Subject: Re: [PATCH] i40e: report correct statistics when XDP is enabled

From: Jesper Dangaard Brouer <[email-masked]>
Date: Fri, 24 Aug 2018 16:00:16 +0200

On Fri, 24 Aug 2018 13:21:59 +0200
Björn Töpel <[email-masked]> wrote:

> When XDP is enabled, the driver will report incorrect
> statistics. Received frames will reported as transmitted frames.
> 
> This commits fixes the i40e implementation of ndo_get_stats64 (struct
> net_device_ops), so that iproute2 will report correct statistics
> (e.g. when running "ip -stats link show dev eth0") even when XDP is
> enabled.
> 
> Reported-by: Jesper Dangaard Brouer <[email-masked]>
> Fixes: 74608d17fe29 ("i40e: add support for XDP_TX action")

Stable candidate:
 $ git describe --contains 74608d17fe29
 v4.13-rc1~157^2~128^2~13

> Signed-off-by: Björn Töpel <[email-masked]>

It works for me:

Tested-by: Jesper Dangaard Brouer <[email-masked]>

I'm explicitly _not_ ACK'ing the patch, as I think the your code changes
below makes it harder to follow whether a TX or RX ring is getting
updated. But it is 100% up to the driver maintainers to say if this is
acceptable from a maintenance PoV.

> ---
>  drivers/net/ethernet/intel/i40e/i40e_main.c | 24 +++++++++++----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index e40c023cc7b6..7c122dd3faa1 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -425,9 +425,9 @@ static void i40e_get_netdev_stats_struct(struct net_device *netdev,
>  				  struct rtnl_link_stats64 *stats)
>  {
>  	struct i40e_netdev_priv *np = netdev_priv(netdev);
> -	struct i40e_ring *tx_ring, *rx_ring;
>  	struct i40e_vsi *vsi = np->vsi;
>  	struct rtnl_link_stats64 *vsi_stats = i40e_get_vsi_stats_struct(vsi);
> +	struct i40e_ring *ring;
>  	int i;
>  
>  	if (test_bit(__I40E_VSI_DOWN, vsi->state))
> @@ -441,24 +441,26 @@ static void i40e_get_netdev_stats_struct(struct net_device *netdev,
>  		u64 bytes, packets;
>  		unsigned int start;
>  
> -		tx_ring = READ_ONCE(vsi->tx_rings[i]);
> -		if (!tx_ring)
> +		ring = READ_ONCE(vsi->tx_rings[i]);
> +		if (!ring)
>  			continue;
> -		i40e_get_netdev_stats_struct_tx(tx_ring, stats);
> +		i40e_get_netdev_stats_struct_tx(ring, stats);
>  
> -		rx_ring = &tx_ring[1];
> +		if (i40e_enabled_xdp_vsi(vsi)) {
> +			ring++;
> +			i40e_get_netdev_stats_struct_tx(ring, stats);
> +		}
>  
> +		ring++;
>  		do {
> -			start = u64_stats_fetch_begin_irq(&rx_ring->syncp);
> -			packets = rx_ring->stats.packets;
> -			bytes   = rx_ring->stats.bytes;
> -		} while (u64_stats_fetch_retry_irq(&rx_ring->syncp, start));
> +			start   = u64_stats_fetch_begin_irq(&ring->syncp);
> +			packets = ring->stats.packets;
> +			bytes   = ring->stats.bytes;
> +		} while (u64_stats_fetch_retry_irq(&ring->syncp, start));
>  
>  		stats->rx_packets += packets;
>  		stats->rx_bytes   += bytes;
>  
> -		if (i40e_enabled_xdp_vsi(vsi))
> -			i40e_get_netdev_stats_struct_tx(&rx_ring[1], stats);
>  	}
>  	rcu_read_unlock();
>  

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer