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>
23 #include "dm-exception-store.h"
25 #define DM_MSG_PREFIX "snapshots"
27 static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
29 #define dm_target_is_snapshot_merge(ti) \
30 ((ti)->type->name == dm_snapshot_merge_target_name)
33 * The size of the mempool used to track chunks in use.
37 #define DM_TRACKED_CHUNK_HASH_SIZE 16
38 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
39 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
41 struct dm_exception_table {
44 struct list_head *table;
48 struct rw_semaphore lock;
50 struct dm_dev *origin;
55 /* List of snapshots per Origin */
56 struct list_head list;
59 * You can't use a snapshot if this is 0 (e.g. if full).
60 * A snapshot-merge target never clears this.
64 /* Origin writes don't trigger exceptions until this is set */
67 atomic_t pending_exceptions_count;
69 mempool_t *pending_pool;
71 struct dm_exception_table pending;
72 struct dm_exception_table complete;
75 * pe_lock protects all pending_exception operations and access
76 * as well as the snapshot_bios list.
80 /* Chunks with outstanding reads */
81 spinlock_t tracked_chunk_lock;
82 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
84 /* The on disk metadata handler */
85 struct dm_exception_store *store;
87 struct dm_kcopyd_client *kcopyd_client;
89 /* Wait for events based on state_bits */
90 unsigned long state_bits;
92 /* Range of chunks currently being merged. */
93 chunk_t first_merging_chunk;
94 int num_merging_chunks;
97 * The merge operation failed if this flag is set.
98 * Failure modes are handled as follows:
99 * - I/O error reading the header
100 * => don't load the target; abort.
101 * - Header does not have "valid" flag set
102 * => use the origin; forget about the snapshot.
103 * - I/O error when reading exceptions
104 * => don't load the target; abort.
105 * (We can't use the intermediate origin state.)
106 * - I/O error while merging
107 * => stop merging; set merge_failed; process I/O normally.
112 * Incoming bios that overlap with chunks being merged must wait
113 * for them to be committed.
115 struct bio_list bios_queued_during_merge;
120 * RUNNING_MERGE - Merge operation is in progress.
121 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
122 * cleared afterwards.
124 #define RUNNING_MERGE 0
125 #define SHUTDOWN_MERGE 1
127 struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
131 EXPORT_SYMBOL(dm_snap_origin);
133 struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
137 EXPORT_SYMBOL(dm_snap_cow);
139 static sector_t chunk_to_sector(struct dm_exception_store *store,
142 return chunk << store->chunk_shift;
145 static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
148 * There is only ever one instance of a particular block
149 * device so we can compare pointers safely.
154 struct dm_snap_pending_exception {
155 struct dm_exception e;
158 * Origin buffers waiting for this to complete are held
161 struct bio_list origin_bios;
162 struct bio_list snapshot_bios;
164 /* Pointer back to snapshot context */
165 struct dm_snapshot *snap;
168 * 1 indicates the exception has already been sent to
174 * For writing a complete chunk, bypassing the copy.
176 struct bio *full_bio;
177 bio_end_io_t *full_bio_end_io;
178 void *full_bio_private;
182 * Hash table mapping origin volumes to lists of snapshots and
183 * a lock to protect it
185 static struct kmem_cache *exception_cache;
186 static struct kmem_cache *pending_cache;
188 struct dm_snap_tracked_chunk {
189 struct hlist_node node;
193 static void init_tracked_chunk(struct bio *bio)
195 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
196 INIT_HLIST_NODE(&c->node);
199 static bool is_bio_tracked(struct bio *bio)
201 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
202 return !hlist_unhashed(&c->node);
205 static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
207 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
211 spin_lock_irq(&s->tracked_chunk_lock);
212 hlist_add_head(&c->node,
213 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
214 spin_unlock_irq(&s->tracked_chunk_lock);
217 static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
219 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
222 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
224 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
227 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
229 struct dm_snap_tracked_chunk *c;
230 struct hlist_node *hn;
233 spin_lock_irq(&s->tracked_chunk_lock);
235 hlist_for_each_entry(c, hn,
236 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
237 if (c->chunk == chunk) {
243 spin_unlock_irq(&s->tracked_chunk_lock);
249 * This conflicting I/O is extremely improbable in the caller,
250 * so msleep(1) is sufficient and there is no need for a wait queue.
252 static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
254 while (__chunk_is_tracked(s, chunk))
259 * One of these per registered origin, held in the snapshot_origins hash
262 /* The origin device */
263 struct block_device *bdev;
265 struct list_head hash_list;
267 /* List of snapshots for this origin */
268 struct list_head snapshots;
272 * Size of the hash table for origin volumes. If we make this
273 * the size of the minors list then it should be nearly perfect
275 #define ORIGIN_HASH_SIZE 256
276 #define ORIGIN_MASK 0xFF
277 static struct list_head *_origins;
278 static struct rw_semaphore _origins_lock;
280 static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
281 static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
282 static uint64_t _pending_exceptions_done_count;
284 static int init_origin_hash(void)
288 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
291 DMERR("unable to allocate memory");
295 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
296 INIT_LIST_HEAD(_origins + i);
297 init_rwsem(&_origins_lock);
302 static void exit_origin_hash(void)
307 static unsigned origin_hash(struct block_device *bdev)
309 return bdev->bd_dev & ORIGIN_MASK;
312 static struct origin *__lookup_origin(struct block_device *origin)
314 struct list_head *ol;
317 ol = &_origins[origin_hash(origin)];
318 list_for_each_entry (o, ol, hash_list)
319 if (bdev_equal(o->bdev, origin))
325 static void __insert_origin(struct origin *o)
327 struct list_head *sl = &_origins[origin_hash(o->bdev)];
328 list_add_tail(&o->hash_list, sl);
332 * _origins_lock must be held when calling this function.
333 * Returns number of snapshots registered using the supplied cow device, plus:
334 * snap_src - a snapshot suitable for use as a source of exception handover
335 * snap_dest - a snapshot capable of receiving exception handover.
336 * snap_merge - an existing snapshot-merge target linked to the same origin.
