linux-kernel - Re: [PATCH 0/4] mm: migrate: more folio conversion

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Date:   Thu, 3 Aug 2023 11:34:59 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Huang Ying <ying.huang@...el.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 0/4] mm: migrate: more folio conversion

On 02.08.23 14:38, Kefeng Wang wrote:
> 
> 
> On 2023/8/2 19:47, David Hildenbrand wrote:
>> On 02.08.23 11:53, Kefeng Wang wrote:
>>> This patch series converts several functions to use folio in migrate.c.
>>
>> Please clearly spell out in the patch descriptions when you are changing
>> mapcount logic and which effects that might have (both, positive and
>> negative) for PTE-mapped THP.
> 
> Oh, I see your comments on another mail[1], the folio_estimated_sharers()
> is not good to evaluate the sharing by multiple processes, will read more
> history of the mail's discussion, maybe just ignore the first three patches.

It might be good enough for some cases right now. My point is that we 
better just clearly spell out the possible effects of such a change.

(so far you didn't even mention them, and that's sub-optimal when buried 
in a "folio" conversion that better shouldn't change the functionality 
without spelling it out)

-- 
Cheers,

David / dhildenb