linux-kernel - Re: [PATCH] fs/exofs: Remove ignored _

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Message-ID: <20181025211925.GA24709@flashbox>
Date:   Thu, 25 Oct 2018 14:19:25 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Boaz Harrosh <ooo@...ctrozaur.com>
Subject: Re: [PATCH] fs/exofs: Remove ignored __weak attribute

On Sun, Sep 30, 2018 at 01:51:26PM -0700, Nathan Chancellor wrote:
> Clang warns that the __weak attribute is going to be ignored on
> g_attr_inode_data because it's not in the correct location (needs to be
> after the type).
> 
> In file included from fs/exofs/dir.c:35:
> In file included from fs/exofs/exofs.h:41:
> fs/exofs/common.h:186:21: warning: 'weak' attribute only applies to
> variables, functions, and classes [-Wignored-attributes]
> static const struct __weak osd_attr g_attr_inode_data = ATTR_DEF(
>                     ^
> 
> Turns out that GCC ignores the attribute too albeit silently because
> moving the attribute after either osd_attr or g_attr_inode_data like
> all other uses of __weak on variables in the kernel causes a build
> error on both GCC and Clang because static variables cannot be weak
> since weak definitions rely on not having internal linkage:
> 
> In file included from fs/exofs/namei.c:34:
> In file included from fs/exofs/exofs.h:41:
> fs/exofs/common.h:186:30: error: weak declaration cannot have internal
> linkage
> static const struct osd_attr __weak g_attr_inode_data = ATTR_DEF(
>                              ^
> 
> Just remove the attribute because it hasn't been correct since the
> initial addition of this file in commit b14f8ab28449 ("exofs: Kbuild,
> Headers and osd utils").
> 
> Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  fs/exofs/common.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/exofs/common.h b/fs/exofs/common.h
> index 7d88ef566213..45da96a1528d 100644
> --- a/fs/exofs/common.h
> +++ b/fs/exofs/common.h
> @@ -183,7 +183,7 @@ struct exofs_fcb {
>  #define EXOFS_INO_ATTR_SIZE	sizeof(struct exofs_fcb)
>  
>  /* This is the Attribute the fcb is stored in */
> -static const struct __weak osd_attr g_attr_inode_data = ATTR_DEF(
> +static const struct osd_attr g_attr_inode_data = ATTR_DEF(
>  	EXOFS_APAGE_FS_DATA,
>  	EXOFS_ATTR_INODE_DATA,
>  	EXOFS_INO_ATTR_SIZE);
> -- 
> 2.19.0
> 

Hi Andrew,

Can you take this with Boaz's ack?

Thanks,
Nathan