337 * There can be at most one snapshot-merge target. The parameter is optional.
339 * Possible return values and states of snap_src and snap_dest.
340 * 0: NULL, NULL - first new snapshot
341 * 1: snap_src, NULL - normal snapshot
342 * 2: snap_src, snap_dest - waiting for handover
343 * 2: snap_src, NULL - handed over, waiting for old to be deleted
344 * 1: NULL, snap_dest - source got destroyed without handover
346 static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
347 struct dm_snapshot **snap_src,
348 struct dm_snapshot **snap_dest,
349 struct dm_snapshot **snap_merge)
351 struct dm_snapshot *s;
356 o = __lookup_origin(snap->origin->bdev);
360 list_for_each_entry(s, &o->snapshots, list) {
361 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
363 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
373 } else if (snap_dest)
384 * On success, returns 1 if this snapshot is a handover destination,
385 * otherwise returns 0.
387 static int __validate_exception_handover(struct dm_snapshot *snap)
389 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
390 struct dm_snapshot *snap_merge = NULL;
392 /* Does snapshot need exceptions handed over to it? */
393 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
394 &snap_merge) == 2) ||
396 snap->ti->error = "Snapshot cow pairing for exception "
397 "table handover failed";
402 * If no snap_src was found, snap cannot become a handover
409 * Non-snapshot-merge handover?
411 if (!dm_target_is_snapshot_merge(snap->ti))
415 * Do not allow more than one merging snapshot.
418 snap->ti->error = "A snapshot is already merging.";
422 if (!snap_src->store->type->prepare_merge ||
423 !snap_src->store->type->commit_merge) {
424 snap->ti->error = "Snapshot exception store does not "
425 "support snapshot-merge.";
432 static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
434 struct dm_snapshot *l;
436 /* Sort the list according to chunk size, largest-first smallest-last */
437 list_for_each_entry(l, &o->snapshots, list)
438 if (l->store->chunk_size < s->store->chunk_size)
440 list_add_tail(&s->list, &l->list);
444 * Make a note of the snapshot and its origin so we can look it
445 * up when the origin has a write on it.
447 * Also validate snapshot exception store handovers.
448 * On success, returns 1 if this registration is a handover destination,
449 * otherwise returns 0.
451 static int register_snapshot(struct dm_snapshot *snap)
453 struct origin *o, *new_o = NULL;
454 struct block_device *bdev = snap->origin->bdev;
457 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
461 down_write(&_origins_lock);
463 r = __validate_exception_handover(snap);
469 o = __lookup_origin(bdev);
476 /* Initialise the struct */
477 INIT_LIST_HEAD(&o->snapshots);
483 __insert_snapshot(o, snap);
486 up_write(&_origins_lock);
492 * Move snapshot to correct place in list according to chunk size.
494 static void reregister_snapshot(struct dm_snapshot *s)
496 struct block_device *bdev = s->origin->bdev;
498 down_write(&_origins_lock);
501 __insert_snapshot(__lookup_origin(bdev), s);
503 up_write(&_origins_lock);
506 static void unregister_snapshot(struct dm_snapshot *s)
510 down_write(&_origins_lock);
511 o = __lookup_origin(s->origin->bdev);
514 if (o && list_empty(&o->snapshots)) {
515 list_del(&o->hash_list);
519 up_write(&_origins_lock);
523 * Implementation of the exception hash tables.
524 * The lowest hash_shift bits of the chunk number are ignored, allowing
525 * some consecutive chunks to be grouped together.
527 static int dm_exception_table_init(struct dm_exception_table *et,
528 uint32_t size, unsigned hash_shift)
532 et->hash_shift = hash_shift;
533 et->hash_mask = size - 1;
534 et->table = dm_vcalloc(size, sizeof(struct list_head));
538 for (i = 0; i < size; i++)
539 INIT_LIST_HEAD(et->table + i);
544 static void dm_exception_table_exit(struct dm_exception_table *et,
545 struct kmem_cache *mem)
547 struct list_head *slot;
548 struct dm_exception *ex, *next;
551 size = et->hash_mask + 1;
552 for (i = 0; i < size; i++) {
553 slot = et->table + i;
555 list_for_each_entry_safe (ex, next, slot, hash_list)
556 kmem_cache_free(mem, ex);
562 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
564 return (chunk >> et->hash_shift) & et->hash_mask;
567 static void dm_remove_exception(struct dm_exception *e)
569 list_del(&e->hash_list);
573 * Return the exception data for a sector, or NULL if not
576 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
579 struct list_head *slot;
580 struct dm_exception *e;
582 slot = &et->table[exception_hash(et, chunk)];
583 list_for_each_entry (e, slot, hash_list)
584 if (chunk >= e->old_chunk &&
585 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
591 static struct dm_exception *alloc_completed_exception(void)
593 struct dm_exception *e;
595 e = kmem_cache_alloc(exception_cache, GFP_NOIO);
597 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
602 static void free_completed_exception(struct dm_exception *e)
604 kmem_cache_free(exception_cache, e);
607 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
609 struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
612 atomic_inc(&s->pending_exceptions_count);
618 static void free_pending_exception(struct dm_snap_pending_exception *pe)
620 struct dm_snapshot *s = pe->snap;
622 mempool_free(pe, s->pending_pool);
623 smp_mb__before_atomic_dec();
624 atomic_dec(&s->pending_exceptions_count);
627 static void dm_insert_exception(struct dm_exception_table *eh,
628 struct dm_exception *new_e)
631 struct dm_exception *e = NULL;
633 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
635 /* Add immediately if this table doesn't support consecutive chunks */
639 /* List is ordered by old_chunk */
640 list_for_each_entry_reverse(e, l, hash_list) {
641 /* Insert after an existing chunk? */
642 if (new_e->old_chunk == (e->old_chunk +
643 dm_consecutive_chunk_count(e) + 1) &&
644 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
645 dm_consecutive_chunk_count(e) + 1)) {
646 dm_consecutive_chunk_count_inc(e);
647 free_completed_exception(new_e);
651 /* Insert before an existing chunk? */
652 if (new_e->old_chunk == (e->old_chunk - 1) &&
653 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
654 dm_consecutive_chunk_count_inc(e);
657 free_completed_exception(new_e);
661 if (new_e->old_chunk > e->old_chunk)
666 list_add(&new_e->hash_list, e ? &e->hash_list : l);
670 * Callback used by the exception stores to load exceptions when
673 static int dm_add_exception(void *context, chunk_t old, chunk_t new)
675 struct dm_snapshot *s = context;
676 struct dm_exception *e;
678 e = alloc_completed_exception();
684 /* Consecutive_count is implicitly initialised to zero */
687 dm_insert_exception(&s->complete, e);
693 * Return a minimum chunk size of all snapshots that have the specified origin.
