4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
6 * This file is released under the GPL.
9 #include <linux/blkdev.h>
10 #include <linux/device-mapper.h>
11 #include <linux/delay.h>
13 #include <linux/init.h>
14 #include <linux/kdev_t.h>
15 #include <linux/list.h>
16 #include <linux/mempool.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/log2.h>
21 #include <linux/dm-kcopyd.h>
22 #include <linux/workqueue.h>
24 #include "dm-exception-store.h"
26 #define DM_MSG_PREFIX "snapshots"
29 * The percentage increment we will wake up users at
31 #define WAKE_UP_PERCENT 5
34 * kcopyd priority of snapshot operations
36 #define SNAPSHOT_COPY_PRIORITY 2
39 * Reserve 1MB for each snapshot initially (with minimum of 1 page).
41 #define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
44 * The size of the mempool used to track chunks in use.
48 #define DM_TRACKED_CHUNK_HASH_SIZE 16
49 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
50 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
52 struct dm_exception_table {
55 struct list_head *table;
59 struct rw_semaphore lock;
61 struct dm_dev *origin;
66 /* List of snapshots per Origin */
67 struct list_head list;
69 /* You can't use a snapshot if this is 0 (e.g. if full) */
72 /* Origin writes don't trigger exceptions until this is set */
75 /* Whether or not owning mapped_device is suspended */
78 mempool_t *pending_pool;
80 atomic_t pending_exceptions_count;
82 struct dm_exception_table pending;
83 struct dm_exception_table complete;
86 * pe_lock protects all pending_exception operations and access
87 * as well as the snapshot_bios list.
91 /* The on disk metadata handler */
92 struct dm_exception_store *store;
94 struct dm_kcopyd_client *kcopyd_client;
96 /* Queue of snapshot writes for ksnapd to flush */
97 struct bio_list queued_bios;
98 struct work_struct queued_bios_work;
100 /* Chunks with outstanding reads */
101 mempool_t *tracked_chunk_pool;
102 spinlock_t tracked_chunk_lock;
103 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
106 struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
110 EXPORT_SYMBOL(dm_snap_cow);
112 static struct workqueue_struct *ksnapd;
113 static void flush_queued_bios(struct work_struct *work);
115 static sector_t chunk_to_sector(struct dm_exception_store *store,
118 return chunk << store->chunk_shift;
121 static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
124 * There is only ever one instance of a particular block
125 * device so we can compare pointers safely.
130 struct dm_snap_pending_exception {
131 struct dm_exception e;
134 * Origin buffers waiting for this to complete are held
137 struct bio_list origin_bios;
138 struct bio_list snapshot_bios;
141 * Short-term queue of pending exceptions prior to submission.
143 struct list_head list;
146 * The primary pending_exception is the one that holds
147 * the ref_count and the list of origin_bios for a
148 * group of pending_exceptions. It is always last to get freed.
149 * These fields get set up when writing to the origin.
151 struct dm_snap_pending_exception *primary_pe;
154 * Number of pending_exceptions processing this chunk.
155 * When this drops to zero we must complete the origin bios.
