On Thu, 2010-06-10 at 18:20 +0300, Michael S. Tsirkin wrote:
> virtio net will never try to overflow the TX ring, so the only reason
> add_buf may fail is out of memory. Thus, we can not stop the
> device until some request completes - there's no guarantee anything
> at all is outstanding.
>
> Make the error message clearer as well: error here does not
> indicate queue full.
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 15 ++++++++-------
> 1 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 85615a3..e48a06f 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -563,7 +563,6 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> struct virtnet_info *vi = netdev_priv(dev);
> int capacity;
>
> -again:
> /* Free up any pending old buffers before queueing new ones. */
> free_old_xmit_skbs(vi);
>
> @@ -572,12 +571,14 @@ again:
>
> /* This can happen with OOM and indirect buffers. */
> if (unlikely(capacity < 0)) {
> - netif_stop_queue(dev);
> - dev_warn(&dev->dev, "Unexpected full queue\n");
> - if (unlikely(!virtqueue_enable_cb(vi->svq))) {
> - virtqueue_disable_cb(vi->svq);
> - netif_start_queue(dev);
> - goto again;
> + if (net_ratelimit()) {
> + if (likely(capacity == -ENOMEM))
> + dev_warn(&dev->dev,
> + "TX queue failure: out of memory\n");
> + else
> + dev_warn(&dev->dev,
> + "Unexpected TX queue failure: %d\n",
> + capacity);
> }
> return NETDEV_TX_BUSY;
> }
It is not clear to me how xmit_skb() can return -ENOMEM.
xmit_skb() calls virtqueue_add_buf_gfp() which can return -ENOSPC.
Even vring_add_indirect() doesn't return -ENOMEM on kmalloc failure.
Thanks
Sridhar
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