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

[Andrew Morton]

On Wed,  7 Aug 2024 15:48:04 -0400 Peter Xu <peterx at 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"?