linux-kernel - Re: [PATCH v4 0/3] Only free healthy pages in high-order has

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Message-ID: <2C382EC0-0FB7-4882-8B87-E467454178D2@nvidia.com>
Date: Wed, 04 Feb 2026 10:48:00 -0500
From: Zi Yan <ziy@...dia.com>
To: Boudewijn van der Heide <boudewijn@...ta-utec.com>
Cc: jiaqiyan@...gle.com, Liam.Howlett@...cle.com, akpm@...ux-foundation.org,
 david@...hat.com, duenwen@...gle.com, hannes@...xchg.org,
 harry.yoo@...cle.com, jackmanb@...gle.com, jane.chu@...cle.com,
 jthoughton@...gle.com, linmiaohe@...wei.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, lorenzo.stoakes@...cle.com, mhocko@...e.com,
 muchun.song@...ux.dev, nao.horiguchi@...il.com, osalvador@...e.de,
 rientjes@...gle.com, rppt@...nel.org, surenb@...gle.com, tony.luck@...el.com,
 vbabka@...e.cz, wangkefeng.wang@...wei.com, william.roche@...cle.com,
 willy@...radead.org
Subject: Re: [PATCH v4 0/3] Only free healthy pages in high-order
 has_hwpoisoned folio

On 4 Feb 2026, at 10:23, Boudewijn van der Heide wrote:

> Hi Jiaqi,
> Thanks for including the THP scenario.
>
>> Another similar situation is when a transparent huge page (THP)
>> is handled by MFR but splitting failed. Such THP will eventually
>> be released to buddy allocator when owning userspace processes
>> are gone, but with certain subpages having HWPoison [9].
>
> I think for failed-split THP, we need to do the following to support them:
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index cf0d526e6d41..3f727038f400 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2479,6 +2479,7 @@ int memory_failure(unsigned long pfn, int flags)
>  		if (err || new_order) {
>  			/* get folio again in case the original one is split */
>  			folio = page_folio(p);
> +			folio_set_has_hwpoisoned(folio);
>  			res = -EHWPOISON;
>  			kill_procs_now(p, pfn, flags, folio);
>  			put_page(p);
>
> We set the PG_has_hwpoison flag here again,
> because when the split partially succeeds (new_order > 0),
> page_folio(p) returns a new smaller-order folio that doesn't have the flag set.

No, split code[1] sets has_hwpoison flag when it split a folio to a non-0 order
folios. If you do not see it in your kernel code, you might need to update
your kernel to latest stable one or one newer than or equal to 6.18.


[1] https://elixir.bootlin.com/linux/v6.18/source/mm/huge_memory.c#L3343


Best Regards,
Yan, Zi