linux-kernel - Re: [PATCH] netfilter: use krealloc() in nf_conntrack

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Message-ID: <4835C41E.2010502@trash.net>
Date:	Thu, 22 May 2008 21:06:06 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Pekka J Enberg <penberg@...helsinki.fi>
CC:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, mpm@...enic.com, clameter@....com
Subject: Re: [PATCH] netfilter: use krealloc() in nf_conntrack_extend.c V2

Pekka J Enberg wrote:
> The ksize() API is going away because it is being abused and it doesn't even
> work consistenly across different allocators. Therefore, convert
> net/netfilter/nf_conntrack_extend.c to use krealloc().
>
> Cc: <netfilter-devel@...r.kernel.org>
> Cc: <netdev@...r.kernel.org>
> Cc: Matt Mackall <mpm@...enic.com>
> Cc: Christoph Lameter <clameter@....com>
> Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
> ---
> Patrick, please use this patch instead. The previous one did the moving
> unconditionally which is wrong. This one moves entries around only if
> krealloc() allocated a new buffer.
>
>  net/netfilter/nf_conntrack_extend.c |   10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> Index: slab-2.6/net/netfilter/nf_conntrack_extend.c
> ===================================================================
> --- slab-2.6.orig/net/netfilter/nf_conntrack_extend.c	2008-05-22 21:52:12.000000000 +0300
> +++ slab-2.6/net/netfilter/nf_conntrack_extend.c	2008-05-22 21:52:26.000000000 +0300
> @@ -88,13 +88,11 @@
>  	newlen = newoff + t->len;
>  	rcu_read_unlock();
>  
> -	if (newlen >= ksize(ct->ext)) {
> -		new = kmalloc(newlen, gfp);
> -		if (!new)
> -			return NULL;
> -
> -		memcpy(new, ct->ext, ct->ext->len);
> +	new = krealloc(ct->ext, newlen, gfp);

Unfortunately this means we'll always have to reallocate, even
if there's still some room left from the previous allocation.
Any chance to avoid that?

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