From 9b1cc9f251affdd27f29fe46d0989ba76c33faf6 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Fri, 23 Jan 2015 10:00:07 +0000 Subject: [PATCH 1/3] dm cache: share cache-metadata object across inactive and active DM tables If a DM table is reloaded with an inactive table when the device is not suspended (normal procedure for LVM2), then there will be two dm-bufio objects that can diverge. This can lead to a situation where the inactive table uses bufio to read metadata at the same time the active table writes metadata -- resulting in the inactive table having stale metadata buffers once it is promoted to the active table slot. Fix this by using reference counting and a global list of cache metadata objects to ensure there is only one metadata object per metadata device. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm-cache-metadata.c | 101 +++++++++++++++++++++++++++++++-- 1 file changed, 95 insertions(+), 6 deletions(-) diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c index 9fc616c2755e..21b156242e42 100644 --- a/drivers/md/dm-cache-metadata.c +++ b/drivers/md/dm-cache-metadata.c @@ -94,6 +94,9 @@ struct cache_disk_superblock { } __packed; struct dm_cache_metadata { + atomic_t ref_count; + struct list_head list; + struct block_device *bdev; struct dm_block_manager *bm; struct dm_space_map *metadata_sm; @@ -669,10 +672,10 @@ static void unpack_value(__le64 value_le, dm_oblock_t *block, unsigned *flags) /*----------------------------------------------------------------*/ -struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, - sector_t data_block_size, - bool may_format_device, - size_t policy_hint_size) +static struct dm_cache_metadata *metadata_open(struct block_device *bdev, + sector_t data_block_size, + bool may_format_device, + size_t policy_hint_size) { int r; struct dm_cache_metadata *cmd; @@ -683,6 +686,7 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, return NULL; } + atomic_set(&cmd->ref_count, 1); init_rwsem(&cmd->root_lock); cmd->bdev = bdev; cmd->data_block_size = data_block_size; @@ -705,10 +709,95 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, return cmd; } +/* + * We keep a little list of ref counted metadata objects to prevent two + * different target instances creating separate bufio instances. This is + * an issue if a table is reloaded before the suspend. + */ +static DEFINE_MUTEX(table_lock); +static LIST_HEAD(table); + +static struct dm_cache_metadata *lookup(struct block_device *bdev) +{ + struct dm_cache_metadata *cmd; + + list_for_each_entry(cmd, &table, list) + if (cmd->bdev == bdev) { + atomic_inc(&cmd->ref_count); + return cmd; + } + + return NULL; +} + +static struct dm_cache_metadata *lookup_or_open(struct block_device *bdev, + sector_t data_block_size, + bool may_format_device, + size_t policy_hint_size) +{ + struct dm_cache_metadata *cmd, *cmd2; + + mutex_lock(&table_lock); + cmd = lookup(bdev); + mutex_unlock(&table_lock); + + if (cmd) + return cmd; + + cmd = metadata_open(bdev, data_block_size, may_format_device, policy_hint_size); + if (cmd) { + mutex_lock(&table_lock); + cmd2 = lookup(bdev); + if (cmd2) { + mutex_unlock(&table_lock); + __destroy_persistent_data_objects(cmd); + kfree(cmd); + return cmd2; + } + list_add(&cmd->list, &table); + mutex_unlock(&table_lock); + } + + return cmd; +} + +static bool same_params(struct dm_cache_metadata *cmd, sector_t data_block_size) +{ + if (cmd->data_block_size != data_block_size) { + DMERR("data_block_size (%llu) different from that in metadata (%llu)\n", + (unsigned long long) data_block_size, + (unsigned long long) cmd->data_block_size); + return false; + } + + return true; +} + +struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, + sector_t data_block_size, + bool may_format_device, + size_t policy_hint_size) +{ + struct dm_cache_metadata *cmd = lookup_or_open(bdev, data_block_size, + may_format_device, policy_hint_size); + if (cmd && !same_params(cmd, data_block_size)) { + dm_cache_metadata_close(cmd); + return NULL; + } + + return cmd; +} + void dm_cache_metadata_close(struct dm_cache_metadata *cmd) { - __destroy_persistent_data_objects(cmd); - kfree(cmd); + if (atomic_dec_and_test(&cmd->ref_count)) { + mutex_lock(&table_lock); + list_del(&cmd->list); + mutex_unlock(&table_lock); + + __destroy_persistent_data_objects(cmd); + kfree(cmd); + } } /* From a59db67656021fa212e9b95a583f13c34eb67cd9 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Fri, 23 Jan 2015 10:16:16 +0000 Subject: [PATCH 2/3] dm cache: fix problematic dual use of a single migration count variable Introduce a new variable to count the number of allocated migration structures. The existing variable cache->nr_migrations became overloaded. It was used to: i) track of the number of migrations in flight for the purposes of quiescing during suspend. ii) to estimate the amount of background IO occuring. Recent discard changes meant that REQ_DISCARD bios are processed with a migration. Discards are not background IO so nr_migrations was not incremented. However this could cause quiescing to complete early. (i) is now handled with a new variable cache->nr_allocated_migrations. cache->nr_migrations has been renamed cache->nr_io_migrations. cleanup_migration() is now called free_io_migration(), since it decrements that variable. Also, remove the unused cache->next_migration variable that got replaced with with prealloc_structs a while ago. