[PATCH] net/hyperv: fix erroneous NETDEV_TX_BUSY use

[Eric Dumazet <eric.dumazet@gmail.com>]

A driver start_xmit() method cannot free skb and return NETDEV_TX_BUSY,
since caller is going to reuse freed skb.

This is mostly a revert of commit bf769375c (staging: hv: fix the return
status of netvsc_start_xmit())

In fact netif_tx_stop_queue() / netif_stop_queue() is needed before
returning NETDEV_TX_BUSY or you can trigger a ksoftirqd fatal loop.

In case of memory allocation error, only safe way is to drop the packet
and return NETDEV_TX_OK

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/hyperv/netvsc_drv.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 0f8e834..2517d20 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -167,7 +167,7 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 
 		dev_kfree_skb(skb);
 		net->stats.tx_dropped++;
-		return NETDEV_TX_BUSY;
+		return NETDEV_TX_OK;
 	}
 
 	packet->vlan_tci = skb->vlan_tci;
@@ -229,7 +229,7 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 		dev_kfree_skb_any(skb);
 	}
 
-	return ret ? NETDEV_TX_BUSY : NETDEV_TX_OK;
+	return NETDEV_TX_OK;
 }
 
 /*