On Tue, Dec 28, 2021 at 04:30:08PM -0500, Mike Snitzer wrote: > Yeah, people use request-based for IO scheduling and more capable path > selectors. Imposing bio-based would be a pretty jarring workaround for > BLK_MQ_F_BLOCKING. request-based DM should properly support it. Given that nvme-tcp is the only blocking driver that has multipath driver that driver explicitly does not intend to support dm-multipath I'm absolutely against adding block layer cruft for this particular use case. SCSI even has this: /* * SCSI never enables blk-mq's BLK_MQ_F_BLOCKING flag so * calling synchronize_rcu() once is enough. */ WARN_ON_ONCE(shost->tag_set.flags & BLK_MQ_F_BLOCKING);
