netdev - Re: [PATCH net-next] net: bridge: update multicast stats from maybe

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Date:   Thu, 4 Apr 2019 14:21:55 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        roopa@...ulusnetworks.com, bridge@...ts.linux-foundation.org,
        nbd@....name
Subject: Re: [PATCH net-next] net: bridge: update multicast stats from
 maybe_deliver()

On Thu, Apr 04, 2019 at 03:02:19PM +0300, Nikolay Aleksandrov wrote:
> On 04/04/2019 14:56, Pablo Neira Ayuso wrote:
> > Simplify this code by updating bridge multicast stats from
> > maybe_deliver().
> > 
> > Note that commit 6db6f0eae605 ("bridge: multicast to unicast"), in case
> > the port flag BR_MULTICAST_TO_UNICAST is set, never updates the previous
> > port pointer, therefore it is always going to be different from the
> > existing port in this deduplicated list iteration.
> > 
> > Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> > ---
> >  net/bridge/br_forward.c | 15 ++++-----------
> >  1 file changed, 4 insertions(+), 11 deletions(-)

This is removing two branches, it is less code to maintain and easier
to read than:

        if (prev == p)

> This was intentional, the reason I didn't add that call to maybe_deliver() is to avoid
> these checks for the standard unicast fast-path.  We need to avoid touching the mcast
> cache lines (and checks) when using unicast.

maybe_deliver() is called from br_flood() and br_multicast_flood(),
not the standard unicast fast-path.

Thanks.