> That's my whole point: sometimes you want atomicity without durability. rename without fsync is how you express that. Except on certain recent filesystems, it's always worked that way. ext4 not putting a write barrier before rename is a regression.
Just because something worked one way in one mode of one file system, doesn't mean it is the only way it can work, nor that applications should rely on it. If you want atomicity without durability, you get it on ext4, even without Ted's most recent patches (i.e. you get the empty file). If you want durability as well, you call fsync.
> And why, pray tell, is writing files to a filesystem a bad thing?
Writing out files that have _not_ changed is a bad thing. Or are you telling me that KDE changes all of its configuration files every few minutes?
BTW, the only reason fsync is slow on ext3, is because it does sync of all files. That's something that must be fixed, because it's nonsense.