From: Paolo Valente paolo.valente@linaro.org
[ Upstream commit bd3664b362381c4c1473753ebedf0ab242a60d1d ]
Since commit 430a67f9d616 ("block, bfq: merge bursts of newly-created queues"), BFQ may schedule a merge between a newly created sync bfq_queue, say Q2, and the last sync bfq_queue created, say Q1. To this goal, BFQ stores the address of Q1 in the field bic->stable_merge_bfqq of the bic associated with Q2. So, when the time for the possible merge arrives, BFQ knows which bfq_queue to merge Q2 with. In particular, BFQ checks for possible merges on request arrivals.
Yet the same bic may also be associated with an async bfq_queue, say Q3. So, if a request for Q3 arrives, then the above check may happen to be executed while the bfq_queue at hand is Q3, instead of Q2. In this case, Q1 happens to be merged with an async bfq_queue. This is not only a conceptual mistake, because async queues are to be kept out of queue merging, but also a bug that leads to inconsistent states.
This commits simply filters async queues out of delayed merges.
Fixes: 430a67f9d616 ("block, bfq: merge bursts of newly-created queues") Tested-by: Holger Hoffstätte holger@applied-asynchrony.com Signed-off-by: Paolo Valente paolo.valente@linaro.org Link: https://lore.kernel.org/r/20210619140948.98712-6-paolo.valente@linaro.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/bfq-iosched.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d00c89f6ba59..7c62bf093199 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2703,7 +2703,13 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, * costly and complicated. */ if (unlikely(!bfqd->nonrot_with_queueing)) { - if (bic->stable_merge_bfqq && + /* + * Make sure also that bfqq is sync, because + * bic->stable_merge_bfqq may point to some queue (for + * stable merging) also if bic is associated with a + * sync queue, but this bfqq is async + */ + if (bfq_bfqq_sync(bfqq) && bic->stable_merge_bfqq && !bfq_bfqq_just_created(bfqq) && time_is_before_jiffies(bfqq->split_time + msecs_to_jiffies(200))) {