Merge tag 'sound-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
[firefly-linux-kernel-4.4.55.git] / drivers / md / dm-snap.c
1 /*
2  * dm-snapshot.c
3  *
4  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
5  *
6  * This file is released under the GPL.
7  */
8
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>
22
23 #include "dm-exception-store.h"
24
25 #define DM_MSG_PREFIX "snapshots"
26
27 static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
28
29 #define dm_target_is_snapshot_merge(ti) \
30         ((ti)->type->name == dm_snapshot_merge_target_name)
31
32 /*
33  * The size of the mempool used to track chunks in use.
34  */
35 #define MIN_IOS 256
36
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))
40
41 struct dm_exception_table {
42         uint32_t hash_mask;
43         unsigned hash_shift;
44         struct list_head *table;
45 };
46
47 struct dm_snapshot {
48         struct rw_semaphore lock;
49
50         struct dm_dev *origin;
51         struct dm_dev *cow;
52
53         struct dm_target *ti;
54
55         /* List of snapshots per Origin */
56         struct list_head list;
57
58         /*
59          * You can't use a snapshot if this is 0 (e.g. if full).
60          * A snapshot-merge target never clears this.
61          */
62         int valid;
63
64         /* Origin writes don't trigger exceptions until this is set */
65         int active;
66
67         atomic_t pending_exceptions_count;
68
69         mempool_t *pending_pool;
70
71         struct dm_exception_table pending;
72         struct dm_exception_table complete;
73
74         /*
75          * pe_lock protects all pending_exception operations and access
76          * as well as the snapshot_bios list.
77          */
78         spinlock_t pe_lock;
79
80         /* Chunks with outstanding reads */
81         spinlock_t tracked_chunk_lock;
82         struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
83
84         /* The on disk metadata handler */
85         struct dm_exception_store *store;
86
87         struct dm_kcopyd_client *kcopyd_client;
88
89         /* Wait for events based on state_bits */
90         unsigned long state_bits;
91
92         /* Range of chunks currently being merged. */
93         chunk_t first_merging_chunk;
94         int num_merging_chunks;
95
96         /*
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.
108          */
109         int merge_failed;
110
111         /*
112          * Incoming bios that overlap with chunks being merged must wait
113          * for them to be committed.
114          */
115         struct bio_list bios_queued_during_merge;
116 };
117
118 /*
119  * state_bits:
120  *   RUNNING_MERGE  - Merge operation is in progress.
121  *   SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
122  *                    cleared afterwards.
123  */
124 #define RUNNING_MERGE          0
125 #define SHUTDOWN_MERGE         1
126
127 DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
128                 "A percentage of time allocated for copy on write");
129
130 struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
131 {
132         return s->origin;
133 }
134 EXPORT_SYMBOL(dm_snap_origin);
135
136 struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
137 {
138         return s->cow;
139 }
140 EXPORT_SYMBOL(dm_snap_cow);
141
142 static sector_t chunk_to_sector(struct dm_exception_store *store,
143                                 chunk_t chunk)
144 {
145         return chunk << store->chunk_shift;
146 }
147
148 static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
149 {
150         /*
151          * There is only ever one instance of a particular block
152          * device so we can compare pointers safely.
153          */
154         return lhs == rhs;
155 }
156
157 struct dm_snap_pending_exception {
158         struct dm_exception e;
159
160         /*
161          * Origin buffers waiting for this to complete are held
162          * in a bio list
163          */
164         struct bio_list origin_bios;
165         struct bio_list snapshot_bios;
166
167         /* Pointer back to snapshot context */
168         struct dm_snapshot *snap;
169
170         /*
171          * 1 indicates the exception has already been sent to
172          * kcopyd.
173          */
174         int started;
175
176         /*
177          * For writing a complete chunk, bypassing the copy.
178          */
179         struct bio *full_bio;
180         bio_end_io_t *full_bio_end_io;
181         void *full_bio_private;
182 };
183
184 /*
185  * Hash table mapping origin volumes to lists of snapshots and
186  * a lock to protect it
187  */
188 static struct kmem_cache *exception_cache;
189 static struct kmem_cache *pending_cache;
190
191 struct dm_snap_tracked_chunk {
192         struct hlist_node node;
193         chunk_t chunk;
194 };
195
196 static void init_tracked_chunk(struct bio *bio)
197 {
198         struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
199         INIT_HLIST_NODE(&c->node);
200 }
201
202 static bool is_bio_tracked(struct bio *bio)
203 {
204         struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
205         return !hlist_unhashed(&c->node);
206 }
207
208 static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
209 {
210         struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
211
212         c->chunk = chunk;
213
214         spin_lock_irq(&s->tracked_chunk_lock);
215         hlist_add_head(&c->node,
216                        &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
217         spin_unlock_irq(&s->tracked_chunk_lock);
218 }
219
220 static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
221 {
222         struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
223         unsigned long flags;
224
225         spin_lock_irqsave(&s->tracked_chunk_lock, flags);
226         hlist_del(&c->node);
227         spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
228 }
229
230 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
231 {
232         struct dm_snap_tracked_chunk *c;
233         int found = 0;
234
235         spin_lock_irq(&s->tracked_chunk_lock);
236
237         hlist_for_each_entry(c,
238             &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
239                 if (c->chunk == chunk) {
240                         found = 1;
241                         break;
242                 }
243         }
244
245         spin_unlock_irq(&s->tracked_chunk_lock);
246
247         return found;
248 }
249
250 /*
251  * This conflicting I/O is extremely improbable in the caller,
252  * so msleep(1) is sufficient and there is no need for a wait queue.
253  */
254 static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
255 {
256         while (__chunk_is_tracked(s, chunk))
257                 msleep(1);
258 }
259
260 /*
261  * One of these per registered origin, held in the snapshot_origins hash
262  */
263 struct origin {
264         /* The origin device */
265         struct block_device *bdev;
266
267         struct list_head hash_list;
268
269         /* List of snapshots for this origin */
270         struct list_head snapshots;
271 };
272
273 /*
274  * Size of the hash table for origin volumes. If we make this
275  * the size of the minors list then it should be nearly perfect
276  */
277 #define ORIGIN_HASH_SIZE 256
278 #define ORIGIN_MASK      0xFF
279 static struct list_head *_origins;
280 static struct rw_semaphore _origins_lock;
281
282 static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
283 static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
284 static uint64_t _pending_exceptions_done_count;
285
286 static int init_origin_hash(void)
287 {
288         int i;
289
290         _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
291                            GFP_KERNEL);
292         if (!_origins) {
293                 DMERR("unable to allocate memory");
294                 return -ENOMEM;
295         }
296
297         for (i = 0; i < ORIGIN_HASH_SIZE; i++)
298                 INIT_LIST_HEAD(_origins + i);
299         init_rwsem(&_origins_lock);
300
301         return 0;
302 }
303
304 static void exit_origin_hash(void)
305 {
306         kfree(_origins);
307 }
308
309 static unsigned origin_hash(struct block_device *bdev)
310 {
311         return bdev->bd_dev & ORIGIN_MASK;
312 }
313
314 static struct origin *__lookup_origin(struct block_device *origin)
315 {
316         struct list_head *ol;
317         struct origin *o;
318
319         ol = &_origins[origin_hash(origin)];
320         list_for_each_entry (o, ol, hash_list)
321                 if (bdev_equal(o->bdev, origin))
322                         return o;
323
324         return NULL;
325 }
326
327 static void __insert_origin(struct origin *o)
328 {
329         struct list_head *sl = &_origins[origin_hash(o->bdev)];
330         list_add_tail(&o->hash_list, sl);
331 }
332
333 /*
334  * _origins_lock must be held when calling this function.
335  * Returns number of snapshots registered using the supplied cow device, plus:
336  * snap_src - a snapshot suitable for use as a source of exception handover
337  * snap_dest - a snapshot capable of receiving exception handover.
338  * snap_merge - an existing snapshot-merge target linked to the same origin.
339  *   There can be at most one snapshot-merge target. The parameter is optional.
340  *
341  * Possible return values and states of snap_src and snap_dest.
