batman-adv: Check return value of try_module_get

New operations should not be started when they need an increased module
reference counter and try_module_get failed.

This patch addresses Coverity #712284: Unchecked return value

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/debugfs.c b/net/batman-adv/debugfs.c
index 391d4fb..bd032bc 100644
--- a/net/batman-adv/debugfs.c
+++ b/net/batman-adv/debugfs.c
@@ -99,15 +99,17 @@
 
 static int batadv_log_open(struct inode *inode, struct file *file)
 {
+	if (!try_module_get(THIS_MODULE))
+		return -EBUSY;
+
 	nonseekable_open(inode, file);
 	file->private_data = inode->i_private;
-	batadv_inc_module_count();
 	return 0;
 }
 
 static int batadv_log_release(struct inode *inode, struct file *file)
 {
-	batadv_dec_module_count();
+	module_put(THIS_MODULE);
 	return 0;
 }