bond: Don't set skb->queue_mapping in netpoll.

From: Tao Ma <boyu.mt@taobao.com>

When we are using netpoll, we don't go through the normal
transmit process. In this case, bond_select_queue is not called
and qdisc_skb_cb(skb)->slave_dev_queue_mapping isn't set.

So when netpoll_send_skb_on_dev calls ndo_start_xmit and we
enter bond_dev_queue_xmit, we will set skb->queue_mapping to
an invalid value and in some cases cause the driver panic the
kernel(We meet with bnx2 panic because of a very large queue_mapping).

This patch skip skb->queue_mapping if we find we are in netpoll.

CC: "David S. Miller" <davem@davemloft.net>
CC: Cong Wang <amwang@redhat.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
---
 drivers/net/bonding/bond_main.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

On Thu, 2013-08-15 at 16:36 +0800, Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
> 
> When we are using netpoll, we don't go through the normal
> transmit process. In this case, bond_select_queue is not called
> and qdisc_skb_cb(skb)->slave_dev_queue_mapping isn't set.
> 

Yes?

In netpoll_send_skb_on_dev() we have:

        if (skb_queue_len(&npinfo->txq) == 0 && !
netpoll_owner_active(dev)) {
                struct netdev_queue *txq;

                txq = netdev_pick_tx(dev, skb);
                ...

where netdev_pick_tx() will call ->ndo_select_queue().


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On 08/15/2013 12:36 PM, Tao Ma wrote:

> From: Tao Ma <boyu.mt@taobao.com>

> When we are using netpoll, we don't go through the normal
> transmit process. In this case, bond_select_queue is not called
> and qdisc_skb_cb(skb)->slave_dev_queue_mapping isn't set.

> So when netpoll_send_skb_on_dev calls ndo_start_xmit and we
> enter bond_dev_queue_xmit, we will set skb->queue_mapping to
> an invalid value and in some cases cause the driver panic the
> kernel(We meet with bnx2 panic because of a very large queue_mapping).

> This patch skip skb->queue_mapping if we find we are in netpoll.

> CC: "David S. Miller" <davem@davemloft.net>
> CC: Cong Wang <amwang@redhat.com>
> CC: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
> ---
>   drivers/net/bonding/bond_main.c |    5 +++--
>   1 files changed, 3 insertions(+), 2 deletions(-)

> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 07f257d..97b2f52 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -405,12 +405,13 @@ int bond_dev_queue_xmit(struct bonding *bond, struct sk_buff *skb,
>
>   	BUILD_BUG_ON(sizeof(skb->queue_mapping) !=
>   		     sizeof(qdisc_skb_cb(skb)->slave_dev_queue_mapping));
> -	skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;
>
>   	if (unlikely(netpoll_tx_running(bond->dev)))
>   		bond_netpoll_send_skb(bond_get_slave_by_dev(bond, slave_dev), skb);
> -	else
> +	else {
> +		skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;
>   		dev_queue_xmit(skb);
> +	}

     According to Documentation/CodingStyle, both arms of the *if* statement 
should have {} if one arm has them.

WBR, Sergei


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