How to set pages mapped to a vma to all zero

Hi, Suppose I have a vma belonging to a user process and in its address range a lot of pages are mapped. What should I do if I want to set the data of all the page frames to zero, without unmapping any of them or mapping any new pages? Can zap_page_range / zap_vma_ptes do that? It seems zap functions would unmap pages. Thanks, Cheng Quan