[PATCH 1/5] blk-iolatency: clear use_delay when io.latency is set to zero

From: Tejun Heo <tj@kernel.org>
To: axboe@kernel.dk, jbacik@fb.com
Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	kernel-team@fb.com, dennis@kernel.org, jack@suse.cz,
	Tejun Heo <tj@kernel.org>,
	stable@vger.kernel.org
Subject: [PATCH 1/5] blk-iolatency: clear use_delay when io.latency is set to zero
Date: Thu, 13 Jun 2019 15:30:37 -0700	[thread overview]
Message-ID: <20190613223041.606735-2-tj@kernel.org> (raw)
In-Reply-To: <20190613223041.606735-1-tj@kernel.org>

If use_delay was non-zero when the latency target of a cgroup was set
to zero, it will stay stuck until io.latency is enabled on the cgroup
again.  This keeps readahead disabled for the cgroup impacting
performance negatively.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Josef Bacik <jbacik@fb.com>
Fixes: d70675121546 ("block: introduce blk-iolatency io controller")
Cc: stable@vger.kernel.org # v4.19+
---
 block/blk-iolatency.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index d22e61bced86..17896bb3aaf2 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -778,8 +778,10 @@ static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val)
 
 	if (!oldval && val)
 		return 1;
-	if (oldval && !val)
+	if (oldval && !val) {
+		blkcg_clear_delay(blkg);
 		return -1;
+	}
 	return 0;
 }
 
-- 
2.17.1

