From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 41D366B00AC for ; Wed, 15 Dec 2010 19:13:02 -0500 (EST) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id oBG0Cww7024895 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 16 Dec 2010 09:12:58 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 5A6A645DE67 for ; Thu, 16 Dec 2010 09:12:58 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 3763545DE68 for ; Thu, 16 Dec 2010 09:12:58 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 269461DB803C for ; Thu, 16 Dec 2010 09:12:58 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id E95151DB803B for ; Thu, 16 Dec 2010 09:12:57 +0900 (JST) Date: Thu, 16 Dec 2010 09:06:57 +0900 From: KAMEZAWA Hiroyuki Subject: Re: PROBLEM: __offline_isolated_pages may offline too many pages Message-Id: <20101216090657.9d3aaa4c.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <4D08899F.4050502@akana.de> References: <4D0786D3.7070007@akana.de> <20101215092134.e2c8849f.kamezawa.hiroyu@jp.fujitsu.com> <4D08899F.4050502@akana.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Ingo Korb Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mel@csn.ul.ie, cl@linux-foundation.org, yinghai@kernel.org, andi.kleen@intel.com, linux-kernel@vger.kernel.org"akpm@linux-foundation.org" List-ID: On Wed, 15 Dec 2010 10:25:51 +0100 Ingo Korb wrote: > On 15.12.2010 01:21, KAMEZAWA Hiroyuki wrote: > > > It's designed for offline memory section> MAX_ORDER. pageblock_nr_pages > > is tend to be smaller than that. > > > > Do you see the problem with _exsisting_ user interface of memory hotplug ? > > I think we have no control other than memory section. > > The existing, exported interface (remove_memory() - the check itself is > in offline_pages()) only checks if both start and end of the > to-be-removed block are aligned to pageblock_nr_pages. As you noted the > actual size and alignment requirements in __offline_isolated_pages can > be larger that that, so I think the checks in offline_pages() should be > changed (if 1<= pageblock_nr_pages) or extended > (if there can be any relation between the two). > Ok, maybe my mistake. This is a fix. Thank you for reporting. == offline_pages()'s sanity check of given range is wrong. It should be aligned to MAX_ORDER. Current exsiting caller uses SECTION_SIZE alignment, so this change has no influence to exsisting callers. Reported-by: Ingo Korb Signed-off-by: KAMEZAWA Hiroyuki --- mm/memory_hotplug.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) Index: linux-2.6.37-rc5/mm/memory_hotplug.c =================================================================== --- linux-2.6.37-rc5.orig/mm/memory_hotplug.c +++ linux-2.6.37-rc5/mm/memory_hotplug.c @@ -798,10 +798,14 @@ static int offline_pages(unsigned long s struct memory_notify arg; BUG_ON(start_pfn >= end_pfn); - /* at least, alignment against pageblock is necessary */ - if (!IS_ALIGNED(start_pfn, pageblock_nr_pages)) + /* + * Considering buddy allocator which joins nearby pages, the range + * in offline should be aligned to MAX_ORDER. If not, isolated + * page will be joined to other (not isolated) pages. + */ + if (!IS_ALIGNED(start_pfn, MAX_ORDER_NR_PAGES)) return -EINVAL; - if (!IS_ALIGNED(end_pfn, pageblock_nr_pages)) + if (!IS_ALIGNED(end_pfn, MAX_ORDER_NR_PAGES)) return -EINVAL; /* This makes hotplug much easier...and readable. we assume this for now. .*/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org