Subject: Re: [v3 Patch 2/3] bridge: make bridge support netpoll

From: Stephen Hemminger <[email-masked]>
Date: Thu, 8 Apr 2010 08:37:10 -0700

On Thu, 8 Apr 2010 02:18:58 -0400
Amerigo Wang <[email-masked]> wrote:

> 
> Based on the previous patch, make bridge support netpoll by:
> 
> 1) implement the 2 methods to support netpoll for bridge;
> 
> 2) modify netpoll during forwarding packets via bridge;
> 
> 3) disable netpoll support of bridge when a netpoll-unabled device
>    is added to bridge;
> 
> 4) enable netpoll support when all underlying devices support netpoll.
> 
> Cc: David Miller <[email-masked]>
> Cc: Neil Horman <[email-masked]>
> Cc: Stephen Hemminger <[email-masked]>
> Cc: Matt Mackall <[email-masked]>
> Signed-off-by: WANG Cong <[email-masked]>
> 
> ---
> 
> Index: linux-2.6/net/bridge/br_device.c
> ===================================================================
> --- linux-2.6.orig/net/bridge/br_device.c
> +++ linux-2.6/net/bridge/br_device.c
> @@ -13,8 +13,10 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/netdevice.h>
> +#include <linux/netpoll.h>
>  #include <linux/etherdevice.h>
>  #include <linux/ethtool.h>
> +#include <linux/list.h>
>  
>  #include <asm/uaccess.h>
>  #include "br_private.h"
> @@ -162,6 +164,59 @@ static int br_set_tx_csum(struct net_dev
>  	return 0;
>  }
>  
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +bool br_devices_support_netpoll(struct net_bridge *br)
> +{
> +	struct net_bridge_port *p;
> +	bool ret = true;
> +	int count = 0;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&br->lock, flags);
> +	list_for_each_entry(p, &br->port_list, list) {
> +		count++;
> +		if (p->dev->priv_flags & IFF_DISABLE_NETPOLL
> +				|| !p->dev->netdev_ops->ndo_poll_controller)
> +			ret = false;
> +	}
> +	spin_unlock_irqrestore(&br->lock, flags);
> +	return count != 0 && ret;
> +}
> +
> +static void br_poll_controller(struct net_device *br_dev)
> +{
> +	struct netpoll *np = br_dev->npinfo->netpoll;
> +
> +	if (np->real_dev != br_dev)
> +		netpoll_poll_dev(np->real_dev);
> +}
> +
> +void br_netpoll_cleanup(struct net_device *br_dev)
> +{
> +	struct net_bridge *br = netdev_priv(br_dev);
> +	struct net_bridge_port *p, *n;
> +	const struct net_device_ops *ops;
> +
> +	br->dev->npinfo = NULL;
> +	list_for_each_entry_safe(p, n, &br->port_list, list) {
> +		if (p->dev) {
> +			ops = p->dev->netdev_ops;
> +			if (ops->ndo_netpoll_cleanup)
> +				ops->ndo_netpoll_cleanup(p->dev);
> +			else
> +				p->dev->npinfo = NULL;
> +		}
> +	}
> +}
> +
> +#else
> +
> +void br_netpoll_cleanup(struct net_device *br_dev)
> +{
> +}
> +
> +#endif

Could you use more stub functions to eliminate #ifdef's in code.

