[PATCH 6.0 0858/1073] block: mark blk_put_queue as potentially blocking

Greg Kroah-Hartman
2022-12-28T16:36:57Z

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 63f93fd6fa5717769a78d6d7bea6f7f9a1ccca8e ]

We can't just say that the last reference release may block, as any
reference dropped could be the last one. So move the might_sleep() from
blk_free_queue to blk_put_queue and update the documentation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221114042637.1009333-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: d36a9ea5e776 ("block: fix use-after-free of q->q_usage_counter")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-core.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 3920e101654f..818002b8be7c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -261,8 +261,6 @@ static void blk_free_queue_rcu(struct rcu_head *rcu_head)

static void blk_free_queue(struct request_queue *q)
{
- might_sleep();
-
percpu_ref_exit(&q->q_usage_counter);

if (q->poll_stat)
@@ -286,11 +284,11 @@ static void blk_free_queue(struct request_queue *q)
* Decrements the refcount of the request_queue and free it when the refcount
* reaches 0.
*
- * Context: Any context, but the last reference must not be dropped from
- * atomic context.
+ * Context: Can sleep.
*/
void blk_put_queue(struct request_queue *q)
{
+ might_sleep();
if (refcount_dec_and_test(&q->refs))
blk_free_queue(q);
}
--
2.35.1