linux-kernel - Re: [PATCH net-next v5 1/6] geneve: rely on rtnl lock in geneve_offload_rx

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Message-ID: <22ec7ed6-9c38-4f81-9ec4-024da12b8710@blackwall.org>
Date: Wed, 18 Jun 2025 18:14:06 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Stanislav Fomichev <stfomichev@...il.com>, netdev@...r.kernel.org
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, skalluru@...vell.com, manishc@...vell.com,
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Subject: Re: [PATCH net-next v5 1/6] geneve: rely on rtnl lock in
 geneve_offload_rx_ports

On 6/16/25 19:21, Stanislav Fomichev wrote:
> udp_tunnel_push_rx_port will grab mutex in the next patch so
> we can't use rcu. geneve_offload_rx_ports is called
> from geneve_netdevice_event for NETDEV_UDP_TUNNEL_PUSH_INFO and
> NETDEV_UDP_TUNNEL_DROP_INFO which both have ASSERT_RTNL.
> Entries are added to and removed from the sock_list under rtnl
> lock as well (when adding or removing a tunneling device).
> 
> Signed-off-by: Stanislav Fomichev <stfomichev@...il.com>
> ---
>  drivers/net/geneve.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
> index ffc15a432689..9efedc6758bf 100644
> --- a/drivers/net/geneve.c
> +++ b/drivers/net/geneve.c
> @@ -41,6 +41,7 @@ MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");
>  /* per-network namespace private data for this module */
>  struct geneve_net {
>  	struct list_head	geneve_list;
> +	/* sock_list is protected by rtnl lock */
>  	struct list_head	sock_list;
>  };
>  
> @@ -1179,8 +1180,9 @@ static void geneve_offload_rx_ports(struct net_device *dev, bool push)
>  	struct geneve_net *gn = net_generic(net, geneve_net_id);
>  	struct geneve_sock *gs;
>  
> -	rcu_read_lock();
> -	list_for_each_entry_rcu(gs, &gn->sock_list, list) {
> +	ASSERT_RTNL();
> +
> +	list_for_each_entry(gs, &gn->sock_list, list) {
>  		if (push) {
>  			udp_tunnel_push_rx_port(dev, gs->sock,
>  						UDP_TUNNEL_TYPE_GENEVE);
> @@ -1189,7 +1191,6 @@ static void geneve_offload_rx_ports(struct net_device *dev, bool push)
>  						UDP_TUNNEL_TYPE_GENEVE);
>  		}
>  	}
> -	rcu_read_unlock();
>  }
>  
>  /* Initialize the device structure. */

Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>