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virtio: wean net driver off NETDEV_TX_BUSY

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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: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Rusty Russell 2008-05-02 21:50:46 -05:00
parent 2e895e4c23
commit 99ffc696d1
1 changed files with 43 additions and 20 deletions
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63
drivers/net/virtio_net.c
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@ -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]);
@ -272,30 +274,51 @@ 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) {
pr_debug("%s: virtio not prepared to send\n", dev->name);
netif_stop_queue(dev);
/* Activate callback for using skbs: if this returns false it
* means some were used in the meantime. */
if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
vi->svq->vq_ops->disable_cb(vi->svq);
netif_start_queue(dev);
goto again;
/* 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;
}
__skb_unlink(skb, &vi->send);
return NETDEV_TX_BUSY;
vi->last_xmit_skb = NULL;
}
vi->svq->vq_ops->kick(vi->svq);
return 0;
/* 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);
/* Activate callback for using skbs: if this returns false it
* means some were used in the meantime. */
if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
vi->svq->vq_ops->disable_cb(vi->svq);
netif_start_queue(dev);
goto again;
}
goto done;
}
#ifdef CONFIG_NET_POLL_CONTROLLER