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Message-Id: <20200416131332.980922688@linuxfoundation.org>
Date: Thu, 16 Apr 2020 15:21:47 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, cki-project@...hat.com,
Paolo Valente <paolo.valente@...aro.org>,
Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.5 056/257] block, bfq: move forward the getting of an extra ref in bfq_bfqq_move
From: Paolo Valente <paolo.valente@...aro.org>
[ Upstream commit fd1bb3ae54a9a2e0c42709de861c69aa146b8955 ]
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@...hat.com
Tested-by: cki-project@...hat.com
Signed-off-by: Paolo Valente <paolo.valente@...aro.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
block/bfq-cgroup.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 5a64607ce7744..a6d42339fb342 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -641,6 +641,12 @@ 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
@@ -651,12 +657,6 @@ 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)
@@ -676,7 +676,7 @@ 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);
}
--
2.20.1
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