From: Ming Lei ming.lei@redhat.com
commit 245a489e81e13dd55ae46d27becf6d5901eb7828 upstream.
elevator_init_mq() is only called before adding disk, when there isn't any FS I/O, only passthrough requests can be queued, so freezing queue plus canceling dispatch work is enough to drain any dispatch activities, then we can avoid synchronize_srcu() in blk_mq_quiesce_queue().
Long boot latency issue can be fixed in case of lots of disks added during booting.
Fixes: 737eb78e82d5 ("block: Delay default elevator initialization") Reported-by: yangerkun yangerkun@huawei.com Cc: Damien Le Moal damien.lemoal@wdc.com Signed-off-by: Ming Lei ming.lei@redhat.com Link: https://lore.kernel.org/r/20211117115502.1600950-1-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/elevator.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/block/elevator.c +++ b/block/elevator.c @@ -694,12 +694,18 @@ void elevator_init_mq(struct request_que if (!e) return;
+ /* + * We are called before adding disk, when there isn't any FS I/O, + * so freezing queue plus canceling dispatch work is enough to + * drain any dispatch activities originated from passthrough + * requests, then no need to quiesce queue which may add long boot + * latency, especially when lots of disks are involved. + */ blk_mq_freeze_queue(q); - blk_mq_quiesce_queue(q); + blk_mq_cancel_work_sync(q);
err = blk_mq_init_sched(q, e);
- blk_mq_unquiesce_queue(q); blk_mq_unfreeze_queue(q);
if (err) {