From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755068Ab2HaVah (ORCPT ); Fri, 31 Aug 2012 17:30:37 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:50748 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754878Ab2HaVae (ORCPT ); Fri, 31 Aug 2012 17:30:34 -0400 Date: Fri, 31 Aug 2012 14:30:32 -0700 From: Andrew Morton To: wency@cn.fujitsu.com Cc: x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org, rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, benh@kernel.crashing.org, paulus@samba.org, cl@linux.com, minchan.kim@gmail.com, kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com Subject: Re: [RFC v8 PATCH 13/20] memory-hotplug: check page type in get_page_bootmem Message-Id: <20120831143032.1343e99a.akpm@linux-foundation.org> In-Reply-To: <1346148027-24468-14-git-send-email-wency@cn.fujitsu.com> References: <1346148027-24468-1-git-send-email-wency@cn.fujitsu.com> <1346148027-24468-14-git-send-email-wency@cn.fujitsu.com> 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 Tue, 28 Aug 2012 18:00:20 +0800 wency@cn.fujitsu.com wrote: > From: Yasuaki Ishimatsu > > There is a possibility that get_page_bootmem() is called to the same page many > times. So when get_page_bootmem is called to the same page, the function only > increments page->_count. I really don't understand this explanation, even after having looked at the code. Can you please have another attempt at the changelog? > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -95,10 +95,17 @@ static void release_memory_resource(struct resource *res) > static void get_page_bootmem(unsigned long info, struct page *page, > unsigned long type) > { > - page->lru.next = (struct list_head *) type; > - SetPagePrivate(page); > - set_page_private(page, info); > - atomic_inc(&page->_count); > + unsigned long page_type; > + > + page_type = (unsigned long) page->lru.next; > + if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE || > + page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){ > + page->lru.next = (struct list_head *) type; > + SetPagePrivate(page); > + set_page_private(page, info); > + atomic_inc(&page->_count); > + } else > + atomic_inc(&page->_count); > } And a code comment which explains what is going on would be good. As is always the case ;)