694 * Return zero if the origin has no snapshots.
696 static uint32_t __minimum_chunk_size(struct origin *o)
698 struct dm_snapshot *snap;
699 unsigned chunk_size = 0;
702 list_for_each_entry(snap, &o->snapshots, list)
703 chunk_size = min_not_zero(chunk_size,
704 snap->store->chunk_size);
706 return (uint32_t) chunk_size;
712 static int calc_max_buckets(void)
714 /* use a fixed size of 2MB */
715 unsigned long mem = 2 * 1024 * 1024;
716 mem /= sizeof(struct list_head);
722 * Allocate room for a suitable hash table.
724 static int init_hash_tables(struct dm_snapshot *s)
726 sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
729 * Calculate based on the size of the original volume or
732 cow_dev_size = get_dev_size(s->cow->bdev);
733 origin_dev_size = get_dev_size(s->origin->bdev);
734 max_buckets = calc_max_buckets();
736 hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
737 hash_size = min(hash_size, max_buckets);
741 hash_size = rounddown_pow_of_two(hash_size);
742 if (dm_exception_table_init(&s->complete, hash_size,
743 DM_CHUNK_CONSECUTIVE_BITS))
747 * Allocate hash table for in-flight exceptions
748 * Make this smaller than the real hash table
754 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
755 dm_exception_table_exit(&s->complete, exception_cache);
762 static void merge_shutdown(struct dm_snapshot *s)
764 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
765 smp_mb__after_clear_bit();
766 wake_up_bit(&s->state_bits, RUNNING_MERGE);
769 static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
771 s->first_merging_chunk = 0;
772 s->num_merging_chunks = 0;
774 return bio_list_get(&s->bios_queued_during_merge);
778 * Remove one chunk from the index of completed exceptions.
780 static int __remove_single_exception_chunk(struct dm_snapshot *s,
783 struct dm_exception *e;
785 e = dm_lookup_exception(&s->complete, old_chunk);
787 DMERR("Corruption detected: exception for block %llu is "
788 "on disk but not in memory",
789 (unsigned long long)old_chunk);
794 * If this is the only chunk using this exception, remove exception.
796 if (!dm_consecutive_chunk_count(e)) {
797 dm_remove_exception(e);
798 free_completed_exception(e);
803 * The chunk may be either at the beginning or the end of a
804 * group of consecutive chunks - never in the middle. We are
805 * removing chunks in the opposite order to that in which they
806 * were added, so this should always be true.
807 * Decrement the consecutive chunk counter and adjust the
808 * starting point if necessary.
810 if (old_chunk == e->old_chunk) {
813 } else if (old_chunk != e->old_chunk +
814 dm_consecutive_chunk_count(e)) {
815 DMERR("Attempt to merge block %llu from the "
816 "middle of a chunk range [%llu - %llu]",
817 (unsigned long long)old_chunk,
818 (unsigned long long)e->old_chunk,
820 e->old_chunk + dm_consecutive_chunk_count(e));
824 dm_consecutive_chunk_count_dec(e);
829 static void flush_bios(struct bio *bio);
831 static int remove_single_exception_chunk(struct dm_snapshot *s)
833 struct bio *b = NULL;
835 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
837 down_write(&s->lock);
840 * Process chunks (and associated exceptions) in reverse order
841 * so that dm_consecutive_chunk_count_dec() accounting works.
844 r = __remove_single_exception_chunk(s, old_chunk);
847 } while (old_chunk-- > s->first_merging_chunk);
849 b = __release_queued_bios_after_merge(s);
859 static int origin_write_extent(struct dm_snapshot *merging_snap,
860 sector_t sector, unsigned chunk_size);
862 static void merge_callback(int read_err, unsigned long write_err,
865 static uint64_t read_pending_exceptions_done_count(void)
867 uint64_t pending_exceptions_done;
869 spin_lock(&_pending_exceptions_done_spinlock);
870 pending_exceptions_done = _pending_exceptions_done_count;
871 spin_unlock(&_pending_exceptions_done_spinlock);
873 return pending_exceptions_done;
876 static void increment_pending_exceptions_done_count(void)
878 spin_lock(&_pending_exceptions_done_spinlock);
879 _pending_exceptions_done_count++;
880 spin_unlock(&_pending_exceptions_done_spinlock);
882 wake_up_all(&_pending_exceptions_done);
885 static void snapshot_merge_next_chunks(struct dm_snapshot *s)
887 int i, linear_chunks;
888 chunk_t old_chunk, new_chunk;
889 struct dm_io_region src, dest;
891 uint64_t previous_count;
893 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
894 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
898 * valid flag never changes during merge, so no lock required.
901 DMERR("Snapshot is invalid: can't merge");
905 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
907 if (linear_chunks <= 0) {
908 if (linear_chunks < 0) {
909 DMERR("Read error in exception store: "
910 "shutting down merge");
911 down_write(&s->lock);
918 /* Adjust old_chunk and new_chunk to reflect start of linear region */
919 old_chunk = old_chunk + 1 - linear_chunks;
920 new_chunk = new_chunk + 1 - linear_chunks;
923 * Use one (potentially large) I/O to copy all 'linear_chunks'
924 * from the exception store to the origin
926 io_size = linear_chunks * s->store->chunk_size;
928 dest.bdev = s->origin->bdev;
929 dest.sector = chunk_to_sector(s->store, old_chunk);
930 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
932 src.bdev = s->cow->bdev;
933 src.sector = chunk_to_sector(s->store, new_chunk);
934 src.count = dest.count;
937 * Reallocate any exceptions needed in other snapshots then
938 * wait for the pending exceptions to complete.
