Btrfs: fixup various fsx failures

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e8f7411..756ea9d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1198,5 +1198,8 @@
 					  struct btrfs_path *path,
 					  u64 objectid, u64 offset,
 					  int cow);
+int btrfs_csum_truncate(struct btrfs_trans_handle *trans,
+			struct btrfs_root *root, struct btrfs_path *path,
+			u64 isize);
 /* super.c */
 #endif