From: Nitin Gupta <ngupta@vflare.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Seth Jennings <sjenning@linux.vnet.ibm.com>,
Dan Magenheimer <dan.magenheimer@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/4] zsmalloc use zs_handle instead of void *
Date: Thu, 10 May 2012 10:47:31 -0400 [thread overview]
Message-ID: <4FABD503.4030808@vflare.org> (raw)
In-Reply-To: <20120510140215.GC26152@phenom.dumpdata.com>
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<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.
>>
>>
>> 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 {
> 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.
We could 'memcpy' struct zs to a void * and then store that directly 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
next prev parent reply other threads:[~2012-05-10 14:47 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-03 6:40 [PATCH 1/4] zsmalloc: rename zspage_order with zspage_pages Minchan Kim
2012-05-03 6:40 ` [PATCH 2/4] zsmalloc: add/fix function comment Minchan Kim
2012-05-03 13:19 ` Nitin Gupta
2012-05-03 6:40 ` [PATCH 3/4] zsmalloc use zs_handle instead of void * Minchan Kim
2012-05-03 13:32 ` Nitin Gupta
2012-05-03 15:23 ` Seth Jennings
2012-05-04 2:24 ` Minchan Kim
2012-05-07 15:01 ` Seth Jennings
2012-05-09 20:19 ` Greg Kroah-Hartman
2012-05-10 2:03 ` Minchan Kim
2012-05-10 14:02 ` Konrad Rzeszutek Wilk
2012-05-10 14:12 ` Greg Kroah-Hartman
2012-05-10 14:47 ` Nitin Gupta [this message]
2012-05-10 15:00 ` Minchan Kim
2012-05-10 15:11 ` Seth Jennings
2012-05-10 15:19 ` Minchan Kim
2012-05-10 15:19 ` Greg Kroah-Hartman
2012-05-10 16:29 ` Nitin Gupta
2012-05-10 16:44 ` Greg Kroah-Hartman
2012-05-10 17:24 ` Nitin Gupta
2012-05-10 17:33 ` Konrad Rzeszutek Wilk
2012-05-10 23:24 ` Minchan Kim
2012-05-10 23:50 ` Dan Magenheimer
2012-05-11 0:14 ` Minchan Kim
2012-05-11 16:31 ` Dan Magenheimer
2012-05-11 19:29 ` Konrad Rzeszutek Wilk
2012-05-11 21:49 ` Seth Jennings
2012-05-14 2:26 ` Minchan Kim
2012-05-11 19:28 ` Konrad Rzeszutek Wilk
2012-05-14 2:18 ` Minchan Kim
2012-05-15 1:57 ` Nitin Gupta
2012-05-15 2:21 ` Minchan Kim
2012-05-15 15:04 ` Konrad Rzeszutek Wilk
2012-05-16 1:36 ` Minchan Kim
2012-05-16 11:06 ` Konrad Rzeszutek Wilk
2012-05-03 6:40 ` [PATCH 4/4] zsmalloc: zsmalloc: align cache line size Minchan Kim
2012-05-03 13:58 ` Nitin Gupta
2012-05-04 2:27 ` Minchan Kim
2012-05-07 7:41 ` Pekka Enberg
2012-05-07 12:40 ` Nitin Gupta
2012-05-08 1:34 ` Minchan Kim
2012-05-08 14:00 ` Dan Magenheimer
2012-05-09 0:58 ` Minchan Kim
2012-05-09 3:08 ` Dan Magenheimer
2012-05-09 4:07 ` Minchan Kim
2012-05-11 0:03 ` Dan Magenheimer
2012-05-11 0:25 ` Minchan Kim
2012-05-11 19:06 ` Konrad Rzeszutek Wilk
2012-05-14 1:55 ` Minchan Kim
2012-05-15 15:18 ` Konrad Rzeszutek Wilk
2012-05-16 1:44 ` Minchan Kim
2012-05-03 13:18 ` [PATCH 1/4] zsmalloc: rename zspage_order with zspage_pages Nitin Gupta
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