diff options
Diffstat (limited to 'drivers/md/dm-snap.c')
| -rw-r--r-- | drivers/md/dm-snap.c | 1279 |
1 files changed, 1017 insertions, 262 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 3a3ba46e6d4b..ee8eb283650d 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -25,6 +25,11 @@ #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 */ @@ -49,7 +54,7 @@ #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ (DM_TRACKED_CHUNK_HASH_SIZE - 1)) -struct exception_table { +struct dm_exception_table { uint32_t hash_mask; unsigned hash_shift; struct list_head *table; @@ -59,22 +64,31 @@ 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) */ + /* + * 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; + /* Whether or not owning mapped_device is suspended */ + int suspended; + mempool_t *pending_pool; atomic_t pending_exceptions_count; - struct exception_table pending; - struct exception_table complete; + struct dm_exception_table pending; + struct dm_exception_table complete; /* * pe_lock protects all pending_exception operations and access @@ -95,8 +109,51 @@ struct dm_snapshot { mempool_t *tracked_chunk_pool; spinlock_t tracked_chunk_lock; struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; + + /* + * 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; + + /* 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; + + /* + * 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_cow(struct dm_snapshot *s) +{ + return s->cow; +} +EXPORT_SYMBOL(dm_snap_cow); + static struct workqueue_struct *ksnapd; static void flush_queued_bios(struct work_struct *work); @@ -116,7 +173,7 @@ static int bdev_equal(struct block_device *lhs, struct block_device *rhs) } struct dm_snap_pending_exception { - struct dm_snap_exception e; + struct dm_exception e; /* * Origin buffers waiting for this to complete are held @@ -125,28 +182,6 @@ struct dm_snap_pending_exception { 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; @@ -222,6 +257,16 @@ static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk) } /* + * 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 { @@ -243,6 +288,10 @@ struct origin { 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; @@ -291,22 +340,144 @@ static void __insert_origin(struct origin *o) } /* + * _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 dm_snapshot *l; - struct origin *o, *new_o; + 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); - o = __lookup_origin(bdev); + r = __validate_exception_handover(snap); + if (r < 0) { + kfree(new_o); + goto out; + } + + o = __lookup_origin(bdev); if (o) kfree(new_o); else { @@ -320,14 +491,27 @@ static int register_snapshot(struct dm_snapshot *snap) __insert_origin(o); } - /* Sort the list according to chunk size, largest-first smallest-last */ - list_for_each_entry(l, &o->snapshots, list) - if (l->store->chunk_size < snap->store->chunk_size) - break; - list_add_tail(&snap->list, &l->list); + __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); - return 0; } static void unregister_snapshot(struct dm_snapshot *s) @@ -338,7 +522,7 @@ static void unregister_snapshot(struct dm_snapshot *s) o = __lookup_origin(s->origin->bdev); list_del(&s->list); - if (list_empty(&o->snapshots)) { + if (o && list_empty(&o->snapshots)) { list_del(&o->hash_list); kfree(o); } @@ -351,8 +535,8 @@ static void unregister_snapshot(struct dm_snapshot *s) * The lowest hash_shift bits of the chunk number are ignored, allowing * some consecutive chunks to be grouped together. */ -static int init_exception_table(struct exception_table *et, uint32_t size, - unsigned hash_shift) +static int dm_exception_table_init(struct dm_exception_table *et, + uint32_t size, unsigned hash_shift) { unsigned int i; @@ -368,10 +552,11 @@ static int init_exception_table(struct exception_table *et, uint32_t size, return 0; } -static void exit_exception_table(struct exception_table *et, struct kmem_cache *mem) +static void dm_exception_table_exit(struct dm_exception_table *et, + struct kmem_cache *mem) { struct list_head *slot; - struct dm_snap_exception *ex, *next; + struct dm_exception *ex, *next; int i, size; size = et->hash_mask + 1; @@ -385,19 +570,12 @@ static void exit_exception_table(struct exception_table *et, struct kmem_cache * vfree(et->table); } -static uint32_t exception_hash(struct exception_table *et, chunk_t chunk) +static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk) { return (chunk >> et->hash_shift) & 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) +static void dm_remove_exception(struct dm_exception *e) { list_del(&e->hash_list); } @@ -406,11 +584,11 @@ static void remove_exception(struct dm_snap_exception *e) * 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) +static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et, + chunk_t chunk) { struct list_head *slot; - struct dm_snap_exception *e; + struct dm_exception *e; slot = &et->table[exception_hash(et, chunk)]; list_for_each_entry (e, slot, hash_list) @@ -421,9 +599,9 @@ static struct dm_snap_exception *lookup_exception(struct exception_table *et, return NULL; } -static struct dm_snap_exception *alloc_exception(void) +static struct dm_exception *alloc_completed_exception(void) { - struct dm_snap_exception *e; + struct dm_exception *e; e = kmem_cache_alloc(exception_cache, GFP_NOIO); if (!e) @@ -432,7 +610,7 @@ static struct dm_snap_exception *alloc_exception(void) return e; } -static void free_exception(struct dm_snap_exception *e) +static void free_completed_exception(struct dm_exception *e) { kmem_cache_free(exception_cache, e); } @@ -457,12 +635,11 @@ static void free_pending_exception(struct dm_snap_pending_exception *pe) atomic_dec(&s->pending_exceptions_count); } -static void insert_completed_exception(struct dm_snapshot *s, - struct dm_snap_exception *new_e) +static void dm_insert_exception(struct dm_exception_table *eh, + struct dm_exception *new_e) { - struct exception_table *eh = &s->complete; struct list_head *l; - struct dm_snap_exception *e = NULL; + struct dm_exception *e = NULL; l = &eh->table[exception_hash(eh, new_e->old_chunk)]; @@ -478,7 +655,7 @@ static void insert_completed_exception(struct dm_snapshot *s, new_e->new_chunk == (dm_chunk_number(e->new_chunk) + dm_consecutive_chunk_count(e) + 1)) { dm_consecutive_chunk_count_inc(e); - free_exception(new_e); + free_completed_exception(new_e); return; } @@ -488,7 +665,7 @@ static void insert_completed_exception(struct dm_snapshot *s, dm_consecutive_chunk_count_inc(e); e->old_chunk--; e->new_chunk--; - free_exception(new_e); + free_completed_exception(new_e); return; } @@ -507,9 +684,9 @@ out: static int dm_add_exception(void *context, chunk_t old, chunk_t new) { struct dm_snapshot *s = context; - struct dm_snap_exception *e; + struct dm_exception *e; - e = alloc_exception(); + e = alloc_completed_exception(); if (!e) return -ENOMEM; @@ -518,11 +695,30 @@ static int dm_add_exception(void *context, chunk_t old, chunk_t new) /* Consecutive_count is implicitly initialised to zero */ e->new_chunk = new; - insert_completed_exception(s, e); + dm_insert_exception(&s->complete, e); return 0; } +#define min_not_zero(l, r) (((l) == 0) ? (r) : (((r) == 0) ? (l) : min(l, r))) + +/* + * 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. */ @@ -546,16 +742,18 @@ static int init_hash_tables(struct dm_snapshot *s) * Calculate based on the size of the original volume or * the COW volume... */ - cow_dev_size = get_dev_size(s->store->cow->bdev); + 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 (init_exception_table(&s->complete, hash_size, - DM_CHUNK_CONSECUTIVE_BITS)) + if (dm_exception_table_init(&s->complete, hash_size, + DM_CHUNK_CONSECUTIVE_BITS)) return -ENOMEM; /* @@ -566,14 +764,284 @@ static int init_hash_tables(struct dm_snapshot *s) if (hash_size < 64) hash_size = 64; - if (init_exception_table(&s->pending, hash_size, 0)) { - exit_exception_table(&s->complete, exception_cache); + 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> */ @@ -582,50 +1050,73 @@ 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; - struct dm_exception_store *store; - unsigned args_used; + 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_args; + goto bad; + } + + if (dm_target_is_snapshot_merge(ti)) { + num_flush_requests = 2; + origin_mode = FMODE_WRITE; } origin_path = argv[0]; argv++; argc--; - r = dm_exception_store_create(ti, argc, argv, &args_used, &store); + s = kmalloc(sizeof(*s), GFP_KERNEL); + if (!s) { + ti->error = "Cannot allocate snapshot context private " + "structure"; + r = -ENOMEM; + goto bad; + } + + cow_path = argv[0]; + argv++; + argc--; + + r = dm_get_device(ti, cow_path, 0, 0, + FMODE_READ | FMODE_WRITE, &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_args; + goto bad_store; } argv += args_used; argc -= args_used; - s = kmalloc(sizeof(*s), GFP_KERNEL); - if (!s) { - ti->error = "Cannot allocate snapshot context private " - "structure"; - r = -ENOMEM; - goto bad_snap; - } - - r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin); + r = dm_get_device(ti, origin_path, 0, ti->len, origin_mode, &s->origin); if (r) { ti->error = "Cannot get origin device"; goto bad_origin; } - s->store = store; + s->ti = ti; s->valid = 1; s->active = 0; + s->suspended = 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)) { @@ -659,39 +1150,55 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) spin_lock_init(&s->tracked_chunk_lock); - /* Metadata must only be loaded into one table at once */ + bio_list_init(&s->queued_bios); + INIT_WORK(&s->queued_bios_work, flush_queued_bios); + + 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_load_and_register; + goto bad_read_metadata; } 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); - if (!s->store->chunk_size) { ti->error = "Chunk size not set"; - goto bad_load_and_register; - } - - /* 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 bad_load_and_register; + goto bad_read_metadata; } - - ti->private = s; ti->split_io = s->store->chunk_size; - ti->num_flush_requests = 1; return 0; +bad_read_metadata: + unregister_snapshot(s); + bad_load_and_register: mempool_destroy(s->tracked_chunk_pool); @@ -702,19 +1209,22 @@ bad_pending_pool: dm_kcopyd_client_destroy(s->kcopyd_client); bad_kcopyd: - exit_exception_table(&s->pending, pending_cache); - exit_exception_table(&s->complete, exception_cache); + dm_exception_table_exit(&s->pending, pending_cache); + dm_exception_table_exit(&s->complete, exception_cache); bad_hash_tables: dm_put_device(ti, s->origin); bad_origin: - kfree(s); + dm_exception_store_destroy(s->store); -bad_snap: - dm_exception_store_destroy(store); +bad_store: + dm_put_device(ti, s->cow); + +bad_cow: + kfree(s); -bad_args: +bad: return r; } @@ -723,8 +1233,39 @@ static void __free_exceptions(struct dm_snapshot *s) dm_kcopyd_client_destroy(s->kcopyd_client); s->kcopyd_client = NULL; - exit_exception_table(&s->pending, pending_cache); - exit_exception_table(&s->complete, exception_cache); + 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) @@ -733,9 +1274,24 @@ static void snapshot_dtr(struct dm_target *ti) int i; #endif struct dm_snapshot *s = ti->private; + struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; flush_workqueue(ksnapd); + 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); @@ -763,6 +1319,8 @@ static void snapshot_dtr(struct dm_target *ti) dm_exception_store_destroy(s->store); + dm_put_device(ti, s->cow); + kfree(s); } @@ -795,6 +1353,26 @@ static void flush_queued_bios(struct work_struct *work) flush_bios(queued_bios); } +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. */ @@ -825,45 +1403,12 @@ static void __invalidate_snapshot(struct dm_snapshot *s, int err) s->valid = 0; - dm_table_event(s->store->ti->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_pending_exception(primary_pe); - } - - /* - * 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); - - return origin_bios; + dm_table_event(s->ti->table); } static void pending_complete(struct dm_snap_pending_exception *pe, int success) { - struct dm_snap_exception *e; + struct dm_exception *e; struct dm_snapshot *s = pe->snap; struct bio *origin_bios = NULL; struct bio *snapshot_bios = NULL; @@ -877,7 +1422,7 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) goto out; } - e = alloc_exception(); + e = alloc_completed_exception(); if (!e) { down_write(&s->lock); __invalidate_snapshot(s, -ENOMEM); @@ -888,28 +1433,27 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) down_write(&s->lock); if (!s->valid) { - free_exception(e); + free_completed_exception(e); error = 1 |