4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
6 * This file is released under the GPL.
9 #include <linux/blkdev.h>
10 #include <linux/ctype.h>
11 #include <linux/device-mapper.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>
22 #include "dm-bio-list.h"
25 #define DM_MSG_PREFIX "snapshots"
28 * The percentage increment we will wake up users at
30 #define WAKE_UP_PERCENT 5
33 * kcopyd priority of snapshot operations
35 #define SNAPSHOT_COPY_PRIORITY 2
38 * Each snapshot reserves this many pages for io
40 #define SNAPSHOT_PAGES 256
42 struct pending_exception {
46 * Origin buffers waiting for this to complete are held
49 struct bio_list origin_bios;
50 struct bio_list snapshot_bios;
53 * Short-term queue of pending exceptions prior to submission.
55 struct list_head list;
58 * The primary pending_exception is the one that holds
59 * the sibling_count and the list of origin_bios for a
60 * group of pending_exceptions. It is always last to get freed.
61 * These fields get set up when writing to the origin.
63 struct pending_exception *primary_pe;
66 * Number of pending_exceptions processing this chunk.
67 * When this drops to zero we must complete the origin bios.
68 * If incrementing or decrementing this, hold pe->snap->lock for
69 * the sibling concerned and not pe->primary_pe->snap->lock unless
72 atomic_t sibling_count;
74 /* Pointer back to snapshot context */
75 struct dm_snapshot *snap;
78 * 1 indicates the exception has already been sent to
85 * Hash table mapping origin volumes to lists of snapshots and
86 * a lock to protect it
88 static kmem_cache_t *exception_cache;
89 static kmem_cache_t *pending_cache;
90 static mempool_t *pending_pool;
93 * One of these per registered origin, held in the snapshot_origins hash
96 /* The origin device */
97 struct block_device *bdev;
99 struct list_head hash_list;
101 /* List of snapshots for this origin */
102 struct list_head snapshots;
106 * Size of the hash table for origin volumes. If we make this
107 * the size of the minors list then it should be nearly perfect
109 #define ORIGIN_HASH_SIZE 256
110 #define ORIGIN_MASK 0xFF
111 static struct list_head *_origins;
112 static struct rw_semaphore _origins_lock;
114 static int init_origin_hash(void)
118 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
121 DMERR("unable to allocate memory");
125 for (i = 0; i < ORIGIN_HASH_SIZE; i++)
126 INIT_LIST_HEAD(_origins + i);
127 init_rwsem(&_origins_lock);
132 static void exit_origin_hash(void)
137 static inline unsigned int origin_hash(struct block_device *bdev)
139 return bdev->bd_dev & ORIGIN_MASK;
142 static struct origin *__lookup_origin(struct block_device *origin)
144 struct list_head *ol;
147 ol = &_origins[origin_hash(origin)];
148 list_for_each_entry (o, ol, hash_list)
149 if (bdev_equal(o->bdev, origin))
155 static void __insert_origin(struct origin *o)
157 struct list_head *sl = &_origins[origin_hash(o->bdev)];
158 list_add_tail(&o->hash_list, sl);
162 * Make a note of the snapshot and its origin so we can look it
163 * up when the origin has a write on it.
165 static int register_snapshot(struct dm_snapshot *snap)
168 struct block_device *bdev = snap->origin->bdev;
170 down_write(&_origins_lock);
171 o = __lookup_origin(bdev);
175 o = kmalloc(sizeof(*o), GFP_KERNEL);
177 up_write(&_origins_lock);
181 /* Initialise the struct */
182 INIT_LIST_HEAD(&o->snapshots);
188 list_add_tail(&snap->list, &o->snapshots);
190 up_write(&_origins_lock);
194 static void unregister_snapshot(struct dm_snapshot *s)
198 down_write(&_origins_lock);
199 o = __lookup_origin(s->origin->bdev);
202 if (list_empty(&o->snapshots)) {
203 list_del(&o->hash_list);
207 up_write(&_origins_lock);
211 * Implementation of the exception hash tables.
