From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Zi Yan <ziy@nvidia.com>
Cc: Kyle Zeng <kylebot@openai.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Nico Pache <nico.pache@linux.dev>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
Usama Arif <usama.arif@linux.dev>,
Kiryl Shutsemau <kas@kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] mm/huge_memory: avoid transient none PMDs during lazyfree reclaim
Date: Fri, 9 Oct 2026 22:44:16 +0200 [thread overview]
Message-ID: <d68cb3de-e471-4ce8-8c6d-c7260d79ec1e@kernel.org> (raw)
In-Reply-To: <55765FF3-18D7-424C-984D-81C316F323E1@nvidia.com>
On 10/9/26 22:27, Zi Yan wrote:
> On 9 Oct 2026, at 16:23, David Hildenbrand (Arm) wrote:
>
>> On 10/9/26 20:17, Zi Yan wrote:
>>>
>>> There are some gaps we need to close before getting this fix in:
>>>
>>> 1. GUP-fast cannot follow the invalidated PMD: riscv and LoongArch need
>>> pmd_access_permitted() that requires _PAGE_PRESENT; s390's
>>> pmdp_invalidate() needs a change.
>>
>> Ugh. We really need pmdp_invalidate() to have reasonable semantics. This whole
>> PMD locking is a mess :(
>>
>>>
>>> 2. sparc64's thp_pte_count can be imbalanced with this change (based on
>>> Lance's offlist feedback).
>>
>> Ack.
>>
>>>
>>> In addition, powerpc has a page table check issue similr to riscv, where riscv
>>> fixed it with commit 9f4a88b8d01a6. This is not related to this issue
>>> but discovered along with the investigation.
>>
>> Zi, do you have the capacity to take over this patch?
>
> Yes, I can take over it. My plan is to send a series including
> patches for 1 and this patch as is. powerpc fix can be a separate one.
>
> Best Regards,
> Yan, Zi
If we need a quick stable fix we could temporarily disable the whole thing until
it is fixed, just a thought.
--
Cheers,
David
next prev parent reply other threads:[~2026-10-09 20:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-09 16:52 Kyle Zeng
2026-10-09 18:00 ` David Hildenbrand (Arm)
2026-10-09 18:17 ` Zi Yan
2026-10-09 20:23 ` David Hildenbrand (Arm)
2026-10-09 20:27 ` Zi Yan
2026-10-09 20:44 ` David Hildenbrand (Arm) [this message]
2026-10-10 1:12 ` Lance Yang
2026-10-10 1:56 ` Zi Yan
2026-10-10 2:04 ` Lance Yang
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