kernfs: move the last knowledge of sysfs out from kernfs

There is still one residue of sysfs remaining: the sb_magic
SYSFS_MAGIC. However this should be kernfs user specific,
so this patch moves it out. Kerrnfs user should specify their
magic number while mouting.

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3f1ca93..ceee0c5 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -33,6 +33,7 @@
 #include <linux/init_task.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
+#include <linux/magic.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/mount.h>
@@ -1604,7 +1605,8 @@
 	if (ret)
 		return ERR_PTR(ret);
 
-	dentry = kernfs_mount(fs_type, flags, root->kf_root, &new_sb);
+	dentry = kernfs_mount(fs_type, flags, root->kf_root,
+				CGROUP_SUPER_MAGIC, &new_sb);
 	if (IS_ERR(dentry) || !new_sb)
 		cgroup_put(&root->cgrp);
 	return dentry;