342  *   0: NULL, NULL  - first new snapshot
343  *   1: snap_src, NULL - normal snapshot
344  *   2: snap_src, snap_dest  - waiting for handover
345  *   2: snap_src, NULL - handed over, waiting for old to be deleted
346  *   1: NULL, snap_dest - source got destroyed without handover
347  */
348 static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
349                                         struct dm_snapshot **snap_src,
350                                         struct dm_snapshot **snap_dest,
351                                         struct dm_snapshot **snap_merge)
352 {
353         struct dm_snapshot *s;
354         struct origin *o;
355         int count = 0;
356         int active;
357
358         o = __lookup_origin(snap->origin->bdev);
359         if (!o)
360                 goto out;
361
362         list_for_each_entry(s, &o->snapshots, list) {
363                 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
364                         *snap_merge = s;
365                 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
366                         continue;
367
368                 down_read(&s->lock);
369                 active = s->active;
370                 up_read(&s->lock);
371
372                 if (active) {
373                         if (snap_src)
374                                 *snap_src = s;
375                 } else if (snap_dest)
376                         *snap_dest = s;
377
378                 count++;
379         }
380
381 out:
382         return count;
383 }
384
385 /*
386  * On success, returns 1 if this snapshot is a handover destination,
387  * otherwise returns 0.
388  */
389 static int __validate_exception_handover(struct dm_snapshot *snap)
390 {
391         struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
392         struct dm_snapshot *snap_merge = NULL;
393
394         /* Does snapshot need exceptions handed over to it? */
395         if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
396                                           &snap_merge) == 2) ||
397             snap_dest) {
398                 snap->ti->error = "Snapshot cow pairing for exception "
399                                   "table handover failed";
400                 return -EINVAL;
401         }
402
403         /*
404          * If no snap_src was found, snap cannot become a handover
405          * destination.
406          */
407         if (!snap_src)
408                 return 0;
409
410         /*
411          * Non-snapshot-merge handover?
412          */
413         if (!dm_target_is_snapshot_merge(snap->ti))
414                 return 1;
415
416         /*
417          * Do not allow more than one merging snapshot.
418          */
419         if (snap_merge) {
420                 snap->ti->error = "A snapshot is already merging.";
421                 return -EINVAL;
422         }
423
424         if (!snap_src->store->type->prepare_merge ||
425             !snap_src->store->type->commit_merge) {
426                 snap->ti->error = "Snapshot exception store does not "
427                                   "support snapshot-merge.";
428                 return -EINVAL;
429         }
430
431         return 1;
432 }
433
434 static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
435 {
436         struct dm_snapshot *l;
437
438         /* Sort the list according to chunk size, largest-first smallest-last */
439         list_for_each_entry(l, &o->snapshots, list)
440                 if (l->store->chunk_size < s->store->chunk_size)
441                         break;
442         list_add_tail(&s->list, &l->list);
443 }
444
445 /*
446  * Make a note of the snapshot and its origin so we can look it
447  * up when the origin has a write on it.
448  *
449  * Also validate snapshot exception store handovers.
450  * On success, returns 1 if this registration is a handover destination,
451  * otherwise returns 0.
452  */
453 static int register_snapshot(struct dm_snapshot *snap)
454 {
455         struct origin *o, *new_o = NULL;
456         struct block_device *bdev = snap->origin->bdev;
457         int r = 0;
458
459         new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
460         if (!new_o)
461                 return -ENOMEM;
462
463         down_write(&_origins_lock);
464
465         r = __validate_exception_handover(snap);
466         if (r < 0) {
467                 kfree(new_o);
468                 goto out;
469         }
470
471         o = __lookup_origin(bdev);
472         if (o)
473                 kfree(new_o);
474         else {
475                 /* New origin */
476                 o = new_o;
477
478                 /* Initialise the struct */
479                 INIT_LIST_HEAD(&o->snapshots);
480                 o->bdev = bdev;
481
482                 __insert_origin(o);
483         }
484
485         __insert_snapshot(o, snap);
486
487 out:
488         up_write(&_origins_lock);
489
490         return r;
491 }
492
493 /*
494  * Move snapshot to correct place in list according to chunk size.
495  */
496 static void reregister_snapshot(struct dm_snapshot *s)
497 {
498         struct block_device *bdev = s->origin->bdev;
499
500         down_write(&_origins_lock);
501
502         list_del(&s->list);
503         __insert_snapshot(__lookup_origin(bdev), s);
504
505         up_write(&_origins_lock);
506 }
507
508 static void unregister_snapshot(struct dm_snapshot *s)
509 {
510         struct origin *o;
511
512         down_write(&_origins_lock);
513         o = __lookup_origin(s->origin->bdev);
514
515         list_del(&s->list);
516         if (o && list_empty(&o->snapshots)) {
517                 list_del(&o->hash_list);
518                 kfree(o);
519         }
520
521         up_write(&_origins_lock);
522 }
523
524 /*
525  * Implementation of the exception hash tables.
526  * The lowest hash_shift bits of the chunk number are ignored, allowing
527  * some consecutive chunks to be grouped together.
528  */
529 static int dm_exception_table_init(struct dm_exception_table *et,
530                                    uint32_t size, unsigned hash_shift)
531 {
532         unsigned int i;
533
534         et->hash_shift = hash_shift;
535         et->hash_mask = size - 1;
536         et->table = dm_vcalloc(size, sizeof(struct list_head));
537         if (!et->table)
538                 return -ENOMEM;
539
540         for (i = 0; i < size; i++)
541                 INIT_LIST_HEAD(et->table + i);
542
543         return 0;
544 }
545
546 static void dm_exception_table_exit(struct dm_exception_table *et,
547                                     struct kmem_cache *mem)
548 {
549         struct list_head *slot;
550         struct dm_exception *ex, *next;
551         int i, size;
552
553         size = et->hash_mask + 1;
554         for (i = 0; i < size; i++) {
555                 slot = et->table + i;
556
557                 list_for_each_entry_safe (ex, next, slot, hash_list)
558                         kmem_cache_free(mem, ex);
559         }
560
561         vfree(et->table);
562 }
563
564 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
565 {
566         return (chunk >> et->hash_shift) & et->hash_mask;
567 }
568
569 static void dm_remove_exception(struct dm_exception *e)
570 {
571         list_del(&e->hash_list);
572 }
573
574 /*
575  * Return the exception data for a sector, or NULL if not
576  * remapped.
577  */
578 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
579                                                 chunk_t chunk)
580 {
581         struct list_head *slot;
582         struct dm_exception *e;
583
584         slot = &et->table[exception_hash(et, chunk)];
585         list_for_each_entry (e, slot, hash_list)
586                 if (chunk >= e->old_chunk &&
587                     chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
588                         return e;
589
590         return NULL;
591 }
592
593 static struct dm_exception *alloc_completed_exception(void)
594 {
595         struct dm_exception *e;
596
597         e = kmem_cache_alloc(exception_cache, GFP_NOIO);
598         if (!e)
599                 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
600
601         return e;
602 }
603
604 static void free_completed_exception(struct dm_exception *e)
605 {
606         kmem_cache_free(exception_cache, e);
607 }
608
609 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
610 {
611         struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
612                                                              GFP_NOIO);
613
614         atomic_inc(&s->pending_exceptions_count);
615         pe->snap = s;
616
617         return pe;
618 }
619
620 static void free_pending_exception(struct dm_snap_pending_exception *pe)
621 {
622         struct dm_snapshot *s = pe->snap;
623
624         mempool_free(pe, s->pending_pool);
625         smp_mb__before_atomic_dec();
626         atomic_dec(&s->pending_exceptions_count);
627 }
628
629 static void dm_insert_exception(struct dm_exception_table *eh,
630                                 struct dm_exception *new_e)
631 {
632         struct list_head *l;
633         struct dm_exception *e = NULL;
634
635         l = &eh->table[exception_hash(eh, new_e->old_chunk)];
636
637         /* Add immediately if this table doesn't support consecutive chunks */
638         if (!eh->hash_shift)
639                 goto out;
640
641         /* List is ordered by old_chunk */
642         list_for_each_entry_reverse(e, l, hash_list) {
643                 /* Insert after an existing chunk? */
644                 if (new_e->old_chunk == (e->old_chunk +
645                                          dm_consecutive_chunk_count(e) + 1) &&
646                     new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
647                                          dm_consecutive_chunk_count(e) + 1)) {
648                         dm_consecutive_chunk_count_inc(e);
649                         free_completed_exception(new_e);
650                         return;
651                 }
652
653                 /* Insert before an existing chunk? */
654                 if (new_e->old_chunk == (e->old_chunk - 1) &&
655                     new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
656                         dm_consecutive_chunk_count_inc(e);
657                         e->old_chunk--;
658                         e->new_chunk--;
659                         free_completed_exception(new_e);
660                         return;
661                 }
662
663                 if (new_e->old_chunk > e->old_chunk)
664                         break;
665         }
666
667 out:
668         list_add(&new_e->hash_list, e ? &e->hash_list : l);
669 }
670
671 /*
672  * Callback used by the exception stores to load exceptions when
673  * initialising.
