wireguard: queueing: simplify wg_cpumask_next_online()

wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
function significantly simpler. While there, fix opencoded cpu_online()
too.

Signed-off-by: Yury Norov <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: YuryNorov

drivers/net/wireguard/queueing.h

@@ -104,16 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
 
 static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
 {
-	unsigned int cpu = *stored_cpu, cpu_index, i;
+	unsigned int cpu = *stored_cpu;
+
+	if (unlikely(cpu >= nr_cpu_ids || !cpu_online(cpu)))
+		cpu = *stored_cpu = cpumask_nth(id % num_online_cpus(), cpu_online_mask);
 
-	if (unlikely(cpu >= nr_cpu_ids ||
-		     !cpumask_test_cpu(cpu, cpu_online_mask))) {
-		cpu_index = id % cpumask_weight(cpu_online_mask);
-		cpu = cpumask_first(cpu_online_mask);
-		for (i = 0; i < cpu_index; ++i)
-			cpu = cpumask_next(cpu, cpu_online_mask);
-		*stored_cpu = cpu;
-	}
 	return cpu;
 }