From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753227Ab1JJWAn (ORCPT ); Mon, 10 Oct 2011 18:00:43 -0400 Received: from mail-yw0-f46.google.com ([209.85.213.46]:43680 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752546Ab1JJWAm (ORCPT ); Mon, 10 Oct 2011 18:00:42 -0400 Date: Mon, 10 Oct 2011 15:00:38 -0700 From: Andrew Morton To: Mel Gorman Cc: linux-mm , LKML , nfont@linux.vnet.ibm.com, KAMEZAWA Hiroyuki , Greg KH Subject: Re: [PATCH] mm: memory hotplug: Check if pages are correctly reserved on a per-section basis Message-Id: <20111010150038.ac161977.akpm@linux-foundation.org> In-Reply-To: <20111010071119.GE6418@suse.de> References: <20111010071119.GE6418@suse.de> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 Oct 2011 08:11:19 +0100 Mel Gorman wrote: > It is expected that memory being brought online is PageReserved > similar to what happens when the page allocator is being brought up. > Memory is onlined in "memory blocks" which consist of one or more > sections. Unfortunately, the code that verifies PageReserved is > currently assuming that the memmap backing all these pages is virtually > contiguous which is only the case when CONFIG_SPARSEMEM_VMEMMAP is set. > As a result, memory hot-add is failing on !VMEMMAP configurations > with the message; > > kernel: section number XXX page number 256 not reserved, was it already online? > > This patch updates the PageReserved check to lookup struct page once > per section to guarantee the correct struct page is being checked. > Nathan's earlier version of this patch is already in linux-next, via Greg. We should drop the old version and get the new one merged instead.