no_sched=[0/1]: Default: 0
0: nullb* use default blk-mq io scheduler.
1: nullb* doesn't use io scheduler.
+
+shared_tags=[0/1]: Default: 0
+ 0: Tag set is not shared.
+ 1: Tag set shared between devices for blk-mq. Only makes sense with
+ nr_devices > 1, otherwise there's no tag set to share.