Re: [PATCH V2 3/3] selftests: ublk: add ublk zero copy test

[Keith Busch <kbusch@kernel.org>]

On Wed, Feb 26, 2025 at 11:58:38PM +0800, Ming Lei wrote:
> +	struct io_uring_sqe *reg;
> +	struct io_uring_sqe *rw;
> +	struct io_uring_sqe *ureg;
> +
> +	if (!zc) {
> +		rw = ublk_queue_alloc_sqe(q);
> +		if (!rw)
> +			return -ENOMEM;
> +
> +		io_uring_prep_rw(op, rw, 1 /*fds[1]*/,
> +				(void *)iod->addr,
> +				iod->nr_sectors << 9,
> +				iod->start_sector << 9);
> +		io_uring_sqe_set_flags(rw, IOSQE_FIXED_FILE);
> +		q->io_inflight++;
> +		/* bit63 marks us as tgt io */
> +		rw->user_data = build_user_data(tag, op, UBLK_IO_TGT_NORMAL, 1);
> +		return 0;
> +	}
> +
> +	ublk_queue_alloc_sqe3(q, &reg, &rw, &ureg);
> +
> +	io_uring_prep_buf_register(reg, 0, tag, q->q_id, tag);
> +	reg->user_data = build_user_data(tag, 0xfe, 1, 1);
> +	reg->flags |= IOSQE_CQE_SKIP_SUCCESS;
> +	reg->flags |= IOSQE_IO_LINK;
> +
> +	io_uring_prep_rw(op, rw, 1 /*fds[1]*/, 0,
> +		iod->nr_sectors << 9,
> +		iod->start_sector << 9);
> +	rw->buf_index = tag;
> +	rw->flags |= IOSQE_FIXED_FILE;
> +	rw->flags |= IOSQE_IO_LINK;
> +	rw->user_data = build_user_data(tag, op, UBLK_IO_TGT_ZC_OP, 1);
> +	q->io_inflight++;
> +
> +	io_uring_prep_buf_unregister(ureg, 0, tag, q->q_id, tag);
> +	ureg->user_data = build_user_data(tag, 0xff, UBLK_IO_TGT_ZC_BUF, 1);

You don't have anything handling the unregister command's completion so
I think you want the IOSQE_CQE_SKIP_SUCCESS flag on it otherwise you get
an unexpected CQE for it.