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=-6.0 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 A4ABCC43381 for ; Mon, 8 Feb 2021 21:43:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 664E564E9A for ; Mon, 8 Feb 2021 21:43:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236984AbhBHVnB (ORCPT ); Mon, 8 Feb 2021 16:43:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:60726 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234822AbhBHVLp (ORCPT ); Mon, 8 Feb 2021 16:11:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A6A8C64E45; Mon, 8 Feb 2021 21:11:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1612818662; bh=rw1M/5Z9nW1OXLXxGPke2t4Sf5KHR4/hWloUz77521A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=2a2mx7n3FKjwwpdOwk8iNmm4Q44kNg+z3ogc4HeFgLbmy/iFjO2aZGXrpgUNJf6hX pbfDUi8vHUc14crCNpbXM6YfZja8m7yxLirMvWPC459Gca3QYSBHJbxPKnewm5zxwu BHWTY6NSNGUbUWAvN+0tDNb9rRPaRu5tnWRc6TGQ= Date: Mon, 8 Feb 2021 13:11:00 -0800 From: Andrew Morton To: Mike Rapoport Cc: Andrea Arcangeli , Baoquan He , Borislav Petkov , Chris Wilson , David Hildenbrand , "H. Peter Anvin" , Ingo Molnar , Linus Torvalds , =?UTF-8?Q?=C5=81ukasz?= Majczak , Mel Gorman , Michal Hocko , Mike Rapoport , Qian Cai , "Sarvela, Tomi P" , Thomas Gleixner , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v5 1/1] mm: refactor initialization of struct page for holes in memory layout Message-Id: <20210208131100.7273d249a5d00cac0d247fcf@linux-foundation.org> In-Reply-To: <20210208110820.6269-1-rppt@kernel.org> References: <20210208110820.6269-1-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 Mon, 8 Feb 2021 13:08:20 +0200 Mike Rapoport wrote: > 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 iterates through PFNs in holes in memblock.memory and if there is a > struct page corresponding to a PFN, the fields of 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); > > because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone link > in struct page) in the same pageblock. > > ... > > > Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions rather > that check each PFN") What are your thoughts on the priority of this (rather large!) fix? Are such systems sufficiently common to warrant a 5.11 merge? -stable?