mm/slab: remove some unused functions

alternate_node_alloc and ____cache_alloc_node are always called when
CONFIG_NUMA. So we can remove the unused !CONFIG_NUMA variant. Also
forward declaration for alternate_node_alloc is unnecessary. Remove
it too.

[ vbabka@suse.cz: move ____cache_alloc_node() declaration closer to
  its callers ]

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20220322091421.25285-1-linmiaohe@huawei.com

Author: MiaoheLin

mm/slab.c

@@ -619,28 +619,13 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
 	return 0;
 }
 
-static inline void *alternate_node_alloc(struct kmem_cache *cachep,
-		gfp_t flags)
-{
-	return NULL;
-}
-
-static inline void *____cache_alloc_node(struct kmem_cache *cachep,
-		 gfp_t flags, int nodeid)
-{
-	return NULL;
-}
-
 static inline gfp_t gfp_exact_node(gfp_t flags)
 {
 	return flags & ~__GFP_NOFAIL;
 }
 
 #else	/* CONFIG_NUMA */
 
-static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
-static void *alternate_node_alloc(struct kmem_cache *, gfp_t);
-
 static struct alien_cache *__alloc_alien_cache(int node, int entries,
 						int batch, gfp_t gfp)
 {
@@ -3056,6 +3041,8 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 }
 
 #ifdef CONFIG_NUMA
+static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
+
 /*
  * Try allocating on another node if PFA_SPREAD_SLAB is a mempolicy is set.
  *