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block, bfq: do not plug I/O for bfq_queues with no proc refs
[ Upstream commitf718b09327
] Commit478de3380c
("block, bfq: deschedule empty bfq_queues not referred by any process") fixed commit3726112ec7
("block, bfq: re-schedule empty queues if they deserve I/O plugging") by descheduling an empty bfq_queue when it remains with not process reference. Yet, this still left a case uncovered: an empty bfq_queue with not process reference that remains in service. This happens for an in-service sync bfq_queue that is deemed to deserve I/O-dispatch plugging when it remains empty. Yet no new requests will arrive for such a bfq_queue if no process sends requests to it any longer. Even worse, the bfq_queue may happen to be prematurely freed while still in service (because there may remain no reference to it any longer). This commit solves this problem by preventing I/O dispatch from being plugged for the in-service bfq_queue, if the latter has no process reference (the bfq_queue is then prevented from remaining in service). Fixes:3726112ec7
("block, bfq: re-schedule empty queues if they deserve I/O plugging") Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Reported-by: Patrick Dung <patdung100@gmail.com> Tested-by: Patrick Dung <patdung100@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 12 additions and 0 deletions
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@ -3444,6 +3444,10 @@ static void bfq_dispatch_remove(struct request_queue *q, struct request *rq)
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static bool idling_needed_for_service_guarantees(struct bfq_data *bfqd,
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struct bfq_queue *bfqq)
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{
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/* No point in idling for bfqq if it won't get requests any longer */
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if (unlikely(!bfqq_process_refs(bfqq)))
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return false;
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return (bfqq->wr_coeff > 1 &&
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(bfqd->wr_busy_queues <
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bfq_tot_busy_queues(bfqd) ||
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@ -4077,6 +4081,10 @@ static bool idling_boosts_thr_without_issues(struct bfq_data *bfqd,
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bfqq_sequential_and_IO_bound,
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idling_boosts_thr;
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/* No point in idling for bfqq if it won't get requests any longer */
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if (unlikely(!bfqq_process_refs(bfqq)))
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return false;
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bfqq_sequential_and_IO_bound = !BFQQ_SEEKY(bfqq) &&
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bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_has_short_ttime(bfqq);
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@ -4170,6 +4178,10 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq)
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struct bfq_data *bfqd = bfqq->bfqd;
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bool idling_boosts_thr_with_no_issue, idling_needed_for_service_guar;
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/* No point in idling for bfqq if it won't get requests any longer */
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if (unlikely(!bfqq_process_refs(bfqq)))
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return false;
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if (unlikely(bfqd->strict_guarantees))
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return true;
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