On Tue, Jul 27, 2021 at 2:27 PM Muchun Song [off-list ref] wrote:

On Tue, Jul 27, 2021 at 5:04 AM Mike Kravetz [off-list ref] wrote:

quoted

On 7/14/21 2:17 AM, Muchun Song wrote:

quoted

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 <redacted>
---
 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

                                           ^^^
Sorry. I mean 0xff...ff00...00 here.

know if this is an unwritten rule. Please correct me if I am
wrong.

Thanks.

quoted

--
Mike Kravetz