Re: [PATCH v2 2/8] mm/hugetlb: Prepare hugetlb_follow_page_mask() for FOLL_PIN

[David Hildenbrand]

On 20.06.23 01:10, Peter Xu wrote:
> follow_page() doesn't use FOLL_PIN, meanwhile hugetlb seems to not be the
> target of FOLL_WRITE either.  However add the checks.
>
> Namely, either the need to CoW due to missing write bit, or proper CoR on
> !AnonExclusive pages over R/O pins to reject the follow page.  That brings
> this function closer to follow_hugetlb_page().
>
> So we don't care before, and also for now.  But we'll care if we switch
> over slow-gup to use hugetlb_follow_page_mask().  We'll also care when to
> return -EMLINK properly, as that's the gup internal api to mean "we should
> do CoR".  Not really needed for follow page path, though.
>
> When at it, switching the try_grab_page() to use WARN_ON_ONCE(), to be
> clear that it just should never fail.

Oh, and does this comment really belong into this patch or am I confused?

--
Cheers,

David / dhildenb