Use deactivate_locked_super

Found by Al Viro.

Signed-off-by: Joern Engel <joern@logfs.org>
diff --git a/fs/logfs/super.c b/fs/logfs/super.c
index 2845c41..9d856c4 100644
--- a/fs/logfs/super.c
+++ b/fs/logfs/super.c
@@ -572,8 +572,7 @@
 	return 0;
 
 err1:
-	up_write(&sb->s_umount);
-	deactivate_super(sb);
+	deactivate_locked_super(sb);
 	return err;
 err0:
 	kfree(super);