synchronized final void flushFailed(SegmentInfo info) throws IOException {
    // TODO: this really should be a tragic
    Collection<String> files;
    try {
      files = info.files();
    } catch (IllegalStateException ise) {
      // OK
      files = null;
    }
    if (files != null) {
      deleter.deleteNewFiles(files);
    }
  }