[PATCH] make kaweth use the sk_buff directly on tx

this change set against 2.5 will make kaweth put its private header
into the sk_buff directly if possible or else allocate a temporary sk_buff.
It saves memory and usually a copy.

diff --git a/drivers/usb/net/kaweth.c b/drivers/usb/net/kaweth.c
index 66102b6f85e759533a95de42362cbe99bb576385..096a8b1aded263e80f0046fef33dbed005f8e877 100644 (file)
--- a/drivers/usb/net/kaweth.c
+++ b/drivers/usb/net/kaweth.c
@@ -220,10 +220,11 @@ struct kaweth_device
        struct urb *rx_urb;
        struct urb *tx_urb;
        struct urb *irq_urb;
+       
+       struct sk_buff *tx_skb;
 
        __u8 *firmware_buf;
        __u8 scratch[KAWETH_SCRATCH_SIZE];
-       __u8 tx_buf[KAWETH_BUF_SIZE];
        __u8 rx_buf[KAWETH_BUF_SIZE];
        __u8 intbuffer[INTBUFFERSIZE];
        __u16 packet_filter_bitmap;
@@ -650,11 +651,13 @@ static int kaweth_ioctl(struct net_device *net, struct ifreq *rq, int cmd)
 static void kaweth_usb_transmit_complete(struct urb *urb)
 {
        struct kaweth_device *kaweth = urb->context;
+       struct sk_buff *skb = kaweth->tx_skb;
 
        if (unlikely(urb->status != 0))
                kaweth_dbg("%s: TX status %d.", kaweth->net->name, urb->status);
 
        netif_wake_queue(kaweth->net);
+       dev_kfree_skb(skb);
 }
 
 /****************************************************************
@@ -663,7 +666,7 @@ static void kaweth_usb_transmit_complete(struct urb *urb)
 static int kaweth_start_xmit(struct sk_buff *skb, struct net_device *net)
 {
        struct kaweth_device *kaweth = net->priv;
-       int count = skb->len;
+       char *private_header;
 
        int res;
 
@@ -679,15 +682,30 @@ static int kaweth_start_xmit(struct sk_buff *skb, struct net_device *net)
        kaweth_async_set_rx_mode(kaweth);
        netif_stop_queue(net);
 
-       *((__u16 *)kaweth->tx_buf) = cpu_to_le16(skb->len);
+       /* We now decide whether we can put our special header into the sk_buff */
+       if (skb_cloned(skb) || skb_headroom(skb) < 2) {
+               /* no such luck - we make our own */
+               struct sk_buff *copied_skb;
+               copied_skb = skb_copy_expand(skb, 2, 0, GFP_ATOMIC);
+               dev_kfree_skb_any(skb);
+               skb = copied_skb;
+               if (!copied_skb) {
+                       kaweth->stats.tx_errors++;
+                       netif_start_queue(net);
+                       spin_unlock(&kaweth->device_lock);
+                       return 0;
+               }
+       }
 
-       memcpy(kaweth->tx_buf + 2, skb->data, skb->len);
+       private_header = __skb_push(skb, 2);
+       *private_header = cpu_to_le16(skb->len);
+       kaweth->tx_skb = skb;
 
        FILL_BULK_URB(kaweth->tx_urb,
                      kaweth->dev,
                      usb_sndbulkpipe(kaweth->dev, 2),
-                     kaweth->tx_buf,
-                     count + 2,
+                     private_header,
+                     skb->len,
                      kaweth_usb_transmit_complete,
                      kaweth);
        kaweth->end = 0;
@@ -699,6 +717,7 @@ static int kaweth_start_xmit(struct sk_buff *skb, struct net_device *net)
                kaweth->stats.tx_errors++;
 
                netif_start_queue(net);
+               dev_kfree_skb(skb);
        }
        else
        {
@@ -707,8 +726,6 @@ static int kaweth_start_xmit(struct sk_buff *skb, struct net_device *net)
                net->trans_start = jiffies;
        }
 
-       dev_kfree_skb(skb);
-
        spin_unlock(&kaweth->device_lock);
 
        return 0;