213 static int init_exception_table(struct exception_table *et, uint32_t size)
217 et->hash_mask = size - 1;
218 et->table = dm_vcalloc(size, sizeof(struct list_head));
222 for (i = 0; i < size; i++)
223 INIT_LIST_HEAD(et->table + i);
228 static void exit_exception_table(struct exception_table *et, kmem_cache_t *mem)
230 struct list_head *slot;
231 struct exception *ex, *next;
234 size = et->hash_mask + 1;
235 for (i = 0; i < size; i++) {
236 slot = et->table + i;
238 list_for_each_entry_safe (ex, next, slot, hash_list)
239 kmem_cache_free(mem, ex);
245 static inline uint32_t exception_hash(struct exception_table *et, chunk_t chunk)
247 return chunk & et->hash_mask;
250 static void insert_exception(struct exception_table *eh, struct exception *e)
252 struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)];
253 list_add(&e->hash_list, l);
256 static inline void remove_exception(struct exception *e)
258 list_del(&e->hash_list);
262 * Return the exception data for a sector, or NULL if not
265 static struct exception *lookup_exception(struct exception_table *et,
268 struct list_head *slot;
271 slot = &et->table[exception_hash(et, chunk)];
272 list_for_each_entry (e, slot, hash_list)
273 if (e->old_chunk == chunk)
279 static inline struct exception *alloc_exception(void)
283 e = kmem_cache_alloc(exception_cache, GFP_NOIO);
285 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
290 static inline void free_exception(struct exception *e)
292 kmem_cache_free(exception_cache, e);
295 static inline struct pending_exception *alloc_pending_exception(void)
297 return mempool_alloc(pending_pool, GFP_NOIO);
300 static inline void free_pending_exception(struct pending_exception *pe)
302 mempool_free(pe, pending_pool);
305 int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
309 e = alloc_exception();
315 insert_exception(&s->complete, e);
322 static int calc_max_buckets(void)
324 /* use a fixed size of 2MB */
325 unsigned long mem = 2 * 1024 * 1024;
326 mem /= sizeof(struct list_head);
332 * Rounds a number down to a power of 2.
334 static inline uint32_t round_down(uint32_t n)
342 * Allocate room for a suitable hash table.
344 static int init_hash_tables(struct dm_snapshot *s)
346 sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
349 * Calculate based on the size of the original volume or
352 cow_dev_size = get_dev_size(s->cow->bdev);
353 origin_dev_size = get_dev_size(s->origin->bdev);
354 max_buckets = calc_max_buckets();
356 hash_size = min(origin_dev_size, cow_dev_size) >> s->chunk_shift;
357 hash_size = min(hash_size, max_buckets);
359 /* Round it down to a power of 2 */
360 hash_size = round_down(hash_size);
361 if (init_exception_table(&s->complete, hash_size))
365 * Allocate hash table for in-flight exceptions
366 * Make this smaller than the real hash table
372 if (init_exception_table(&s->pending, hash_size)) {
373 exit_exception_table(&s->complete, exception_cache);
381 * Round a number up to the nearest 'size' boundary. size must
384 static inline ulong round_up(ulong n, ulong size)
387 return (n + size) & ~size;
390 static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg,
393 unsigned long chunk_size;
396 chunk_size = simple_strtoul(chunk_size_arg, &value, 10);
397 if (*chunk_size_arg == '\0' || *value != '\0') {
398 *error = "Invalid chunk size";
403 s->chunk_size = s->chunk_mask = s->chunk_shift = 0;
408 * Chunk size must be multiple of page size. Silently
409 * round up if it's not.
