From patchwork Fri Aug 8 20:40:24 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kamal Mostafa X-Patchwork-Id: 378606 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id DCED814017B; Sat, 9 Aug 2014 06:54:00 +1000 (EST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1XFrAj-0005aC-VB; Fri, 08 Aug 2014 20:53:57 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1XFrA0-0005Bi-F1 for kernel-team@lists.ubuntu.com; Fri, 08 Aug 2014 20:53:12 +0000 Received: from c-67-160-228-185.hsd1.ca.comcast.net ([67.160.228.185] helo=fourier) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1XFqz0-0000vn-0D; Fri, 08 Aug 2014 20:41:50 +0000 Received: from kamal by fourier with local (Exim 4.82) (envelope-from ) id 1XFqyy-0001VY-3f; Fri, 08 Aug 2014 13:41:48 -0700 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH 3.13 201/259] dm cache: fix race affecting dirty block count Date: Fri, 8 Aug 2014 13:40:24 -0700 Message-Id: <1407530482-4483-202-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1407530482-4483-1-git-send-email-kamal@canonical.com> References: <1407530482-4483-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Cc: Anssi Hannula , Joe Thornber , Kamal Mostafa , Mike Snitzer X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 3.13.11.6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Anssi Hannula commit 44fa816bb778edbab6b6ddaaf24908dd6295937e upstream. nr_dirty is updated without locking, causing it to drift so that it is non-zero (either a small positive integer, or a very large one when an underflow occurs) even when there are no actual dirty blocks. This was due to a race between the workqueue and map function accessing nr_dirty in parallel without proper protection. People were seeing under runs due to a race on increment/decrement of nr_dirty, see: https://lkml.org/lkml/2014/6/3/648 Fix this by using an atomic_t for nr_dirty. Reported-by: roma1390@gmail.com Signed-off-by: Anssi Hannula Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer [ luis: backported to 3.11: adjusted context ] Signed-off-by: Luis Henriques Signed-off-by: Kamal Mostafa --- drivers/md/dm-cache-target.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index fd92101..ae73ee5 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -225,7 +225,7 @@ struct cache { /* * cache_size entries, dirty if set */ - dm_cblock_t nr_dirty; + atomic_t nr_dirty; unsigned long *dirty_bitset; /* @@ -487,7 +487,7 @@ static bool is_dirty(struct cache *cache, dm_cblock_t b) static void set_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock) { if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) { - cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) + 1); + atomic_inc(&cache->nr_dirty); policy_set_dirty(cache->policy, oblock); } } @@ -496,8 +496,7 @@ static void clear_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cbl { if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) { policy_clear_dirty(cache->policy, oblock); - cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) - 1); - if (!from_cblock(cache->nr_dirty)) + if (atomic_dec_return(&cache->nr_dirty) == 0) dm_table_event(cache->ti->table); } } @@ -2275,7 +2274,7 @@ static int cache_create(struct cache_args *ca, struct cache **result) atomic_set(&cache->quiescing_ack, 0); r = -ENOMEM; - cache->nr_dirty = 0; + atomic_set(&cache->nr_dirty, 0); cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size)); if (!cache->dirty_bitset) { *error = "could not allocate dirty bitset"; @@ -2816,7 +2815,7 @@ static void cache_status(struct dm_target *ti, status_type_t type, residency = policy_residency(cache->policy); - DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ", + DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %lu ", (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata), (unsigned long long)nr_blocks_metadata, (unsigned) atomic_read(&cache->stats.read_hit), @@ -2826,7 +2825,7 @@ static void cache_status(struct dm_target *ti, status_type_t type, (unsigned) atomic_read(&cache->stats.demotion), (unsigned) atomic_read(&cache->stats.promotion), (unsigned long long) from_cblock(residency), - cache->nr_dirty); + (unsigned long) atomic_read(&cache->nr_dirty)); if (writethrough_mode(&cache->features)) DMEMIT("1 writethrough ");