The most general thing -- involving the fewest new interfaces, even if the implementation is a big deal, would be an anonymous tmpfs. Where applications could

The most general thing -- involving the fewest new interfaces, even if the implementation is a big deal, would be an anonymous tmpfs. Where applications could stage a sort of poor-mans transaction. The hard bit is that for it to be useful, you would need atomic renames from the TMPFS to some other arbitrary filesystem. I guess abolishing the EXDEV error would be possible where the target filesystem has journaling, but it sounds like a big job to me.