674  */
675 static int dm_add_exception(void *context, chunk_t old, chunk_t new)
676 {
677         struct dm_snapshot *s = context;
678         struct dm_exception *e;
679
680         e = alloc_completed_exception();
681         if (!e)
682                 return -ENOMEM;
683
684         e->old_chunk = old;
685
686         /* Consecutive_count is implicitly initialised to zero */
687         e->new_chunk = new;
688
689         dm_insert_exception(&s->complete, e);
690
691         return 0;
692 }
693
694 /*
695  * Return a minimum chunk size of all snapshots that have the specified origin.
696  * Return zero if the origin has no snapshots.
697  */
698 static uint32_t __minimum_chunk_size(struct origin *o)
699 {
700         struct dm_snapshot *snap;
701         unsigned chunk_size = 0;
702
703         if (o)
704                 list_for_each_entry(snap, &o->snapshots, list)
705                         chunk_size = min_not_zero(chunk_size,
706                                                   snap->store->chunk_size);
707
708         return (uint32_t) chunk_size;
709 }
710
711 /*
712  * Hard coded magic.
713  */
714 static int calc_max_buckets(void)
715 {
716         /* use a fixed size of 2MB */
717         unsigned long mem = 2 * 1024 * 1024;
718         mem /= sizeof(struct list_head);
719
720         return mem;
721 }
722
723 /*
724  * Allocate room for a suitable hash table.
725  */
726 static int init_hash_tables(struct dm_snapshot *s)
727 {
728         sector_t hash_size, cow_dev_size, max_buckets;
729
730         /*
731          * Calculate based on the size of the original volume or
732          * the COW volume...
733          */
734         cow_dev_size = get_dev_size(s->cow->bdev);
735         max_buckets = calc_max_buckets();
736
737         hash_size = cow_dev_size >> s->store->chunk_shift;
738         hash_size = min(hash_size, max_buckets);
739
740         if (hash_size < 64)
741                 hash_size = 64;
742         hash_size = rounddown_pow_of_two(hash_size);
743         if (dm_exception_table_init(&s->complete, hash_size,
744                                     DM_CHUNK_CONSECUTIVE_BITS))
745                 return -ENOMEM;
746
747         /*
748          * Allocate hash table for in-flight exceptions
749          * Make this smaller than the real hash table
750          */
751         hash_size >>= 3;
752         if (hash_size < 64)
753                 hash_size = 64;
754
755         if (dm_exception_table_init(&s->pending, hash_size, 0)) {
756                 dm_exception_table_exit(&s->complete, exception_cache);
757                 return -ENOMEM;
758         }
759
760         return 0;
761 }
762
763 static void merge_shutdown(struct dm_snapshot *s)
764 {
765         clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
766         smp_mb__after_clear_bit();
767         wake_up_bit(&s->state_bits, RUNNING_MERGE);
768 }
769
770 static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
771 {
772         s->first_merging_chunk = 0;
773         s->num_merging_chunks = 0;
774
775         return bio_list_get(&s->bios_queued_during_merge);
776 }
777
778 /*
779  * Remove one chunk from the index of completed exceptions.
780  */
781 static int __remove_single_exception_chunk(struct dm_snapshot *s,
782                                            chunk_t old_chunk)
783 {
784         struct dm_exception *e;
785
786         e = dm_lookup_exception(&s->complete, old_chunk);
787         if (!e) {
788                 DMERR("Corruption detected: exception for block %llu is "
789                       "on disk but not in memory",
790                       (unsigned long long)old_chunk);
791                 return -EINVAL;
792         }
793
794         /*
795          * If this is the only chunk using this exception, remove exception.
796          */
797         if (!dm_consecutive_chunk_count(e)) {
798                 dm_remove_exception(e);
799                 free_completed_exception(e);
800                 return 0;
801         }
802
803         /*
804          * The chunk may be either at the beginning or the end of a
805          * group of consecutive chunks - never in the middle.  We are
806          * removing chunks in the opposite order to that in which they
807          * were added, so this should always be true.
808          * Decrement the consecutive chunk counter and adjust the
809          * starting point if necessary.
810          */
811         if (old_chunk == e->old_chunk) {
812                 e->old_chunk++;
813                 e->new_chunk++;
814         } else if (old_chunk != e->old_chunk +
815                    dm_consecutive_chunk_count(e)) {
816                 DMERR("Attempt to merge block %llu from the "
817                       "middle of a chunk range [%llu - %llu]",
818                       (unsigned long long)old_chunk,
819                       (unsigned long long)e->old_chunk,
820                       (unsigned long long)
821                       e->old_chunk + dm_consecutive_chunk_count(e));
822                 return -EINVAL;
823         }
824
825         dm_consecutive_chunk_count_dec(e);
826
827         return 0;
828 }
829
830 static void flush_bios(struct bio *bio);
831
832 static int remove_single_exception_chunk(struct dm_snapshot *s)
833 {
834         struct bio *b = NULL;
835         int r;
836         chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
837
838         down_write(&s->lock);
839
840         /*
841          * Process chunks (and associated exceptions) in reverse order
842          * so that dm_consecutive_chunk_count_dec() accounting works.
843          */
844         do {
845                 r = __remove_single_exception_chunk(s, old_chunk);
846                 if (r)
847                         goto out;
848         } while (old_chunk-- > s->first_merging_chunk);
849
850         b = __release_queued_bios_after_merge(s);
851
852 out:
853         up_write(&s->lock);
854         if (b)
855                 flush_bios(b);
856
857         return r;
858 }
859
860 static int origin_write_extent(struct dm_snapshot *merging_snap,
861                                sector_t sector, unsigned chunk_size);
862
863 static void merge_callback(int read_err, unsigned long write_err,
864                            void *context);
865
866 static uint64_t read_pending_exceptions_done_count(void)
867 {
868         uint64_t pending_exceptions_done;
869
870         spin_lock(&_pending_exceptions_done_spinlock);
871         pending_exceptions_done = _pending_exceptions_done_count;
872         spin_unlock(&_pending_exceptions_done_spinlock);
873
874         return pending_exceptions_done;
875 }
876
877 static void increment_pending_exceptions_done_count(void)
878 {
879         spin_lock(&_pending_exceptions_done_spinlock);
880         _pending_exceptions_done_count++;
881         spin_unlock(&_pending_exceptions_done_spinlock);
882
883         wake_up_all(&_pending_exceptions_done);
884 }
885
886 static void snapshot_merge_next_chunks(struct dm_snapshot *s)
887 {
888         int i, linear_chunks;
889         chunk_t old_chunk, new_chunk;
890         struct dm_io_region src, dest;
891         sector_t io_size;
892         uint64_t previous_count;
893
894         BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
895         if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
896                 goto shut;
897
898         /*
899          * valid flag never changes during merge, so no lock required.
900          */
901         if (!s->valid) {
902                 DMERR("Snapshot is invalid: can't merge");
903                 goto shut;
904         }
905
906         linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
907                                                       &new_chunk);
908         if (linear_chunks <= 0) {
909                 if (linear_chunks < 0) {
910                         DMERR("Read error in exception store: "
911                               "shutting down merge");
912                         down_write(&s->lock);
913                         s->merge_failed = 1;
914                         up_write(&s->lock);
915                 }
916                 goto shut;
917         }
918
919         /* Adjust old_chunk and new_chunk to reflect start of linear region */
920         old_chunk = old_chunk + 1 - linear_chunks;
921         new_chunk = new_chunk + 1 - linear_chunks;
922
923         /*
924          * Use one (potentially large) I/O to copy all 'linear_chunks'
925          * from the exception store to the origin
926          */
927         io_size = linear_chunks * s->store->chunk_size;
928
929         dest.bdev = s->origin->bdev;
930         dest.sector = chunk_to_sector(s->store, old_chunk);
931         dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
932
933         src.bdev = s->cow->bdev;
934         src.sector = chunk_to_sector(s->store, new_chunk);
935         src.count = dest.count;
936
937         /*
938          * Reallocate any exceptions needed in other snapshots then
939          * wait for the pending exceptions to complete.
