Am 12.11.2020 um 12:11 schrieb Lev Stipakov:
> Commit d3fd65484c781 ("net: core: add dev_sw_netstats_tx_add") has added
> function "dev_sw_netstats_tx_add()" to update net device per-cpu TX
> stats.
>
> Use this function instead of own code. While on it, replace
> "len" variable with "skb->len".
>
Using dev_sw_netstats_tx_add() is fine, however you have to keep
variable len, see remark in the code.
In addition you can replace internal_get_stats() with dev_get_tstats64().
> Signed-off-by: Lev Stipakov <l...@openvpn.net>
> ---
> net/openvswitch/vport-internal_dev.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/net/openvswitch/vport-internal_dev.c
> b/net/openvswitch/vport-internal_dev.c
> index 1e30d8df3ba5..116738d36e02 100644
> --- a/net/openvswitch/vport-internal_dev.c
> +++ b/net/openvswitch/vport-internal_dev.c
> @@ -33,23 +33,17 @@ static struct internal_dev *internal_dev_priv(struct
> net_device *netdev)
> static netdev_tx_t
> internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev)
> {
> - int len, err;
> + int err;
>
> - len = skb->len;
> rcu_read_lock();
> err = ovs_vport_receive(internal_dev_priv(netdev)->vport, skb, NULL);
We would have a well-hidden problem here. ovs_vport_receive() calls function
ovs_dp_process_packet() that frees the skb under certain circumstances.
Note that the skb can be freed even if ovs_vport_receive() returns OK.
Using skb->len after calling ovs_vport_receive() could result in a
use-after-free therefore. So you have to keep variable len.
> rcu_read_unlock();
>
> - if (likely(!err)) {
> - struct pcpu_sw_netstats *tstats = this_cpu_ptr(netdev->tstats);
> -
> - u64_stats_update_begin(&tstats->syncp);
> - tstats->tx_bytes += len;
> - tstats->tx_packets++;
> - u64_stats_update_end(&tstats->syncp);
> - } else {
> + if (likely(!err))
> + dev_sw_netstats_tx_add(netdev, 1, skb->len);
> + else
> netdev->stats.tx_errors++;
> - }
> +
> return NETDEV_TX_OK;
> }
>
>
