code: public synchronized FileSystem getFs() throws IOException {
      if (this.fs == null) {
        Path sysDir = getSystemDir();
        this.fs = sysDir.getFileSystem(getConf());
      }
      return fs;
    }
docs: Get a filesystem handle.  We need this to prepare jobs
  for submission to the MapReduce system.
  
  @return the filesystem handle.