939 * Each time any pending exception (globally on the system)
940 * completes we are woken and repeat the process to find out
941 * if we can proceed. While this may not seem a particularly
942 * efficient algorithm, it is not expected to have any
943 * significant impact on performance.
945 previous_count = read_pending_exceptions_done_count();
946 while (origin_write_extent(s, dest.sector, io_size)) {
947 wait_event(_pending_exceptions_done,
948 (read_pending_exceptions_done_count() !=
950 /* Retry after the wait, until all exceptions are done. */
951 previous_count = read_pending_exceptions_done_count();
954 down_write(&s->lock);
955 s->first_merging_chunk = old_chunk;
956 s->num_merging_chunks = linear_chunks;
959 /* Wait until writes to all 'linear_chunks' drain */
960 for (i = 0; i < linear_chunks; i++)
961 __check_for_conflicting_io(s, old_chunk + i);
963 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
970 static void error_bios(struct bio *bio);
972 static void merge_callback(int read_err, unsigned long write_err, void *context)
974 struct dm_snapshot *s = context;
975 struct bio *b = NULL;
977 if (read_err || write_err) {
979 DMERR("Read error: shutting down merge.");
981 DMERR("Write error: shutting down merge.");
985 if (s->store->type->commit_merge(s->store,
986 s->num_merging_chunks) < 0) {
987 DMERR("Write error in exception store: shutting down merge");
991 if (remove_single_exception_chunk(s) < 0)
994 snapshot_merge_next_chunks(s);
999 down_write(&s->lock);
1000 s->merge_failed = 1;
1001 b = __release_queued_bios_after_merge(s);
1008 static void start_merge(struct dm_snapshot *s)
1010 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1011 snapshot_merge_next_chunks(s);
1014 static int wait_schedule(void *ptr)
1022 * Stop the merging process and wait until it finishes.
1024 static void stop_merge(struct dm_snapshot *s)
1026 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1027 wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule,
1028 TASK_UNINTERRUPTIBLE);
1029 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1033 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
1035 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1037 struct dm_snapshot *s;
1040 char *origin_path, *cow_path;
1041 unsigned args_used, num_flush_requests = 1;
1042 fmode_t origin_mode = FMODE_READ;
1045 ti->error = "requires exactly 4 arguments";
1050 if (dm_target_is_snapshot_merge(ti)) {
1051 num_flush_requests = 2;
1052 origin_mode = FMODE_WRITE;
1055 s = kmalloc(sizeof(*s), GFP_KERNEL);
1057 ti->error = "Cannot allocate private snapshot structure";
1062 origin_path = argv[0];
1066 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1068 ti->error = "Cannot get origin device";
1076 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1078 ti->error = "Cannot get COW device";
1082 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1084 ti->error = "Couldn't create exception store";
1095 atomic_set(&s->pending_exceptions_count, 0);
1096 init_rwsem(&s->lock);
1097 INIT_LIST_HEAD(&s->list);
1098 spin_lock_init(&s->pe_lock);
1100 s->merge_failed = 0;
1101 s->first_merging_chunk = 0;
1102 s->num_merging_chunks = 0;
1103 bio_list_init(&s->bios_queued_during_merge);
1105 /* Allocate hash table for COW data */
1106 if (init_hash_tables(s)) {
1107 ti->error = "Unable to allocate hash table space";
1109 goto bad_hash_tables;
1112 s->kcopyd_client = dm_kcopyd_client_create();
1113 if (IS_ERR(s->kcopyd_client)) {
1114 r = PTR_ERR(s->kcopyd_client);
1115 ti->error = "Could not create kcopyd client";
1119 s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
1120 if (!s->pending_pool) {
1121 ti->error = "Could not allocate mempool for pending exceptions";
1122 goto bad_pending_pool;
1125 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1126 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1128 spin_lock_init(&s->tracked_chunk_lock);
1131 ti->num_flush_requests = num_flush_requests;
1132 ti->per_bio_data_size = sizeof(struct dm_snap_tracked_chunk);
1134 /* Add snapshot to the list of snapshots for this origin */
1135 /* Exceptions aren't triggered till snapshot_resume() is called */
1136 r = register_snapshot(s);
1138 ti->error = "Snapshot origin struct allocation failed";
1139 goto bad_load_and_register;
1141 /* invalid handover, register_snapshot has set ti->error */
1142 goto bad_load_and_register;
1146 * Metadata must only be loaded into one table at once, so skip this
1147 * if metadata will be handed over during resume.
1148 * Chunk size will be set during the handover - set it to zero to
1149 * ensure it's ignored.
1152 s->store->chunk_size = 0;
1156 r = s->store->type->read_metadata(s->store, dm_add_exception,
1159 ti->error = "Failed to read snapshot metadata";
1160 goto bad_read_metadata;
1163 DMWARN("Snapshot is marked invalid.");
1166 if (!s->store->chunk_size) {
1167 ti->error = "Chunk size not set";
1168 goto bad_read_metadata;
1171 r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1173 goto bad_read_metadata;
1178 unregister_snapshot(s);
1180 bad_load_and_register:
1181 mempool_destroy(s->pending_pool);
1184 dm_kcopyd_client_destroy(s->kcopyd_client);
1187 dm_exception_table_exit(&s->pending, pending_cache);
1188 dm_exception_table_exit(&s->complete, exception_cache);
1191 dm_exception_store_destroy(s->store);
1194 dm_put_device(ti, s->cow);
1197 dm_put_device(ti, s->origin);
1206 static void __free_exceptions(struct dm_snapshot *s)
1208 dm_kcopyd_client_destroy(s->kcopyd_client);
1209 s->kcopyd_client = NULL;
1211 dm_exception_table_exit(&s->pending, pending_cache);
1212 dm_exception_table_exit(&s->complete, exception_cache);
1215 static void __handover_exceptions(struct dm_snapshot *snap_src,
1216 struct dm_snapshot *snap_dest)
1219 struct dm_exception_table table_swap;
1220 struct dm_exception_store *store_swap;
1224 * Swap all snapshot context information between the two instances.
