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Date:   Sat, 6 Jul 2019 20:37:45 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
Cc:     Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>,
        linux-nilfs@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        Greg KH <gregkh@linuxfoundation.org>,
        Joe Perches <joe@perches.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] nilfs2: do not use unexported
 cpu_to_le32()/le32_to_cpu() in uapi header
Message-Id: <20190706203745.af0bf9bd5dd46e94fa5e1ff9@linux-foundation.org>
In-Reply-To: <20190605053006.14332-1-yamada.masahiro@socionext.com>
References: <20190605053006.14332-1-yamada.masahiro@socionext.com>
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On Wed,  5 Jun 2019 14:30:06 +0900 Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> cpu_to_le32/le32_to_cpu is defined in include/linux/byteorder/generic.h,
> which is not exported to user-space.
> 
> UAPI headers must use the ones prefixed with double-underscore.
> 
> Detected by compile-testing exported headers:
> 
> ./usr/include/linux/nilfs2_ondisk.h: In function ‘nilfs_checkpoint_set_snapshot’:
> ./usr/include/linux/nilfs2_ondisk.h:536:17: error: implicit declaration of function ‘cpu_to_le32’ [-Werror=implicit-function-declaration]
>   cp->cp_flags = cpu_to_le32(le32_to_cpu(cp->cp_flags) |  \
>                  ^
> ./usr/include/linux/nilfs2_ondisk.h:552:1: note: in expansion of macro ‘NILFS_CHECKPOINT_FNS’
>  NILFS_CHECKPOINT_FNS(SNAPSHOT, snapshot)
>  ^~~~~~~~~~~~~~~~~~~~
> ./usr/include/linux/nilfs2_ondisk.h:536:29: error: implicit declaration of function ‘le32_to_cpu’ [-Werror=implicit-function-declaration]
>   cp->cp_flags = cpu_to_le32(le32_to_cpu(cp->cp_flags) |  \
>                              ^
> ./usr/include/linux/nilfs2_ondisk.h:552:1: note: in expansion of macro ‘NILFS_CHECKPOINT_FNS’
>  NILFS_CHECKPOINT_FNS(SNAPSHOT, snapshot)
>  ^~~~~~~~~~~~~~~~~~~~
> ./usr/include/linux/nilfs2_ondisk.h: In function ‘nilfs_segment_usage_set_clean’:
> ./usr/include/linux/nilfs2_ondisk.h:622:19: error: implicit declaration of function ‘cpu_to_le64’ [-Werror=implicit-function-declaration]
>   su->su_lastmod = cpu_to_le64(0);
>                    ^~~~~~~~~~~

Seems fairly serious.  I'm thinking this needs a cc:stable?