gianfar: fix headroom expansion code

The code that was added to increase headroom was wrong.
It doesn't handle the case where gfar_add_fcb() changes the skb.
Better to do check at start of transmit (outside of lock), where
error handling is better anyway.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 22 deletions

diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index 9d81e7a48dba..a7a67376615b 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -1239,19 +1239,9 @@ static int gfar_enet_open(struct net_device *dev)
         return err;
 }
 
-static inline struct txfcb *gfar_add_fcb(struct sk_buff **skbp)
+static inline struct txfcb *gfar_add_fcb(struct sk_buff *skb)
 {
-        struct txfcb *fcb;
-        struct sk_buff *skb = *skbp;
-
-        if (unlikely(skb_headroom(skb) < GMAC_FCB_LEN)) {
-                struct sk_buff *old_skb = skb;
-                skb = skb_realloc_headroom(old_skb, GMAC_FCB_LEN);
-                if (!skb)
-                        return NULL;
-                dev_kfree_skb_any(old_skb);
-        }
-        fcb = (struct txfcb *)skb_push(skb, GMAC_FCB_LEN);
+        struct txfcb *fcb = (struct txfcb *)skb_push(skb, GMAC_FCB_LEN);
         cacheable_memzero(fcb, GMAC_FCB_LEN);
 
         return fcb;
@@ -1320,6 +1310,20 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
         base = priv->tx_bd_base;
 
+        /* make space for additional header */
+        if (skb_headroom(skb) < GMAC_FCB_LEN) {
+                struct sk_buff *skb_new;
+
+                skb_new = skb_realloc_headroom(skb, GMAC_FCB_LEN);
+                if (!skb_new) {
+                        dev->stats.tx_errors++;
+                        kfree(skb);
+                        return NETDEV_TX_OK;
+                }
+                kfree_skb(skb);
+                skb = skb_new;
+        }
+
         /* total number of fragments in the SKB */
         nr_frags = skb_shinfo(skb)->nr_frags;
 
@@ -1372,20 +1376,18 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
         /* Set up checksumming */
         if (CHECKSUM_PARTIAL == skb->ip_summed) {
-                fcb = gfar_add_fcb(&skb);
-                if (likely(fcb != NULL)) {
-                        lstatus |= BD_LFLAG(TXBD_TOE);
-                        gfar_tx_checksum(skb, fcb);
-                }
+                fcb = gfar_add_fcb(skb);
+                lstatus |= BD_LFLAG(TXBD_TOE);
+                gfar_tx_checksum(skb, fcb);
         }
 
         if (priv->vlgrp && vlan_tx_tag_present(skb)) {
-                if (unlikely(NULL == fcb))
-                        fcb = gfar_add_fcb(&skb);
-                if (likely(fcb != NULL)) {
+                if (unlikely(NULL == fcb)) {
+                        fcb = gfar_add_fcb(skb);
                         lstatus |= BD_LFLAG(TXBD_TOE);
-                        gfar_tx_vlan(skb, fcb);
                 }
+
+                gfar_tx_vlan(skb, fcb);
         }
 
         /* setup the TxBD length and buffer pointer for the first BD */
@@ -1433,7 +1435,7 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         /* Unlock priv */
         spin_unlock_irqrestore(&priv->txlock, flags);
 
-        return 0;
+        return NETDEV_TX_OK;
 }
 
 /* Stops the kernel queue, and halts the controller */