From: Paolo Valente paolo.valente@linaro.org
[ Upstream commit f718b093277df582fbf8775548a4f163e664d282 ]
Commit 478de3380c1c ("block, bfq: deschedule empty bfq_queues not referred by any process") fixed commit 3726112ec731 ("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: 3726112ec731 ("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 --- block/bfq-iosched.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 0c6214497fcc1..5498d05b873d3 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -3444,6 +3444,10 @@ static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) static bool idling_needed_for_service_guarantees(struct bfq_data *bfqd, struct bfq_queue *bfqq) { + /* No point in idling for bfqq if it won't get requests any longer */ + if (unlikely(!bfqq_process_refs(bfqq))) + return false; + return (bfqq->wr_coeff > 1 && (bfqd->wr_busy_queues < bfq_tot_busy_queues(bfqd) || @@ -4077,6 +4081,10 @@ static bool idling_boosts_thr_without_issues(struct bfq_data *bfqd, bfqq_sequential_and_IO_bound, idling_boosts_thr;
+ /* No point in idling for bfqq if it won't get requests any longer */ + if (unlikely(!bfqq_process_refs(bfqq))) + return false; + bfqq_sequential_and_IO_bound = !BFQQ_SEEKY(bfqq) && bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_has_short_ttime(bfqq);
@@ -4170,6 +4178,10 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq) struct bfq_data *bfqd = bfqq->bfqd; bool idling_boosts_thr_with_no_issue, idling_needed_for_service_guar;
+ /* No point in idling for bfqq if it won't get requests any longer */ + if (unlikely(!bfqq_process_refs(bfqq))) + return false; + if (unlikely(bfqd->strict_guarantees)) return true;