Re: [RFC 2/3] mm: export zap_page_range()

[Ming Lei <ming.lei@redhat.com>]

On Fri, Mar 18, 2022 at 05:55:30PM +0800, Xiaoguang Wang wrote:
> Module target_core_user will use it to implement zero copy feature.
> 
> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
> ---
>  mm/memory.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 1f745e4d11c2..9974d0406dad 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1664,6 +1664,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
>  	mmu_notifier_invalidate_range_end(&range);
>  	tlb_finish_mmu(&tlb);
>  }
> +EXPORT_SYMBOL_GPL(zap_page_range);

BTW, what is the counter part api of remap_pfn_range() for serving the
unmap? Or does it really need to unmap the vm space for this zero-copy
case?

If it isn't necessary to unmap, maybe remap_pfn_range() is faster than
vm_insert_page(s)_mkspecial + zap_page_range() since zap_page_range()
looks a bit heavy.


Thanks,
Ming