| /* |
| * dm-snapshot.c |
| * |
| * Copyright (C) 2001-2002 Sistina Software (UK) Limited. |
| * |
| * This file is released under the GPL. |
| */ |
| |
| #include <linux/blkdev.h> |
| #include <linux/device-mapper.h> |
| #include <linux/delay.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 <linux/dm-kcopyd.h> |
| |
| #include "dm-exception-store.h" |
| |
| #define DM_MSG_PREFIX "snapshots" |
| |
| static const char dm_snapshot_merge_target_name[] = "snapshot-merge"; |
| |
| #define dm_target_is_snapshot_merge(ti) \ |
| ((ti)->type->name == dm_snapshot_merge_target_name) |
| |
| /* |
| * The percentage increment we will wake up users at |
| */ |
| #define WAKE_UP_PERCENT 5 |
| |
| /* |
| * kcopyd priority of snapshot operations |
| */ |
| #define SNAPSHOT_COPY_PRIORITY 2 |
| |
| /* |
| * The size of the mempool used to track chunks in use. |
| */ |
| #define MIN_IOS 256 |
| |
| #define DM_TRACKED_CHUNK_HASH_SIZE 16 |
| #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ |
| (DM_TRACKED_CHUNK_HASH_SIZE - 1)) |
| |
| struct dm_exception_table { |
| uint32_t hash_mask; |
| unsigned hash_shift; |
| struct list_head *table; |
| }; |
| |
| struct dm_snapshot { |
| struct rw_semaphore lock; |
| |
| struct dm_dev *origin; |
| struct dm_dev *cow; |
| |
| struct dm_target *ti; |
| |
| /* List of snapshots per Origin */ |
| struct list_head list; |
| |
| /* |
| * You can't use a snapshot if this is 0 (e.g. if full). |
| * A snapshot-merge target never clears this. |
| */ |
| int valid; |
| |
| /* Origin writes don't trigger exceptions until this is set */ |
| int active; |
| |
| atomic_t pending_exceptions_count; |
| |
| mempool_t *pending_pool; |
| |
| struct dm_exception_table pending; |
| struct dm_exception_table complete; |
| |
| /* |
| * pe_lock protects all pending_exception operations and access |
| * as well as the snapshot_bios list. |
| */ |
| spinlock_t pe_lock; |
| |
| /* Chunks with outstanding reads */ |
| spinlock_t tracked_chunk_lock; |
| mempool_t *tracked_chunk_pool; |
| struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; |
| |
| /* The on disk metadata handler */ |
| struct dm_exception_store *store; |
| |
| struct dm_kcopyd_client *kcopyd_client; |
| |
| /* Wait for events based on state_bits */ |
| unsigned long state_bits; |
| |
| /* Range of chunks currently being merged. */ |
| chunk_t first_merging_chunk; |
| int num_merging_chunks; |
| |
| /* |
| * The merge operation failed if this flag is set. |
| * Failure modes are handled as follows: |
| * - I/O error reading the header |
| * => don't load the target; abort. |
| * - Header does not have "valid" flag set |
| * => use the origin; forget about the snapshot. |
| * - I/O error when reading exceptions |
| * => don't load the target; abort. |
| * (We can't use the intermediate origin state.) |
| * - I/O error while merging |
| * => stop merging; set merge_failed; process I/O normally. |
| */ |
| int merge_failed; |
| |
| /* |
| * Incoming bios that overlap with chunks being merged must wait |
| * for them to be committed. |
| */ |
| struct bio_list bios_queued_during_merge; |
| }; |
| |
| /* |
| * state_bits: |
| * RUNNING_MERGE - Merge operation is in progress. |
| * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped; |
| * cleared afterwards. |
| */ |
| #define RUNNING_MERGE 0 |
| #define SHUTDOWN_MERGE 1 |
| |
| struct dm_dev *dm_snap_origin(struct dm_snapshot *s) |
| { |
| return s->origin; |
| } |
| EXPORT_SYMBOL(dm_snap_origin); |
| |
| struct dm_dev *dm_snap_cow(struct dm_snapshot *s) |
| { |
| return s->cow; |
| } |
| EXPORT_SYMBOL(dm_snap_cow); |
| |
| static sector_t chunk_to_sector(struct dm_exception_store *store, |
| chunk_t chunk) |
| { |
| return chunk << store->chunk_shift; |
| } |
| |
| static int bdev_equal(struct block_device *lhs, struct block_device *rhs) |
| { |
| /* |
| * There is only ever one instance of a particular block |
| * device so we can compare pointers safely. |
| */ |
| return lhs == rhs; |
| } |
| |
| struct dm_snap_pending_exception { |
| struct dm_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; |
| |
| /* 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; |
| |
| struct dm_snap_tracked_chunk { |
| struct hlist_node node; |
| chunk_t chunk; |
| }; |
| |
| static struct kmem_cache *tracked_chunk_cache; |
| |
| static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s, |
| chunk_t chunk) |
| { |
| struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool, |
| GFP_NOIO); |
| unsigned long flags; |
| |
| c->chunk = chunk; |
| |
| spin_lock_irqsave(&s->tracked_chunk_lock, flags); |
| hlist_add_head(&c->node, |
| &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]); |
| spin_unlock_irqrestore(&s->tracked_chunk_lock, flags); |
| |
| return c; |
| } |
| |
| static void stop_tracking_chunk(struct dm_snapshot *s, |
| struct dm_snap_tracked_chunk *c) |
| { |
| unsigned long flags; |
| |
| spin_lock_irqsave(&s->tracked_chunk_lock, flags); |
| hlist_del(&c->node); |
| spin_unlock_irqrestore(&s->tracked_chunk_lock, flags); |
| |
| mempool_free(c, s->tracked_chunk_pool); |
| } |
| |
| static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk) |
| { |
| struct dm_snap_tracked_chunk *c; |
| struct hlist_node *hn; |
| int found = 0; |
| |
| spin_lock_irq(&s->tracked_chunk_lock); |
| |
| hlist_for_each_entry(c, hn, |
| &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) { |
| if (c->chunk == chunk) { |
| found = 1; |
| break; |
| } |
| } |
| |
| spin_unlock_irq(&s->tracked_chunk_lock); |
| |
| return found; |
| } |
| |
| /* |
| * This conflicting I/O is extremely improbable in the caller, |
| * so msleep(1) is sufficient and there is no need for a wait queue. |
| */ |
| static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk) |
| { |
| while (__chunk_is_tracked(s, chunk)) |
| msleep(1); |
| } |
| |
| /* |
| * 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 DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done); |
| static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock); |
| static uint64_t _pending_exceptions_done_count; |
| |
| 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); |
| } |
| |
| /* |
| * _origins_lock must be held when calling this function. |
| * Returns number of snapshots registered using the supplied cow device, plus: |
