WTF is d_add_ci() doing with negative dentries?

[Al Viro <viro@ZenIV.linux.org.uk>]

	AFAICS, if d_add_ci() ever finds a negative hashed dentry for
exact name, it's already buggered.  Because right *before* that
d_add_ci() lookup for exact name would've turned valid negative.
IOW, the whole thing ought to be
        found = d_hash_and_lookup(dentry->d_parent, name);
	if (found) {
		iput(inode);
		return found;
	}
	new = d_alloc(dentry->d_parent, name);
	if (!new) {
		iput(inode);
		return ERR_PTR(-ENOMEM);
	}
	found = d_splice_alias(inode, new);
	if (found) {
		dput(new);
		return found;
	}
	return new;
Moreover, it might very well be better to pass dentry->d_parent instead
of dentry...  Objections?