Most of times, flush plug should be the hottest I/O path,
so mark ctx as pending after all requests in the list are
inserted.
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NJens Axboe <axboe@fb.com>