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Date: Fri, 10 Jan 2014 09:37:56 -0800 From: John Fastabend <john.r.fastabend@...el.com> To: Jason Wang <jasowang@...hat.com> CC: davem@...emloft.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, mst@...hat.com, Neil Horman <nhorman@...driver.com>, e1000-devel@...ts.sourceforge.net Subject: Re: [PATCH net V3 2/2] net: core: explicitly select a txq before doing l2 forwarding On 1/10/2014 12:18 AM, 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. netdev_pick_tx() was also > extended to accept this parameter and dev_queue_xmit_accel() was used to do l2 > forwarding transmission. > > 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() and we can just reuse the code of > dev_queue_xmit() to do the transmission. > > 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@...el.com> > Cc: Neil Horman <nhorman@...driver.com> > Cc: e1000-devel@...ts.sourceforge.net > Signed-off-by: Jason Wang <jasowang@...hat.com> > > --- > Changes from V2: > - Reuse dev_queue_xmit() instead of re-inventing dfwd_direct_xmit() > - remove the unnecessary braces > 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 > --- Looks good to me thanks, I tested my macvlan use cases and everything works as expected. Acked-by: John Fastabend <john.r.fastabend@...el.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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