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 17544606A31C for ; Thu, 29 Oct 2026 20:37:45 +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=h9IpVMZX Received: by kanga.kvack.org (Postfix) id 3A4EA6B05CD; Thu, 29 Oct 2026 16:37:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 37EC16B05CE; Thu, 29 Oct 2026 16:37:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 26CBD6B05CF; Thu, 29 Oct 2026 16:37:44 -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 031B46B05CD for ; Thu, 29 Oct 2026 16:37:43 -0400 (EDT) Received: from smtpin22.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 88DE616042F for ; Thu, 29 Oct 2026 20:37:43 +0000 (UTC) X-FDA: 85376824806.22.AAF82F3 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf07.hostedemail.com (Postfix) with ESMTP id BCD8E40007 for ; Thu, 29 Oct 2026 20:37:41 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=h9IpVMZX; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1793306261; 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=JkKpOpVy4nNTHYLS6i5ceIs+WZNAThsPIEqAOiy3hwo=; b=UMwxN90jPg0VakpuJbmxcnOT8dzm+1HfFUs0VcaDFR8IrEtOaa+wRw5qFh49ah4XJthXvv dHw74XF/BaP1VtZzaBQleGITh5r4FYW7Im8gCCjUWmPSO2qdFh3SErVXPKb3AGR/DWhwqD 316hJWrEHEtGHepZf4nYJ/VMEQe+5C0= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793306261; b=3zph90sUtdUO3db09hrWaiCBr3+PmLd+vZgBjPUc18yOEhJigBtLx2TUDBV+4wqzKxuhid Vo+YI/6KR8t1JpAAUBLzt6OW1EBRpMH5MiL2b9ReAmR96lTW1uQ5Y0Qzn8sfWn2WtEc8+U 16sPasymp8j27V+CpMVEx4PKXoxzCiU= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=h9IpVMZX; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 64C806020F; Thu, 29 Oct 2026 20:37:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 234EE1F01825; Thu, 29 Oct 2026 20:37:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306261; bh=JkKpOpVy4nNTHYLS6i5ceIs+WZNAThsPIEqAOiy3hwo=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=h9IpVMZXhE9Hn2ObjyXapG1VQ5Spd0s63yzi81dMPuivmY4xxxMaIhVJalbhQK3l/ pPic2KzleKT4LwVF9PdrT5Vfz+/2baBkDRwIcP/Oc6mI+rZId/hxzlKNyi/dTsIW0k 4mKSwQ+v7UsXIjr4p2jofqTscsM+BlLhL4mhqUDnKfM+awKQy0TDW/2GkayYcoE1od 2Kr1F/zEK9k3bRpeABQdrlGXkzrF18Cmys1v5Ugm1MiHJ6dStoKQzKVMlfjIZLee8H WXkxH2wVlVVoqDBPYUj9HIm+ZDRGRuy5E5n3ZOa1Ax+81CZKB2cvAF3QmuDHKdINHl 0wl3DQs6BOgnA== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:12 +0100 Subject: [PATCH v2 17/47] mm/khugepaged: preserve dirty bits when collapsing PTE-mapped THPs X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-17-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: 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 , 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: 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, Chris Mason , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2189; i=david@kernel.org; h=from:subject:message-id; bh=te5lCngEDLVmEXnC8RjOJPUhL4oSTpvZoR4pTc9h1QU=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer20z2uc41Uxnho7Oqu/K//7Mr3HR43XYu/PymyVfn 1cf+F+yt6OUhUGMg0FWTJElKPi+wcuX62qr3fiYYeawMoEMYeDiFICJVO9g+Ctrv2H+tKAkAT7/ q8x6Z+YmCZ3KKxV6c8G7YMJ/v0ut3esZ/hl3mvNIPGmK/3lux+cqZ9WrXDy1/822Srj+m/7+uZf PKj4A