411 chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
413 /* Check chunk_size is a power of 2 */
414 if (chunk_size & (chunk_size - 1)) {
415 *error = "Chunk size is not a power of 2";
419 /* Validate the chunk size against the device block size */
420 if (chunk_size % (bdev_hardsect_size(s->cow->bdev) >> 9)) {
421 *error = "Chunk size is not a multiple of device blocksize";
425 s->chunk_size = chunk_size;
426 s->chunk_mask = chunk_size - 1;
427 s->chunk_shift = ffs(chunk_size) - 1;
433 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
435 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
437 struct dm_snapshot *s;
444 ti->error = "requires exactly 4 arguments";
449 origin_path = argv[0];
451 persistent = toupper(*argv[2]);
453 if (persistent != 'P' && persistent != 'N') {
454 ti->error = "Persistent flag is not P or N";
459 s = kmalloc(sizeof(*s), GFP_KERNEL);
461 ti->error = "Cannot allocate snapshot context private "
467 r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
469 ti->error = "Cannot get origin device";
473 r = dm_get_device(ti, cow_path, 0, 0,
474 FMODE_READ | FMODE_WRITE, &s->cow);
476 dm_put_device(ti, s->origin);
477 ti->error = "Cannot get COW device";
481 r = set_chunk_size(s, argv[3], &ti->error);
485 s->type = persistent;
490 init_rwsem(&s->lock);
491 s->table = ti->table;
493 /* Allocate hash table for COW data */
494 if (init_hash_tables(s)) {
495 ti->error = "Unable to allocate hash table space";
502 if (persistent == 'P')
503 r = dm_create_persistent(&s->store);
505 r = dm_create_transient(&s->store);
508 ti->error = "Couldn't create exception store";
513 r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
515 ti->error = "Could not create kcopyd client";
519 /* Metadata must only be loaded into one table at once */
520 r = s->store.read_metadata(&s->store);
522 ti->error = "Failed to read snapshot metadata";
526 /* Add snapshot to the list of snapshots for this origin */
527 /* Exceptions aren't triggered till snapshot_resume() is called */
528 if (register_snapshot(s)) {
530 ti->error = "Cannot register snapshot origin";
535 ti->split_io = s->chunk_size;
540 kcopyd_client_destroy(s->kcopyd_client);
543 s->store.destroy(&s->store);
546 exit_exception_table(&s->pending, pending_cache);
547 exit_exception_table(&s->complete, exception_cache);
550 dm_put_device(ti, s->cow);
551 dm_put_device(ti, s->origin);
560 static void snapshot_dtr(struct dm_target *ti)
562 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
564 /* Prevent further origin writes from using this snapshot. */
565 /* After this returns there can be no new kcopyd jobs. */
566 unregister_snapshot(s);
568 kcopyd_client_destroy(s->kcopyd_client);
570 exit_exception_table(&s->pending, pending_cache);
571 exit_exception_table(&s->complete, exception_cache);
573 /* Deallocate memory used */
574 s->store.destroy(&s->store);
576 dm_put_device(ti, s->origin);
577 dm_put_device(ti, s->cow);
583 * Flush a list of buffers.
585 static void flush_bios(struct bio *bio)
592 generic_make_request(bio);
598 * Error a list of buffers.
600 static void error_bios(struct bio *bio)
607 bio_io_error(bio, bio->bi_size);
612 static void __invalidate_snapshot(struct dm_snapshot *s,
613 struct pending_exception *pe, int err)
619 DMERR("Invalidating snapshot: Error reading/writing.");
620 else if (err == -ENOMEM)
621 DMERR("Invalidating snapshot: Unable to allocate exception.");
624 remove_exception(&pe->e);
626 if (s->store.drop_snapshot)
627 s->store.drop_snapshot(&s->store);
631 dm_table_event(s->table);
634 static void pending_complete(struct pending_exception *pe, int success)
637 struct pending_exception *primary_pe;
638 struct dm_snapshot *s = pe->snap;
639 struct bio *origin_bios = NULL;
640 struct bio *snapshot_bios = NULL;
644 /* Read/write error - snapshot is unusable */
645 down_write(&s->lock);
646 __invalidate_snapshot(s, pe, -EIO);
651 e = alloc_exception();
653 down_write(&s->lock);
654 __invalidate_snapshot(s, pe, -ENOMEM);
660 down_write(&s->lock);
668 * Add a proper exception, and remove the
669 * in-flight exception from the list.
671 insert_exception(&s->complete, e);
672 remove_exception(&pe->e);
675 snapshot_bios = bio_list_get(&pe->snapshot_bios);
677 primary_pe = pe->primary_pe;
680 * If this pe is involved in a write to the origin and
681 * it is the last sibling to complete then release
682 * the bios for the original write to the origin.
685 atomic_dec_and_test(&primary_pe->sibling_count))
686 origin_bios = bio_list_get(&primary_pe->origin_bios);
689 * Free the pe if it's not linked to an origin write or if
690 * it's not itself a primary pe.