940          * Each time any pending exception (globally on the system)
941          * completes we are woken and repeat the process to find out
942          * if we can proceed.  While this may not seem a particularly
943          * efficient algorithm, it is not expected to have any
944          * significant impact on performance.
945          */
946         previous_count = read_pending_exceptions_done_count();
947         while (origin_write_extent(s, dest.sector, io_size)) {
948                 wait_event(_pending_exceptions_done,
949                            (read_pending_exceptions_done_count() !=
950                             previous_count));
951                 /* Retry after the wait, until all exceptions are done. */
952                 previous_count = read_pending_exceptions_done_count();
953         }
954
955         down_write(&s->lock);
956         s->first_merging_chunk = old_chunk;
957         s->num_merging_chunks = linear_chunks;
958         up_write(&s->lock);
959
960         /* Wait until writes to all 'linear_chunks' drain */
961         for (i = 0; i < linear_chunks; i++)
962                 __check_for_conflicting_io(s, old_chunk + i);
963
964         dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
965         return;
966
967 shut:
968         merge_shutdown(s);
969 }
970
971 static void error_bios(struct bio *bio);
972
973 static void merge_callback(int read_err, unsigned long write_err, void *context)
974 {
975         struct dm_snapshot *s = context;
976         struct bio *b = NULL;
977
978         if (read_err || write_err) {
979                 if (read_err)
980                         DMERR("Read error: shutting down merge.");
981                 else
982                         DMERR("Write error: shutting down merge.");
983                 goto shut;
984         }
985
986         if (s->store->type->commit_merge(s->store,
987                                          s->num_merging_chunks) < 0) {
988                 DMERR("Write error in exception store: shutting down merge");
989                 goto shut;
990         }
991
992         if (remove_single_exception_chunk(s) < 0)
993                 goto shut;
994
995         snapshot_merge_next_chunks(s);
996
997         return;
998
999 shut:
1000         down_write(&s->lock);
1001         s->merge_failed = 1;
1002         b = __release_queued_bios_after_merge(s);
1003         up_write(&s->lock);
1004         error_bios(b);
1005
1006         merge_shutdown(s);
1007 }
1008
1009 static void start_merge(struct dm_snapshot *s)
1010 {
1011         if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1012                 snapshot_merge_next_chunks(s);
1013 }
1014
1015 static int wait_schedule(void *ptr)
1016 {
1017         schedule();
1018
1019         return 0;
1020 }
1021
1022 /*
1023  * Stop the merging process and wait until it finishes.
1024  */
1025 static void stop_merge(struct dm_snapshot *s)
1026 {
1027         set_bit(SHUTDOWN_MERGE, &s->state_bits);
1028         wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule,
1029                     TASK_UNINTERRUPTIBLE);
1030         clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1031 }
1032
1033 /*
1034  * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
1035  */
1036 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1037 {
1038         struct dm_snapshot *s;
1039         int i;
1040         int r = -EINVAL;
1041         char *origin_path, *cow_path;
1042         unsigned args_used, num_flush_bios = 1;
1043         fmode_t origin_mode = FMODE_READ;
1044
1045         if (argc != 4) {
1046                 ti->error = "requires exactly 4 arguments";
1047                 r = -EINVAL;
1048                 goto bad;
1049         }
1050
1051         if (dm_target_is_snapshot_merge(ti)) {
1052                 num_flush_bios = 2;
1053                 origin_mode = FMODE_WRITE;
1054         }
1055
1056         s = kmalloc(sizeof(*s), GFP_KERNEL);
1057         if (!s) {
1058                 ti->error = "Cannot allocate private snapshot structure";
1059                 r = -ENOMEM;
1060                 goto bad;
1061         }
1062
1063         origin_path = argv[0];
1064         argv++;
1065         argc--;
1066
1067         r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1068         if (r) {
1069                 ti->error = "Cannot get origin device";
1070                 goto bad_origin;
1071         }
1072
1073         cow_path = argv[0];
1074         argv++;
1075         argc--;
1076
1077         r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1078         if (r) {
1079                 ti->error = "Cannot get COW device";
1080                 goto bad_cow;
1081         }
1082
1083         r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1084         if (r) {
1085                 ti->error = "Couldn't create exception store";
1086                 r = -EINVAL;
1087                 goto bad_store;
1088         }
1089
1090         argv += args_used;
1091         argc -= args_used;
1092
1093         s->ti = ti;
1094         s->valid = 1;
1095         s->active = 0;
1096         atomic_set(&s->pending_exceptions_count, 0);
1097         init_rwsem(&s->lock);
1098         INIT_LIST_HEAD(&s->list);
1099         spin_lock_init(&s->pe_lock);
1100         s->state_bits = 0;
1101         s->merge_failed = 0;
1102         s->first_merging_chunk = 0;
1103         s->num_merging_chunks = 0;
1104         bio_list_init(&s->bios_queued_during_merge);
1105
1106         /* Allocate hash table for COW data */
1107         if (init_hash_tables(s)) {
1108                 ti->error = "Unable to allocate hash table space";
1109                 r = -ENOMEM;
1110                 goto bad_hash_tables;
1111         }
1112
1113         s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1114         if (IS_ERR(s->kcopyd_client)) {
1115                 r = PTR_ERR(s->kcopyd_client);
1116                 ti->error = "Could not create kcopyd client";
1117                 goto bad_kcopyd;
1118         }
1119
1120         s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
1121         if (!s->pending_pool) {
1122                 ti->error = "Could not allocate mempool for pending exceptions";
1123                 r = -ENOMEM;
1124                 goto bad_pending_pool;
1125         }
1126
1127         for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1128                 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1129
1130         spin_lock_init(&s->tracked_chunk_lock);
1131
1132         ti->private = s;
1133         ti->num_flush_bios = num_flush_bios;
1134         ti->per_bio_data_size = sizeof(struct dm_snap_tracked_chunk);
1135
1136         /* Add snapshot to the list of snapshots for this origin */
1137         /* Exceptions aren't triggered till snapshot_resume() is called */
1138         r = register_snapshot(s);
1139         if (r == -ENOMEM) {
1140                 ti->error = "Snapshot origin struct allocation failed";
1141                 goto bad_load_and_register;
1142         } else if (r < 0) {
1143                 /* invalid handover, register_snapshot has set ti->error */
1144                 goto bad_load_and_register;
1145         }
1146
1147         /*
1148          * Metadata must only be loaded into one table at once, so skip this
1149          * if metadata will be handed over during resume.
1150          * Chunk size will be set during the handover - set it to zero to
1151          * ensure it's ignored.
1152          */
1153         if (r > 0) {
1154                 s->store->chunk_size = 0;
1155                 return 0;
1156         }
1157
1158         r = s->store->type->read_metadata(s->store, dm_add_exception,
1159                                           (void *)s);
1160         if (r < 0) {
1161                 ti->error = "Failed to read snapshot metadata";
1162                 goto bad_read_metadata;
1163         } else if (r > 0) {
1164                 s->valid = 0;
1165                 DMWARN("Snapshot is marked invalid.");
1166         }
1167
1168         if (!s->store->chunk_size) {
1169                 ti->error = "Chunk size not set";
1170                 goto bad_read_metadata;
1171         }
1172
1173         r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1174         if (r)
1175                 goto bad_read_metadata;
1176
1177         return 0;
1178
1179 bad_read_metadata:
1180         unregister_snapshot(s);
1181
1182 bad_load_and_register:
1183         mempool_destroy(s->pending_pool);
1184
1185 bad_pending_pool:
1186         dm_kcopyd_client_destroy(s->kcopyd_client);
1187
1188 bad_kcopyd:
1189         dm_exception_table_exit(&s->pending, pending_cache);
1190         dm_exception_table_exit(&s->complete, exception_cache);
1191
1192 bad_hash_tables:
1193         dm_exception_store_destroy(s->store);
1194
1195 bad_store:
1196         dm_put_device(ti, s->cow);
1197
1198 bad_cow:
1199         dm_put_device(ti, s->origin);
1200
1201 bad_origin:
1202         kfree(s);
1203
1204 bad:
1205         return r;
1206 }
1207
1208 static void __free_exceptions(struct dm_snapshot *s)
1209 {
1210         dm_kcopyd_client_destroy(s->kcopyd_client);
1211         s->kcopyd_client = NULL;
1212
1213         dm_exception_table_exit(&s->pending, pending_cache);
1214         dm_exception_table_exit(&s->complete, exception_cache);
1215 }
1216
1217 static void __handover_exceptions(struct dm_snapshot *snap_src,
1218                                   struct dm_snapshot *snap_dest)
1219 {
1220         union {
1221                 struct dm_exception_table table_swap;
1222                 struct dm_exception_store *store_swap;
1223         } u;
1224
1225         /*
1226          * Swap all snapshot context information between the two instances.
