On 7/10/24 11:40 PM, Suren Baghdasaryan wrote: > On Wed, Jul 10, 2024 at 8:02 AM Nathan Chancellor <nathan@xxxxxxxxxx> 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@xxxxxx wrote: >> > > From: Xiongwei Song <xiongwei.song@xxxxxxxxx> >> > > >> > > 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@xxxxxxxxxx/. > 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 <lkp@xxxxxxxxx> >> > > Closes: https://lore.kernel.org/oe-kbuild-all/202407050845.zNONqauD-lkp@xxxxxxxxx/ >> > > Signed-off-by: Xiongwei Song <xiongwei.song@xxxxxxxxx> >> > > --- >> > > 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 >> > > >> > >