CGroups _s64 files: use read_s64/write_s64 in CFS cgroup for rt_runtime file

This removes some filesystem boilerplate from the CFS cgroup subsystem.
Signed-off-by: Paul Menage <menage@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sched.c

@@ -9073,48 +9073,14 @@ static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft)
 
 #ifdef CONFIG_RT_GROUP_SCHED
 static ssize_t cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
-				struct file *file,
-				const char __user *userbuf,
-				size_t nbytes, loff_t *unused_ppos)
+				s64 val)
 {
-	char buffer[64];
-	int retval = 0;
-	s64 val;
-	char *end;
-
-	if (!nbytes)
-		return -EINVAL;
-	if (nbytes >= sizeof(buffer))
-		return -E2BIG;
-	if (copy_from_user(buffer, userbuf, nbytes))
-		return -EFAULT;
-
-	buffer[nbytes] = 0;     /* nul-terminate */
-
-	/* strip newline if necessary */
-	if (nbytes && (buffer[nbytes-1] == '\n'))
-		buffer[nbytes-1] = 0;
-	val = simple_strtoll(buffer, &end, 0);
-	if (*end)
-		return -EINVAL;
-
-	/* Pass to subsystem */
-	retval = sched_group_set_rt_runtime(cgroup_tg(cgrp), val);
-	if (!retval)
-		retval = nbytes;
-	return retval;
+	return sched_group_set_rt_runtime(cgroup_tg(cgrp), val);
 }
 
-static ssize_t cpu_rt_runtime_read(struct cgroup *cgrp, struct cftype *cft,
-				   struct file *file,
-				   char __user *buf, size_t nbytes,
-				   loff_t *ppos)
+static s64 cpu_rt_runtime_read(struct cgroup *cgrp, struct cftype *cft)
 {
-	char tmp[64];
-	long val = sched_group_rt_runtime(cgroup_tg(cgrp));
-	int len = sprintf(tmp, "%ld\n", val);
-
-	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
+	return sched_group_rt_runtime(cgroup_tg(cgrp));
 }
 
 static int cpu_rt_period_write_uint(struct cgroup *cgrp, struct cftype *cftype,
@@ -9140,8 +9106,8 @@ static struct cftype cpu_files[] = {
 #ifdef CONFIG_RT_GROUP_SCHED
 	{
 		.name = "rt_runtime_us",
-		.read = cpu_rt_runtime_read,
-		.write = cpu_rt_runtime_write,
+		.read_s64 = cpu_rt_runtime_read,
+		.write_s64 = cpu_rt_runtime_write,
 	},
 	{
 		.name = "rt_period_us",