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

[Yu, Yu-cheng]

On 5/21/2021 3:25 PM, Axel Rasmussen wrote:
> 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>

Thanks!

Yu-cheng

> 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