1226 u.table_swap = snap_dest->complete;
1227 snap_dest->complete = snap_src->complete;
1228 snap_src->complete = u.table_swap;
1230 u.store_swap = snap_dest->store;
1231 snap_dest->store = snap_src->store;
1232 snap_src->store = u.store_swap;
1234 snap_dest->store->snap = snap_dest;
1235 snap_src->store->snap = snap_src;
1237 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1238 snap_dest->valid = snap_src->valid;
1241 * Set source invalid to ensure it receives no further I/O.
1243 snap_src->valid = 0;
1246 static void snapshot_dtr(struct dm_target *ti)
1248 #ifdef CONFIG_DM_DEBUG
1251 struct dm_snapshot *s = ti->private;
1252 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1254 down_read(&_origins_lock);
1255 /* Check whether exception handover must be cancelled */
1256 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1257 if (snap_src && snap_dest && (s == snap_src)) {
1258 down_write(&snap_dest->lock);
1259 snap_dest->valid = 0;
1260 up_write(&snap_dest->lock);
1261 DMERR("Cancelling snapshot handover.");
1263 up_read(&_origins_lock);
1265 if (dm_target_is_snapshot_merge(ti))
1268 /* Prevent further origin writes from using this snapshot. */
1269 /* After this returns there can be no new kcopyd jobs. */
1270 unregister_snapshot(s);
1272 while (atomic_read(&s->pending_exceptions_count))
1275 * Ensure instructions in mempool_destroy aren't reordered
1276 * before atomic_read.
1280 #ifdef CONFIG_DM_DEBUG
1281 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1282 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1285 __free_exceptions(s);
1287 mempool_destroy(s->pending_pool);
1289 dm_exception_store_destroy(s->store);
1291 dm_put_device(ti, s->cow);
1293 dm_put_device(ti, s->origin);
1299 * Flush a list of buffers.
1301 static void flush_bios(struct bio *bio)
1307 bio->bi_next = NULL;
1308 generic_make_request(bio);
1313 static int do_origin(struct dm_dev *origin, struct bio *bio);
1316 * Flush a list of buffers.
1318 static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1325 bio->bi_next = NULL;
1326 r = do_origin(s->origin, bio);
1327 if (r == DM_MAPIO_REMAPPED)
1328 generic_make_request(bio);
1334 * Error a list of buffers.
1336 static void error_bios(struct bio *bio)
1342 bio->bi_next = NULL;
1348 static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1354 DMERR("Invalidating snapshot: Error reading/writing.");
1355 else if (err == -ENOMEM)
1356 DMERR("Invalidating snapshot: Unable to allocate exception.");
1358 if (s->store->type->drop_snapshot)
1359 s->store->type->drop_snapshot(s->store);
1363 dm_table_event(s->ti->table);
1366 static void pending_complete(struct dm_snap_pending_exception *pe, int success)
1368 struct dm_exception *e;
1369 struct dm_snapshot *s = pe->snap;
1370 struct bio *origin_bios = NULL;
1371 struct bio *snapshot_bios = NULL;
1372 struct bio *full_bio = NULL;
1376 /* Read/write error - snapshot is unusable */
1377 down_write(&s->lock);
1378 __invalidate_snapshot(s, -EIO);
1383 e = alloc_completed_exception();
1385 down_write(&s->lock);
1386 __invalidate_snapshot(s, -ENOMEM);
1392 down_write(&s->lock);
1394 free_completed_exception(e);
1399 /* Check for conflicting reads */
1400 __check_for_conflicting_io(s, pe->e.old_chunk);
1403 * Add a proper exception, and remove the
1404 * in-flight exception from the list.
1406 dm_insert_exception(&s->complete, e);
1409 dm_remove_exception(&pe->e);
1410 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1411 origin_bios = bio_list_get(&pe->origin_bios);
1412 full_bio = pe->full_bio;
1414 full_bio->bi_end_io = pe->full_bio_end_io;
1415 full_bio->bi_private = pe->full_bio_private;
1417 free_pending_exception(pe);
1419 increment_pending_exceptions_done_count();
1423 /* Submit any pending write bios */
1426 bio_io_error(full_bio);
1427 error_bios(snapshot_bios);
1430 bio_endio(full_bio, 0);
1431 flush_bios(snapshot_bios);
1434 retry_origin_bios(s, origin_bios);
1437 static void commit_callback(void *context, int success)
1439 struct dm_snap_pending_exception *pe = context;
1441 pending_complete(pe, success);
1445 * Called when the copy I/O has finished. kcopyd actually runs
1446 * this code so don't block.
1448 static void copy_callback(int read_err, unsigned long write_err, void *context)
1450 struct dm_snap_pending_exception *pe = context;
1451 struct dm_snapshot *s = pe->snap;
1453 if (read_err || write_err)
1454 pending_complete(pe, 0);
1457 /* Update the metadata if we are persistent */
1458 s->store->type->commit_exception(s->store, &pe->e,
1459 commit_callback, pe);
1463 * Dispatches the copy operation to kcopyd.
1465 static void start_copy(struct dm_snap_pending_exception *pe)
1467 struct dm_snapshot *s = pe->snap;
1468 struct dm_io_region src, dest;
1469 struct block_device *bdev = s->origin->bdev;
1472 dev_size = get_dev_size(bdev);
1475 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1476 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1478 dest.bdev = s->cow->bdev;
1479 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1480 dest.count = src.count;
1482 /* Hand over to kcopyd */
1483 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1486 static void full_bio_end_io(struct bio *bio, int error)
1488 void *callback_data = bio->bi_private;
1490 dm_kcopyd_do_callback(callback_data, 0, error ? 1 : 0);
1493 static void start_full_bio(struct dm_snap_pending_exception *pe,
1496 struct dm_snapshot *s = pe->snap;
1497 void *callback_data;
1500 pe->full_bio_end_io = bio->bi_end_io;
1501 pe->full_bio_private = bio->bi_private;
1503 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1506 bio->bi_end_io = full_bio_end_io;
1507 bio->bi_private = callback_data;
1509 generic_make_request(bio);
1512 static struct dm_snap_pending_exception *
1513 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1515 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1520 return container_of(e, struct dm_snap_pending_exception, e);
1524 * Looks to see if this snapshot already has a pending exception
1525 * for this chunk, otherwise it allocates a new one and inserts
1526 * it into the pending table.
