sfc: Don't use enums as a bitmask.
[zen-stable.git] / drivers / md / dm-snap.c
bloba2d330942cb29f824c029973ae12a98a2d39efec
1 /*
2 * dm-snapshot.c
4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
6 * This file is released under the GPL.
7 */
9 #include <linux/blkdev.h>
10 #include <linux/device-mapper.h>
11 #include <linux/delay.h>
12 #include <linux/fs.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 percentage increment we will wake up users at
35 #define WAKE_UP_PERCENT 5
38 * kcopyd priority of snapshot operations
40 #define SNAPSHOT_COPY_PRIORITY 2
43 * Reserve 1MB for each snapshot initially (with minimum of 1 page).
45 #define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
48 * The size of the mempool used to track chunks in use.
50 #define MIN_IOS 256
52 #define DM_TRACKED_CHUNK_HASH_SIZE 16
53 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
54 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
56 struct dm_exception_table {
57 uint32_t hash_mask;
58 unsigned hash_shift;
59 struct list_head *table;
62 struct dm_snapshot {
63 struct rw_semaphore lock;
65 struct dm_dev *origin;
66 struct dm_dev *cow;
68 struct dm_target *ti;
70 /* List of snapshots per Origin */
71 struct list_head list;
74 * You can't use a snapshot if this is 0 (e.g. if full).
75 * A snapshot-merge target never clears this.
77 int valid;
79 /* Origin writes don't trigger exceptions until this is set */
80 int active;
82 atomic_t pending_exceptions_count;
84 mempool_t *pending_pool;
86 struct dm_exception_table pending;
87 struct dm_exception_table complete;
90 * pe_lock protects all pending_exception operations and access
91 * as well as the snapshot_bios list.
93 spinlock_t pe_lock;
95 /* Chunks with outstanding reads */
96 spinlock_t tracked_chunk_lock;
97 mempool_t *tracked_chunk_pool;
98 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
100 /* The on disk metadata handler */
101 struct dm_exception_store *store;
103 struct dm_kcopyd_client *kcopyd_client;
105 /* Wait for events based on state_bits */
106 unsigned long state_bits;
108 /* Range of chunks currently being merged. */
109 chunk_t first_merging_chunk;
110 int num_merging_chunks;
113 * The merge operation failed if this flag is set.
114 * Failure modes are handled as follows:
115 * - I/O error reading the header
116 * => don't load the target; abort.
117 * - Header does not have "valid" flag set
118 * => use the origin; forget about the snapshot.
119 * - I/O error when reading exceptions
120 * => don't load the target; abort.
121 * (We can't use the intermediate origin state.)
122 * - I/O error while merging
123 * => stop merging; set merge_failed; process I/O normally.
125 int merge_failed;
128 * Incoming bios that overlap with chunks being merged must wait
129 * for them to be committed.
131 struct bio_list bios_queued_during_merge;
135 * state_bits:
136 * RUNNING_MERGE - Merge operation is in progress.
137 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
138 * cleared afterwards.
140 #define RUNNING_MERGE 0
141 #define SHUTDOWN_MERGE 1
143 struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
145 return s->origin;
147 EXPORT_SYMBOL(dm_snap_origin);
149 struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
151 return s->cow;
153 EXPORT_SYMBOL(dm_snap_cow);
155 static sector_t chunk_to_sector(struct dm_exception_store *store,
156 chunk_t chunk)
158 return chunk << store->chunk_shift;
161 static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
164 * There is only ever one instance of a particular block
165 * device so we can compare pointers safely.
167 return lhs == rhs;
170 struct dm_snap_pending_exception {
171 struct dm_exception e;
174 * Origin buffers waiting for this to complete are held
175 * in a bio list
177 struct bio_list origin_bios;
178 struct bio_list snapshot_bios;
180 /* Pointer back to snapshot context */
181 struct dm_snapshot *snap;
184 * 1 indicates the exception has already been sent to
185 * kcopyd.
187 int started;
191 * Hash table mapping origin volumes to lists of snapshots and
192 * a lock to protect it
194 static struct kmem_cache *exception_cache;
195 static struct kmem_cache *pending_cache;
197 struct dm_snap_tracked_chunk {
198 struct hlist_node node;
199 chunk_t chunk;
202 static struct kmem_cache *tracked_chunk_cache;
204 static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
205 chunk_t chunk)
207 struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
208 GFP_NOIO);
209 unsigned long flags;
211 c->chunk = chunk;
213 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
214 hlist_add_head(&c->node,
215 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
216 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
218 return c;
221 static void stop_tracking_chunk(struct dm_snapshot *s,
222 struct dm_snap_tracked_chunk *c)
224 unsigned long flags;
226 spin_lock_irqsave(&s->tracked_chunk_lock, flags);
227 hlist_del(&c->node);
228 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
230 mempool_free(c, s->tracked_chunk_pool);
233 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
235 struct dm_snap_tracked_chunk *c;
236 struct hlist_node *hn;
237 int found = 0;
239 spin_lock_irq(&s->tracked_chunk_lock);
241 hlist_for_each_entry(c, hn,
242 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
243 if (c->chunk == chunk) {
244 found = 1;
245 break;
249 spin_unlock_irq(&s->tracked_chunk_lock);
251 return found;
255 * This conflicting I/O is extremely improbable in the caller,
256 * so msleep(1) is sufficient and there is no need for a wait queue.
258 static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
260 while (__chunk_is_tracked(s, chunk))
261 msleep(1);
265 * One of these per registered origin, held in the snapshot_origins hash
267 struct origin {
268 /* The origin device */
269 struct block_device *bdev;
271 struct list_head hash_list;
273 /* List of snapshots for this origin */
274 struct list_head snapshots;
278 * Size of the hash table for origin volumes. If we make this
279 * the size of the minors list then it should be nearly perfect
281 #define ORIGIN_HASH_SIZE 256
282 #define ORIGIN_MASK 0xFF
283 static struct list_head *_origins;
284 static struct rw_semaphore _origins_lock;
286 static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
287 static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
288 static uint64_t _pending_exceptions_done_count;
290 static int init_origin_hash(void)
292 int i;
294 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
295 GFP_KERNEL);
296 if (!_origins) {
297 DMERR("unable to allocate memory");
298 return -ENOMEM;
301 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
302 INIT_LIST_HEAD(_origins + i);
303 init_rwsem(&_origins_lock);
305 return 0;
308 static void exit_origin_hash(void)
310 kfree(_origins);
313 static unsigned origin_hash(struct block_device *bdev)
315 return bdev->bd_dev & ORIGIN_MASK;
318 static struct origin *__lookup_origin(struct block_device *origin)
320 struct list_head *ol;
321 struct origin *o;
323 ol = &_origins[origin_hash(origin)];
324 list_for_each_entry (o, ol, hash_list)
325 if (bdev_equal(o->bdev, origin))
326 return o;
328 return NULL;
331 static void __insert_origin(struct origin *o)
333 struct list_head *sl = &_origins[origin_hash(o->bdev)];
334 list_add_tail(&o->hash_list, sl);
338 * _origins_lock must be held when calling this function.
339 * Returns number of snapshots registered using the supplied cow device, plus:
340 * snap_src - a snapshot suitable for use as a source of exception handover
341 * snap_dest - a snapshot capable of receiving exception handover.
342 * snap_merge - an existing snapshot-merge target linked to the same origin.
343 * There can be at most one snapshot-merge target. The parameter is optional.
