cache->lock);
1964 bio_list_init(&cache->deferred_bios);
1965 bio_list_init(&cache->deferred_flush_bios);
1966 bio_list_init(&cache->deferred_writethrough_bios);
1967 INIT_LIST_HEAD(&cache->quiesced_migrations);
1968 INIT_LIST_HEAD(&cache->completed_migrations);
1969 INIT_LIST_HEAD(&cache->need_commit_migrations);
1970 cache->migration_threshold = DEFAULT_MIGRATION_THRESHOLD;
1971 atomic_set(&cache->nr_migrations, 0);
1972 init_waitqueue_head(&cache->migration_wait);
1975 cache->nr_dirty = 0;
1976 cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size));
1977 if (!cache->dirty_bitset) {
1978 *error = "could not allocate dirty bitset";
1981 clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size));
1983 cache->discard_block_size =
1984 calculate_discard_block_size(cache->sectors_per_block,
1985 cache->origin_sectors);
1986 cache->discard_nr_blocks = oblock_to_dblock(cache, cache->origin_blocks);
1987 cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks));
1988 if (!cache->discard_bitset) {
1989 *error = "could not allocate discard bitset";
1992 clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks));
1994 cache->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1995 if (IS_ERR(cache->copier)) {
1996 *error = "could not create kcopyd client";
1997 r = PTR_ERR(cache->copier);
2001 cache->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
2003 *error = "could not create workqueue for metadata object";
2006 INIT_WORK(&cache->worker, do_worker);
2007 INIT_DELAYED_WORK(&cache->waker, do_waker);
2008 cache->last_commit_jiffies = jiffies;
2010 cache->prison = dm_bio_prison_create(PRISON_CELLS);
2011 if (!cache->prison) {
2012 *error = "could not create bio prison";
2016 cache->all_io_ds = dm_deferred_set_create();
2017 if (!cache->all_io_ds) {
2018 *error = "could not create all_io deferred set";
2022 cache->migration_pool = mempool_create_slab_pool(MIGRATION_POOL_SIZE,
2024 if (!cache->migration_pool) {
2025 *error = "Error creating cache's migration mempool";
2029 cache->next_migration = NULL;
2031 cache->need_tick_bio = true;
2032 cache->sized = false;
2033 cache->quiescing = false;
2034 cache->commit_requested = false;
2035 cache->loaded_mappings = false;
2036 cache->loaded_discards = false;
2040 atomic_set(&cache->stats.demotion, 0);
2041 atomic_set(&cache->stats.promotion, 0);
2042 atomic_set(&cache->stats.copies_avoided, 0);
2043 atomic_set(&cache->stats.cache_cell_clash, 0);
2044 atomic_set(&cache->stats.commit_count, 0);
2045 atomic_set(&cache->stats.discard_count, 0);
2055 static int copy_ctr_args(struct cache *cache, int argc, const char **argv)
2060 copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL);
2063 for (i = 0; i < argc; i++) {
2064 copy[i] = kstrdup(argv[i], GFP_KERNEL);
2073 cache->nr_ctr_args = argc;
2074 cache->ctr_args = copy;
2079 static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
2082 struct cache_args *ca;
2083 struct cache *cache = NULL;
2085 ca = kzalloc(sizeof(*ca), GFP_KERNEL);
2087 ti->error = "Error allocating memory for cache";
2092 r = parse_cache_args(ca, argc, argv, &ti->error);
2096 r = cache_create(ca, &cache);
2100 r = copy_ctr_args(cache, argc - 3, (const char **)argv + 3);
2106 ti->private = cache;
2109 destroy_cache_args(ca);
2113 static int cache_map(struct dm_target *ti, struct bio *bio)
2115 struct cache *cache = ti->private;
2118 dm_oblock_t block = get_bio_block(cache, bio);
2119 size_t pb_data_size = get_per_bio_data_size(cache);
2120 bool can_migrate = false;
2121 bool discarded_block;
2122 struct dm_bio_prison_cell *cell;
2123 struct policy_result lookup_result;
2124 struct per_bio_data *pb;
2126 if (from_oblock(block) > from_oblock(cache->origin_blocks)) {
2128 * This can only occur if the io goes to a partial block at
2129 * the end of the origin device. We don't cache these.
2130 * Just remap to the origin and carry on.
