hsr: add hsr root debugfs directory

In current hsr code, when hsr interface is created, it creates debugfs
directory /sys/kernel/debug/<interface name>.
If there is same directory or file name in there, it fails.
In order to reduce possibility of failure of creation of debugfs,
this patch adds root directory.

Test commands:
    ip link add dummy0 type dummy
    ip link add dummy1 type dummy
    ip link add hsr0 type hsr slave1 dummy0 slave2 dummy1

Before this patch:
    /sys/kernel/debug/hsr0/node_table

After this patch:
    /sys/kernel/debug/hsr/hsr0/node_table
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/hsr/hsr_debugfs.c

@@ -20,6 +20,8 @@
 #include "hsr_main.h"
 #include "hsr_framereg.h"
 
+static struct dentry *hsr_debugfs_root_dir;
+
 static void print_mac_address(struct seq_file *sfp, unsigned char *mac)
 {
 	seq_printf(sfp, "%02x:%02x:%02x:%02x:%02x:%02x:",
@@ -81,9 +83,9 @@ void hsr_debugfs_init(struct hsr_priv *priv, struct net_device *hsr_dev)
 {
 	struct dentry *de = NULL;
 
-	de = debugfs_create_dir(hsr_dev->name, NULL);
+	de = debugfs_create_dir(hsr_dev->name, hsr_debugfs_root_dir);
 	if (IS_ERR(de)) {
-		pr_err("Cannot create hsr debugfs root\n");
+		pr_err("Cannot create hsr debugfs directory\n");
 		return;
 	}
 
@@ -93,7 +95,7 @@ void hsr_debugfs_init(struct hsr_priv *priv, struct net_device *hsr_dev)
 				 priv->node_tbl_root, priv,
 				 &hsr_fops);
 	if (IS_ERR(de)) {
-		pr_err("Cannot create hsr node_table directory\n");
+		pr_err("Cannot create hsr node_table file\n");
 		debugfs_remove(priv->node_tbl_root);
 		priv->node_tbl_root = NULL;
 		return;
@@ -115,3 +117,18 @@ hsr_debugfs_term(struct hsr_priv *priv)
 	debugfs_remove(priv->node_tbl_root);
 	priv->node_tbl_root = NULL;
 }
+
+void hsr_debugfs_create_root(void)
+{
+	hsr_debugfs_root_dir = debugfs_create_dir("hsr", NULL);
+	if (IS_ERR(hsr_debugfs_root_dir)) {
+		pr_err("Cannot create hsr debugfs root directory\n");
+		hsr_debugfs_root_dir = NULL;
+	}
+}
+
+void hsr_debugfs_remove_root(void)
+{
+	/* debugfs_remove() internally checks NULL and ERROR */
+	debugfs_remove(hsr_debugfs_root_dir);
+}

net/hsr/hsr_main.c

@@ -123,6 +123,7 @@ static void __exit hsr_exit(void)
 {
 	unregister_netdevice_notifier(&hsr_nb);
 	hsr_netlink_exit();
+	hsr_debugfs_remove_root();
 }
 
 module_init(hsr_init);

net/hsr/hsr_main.h

@@ -186,12 +186,18 @@ static inline u16 hsr_get_skb_sequence_nr(struct sk_buff *skb)
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 void hsr_debugfs_init(struct hsr_priv *priv, struct net_device *hsr_dev);
 void hsr_debugfs_term(struct hsr_priv *priv);
+void hsr_debugfs_create_root(void);
+void hsr_debugfs_remove_root(void);
 #else
 static inline void hsr_debugfs_init(struct hsr_priv *priv,
 				    struct net_device *hsr_dev)
 {}
 static inline void hsr_debugfs_term(struct hsr_priv *priv)
 {}
+static inline void hsr_debugfs_create_root(void)
+{}
+static inline void hsr_debugfs_remove_root(void)
+{}
 #endif
 
 #endif /*  __HSR_PRIVATE_H */

net/hsr/hsr_netlink.c

@@ -476,6 +476,7 @@ int __init hsr_netlink_init(void)
 	if (rc)
 		goto fail_genl_register_family;
 
+	hsr_debugfs_create_root();
 	return 0;
 
 fail_genl_register_family: