diff options
Diffstat (limited to 'ANDROID_3.4.5/drivers/md/dm-snap.c')
| -rw-r--r-- | ANDROID_3.4.5/drivers/md/dm-snap.c | 2329 |
1 files changed, 0 insertions, 2329 deletions
diff --git a/ANDROID_3.4.5/drivers/md/dm-snap.c b/ANDROID_3.4.5/drivers/md/dm-snap.c deleted file mode 100644 index 6f758870..00000000 --- a/ANDROID_3.4.5/drivers/md/dm-snap.c +++ /dev/null @@ -1,2329 +0,0 @@ -/* - * 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 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; - - /* - * For writing a complete chunk, bypassing the copy. - */ - struct bio *full_bio; - bio_end_io_t *full_bio_end_io; - void *full_bio_private; -}; - -/* - * 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 private snapshot 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; - } - - s->kcopyd_client = dm_kcopyd_client_create(); - if (IS_ERR(s->kcopyd_client)) { - r = PTR_ERR(s->kcopyd_client); - 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; - struct bio *full_bio = 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); - full_bio = pe->full_bio; - if (full_bio) { - full_bio->bi_end_io = pe->full_bio_end_io; - full_bio->bi_private = pe->full_bio_private; - } - free_pending_exception(pe); - - increment_pending_exceptions_done_count(); - - up_write(&s->lock); - - /* Submit any pending write bios */ - if (error) { - if (full_bio) - bio_io_error(full_bio); - error_bios(snapshot_bios); - } else { - if (full_bio) - bio_endio(full_bio, 0); - 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 void full_bio_end_io(struct bio *bio, int error) -{ - void *callback_data = bio->bi_private; - - dm_kcopyd_do_callback(callback_data, 0, error ? 1 : 0); -} - -static void start_full_bio(struct dm_snap_pending_exception *pe, - struct bio *bio) -{ - struct dm_snapshot *s = pe->snap; - void *callback_data; - - pe->full_bio = bio; - pe->full_bio_end_io = bio->bi_end_io; - pe->full_bio_private = bio->bi_private; - - callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client, - copy_callback, pe); - - bio->bi_end_io = full_bio_end_io; - bio->bi_private = callback_data; - - generic_make_request(bio); -} - -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; - pe->full_bio = NULL; - - 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); - - r = DM_MAPIO_SUBMITTED; - - if (!pe->started && - bio->bi_size == (s->store->chunk_size << SECTOR_SHIFT)) { - pe->started = 1; - up_write(&s->lock); - start_full_bio(pe, bio); - goto out; - } - - bio_list_add(&pe->snapshot_bios, bio); - - if (!pe->started) { - /* this is protected by snap->lock */ - pe->started = 1; - up_write(&s->lock); - start_copy(pe); - 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"); |