Re: [PATCH v4 0/7] mm/mprotect: Fix dax puds

Andrew Morton
2024-08-07T21:17:05Z

On Wed, 7 Aug 2024 15:48:04 -0400 Peter Xu <peterx@redhat.com> wrote:

>
> Dax supports pud pages for a while, but mprotect on puds was missing since
> the start. This series tries to fix that by providing pud handling in
> mprotect(). The goal is to add more types of pud mappings like hugetlb or
> pfnmaps. This series paves way for it by fixing known pud entries.
>
> Considering nobody reported this until when I looked at those other types
> of pud mappings, I am thinking maybe it doesn't need to be a fix for stable
> and this may not need to be backported. I would guess whoever cares about
> mprotect() won't care 1G dax puds yet, vice versa. I hope fixing that in
> new kernels would be fine, but I'm open to suggestions.

Yes, I'm not sure this is a "fix" at all. We're implementing something
which previously wasn't there. Perhaps the entire series should be
called "mm: implement mprotect() for DAX PUDs"?