From: Tejun Heo <tj@kernel.org>
Date: Thu, 13 Jun 2019 22:30:37 +0000 (-0700)
Subject: blk-iolatency: clear use_delay when io.latency is set to zero
X-Git-Tag: v5.1.20~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bea58a0e6844f244d8d1789f08dab3678483f24c;p=thirdparty%2Fkernel%2Fstable.git

blk-iolatency: clear use_delay when io.latency is set to zero

commit 5de0073fcd50cc1f150895a7bb04d3cf8067b1d7 upstream.

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+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 072e1edcf83d1..51070a730e3cd 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -758,8 +758,10 @@ 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;
 }