[dm-devel] [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq

[Jeff Moyer]

Christoph Hellwig <hch at infradead.org> writes:

> 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.

Maybe I have bad taste, but the patches didn't look like cruft to me.
:)

I'm not sure why we'd prevent users from using dm-mpath on nvmeof.  I
think there's agreement that the nvme native multipath implementation is
the preferred way (that's the default in rhel9, even), but I don't think
that's a reason to nack this patch set.

Or have I missed your point entirely?

Thanks!
Jeff