[PATCH 4.19 267/271] blk-iolatency: clear use_delay when io.latency is set to zero

[Greg Kroah-Hartman]

From: Tejun Heo <t...@kernel.org>

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 <t...@kernel.org>
Cc: Josef Bacik <jba...@fb.com>
Fixes: d70675121546 ("block: introduce blk-iolatency io controller")
Cc: sta...@vger.kernel.org # v4.19+
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 block/blk-iolatency.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -746,8 +746,10 @@ static int iolatency_set_min_lat_nsec(st
 
        if (!oldval && val)
                return 1;
-       if (oldval && !val)
+       if (oldval && !val) {
+               blkcg_clear_delay(blkg);
                return -1;
+       }
        return 0;
 }