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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 0861EC6369E for ; Wed, 2 Dec 2020 23:48:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB52821D93 for ; Wed, 2 Dec 2020 23:48:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728065AbgLBXsS (ORCPT ); Wed, 2 Dec 2020 18:48:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:45878 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726958AbgLBXsS (ORCPT ); Wed, 2 Dec 2020 18:48:18 -0500 Date: Wed, 2 Dec 2020 15:47:36 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1606952857; bh=9u2sLsqA/pgqgw1aASdJJWXFrLINqvAmzHh0/6/9ogo=; h=From:To:Cc:Subject:In-Reply-To:References:From; b=KGKt739KlwoUynzZmZtSCcV9nJh3WdbCt28K/PjS2aATmTdqX4KrUcbs+Ues9BUGG s5j32+z0hgdCndbzXWGbdl7kFu5dhH03Pg2eIwM3ogjo75yCEFJ1rvJUflEFLN8+3n 9BeEpoh99RcfbSeyj2j+y357sAqBk5OxNHV+zhU0= From: Andrew Morton To: Mike Rapoport 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: <20201202154736.5799e01b4c27a75b98e863fc@linux-foundation.org> In-Reply-To: <20201201181502.2340-1-rppt@kernel.org> References: <20201201181502.2340-1-rppt@kernel.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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:?