forcedeth: Stay in NAPI as long as there's work

The following does the same thing without the extra overhead
of testing all the registers. It also handles the out of memory
case.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Tested-by: NTom Herbert <therbert@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/forcedeth.c

@@ -3743,23 +3743,26 @@ static int nv_napi_poll(struct napi_struct *napi, int budget)
 	u8 __iomem *base = get_hwbase(dev);
 	unsigned long flags;
 	int retcode;
-	int tx_work, rx_work;
+	int rx_count, tx_work=0, rx_work=0;
 
-	if (!nv_optimized(np)) {
-		spin_lock_irqsave(&np->lock, flags);
-		tx_work = nv_tx_done(dev, np->tx_ring_size);
-		spin_unlock_irqrestore(&np->lock, flags);
+	do {
+		if (!nv_optimized(np)) {
+			spin_lock_irqsave(&np->lock, flags);
+			tx_work += nv_tx_done(dev, np->tx_ring_size);
+			spin_unlock_irqrestore(&np->lock, flags);
 
-		rx_work = nv_rx_process(dev, budget);
-		retcode = nv_alloc_rx(dev);
-	} else {
-		spin_lock_irqsave(&np->lock, flags);
-		tx_work = nv_tx_done_optimized(dev, np->tx_ring_size);
-		spin_unlock_irqrestore(&np->lock, flags);
+			rx_count = nv_rx_process(dev, budget);
+			retcode = nv_alloc_rx(dev);
+		} else {
+			spin_lock_irqsave(&np->lock, flags);
+			tx_work += nv_tx_done_optimized(dev, np->tx_ring_size);
+			spin_unlock_irqrestore(&np->lock, flags);
 
-		rx_work = nv_rx_process_optimized(dev, budget);
-		retcode = nv_alloc_rx_optimized(dev);
-	}
+			rx_count = nv_rx_process_optimized(dev, budget);
+			retcode = nv_alloc_rx_optimized(dev);
+		}
+	} while (retcode == 0 &&
+		 rx_count > 0 && (rx_work += rx_count) < budget);
 
 	if (retcode) {
 		spin_lock_irqsave(&np->lock, flags);