linux-kernel - Re: [PATCH] mm/page_alloc: Fix freeing of failed-split poisoned compound pages

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Message-ID: <20260116141157.29578-1-boudewijn@delta-utec.com>
Date: Fri, 16 Jan 2026 15:11:57 +0100
From: Boudewijn van der Heide <boudewijn@...ta-utec.com>
To: jiaqiyan@...gle.com
Cc: akpm@...ux-foundation.org,
	boudewijn@...ta-utec.com,
	hannes@...xchg.org,
	jackmanb@...gle.com,
	linmiaohe@...wei.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	mhocko@...e.com,
	nao.horiguchi@...il.com,
	osalvador@...e.de,
	surenb@...gle.com,
	vbabka@...e.cz,
	ziy@...dia.com
Subject: Re: [PATCH] mm/page_alloc: Fix freeing of failed-split poisoned compound pages

Thanks Jiaqi for the feedback, that is very helpful.
(and thanks Miaohe for connecting the issues.)

After going through the memory_failure(),
I can see it indeed puts the PG_HWPoison flag on the specific subpage pointer,
and therefore my fix won't work as-is.

> >
> > Yes, this is also a problematic scenario for Hugetlb HugePage. And Jiaqi works on
> > it now [1]. I think Jiaqi's patches might apply to THP scenario too. Add @Jiaqi to
> > verify this.
> 
> Yep, I think my work will also help solve the concern when
> try_to_split_thp_page() fails.

Your fix makes a lot of sense for hugetlb,
as it linearly scans through all the pages.
>From my understanding, 
your fix also provides the perfect architecture for also checking THP,
though it doesn't yet cover the in-use THP case outlined.

For THP I would need to trace the failed-split paths more carefully,
to check where the equivalent path for THP would be. 

If there is work needed for THP, I'm happy to help.
Would you prefer I work on THP support as a separate follow-up patch,
after yours is merged,
or do you prefer to integrate it in your patch series?

> >
> > [1]: https://lore.kernel.org/all/20260112004923.888429-1-jiaqiyan@google.com/
> >
> > Thanks.
> > .

Thanks,
Boudewijn