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Commit b2c3fa54 authored by Dennis Zhou's avatar Dennis Zhou Committed by Jens Axboe
Browse files

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: e2b09899 ("blkcg: cleanup and make blk_get_rl use blkg_lookup_create")
Signed-off-by: default avatarDennis Zhou <dennis@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent bbc15282

include/linux/blk-cgroup.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -597,7 +597,7 @@ static inline struct request_list *blk_get_rl(struct request_queue *q, 
	if (unlikely(!blkg))

	if (unlikely(!blkg))

		blkg = __blkg_lookup_create(blkcg, q);

		blkg = __blkg_lookup_create(blkcg, q);





	if (!blkg_tryget(blkg))

	if (blkg->blkcg == &blkcg_root || !blkg_tryget(blkg))

		goto rl_use_root;

		goto rl_use_root;





	rcu_read_unlock();

	rcu_read_unlock();