Re: [RFC V2 02/14] mm: Add read-write accessors for vm_page_prot

[Mike Rapoport]

On Wed, May 13, 2026 at 10:15:35AM +0530, Anshuman Khandual wrote:
> Currently vma->vm_page_prot is safely read from and written to, without any
> locks with READ_ONCE() and WRITE_ONCE(). But with introduction of D128 page
> tables on arm64 platform, vm_page_prot grows to 128 bits which can't safely
> be handled with READ_ONCE() and WRITE_ONCE().
> 
> Add read and write accessors for vm_page_prot like pgprot_[read|write]()
> which any platform can override when required, although still defaulting as
> READ_ONCE() and WRITE_ONCE(), thus preserving the functionality for others.
> 
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> Cc: Mike Rapoport <rppt@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>

Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>

> ---
> Changes in RFC V2:
> 
> - Dropped _once from pgprot_[read|write]() callbacks per Mike
> 
>  include/linux/pgtable.h | 14 ++++++++++++++
>  mm/huge_memory.c        |  4 ++--
>  mm/memory.c             |  2 +-
>  mm/migrate.c            |  2 +-
>  mm/mmap.c               |  2 +-
>  5 files changed, 19 insertions(+), 5 deletions(-)

-- 
Sincerely yours,
Mike.