mm, slab: move prepare_slab_obj_exts_hook under CONFIG_MEM_ALLOC_PROFILING

The only place prepare_slab_obj_exts_hook() is currently being used is
from alloc_tagging_slab_alloc_hook() when CONFIG_MEM_ALLOC_PROFILING=y.
Move its definition under CONFIG_MEM_ALLOC_PROFILING to prevent unused
function warning for CONFIG_SLAB_OBJ_EXT=n case.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407050845.zNONqauD-lkp@intel.com/Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Xiongwei Song <xiongwei.song@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slub.c

@@ -2009,30 +2009,6 @@ static inline bool need_slab_obj_ext(void)
 	return false;
 }
 
-static inline struct slabobj_ext *
-prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
-{
-	struct slab *slab;
-
-	if (!p)
-		return NULL;
-
-	if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE))
-		return NULL;
-
-	if (flags & __GFP_NO_OBJ_EXT)
-		return NULL;
-
-	slab = virt_to_slab(p);
-	if (!slab_obj_exts(slab) &&
-	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
-		 "%s, %s: Failed to create slab extension vector!\n",
-		 __func__, s->name))
-		return NULL;
-
-	return slab_obj_exts(slab) + obj_to_index(s, slab, p);
-}
-
 #else /* CONFIG_SLAB_OBJ_EXT */
 
 static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
@@ -2050,15 +2026,33 @@ static inline bool need_slab_obj_ext(void)
 	return false;
 }
 
+#endif /* CONFIG_SLAB_OBJ_EXT */
+
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+
 static inline struct slabobj_ext *
 prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
 {
+	struct slab *slab;
+
+	if (!p)
 		return NULL;
-}
 
-#endif /* CONFIG_SLAB_OBJ_EXT */
+	if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE))
+		return NULL;
 
-#ifdef CONFIG_MEM_ALLOC_PROFILING
+	if (flags & __GFP_NO_OBJ_EXT)
+		return NULL;
+
+	slab = virt_to_slab(p);
+	if (!slab_obj_exts(slab) &&
+	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
+		 "%s, %s: Failed to create slab extension vector!\n",
+		 __func__, s->name))
+		return NULL;
+
+	return slab_obj_exts(slab) + obj_to_index(s, slab, p);
+}
 
 static inline void
 alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)