Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757948Ab2EJQ3s (ORCPT ); Thu, 10 May 2012 12:29:48 -0400 Received: from mail-yw0-f46.google.com ([209.85.213.46]:46048 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757759Ab2EJQ3o (ORCPT ); Thu, 10 May 2012 12:29:44 -0400 Message-ID: <4FABECF5.8040602@vflare.org> Date: Thu, 10 May 2012 12:29:41 -0400 From: Nitin Gupta User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Greg Kroah-Hartman CC: Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , Dan Magenheimer , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 3/4] zsmalloc use zs_handle instead of void * References: <1336027242-372-1-git-send-email-minchan@kernel.org> <1336027242-372-3-git-send-email-minchan@kernel.org> <4FA28907.9020300@vflare.org> <4FA2A2F0.3030509@linux.vnet.ibm.com> <4FA33DF6.8060107@kernel.org> <20120509201918.GA7288@kroah.com> <4FAB21E7.7020703@kernel.org> <20120510140215.GC26152@phenom.dumpdata.com> <4FABD503.4030808@vflare.org> <4FABDA9F.1000105@linux.vnet.ibm.com> <20120510151941.GA18302@kroah.com> In-Reply-To: <20120510151941.GA18302@kroah.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1584 Lines: 45 On 5/10/12 11:19 AM, Greg Kroah-Hartman wrote: > On Thu, May 10, 2012 at 10:11:27AM -0500, Seth Jennings wrote: >> On 05/10/2012 09:47 AM, Nitin Gupta wrote: >> >>> On 5/10/12 10:02 AM, Konrad Rzeszutek Wilk wrote: >>>> struct zs { >>>> void *ptr; >>>> }; >>>> >>>> And pass that structure around? >>>> >>> >>> A minor problem is that we store this handle value in a radix tree node. >>> If we wrap it as a struct, then we will not be able to store it directly >>> in the node -- the node will have to point to a 'struct zs'. This will >>> unnecessarily waste sizeof(void *) for every object stored. >> >> >> I don't think so. You can use the fact that for a struct zs var,&var >> and&var->ptr are the same. >> >> For the structure above: >> >> void * zs_to_void(struct zs *p) { return p->ptr; } >> struct zs * void_to_zs(void *p) { return (struct zs *)p; } > > Do like what the rest of the kernel does and pass around *ptr and use > container_of to get 'struct zs'. Yes, they resolve to the same pointer > right now, but you shouldn't "expect" to to be the same. > > I think we can just use unsigned long as zs handle type since all we have to do is tell the user that the returned value is not a pointer. This will be less pretty than a typedef but still better than a single entry struct + container_of stuff. Thanks, Nitin -- 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/