Re: [PATCH v27 13/31] mm: Move VM_UFFD_MINOR_BIT from 37 to 38

[Axel Rasmussen]

This seems reasonable to me. The particular bit used isn't so
important from my perspective. I can't think of a way this would break
backward compatibility or such. So:

Reviewed-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>

On Fri, May 21, 2021 at 3:13 PM Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> wrote:
>
> To introduce VM_SHADOW_STACK as VM_HIGH_ARCH_BIT (37), and make all
> VM_HIGH_ARCH_BITs stay together, move VM_UFFD_MINOR_BIT from 37 to 38.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
> Cc: Peter Xu <peterx@xxxxxxxxxx>
> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
>  include/linux/mm.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index c274f75efcf9..923f89b9f1b5 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -373,7 +373,7 @@ extern unsigned int kobjsize(const void *objp);
>  #endif
>
>  #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
> -# define VM_UFFD_MINOR_BIT     37
> +# define VM_UFFD_MINOR_BIT     38
>  # define VM_UFFD_MINOR         BIT(VM_UFFD_MINOR_BIT)  /* UFFD minor faults */
>  #else /* !CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
>  # define VM_UFFD_MINOR         VM_NONE
> --
> 2.21.0
>