allow attaching fs_pin to a group not associated with some superblock

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/internal.h b/fs/internal.h
index e9a61fe..a6efd2f 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -145,7 +145,7 @@
 /*
  * fs_pin.c
  */
-extern void sb_pin_kill(struct super_block *sb);
+extern void group_pin_kill(struct hlist_head *p);
 extern void mnt_pin_kill(struct mount *m);
 
 /*