On Sun, Oct 18, 2020 at 12:36:00AM +0300, Vladimir Oltean wrote:
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index d4326940233c..790f5c8deb13 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -548,6 +548,36 @@ netdev_tx_t dsa_enqueue_skb(struct sk_buff *skb, struct
> net_device *dev)
> }
> EXPORT_SYMBOL_GPL(dsa_enqueue_skb);
>
> +static int dsa_realloc_skb(struct sk_buff *skb, struct net_device *dev)
I forgot to actually pad the skb here, if it's a tail tagger, silly me.
The following changes should do the trick.
> +{
> + struct net_device *master = dsa_slave_to_master(dev);
The addition of master->needed_headroom and master->needed_tailroom used
to be here, that's why this unused variable is here.
> + struct dsa_slave_priv *p = netdev_priv(dev);
> + struct dsa_slave_stats *e;
> + int headroom, tailroom;
int padlen = 0, err;
> +
> + headroom = dev->needed_headroom;
> + tailroom = dev->needed_tailroom;
> + /* For tail taggers, we need to pad short frames ourselves, to ensure
> + * that the tail tag does not fail at its role of being at the end of
> + * the packet, once the master interface pads the frame.
> + */
> + if (unlikely(tailroom && skb->len < ETH_ZLEN))
> + tailroom += ETH_ZLEN - skb->len;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
padlen = ETH_ZLEN - skb->len;
tailroom += padlen;
> +
> + if (likely(skb_headroom(skb) >= headroom &&
> + skb_tailroom(skb) >= tailroom) &&
> + !skb_cloned(skb))
> + /* No reallocation needed, yay! */
> + return 0;
> +
> + e = this_cpu_ptr(p->extra_stats);
> + u64_stats_update_begin(&e->syncp);
> + e->tx_reallocs++;
> + u64_stats_update_end(&e->syncp);
> +
> + return pskb_expand_head(skb, headroom, tailroom, GFP_ATOMIC);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
err = pskb_expand_head(skb, headroom, tailroom, GFP_ATOMIC);
if (err < 0 || !padlen)
return err;
return __skb_put_padto(skb, padlen, false);
> +}
> +
> static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device
> *dev)
> {
> struct dsa_slave_priv *p = netdev_priv(dev);
> @@ -567,6 +597,11 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb,
> struct net_device *dev)
> */
> dsa_skb_tx_timestamp(p, skb);
>
> + if (dsa_realloc_skb(skb, dev)) {
> + kfree_skb(skb);
> + return NETDEV_TX_OK;
> + }
> +
> /* Transmit function may have to reallocate the original SKB,
> * in which case it must have freed it. Only free it here on error.
> */
> @@ -1802,6 +1837,14 @@ int dsa_slave_create(struct dsa_port *port)
> slave_dev->netdev_ops = &dsa_slave_netdev_ops;
> if (ds->ops->port_max_mtu)
> slave_dev->max_mtu = ds->ops->port_max_mtu(ds, port->index);
> + /* Try to save one extra realloc later in the TX path (in the master)
> + * by also inheriting the master's needed headroom and tailroom.
> + * The 8021q driver also does this.
> + */
Also, this comment is bogus given the current code. It should be removed
from here, and...
> + if (cpu_dp->tag_ops->tail_tag)
> + slave_dev->needed_tailroom = cpu_dp->tag_ops->overhead;
> + else
> + slave_dev->needed_headroom = cpu_dp->tag_ops->overhead;
...put here, along with:
slave_dev->needed_headroom += master->needed_headroom;
slave_dev->needed_tailroom += master->needed_tailroom;
> SET_NETDEV_DEVTYPE(slave_dev, &dsa_type);
>
> netdev_for_each_tx_queue(slave_dev, dsa_slave_set_lockdep_class_one,
> --
> 2.25.1
>