2132 remap_to_origin_clear_discard(cache, bio, block);
2133 return DM_MAPIO_REMAPPED;
2136 pb = init_per_bio_data(bio, pb_data_size);
2138 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA | REQ_DISCARD)) {
2139 defer_bio(cache, bio);
2140 return DM_MAPIO_SUBMITTED;
2144 * Check to see if that block is currently migrating.
2146 cell = alloc_prison_cell(cache);
2148 defer_bio(cache, bio);
2149 return DM_MAPIO_SUBMITTED;
2152 r = bio_detain(cache, block, bio, cell,
2153 (cell_free_fn) free_prison_cell,
2157 defer_bio(cache, bio);
2159 return DM_MAPIO_SUBMITTED;
2162 discarded_block = is_discarded_oblock(cache, block);
2164 r = policy_map(cache->policy, block, false, can_migrate, discarded_block,
2165 bio, &lookup_result);
2166 if (r == -EWOULDBLOCK) {
2167 cell_defer(cache, cell, true);
2168 return DM_MAPIO_SUBMITTED;
2171 DMERR_LIMIT("Unexpected return from cache replacement policy: %d", r);
2173 return DM_MAPIO_SUBMITTED;
2176 switch (lookup_result.op) {
2178 inc_hit_counter(cache, bio);
2179 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
2181 if (is_writethrough_io(cache, bio, lookup_result.cblock))
2182 remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
2184 remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
2186 cell_defer(cache, cell, false);
2190 inc_miss_counter(cache, bio);
2191 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
2193 if (pb->req_nr != 0) {
2195 * This is a duplicate writethrough io that is no
2196 * longer needed because the block has been demoted.
2199 cell_defer(cache, cell, false);
2200 return DM_MAPIO_SUBMITTED;
2202 remap_to_origin_clear_discard(cache, bio, block);
2203 cell_defer(cache, cell, false);
2208 DMERR_LIMIT("%s: erroring bio: unknown policy op: %u", __func__,
2209 (unsigned) lookup_result.op);
2211 return DM_MAPIO_SUBMITTED;
2214 return DM_MAPIO_REMAPPED;
2217 static int cache_end_io(struct dm_target *ti, struct bio *bio, int error)
2219 struct cache *cache = ti->private;
2220 unsigned long flags;
2221 size_t pb_data_size = get_per_bio_data_size(cache);
2222 struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
2225 policy_tick(cache->policy);
2227 spin_lock_irqsave(&cache->lock, flags);
2228 cache->need_tick_bio = true;
2229 spin_unlock_irqrestore(&cache->lock, flags);
2232 check_for_quiesced_migrations(cache, pb);
2237 static int write_dirty_bitset(struct cache *cache)
2241 for (i = 0; i < from_cblock(cache->cache_size); i++) {
2242 r = dm_cache_set_dirty(cache->cmd, to_cblock(i),
2243 is_dirty(cache, to_cblock(i)));
2251 static int write_discard_bitset(struct cache *cache)
2255 r = dm_cache_discard_bitset_resize(cache->cmd, cache->discard_block_size,
2256 cache->discard_nr_blocks);
2258 DMERR("could not resize on-disk discard bitset");
2262 for (i = 0; i < from_dblock(cache->discard_nr_blocks); i++) {
2263 r = dm_cache_set_discard(cache->cmd, to_dblock(i),
2264 is_discarded(cache, to_dblock(i)));
2272 static int save_hint(void *context, dm_cblock_t cblock, dm_oblock_t oblock,
2275 struct cache *cache = context;
2276 return dm_cache_save_hint(cache->cmd, cblock, hint);
2279 static int write_hints(struct cache *cache)
2283 r = dm_cache_begin_hints(cache->cmd, cache->policy);
2285 DMERR("dm_cache_begin_hints failed");
2289 r = policy_walk_mappings(cache->policy, save_hint, cache);
2291 DMERR("policy_walk_mappings failed");
2297 * returns true on success
2299 static bool sync_metadata(struct cache *cache)
2303 r1 = write_dirty_bitset(cache);
2305 DMERR("could not write dirty bitset");
2307 r2 = write_discard_bitset(cache);
2309 DMERR("could not write discard bitset");
2313 r3 = write_hints(cache);
2315 DMERR("could not write hints");
2318 * If writing the above metadata failed, we still commit, but don't
2319 * set the clean shutdown flag. This will effectively force every
2320 * dirty bit to be set on reload.