>  static const struct ethtool_ops br_ethtool_ops = {
>  	.get_drvinfo    = br_getinfo,
>  	.get_link	= ethtool_op_get_link,
> @@ -184,6 +239,10 @@ static const struct net_device_ops br_ne
>  	.ndo_set_multicast_list	 = br_dev_set_multicast_list,
>  	.ndo_change_mtu		 = br_change_mtu,
>  	.ndo_do_ioctl		 = br_dev_ioctl,
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +	.ndo_netpoll_cleanup	 = br_netpoll_cleanup,
> +	.ndo_poll_controller	 = br_poll_controller,
> +#endif
>  };
>  
>  void br_dev_setup(struct net_device *dev)
> Index: linux-2.6/net/bridge/br_forward.c
> ===================================================================
> --- linux-2.6.orig/net/bridge/br_forward.c
> +++ linux-2.6/net/bridge/br_forward.c
> @@ -15,6 +15,7 @@
>  #include <linux/slab.h>
>  #include <linux/kernel.h>
>  #include <linux/netdevice.h>
> +#include <linux/netpoll.h>
>  #include <linux/skbuff.h>
>  #include <linux/if_vlan.h>
>  #include <linux/netfilter_bridge.h>
> @@ -50,7 +51,13 @@ int br_dev_queue_push_xmit(struct sk_buf
>  		else {
>  			skb_push(skb, ETH_HLEN);
>  
> -			dev_queue_xmit(skb);
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +			if (skb->dev->priv_flags & IFF_IN_NETPOLL) {
> +				netpoll_send_skb(skb->dev->npinfo->netpoll, skb);
> +				skb->dev->priv_flags &= ~IFF_IN_NETPOLL;
> +			} else
> +#endif

There is no protection on dev->priv_flags for SMP access.
It would better bit value in dev->state if you are using it as control flag.

Then you could use 
			if (unlikely(test_and_clear_bit(__IN_NETPOLL, &skb->dev->state)))
				netpoll_send_skb(...)

> +				dev_queue_xmit(skb);
>  		}
>  	}
>  
> @@ -66,9 +73,23 @@ int br_forward_finish(struct sk_buff *sk
>  
>  static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
>  {
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +	struct net_bridge *br = to->br;
> +	if (br->dev->priv_flags & IFF_IN_NETPOLL) {
> +		struct netpoll *np;
> +		to->dev->npinfo = skb->dev->npinfo;
> +		np = skb->dev->npinfo->netpoll;
> +		np->real_dev = np->dev = to->dev;
> +		to->dev->priv_flags |= IFF_IN_NETPOLL;
> +	}
> +#endif

This is n hot path, so use unlikely()

>  	skb->dev = to->dev;
>  	NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
>  			br_forward_finish);
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +	if (skb->dev->npinfo)
> +		skb->dev->npinfo->netpoll->dev = br->dev;
> +#endif
>  }
>  
>  static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
> Index: linux-2.6/net/bridge/br_if.c
> ===================================================================
> --- linux-2.6.orig/net/bridge/br_if.c
> +++ linux-2.6/net/bridge/br_if.c
> @@ -13,6 +13,7 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/netdevice.h>
> +#include <linux/netpoll.h>
>  #include <linux/ethtool.h>
>  #include <linux/if_arp.h>
>  #include <linux/module.h>
> @@ -153,6 +154,14 @@ static void del_nbp(struct net_bridge_po
>  	kobject_uevent(&p->kobj, KOBJ_REMOVE);
>  	kobject_del(&p->kobj);
>  
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +	if (br_devices_support_netpoll(br))
> +		br->dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
> +	if (dev->netdev_ops->ndo_netpoll_cleanup)
> +		dev->netdev_ops->ndo_netpoll_cleanup(dev);
> +	else
> +		dev->npinfo = NULL;
> +#endif
>  	call_rcu(&p->rcu, destroy_nbp_rcu);
>  }
>  
> @@ -165,6 +174,8 @@ static void del_br(struct net_bridge *br
>  		del_nbp(p);
>  	}
>  
> +	br_netpoll_cleanup(br->dev);
> +
>  	del_timer_sync(&br->gc_timer);
>  
>  	br_sysfs_delbr(br->dev);
> @@ -438,6 +449,20 @@ int br_add_if(struct net_bridge *br, str
>  
>  	kobject_uevent(&p->kobj, KOBJ_ADD);
>  
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +	if (br_devices_support_netpoll(br)) {
> +		br->dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
> +		if (br->dev->npinfo)
> +			dev->npinfo = br->dev->npinfo;
> +	} else if (!(br->dev->priv_flags & IFF_DISABLE_NETPOLL)) {
> +		br->dev->priv_flags |= IFF_DISABLE_NETPOLL;
> +		printk(KERN_INFO "New device %s does not support netpoll\n",
> +			dev->name);
> +		printk(KERN_INFO "Disabling netpoll for %s\n",
> +			br->dev->name);

One message is sufficient.

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