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From: Muchun Song <songmuchun@bytedance.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Oscar Salvador <osalvador@suse.de>,
	Michal Hocko <mhocko@suse.com>,
	"Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
	David Hildenbrand <david@redhat.com>,
	Chen Huang <chenhuang5@huawei.com>,
	"Bodeddula, Balasubramaniam" <bodeddub@amazon.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Xiongchun duan <duanxiongchun@bytedance.com>,
	fam.zheng@bytedance.com, linux-doc@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Qi Zheng <zhengqi.arch@bytedance.com>
Subject: Re: [PATCH 1/5] mm: introduce PAGEFLAGS_MASK to replace ((1UL << NR_PAGEFLAGS) - 1)
Date: Tue, 27 Jul 2021 14:27:31 +0800	[thread overview]
Message-ID: <CAMZfGtUtk9uyO7v0v94YqLaHhrZ-CoFvVH60n54apib7PHPcKw@mail.gmail.com> (raw)
In-Reply-To: <cf279a44-2a1a-6385-8230-86e083e11ba0@oracle.com>

On Tue, Jul 27, 2021 at 5:04 AM Mike Kravetz <mike.kravetz@oracle.com> 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@bytedance.com>
> > ---
> >  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

  reply	other threads:[~2021-07-27  6:28 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14  9:17 [PATCH 0/5] Free the 2nd vmemmap page associated with each HugeTLB page Muchun Song
2021-07-14  9:17 ` [PATCH 1/5] mm: introduce PAGEFLAGS_MASK to replace ((1UL << NR_PAGEFLAGS) - 1) Muchun Song
2021-07-26 21:04   ` Mike Kravetz
2021-07-27  6:27     ` Muchun Song [this message]
2021-07-29  6:00       ` Muchun Song
2021-07-14  9:17 ` [PATCH 2/5] mm: introduce save_page_flags to cooperate with show_page_flags Muchun Song
2021-07-26 23:18   ` Mike Kravetz
2021-07-27  7:06     ` Muchun Song
2021-07-14  9:17 ` [PATCH 3/5] mm: hugetlb: free the 2nd vmemmap page associated with each HugeTLB page Muchun Song
2021-07-26 21:16   ` Matthew Wilcox
2021-07-26 23:56     ` Mike Kravetz
2021-07-27  7:15     ` Muchun Song
2021-07-14  9:17 ` [PATCH 4/5] mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key Muchun Song
2021-07-14  9:18 ` [PATCH 5/5] mm: sparsemem: use page table lock to protect kernel pmd operations Muchun Song

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