linux-kernel - Re: [PATCH 1/3] mm: set folio swapbacked iff folios are dirty in try_to_unmap

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Message-ID: <CAGsJ_4wMuDYxuEMcA0jYvekt26Uvz86kjWbo0nz-ZZzuiyEOQQ@mail.gmail.com>
Date: Mon, 6 Jan 2025 22:03:48 +1300
From: Barry Song <21cnbao@...il.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-arm-kernel@...ts.infradead.org, x86@...nel.org, 
	linux-kernel@...r.kernel.org, ioworker0@...il.com, david@...hat.com, 
	ryan.roberts@....com, zhengtangquan@...o.com, ying.huang@...el.com, 
	kasong@...cent.com, chrisl@...nel.org, Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH 1/3] mm: set folio swapbacked iff folios are dirty in try_to_unmap_one

On Mon, Jan 6, 2025 at 7:40 PM Baolin Wang
<baolin.wang@...ux.alibaba.com> wrote:
>
>
>
> On 2025/1/6 11:17, Barry Song wrote:
> > From: Barry Song <v-songbaohua@...o.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@...hat.com>
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
>
> The changes look good to me. While we are at it, could you also change
> the __discard_anon_folio_pmd_locked() to follow the same strategy for
> lazy-freed PMD-sized folio?

it seems you mean __discard_anon_folio_pmd_locked() is lacking
folio_set_swapbacked(folio) for dirty pmd-mapped folios?
and it seems !(vma->vm_flags & VM_DROPPABLE) is also not
handled properly?

Thanks
barry