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm-cache-target.c | 89 ++++++++++++++++++++---------------- 1 file changed, 50 insertions(+), 39 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 1e96d7889f51..e1650539cc2f 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -221,7 +221,13 @@ struct cache { struct list_head need_commit_migrations; sector_t migration_threshold; wait_queue_head_t migration_wait; - atomic_t nr_migrations; + atomic_t nr_allocated_migrations; + + /* + * The number of in flight migrations that are performing + * background io. eg, promotion, writeback. + */ + atomic_t nr_io_migrations; wait_queue_head_t quiescing_wait; atomic_t quiescing; @@ -258,7 +264,6 @@ struct cache { struct dm_deferred_set *all_io_ds; mempool_t *migration_pool; - struct dm_cache_migration *next_migration; struct dm_cache_policy *policy; unsigned policy_nr_args; @@ -350,10 +355,31 @@ static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell *cel dm_bio_prison_free_cell(cache->prison, cell); } +static struct dm_cache_migration *alloc_migration(struct cache *cache) +{ + struct dm_cache_migration *mg; + + mg = mempool_alloc(cache->migration_pool, GFP_NOWAIT); + if (mg) { + mg->cache = cache; + atomic_inc(&mg->cache->nr_allocated_migrations); + } + + return mg; +} + +static void free_migration(struct dm_cache_migration *mg) +{ + if (atomic_dec_and_test(&mg->cache->nr_allocated_migrations)) + wake_up(&mg->cache->migration_wait); + + mempool_free(mg, mg->cache->migration_pool); +} + static int prealloc_data_structs(struct cache *cache, struct prealloc *p) { if (!p->mg) { - p->mg = mempool_alloc(cache->migration_pool, GFP_NOWAIT); + p->mg = alloc_migration(cache); if (!p->mg) return -ENOMEM; } @@ -382,7 +408,7 @@ static void prealloc_free_structs(struct cache *cache, struct prealloc *p) free_prison_cell(cache, p->cell1); if (p->mg) - mempool_free(p->mg, cache->migration_pool); + free_migration(p->mg); } static struct dm_cache_migration *prealloc_get_migration(struct prealloc *p) @@ -854,24 +880,14 @@ static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio, * Migration covers moving data from the origin device to the cache, or * vice versa. *--------------------------------------------------------------*/ -static void free_migration(struct dm_cache_migration *mg) +static void inc_io_migrations(struct cache *cache) { - mempool_free(mg, mg->cache->migration_pool); + atomic_inc(&cache->nr_io_migrations); } -static void inc_nr_migrations(struct cache *cache) +static void dec_io_migrations(struct cache *cache) { - atomic_inc(&cache->nr_migrations); -} - -static void dec_nr_migrations(struct cache *cache) -{ - atomic_dec(&cache->nr_migrations); - - /* - * Wake the worker in case we're suspending the target. - */ - wake_up(&cache->migration_wait); + atomic_dec(&cache->nr_io_migrations); } static void __cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell, @@ -894,11 +910,10 @@ static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell, wake_worker(cache); } -static void cleanup_migration(struct dm_cache_migration *mg) +static void free_io_migration(struct dm_cache_migration *mg) { - struct cache *cache = mg->cache; + dec_io_migrations(mg->cache); free_migration(mg); - dec_nr_migrations(cache); } static void migration_failure(struct dm_cache_migration *mg) @@ -923,7 +938,7 @@ static void migration_failure(struct dm_cache_migration *mg) cell_defer(cache, mg->new_ocell, true); } - cleanup_migration(mg); + free_io_migration(mg); } static void migration_success_pre_commit(struct dm_cache_migration *mg) @@ -934,7 +949,7 @@ static void migration_success_pre_commit(struct dm_cache_migration *mg) if (mg->writeback) { clear_dirty(cache, mg->old_oblock, mg->cblock); cell_defer(cache, mg->old_ocell, false); - cleanup_migration(mg); + free_io_migration(mg); return; } else if (mg->demote) { @@ -944,14 +959,14 @@ static void migration_success_pre_commit(struct dm_cache_migration *mg) mg->old_oblock); if (mg->promote) cell_defer(cache, mg->new_ocell, true); - cleanup_migration(mg); + free_io_migration(mg); return; } } else { if (dm_cache_insert_mapping(cache->cmd, mg->cblock, mg->new_oblock)) { DMWARN_LIMIT("promotion