345 * Possible return values and states of snap_src and snap_dest.
346 * 0: NULL, NULL - first new snapshot
347 * 1: snap_src, NULL - normal snapshot
348 * 2: snap_src, snap_dest - waiting for handover
349 * 2: snap_src, NULL - handed over, waiting for old to be deleted
350 * 1: NULL, snap_dest - source got destroyed without handover
352 static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
353 struct dm_snapshot **snap_src,
354 struct dm_snapshot **snap_dest,
355 struct dm_snapshot **snap_merge)
357 struct dm_snapshot *s;
358 struct origin *o;
359 int count = 0;
360 int active;
362 o = __lookup_origin(snap->origin->bdev);
363 if (!o)
364 goto out;
366 list_for_each_entry(s, &o->snapshots, list) {
367 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
368 *snap_merge = s;
369 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
370 continue;
372 down_read(&s->lock);
373 active = s->active;
374 up_read(&s->lock);
376 if (active) {
377 if (snap_src)
378 *snap_src = s;
379 } else if (snap_dest)
380 *snap_dest = s;
382 count++;
385 out:
386 return count;
390 * On success, returns 1 if this snapshot is a handover destination,
391 * otherwise returns 0.
393 static int __validate_exception_handover(struct dm_snapshot *snap)
395 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
396 struct dm_snapshot *snap_merge = NULL;
398 /* Does snapshot need exceptions handed over to it? */
399 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
400 &snap_merge) == 2) ||
401 snap_dest) {
402 snap->ti->error = "Snapshot cow pairing for exception "
403 "table handover failed";
404 return -EINVAL;
408 * If no snap_src was found, snap cannot become a handover
409 * destination.
411 if (!snap_src)
412 return 0;
415 * Non-snapshot-merge handover?
417 if (!dm_target_is_snapshot_merge(snap->ti))
418 return 1;
421 * Do not allow more than one merging snapshot.
423 if (snap_merge) {
424 snap->ti->error = "A snapshot is already merging.";
425 return -EINVAL;
428 if (!snap_src->store->type->prepare_merge ||
429 !snap_src->store->type->commit_merge) {
430 snap->ti->error = "Snapshot exception store does not "
431 "support snapshot-merge.";
432 return -EINVAL;
435 return 1;
438 static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
440 struct dm_snapshot *l;
442 /* Sort the list according to chunk size, largest-first smallest-last */
443 list_for_each_entry(l, &o->snapshots, list)
444 if (l->store->chunk_size < s->store->chunk_size)
445 break;
446 list_add_tail(&s->list, &l->list);
450 * Make a note of the snapshot and its origin so we can look it
451 * up when the origin has a write on it.
453 * Also validate snapshot exception store handovers.
454 * On success, returns 1 if this registration is a handover destination,
455 * otherwise returns 0.
457 static int register_snapshot(struct dm_snapshot *snap)
459 struct origin *o, *new_o = NULL;
460 struct block_device *bdev = snap->origin->bdev;
461 int r = 0;
463 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
464 if (!new_o)
465 return -ENOMEM;
467 down_write(&_origins_lock);
469 r = __validate_exception_handover(snap);
470 if (r < 0) {
471 kfree(new_o);
472 goto out;
475 o = __lookup_origin(bdev);
476 if (o)
477 kfree(new_o);
478 else {
479 /* New origin */
480 o = new_o;
482 /* Initialise the struct */
483 INIT_LIST_HEAD(&o->snapshots);
484 o->bdev = bdev;
486 __insert_origin(o);
489 __insert_snapshot(o, snap);
491 out:
492 up_write(&_origins_lock);
494 return r;
498 * Move snapshot to correct place in list according to chunk size.
500 static void reregister_snapshot(struct dm_snapshot *s)
502 struct block_device *bdev = s->origin->bdev;
504 down_write(&_origins_lock);
506 list_del(&s->list);
507 __insert_snapshot(__lookup_origin(bdev), s);
509 up_write(&_origins_lock);
512 static void unregister_snapshot(struct dm_snapshot *s)
514 struct origin *o;
516 down_write(&_origins_lock);
517 o = __lookup_origin(s->origin->bdev);
519 list_del(&s->list);
520 if (o && list_empty(&o->snapshots)) {
521 list_del(&o->hash_list);
522 kfree(o);
525 up_write(&_origins_lock);
529 * Implementation of the exception hash tables.
530 * The lowest hash_shift bits of the chunk number are ignored, allowing
531 * some consecutive chunks to be grouped together.
533 static int dm_exception_table_init(struct dm_exception_table *et,
534 uint32_t size, unsigned hash_shift)
536 unsigned int i;
538 et->hash_shift = hash_shift;
539 et->hash_mask = size - 1;
540 et->table = dm_vcalloc(size, sizeof(struct list_head));
541 if (!et->table)
542 return -ENOMEM;
544 for (i = 0; i < size; i++)
545 INIT_LIST_HEAD(et->table + i);
547 return 0;
550 static void dm_exception_table_exit(struct dm_exception_table *et,
551 struct kmem_cache *mem)
553 struct list_head *slot;
554 struct dm_exception *ex, *next;
555 int i, size;
557 size = et->hash_mask + 1;
558 for (i = 0; i < size; i++) {
559 slot = et->table + i;
561 list_for_each_entry_safe (ex, next, slot, hash_list)
562 kmem_cache_free(mem, ex);
565 vfree(et->table);
568 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
570 return (chunk >> et->hash_shift) & et->hash_mask;
573 static void dm_remove_exception(struct dm_exception *e)
575 list_del(&e->hash_list);
579 * Return the exception data for a sector, or NULL if not
580 * remapped.
582 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
583 chunk_t chunk)
585 struct list_head *slot;
586 struct dm_exception *e;
588 slot = &et->table[exception_hash(et, chunk)];
589 list_for_each_entry (e, slot, hash_list)
590 if (chunk >= e->old_chunk &&
591 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
592 return e;
594 return NULL;
597 static struct dm_exception *alloc_completed_exception(void)
599 struct dm_exception *e;
601 e = kmem_cache_alloc(exception_cache, GFP_NOIO);
602 if (!e)
603 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
605 return e;
608 static void free_completed_exception(struct dm_exception *e)
610 kmem_cache_free(exception_cache, e);
613 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
615 struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
616 GFP_NOIO);
618 atomic_inc(&s->pending_exceptions_count);
619 pe->snap = s;
621 return pe;
624 static void free_pending_exception(struct dm_snap_pending_exception *pe)
626 struct dm_snapshot *s = pe->snap;
628 mempool_free(pe, s->pending_pool);
629 smp_mb__before_atomic_dec();
630 atomic_dec(&s->pending_exceptions_count);
633 static void dm_insert_exception(struct dm_exception_table *eh,
634 struct dm_exception *new_e)
636 struct list_head *l;
637 struct dm_exception *e = NULL;
639 l = &eh->table[exception_hash(eh, new_e->old_chunk)];
641 /* Add immediately if this table doesn't support consecutive chunks */
642 if (!eh->hash_shift)
643 goto out;
645 /* List is ordered by old_chunk */
646 list_for_each_entry_reverse(e, l, hash_list) {
647 /* Insert after an existing chunk? */
648 if (new_e->old_chunk == (e->old_chunk +
649 dm_consecutive_chunk_count(e) + 1) &&
650 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
651 dm_consecutive_chunk_count(e) + 1)) {
652 dm_consecutive_chunk_count_inc(e);
653 free_completed_exception(new_e);
654 return;
657 /* Insert before an existing chunk? */
658 if (new_e->old_chunk == (e->old_chunk - 1) &&
659 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
660 dm_consecutive_chunk_count_inc(e);
661 e->old_chunk--;
662 e->new_chunk--;
663 free_completed_exception(new_e);
664 return;
667 if (new_e->old_chunk > e->old_chunk)
668 break;
671 out:
672 list_add(&new_e->hash_list, e ? &e->hash_list : l);
676 * Callback used by the exception stores to load exceptions when
677 * initialising.
