> There is no performance or correctness upside to rename working the way you insist.
I'll just answer about correctness. If you take a broken application to a perfectly good system that doesn't order renames, because it doesn't have to, you will lose data. So, there is an upside to programming correctly and according to spec.
I think I answered the performance bit elsewhere, but you don't want to accept it. Which is fine by me.
> You don't want to admit that POSIX may allow something that is nevertheless nonsensical.
POSIX is not nonsensical, it is completely asynchronous and unordered, which is what you don't seem to like. Sure, we could have another mechanism for ordered renames - I don't deny that. It's just that current rename() isn't it, which you don't seem to be able to understand.