From: Dennis Zhou Date: Sat, 20 Oct 2018 18:56:11 +0000 (-0400) Subject: blkcg: fix edge case for blk_get_rl() under memory pressure X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=b2c3fa546705;p=openwrt%2Fstaging%2Fblogic.git blkcg: fix edge case for blk_get_rl() under memory pressure 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 Signed-off-by: Jens Axboe --- 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();