cgroup: we can use simple_lookup() now

Signed-off-by: Al Viro <[e-mail]>

kernel/cgroup.c

···
  */
 
 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
-static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
 static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
 			       unsigned long subsys_mask);
···
 };
 
 static const struct inode_operations cgroup_dir_inode_operations = {
-	.lookup = cgroup_lookup,
+	.lookup = simple_lookup,
 	.mkdir = cgroup_mkdir,
 	.rmdir = cgroup_rmdir,
 	.rename = cgroup_rename,
···
 	.listxattr = cgroup_listxattr,
 	.removexattr = cgroup_removexattr,
 };
-
-static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
-{
-	if (dentry->d_name.len > NAME_MAX)
-		return ERR_PTR(-ENAMETOOLONG);
-	d_add(dentry, NULL);
-	return NULL;
-}
 
 /*
  * Check if a file is a control file