1227          */
1228         u.table_swap = snap_dest->complete;
1229         snap_dest->complete = snap_src->complete;
1230         snap_src->complete = u.table_swap;
1231
1232         u.store_swap = snap_dest->store;
1233         snap_dest->store = snap_src->store;
1234         snap_src->store = u.store_swap;
1235
1236         snap_dest->store->snap = snap_dest;
1237         snap_src->store->snap = snap_src;
1238
1239         snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1240         snap_dest->valid = snap_src->valid;
1241
1242         /*
1243          * Set source invalid to ensure it receives no further I/O.
1244          */
1245         snap_src->valid = 0;
1246 }
1247
1248 static void snapshot_dtr(struct dm_target *ti)
1249 {
1250 #ifdef CONFIG_DM_DEBUG
1251         int i;
1252 #endif
1253         struct dm_snapshot *s = ti->private;
1254         struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1255
1256         down_read(&_origins_lock);
1257         /* Check whether exception handover must be cancelled */
1258         (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1259         if (snap_src && snap_dest && (s == snap_src)) {
1260                 down_write(&snap_dest->lock);
1261                 snap_dest->valid = 0;
1262                 up_write(&snap_dest->lock);
1263                 DMERR("Cancelling snapshot handover.");
1264         }
1265         up_read(&_origins_lock);
1266
1267         if (dm_target_is_snapshot_merge(ti))
1268                 stop_merge(s);
1269
1270         /* Prevent further origin writes from using this snapshot. */
1271         /* After this returns there can be no new kcopyd jobs. */
1272         unregister_snapshot(s);
1273
1274         while (atomic_read(&s->pending_exceptions_count))
1275                 msleep(1);
1276         /*
1277          * Ensure instructions in mempool_destroy aren't reordered
1278          * before atomic_read.
1279          */
1280         smp_mb();
1281
1282 #ifdef CONFIG_DM_DEBUG
1283         for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1284                 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1285 #endif
1286
1287         __free_exceptions(s);
1288
1289         mempool_destroy(s->pending_pool);
1290
1291         dm_exception_store_destroy(s->store);
1292
1293         dm_put_device(ti, s->cow);
1294
1295         dm_put_device(ti, s->origin);
1296
1297         kfree(s);
1298 }
1299
1300 /*
1301  * Flush a list of buffers.
1302  */
1303 static void flush_bios(struct bio *bio)
1304 {
1305         struct bio *n;
1306
1307         while (bio) {
1308                 n = bio->bi_next;
1309                 bio->bi_next = NULL;
1310                 generic_make_request(bio);
1311                 bio = n;
1312         }
1313 }
1314
1315 static int do_origin(struct dm_dev *origin, struct bio *bio);
1316
1317 /*
1318  * Flush a list of buffers.
1319  */
1320 static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1321 {
1322         struct bio *n;
1323         int r;
1324
1325         while (bio) {
1326                 n = bio->bi_next;
1327                 bio->bi_next = NULL;
1328                 r = do_origin(s->origin, bio);
1329                 if (r == DM_MAPIO_REMAPPED)
1330                         generic_make_request(bio);
1331                 bio = n;
1332         }
1333 }
1334
1335 /*
1336  * Error a list of buffers.
1337  */
1338 static void error_bios(struct bio *bio)
1339 {
1340         struct bio *n;
1341
1342         while (bio) {
1343                 n = bio->bi_next;
1344                 bio->bi_next = NULL;
1345                 bio_io_error(bio);
1346                 bio = n;
1347         }
1348 }
1349
1350 static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1351 {
1352         if (!s->valid)
1353                 return;
1354
1355         if (err == -EIO)
1356                 DMERR("Invalidating snapshot: Error reading/writing.");
1357         else if (err == -ENOMEM)
1358                 DMERR("Invalidating snapshot: Unable to allocate exception.");
1359
1360         if (s->store->type->drop_snapshot)
1361                 s->store->type->drop_snapshot(s->store);
1362
1363         s->valid = 0;
1364
1365         dm_table_event(s->ti->table);
1366 }
1367
1368 static void pending_complete(struct dm_snap_pending_exception *pe, int success)
1369 {
1370         struct dm_exception *e;
1371         struct dm_snapshot *s = pe->snap;
1372         struct bio *origin_bios = NULL;
1373         struct bio *snapshot_bios = NULL;
1374         struct bio *full_bio = NULL;
1375         int error = 0;
1376
1377         if (!success) {
1378                 /* Read/write error - snapshot is unusable */
1379                 down_write(&s->lock);
1380                 __invalidate_snapshot(s, -EIO);
1381                 error = 1;
1382                 goto out;
1383         }
1384
1385         e = alloc_completed_exception();
1386         if (!e) {
1387                 down_write(&s->lock);
1388                 __invalidate_snapshot(s, -ENOMEM);
1389                 error = 1;
1390                 goto out;
1391         }
1392         *e = pe->e;
1393
1394         down_write(&s->lock);
1395         if (!s->valid) {
1396                 free_completed_exception(e);
1397                 error = 1;
1398                 goto out;
1399         }
1400
1401         /* Check for conflicting reads */
1402         __check_for_conflicting_io(s, pe->e.old_chunk);
1403
1404         /*
1405          * Add a proper exception, and remove the
1406          * in-flight exception from the list.
1407          */
1408         dm_insert_exception(&s->complete, e);
1409
1410 out:
1411         dm_remove_exception(&pe->e);
1412         snapshot_bios = bio_list_get(&pe->snapshot_bios);
1413         origin_bios = bio_list_get(&pe->origin_bios);
1414         full_bio = pe->full_bio;
1415         if (full_bio) {
1416                 full_bio->bi_end_io = pe->full_bio_end_io;
1417                 full_bio->bi_private = pe->full_bio_private;
1418         }
1419         free_pending_exception(pe);
1420
1421         increment_pending_exceptions_done_count();
1422
1423         up_write(&s->lock);
1424
1425         /* Submit any pending write bios */
1426         if (error) {
1427                 if (full_bio)
1428                         bio_io_error(full_bio);
1429                 error_bios(snapshot_bios);
1430         } else {
1431                 if (full_bio)
1432                         bio_endio(full_bio, 0);
1433                 flush_bios(snapshot_bios);
1434         }
1435
1436         retry_origin_bios(s, origin_bios);
1437 }
1438
1439 static void commit_callback(void *context, int success)
1440 {
1441         struct dm_snap_pending_exception *pe = context;
1442
1443         pending_complete(pe, success);
1444 }
1445
1446 /*
1447  * Called when the copy I/O has finished.  kcopyd actually runs
1448  * this code so don't block.
1449  */
1450 static void copy_callback(int read_err, unsigned long write_err, void *context)
1451 {
1452         struct dm_snap_pending_exception *pe = context;
1453         struct dm_snapshot *s = pe->snap;
1454
1455         if (read_err || write_err)
1456                 pending_complete(pe, 0);
1457
1458         else
1459                 /* Update the metadata if we are persistent */
1460                 s->store->type->commit_exception(s->store, &pe->e,
1461                                                  commit_callback, pe);
1462 }
1463
1464 /*
1465  * Dispatches the copy operation to kcopyd.
