/* * dm-snapshot.c * * Copyright (C) 2001-2002 Sistina Software (UK) Limited. * * This file is released under the GPL. */ #include <linux/blkdev.h> #include <linux/config.h> #include <linux/ctype.h> #include <linux/device-mapper.h> #include <linux/fs.h> #include <linux/init.h> #include <linux/kdev_t.h> #include <linux/list.h> #include <linux/mempool.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include "dm-snap.h" #include "dm-bio-list.h" #include "kcopyd.h" /* * The percentage increment we will wake up users at */ #define WAKE_UP_PERCENT 5 /* * kcopyd priority of snapshot operations */ #define SNAPSHOT_COPY_PRIORITY 2 /* * Each snapshot reserves this many pages for io */ #define SNAPSHOT_PAGES 256 struct pending_exception { struct exception e; /* * Origin buffers waiting for this to complete are held * in a bio list */ struct bio_list origin_bios; struct bio_list snapshot_bios; /* * Other pending_exceptions that are processing this * chunk. When this list is empty, we know we can * complete the origins. */ struct list_head siblings; /* Pointer back to snapshot context */ struct dm_snapshot *snap; /* * 1 indicates the exception has already been sent to * kcopyd. */ int started; }; /* * Hash table mapping origin volumes to lists of snapshots and * a lock to protect it */ static kmem_cache_t *exception_cache; static kmem_cache_t *pending_cache; static mempool_t *pending_pool; /* * One of these per registered origin, held in the snapshot_origins hash */ struct origin { /* The origin device */ struct block_device *bdev; struct list_head hash_list; /* List of snapshots for this origin */ struct list_head snapshots; }; /* * Size of the hash table for origin volumes. If we make this * the size of the minors list then it should be nearly perfect */ #define ORIGIN_HASH_SIZE 256 #define ORIGIN_MASK 0xFF static struct list_head *_origins; static struct rw_semaphore _origins_lock; static int init_origin_hash(void) { int i; _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head), GFP_KERNEL); if (!_origins) { DMERR("Device mapper: Snapshot: unable to allocate memory"); return -ENOMEM; } for (i = 0; i < ORIGIN_HASH_SIZE; i++) INIT_LIST_HEAD(_origins + i); init_rwsem(&_origins_lock); return 0; } static void exit_origin_hash(void) { kfree(_origins); } static inline unsigned int origin_hash(struct block_device *bdev) { return bdev->bd_dev & ORIGIN_MASK; } static struct origin *__lookup_origin(struct block_device *origin) { struct list_head *ol; struct origin *o; ol = &_origins[origin_hash(origin)]; list_for_each_entry (o, ol, hash_list) if (bdev_equal(o->bdev, origin)) return o; return NULL; } static void __insert_origin(struct origin *o) { struct list_head *sl = &_origins[origin_hash(o->bdev)]; list_add_tail(&o->hash_list, sl); } /* * Make a note of the snapshot and its origin so we can look it * up when the origin has a write on it. */ static int register_snapshot(struct dm_snapshot *snap) { struct origin *o; struct block_device *bdev = snap->origin->bdev; down_write(&_origins_lock); o = __lookup_origin(bdev); if (!o) { /* New origin */ o = kmalloc(sizeof(*o), GFP_KERNEL); if (!o) { up_write(&_origins_lock); return -ENOMEM; } /* Initialise the struct */ INIT_LIST_HEAD(&o->snapshots); o->bdev = bdev; __insert_origin(o); } list_add_tail(&snap->list, &o->snapshots); up_write(&_origins_lock); return 0; } static void unregister_snapshot(struct dm_snapshot *s) { struct origin *o; down_write(&_origins_lock); o = __lookup_origin(s->origin->bdev); list_del(&s->list); if (list_empty(&o->snapshots)) { list_del(&o->hash_list); kfree(o); } up_write(&_origins_lock); } /* * Implementation of the exception hash tables. */ static int init_exception_table(struct exception_table *et, uint32_t size) { unsigned int i; et->hash_mask = size - 1; et->table = dm_vcalloc(size, sizeof(struct list_head)); if (!et->table) return -ENOMEM; for (i = 0; i < size; i++) INIT_LIST_HEAD(et->table + i); return 0; } static void exit_exception_table(struct