CGroup API files: use read_u64 in memory controller

Update the memory controller to use read_u64 for its limit/usage/failcnt
control files, calling the new res_counter_read_u64() function.
Signed-off-by: Paul Menage <menage@google.com>
Cc: "Li Zefan" <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "YAMAMOTO Takashi" <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -853,13 +853,10 @@ static int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
 	return 0;
 }
 
-static ssize_t mem_cgroup_read(struct cgroup *cont,
-			struct cftype *cft, struct file *file,
-			char __user *userbuf, size_t nbytes, loff_t *ppos)
+static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
 {
-	return res_counter_read(&mem_cgroup_from_cont(cont)->res,
-				cft->private, userbuf, nbytes, ppos,
-				NULL);
+	return res_counter_read_u64(&mem_cgroup_from_cont(cont)->res,
+				    cft->private);
 }
 
 static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
@@ -950,18 +947,18 @@ static struct cftype mem_cgroup_files[] = {
 	{
 		.name = "usage_in_bytes",
 		.private = RES_USAGE,
-		.read = mem_cgroup_read,
+		.read_u64 = mem_cgroup_read,
 	},
 	{
 		.name = "limit_in_bytes",
 		.private = RES_LIMIT,
 		.write = mem_cgroup_write,
-		.read = mem_cgroup_read,
+		.read_u64 = mem_cgroup_read,
 	},
 	{
 		.name = "failcnt",
 		.private = RES_FAILCNT,
-		.read = mem_cgroup_read,
+		.read_u64 = mem_cgroup_read,
 	},
 	{
 		.name = "force_empty",