[IrDA]: irda-usb TX path optimization (was Re: IrDA spams logfiles - since 2.6.19)

Since we stop using dev_alloc_skb on the IrDA TX frame, we constantly run
into the case of the skb headroom being 0, and thus we call skb_cow for
every IrDA TX frame.
This patch uses a local buffer and memcpy the skb to it, saving us a
kmalloc for each of those IrDA TX frames.

Signed-off-by: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 21 insertions, 23 deletions

diff --git a/drivers/net/irda/irda-usb.c b/drivers/net/irda/irda-usb.c
index 3ca1082ec776..80cbf3f80432 100644
--- a/drivers/net/irda/irda-usb.c
+++ b/drivers/net/irda/irda-usb.c
@@ -441,25 +441,13 @@ static int irda_usb_hard_xmit(struct sk_buff *skb, struct net_device *netdev)
                 goto drop;
         }
 
-        /* Make sure there is room for IrDA-USB header. The actual
-         * allocation will be done lower in skb_push().
-         * Also, we don't use directly skb_cow(), because it require
-         * headroom >= 16, which force unnecessary copies - Jean II */
-        if (skb_headroom(skb) < self->header_length) {
-                IRDA_DEBUG(0, "%s(), Insuficient skb headroom.\n", __FUNCTION__);
-                if (skb_cow(skb, self->header_length)) {
-                        IRDA_WARNING("%s(), failed skb_cow() !!!\n", __FUNCTION__);
-                        goto drop;
-                }
-        }
+        memcpy(self->tx_buff + self->header_length, skb->data, skb->len);
 
         /* Change setting for next frame */
-
         if (self->capability & IUC_STIR421X) {
                 __u8 turnaround_time;
-                __u8* frame;
+                __u8* frame = self->tx_buff;
                 turnaround_time = get_turnaround_time( skb );
-                frame= skb_push(skb, self->header_length);
                 irda_usb_build_header(self, frame, 0);
                 frame[2] = turnaround_time;
                 if ((skb->len != 0) &&
@@ -472,17 +460,17 @@ static int irda_usb_hard_xmit(struct sk_buff *skb, struct net_device *netdev)
                         frame[1] = 0;
                 }
         } else {
-                irda_usb_build_header(self, skb_push(skb, self->header_length), 0);
+                irda_usb_build_header(self, self->tx_buff, 0);
         }
 
         /* FIXME: Make macro out of this one */
         ((struct irda_skb_cb *)skb->cb)->context = self;
 
-        usb_fill_bulk_urb(urb, self->usbdev, 
+        usb_fill_bulk_urb(urb, self->usbdev,
                       usb_sndbulkpipe(self->usbdev, self->bulk_out_ep),
-                      skb->data, IRDA_SKB_MAX_MTU,
+                      self->tx_buff, skb->len + self->header_length,
                       write_bulk_callback, skb);
-        urb->transfer_buffer_length = skb->len;
+
         /* This flag (URB_ZERO_PACKET) indicates that what we send is not
          * a continuous stream of data but separate packets.
          * In this case, the USB layer will insert an empty USB frame (TD)
@@ -1455,6 +1443,9 @@ static inline void irda_usb_close(struct irda_usb_cb *self)
         /* Remove the speed buffer */
         kfree(self->speed_buff);
         self->speed_buff = NULL;
+
+        kfree(self->tx_buff);
+        self->tx_buff = NULL;
 }
 
 /********************** USB CONFIG SUBROUTINES **********************/
@@ -1753,9 +1744,14 @@ static int irda_usb_probe(struct usb_interface *intf,
 
         memset(self->speed_buff, 0, IRDA_USB_SPEED_MTU);
 
+        self->tx_buff = kzalloc(IRDA_SKB_MAX_MTU + self->header_length,
+                                GFP_KERNEL);
+        if (self->tx_buff == NULL)
+                goto err_out_4;
+
         ret = irda_usb_open(self);
         if (ret) 
-                goto err_out_4;
+                goto err_out_5;
 
         IRDA_MESSAGE("IrDA: Registered device %s\n", net->name);
         usb_set_intfdata(intf, self);
@@ -1766,14 +1762,14 @@ static int irda_usb_probe(struct usb_interface *intf,
                 self->needspatch = (ret < 0);
                 if (self->needspatch) {
                         IRDA_ERROR("STIR421X: Couldn't upload patch\n");
-                        goto err_out_5;
+                        goto err_out_6;
                 }
 
                 /* replace IrDA class descriptor with what patched device is now reporting */
                 irda_desc = irda_usb_find_class_desc (self->usbintf);
                 if (irda_desc == NULL) {
                         ret = -ENODEV;
-                        goto err_out_5;
+                        goto err_out_6;
                 }
                 if (self->irda_desc)
                         kfree (self->irda_desc);
@@ -1782,9 +1778,10 @@ static int irda_usb_probe(struct usb_interface *intf,
         }
 
         return 0;
-
-err_out_5:
+err_out_6:
         unregister_netdev(self->netdev);
+err_out_5:
+        kfree(self->tx_buff);
 err_out_4:
         kfree(self->speed_buff);
 err_out_3:
diff --git a/drivers/net/irda/irda-usb.h b/drivers/net/irda/irda-usb.h
index 6b2271f18e77..e846c38224a3 100644
--- a/drivers/net/irda/irda-usb.h
+++ b/drivers/net/irda/irda-usb.h
@@ -156,6 +156,7 @@ struct irda_usb_cb {
         struct irlap_cb   *irlap;       /* The link layer we are binded to */
         struct qos_info qos;
         char *speed_buff;               /* Buffer for speed changes */
+        char *tx_buff;
 
         struct timeval stamp;
         struct timeval now;