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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: e2b0989954 ("blkcg: cleanup and make blk_get_rl use blkg_lookup_create")
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dennis Zhou 2018-10-20 14:56:11 -04:00 committed by Jens Axboe
parent bbc152825a
commit b2c3fa5467
1 changed files with 1 additions and 1 deletions
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2
include/linux/blk-cgroup.h
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@ -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();