netdev - Re: [Patch net-next-2.6] netpoll: disable netpoll when enslave a device

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Date:	Wed, 18 May 2011 06:56:48 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Neil Horman <nhorman@...hat.com>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Ferenc Wagner <wferi@...f.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Ian Campbell <ian.campbell@...rix.com>, netdev@...r.kernel.org
Subject: Re: [Patch net-next-2.6] netpoll: disable netpoll when enslave a
 device

On Wed, May 18, 2011 at 06:00:35PM +0800, Amerigo Wang wrote:
> Currently we do nothing when we enslave a net device which is running netconsole.
> Neil pointed out that we may get weird results in such case, so let's disable
> netpoll on the device being enslaved. I think it is too harsh to prevent
> the device being ensalved if it is running netconsole.
> 
> By the way, this patch also removes the NETDEV_GOING_DOWN from netconsole
> netdev notifier, because netpoll will check if the device is running or not
> and we don't handle NETDEV_PRE_UP neither.
> 
> Signed-off-by: WANG Cong <amwang@...hat.com>
> Cc: Neil Horman <nhorman@...hat.com>
> 
> ---
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 088fd84..b9c70c5 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1640,6 +1640,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>  		}
>  	}
>  
> +	netdev_bonding_change(slave_dev, NETDEV_ENSLAVE);
> +
>  	/* If this is the first slave, then we need to set the master's hardware
>  	 * address to be the same as the slave's. */
>  	if (is_zero_ether_addr(bond->dev->dev_addr))
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index a83e101..0c3e8de 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -621,7 +621,8 @@ static int netconsole_netdev_event(struct notifier_block *this,
>  	bool stopped = false;
>  
>  	if (!(event == NETDEV_CHANGENAME || event == NETDEV_UNREGISTER ||
> -	      event == NETDEV_BONDING_DESLAVE || event == NETDEV_GOING_DOWN))
> +	      event == NETDEV_BONDING_DESLAVE || event == NETDEV_GOING_DOWN ||
> +	      event == NETDEV_ENSLAVE))
>  		goto done;
>  
>  	spin_lock_irqsave(&target_list_lock, flags);
> @@ -650,8 +651,8 @@ restart:
>  					goto restart;
>  				}
>  				/* Fall through */
> -			case NETDEV_GOING_DOWN:
>  			case NETDEV_BONDING_DESLAVE:
> +			case NETDEV_ENSLAVE:
>  				nt->enabled = 0;
>  				stopped = true;
>  				break;
This wasn't introduced by this patch, but looking at it made me realize that
nt->enabled, if it passes through this code path, doesn't properly track weather
or not netpoll_setup has been called on this interface.  If you look at
drop_netconsole_target, you'll see we only call netpoll_cleanup_target if
nt->enabled is set.  We should probably change the nt->enabled check there, and
in store_enabled to be if (nt->np.dev), like we do in the NETDEV_UNREGISTER case
in netconsole_netdev_event.

> @@ -660,10 +661,21 @@ restart:
>  		netconsole_target_put(nt);
>  	}
>  	spin_unlock_irqrestore(&target_list_lock, flags);
> -	if (stopped && (event == NETDEV_UNREGISTER || event == NETDEV_BONDING_DESLAVE))
> +	if (stopped) {
>  		printk(KERN_INFO "netconsole: network logging stopped on "
> -			"interface %s as it %s\n",  dev->name,
> -			event == NETDEV_UNREGISTER ? "unregistered" : "released slaves");
> +		       "interface %s as it ", dev->name);
> +		switch (event) {
> +		case NETDEV_UNREGISTER:
> +			printk(KERN_CONT "unregistered\n");
> +			break;
> +		case NETDEV_BONDING_DESLAVE:
> +			printk(KERN_CONT "released slaves\n");
> +			break;
> +		case NETDEV_ENSLAVE:
> +			printk(KERN_CONT "is enslaved\n");
> +			break;
> +		}
> +	}
>  
>  done:
>  	return NOTIFY_DONE;
> diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> index 621dfa1..3d82867 100644
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h
> @@ -211,6 +211,7 @@ static inline int notifier_to_errno(int ret)
>  #define NETDEV_UNREGISTER_BATCH 0x0011
>  #define NETDEV_BONDING_DESLAVE  0x0012
>  #define NETDEV_NOTIFY_PEERS	0x0013
> +#define NETDEV_ENSLAVE		0x0014
>  
Nit:
Shouldn't this be NETDEV_BONDING_ENSLAVE, to keep it in line with
NETDEV_BONDING_DESLAVE above?

>  #define SYS_DOWN	0x0001	/* Notify of system down */
>  #define SYS_RESTART	SYS_DOWN
> 


Other than those two points, this looks good to me
Thanks!
Neil

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