mm: memcg: move swapin charge functions above callsites

Charging cache pages may require swapin in the shmem case.  Save the
forward declaration and just move the swapin functions above the cache
charging functions.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Wanpeng Li <liwp.linux@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2796,37 +2796,6 @@ int mem_cgroup_newpage_charge(struct page *page,
 					MEM_CGROUP_CHARGE_TYPE_ANON);
 }
 
-static void
-__mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
-					enum charge_type ctype);
-
-int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
-				gfp_t gfp_mask)
-{
-	struct mem_cgroup *memcg = NULL;
-	enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
-	int ret;
-
-	if (mem_cgroup_disabled())
-		return 0;
-	if (PageCompound(page))
-		return 0;
-
-	if (unlikely(!mm))
-		mm = &init_mm;
-	if (!page_is_file_cache(page))
-		type = MEM_CGROUP_CHARGE_TYPE_SHMEM;
-
-	if (!PageSwapCache(page))
-		ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
-	else { /* page is swapcache/shmem */
-		ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &memcg);
-		if (!ret)
-			__mem_cgroup_commit_charge_swapin(page, memcg, type);
-	}
-	return ret;
-}
-
 /*
  * While swap-in, try_charge -> commit or cancel, the page is locked.
  * And when try_charge() successfully returns, one refcnt to memcg without
@@ -2873,6 +2842,15 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
 	return ret;
 }
 
+void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *memcg)
+{
+	if (mem_cgroup_disabled())
+		return;
+	if (!memcg)
+		return;
+	__mem_cgroup_cancel_charge(memcg, 1);
+}
+
 static void
 __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
 					enum charge_type ctype)
@@ -2910,13 +2888,31 @@ void mem_cgroup_commit_charge_swapin(struct page *page,
 					  MEM_CGROUP_CHARGE_TYPE_ANON);
 }
 
-void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *memcg)
+int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
+				gfp_t gfp_mask)
 {
+	struct mem_cgroup *memcg = NULL;
+	enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
+	int ret;
+
 	if (mem_cgroup_disabled())
-		return;
-	if (!memcg)
-		return;
-	__mem_cgroup_cancel_charge(memcg, 1);
+		return 0;
+	if (PageCompound(page))
+		return 0;
+
+	if (unlikely(!mm))
+		mm = &init_mm;
+	if (!page_is_file_cache(page))
+		type = MEM_CGROUP_CHARGE_TYPE_SHMEM;
+
+	if (!PageSwapCache(page))
+		ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
+	else { /* page is swapcache/shmem */
+		ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &memcg);
+		if (!ret)
+			__mem_cgroup_commit_charge_swapin(page, memcg, type);
+	}
+	return ret;
 }
 
 static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg,