Re: [PATCH v2 1/4] mm: Set folio swapbacked iff folios are dirty in try_to_unmap_one

Barry Song
2025-01-13T22:05:14Z

On Tue, Jan 14, 2025 at 2:21 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 13.01.25 14:19, David Hildenbrand wrote:
> > On 13.01.25 04:38, Barry Song wrote:
> >> From: Barry Song <v-songbaohua@oppo.com>
> >>
> >> The refcount may be temporarily or long-term increased, but this does
> >> not change the fundamental nature of the folio already being lazy-
> >> freed. Therefore, we only reset 'swapbacked' when we are certain the
> >> folio is dirty and not droppable.
> >>
> >> Suggested-by: David Hildenbrand <david@redhat.com>
> >> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> >> ---
> >
> > Acked-by: David Hildenbrand <david@redhat.com>
> >

Thanks!

>
> Ah, should this have a Fixes: ?

That makes sense to me.

>
> Because of a speculative reference, we might not reclaim MADV_FREE
> folios as we silently mark them as swapbacked again, which sounds fairly
> wrong.
>

I assume the tag should be applied to Mauricio's commit 6c8e2a256915a2 ("mm:
fix race between MADV_FREE reclaim and blkdev direct IO read") and also
Mauricio is CC'ed.

> --
> Cheers,
>
> David / dhildenb
>

Thanks
Barry