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Mon, 26 Jul 2021 23:28:08 -0700 (PDT) MIME-Version: 1.0 References: <20210714091800.42645-1-songmuchun@bytedance.com> <20210714091800.42645-2-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Tue, 27 Jul 2021 14:27:31 +0800 Message-ID: Subject: Re: [PATCH 1/5] mm: introduce PAGEFLAGS_MASK to replace ((1UL << NR_PAGEFLAGS) - 1) To: Mike Kravetz Cc: Andrew Morton , Oscar Salvador , Michal Hocko , "Song Bao Hua (Barry Song)" , David Hildenbrand , Chen Huang , "Bodeddula, Balasubramaniam" , Jonathan Corbet , Xiongchun duan , fam.zheng@bytedance.com, linux-doc@vger.kernel.org, LKML , Linux Memory Management List , Qi Zheng Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 124E2D0160B6 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=bytedance-com.20150623.gappssmtp.com header.s=20150623 header.b=FrPUfnll; spf=pass (imf21.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.180 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Stat-Signature: tha5ccjyrfgwy1kiz17ffj7mc793zonh X-HE-Tag: 1627367289-126753 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 Tue, Jul 27, 2021 at 5:04 AM Mike Kravetz 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 > > --- > > 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