[net] ixgbe: simplify padding and length checks

[net] ixgbe: simplify padding and length checks

[Jeff Kirsher]

From: Stephen Hemminger <shemminger@vyatta.com>

The check for length <= 0 is bogus because length is unsigned, and network
stack never sends zero length packets (unless it is totally broken).

The check for really small packets can be optimized (using unlikely)
and calling skb_pad directly.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |    9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index cbb05d6..9afe0cb 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -6383,17 +6383,12 @@ static netdev_tx_t ixgbe_xmit_frame(struct sk_buff *skb,
 	struct ixgbe_adapter *adapter = netdev_priv(netdev);
 	struct ixgbe_ring *tx_ring;
 
-	if (skb->len <= 0) {
-		dev_kfree_skb_any(skb);
-		return NETDEV_TX_OK;
-	}
-
 	/*
 	 * The minimum packet size for olinfo paylen is 17 so pad the skb
 	 * in order to meet this minimum size requirement.
 	 */
-	if (skb->len < 17) {
-		if (skb_padto(skb, 17))
+	if (unlikely(skb->len < 17)) {
+		if (skb_pad(skb, 17 - skb->len))
 			return NETDEV_TX_OK;
 		skb->len = 17;
 	}
-- 
1.7.10.2

Re: [net] ixgbe: simplify padding and length checks

[David Miller]

From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Date: Thu, 21 Jun 2012 05:15:10 -0700

> From: Stephen Hemminger <shemminger@vyatta.com>
> 
> The check for length <= 0 is bogus because length is unsigned, and network
> stack never sends zero length packets (unless it is totally broken).
> 
> The check for really small packets can be optimized (using unlikely)
> and calling skb_pad directly.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
> Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

Not really fixing anything and more of a cleanup, so maybe 'net-next'
instead of 'net' for this guy instead?

Re: [net] ixgbe: simplify padding and length checks

[Jeff Kirsher]

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On Thu, 2012-06-21 at 13:38 -0700, David Miller wrote:
> From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Date: Thu, 21 Jun 2012 05:15:10 -0700
> 
> > From: Stephen Hemminger <shemminger@vyatta.com>
> > 
> > The check for length <= 0 is bogus because length is unsigned, and network
> > stack never sends zero length packets (unless it is totally broken).
> > 
> > The check for really small packets can be optimized (using unlikely)
> > and calling skb_pad directly.
> > 
> > Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
> > Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
> > Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> 
> Not really fixing anything and more of a cleanup, so maybe 'net-next'
> instead of 'net' for this guy instead?

Yeah, net-next is fine.  I just verified that the patch applies cleanly
to net-next as well.

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Re: [net] ixgbe: simplify padding and length checks

[David Miller]

From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Date: Thu, 21 Jun 2012 14:28:09 -0700

> On Thu, 2012-06-21 at 13:38 -0700, David Miller wrote:
>> From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
>> Date: Thu, 21 Jun 2012 05:15:10 -0700
>> 
>> > From: Stephen Hemminger <shemminger@vyatta.com>
>> > 
>> > The check for length <= 0 is bogus because length is unsigned, and network
>> > stack never sends zero length packets (unless it is totally broken).
>> > 
>> > The check for really small packets can be optimized (using unlikely)
>> > and calling skb_pad directly.
>> > 
>> > Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
>> > Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
>> > Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
>> 
>> Not really fixing anything and more of a cleanup, so maybe 'net-next'
>> instead of 'net' for this guy instead?
> 
> Yeah, net-next is fine.  I just verified that the patch applies cleanly
> to net-next as well.

Great, applied, thanks.