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Subject: Re: bridge/netfilter: regression in 2.6.39.1
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Neil Horman <nhorman@tuxdriver.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
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Date: Mon, 06 Jun 2011 18:11:45 +0200
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Le lundi 06 juin 2011 à 11:32 -0400, Neil Horman a écrit :

> 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


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