156 * If incrementing or decrementing this, hold pe->snap->lock for
157 * the sibling concerned and not pe->primary_pe->snap->lock unless
162 /* Pointer back to snapshot context */
163 struct dm_snapshot *snap;
166 * 1 indicates the exception has already been sent to
173 * Hash table mapping origin volumes to lists of snapshots and
174 * a lock to protect it
176 static struct kmem_cache *exception_cache;
177 static struct kmem_cache *pending_cache;
179 struct dm_snap_tracked_chunk {
180 struct hlist_node node;
184 static struct kmem_cache *tracked_chunk_cache;
186 static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
189 struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
195 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
196 hlist_add_head(&c->node,
197 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
198 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
203 static void stop_tracking_chunk(struct dm_snapshot *s,
204 struct dm_snap_tracked_chunk *c)
208 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
210 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
212 mempool_free(c, s->tracked_chunk_pool);
215 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
217 struct dm_snap_tracked_chunk *c;
218 struct hlist_node *hn;
221 spin_lock_irq(&s->tracked_chunk_lock);
223 hlist_for_each_entry(c, hn,
224 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
225 if (c->chunk == chunk) {
231 spin_unlock_irq(&s->tracked_chunk_lock);
237 * One of these per registered origin, held in the snapshot_origins hash
240 /* The origin device */
241 struct block_device *bdev;
243 struct list_head hash_list;
245 /* List of snapshots for this origin */
246 struct list_head snapshots;
250 * Size of the hash table for origin volumes. If we make this
251 * the size of the minors list then it should be nearly perfect
253 #define ORIGIN_HASH_SIZE 256
254 #define ORIGIN_MASK 0xFF
255 static struct list_head *_origins;
256 static struct rw_semaphore _origins_lock;
258 static int init_origin_hash(void)
262 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
265 DMERR("unable to allocate memory");
269 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
270 INIT_LIST_HEAD(_origins + i);
271 init_rwsem(&_origins_lock);
276 static void exit_origin_hash(void)
281 static unsigned origin_hash(struct block_device *bdev)
283 return bdev->bd_dev & ORIGIN_MASK;
286 static struct origin *__lookup_origin(struct block_device *origin)
288 struct list_head *ol;
291 ol = &_origins[origin_hash(origin)];
292 list_for_each_entry (o, ol, hash_list)
293 if (bdev_equal(o->bdev, origin))
299 static void __insert_origin(struct origin *o)
301 struct list_head *sl = &_origins[origin_hash(o->bdev)];
302 list_add_tail(&o->hash_list, sl);
306 * Make a note of the snapshot and its origin so we can look it
307 * up when the origin has a write on it.
309 static int register_snapshot(struct dm_snapshot *snap)
311 struct dm_snapshot *l;
312 struct origin *o, *new_o;
313 struct block_device *bdev = snap->origin->bdev;
315 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
319 down_write(&_origins_lock);
320 o = __lookup_origin(bdev);
328 /* Initialise the struct */
329 INIT_LIST_HEAD(&o->snapshots);
335 /* Sort the list according to chunk size, largest-first smallest-last */
336 list_for_each_entry(l, &o->snapshots, list)
337 if (l->store->chunk_size < snap->store->chunk_size)
339 list_add_tail(&snap->list, &l->list);
341 up_write(&_origins_lock);
345 static void unregister_snapshot(struct dm_snapshot *s)
349 down_write(&_origins_lock);
350 o = __lookup_origin(s->origin->bdev);
353 if (list_empty(&o->snapshots)) {
354 list_del(&o->hash_list);
358 up_write(&_origins_lock);
362 * Implementation of the exception hash tables.
363 * The lowest hash_shift bits of the chunk number are ignored, allowing
364 * some consecutive chunks to be grouped together.
366 static int dm_exception_table_init(struct dm_exception_table *et,
367 uint32_t size, unsigned hash_shift)
371 et->hash_shift = hash_shift;
372 et->hash_mask = size - 1;
373 et->table = dm_vcalloc(size, sizeof(struct list_head));
377 for (i = 0; i < size; i++)
378 INIT_LIST_HEAD(et->table + i);
383 static void dm_exception_table_exit(struct dm_exception_table *et,
384 struct kmem_cache *mem)
