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

Jason Gunthorpe
2020-11-09T20:19:53Z

On Mon, Nov 09, 2020 at 09:44:02AM +0100, Thomas Hellström wrote:
> static inline bool vma_is_special_huge(const struct vm_area_struct
> *vma)
> {
> return vma_is_dax(vma) || (vma->vm_file &&
> (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)));
> }

That is testing a VMA, not a PTE, which doesn't help protect
get_user_pages_fast.

Sounds like is has opened a big user crashy problem in DRM and the
huge page stuff needs to be revereted..

Dan?

Jason