| * snap_src - a snapshot suitable for use as a source of exception handover |
| * snap_dest - a snapshot capable of receiving exception handover. |
| * snap_merge - an existing snapshot-merge target linked to the same origin. |
| * There can be at most one snapshot-merge target. The parameter is optional. |
| * |
| * Possible return values and states of snap_src and snap_dest. |
| * 0: NULL, NULL - first new snapshot |
| * 1: snap_src, NULL - normal snapshot |
| * 2: snap_src, snap_dest - waiting for handover |
| * 2: snap_src, NULL - handed over, waiting for old to be deleted |
| * 1: NULL, snap_dest - source got destroyed without handover |
| */ |
| static int __find_snapshots_sharing_cow(struct dm_snapshot *snap, |
| struct dm_snapshot **snap_src, |
| struct dm_snapshot **snap_dest, |
| struct dm_snapshot **snap_merge) |
| { |
| struct dm_snapshot *s; |
| struct origin *o; |
| int count = 0; |
| int active; |
| |
| o = __lookup_origin(snap->origin->bdev); |
| if (!o) |
| goto out; |
| |
| list_for_each_entry(s, &o->snapshots, list) { |
| if (dm_target_is_snapshot_merge(s->ti) && snap_merge) |
| *snap_merge = s; |
| if (!bdev_equal(s->cow->bdev, snap->cow->bdev)) |
| continue; |
| |
| down_read(&s->lock); |
| active = s->active; |
| up_read(&s->lock); |
| |
| if (active) { |
| if (snap_src) |
| *snap_src = s; |
| } else if (snap_dest) |
| *snap_dest = s; |
| |
| count++; |
| } |
| |
| out: |
| return count; |
| } |
| |
| /* |
| * On success, returns 1 if this snapshot is a handover destination, |
| * otherwise returns 0. |
| */ |
| static int __validate_exception_handover(struct dm_snapshot *snap) |
| { |
| struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
| struct dm_snapshot *snap_merge = NULL; |
| |
| /* Does snapshot need exceptions handed over to it? */ |
| if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, |
| &snap_merge) == 2) || |
| snap_dest) { |
| snap->ti->error = "Snapshot cow pairing for exception " |
| "table handover failed"; |
| return -EINVAL; |
| } |
| |
| /* |
| * If no snap_src was found, snap cannot become a handover |
| * destination. |
| */ |
| if (!snap_src) |
| return 0; |
| |
| /* |
| * Non-snapshot-merge handover? |
| */ |
| if (!dm_target_is_snapshot_merge(snap->ti)) |
| return 1; |
| |
| /* |
| * Do not allow more than one merging snapshot. |
| */ |
| if (snap_merge) { |
| snap->ti->error = "A snapshot is already merging."; |
| return -EINVAL; |
| } |
| |
| if (!snap_src->store->type->prepare_merge || |
| !snap_src->store->type->commit_merge) { |
| snap->ti->error = "Snapshot exception store does not " |
| "support snapshot-merge."; |
| return -EINVAL; |
| } |
| |
| return 1; |
| } |
| |
| static void __insert_snapshot(struct origin *o, struct dm_snapshot *s) |
| { |
| struct dm_snapshot *l; |
| |
| /* Sort the list according to chunk size, largest-first smallest-last */ |
| list_for_each_entry(l, &o->snapshots, list) |
| if (l->store->chunk_size < s->store->chunk_size) |
| break; |
| list_add_tail(&s->list, &l->list); |
| } |
| |
| /* |
| * Make a note of the snapshot and its origin so we can look it |
| * up when the origin has a write on it. |
| * |
| * Also validate snapshot exception store handovers. |
| * On success, returns 1 if this registration is a handover destination, |
| * otherwise returns 0. |
| */ |
| static int register_snapshot(struct dm_snapshot *snap) |
| { |
| struct origin *o, *new_o = NULL; |
| struct block_device *bdev = snap->origin->bdev; |
| int r = 0; |
| |
| new_o = kmalloc(sizeof(*new_o), GFP_KERNEL); |
| if (!new_o) |
| return -ENOMEM; |
| |
| down_write(&_origins_lock); |
| |
| r = __validate_exception_handover(snap); |
| if (r < 0) { |
| kfree(new_o); |
| goto out; |
| } |
| |
| o = __lookup_origin(bdev); |
| if (o) |
| kfree(new_o); |
| else { |
| /* New origin */ |
| o = new_o; |
| |
| /* Initialise the struct */ |
| INIT_LIST_HEAD(&o->snapshots); |
| o->bdev = bdev; |
| |
| __insert_origin(o); |
| } |
| |
| __insert_snapshot(o, snap); |
| |
| out: |
| up_write(&_origins_lock); |
| |
| return r; |
| } |
| |
| /* |
| * Move snapshot to correct place in list according to chunk size. |
| */ |
| static void reregister_snapshot(struct dm_snapshot *s) |
| { |
| struct block_device *bdev = s->origin->bdev; |
| |
| down_write(&_origins_lock); |
| |
| list_del(&s->list); |
| __insert_snapshot(__lookup_origin(bdev), s); |
| |
| up_write(&_origins_lock); |
| } |
| |
| 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 (o && list_empty(&o->snapshots)) { |
| list_del(&o->hash_list); |
| kfree(o); |
| } |
| |
| up_write(&_origins_lock); |
| } |
| |
| /* |
| * Implementation of the exception hash tables. |
| * The lowest hash_shift bits of the chunk number are ignored, allowing |
| * some consecutive chunks to be grouped together. |
| */ |
| static int dm_exception_table_init(struct dm_exception_table *et, |
| uint32_t size, unsigned hash_shift) |
| { |
| unsigned int i; |
| |
| et->hash_shift = hash_shift; |
| 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 dm_exception_table_exit(struct dm_exception_table *et, |
| struct kmem_cache *mem) |
| { |
| struct list_head *slot; |
| struct dm_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 dm_exception_table *et, chunk_t chunk) |
| { |
| return (chunk >> et->hash_shift) & et->hash_mask; |
| } |
| |
| static void dm_remove_exception(struct dm_exception *e) |
| { |
| list_del(&e->hash_list); |
| } |
| |
| /* |
| * Return the exception data for a sector, or NULL if not |
| * remapped. |
| */ |
| static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et, |
| chunk_t chunk) |
| { |
| struct list_head *slot; |
| struct dm_exception *e; |
| |
| slot = &et->table[exception_hash(et, chunk)]; |
| list_for_each_entry (e, slot, hash_list) |
| if (chunk >= e->old_chunk && |
| chunk <= e->old_chunk + dm_consecutive_chunk_count(e)) |
| return e; |
| |
| return NULL; |
| } |
| |
| static struct dm_exception *alloc_completed_exception(void) |
| { |
| struct dm_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_completed_exception(struct dm_exception *e) |
| { |
| kmem_cache_free(exception_cache, e); |
| } |
| |
| static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s) |
| { |
| struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool, |
| GFP_NOIO); |
| |