exception_table *et, kmem_cache_t *mem) { struct list_head *slot; struct exception *ex, *next; int i, size; size = et->hash_mask + 1; for (i = 0; i < size; i++) { slot = et->table + i; list_for_each_entry_safe (ex, next, slot, hash_list) kmem_cache_free(mem, ex); } vfree(et->table); } static inline uint32_t exception_hash(struct exception_table *et, chunk_t chunk) { return chunk & et->hash_mask; } static void insert_exception(struct exception_table *eh, struct exception *e) { struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)]; list_add(&e->hash_list, l); } static inline void remove_exception(struct exception *e) { list_del(&e->hash_list); } /* * Return the exception data for a sector, or NULL if not * remapped. */ static struct exception *lookup_exception(struct exception_table *et, chunk_t chunk) { struct list_head *slot; struct exception *e; slot = &et->table[exception_hash(et, chunk)]; list_for_each_entry (e, slot, hash_list) if (e->old_chunk == chunk) return e; return NULL; } static inline struct exception *alloc_exception(void) { struct exception *e; e = kmem_cache_alloc(exception_cache, GFP_NOIO); if (!e) e = kmem_cache_alloc(exception_cache, GFP_ATOMIC); return e; } static inline void free_exception(struct exception *e) { kmem_cache_free(exception_cache, e); } static inline struct pending_exception *alloc_pending_exception(void) { return mempool_alloc(pending_pool, GFP_NOIO); } static inline void free_pending_exception(struct pending_exception *pe) { mempool_free(pe, pending_pool); } int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new) { struct exception *e; e = alloc_exception(); if (!e) return -ENOMEM; e->old_chunk = old; e->new_chunk = new; insert_exception(&s->complete, e); return 0; } /* * Hard coded magic. */ static int calc_max_buckets(void) { /* use a fixed size of 2MB */ unsigned long mem = 2 * 1024 * 1024; mem /= sizeof(struct list_head); return mem; } /* * Rounds a number down to a power of 2. */ static inline uint32_t round_down(uint32_t n) { while (n & (n - 1)) n &= (n - 1); return n; } /* * Allocate room for a suitable hash table. */ static int init_hash_tables(struct dm_snapshot *s) { sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets; /* * Calculate based on the size of the original volume or * the COW volume... */ cow_dev_size = get_dev_size(s->cow->bdev); origin_dev_size = get_dev_size(s->origin->bdev); max_buckets = calc_max_buckets(); hash_size = min(origin_dev_size, cow_dev_size) >> s->chunk_shift; hash_size = min(hash_size, max_buckets); /* Round it down to a power of 2 */ hash_size = round_down(hash_size); if (init_exception_table(&s->complete, hash_size)) return -ENOMEM; /* * Allocate hash table for in-flight exceptions * Make this smaller than the real hash table */ hash_size >>= 3; if (hash_size < 64) hash_size = 64; if (init_exception_table(&s->pending, hash_size)) { exit_exception_table(&s->complete, exception_cache); return -ENOMEM; } return 0; } /* * Round a number up to the nearest 'size' boundary. size must * be a power of 2. */ static inline ulong round_up(ulong n, ulong size) { size--; return (n + size) & ~size; } /* * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size> */ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) { struct dm_snapshot *s; unsigned long chunk_size; int r = -EINVAL; char persistent; char *origin_path; char *cow_path; char *value; int blocksize; if (argc < 4) { ti->error = "dm-snapshot: requires exactly 4 arguments"; r = -EINVAL; goto bad1; } origin_path = argv[0]; cow_path = argv[1]; persistent = toupper(*argv[2]); if (persistent != 'P' && persistent != 'N') { ti->error = "Persistent flag is not P or N"; r = -EINVAL; goto bad1; } chunk_size = simple_strtoul(argv[3], &value, 10); if (chunk_size == 0 || value == NULL) { ti->error = "Invalid chunk size"; r = -EINVAL; goto bad1; } s = kmalloc(sizeof(*s), GFP_KERNEL); if (s == NULL) { ti->error = "Cannot allocate snapshot context private " "structure"; r = -ENOMEM; goto bad1; } r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin); if (r) { ti->error = "Cannot get origin device"; goto bad2; } r = dm_get_device(ti, cow_path, 0, 0, FMODE_READ | FMODE_WRITE, &s->cow); if (r) { dm_put_device(ti, s->origin); ti->error = "Cannot get COW device"; goto bad2; } /* * Chunk size must be multiple of page size. Silently * round up if it's not. */ chunk_size = round_up(chunk_size, PAGE_SIZE >> 9); /* Validate the chunk size against the device block size */ blocksize = s->cow->bdev->bd_disk->queue->hardsect_size; if (chunk_size % (blocksize >> 9)) { ti->error = "Chunk size is not a multiple of device blocksize"; r = -EINVAL; goto bad3; } /* Check chunk_size is a power of 2 */ if (chunk_size & (chunk_size - 1)) { ti->error = "Chunk size is not a power of 2"; r = -EINVAL; goto bad3; } s->chunk_size = chunk_size; s->chunk_mask = chunk_size - 1; s->type = persistent; s->chunk_shift = ffs(chunk_size) - 1; s->valid = 1; s->have_metadata = 0; s->last_percent = 0; init_rwsem(&s->lock); s->table = ti->table; /* Allocate hash table for COW data */ if (init_hash_tables(s)) { ti->error = "Unable to allocate hash table space"; r = -ENOMEM; goto bad3; } /* * Check the persistent flag - done here because we need the iobuf * to check the LV header */ s->store.snap = s; if (persistent == 'P') r = dm_create_persistent(&s->store, chunk_size); else r = dm_create_transient(&s->store, s, blocksize); if (r) { ti->error = "Couldn't create exception store"; r = -EINVAL; goto bad4; } r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client); if (r) { ti->error = "Could not create kcopyd client"; goto bad5; } /* Add snapshot to the list of snapshots for this origin */ if (register_snapshot(s)) { r = -EINVAL; ti->error = "Cannot register snapshot origin"; goto bad6; } ti->private = s; ti->split_io = chunk_size; return 0; bad6: kcopyd_client_destroy(s->kcopyd_client); bad5: s->store.destroy(&s->store); bad4: exit_exception_table(&s->pending, pending_cache); exit_exception_table(&s->complete, exception_cache); bad3: dm_put_device(ti, s->cow); dm_put_device(ti, s->origin); bad2: kfree(s); bad1: return r; } static void snapshot_dtr(struct dm_target *ti) { struct dm_snapshot *s = (struct dm_snapshot *) ti->private; unregister_snapshot(s); exit_exception_table(&s->pending, pending_cache); exit_exception_table(&s->complete, exception_cache); /* Deallocate memory used */ s->store.destroy(&s->store); dm_put_device(ti, s->origin); dm_put_device(ti, s->cow); kcopyd_client_destroy(s->kcopyd_client); kfree(s); } /* * Flush a list of buffers. */ static void flush_bios(struct bio *bio) { struct bio *n; while (bio) { n = bio->bi_next; bio->bi_next = NULL; generic_make_request(bio); bio = n; } } /* * Error a list of buffers. */ static void error_bios(struct bio *bio) { struct bio *n; while (bio) { n = bio->bi_next; bio->bi_next = NULL; bio_io_error(bio, bio->bi_size); bio = n; } } static struct bio *__flush_bios(struct pending_exception *pe) { struct pending_exception *sibling; if (list_empty(&pe->siblings)) return bio_list_get(&pe->origin_bios); sibling = list_entry(pe->siblings.next, struct pending_exception, siblings); list_del(&pe->siblings); /* This is fine as long as kcopyd is single-threaded. If kcopyd * becomes multi-threaded, we'll need some locking here. */ bio_list_merge(&sibling->origin_bios, &pe->origin_bios); return NULL; } static void pending_complete(struct pending_exception *pe, int success) { struct exception *e; struct dm_snapshot *s = pe->snap; struct bio *flush = NULL; if (success) { e = alloc_exception(); if (!e) { DMWARN("Unable to allocate exception."); down_write(&s->lock); s->store.drop_snapshot(&s->store); s->valid = 0; flush = __flush_bios(pe); up_write(&s->lock); error_bios(bio_list_get(&pe->snapshot_bios)); goto out; } *e = pe->e; /* * Add a proper exception, and remove the * in-flight exception from the list. */ down_write(&s->lock); insert_exception(&s->complete, e); remove_exception(&pe->e); flush = __flush_bios(pe); /* Submit any pending write bios */ up_write(&s->lock); flush_bios(bio_list_get(&pe->snapshot_bios)); } else { /* Read/write error - snapshot is unusable */ down_write(&s->lock); if (s->valid) DMERR("Error reading/writing snapshot"); s->store.drop_snapshot(&s->store); s->valid = 0; remove_exception(&pe->e); flush = __flush_bios(pe); up_write(&s->lock); error_bios(bio_list_get(&pe->snapshot_bios)); dm_table_event(s->table); } out: free_pending_exception(pe); if (flush) flush_bios(flush); } static void commit_callback(void *context, int success) { struct pending_exception *pe = (struct pending_exception *) context; pending_complete(pe, success); } /* * Called when the copy I/O has finished. kcopyd actually runs * this code so don't block. */ static void copy_callback(int read_err, unsigned int write_err, void *context) { struct pending_exception *pe = (struct pending_exception *) context; struct dm_snapshot *s = pe->snap; if (read_err || write_err) pending_complete(pe, 0); else /* Update the metadata if we are persistent */ s->store.commit_exception(&s->store, &pe->e, commit_callback, pe); } /* * Dispatches the copy operation to kcopyd. */ static inline void start_copy(struct pending_exception *pe) { struct dm_snapshot *s = pe->snap; struct io_region src, dest; struct block_device *bdev = s->origin->bdev; sector_t dev_size; dev_size = get_dev_size(bdev); src.bdev = bdev; src.sector = chunk_to_sector(s, pe->e.old_chunk); src.count = min(s->chunk_size, dev_size - src.sector); dest.bdev = s->cow->bdev; dest.sector = chunk_to_sector(s, pe->e.new_chunk); dest.count = src.count; /* Hand over to kcopyd */ kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe); } /* * Looks to see if this snapshot already has a pending exception * for this chunk, otherwise it allocates a new one and inserts * it into the pending table. * * NOTE: a write lock must be held on snap->lock before calling * this. */ static struct pending_exception * __find_pending_exception(struct dm_snapshot *s, struct bio *bio) { struct exception *e; struct pending_exception *pe; chunk_t chunk = sector_to_chunk(s, bio->bi_sector); /* * Is there a pending exception for this already ? */ e = lookup_exception(&s->pending, chunk); if (e) { /* cast the exception to a pending exception */ pe = container_of(e, struct pending_exception, e); } else { /* * Create a new pending exception, we don't want * to hold the lock while we do this. */ up_write(&s->lock); pe = alloc_pending_exception(); down_write(&s->lock); e = lookup_exception(&s->pending, chunk); if (e) { free_pending_exception(pe); pe = container_of(e, struct pending_exception, e); } else { pe->e.old_chunk = chunk; bio_list_init(&pe->origin_bios); bio_list_init(&pe->snapshot_bios); INIT_LIST_HEAD(&pe->siblings); pe->snap = s; pe->started = 0; if (s->store.prepare_exception(&s->store, &pe->e)) { free_pending_exception(pe); s->valid = 0; return NULL; } insert_exception(&s->pending, &pe->e); } } return pe; } static inline void remap_exception(struct dm_snapshot *s, struct exception *e, struct bio *bio) { bio->bi_bdev = s->cow->bdev; bio->bi_sector = chunk_to_sector(s, e->new_chunk) + (bio->bi_sector & s->chunk_mask); } static int snapshot_map(struct dm_target *ti, struct bio *bio, union map_info *map_context) { struct exception *e; struct dm_snapshot *s = (struct dm_snapshot *) ti->private; int r = 1; chunk_t chunk; struct pending_exception *pe; chunk = sector_to_chunk(s, bio->bi_sector); /* Full snapshots are not usable */ if (!s->valid) return -EIO; /* * Write to snapshot - higher level takes care of RW/RO * flags so we should only get this if we are * writeable. */ if (bio_rw(bio) == WRITE) { /* FIXME: should only take write lock if we need * to copy an exception */ down_write(&s->lock); /* If the block is already remapped - use that, else remap it */ e = lookup_exception(&s->complete, chunk); if (e) { remap_exception(s, e, bio); up_write(&s->lock); } else { pe = __find_pending_exception(s, bio); if (!pe) { if (s->store.drop_snapshot) s->store.drop_snapshot(&s->store); s->valid = 0; r = -EIO; up_write(&s->lock); } else { remap_exception(s, &pe->e, bio); bio_list_add(&pe->snapshot_bios, bio); if (!pe->started) { /* this is protected by snap->lock */ pe->started = 1; up_write(&s->lock); start_copy(pe); } else up_write(&s->lock); r = 0; } } } else { /* * FIXME: this read path scares me because we * always use the origin when we have a pending * exception. However I can't think of a * situation where this is wrong - ejt. */ /* Do reads */ down_read(&s->lock); /* See if it it has been remapped */ e = lookup_exception(&s->complete, chunk); if (e) remap_exception(s, e, bio); else bio->bi_bdev = s->origin->bdev; up_read(&s->lock); } return r; } static void snapshot_resume(struct dm_target *ti) { struct dm_snapshot *s = (struct dm_snapshot *) ti->private; if (s->have_metadata) return; if (s->store.read_metadata(&s->store)) { down_write(&s->lock); s->valid = 0; up_write(&s->lock); } s->have_metadata = 1; } static int snapshot_status(struct dm_target *ti, status_type_t type, char *result, unsigned int maxlen) { struct dm_snapshot *snap = (struct dm_snapshot *) ti->private; switch (type) { case STATUSTYPE_INFO: if (!snap->valid) snprintf(result, maxlen, "Invalid"); else { if (snap->store.fraction_full) { sector_t numerator, denominator; snap->store.fraction_full(&snap->store, &numerator, &denominator); snprintf(result, maxlen, SECTOR_FORMAT "/" SECTOR_FORMAT, numerator, denominator); } else snprintf(result, maxlen, "Unknown"); } break; case STATUSTYPE_TABLE: /* * kdevname returns a static pointer so we need * to make private copies if the output is to * make sense. */ snprintf(result, maxlen, "%s %s %c " SECTOR_FORMAT, snap->origin->name, snap->cow->name, snap->type, snap->chunk_size); break; } return 0; } /*----------------------------------------------------------------- * Origin methods *---------------------------------------------------------------*/ static void list_merge(struct list_head *l1, struct list_head *l2) { struct list_head *l1_n, *l2_p; l1_n = l1->next; l2_p = l2->prev; l1->next = l2; l2->prev = l1; l2_p->next = l1_n; l1_n->prev = l2_p; } static int __origin_write(struct list_head *snapshots, struct bio *bio) { int r = 1, first = 1; struct dm_snapshot *snap; struct exception *e; struct pending_exception *pe, *last = NULL; chunk_t chunk; /* Do all the snapshots on this origin */ list_for_each_entry (snap, snapshots, list) { /* Only deal with valid snapshots */ if (!snap->valid) continue; /* Nothing to do if writing beyond end of snapshot */ if (bio->bi_sector >= dm_table_get_size(snap->table)) continue; down_write(&snap->lock); /* * Remember, different snapshots can have * different chunk sizes. */ chunk = sector_to_chunk(snap, bio->bi_sector); /* * Check exception table to see if block * is already remapped in this snapshot * and trigger an exception if not. */ e = lookup_exception(&snap->complete, chunk); if (!e) { pe = __find_pending_exception(snap, bio); if (!pe) { snap->store.drop_snapshot(&snap->store); snap->valid = 0; } else { if (last) list_merge(&pe->siblings, &last->siblings); last = pe; r = 0; } } up_write(&snap->lock); } /* * Now that we have a complete pe list we can start the copying. */ if (last) { pe = last; do { down_write(&pe->snap->lock); if (first) bio_list_add(&pe->origin_bios, bio); if (!pe->started) { pe->started = 1; up_write(&pe->snap->lock); start_copy(pe); } else up_write(&pe->snap->lock); first = 0; pe = list_entry(pe->siblings.next, struct pending_exception, siblings); } while (pe != last); } return r; } /* * Called on a write from the origin driver. */ static int do_origin(struct dm_dev *origin, struct bio *bio) { struct origin *o; int r = 1; down_read(&_origins_lock); o = __lookup_origin(origin->bdev); if (o) r = __origin_write(&o->snapshots, bio); up_read(&_origins_lock); return r; } /* * Origin: maps a linear range of a device, with hooks