From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 116A14F85CD; Fri, 9 Oct 2026 20:44:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791578664; cv=none; b=Y+uk+1vjz5h/pRW20mo4ScMIUfPuUOWKtbHekQ1zMiHQDqp5bP06UD8IQWoq9bi1HxVK7P9luKgnAlpJRTT986vxVQXlhIme6r/Kc19fulSbU1zpnXrM0Oj4dqXVGvRYt4OCQT90GfsPSfBcIBCy/6frfuoIwCdH2KmuA9wWPdw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791578664; c=relaxed/simple; bh=D7sn6sT0u6pHQBn4qWRWU79pBDxGUc6f5pWxF4yuAK4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qLUAeRDtvfXlYJf9a/8ARqezuJnhUaWCByYheDgqxFVFq4HuM4Rwj4tiIyC/TCOHd4I72TvEkUdSLVJc/hjJvKllOdqlaxw9HVYZam8R2pohTO5BLH3O3sGuFy+St+vetU0pwya8coEMLtHlugJqNUd77XmK3KdNTXwDZDRhhk4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Y58b6cPM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y58b6cPM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 423C61F000FF; Fri, 9 Oct 2026 20:44:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791578663; bh=4ok5atQOO1xLnZqvIcvpZUo24bgiy5hkUKsL64Z4m34=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Y58b6cPMVo8J2OhRDndnK6601iFosf6b+BWTdqJuf5TJgY13o+V1z2ytjetxDbLvX cM8AS5OrOQi3t/QGgRVc/f0+K51FqRS/JpG/w1NpWGy15QzStMqQjuGtVNOA5eHpdH Ik/79viha99pjTJ2h+Fuk3sYEN9AgebCFUCGMkNer0Ui1eMD4wTKRsgl6JA4RHOe3w viW6yVFbBp5us5+6/Yt6lMrUkmBi0bOVfPiJXTKvUwKd9qYLdPziUuhCfhgKpfMGet VhMVV2+RAPJgLUyDBaUpXR6DeyuHyg++GYOtcy1nMuBBZOJ8Rj9jn9C7okb1+Q57c8 A05H/8TzZFXxA== Message-ID: Date: Fri, 9 Oct 2026 22:44:16 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: avoid transient none PMDs during lazyfree reclaim To: Zi Yan Cc: Kyle Zeng , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , stable@vger.kernel.org References: <20261009165214.40212-2-kylebot@openai.com> <8db35dc0-eb06-42e4-90f9-534522e810e1@kernel.org> <55765FF3-18D7-424C-984D-81C316F323E1@nvidia.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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