| From afdab1dc5ea5408afb1214e18512f880a7094d12 Mon Sep 17 00:00:00 2001 |
| From: Paolo Valente <paolo.valente@linaro.org> |
| Date: Sat, 21 Mar 2020 10:45:18 +0100 |
| Subject: [PATCH] block, bfq: move forward the getting of an extra ref in |
| bfq_bfqq_move |
| |
| commit fd1bb3ae54a9a2e0c42709de861c69aa146b8955 upstream. |
| |
| Commit ecedd3d7e199 ("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 ecedd3d7e199 ("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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c |
| index 31f29db65a89..2b3122fe8602 100644 |
| --- a/block/bfq-cgroup.c |
| +++ b/block/bfq-cgroup.c |
| @@ -548,6 +548,12 @@ 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 |
| @@ -558,12 +564,6 @@ 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) |
| @@ -583,7 +583,7 @@ 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); |
| } |
| |
| -- |
| 2.7.4 |
| |