Re: [PATCH v1 0/7] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of anonymous pages

[Jason Gunthorpe]

On Tue, Mar 15, 2022 at 03:18:30PM +0100, David Hildenbrand wrote:
> This is just the natural follow-up of part 2, that will also further
> reduce "wrong COW" on the swapin path, for example, when we cannot remove
> a page from the swapcache due to concurrent writeback, or if we have two
> threads faulting on the same swapped-out page. Fixing O_DIRECT is just a
> nice side-product :)

I know I would benefit alot from a description of the swap specific
issue a bit more. Most of this message talks about clear_refs which I
do understand a bit better.

Is this talking about what happens after a page gets swapped back in?
eg the exclusive bit is missing when the page is recreated?

Otherwise nothing stood out to me here, but I know almost nothing
about swap.

Thanks,
Jason