2322 r4 = dm_cache_commit(cache->cmd, !r1 && !r2 && !r3);
2324 DMERR("could not write cache metadata. Data loss may occur.");
2326 return !r1 && !r2 && !r3 && !r4;
2329 static void cache_postsuspend(struct dm_target *ti)
2331 struct cache *cache = ti->private;
2333 start_quiescing(cache);
2334 wait_for_migrations(cache);
2336 requeue_deferred_io(cache);
2337 stop_quiescing(cache);
2339 (void) sync_metadata(cache);
2342 static int load_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock,
2343 bool dirty, uint32_t hint, bool hint_valid)
2346 struct cache *cache = context;
2348 r = policy_load_mapping(cache->policy, oblock, cblock, hint, hint_valid);
2353 set_dirty(cache, oblock, cblock);
2355 clear_dirty(cache, oblock, cblock);
2360 static int load_discard(void *context, sector_t discard_block_size,
2361 dm_dblock_t dblock, bool discard)
2363 struct cache *cache = context;
2365 /* FIXME: handle mis-matched block size */
2368 set_discard(cache, dblock);
2370 clear_discard(cache, dblock);
2375 static int cache_preresume(struct dm_target *ti)
2378 struct cache *cache = ti->private;
2379 sector_t actual_cache_size = get_dev_size(cache->cache_dev);
2380 (void) sector_div(actual_cache_size, cache->sectors_per_block);
2383 * Check to see if the cache has resized.
2385 if (from_cblock(cache->cache_size) != actual_cache_size || !cache->sized) {
2386 cache->cache_size = to_cblock(actual_cache_size);
2388 r = dm_cache_resize(cache->cmd, cache->cache_size);
2390 DMERR("could not resize cache metadata");
2394 cache->sized = true;
2397 if (!cache->loaded_mappings) {
2398 r = dm_cache_load_mappings(cache->cmd, cache->policy,
2399 load_mapping, cache);
2401 DMERR("could not load cache mappings");
2405 cache->loaded_mappings = true;
2408 if (!cache->loaded_discards) {
2409 r = dm_cache_load_discards(cache->cmd, load_discard, cache);
2411 DMERR("could not load origin discards");
2415 cache->loaded_discards = true;
2421 static void cache_resume(struct dm_target *ti)
2423 struct cache *cache = ti->private;
2425 cache->need_tick_bio = true;
2426 do_waker(&cache->waker.work);
2432 * <#used metadata blocks>/<#total metadata blocks>
2433 * <#read hits> <#read misses> <#write hits> <#write misses>
2434 * <#demotions> <#promotions> <#blocks in cache> <#dirty>
2435 * <#features> <features>*
2436 * <#core args> <core args>
2437 * <#policy args> <policy args>*
2439 static void cache_status(struct dm_target *ti, status_type_t type,
2440 unsigned status_flags, char *result, unsigned maxlen)
2445 dm_block_t nr_free_blocks_metadata = 0;
2446 dm_block_t nr_blocks_metadata = 0;
2447 char buf[BDEVNAME_SIZE];
2448 struct cache *cache = ti->private;
2449 dm_cblock_t residency;
2452 case STATUSTYPE_INFO:
2453 /* Commit to ensure statistics aren't out-of-date */
2454 if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti)) {
2455 r = dm_cache_commit(cache->cmd, false);
2457 DMERR("could not commit metadata for accurate status");
2460 r = dm_cache_get_free_metadata_block_count(cache->cmd,
2461 &nr_free_blocks_metadata);
2463 DMERR("could not get metadata free block count");
2467 r = dm_cache_get_metadata_dev_size(cache->cmd, &nr_blocks_metadata);
2469 DMERR("could not get metadata device size");
2473 residency = policy_residency(cache->policy);
2475 DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
2476 (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
2477 (unsigned long long)nr_blocks_metadata,
2478 (unsigned) atomic_read(&cache->stats.read_hit),
2479 (unsigned) atomic_read(&cache->stats.read_miss),
2480 (unsigned) atomic_read(&cache->stats.write_hit),
2481 (unsigned) atomic_read(&cache->stats.write_miss),
2482 (unsigned) atomic_read(&cache->stats.demotion),
2483 (unsigned) atomic_read(&cache->stats.promotion),
2484 (unsigned long long) from_cblock(residency),
