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=-6.6 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 EFF3AC433DB for ; Mon, 8 Feb 2021 21:28:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A574A64E26 for ; Mon, 8 Feb 2021 21:28:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236349AbhBHV1d (ORCPT ); Mon, 8 Feb 2021 16:27:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:35390 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236257AbhBHV0T (ORCPT ); Mon, 8 Feb 2021 16:26:19 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 023D364E6F; Mon, 8 Feb 2021 21:25:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612819538; bh=ibRblMMQB/f4N6UUddTxgf3Y0DdL2/6jIMsoXEp/dFU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EbeA5IstB6PsRvXyj6rFpshYxdeBcj7ak4hAm+xhqzO9/xK16bZnvJsymuZuJtfaU 6C4vzGBY4ceak1voPKgvAzKTj1zqZqB4mXDsyht+FHrCYclZFOTikE/XisjmfEXoaN GYKLmW76MK5fY9SlAoS5leUt1F3HQxe9AU++M5qJwXQkISykZiJHQBGGq+cfFuli4h lMGYthqSk9gHiuxIosF7L/uqZRRbdyGLGpC/8C6KMgXJQmQIqHMhMS7drLlrrCYYmG iHatanR76Pk54PBvSG4VzKTs0W3yzCufp9S9+zEWTj8rkBoX5+AWPhx0sqV6LTkuh1 NHdlFm3chD6YA== Date: Mon, 8 Feb 2021 23:25:26 +0200 From: Mike Rapoport To: Andrew Morton 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: <20210208212526.GW242749@kernel.org> References: <20210208110820.6269-1-rppt@kernel.org> <20210208131100.7273d249a5d00cac0d247fcf@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210208131100.7273d249a5d00cac0d247fcf@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Feb 08, 2021 at 01:11:00PM -0800, Andrew Morton wrote: > 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? I don't know how common are such systems, but the bug is exposed only for builds with DEBUG_VM=y, so after problems with previous versions discovered by various CI systems I'd say to hold it off till 5.11 is out. If this time the fix works it'll make it to -stable anyway :) -- Sincerely yours, Mike.