xfrm: move the checking for old xfrm_policy hold_queue to beginning

if hold_queue of old xfrm_policy is NULL, return directly, then not need to
run other codes, especially take the spin lock

Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_policy.c

@@ -700,6 +700,9 @@ static void xfrm_policy_requeue(struct xfrm_policy *old,
 	struct xfrm_policy_queue *pq = &old->polq;
 	struct sk_buff_head list;
 
+	if (skb_queue_empty(&pq->hold_queue))
+		return;
+
 	__skb_queue_head_init(&list);
 
 	spin_lock_bh(&pq->hold_queue.lock);
@@ -708,9 +711,6 @@ static void xfrm_policy_requeue(struct xfrm_policy *old,
 		xfrm_pol_put(old);
 	spin_unlock_bh(&pq->hold_queue.lock);
 
-	if (skb_queue_empty(&list))
-		return;
-
 	pq = &new->polq;
 
 	spin_lock_bh(&pq->hold_queue.lock);