1528 * NOTE: a write lock must be held on snap->lock before calling
1531 static struct dm_snap_pending_exception *
1532 __find_pending_exception(struct dm_snapshot *s,
1533 struct dm_snap_pending_exception *pe, chunk_t chunk)
1535 struct dm_snap_pending_exception *pe2;
1537 pe2 = __lookup_pending_exception(s, chunk);
1539 free_pending_exception(pe);
1543 pe->e.old_chunk = chunk;
1544 bio_list_init(&pe->origin_bios);
1545 bio_list_init(&pe->snapshot_bios);
1547 pe->full_bio = NULL;
1549 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1550 free_pending_exception(pe);
1554 dm_insert_exception(&s->pending, &pe->e);
1559 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1560 struct bio *bio, chunk_t chunk)
1562 bio->bi_bdev = s->cow->bdev;
1563 bio->bi_sector = chunk_to_sector(s->store,
1564 dm_chunk_number(e->new_chunk) +
1565 (chunk - e->old_chunk)) +
1567 s->store->chunk_mask);
1570 static int snapshot_map(struct dm_target *ti, struct bio *bio)
1572 struct dm_exception *e;
1573 struct dm_snapshot *s = ti->private;
1574 int r = DM_MAPIO_REMAPPED;
1576 struct dm_snap_pending_exception *pe = NULL;
1578 init_tracked_chunk(bio);
1580 if (bio->bi_rw & REQ_FLUSH) {
1581 bio->bi_bdev = s->cow->bdev;
1582 return DM_MAPIO_REMAPPED;
1585 chunk = sector_to_chunk(s->store, bio->bi_sector);
1587 /* Full snapshots are not usable */
1588 /* To get here the table must be live so s->active is always set. */
1592 /* FIXME: should only take write lock if we need
1593 * to copy an exception */
1594 down_write(&s->lock);
1601 /* If the block is already remapped - use that, else remap it */
1602 e = dm_lookup_exception(&s->complete, chunk);
1604 remap_exception(s, e, bio, chunk);
1609 * Write to snapshot - higher level takes care of RW/RO
1610 * flags so we should only get this if we are
1613 if (bio_rw(bio) == WRITE) {
1614 pe = __lookup_pending_exception(s, chunk);
1617 pe = alloc_pending_exception(s);
1618 down_write(&s->lock);
1621 free_pending_exception(pe);
1626 e = dm_lookup_exception(&s->complete, chunk);
1628 free_pending_exception(pe);
1629 remap_exception(s, e, bio, chunk);
1633 pe = __find_pending_exception(s, pe, chunk);
1635 __invalidate_snapshot(s, -ENOMEM);
1641 remap_exception(s, &pe->e, bio, chunk);
1643 r = DM_MAPIO_SUBMITTED;
1646 bio->bi_size == (s->store->chunk_size << SECTOR_SHIFT)) {
1649 start_full_bio(pe, bio);
1653 bio_list_add(&pe->snapshot_bios, bio);
1656 /* this is protected by snap->lock */
1663 bio->bi_bdev = s->origin->bdev;
1664 track_chunk(s, bio, chunk);
1674 * A snapshot-merge target behaves like a combination of a snapshot
1675 * target and a snapshot-origin target. It only generates new
1676 * exceptions in other snapshots and not in the one that is being
1679 * For each chunk, if there is an existing exception, it is used to
1680 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
1681 * which in turn might generate exceptions in other snapshots.
1682 * If merging is currently taking place on the chunk in question, the
1683 * I/O is deferred by adding it to s->bios_queued_during_merge.
1685 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
1687 struct dm_exception *e;
1688 struct dm_snapshot *s = ti->private;
1689 int r = DM_MAPIO_REMAPPED;
1692 init_tracked_chunk(bio);
1694 if (bio->bi_rw & REQ_FLUSH) {
1695 if (!dm_bio_get_target_request_nr(bio))
1696 bio->bi_bdev = s->origin->bdev;
1698 bio->bi_bdev = s->cow->bdev;
1699 return DM_MAPIO_REMAPPED;
1702 chunk = sector_to_chunk(s->store, bio->bi_sector);
1704 down_write(&s->lock);
1706 /* Full merging snapshots are redirected to the origin */
1708 goto redirect_to_origin;
1710 /* If the block is already remapped - use that */
1711 e = dm_lookup_exception(&s->complete, chunk);
1713 /* Queue writes overlapping with chunks being merged */
1714 if (bio_rw(bio) == WRITE &&
1715 chunk >= s->first_merging_chunk &&
1716 chunk < (s->first_merging_chunk +
1717 s->num_merging_chunks)) {
1718 bio->bi_bdev = s->origin->bdev;
1719 bio_list_add(&s->bios_queued_during_merge, bio);
1720 r = DM_MAPIO_SUBMITTED;
1724 remap_exception(s, e, bio, chunk);
1726 if (bio_rw(bio) == WRITE)
1727 track_chunk(s, bio, chunk);
1732 bio->bi_bdev = s->origin->bdev;
1734 if (bio_rw(bio) == WRITE) {
1736 return do_origin(s->origin, bio);
1745 static int snapshot_end_io(struct dm_target *ti, struct bio *bio, int error)
1747 struct dm_snapshot *s = ti->private;
1749 if (is_bio_tracked(bio))
1750 stop_tracking_chunk(s, bio);
1755 static void snapshot_merge_presuspend(struct dm_target *ti)
1757 struct dm_snapshot *s = ti->private;
1762 static int snapshot_preresume(struct dm_target *ti)
1765 struct dm_snapshot *s = ti->private;
1766 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1768 down_read(&_origins_lock);
1769 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1770 if (snap_src && snap_dest) {
1771 down_read(&snap_src->lock);
1772 if (s == snap_src) {
1773 DMERR("Unable to resume snapshot source until "
1774 "handover completes.");
1776 } else if (!dm_suspended(snap_src->ti)) {
1777 DMERR("Unable to perform snapshot handover until "
1778 "source is suspended.");
1781 up_read(&snap_src->lock);
1783 up_read(&_origins_lock);
1788 static void snapshot_resume(struct dm_target *ti)
1790 struct dm_snapshot *s = ti->private;
1791 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1793 down_read(&_origins_lock);
1794 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1795 if (snap_src && snap_dest) {
1796 down_write(&snap_src->lock);
1797 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1798 __handover_exceptions(snap_src, snap_dest);
1799 up_write(&snap_dest->lock);
1800 up_write(&snap_src->lock);
1802 up_read(&_origins_lock);
1804 /* Now we have correct chunk size, reregister */
1805 reregister_snapshot(s);
1807 down_write(&s->lock);
1812 static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
1814 uint32_t min_chunksize;
1816 down_read(&_origins_lock);
1817 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
1818 up_read(&_origins_lock);
1820 return min_chunksize;
1823 static void snapshot_merge_resume(struct dm_target *ti)
1825 struct dm_snapshot *s = ti->private;
1828 * Handover exceptions from existing snapshot.
