block, bfq: reset waker pointer with shared queues

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[ Upstream commit 9a2ac41b13 ]

Commit 85686d0dc1 ("block, bfq: keep shared queues out of the waker
mechanism") leaves shared bfq_queues out of the waker-detection
mechanism. It attains this goal by not updating the pointer
last_completed_rq_bfqq, if the last request completed belongs to a
shared bfq_queue (so that the pointer will not point to the shared
bfq_queue).

Yet this has a side effect: the pointer last_completed_rq_bfqq keeps
pointing, deceptively, to a bfq_queue that actually is not the last
one to have had a request completed. As a consequence, such a
bfq_queue may deceptively be considered as a waker of some bfq_queue,
even of some shared bfq_queue.

To address this issue, reset last_completed_rq_bfqq if the last
request completed belongs to a shared queue.

Fixes: 85686d0dc1 ("block, bfq: keep shared queues out of the waker mechanism")
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-8-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Paolo Valente 2021-06-19 16:09:48 +02:00 • committed by Greg Kroah-Hartman

parent 833cf2c80a

commit ad90f92825

1 changed files with 4 additions and 2 deletions

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block/bfq-iosched.c

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