for snapshotting. */ /* * Construct an origin mapping: <dev_path> * The context for an origin is merely a 'struct dm_dev *' * pointing to the real device. */ static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv) { int r; struct dm_dev *dev; if (argc != 1) { ti->error = "dm-origin: incorrect number of arguments"; return -EINVAL; } r = dm_get_device(ti, argv[0], 0, ti->len, dm_table_get_mode(ti->table), &dev); if (r) { ti->error = "Cannot get target device"; return r; } ti->private = dev; return 0; } static void origin_dtr(struct dm_target *ti) { struct dm_dev *dev = (struct dm_dev *) ti->private; dm_put_device(ti, dev); } static int origin_map(struct dm_target *ti, struct bio *bio, union map_info *map_context) { struct dm_dev *dev = (struct dm_dev *) ti->private; bio->bi_bdev = dev->bdev; /* Only tell snapshots if this is a write */ return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1; } #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r)) /* * Set the target "split_io" field to the minimum of all the snapshots' * chunk sizes. */ static void origin_resume(struct dm_target *ti) { struct dm_dev *dev = (struct dm_dev *) ti->private; struct dm_snapshot *snap; struct origin *o; chunk_t chunk_size = 0; down_read(&_origins_lock); o = __lookup_origin(dev->bdev); if (o) list_for_each_entry (snap, &o->snapshots, list) chunk_size = min_not_zero(chunk_size, snap->chunk_size); up_read(&_origins_lock); ti->split_io = chunk_size; } static int origin_status(struct dm_target *ti, status_type_t type, char *result, unsigned int maxlen) { struct dm_dev *dev = (struct dm_dev *) ti->private; switch (type) { case STATUSTYPE_INFO: result[0] = '\0'; break; case STATUSTYPE_TABLE: snprintf(result, maxlen, "%s", dev->name); break; } return 0; } static struct target_type origin_target = { .name = "snapshot-origin", .version = {1, 0, 1}, .module = THIS_MODULE, .ctr = origin_ctr, .dtr = origin_dtr, .map = origin_map, .resume = origin_resume, .status = origin_status, }; static struct target_type snapshot_target = { .name = "snapshot", .version = {1, 0, 1}, .module = THIS_MODULE, .ctr = snapshot_ctr, .dtr = snapshot_dtr, .map = snapshot_map, .resume = snapshot_resume, .status = snapshot_status, }; static int __init dm_snapshot_init(void) { int r; r = dm_register_target(&snapshot_target); if (r) { DMERR("snapshot target register failed %d", r); return r; } r = dm_register_target(&origin_target); if (r < 0) { DMERR("Device mapper: Origin: register failed %d\n", r); goto bad1; } r = init_origin_hash(); if (r) { DMERR("init_origin_hash failed."); goto bad2; } exception_cache = kmem_cache_create("dm-snapshot-ex", sizeof(struct exception), __alignof__(struct exception), 0, NULL, NULL); if (!exception_cache) { DMERR("Couldn't create exception cache."); r = -ENOMEM; goto bad3; } pending_cache = kmem_cache_create("dm-snapshot-in", sizeof(struct pending_exception), __alignof__(struct pending_exception), 0, NULL, NULL); if (!pending_cache) { DMERR("Couldn't create pending cache."); r = -ENOMEM; goto bad4; } pending_pool = mempool_create(128, mempool_alloc_slab, mempool_free_slab, pending_cache); if (!pending_pool) { DMERR("Couldn't create pending pool."); r = -ENOMEM; goto bad5; } return 0; bad5: kmem_cache_destroy(pending_cache); bad4: kmem_cache_destroy(exception_cache); bad3: exit_origin_hash(); bad2: dm_unregister_target(&origin_target); bad1: dm_unregister_target(&snapshot_target); return r; } static void __exit dm_snapshot_exit(void) { int r; r = dm_unregister_target(&snapshot_target); if (r) DMERR("snapshot unregister failed %d", r); r = dm_unregister_target(&origin_target); if (r) DMERR("origin unregister failed %d", r); exit_origin_hash(); mempool_destroy(pending_pool); kmem_cache_destroy(pending_cache); kmem_cache_destroy(exception_cache); } /* Module hooks */ module_init(dm_snapshot_init); module_exit(dm_snapshot_exit); MODULE_DESCRIPTION(DM_NAME " snapshot target"); MODULE_AUTHOR("Joe Thornber"); MODULE_LICENSE("GPL");