hppfs_lookup(): don't open-code lookup_one_len()

... and it's getting it wrong, too - missing ->d_revalidate() calls when
it's dealing with filesystem (procfs) that has non-trivial ->d_revalidate()...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/hppfs/hppfs.c

@@ -139,7 +139,8 @@ static int file_removed(struct dentry *dentry, const char *file)
 static struct dentry *hppfs_lookup(struct inode *ino, struct dentry *dentry,
 				   struct nameidata *nd)
 {
-	struct dentry *proc_dentry, *new, *parent;
+	struct dentry *proc_dentry, *parent;
+	struct qstr *name = &dentry->d_name;
 	struct inode *inode;
 	int err, deleted;
 
@@ -149,23 +150,9 @@ static struct dentry *hppfs_lookup(struct inode *ino, struct dentry *dentry,
 	else if (deleted)
 		return ERR_PTR(-ENOENT);
 
-	err = -ENOMEM;
 	parent = HPPFS_I(ino)->proc_dentry;
 	mutex_lock(&parent->d_inode->i_mutex);
-	proc_dentry = d_lookup(parent, &dentry->d_name);
-	if (proc_dentry == NULL) {
-		proc_dentry = d_alloc(parent, &dentry->d_name);
-		if (proc_dentry == NULL) {
-			mutex_unlock(&parent->d_inode->i_mutex);
-			goto out;
-		}
-		new = (*parent->d_inode->i_op->lookup)(parent->d_inode,
-						       proc_dentry, NULL);
-		if (new) {
-			dput(proc_dentry);
-			proc_dentry = new;
-		}
-	}
+	proc_dentry = lookup_one_len(name->name, parent, name->len);
 	mutex_unlock(&parent->d_inode->i_mutex);
 
 	if (IS_ERR(proc_dentry))