[PATCH] dma-buf: Require VM_PFNMAP vma for mmap

[Jason Gunthorpe]

On Tue, Nov 22, 2022 at 08:29:05PM +0100, Daniel Vetter wrote:

> You nuke all the ptes. Drivers that move have slightly more than a
> bare struct file, they also have a struct address_space so that
> invalidate_mapping_range() works.

Okay, this is one of the ways that this can be made to work correctly,
as long as you never allow GUP/GUP_fast to succeed on the PTEs. (this
was the DAX mistake)

Jason