From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Snitzer <snitzer@redhat.com>
Subject: Re: dm: remove pointless comparison
Date: Tue, 7 Jan 2014 13:17:09 -0500
Message-ID: <20140107181708.GA8715@redhat.com>
References: <alpine.LRH.2.02.1401062249200.17811@file01.intranet.prod.int.rdu2.redhat.com>
	<20140107103930.GA11734@debian> <20140107155252.GB7983@redhat.com>
	<52CC392F.1070804@gmail.com>
Reply-To: device-mapper development <dm-devel@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <dm-devel-bounces@redhat.com>
Content-Disposition: inline
In-Reply-To: <52CC392F.1070804@gmail.com>
List-Unsubscribe: <https://www.redhat.com/mailman/options/dm-devel>,
	<mailto:dm-devel-request@redhat.com?subject=unsubscribe>
List-Archive: <https://www.redhat.com/archives/dm-devel>
List-Post: <mailto:dm-devel@redhat.com>
List-Help: <mailto:dm-devel-request@redhat.com?subject=help>
List-Subscribe: <https://www.redhat.com/mailman/listinfo/dm-devel>,
	<mailto:dm-devel-request@redhat.com?subject=subscribe>
Sender: dm-devel-bounces@redhat.com
Errors-To: dm-devel-bounces@redhat.com
To: Milan Broz <gmazyland@gmail.com>
Cc: device-mapper development <dm-devel@redhat.com>, Mikulas Patocka <mpatocka@redhat.com>, ejt@redhat.com, "Alasdair G. Kergon" <agk@redhat.com>
List-Id: dm-devel.ids

On Tue, Jan 07 2014 at 12:28pm -0500,
Milan Broz <gmazyland@gmail.com> wrote:

> On 01/07/2014 04:52 PM, Mike Snitzer wrote:
> > On Tue, Jan 07 2014 at  5:39am -0500,
> > Joe Thornber <thornber@redhat.com> wrote:
> > 
> >> On Mon, Jan 06, 2014 at 10:53:28PM -0500, Mikulas Patocka wrote:
> >>> Remove pointless comparison in dm_get_from_kobject. The comparison is
> >>> always true and the compiler optimizes it out anyway.
> >>>gmane.linux.kernel.device-mapper.devel
> >>> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> >>>
> >>> ---
> >>>  drivers/md/dm.c |    2 --
> >>>  1 file changed, 2 deletions(-)
> >>>
> >>> Index: linux-3.13-rc7/drivers/md/dm.c
> >>> ===================================================================
> >>> --- linux-3.13-rc7.orig/drivers/md/dm.c	2014-01-07 01:28:27.000000000 +0100
> >>> +++ linux-3.13-rc7/drivers/md/dm.c	2014-01-07 01:28:39.000000000 +0100
> >>> @@ -2922,8 +2922,6 @@ struct mapped_device *dm_get_from_kobjec
> >>>  	struct mapped_device *md;
> >>>  
> >>>  	md = container_of(kobj, struct mapped_device, kobj);
> >>> -	if (&md->kobj != kobj)
> >>> -		return NULL;
> >>
> >> What were they trying to check?  The compiler?
> >>
> > 
> > Milan's commit 784aae735d, and the current dm.c code, offers this
> > comment above dm_get_from_kobject:
> > 
> > /*
> >  * struct mapped_device should not be exported outside of dm.c
> >  * so use this check to verify that kobj is part of md structure
> >  */
> > 
> > I'm lacking the vision to _know_ why the kobject would suddenly be
> > outside of the mapped_device without us knowing via code change..
> > 
> > The check does seem overly cautious/useless (if we remove it the above
> > comment should be removed too).
> 
> Yes, please remove both :) The check doesn't make sense.

Ok, I'll take that as your Acked-by, thanks.