rhashtable: Add annotation to nested lock

Commit aa34a6cb0478842452bac58edb50d3ef9e178c92 ("rhashtable:
Add arbitrary rehash function") killed the annotation on the
nested lock which leads to bitching from lockdep.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index b1c19c5..d7f3db5 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -234,7 +234,7 @@
 
 	new_bucket_lock = bucket_lock(new_tbl, new_hash);
 
-	spin_lock(new_bucket_lock);
+	spin_lock_nested(new_bucket_lock, RHT_LOCK_NESTED);
 	head = rht_dereference_bucket(new_tbl->buckets[new_hash],
 				      new_tbl, new_hash);
 
@@ -415,7 +415,7 @@
 	tbl = rht_dereference_rcu(ht->future_tbl, ht);
 	if (tbl != old_tbl) {
 		hash = obj_raw_hashfn(ht, tbl, rht_obj(ht, obj));
-		spin_lock(bucket_lock(tbl, hash));
+		spin_lock_nested(bucket_lock(tbl, hash), RHT_LOCK_NESTED);
 	}
 
 	if (compare &&