linux-kernel - Re: [PATCH] slab: deal with NULL pointers passed to kmem_cache

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Date:	Mon, 19 Mar 2007 23:25:36 +0200 (EET)
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	akpm@...ux-foundation.org, mpm@...enic.com
CC:	"Christoph Lameter" <clameter@....com>,
	"Pekka J Enberg" <penberg@...helsinki.fi>,
	"ast@...dv.de" <ast@...dv.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slab: deal with NULL pointers passed to kmem_cache_free


On 3/19/2007, "Andrew Morton" <akpm@...ux-foundation.org> wrote:
> Would prefer to do:
> 
> static inline void kmem_cache_free_if_not_null(struct kmem_cache *cachep,
> 						void *objp)
> {
> 	if (objp)
> 		kmem_cache_free(cachep, objp);
> }
> 
> so that we don't add extra overhead to all the thousands of existing,
> well-behaved callsites.

That bloats kernel text all the same so it's much cleaner to just make
the callers explicitly check for NULL then. That said, I'm sorry but I
just don't buy the "overhead" part of your argument since it's one
branch and no extra data cache pressure especially as we're already
doing the BUG_ON and page flag checking.

But, since you're NAKing my patch, we need to get the mempool for from
the original thread in to fix the oops.

                                     Pekka
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