Wishful thinking

> First of all, you're most likely never going to see gigabytes of dirty blocks for a single file.

You are right. And nobody will ever need more than 640 kB of RAM ;-)

> They'll have been flushed well before your rename!

Not if someone calls fsync on that directory. Or kernel decides (for whatever reason) that this directory must go out to disk.

But look, you obviously don't want to accept that:

1. This happens.
2. POSIX says what it says.
3. Kernel is allowed to do what POSIX says.

That's OK. The documentation is crystal clear on this. It is all in the manual pages for close() and rename(). Unfortunately, people choose to ignore it.

Sure, it would be nice to have a call that guarantees all this, but thinking that rename() is that call is simply false.