The fundamental problem is that fsync is too powerful. Most of the time, what you really want is a write barrier --- you don't care about when writes happen, but you do care about their order. fsync is a write barrier, but it's also a synchronous flush.

But don't listen to me. I like TxF too.

Or in short, calling fsync() twice is a tweak under-known: the file itself needs to be flushed, as well as its parent directory.