From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759814Ab2EJPAy (ORCPT ); Thu, 10 May 2012 11:00:54 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:35438 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759753Ab2EJPAx (ORCPT ); Thu, 10 May 2012 11:00:53 -0400 Date: Fri, 11 May 2012 00:00:42 +0900 From: Minchan Kim To: Nitin Gupta Cc: Konrad Rzeszutek Wilk , Minchan Kim , Greg Kroah-Hartman , Seth Jennings , 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: <20120510150042.GA2394@barrios> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FABD503.4030808@vflare.org> 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 Thu, May 10, 2012 at 10:47:31AM -0400, Nitin Gupta wrote: > On 5/10/12 10:02 AM, Konrad Rzeszutek Wilk wrote: > >On Thu, May 10, 2012 at 11:03:19AM +0900, Minchan Kim wrote: > >>On 05/10/2012 05:19 AM, Greg Kroah-Hartman wrote: > >> > >>>On Fri, May 04, 2012 at 11:24:54AM +0900, Minchan Kim wrote: > >>>>On 05/04/2012 12:23 AM, Seth Jennings wrote: > >>>> > >>>>>On 05/03/2012 08:32 AM, Nitin Gupta wrote: > >>>>> > >>>>>>On 5/3/12 2:40 AM, Minchan Kim wrote: > >>>>>>>We should use zs_handle instead of void * to avoid any > >>>>>>>confusion. Without this, users may just treat zs_malloc return value as > >>>>>>>a pointer and try to deference it. > >>>>>>> > >>>>>>>Cc: Dan Magenheimer > >>>>>>>Cc: Konrad Rzeszutek Wilk > >>>>>>>Signed-off-by: Minchan Kim > >>>>>>>--- > >>>>>>> drivers/staging/zcache/zcache-main.c | 8 ++++---- > >>>>>>> drivers/staging/zram/zram_drv.c | 8 ++++---- > >>>>>>> drivers/staging/zram/zram_drv.h | 2 +- > >>>>>>> drivers/staging/zsmalloc/zsmalloc-main.c | 28 > >>>>>>>++++++++++++++-------------- > >>>>>>> drivers/staging/zsmalloc/zsmalloc.h | 15 +++++++++++---- > >>>>>>> 5 files changed, 34 insertions(+), 27 deletions(-) > >>>>>> > >>>>>>This was a long pending change. Thanks! > >>>>> > >>>>> > >>>>>The reason I hadn't done it before is that it introduces a checkpatch > >>>>>warning: > >>>>> > >>>>>WARNING: do not add new typedefs > >>>>>#303: FILE: drivers/staging/zsmalloc/zsmalloc.h:19: > >>>>>+typedef void * zs_handle; > >>>>> > >>>> > >>>> > >>>>Yes. I did it but I think we are (a) of chapter 5: Typedefs in Documentation/CodingStyle. > >>>> > >>>> (a) totally opaque objects (where the typedef is actively used to _hide_ > >>>> what the object is). > >>>> > >>>>No? > >>> > >>>No. > >>> > >>>Don't add new typedefs to the kernel. Just use a structure if you need > >>>to. > >> > >> > >>I tried it but failed because there were already tightly coupling between [zcache|zram] > >>and zsmalloc. > >>They already knows handle's internal well so they used it as pointer, even zcache keeps > >>handle's value as some key in tmem_put and tmem_get > >>AFAIK, ramster also will use zsmalloc sooner or later and add more coupling codes. Sigh. > >>Please fix it as soon as possible. > >> > >>Dan, Seth > >>Any ideas? > > > >struct zs { I like struct zs_handle. > > 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 That was my point and I think it's not minor problem. > zs'. This will unnecessarily waste sizeof(void *) for every object > stored. > > We could 'memcpy' struct zs to a void * and then store that directly I don't like it because it still coupled with zsmalloc which means zcache already know zs's internal so we should avoid it. > in the radix node but not sure if that would be less ugly than just > returning the handle as a void * as is done currently. > > Thanks, > Nitin