Ts'o: Delayed allocation and the zero-length file problem

Every rename() call does not need to preceded by fsync(). If the source file is known to be on disk already, there's no point in calling fsync(). This is code that knowingly creates a new file, does not call fsync() so that there is no reason whatsoever to assume that the data is on disk, and then calls rename() to replace an existing file. I do think that the behavior of persisting the update to the directory before saving the new file's data is bizarre and likely to cause problems, though. There may not be a required ordering for those operations, but having them reordered is clearly confusing.