btrfs provides a helpful demonstration of how to export
a global variable via debugfs; however, it is unique among
other debugfs files in that it is world-writable, which causes
some concern to people who are not familiar with its purpose.

Fix it so that it is only user-writable.

Signed-off-by: Eric Sandeen <redacted>
---

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 4879656..fb84685 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c

@@ -834,7 +834,7 @@ static int btrfs_init_debugfs(void)
 	if (!btrfs_debugfs_root_dentry)
 		return -ENOMEM;
 
-	debugfs_create_u64("test", S_IRUGO | S_IWUGO, btrfs_debugfs_root_dentry,
+	debugfs_create_u64("test", S_IRUGO | S_IWUSR, btrfs_debugfs_root_dentry,
 			&btrfs_debugfs_test);
 #endif
 	return 0;