/* * dm-snapshot.c * * Copyright (C) 2001-2002 Sistina Software (UK) Limited. * * This file is released under the GPL. */ #include <linux/blkdev.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 <linux/log2.h> #include "dm-snap.h" #include "dm-bio-list.h" #include "kcopyd.h" #define DM_MSG_PREFIX "snapshots" /* * 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 static struct workqueue_struct *ksnapd; static void flush_queued_bios(struct work_struct *work); struct dm_snap_pending_exception { struct dm_snap_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; /* * Short-term queue of pending exceptions prior to submission. */ struct list_head list; /* * The primary pending_exception is the one that holds * the ref_count and the list of origin_bios for a * group of pending_exceptions. It is always last to get freed. * These fields get set up when writing to the origin. */ struct dm_snap_pending_exception *primary_pe; /* * Number of pending_exceptions processing this chunk. * When this drops to zero we must complete the origin bios. * If incrementing or decrementing this, hold pe->snap->lock for * the sibling concerned and not pe->primary_pe->snap->lock unless * they are the same. */ atomic_t ref_count; /* 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 struct kmem_cache *exception_cache; static struct kmem_cache *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("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 unsigned 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, struct kmem_cache *mem) { struct list_head *slot; struct dm_snap_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 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 dm_snap_exception *e) { struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)]; list_add(&e->hash_list, l); } static void remove_exception(struct dm_snap_exception *e) { list_del(&e->hash_list); } /* * Return the exception data for a sector, or NULL if not * remapped. */ static struct dm_snap_exception *lookup_exception(struct exception_table *et, chunk_t chunk) { struct list_head *slot; struct dm_snap_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 struct dm_snap_exception *alloc_exception(void) { struct dm_snap_exception *e; e = kmem_cache_alloc(exception_cache, GFP_NOIO); if (!e) e = kmem_cache_alloc(exception_cache, GFP_ATOMIC); return e; } static void free_exception(struct dm_snap_exception *e) { kmem_cache_free(exception_cache, e); } static struct dm_snap_pending_exception *alloc_pending_exception(void) { return mempool_alloc(pending_pool, GFP_NOIO); } static void free_pending_exception(struct dm_snap_pending_exception *pe) { mempool_free(pe, pending_pool); } int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new) { struct dm_snap_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 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 ulong round_up(ulong n, ulong size) { size--; return (n + size) & ~size; } static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg, char **error) { unsigned long chunk_size; char *value; chunk_size = simple_strtoul(chunk_size_arg, &value, 10); if (*chunk_size_arg == '\0' || *value != '\0') { *error = "Invalid chunk size"; return -EINVAL; } if (!chunk_size) { s->chunk_size = s->chunk_mask = s->chunk_shift = 0; return 0; } /* * Chunk size must be multiple of page size. Silently * round up if it's not. */ chunk_size = round_up(chunk_size, PAGE_SIZE >> 9); /* Check chunk_size is a power of 2 */ if (!is_power_of_2(chunk_size)) { *error = "Chunk size is not a power of 2"; return -EINVAL; } /* Validate the chunk size against the device block size */ if (chunk_size % (bdev_hardsect_size(s->cow->bdev) >> 9)) { *error = "Chunk size is not a multiple of device blocksize"; return -EINVAL; } s->chunk_size = chunk_size; s->chunk_mask = chunk_size - 1; s->chunk_shift = ffs(chunk_size) - 1; return 0; } /* * 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; int r = -EINVAL; char persistent; char *origin_path; char *cow_path; if (argc != 4) { ti->error = "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; } 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; } r = set_chunk_size(s, argv[3], &ti->error); if (r) goto bad3; s->type = persistent; s->valid = 1; s->active = 0; s->last_percent = 0; init_rwsem(&s->lock); spin_lock_init(&s->pe_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; } s->store.snap = s; if (persistent == 'P') r = dm_create_persistent(&s->store); else r = dm_create_transient(&s->store); 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; } /* Metadata must only be loaded into one table at once */ r = s->store.read_metadata(&s->store); if (r < 0) { ti->error = "Failed to read snapshot metadata"; goto bad6; } else if (r > 0) { s->valid = 0; DMWARN("Snapshot is marked invalid."); } bio_list_init(&s->queued_bios); INIT_WORK(&s->queued_bios_work, flush_queued_bios); /* Add snapshot to the list of snapshots for this origin */ /* Exceptions aren't triggered till snapshot_resume() is called */ if (register_snapshot(s)) { r = -EINVAL; ti->error = "Cannot register snapshot