Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760023Ab2EJPTr (ORCPT ); Thu, 10 May 2012 11:19:47 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:45223 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757805Ab2EJPTp (ORCPT ); Thu, 10 May 2012 11:19:45 -0400 Date: Thu, 10 May 2012 08:19:41 -0700 From: Greg Kroah-Hartman To: Seth Jennings Cc: Nitin Gupta , 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 * Message-ID: <20120510151941.GA18302@kroah.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FABDA9F.1000105@linux.vnet.ibm.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 Content-Length: 1265 Lines: 35 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. greg k-h -- 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/