386 struct list_head *slot;
387 struct dm_exception *ex, *next;
390 size = et->hash_mask + 1;
391 for (i = 0; i < size; i++) {
392 slot = et->table + i;
394 list_for_each_entry_safe (ex, next, slot, hash_list)
395 kmem_cache_free(mem, ex);
401 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
403 return (chunk >> et->hash_shift) & et->hash_mask;
406 static void dm_remove_exception(struct dm_exception *e)
408 list_del(&e->hash_list);
412 * Return the exception data for a sector, or NULL if not
415 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
418 struct list_head *slot;
419 struct dm_exception *e;
421 slot = &et->table[exception_hash(et, chunk)];
422 list_for_each_entry (e, slot, hash_list)
423 if (chunk >= e->old_chunk &&
424 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
430 static struct dm_exception *alloc_completed_exception(void)
432 struct dm_exception *e;
434 e = kmem_cache_alloc(exception_cache, GFP_NOIO);
436 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
441 static void free_completed_exception(struct dm_exception *e)
443 kmem_cache_free(exception_cache, e);
446 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
448 struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
451 atomic_inc(&s->pending_exceptions_count);
457 static void free_pending_exception(struct dm_snap_pending_exception *pe)
459 struct dm_snapshot *s = pe->snap;
461 mempool_free(pe, s->pending_pool);
462 smp_mb__before_atomic_dec();
463 atomic_dec(&s->pending_exceptions_count);
466 static void dm_insert_exception(struct dm_exception_table *eh,
467 struct dm_exception *new_e)
470 struct dm_exception *e = NULL;
472 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
474 /* Add immediately if this table doesn't support consecutive chunks */
478 /* List is ordered by old_chunk */
479 list_for_each_entry_reverse(e, l, hash_list) {
480 /* Insert after an existing chunk? */
481 if (new_e->old_chunk == (e->old_chunk +
482 dm_consecutive_chunk_count(e) + 1) &&
483 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
484 dm_consecutive_chunk_count(e) + 1)) {
485 dm_consecutive_chunk_count_inc(e);
486 free_completed_exception(new_e);
490 /* Insert before an existing chunk? */
491 if (new_e->old_chunk == (e->old_chunk - 1) &&
492 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
493 dm_consecutive_chunk_count_inc(e);
496 free_completed_exception(new_e);
500 if (new_e->old_chunk > e->old_chunk)
505 list_add(&new_e->hash_list, e ? &e->hash_list : l);
509 * Callback used by the exception stores to load exceptions when
512 static int dm_add_exception(void *context, chunk_t old, chunk_t new)
514 struct dm_snapshot *s = context;
515 struct dm_exception *e;
517 e = alloc_completed_exception();
523 /* Consecutive_count is implicitly initialised to zero */
526 dm_insert_exception(&s->complete, e);
531 #define min_not_zero(l, r) (((l) == 0) ? (r) : (((r) == 0) ? (l) : min(l, r)))
534 * Return a minimum chunk size of all snapshots that have the specified origin.
535 * Return zero if the origin has no snapshots.
537 static sector_t __minimum_chunk_size(struct origin *o)
539 struct dm_snapshot *snap;
540 unsigned chunk_size = 0;
543 list_for_each_entry(snap, &o->snapshots, list)
544 chunk_size = min_not_zero(chunk_size,
545 snap->store->chunk_size);
553 static int calc_max_buckets(void)
555 /* use a fixed size of 2MB */
556 unsigned long mem = 2 * 1024 * 1024;
557 mem /= sizeof(struct list_head);
563 * Allocate room for a suitable hash table.
565 static int init_hash_tables(struct dm_snapshot *s)
567 sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
570 * Calculate based on the size of the original volume or
573 cow_dev_size = get_dev_size(s->cow->bdev);
574 origin_dev_size = get_dev_size(s->origin->bdev);
575 max_buckets = calc_max_buckets();
577 hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
578 hash_size = min(hash_size, max_buckets);
582 hash_size = rounddown_pow_of_two(hash_size);
583 if (dm_exception_table_init(&s->complete, hash_size,
584 DM_CHUNK_CONSECUTIVE_BITS))
588 * Allocate hash table for in-flight exceptions
589 * Make this smaller than the real hash table
595 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
596 dm_exception_table_exit(&s->complete, exception_cache);
604 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
