Re: [PATCH v2 06/22] PCI/P2PDMA: Attempt to set map_type if it has not been set

On Thu, May 13, 2021 at 04:31:47PM -0600, Logan Gunthorpe wrote:

Attempt to find the mapping type for P2PDMA pages on the first
DMA map attempt if it has not been done ahead of time.

Previously, the mapping type was expected to be calculated ahead of
time, but if pages are to come from userspace then there's no
way to ensure the path was checked ahead of time.

With this change it's no longer invalid to call pci_p2pdma_map_sg()
before the mapping type is calculated so drop the WARN_ON when that
is the case.

Why?