diff options
| -rw-r--r-- | drivers/md/dm-snap.c | 82 | ||||
| -rw-r--r-- | drivers/md/dm-snap.h | 50 |
2 files changed, 116 insertions, 16 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index fad84654b045..ae24eab8cd81 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -213,11 +213,15 @@ static void unregister_snapshot(struct dm_snapshot *s) /* * 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 init_exception_table(struct exception_table *et, uint32_t size) +static int init_exception_table(struct 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) @@ -248,7 +252,7 @@ static void exit_exception_table(struct exception_table *et, struct kmem_cache * static uint32_t exception_hash(struct exception_table *et, chunk_t chunk) { - return chunk & et->hash_mask; + return (chunk >> et->hash_shift) & et->hash_mask; } static void insert_exception(struct exception_table *eh, @@ -275,7 +279,8 @@ static struct dm_snap_exception *lookup_exception(struct exception_table *et, slot = &et->table[exception_hash(et, chunk)]; list_for_each_entry (e, slot, hash_list) - if (e->old_chunk == chunk) + if (chunk >= e->old_chunk && + chunk <= e->old_chunk + dm_consecutive_chunk_count(e)) return e; return NULL; @@ -307,6 +312,49 @@ static void free_pending_exception(struct dm_snap_pending_exception *pe) mempool_free(pe, pending_pool); } +static void insert_completed_exception(struct dm_snapshot *s, + struct dm_snap_exception *new_e) +{ + struct exception_table *eh = &s->complete; + struct list_head *l; + struct dm_snap_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_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_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); +} + int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new) { struct dm_snap_exception *e; @@ -316,8 +364,12 @@ int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new) return -ENOMEM; e->old_chunk = old; + + /* Consecutive_count is implicitly initialised to zero */ e->new_chunk = new; - insert_exception(&s->complete, e); + + insert_completed_exception(s, e); + return 0; } @@ -352,7 +404,8 @@ static int init_hash_tables(struct dm_snapshot *s) hash_size = min(hash_size, max_buckets); hash_size = rounddown_pow_of_two(hash_size); - if (init_exception_table(&s->complete, hash_size)) + if (init_exception_table(&s->complete, hash_size, + DM_CHUNK_CONSECUTIVE_BITS)) return -ENOMEM; /* @@ -363,7 +416,7 @@ static int init_hash_tables(struct dm_snapshot *s) if (hash_size < 64) hash_size = 64; - if (init_exception_table(&s->pending, hash_size)) { + if (init_exception_table(&s->pending, hash_size, 0)) { exit_exception_table(&s->complete, exception_cache); return -ENOMEM; } @@ -722,7 +775,7 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) * Add a proper exception, and remove the * in-flight exception from the list. */ - insert_exception(&s->complete, e); + insert_completed_exception(s, e); out: remove_exception(&pe->e); @@ -856,11 +909,12 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio) } static void remap_exception(struct dm_snapshot *s, struct dm_snap_exception *e, - struct bio *bio) + struct bio *bio, chunk_t chunk) { bio->bi_bdev = s->cow->bdev; - bio->bi_sector = chunk_to_sector(s, e->new_chunk) + - (bio->bi_sector & s->chunk_mask); + bio->bi_sector = chunk_to_sector(s, dm_chunk_number(e->new_chunk) + + (chunk - e->old_chunk)) + + (bio->bi_sector & s->chunk_mask); } static int snapshot_map(struct dm_target *ti, struct bio *bio, @@ -891,7 +945,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, /* If the block is already remapped - use that, else remap it */ e = lookup_exception(&s->complete, chunk); if (e) { - remap_exception(s, e, bio); + remap_exception(s, e, bio, chunk); goto out_unlock; } @@ -908,7 +962,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, goto out_unlock; } - remap_exception(s, &pe->e, bio); + remap_exception(s, &pe->e, bio, chunk); bio_list_add(&pe->snapshot_bios, bio); r = DM_MAPIO_SUBMITTED; @@ -1196,7 +1250,7 @@ static int origin_status(struct dm_target *ti, status_type_t type, char *result, static struct target_type origin_target = { .name = "snapshot-origin", - .version = {1, 5, 0}, + .version = {1, 6, 0}, .module = THIS_MODULE, .ctr = origin_ctr, .dtr = origin_dtr, @@ -1207,7 +1261,7 @@ static struct target_type origin_target = { static struct target_type snapshot_target = { .name = "snapshot", - .version = {1, 5, 0}, + .version = {1, 6, 0}, .module = THIS_MODULE, .ctr = snapshot_ctr, .dtr = snapshot_dtr, diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h index 650e0f1f51d8..93bce5d49742 100644 --- a/drivers/md/dm-snap.h +++ b/drivers/md/dm-snap.h @@ -16,19 +16,22 @@ struct exception_table { uint32_t hash_mask; + unsigned hash_shift; struct list_head *table; }; /* * The snapshot code deals with largish chunks of the disk at a - * time. Typically 64k - 256k. + * time. Typically 32k - 512k. */ -/* FIXME: can we get away with limiting these to a uint32_t ? */ typedef sector_t chunk_t; /* * An exception is used where an old chunk of data has been * replaced by a new one. + * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number + * of chunks that follow contiguously. Remaining bits hold the number of the + * chunk within the device. */ struct dm_snap_exception { struct list_head hash_list; @@ -38,6 +41,49 @@ struct dm_snap_exception { }; /* + * Funtions to manipulate consecutive chunks + */ +# if defined(CONFIG_LBD) || (BITS_PER_LONG == 64) +# define DM_CHUNK_CONSECUTIVE_BITS 8 +# define DM_CHUNK_NUMBER_BITS 56 + +static inline chunk_t dm_chunk_number(chunk_t chunk) +{ + return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); +} + +static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) +{ + return e->new_chunk >> DM_CHUNK_NUMBER_BITS; +} + +static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) +{ + e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); + + BUG_ON(!dm_consecutive_chunk_count(e)); +} + +# else +# define DM_CHUNK_CONSECUTIVE_BITS 0 + +static inline chunk_t dm_chunk_number(chunk_t chunk) +{ + return chunk; +} + +static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) +{ + return 0; +} + +static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) +{ +} + +# endif + +/* * Abstraction to handle the meta/layout of exception stores (the * COW device). */ |