606 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
608 struct dm_snapshot *s;
611 char *origin_path, *cow_path;
615 ti->error = "requires exactly 4 arguments";
620 origin_path = argv[0];
624 s = kmalloc(sizeof(*s), GFP_KERNEL);
626 ti->error = "Cannot allocate snapshot context private "
636 r = dm_get_device(ti, cow_path, 0, 0,
637 FMODE_READ | FMODE_WRITE, &s->cow);
639 ti->error = "Cannot get COW device";
643 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
645 ti->error = "Couldn't create exception store";
653 r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
655 ti->error = "Cannot get origin device";
663 atomic_set(&s->pending_exceptions_count, 0);
664 init_rwsem(&s->lock);
665 spin_lock_init(&s->pe_lock);
667 /* Allocate hash table for COW data */
668 if (init_hash_tables(s)) {
669 ti->error = "Unable to allocate hash table space";
671 goto bad_hash_tables;
674 r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
676 ti->error = "Could not create kcopyd client";
680 s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
681 if (!s->pending_pool) {
682 ti->error = "Could not allocate mempool for pending exceptions";
683 goto bad_pending_pool;
686 s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
687 tracked_chunk_cache);
688 if (!s->tracked_chunk_pool) {
689 ti->error = "Could not allocate tracked_chunk mempool for "
691 goto bad_tracked_chunk_pool;
694 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
695 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
697 spin_lock_init(&s->tracked_chunk_lock);
699 /* Metadata must only be loaded into one table at once */
700 r = s->store->type->read_metadata(s->store, dm_add_exception,
703 ti->error = "Failed to read snapshot metadata";
704 goto bad_load_and_register;
707 DMWARN("Snapshot is marked invalid.");
710 bio_list_init(&s->queued_bios);
711 INIT_WORK(&s->queued_bios_work, flush_queued_bios);
713 if (!s->store->chunk_size) {
714 ti->error = "Chunk size not set";
715 goto bad_load_and_register;
718 /* Add snapshot to the list of snapshots for this origin */
719 /* Exceptions aren't triggered till snapshot_resume() is called */
720 if (register_snapshot(s)) {
722 ti->error = "Cannot register snapshot origin";
723 goto bad_load_and_register;
727 ti->split_io = s->store->chunk_size;
728 ti->num_flush_requests = 1;
732 bad_load_and_register:
733 mempool_destroy(s->tracked_chunk_pool);
735 bad_tracked_chunk_pool:
736 mempool_destroy(s->pending_pool);
739 dm_kcopyd_client_destroy(s->kcopyd_client);
742 dm_exception_table_exit(&s->pending, pending_cache);
743 dm_exception_table_exit(&s->complete, exception_cache);
746 dm_put_device(ti, s->origin);
749 dm_exception_store_destroy(s->store);
752 dm_put_device(ti, s->cow);
761 static void __free_exceptions(struct dm_snapshot *s)
763 dm_kcopyd_client_destroy(s->kcopyd_client);
764 s->kcopyd_client = NULL;
766 dm_exception_table_exit(&s->pending, pending_cache);
767 dm_exception_table_exit(&s->complete, exception_cache);
770 static void snapshot_dtr(struct dm_target *ti)
772 #ifdef CONFIG_DM_DEBUG
775 struct dm_snapshot *s = ti->private;
777 flush_workqueue(ksnapd);
779 /* Prevent further origin writes from using this snapshot. */
780 /* After this returns there can be no new kcopyd jobs. */
781 unregister_snapshot(s);
783 while (atomic_read(&s->pending_exceptions_count))
786 * Ensure instructions in mempool_destroy aren't reordered
787 * before atomic_read.
791 #ifdef CONFIG_DM_DEBUG
792 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
793 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
796 mempool_destroy(s->tracked_chunk_pool);
798 __free_exceptions(s);
800 mempool_destroy(s->pending_pool);
802 dm_put_device(ti, s->origin);
804 dm_exception_store_destroy(s->store);
806 dm_put_device(ti, s->cow);
812 * Flush a list of buffers.
814 static void flush_bios(struct bio *bio)
821 generic_make_request(bio);
826 static void flush_queued_bios(struct work_struct *work)
828 struct dm_snapshot *s =
829 container_of(work, struct dm_snapshot, queued_bios_work);
830 struct bio *queued_bios;
833 spin_lock_irqsave(&s->pe_lock, flags);
834 queued_bios = bio_list_get(&s->queued_bios);
835 spin_unlock_irqrestore(&s->pe_lock, flags);
837 flush_bios(queued_bios);
841 * Error a list of buffers.
