Commit ecedd3d7 authored Feb 03, 2020 by Paolo Valente Committed by Jens Axboe Feb 03, 2020

block, bfq: get extra ref to prevent a queue from being freed during a group move



In bfq_bfqq_move(), the bfq_queue, say Q, to be moved to a new group
may happen to be deactivated in the scheduling data structures of the
source group (and then activated in the destination group). If Q is
referred only by the data structures in the source group when the
deactivation happens, then Q is freed upon the deactivation.

This commit addresses this issue by getting an extra reference before
the possible deactivation, and releasing this extra reference after Q
has been moved.

Tested-by: Chris Evich <cevich@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 32c59e3a

block/bfq-cgroup.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -651,6 +651,12 @@ void bfq_bfqq_move(struct bfq_data bfqd, struct bfq_queue bfqq,
		bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
		false, BFQQE_PREEMPTED);

		/*
		* get extra reference to prevent bfqq from being freed in
		* next possible deactivate
		*/
		bfqq->ref++;

		if (bfq_bfqq_busy(bfqq))
		bfq_deactivate_bfqq(bfqd, bfqq, false, false);
		else if (entity->on_st)
		@@ -670,6 +676,8 @@ void bfq_bfqq_move(struct bfq_data bfqd, struct bfq_queue bfqq,

		if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
		bfq_schedule_dispatch(bfqd);
		/* release extra ref taken above */
		bfq_put_queue(bfqq);
		}

		/**

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