netdev - Re: [PATCH RFC net-next 03/13] net: bridge: minor refactor of br

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Message-ID: <76490693-ea6d-7174-0546-b9361ab5088c@blackwall.org>
Date:   Tue, 12 Apr 2022 21:36:34 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Joachim Wiberg <troglobit@...il.com>,
        Roopa Prabhu <roopa@...dia.com>
Cc:     netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Tobias Waldekranz <tobias@...dekranz.com>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH RFC net-next 03/13] net: bridge: minor refactor of
 br_setlink() for readability

On 11/04/2022 16:38, Joachim Wiberg wrote:
> The br_setlink() function extracts the struct net_bridge pointer a bit
> sloppy.  It's easy to interpret the code wrong.  This patch attempts to
> clear things up a bit.
> 
> Signed-off-by: Joachim Wiberg <troglobit@...il.com>
> ---
>  net/bridge/br_netlink.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 

I think you can make it more straight-forward, remove the first br = netdev_priv
and do something like (completely untested):
...
struct net_bridge_port *p = NULL;
...
if (netif_is_bridge_master(dev)) {
 br = netdev_priv(dev);
} else {
 p = br_port_get_rtnl(dev);
 if (WARN_ON(!p))
	return -EINVAL;
 br = p->br;
}

So br is always and only set in this block.

> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 7fca8ff13ec7..8f4297287b32 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -1040,6 +1040,8 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh, u16 flags,
>  		return 0;
>  
>  	p = br_port_get_rtnl(dev);
> +	if (p)
> +		br = p->br;
>  	/* We want to accept dev as bridge itself if the AF_SPEC
>  	 * is set to see if someone is setting vlan info on the bridge
>  	 */
> @@ -1055,17 +1057,17 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh, u16 flags,
>  			if (err)
>  				return err;
>  
> -			spin_lock_bh(&p->br->lock);
> +			spin_lock_bh(&br->lock);
>  			err = br_setport(p, tb, extack);
> -			spin_unlock_bh(&p->br->lock);
> +			spin_unlock_bh(&br->lock);
>  		} else {
>  			/* Binary compatibility with old RSTP */
>  			if (nla_len(protinfo) < sizeof(u8))
>  				return -EINVAL;
>  
> -			spin_lock_bh(&p->br->lock);
> +			spin_lock_bh(&br->lock);
>  			err = br_set_port_state(p, nla_get_u8(protinfo));
> -			spin_unlock_bh(&p->br->lock);
> +			spin_unlock_bh(&br->lock);
>  		}
>  		if (err)
>  			goto out;