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Date:   Wed, 30 Mar 2022 19:57:59 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>,
        Muchun Song <smuchun@gmail.com>
Subject: Re: [PATCH v6 1/4] mm: hugetlb_vmemmap: introduce
 STRUCT_PAGE_SIZE_IS_POWER_OF_2
Message-Id: <20220330195759.6da783a678229008ac2a6851@linux-foundation.org>
In-Reply-To: <CAMZfGtXsMZ7ZwAzV5yZ39TB-=Q7Lw8oyjq2m65SXqHGwHQfj9w@mail.gmail.com>
References: <20220330153745.20465-1-songmuchun@bytedance.com>
        <20220330153745.20465-2-songmuchun@bytedance.com>
        <20220330192827.4b95e3d7fb149ef9cc687ccb@linux-foundation.org>
        <CAMZfGtXsMZ7ZwAzV5yZ39TB-=Q7Lw8oyjq2m65SXqHGwHQfj9w@mail.gmail.com>
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On Thu, 31 Mar 2022 10:52:58 +0800 Muchun Song <songmuchun@bytedance.com> wrote:

> > > +int main(void)
> > > +{
> > > +     if (is_power_of_2(sizeof(struct page)))
> > > +             DEFINE(STRUCT_PAGE_SIZE_IS_POWER_OF_2, is_power_of_2(sizeof(struct page)));
> >
> > Why not
> >
> >         DEFINE(STRUCT_PAGE_SIZE_IS_POWER_OF_2, 1);
> >
> 
> Yep, this is more simple.  But the 2nd parameter of DEFINE() will
> go into the comments.  I want to make it more clear when someone
> reads the code of this macro.  The two different sentences will
> generate the following two different comments.  Which one do
> you think is better?
> 
> #define STRUCT_PAGE_SIZE_IS_POWER_OF_2 1 /*
> is_power_of_2(sizeof(struct page)) */
> #define STRUCT_PAGE_SIZE_IS_POWER_OF_2 1 /* 1 */

The former ;)