[PATCH blktests] block tests: nvme metadata passthrough

[Anuj gupta]

> +       /* this should directly use the user space buffer */
> +       meta = mptr;
> +       cmd = (struct nvme_passthru_cmd) {
> +               .opcode         = 1,
> +               .nsid           = 1,

Minor nit: should use `.nsid = nsid` instead of hardcoded `1`

> +       /* This should not be mappable for write commands */

Maybe reword this to:
/* This buffer is read-only, so using it for write passthrough should fail */
-- makes the intent clearer.

--
Anuj Gupta