block, bfq: move forward the getting of an extra ref in bfq_bfqq_move (fd1bb3ae) · Commits · 戴 / test

Commit ("block, bfq: get extra ref to prevent a queue from being freed during a group move") gets an extra reference to a bfq_queue before possibly deactivating it (temporarily), in bfq_bfqq_move(). This prevents the bfq_queue from disappearing before being reactivated in its new group. Yet, the bfq_queue may also be expired (i.e., its service may be stopped) before the bfq_queue is deactivated. And also an expiration may lead to a premature freeing. This commit fixes this issue by simply moving forward the getting of the extra reference already introduced by commit ("block, bfq: get extra ref to prevent a queue from being freed during a group move"). Reported-by:

<cki-project@redhat.com> Tested-by:

<cki-project@redhat.com> Signed-off-by:

Paolo Valente <paolo.valente@linaro.org> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/bfq-cgroup.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -642,6 +642,12 @@ void bfq_bfqq_move(struct bfq_data bfqd, struct bfq_queue bfqq,
		{
		struct bfq_entity *entity = &bfqq->entity;

		/*
		* Get extra reference to prevent bfqq from being freed in
		* next possible expire or deactivate.
		*/
		bfqq->ref++;

		/* If bfqq is empty, then bfq_bfqq_expire also invokes
		* bfq_del_bfqq_busy, thereby removing bfqq and its entity
		* from data structures related to current group. Otherwise we
		@@ -652,12 +658,6 @@ 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_or_in_serv)
		@@ -677,7 +677,7 @@ 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 */
		/* release extra ref taken above, bfqq may happen to be freed now */
		bfq_put_queue(bfqq);
		}

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