linux-kernel - Re: [PATCH] mm/huge_memory: softleaf device private fixes in remove_migration

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Message-ID: <a9c8fd41-66c6-4cb4-a033-4138be701b3f@nvidia.com>
Date: Thu, 13 Nov 2025 16:03:43 +1100
From: Balbir Singh <balbirs@...dia.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.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>
Subject: Re: [PATCH] mm/huge_memory: softleaf device private fixes in
 remove_migration_pmd()

On 11/12/25 22:37, David Hildenbrand (Red Hat) wrote:
> On 12.11.25 05:46, Balbir Singh wrote:
>> commit a6ca2ba46390 ("mm: replace pmd_to_swp_entry() with softleaf_from_pmd()")
> 
> So should this be squashed into Lorenzo patch, or incorporated in his series in case he has to resend?
> 
>> does not work with device private THP entries. softleaf_is_migration_young()
>> asserts that the entry be a migration entry, but in the current code, the
>> entry might already be replaced by a device private entry by the time the
>> check is made. The issue exists with commit
>> 7385dbdbf841 ("mm/rmap: extend rmap and migration support device-private entries")
>>
> 
> Because this confuses me. If it's already a problem in the commit-to-go-upstream-first, it should be fixed in that commit?
> 

Not sure how to handle this, because that would break rebase of mm/mm-new
or I'd have to send a replacement patch for the original patch from Lorenzo
(which does not seem right).

I'll post a simpler patch, but it needs to be on top of the series

Balbir