memcontrol: move mm_cgroup to header file

Inline functions must preceed their use, so mm_cgroup() should be defined
in linux/memcontrol.h.

include/linux/memcontrol.h:48: warning: 'mm_cgroup' declared inline after
	being called
include/linux/memcontrol.h:48: warning: previous declaration of
	'mm_cgroup' was here

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: nuther build fix]
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -20,6 +20,9 @@
 #ifndef _LINUX_MEMCONTROL_H
 #define _LINUX_MEMCONTROL_H
 
+#include <linux/rcupdate.h>
+#include <linux/mm.h>
+
 struct mem_cgroup;
 struct page_cgroup;
 struct page;
@@ -45,7 +48,11 @@ extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 extern void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask);
 extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 					gfp_t gfp_mask);
-extern struct mem_cgroup *mm_cgroup(struct mm_struct *mm);
+
+static inline struct mem_cgroup *mm_cgroup(const struct mm_struct *mm)
+{
+	return rcu_dereference(mm->mem_cgroup);
+}
 
 static inline void mem_cgroup_uncharge_page(struct page *page)
 {
@@ -98,7 +105,7 @@ static inline int mem_cgroup_cache_charge(struct page *page,
 	return 0;
 }
 
-static inline struct mem_cgroup *mm_cgroup(struct mm_struct *mm)
+static inline struct mem_cgroup *mm_cgroup(const struct mm_struct *mm)
 {
 	return NULL;
 }

mm/memcontrol.c

@@ -110,11 +110,6 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
 				struct mem_cgroup, css);
 }
 
-inline struct mem_cgroup *mm_cgroup(struct mm_struct *mm)
-{
-	return rcu_dereference(mm->mem_cgroup);
-}
-
 void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p)
 {
 	struct mem_cgroup *mem;