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Thu, 11 Jul 2024 07:43:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PWwtKimNj2aXFQAAD6G6ig (envelope-from ); Thu, 11 Jul 2024 07:43:37 +0000 Message-ID: <4b533d6c-b2f3-49eb-a7fb-807af482def8@suse.cz> Date: Thu, 11 Jul 2024 09:43:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slub: quiet the clang warning with -Wunused-function enabled Content-Language: en-US To: Suren Baghdasaryan , Nathan Chancellor Cc: Matthew Wilcox , sxwjean@me.com, cl@linux.co, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, xiongwei.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel test robot , llvm@lists.linux.dev, Nick Desaulniers References: <20240710025418.394321-1-sxwjean@me.com> <20240710150154.GA1684801@thelio-3990X> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 15A37A0012 X-Stat-Signature: afeij3hbe91cd6tx45h81oxh4d3t9pnu X-HE-Tag: 1720683820-61014 X-HE-Meta: U2FsdGVkX1+9qqUx7FpVRV3Ip7ITpvZ9IeMqnxIb2E1I2ojivPlmrc3MnPxxI3k34SWMLeVrI26wMnJ+AREP8Ow2rMNeUVRCOWQuvskJGQDUUyEN7TTYllg7naPm/61UTC8OusCXUof/rOcBuNmF4XcDD+6vrjgwvadzxkVOJL1DMC+I/EDK2fwwTU2g/KQXn+HRNqRNKHXS2D9DHDsaNMkwGXzK8N5ixLj5t1EOeqDCrcMbbjfDtEdKegCim+6ojqlexPAKtsW+xbv8F6iyMxQFczez7+t4bO6qo24GZp7O+0k48p9pERnTe7VxsmsrtcmpXN7EjvAkpxbRSdHJDM68QpHLSjL/9B7L9AZ583Cofr6RCILTI75lrsXm85tp/crLf+M4LA7JhSRQklm/pLnnUkvD1JyxLPPbtFTocO5qAzKkMT9KBx5ZHQAD7kjIgADZ0wlwF5kumGCrJQ5ySP6PX60KJiFYB0FYW04RPoioxcl8Aw2IfveHdHmhbHPrp16n+6+LhSj+c490877Pv+UVxHtwBLNbPpBCZzDRhOQfEGRbqEvCP2a1Ocy9WX/o4cqNf5CUMqPMUc7KmPxIIPAxEbNySx/VlmlXCCYMx2awy7NYTsaHuke6pOjFRawnTq0BmzFJB1dyh6d3OdrtJ7yTLpzIBZoVJWkw4CvHmu6t5I2j1MNWWkoiNkQ6hcjcJU+lW0wZR3ZjiIHQoXCF8x0qqimn6H0HUh4/pZr18YaZYXLnBLWhnaC2+NySgT+vt9LnZ/W+1Yq/eU2EfyuX1CTzSXcWAGh+SMfY/1PNE5s458ibxmQUCHCVs0eYBK9kZTVAGkRS3RbkLTTg8Ah80xwCUsFJr38y4u13zBZ3X0FaJ9ze0AMza+0H01Sdez59XVYdvVOEOmaaN9eyWjiFTv3ktjshpNf6TL8g2HUUqDDHXcz+Sn8CAmJbgmxbzoFy3k44ltX7OMs5/yeKvqW pXc0zXJ7 ZkQxPR2I9NrAgquhVHdFU4Thg/1fJ0dFtZTCYXqEB3O9Darzyp9Xx77zjWWlLjTpOHLjZjKU1DyY1kAhFJAONKhHpls3Sba0jmVC4PJ86U5pZScE2DKz/Bhmv9pKsB07dPwHrIUrxe725Is6gnc82HpRFttJUBTdT1p15/tULt17DLPCk40M3Wcpk0jIiuUwImx/yxAREmJJ8Ndf742M+SE6+Pn+0+hJ+9bvEXKnAmjOi6s1+gtBkQLFlEsJmS8kHZnh+adCBkpR5IH41ZCRSPGCXkpqvlaHKY0UKS4zVc+OLGYzm1ILZljD1wHxOTzH3+yvBlLdUHJfHV6zhiUzURVF1TAL45F08bBMjcvYIazqA6eH+nALVkVV67RLBgECe0dBJWT3dZSVh134jDZvAiH1njyLIdyyKuUrE2mOv7fV/wiRTebFJO8nUudHmFiLGaym3VfetAbSPOI43IkZdx3QIR6nZ6OndLvSlKyVV3kgoWTk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/10/24 11:40 PM, Suren Baghdasaryan wrote: > On Wed, Jul 10, 2024 at 8:02 AM Nathan Chancellor wrote: >> >> On Wed, Jul 10, 2024 at 04:03:33AM +0100, Matthew Wilcox wrote: >> > On Wed, Jul 10, 2024 at 10:54:18AM +0800, sxwjean@me.com wrote: >> > > From: Xiongwei Song >> > > >> > > 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? >> >> Clang only differs from GCC on warning for unused static inline functions in .c >> files, not .h files. The kernel already handles this in >> include/linux/compiler_types.h but it disables this workaround for W=1 to catch >> unused functions like this as a result of commit 6863f5643dd7 ("kbuild: allow >> Clang to find unused static inline functions for W=1 build"): >> >> /* >> * GCC does not warn about unused static inline functions for -Wunused-function. >> * Suppress the warning in clang as well by using __maybe_unused, but enable it >> * for W=1 build. This will allow clang to find unused functions. Remove the >> * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings. >> */ >> #ifdef KBUILD_EXTRA_WARN1 >> #define __inline_maybe_unused >> #else >> #define __inline_maybe_unused __maybe_unused >> #endif >> >> So I don't really think there is much for clang to do here and I think having >> the ability to find unused static inline functions in .c files is useful (you >> might disagree, perhaps a revert could still be discussed). I guess >> IS_ENABLED() can't be used there, so it seems like either taking this patch, >> ignoring the warning, or refactoring the code in some other way are the only >> options I see. > > I think this is the consequence of the recent refactoring I've done in > https://lore.kernel.org/all/20240704135941.1145038-1-surenb@google.com/. > There should be a cleaner way to fix this. I'll post it later today or > tomorrow morning. Yeah looks like the non-empty prepare_slab_obj_exts_hook() could move to the #ifdef CONFIG_MEM_ALLOC_PROFILING section above alloc_tagging_slab_alloc_hook() and the empty one just removed. > Thanks, > Suren. > >> >> > > Reported-by: kernel test robot >> > > Closes: https://lore.kernel.org/oe-kbuild-all/202407050845.zNONqauD-lkp@intel.com/ >> > > Signed-off-by: Xiongwei Song >> > > --- >> > > 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 >> > > >> > >