linux-kernel - Re: [PATCH mm-new v2 2/3] mm/khugepaged: use VM_WARN_ON_FOLIO instead of VM_BUG_ON

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Message-ID: <0d1bcfdc-031f-4841-b0f3-15ae1d1ffb8e@arm.com>
Date: Tue, 7 Oct 2025 10:09:22 +0530
From: Dev Jain <dev.jain@....com>
To: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org,
 david@...hat.com, lorenzo.stoakes@...cle.com
Cc: ziy@...dia.com, baolin.wang@...ux.alibaba.com, Liam.Howlett@...cle.com,
 npache@...hat.com, ryan.roberts@....com, baohua@...nel.org,
 ioworker0@...il.com, richard.weiyang@...il.com,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH mm-new v2 2/3] mm/khugepaged: use VM_WARN_ON_FOLIO instead
 of VM_BUG_ON_FOLIO for non-anon folios


On 06/10/25 8:13 pm, Lance Yang wrote:
> From: Lance Yang <lance.yang@...ux.dev>
>
> As Zi pointed out, we should avoid crashing the kernel for conditions
> that can be handled gracefully. Encountering a non-anonymous folio in an
> anonymous VMA is a bug, but a warning is sufficient.
>
> This patch changes the VM_BUG_ON_FOLIO(!folio_test_anon(folio)) to a
> VM_WARN_ON_FOLIO() in both __collapse_huge_page_isolate() and
> hpage_collapse_scan_pmd(), and then aborts the scan with SCAN_PAGE_ANON.
>
> Making more of the scanning logic common between hpage_collapse_scan_pmd()
> and __collapse_huge_page_isolate(), as suggested by Dev.
>
> Suggested-by: Dev Jain <dev.jain@....com>
> Suggested-by: Zi Yan <ziy@...dia.com>
> Signed-off-by: Lance Yang <lance.yang@...ux.dev>
> ---
>   

Reviewed-by: Dev Jain <dev.jain@....com>