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 void read_snapshot_metadata(struct dm_snapshot *s)
392 if (s->store.read_metadata(&s->store)) {
393 down_write(&s->lock);
397 dm_table_event(s->table);
401 static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg,
404 unsigned long chunk_size;
407 chunk_size = simple_strtoul(chunk_size_arg, &value, 10);
408 if (*chunk_size_arg == '\0' || *value != '\0') {
409 *error = "Invalid chunk size";
414 s->chunk_size = s->chunk_mask = s->chunk_shift = 0;
419 * Chunk size must be multiple of page size. Silently
420 * round up if it's not.
422 chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
424 /* Check chunk_size is a power of 2 */
425 if (chunk_size & (chunk_size - 1)) {
426 *error = "Chunk size is not a power of 2";
430 /* Validate the chunk size against the device block size */
431 if (chunk_size % (bdev_hardsect_size(s->cow->bdev) >> 9)) {
432 *error = "Chunk size is not a multiple of device blocksize";
436 s->chunk_size = chunk_size;
437 s->chunk_mask = chunk_size - 1;
438 s->chunk_shift = ffs(chunk_size) - 1;
444 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
446 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
448 struct dm_snapshot *s;
455 ti->error = "requires exactly 4 arguments";
460 origin_path = argv[0];
462 persistent = toupper(*argv[2]);
464 if (persistent != 'P' && persistent != 'N') {
465 ti->error = "Persistent flag is not P or N";
470 s = kmalloc(sizeof(*s), GFP_KERNEL);
472 ti->error = "Cannot allocate snapshot context private "
478 r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
480 ti->error = "Cannot get origin device";
484 r = dm_get_device(ti, cow_path, 0, 0,
485 FMODE_READ | FMODE_WRITE, &s->cow);
487 dm_put_device(ti, s->origin);
488 ti->error = "Cannot get COW device";
492 r = set_chunk_size(s, argv[3], &ti->error);
496 s->type = persistent;
501 init_rwsem(&s->lock);
502 s->table = ti->table;
504 /* Allocate hash table for COW data */
505 if (init_hash_tables(s)) {
506 ti->error = "Unable to allocate hash table space";
513 if (persistent == 'P')
514 r = dm_create_persistent(&s->store);
516 r = dm_create_transient(&s->store);
519 ti->error = "Couldn't create exception store";
524 r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
526 ti->error = "Could not create kcopyd client";
530 /* Metadata must only be loaded into one table at once */
531 read_snapshot_metadata(s);
533 /* Add snapshot to the list of snapshots for this origin */
534 /* Exceptions aren't triggered till snapshot_resume() is called */
535 if (register_snapshot(s)) {
537 ti->error = "Cannot register snapshot origin";
542 ti->split_io = s->chunk_size;
547 kcopyd_client_destroy(s->kcopyd_client);
550 s->store.destroy(&s->store);
553 exit_exception_table(&s->pending, pending_cache);
554 exit_exception_table(&s->complete, exception_cache);
557 dm_put_device(ti, s->cow);
558 dm_put_device(ti, s->origin);
567 static void snapshot_dtr(struct dm_target *ti)
569 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
571 /* Prevent further origin writes from using this snapshot. */
572 /* After this returns there can be no new kcopyd jobs. */
573 unregister_snapshot(s);
575 kcopyd_client_destroy(s->kcopyd_client);
577 exit_exception_table(&s->pending, pending_cache);
578 exit_exception_table(&s->complete, exception_cache);
580 /* Deallocate memory used */
581 s->store.destroy(&s->store);
583 dm_put_device(ti, s->origin);
584 dm_put_device(ti, s->cow);
590 * Flush a list of buffers.
592 static void flush_bios(struct bio *bio)
599 generic_make_request(bio);
605 * Error a list of buffers.
607 static void error_bios(struct bio *bio)
614 bio_io_error(bio, bio->bi_size);
619 static inline void error_snapshot_bios(struct pending_exception *pe)
621 error_bios(bio_list_get(&pe->snapshot_bios));
624 static struct bio *__flush_bios(struct pending_exception *pe)
627 * If this pe is involved in a write to the origin and
628 * it is the last sibling to complete then release
629 * the bios for the original write to the origin.
