+/**
+ * bio_truncate - truncate the bio to small size of @new_size
+ * @bio: the bio to be truncated
+ * @new_size: new size for truncating the bio
+ *
+ * Description:
+ * Truncate the bio to new size of @new_size. If bio_op(bio) is
+ * REQ_OP_READ, zero the truncated part. This function should only
+ * be used for handling corner cases, such as bio eod.
+ */