linux-kernel - Re: [PATCH v4 0/3] Optimize folio split in memory failure

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Message-ID: <2F077EE8-9E34-4EE8-B2BB-90FBE5680C05@nvidia.com>
Date: Fri, 31 Oct 2025 11:42:19 -0400
From: Zi Yan <ziy@...dia.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linmiaohe@...wei.com, david@...hat.com, jane.chu@...cle.com,
 kernel@...kajraghav.com, mcgrof@...nel.org, nao.horiguchi@...il.com,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Lance Yang <lance.yang@...ux.dev>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 Wei Yang <richard.weiyang@...il.com>, Yang Shi <shy828301@...il.com>,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH v4 0/3] Optimize folio split in memory failure

On 30 Oct 2025, at 23:42, Andrew Morton wrote:

> On Wed, 29 Oct 2025 21:40:17 -0400 Zi Yan <ziy@...dia.com> wrote:
>
>> This patchset is a follow-up of "[PATCH v3] mm/huge_memory: do not change
>> split_huge_page*() target order silently."[1] and
>> [PATCH v4] mm/huge_memory: preserve PG_has_hwpoisoned if a folio is split
>> to >0 order[2], since both are separated out as hotfixes. It improves how
>> memory failure code handles large block size(LBS) folios with
>> min_order_for_split() > 0. By splitting a large folio containing HW
>> poisoned pages to min_order_for_split(), the after-split folios without
>> HW poisoned pages could be freed for reuse. To achieve this, folio split
>> code needs to set has_hwpoisoned on after-split folios containing HW
>> poisoned pages and it is done in the hotfix in [2].
>>
>> This patchset includes:
>> 1. A patch adds split_huge_page_to_order(),
>> 2. Patch 2 and Patch 3 of "[PATCH v2 0/3] Do not change split folio target
>>    order"[3],
>
> Sorry, but best I can tell, none of this tells anyone anything about
> this patchset!
>
> Could we please have a [0/N] which provides the usual overview of these
> three patches?
>
> Please put yourself in the position of someone reading Linus's tree in
> 2028 wondering "hm, what does this series do".  All this short-term
> transient patch-timing development-time stuff is of no interest to
> them and is best placed below the ^---$ separator.
>

How about?

The patchset optimizes folio split operations in memory failure code by:
always splitting a folio to min_order_for_split() to minimize unusable
pages, even if min_order_for_split() is non zero and memory failure code
would take the failed path eventually. This means instead of making
the entire original folio unusable memory failure code would only make
its after-split folio, with min_order_for_split() and containing the
page marked as HWPoisoned, unusable. For soft offline case, since the
original folio is still accessible, do not split it. In addition,
add split_huge_page_to_order() to improve code readability and fix
kernel-doc comment format for folio_split() and other related functions.

--
Best Regards,
Yan, Zi