Re: [PATCH v8 2/2] mm: remove zap_page_range and change callers to use zap_vma_range

Nadav Amit
2022-11-10T21:09:48Z

On Nov 7, 2022, at 5:19 PM, Mike Kravetz <mike.kravetz@oracle.com> wrote:

> zap_page_range was originally designed to unmap pages within an address
> range that could span multiple vmas. However, today all callers of
> zap_page_range pass a range entirely within a single vma. In addition,
> the mmu notification call within zap_page range is not correct as it
> should be vma specific.
>
> Instead of fixing zap_page_range, change all callers to use zap_vma_range
> as it is designed for ranges within a single vma.

I understand the argument about mmu notifiers being broken (which is of
course fixable).

But, are the callers really able to guarantee that the ranges are all in a
single VMA? I am not familiar with the users, but how for instance
tcp_zerocopy_receive() can guarantee that no one did some mprotect() of some
sorts that caused the original VMA to be split?