| atomic_inc(&s->pending_exceptions_count); |
| pe->snap = s; |
| |
| return pe; |
| } |
| |
| static void free_pending_exception(struct dm_snap_pending_exception *pe) |
| { |
| struct dm_snapshot *s = pe->snap; |
| |
| mempool_free(pe, s->pending_pool); |
| smp_mb__before_atomic_dec(); |
| atomic_dec(&s->pending_exceptions_count); |
| } |
| |
| static void dm_insert_exception(struct dm_exception_table *eh, |
| struct dm_exception *new_e) |
| { |
| struct list_head *l; |
| struct dm_exception *e = NULL; |
| |
| l = &eh->table[exception_hash(eh, new_e->old_chunk)]; |
| |
| /* Add immediately if this table doesn't support consecutive chunks */ |
| if (!eh->hash_shift) |
| goto out; |
| |
| /* List is ordered by old_chunk */ |
| list_for_each_entry_reverse(e, l, hash_list) { |
| /* Insert after an existing chunk? */ |
| if (new_e->old_chunk == (e->old_chunk + |
| dm_consecutive_chunk_count(e) + 1) && |
| new_e->new_chunk == (dm_chunk_number(e->new_chunk) + |
| dm_consecutive_chunk_count(e) + 1)) { |
| dm_consecutive_chunk_count_inc(e); |
| free_completed_exception(new_e); |
| return; |
| } |
| |
| /* Insert before an existing chunk? */ |
| if (new_e->old_chunk == (e->old_chunk - 1) && |
| new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) { |
| dm_consecutive_chunk_count_inc(e); |
| e->old_chunk--; |
| e->new_chunk--; |
| free_completed_exception(new_e); |
| return; |
| } |
| |
| if (new_e->old_chunk > e->old_chunk) |
| break; |
| } |
| |
| out: |
| list_add(&new_e->hash_list, e ? &e->hash_list : l); |
| } |
| |
| /* |
| * Callback used by the exception stores to load exceptions when |
| * initialising. |
| */ |
| static int dm_add_exception(void *context, chunk_t old, chunk_t new) |
| { |
| struct dm_snapshot *s = context; |
| struct dm_exception *e; |
| |
| e = alloc_completed_exception(); |
| if (!e) |
| return -ENOMEM; |
| |
| e->old_chunk = old; |
| |
| /* Consecutive_count is implicitly initialised to zero */ |
| e->new_chunk = new; |
| |
| dm_insert_exception(&s->complete, e); |
| |
| return 0; |
| } |
| |
| /* |
| * Return a minimum chunk size of all snapshots that have the specified origin. |
| * Return zero if the origin has no snapshots. |
| */ |
| static sector_t __minimum_chunk_size(struct origin *o) |
| { |
| struct dm_snapshot *snap; |
| unsigned chunk_size = 0; |
| |
| if (o) |
| list_for_each_entry(snap, &o->snapshots, list) |
| chunk_size = min_not_zero(chunk_size, |
| snap->store->chunk_size); |
| |
| return chunk_size; |
| } |
| |
| /* |
| * 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; |
| } |
| |
| /* |
| * 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->store->chunk_shift; |
| hash_size = min(hash_size, max_buckets); |
| |
| if (hash_size < 64) |
| hash_size = 64; |
| hash_size = rounddown_pow_of_two(hash_size); |
| if (dm_exception_table_init(&s->complete, hash_size, |
| DM_CHUNK_CONSECUTIVE_BITS)) |
| 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 (dm_exception_table_init(&s->pending, hash_size, 0)) { |
| dm_exception_table_exit(&s->complete, exception_cache); |
| return -ENOMEM; |
| } |
| |
| return 0; |
| } |
| |
| static void merge_shutdown(struct dm_snapshot *s) |
| { |
| clear_bit_unlock(RUNNING_MERGE, &s->state_bits); |
| smp_mb__after_clear_bit(); |
| wake_up_bit(&s->state_bits, RUNNING_MERGE); |
| } |
| |
| static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s) |
| { |
| s->first_merging_chunk = 0; |
| s->num_merging_chunks = 0; |
| |
| return bio_list_get(&s->bios_queued_during_merge); |
| } |
| |
| /* |
| * Remove one chunk from the index of completed exceptions. |
| */ |
| static int __remove_single_exception_chunk(struct dm_snapshot *s, |
| chunk_t old_chunk) |
| { |
| struct dm_exception *e; |
| |
| e = dm_lookup_exception(&s->complete, old_chunk); |
| if (!e) { |
| DMERR("Corruption detected: exception for block %llu is " |
| "on disk but not in memory", |
| (unsigned long long)old_chunk); |
| return -EINVAL; |
| } |
| |
| /* |
| * If this is the only chunk using this exception, remove exception. |
| */ |
| if (!dm_consecutive_chunk_count(e)) { |
| dm_remove_exception(e); |
| free_completed_exception(e); |
| return 0; |
| } |
| |
| /* |
| * The chunk may be either at the beginning or the end of a |
| * group of consecutive chunks - never in the middle. We are |
| * removing chunks in the opposite order to that in which they |
| * were added, so this should always be true. |
| * Decrement the consecutive chunk counter and adjust the |
| * starting point if necessary. |
| */ |
| if (old_chunk == e->old_chunk) { |
| e->old_chunk++; |
| e->new_chunk++; |
| } else if (old_chunk != e->old_chunk + |
| dm_consecutive_chunk_count(e)) { |
| DMERR("Attempt to merge block %llu from the " |
| "middle of a chunk range [%llu - %llu]", |
| (unsigned long long)old_chunk, |
| (unsigned long long)e->old_chunk, |
| (unsigned long long) |
| e->old_chunk + dm_consecutive_chunk_count(e)); |
| return -EINVAL; |
| } |
| |
| dm_consecutive_chunk_count_dec(e); |
| |
| return 0; |
| } |
| |
| static void flush_bios(struct bio *bio); |
| |
| static int remove_single_exception_chunk(struct dm_snapshot *s) |
| { |
| struct bio *b = NULL; |
| int r; |
| chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1; |
| |
| down_write(&s->lock); |
| |
| /* |
| * Process chunks (and associated exceptions) in reverse order |
| * so that dm_consecutive_chunk_count_dec() accounting works. |
| */ |
| do { |
| r = __remove_single_exception_chunk(s, old_chunk); |
| if (r) |
| goto out; |
| } while (old_chunk-- > s->first_merging_chunk); |
| |
| b = __release_queued_bios_after_merge(s); |
| |
| out: |
| up_write(&s->lock); |
| if (b) |
| flush_bios(b); |
| |
| return r; |
| } |
| |
| static int origin_write_extent(struct dm_snapshot *merging_snap, |
| sector_t sector, unsigned chunk_size); |
| |
| static void merge_callback(int read_err, unsigned long write_err, |
| void *context); |
| |
| static uint64_t read_pending_exceptions_done_count(void) |
| { |
| uint64_t pending_exceptions_done; |
| |
| spin_lock(&_pending_exceptions_done_spinlock); |
| pending_exceptions_done = _pending_exceptions_done_count; |
| spin_unlock(&_pending_exceptions_done_spinlock); |
| |
| return pending_exceptions_done; |
| } |
| |
| static void increment_pending_exceptions_done_count(void) |
