From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A8F7606A31A for ; Fri, 30 Oct 2026 03:41:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=Nl4f1ucc; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dnQLwV7r DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date: Content-Transfer-Encoding:Content-Type:References:In-Reply-To:Cc:To:Subject: From:Message-ID:MIME-Version:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Unsubscribe-Post:List-Owner; bh=2ZbYjkVO/Tyj9ADMpjxCj4P7o1XYmQvtTAdXyF+oamY=; b=Nl4f1ucc1OcgMVBTb99up+HCGF 4FWQwqKxK0SY/nBTzJmEGOCfVEFAhtZ6ExwUAFp3i4/sRI3mp1lFlBRkf/WR2Cb3Ar7JI1OtVptTF w9L0rkoOo5Pzih5X/KhYXA3p6pJycirTnLIOlo50ei2jd9tiA/k44UZVIH73cthtrrLH0PGZCBdjl m7zJp4DVTFva6khckvHrVu/S8fE3DHYuJiPZASOZVdYVspnVrfglrM/AG84R+JdcIVo0vT5aNvQ/r VuA73owp0kvaEktBsnCawFtBxU+rhc3vMLlVxsBRH3P25rEvsXsWUNlncEA9YQ1Lqo30v47W39b41 lQFCfJkQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMdUL-0000000AkGI-3kLF; Fri, 30 Oct 2026 03:41:09 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMdUK-0000000AkFL-1mKg for kexec@lists.infradead.org; Fri, 30 Oct 2026 03:41:08 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id BF2CD600C8; Fri, 30 Oct 2026 03:41:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF62E1F000C1; Fri, 30 Oct 2026 03:41:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793331667; bh=2ZbYjkVO/Tyj9ADMpjxCj4P7o1XYmQvtTAdXyF+oamY=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=dnQLwV7rNK0l+RMc8F8tqEU6c77p8Ys3neVXEGqK4t2bh5dl/newEegjwUMJBfw+s OH9eBsy8cJo6nadnBZWtaPpj4pWQg4fEsq6L5SUXj0tc02JNzpCGKLKPcHIr0WKrHc 9iKNguX6399k5Y44xI90E7AW+RWdnt07mfuW/6/nGxbgKFOuk5I+74P+6HY3017AHe xNMwxMtVxtIZBzUCwNcnJAFHHm9Sg+qspYbcOGiYbmXPCqAo9S61JgZLeMUMYm1AmS k9XetslwWQtdJA5/xntGrxmWVFDuum/kY8SO3dnUuh54J/fPT1v2akxyqh75qG/mbZ 02aw/s1W4vosQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 17/47] mm/khugepaged: preserve dirty bits when collapsing PTE-mapped THPs To: =?utf-8?b?RGF2aWQgSGlsZGVuYnJhbmQgKEFybSk=?= , "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" , =?utf-8?b?TWF0dGhldyBXaWxjb3ggKE9yYWNsZSk=?= , "Jan Kara" , "Zi Yan" , "Lance Yang" , "Rik van Riel" , "Harry Yoo" , "Alistair Popple" , "Nico Pache" , "Ryan Roberts" , "Dev Jain" , "Usama Arif" , "Kiryl Shutsemau" , "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" Cc: kexec@lists.infradead.org, "Chris Mason" In-Reply-To: <20261029-fixes_core-v2-17-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> <20261029-fixes_core-v2-17-a64ce7f83abb@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 30 Oct 2026 03:41:04 +0000 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "kexec" X-Spam-Status: No, score=-10.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: > From: Chris Mason >=20 > try_collapse_pte_mapped_thp() clears PTEs without transferring their dirty > bits to the folio. A shmem read fault can map a clean folio writable, so > a later store only dirties the PTE. Losing that dirty bit allows reclaim > to discard modified data. >=20 > The assumption that regular files are read-only is also obsolete since > commit 1b6444331bebb ("mm/khugepaged: enable clean pagecache folio collap= se > for writable files"). In any case, transferring PTE dirty bits to the fol= io > when removing mappings (and while the folio is still mapped) is the right > thing to do. >=20 > Use get_and_clear_ptes() to collect the dirty bits and mark the folio > dirty before unmapping it. Update the comment. >=20 > This was reproduced with shmem using MADV_COLLAPSE followed by > MADV_PAGEOUT. >=20 > Fix generated by an LLM and sent by Chris Mason in private. >=20 > Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP") > Fixes: 1b6444331bebb ("mm/khugepaged: enable clean pagecache folio collap= se for writable files") > Cc: stable@vger.kernel.org > Signed-off-by: Chris Mason > [ david: adjust comment; simplify description; cover file-thp as well ] > Reviewed-by: Pedro Falcato > Reviewed-by: Gregory Price (Meta) > Tested-by: Gregory Price (Meta) > Signed-off-by: David Hildenbrand (Arm) Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261029-fixes_core= -v2-0-a64ce7f83abb@kernel.org?part=3D17