2487 if (cache->features.write_through)
2488 DMEMIT("1 writethrough ");
2492 DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
2494 r = policy_emit_config_values(cache->policy, result + sz, maxlen - sz);
2496 DMERR("policy_emit_config_values returned %d", r);
2501 case STATUSTYPE_TABLE:
2502 format_dev_t(buf, cache->metadata_dev->bdev->bd_dev);
2504 format_dev_t(buf, cache->cache_dev->bdev->bd_dev);
2506 format_dev_t(buf, cache->origin_dev->bdev->bd_dev);
2509 for (i = 0; i < cache->nr_ctr_args - 1; i++)
2510 DMEMIT(" %s", cache->ctr_args[i]);
2511 if (cache->nr_ctr_args)
2512 DMEMIT(" %s", cache->ctr_args[cache->nr_ctr_args - 1]);
2521 #define NOT_CORE_OPTION 1
2523 static int process_config_option(struct cache *cache, char **argv)
2527 if (!strcasecmp(argv[0], "migration_threshold")) {
2528 if (kstrtoul(argv[1], 10, &tmp))
2531 cache->migration_threshold = tmp;
2535 return NOT_CORE_OPTION;
2539 * Supports <key> <value>.
2541 * The key migration_threshold is supported by the cache target core.
2543 static int cache_message(struct dm_target *ti, unsigned argc, char **argv)
2546 struct cache *cache = ti->private;
2551 r = process_config_option(cache, argv);
2552 if (r == NOT_CORE_OPTION)
2553 return policy_set_config_value(cache->policy, argv[0], argv[1]);
2558 static int cache_iterate_devices(struct dm_target *ti,
2559 iterate_devices_callout_fn fn, void *data)
2562 struct cache *cache = ti->private;
2564 r = fn(ti, cache->cache_dev, 0, get_dev_size(cache->cache_dev), data);
2566 r = fn(ti, cache->origin_dev, 0, ti->len, data);
2572 * We assume I/O is going to the origin (which is the volume
2573 * more likely to have restrictions e.g. by being striped).
2574 * (Looking up the exact location of the data would be expensive
2575 * and could always be out of date by the time the bio is submitted.)
2577 static int cache_bvec_merge(struct dm_target *ti,
2578 struct bvec_merge_data *bvm,
2579 struct bio_vec *biovec, int max_size)
2581 struct cache *cache = ti->private;
2582 struct request_queue *q = bdev_get_queue(cache->origin_dev->bdev);
2584 if (!q->merge_bvec_fn)
2587 bvm->bi_bdev = cache->origin_dev->bdev;
2588 return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2591 static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
2594 * FIXME: these limits may be incompatible with the cache device
2596 limits->max_discard_sectors = cache->discard_block_size * 1024;
2597 limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
2600 static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
2602 struct cache *cache = ti->private;
2604 blk_limits_io_min(limits, 0);
2605 blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
2606 set_discard_limits(cache, limits);
2609 /*----------------------------------------------------------------*/
2611 static struct target_type cache_target = {
2613 .version = {1, 1, 0},
2614 .module = THIS_MODULE,
2618 .end_io = cache_end_io,
2619 .postsuspend = cache_postsuspend,
2620 .preresume = cache_preresume,
2621 .resume = cache_resume,
2622 .status = cache_status,
2623 .message = cache_message,
2624 .iterate_devices = cache_iterate_devices,
2625 .merge = cache_bvec_merge,
2626 .io_hints = cache_io_hints,
2629 static int __init dm_cache_init(void)
2633 r = dm_register_target(&cache_target);
2635 DMERR("cache target registration failed: %d", r);
2639 migration_cache = KMEM_CACHE(dm_cache_migration, 0);
2640 if (!migration_cache) {
2641 dm_unregister_target(&cache_target);
2648 static void __exit dm_cache_exit(void)
2650 dm_unregister_target(&cache_target);
2651 kmem_cache_destroy(migration_cache);
2654 module_init(dm_cache_init);
2655 module_exit(dm_cache_exit);
2657 MODULE_DESCRIPTION(DM_NAME " cache target");
2658 MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
2659 MODULE_LICENSE("GPL");