vfs: for usbfs, etc. internal vfsmounts ->mnt_sb->s_root == ->mnt_root

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 9a37a9b..36b1d7a 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -312,7 +312,7 @@
 	if (item->ci_parent)
 		parent = item->ci_parent->ci_dentry;
 	else if (configfs_mount && configfs_mount->mnt_sb)
-		parent = configfs_mount->mnt_sb->s_root;
+		parent = configfs_mount->mnt_root;
 	else
 		return -EFAULT;
 
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index f3a257d..c9dc08d 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -160,7 +160,7 @@
 	 * have around.
 	 */
 	if (!parent)
-		parent = debugfs_mount->mnt_sb->s_root;
+		parent = debugfs_mount->mnt_root;
 
 	*dentry = NULL;
 	mutex_lock(&parent->d_inode->i_mutex);
diff --git a/fs/hppfs/hppfs.c b/fs/hppfs/hppfs.c
index 30883a7..d92f4ce 100644
--- a/fs/hppfs/hppfs.c
+++ b/fs/hppfs/hppfs.c
@@ -725,7 +725,7 @@
 	sb->s_fs_info = proc_mnt;
 
 	err = -ENOMEM;
-	root_inode = get_inode(sb, dget(proc_mnt->mnt_sb->s_root));
+	root_inode = get_inode(sb, dget(proc_mnt->mnt_root));
 	if (!root_inode)
 		goto out_mntput;