On Mon, Jul 31, 2017 at 03:35:02PM -0700, Cong Wang wrote:

On Mon, Jul 31, 2017 at 3:19 PM, Shaohua Li [off-list ref] wrote:

quoted

 static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
                                        __be32 flowlabel, bool autolabel,
-                                       struct flowi6 *fl6)
+                                       struct flowi6 *fl6, u32 hash)
 {
-       u32 hash;
-
        /* @flowlabel may include more than a flow label, eg, the traffic class.
         * Here we want only the flow label value.
         */

@@ -788,7 +786,8 @@ static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
             net->ipv6.sysctl.auto_flowlabels != IP6_AUTO_FLOW_LABEL_FORCED))
                return flowlabel;

-       hash = skb_get_hash_flowi6(skb, fl6);
+       if (skb)
+               hash = skb_get_hash_flowi6(skb, fl6);

Why not just move skb_get_hash_flowi6() to its caller?
This check is not necessary. If you don't want to touch
existing callers, you can just introduce a wrapper:


static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
                                        __be32 flowlabel, bool autolabel,
                                        struct flowi6 *fl6)
{
  u32 hash = skb_get_hash_flowi6(skb, fl6);
  return __ip6_make_flowlabel(net, flowlabel, autolabel, hash);
}

this will always call skb_get_hash_flowi6 for the fast path even auto flowlabel
is disabled. I thought we should avoid this.

And your code can just call:

__ip6_make_flowlabel(net, flowlabel, autolabel, sk->sk_txhash);