679 static int dm_add_exception(void *context, chunk_t old, chunk_t new)
681 struct dm_snapshot *s = context;
682 struct dm_exception *e;
684 e = alloc_completed_exception();
685 if (!e)
686 return -ENOMEM;
688 e->old_chunk = old;
690 /* Consecutive_count is implicitly initialised to zero */
691 e->new_chunk = new;
693 dm_insert_exception(&s->complete, e);
695 return 0;
699 * Return a minimum chunk size of all snapshots that have the specified origin.
700 * Return zero if the origin has no snapshots.
702 static sector_t __minimum_chunk_size(struct origin *o)
704 struct dm_snapshot *snap;
705 unsigned chunk_size = 0;
707 if (o)
708 list_for_each_entry(snap, &o->snapshots, list)
709 chunk_size = min_not_zero(chunk_size,
710 snap->store->chunk_size);
712 return chunk_size;
716 * Hard coded magic.
718 static int calc_max_buckets(void)
720 /* use a fixed size of 2MB */
721 unsigned long mem = 2 * 1024 * 1024;
722 mem /= sizeof(struct list_head);
724 return mem;
728 * Allocate room for a suitable hash table.
730 static int init_hash_tables(struct dm_snapshot *s)
732 sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
735 * Calculate based on the size of the original volume or
736 * the COW volume...
738 cow_dev_size = get_dev_size(s->cow->bdev);
739 origin_dev_size = get_dev_size(s->origin->bdev);
740 max_buckets = calc_max_buckets();
742 hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
743 hash_size = min(hash_size, max_buckets);
745 if (hash_size < 64)
746 hash_size = 64;
747 hash_size = rounddown_pow_of_two(hash_size);
748 if (dm_exception_table_init(&s->complete, hash_size,
749 DM_CHUNK_CONSECUTIVE_BITS))
750 return -ENOMEM;
753 * Allocate hash table for in-flight exceptions
754 * Make this smaller than the real hash table
756 hash_size >>= 3;
757 if (hash_size < 64)
758 hash_size = 64;
760 if (dm_exception_table_init(&s->pending, hash_size, 0)) {
761 dm_exception_table_exit(&s->complete, exception_cache);
762 return -ENOMEM;
765 return 0;
768 static void merge_shutdown(struct dm_snapshot *s)
770 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
771 smp_mb__after_clear_bit();
772 wake_up_bit(&s->state_bits, RUNNING_MERGE);
775 static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
777 s->first_merging_chunk = 0;
778 s->num_merging_chunks = 0;
780 return bio_list_get(&s->bios_queued_during_merge);
784 * Remove one chunk from the index of completed exceptions.
786 static int __remove_single_exception_chunk(struct dm_snapshot *s,
787 chunk_t old_chunk)
789 struct dm_exception *e;
791 e = dm_lookup_exception(&s->complete, old_chunk);
792 if (!e) {
793 DMERR("Corruption detected: exception for block %llu is "
794 "on disk but not in memory",
795 (unsigned long long)old_chunk);
796 return -EINVAL;
800 * If this is the only chunk using this exception, remove exception.
802 if (!dm_consecutive_chunk_count(e)) {
803 dm_remove_exception(e);
804 free_completed_exception(e);
805 return 0;
809 * The chunk may be either at the beginning or the end of a
810 * group of consecutive chunks - never in the middle. We are
811 * removing chunks in the opposite order to that in which they
812 * were added, so this should always be true.
813 * Decrement the consecutive chunk counter and adjust the
814 * starting point if necessary.
816 if (old_chunk == e->old_chunk) {
817 e->old_chunk++;
818 e->new_chunk++;
819 } else if (old_chunk != e->old_chunk +
820 dm_consecutive_chunk_count(e)) {
821 DMERR("Attempt to merge block %llu from the "
822 "middle of a chunk range [%llu - %llu]",
823 (unsigned long long)old_chunk,
824 (unsigned long long)e->old_chunk,
825 (unsigned long long)
826 e->old_chunk + dm_consecutive_chunk_count(e));
827 return -EINVAL;
830 dm_consecutive_chunk_count_dec(e);
832 return 0;
835 static void flush_bios(struct bio *bio);
837 static int remove_single_exception_chunk(struct dm_snapshot *s)
839 struct bio *b = NULL;
840 int r;
841 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
843 down_write(&s->lock);
846 * Process chunks (and associated exceptions) in reverse order
847 * so that dm_consecutive_chunk_count_dec() accounting works.
849 do {
850 r = __remove_single_exception_chunk(s, old_chunk);
851 if (r)
852 goto out;
853 } while (old_chunk-- > s->first_merging_chunk);
855 b = __release_queued_bios_after_merge(s);
857 out:
858 up_write(&s->lock);
859 if (b)
860 flush_bios(b);
862 return r;
865 static int origin_write_extent(struct dm_snapshot *merging_snap,
866 sector_t sector, unsigned chunk_size);
868 static void merge_callback(int read_err, unsigned long write_err,
869 void *context);
871 static uint64_t read_pending_exceptions_done_count(void)
873 uint64_t pending_exceptions_done;
875 spin_lock(&_pending_exceptions_done_spinlock);
876 pending_exceptions_done = _pending_exceptions_done_count;
877 spin_unlock(&_pending_exceptions_done_spinlock);
879 return pending_exceptions_done;
882 static void increment_pending_exceptions_done_count(void)
884 spin_lock(&_pending_exceptions_done_spinlock);
885 _pending_exceptions_done_count++;
886 spin_unlock(&_pending_exceptions_done_spinlock);
888 wake_up_all(&_pending_exceptions_done);
891 static void snapshot_merge_next_chunks(struct dm_snapshot *s)
893 int i, linear_chunks;
894 chunk_t old_chunk, new_chunk;
895 struct dm_io_region src, dest;
896 sector_t io_size;
897 uint64_t previous_count;
899 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
900 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
901 goto shut;
904 * valid flag never changes during merge, so no lock required.
906 if (!s->valid) {
907 DMERR("Snapshot is invalid: can't merge");
908 goto shut;
911 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
912 &new_chunk);
913 if (linear_chunks <= 0) {
914 if (linear_chunks < 0) {
915 DMERR("Read error in exception store: "
916 "shutting down merge");
917 down_write(&s->lock);
918 s->merge_failed = 1;
919 up_write(&s->lock);
921 goto shut;
924 /* Adjust old_chunk and new_chunk to reflect start of linear region */
925 old_chunk = old_chunk + 1 - linear_chunks;
926 new_chunk = new_chunk + 1 - linear_chunks;
929 * Use one (potentially large) I/O to copy all 'linear_chunks'
930 * from the exception store to the origin
932 io_size = linear_chunks * s->store->chunk_size;
934 dest.bdev = s->origin->bdev;
935 dest.sector = chunk_to_sector(s->store, old_chunk);
936 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
938 src.bdev = s->cow->bdev;
939 src.sector = chunk_to_sector(s->store, new_chunk);
940 src.count = dest.count;
943 * Reallocate any exceptions needed in other snapshots then
944 * wait for the pending exceptions to complete.
