@@ -3443,6 +3443,10 @@ 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) ||
@@ -4076,6 +4080,10 @@ 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);
@@ -4169,6 +4177,10 @@ 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;
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") Reported-by: Patrick Dung <patdung100@gmail.com> Tested-by: Patrick Dung <patdung100@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> --- block/bfq-iosched.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)