code: func (a *attacherDefaults) MountDevice(spec *volume.Spec, devicePath string, deviceMountPath string, mounter mount.Interface) error {
  	klog.Warning(logPrefix(a.plugin.flexVolumePlugin), "using default MountDevice for volume ", spec.Name(), ", device ", devicePath, ", deviceMountPath ", deviceMountPath)
  
  	volSourceFSType, err := getFSType(spec)
  	if err != nil {
  		return err
  	}
  
  	readOnly, err := getReadOnly(spec)
  	if err != nil {
  		return err
  	}
  
  	options := make([]string, 0)
  
  	if readOnly {
  		options = append(options, "ro")
  	} else {
  		options = append(options, "rw")
  	}
  
  	diskMounter := &mount.SafeFormatAndMount{Interface: mounter, Exec: a.plugin.host.GetExec(a.plugin.GetPluginName())}
  
  	return diskMounter.FormatAndMount(devicePath, deviceMountPath, volSourceFSType, options)
  }
docs: // MountDevice is part of the volume.Attacher interface