945 * Each time any pending exception (globally on the system)
946 * completes we are woken and repeat the process to find out
947 * if we can proceed. While this may not seem a particularly
948 * efficient algorithm, it is not expected to have any
949 * significant impact on performance.
951 previous_count = read_pending_exceptions_done_count();
952 while (origin_write_extent(s, dest.sector, io_size)) {
953 wait_event(_pending_exceptions_done,
954 (read_pending_exceptions_done_count() !=
955 previous_count));
956 /* Retry after the wait, until all exceptions are done. */
957 previous_count = read_pending_exceptions_done_count();
960 down_write(&s->lock);
961 s->first_merging_chunk = old_chunk;
962 s->num_merging_chunks = linear_chunks;
963 up_write(&s->lock);
965 /* Wait until writes to all 'linear_chunks' drain */
966 for (i = 0; i < linear_chunks; i++)
967 __check_for_conflicting_io(s, old_chunk + i);
969 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
970 return;
972 shut:
973 merge_shutdown(s);
976 static void error_bios(struct bio *bio);
978 static void merge_callback(int read_err, unsigned long write_err, void *context)
980 struct dm_snapshot *s = context;
981 struct bio *b = NULL;
983 if (read_err || write_err) {
984 if (read_err)
985 DMERR("Read error: shutting down merge.");
986 else
987 DMERR("Write error: shutting down merge.");
988 goto shut;
991 if (s->store->type->commit_merge(s->store,
992 s->num_merging_chunks) < 0) {
993 DMERR("Write error in exception store: shutting down merge");
994 goto shut;
997 if (remove_single_exception_chunk(s) < 0)
998 goto shut;
1000 snapshot_merge_next_chunks(s);
1002 return;
1004 shut:
1005 down_write(&s->lock);
1006 s->merge_failed = 1;
1007 b = __release_queued_bios_after_merge(s);
1008 up_write(&s->lock);
1009 error_bios(b);
1011 merge_shutdown(s);
1014 static void start_merge(struct dm_snapshot *s)
1016 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1017 snapshot_merge_next_chunks(s);
1020 static int wait_schedule(void *ptr)
1022 schedule();
1024 return 0;
1028 * Stop the merging process and wait until it finishes.
1030 static void stop_merge(struct dm_snapshot *s)
1032 set_bit(SHUTDOWN_MERGE, &s->state_bits);
1033 wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule,
1034 TASK_UNINTERRUPTIBLE);
1035 clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1039 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
1041 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1043 struct dm_snapshot *s;
1044 int i;
1045 int r = -EINVAL;
1046 char *origin_path, *cow_path;
1047 unsigned args_used, num_flush_requests = 1;
1048 fmode_t origin_mode = FMODE_READ;
1050 if (argc != 4) {
1051 ti->error = "requires exactly 4 arguments";
1052 r = -EINVAL;
1053 goto bad;
1056 if (dm_target_is_snapshot_merge(ti)) {
1057 num_flush_requests = 2;
1058 origin_mode = FMODE_WRITE;
1061 s = kmalloc(sizeof(*s), GFP_KERNEL);
1062 if (!s) {
1063 ti->error = "Cannot allocate snapshot context private "
1064 "structure";
1065 r = -ENOMEM;
1066 goto bad;
1069 origin_path = argv[0];
1070 argv++;
1071 argc--;
1073 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1074 if (r) {
1075 ti->error = "Cannot get origin device";
1076 goto bad_origin;
1079 cow_path = argv[0];
1080 argv++;
1081 argc--;
1083 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1084 if (r) {
1085 ti->error = "Cannot get COW device";
1086 goto bad_cow;
1089 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1090 if (r) {
1091 ti->error = "Couldn't create exception store";
1092 r = -EINVAL;
1093 goto bad_store;
1096 argv += args_used;
1097 argc -= args_used;
1099 s->ti = ti;
1100 s->valid = 1;
1101 s->active = 0;
1102 atomic_set(&s->pending_exceptions_count, 0);
1103 init_rwsem(&s->lock);
1104 INIT_LIST_HEAD(&s->list);
1105 spin_lock_init(&s->pe_lock);
1106 s->state_bits = 0;
1107 s->merge_failed = 0;
1108 s->first_merging_chunk = 0;
1109 s->num_merging_chunks = 0;
1110 bio_list_init(&s->bios_queued_during_merge);
1112 /* Allocate hash table for COW data */
1113 if (init_hash_tables(s)) {
1114 ti->error = "Unable to allocate hash table space";
1115 r = -ENOMEM;
1116 goto bad_hash_tables;
1119 r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
1120 if (r) {
1121 ti->error = "Could not create kcopyd client";
1122 goto bad_kcopyd;
1125 s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
1126 if (!s->pending_pool) {
1127 ti->error = "Could not allocate mempool for pending exceptions";
1128 goto bad_pending_pool;
1131 s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
1132 tracked_chunk_cache);
1133 if (!s->tracked_chunk_pool) {
1134 ti->error = "Could not allocate tracked_chunk mempool for "
1135 "tracking reads";
1136 goto bad_tracked_chunk_pool;
1139 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1140 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1142 spin_lock_init(&s->tracked_chunk_lock);
1144 ti->private = s;
1145 ti->num_flush_requests = num_flush_requests;
1147 /* Add snapshot to the list of snapshots for this origin */
1148 /* Exceptions aren't triggered till snapshot_resume() is called */
1149 r = register_snapshot(s);
1150 if (r == -ENOMEM) {
1151 ti->error = "Snapshot origin struct allocation failed";
1152 goto bad_load_and_register;
1153 } else if (r < 0) {
1154 /* invalid handover, register_snapshot has set ti->error */
1155 goto bad_load_and_register;
1159 * Metadata must only be loaded into one table at once, so skip this
1160 * if metadata will be handed over during resume.
1161 * Chunk size will be set during the handover - set it to zero to
1162 * ensure it's ignored.
1164 if (r > 0) {
1165 s->store->chunk_size = 0;
1166 return 0;
1169 r = s->store->type->read_metadata(s->store, dm_add_exception,
1170 (void *)s);
1171 if (r < 0) {
1172 ti->error = "Failed to read snapshot metadata";
1173 goto bad_read_metadata;
1174 } else if (r > 0) {
1175 s->valid = 0;
1176 DMWARN("Snapshot is marked invalid.");
1179 if (!s->store->chunk_size) {
1180 ti->error = "Chunk size not set";
1181 goto bad_read_metadata;
1183 ti->split_io = s->store->chunk_size;
1185 return 0;
1187 bad_read_metadata:
1188 unregister_snapshot(s);
1190 bad_load_and_register:
1191 mempool_destroy(s->tracked_chunk_pool);
1193 bad_tracked_chunk_pool:
1194 mempool_destroy(s->pending_pool);
1196 bad_pending_pool:
1197 dm_kcopyd_client_destroy(s->kcopyd_client);
1199 bad_kcopyd:
1200 dm_exception_table_exit(&s->pending, pending_cache);
1201 dm_exception_table_exit(&s->complete, exception_cache);
1203 bad_hash_tables:
1204 dm_exception_store_destroy(s->store);
1206 bad_store:
1207 dm_put_device(ti, s->cow);
1209 bad_cow:
1210 dm_put_device(ti, s->origin);
1212 bad_origin:
1213 kfree(s);
1215 bad:
1216 return r;
1219 static void __free_exceptions(struct dm_snapshot *s)
1221 dm_kcopyd_client_destroy(s->kcopyd_client);
1222 s->kcopyd_client = NULL;
1224 dm_exception_table_exit(&s->pending, pending_cache);
1225 dm_exception_table_exit(&s->complete, exception_cache);
1228 static void __handover_exceptions(struct dm_snapshot *snap_src,
1229 struct dm_snapshot *snap_dest)
1231 union {
1232 struct dm_exception_table table_swap;
1233 struct dm_exception_store *store_swap;
1234 } u;
1237 * Swap all snapshot context information between the two instances.
