linux-kernel - [105/205] virtio_net: fix oom handling on tx

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Message-Id: <20100730175143.362110039@clark.site>
Date:	Fri, 30 Jul 2010 10:52:02 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"David S. Miller" <davem@...emloft.net>
Subject: [105/205] virtio_net: fix oom handling on tx

2.6.34-stable review patch.  If anyone has any objections, please let us know.

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

From: Rusty Russell <rusty@...tcorp.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@...hat.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.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
@@ -566,7 +566,6 @@ 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);
 
@@ -575,14 +574,20 @@ 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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