Date: Mon, 6 Jun 2011 13:07:46 -0400
From: Neil Horman <nhorman@tuxdriver.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Alexander Holler <holler@ahsoftware.de>, linux-kernel@vger.kernel.org,
        David Miller <davem@davemloft.net>,
        Herbert Xu <herbert@gondor.hengli.com.au>, netdev@vger.kernel.org
Subject: Re: bridge/netfilter: regression in 2.6.39.1
Message-ID: <20110606170746.GD1000@hmsreliant.think-freely.org>
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On Mon, Jun 06, 2011 at 06:11:45PM +0200, Eric Dumazet wrote:
> Le lundi 06 juin 2011 ? 11:32 -0400, Neil Horman a ?crit :
> 
> > Not to drag this out further, but since you illustrated the correct way to do
> > this with the blackhole_ops test, and this modification now gives us two
> > instances of that case, would it perhaps be better to just do this in
> > dst_metrics_write_ptr:
> > 
> > return dst->ops->cow_metrics ? return dst->ops->cow_metrics(dst, p) : NULL;
> > 
> > Then we could eliminate the two functions that do nothing be retun NULL (along
> > with their respective call instructions), and save any future users from having
> > to remember to include a dummy cow_metrics method if they happen to set the read
> > only flag on thier dst_ops?
> 
> Well, I prefer how David coded the thing.
> We can add selective traces where we want.
> 
> Having a default behavior might give much more work to find a bug in
> this area. A NULL pointer access gives us an immediate indication.
> 
> Its a bit late to add an "if (dst->ops->cow_metrics)" test now that we
> covered all call sites ;)
> 
> But we probably have more bugs elsewhere, because of many dst changes in
> 2.6.39
Ok, sounds reasonable to me.

Reviewed-by: Neil Horman <nhorman@tuxdriver.com>

> 
> 
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