1239 u.table_swap = snap_dest->complete;
1240 snap_dest->complete = snap_src->complete;
1241 snap_src->complete = u.table_swap;
1243 u.store_swap = snap_dest->store;
1244 snap_dest->store = snap_src->store;
1245 snap_src->store = u.store_swap;
1247 snap_dest->store->snap = snap_dest;
1248 snap_src->store->snap = snap_src;
1250 snap_dest->ti->split_io = snap_dest->store->chunk_size;
1251 snap_dest->valid = snap_src->valid;
1254 * Set source invalid to ensure it receives no further I/O.
1256 snap_src->valid = 0;
1259 static void snapshot_dtr(struct dm_target *ti)
1261 #ifdef CONFIG_DM_DEBUG
1262 int i;
1263 #endif
1264 struct dm_snapshot *s = ti->private;
1265 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1267 down_read(&_origins_lock);
1268 /* Check whether exception handover must be cancelled */
1269 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1270 if (snap_src && snap_dest && (s == snap_src)) {
1271 down_write(&snap_dest->lock);
1272 snap_dest->valid = 0;
1273 up_write(&snap_dest->lock);
1274 DMERR("Cancelling snapshot handover.");
1276 up_read(&_origins_lock);
1278 if (dm_target_is_snapshot_merge(ti))
1279 stop_merge(s);
1281 /* Prevent further origin writes from using this snapshot. */
1282 /* After this returns there can be no new kcopyd jobs. */
1283 unregister_snapshot(s);
1285 while (atomic_read(&s->pending_exceptions_count))
1286 msleep(1);
1288 * Ensure instructions in mempool_destroy aren't reordered
1289 * before atomic_read.
1291 smp_mb();
1293 #ifdef CONFIG_DM_DEBUG
1294 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1295 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1296 #endif
1298 mempool_destroy(s->tracked_chunk_pool);
1300 __free_exceptions(s);
1302 mempool_destroy(s->pending_pool);
1304 dm_exception_store_destroy(s->store);
1306 dm_put_device(ti, s->cow);
1308 dm_put_device(ti, s->origin);
1310 kfree(s);
1314 * Flush a list of buffers.
1316 static void flush_bios(struct bio *bio)
1318 struct bio *n;
1320 while (bio) {
1321 n = bio->bi_next;
1322 bio->bi_next = NULL;
1323 generic_make_request(bio);
1324 bio = n;
1328 static int do_origin(struct dm_dev *origin, struct bio *bio);
1331 * Flush a list of buffers.
1333 static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1335 struct bio *n;
1336 int r;
1338 while (bio) {
1339 n = bio->bi_next;
1340 bio->bi_next = NULL;
1341 r = do_origin(s->origin, bio);
1342 if (r == DM_MAPIO_REMAPPED)
1343 generic_make_request(bio);
1344 bio = n;
1349 * Error a list of buffers.
1351 static void error_bios(struct bio *bio)
1353 struct bio *n;
1355 while (bio) {
1356 n = bio->bi_next;
1357 bio->bi_next = NULL;
1358 bio_io_error(bio);
1359 bio = n;
1363 static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1365 if (!s->valid)
1366 return;
1368 if (err == -EIO)
1369 DMERR("Invalidating snapshot: Error reading/writing.");
1370 else if (err == -ENOMEM)
1371 DMERR("Invalidating snapshot: Unable to allocate exception.");
1373 if (s->store->type->drop_snapshot)
1374 s->store->type->drop_snapshot(s->store);
1376 s->valid = 0;
1378 dm_table_event(s->ti->table);
1381 static void pending_complete(struct dm_snap_pending_exception *pe, int success)
1383 struct dm_exception *e;
1384 struct dm_snapshot *s = pe->snap;
1385 struct bio *origin_bios = NULL;
1386 struct bio *snapshot_bios = NULL;
1387 int error = 0;
1389 if (!success) {
1390 /* Read/write error - snapshot is unusable */
1391 down_write(&s->lock);
1392 __invalidate_snapshot(s, -EIO);
1393 error = 1;
1394 goto out;
1397 e = alloc_completed_exception();
1398 if (!e) {
1399 down_write(&s->lock);
1400 __invalidate_snapshot(s, -ENOMEM);
1401 error = 1;
1402 goto out;
1404 *e = pe->e;
1406 down_write(&s->lock);
1407 if (!s->valid) {
1408 free_completed_exception(e);
1409 error = 1;
1410 goto out;
1413 /* Check for conflicting reads */
1414 __check_for_conflicting_io(s, pe->e.old_chunk);
1417 * Add a proper exception, and remove the
1418 * in-flight exception from the list.
1420 dm_insert_exception(&s->complete, e);
1422 out:
1423 dm_remove_exception(&pe->e);
1424 snapshot_bios = bio_list_get(&pe->snapshot_bios);
1425 origin_bios = bio_list_get(&pe->origin_bios);
1426 free_pending_exception(pe);
1428 increment_pending_exceptions_done_count();
1430 up_write(&s->lock);
1432 /* Submit any pending write bios */
1433 if (error)
1434 error_bios(snapshot_bios);
1435 else
1436 flush_bios(snapshot_bios);
1438 retry_origin_bios(s, origin_bios);
1441 static void commit_callback(void *context, int success)
1443 struct dm_snap_pending_exception *pe = context;
1445 pending_complete(pe, success);
1449 * Called when the copy I/O has finished. kcopyd actually runs
1450 * this code so don't block.
1452 static void copy_callback(int read_err, unsigned long write_err, void *context)
1454 struct dm_snap_pending_exception *pe = context;
1455 struct dm_snapshot *s = pe->snap;
1457 if (read_err || write_err)
1458 pending_complete(pe, 0);
1460 else
1461 /* Update the metadata if we are persistent */
1462 s->store->type->commit_exception(s->store, &pe->e,
1463 commit_callback, pe);
1467 * Dispatches the copy operation to kcopyd.
1469 static void start_copy(struct dm_snap_pending_exception *pe)
1471 struct dm_snapshot *s = pe->snap;
1472 struct dm_io_region src, dest;
1473 struct block_device *bdev = s->origin->bdev;
1474 sector_t dev_size;
1476 dev_size = get_dev_size(bdev);
1478 src.bdev = bdev;
1479 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1480 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1482 dest.bdev = s->cow->bdev;
1483 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1484 dest.count = src.count;
1486 /* Hand over to kcopyd */
1487 dm_kcopyd_copy(s->kcopyd_client,
1488 &src, 1, &dest, 0, copy_callback, pe);
1491 static struct dm_snap_pending_exception *
1492 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1494 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1496 if (!e)
1497 return NULL;
1499 return container_of(e, struct dm_snap_pending_exception, e);
1503 * Looks to see if this snapshot already has a pending exception
1504 * for this chunk, otherwise it allocates a new one and inserts
1505 * it into the pending table.
