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dkim=pass header.d=fb.com header.s=facebook header.b="Chx/TCyS"; dmarc=pass (policy=reject) header.from=fb.com; spf=pass (imf02.hostedemail.com: domain of "prvs=786498ca91=guro@fb.com" designates 67.231.153.30 as permitted sender) smtp.mailfrom="prvs=786498ca91=guro@fb.com" X-HE-Tag: 1629261891-293722 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 18, 2021 at 12:35:08PM +0800, Muchun Song wrote: > On Wed, Aug 18, 2021 at 10:16 AM Roman Gushchin wrote: > > > > On Tue, Aug 17, 2021 at 11:30:32AM +0800, 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 > > > --- > > > 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 54c4af35c628..1f951ac24a5e 100644 > > > --- a/include/linux/page-flags.h > > > +++ b/include/linux/page-flags.h > > > @@ -180,6 +180,8 @@ enum pageflags { > > > PG_reported = PG_uptodate, > > > }; > > > > > > +#define PAGEFLAGS_MASK (~((1UL << NR_PAGEFLAGS) - 1)) > > > > Hm, isn't it better to invert it? Like > > #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) > > > > It feels more usual and will simplify the rest of the patch. > > Actually, I learned from PAGE_MASK. So I thought the macro > like xxx_MASK should be the format of 0xff...ff00...00. I don't > know if it is an unwritten rule. I can invert PAGEFLAGS_MASK > if it's not a rule. There are many examples of both approached in the kernel tree, however I'd say the more common is without "~" (out of my head). It's definitely OK to define it like #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) Thanks!