bonding: fix active-backup transition

Earlier patch c4adfc822bf5 ("bonding: make speed, duplex setting
consistent with link state") made an attempt to keep slave state
consistent with speed and duplex settings. Unfortunately link-state
transition is used to change the active link especially when used
in conjunction with mii-mon. The above mentioned patch broke that
logic. Also when speed and duplex settings for a link are updated
during a link-event, the link-status should not be changed to
invoke correct transition logic.

This patch fixes this issue by moving the link-state update outside
of the bond_update_speed_duplex() fn and to the places where this fn
is called and update link-state selectively.

Fixes: c4adfc822bf5 ("bonding: make speed, duplex setting consistent
with link state")
Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Reviewed-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -378,20 +378,15 @@ static int bond_update_speed_duplex(struct slave *slave)
 	slave->duplex = DUPLEX_UNKNOWN;
 
 	res = __ethtool_get_link_ksettings(slave_dev, &ecmd);
-	if (res < 0) {
-		slave->link = BOND_LINK_DOWN;
+	if (res < 0)
 		return 1;
-	}
-	if (ecmd.base.speed == 0 || ecmd.base.speed == ((__u32)-1)) {
-		slave->link = BOND_LINK_DOWN;
+	if (ecmd.base.speed == 0 || ecmd.base.speed == ((__u32)-1))
 		return 1;
-	}
 	switch (ecmd.base.duplex) {
 	case DUPLEX_FULL:
 	case DUPLEX_HALF:
 		break;
 	default:
-		slave->link = BOND_LINK_DOWN;
 		return 1;
 	}
 
@@ -1563,7 +1558,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 	new_slave->delay = 0;
 	new_slave->link_failure_count = 0;
 
-	bond_update_speed_duplex(new_slave);
+	if (bond_update_speed_duplex(new_slave))
+		new_slave->link = BOND_LINK_DOWN;
 
 	new_slave->last_rx = jiffies -
 		(msecs_to_jiffies(bond->params.arp_interval) + 1);
@@ -2126,6 +2122,7 @@ static void bond_miimon_commit(struct bonding *bond)
 
 		case BOND_LINK_UP:
 			if (bond_update_speed_duplex(slave)) {
+				slave->link = BOND_LINK_DOWN;
 				netdev_warn(bond->dev,
 					    "failed to get link speed/duplex for %s\n",
 					    slave->dev->name);