692 if (!primary_pe || primary_pe != pe)
693 free_pending_exception(pe);
696 * Free the primary pe if nothing references it.
698 if (primary_pe && !atomic_read(&primary_pe->sibling_count))
699 free_pending_exception(primary_pe);
703 /* Submit any pending write bios */
705 error_bios(snapshot_bios);
707 flush_bios(snapshot_bios);
709 flush_bios(origin_bios);
712 static void commit_callback(void *context, int success)
714 struct pending_exception *pe = (struct pending_exception *) context;
715 pending_complete(pe, success);
719 * Called when the copy I/O has finished. kcopyd actually runs
720 * this code so don't block.
722 static void copy_callback(int read_err, unsigned int write_err, void *context)
724 struct pending_exception *pe = (struct pending_exception *) context;
725 struct dm_snapshot *s = pe->snap;
727 if (read_err || write_err)
728 pending_complete(pe, 0);
731 /* Update the metadata if we are persistent */
732 s->store.commit_exception(&s->store, &pe->e, commit_callback,
737 * Dispatches the copy operation to kcopyd.
739 static void start_copy(struct pending_exception *pe)
741 struct dm_snapshot *s = pe->snap;
742 struct io_region src, dest;
743 struct block_device *bdev = s->origin->bdev;
746 dev_size = get_dev_size(bdev);
749 src.sector = chunk_to_sector(s, pe->e.old_chunk);
750 src.count = min(s->chunk_size, dev_size - src.sector);
752 dest.bdev = s->cow->bdev;
753 dest.sector = chunk_to_sector(s, pe->e.new_chunk);
754 dest.count = src.count;
756 /* Hand over to kcopyd */
757 kcopyd_copy(s->kcopyd_client,
758 &src, 1, &dest, 0, copy_callback, pe);
762 * Looks to see if this snapshot already has a pending exception
763 * for this chunk, otherwise it allocates a new one and inserts
764 * it into the pending table.
766 * NOTE: a write lock must be held on snap->lock before calling
769 static struct pending_exception *
770 __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
773 struct pending_exception *pe;
774 chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
777 * Is there a pending exception for this already ?
779 e = lookup_exception(&s->pending, chunk);
781 /* cast the exception to a pending exception */
782 pe = container_of(e, struct pending_exception, e);
787 * Create a new pending exception, we don't want
788 * to hold the lock while we do this.
791 pe = alloc_pending_exception();
792 down_write(&s->lock);
795 free_pending_exception(pe);
799 e = lookup_exception(&s->pending, chunk);
801 free_pending_exception(pe);
802 pe = container_of(e, struct pending_exception, e);
806 pe->e.old_chunk = chunk;
807 bio_list_init(&pe->origin_bios);
808 bio_list_init(&pe->snapshot_bios);
809 pe->primary_pe = NULL;
810 atomic_set(&pe->sibling_count, 1);
814 if (s->store.prepare_exception(&s->store, &pe->e)) {
815 free_pending_exception(pe);
819 insert_exception(&s->pending, &pe->e);
825 static inline void remap_exception(struct dm_snapshot *s, struct exception *e,
828 bio->bi_bdev = s->cow->bdev;
829 bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
830 (bio->bi_sector & s->chunk_mask);
833 static int snapshot_map(struct dm_target *ti, struct bio *bio,
834 union map_info *map_context)
837 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
840 struct pending_exception *pe = NULL;
842 chunk = sector_to_chunk(s, bio->bi_sector);
844 /* Full snapshots are not usable */
845 /* To get here the table must be live so s->active is always set. */
849 if (unlikely(bio_barrier(bio)))
852 /* FIXME: should only take write lock if we need
853 * to copy an exception */
854 down_write(&s->lock);
861 /* If the block is already remapped - use that, else remap it */
862 e = lookup_exception(&s->complete, chunk);
864 remap_exception(s, e, bio);
869 * Write to snapshot - higher level takes care of RW/RO
870 * flags so we should only get this if we are
873 if (bio_rw(bio) == WRITE) {
874 pe = __find_pending_exception(s, bio);
876 __invalidate_snapshot(s, pe, -ENOMEM);
881 remap_exception(s, &pe->e, bio);
882 bio_list_add(&pe->snapshot_bios, bio);
887 /* this is protected by snap->lock */
895 * FIXME: this read path scares me because we
896 * always use the origin when we have a pending
897 * exception. However I can't think of a
898 * situation where this is wrong - ejt.
