linux-kernel - Re: [PATCH] mm/slub: quiet the clang warning with -Wunused-function enabled

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Message-ID: <Zo36BTqhzGkukyT_@casper.infradead.org>
Date: Wed, 10 Jul 2024 04:03:33 +0100
From: Matthew Wilcox <willy@...radead.org>
To: sxwjean@...com
Cc: vbabka@...e.cz, surenb@...gle.com, cl@...ux.co, penberg@...nel.org,
	rientjes@...gle.com, iamjoonsoo.kim@....com,
	akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
	42.hyeyoo@...il.com, xiongwei.song@...ux.dev, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
	Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev,
	Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] mm/slub: quiet the clang warning with -Wunused-function
 enabled

On Wed, Jul 10, 2024 at 10:54:18AM +0800, sxwjean@...com wrote:
> From: Xiongwei Song <xiongwei.song@...ux.dev>
> 
> The only user of prepare_slab_obj_exts_hook() is
> alloc_tagging_slab_alloc_hook(), which can build with
> CONFIG_MEM_ALLOC_PROFILING enabled. So, the warning was triggerred
> when disabling CONFIG_MEM_ALLOC_PROFILING. Let's add "__maybe_unused"
> for prepare_slab_obj_exts_hook().

Perhaps instead clang can be fixed to match gcc's behaviour?

> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202407050845.zNONqauD-lkp@intel.com/
> Signed-off-by: Xiongwei Song <xiongwei.song@...ux.dev>
> ---
>  mm/slub.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index ce39544acf7c..2e26f20759c0 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2027,7 +2027,7 @@ static inline bool need_slab_obj_ext(void)
>  	return false;
>  }
>  
> -static inline struct slabobj_ext *
> +static inline struct slabobj_ext * __maybe_unused
>  prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
>  {
>  	struct slab *slab;
> @@ -2068,7 +2068,7 @@ static inline bool need_slab_obj_ext(void)
>  	return false;
>  }
>  
> -static inline struct slabobj_ext *
> +static inline struct slabobj_ext * __maybe_unused
>  prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
>  {
>  	return NULL;
> -- 
> 2.34.1
> 
>