Merge branch 'netdev-name-in-use'

Antoine Tenart says:

====================
net: introduce a function to check if a netdev name is in use

This was initially part of an RFC series[1] but has value on its own;
hence the standalone report. (It will also help in not having a series
too large).

From patch 1:

"""
__dev_get_by_name is currently used to either retrieve a net device
reference using its name or to check if a name is already used by a
registered net device (per ns). In the later case there is no need to
return a reference to a net device.

Introduce a new helper, netdev_name_in_use, to check if a name is
currently used by a registered net device without leaking a reference
the corresponding net device. This helper uses netdev_name_node_lookup
instead of __dev_get_by_name as we don't need the extra logic retrieving
a reference to the corresponding net device.
"""

Two uses[2] of __dev_get_by_name weren't converted to this new function,
as they are really looking for a net device, not only checking if a net
device name is in use. While checking one or the other currently has
the same result, that might change if the initial RFC series moves
forward. I'll convert them later depending on the outcome of the initial
series.

Thanks,
Antoine

[1] https://lore.kernel.org/all/20210928125500.167943-1-atenart@kernel.org/
[2] drivers/net/Space.c:130 & drivers/nvme/host/tcp.c:2550
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_sysfs.c

@@ -811,8 +811,8 @@ int bond_create_sysfs(struct bond_net *bn)
 	 */
 	if (ret == -EEXIST) {
 		/* Is someone being kinky and naming a device bonding_master? */
-		if (__dev_get_by_name(bn->net,
-				      class_attr_bonding_masters.attr.name))
+		if (netdev_name_in_use(bn->net,
+				       class_attr_bonding_masters.attr.name))
 			pr_err("network device named %s already exists in sysfs\n",
 			       class_attr_bonding_masters.attr.name);
 		ret = 0;

drivers/net/ppp/ppp_generic.c

@@ -1161,7 +1161,7 @@ static int ppp_unit_register(struct ppp *ppp, int unit, bool ifname_is_set)
 		if (!ifname_is_set) {
 			while (1) {
 				snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ret);
-				if (!__dev_get_by_name(ppp->ppp_net, ppp->dev->name))
+				if (!netdev_name_in_use(ppp->ppp_net, ppp->dev->name))
 					break;
 				unit_put(&pn->units_idr, ret);
 				ret = unit_get(&pn->units_idr, ppp, ret + 1);

include/linux/netdevice.h

@@ -2955,6 +2955,7 @@ struct net_device *__dev_get_by_flags(struct net *net, unsigned short flags,
 struct net_device *dev_get_by_name(struct net *net, const char *name);
 struct net_device *dev_get_by_name_rcu(struct net *net, const char *name);
 struct net_device *__dev_get_by_name(struct net *net, const char *name);
+bool netdev_name_in_use(struct net *net, const char *name);
 int dev_alloc_name(struct net_device *dev, const char *name);
 int dev_open(struct net_device *dev, struct netlink_ext_ack *extack);
 void dev_close(struct net_device *dev);

net/core/dev.c

@@ -303,6 +303,12 @@ static struct netdev_name_node *netdev_name_node_lookup_rcu(struct net *net,
 	return NULL;
 }
 
+bool netdev_name_in_use(struct net *net, const char *name)
+{
+	return netdev_name_node_lookup(net, name);
+}
+EXPORT_SYMBOL(netdev_name_in_use);
+
 int netdev_name_node_alt_create(struct net_device *dev, const char *name)
 {
 	struct netdev_name_node *name_node;
@@ -1133,7 +1139,7 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
 	}
 
 	snprintf(buf, IFNAMSIZ, name, i);
-	if (!__dev_get_by_name(net, buf))
+	if (!netdev_name_in_use(net, buf))
 		return i;
 
 	/* It is possible to run out of possible slots
@@ -1187,7 +1193,7 @@ static int dev_get_valid_name(struct net *net, struct net_device *dev,
 
 	if (strchr(name, '%'))
 		return dev_alloc_name_ns(net, dev, name);
-	else if (__dev_get_by_name(net, name))
+	else if (netdev_name_in_use(net, name))
 		return -EEXIST;
 	else if (dev->name != name)
 		strlcpy(dev->name, name, IFNAMSIZ);
@@ -11153,7 +11159,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	 * we can use it in the destination network namespace.
 	 */
 	err = -EEXIST;
-	if (__dev_get_by_name(net, dev->name)) {
+	if (netdev_name_in_use(net, dev->name)) {
 		/* We get here if we can't use the current device name */
 		if (!pat)
 			goto out;
@@ -11506,7 +11512,7 @@ static void __net_exit default_device_exit(struct net *net)
 
 		/* Push remaining network devices to init_net */
 		snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
-		if (__dev_get_by_name(&init_net, fb_name))
+		if (netdev_name_in_use(&init_net, fb_name))
 			snprintf(fb_name, IFNAMSIZ, "dev%%d");
 		err = dev_change_net_namespace(dev, &init_net, fb_name);
 		if (err) {