843 static void error_bios(struct bio *bio)
855 static void __invalidate_snapshot(struct dm_snapshot *s, int err)
861 DMERR("Invalidating snapshot: Error reading/writing.");
862 else if (err == -ENOMEM)
863 DMERR("Invalidating snapshot: Unable to allocate exception.");
865 if (s->store->type->drop_snapshot)
866 s->store->type->drop_snapshot(s->store);
870 dm_table_event(s->ti->table);
873 static void get_pending_exception(struct dm_snap_pending_exception *pe)
875 atomic_inc(&pe->ref_count);
878 static struct bio *put_pending_exception(struct dm_snap_pending_exception *pe)
880 struct dm_snap_pending_exception *primary_pe;
881 struct bio *origin_bios = NULL;
883 primary_pe = pe->primary_pe;
886 * If this pe is involved in a write to the origin and
887 * it is the last sibling to complete then release
888 * the bios for the original write to the origin.
891 atomic_dec_and_test(&primary_pe->ref_count)) {
892 origin_bios = bio_list_get(&primary_pe->origin_bios);
893 free_pending_exception(primary_pe);
897 * Free the pe if it's not linked to an origin write or if
898 * it's not itself a primary pe.
900 if (!primary_pe || primary_pe != pe)
901 free_pending_exception(pe);
906 static void pending_complete(struct dm_snap_pending_exception *pe, int success)
908 struct dm_exception *e;
909 struct dm_snapshot *s = pe->snap;
910 struct bio *origin_bios = NULL;
911 struct bio *snapshot_bios = NULL;
915 /* Read/write error - snapshot is unusable */
916 down_write(&s->lock);
917 __invalidate_snapshot(s, -EIO);
922 e = alloc_completed_exception();
924 down_write(&s->lock);
925 __invalidate_snapshot(s, -ENOMEM);
931 down_write(&s->lock);
933 free_completed_exception(e);
939 * Check for conflicting reads. This is extremely improbable,
940 * so msleep(1) is sufficient and there is no need for a wait queue.
942 while (__chunk_is_tracked(s, pe->e.old_chunk))
946 * Add a proper exception, and remove the
947 * in-flight exception from the list.
949 dm_insert_exception(&s->complete, e);
952 dm_remove_exception(&pe->e);
953 snapshot_bios = bio_list_get(&pe->snapshot_bios);
954 origin_bios = put_pending_exception(pe);
958 /* Submit any pending write bios */
960 error_bios(snapshot_bios);
962 flush_bios(snapshot_bios);
964 flush_bios(origin_bios);
967 static void commit_callback(void *context, int success)
969 struct dm_snap_pending_exception *pe = context;
971 pending_complete(pe, success);
975 * Called when the copy I/O has finished. kcopyd actually runs
976 * this code so don't block.
978 static void copy_callback(int read_err, unsigned long write_err, void *context)
980 struct dm_snap_pending_exception *pe = context;
981 struct dm_snapshot *s = pe->snap;
983 if (read_err || write_err)
984 pending_complete(pe, 0);
987 /* Update the metadata if we are persistent */
988 s->store->type->commit_exception(s->store, &pe->e,
989 commit_callback, pe);
993 * Dispatches the copy operation to kcopyd.
995 static void start_copy(struct dm_snap_pending_exception *pe)
997 struct dm_snapshot *s = pe->snap;
998 struct dm_io_region src, dest;
999 struct block_device *bdev = s->origin->bdev;
1002 dev_size = get_dev_size(bdev);
1005 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1006 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1008 dest.bdev = s->cow->bdev;
1009 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1010 dest.count = src.count;
1012 /* Hand over to kcopyd */
1013 dm_kcopyd_copy(s->kcopyd_client,
1014 &src, 1, &dest, 0, copy_callback, pe);
1017 static struct dm_snap_pending_exception *
1018 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1020 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1025 return container_of(e, struct dm_snap_pending_exception, e);
1029 * Looks to see if this snapshot already has a pending exception
1030 * for this chunk, otherwise it allocates a new one and inserts
1031 * it into the pending table.
