linux-kernel - Re: [PATCH] lib/lz4: remove the exporting of LZ4HC

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Date:   Tue, 10 Sep 2019 15:13:16 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Sven Schmidt <4sschmid@...ormatik.uni-hamburg.de>,
        Arnd Bergmann <arnd@...db.de>,
        Bongkyu Kim <bongkyu.kim@....com>,
        Rui Salvaterra <rsalvaterra@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH] lib/lz4: remove the exporting of LZ4HC_setExternalDict

+Cc: Andrew Morton <akpm@...ux-foundation.org>,
     Masahiro Yamada <yamada.masahiro@...ionext.com>

Hi,

On 7/8/19 6:15 PM, Denis Efremov wrote:
> The function LZ4HC_setExternalDict is declared static and marked
> EXPORT_SYMBOL, which is at best an odd combination. Because the function
> is not used outside of the lib/lz4/lz4hc_compress.c file it is defined in,
> this commit removes the EXPORT_SYMBOL() marking.
> 
> Signed-off-by: Denis Efremov <efremov@...ux.com>
> ---
>  lib/lz4/lz4hc_compress.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/lib/lz4/lz4hc_compress.c b/lib/lz4/lz4hc_compress.c
> index 176f03b83e56..1b61d874e337 100644
> --- a/lib/lz4/lz4hc_compress.c
> +++ b/lib/lz4/lz4hc_compress.c
> @@ -663,7 +663,6 @@ static void LZ4HC_setExternalDict(
>  	/* match referencing will resume from there */
>  	ctxPtr->nextToUpdate = ctxPtr->dictLimit;
>  }
> -EXPORT_SYMBOL(LZ4HC_setExternalDict);
>  
>  static int LZ4_compressHC_continue_generic(
>  	LZ4_streamHC_t *LZ4_streamHCPtr,
> 

Andrew, could you please look at this patch and accept it if everybody agrees?
static LZ4HC_setExternalDict will trigger a warning after this check
will be in tree https://lkml.org/lkml/2019/7/14/118

There is also a different fix by Arnd Bergmann with making this function non-static:
https://lkml.org/lkml/2019/9/6/669

But since there is no uses of this EXPORT_SYMBOL in kernel and LZ4HC_setExternalDict
is indeed static in the original library https://github.com/lz4/lz4/blob/dev/lib/lz4hc.c#L1054
we came to the conclusion that it will be better to simply unexport the symbol.

Thanks,
Denis