From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1525519-1519995688-2-2885339196326040829 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1519995687; b=rvbwnXz6sYxL9E4hgC6AF1Eg3i3jYY0hb1OWFqsc8hgR4Om rKFYb8JsR+oExHbdElYBQhf7Cv086u+Mg/DA+QU8vvARKQidO7srCaru+4TpdUNn K9EhRwml/XxIfqkI1Yn4dE0kgE8MfR0BPUkIYhDEk3bM7KVa0ul8ow7rmcLDYUqY qvOSwq+RxIeJ5lKRcbvflzt5OJHfeKy5qg+xUHvBqQl7yC39QbLjCdKS9Dq8pPPj k7be8KO64UChRBmXtqWubYc2fp2He1KPR/ArrQVcjqhWcK70LGFLvQVnjAmQ8xTM XAsDwwE3L3He7JM2a0gA0/p2G9NIgTXMPC7bJ3g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1519995687; bh=Yzu+K66kupk8PnCvbdm/1b6r4z f2EbSLlkDB10TTyrU=; b=QQSSw5oAqEqCbMtmfD6aVGQL2p2pJSwMxpwRWRTdsm J45x7XEMnNWsRBMwiXII+sLd74y/57xeQ68aUC4crBomW6H69U62tIaNECPjv0vK N/UGpXK3X98/5q4Ly74qnBRyYosTgo98Y6D4sWU8A4305WcblegSsaf0Oj/pnA9Z Bnyv/3UiEe3EWhy7lxe7ebXIVGCGwp2QSGtRYXIrnecLYI57MKZPWdjo3IcrTdSd xFl+aI6CljL9cA+l131IBKkeGFky17aioeoimpRG7t2i0/htkSixC/PjqKzDqcbv J2yPyGghnyvo4vJxrRAkdhXM7xPHX/zX69ybr+xkhq0w== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=kernel.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=orgdomain_pass; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=kernel.org header.result=pass header_is_org_domain=yes Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=kernel.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=orgdomain_pass; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=kernel.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422981AbeCBNBY (ORCPT ); Fri, 2 Mar 2018 08:01:24 -0500 Received: from mx2.suse.de ([195.135.220.15]:50396 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1164700AbeCBNBW (ORCPT ); Fri, 2 Mar 2018 08:01:22 -0500 Date: Fri, 2 Mar 2018 14:01:20 +0100 From: Michal Hocko To: Daniel Vacek Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Mel Gorman , Pavel Tatashin , Paul Burton , stable@vger.kernel.org Subject: Re: [PATCH] mm/page_alloc: fix memmap_init_zone pageblock alignment Message-ID: <20180302130052.GN15057@dhcp22.suse.cz> References: <1519908465-12328-1-git-send-email-neelx@redhat.com> <20180301131033.GH15057@dhcp22.suse.cz> <20180301152729.GM15057@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.3 (2018-01-21) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Thu 01-03-18 17:20:04, Daniel Vacek wrote: > On Thu, Mar 1, 2018 at 4:27 PM, Michal Hocko wrote: > > On Thu 01-03-18 16:09:35, Daniel Vacek wrote: > > [...] > >> $ grep 7b7ff000 /proc/iomem > >> 7b7ff000-7b7fffff : System RAM > > [...] > >> After commit b92df1de5d28 machine eventually crashes with: > >> > >> BUG at mm/page_alloc.c:1913 > >> > >> > VM_BUG_ON(page_zone(start_page) != page_zone(end_page)); > > > > This is an important information that should be in the changelog. > > And that's exactly what my seven very first words tried to express in > human readable form instead of mechanically pasting the source code. I > guess that's a matter of preference. Though I see grepping later can > be an issue here. Do not get me wrong I do not want to nag just for fun of it. The changelog should be really clear about the problem. What might be clear to you based on the debugging might not be so clear to others. And the struct page initialization code is far from trivial especially when we have different alignment requirements by the memory model and the page allocator. Therefore being as clear as possible is really valuable. So I would really love to see the changelog to contain. - What is going on - VM_BUG_ON in move_freepages along with the crash report - memory ranges exported by BIOS/FW - explain why is the pageblock alignment the proper one. How does the range look from the memory section POV (with SPARSEMEM). - What about those unaligned pages which are not backed by any memory? Are they reserved so that they will never get used? And just to be clear. I am not saying your patch is wrong. It just raises more questions than answers and I suspect it just papers over some more fundamental problem. I might be clearly wrong and I cannot deserve this more time for the next week because I will be offline but I would _really_ appreciate if this all got explained. Thanks! -- Michal Hocko SUSE Labs