mm: kmem: make __memcg_kmem_(un)charge static

I've noticed that __memcg_kmem_charge() and __memcg_kmem_uncharge() are
not used anywhere except memcontrol.c.  Yet they are not declared as
non-static and are declared in memcontrol.h.

This patch makes them static.

Link: https://lkml.kernel.org/r/20210108020332.4096911-1-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -1592,9 +1592,6 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
 #endif
 
 #ifdef CONFIG_MEMCG_KMEM
-int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
-			unsigned int nr_pages);
-void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages);
 int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order);
 void __memcg_kmem_uncharge_page(struct page *page, int order);
 

mm/memcontrol.c

@@ -255,6 +255,11 @@ struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr)
 #ifdef CONFIG_MEMCG_KMEM
 extern spinlock_t css_set_lock;
 
+static int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
+			       unsigned int nr_pages);
+static void __memcg_kmem_uncharge(struct mem_cgroup *memcg,
+				  unsigned int nr_pages);
+
 static void obj_cgroup_release(struct percpu_ref *ref)
 {
 	struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt);
@@ -3087,7 +3092,7 @@ static void memcg_free_cache_id(int id)
  *
  * Returns 0 on success, an error code on failure.
  */
-int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
+static int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
 			       unsigned int nr_pages)
 {
 	struct page_counter *counter;
@@ -3120,7 +3125,7 @@ int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
  * @memcg: memcg to uncharge
  * @nr_pages: number of pages to uncharge
  */
-void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages)
+static void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		page_counter_uncharge(&memcg->kmem, nr_pages);