632 if (pe->primary_pe &&
633 atomic_dec_and_test(&pe->primary_pe->sibling_count))
634 return bio_list_get(&pe->primary_pe->origin_bios);
639 static void __invalidate_snapshot(struct dm_snapshot *s,
640 struct pending_exception *pe, int err)
646 DMERR("Invalidating snapshot: Error reading/writing.");
647 else if (err == -ENOMEM)
648 DMERR("Invalidating snapshot: Unable to allocate exception.");
651 remove_exception(&pe->e);
653 if (s->store.drop_snapshot)
654 s->store.drop_snapshot(&s->store);
658 dm_table_event(s->table);
661 static void pending_complete(struct pending_exception *pe, int success)
664 struct pending_exception *primary_pe;
665 struct dm_snapshot *s = pe->snap;
666 struct bio *flush = NULL;
669 /* Read/write error - snapshot is unusable */
670 down_write(&s->lock);
671 __invalidate_snapshot(s, pe, -EIO);
672 flush = __flush_bios(pe);
675 error_snapshot_bios(pe);
679 e = alloc_exception();
681 down_write(&s->lock);
682 __invalidate_snapshot(s, pe, -ENOMEM);
683 flush = __flush_bios(pe);
686 error_snapshot_bios(pe);
692 * Add a proper exception, and remove the
693 * in-flight exception from the list.
695 down_write(&s->lock);
697 flush = __flush_bios(pe);
702 error_snapshot_bios(pe);
706 insert_exception(&s->complete, e);
707 remove_exception(&pe->e);
708 flush = __flush_bios(pe);
712 /* Submit any pending write bios */
713 flush_bios(bio_list_get(&pe->snapshot_bios));
716 primary_pe = pe->primary_pe;
719 * Free the pe if it's not linked to an origin write or if
720 * it's not itself a primary pe.
722 if (!primary_pe || primary_pe != pe)
723 free_pending_exception(pe);
726 * Free the primary pe if nothing references it.
728 if (primary_pe && !atomic_read(&primary_pe->sibling_count))
729 free_pending_exception(primary_pe);
735 static void commit_callback(void *context, int success)
737 struct pending_exception *pe = (struct pending_exception *) context;
738 pending_complete(pe, success);
742 * Called when the copy I/O has finished. kcopyd actually runs
743 * this code so don't block.
745 static void copy_callback(int read_err, unsigned int write_err, void *context)
747 struct pending_exception *pe = (struct pending_exception *) context;
748 struct dm_snapshot *s = pe->snap;
750 if (read_err || write_err)
751 pending_complete(pe, 0);
754 /* Update the metadata if we are persistent */
755 s->store.commit_exception(&s->store, &pe->e, commit_callback,
760 * Dispatches the copy operation to kcopyd.
762 static void start_copy(struct pending_exception *pe)
764 struct dm_snapshot *s = pe->snap;
765 struct io_region src, dest;
766 struct block_device *bdev = s->origin->bdev;
769 dev_size = get_dev_size(bdev);
772 src.sector = chunk_to_sector(s, pe->e.old_chunk);
773 src.count = min(s->chunk_size, dev_size - src.sector);
775 dest.bdev = s->cow->bdev;
776 dest.sector = chunk_to_sector(s, pe->e.new_chunk);
777 dest.count = src.count;
779 /* Hand over to kcopyd */
780 kcopyd_copy(s->kcopyd_client,
781 &src, 1, &dest, 0, copy_callback, pe);
785 * Looks to see if this snapshot already has a pending exception
786 * for this chunk, otherwise it allocates a new one and inserts
787 * it into the pending table.
789 * NOTE: a write lock must be held on snap->lock before calling
792 static struct pending_exception *
793 __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
796 struct pending_exception *pe;
797 chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
800 * Is there a pending exception for this already ?
802 e = lookup_exception(&s->pending, chunk);
804 /* cast the exception to a pending exception */
805 pe = container_of(e, struct pending_exception, e);
810 * Create a new pending exception, we don't want
811 * to hold the lock while we do this.
814 pe = alloc_pending_exception();
815 down_write(&s->lock);
818 free_pending_exception(pe);
822 e = lookup_exception(&s->pending, chunk);
824 free_pending_exception(pe);
825 pe = container_of(e, struct pending_exception, e);
829 pe->e.old_chunk = chunk;
830 bio_list_init(&pe->origin_bios);
831 bio_list_init(&pe->snapshot_bios);
832 pe->primary_pe = NULL;
833 atomic_set(&pe->sibling_count, 1);
837 if (s->store.prepare_exception(&s->store, &pe->e)) {
838 free_pending_exception(pe);
842 insert_exception(&s->pending, &pe->e);
848 static inline void remap_exception(struct dm_snapshot *s, struct exception *e,
851 bio->bi_bdev = s->cow->bdev;
852 bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
853 (bio->bi_sector & s->chunk_mask);
856 static int snapshot_map(struct dm_target *ti, struct bio *bio,
857 union map_info *map_context)
860 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
864 struct pending_exception *pe = NULL;
866 chunk = sector_to_chunk(s, bio->bi_sector);
868 /* Full snapshots are not usable */
869 /* To get here the table must be live so s->active is always set. */
873 if (unlikely(bio_barrier(bio)))
877 * Write to snapshot - higher level takes care of RW/RO
878 * flags so we should only get this if we are
881 if (bio_rw(bio) == WRITE) {
883 /* FIXME: should only take write lock if we need
884 * to copy an exception */
885 down_write(&s->lock);
892 /* If the block is already remapped - use that, else remap it */
893 e = lookup_exception(&s->complete, chunk);
895 remap_exception(s, e, bio);
899 pe = __find_pending_exception(s, bio);
901 __invalidate_snapshot(s, pe, -ENOMEM);
906 remap_exception(s, &pe->e, bio);
907 bio_list_add(&pe->snapshot_bios, bio);
910 /* this is protected by snap->lock */
924 * FIXME: this read path scares me because we
925 * always use the origin when we have a pending
926 * exception. However I can't think of a
927 * situation where this is wrong - ejt.
