netdev - Re: [RFC PATCH net-next 1/3] net: core: introduce netdev_notify_peers

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Message-ID: <20201208154905.23151fe4@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com>
Date:   Tue, 8 Dec 2020 15:49:05 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lijun Pan <ljp@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, Nathan Lynch <nathanl@...ux.ibm.com>
Subject: Re: [RFC PATCH net-next 1/3] net: core: introduce
 netdev_notify_peers_locked

On Sat,  5 Dec 2020 23:21:25 -0600 Lijun Pan wrote:
> There are some use cases for netdev_notify_peers in the context
> when rtnl lock is already held. Introduce lockless version
> of netdev_notify_peers call to save the extra code to call
> 	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
> 	call_netdevice_notifiers(NETDEV_RESEND_IGMP, dev);
> 
> Suggested-by: Nathan Lynch <nathanl@...ux.ibm.com>
> Signed-off-by: Lijun Pan <ljp@...ux.ibm.com>

> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -1488,6 +1488,25 @@ void netdev_notify_peers(struct net_device *dev)
>  }
>  EXPORT_SYMBOL(netdev_notify_peers);

Why not convert netdev_notify_peers to call the new helper?
That way the chance they will get out of sync is way smaller.

> +/**
> + * netdev_notify_peers_locked - notify network peers about existence of @dev,
> + * to be called in the context when rtnl lock is already held.
> + * @dev: network device
> + *
> + * Generate traffic such that interested network peers are aware of
> + * @dev, such as by generating a gratuitous ARP. This may be used when
> + * a device wants to inform the rest of the network about some sort of
> + * reconfiguration such as a failover event or virtual machine
> + * migration.
> + */
> +void netdev_notify_peers_locked(struct net_device *dev)

I think __netdev_notify_peers() would be a more typical name for
a core kernel function like this.

> +{
> +	ASSERT_RTNL();
> +	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
> +	call_netdevice_notifiers(NETDEV_RESEND_IGMP, dev);
> +}
> +EXPORT_SYMBOL(netdev_notify_peers_locked);

Otherwise LGTM, seems like a good cleanup.