1507 * NOTE: a write lock must be held on snap->lock before calling
1508 * this.
1510 static struct dm_snap_pending_exception *
1511 __find_pending_exception(struct dm_snapshot *s,
1512 struct dm_snap_pending_exception *pe, chunk_t chunk)
1514 struct dm_snap_pending_exception *pe2;
1516 pe2 = __lookup_pending_exception(s, chunk);
1517 if (pe2) {
1518 free_pending_exception(pe);
1519 return pe2;
1522 pe->e.old_chunk = chunk;
1523 bio_list_init(&pe->origin_bios);
1524 bio_list_init(&pe->snapshot_bios);
1525 pe->started = 0;
1527 if (s->store->type->prepare_exception(s->store, &pe->e)) {
1528 free_pending_exception(pe);
1529 return NULL;
1532 dm_insert_exception(&s->pending, &pe->e);
1534 return pe;
1537 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1538 struct bio *bio, chunk_t chunk)
1540 bio->bi_bdev = s->cow->bdev;
1541 bio->bi_sector = chunk_to_sector(s->store,
1542 dm_chunk_number(e->new_chunk) +
1543 (chunk - e->old_chunk)) +
1544 (bio->bi_sector &
1545 s->store->chunk_mask);
1548 static int snapshot_map(struct dm_target *ti, struct bio *bio,
1549 union map_info *map_context)
1551 struct dm_exception *e;
1552 struct dm_snapshot *s = ti->private;
1553 int r = DM_MAPIO_REMAPPED;
1554 chunk_t chunk;
1555 struct dm_snap_pending_exception *pe = NULL;
1557 if (bio->bi_rw & REQ_FLUSH) {
1558 bio->bi_bdev = s->cow->bdev;
1559 return DM_MAPIO_REMAPPED;
1562 chunk = sector_to_chunk(s->store, bio->bi_sector);
1564 /* Full snapshots are not usable */
1565 /* To get here the table must be live so s->active is always set. */
1566 if (!s->valid)
1567 return -EIO;
1569 /* FIXME: should only take write lock if we need
1570 * to copy an exception */
1571 down_write(&s->lock);
1573 if (!s->valid) {
1574 r = -EIO;
1575 goto out_unlock;
1578 /* If the block is already remapped - use that, else remap it */
1579 e = dm_lookup_exception(&s->complete, chunk);
1580 if (e) {
1581 remap_exception(s, e, bio, chunk);
1582 goto out_unlock;
1586 * Write to snapshot - higher level takes care of RW/RO
1587 * flags so we should only get this if we are
1588 * writeable.
1590 if (bio_rw(bio) == WRITE) {
1591 pe = __lookup_pending_exception(s, chunk);
1592 if (!pe) {
1593 up_write(&s->lock);
1594 pe = alloc_pending_exception(s);
1595 down_write(&s->lock);
1597 if (!s->valid) {
1598 free_pending_exception(pe);
1599 r = -EIO;
1600 goto out_unlock;
1603 e = dm_lookup_exception(&s->complete, chunk);
1604 if (e) {
1605 free_pending_exception(pe);
1606 remap_exception(s, e, bio, chunk);
1607 goto out_unlock;
1610 pe = __find_pending_exception(s, pe, chunk);
1611 if (!pe) {
1612 __invalidate_snapshot(s, -ENOMEM);
1613 r = -EIO;
1614 goto out_unlock;
1618 remap_exception(s, &pe->e, bio, chunk);
1619 bio_list_add(&pe->snapshot_bios, bio);
1621 r = DM_MAPIO_SUBMITTED;
1623 if (!pe->started) {
1624 /* this is protected by snap->lock */
1625 pe->started = 1;
1626 up_write(&s->lock);
1627 start_copy(pe);
1628 goto out;
1630 } else {
1631 bio->bi_bdev = s->origin->bdev;
1632 map_context->ptr = track_chunk(s, chunk);
1635 out_unlock:
1636 up_write(&s->lock);
1637 out:
1638 return r;
1642 * A snapshot-merge target behaves like a combination of a snapshot
1643 * target and a snapshot-origin target. It only generates new
1644 * exceptions in other snapshots and not in the one that is being
1645 * merged.
1647 * For each chunk, if there is an existing exception, it is used to
1648 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,
1649 * which in turn might generate exceptions in other snapshots.
1650 * If merging is currently taking place on the chunk in question, the
1651 * I/O is deferred by adding it to s->bios_queued_during_merge.
1653 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
1654 union map_info *map_context)
1656 struct dm_exception *e;
1657 struct dm_snapshot *s = ti->private;
1658 int r = DM_MAPIO_REMAPPED;
1659 chunk_t chunk;
1661 if (bio->bi_rw & REQ_FLUSH) {
1662 if (!map_context->target_request_nr)
1663 bio->bi_bdev = s->origin->bdev;
1664 else
1665 bio->bi_bdev = s->cow->bdev;
1666 map_context->ptr = NULL;
1667 return DM_MAPIO_REMAPPED;
1670 chunk = sector_to_chunk(s->store, bio->bi_sector);
1672 down_write(&s->lock);
1674 /* Full merging snapshots are redirected to the origin */
1675 if (!s->valid)
1676 goto redirect_to_origin;
1678 /* If the block is already remapped - use that */
1679 e = dm_lookup_exception(&s->complete, chunk);
1680 if (e) {
1681 /* Queue writes overlapping with chunks being merged */
1682 if (bio_rw(bio) == WRITE &&
1683 chunk >= s->first_merging_chunk &&
1684 chunk < (s->first_merging_chunk +
1685 s->num_merging_chunks)) {
1686 bio->bi_bdev = s->origin->bdev;
1687 bio_list_add(&s->bios_queued_during_merge, bio);
1688 r = DM_MAPIO_SUBMITTED;
1689 goto out_unlock;
1692 remap_exception(s, e, bio, chunk);
1694 if (bio_rw(bio) == WRITE)
1695 map_context->ptr = track_chunk(s, chunk);
1696 goto out_unlock;
1699 redirect_to_origin:
1700 bio->bi_bdev = s->origin->bdev;
1702 if (bio_rw(bio) == WRITE) {
1703 up_write(&s->lock);
1704 return do_origin(s->origin, bio);
1707 out_unlock:
1708 up_write(&s->lock);
1710 return r;
1713 static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
1714 int error, union map_info *map_context)
1716 struct dm_snapshot *s = ti->private;
1717 struct dm_snap_tracked_chunk *c = map_context->ptr;
1719 if (c)
1720 stop_tracking_chunk(s, c);
1722 return 0;
1725 static void snapshot_merge_presuspend(struct dm_target *ti)
1727 struct dm_snapshot *s = ti->private;
1729 stop_merge(s);
1732 static int snapshot_preresume(struct dm_target *ti)
1734 int r = 0;
1735 struct dm_snapshot *s = ti->private;
1736 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1738 down_read(&_origins_lock);
1739 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1740 if (snap_src && snap_dest) {
1741 down_read(&snap_src->lock);
1742 if (s == snap_src) {
1743 DMERR("Unable to resume snapshot source until "
1744 "handover completes.");
1745 r = -EINVAL;
1746 } else if (!dm_suspended(snap_src->ti)) {
1747 DMERR("Unable to perform snapshot handover until "
1748 "source is suspended.");
1749 r = -EINVAL;
1751 up_read(&snap_src->lock);
1753 up_read(&_origins_lock);
1755 return r;
1758 static void snapshot_resume(struct dm_target *ti)
1760 struct dm_snapshot *s = ti->private;
1761 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1763 down_read(&_origins_lock);
1764 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1765 if (snap_src && snap_dest) {
1766 down_write(&snap_src->lock);
1767 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1768 __handover_exceptions(snap_src, snap_dest);
1769 up_write(&snap_dest->lock);
1770 up_write(&snap_src->lock);
1772 up_read(&_origins_lock);
1774 /* Now we have correct chunk size, reregister */
1775 reregister_snapshot(s);
1777 down_write(&s->lock);
1778 s->active = 1;
1779 up_write(&s->lock);
1782 static sector_t get_origin_minimum_chunksize(struct block_device *bdev)
1784 sector_t min_chunksize;
1786 down_read(&_origins_lock);
1787 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
1788 up_read(&_origins_lock);
1790 return min_chunksize;
1793 static void snapshot_merge_resume(struct dm_target *ti)
1795 struct dm_snapshot *s = ti->private;
1798 * Handover exceptions from existing snapshot.