938 /* See if it it has been remapped */
939 e = lookup_exception(&s->complete, chunk);
941 remap_exception(s, e, bio);
943 bio->bi_bdev = s->origin->bdev;
951 static void snapshot_resume(struct dm_target *ti)
953 struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
955 down_write(&s->lock);
960 static int snapshot_status(struct dm_target *ti, status_type_t type,
961 char *result, unsigned int maxlen)
963 struct dm_snapshot *snap = (struct dm_snapshot *) ti->private;
966 case STATUSTYPE_INFO:
968 snprintf(result, maxlen, "Invalid");
970 if (snap->store.fraction_full) {
971 sector_t numerator, denominator;
972 snap->store.fraction_full(&snap->store,
975 snprintf(result, maxlen, "%llu/%llu",
976 (unsigned long long)numerator,
977 (unsigned long long)denominator);
980 snprintf(result, maxlen, "Unknown");
984 case STATUSTYPE_TABLE:
986 * kdevname returns a static pointer so we need
987 * to make private copies if the output is to
990 snprintf(result, maxlen, "%s %s %c %llu",
991 snap->origin->name, snap->cow->name,
993 (unsigned long long)snap->chunk_size);
1000 /*-----------------------------------------------------------------
1002 *---------------------------------------------------------------*/
1003 static int __origin_write(struct list_head *snapshots, struct bio *bio)
1005 int r = 1, first = 0;
1006 struct dm_snapshot *snap;
1007 struct exception *e;
1008 struct pending_exception *pe, *next_pe, *primary_pe = NULL;
1010 LIST_HEAD(pe_queue);
1012 /* Do all the snapshots on this origin */
1013 list_for_each_entry (snap, snapshots, list) {
1015 down_write(&snap->lock);
1017 /* Only deal with valid and active snapshots */
1018 if (!snap->valid || !snap->active)
1021 /* Nothing to do if writing beyond end of snapshot */
1022 if (bio->bi_sector >= dm_table_get_size(snap->table))
1026 * Remember, different snapshots can have
1027 * different chunk sizes.
1029 chunk = sector_to_chunk(snap, bio->bi_sector);
1032 * Check exception table to see if block
1033 * is already remapped in this snapshot
1034 * and trigger an exception if not.
1036 * sibling_count is initialised to 1 so pending_complete()
1037 * won't destroy the primary_pe while we're inside this loop.
1039 e = lookup_exception(&snap->complete, chunk);
1043 pe = __find_pending_exception(snap, bio);
1045 __invalidate_snapshot(snap, pe, -ENOMEM);
1051 * Either every pe here has same
1052 * primary_pe or none has one yet.
1055 primary_pe = pe->primary_pe;
1061 bio_list_add(&primary_pe->origin_bios, bio);
1066 if (!pe->primary_pe) {
1067 atomic_inc(&primary_pe->sibling_count);
1068 pe->primary_pe = primary_pe;
1073 list_add_tail(&pe->list, &pe_queue);
1077 up_write(&snap->lock);
1084 * If this is the first time we're processing this chunk and
1085 * sibling_count is now 1 it means all the pending exceptions
1086 * got completed while we were in the loop above, so it falls to
1087 * us here to remove the primary_pe and submit any origin_bios.
1090 if (first && atomic_dec_and_test(&primary_pe->sibling_count)) {
1091 flush_bios(bio_list_get(&primary_pe->origin_bios));
1092 free_pending_exception(primary_pe);
1093 /* If we got here, pe_queue is necessarily empty. */
1098 * Now that we have a complete pe list we can start the copying.
1100 list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
1108 * Called on a write from the origin driver.
