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