1033 * NOTE: a write lock must be held on snap->lock before calling
1036 static struct dm_snap_pending_exception *
1037 __find_pending_exception(struct dm_snapshot *s,
1038 struct dm_snap_pending_exception *pe, chunk_t chunk)
1040 struct dm_snap_pending_exception *pe2;
1042 pe2 = __lookup_pending_exception(s, chunk);
1044 free_pending_exception(pe);
1048 pe->e.old_chunk = chunk;
1049 bio_list_init(&pe->origin_bios);
1050 bio_list_init(&pe->snapshot_bios);
1051 pe->primary_pe = NULL;
1052 atomic_set(&pe->ref_count, 0);
1055 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1056 free_pending_exception(pe);
1060 get_pending_exception(pe);
1061 dm_insert_exception(&s->pending, &pe->e);
1066 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1067 struct bio *bio, chunk_t chunk)
1069 bio->bi_bdev = s->cow->bdev;
1070 bio->bi_sector = chunk_to_sector(s->store,
1071 dm_chunk_number(e->new_chunk) +
1072 (chunk - e->old_chunk)) +
1074 s->store->chunk_mask);
1077 static int snapshot_map(struct dm_target *ti, struct bio *bio,
1078 union map_info *map_context)
1080 struct dm_exception *e;
1081 struct dm_snapshot *s = ti->private;
1082 int r = DM_MAPIO_REMAPPED;
1084 struct dm_snap_pending_exception *pe = NULL;
1086 if (unlikely(bio_empty_barrier(bio))) {
1087 bio->bi_bdev = s->cow->bdev;
1088 return DM_MAPIO_REMAPPED;
1091 chunk = sector_to_chunk(s->store, bio->bi_sector);
1093 /* Full snapshots are not usable */
1094 /* To get here the table must be live so s->active is always set. */
1098 /* FIXME: should only take write lock if we need
1099 * to copy an exception */
1100 down_write(&s->lock);
1107 /* If the block is already remapped - use that, else remap it */
1108 e = dm_lookup_exception(&s->complete, chunk);
1110 remap_exception(s, e, bio, chunk);
1115 * Write to snapshot - higher level takes care of RW/RO
1116 * flags so we should only get this if we are
1119 if (bio_rw(bio) == WRITE) {
1120 pe = __lookup_pending_exception(s, chunk);
1123 pe = alloc_pending_exception(s);
1124 down_write(&s->lock);
1127 free_pending_exception(pe);
1132 e = dm_lookup_exception(&s->complete, chunk);
1134 free_pending_exception(pe);
1135 remap_exception(s, e, bio, chunk);
1139 pe = __find_pending_exception(s, pe, chunk);
1141 __invalidate_snapshot(s, -ENOMEM);
1147 remap_exception(s, &pe->e, bio, chunk);
1148 bio_list_add(&pe->snapshot_bios, bio);
1150 r = DM_MAPIO_SUBMITTED;
1153 /* this is protected by snap->lock */
1160 bio->bi_bdev = s->origin->bdev;
1161 map_context->ptr = track_chunk(s, chunk);
1170 static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
1171 int error, union map_info *map_context)
1173 struct dm_snapshot *s = ti->private;
1174 struct dm_snap_tracked_chunk *c = map_context->ptr;
1177 stop_tracking_chunk(s, c);
1182 static void snapshot_postsuspend(struct dm_target *ti)
1184 struct dm_snapshot *s = ti->private;
1186 down_write(&s->lock);
1191 static void snapshot_resume(struct dm_target *ti)
1193 struct dm_snapshot *s = ti->private;
1195 down_write(&s->lock);
1201 static int snapshot_status(struct dm_target *ti, status_type_t type,
1202 char *result, unsigned int maxlen)
1205 struct dm_snapshot *snap = ti->private;
1208 case STATUSTYPE_INFO:
1210 down_write(&snap->lock);
1215 if (snap->store->type->usage) {
1216 sector_t total_sectors, sectors_allocated,
1218 snap->store->type->usage(snap->store,
1222 DMEMIT("%llu/%llu %llu",
1223 (unsigned long long)sectors_allocated,
1224 (unsigned long long)total_sectors,
1225 (unsigned long long)metadata_sectors);
1231 up_write(&snap->lock);
1235 case STATUSTYPE_TABLE:
1237 * kdevname returns a static pointer so we need
1238 * to make private copies if the output is to
1241 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
1242 snap->store->type->status(snap->store, type, result + sz,
1250 static int snapshot_iterate_devices(struct dm_target *ti,
1251 iterate_devices_callout_fn fn, void *data)
1253 struct dm_snapshot *snap = ti->private;
1255 return fn(ti, snap->origin, 0, ti->len, data);
1259 /*-----------------------------------------------------------------
1261 *---------------------------------------------------------------*/
1262 static int __origin_write(struct list_head *snapshots, struct bio *bio)
1264 int r = DM_MAPIO_REMAPPED, first = 0;
1265 struct dm_snapshot *snap;
1266 struct dm_exception *e;
1267 struct dm_snap_pending_exception *pe, *next_pe, *primary_pe = NULL;
1269 LIST_HEAD(pe_queue);
1271 /* Do all the snapshots on this origin */
1272 list_for_each_entry (snap, snapshots, list) {
1274 down_write(&snap->lock);
1276 /* Only deal with valid and active snapshots */
1277 if (!snap->valid || !snap->active)
1280 /* Nothing to do if writing beyond end of snapshot */
1281 if (bio->bi_sector >= dm_table_get_size(snap->ti->table))
1285 * Remember, different snapshots can have
1286 * different chunk sizes.