1110 static int do_origin(struct dm_dev *origin, struct bio *bio)
1115 down_read(&_origins_lock);
1116 o = __lookup_origin(origin->bdev);
1118 r = __origin_write(&o->snapshots, bio);
1119 up_read(&_origins_lock);
1125 * Origin: maps a linear range of a device, with hooks for snapshotting.
1129 * Construct an origin mapping: <dev_path>
1130 * The context for an origin is merely a 'struct dm_dev *'
1131 * pointing to the real device.
1133 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1139 ti->error = "origin: incorrect number of arguments";
1143 r = dm_get_device(ti, argv[0], 0, ti->len,
1144 dm_table_get_mode(ti->table), &dev);
1146 ti->error = "Cannot get target device";
1154 static void origin_dtr(struct dm_target *ti)
1156 struct dm_dev *dev = (struct dm_dev *) ti->private;
1157 dm_put_device(ti, dev);
1160 static int origin_map(struct dm_target *ti, struct bio *bio,
1161 union map_info *map_context)
1163 struct dm_dev *dev = (struct dm_dev *) ti->private;
1164 bio->bi_bdev = dev->bdev;
1166 if (unlikely(bio_barrier(bio)))
1169 /* Only tell snapshots if this is a write */
1170 return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
1173 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
1176 * Set the target "split_io" field to the minimum of all the snapshots'
1179 static void origin_resume(struct dm_target *ti)
1181 struct dm_dev *dev = (struct dm_dev *) ti->private;
1182 struct dm_snapshot *snap;
1184 chunk_t chunk_size = 0;
1186 down_read(&_origins_lock);
1187 o = __lookup_origin(dev->bdev);
1189 list_for_each_entry (snap, &o->snapshots, list)
1190 chunk_size = min_not_zero(chunk_size, snap->chunk_size);
1191 up_read(&_origins_lock);
1193 ti->split_io = chunk_size;
1196 static int origin_status(struct dm_target *ti, status_type_t type, char *result,
1197 unsigned int maxlen)
1199 struct dm_dev *dev = (struct dm_dev *) ti->private;
1202 case STATUSTYPE_INFO:
1206 case STATUSTYPE_TABLE:
1207 snprintf(result, maxlen, "%s", dev->name);
1214 static struct target_type origin_target = {
1215 .name = "snapshot-origin",
1216 .version = {1, 5, 0},
1217 .module = THIS_MODULE,
1221 .resume = origin_resume,
1222 .status = origin_status,
1225 static struct target_type snapshot_target = {
1227 .version = {1, 5, 0},
1228 .module = THIS_MODULE,
1229 .ctr = snapshot_ctr,
1230 .dtr = snapshot_dtr,
1231 .map = snapshot_map,
1232 .resume = snapshot_resume,
1233 .status = snapshot_status,
1236 static int __init dm_snapshot_init(void)
1240 r = dm_register_target(&snapshot_target);
1242 DMERR("snapshot target register failed %d", r);
1246 r = dm_register_target(&origin_target);
1248 DMERR("Origin target register failed %d", r);
1252 r = init_origin_hash();
1254 DMERR("init_origin_hash failed.");
1258 exception_cache = kmem_cache_create("dm-snapshot-ex",
1259 sizeof(struct exception),
1260 __alignof__(struct exception),
1262 if (!exception_cache) {
1263 DMERR("Couldn't create exception cache.");
1269 kmem_cache_create("dm-snapshot-in",
1270 sizeof(struct pending_exception),
1271 __alignof__(struct pending_exception),
1273 if (!pending_cache) {
1274 DMERR("Couldn't create pending cache.");
1279 pending_pool = mempool_create_slab_pool(128, pending_cache);
1280 if (!pending_pool) {
1281 DMERR("Couldn't create pending pool.");
1289 kmem_cache_destroy(pending_cache);
1291 kmem_cache_destroy(exception_cache);
1295 dm_unregister_target(&origin_target);
1297 dm_unregister_target(&snapshot_target);
1301 static void __exit dm_snapshot_exit(void)
1305 r = dm_unregister_target(&snapshot_target);
1307 DMERR("snapshot unregister failed %d", r);
1309 r = dm_unregister_target(&origin_target);
1311 DMERR("origin unregister failed %d", r);
1314 mempool_destroy(pending_pool);
1315 kmem_cache_destroy(pending_cache);
1316 kmem_cache_destroy(exception_cache);
1320 module_init(dm_snapshot_init);
1321 module_exit(dm_snapshot_exit);
1323 MODULE_DESCRIPTION(DM_NAME " snapshot target");
1324 MODULE_AUTHOR("Joe Thornber");
1325 MODULE_LICENSE("GPL");