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; }