core: Factor out flow calculation from get_rps_cpu

Factor out flow calculation code from get_rps_cpu, since other
functions can use the same code.

Revisions:

v2 (Ben): Separate flow calcuation out and use in select queue.
v3 (Arnd): Don't re-implement MIN.
v4 (Changli): skb->data points to ethernet header in macvtap, and
	make a fast path. Tested macvtap with this patch.
v5 (Changli):
	- Cache skb->rxhash in skb_get_rxhash
	- macvtap may not have pow(2) queues, so change code for
	  queue selection.
    (Arnd):
	- Use first available queue if all fails.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 77eb60d2b496..d8050382b189 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -558,6 +558,15 @@ extern unsigned int   skb_find_text(struct sk_buff *skb, unsigned int from,
                                     unsigned int to, struct ts_config *config,
                                     struct ts_state *state);
 
+extern __u32 __skb_get_rxhash(struct sk_buff *skb);
+static inline __u32 skb_get_rxhash(struct sk_buff *skb)
+{
+        if (!skb->rxhash)
+                skb->rxhash = __skb_get_rxhash(skb);
+
+        return skb->rxhash;
+}
+
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
 {