| { |
| spin_lock(&_pending_exceptions_done_spinlock); |
| _pending_exceptions_done_count++; |
| spin_unlock(&_pending_exceptions_done_spinlock); |
| |
| wake_up_all(&_pending_exceptions_done); |
| } |
| |
| static void snapshot_merge_next_chunks(struct dm_snapshot *s) |
| { |
| int i, linear_chunks; |
| chunk_t old_chunk, new_chunk; |
| struct dm_io_region src, dest; |
| sector_t io_size; |
| uint64_t previous_count; |
| |
| BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits)); |
| if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits))) |
| goto shut; |
| |
| /* |
| * valid flag never changes during merge, so no lock required. |
| */ |
| if (!s->valid) { |
| DMERR("Snapshot is invalid: can't merge"); |
| goto shut; |
| } |
| |
| linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk, |
| &new_chunk); |
| if (linear_chunks <= 0) { |
| if (linear_chunks < 0) { |
| DMERR("Read error in exception store: " |
| "shutting down merge"); |
| down_write(&s->lock); |
| s->merge_failed = 1; |
| up_write(&s->lock); |
| } |
| goto shut; |
| } |
| |
| /* Adjust old_chunk and new_chunk to reflect start of linear region */ |
| old_chunk = old_chunk + 1 - linear_chunks; |
| new_chunk = new_chunk + 1 - linear_chunks; |
| |
| /* |
| * Use one (potentially large) I/O to copy all 'linear_chunks' |
| * from the exception store to the origin |
| */ |
| io_size = linear_chunks * s->store->chunk_size; |
| |
| dest.bdev = s->origin->bdev; |
| dest.sector = chunk_to_sector(s->store, old_chunk); |
| dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector); |
| |
| src.bdev = s->cow->bdev; |
| src.sector = chunk_to_sector(s->store, new_chunk); |
| src.count = dest.count; |
| |
| /* |
| * Reallocate any exceptions needed in other snapshots then |
| * wait for the pending exceptions to complete. |
| * Each time any pending exception (globally on the system) |
| * completes we are woken and repeat the process to find out |
| * if we can proceed. While this may not seem a particularly |
| * efficient algorithm, it is not expected to have any |
| * significant impact on performance. |
| */ |
| previous_count = read_pending_exceptions_done_count(); |
| while (origin_write_extent(s, dest.sector, io_size)) { |
| wait_event(_pending_exceptions_done, |
| (read_pending_exceptions_done_count() != |
| previous_count)); |
| /* Retry after the wait, until all exceptions are done. */ |
| previous_count = read_pending_exceptions_done_count(); |
| } |
| |
| down_write(&s->lock); |
| s->first_merging_chunk = old_chunk; |
| s->num_merging_chunks = linear_chunks; |
| up_write(&s->lock); |
| |
| /* Wait until writes to all 'linear_chunks' drain */ |
| for (i = 0; i < linear_chunks; i++) |
| __check_for_conflicting_io(s, old_chunk + i); |
| |
| dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s); |
| return; |
| |
| shut: |
| merge_shutdown(s); |
| } |
| |
| static void error_bios(struct bio *bio); |
| |
| static void merge_callback(int read_err, unsigned long write_err, void *context) |
| { |
| struct dm_snapshot *s = context; |
| struct bio *b = NULL; |
| |
| if (read_err || write_err) { |
| if (read_err) |
| DMERR("Read error: shutting down merge."); |
| else |
| DMERR("Write error: shutting down merge."); |
| goto shut; |
| } |
| |
| if (s->store->type->commit_merge(s->store, |
| s->num_merging_chunks) < 0) { |
| DMERR("Write error in exception store: shutting down merge"); |
| goto shut; |
| } |
| |
| if (remove_single_exception_chunk(s) < 0) |
| goto shut; |
| |
| snapshot_merge_next_chunks(s); |
| |
| return; |
| |
| shut: |
| down_write(&s->lock); |
| s->merge_failed = 1; |
| b = __release_queued_bios_after_merge(s); |
| up_write(&s->lock); |
| error_bios(b); |
| |
| merge_shutdown(s); |
| } |
| |
| static void start_merge(struct dm_snapshot *s) |
| { |
| if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits)) |
| snapshot_merge_next_chunks(s); |
| } |
| |
| static int wait_schedule(void *ptr) |
| { |
| schedule(); |
| |
| return 0; |
| } |
| |
| /* |
| * Stop the merging process and wait until it finishes. |
| */ |
| static void stop_merge(struct dm_snapshot *s) |
| { |
| set_bit(SHUTDOWN_MERGE, &s->state_bits); |
| wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule, |
| TASK_UNINTERRUPTIBLE); |
| clear_bit(SHUTDOWN_MERGE, &s->state_bits); |
| } |
| |
| /* |
| * 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 i; |
| int r = -EINVAL; |
| char *origin_path, *cow_path; |
| unsigned args_used, num_flush_requests = 1; |
| fmode_t origin_mode = FMODE_READ; |
| |
| if (argc != 4) { |
| ti->error = "requires exactly 4 arguments"; |
| r = -EINVAL; |
| goto bad; |
| } |
| |
| if (dm_target_is_snapshot_merge(ti)) { |
| num_flush_requests = 2; |
| origin_mode = FMODE_WRITE; |
| } |
| |
| s = kmalloc(sizeof(*s), GFP_KERNEL); |
| if (!s) { |
| ti->error = "Cannot allocate snapshot context private " |
| "structure"; |
| r = -ENOMEM; |
| goto bad; |
| } |
| |
| origin_path = argv[0]; |
| argv++; |
| argc--; |
| |
| r = dm_get_device(ti, origin_path, origin_mode, &s->origin); |
| if (r) { |
| ti->error = "Cannot get origin device"; |
| goto bad_origin; |
| } |
| |
| cow_path = argv[0]; |
| argv++; |
| argc--; |
| |
| r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow); |
| if (r) { |
| ti->error = "Cannot get COW device"; |
| goto bad_cow; |
| } |
| |
| r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store); |
| if (r) { |
| ti->error = "Couldn't create exception store"; |
| r = -EINVAL; |
| goto bad_store; |
| } |
| |
| argv += args_used; |
| argc -= args_used; |
| |
| s->ti = ti; |
| s->valid = 1; |
| s->active = 0; |
| atomic_set(&s->pending_exceptions_count, 0); |
| init_rwsem(&s->lock); |
| INIT_LIST_HEAD(&s->list); |
| spin_lock_init(&s->pe_lock); |
| s->state_bits = 0; |
| s->merge_failed = 0; |
| s->first_merging_chunk = 0; |
| s->num_merging_chunks = 0; |
| bio_list_init(&s->bios_queued_during_merge); |
| |
| /* Allocate hash table for COW data */ |
| if (init_hash_tables(s)) { |
| ti->error = "Unable to allocate hash table space"; |
| r = -ENOMEM; |
| goto bad_hash_tables; |
| } |
| |
| r = dm_kcopyd_client_create(&s->kcopyd_client); |
| if (r) { |
| ti->error = "Could not create kcopyd client"; |
| goto bad_kcopyd; |
| } |
| |
| s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache); |
