kernfs: make kernfs_get_inode() public

Move kernfs_get_inode() prototype from fs/kernfs/kernfs-internal.h to
include/linux/kernfs.h.  It obtains the matching inode for a
kernfs_node.

It will be used by cgroup for inode based permission checks for now
but is generally useful.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 71ecdab..e6b2f7d 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -277,6 +277,7 @@
 
 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
+struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
 
 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
 				       unsigned int flags, void *priv);
@@ -352,6 +353,10 @@
 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
 { return NULL; }
 
+static inline struct inode *
+kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
+{ return NULL; }
+
 static inline struct kernfs_root *
 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
 		   void *priv)