code: func ValidatePersistentVolumeStatusUpdate(newPv, oldPv *api.PersistentVolume) field.ErrorList {
  	allErrs := ValidateObjectMetaUpdate(&newPv.ObjectMeta, &oldPv.ObjectMeta, field.NewPath("metadata"))
  	if len(newPv.ResourceVersion) == 0 {
  		allErrs = append(allErrs, field.Required(field.NewPath("resourceVersion"), ""))
  	}
  	newPv.Spec = oldPv.Spec
  	return allErrs
  }
docs: // ValidatePersistentVolumeStatusUpdate tests to see if the status update is legal for an end user to make.
  // newPv is updated with fields that cannot be changed.