failed; couldn't update on disk metadata"); policy_remove_mapping(cache->policy, mg->new_oblock); - cleanup_migration(mg); + free_io_migration(mg); return; } } @@ -984,7 +999,7 @@ static void migration_success_post_commit(struct dm_cache_migration *mg) } else { if (mg->invalidate) policy_remove_mapping(cache->policy, mg->old_oblock); - cleanup_migration(mg); + free_io_migration(mg); } } else { @@ -999,7 +1014,7 @@ static void migration_success_post_commit(struct dm_cache_migration *mg) bio_endio(mg->new_ocell->holder, 0); cell_defer(cache, mg->new_ocell, false); } - cleanup_migration(mg); + free_io_migration(mg); } } @@ -1251,7 +1266,7 @@ static void promote(struct cache *cache, struct prealloc *structs, mg->new_ocell = cell; mg->start_jiffies = jiffies; - inc_nr_migrations(cache); + inc_io_migrations(cache); quiesce_migration(mg); } @@ -1275,7 +1290,7 @@ static void writeback(struct cache *cache, struct prealloc *structs, mg->new_ocell = NULL; mg->start_jiffies = jiffies; - inc_nr_migrations(cache); + inc_io_migrations(cache); quiesce_migration(mg); } @@ -1302,7 +1317,7 @@ static void demote_then_promote(struct cache *cache, struct prealloc *structs, mg->new_ocell = new_ocell; mg->start_jiffies = jiffies; - inc_nr_migrations(cache); + inc_io_migrations(cache); quiesce_migration(mg); } @@ -1330,7 +1345,7 @@ static void invalidate(struct cache *cache, struct prealloc *structs, mg->new_ocell = NULL; mg->start_jiffies = jiffies; - inc_nr_migrations(cache); + inc_io_migrations(cache); quiesce_migration(mg); } @@ -1412,7 +1427,7 @@ static void process_discard_bio(struct cache *cache, struct prealloc *structs, static bool spare_migration_bandwidth(struct cache *cache) { - sector_t current_volume = (atomic_read(&cache->nr_migrations) + 1) * + sector_t current_volume = (atomic_read(&cache->nr_io_migrations) + 1) * cache->sectors_per_block; return current_volume < cache->migration_threshold; } @@ -1764,7 +1779,7 @@ static void stop_quiescing(struct cache *cache) static void wait_for_migrations(struct cache *cache) { - wait_event(cache->migration_wait, !atomic_read(&cache->nr_migrations)); + wait_event(cache->migration_wait, !atomic_read(&cache->nr_allocated_migrations)); } static void stop_worker(struct cache *cache) @@ -1876,9 +1891,6 @@ static void destroy(struct cache *cache) { unsigned i; - if (cache->next_migration) - mempool_free(cache->next_migration, cache->migration_pool); - if (cache->migration_pool) mempool_destroy(cache->migration_pool); @@ -2424,7 +2436,8 @@ static int cache_create(struct cache_args *ca, struct cache **result) INIT_LIST_HEAD(&cache->quiesced_migrations); INIT_LIST_HEAD(&cache->completed_migrations); INIT_LIST_HEAD(&cache->need_commit_migrations); - atomic_set(&cache->nr_migrations, 0); + atomic_set(&cache->nr_allocated_migrations, 0); + atomic_set(&cache->nr_io_migrations, 0); init_waitqueue_head(&cache->migration_wait); init_waitqueue_head(&cache->quiescing_wait); @@ -2487,8 +2500,6 @@ static int cache_create(struct cache_args *ca, struct cache **result) goto bad; } - cache->next_migration = NULL; - cache->need_tick_bio = true; cache->sized = false; cache->invalidate = false; From 96b26c8c64c7a30488b8b404f7a63346df4c3bff Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 8 Jan 2015 18:52:26 -0500 Subject: [PATCH 3/3] dm: fix handling of multiple internal suspends Commit ffcc393641 ("dm: enhance internal suspend and resume interface") attempted to handle multiple internal suspends on the same device, but it did that incorrectly. When these functions are called in this order on the same device the device is no longer suspended, but it should be: dm_internal_suspend_noflush dm_internal_suspend_noflush dm_internal_resume Fix this bug by maintaining an 'internal_suspend_count' and resuming the device when this count drops to zero. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index b98cd9d84435..2caf5b374649 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -206,6 +206,9 @@ struct mapped_device { /* zero-length flush that will be cloned and submitted to targets */ struct bio flush_bio; + /* the number of internal suspends */ + unsigned internal_suspend_count; + struct dm_stats stats; }; @@ -2928,7 +2931,7 @@ static void __dm_internal_suspend(struct mapped_device *md, unsigned suspend_fla { struct dm_table *map = NULL; - if (dm_suspended_internally_md(md)) + if (md->internal_suspend_count++) return; /* nested internal suspend */ if (dm_suspended_md(md)) { @@ -2953,7 +2956,9 @@ static void __dm_internal_suspend(struct mapped_device *md, unsigned suspend_fla static void __dm_internal_resume(struct mapped_device *md) { - if (!dm_suspended_internally_md(md)) + BUG_ON(!md->internal_suspend_count); + + if (--md->internal_suspend_count) return; /* resume from nested internal suspend */ if (dm_suspended_md(md))