[PATCH 5.4 34/85] blk-iolatency: error out if blk_get_queue() failed in iolatency_set_limit()

Greg Kroah-Hartman
2021-08-10T17:36:16Z

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 8d75d0eff6887bcac7225e12b9c75595e523d92d ]

If queue is dying while iolatency_set_limit() is in progress,
blk_get_queue() won't increment the refcount of the queue. However,
blk_put_queue() will still decrement the refcount later, which will
cause the refcout to be unbalanced.

Thus error out in such case to fix the problem.

Fixes: 8c772a9bfc7c ("blk-iolatency: fix IO hang due to negative inflight counter")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210805124645.543797-1-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-iolatency.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index c128d50cb410..71a82528d4bf 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -832,7 +832,11 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,

enable = iolatency_set_min_lat_nsec(blkg, lat_val);
if (enable) {
- WARN_ON_ONCE(!blk_get_queue(blkg->q));
+ if (!blk_get_queue(blkg->q)) {
+ ret = -ENODEV;
+ goto out;
+ }
+
blkg_get(blkg);
}

--
2.30.2