net: introduce netif_addr_lock_nested() and call if when appropriate

dev_uc_sync() and dev_mc_sync() are acquiring netif_addr_lock for
destination device of synchronization. Since netif_addr_lock is
already held at the time for source device, this triggers lockdep
deadlock warning.

There's no way this deadlock can happen so use spin_lock_nested() to
silence the warning.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev_addr_lists.c

diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c
index c34ce9f..29c07fe 100644
--- a/net/core/dev_addr_lists.c
+++ b/net/core/dev_addr_lists.c
@@ -439,11 +439,11 @@
 	if (to->addr_len != from->addr_len)
 		return -EINVAL;
 
-	netif_addr_lock_bh(to);
+	netif_addr_lock_nested(to);
 	err = __hw_addr_sync(&to->uc, &from->uc, to->addr_len);
 	if (!err)
 		__dev_set_rx_mode(to);
-	netif_addr_unlock_bh(to);
+	netif_addr_unlock(to);
 	return err;
 }
 EXPORT_SYMBOL(dev_uc_sync);
@@ -463,7 +463,7 @@
 		return;
 
 	netif_addr_lock_bh(from);
-	netif_addr_lock(to);
+	netif_addr_lock_nested(to);
 	__hw_addr_unsync(&to->uc, &from->uc, to->addr_len);
 	__dev_set_rx_mode(to);
 	netif_addr_unlock(to);
@@ -602,11 +602,11 @@
 	if (to->addr_len != from->addr_len)
 		return -EINVAL;
 
-	netif_addr_lock_bh(to);
+	netif_addr_lock_nested(to);
 	err = __hw_addr_sync(&to->mc, &from->mc, to->addr_len);
 	if (!err)
 		__dev_set_rx_mode(to);
-	netif_addr_unlock_bh(to);
+	netif_addr_unlock(to);
 	return err;
 }
 EXPORT_SYMBOL(dev_mc_sync);
@@ -626,7 +626,7 @@
 		return;
 
 	netif_addr_lock_bh(from);
-	netif_addr_lock(to);
+	netif_addr_lock_nested(to);
 	__hw_addr_unsync(&to->mc, &from->mc, to->addr_len);
 	__dev_set_rx_mode(to);
 	netif_addr_unlock(to);