rolling_buffer_append
added = rolling_buffer_append(&rreq->buffer, folio, rollbuf_flags);
if (rolling_buffer_append(&creq->buffer, folio, 0) < 0) {
rolling_buffer_append(&wreq->buffer, folio, 0);
rolling_buffer_append(&wreq->buffer, folio, NETFS_ROLLBUF_PUT_MARK);
ssize_t rolling_buffer_append(struct rolling_buffer *roll, struct folio *folio,