| if (!s->pending_pool) { |
| ti->error = "Could not allocate mempool for pending exceptions"; |
| goto bad_pending_pool; |
| } |
| |
| s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS, |
| tracked_chunk_cache); |
| if (!s->tracked_chunk_pool) { |
| ti->error = "Could not allocate tracked_chunk mempool for " |
| "tracking reads"; |
| goto bad_tracked_chunk_pool; |
| } |
| |
| for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) |
| INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]); |
| |
| spin_lock_init(&s->tracked_chunk_lock); |
| |
| ti->private = s; |
| ti->num_flush_requests = num_flush_requests; |
| |
| /* Add snapshot to the list of snapshots for this origin */ |
| /* Exceptions aren't triggered till snapshot_resume() is called */ |
| r = register_snapshot(s); |
| if (r == -ENOMEM) { |
| ti->error = "Snapshot origin struct allocation failed"; |
| goto bad_load_and_register; |
| } else if (r < 0) { |
| /* invalid handover, register_snapshot has set ti->error */ |
| goto bad_load_and_register; |
| } |
| |
| /* |
| * Metadata must only be loaded into one table at once, so skip this |
| * if metadata will be handed over during resume. |
| * Chunk size will be set during the handover - set it to zero to |
| * ensure it's ignored. |
| */ |
| if (r > 0) { |
| s->store->chunk_size = 0; |
| return 0; |
| } |
| |
| r = s->store->type->read_metadata(s->store, dm_add_exception, |
| (void *)s); |
| if (r < 0) { |
| ti->error = "Failed to read snapshot metadata"; |
| goto bad_read_metadata; |
| } else if (r > 0) { |
| s->valid = 0; |
| DMWARN("Snapshot is marked invalid."); |
| } |
| |
| if (!s->store->chunk_size) { |
| ti->error = "Chunk size not set"; |
| goto bad_read_metadata; |
| } |
| ti->split_io = s->store->chunk_size; |
| |
| return 0; |
| |
| bad_read_metadata: |
| unregister_snapshot(s); |
| |
| bad_load_and_register: |
| mempool_destroy(s->tracked_chunk_pool); |
| |
| bad_tracked_chunk_pool: |
| mempool_destroy(s->pending_pool); |
| |
| bad_pending_pool: |
| dm_kcopyd_client_destroy(s->kcopyd_client); |
| |
| bad_kcopyd: |
| dm_exception_table_exit(&s->pending, pending_cache); |
| dm_exception_table_exit(&s->complete, exception_cache); |
| |
| bad_hash_tables: |
| dm_exception_store_destroy(s->store); |
| |
| bad_store: |
| dm_put_device(ti, s->cow); |
| |
| bad_cow: |
| dm_put_device(ti, s->origin); |
| |
| bad_origin: |
| kfree(s); |
| |
| bad: |
| return r; |
| } |
| |
| static void __free_exceptions(struct dm_snapshot *s) |
| { |
| dm_kcopyd_client_destroy(s->kcopyd_client); |
| s->kcopyd_client = NULL; |
| |
| dm_exception_table_exit(&s->pending, pending_cache); |
| dm_exception_table_exit(&s->complete, exception_cache); |
| } |
| |
| static void __handover_exceptions(struct dm_snapshot *snap_src, |
| struct dm_snapshot *snap_dest) |
| { |
| union { |
| struct dm_exception_table table_swap; |
| struct dm_exception_store *store_swap; |
| } u; |
| |
| /* |
| * Swap all snapshot context information between the two instances. |
| */ |
| u.table_swap = snap_dest->complete; |
| snap_dest->complete = snap_src->complete; |
| snap_src->complete = u.table_swap; |
| |
| u.store_swap = snap_dest->store; |
| snap_dest->store = snap_src->store; |
| snap_src->store = u.store_swap; |
| |
| snap_dest->store->snap = snap_dest; |
| snap_src->store->snap = snap_src; |
| |
| snap_dest->ti->split_io = snap_dest->store->chunk_size; |
| snap_dest->valid = snap_src->valid; |
| |
| /* |
| * Set source invalid to ensure it receives no further I/O. |
| */ |
| snap_src->valid = 0; |
| } |
| |
| static void snapshot_dtr(struct dm_target *ti) |
| { |
| #ifdef CONFIG_DM_DEBUG |
| int i; |
| #endif |
| struct dm_snapshot *s = ti->private; |
| struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
| |
| down_read(&_origins_lock); |
| /* Check whether exception handover must be cancelled */ |
| (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); |
| if (snap_src && snap_dest && (s == snap_src)) { |
| down_write(&snap_dest->lock); |
| snap_dest->valid = 0; |
| up_write(&snap_dest->lock); |
| DMERR("Cancelling snapshot handover."); |
| } |
| up_read(&_origins_lock); |
| |
| if (dm_target_is_snapshot_merge(ti)) |
| stop_merge(s); |
| |
| /* Prevent further origin writes from using this snapshot. */ |
| /* After this returns there can be no new kcopyd jobs. */ |
| unregister_snapshot(s); |
| |
| while (atomic_read(&s->pending_exceptions_count)) |
| msleep(1); |
| /* |
| * Ensure instructions in mempool_destroy aren't reordered |
| * before atomic_read. |
| */ |
| smp_mb(); |
| |
| #ifdef CONFIG_DM_DEBUG |
| for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) |
| BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i])); |
| #endif |
| |
| mempool_destroy(s->tracked_chunk_pool); |
| |
| __free_exceptions(s); |
| |
| mempool_destroy(s->pending_pool); |
| |
| dm_exception_store_destroy(s->store); |
| |
| dm_put_device(ti, s->cow); |
| |
| dm_put_device(ti, s->origin); |
| |
| 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 int do_origin(struct dm_dev *origin, struct bio *bio); |
| |
| /* |
| * Flush a list of buffers. |
| */ |
| static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) |
| { |
| struct bio *n; |
| int r; |
| |
| while (bio) { |
| n = bio->bi_next; |
| bio->bi_next = NULL; |
| r = do_origin(s->origin, bio); |
| if (r == DM_MAPIO_REMAPPED) |
| 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 = 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->type->drop_snapshot) |
| s->store->type->drop_snapshot(s->store); |
| |
| s->valid = 0; |
| |
| dm_table_event(s->ti->table); |
| } |
| |
| static void pending_complete(struct dm_snap_pending_exception *pe, int success) |
| { |
| struct dm_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_completed_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_completed_exception(e); |
| error = 1; |
| goto out; |
| } |
| |
| /* Check for conflicting reads */ |
| __check_for_conflicting_io(s, pe->e.old_chunk); |
| |
| /* |
| * Add a proper exception, and remove the |
| * in-flight exception from the list. |
| */ |
| dm_insert_exception(&s->complete, e); |
| |
| out: |
| dm_remove_exception(&pe->e); |
| snapshot_bios = bio_list_get(&pe->snapshot_bios); |
| origin_bios = bio_list_get(&pe->origin_bios); |
