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Date: Wed, 21 Mar 2007 14:13:52 +0200
From: "Pekka Enberg" <penberg@cs.helsinki.fi>
To: "Jarek Poplawski" <jarkao2@o2.pl>
Subject: Re: [PATCH] slab: deal with NULL pointers passed to kmem_cache_free
Cc: "Eric Dumazet" <dada1@cosmosbay.com>,
       "Andrew Morton" <akpm@linux-foundation.org>, mpm@selenic.com,
       "Christoph Lameter" <clameter@sgi.com>, "ast@domdv.de" <ast@domdv.de>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On 3/21/07, Jarek Poplawski <jarkao2@o2.pl> wrote:
> I think Pekka was right (it looks he changed his mind now) something
> should be done here. I think something like this should be a minimum:
>
> BUG_ON(!objp || virt_to_cache(objp) != cachep);
>
> to show distinctly what's going on.

No, if we were to add a NULL check in kmem_cache_free(), it should
behave like kfree() does. Anyway, if you feel about this strongly I
suspect the best solution is to add a __kmem_cache_free which does
_not_ have the NULL check and convert those super-hot paths to use it.
Sort of what Andrew suggested already.