ipv6: Re-arrange code in rt6_probe()

It is a prep work for the next patch to remove write_lock
from rt6_probe().

1. Reduce the number of if(neigh) check.  From 4 to 1.
2. Bring the write_(un)lock() closer to the operations that the
   lock is protecting.

Hopefully, the above make rt6_probe() more readable.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: YOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: iamkafai

net/ipv6/route.c

@@ -545,6 +545,7 @@ static void rt6_probe_deferred(struct work_struct *w)
 
 static void rt6_probe(struct rt6_info *rt)
 {
+	struct __rt6_probe_work *work;
 	struct neighbour *neigh;
 	/*
 	 * Okay, this does not seem to be appropriate
@@ -559,34 +560,29 @@ static void rt6_probe(struct rt6_info *rt)
 	rcu_read_lock_bh();
 	neigh = __ipv6_neigh_lookup_noref(rt->dst.dev, &rt->rt6i_gateway);
 	if (neigh) {
+		work = NULL;
 		write_lock(&neigh->lock);
-		if (neigh->nud_state & NUD_VALID)
-			goto out;
-	}
-
-	if (!neigh ||
-	    time_after(jiffies, neigh->updated + rt->rt6i_idev->cnf.rtr_probe_interval)) {
-		struct __rt6_probe_work *work;
-
-		work = kmalloc(sizeof(*work), GFP_ATOMIC);
-
-		if (neigh && work)
-			__neigh_set_probe_once(neigh);
-
-		if (neigh)
-			write_unlock(&neigh->lock);
-
-		if (work) {
-			INIT_WORK(&work->work, rt6_probe_deferred);
-			work->target = rt->rt6i_gateway;
-			dev_hold(rt->dst.dev);
-			work->dev = rt->dst.dev;
-			schedule_work(&work->work);
+		if (!(neigh->nud_state & NUD_VALID) &&
+		    time_after(jiffies,
+			       neigh->updated +
+			       rt->rt6i_idev->cnf.rtr_probe_interval)) {
+			work = kmalloc(sizeof(*work), GFP_ATOMIC);
+			if (work)
+				__neigh_set_probe_once(neigh);
 		}
-	} else {
-out:
 		write_unlock(&neigh->lock);
+	} else {
+		work = kmalloc(sizeof(*work), GFP_ATOMIC);
+	}
+
+	if (work) {
+		INIT_WORK(&work->work, rt6_probe_deferred);
+		work->target = rt->rt6i_gateway;
+		dev_hold(rt->dst.dev);
+		work->dev = rt->dst.dev;
+		schedule_work(&work->work);
 	}
+
 	rcu_read_unlock_bh();
 }
 #else