From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: From: Dennis Zhou To: Jens Axboe Cc: Tejun Heo , Valdis Kletnieks , kernel-team@fb.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Dennis Zhou Subject: [PATCH 1/2] blkcg: fix edge case for blk_get_rl() under memory pressure Date: Sat, 20 Oct 2018 14:56:11 -0400 Message-Id: <20181020185612.51587-2-dennis@kernel.org> In-Reply-To: <20181020185612.51587-1-dennis@kernel.org> References: <20181020185612.51587-1-dennis@kernel.org> List-ID: It is possible for blkg creation to fail when in blk_get_rl(). In this situation, the fallback logic returns the nearest created blkg. There is however special handling for the request_list for the root blkcg. This fixes the missing edge case from the earlier series changing blk_get_rl(). Fixes: e2b0989954ae ("blkcg: cleanup and make blk_get_rl use blkg_lookup_create") Signed-off-by: Dennis Zhou --- include/linux/blk-cgroup.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index b7fd08013de2..1e76ceebeb5d 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -597,7 +597,7 @@ static inline struct request_list *blk_get_rl(struct request_queue *q, if (unlikely(!blkg)) blkg = __blkg_lookup_create(blkcg, q); - if (!blkg_tryget(blkg)) + if (blkg->blkcg == &blkcg_root || !blkg_tryget(blkg)) goto rl_use_root; rcu_read_unlock(); -- 2.17.1