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Date: Wed, 9 May 2012 13:19:18 -0700
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>,
        Nitin Gupta <ngupta@vflare.org>,
        Dan Magenheimer <dan.magenheimer@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH 3/4] zsmalloc use zs_handle instead of void *
Message-ID: <20120509201918.GA7288@kroah.com>
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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<dan.magenheimer@oracle.com>
> >>> Cc: Konrad Rzeszutek Wilk<konrad.wilk@oracle.com>
> >>> Signed-off-by: Minchan Kim<minchan@kernel.org>
> >>> ---
> >>>   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.

Vague "handles" are almost never what you want to do in Linux, sorry, I
can't take this patch.

greg k-h