origin"; goto bad6; } ti->private = s; ti->split_io = s->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 __free_exceptions(struct dm_snapshot *s) { kcopyd_client_destroy(s->kcopyd_client); s->kcopyd_client = NULL; exit_exception_table(&s->pending, pending_cache); exit_exception_table(&s->complete, exception_cache); s->store.destroy(&s->store); } static void snapshot_dtr(struct dm_target *ti) { struct dm_snapshot *s = ti->private; flush_workqueue(ksnapd); /* Prevent further origin writes from using this snapshot. */ /* After this returns there can be no new kcopyd jobs. */ unregister_snapshot(s); __free_exceptions(s); dm_put_device(ti, s->origin); dm_put_device(ti, s->cow); 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; } } static void flush_queued_bios(struct work_struct *work) { struct dm_snapshot *s = container_of(work, struct dm_snapshot, queued_bios_work); struct bio *queued_bios; unsigned long flags; spin_lock_irqsave(&s->pe_lock, flags); queued_bios = bio_list_get(&s->queued_bios); spin_unlock_irqrestore(&s->pe_lock, flags); flush_bios(queued_bios); } /* * 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 = n; } } static void __invalidate_snapshot(struct dm_snapshot *s, int err) { if (!s->valid) return; if (err == -EIO) DMERR("Invalidating snapshot: Error reading/writing."); else if (err == -ENOMEM) DMERR("Invalidating snapshot: Unable to allocate exception."); if (s->store.drop_snapshot) s->store.drop_snapshot(&s->store); s->valid = 0; dm_table_event(s->table); } static void get_pending_exception(struct dm_snap_pending_exception *pe) { atomic_inc(&pe->ref_count); } static struct bio *put_pending_exception(struct dm_snap_pending_exception *pe) { struct dm_snap_pending_exception *primary_pe; struct bio *origin_bios = NULL; primary_pe = pe->primary_pe; /* * If this pe is involved in a write to the origin and * it is the last sibling to complete then release * the bios for the original write to the origin. */ if (primary_pe && atomic_dec_and_test(&primary_pe->ref_count)) origin_bios = bio_list_get(&primary_pe->origin_bios); /* * Free the pe if it's not linked to an origin write or if * it's not itself a primary pe. */ if (!primary_pe || primary_pe != pe) free_pending_exception(pe); /* * Free the primary pe if nothing references it. */ if (primary_pe && !atomic_read(&primary_pe->ref_count)) free_pending_exception(primary_pe); return origin_bios; } static void pending_complete(struct dm_snap_pending_exception *pe, int success) { struct dm_snap_exception *e; struct dm_snapshot *s = pe->snap; struct bio *origin_bios = NULL; struct bio *snapshot_bios = NULL; int error = 0; if (!success) { /* Read/write error - snapshot is unusable */ down_write(&s->lock); __invalidate_snapshot(s, -EIO); error = 1; goto out; } e = alloc_exception(); if (!e) { down_write(&s->lock); __invalidate_snapshot(s, -ENOMEM); error = 1; goto out; } *e = pe->e; down_write(&s->lock); if (!s->valid) { free_exception(e); error = 1; goto out; } /* * Add a proper exception, and remove the * in-flight exception from the list. */ insert_exception(&s->complete, e); out: remove_exception(&pe->e); snapshot_bios = bio_list_get(&pe->snapshot_bios); origin_bios = put_pending_exception(pe); up_write(&s->lock); /* Submit any pending write bios */ if (error) error_bios(snapshot_bios); else flush_bios(snapshot_bios); flush_bios(origin_bios); } static void commit_callback(void *context, int success) { struct dm_snap_pending_exception *pe = 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 dm_snap_pending_exception *pe = 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 void start_copy(struct dm_snap_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 dm_snap_pending_exception * __find_pending_exception(struct dm_snapshot *s, struct bio *bio) { struct dm_snap_exception *e; struct dm_snap_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 dm_snap_pending_exception, e); goto out; } /* * 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); if (!s->valid) { free_pending_exception(pe); return NULL; } e = lookup_exception(&s->pending, chunk); if (e) { free_pending_exception(pe); pe = container_of(e, struct dm_snap_pending_exception, e); goto out; } pe->e.old_chunk = chunk; bio_list_init(&pe->origin_bios); bio_list_init(&pe->snapshot_bios); pe->primary_pe = NULL; atomic_set(&pe->ref_count, 0); pe->snap = s; pe->started = 0; if (s->store.prepare_exception(&s->store, &pe->e)) { free_pending_exception(pe); return NULL; } get_pending_exception(pe); insert_exception(&s->pending, &pe->e); out: return pe; } static void remap_exception(struct dm_snapshot *s, struct dm_snap_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 dm_snap_exception *e; struct dm_snapshot *s = ti->private; int r = DM_MAPIO_REMAPPED; chunk_t chunk; struct dm_snap_pending_exception *pe = NULL; chunk = sector_to_chunk(s, bio->bi_sector); /* Full snapshots are not usable */ /* To get here the table must be live so s->active is always set. */ if (!s->valid) return -EIO; /* FIXME: should only take write lock if we need * to copy an exception */ down_write(&s->lock); if (!s->valid) { r = -EIO; goto out_unlock; } /* If the block is already remapped - use that, else remap it */ e = lookup_exception(&s->complete, chunk); if (e) { remap_exception(s, e, bio); goto out_unlock; } /* * 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) { pe = __find_pending_exception(s, bio); if (!pe) { __invalidate_snapshot(s, -ENOMEM); r = -EIO; goto out_unlock; } remap_exception(s, &pe->e, bio); bio_list_add(&pe->snapshot_bios, bio); r = DM_MAPIO_SUBMITTED; if (!pe->started) { /* this is protected by snap->lock */ pe->started = 1; up_write(&s->lock); start_copy(pe); goto out; } } 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. */ bio->bi_bdev = s->origin->bdev; out_unlock: up_write(&s->lock); out: return r; } static void snapshot_resume(struct dm_target *ti) { struct dm_snapshot *s = ti->private; down_write(&s->lock); s->active = 1; up_write(&s->lock); } static int snapshot_status(struct dm_target *ti, status_type_t type, char *result, unsigned int maxlen) { struct dm_snapshot *snap = 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, "%llu/%llu", (unsigned long long)numerator, (unsigned long long)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 %llu", snap->origin->name, snap->cow->name, snap->type, (unsigned long long)snap->chunk_size); break; } return 0; } /*----------------------------------------------------------------- * Origin methods *---------------------------------------------------------------*/ static int __origin_write(struct list_head *snapshots, struct bio *bio) { int r = DM_MAPIO_REMAPPED, first = 0; struct dm_snapshot *snap; struct dm_snap_exception *e; struct dm_snap_pending_exception *pe, *next_pe, *primary_pe = NULL; chunk_t chunk; LIST_HEAD(pe_queue); /* Do all the snapshots on this origin */ list_for_each_entry (snap, snapshots, list) { down_write(&snap->lock); /* Only deal with valid and active snapshots */ if (!snap->valid || !snap->active) goto next_snapshot; /* Nothing to do if writing beyond end of snapshot */ if (bio->bi_sector >= dm_table_get_size(snap->table)) goto next_snapshot; /* * 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. * * ref_count is initialised to 1 so pending_complete() * won't destroy the primary_pe while we're inside this loop. */ e = lookup_exception(&snap->complete, chunk); if (e) goto next_snapshot; pe = __find_pending_exception(snap, bio); if (!pe) { __invalidate_snapshot(snap, -ENOMEM); goto next_snapshot; } if (!primary_pe) { /* * Either every pe here has same * primary_pe or none has one yet. */ if (pe->primary_pe) primary_pe = pe->primary_pe; else { primary_pe = pe; first = 1; } bio_list_add(&primary_pe->origin_bios, bio); r = DM_MAPIO_SUBMITTED; } if (!pe->primary_pe) { pe->primary_pe = primary_pe; get_pending_exception(primary_pe); } if (!pe->started) { pe->started = 1; list_add_tail(&pe->list, &pe_queue); } next_snapshot: up_write(&snap->lock); } if (!primary_pe) return r; /* * If this is the first time we're processing this chunk and * ref_count is now 1 it means all the pending exceptions * got completed while we were in the loop above, so it falls to * us here to remove the primary_pe and submit any origin_bios. */ if (first && atomic_dec_and_test(&primary_pe->ref_count)) { flush_bios(bio_list_get(&primary_pe->origin_bios)); free_pending_exception(primary_pe); /* If we got here, pe_queue is necessarily empty. */ return r; } /* * Now that we have a complete pe list we can start the copying. */ list_for_each_entry_safe(pe, next_pe, &pe_queue, list) start_copy(pe); 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 = DM_MAPIO_REMAPPED; 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 = "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 = 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 = ti->private; bio->bi_bdev = dev->bdev; /* Only tell snapshots if this is a write */ return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED; } #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 = 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 = 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, 5, 0}, .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, 5, 0}, .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("Origin target register failed %d", r); goto bad1; } r = init_origin_hash(); if (r) { DMERR("init_origin_hash failed."); goto bad2; } exception_cache = KMEM_CACHE(dm_snap_exception, 0); if (!exception_cache) { DMERR("Couldn't create exception cache."); r = -ENOMEM; goto bad3; } pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0); if (!pending_cache) { DMERR("Couldn't create pending cache."); r = -ENOMEM; goto bad4; } pending_pool = mempool_create_slab_pool(128, pending_cache); if (!pending_pool) { DMERR("Couldn't create pending pool."); r = -ENOMEM; goto bad5; } ksnapd = create_singlethread_workqueue("ksnapd"); if (!ksnapd) { DMERR("Failed to create ksnapd workqueue."); r = -ENOMEM; goto bad6; } return 0; bad6: mempool_destroy(pending_pool); 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; destroy_workqueue(ksnapd); 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");