From: Minchan Kim <minchan@kernel.org>
To: Nitin Gupta <ngupta@vflare.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
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: Fri, 11 May 2012 00:00:42 +0900 [thread overview]
Message-ID: <20120510150042.GA2394@barrios> (raw)
In-Reply-To: <4FABD503.4030808@vflare.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<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 {
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
next prev parent reply other threads:[~2012-05-10 15:00 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
2012-05-10 15:00 ` Minchan Kim [this message]
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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