900 bio->bi_bdev = s->origin->bdev;
908 static void snapshot_resume(struct dm_target *ti)
910 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
912 down_write(&s->lock);
917 static int snapshot_status(struct dm_target *ti, status_type_t type,
918 char *result, unsigned int maxlen)
920 struct dm_snapshot *snap = (struct dm_snapshot *) ti->private;
923 case STATUSTYPE_INFO:
925 snprintf(result, maxlen, "Invalid");
927 if (snap->store.fraction_full) {
928 sector_t numerator, denominator;
929 snap->store.fraction_full(&snap->store,
932 snprintf(result, maxlen, "%llu/%llu",
933 (unsigned long long)numerator,
934 (unsigned long long)denominator);
937 snprintf(result, maxlen, "Unknown");
941 case STATUSTYPE_TABLE:
943 * kdevname returns a static pointer so we need
944 * to make private copies if the output is to
947 snprintf(result, maxlen, "%s %s %c %llu",
948 snap->origin->name, snap->cow->name,
950 (unsigned long long)snap->chunk_size);
957 /*-----------------------------------------------------------------
959 *---------------------------------------------------------------*/
960 static int __origin_write(struct list_head *snapshots, struct bio *bio)
962 int r = 1, first = 0;
963 struct dm_snapshot *snap;
965 struct pending_exception *pe, *next_pe, *primary_pe = NULL;
969 /* Do all the snapshots on this origin */
970 list_for_each_entry (snap, snapshots, list) {
972 down_write(&snap->lock);
974 /* Only deal with valid and active snapshots */
975 if (!snap->valid || !snap->active)
978 /* Nothing to do if writing beyond end of snapshot */
979 if (bio->bi_sector >= dm_table_get_size(snap->table))
983 * Remember, different snapshots can have
984 * different chunk sizes.
986 chunk = sector_to_chunk(snap, bio->bi_sector);
989 * Check exception table to see if block
990 * is already remapped in this snapshot
991 * and trigger an exception if not.
993 * sibling_count is initialised to 1 so pending_complete()
994 * won't destroy the primary_pe while we're inside this loop.
996 e = lookup_exception(&snap->complete, chunk);
1000 pe = __find_pending_exception(snap, bio);
1002 __invalidate_snapshot(snap, pe, -ENOMEM);
1008 * Either every pe here has same
1009 * primary_pe or none has one yet.
1012 primary_pe = pe->primary_pe;
1018 bio_list_add(&primary_pe->origin_bios, bio);
1023 if (!pe->primary_pe) {
1024 atomic_inc(&primary_pe->sibling_count);
1025 pe->primary_pe = primary_pe;
1030 list_add_tail(&pe->list, &pe_queue);
1034 up_write(&snap->lock);
1041 * If this is the first time we're processing this chunk and
1042 * sibling_count is now 1 it means all the pending exceptions
1043 * got completed while we were in the loop above, so it falls to
1044 * us here to remove the primary_pe and submit any origin_bios.
1047 if (first && atomic_dec_and_test(&primary_pe->sibling_count)) {
1048 flush_bios(bio_list_get(&primary_pe->origin_bios));
1049 free_pending_exception(primary_pe);
1050 /* If we got here, pe_queue is necessarily empty. */
1055 * Now that we have a complete pe list we can start the copying.
1057 list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
1065 * Called on a write from the origin driver.
1067 static int do_origin(struct dm_dev *origin, struct bio *bio)
1072 down_read(&_origins_lock);
1073 o = __lookup_origin(origin->bdev);
1075 r = __origin_write(&o->snapshots, bio);
1076 up_read(&_origins_lock);
1082 * Origin: maps a linear range of a device, with hooks for snapshotting.
1086 * Construct an origin mapping: <dev_path>
1087 * The context for an origin is merely a 'struct dm_dev *'
1088 * pointing to the real device.