1466  */
1467 static void start_copy(struct dm_snap_pending_exception *pe)
1468 {
1469         struct dm_snapshot *s = pe->snap;
1470         struct dm_io_region src, dest;
1471         struct block_device *bdev = s->origin->bdev;
1472         sector_t dev_size;
1473
1474         dev_size = get_dev_size(bdev);
1475
1476         src.bdev = bdev;
1477         src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1478         src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1479
1480         dest.bdev = s->cow->bdev;
1481         dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1482         dest.count = src.count;
1483
1484         /* Hand over to kcopyd */
1485         dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1486 }
1487
1488 static void full_bio_end_io(struct bio *bio, int error)
1489 {
1490         void *callback_data = bio->bi_private;
1491
1492         dm_kcopyd_do_callback(callback_data, 0, error ? 1 : 0);
1493 }
1494
1495 static void start_full_bio(struct dm_snap_pending_exception *pe,
1496                            struct bio *bio)
1497 {
1498         struct dm_snapshot *s = pe->snap;
1499         void *callback_data;
1500
1501         pe->full_bio = bio;
1502         pe->full_bio_end_io = bio->bi_end_io;
1503         pe->full_bio_private = bio->bi_private;
1504
1505         callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1506                                                    copy_callback, pe);
1507
1508         bio->bi_end_io = full_bio_end_io;
1509         bio->bi_private = callback_data;
1510
1511         generic_make_request(bio);
1512 }
1513
1514 static struct dm_snap_pending_exception *
1515 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1516 {
1517         struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1518
1519         if (!e)
1520                 return NULL;
1521
1522         return container_of(e, struct dm_snap_pending_exception, e);
1523 }
1524
1525 /*
1526  * Looks to see if this snapshot already has a pending exception
1527  * for this chunk, otherwise it allocates a new one and inserts
1528  * it into the pending table.
1529  *
1530  * NOTE: a write lock must be held on snap->lock before calling
1531  * this.
1532  */
1533 static struct dm_snap_pending_exception *
1534 __find_pending_exception(struct dm_snapshot *s,
1535                          struct dm_snap_pending_exception *pe, chunk_t chunk)
1536 {
1537         struct dm_snap_pending_exception *pe2;
1538
1539         pe2 = __lookup_pending_exception(s, chunk);
1540         if (pe2) {
1541                 free_pending_exception(pe);
1542                 return pe2;
1543         }
1544
1545         pe->e.old_chunk = chunk;
1546         bio_list_init(&pe->origin_bios);
1547         bio_list_init(&pe->snapshot_bios);
1548         pe->started = 0;
1549         pe->full_bio = NULL;
1550
1551         if (s->store->type->prepare_exception(s->store, &pe->e)) {
1552                 free_pending_exception(pe);
1553                 return NULL;
1554         }
1555
1556         dm_insert_exception(&s->pending, &pe->e);
1557
1558         return pe;
1559 }
1560
1561 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1562                             struct bio *bio, chunk_t chunk)
1563 {
1564         bio->bi_bdev = s->cow->bdev;
1565         bio->bi_sector = chunk_to_sector(s->store,
1566                                          dm_chunk_number(e->new_chunk) +
1567                                          (chunk - e->old_chunk)) +
1568                                          (bio->bi_sector &
1569                                           s->store->chunk_mask);
1570 }
1571
1572 static int snapshot_map(struct dm_target *ti, struct bio *bio)
1573 {
1574         struct dm_exception *e;
1575         struct dm_snapshot *s = ti->private;
1576         int r = DM_MAPIO_REMAPPED;
1577         chunk_t chunk;
1578         struct dm_snap_pending_exception *pe = NULL;
1579
1580         init_tracked_chunk(bio);
1581
1582         if (bio->bi_rw & REQ_FLUSH) {
1583                 bio->bi_bdev = s->cow->bdev;
1584                 return DM_MAPIO_REMAPPED;
1585         }
1586
1587         chunk = sector_to_chunk(s->store, bio->bi_sector);
1588
1589         /* Full snapshots are not usable */
1590         /* To get here the table must be live so s->active is always set. */
1591         if (!s->valid)
1592                 return -EIO;
1593
1594         /* FIXME: should only take write lock if we need
1595          * to copy an exception */
1596         down_write(&s->lock);
1597
1598         if (!s->valid) {
1599                 r = -EIO;
1600                 goto out_unlock;
1601         }
1602
1603         /* If the block is already remapped - use that, else remap it */
1604         e = dm_lookup_exception(&s->complete, chunk);
1605         if (e) {
1606                 remap_exception(s, e, bio, chunk);
1607                 goto out_unlock;
1608         }
1609
1610         /*
1611          * Write to snapshot - higher level takes care of RW/RO
1612          * flags so we should only get this if we are
1613          * writeable.
1614          */
1615         if (bio_rw(bio) == WRITE) {
1616                 pe = __lookup_pending_exception(s, chunk);
1617                 if (!pe) {
1618                         up_write(&s->lock);
1619                         pe = alloc_pending_exception(s);
1620                         down_write(&s->lock);
1621
1622                         if (!s->valid) {
1623                                 free_pending_exception(pe);
1624                                 r = -EIO;
1625                                 goto out_unlock;
1626                         }
1627
1628                         e = dm_lookup_exception(&s->complete, chunk);
1629                         if (e) {
1630                                 free_pending_exception(pe);
1631                                 remap_exception(s, e, bio, chunk);
1632                                 goto out_unlock;
1633                         }
1634
1635                         pe = __find_pending_exception(s, pe, chunk);
1636                         if (!pe) {
1637                                 __invalidate_snapshot(s, -ENOMEM);
1638                                 r = -EIO;
1639                                 goto out_unlock;
1640                         }
1641                 }
1642
1643                 remap_exception(s, &pe->e, bio, chunk);
1644
1645                 r = DM_MAPIO_SUBMITTED;
1646
1647                 if (!pe->started &&
1648                     bio->bi_size == (s->store->chunk_size << SECTOR_SHIFT)) {
1649                         pe->started = 1;
1650                         up_write(&s->lock);
1651                         start_full_bio(pe, bio);
1652                         goto out;
1653                 }
1654
1655                 bio_list_add(&pe->snapshot_bios, bio);
1656
1657                 if (!pe->started) {
1658                         /* this is protected by snap->lock */
1659                         pe->started = 1;
1660                         up_write(&s->lock);
1661                         start_copy(pe);
1662                         goto out;
1663                 }
1664         } else {
1665                 bio->bi_bdev = s->origin->bdev;
1666                 track_chunk(s, bio, chunk);
1667         }
1668
1669 out_unlock:
1670         up_write(&s->lock);
1671 out:
1672         return r;
1673 }
1674
1675 /*
1676  * A snapshot-merge target behaves like a combination of a snapshot
1677  * target and a snapshot-origin target.  It only generates new
1678  * exceptions in other snapshots and not in the one that is being
1679  * merged.
1680  *
1681  * For each chunk, if there is an existing exception, it is used to
1682  * redirect I/O to the cow device.  Otherwise I/O is sent to the origin,
1683  * which in turn might generate exceptions in other snapshots.
1684  * If merging is currently taking place on the chunk in question, the
1685  * I/O is deferred by adding it to s->bios_queued_during_merge.