1830 snapshot_resume(ti);
1833 * snapshot-merge acts as an origin, so set ti->max_io_len
1835 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
1840 static int snapshot_status(struct dm_target *ti, status_type_t type,
1841 unsigned status_flags, char *result, unsigned maxlen)
1844 struct dm_snapshot *snap = ti->private;
1847 case STATUSTYPE_INFO:
1849 down_write(&snap->lock);
1853 else if (snap->merge_failed)
1854 DMEMIT("Merge failed");
1856 if (snap->store->type->usage) {
1857 sector_t total_sectors, sectors_allocated,
1859 snap->store->type->usage(snap->store,
1863 DMEMIT("%llu/%llu %llu",
1864 (unsigned long long)sectors_allocated,
1865 (unsigned long long)total_sectors,
1866 (unsigned long long)metadata_sectors);
1872 up_write(&snap->lock);
1876 case STATUSTYPE_TABLE:
1878 * kdevname returns a static pointer so we need
1879 * to make private copies if the output is to
1882 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
1883 snap->store->type->status(snap->store, type, result + sz,
1891 static int snapshot_iterate_devices(struct dm_target *ti,
1892 iterate_devices_callout_fn fn, void *data)
1894 struct dm_snapshot *snap = ti->private;
1897 r = fn(ti, snap->origin, 0, ti->len, data);
1900 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
1906 /*-----------------------------------------------------------------
1908 *---------------------------------------------------------------*/
1911 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
1912 * supplied bio was ignored. The caller may submit it immediately.
1913 * (No remapping actually occurs as the origin is always a direct linear
1916 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
1917 * and any supplied bio is added to a list to be submitted once all
1918 * the necessary exceptions exist.
1920 static int __origin_write(struct list_head *snapshots, sector_t sector,
1923 int r = DM_MAPIO_REMAPPED;
1924 struct dm_snapshot *snap;
1925 struct dm_exception *e;
1926 struct dm_snap_pending_exception *pe;
1927 struct dm_snap_pending_exception *pe_to_start_now = NULL;
1928 struct dm_snap_pending_exception *pe_to_start_last = NULL;
1931 /* Do all the snapshots on this origin */
1932 list_for_each_entry (snap, snapshots, list) {
1934 * Don't make new exceptions in a merging snapshot
1935 * because it has effectively been deleted
1937 if (dm_target_is_snapshot_merge(snap->ti))
1940 down_write(&snap->lock);
1942 /* Only deal with valid and active snapshots */
1943 if (!snap->valid || !snap->active)
1946 /* Nothing to do if writing beyond end of snapshot */
1947 if (sector >= dm_table_get_size(snap->ti->table))
1951 * Remember, different snapshots can have
1952 * different chunk sizes.
1954 chunk = sector_to_chunk(snap->store, sector);
1957 * Check exception table to see if block
1958 * is already remapped in this snapshot
1959 * and trigger an exception if not.
1961 e = dm_lookup_exception(&snap->complete, chunk);
1965 pe = __lookup_pending_exception(snap, chunk);
1967 up_write(&snap->lock);
1968 pe = alloc_pending_exception(snap);
1969 down_write(&snap->lock);
1972 free_pending_exception(pe);
1976 e = dm_lookup_exception(&snap->complete, chunk);
1978 free_pending_exception(pe);
1982 pe = __find_pending_exception(snap, pe, chunk);
1984 __invalidate_snapshot(snap, -ENOMEM);
1989 r = DM_MAPIO_SUBMITTED;
1992 * If an origin bio was supplied, queue it to wait for the
1993 * completion of this exception, and start this one last,
1994 * at the end of the function.
1997 bio_list_add(&pe->origin_bios, bio);
2002 pe_to_start_last = pe;
2008 pe_to_start_now = pe;
2012 up_write(&snap->lock);
2014 if (pe_to_start_now) {
2015 start_copy(pe_to_start_now);
2016 pe_to_start_now = NULL;
2021 * Submit the exception against which the bio is queued last,
2022 * to give the other exceptions a head start.
2024 if (pe_to_start_last)
2025 start_copy(pe_to_start_last);
2031 * Called on a write from the origin driver.
2033 static int do_origin(struct dm_dev *origin, struct bio *bio)
2036 int r = DM_MAPIO_REMAPPED;
2038 down_read(&_origins_lock);
2039 o = __lookup_origin(origin->bdev);
2041 r = __origin_write(&o->snapshots, bio->bi_sector, bio);
2042 up_read(&_origins_lock);
2048 * Trigger exceptions in all non-merging snapshots.
2050 * The chunk size of the merging snapshot may be larger than the chunk
2051 * size of some other snapshot so we may need to reallocate multiple
2052 * chunks in other snapshots.