1090 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1096 ti->error = "origin: incorrect number of arguments";
1100 r = dm_get_device(ti, argv[0], 0, ti->len,
1101 dm_table_get_mode(ti->table), &dev);
1103 ti->error = "Cannot get target device";
1111 static void origin_dtr(struct dm_target *ti)
1113 struct dm_dev *dev = (struct dm_dev *) ti->private;
1114 dm_put_device(ti, dev);
1117 static int origin_map(struct dm_target *ti, struct bio *bio,
1118 union map_info *map_context)
1120 struct dm_dev *dev = (struct dm_dev *) ti->private;
1121 bio->bi_bdev = dev->bdev;
1123 if (unlikely(bio_barrier(bio)))
1126 /* Only tell snapshots if this is a write */
1127 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
1130 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
1133 * Set the target "split_io" field to the minimum of all the snapshots'
1136 static void origin_resume(struct dm_target *ti)
1138 struct dm_dev *dev = (struct dm_dev *) ti->private;
1139 struct dm_snapshot *snap;
1141 chunk_t chunk_size = 0;
1143 down_read(&_origins_lock);
1144 o = __lookup_origin(dev->bdev);
1146 list_for_each_entry (snap, &o->snapshots, list)
1147 chunk_size = min_not_zero(chunk_size, snap->chunk_size);
1148 up_read(&_origins_lock);
1150 ti->split_io = chunk_size;
1153 static int origin_status(struct dm_target *ti, status_type_t type, char *result,
1154 unsigned int maxlen)
1156 struct dm_dev *dev = (struct dm_dev *) ti->private;
1159 case STATUSTYPE_INFO:
1163 case STATUSTYPE_TABLE:
1164 snprintf(result, maxlen, "%s", dev->name);
1171 static struct target_type origin_target = {
1172 .name = "snapshot-origin",
1173 .version = {1, 5, 0},
1174 .module = THIS_MODULE,
1178 .resume = origin_resume,
1179 .status = origin_status,
1182 static struct target_type snapshot_target = {
1184 .version = {1, 5, 0},
1185 .module = THIS_MODULE,
1186 .ctr = snapshot_ctr,
1187 .dtr = snapshot_dtr,
1188 .map = snapshot_map,
1189 .resume = snapshot_resume,
1190 .status = snapshot_status,
1193 static int __init dm_snapshot_init(void)
1197 r = dm_register_target(&snapshot_target);
1199 DMERR("snapshot target register failed %d", r);
1203 r = dm_register_target(&origin_target);
1205 DMERR("Origin target register failed %d", r);
1209 r = init_origin_hash();
1211 DMERR("init_origin_hash failed.");
1215 exception_cache = kmem_cache_create("dm-snapshot-ex",
1216 sizeof(struct exception),
1217 __alignof__(struct exception),
1219 if (!exception_cache) {
1220 DMERR("Couldn't create exception cache.");
1226 kmem_cache_create("dm-snapshot-in",
1227 sizeof(struct pending_exception),
1228 __alignof__(struct pending_exception),
1230 if (!pending_cache) {
1231 DMERR("Couldn't create pending cache.");
1236 pending_pool = mempool_create_slab_pool(128, pending_cache);
1237 if (!pending_pool) {
1238 DMERR("Couldn't create pending pool.");
1246 kmem_cache_destroy(pending_cache);
1248 kmem_cache_destroy(exception_cache);
1252 dm_unregister_target(&origin_target);
1254 dm_unregister_target(&snapshot_target);
1258 static void __exit dm_snapshot_exit(void)
1262 r = dm_unregister_target(&snapshot_target);
1264 DMERR("snapshot unregister failed %d", r);
1266 r = dm_unregister_target(&origin_target);
1268 DMERR("origin unregister failed %d", r);
1271 mempool_destroy(pending_pool);
1272 kmem_cache_destroy(pending_cache);
1273 kmem_cache_destroy(exception_cache);
1277 module_init(dm_snapshot_init);
1278 module_exit(dm_snapshot_exit);
1280 MODULE_DESCRIPTION(DM_NAME " snapshot target");
1281 MODULE_AUTHOR("Joe Thornber");
1282 MODULE_LICENSE("GPL");