Re: [PATCH 0/2] page_count can't be used to decide when wp_page_copy

[Linus Torvalds]

On Thu, Jan 7, 2021 at 2:03 PM Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote:
>
> If you could stop mentioning UFFDIO_WRITEPROTECT and only focus on
> softdirty/clear_refs, maybe you wouldn't think my judgment is biased
> towards clear_refs/softdirty too.

So I think we can agree that even that softdirty case we can just
handle by "don't do that then".

if a page is pinned, the dirty bit of it makes no sense, because it
might be dirtied complately asynchronously by the pinner.

So I think none of the softdirty stuff should touch pinned pages. I
think it falls solidly under that "don't do it then".

Just skipping over them in clear_soft_dirty[_pmd]() doesn't look that
hard, does it?

            Linus