netdev - Re: [PATCH net v2] net: bridge: multicast: notify switchdev driver whenever MC processing gets disabled

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Date:   Tue, 15 Feb 2022 18:56:31 +0200
From:   Nikolay Aleksandrov <nikolay@...dia.com>
To:     Oleksandr Mazur <oleksandr.mazur@...ision.eu>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Ivan Vecera <ivecera@...hat.com>,
        Yotam Gigi <yotamg@...lanox.com>,
        Nogah Frankel <nogahf@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>
CC:     <taras.chornyi@...ision.eu>, <volodymyr.mytnyk@...ision.eu>,
        <mickeyr@...vell.com>, <bridge@...ts.linux-foundation.org>,
        <vladimir.oltean@....com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v2] net: bridge: multicast: notify switchdev driver
 whenever MC processing gets disabled

On 15/02/2022 18:53, Oleksandr Mazur wrote:
> Whenever bridge driver hits the max capacity of MDBs, it disables
> the MC processing (by setting corresponding bridge option), but never
> notifies switchdev about such change (the notifiers are called only upon
> explicit setting of this option, through the registered netlink interface).
> 
> This could lead to situation when Software MDB processing gets disabled,
> but this event never gets offloaded to the underlying Hardware.
> 
> Fix this by adding a notify message in such case.
> 
> Fixes: 147c1e9b902c ("switchdev: bridge: Offload multicast disabled")
> 
> Signed-off-by: Oleksandr Mazur <oleksandr.mazur@...ision.eu>
> ---
> V2:
>   - target 'net' tree;
>   - add missed 'Fixes' tag;
>   - remove mc_disabled retcode check, as well as WARN_ON in case of err;
> ---
>  net/bridge/br_multicast.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index de2409889489..db4f2641d1cd 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -82,6 +82,9 @@ static void br_multicast_find_del_pg(struct net_bridge *br,
>  				     struct net_bridge_port_group *pg);
>  static void __br_multicast_stop(struct net_bridge_mcast *brmctx);
>  
> +static int br_mc_disabled_update(struct net_device *dev, bool value,
> +				 struct netlink_ext_ack *extack);
> +
>  static struct net_bridge_port_group *
>  br_sg_port_find(struct net_bridge *br,
>  		struct net_bridge_port_group_sg_key *sg_p)
> @@ -1156,6 +1159,7 @@ struct net_bridge_mdb_entry *br_multicast_new_group(struct net_bridge *br,
>  		return mp;
>  
>  	if (atomic_read(&br->mdb_hash_tbl.nelems) >= br->hash_max) {
> +		br_mc_disabled_update(br->dev, false, NULL);
>  		br_opt_toggle(br, BROPT_MULTICAST_ENABLED, false);
>  		return ERR_PTR(-E2BIG);
>  	}

nit: you don't have to leave empty new line between Fixes and Signed-off-by.
Patch looks good to me.

Acked-by: Nikolay Aleksandrov <nikolay@...dia.com>