1288 chunk = sector_to_chunk(snap->store, bio->bi_sector);
1291 * Check exception table to see if block
1292 * is already remapped in this snapshot
1293 * and trigger an exception if not.
1295 * ref_count is initialised to 1 so pending_complete()
1296 * won't destroy the primary_pe while we're inside this loop.
1298 e = dm_lookup_exception(&snap->complete, chunk);
1302 pe = __lookup_pending_exception(snap, chunk);
1304 up_write(&snap->lock);
1305 pe = alloc_pending_exception(snap);
1306 down_write(&snap->lock);
1309 free_pending_exception(pe);
1313 e = dm_lookup_exception(&snap->complete, chunk);
1315 free_pending_exception(pe);
1319 pe = __find_pending_exception(snap, pe, chunk);
1321 __invalidate_snapshot(snap, -ENOMEM);
1328 * Either every pe here has same
1329 * primary_pe or none has one yet.
1332 primary_pe = pe->primary_pe;
1338 bio_list_add(&primary_pe->origin_bios, bio);
1340 r = DM_MAPIO_SUBMITTED;
1343 if (!pe->primary_pe) {
1344 pe->primary_pe = primary_pe;
1345 get_pending_exception(primary_pe);
1350 list_add_tail(&pe->list, &pe_queue);
1354 up_write(&snap->lock);
1361 * If this is the first time we're processing this chunk and
1362 * ref_count is now 1 it means all the pending exceptions
1363 * got completed while we were in the loop above, so it falls to
1364 * us here to remove the primary_pe and submit any origin_bios.
1367 if (first && atomic_dec_and_test(&primary_pe->ref_count)) {
1368 flush_bios(bio_list_get(&primary_pe->origin_bios));
1369 free_pending_exception(primary_pe);
1370 /* If we got here, pe_queue is necessarily empty. */
1375 * Now that we have a complete pe list we can start the copying.
1377 list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
1384 * Called on a write from the origin driver.
1386 static int do_origin(struct dm_dev *origin, struct bio *bio)
1389 int r = DM_MAPIO_REMAPPED;
1391 down_read(&_origins_lock);
1392 o = __lookup_origin(origin->bdev);
1394 r = __origin_write(&o->snapshots, bio);
1395 up_read(&_origins_lock);
1401 * Origin: maps a linear range of a device, with hooks for snapshotting.
1405 * Construct an origin mapping: <dev_path>
1406 * The context for an origin is merely a 'struct dm_dev *'
1407 * pointing to the real device.
