[PATCH net-next] net/core: Allow live renaming when an interface is up

[Andy Ren]

This patch allows a network interface to be renamed when the interface
is up.

Live renaming was added as a failover in the past, and there has been no
arising issues of user space breaking. Furthermore, it seems that this
flag was added because in the past, IOCTL was used for renaming, which
would not notify the user space. Nowadays, it appears that the user
space receives notifications regardless of the state of the network
device (e.g. rtnetlink_event()). The listeners for NETDEV_CHANGENAME
also do not strictly ensure that the netdev is up or not.

Hence, this patch seeks to remove the live renaming flag and checks due
to the aforementioned reasons.

The changes are of following:
- Remove IFF_LIVE_RENAME_OK flag declarations
- Remove check in dev_change_name that checks whether device is up and
if IFF_LIVE_RENAME_OK is set by the network device's priv_flags
- Remove references of IFF_LIVE_RENAME_OK in the failover module

Signed-off-by: Andy Ren <andy.ren@xxxxxxxxxxxxx>
---
 include/linux/netdevice.h | 3 ---
 net/core/dev.c            | 4 ----
 net/core/failover.c       | 6 +++---
 3 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4b5052db978f..e2ff45aa17f5 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1655,7 +1655,6 @@ struct net_device_ops {
  * @IFF_FAILOVER: device is a failover master device
  * @IFF_FAILOVER_SLAVE: device is lower dev of a failover master device
  * @IFF_L3MDEV_RX_HANDLER: only invoke the rx handler of L3 master device
- * @IFF_LIVE_RENAME_OK: rename is allowed while device is up and running
  * @IFF_TX_SKB_NO_LINEAR: device/driver is capable of xmitting frames with
  *	skb_headlen(skb) == 0 (data starts from frag0)
  * @IFF_CHANGE_PROTO_DOWN: device supports setting carrier via IFLA_PROTO_DOWN
@@ -1691,7 +1690,6 @@ enum netdev_priv_flags {
 	IFF_FAILOVER			= 1<<27,
 	IFF_FAILOVER_SLAVE		= 1<<28,
 	IFF_L3MDEV_RX_HANDLER		= 1<<29,
-	IFF_LIVE_RENAME_OK		= 1<<30,
 	IFF_TX_SKB_NO_LINEAR		= BIT_ULL(31),
 	IFF_CHANGE_PROTO_DOWN		= BIT_ULL(32),
 };
@@ -1726,7 +1724,6 @@ enum netdev_priv_flags {
 #define IFF_FAILOVER			IFF_FAILOVER
 #define IFF_FAILOVER_SLAVE		IFF_FAILOVER_SLAVE
 #define IFF_L3MDEV_RX_HANDLER		IFF_L3MDEV_RX_HANDLER
-#define IFF_LIVE_RENAME_OK		IFF_LIVE_RENAME_OK
 #define IFF_TX_SKB_NO_LINEAR		IFF_TX_SKB_NO_LINEAR
 
 /* Specifies the type of the struct net_device::ml_priv pointer */
diff --git a/net/core/dev.c b/net/core/dev.c
index 2e4f1c97b59e..dd373b86b3d2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1175,10 +1175,6 @@ int dev_change_name(struct net_device *dev, const char *newname)
 	 * they are supposed to operate on master interface
 	 * directly.
 	 */
-	if (dev->flags & IFF_UP &&
-	    likely(!(dev->priv_flags & IFF_LIVE_RENAME_OK)))
-		return -EBUSY;
-
 	down_write(&devnet_rename_sem);
 
 	if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {
diff --git a/net/core/failover.c b/net/core/failover.c
index 864d2d83eff4..655411c4ca51 100644
--- a/net/core/failover.c
+++ b/net/core/failover.c
@@ -80,14 +80,14 @@ static int failover_slave_register(struct net_device *slave_dev)
 		goto err_upper_link;
 	}
 
-	slave_dev->priv_flags |= (IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
+	slave_dev->priv_flags |= IFF_FAILOVER_SLAVE;
 
 	if (fops && fops->slave_register &&
 	    !fops->slave_register(slave_dev, failover_dev))
 		return NOTIFY_OK;
 
 	netdev_upper_dev_unlink(slave_dev, failover_dev);
-	slave_dev->priv_flags &= ~(IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
+	slave_dev->priv_flags &= ~IFF_FAILOVER_SLAVE;
 err_upper_link:
 	netdev_rx_handler_unregister(slave_dev);
 done:
@@ -121,7 +121,7 @@ int failover_slave_unregister(struct net_device *slave_dev)
 
 	netdev_rx_handler_unregister(slave_dev);
 	netdev_upper_dev_unlink(slave_dev, failover_dev);
-	slave_dev->priv_flags &= ~(IFF_FAILOVER_SLAVE | IFF_LIVE_RENAME_OK);
+	slave_dev->priv_flags &= ~IFF_FAILOVER_SLAVE;
 
 	if (fops && fops->slave_unregister &&
 	    !fops->slave_unregister(slave_dev, failover_dev))
-- 
2.38.1