[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>
diff --git a/net/ipv4/multipath_wrandom.c b/net/ipv4/multipath_wrandom.c
index d34a9fa..342d0b9 100644
--- a/net/ipv4/multipath_wrandom.c
+++ b/net/ipv4/multipath_wrandom.c
@@ -228,7 +228,7 @@
 	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 @@
 	 * 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 @@
 	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 @@
 				 __multipath_free);
 		}
 
-		spin_unlock(&state[i].lock);
+		spin_unlock_bh(&state[i].lock);
 	}
 }