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    Subject[087/143] virtio_net: fix oom handling on tx
    2.6.32-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Rusty Russell <rusty@rustcorp.com.au>

    commit 58eba97d0774c69b1cf3e5a8ac74419409d1abbf upstream.

    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@redhat.com>
    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    drivers/net/virtio_net.c | 21 +++++++++++++--------
    1 file changed, 13 insertions(+), 8 deletions(-)

    --- a/drivers/net/virtio_net.c
    +++ b/drivers/net/virtio_net.c
    @@ -525,7 +525,6 @@ static netdev_tx_t start_xmit(struct sk_
    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);

    @@ -534,14 +533,20 @@ 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(!vi->svq->vq_ops->enable_cb(vi->svq))) {
    - vi->svq->vq_ops->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->stats.tx_fifo_errors++;
    + dev_warn(&dev->dev,
    + "Unexpected TX queue failure: %d\n",
    + capacity);
    + }
    }
    - return NETDEV_TX_BUSY;
    + dev->stats.tx_dropped++;
    + kfree_skb(skb);
    + return NETDEV_TX_OK;
    }
    vi->svq->vq_ops->kick(vi->svq);




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