ipvs: fix dst_lock locking on dest update

Fix dst_lock usage in __ip_vs_update_dest. We need
_bh locking because destination is updated in user context.
Can cause lockups on frequent destination updates.
Problem reported by Simon Kirby. Bug was introduced
in 2.6.37 from the "ipvs: changes for local real server"
change.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Hans Schillstrom <hans@schillstrom.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

net/netfilter/ipvs/ip_vs_ctl.c

@@ -808,9 +808,9 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest,
 	dest->u_threshold = udest->u_threshold;
 	dest->l_threshold = udest->l_threshold;
 
-	spin_lock(&dest->dst_lock);
+	spin_lock_bh(&dest->dst_lock);
 	ip_vs_dst_reset(dest);
-	spin_unlock(&dest->dst_lock);
+	spin_unlock_bh(&dest->dst_lock);
 
 	if (add)
 		ip_vs_new_estimator(&dest->stats);