[Trusty][SRU][PATCH 3/3] net: rename sysfs symlinks on device name change

[Chris J Arges]

From: Veaceslav Falico <vfalico at redhat.com>

BugLink: http://bugs.launchpad.net/bugs/1410852

Currently, we don't rename the upper/lower_ifc symlinks in
/sys/class/net/*/ , which might result stale/duplicate links/names.

Fix this by adding netdev_adjacent_rename_links(dev, oldname) which renames
all the upper/lower interface's links to dev from the upper/lower_oldname
to the new name.

We don't need a rollback because only we control these symlinks and if we
fail to rename them - sysfs will anyway complain.

Reported-by: Ding Tianhong <dingtianhong at huawei.com>
CC: Ding Tianhong <dingtianhong at huawei.com>
CC: "David S. Miller" <davem at davemloft.net>
CC: Eric Dumazet <edumazet at google.com>
CC: Nicolas Dichtel <nicolas.dichtel at 6wind.com>
CC: Cong Wang <amwang at redhat.com>
Signed-off-by: Veaceslav Falico <vfalico at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit 5bb025fae53889cc99a21058c5dd369bf8cce820)
Signed-off-by: Chris J Arges <chris.j.arges at canonical.com>

Conflicts:
	include/linux/netdevice.h
	net/core/dev.c
---
 include/linux/netdevice.h |  3 +--
 net/core/dev.c            | 27 +++++++++++++++++----------
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c46b3b2..d11aef3 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2937,8 +2937,7 @@ int netdev_master_upper_dev_link_private(struct net_device *dev,
 					 void *private);
 void netdev_upper_dev_unlink(struct net_device *dev,
 			     struct net_device *upper_dev);
-void *netdev_lower_dev_get_private_rcu(struct net_device *dev,
-				       struct net_device *lower_dev);
+void netdev_adjacent_rename_links(struct net_device *dev, char *oldname);
 void *netdev_lower_dev_get_private(struct net_device *dev,
 				   struct net_device *lower_dev);
 int dev_get_nest_level(struct net_device *dev,
diff --git a/net/core/dev.c b/net/core/dev.c
index 924beb2..25cf972 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1118,6 +1118,8 @@ rollback:
 
 	write_seqcount_end(&devnet_rename_seq);
 
+	netdev_adjacent_rename_links(dev, oldname);
+
 	write_lock_bh(&dev_base_lock);
 	hlist_del_rcu(&dev->name_hlist);
 	write_unlock_bh(&dev_base_lock);
@@ -1137,6 +1139,7 @@ rollback:
 			err = ret;
 			write_seqcount_begin(&devnet_rename_seq);
 			memcpy(dev->name, oldname, IFNAMSIZ);
+			memcpy(oldname, newname, IFNAMSIZ);
 			goto rollback;
 		} else {
 			pr_err("%s: name change rollback failed: %d\n",
@@ -5035,20 +5038,24 @@ void netdev_upper_dev_unlink(struct net_device *dev,
 }
 EXPORT_SYMBOL(netdev_upper_dev_unlink);
 
-void *netdev_lower_dev_get_private_rcu(struct net_device *dev,
-				       struct net_device *lower_dev)
+void netdev_adjacent_rename_links(struct net_device *dev, char *oldname)
 {
-	struct netdev_adjacent *lower;
+	struct netdev_adjacent *iter;
 
-	if (!lower_dev)
-		return NULL;
-	lower = __netdev_find_adj_rcu(dev, lower_dev, &dev->adj_list.lower);
-	if (!lower)
-		return NULL;
+	list_for_each_entry(iter, &dev->adj_list.upper, list) {
+		netdev_adjacent_sysfs_del(iter->dev, oldname,
+					  &iter->dev->adj_list.lower);
+		netdev_adjacent_sysfs_add(iter->dev, dev,
+					  &iter->dev->adj_list.lower);
+	}
 
-	return lower->private;
+	list_for_each_entry(iter, &dev->adj_list.lower, list) {
+		netdev_adjacent_sysfs_del(iter->dev, oldname,
+					  &iter->dev->adj_list.upper);
+		netdev_adjacent_sysfs_add(iter->dev, dev,
+					  &iter->dev->adj_list.upper);
+	}
 }
-EXPORT_SYMBOL(netdev_lower_dev_get_private_rcu);
 
 void *netdev_lower_dev_get_private(struct net_device *dev,
 				   struct net_device *lower_dev)
-- 
1.9.1