From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793056957; b=hi5Plz2nU3teu1/zXpw6TTpkGtdD3R3yEkyxl7JE6tBhU7rDVeFTtn4CBFyd/Z7hYG6I Ed8xOqdQLzJOwTKBhGi9afbwPEUIqzrblx5ZE8OHnGrc+1b3uKNe0LUVFXXaphC/GXq/h gsD47stu6fQSAtj3bJ51+7I6qnG4s45WKHVOvvpbbNAq7S8xu3JZEPSCaEkNjEjADpAlm O4njdChy/TahZY5sm7W93geUrMgDmNDCewiV4V9HvuLrJR0MGXcvMYGtBsrvNUE3hPpwr KMtZJtAIqCIaHdiFUfihTseMjOsrFOBvfrHj2HICk0tpscO8GADM5HAeLDlgFJPIjrQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793056957; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=9PONecBNGwAC37JtDon9HRvZi6sk21qH9zGaaJ3qYwM=; b=e5R374AiSvy9jbcofSaQffNGQ7j3ltyfm/KMayQGCdvtzKGpOo2VmOd64uyQqy0UomXg 3CKgkehTeNMsdGqN/eFRb+vP0Fp6qArNFRqhEs3417gVW6sCTE23QOK9LfhZcab8XVxMZ Xwy1BWx1oYc5JsoKXdl2u+pDXkMYi/sZ9YOCDboU+t0Ag8F+KMT12bcFgG2K6Z1gpp1Ly ckYKN+p1zkHcFpKUBOIzdvyUe0FTPzKrCf2z/bK2A4jvWbT4hy2A2chtW6gwyYgLI85uu S+CHCkxlGu02grMTkUU+N899/76rRRjwQbWouobb4DB4e2IBM5CSE/FRCIUncQai6YA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PVvbRksS; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7E24606A323; Mon, 26 Oct 2026 23:22:36 +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=PVvbRksS Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33E7D1F01825; Mon, 26 Oct 2026 23:22:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793056956; bh=9PONecBNGwAC37JtDon9HRvZi6sk21qH9zGaaJ3qYwM=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=PVvbRksSFwPLqVK97JfuGRK/yyQ7vgKqfwNLBuwg7tRyER/6D481w8uhIlExbvJlF 3Bu3BiC6oN4wuYX83Y+otwZqJERUGRe1XFi0KZ7UsLHZ/O4mJV3ZcTn/vc9WZT9EJX wPLTosWMrpja6FYcetEEULvCUUTsRwH1Wx4GCZRVT5tvL3HyQE+itWahkkZ0Dz60Ct XlR6V2Yu3twGvjCbCxFmeWQT5axPeMCrXg6qf9ZLt0Dkzq7EMrgWGUq4VcoD45xmNI 0JiJEmKhSJUPzB+HtPGHZQbcS0lXuOgWw7vLR2o9H5MUKaVvozkgATVGIROQa8biF8 hMVaFTFvhIV7Q== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:35 +0100 Subject: [PATCH 15/46] mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp() X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261027-fixes_core-v1-15-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@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, Josef Bacik , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1502; i=david@kernel.org; h=from:subject:message-id; bh=tUVUPC0JtoDS0vcvc31VLhuGDhArP2SMJJKTyHtlpxc=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu359SPM9j88bSt686WqQe8L9xbvg+r1Tw8tRHcz37n s7RmJFY1FHKwiDGwSArpsgSFHzf4OXLdbXVbnzMMHNYmUCGMHBxCsBE5jcx/BU29ki5fl+GO4jN wXS6x7vf0VKJzI6z82R5Fk6a9kRS25nhv2NW248SjrK9fx+kGgX4OdfM0y+eYzZ9l+uy4BN7Is4 9ZAAA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A From: Josef Bacik try_collapse_pte_mapped_thp() drops the PTE lock after it has cleared the page table, and takes the PMD lock and the PTE lock to remove it. In between, MADV_DONTNEED with CONFIG_PT_RECLAIM can reclaim the page table. The pmd_same() check is supposed to handle this, but it is only done with CONFIG_SPLIT_PTE_PTLOCKS. Fix it by performing the check unconditionally. Fix generated by an LLM and sent by Josef Bacik in private. Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik [ david: adjust description ] Signed-off-by: David Hildenbrand (Arm) --- mm/khugepaged.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 4b71d010b2aff..f53c50507c83d 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2013,12 +2013,11 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign /* step 4: remove empty page table */ if (!pml) { pml = pmd_lock(mm, pmd); - if (ptl != pml) { + if (ptl != pml) spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); - if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) { - flush_tlb_mm(mm); - goto unlock; - } + if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) { + flush_tlb_mm(mm); + goto unlock; } } pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd); -- 2.43.0