def check_valid_device(self, path, run_as_root=True):
        """Verify an existing RBD handle is connected and valid."""
        if self.im_root:
            try:
                with open(path, 'r') as f:
                    f.read(4096)
            except Exception:
                return False
            return True

        try:
            self._execute('dd', 'if=' + path, 'of=/dev/null', 'bs=4096',
                          'count=1', root_helper=self._root_helper,
                          run_as_root=True)
        except putils.ProcessExecutionError:
            return False
        return True
Verify an existing RBD handle is connected and valid.