From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 66DB0606A31E for ; Thu, 29 Oct 2026 15:40:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=HEX1DhI/ Received: by kanga.kvack.org (Postfix) id 7C2096B05C8; Thu, 29 Oct 2026 11:40:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 772446B05CB; Thu, 29 Oct 2026 11:40:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 639F06B05CC; Thu, 29 Oct 2026 11:40:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 2B9476B05C8 for ; Thu, 29 Oct 2026 11:40:25 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id BCD981C3B5F for ; Thu, 29 Oct 2026 15:40:24 +0000 (UTC) X-FDA: 85376075568.28.1696123 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf06.hostedemail.com (Postfix) with ESMTP id 001FB18000A for ; Thu, 29 Oct 2026 15:40:22 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="HEX1DhI/"; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793288423; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=dYZCc2lNTUYj2t2pu6YWJRD5XfL+7XVbwTmCwIjHH9M=; b=HD3lxGSybWhqbOy131rG5fhaChH9dPjRpalViDSZ9TSRSCw/4/lJM1QRjPvbTeCSIDlR1u 3qAmI8d3RM32W0yC9u1DFI+KulT4mde8+nNPgJv+BqAcC2mjWEczHV1CAvWWQqusP38clF ZRqQG217d5KFq11+Yd0EddI4/OMoT28= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="HEX1DhI/"; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793288423; b=ZK6GeCdwZRIhHLkNXfDzFQ5Mjzlt7RSUGSdFHlK0mo48yL/C9OyUufvC84lLJfc3rK6V0w odte43K/bWBOZDZL7mb/lK2TaEp6qE+UetPUQMxNM36qDiM7/CejjggcESiT+sI3+poF49 4vt/dF1l8bUPFhxfXoE5aDN6fGHLY9w= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0302A40AE6; Thu, 29 Oct 2026 15:40:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 499621F01825; Thu, 29 Oct 2026 15:40:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793288421; bh=dYZCc2lNTUYj2t2pu6YWJRD5XfL+7XVbwTmCwIjHH9M=; h=Date:Subject:From:To:Cc:References:In-Reply-To; b=HEX1DhI/2X9DdajitxhgBddyoyv6FilOfCQpBtJ2ki6f9+zZe3m32dX/laOZm+NZo 3+VL/GiUGc80vUKeQiNpy6rLscll7ooEz/oJamgMcs95z6H+FVJQg+52LWBiQT1ZCx B9pxDJe4nQgtjxOWTILlUSTrEi2JyqBWO1I7gYZgjRXXO4yRuTE8lvOm+XgdNCMIDE eb3G/knwjTXKSL2d4wyVlA0FBRRSDCVk8B2OABs84uw416YI5ZzgLVFhsSp4M7PYYh yvucyVCRSRnO1+W+WGDTO/DlXwK9M4Gd0oL8Iez7I1bLu5UTiPlfESH9LjxdMY4Zdz hoQaZEWRjMyTQ== Message-ID: Date: Thu, 29 Oct 2026 16:35:46 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 42/46] mm/huge_memory: split huge PUDs when adjusting VMA boundaries From: "David Hildenbrand (Arm)" To: Kiryl Shutsemau Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-42-6f74bec9a5bb@kernel.org> <9f4128a4-85fc-4f4b-ac41-b9d348f56e37@kernel.org> Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 001FB18000A X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Stat-Signature: eou19phuq9noijut8f7rnpth1gmh3wmx X-HE-Tag: 1793288422-575036 X-HE-Meta: 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 ZNPXY10j Yzj6kmqy2wuqrwnA/kkdBNnGuPLeXx09dy7GiBQUqW72qXCoyRcIZHjpaN2F3FxBiQz7ivO0xEwQ228MsXFAByqEW8XF14SddS3chQWsEcJkmeWcBN3VZC26tlLq4CPWLj2GZwvLcu2da07HnTTuAyxLYTTmjw7Vhd+pDqqJpxflDda9GjbeeQTbg2eRw2pDUYWQLz+l1Rf4xLdQ/Jl/C9qfgBERMdUgQ3jDcgf97DLQ9jFzM9++PZF75lB6NR5h+qC9G1n8PKhlG4projg6+LFt5pH5w7jOk2XnGjVeoexlMU+RgZeYiljch47ENb7/JYLVDb3yy+QWFRgdHZ6SA9FgfBmOv4eCsQcAWgkn8jAE9nWl4w1+1/iXzXWXbCYYf9tcb Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/29/26 15:40, David Hildenbrand (Arm) wrote: > On 10/29/26 15:31, Kiryl Shutsemau wrote: >> On Thu, Oct 29, 2026 at 03:24:29PM +0100, David Hildenbrand (Arm) wrote: >>> >>> __split_huge_pud() must split a leave. Either by zapping it (what we do right >>> now) or by populating page tables (as in Usama's PoC). >> >> No, meant the situation when pud_leaf() is true, but split_pud is false, >> so __split_huge_pud() is never hit. pud_present() is true so we proceed >> to pmd_offset() > > Oh, yeah, I can add a WARN_ON_ONCE() for that, it would be a bug in the software. Ah, or I can just drop the split_pud check. Let me do that. +static void split_huge_leaf(struct vm_area_struct *vma, + unsigned long address) +{ + const bool split_pud = pud_split_required(vma, address); + const bool split_pmd = pmd_split_required(vma, address); + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + + /* + * mmap, VMA and rmap write locks protect the walk; the split helpers + * take the page table locks. + */ + if (!split_pud && !split_pmd) + return; + + pgd = pgd_offset(vma->vm_mm, address); + if (!pgd_present(*pgd)) + return; + + p4d = p4d_offset(pgd, address); + if (!p4d_present(*p4d)) + return; + + pud = pud_offset(p4d, address); + if (pud_leaf(*pud)) + __split_huge_pud(vma, pud, address); + if (!split_pmd || !pud_present(*pud)) + return; + + pmd = pmd_offset(pud, address); + __split_huge_pmd(vma, pmd, address, false); } -- Cheers, David