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 86AD2606A31A for ; Fri, 30 Oct 2026 03:41:12 +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=csojoJO6; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CBY4cN8r 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=h3wIpY6vHa1RWex7hAszkeoTd27MCJIXZVzzxBnwc/g=; b=csojoJO6rA1R6gQoUijhnvnypc 6oxKazft4EEds+t5dMblg0AnmSTzyOpr1XZUMajtGcKhG2doQQDIX3jb7PCHcv3AiI42a0PN+rf5Z Ks0LabxJQ9+XO0jKXkQC4PzrJ8Tz2taLbQcHgkD0v+JzyYf+Tc33B4imwK7EJyOGlv+blBY/CQ4KP fwHFNVduYMtXvxt2D+tXctKig6nDwIFliaGZavBJcw7+igWhOs8XXL7G3kUnFiUUeaXFE9sqDFJ3P M3U2zYTshTO/RCZ1sbb9Llr5uTGRcM0cq3dPWU4+RL3Ug3Mmk6l1FIITQEdKBddj67+yonl49pGrn CdicsPOA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMdUO-0000000AkI4-16MM; Fri, 30 Oct 2026 03:41:12 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMdUN-0000000AkHQ-1uic for kexec@lists.infradead.org; Fri, 30 Oct 2026 03:41:11 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id DF606600E4; Fri, 30 Oct 2026 03:41:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF0391F0093A; Fri, 30 Oct 2026 03:41:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793331670; bh=h3wIpY6vHa1RWex7hAszkeoTd27MCJIXZVzzxBnwc/g=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=CBY4cN8rY6OoX25Sb46cpjYcjtx+96UO7PE2C8dcFhDa5iEyKG/jQXLVXnuupS1zJ cyCqIx8TKhOSv18T8DnIKNH/jXNSBIQ6mZyT5Xv5Fbpi7QhMv4gp4KfscAP0Tti0VQ W0BNx5jQcFJeZgcgyyCQXl8GEhvO3ScenA39n6FByExdi8VhYbpLPKZSxHe1+o2umX vpbSxLT338Qx55OKvYdQBv9WgcfdAI42/atrt2mF1Cpm15oSGUR89p/Ms+42RVoy7m 4T3PSNhsBqAwBNofo5wi7yjzBTOgERJWM2p7gfVivdf3HDu94baYIyYdXimoKDR385 au10aj1iCSL/w== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 18/47] mm/khugepaged: check if PTE table is empty in try_collapse_pte_mapped_thp() 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-v2-18-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> <20261029-fixes_core-v2-18-a64ce7f83abb@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 30 Oct 2026 03:41:07 +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: > The existing code is rather horrible and already resulted in bugs in the > past: we special-case UFFD inserting anonymous folios by grabbing the PMD > lock early, but ignore any other markers (guard, poison through uffd) that > could have been inserted into the page table in the meantime, effectively > dropping them. >=20 > Let's just unify and simplify the locking: try to grab the PMD table > lock and if that fails, flush the TLB, drop the PTE lock, take PT locks in > the right order and check if the page table is still empty. >=20 > We still perform the heavy lifting (zapping the folio ptes) under PTE tab= le > lock only. >=20 > Include for now, as x86's flush_tlb_range() macro > depends on hugetlb helpers. This dependency needs a separate cleanup. >=20 > Both issues this fixes are rather corner cases. Let's not CC stable for > now. >=20 > Fixes: f807123d578d ("mm: allow guard regions in file-backed and read-onl= y mappings") > Fixes: 1043173eb5eb ("mm/khugepaged: collapse_pte_mapped_thp() with mmap_= read_lock()") > Tested-by: Gregory Price (Meta) > Reviewed-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=3D18