-/*
- * The ->queue() hook is responsible for initiating io on the io_u
- * being passed in. If the io engine is a synchronous one, io may complete
- * before ->queue() returns. Required.
- *
- * The io engine must transfer in the direction noted by io_u->ddir
- * to the buffer pointed to by io_u->xfer_buf for as many bytes as
- * io_u->xfer_buflen. Residual data count may be set in io_u->resid
- * for a short read/write.
- */