1686  */
1687 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
1688 {
1689         struct dm_exception *e;
1690         struct dm_snapshot *s = ti->private;
1691         int r = DM_MAPIO_REMAPPED;
1692         chunk_t chunk;
1693
1694         init_tracked_chunk(bio);
1695
1696         if (bio->bi_rw & REQ_FLUSH) {
1697                 if (!dm_bio_get_target_bio_nr(bio))
1698                         bio->bi_bdev = s->origin->bdev;
1699                 else
1700                         bio->bi_bdev = s->cow->bdev;
1701                 return DM_MAPIO_REMAPPED;
1702         }
1703
1704         chunk = sector_to_chunk(s->store, bio->bi_sector);
1705
1706         down_write(&s->lock);
1707
1708         /* Full merging snapshots are redirected to the origin */
1709         if (!s->valid)
1710                 goto redirect_to_origin;
1711
1712         /* If the block is already remapped - use that */
1713         e = dm_lookup_exception(&s->complete, chunk);
1714         if (e) {
1715                 /* Queue writes overlapping with chunks being merged */
1716                 if (bio_rw(bio) == WRITE &&
1717                     chunk >= s->first_merging_chunk &&
1718                     chunk < (s->first_merging_chunk +
1719                              s->num_merging_chunks)) {
1720                         bio->bi_bdev = s->origin->bdev;
1721                         bio_list_add(&s->bios_queued_during_merge, bio);
1722                         r = DM_MAPIO_SUBMITTED;
1723                         goto out_unlock;
1724                 }
1725
1726                 remap_exception(s, e, bio, chunk);
1727
1728                 if (bio_rw(bio) == WRITE)
1729                         track_chunk(s, bio, chunk);
1730                 goto out_unlock;
1731         }
1732
1733 redirect_to_origin:
1734         bio->bi_bdev = s->origin->bdev;
1735
1736         if (bio_rw(bio) == WRITE) {
1737                 up_write(&s->lock);
1738                 return do_origin(s->origin, bio);
1739         }
1740
1741 out_unlock:
1742         up_write(&s->lock);
1743
1744         return r;
1745 }
1746
1747 static int snapshot_end_io(struct dm_target *ti, struct bio *bio, int error)
1748 {
1749         struct dm_snapshot *s = ti->private;
1750
1751         if (is_bio_tracked(bio))
1752                 stop_tracking_chunk(s, bio);
1753
1754         return 0;
1755 }
1756
1757 static void snapshot_merge_presuspend(struct dm_target *ti)
1758 {
1759         struct dm_snapshot *s = ti->private;
1760
1761         stop_merge(s);
1762 }
1763
1764 static int snapshot_preresume(struct dm_target *ti)
1765 {
1766         int r = 0;
1767         struct dm_snapshot *s = ti->private;
1768         struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1769
1770         down_read(&_origins_lock);
1771         (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1772         if (snap_src && snap_dest) {
1773                 down_read(&snap_src->lock);
1774                 if (s == snap_src) {
1775                         DMERR("Unable to resume snapshot source until "
1776                               "handover completes.");
1777                         r = -EINVAL;
1778                 } else if (!dm_suspended(snap_src->ti)) {
1779                         DMERR("Unable to perform snapshot handover until "
1780                               "source is suspended.");
1781                         r = -EINVAL;
1782                 }
1783                 up_read(&snap_src->lock);
1784         }
1785         up_read(&_origins_lock);
1786
1787         return r;
1788 }
1789
1790 static void snapshot_resume(struct dm_target *ti)
1791 {
1792         struct dm_snapshot *s = ti->private;
1793         struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1794
1795         down_read(&_origins_lock);
1796         (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1797         if (snap_src && snap_dest) {
1798                 down_write(&snap_src->lock);
1799                 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1800                 __handover_exceptions(snap_src, snap_dest);
1801                 up_write(&snap_dest->lock);
1802                 up_write(&snap_src->lock);
1803         }
1804         up_read(&_origins_lock);
1805
1806         /* Now we have correct chunk size, reregister */
1807         reregister_snapshot(s);
1808
1809         down_write(&s->lock);
1810         s->active = 1;
1811         up_write(&s->lock);
1812 }
1813
1814 static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
1815 {
1816         uint32_t min_chunksize;
1817
1818         down_read(&_origins_lock);
1819         min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
1820         up_read(&_origins_lock);
1821
1822         return min_chunksize;
1823 }
1824
1825 static void snapshot_merge_resume(struct dm_target *ti)
1826 {
1827         struct dm_snapshot *s = ti->private;
1828
1829         /*
1830          * Handover exceptions from existing snapshot.
1831          */
1832         snapshot_resume(ti);
1833
1834         /*
1835          * snapshot-merge acts as an origin, so set ti->max_io_len
1836          */
1837         ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
1838
1839         start_merge(s);
1840 }
1841
1842 static void snapshot_status(struct dm_target *ti, status_type_t type,
1843                             unsigned status_flags, char *result, unsigned maxlen)
1844 {
1845         unsigned sz = 0;
1846         struct dm_snapshot *snap = ti->private;
1847
1848         switch (type) {
1849         case STATUSTYPE_INFO:
1850
1851                 down_write(&snap->lock);
1852
1853                 if (!snap->valid)
1854                         DMEMIT("Invalid");
1855                 else if (snap->merge_failed)
1856                         DMEMIT("Merge failed");
1857                 else {
1858                         if (snap->store->type->usage) {
1859                                 sector_t total_sectors, sectors_allocated,
1860                                          metadata_sectors;
1861                                 snap->store->type->usage(snap->store,
1862                                                          &total_sectors,
1863                                                          &sectors_allocated,
1864                                                          &metadata_sectors);
1865                                 DMEMIT("%llu/%llu %llu",
1866                                        (unsigned long long)sectors_allocated,
1867                                        (unsigned long long)total_sectors,
1868                                        (unsigned long long)metadata_sectors);
1869                         }
1870                         else
1871                                 DMEMIT("Unknown");
1872                 }
1873
1874                 up_write(&snap->lock);
1875
1876                 break;
1877
1878         case STATUSTYPE_TABLE:
1879                 /*
1880                  * kdevname returns a static pointer so we need
1881                  * to make private copies if the output is to
1882                  * make sense.
1883                  */
1884                 DMEMIT("%s %s", snap->origin->name, snap->cow->name);
1885                 snap->store->type->status(snap->store, type, result + sz,
1886                                           maxlen - sz);
1887                 break;
1888         }
1889 }
1890
1891 static int snapshot_iterate_devices(struct dm_target *ti,
1892                                     iterate_devices_callout_fn fn, void *data)
1893 {
1894         struct dm_snapshot *snap = ti->private;
1895         int r;
1896
1897         r = fn(ti, snap->origin, 0, ti->len, data);
1898
1899         if (!r)
1900                 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
1901
1902         return r;
1903 }
1904
1905
1906 /*-----------------------------------------------------------------
1907  * Origin methods
1908  *---------------------------------------------------------------*/
1909
1910 /*
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
1914  * map.)
1915  *
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.
1919  */
1920 static int __origin_write(struct list_head *snapshots, sector_t sector,
1921                           struct bio *bio)
1922 {
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;
1929         chunk_t chunk;
1930
1931         /* Do all the snapshots on this origin */
1932         list_for_each_entry (snap, snapshots, list) {
1933                 /*
1934                  * Don't make new exceptions in a merging snapshot
1935                  * because it has effectively been deleted
1936                  */
1937                 if (dm_target_is_snapshot_merge(snap->ti))
1938                         continue;
1939
1940                 down_write(&snap->lock);
1941
1942                 /* Only deal with valid and active snapshots */
1943                 if (!snap->valid || !snap->active)
1944                         goto next_snapshot;
1945
1946                 /* Nothing to do if writing beyond end of snapshot */
1947                 if (sector >= dm_table_get_size(snap->ti->table))
1948                         goto next_snapshot;
1949
1950                 /*
1951                  * Remember, different snapshots can have
1952                  * different chunk sizes.
1953                  */
1954                 chunk = sector_to_chunk(snap->store, sector);
1955
1956                 /*
1957                  * Check exception table to see if block
1958                  * is already remapped in this snapshot
1959                  * and trigger an exception if not.
1960                  */
1961                 e = dm_lookup_exception(&snap->complete, chunk);
1962                 if (e)
1963                         goto next_snapshot;
1964
1965                 pe = __lookup_pending_exception(snap, chunk);
1966                 if (!pe) {
1967                         up_write(&snap->lock);
1968                         pe = alloc_pending_exception(snap);
1969                         down_write(&snap->lock);
1970
1971                         if (!snap->valid) {
1972                                 free_pending_exception(pe);
1973                                 goto next_snapshot;
1974                         }
1975
1976                         e = dm_lookup_exception(&snap->complete, chunk);
1977                         if (e) {
1978                                 free_pending_exception(pe);
1979                                 goto next_snapshot;
1980                         }
1981
1982                         pe = __find_pending_exception(snap, pe, chunk);
1983                         if (!pe) {
1984                                 __invalidate_snapshot(snap, -ENOMEM);
1985                                 goto next_snapshot;
1986                         }
1987                 }
1988
1989                 r = DM_MAPIO_SUBMITTED;
1990
1991                 /*
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.
1995                  */
1996                 if (bio) {
1997                         bio_list_add(&pe->origin_bios, bio);
1998                         bio = NULL;
1999
2000                         if (!pe->started) {
2001                                 pe->started = 1;
2002                                 pe_to_start_last = pe;
2003                         }
2004                 }
2005
2006                 if (!pe->started) {
2007                         pe->started = 1;
2008                         pe_to_start_now = pe;
2009                 }
2010
2011 next_snapshot:
2012                 up_write(&snap->lock);
2013
2014                 if (pe_to_start_now) {
2015                         start_copy(pe_to_start_now);
2016                         pe_to_start_now = NULL;
2017                 }
2018         }
2019
2020         /*
2021          * Submit the exception against which the bio is queued last,
2022          * to give the other exceptions a head start.
2023          */
2024         if (pe_to_start_last)
2025                 start_copy(pe_to_start_last);
2026
2027         return r;
2028 }
2029
2030 /*
2031  * Called on a write from the origin driver.
