[NET]: Avoid allocating skb in skb_pad

First of all it is unnecessary to allocate a new skb in skb_pad since
the existing one is not shared.  More importantly, our hard_start_xmit
interface does not allow a new skb to be allocated since that breaks
requeueing.

This patch uses pskb_expand_head to expand the existing skb and linearize
it if needed.  Actually, someone should sift through every instance of
skb_pad on a non-linear skb as they do not fit the reasons why this was
originally created.

Incidentally, this fixes a minor bug when the skb is cloned (tcpdump,
TCP, etc.).  As it is skb_pad will simply write over a cloned skb.  Because
of the position of the write it is unlikely to cause problems but still
it's best if we don't do it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/net/myri10ge/myri10ge.c b/drivers/net/myri10ge/myri10ge.c
index 5a74f63618bc..b983e1e04348 100644
--- a/drivers/net/myri10ge/myri10ge.c
+++ b/drivers/net/myri10ge/myri10ge.c
@@ -1939,8 +1939,7 @@ again:
 
                 /* pad frames to at least ETH_ZLEN bytes */
                 if (unlikely(skb->len < ETH_ZLEN)) {
-                        skb = skb_padto(skb, ETH_ZLEN);
-                        if (skb == NULL) {
+                        if (skb_padto(skb, ETH_ZLEN)) {
                                 /* The packet is gone, so we must
                                  * return 0 */
                                 mgp->stats.tx_dropped += 1;