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Commit 99ffc696 authored by Rusty Russell's avatar Rusty Russell
Browse files

virtio: wean net driver off NETDEV_TX_BUSY 



Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is
seen as a poor thing to do; we should cache the packet and stop the queue.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Acked-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 2e895e4c

drivers/net/virtio_net.c

+43 −20
Original line number Diff line number Diff line
@@ -41,6 +41,9 @@ struct virtnet_info 
	struct net_device *dev;

	struct napi_struct napi;



	/* The skb we couldn't send because buffers were full. */

	struct sk_buff *last_xmit_skb;



	/* Number of input buffers, and max we've ever had. */

	unsigned int num, max;
@@ -227,17 +230,16 @@ static void free_old_xmit_skbs(struct virtnet_info *vi) 
	}

}



static int start_xmit(struct sk_buff *skb, struct net_device *dev)

static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)

{

	struct virtnet_info *vi = netdev_priv(dev);

	int num, err;

	int num;

	struct scatterlist sg[2+MAX_SKB_FRAGS];

	struct virtio_net_hdr *hdr;

	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;



	sg_init_table(sg, 2+MAX_SKB_FRAGS);



	pr_debug("%s: xmit %p " MAC_FMT "\n", dev->name, skb,

	pr_debug("%s: xmit %p " MAC_FMT "\n", vi->dev->name, skb,

		 dest[0], dest[1], dest[2],

		 dest[3], dest[4], dest[5]);
@@ -272,13 +274,40 @@ static int start_xmit(struct sk_buff *skb, struct net_device *dev) 


	vnet_hdr_to_sg(sg, skb);

	num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;

	__skb_queue_head(&vi->send, skb);



	return vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);

}



static int start_xmit(struct sk_buff *skb, struct net_device *dev)

{

	struct virtnet_info *vi = netdev_priv(dev);



again:

	/* Free up any pending old buffers before queueing new ones. */

	free_old_xmit_skbs(vi);

	err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);

	if (err) {



	/* If we has a buffer left over from last time, send it now. */

	if (vi->last_xmit_skb) {

		if (xmit_skb(vi, vi->last_xmit_skb) != 0) {

			/* Drop this skb: we only queue one. */

			vi->dev->stats.tx_dropped++;

			kfree_skb(skb);

			goto stop_queue;

		}

		vi->last_xmit_skb = NULL;

	}



	/* Put new one in send queue and do transmit */

	__skb_queue_head(&vi->send, skb);

	if (xmit_skb(vi, skb) != 0) {

		vi->last_xmit_skb = skb;

		goto stop_queue;

	}

done:

	vi->svq->vq_ops->kick(vi->svq);

	return NETDEV_TX_OK;



stop_queue:

	pr_debug("%s: virtio not prepared to send\n", dev->name);

	netif_stop_queue(dev);
@@ -289,13 +318,7 @@ static int start_xmit(struct sk_buff *skb, struct net_device *dev) 
		netif_start_queue(dev);

		goto again;

	}

		__skb_unlink(skb, &vi->send);



		return NETDEV_TX_BUSY;

	}

	vi->svq->vq_ops->kick(vi->svq);



	return 0;

	goto done;

}



#ifdef CONFIG_NET_POLL_CONTROLLER