diff options
Diffstat (limited to 'drivers/md/dm-snap.c')
| -rw-r--r-- | drivers/md/dm-snap.c | 1208 |
1 files changed, 1208 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c new file mode 100644 index 0000000..7e691ab --- /dev/null +++ b/drivers/md/dm-snap.c @@ -0,0 +1,1208 @@ +/* + * 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 -1; + + /* + * 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; + + 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"); |