| free_pending_exception(pe); |
| |
| increment_pending_exceptions_done_count(); |
| |
| up_write(&s->lock); |
| |
| /* Submit any pending write bios */ |
| if (error) |
| error_bios(snapshot_bios); |
| else |
| flush_bios(snapshot_bios); |
| |
| retry_origin_bios(s, 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 long 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->type->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 dm_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->store, pe->e.old_chunk); |
| src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector); |
| |
| dest.bdev = s->cow->bdev; |
| dest.sector = chunk_to_sector(s->store, pe->e.new_chunk); |
| dest.count = src.count; |
| |
| /* Hand over to kcopyd */ |
| dm_kcopyd_copy(s->kcopyd_client, |
| &src, 1, &dest, 0, copy_callback, pe); |
| } |
| |
| static struct dm_snap_pending_exception * |
| __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk) |
| { |
| struct dm_exception *e = dm_lookup_exception(&s->pending, chunk); |
| |
| if (!e) |
| return NULL; |
| |
| return container_of(e, struct dm_snap_pending_exception, e); |
| } |
| |
| /* |
| * 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 dm_snap_pending_exception *pe, chunk_t chunk) |
| { |
| struct dm_snap_pending_exception *pe2; |
| |
| pe2 = __lookup_pending_exception(s, chunk); |
| if (pe2) { |
| free_pending_exception(pe); |
| return pe2; |
| } |
| |
| pe->e.old_chunk = chunk; |
| bio_list_init(&pe->origin_bios); |
| bio_list_init(&pe->snapshot_bios); |
| pe->started = 0; |
| |
| if (s->store->type->prepare_exception(s->store, &pe->e)) { |
| free_pending_exception(pe); |
| return NULL; |
| } |
| |
| dm_insert_exception(&s->pending, &pe->e); |
| |
| return pe; |
| } |
| |
| static void remap_exception(struct dm_snapshot *s, struct dm_exception *e, |
| struct bio *bio, chunk_t chunk) |
| { |
| bio->bi_bdev = s->cow->bdev; |
| bio->bi_sector = chunk_to_sector(s->store, |
| dm_chunk_number(e->new_chunk) + |
| (chunk - e->old_chunk)) + |
| (bio->bi_sector & |
| s->store->chunk_mask); |
| } |
| |
| static int snapshot_map(struct dm_target *ti, struct bio *bio, |
| union map_info *map_context) |
| { |
| struct dm_exception *e; |
| struct dm_snapshot *s = ti->private; |
| int r = DM_MAPIO_REMAPPED; |
| chunk_t chunk; |
| struct dm_snap_pending_exception *pe = NULL; |
| |
| if (bio->bi_rw & REQ_FLUSH) { |
| bio->bi_bdev = s->cow->bdev; |
| return DM_MAPIO_REMAPPED; |
| } |
| |
| chunk = sector_to_chunk(s->store, 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 = dm_lookup_exception(&s->complete, chunk); |
| if (e) { |
| remap_exception(s, e, bio, chunk); |
| 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 = __lookup_pending_exception(s, chunk); |
| if (!pe) { |
| up_write(&s->lock); |
| pe = alloc_pending_exception(s); |
| down_write(&s->lock); |
| |
| if (!s->valid) { |
| free_pending_exception(pe); |
| r = -EIO; |
| goto out_unlock; |
| } |
| |
| e = dm_lookup_exception(&s->complete, chunk); |
| if (e) { |
| free_pending_exception(pe); |
| remap_exception(s, e, bio, chunk); |
| goto out_unlock; |
| } |
| |
| pe = __find_pending_exception(s, pe, chunk); |
| if (!pe) { |
| __invalidate_snapshot(s, -ENOMEM); |
| r = -EIO; |
| goto out_unlock; |
| } |
| } |
| |
| remap_exception(s, &pe->e, bio, chunk); |
| 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 { |
| bio->bi_bdev = s->origin->bdev; |
| map_context->ptr = track_chunk(s, chunk); |
| } |
| |
| out_unlock: |
| up_write(&s->lock); |
| out: |
| return r; |
| } |
| |
| /* |
| * A snapshot-merge target behaves like a combination of a snapshot |
| * target and a snapshot-origin target. It only generates new |
| * exceptions in other snapshots and not in the one that is being |
| * merged. |
| * |
| * For each chunk, if there is an existing exception, it is used to |
| * redirect I/O to the cow device. Otherwise I/O is sent to the origin, |
| * which in turn might generate exceptions in other snapshots. |
| * If merging is currently taking place on the chunk in question, the |
| * I/O is deferred by adding it to s->bios_queued_during_merge. |
| */ |
| static int snapshot_merge_map(struct dm_target *ti, struct bio *bio, |
| union map_info *map_context) |
| { |
| struct dm_exception *e; |
| struct dm_snapshot *s = ti->private; |
| int r = DM_MAPIO_REMAPPED; |
| chunk_t chunk; |
| |
| if (bio->bi_rw & REQ_FLUSH) { |
| if (!map_context->target_request_nr) |
| bio->bi_bdev = s->origin->bdev; |
| else |
| bio->bi_bdev = s->cow->bdev; |
| map_context->ptr = NULL; |
| return DM_MAPIO_REMAPPED; |
| } |
| |
| chunk = sector_to_chunk(s->store, bio->bi_sector); |
| |
| down_write(&s->lock); |
| |
| /* Full merging snapshots are redirected to the origin */ |
| if (!s->valid) |
| goto redirect_to_origin; |
| |
| /* If the block is already remapped - use that */ |
| e = dm_lookup_exception(&s->complete, chunk); |
| if (e) { |
| /* Queue writes overlapping with chunks being merged */ |
| if (bio_rw(bio) == WRITE && |
| chunk >= s->first_merging_chunk && |
| chunk < (s->first_merging_chunk + |
| s->num_merging_chunks)) { |
| bio->bi_bdev = s->origin->bdev; |
| bio_list_add(&s->bios_queued_during_merge, bio); |
| r = DM_MAPIO_SUBMITTED; |
| goto out_unlock; |
| } |
| |
| remap_exception(s, e, bio, chunk); |
| |
| if (bio_rw(bio) == WRITE) |
| map_context->ptr = track_chunk(s, chunk); |
| goto out_unlock; |
| } |
| |
| redirect_to_origin: |
| bio->bi_bdev = s->origin->bdev; |
| |
| if (bio_rw(bio) == WRITE) { |
| up_write(&s->lock); |
| return do_origin(s->origin, bio); |
| } |
| |
| out_unlock: |
| up_write(&s->lock); |
| |
| return r; |
| } |
| |
| static int snapshot_end_io(struct dm_target *ti, struct bio *bio, |
| int error, union map_info *map_context) |
| { |
| struct dm_snapshot *s = ti->private; |
| struct dm_snap_tracked_chunk *c = map_context->ptr; |
| |
| if (c) |
| stop_tracking_chunk(s, c); |
| |
| return 0; |
| } |
| |
| static void snapshot_merge_presuspend(struct dm_target *ti) |
| { |
| struct dm_snapshot *s = ti->private; |
| |
| stop_merge(s); |
| } |
| |
| static int snapshot_preresume(struct dm_target *ti) |
| { |
| int r = 0; |
| struct dm_snapshot *s = ti->private; |
| struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
| |
| down_read(&_origins_lock); |
