f2fs: fix error path handling in truncate_dnode()

If truncate_node() fails in truncate_dnode(), it missed to call
f2fs_put_page(), fix it.

Fixes: 7735730d ("f2fs: fix to propagate error from __get_meta_page()")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -943,8 +943,10 @@ static int truncate_dnode(struct dnode_of_data *dn)
 	dn->ofs_in_node = 0;
 	f2fs_truncate_data_blocks(dn);
 	err = truncate_node(dn);
-	if (err)
+	if (err) {
+		f2fs_put_page(page, 1);
 		return err;
+	}
 
 	return 1;
 }