X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BCD8E40007 X-Stat-Signature: 8fbj9y1sbzey6hyahhryhb3tkdwsr5n7 X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793306261-855191 X-HE-Meta: U2FsdGVkX1/EL5gM3TFLuckGmAiI2UrBIRNz2MJAmv1+SRcpMnwdqbVx7MuANmL1VtfEM1wp/iFwXncirDbTc4O55z0nNBgLASKAjyB91wgobzEzKKHUJeXLqrYFfWJYCq8I5mJW8a6jCEDrFLBQOvFnOxbCvlBwtZgoqaMoV8sK0/OsnA2Spm6ohVxXeO1EQUKQwcuVX3We+GyIXib0lEGRVy8NK3zy58Kg6JEVvprK4wZG091gqazMTlUIx9uya45V1t5v+c4jSghMWrG8tCMwyxB07YsVAG0Vr8gr7RcuLr7k1AcwgtqymjPUv+jni7EXF/Sf9X7nUr9XK1LaTcwVuXg4qfyZlTtYFwgKgWk9l7L4Z28mXs99hjyQSyhulDsg+0saUkfSeH5Uj0LDTeDrJkYf8LQWbcvuoYkeK0W0snph4tAj2zpd97Y9B63w3WSh8OGjG0mu74B9rVnnwmiq6knD2ZEVNWLPnHxmaL7rCfXUzPVPppZx2JcRrY/Zi/OoG2n2AxgWPoS4A1FqzCSkchs4JZ73GRs1m1DxmpwBm/LnYH1U/M09dNeCFl6fck6MC62QOJQIK7If2rJM6Q0BFG/nWhAKmYqMuTkx1F9ZJl+La6D28S82BWf58VjRahFEtOIKcaaG+a59Cc6y2rx5LUN5HXBNalwc++Y6mkTxj1FGmPamaD10Nz77Obq6I0kM0+7+Jb+zdboSZ/F0OSMOkdpm+RZDNJNm4W8FvsU5S07jwYJMkCnfCdYy0rDMdlqOSfq9sztRY4i+EeW5AZA974D+z3k41lxyyVuFPtSSASCgDTIUkcDAzQ9ASrq4Snjtp8SaMcCiRLETqrIV2jshH2l677ZMZ8cCcebeigPiRreNNAi341H1D0ANqTZdNztvd+1FTBqLTxHFrwarqbXO49FshdTq4vaAw8H33JseSW2cQBytit38cfofMeMRXp0F31Xh4rwf/GheDKj 12s05iqK MSbfTi8qBOxWvwrjh0CW1rCSdSJ3SkGsusC0GkELM3AvmZ8AvYmhilzYxYAr/Yr0O5fHKolY1sDijACUjdO4QIZWIWZFRT+vYDrlx5lfG5ukXf/u6D8m5Uvx51ZzeDGF6OXyKGnCf94UV0Mbq9TQ1eRrdTjgyG/JQjdwVN0rWu/qSpPssgfLF1ndyYXdHP1n+HZFzPHoWbIBBSPd5snf3A0tFFapeQG0UkGJtEYGIHaU+gyKa7vECtIDxGF79KvLvsVjjlKTKdmCKEvXpCudw6GkmQlV3pKjkk8ibCxqUg7xudEYi7LvVeiYChFVenUaPNLQJRaExA7tH7pw/RamqELxV9b3Vzg/4ehLpcsBeGbwtxoFpP+z36udlekLWgClKudFv 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 From: Chris Mason 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. The assumption that regular files are read-only is also obsolete since commit 1b6444331bebb ("mm/khugepaged: enable clean pagecache folio collapse for writable files"). In any case, transferring PTE dirty bits to the folio when removing mappings (and while the folio is still mapped) is the right thing to do. Use get_and_clear_ptes() to collect the dirty bits and mark the folio dirty before unmapping it. Update the comment. This was reproduced with shmem using MADV_COLLAPSE followed by MADV_PAGEOUT. Fix generated by an LLM and sent by Chris Mason in private. Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP") Fixes: 1b6444331bebb ("mm/khugepaged: enable clean pagecache folio collapse 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) --- mm/khugepaged.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 04d9bb21ff52..dd17c3dae800 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1995,9 +1995,10 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign /* * Must clear entry, or a racing truncate may re-remove it. * TLB flush can be left until pmdp_collapse_flush() does it. - * PTE dirty? Shmem page is already dirty; file is read-only. */ - clear_ptes(mm, addr, pte, nr_batch_ptes); + ptent = get_and_clear_ptes(mm, addr, pte, nr_batch_ptes); + if (pte_dirty(ptent)) + folio_mark_dirty(folio); folio_remove_rmap_ptes(folio, page, nr_batch_ptes, vma); nr_mapped_ptes += nr_batch_ptes; } -- 2.43.0