From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754892Ab3ADO4m (ORCPT ); Fri, 4 Jan 2013 09:56:42 -0500 Received: from mail-qc0-f171.google.com ([209.85.216.171]:51710 "EHLO mail-qc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754818Ab3ADO4j (ORCPT ); Fri, 4 Jan 2013 09:56:39 -0500 Date: Fri, 4 Jan 2013 09:56:35 -0500 From: Tejun Heo To: Lin Feng Cc: akpm@linux-foundation.org, mingo@kernel.org, yinghai@kernel.org, liwanp@linux.vnet.ibm.com, benh@kernel.crashing.org, tangchen@cn.fujitsu.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm: memblock: fix wrong memmove size in memblock_merge_regions() Message-ID: <20130104145635.GA15633@mtj.dyndns.org> References: <1357290650-25544-1-git-send-email-linfeng@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1357290650-25544-1-git-send-email-linfeng@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 04, 2013 at 05:10:50PM +0800, Lin Feng wrote: > The memmove span covers from (next+1) to the end of the array, and the index > of next is (i+1), so the index of (next+1) is (i+2). So the size of remaining > array elements is (type->cnt - (i + 2)). > > PS. It seems that memblock_merge_regions() could be made some improvement: > we need't memmove the remaining array elements until we find a none-mergable > element, but now we memmove everytime we find a neighboring compatible region. > I'm not sure if the trial is worth though. > > Cc: Tejun Heo > Signed-off-by: Lin Feng > --- > mm/memblock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index 6259055..85ce056 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -314,7 +314,7 @@ static void __init_memblock memblock_merge_regions(struct memblock_type *type) > } > > this->size += next->size; > - memmove(next, next + 1, (type->cnt - (i + 1)) * sizeof(*next)); > + memmove(next, next + 1, (type->cnt - (i + 2)) * sizeof(*next)); Heh, that's confusing. Nice catch. Can you please also add a comment explaning the index so that it's less confusing for the future readers? Thanks. -- tejun