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

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>

1 files changed, 3 insertions, 1 deletions

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;
 }