1800 snapshot_resume(ti);
1803 * snapshot-merge acts as an origin, so set ti->split_io
1805 ti->split_io = get_origin_minimum_chunksize(s->origin->bdev);
1807 start_merge(s);
1810 static int snapshot_status(struct dm_target *ti, status_type_t type,
1811 char *result, unsigned int maxlen)
1813 unsigned sz = 0;
1814 struct dm_snapshot *snap = ti->private;
1816 switch (type) {
1817 case STATUSTYPE_INFO:
1819 down_write(&snap->lock);
1821 if (!snap->valid)
1822 DMEMIT("Invalid");
1823 else if (snap->merge_failed)
1824 DMEMIT("Merge failed");
1825 else {
1826 if (snap->store->type->usage) {
1827 sector_t total_sectors, sectors_allocated,
1828 metadata_sectors;
1829 snap->store->type->usage(snap->store,
1830 &total_sectors,
1831 &sectors_allocated,
1832 &metadata_sectors);
1833 DMEMIT("%llu/%llu %llu",
1834 (unsigned long long)sectors_allocated,
1835 (unsigned long long)total_sectors,
1836 (unsigned long long)metadata_sectors);
1838 else
1839 DMEMIT("Unknown");
1842 up_write(&snap->lock);
1844 break;
1846 case STATUSTYPE_TABLE:
1848 * kdevname returns a static pointer so we need
1849 * to make private copies if the output is to
1850 * make sense.
1852 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
1853 snap->store->type->status(snap->store, type, result + sz,
1854 maxlen - sz);
1855 break;
1858 return 0;
1861 static int snapshot_iterate_devices(struct dm_target *ti,
1862 iterate_devices_callout_fn fn, void *data)
1864 struct dm_snapshot *snap = ti->private;
1865 int r;
1867 r = fn(ti, snap->origin, 0, ti->len, data);
1869 if (!r)
1870 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
1872 return r;
1876 /*-----------------------------------------------------------------
1877 * Origin methods
1878 *---------------------------------------------------------------*/
1881 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
1882 * supplied bio was ignored. The caller may submit it immediately.
1883 * (No remapping actually occurs as the origin is always a direct linear
1884 * map.)
1886 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
1887 * and any supplied bio is added to a list to be submitted once all
1888 * the necessary exceptions exist.
1890 static int __origin_write(struct list_head *snapshots, sector_t sector,
1891 struct bio *bio)
1893 int r = DM_MAPIO_REMAPPED;
1894 struct dm_snapshot *snap;
1895 struct dm_exception *e;
1896 struct dm_snap_pending_exception *pe;
1897 struct dm_snap_pending_exception *pe_to_start_now = NULL;
1898 struct dm_snap_pending_exception *pe_to_start_last = NULL;
1899 chunk_t chunk;
1901 /* Do all the snapshots on this origin */
1902 list_for_each_entry (snap, snapshots, list) {
1904 * Don't make new exceptions in a merging snapshot
1905 * because it has effectively been deleted
1907 if (dm_target_is_snapshot_merge(snap->ti))
1908 continue;
1910 down_write(&snap->lock);
1912 /* Only deal with valid and active snapshots */
1913 if (!snap->valid || !snap->active)
1914 goto next_snapshot;
1916 /* Nothing to do if writing beyond end of snapshot */
1917 if (sector >= dm_table_get_size(snap->ti->table))
1918 goto next_snapshot;
1921 * Remember, different snapshots can have
1922 * different chunk sizes.
1924 chunk = sector_to_chunk(snap->store, sector);
1927 * Check exception table to see if block
1928 * is already remapped in this snapshot
1929 * and trigger an exception if not.
1931 e = dm_lookup_exception(&snap->complete, chunk);
1932 if (e)
1933 goto next_snapshot;
1935 pe = __lookup_pending_exception(snap, chunk);
1936 if (!pe) {
1937 up_write(&snap->lock);
1938 pe = alloc_pending_exception(snap);
1939 down_write(&snap->lock);
1941 if (!snap->valid) {
1942 free_pending_exception(pe);
1943 goto next_snapshot;
1946 e = dm_lookup_exception(&snap->complete, chunk);
1947 if (e) {
1948 free_pending_exception(pe);
1949 goto next_snapshot;
1952 pe = __find_pending_exception(snap, pe, chunk);
1953 if (!pe) {
1954 __invalidate_snapshot(snap, -ENOMEM);
1955 goto next_snapshot;
1959 r = DM_MAPIO_SUBMITTED;
1962 * If an origin bio was supplied, queue it to wait for the
1963 * completion of this exception, and start this one last,
1964 * at the end of the function.
1966 if (bio) {
1967 bio_list_add(&pe->origin_bios, bio);
1968 bio = NULL;
1970 if (!pe->started) {
1971 pe->started = 1;
1972 pe_to_start_last = pe;
1976 if (!pe->started) {
1977 pe->started = 1;
1978 pe_to_start_now = pe;
1981 next_snapshot:
1982 up_write(&snap->lock);
1984 if (pe_to_start_now) {
1985 start_copy(pe_to_start_now);
1986 pe_to_start_now = NULL;
1991 * Submit the exception against which the bio is queued last,
1992 * to give the other exceptions a head start.
1994 if (pe_to_start_last)
1995 start_copy(pe_to_start_last);
1997 return r;
2001 * Called on a write from the origin driver.
2003 static int do_origin(struct dm_dev *origin, struct bio *bio)
2005 struct origin *o;
2006 int r = DM_MAPIO_REMAPPED;
2008 down_read(&_origins_lock);
2009 o = __lookup_origin(origin->bdev);
2010 if (o)
2011 r = __origin_write(&o->snapshots, bio->bi_sector, bio);
2012 up_read(&_origins_lock);
2014 return r;
2018 * Trigger exceptions in all non-merging snapshots.
2020 * The chunk size of the merging snapshot may be larger than the chunk
2021 * size of some other snapshot so we may need to reallocate multiple
2022 * chunks in other snapshots.
2024 * We scan all the overlapping exceptions in the other snapshots.
2025 * Returns 1 if anything was reallocated and must be waited for,
2026 * otherwise returns 0.
2028 * size must be a multiple of merging_snap's chunk_size.