2054 * We scan all the overlapping exceptions in the other snapshots.
2055 * Returns 1 if anything was reallocated and must be waited for,
2056 * otherwise returns 0.
2058 * size must be a multiple of merging_snap's chunk_size.
2060 static int origin_write_extent(struct dm_snapshot *merging_snap,
2061 sector_t sector, unsigned size)
2068 * The origin's __minimum_chunk_size() got stored in max_io_len
2069 * by snapshot_merge_resume().
2071 down_read(&_origins_lock);
2072 o = __lookup_origin(merging_snap->origin->bdev);
2073 for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2074 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2077 up_read(&_origins_lock);
2083 * Origin: maps a linear range of a device, with hooks for snapshotting.
2087 * Construct an origin mapping: <dev_path>
2088 * The context for an origin is merely a 'struct dm_dev *'
2089 * pointing to the real device.
2091 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2097 ti->error = "origin: incorrect number of arguments";
2101 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dev);
2103 ti->error = "Cannot get target device";
2108 ti->num_flush_requests = 1;
2113 static void origin_dtr(struct dm_target *ti)
2115 struct dm_dev *dev = ti->private;
2116 dm_put_device(ti, dev);
2119 static int origin_map(struct dm_target *ti, struct bio *bio)
2121 struct dm_dev *dev = ti->private;
2122 bio->bi_bdev = dev->bdev;
2124 if (bio->bi_rw & REQ_FLUSH)
2125 return DM_MAPIO_REMAPPED;
2127 /* Only tell snapshots if this is a write */
2128 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
2132 * Set the target "max_io_len" field to the minimum of all the snapshots'
2135 static void origin_resume(struct dm_target *ti)
2137 struct dm_dev *dev = ti->private;
2139 ti->max_io_len = get_origin_minimum_chunksize(dev->bdev);
2142 static int origin_status(struct dm_target *ti, status_type_t type,
2143 unsigned status_flags, char *result, unsigned maxlen)
2145 struct dm_dev *dev = ti->private;
2148 case STATUSTYPE_INFO:
2152 case STATUSTYPE_TABLE:
2153 snprintf(result, maxlen, "%s", dev->name);
2160 static int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
2161 struct bio_vec *biovec, int max_size)
2163 struct dm_dev *dev = ti->private;
2164 struct request_queue *q = bdev_get_queue(dev->bdev);
2166 if (!q->merge_bvec_fn)
2169 bvm->bi_bdev = dev->bdev;
2171 return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2174 static int origin_iterate_devices(struct dm_target *ti,
2175 iterate_devices_callout_fn fn, void *data)
2177 struct dm_dev *dev = ti->private;
2179 return fn(ti, dev, 0, ti->len, data);
2182 static struct target_type origin_target = {
2183 .name = "snapshot-origin",
2184 .version = {1, 8, 0},
2185 .module = THIS_MODULE,
2189 .resume = origin_resume,
2190 .status = origin_status,
2191 .merge = origin_merge,
2192 .iterate_devices = origin_iterate_devices,
2195 static struct target_type snapshot_target = {
2197 .version = {1, 11, 0},
2198 .module = THIS_MODULE,
2199 .ctr = snapshot_ctr,
2200 .dtr = snapshot_dtr,
2201 .map = snapshot_map,
2202 .end_io = snapshot_end_io,
2203 .preresume = snapshot_preresume,
2204 .resume = snapshot_resume,
2205 .status = snapshot_status,
2206 .iterate_devices = snapshot_iterate_devices,
2209 static struct target_type merge_target = {
2210 .name = dm_snapshot_merge_target_name,
2211 .version = {1, 2, 0},
2212 .module = THIS_MODULE,
2213 .ctr = snapshot_ctr,
2214 .dtr = snapshot_dtr,
2215 .map = snapshot_merge_map,
2216 .end_io = snapshot_end_io,
2217 .presuspend = snapshot_merge_presuspend,
2218 .preresume = snapshot_preresume,
2219 .resume = snapshot_merge_resume,
2220 .status = snapshot_status,
2221 .iterate_devices = snapshot_iterate_devices,
2224 static int __init dm_snapshot_init(void)
2228 r = dm_exception_store_init();
2230 DMERR("Failed to initialize exception stores");
2234 r = dm_register_target(&snapshot_target);
2236 DMERR("snapshot target register failed %d", r);
2237 goto bad_register_snapshot_target;
2240 r = dm_register_target(&origin_target);
2242 DMERR("Origin target register failed %d", r);
2243 goto bad_register_origin_target;
2246 r = dm_register_target(&merge_target);
2248 DMERR("Merge target register failed %d", r);
2249 goto bad_register_merge_target;
2252 r = init_origin_hash();
2254 DMERR("init_origin_hash failed.");
2255 goto bad_origin_hash;
2258 exception_cache = KMEM_CACHE(dm_exception, 0);
2259 if (!exception_cache) {
2260 DMERR("Couldn't create exception cache.");
2262 goto bad_exception_cache;
2265 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2266 if (!pending_cache) {
2267 DMERR("Couldn't create pending cache.");
2269 goto bad_pending_cache;
2275 kmem_cache_destroy(exception_cache);
2276 bad_exception_cache:
2279 dm_unregister_target(&merge_target);
2280 bad_register_merge_target:
2281 dm_unregister_target(&origin_target);
2282 bad_register_origin_target:
2283 dm_unregister_target(&snapshot_target);
2284 bad_register_snapshot_target:
2285 dm_exception_store_exit();
2290 static void __exit dm_snapshot_exit(void)
2292 dm_unregister_target(&snapshot_target);
2293 dm_unregister_target(&origin_target);
2294 dm_unregister_target(&merge_target);
2297 kmem_cache_destroy(pending_cache);
2298 kmem_cache_destroy(exception_cache);
2300 dm_exception_store_exit();
2304 module_init(dm_snapshot_init);
2305 module_exit(dm_snapshot_exit);
2307 MODULE_DESCRIPTION(DM_NAME " snapshot target");
2308 MODULE_AUTHOR("Joe Thornber");
2309 MODULE_LICENSE("GPL");