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/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8794423..8a49486 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -13,6 +13,7 @@
 #define DEBUG
 
 #include <linux/fs.h>
+#include <linux/magic.h>
 #include <linux/mount.h>
 #include <linux/init.h>
 #include <linux/user_namespace.h>
@@ -38,7 +39,8 @@
 	}
 
 	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
-	root = kernfs_mount_ns(fs_type, flags, sysfs_root, &new_sb, ns);
+	root = kernfs_mount_ns(fs_type, flags, sysfs_root,
+				SYSFS_MAGIC, &new_sb, ns);
 	if (IS_ERR(root) || !new_sb)
 		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
 	return root;