sched: place state, next_sched and gso_skb in same cacheline again

Earlier commits removed two members from struct Qdisc which places
next_sched/gso_skb into a different cacheline than ->state.

This restores the struct layout to what it was before the removal.
Move the two members, then add an annotation so they all reside in the
same cacheline.

This adds a 16 byte hole after cpu_qstats.

The hole could be closed but as it doesn't decrease total struct size just
do it this way.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Florian Westphal

include/net/sch_generic.h

@@ -71,11 +71,11 @@ struct Qdisc {
 	struct gnet_stats_basic_cpu __percpu *cpu_bstats;
 	struct gnet_stats_queue	__percpu *cpu_qstats;
 
-	struct Qdisc		*next_sched;
-	struct sk_buff		*gso_skb;
 	/*
 	 * For performance sake on SMP, we put highly modified fields at the end
 	 */
+	struct Qdisc		*next_sched ____cacheline_aligned_in_smp;
+	struct sk_buff		*gso_skb;
 	unsigned long		state;
 	struct sk_buff_head	q;
 	struct gnet_stats_basic_packed bstats;