eql: use __dev_get_by_name instead of dev_get_by_name to find interface

The following call chain indicates that eql_ioctl(), eql_enslave(),
eql_emancipate(), eql_g_slave_cfg() and eql_s_slave_cfg() are
protected under rtnl_lock. So if we use __dev_get_by_name() instead
of dev_get_by_name() to find interface handlers in them, this would
help us avoid to change interface reference counters.

dev_ioctl()
  rtnl_lock()
    dev_ifsioc()
      eql_ioctl()
        eql_enslave()
	eql_emancipate()
	eql_g_slave_cfg()
	eql_s_slave_cfg()
  rtnl_unlock()

Additionally we also change their return values from -EINVAL to
-ENODEV in case that interfaces are no found.
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/eql.c

@@ -395,6 +395,7 @@ static int __eql_insert_slave(slave_queue_t *queue, slave_t *slave)
 		if (duplicate_slave)
 			eql_kill_one_slave(queue, duplicate_slave);
 
+		dev_hold(slave->dev);
 		list_add(&slave->list, &queue->all_slaves);
 		queue->num_slaves++;
 		slave->dev->flags |= IFF_SLAVE;
@@ -413,20 +414,19 @@ static int eql_enslave(struct net_device *master_dev, slaving_request_t __user *
 	if (copy_from_user(&srq, srqp, sizeof (slaving_request_t)))
 		return -EFAULT;
 
-	slave_dev  = dev_get_by_name(&init_net, srq.slave_name);
-	if (slave_dev) {
+	slave_dev = __dev_get_by_name(&init_net, srq.slave_name);
+	if (!slave_dev)
+		return -ENODEV;
+
 	if ((master_dev->flags & IFF_UP) == IFF_UP) {
 		/* slave is not a master & not already a slave: */
-			if (!eql_is_master(slave_dev) &&
-			    !eql_is_slave(slave_dev)) {
+		if (!eql_is_master(slave_dev) && !eql_is_slave(slave_dev)) {
 			slave_t *s = kmalloc(sizeof(*s), GFP_KERNEL);
 			equalizer_t *eql = netdev_priv(master_dev);
 			int ret;
 
-				if (!s) {
-					dev_put(slave_dev);
+			if (!s)
 				return -ENOMEM;
-				}
 
 			memset(s, 0, sizeof(*s));
 			s->dev = slave_dev;
@@ -436,17 +436,14 @@ static int eql_enslave(struct net_device *master_dev, slaving_request_t __user *
 
 			spin_lock_bh(&eql->queue.lock);
 			ret = __eql_insert_slave(&eql->queue, s);
-				if (ret) {
-					dev_put(slave_dev);
+			if (ret)
 				kfree(s);
-				}
+
 			spin_unlock_bh(&eql->queue.lock);
 
 			return ret;
 		}
 	}
-		dev_put(slave_dev);
-	}
 
 	return -EINVAL;
 }
@@ -461,24 +458,20 @@ static int eql_emancipate(struct net_device *master_dev, slaving_request_t __use
 	if (copy_from_user(&srq, srqp, sizeof (slaving_request_t)))
 		return -EFAULT;
 
-	slave_dev = dev_get_by_name(&init_net, srq.slave_name);
+	slave_dev = __dev_get_by_name(&init_net, srq.slave_name);
+	if (!slave_dev)
+		return -ENODEV;
+
 	ret = -EINVAL;
-	if (slave_dev) {
 	spin_lock_bh(&eql->queue.lock);
-
 	if (eql_is_slave(slave_dev)) {
-			slave_t *slave = __eql_find_slave_dev(&eql->queue,
-							      slave_dev);
-
+		slave_t *slave = __eql_find_slave_dev(&eql->queue, slave_dev);
 		if (slave) {
 			eql_kill_one_slave(&eql->queue, slave);
 			ret = 0;
 		}
 	}
-		dev_put(slave_dev);
-
 	spin_unlock_bh(&eql->queue.lock);
-	}
 
 	return ret;
 }
@@ -494,7 +487,7 @@ static int eql_g_slave_cfg(struct net_device *dev, slave_config_t __user *scp)
 	if (copy_from_user(&sc, scp, sizeof (slave_config_t)))
 		return -EFAULT;
 
-	slave_dev = dev_get_by_name(&init_net, sc.slave_name);
+	slave_dev = __dev_get_by_name(&init_net, sc.slave_name);
 	if (!slave_dev)
 		return -ENODEV;
 
@@ -510,8 +503,6 @@ static int eql_g_slave_cfg(struct net_device *dev, slave_config_t __user *scp)
 	}
 	spin_unlock_bh(&eql->queue.lock);
 
-	dev_put(slave_dev);
-
 	if (!ret && copy_to_user(scp, &sc, sizeof (slave_config_t)))
 		ret = -EFAULT;
 
@@ -529,7 +520,7 @@ static int eql_s_slave_cfg(struct net_device *dev, slave_config_t __user *scp)
 	if (copy_from_user(&sc, scp, sizeof (slave_config_t)))
 		return -EFAULT;
 
-	slave_dev = dev_get_by_name(&init_net, sc.slave_name);
+	slave_dev = __dev_get_by_name(&init_net, sc.slave_name);
 	if (!slave_dev)
 		return -ENODEV;
 
@@ -548,8 +539,6 @@ static int eql_s_slave_cfg(struct net_device *dev, slave_config_t __user *scp)
 	}
 	spin_unlock_bh(&eql->queue.lock);
 
-	dev_put(slave_dev);
-
 	return ret;
 }