bonding: ratelimit failed speed/duplex update warning

bond_miimon_commit() handles the UP transition for each slave of a bond
in the case of MII. It is triggered 10 times per second for the default
MII Polling interval of 100ms. For device drivers that do not implement
__ethtool_get_link_ksettings() the call to bond_update_speed_duplex()
fails persistently while the MII status could remain UP. That is, in
this and other cases where the speed/duplex update keeps failing over a
longer period of time while the MII state is UP, a warning is printed
every MII polling interval.

To address these excessive warnings net_ratelimit() should be used.
Printing a warning once would not be sufficient since the call to
bond_update_speed_duplex() could recover to succeed and fail again
later. In that case there would be no new indication what went wrong.

Fixes: b5bf0f5b16b9c (bonding: correctly update link status during mii-commit phase)
Signed-off-by: Andreas Born <futur.andy@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -2144,9 +2144,10 @@ static void bond_miimon_commit(struct bonding *bond)
 			if (bond_update_speed_duplex(slave) &&
 			    bond_needs_speed_duplex(bond)) {
 				slave->link = BOND_LINK_DOWN;
-				netdev_warn(bond->dev,
-					    "failed to get link speed/duplex for %s\n",
-					    slave->dev->name);
+				if (net_ratelimit())
+					netdev_warn(bond->dev,
+						    "failed to get link speed/duplex for %s\n",
+						    slave->dev->name);
 				continue;
 			}
 			bond_set_slave_link_state(slave, BOND_LINK_UP,