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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 A5E63C433E1 for ; Thu, 21 May 2020 09:36:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F483207D3 for ; Thu, 21 May 2020 09:36:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729008AbgEUJgM (ORCPT ); Thu, 21 May 2020 05:36:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:36876 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728720AbgEUJgL (ORCPT ); Thu, 21 May 2020 05:36:11 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 08C3FABE4; Thu, 21 May 2020 09:36:12 +0000 (UTC) Date: Thu, 21 May 2020 10:36:06 +0100 From: Mel Gorman To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, cai@lca.pw, mhocko@kernel.org, rppt@linux.ibm.com Subject: Re: [PATCH] mm/compaction: Fix the incorrect hole in fast_isolate_freepages() Message-ID: <20200521093606.GA7110@suse.de> References: <20200521014407.29690-1-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20200521014407.29690-1-bhe@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 21, 2020 at 09:44:07AM +0800, Baoquan He wrote: > After investigation, it turns out that this is introduced by commit of > linux-next: commit f6edbdb71877 ("mm: memmap_init: iterate over memblock > regions rather that check each PFN"). > > After investigation, it turns out that this is introduced by commit of > linux-next, the patch subject is: > "mm: memmap_init: iterate over memblock regions rather that check each PFN". > Some repetition here. I assume it's because the commit ID is not stable because it's in linux-next. > Qian added debugging code. The debugging log shows that the fault page is > 0x2a800000. From the system e820 map which is pasted at bottom, the page > is in e820 reserved range: > BIOS-e820: [mem 0x0000000029ffe000-0x000000002a80afff] reserved > And it's in section [0x28000000, 0x2fffffff]. In that secion, there are > several usable ranges and some e820 reserved ranges. > > For this kind of e820 reserved range, it won't be added to memblock allocator. > However, init_unavailable_mem() will initialize to add them into node 0, > zone 0. Why is it appropriate for init_unavailable_mem to add a e820 reserved range to the zone at all? The bug being triggered indicates there is a mismatch between the zone of a struct page and the PFN passed in. > Before that commit, later, memmap_init() will add e820 reserved > ranges into the zone where they are contained, because it can pass > the checking of early_pfn_valid() and early_pfn_in_nid(). In this case, > the e820 reserved range where fault page 0x2a800000 is located is added > into DMA32 zone. After that commit, the e820 reserved rgions are kept > in node 0, zone 0, since we iterate over memblock regions to iniatialize > in memmap_init() instead, their node and zone won't be changed. > This implies that we have struct pages that should never be used (e820 reserved) but exist somehow in a zone range but with broken linkages to their node and zone. > Reported-by: Qian Cai > Signed-off-by: Baoquan He > --- > mm/compaction.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 67fd317f78db..9ce4cff4d407 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1418,7 +1418,9 @@ fast_isolate_freepages(struct compact_control *cc) > cc->free_pfn = highest; > } else { > if (cc->direct_compaction && pfn_valid(min_pfn)) { > - page = pfn_to_page(min_pfn); > + page = pageblock_pfn_to_page(min_pfn, > + pageblock_end_pfn(min_pfn), > + cc->zone); > cc->free_pfn = min_pfn; > } > } Why is the correct fix not to avoid creating struct pages for e820 ranges and make sure that struct pages that are reachable have proper node and zone linkages? -- Mel Gorman SUSE Labs