From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3625BC64E7A for ; Thu, 3 Dec 2020 06:26:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D18C020705 for ; Thu, 3 Dec 2020 06:26:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728560AbgLCG0j (ORCPT ); Thu, 3 Dec 2020 01:26:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:46382 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725984AbgLCG0j (ORCPT ); Thu, 3 Dec 2020 01:26:39 -0500 Date: Thu, 3 Dec 2020 08:25:49 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1606976758; bh=fG6F0yV3WbLa0cb7k6rq9oA20/ozyUgqvrBOtlDU1Ck=; h=From:To:Cc:Subject:References:In-Reply-To:From; b=JfwqIdRZwhgbkHv64aE2ZfYC1P7LJZdagDQPvjet5qFdNAkcwqm9aZ4E4ZZoUaGiT eyhhz6kkFFkUzIHOexv+V2Det/UAEYMTqYSi4hLzqOwWcgbUOIqnzV4b1d3TQCG2gw Wt4N2mMFWU2lD4O1Np0G+sP/QxhQisLa10c5pyUkQHpLtx9hQBud7/qJ2cO17MKrYX ZHnyK6vBeb2emMHleGiyDEAdug+3wYEPdS2QnANlj2VwUjEyI81CKPRq7Nfp40hhuz KbcPZgneOOoRYMF+aTceHOEJ/rh59wri5D7D+BuxoR4Rdpo3c5XIH02VysDX9c3J16 P57gUw+KIoy0w== From: Mike Rapoport To: Andrew Morton Cc: linux-mm@kvack.org, Andrea Arcangeli , Baoquan He , David Hildenbrand , Mel Gorman , Michal Hocko , Mike Rapoport , Qian Cai , Vlastimil Babka , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: refactor initialization of stuct page for holes in memory layout Message-ID: <20201203062549.GG751215@kernel.org> References: <20201201181502.2340-1-rppt@kernel.org> <20201202154736.5799e01b4c27a75b98e863fc@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201202154736.5799e01b4c27a75b98e863fc@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 02, 2020 at 03:47:36PM -0800, Andrew Morton wrote: > On Tue, 1 Dec 2020 20:15:02 +0200 Mike Rapoport wrote: > > > From: Mike Rapoport > > > > There could be struct pages that are not backed by actual physical memory. > > This can happen when the actual memory bank is not a multiple of > > SECTION_SIZE or when an architecture does not register memory holes > > reserved by the firmware as memblock.memory. > > > > Such pages are currently initialized using init_unavailable_mem() function > > that iterated through PFNs in holes in memblock.memory and if there is a > > struct page corresponding to a PFN, the fields if this page are set to > > default values and it is marked as Reserved. > > > > init_unavailable_mem() does not take into account zone and node the page > > belongs to and sets both zone and node links in struct page to zero. > > > > On a system that has firmware reserved holes in a zone above ZONE_DMA, for > > instance in a configuration below: > > > > # grep -A1 E820 /proc/iomem > > 7a17b000-7a216fff : Unknown E820 type > > 7a217000-7bffffff : System RAM > > > > unset zone link in struct page will trigger > > > > VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); > > That sounds pretty serious. > > > because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone link in > > struct page) in the same pageblock. > > > > Interleave initialization of pages that correspond to holes with the > > initialization of memory map, so that zone and node information will be > > properly set on such pages. > > > > Should this be backported to -stable? If so, do we have a suitable Fixes:? Sorry, I forgot to add Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions rather that check each PFN") -- Sincerely yours, Mike.