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>

1 files changed, 10 insertions, 4 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 16ab09b6a7f8..1594cd2955ba 100644
--- a/net/core/dev.c
+++ b/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) {