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 910B7606A31A for ; Tue, 27 Oct 2026 00:13:05 +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=nw2yLTJz; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dXS7sKKL 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=+tXReI7wCMf+vtxRNrBn0q0GYi0LF14nu7zCvb1wKcY=; b=nw2yLTJzZMIEPGrXjS3J+h6RRF YD793GBZdb4uKhqTXpyg+pj6pv/LdgnBC+QHQ6L/xzbGYzmQJLlYQRiAOGPj4A77e+braO/m+snuk 2DMJQ2fceMGGV/5JApPxjRaGc43qxlc4j3qbPWk7eAgced4HAx18b/rdiJZJUyuX8gAMh73CmBU2Z fOVh9QeE0DX43LnBynMnyQVPwrQ2qgRUemwbn2xtNcYAFlGrRQZ910HSVWzGgc4qh8iPu33F2+GLc yGxo5RxC9iySlSntcK47jdMmrN+dpBLm0GQZYQ8RWvE1xiAWqgsY1w4rDllljQdvRUJjFMvdKaQAs 0V6yxRUA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLUoL-00000003VHy-0T24; Tue, 27 Oct 2026 00:13:05 +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 1xLUoK-00000003VHY-0k8P for kexec@lists.infradead.org; Tue, 27 Oct 2026 00:13:04 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id DD92B408F7; Tue, 27 Oct 2026 00:13:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 496CF1F01829; Tue, 27 Oct 2026 00:13:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793059983; bh=+tXReI7wCMf+vtxRNrBn0q0GYi0LF14nu7zCvb1wKcY=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=dXS7sKKLcbrgZvgc5QpzQbB8G8tKiTFcCOuI+yRZMaVES6PAZvZH7QfBC5spRLKs+ 2PiuRMkHBNhBYUQOQoJcrMRABb5+0m3ooqQVlmPhBTQ88mmbNr1I6+quvUNBxxEDVg IP8A8wPfPBYXU5YsM2/HQeT6AwmB3NEoSUP3nLPb5GXwjj7FXE4JtXW+CP8a6clZsE bSySMzoUHch+ZkA+QGbxgzFEs6PPkJTjTADcZ6DFvmTe2/XaHrpTCX/FwNpbF0KJCf 8nkANNORGQ5QDc/kvPP7W3sm8qMMOcju9QLtCCc/8ZUkwXusROTYnEy0y09Pq4eTO9 DNALYxThzWboA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 19/46] mm/gup: recheck the PUD under PTL in follow_pud_mask() 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, "Josef Bacik" In-Reply-To: <20261027-fixes_core-v1-19-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-19-6f74bec9a5bb@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 27 Oct 2026 00:13:00 +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=-11.2 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: > follow_pud_mask() reads the PUD without a lock. If it is a leaf, it takes > the lock and calls follow_huge_pud(), which reads the entry again, but > only tests whether it is present. >=20 > A leaf can be zapped concurrently and a page fault can fill the empty > entry with a page table. >=20 > This currently only applies when device-dax makes use of PUD entries, > and the fault after e.g., MADV_DONTNEED would find THPs to be disabled. >=20 > That requires a sequence like >=20 > 1) Fault in the PUD > 2) Disable THP > 3) Have GUP race against concurrent MADV_DONTNEED + refault > [ ... ] >=20 > Fixes: 1b1676180246 ("mm/gup: handle huge pud for follow_pud_mask()") > Cc: stable@vger.kernel.org > Reported-by: Josef Bacik > 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/20261027-fixes_core= -v1-0-6f74bec9a5bb@kernel.org?part=3D19