On Tue, Jul 27, 2021 at 5:04 AM Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
>
> On 7/14/21 2:17 AM, Muchun Song wrote:
> > Instead of hard-coding ((1UL << NR_PAGEFLAGS) - 1) everywhere, introducing
> > PAGEFLAGS_MASK to make the code clear to get the page flags.
> >
> > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > ---
> > include/linux/page-flags.h | 4 +++-
> > include/trace/events/page_ref.h | 4 ++--
> > lib/test_printf.c | 2 +-
> > lib/vsprintf.c | 2 +-
> > 4 files changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> > index 5922031ffab6..358d3f6fa976 100644
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -178,6 +178,8 @@ enum pageflags {
> > PG_reported = PG_uptodate,
> > };
> >
> > +#define PAGEFLAGS_MASK (~((1UL << NR_PAGEFLAGS) - 1))
>
> Can you explain why you chose this definition instead of
>
> #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1)
>
> and mostly use ~PAGEFLAGS_MASK below?
Hi Mike,
Actually, I learned from PAGE_MASK. So I thought the macro
like xxx_MASK should be the format of 0x00...00ff...ff. I don't
know if this is an unwritten rule. Please correct me if I am
wrong.
Thanks.
> --
> Mike Kravetz
