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

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Message-ID: <b65e145b-a754-41bb-8322-f93c24f6b7d1@linux.alibaba.com>
Date: Mon, 6 Jan 2025 17:34:15 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Barry Song <21cnbao@...il.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 2025/1/6 17:03, Barry Song wrote:
> 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?

Right.