| From 80e342252aaaa7c436b7103d74e12022369b5a6b Mon Sep 17 00:00:00 2001 |
| From: Paolo Valente <paolo.valente@linaro.org> |
| Date: Mon, 3 Feb 2020 11:40:56 +0100 |
| Subject: [PATCH] block, bfq: get extra ref to prevent a queue from being freed |
| during a group move |
| |
| commit ecedd3d7e19911ab8fe42f17b77c0a30fe7f4db3 upstream. |
| |
| 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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c |
| index b3796a40a61a..ce7377917b8c 100644 |
| --- a/block/bfq-cgroup.c |
| +++ b/block/bfq-cgroup.c |
| @@ -557,6 +557,12 @@ 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) |
| @@ -576,6 +582,8 @@ 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); |
| } |
| |
| /** |
| -- |
| 2.7.4 |
| |
