netdev - Re: [PATCH v3 net-next 03/11] net: bridge: vlan: make __vlan_add

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Message-ID: <79237e2d-e1d2-c6cd-975d-b28f064a2c20@nvidia.com>
Date:   Wed, 16 Feb 2022 13:03:54 +0200
From:   Nikolay Aleksandrov <nikolay@...dia.com>
To:     Vladimir Oltean <vladimir.oltean@....com>, <netdev@...r.kernel.org>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "Vivien Didelot" <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Roopa Prabhu <roopa@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        Rafael Richter <rafael.richter@....de>,
        Daniel Klauer <daniel.klauer@....de>,
        Tobias Waldekranz <tobias@...dekranz.com>
Subject: Re: [PATCH v3 net-next 03/11] net: bridge: vlan: make
 __vlan_add_flags react only to PVID and UNTAGGED

On 15/02/2022 19:02, Vladimir Oltean wrote:
> Currently there is a very subtle aspect to the behavior of
> __vlan_add_flags(): it changes the struct net_bridge_vlan flags and
> pvid, yet it returns true ("changed") even if none of those changed,
> just a transition of br_vlan_is_brentry(v) took place from false to
> true.
> 
> This can be seen in br_vlan_add_existing(), however we do not actually
> rely on this subtle behavior, since the "if" condition that checks that
> the vlan wasn't a brentry before had a useless (until now) assignment:
> 
> 	*changed = true;
> 
> Make things more obvious by actually making __vlan_add_flags() do what's
> written on the box, and be more specific about what is actually written
> on the box. This is needed because further transformations will be done
> to __vlan_add_flags().
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
> v2->v3: patch is new
> 
>  net/bridge/br_vlan.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index 498cc297b492..89e2cfed7bdb 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -58,7 +58,9 @@ static bool __vlan_delete_pvid(struct net_bridge_vlan_group *vg, u16 vid)
>  	return true;
>  }
>  
> -/* return true if anything changed, false otherwise */
> +/* Returns true if the BRIDGE_VLAN_INFO_PVID and BRIDGE_VLAN_INFO_UNTAGGED bits
> + * of @flags produced any change onto @v, false otherwise
> + */
>  static bool __vlan_add_flags(struct net_bridge_vlan *v, u16 flags)
>  {
>  	struct net_bridge_vlan_group *vg;
> @@ -80,7 +82,7 @@ static bool __vlan_add_flags(struct net_bridge_vlan *v, u16 flags)
>  	else
>  		v->flags &= ~BRIDGE_VLAN_INFO_UNTAGGED;
>  
> -	return ret || !!(old_flags ^ v->flags);
> +	return ret || !!((old_flags ^ v->flags) & BRIDGE_VLAN_INFO_UNTAGGED);
>  }
>  
>  static int __vlan_vid_add(struct net_device *dev, struct net_bridge *br,

This patch is unnecessary and can be dropped given the next one.