// Do a crazy dance with lots of fsync()s to be overly cautious here...
// We never want to end up in a state where we've lost the old data, or end up using the
// old data on power loss after we've returned.
// The way to atomically write a file on Unix platforms is:
// open(tmpname), write(tmpfile), fsync(tmpfile), close(tmpfile), rename(), fsync(dir)
// Do a crazy dance with lots of fsync()s to be overly cautious here...
// We never want to end up in a state where we've lost the old data, or end up using the
// old data on power loss after we've returned.
// The way to atomically write a file on Unix platforms is:
// open(tmpname), write(tmpfile), fsync(tmpfile), close(tmpfile), rename(), fsync(dir)