isofs: inode leak on mount failure

d_alloc_root() failure leaves root inode leaked...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/isofs/inode.c

@@ -948,8 +948,11 @@ static int isofs_fill_super(struct super_block *s, void *data, int silent)
 
 	/* get the root dentry */
 	s->s_root = d_alloc_root(inode);
-	if (!(s->s_root))
-		goto out_no_root;
+	if (!(s->s_root)) {
+		iput(inode);
+		error = -ENOMEM;
+		goto out_no_inode;
+	}
 
 	kfree(opt.iocharset);