code: func (persistentvolumeStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) {
  	newPv := obj.(*api.PersistentVolume)
  	oldPv := old.(*api.PersistentVolume)
  	newPv.Status = oldPv.Status
  
  	pvutil.DropDisabledFields(&newPv.Spec, &oldPv.Spec)
  }
docs: // PrepareForUpdate sets the Status fields which is not allowed to be set by an end user updating a PV