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Date: Fri, 25 Apr 2014 00:49:41 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>, Jan Kara <jack@suse.cz>,
        Dave Jones <davej@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Glauber Costa <glommer@parallels.com>,
        Christoph Lameter <cl@linux.com>
Subject: Re: fs: dcookie: freeing active timer
Message-ID: <20140424234941.GA18016@ZenIV.linux.org.uk>
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On Thu, Apr 24, 2014 at 10:55:58PM +0100, Al Viro wrote:
> On Thu, Apr 24, 2014 at 01:34:14PM -0400, Sasha Levin wrote:
> 
> > > Why does that code bother with destroying/creating that sucker dynamically?
> > > Is there any point at all?
> > 
> > I'm not sure about the dynamic allocation part, but I fear that if we just
> > switch to using static allocations it'll hide the underlying issue that
> > triggered this bug instead of fixing it.
> 
> FWIW, slub.c variant of kmem_cache_destroy() is buggered - struct kobject
> embedded into struct kmem_cache, its ktype is slab_ktype, which has
> NULL ->release()...

BTW, if your config has CONFIG_DEBUG_KOBJECT_RELEASE, that's exactly where
that warning comes from.  Got broken by commit b7454a,
Author: Glauber Costa <glommer@parallels.com>
Date:   Fri Oct 19 18:20:25 2012 +0400

    mm/sl[au]b: Move slabinfo processing to slab_common.c

We *do* need ->release().  Greg and guilty parties Cc'd...