Messages in this thread | | | Date | Thu, 9 Jan 2014 07:31:44 -0500 | From | Neil Horman <> | Subject | Re: [PATCH net V2 2/2] net: core: explicitly select a txq before doing l2 forwarding |
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On Thu, Jan 09, 2014 at 05:37:32PM +0800, Jason Wang wrote: > Currently, the tx queue were selected implicitly in ndo_dfwd_start_xmit(). The > will cause several issues: > > - NETIF_F_LLTX were removed for macvlan, so txq lock were done for macvlan > instead of lower device which misses the necessary txq synchronization for > lower device such as txq stopping or frozen required by dev watchdog or > control path. > - dev_hard_start_xmit() was called with NULL txq which bypasses the net device > watchdog. > - dev_hard_start_xmit() does not check txq everywhere which will lead a crash > when tso is disabled for lower device. > > Fix this by explicitly introducing a new param for .ndo_select_queue() for just > selecting queues in the case of l2 forwarding offload. And also introducing > dfwd_direct_xmit() to do the queue selecting, txq holding and transmitting for > l2 forwarding. > > With this fixes, NETIF_F_LLTX could be preserved for macvlan and there's no need > to check txq against NULL in dev_hard_start_xmit(). Also there's no need to keep > a dedicated ndo_dfwd_start_xmit(). > > In the future, it was also required for macvtap l2 forwarding support since it > provides a necessary synchronization method. > > Cc: John Fastabend <john.r.fastabend@intel.com> > Cc: Neil Horman <nhorman@tuxdriver.com> > Cc: e1000-devel@lists.sourceforge.net > Signed-off-by: Jason Wang <jasowang@redhat.com> > > --- > Changes from V1: > - Adding a new parameter to ndo_select_queue instead of a new method to select > queue for l2 forwarding. > - Remove the unnecessary ndo_dfwd_start_xmit() since txq was selected > explicitly. > - Keep NETIF_F_LLTX when netdev feature is changed. > - Shape the commit log
A few minor nits inline. ><snip>
> } > diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c > index 5360f73..7eb4c82 100644 > --- a/drivers/net/macvlan.c > +++ b/drivers/net/macvlan.c > @@ -299,7 +299,7 @@ netdev_tx_t macvlan_start_xmit(struct sk_buff *skb, > > if (vlan->fwd_priv) { > skb->dev = vlan->lowerdev; > - ret = dev_hard_start_xmit(skb, skb->dev, NULL, vlan->fwd_priv); > + ret = dfwd_direct_xmit(skb, skb->dev, vlan->fwd_priv); > } else { > ret = macvlan_queue_xmit(skb, dev); > } > @@ -366,7 +366,6 @@ static int macvlan_open(struct net_device *dev) > if (IS_ERR_OR_NULL(vlan->fwd_priv)) { > vlan->fwd_priv = NULL; > } else { > - dev->features &= ~NETIF_F_LLTX; > return 0; > } After removing the features flag operation here, you don't need the braces around the else statement either.
><snip> > +int dfwd_direct_xmit(struct sk_buff *skb, struct net_device *dev, > + void *accel_priv) > +{ > + struct netdev_queue *txq; > + int ret = NETDEV_TX_BUSY; > + int index; > + > + BUG_ON(!dev->netdev_ops->ndo_select_queue); > + index = dev->netdev_ops->ndo_select_queue(dev, skb, accel_priv); > + > + local_bh_disable(); > + > + skb_set_queue_mapping(skb, index); > + txq = netdev_get_tx_queue(dev, index); > + > + HARD_TX_LOCK(dev, txq, smp_processor_id()); > + if (!netif_xmit_frozen_or_stopped(txq)) > + ret = dev_hard_start_xmit(skb, dev, txq); > + HARD_TX_UNLOCK(dev, txq); > + > + local_bh_enable(); > + return ret; > +} > +EXPORT_SYMBOL_GPL(dfwd_direct_xmit); > + Now that we're using the common path to select a queue, can we just use dev_queue_xmit here instead of creating our own transmit function? The txq we select from the ixgbe card will just have a pfifo_fast queue on it (if not a noop queue), so dev_queue_xmit should just fall into the dev_hard_start_xmit path, and save us this extra coding.
Neil
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