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

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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>
This commit is contained in:
Paolo Valente 2020-02-03 11:40:56 +01:00 committed by Jens Axboe
parent 32c59e3a9a
commit ecedd3d7e1
1 changed files with 8 additions and 0 deletions
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8
block/bfq-cgroup.c
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@ -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);
}
/**