On Tue, 2013-06-18 at 10:56 -0700, Robert Love wrote: > fcoe_xmit was coded such that it would skip the vlan net device/layer > and instead set some vlan flags and transmit on the real net device. > The real net device has code that would add the vlan tag for fcoe skbs. > This avoids some extra processing for data frames and provides a small > performance improvement. >
Given it was small performance gain and that too while ago, to my recollection it was just 25K w/ only small size IOs. Now with newer platforms this may not noticeable with significantly higher net IOPS. Also skipping VLAN layer violates layering as patch adds VLAN tag while using real dev, so instead I suggest just always use the device on which FCoE exist and that would use vlan and real dev correctly according to FCoE instance created on them to tag or not per underlying device in use. This will make FCoE stack agonistic of VLAN or real device on TX path and would also eliminate any such issue as this one fixed by the patch in the future, I mean FCoE would go thru VLAN layer to inherit any changes to vlan layer instead by-passing vlan layer and not aware of any such changes to vlan layer/driver. Thanks Vasu > Since fcoe_xmit was not using the vlan net device, __vlan_put_tag > within the real net device's xmit routine was ultimately being > called to set the vlan tag. > > With the below change the behavior of __vlan_put_tag changed slightly, > it now sets the skb->protocol = vlan_proto. vlan_proto was not a field > being set by fcoe_xmit, so the skb->protocol is now not being set to > ETH_P_8021Q, as it should be. > > This patch converts fcoe_xmit to use the vlan_put_tag routine which > will tag the skb and fcoe will continue to transmit fcoe skbs on the > real net device. > > For reference, the below change was the one that altered the > __vlan_put_tag behavior. > > commit 86a9bad3ab6b6f858fd4443b48738cabbb6d094c > Author: Patrick McHardy <[email protected]> > Date: Fri Apr 19 02:04:30 2013 +0000 > > net: vlan: add protocol argument to packet tagging functions > > Add a protocol argument to the VLAN packet tagging functions. In case > of HW > tagging, we need that protocol available in the ndo_start_xmit > functions, > so it is stored in a new field in the skb. The new field fits into a > hole > (on 64 bit) and doesn't increase the sks's size. > > Signed-off-by: Robert Love <[email protected]> > Acked-by: Neil Horman <[email protected]> > --- > drivers/scsi/fcoe/fcoe.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c > index fc7bb1f..7efc5df 100644 > --- a/drivers/scsi/fcoe/fcoe.c > +++ b/drivers/scsi/fcoe/fcoe.c > @@ -1660,9 +1660,12 @@ static int fcoe_xmit(struct fc_lport *lport, struct > fc_frame *fp) > > if (fcoe->netdev->priv_flags & IFF_802_1Q_VLAN && > fcoe->realdev->features & NETIF_F_HW_VLAN_CTAG_TX) { > - skb->vlan_tci = VLAN_TAG_PRESENT | > - vlan_dev_vlan_id(fcoe->netdev); > + /* must set skb->dev before calling vlan_put_tag */ > skb->dev = fcoe->realdev; > + skb = vlan_put_tag(skb, htons(ETH_P_8021Q), > + vlan_dev_vlan_id(fcoe->netdev)); > + if (!skb) > + return -ENOMEM; > } else > skb->dev = fcoe->netdev; _______________________________________________ fcoe-devel mailing list [email protected] http://lists.open-fcoe.org/mailman/listinfo/fcoe-devel
