From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756356AbbA2JAi (ORCPT ); Thu, 29 Jan 2015 04:00:38 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:44737 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756097AbbA2JAc (ORCPT ); Thu, 29 Jan 2015 04:00:32 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Joe Thornber , Mike Snitzer , Jiri Slaby Subject: [PATCH 3.12 149/176] dm cache: fix problematic dual use of a single migration count variable Date: Wed, 28 Jan 2015 15:29:39 +0100 Message-Id: <930a0efdcff8eadc3ad094a5851e0ed030e7db68.1422455352.git.jslaby@suse.cz> X-Mailer: git-send-email 2.2.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joe Thornber 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit a59db67656021fa212e9b95a583f13c34eb67cd9 upstream. 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 Signed-off-by: Jiri Slaby --- drivers/md/dm-cache-target.c | 87 +++++++++++++++++++++++++------------------- 1 file changed, 49 insertions(+), 38 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 843af26e9050..17718456587c 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -146,7 +146,13 @@ 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_ack; @@ -182,7 +188,6 @@ 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; @@ -265,10 +270,31 @@ 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; } @@ -297,7 +323,7 @@ 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) @@ -708,24 +734,14 @@ 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) -{ - mempool_free(mg, mg->cache->migration_pool); -} - -static void inc_nr_migrations(struct cache *cache) +static void inc_io_migrations(struct cache *cache) { - atomic_inc(&cache->nr_migrations); + atomic_inc(&cache->nr_io_migrations); } -static void dec_nr_migrations(struct cache *cache) +static void dec_io_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, @@ -748,11 +764,10 @@ 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) @@ -777,7 +792,7 @@ static void migration_failure(struct dm_cache_migration *mg) cell_defer(cache, mg->new_ocell, 1); } - cleanup_migration(mg); + free_io_migration(mg); } static void migration_success_pre_commit(struct dm_cache_migration *mg) @@ -788,7 +803,7 @@ 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) { @@ -798,14 +813,14 @@ 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; } } @@ -836,12 +851,12 @@ static void migration_success_post_commit(struct dm_cache_migration *mg) spin_unlock_irqrestore(&cache->lock, flags); } else - cleanup_migration(mg); + free_io_migration(mg); } else { clear_dirty(cache, mg->new_oblock, mg->cblock); cell_defer(cache, mg->new_ocell, true); - cleanup_migration(mg); + free_io_migration(mg); } } @@ -1002,7 +1017,7 @@ 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); } @@ -1023,7 +1038,7 @@ 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); } @@ -1047,7 +1062,7 @@ 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); } @@ -1108,7 +1123,7 @@ static void process_discard_bio(struct cache *cache, struct bio *bio) 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; } @@ -1399,7 +1414,7 @@ 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) @@ -1508,9 +1523,6 @@ 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); @@ -1998,7 +2010,8 @@ 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); @@ -2057,8 +2070,6 @@ 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->quiescing = false; -- 2.2.2