2032  */
2033 static int do_origin(struct dm_dev *origin, struct bio *bio)
2034 {
2035         struct origin *o;
2036         int r = DM_MAPIO_REMAPPED;
2037
2038         down_read(&_origins_lock);
2039         o = __lookup_origin(origin->bdev);
2040         if (o)
2041                 r = __origin_write(&o->snapshots, bio->bi_sector, bio);
2042         up_read(&_origins_lock);
2043
2044         return r;
2045 }
2046
2047 /*
2048  * Trigger exceptions in all non-merging snapshots.
2049  *
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.
2053  *
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.
2057  *
2058  * size must be a multiple of merging_snap's chunk_size.
2059  */
2060 static int origin_write_extent(struct dm_snapshot *merging_snap,
2061                                sector_t sector, unsigned size)
2062 {
2063         int must_wait = 0;
2064         sector_t n;
2065         struct origin *o;
2066
2067         /*
2068          * The origin's __minimum_chunk_size() got stored in max_io_len
2069          * by snapshot_merge_resume().
2070          */
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) ==
2075                     DM_MAPIO_SUBMITTED)
2076                         must_wait = 1;
2077         up_read(&_origins_lock);
2078
2079         return must_wait;
2080 }
2081
2082 /*
2083  * Origin: maps a linear range of a device, with hooks for snapshotting.
2084  */
2085
2086 /*
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.
2090  */
2091 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2092 {
2093         int r;
2094         struct dm_dev *dev;
2095
2096         if (argc != 1) {
2097                 ti->error = "origin: incorrect number of arguments";
2098                 return -EINVAL;
2099         }
2100
2101         r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dev);
2102         if (r) {
2103                 ti->error = "Cannot get target device";
2104                 return r;
2105         }
2106
2107         ti->private = dev;
2108         ti->num_flush_bios = 1;
2109
2110         return 0;
2111 }
2112
2113 static void origin_dtr(struct dm_target *ti)
2114 {
2115         struct dm_dev *dev = ti->private;
2116         dm_put_device(ti, dev);
2117 }
2118
2119 static int origin_map(struct dm_target *ti, struct bio *bio)
2120 {
2121         struct dm_dev *dev = ti->private;
2122         bio->bi_bdev = dev->bdev;
2123
2124         if (bio->bi_rw & REQ_FLUSH)
2125                 return DM_MAPIO_REMAPPED;
2126
2127         /* Only tell snapshots if this is a write */
2128         return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
2129 }
2130
2131 /*
2132  * Set the target "max_io_len" field to the minimum of all the snapshots'
2133  * chunk sizes.
2134  */
2135 static void origin_resume(struct dm_target *ti)
2136 {
2137         struct dm_dev *dev = ti->private;
2138
2139         ti->max_io_len = get_origin_minimum_chunksize(dev->bdev);
2140 }
2141
2142 static void origin_status(struct dm_target *ti, status_type_t type,
2143                           unsigned status_flags, char *result, unsigned maxlen)
2144 {
2145         struct dm_dev *dev = ti->private;
2146
2147         switch (type) {
2148         case STATUSTYPE_INFO:
2149                 result[0] = '\0';
2150                 break;
2151
2152         case STATUSTYPE_TABLE:
2153                 snprintf(result, maxlen, "%s", dev->name);
2154                 break;
2155         }
2156 }
2157
2158 static int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
2159                         struct bio_vec *biovec, int max_size)
2160 {
2161         struct dm_dev *dev = ti->private;
2162         struct request_queue *q = bdev_get_queue(dev->bdev);
2163
2164         if (!q->merge_bvec_fn)
2165                 return max_size;
2166
2167         bvm->bi_bdev = dev->bdev;
2168
2169         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2170 }
2171
2172 static int origin_iterate_devices(struct dm_target *ti,
2173                                   iterate_devices_callout_fn fn, void *data)
2174 {
2175         struct dm_dev *dev = ti->private;
2176
2177         return fn(ti, dev, 0, ti->len, data);
2178 }
2179
2180 static struct target_type origin_target = {
2181         .name    = "snapshot-origin",
2182         .version = {1, 8, 1},
2183         .module  = THIS_MODULE,
2184         .ctr     = origin_ctr,
2185         .dtr     = origin_dtr,
2186         .map     = origin_map,
2187         .resume  = origin_resume,
2188         .status  = origin_status,
2189         .merge   = origin_merge,
2190         .iterate_devices = origin_iterate_devices,
2191 };
2192
2193 static struct target_type snapshot_target = {
2194         .name    = "snapshot",
2195         .version = {1, 11, 1},
2196         .module  = THIS_MODULE,
2197         .ctr     = snapshot_ctr,
2198         .dtr     = snapshot_dtr,
2199         .map     = snapshot_map,
2200         .end_io  = snapshot_end_io,
2201         .preresume  = snapshot_preresume,
2202         .resume  = snapshot_resume,
2203         .status  = snapshot_status,
2204         .iterate_devices = snapshot_iterate_devices,
2205 };
2206
2207 static struct target_type merge_target = {
2208         .name    = dm_snapshot_merge_target_name,
2209         .version = {1, 2, 0},
2210         .module  = THIS_MODULE,
2211         .ctr     = snapshot_ctr,
2212         .dtr     = snapshot_dtr,
2213         .map     = snapshot_merge_map,
2214         .end_io  = snapshot_end_io,
2215         .presuspend = snapshot_merge_presuspend,
2216         .preresume  = snapshot_preresume,
2217         .resume  = snapshot_merge_resume,
2218         .status  = snapshot_status,
2219         .iterate_devices = snapshot_iterate_devices,
2220 };
2221
2222 static int __init dm_snapshot_init(void)
2223 {
2224         int r;
2225
2226         r = dm_exception_store_init();
2227         if (r) {
2228                 DMERR("Failed to initialize exception stores");
2229                 return r;
2230         }
2231
2232         r = dm_register_target(&snapshot_target);
2233         if (r < 0) {
2234                 DMERR("snapshot target register failed %d", r);
2235                 goto bad_register_snapshot_target;
2236         }
2237
2238         r = dm_register_target(&origin_target);
2239         if (r < 0) {
2240                 DMERR("Origin target register failed %d", r);
2241                 goto bad_register_origin_target;
2242         }
2243
2244         r = dm_register_target(&merge_target);
2245         if (r < 0) {
2246                 DMERR("Merge target register failed %d", r);
2247                 goto bad_register_merge_target;
2248         }
2249
2250         r = init_origin_hash();
2251         if (r) {
2252                 DMERR("init_origin_hash failed.");
2253                 goto bad_origin_hash;
2254         }
2255
2256         exception_cache = KMEM_CACHE(dm_exception, 0);
2257         if (!exception_cache) {
2258                 DMERR("Couldn't create exception cache.");
2259                 r = -ENOMEM;
2260                 goto bad_exception_cache;
2261         }
2262
2263         pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2264         if (!pending_cache) {
2265                 DMERR("Couldn't create pending cache.");
2266                 r = -ENOMEM;
2267                 goto bad_pending_cache;
2268         }
2269
2270         return 0;
2271
2272 bad_pending_cache:
2273         kmem_cache_destroy(exception_cache);
2274 bad_exception_cache:
2275         exit_origin_hash();
2276 bad_origin_hash:
2277         dm_unregister_target(&merge_target);
2278 bad_register_merge_target:
2279         dm_unregister_target(&origin_target);
2280 bad_register_origin_target:
2281         dm_unregister_target(&snapshot_target);
2282 bad_register_snapshot_target:
2283         dm_exception_store_exit();
2284
2285         return r;
2286 }
2287
2288 static void __exit dm_snapshot_exit(void)
2289 {
2290         dm_unregister_target(&snapshot_target);
2291         dm_unregister_target(&origin_target);
2292         dm_unregister_target(&merge_target);
2293
2294         exit_origin_hash();
2295         kmem_cache_destroy(pending_cache);
2296         kmem_cache_destroy(exception_cache);
2297
2298         dm_exception_store_exit();
2299 }
2300
2301 /* Module hooks */
2302 module_init(dm_snapshot_init);
2303 module_exit(dm_snapshot_exit);
2304
2305 MODULE_DESCRIPTION(DM_NAME " snapshot target");
2306 MODULE_AUTHOR("Joe Thornber");
2307 MODULE_LICENSE("GPL");
2308 MODULE_ALIAS("dm-snapshot-origin");
2309 MODULE_ALIAS("dm-snapshot-merge");