virtio_net: fix oom handling on tx

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> (...and avoid TX_BUSY)
Cc: stable@kernel.org  # .34.x (s/virtqueue_/vi->svq->vq_ops->/)
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 8 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ee7571195b10..bb6b67f6b0cc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -562,7 +562,6 @@ 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);
 
@@ -571,14 +570,20 @@ 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(!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->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;
         }
         virtqueue_kick(vi->svq);