linux-kernel - Re: [bug] SCSI/SLUB - latest -git: WARNING: at mm/slub.c:2443 kmem_cache_destroy, scsi_put_host_cmd

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Message-Id: <1208871600.3105.1.camel@localhost.localdomain>
Date:	Tue, 22 Apr 2008 08:39:59 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Christoph Lameter <clameter@....com>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [bug] SCSI/SLUB - latest -git: WARNING: at mm/slub.c:2443
	kmem_cache_destroy, scsi_put_host_cmd_pool()

On Tue, 2008-04-22 at 15:10 +0200, Ingo Molnar wrote:
> * James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> 
> > Thanks ... it looks like we may have trouble from devices that alter 
> > the unchecked isa dma flag after scsi_host_alloc.  The guilty parties 
> > appear to be gdth, eata, u14-34f, ultrastor, BusLogic and advansys.
> > 
> > The trouble is that if you alloc the host with it one way and free it 
> > with it the other, the wrong freelist is used and the ref counts are 
> > invalid.
> > 
> > Try this pseudo fix: it avoids allocating the freelist until add time 
> > (by which time they should all have fixed the flag).  It still doesn't 
> > change the fact that the host is allocated in the wrong region, but 
> > that shouldn't matter too much.
> 
> ok - do you intend to push this pseudo-fix upstream? If yes then please 
> consider it fixed as far as i'm concerned - i'll re-reply if the warning 
> resurfaces (it wasnt lethal to the bootup otherwise). Or if you've got 
> some other approach/fix then i can test that too.

It's certainly the line of least resistance.  The more correct fix would
be to haul unchecked_isa_dma out of the host and make everything use the
template, so it becomes immutable (as it should be).  However, that's a
lot of work and given that Andi's gunning for unchecked_isa_dma anyway,
probably not worth it.

So, unless I think of something better in the next few days, this is the
way I'll fix it.

James


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