2030 static int origin_write_extent(struct dm_snapshot *merging_snap,
2031 sector_t sector, unsigned size)
2033 int must_wait = 0;
2034 sector_t n;
2035 struct origin *o;
2038 * The origin's __minimum_chunk_size() got stored in split_io
2039 * by snapshot_merge_resume().
2041 down_read(&_origins_lock);
2042 o = __lookup_origin(merging_snap->origin->bdev);
2043 for (n = 0; n < size; n += merging_snap->ti->split_io)
2044 if (__origin_write(&o->snapshots, sector + n, NULL) ==
2045 DM_MAPIO_SUBMITTED)
2046 must_wait = 1;
2047 up_read(&_origins_lock);
2049 return must_wait;
2053 * Origin: maps a linear range of a device, with hooks for snapshotting.
2057 * Construct an origin mapping: <dev_path>
2058 * The context for an origin is merely a 'struct dm_dev *'
2059 * pointing to the real device.
2061 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2063 int r;
2064 struct dm_dev *dev;
2066 if (argc != 1) {
2067 ti->error = "origin: incorrect number of arguments";
2068 return -EINVAL;
2071 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dev);
2072 if (r) {
2073 ti->error = "Cannot get target device";
2074 return r;
2077 ti->private = dev;
2078 ti->num_flush_requests = 1;
2080 return 0;
2083 static void origin_dtr(struct dm_target *ti)
2085 struct dm_dev *dev = ti->private;
2086 dm_put_device(ti, dev);
2089 static int origin_map(struct dm_target *ti, struct bio *bio,
2090 union map_info *map_context)
2092 struct dm_dev *dev = ti->private;
2093 bio->bi_bdev = dev->bdev;
2095 if (bio->bi_rw & REQ_FLUSH)
2096 return DM_MAPIO_REMAPPED;
2098 /* Only tell snapshots if this is a write */
2099 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
2103 * Set the target "split_io" field to the minimum of all the snapshots'
2104 * chunk sizes.
2106 static void origin_resume(struct dm_target *ti)
2108 struct dm_dev *dev = ti->private;
2110 ti->split_io = get_origin_minimum_chunksize(dev->bdev);
2113 static int origin_status(struct dm_target *ti, status_type_t type, char *result,
2114 unsigned int maxlen)
2116 struct dm_dev *dev = ti->private;
2118 switch (type) {
2119 case STATUSTYPE_INFO:
2120 result[0] = '\0';
2121 break;
2123 case STATUSTYPE_TABLE:
2124 snprintf(result, maxlen, "%s", dev->name);
2125 break;
2128 return 0;
2131 static int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
2132 struct bio_vec *biovec, int max_size)
2134 struct dm_dev *dev = ti->private;
2135 struct request_queue *q = bdev_get_queue(dev->bdev);
2137 if (!q->merge_bvec_fn)
2138 return max_size;
2140 bvm->bi_bdev = dev->bdev;
2141 bvm->bi_sector = bvm->bi_sector;
2143 return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2146 static int origin_iterate_devices(struct dm_target *ti,
2147 iterate_devices_callout_fn fn, void *data)
2149 struct dm_dev *dev = ti->private;
2151 return fn(ti, dev, 0, ti->len, data);
2154 static struct target_type origin_target = {
2155 .name = "snapshot-origin",
2156 .version = {1, 7, 1},
2157 .module = THIS_MODULE,
2158 .ctr = origin_ctr,
2159 .dtr = origin_dtr,
2160 .map = origin_map,
2161 .resume = origin_resume,
2162 .status = origin_status,
2163 .merge = origin_merge,
2164 .iterate_devices = origin_iterate_devices,
2167 static struct target_type snapshot_target = {
2168 .name = "snapshot",
2169 .version = {1, 10, 0},
2170 .module = THIS_MODULE,
2171 .ctr = snapshot_ctr,
2172 .dtr = snapshot_dtr,
2173 .map = snapshot_map,
2174 .end_io = snapshot_end_io,
2175 .preresume = snapshot_preresume,
2176 .resume = snapshot_resume,
2177 .status = snapshot_status,
2178 .iterate_devices = snapshot_iterate_devices,
2181 static struct target_type merge_target = {
2182 .name = dm_snapshot_merge_target_name,
2183 .version = {1, 1, 0},
2184 .module = THIS_MODULE,
2185 .ctr = snapshot_ctr,
2186 .dtr = snapshot_dtr,
2187 .map = snapshot_merge_map,
2188 .end_io = snapshot_end_io,
2189 .presuspend = snapshot_merge_presuspend,
2190 .preresume = snapshot_preresume,
2191 .resume = snapshot_merge_resume,
2192 .status = snapshot_status,
2193 .iterate_devices = snapshot_iterate_devices,
2196 static int __init dm_snapshot_init(void)
2198 int r;
2200 r = dm_exception_store_init();
2201 if (r) {
2202 DMERR("Failed to initialize exception stores");
2203 return r;
2206 r = dm_register_target(&snapshot_target);
2207 if (r < 0) {
2208 DMERR("snapshot target register failed %d", r);
2209 goto bad_register_snapshot_target;
2212 r = dm_register_target(&origin_target);
2213 if (r < 0) {
2214 DMERR("Origin target register failed %d", r);
2215 goto bad_register_origin_target;
2218 r = dm_register_target(&merge_target);
2219 if (r < 0) {
2220 DMERR("Merge target register failed %d", r);
2221 goto bad_register_merge_target;
2224 r = init_origin_hash();
2225 if (r) {
2226 DMERR("init_origin_hash failed.");
2227 goto bad_origin_hash;
2230 exception_cache = KMEM_CACHE(dm_exception, 0);
2231 if (!exception_cache) {
2232 DMERR("Couldn't create exception cache.");
2233 r = -ENOMEM;
2234 goto bad_exception_cache;
2237 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2238 if (!pending_cache) {
2239 DMERR("Couldn't create pending cache.");
2240 r = -ENOMEM;
2241 goto bad_pending_cache;
2244 tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
2245 if (!tracked_chunk_cache) {
2246 DMERR("Couldn't create cache to track chunks in use.");
2247 r = -ENOMEM;
2248 goto bad_tracked_chunk_cache;
2251 return 0;
2253 bad_tracked_chunk_cache:
2254 kmem_cache_destroy(pending_cache);
2255 bad_pending_cache:
2256 kmem_cache_destroy(exception_cache);
2257 bad_exception_cache:
2258 exit_origin_hash();
2259 bad_origin_hash:
2260 dm_unregister_target(&merge_target);
2261 bad_register_merge_target:
2262 dm_unregister_target(&origin_target);
2263 bad_register_origin_target:
2264 dm_unregister_target(&snapshot_target);
2265 bad_register_snapshot_target:
2266 dm_exception_store_exit();
2268 return r;
2271 static void __exit dm_snapshot_exit(void)
2273 dm_unregister_target(&snapshot_target);
2274 dm_unregister_target(&origin_target);
2275 dm_unregister_target(&merge_target);
2277 exit_origin_hash();
2278 kmem_cache_destroy(pending_cache);
2279 kmem_cache_destroy(exception_cache);
2280 kmem_cache_destroy(tracked_chunk_cache);
2282 dm_exception_store_exit();
2285 /* Module hooks */
2286 module_init(dm_snapshot_init);
2287 module_exit(dm_snapshot_exit);
2289 MODULE_DESCRIPTION(DM_NAME " snapshot target");
2290 MODULE_AUTHOR("Joe Thornber");
2291 MODULE_LICENSE("GPL");