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 85371606A31A for ; Fri, 30 Oct 2026 03:41:56 +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=s67tafyL; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=gFEHCcUA 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=WWHlJvm4sYewhU38umcbZ0ROTrmcfZhQeV3HCRulFDQ=; b=s67tafyL93qASo92alpd1sMxAW kXKVJT8haocLJj+HrQbToR3UhvrWo459IDNkjjM0ZNMo/vKnlmDfvyyoEyOkeWCK8vNM4Nb4HX1V+ lrJiB0CGgyzyaAP7/UJN74S13OZFf+NQk8SIyIjSjnj4op3ikCzTzT9estCnQUX8vTOMHn8X3gxAB OJ8vclzY0xISnTV6FMsaBCN0B5zCgff8OILOv/I5D8CO9Jq+ylYijP3VSQ2rVtszslnf4UIj5gHjK I6YUDeurCgjJ1ObpolwmsJIu9SO8IwKbWBmWjcCY3aNq6Ogy3uxMi5huos008WL8O2SOg5F/k9Soi R3N8hREw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMdV6-0000000Akkg-0pfF; Fri, 30 Oct 2026 03:41:56 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMdV4-0000000Akjm-38Mt for kexec@lists.infradead.org; Fri, 30 Oct 2026 03:41:54 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 7A21F42A9C; Fri, 30 Oct 2026 03:41:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D8421F000C1; Fri, 30 Oct 2026 03:41:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793331714; bh=WWHlJvm4sYewhU38umcbZ0ROTrmcfZhQeV3HCRulFDQ=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=gFEHCcUAJ73UlIzKp4w1Ztp5h4592qFsZ9sHNRG5dVP0q9DgDRk0IbHFKCSr/AOru CeRaXBpbQz3CDJkQbfPOqzJEOAq0aCWC3jJsikNkX9hI2VvShru/1QVonMz5FzX4cV hSHayMPVXKUORlb7Q1g2t+UcrGuPwZGikOzPaHI2og7p8saSR5CHrsHt5ZEQo1qB6t WNNiCwnJu8OX6lqWBI8+S+fKvYxDe/vAIj/G2SE1FrDlxQJJB8CW0LtoZZkFuBr89d LrjVvpyCykCLFkN5ROF3HGCXd4SXiGxOMSeAxZJsqxijpKtwJ3K+lNGbjcFPWwY1CI /TZx+cc9qxMuA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 31/47] mm/mremap: recheck PUDs under the page table lock 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 In-Reply-To: <20261029-fixes_core-v2-31-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> <20261029-fixes_core-v2-31-a64ce7f83abb@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 30 Oct 2026 03:41:50 +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: > Once get_old_pud() is fixed to accept PUD leaves, unmap_mapping_range() c= an > clear a leaf between the lookup and the move. Holding mmap_lock in write > mode does not prevent this. >=20 > If the zap happens before move_page_tables() tests the entry, an empty > PUD can reach move_normal_pud(), where pud_populate() turns it into a > present page table entry. If it happens after the test, move_huge_pud() > can instead try to move an empty entry, triggering CONFIG_DEBUG_VM > warnings on powerpc. >=20 > Recheck the source under the page table lock in both helpers. Treat an > empty source in move_normal_pud() as a completed move, and use > __pud_trans_huge_lock() in move_huge_pud(). >=20 > In the future we should likely have the code lookup a PUD/PMD lockless > once, instead of multiple times, because one of the problematic bits > here is the: >=20 > pud_trans_huge(*old_pud) >=20 > Fixes: 0881ace292b6 ("mm/mremap: use pmd/pud_poplulate to update page tab= le entries") > Cc: stable@vger.kernel.org > Reviewed-by: Lorenzo Stoakes (ARM) > Reviewed-by: Pedro Falcato > 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=3D31