Re: [PATCH v2 01/17] mm/gup: Fixup p*_access_permitted()

[Linus Torvalds]

On Fri, Dec 15, 2017 at 6:48 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> Treating protection key bits as "escalate to page fault and let that
> deal with the checks" should be fine

Well, it's *semantically* fine and I think it's the right model from
that standpoint.

However, since the main use case of protection keys is probably
databases (Dave?) and since those also might be performance-sensitive
about direct-IO doing page table lookups, it might not be great in
practice.

             Linus