1409 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1415 ti->error = "origin: incorrect number of arguments";
1419 r = dm_get_device(ti, argv[0], 0, ti->len,
1420 dm_table_get_mode(ti->table), &dev);
1422 ti->error = "Cannot get target device";
1427 ti->num_flush_requests = 1;
1432 static void origin_dtr(struct dm_target *ti)
1434 struct dm_dev *dev = ti->private;
1435 dm_put_device(ti, dev);
1438 static int origin_map(struct dm_target *ti, struct bio *bio,
1439 union map_info *map_context)
1441 struct dm_dev *dev = ti->private;
1442 bio->bi_bdev = dev->bdev;
1444 if (unlikely(bio_empty_barrier(bio)))
1445 return DM_MAPIO_REMAPPED;
1447 /* Only tell snapshots if this is a write */
1448 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
1452 * Set the target "split_io" field to the minimum of all the snapshots'
1455 static void origin_resume(struct dm_target *ti)
1457 struct dm_dev *dev = ti->private;
1459 down_read(&_origins_lock);
1461 ti->split_io = __minimum_chunk_size(__lookup_origin(dev->bdev));
1463 up_read(&_origins_lock);
1466 static int origin_status(struct dm_target *ti, status_type_t type, char *result,
1467 unsigned int maxlen)
1469 struct dm_dev *dev = ti->private;
1472 case STATUSTYPE_INFO:
1476 case STATUSTYPE_TABLE:
1477 snprintf(result, maxlen, "%s", dev->name);
1484 static int origin_iterate_devices(struct dm_target *ti,
1485 iterate_devices_callout_fn fn, void *data)
1487 struct dm_dev *dev = ti->private;
1489 return fn(ti, dev, 0, ti->len, data);
1492 static struct target_type origin_target = {
1493 .name = "snapshot-origin",
1494 .version = {1, 7, 0},
1495 .module = THIS_MODULE,
1499 .resume = origin_resume,
1500 .status = origin_status,
1501 .iterate_devices = origin_iterate_devices,
1504 static struct target_type snapshot_target = {
1506 .version = {1, 9, 0},
1507 .module = THIS_MODULE,
1508 .ctr = snapshot_ctr,
1509 .dtr = snapshot_dtr,
1510 .map = snapshot_map,
1511 .end_io = snapshot_end_io,
1512 .postsuspend = snapshot_postsuspend,
1513 .resume = snapshot_resume,
1514 .status = snapshot_status,
1515 .iterate_devices = snapshot_iterate_devices,
1518 static int __init dm_snapshot_init(void)
1522 r = dm_exception_store_init();
1524 DMERR("Failed to initialize exception stores");
1528 r = dm_register_target(&snapshot_target);
1530 DMERR("snapshot target register failed %d", r);
1531 goto bad_register_snapshot_target;
1534 r = dm_register_target(&origin_target);
1536 DMERR("Origin target register failed %d", r);
1540 r = init_origin_hash();
1542 DMERR("init_origin_hash failed.");
1546 exception_cache = KMEM_CACHE(dm_exception, 0);
1547 if (!exception_cache) {
1548 DMERR("Couldn't create exception cache.");
1553 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
1554 if (!pending_cache) {
1555 DMERR("Couldn't create pending cache.");
1560 tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
1561 if (!tracked_chunk_cache) {
1562 DMERR("Couldn't create cache to track chunks in use.");
1567 ksnapd = create_singlethread_workqueue("ksnapd");
1569 DMERR("Failed to create ksnapd workqueue.");
1571 goto bad_pending_pool;
1577 kmem_cache_destroy(tracked_chunk_cache);
1579 kmem_cache_destroy(pending_cache);
1581 kmem_cache_destroy(exception_cache);
1585 dm_unregister_target(&origin_target);
1587 dm_unregister_target(&snapshot_target);
1589 bad_register_snapshot_target:
1590 dm_exception_store_exit();
1594 static void __exit dm_snapshot_exit(void)
1596 destroy_workqueue(ksnapd);
1598 dm_unregister_target(&snapshot_target);
1599 dm_unregister_target(&origin_target);
1602 kmem_cache_destroy(pending_cache);
1603 kmem_cache_destroy(exception_cache);
1604 kmem_cache_destroy(tracked_chunk_cache);
1606 dm_exception_store_exit();
1610 module_init(dm_snapshot_init);
1611 module_exit(dm_snapshot_exit);
1613 MODULE_DESCRIPTION(DM_NAME " snapshot target");
1614 MODULE_AUTHOR("Joe Thornber");
1615 MODULE_LICENSE("GPL");