[IPV4] multipath_wrandom: Fix softirq-unsafe spin lock usage

The spin locks in multipath_wrandom may be obtained from either process
context or softirq context depending on whether the packet is locally
or remotely generated.  Therefore we need to disable BH processing when
taking these locks.

This bug was found by Ingo's lock validator.
 
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/multipath_wrandom.c

@@ -228,7 +228,7 @@ static void wrandom_set_nhinfo(__u32 network,
 	struct multipath_dest *d, *target_dest = NULL;
 
 	/* store the weight information for a certain route */
-	spin_lock(&state[state_idx].lock);
+	spin_lock_bh(&state[state_idx].lock);
 
 	/* find state entry for gateway or add one if necessary */
 	list_for_each_entry_rcu(r, &state[state_idx].head, list) {
@@ -276,7 +276,7 @@ static void wrandom_set_nhinfo(__u32 network,
 	 * we are finished
 	 */
 
-	spin_unlock(&state[state_idx].lock);
+	spin_unlock_bh(&state[state_idx].lock);
 }
 
 static void __multipath_free(struct rcu_head *head)
@@ -302,7 +302,7 @@ static void wrandom_flush(void)
 	for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
 		struct multipath_route *r;
 
-		spin_lock(&state[i].lock);
+		spin_lock_bh(&state[i].lock);
 		list_for_each_entry_rcu(r, &state[i].head, list) {
 			struct multipath_dest *d;
 			list_for_each_entry_rcu(d, &r->dests, list) {
@@ -315,7 +315,7 @@ static void wrandom_flush(void)
 				 __multipath_free);
 		}
 
-		spin_unlock(&state[i].lock);
+		spin_unlock_bh(&state[i].lock);
 	}
 }