to #29361128

commit d7bd15a138aef3be227818aad9c501e43c89c8c5 upstream.

When over-budget IOs are force-issued through root cgroup,
iocg_kick_delay() adjusts the async delay accordingly but doesn't
actually schedule async throttle for the issuing task.  This bug is
pretty well masked because sooner or later the offending threads are
gonna get directly throttled on regular IOs or have async delay
scheduled by mem_cgroup_throttle_swaprate().

However, it can affect control quality on filesystem metadata heavy
operations.  Let's fix it by invoking blkcg_schedule_throttle() when
iocg_kick_delay() says async delay is needed.
Signed-off-by: NTejun Heo <tj@kernel.org>
Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
Cc: stable@vger.kernel.org
Reported-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NJiufei Xue <jiufei.xue@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>