Re: [PATCH v5 05/15] mm/frame-vector: Use FOLL_LONGTERM

[Jason Gunthorpe]

On Sun, Nov 01, 2020 at 11:50:39PM +0100, Daniel Vetter wrote:

> It's not device drivers, but everyone else. At least my understanding
> is that VM_IO | VM_PFNMAP means "even if it happens to be backed by a
> struct page, do not treat it like normal memory". And gup/pup_fast
> happily break that. I tried to chase the history of that test, didn't
> turn up anything I understood much:

VM_IO isn't suppose do thave struct pages, so how can gup_fast return
them?

I thought some magic in the PTE flags excluded this?

Jason