Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759752Ab3E3Ayr (ORCPT ); Wed, 29 May 2013 20:54:47 -0400 Received: from mail-pd0-f179.google.com ([209.85.192.179]:36176 "EHLO mail-pd0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759639Ab3E3Ayj (ORCPT ); Wed, 29 May 2013 20:54:39 -0400 Message-ID: <51A6A34B.6020907@gmail.com> Date: Thu, 30 May 2013 08:54:35 +0800 From: Jiang Liu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130404 Thunderbird/17.0.5 MIME-Version: 1.0 To: Cody P Schafer CC: LKML , Linux MM , Andrew Morton Subject: Re: [PATCH] mm: sparse: use __aligned() instead of manual padding in mem_section References: <1369869279-20155-1-git-send-email-cody@linux.vnet.ibm.com> In-Reply-To: <1369869279-20155-1-git-send-email-cody@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1744 Lines: 50 On Thu 30 May 2013 07:14:39 AM CST, Cody P Schafer wrote: > Instead of leaving a trap for the next person who comes along and wants > to add something to mem_section, add an __aligned() and remove the > manual padding added for MEMCG. > > Signed-off-by: Cody P Schafer > --- > include/linux/mmzone.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > --- > > Also, does anyone know what causes this alignment to be required here? I found > this was breaking things in a patchset I'm working on (WARNs in sysfs code > about duplicate filenames when initing mem_sections). Adding some documentation > for the reason would be appreciated. Hi Cody, I think the alignment requirement is caused by the way the mem_section array is organized. Basically it requires that PAGE_SIZE could be divided by sizeof(struct mem_section). So your change seems risky too because it should be aligned to power of two instead of 2 * sizeof(long). Regards! Gerry > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 131989a..a8e8056 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1125,9 +1125,8 @@ struct mem_section { > * section. (see memcontrol.h/page_cgroup.h about this.) > */ > struct page_cgroup *page_cgroup; > - unsigned long pad; > #endif > -}; > +} __aligned(2 * sizeof(unsigned long)); > > #ifdef CONFIG_SPARSEMEM_EXTREME > #define SECTIONS_PER_ROOT (PAGE_SIZE / sizeof (struct mem_section)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/