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

Yu, Yu-cheng
2021-05-22T01:58:21Z

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@google.com>

Thanks!

Yu-cheng

>
> On Fri, May 21, 2021 at 3:13 PM Yu-cheng Yu <yu-cheng.yu@intel.com> 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@intel.com>
>> Cc: Axel Rasmussen <axelrasmussen@google.com>
>> Cc: Peter Xu <peterx@redhat.com>
>> Cc: Mike Kravetz <mike.kravetz@oracle.com>
>> ---
>> 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
>>