On Wed, Oct 17, 2012 at 12:00:51AM +1030, Rusty Russell wrote:
> Now we can easily use vq->num_free to determine if there are descriptors
> left in the queue, we're about to change virtqueue_add_buf() to return 0
> on success. The virtio_net driver is the only one which actually uses
> the return value, so change that.
>
> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 33 +++++++++++++--------------------
> 1 file changed, 13 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 6c094c8..7c7f5a9 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -471,10 +471,11 @@ static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
> err = add_recvbuf_small(vi, gfp);
>
> oom = err == -ENOMEM;
> - if (err < 0)
> + if (err)
> break;
> ++vi->num;
> - } while (err > 0);
> + } while (vi->rvq->num_free);
> +
> if (unlikely(vi->num > vi->max))
> vi->max = vi->num;
> virtqueue_kick(vi->rvq);
I like this, it always bothered me that RX intentionally
triggers a failure path in virtqueue_add_buf.
> @@ -625,27 +626,20 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
> static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> - int capacity;
> + int err;
>
> /* Free up any pending old buffers before queueing new ones. */
> free_old_xmit_skbs(vi);
>
> /* Try to transmit */
> - capacity = xmit_skb(vi, skb);
> + err = xmit_skb(vi, skb);
>
> - /* This can happen with OOM and indirect buffers. */
> - if (unlikely(capacity < 0)) {
> - if (likely(capacity == -ENOMEM)) {
> - if (net_ratelimit())
> - dev_warn(&dev->dev,
> - "TX queue failure: out of memory\n");
> - } else {
> - dev->stats.tx_fifo_errors++;
> - if (net_ratelimit())
> - dev_warn(&dev->dev,
> - "Unexpected TX queue failure: %d\n",
> - capacity);
> - }
> + /* This should not happen! */
> + if (unlikely(err < 0)) {
> + dev->stats.tx_fifo_errors++;
> + if (net_ratelimit())
> + dev_warn(&dev->dev,
> + "Unexpected TX queue failure: %d\n", err);
> dev->stats.tx_dropped++;
> kfree_skb(skb);
> return NETDEV_TX_OK;
> @@ -658,13 +652,12 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
>
> /* Apparently nice girls don't return TX_BUSY; stop the queue
> * before it gets out of hand. Naturally, this wastes entries. */
> - if (capacity < 2+MAX_SKB_FRAGS) {
> + if (vi->svq->num_free < 2+MAX_SKB_FRAGS) {
> netif_stop_queue(dev);
> if (unlikely(!virtqueue_enable_cb_delayed(vi->svq))) {
> /* More just got used, free them then recheck. */
> free_old_xmit_skbs(vi);
> - capacity = vi->svq->num_free;
> - if (capacity >= 2+MAX_SKB_FRAGS) {
> + if (vi->svq->num_free >= 2+MAX_SKB_FRAGS) {
> netif_start_queue(dev);
> virtqueue_disable_cb(vi->svq);
> }
> --
> 1.7.9.5
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