blk-iolatency: error out if blk_get_queue() failed in iolatency_set_limit()

BugLink: https://bugs.launchpad.net/bugs/1941798
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index c128d50cb4107969cab6460e3447b93f7c54553f..71a82528d4bfe454185021db8750c662532dc825 100644 (file)
--- 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);
        }