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

[sxwjean]

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().

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