| (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); |
| if (snap_src && snap_dest) { |
| down_read(&snap_src->lock); |
| if (s == snap_src) { |
| DMERR("Unable to resume snapshot source until " |
| "handover completes."); |
| r = -EINVAL; |
| } else if (!dm_suspended(snap_src->ti)) { |
| DMERR("Unable to perform snapshot handover until " |
| "source is suspended."); |
| r = -EINVAL; |
| } |
| up_read(&snap_src->lock); |
| } |
| up_read(&_origins_lock); |
| |
| return r; |
| } |
| |
| static void snapshot_resume(struct dm_target *ti) |
| { |
| struct dm_snapshot *s = ti->private; |
| struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
| |
| down_read(&_origins_lock); |
| (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); |
| if (snap_src && snap_dest) { |
| down_write(&snap_src->lock); |
| down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING); |
| __handover_exceptions(snap_src, snap_dest); |
| up_write(&snap_dest->lock); |
| up_write(&snap_src->lock); |
| } |
| up_read(&_origins_lock); |
| |
| /* Now we have correct chunk size, reregister */ |
| reregister_snapshot(s); |
| |
| down_write(&s->lock); |
| s->active = 1; |
| up_write(&s->lock); |
| } |
| |
| static sector_t get_origin_minimum_chunksize(struct block_device *bdev) |
| { |
| sector_t min_chunksize; |
| |
| down_read(&_origins_lock); |
| min_chunksize = __minimum_chunk_size(__lookup_origin(bdev)); |
| up_read(&_origins_lock); |
| |
| return min_chunksize; |
| } |
| |
| static void snapshot_merge_resume(struct dm_target *ti) |
| { |
| struct dm_snapshot *s = ti->private; |
| |
| /* |
| * Handover exceptions from existing snapshot. |
| */ |
| snapshot_resume(ti); |
| |
| /* |
| * snapshot-merge acts as an origin, so set ti->split_io |
| */ |
| ti->split_io = get_origin_minimum_chunksize(s->origin->bdev); |
| |
| start_merge(s); |
| } |
| |
| static int snapshot_status(struct dm_target *ti, status_type_t type, |
| char *result, unsigned int maxlen) |
| { |
| unsigned sz = 0; |
| struct dm_snapshot *snap = ti->private; |
| |
| switch (type) { |
| case STATUSTYPE_INFO: |
| |
| down_write(&snap->lock); |
| |
| if (!snap->valid) |
| DMEMIT("Invalid"); |
| else if (snap->merge_failed) |
| DMEMIT("Merge failed"); |
| else { |
| if (snap->store->type->usage) { |
| sector_t total_sectors, sectors_allocated, |
| metadata_sectors; |
| snap->store->type->usage(snap->store, |
| &total_sectors, |
| §ors_allocated, |
| &metadata_sectors); |
| DMEMIT("%llu/%llu %llu", |
| (unsigned long long)sectors_allocated, |
| (unsigned long long)total_sectors, |
| (unsigned long long)metadata_sectors); |
| } |
| else |
| DMEMIT("Unknown"); |
| } |
| |
| up_write(&snap->lock); |
| |
| break; |
| |
| case STATUSTYPE_TABLE: |
| /* |
| * kdevname returns a static pointer so we need |
| * to make private copies if the output is to |
| * make sense. |
| */ |
| DMEMIT("%s %s", snap->origin->name, snap->cow->name); |
| snap->store->type->status(snap->store, type, result + sz, |
| maxlen - sz); |
| break; |
| } |
| |
| return 0; |
| } |
| |
| static int snapshot_iterate_devices(struct dm_target *ti, |
| iterate_devices_callout_fn fn, void *data) |
| { |
| struct dm_snapshot *snap = ti->private; |
| int r; |
| |
| r = fn(ti, snap->origin, 0, ti->len, data); |
| |
| if (!r) |
| r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data); |
| |
| return r; |
| } |
| |
| |
| /*----------------------------------------------------------------- |
| * Origin methods |
| *---------------------------------------------------------------*/ |
| |
| /* |
| * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any |
| * supplied bio was ignored. The caller may submit it immediately. |
| * (No remapping actually occurs as the origin is always a direct linear |
| * map.) |
| * |
| * If further exceptions are required, DM_MAPIO_SUBMITTED is returned |
| * and any supplied bio is added to a list to be submitted once all |
| * the necessary exceptions exist. |
| */ |
| static int __origin_write(struct list_head *snapshots, sector_t sector, |
| struct bio *bio) |
| { |
| int r = DM_MAPIO_REMAPPED; |
| struct dm_snapshot *snap; |
| struct dm_exception *e; |
| struct dm_snap_pending_exception *pe; |
| struct dm_snap_pending_exception *pe_to_start_now = NULL; |
| struct dm_snap_pending_exception *pe_to_start_last = NULL; |
| chunk_t chunk; |
| |
| /* Do all the snapshots on this origin */ |
| list_for_each_entry (snap, snapshots, list) { |
| /* |
| * Don't make new exceptions in a merging snapshot |
| * because it has effectively been deleted |
| */ |
| if (dm_target_is_snapshot_merge(snap->ti)) |
| continue; |
| |
| 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 (sector >= dm_table_get_size(snap->ti->table)) |
| goto next_snapshot; |
| |
| /* |
| * Remember, different snapshots can have |
| * different chunk sizes. |
| */ |
| chunk = sector_to_chunk(snap->store, sector); |
| |
| /* |
| * Check exception table to see if block |
| * is already remapped in this snapshot |
| * and trigger an exception if not. |
| */ |
| e = dm_lookup_exception(&snap->complete, chunk); |
| if (e) |
| goto next_snapshot; |
| |
| pe = __lookup_pending_exception(snap, chunk); |
| if (!pe) { |
| up_write(&snap->lock); |
| pe = alloc_pending_exception(snap); |
| down_write(&snap->lock); |
| |
| if (!snap->valid) { |
| free_pending_exception(pe); |
| goto next_snapshot; |
| } |
| |
| e = dm_lookup_exception(&snap->complete, chunk); |
| if (e) { |
| free_pending_exception(pe); |
| goto next_snapshot; |
| } |
| |
| pe = __find_pending_exception(snap, pe, chunk); |
| if (!pe) { |
| __invalidate_snapshot(snap, -ENOMEM); |
| goto next_snapshot; |
| } |
| } |
| |
| r = DM_MAPIO_SUBMITTED; |
| |
| /* |
| * If an origin bio was supplied, queue it to wait for the |
| * completion of this exception, and start this one last, |
| * at the end of the function. |
| */ |
| if (bio) { |
| bio_list_add(&pe->origin_bios, bio); |
| bio = NULL; |
| |
| if (!pe->started) { |
| pe->started = 1; |
| pe_to_start_last = pe; |
| } |
| } |
| |
| if (!pe->started) { |
| pe->started = 1; |
| pe_to_start_now = pe; |
| } |
| |
| next_snapshot: |
| up_write(&snap->lock); |
| |
| if (pe_to_start_now) { |
| start_copy(pe_to_start_now); |
| pe_to_start_now = NULL; |
| } |
| } |
| |
| /* |
| * Submit the exception against which the bio is queued last, |
