fs/proc/task_nommu.c: change maps_open() to use __seq_open_private()

Cleanup and preparation. maps_open() can use __seq_open_private()
like proc_maps_open() does.

[akpm@linux-foundation.org: deuglify]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/task_nommu.c

@@ -269,20 +269,13 @@ static int maps_open(struct inode *inode, struct file *file,
 		     const struct seq_operations *ops)
 {
 	struct proc_maps_private *priv;
-	int ret = -ENOMEM;
-
-	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
-	if (priv) {
-		priv->pid = proc_pid(inode);
-		ret = seq_open(file, ops);
-		if (!ret) {
-			struct seq_file *m = file->private_data;
-			m->private = priv;
-		} else {
-			kfree(priv);
-		}
-	}
-	return ret;
+
+	priv = __seq_open_private(file, ops, sizeof(struct proc_maps_private));
+	if (!priv)
+		return -ENOMEM;
+
+	priv->pid = proc_pid(inode);
+	return 0;
 }
 
 static int pid_maps_open(struct inode *inode, struct file *file)