This is a note to let you know that I've just added the patch titled
block: Drop spurious might_sleep() from blk_put_queue()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
block-drop-spurious-might_sleep-from-blk_put_queue.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9ac03e3fd8e1bdbf1bca0fa281849d2257ee8329
Author: Tejun Heo <tj@xxxxxxxxxx>
Date: Fri Jan 6 10:34:10 2023 -1000
block: Drop spurious might_sleep() from blk_put_queue()
[ Upstream commit 49e4d04f0486117ac57a97890eb1db6d52bf82b3 ]
Dan reports the following smatch detected the following:
block/blk-cgroup.c:1863 blkcg_schedule_throttle() warn: sleeping in atomic context
caused by blkcg_schedule_throttle() calling blk_put_queue() in an
non-sleepable context.
blk_put_queue() acquired might_sleep() in 63f93fd6fa57 ("block: mark
blk_put_queue as potentially blocking") which transferred the might_sleep()
from blk_free_queue().
blk_free_queue() acquired might_sleep() in e8c7d14ac6c3 ("block: revert back
to synchronous request_queue removal") while turning request_queue removal
synchronous. However, this isn't necessary as nothing in the free path
actually requires sleeping.
It's pretty unusual to require a sleeping context in a put operation and
it's not needed in the first place. Let's drop it.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Dan Carpenter <error27@xxxxxxxxx>
Link: https://lkml.kernel.org/r/Y7g3L6fntnTtOm63@kili
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Fixes: e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal") # v5.9+
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/r/Y7iFwjN+XzWvLv3y@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/block/blk-core.c b/block/blk-core.c
index 815ffce6b988..f5ae527fb0c3 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -282,12 +282,9 @@ 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: Can sleep.
*/
void blk_put_queue(struct request_queue *q)
{
- might_sleep();
if (refcount_dec_and_test(&q->refs))
blk_free_queue(q);
}