| * to give the other exceptions a head start. |
| */ |
| if (pe_to_start_last) |
| start_copy(pe_to_start_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 = DM_MAPIO_REMAPPED; |
| |
| down_read(&_origins_lock); |
| o = __lookup_origin(origin->bdev); |
| if (o) |
| r = __origin_write(&o->snapshots, bio->bi_sector, bio); |
| up_read(&_origins_lock); |
| |
| return r; |
| } |
| |
| /* |
| * Trigger exceptions in all non-merging snapshots. |
| * |
| * The chunk size of the merging snapshot may be larger than the chunk |
| * size of some other snapshot so we may need to reallocate multiple |
| * chunks in other snapshots. |
| * |
| * We scan all the overlapping exceptions in the other snapshots. |
| * Returns 1 if anything was reallocated and must be waited for, |
| * otherwise returns 0. |
| * |
| * size must be a multiple of merging_snap's chunk_size. |
| */ |
| static int origin_write_extent(struct dm_snapshot *merging_snap, |
| sector_t sector, unsigned size) |
| { |
| int must_wait = 0; |
| sector_t n; |
| struct origin *o; |
| |
| /* |
| * The origin's __minimum_chunk_size() got stored in split_io |
| * by snapshot_merge_resume(). |
| */ |
| down_read(&_origins_lock); |
| o = __lookup_origin(merging_snap->origin->bdev); |
| for (n = 0; n < size; n += merging_snap->ti->split_io) |
| if (__origin_write(&o->snapshots, sector + n, NULL) == |
| DM_MAPIO_SUBMITTED) |
| must_wait = 1; |
| up_read(&_origins_lock); |
| |
| return must_wait; |
| } |
| |
| /* |
| * 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], dm_table_get_mode(ti->table), &dev); |
| if (r) { |
| ti->error = "Cannot get target device"; |
| return r; |
| } |
| |
| ti->private = dev; |
| ti->num_flush_requests = 1; |
| |
| 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; |
| |
| if (bio->bi_rw & REQ_FLUSH) |
| return DM_MAPIO_REMAPPED; |
| |
| /* Only tell snapshots if this is a write */ |
| return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED; |
| } |
| |
| /* |
| * 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; |
| |
| ti->split_io = get_origin_minimum_chunksize(dev->bdev); |
| } |
| |
| 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 int origin_merge(struct dm_target *ti, struct bvec_merge_data *bvm, |
| struct bio_vec *biovec, int max_size) |
| { |
| struct dm_dev *dev = ti->private; |
| struct request_queue *q = bdev_get_queue(dev->bdev); |
| |
| if (!q->merge_bvec_fn) |
| return max_size; |
| |
| bvm->bi_bdev = dev->bdev; |
| bvm->bi_sector = bvm->bi_sector; |
| |
| return min(max_size, q->merge_bvec_fn(q, bvm, biovec)); |
| } |
| |
| static int origin_iterate_devices(struct dm_target *ti, |
| iterate_devices_callout_fn fn, void *data) |
| { |
| struct dm_dev *dev = ti->private; |
| |
| return fn(ti, dev, 0, ti->len, data); |
| } |
| |
| static struct target_type origin_target = { |
| .name = "snapshot-origin", |
| .version = {1, 7, 1}, |
| .module = THIS_MODULE, |
| .ctr = origin_ctr, |
| .dtr = origin_dtr, |
| .map = origin_map, |
| .resume = origin_resume, |
| .status = origin_status, |
| .merge = origin_merge, |
| .iterate_devices = origin_iterate_devices, |
| }; |
| |
| static struct target_type snapshot_target = { |
| .name = "snapshot", |
| .version = {1, 10, 0}, |
| .module = THIS_MODULE, |
| .ctr = snapshot_ctr, |
| .dtr = snapshot_dtr, |
| .map = snapshot_map, |
| .end_io = snapshot_end_io, |
| .preresume = snapshot_preresume, |
| .resume = snapshot_resume, |
| .status = snapshot_status, |
| .iterate_devices = snapshot_iterate_devices, |
| }; |
| |
| static struct target_type merge_target = { |
| .name = dm_snapshot_merge_target_name, |
| .version = {1, 1, 0}, |
| .module = THIS_MODULE, |
| .ctr = snapshot_ctr, |
| .dtr = snapshot_dtr, |
| .map = snapshot_merge_map, |
| .end_io = snapshot_end_io, |
| .presuspend = snapshot_merge_presuspend, |
| .preresume = snapshot_preresume, |
| .resume = snapshot_merge_resume, |
| .status = snapshot_status, |
| .iterate_devices = snapshot_iterate_devices, |
| }; |
| |
| static int __init dm_snapshot_init(void) |
| { |
| int r; |
| |
| r = dm_exception_store_init(); |
| if (r) { |
| DMERR("Failed to initialize exception stores"); |
| return r; |
| } |
| |
| r = dm_register_target(&snapshot_target); |
| if (r < 0) { |
| DMERR("snapshot target register failed %d", r); |
| goto bad_register_snapshot_target; |
| } |
| |
| r = dm_register_target(&origin_target); |
| if (r < 0) { |
| DMERR("Origin target register failed %d", r); |
| goto bad_register_origin_target; |
| } |
| |
| r = dm_register_target(&merge_target); |
| if (r < 0) { |
| DMERR("Merge target register failed %d", r); |
| goto bad_register_merge_target; |
| } |
| |
| r = init_origin_hash(); |
| if (r) { |
| DMERR("init_origin_hash failed."); |
| goto bad_origin_hash; |
| } |
| |
| exception_cache = KMEM_CACHE(dm_exception, 0); |
| if (!exception_cache) { |
| DMERR("Couldn't create exception cache."); |
| r = -ENOMEM; |
| goto bad_exception_cache; |
| } |
| |
| pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0); |
| if (!pending_cache) { |
| DMERR("Couldn't create pending cache."); |
| r = -ENOMEM; |
| goto bad_pending_cache; |
| } |
| |
| tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0); |
| if (!tracked_chunk_cache) { |
| DMERR("Couldn't create cache to track chunks in use."); |
| r = -ENOMEM; |
| goto bad_tracked_chunk_cache; |
| } |
| |
| return 0; |
| |
| bad_tracked_chunk_cache: |
| kmem_cache_destroy(pending_cache); |
| bad_pending_cache: |
| kmem_cache_destroy(exception_cache); |
| bad_exception_cache: |
| exit_origin_hash(); |
| bad_origin_hash: |
| dm_unregister_target(&merge_target); |
| bad_register_merge_target: |
| dm_unregister_target(&origin_target); |
| bad_register_origin_target: |
| dm_unregister_target(&snapshot_target); |
| bad_register_snapshot_target: |
| dm_exception_store_exit(); |
| |
| return r; |
| } |
| |
| static void __exit dm_snapshot_exit(void) |
| { |
| dm_unregister_target(&snapshot_target); |
| dm_unregister_target(&origin_target); |
| dm_unregister_target(&merge_target); |
| |
| exit_origin_hash(); |
| kmem_cache_destroy(pending_cache); |
| kmem_cache_destroy(exception_cache); |
| kmem_cache_destroy(tracked_chunk_cache); |
| |
| dm_exception_store_exit(); |
| } |
| |
| /* 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"); |