memcg: extract mem_group_usage() from mem_cgroup_read()

Helper to get memory or mem+swap usage of the cgroup.
Signed-off-by: NKirill A. Shutemov <kirill@shutemov.name>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Dan Malek <dan@embeddedalley.com>
Cc: Vladislav Buzov <vbuzov@embeddedalley.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Alexander Shishkin <virtuoso@slind.org>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2857,40 +2857,50 @@ mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
 	*val = d.val;
 }
 
+static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
+{
+	u64 idx_val, val;
+
+	if (!mem_cgroup_is_root(mem)) {
+		if (!swap)
+			return res_counter_read_u64(&mem->res, RES_USAGE);
+		else
+			return res_counter_read_u64(&mem->memsw, RES_USAGE);
+	}
+
+	mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE, &idx_val);
+	val = idx_val;
+	mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS, &idx_val);
+	val += idx_val;
+
+	if (swap) {
+		mem_cgroup_get_recursive_idx_stat(mem,
+				MEM_CGROUP_STAT_SWAPOUT, &idx_val);
+		val += idx_val;
+	}
+
+	return val << PAGE_SHIFT;
+}
+
 static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
 {
 	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
-	u64 idx_val, val;
+	u64 val;
 	int type, name;
 
 	type = MEMFILE_TYPE(cft->private);
 	name = MEMFILE_ATTR(cft->private);
 	switch (type) {
 	case _MEM:
-		if (name == RES_USAGE && mem_cgroup_is_root(mem)) {
-			mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_CACHE, &idx_val);
-			val = idx_val;
-			mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_RSS, &idx_val);
-			val += idx_val;
-			val <<= PAGE_SHIFT;
-		} else
+		if (name == RES_USAGE)
+			val = mem_cgroup_usage(mem, false);
+		else
 			val = res_counter_read_u64(&mem->res, name);
 		break;
 	case _MEMSWAP:
-		if (name == RES_USAGE && mem_cgroup_is_root(mem)) {
-			mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_CACHE, &idx_val);
-			val = idx_val;
-			mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_RSS, &idx_val);
-			val += idx_val;
-			mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_SWAPOUT, &idx_val);
-			val += idx_val;
-			val <<= PAGE_SHIFT;
-		} else
+		if (name == RES_USAGE)
+			val = mem_cgroup_usage(mem, true);
+		else
 			val = res_counter_read_u64(&mem->memsw, name);
 		break;
 	default: