[RFC PATCH v1 00/18] Provide a new two step DMA API mapping API

[Christoph Hellwig]

On Thu, Jul 11, 2024 at 08:29:17PM -0300, Jason Gunthorpe wrote:
> So this little detail needs to be taken care of somehow as well, and I
> didn't see it in this RFC.

Yes.  Same about generally not mixing P2P and non-P2P.

> 
> > For the block layer just having one kind per BIO is fine right now,
> > although I could see use cases where people would want to combine
> > them.  We can probably defer that until it is needed, though.
> 
> Do you have an application in mind that would want multi-kind per BIO?

If you are doing say garbage collection in a file system, and do write
that sources data from multiple devices, where some sit directly on the
root port and others behind a switch.

This is all purely hypothetical, and I'm happy to just check for it
and reject it for it now.