linux-kernel - RE: [PATCH 1/1] mm: prevent poison consumption when splitting THP

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Message-ID: <SA1PR11MB71306ECC0662B9A952EA3534891BA@SA1PR11MB7130.namprd11.prod.outlook.com>
Date: Mon, 29 Sep 2025 13:57:10 +0000
From: "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
To: Miaohe Lin <linmiaohe@...wei.com>, Jiaqi Yan <jiaqiyan@...gle.com>
CC: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"david@...hat.com" <david@...hat.com>, "lorenzo.stoakes@...cle.com"
	<lorenzo.stoakes@...cle.com>, "Luck, Tony" <tony.luck@...el.com>,
	"ziy@...dia.com" <ziy@...dia.com>, "baolin.wang@...ux.alibaba.com"
	<baolin.wang@...ux.alibaba.com>, "Liam.Howlett@...cle.com"
	<Liam.Howlett@...cle.com>, "npache@...hat.com" <npache@...hat.com>,
	"ryan.roberts@....com" <ryan.roberts@....com>, "dev.jain@....com"
	<dev.jain@....com>, "baohua@...nel.org" <baohua@...nel.org>,
	"nao.horiguchi@...il.com" <nao.horiguchi@...il.com>, "Chen, Farrah"
	<farrah.chen@...el.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Andrew
 Zaborowski" <andrew.zaborowski@...el.com>
Subject: RE: [PATCH 1/1] mm: prevent poison consumption when splitting THP

Hi Miaohe,

> From: Miaohe Lin <linmiaohe@...wei.com>
> [...]
> >>   First Machine Check occurs // [1]
> >>     memory_failure()         // [2]
> >>       try_to_split_thp_page()
> >>         split_huge_page()
> >>           split_huge_page_to_list_to_order()
> >>             __folio_split()  // [3]
> >>               remap_page()
> >>                 remove_migration_ptes()
> >>                   remove_migration_pte()
> >>                     try_to_map_unused_to_zeropage()
> >
> > Just an observation: Unfortunately THP only has PageHasHWPoisoned and
> > don't know the exact HWPoisoned page. Otherwise, we may still use
> > zeropage for these not HWPoisoned.
> 
> IIUC, the raw error page will have HWPoisoned flag set while the THP has
> PageHasHWPoisoned set. So I think we could use zeropage for healthy sub-
> pages.

Good point. 

David's suggested diff in another e-mail checked the raw error page instead of
entire folio. And I tested that diff and it worked well.  

-Qiuxu