gro: Avoid unnecessary comparison after skb_gro_header

For the overwhelming majority of cases, skb_gro_header's return
value cannot be NULL.  Yet we must check it because of its current
form.  This patch splits it up into multiple functions in order
to avoid this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 5 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index b1722a2d1fbe..cd29e613bc5a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2590,17 +2590,24 @@ struct sk_buff *napi_frags_skb(struct napi_struct *napi)
 {
         struct sk_buff *skb = napi->skb;
         struct ethhdr *eth;
+        unsigned int hlen;
+        unsigned int off;
 
         napi->skb = NULL;
 
         skb_reset_mac_header(skb);
         skb_gro_reset_offset(skb);
 
-        eth = skb_gro_header(skb, sizeof(*eth));
-        if (!eth) {
-                napi_reuse_skb(napi, skb);
-                skb = NULL;
-                goto out;
+        off = skb_gro_offset(skb);
+        hlen = off + sizeof(*eth);
+        eth = skb_gro_header_fast(skb, off);
+        if (skb_gro_header_hard(skb, hlen)) {
+                eth = skb_gro_header_slow(skb, hlen, off);
+                if (unlikely(!eth)) {
+                        napi_reuse_skb(napi, skb);
+                        skb = NULL;
+                        goto out;
+                }
         }
 
         skb_gro_pull(skb, sizeof(*eth));