A couple of places use f.flush(), os.fsync(f.fileno()) or os.fdatasync(f.fileno()) sync to flush file content to disk. However that is not enough. f.flush() only flushes file buffer to file descriptor. os.fsync(f.fileno()) needs to be accompanied by f.flush(). For new files, it does not sync the directory inode to disk.

PR 1257 introduces ipautil.flush_sync(f), which does all magic in correct order. All calls to flush and fsync should be replaced with the helper method.