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Date: Wed, 21 Feb 2007 09:53:15 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Pekka J Enberg <penberg@cs.helsinki.fi>
cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       jsipek@fsl.cs.sunysb.edu, unionfs@filesystems.org, bunk@stusta.de,
       hooanon05@yahoo.co.jp
Subject: Re: [PATCH 1/3] slab: introduce krealloc
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On Wed, 21 Feb 2007, Pekka J Enberg wrote:

> +void *krealloc(const void *p, size_t new_size, gfp_t flags)
> +{
> +	void *ret;
> +
> +	if (unlikely(!p))
> +		return kmalloc_track_caller(new_size, flags);
> +
> +	if (unlikely(!new_size)) {
> +		kfree(p);
> +		return NULL;
> +	}
> +
> +	ret = kmalloc_track_caller(new_size, flags);
> +	if (!ret)
> +		return NULL;
> +
> +	memcpy(ret, p, min(new_size, ksize(p)));
> +	kfree(p);
> +	return ret;
> +}
> +EXPORT_SYMBOL(krealloc);

Well could you check ksize for the old object first and if ksize <= new 
size then just skip the copy? I think this may allow you 
to get rid of the ksize callers.