memcg: get rid of extern for functions in memcontrol.h

Most of the exported functions in this header are not marked extern so
change the rest to follow the same style.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -306,10 +306,10 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *, struct zone *);
 
 bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);
 
-extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
-extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
+struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
+struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
 
-extern struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
+struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
 static inline
 struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css){
 	return css ? container_of(css, struct mem_cgroup, css) : NULL;
@@ -344,7 +344,7 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
 	return match;
 }
 
-extern struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page);
+struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page);
 
 static inline bool mem_cgroup_disabled(void)
 {
@@ -403,7 +403,7 @@ static inline int mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec)
 	return inactive * inactive_ratio < active;
 }
 
-extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
+void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
 				struct task_struct *p);
 
 static inline void mem_cgroup_oom_enable(void)
@@ -719,8 +719,8 @@ static inline void sock_release_memcg(struct sock *sk)
 extern struct static_key memcg_kmem_enabled_key;
 
 extern int memcg_nr_cache_ids;
-extern void memcg_get_cache_ids(void);
-extern void memcg_put_cache_ids(void);
+void memcg_get_cache_ids(void);
+void memcg_put_cache_ids(void);
 
 /*
  * Helper macro to loop through all memcg-specific caches. Callers must still