gianfar: reallocate skb when headroom is not enough for fcb

Gianfar uses a hardware header FCB for offloading.  However when used
with bridging or IP forwarding, TX skb might not have enough headroom
for the FCB.  Reallocate skb for such cases.

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 10 deletions

diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index 8a51df045e84..9d81e7a48dba 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -1239,10 +1239,19 @@ static int gfar_enet_open(struct net_device *dev)
         return err;
 }
 
-static inline struct txfcb *gfar_add_fcb(struct sk_buff *skb)
+static inline struct txfcb *gfar_add_fcb(struct sk_buff **skbp)
 {
-        struct txfcb *fcb = (struct txfcb *)skb_push (skb, GMAC_FCB_LEN);
-
+        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);
         cacheable_memzero(fcb, GMAC_FCB_LEN);
 
         return fcb;
@@ -1363,18 +1372,20 @@ 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);
-                lstatus |= BD_LFLAG(TXBD_TOE);
-                gfar_tx_checksum(skb, fcb);
+                fcb = gfar_add_fcb(&skb);
+                if (likely(fcb != NULL)) {
+                        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 (unlikely(NULL == fcb))
+                        fcb = gfar_add_fcb(&skb);
+                if (likely(fcb != NULL)) {
                         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 */