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Date: Mon, 2 Dec 2013 08:40:39 -0800
From: Greg KH <greg@kroah.com>
To: Christoph Lameter <cl@linux.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
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        netdev@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: netfilter: active obj WARN when cleaning up
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On Mon, Dec 02, 2013 at 04:33:20PM +0000, Christoph Lameter wrote:
> On Wed, 27 Nov 2013, Greg KH wrote:
> 
> > Just make the kobject "dynamic" instead of embedded in struct kmem_cache
> > and all will be fine.  I can't believe this code has been broken for
> > this long.
> 
> The slub code is was designed to use an embedded structure since we
> only get the kobj  pointer passed to us from sysfs. If kobj is not
> embedded then how can we get from the sysfs object to the kmem_cache
> structure from the sysfs callbacks? Sysfs was designed to have embedded
> objects as far as I can recall.

Yes, it's designed to have embedded objects, so then use it that way and
clean up the structure when the kobject goes away.  Don't use a
different reference count for your structure than the one in the kobject
and think that all will be fine.

greg k-h