From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753542AbYJ1NBI (ORCPT ); Tue, 28 Oct 2008 09:01:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751962AbYJ1NAz (ORCPT ); Tue, 28 Oct 2008 09:00:55 -0400 Received: from mtagate7.uk.ibm.com ([195.212.29.140]:43040 "EHLO mtagate7.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751917AbYJ1NAy (ORCPT ); Tue, 28 Oct 2008 09:00:54 -0400 Subject: Re: [PATCH] memory hotplug: fix page_zone() calculation in test_pages_isolated() From: Gerald Schaefer To: KAMEZAWA Hiroyuki Cc: Dave Hansen , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, y-goto@jp.fujitsu.com In-Reply-To: <20081028093224.a0de9f64.kamezawa.hiroyu@jp.fujitsu.com> References: <4905F114.3030406@de.ibm.com> <1225128359.12673.101.camel@nimitz> <1225130369.20384.33.camel@localhost.localdomain> <20081028093224.a0de9f64.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain Date: Tue, 28 Oct 2008 14:00:01 +0100 Message-Id: <1225198802.10037.7.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-8.el5_2.2) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-10-28 at 09:32 +0900, KAMEZAWA Hiroyuki wrote: > But > - "pfn" and "end_pfn" (and pfn in the middle of them) can be in different zone on strange machine. > > Now: test_pages_isolated() is called in following sequence. > > check_page_isolated() > walk_memory_resource() # read resource range and get start/end of pfn > -> chcek_page_isolated_cb() > -> test_page_isolated(). > > I think all pages within [start, end) passed to test_pages_isolated() should be in the same zone. > > please change this to > check_page_isolated() > walk_memory_resource() > -> check_page_isolated_cb() > -> walk_page_range_in_same_zone() # get page range in the same zone. > -> test_page_isolated(). > > Could you try ? There is already a "same zone" check at the beginning of offline_pages(): > if (!test_pages_in_a_zone(start_pfn, end_pfn)) > return -EINVAL; So we should be safe here, the only problem that I see is that my zone->lock patch in test_pages_isolated() is broken. As explained, the pfn used in my page_zone(pfn_to_page(pfn)) is >= end_pfn. I'll send a new patch to fix this, using __first_valid_page() again, as described in my reply to Daves mail. The only other solution that I see would be to remember the first/last !NULL page that was found inside the for() loop. Not sure which is better, but I think I like the first one more. Any other ideas? Thanks, Gerald