Re: [PATCH V6 07/24] ublk: add batch I/O dispatch infrastructure

[Ming Lei <ming.lei@redhat.com>]

On Thu, Jan 22, 2026 at 08:32:25PM -0700, Jens Axboe wrote:
> Claude says:
> 
> > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> > index e5db5a552357..e7bd7e7b1731 100644
> > --- a/drivers/block/ublk_drv.c
> > +++ b/drivers/block/ublk_drv.c
> 
> [ ... ]
> 
> > +static bool __ublk_batch_prep_dispatch(struct ublk_queue *ubq,
> > +				       const struct ublk_batch_io_data *data,
> > +				       unsigned short tag)
> > +{
> > +	struct ublk_device *ub = data->ub;
> > +	struct ublk_io *io = &ubq->ios[tag];
> > +	struct request *req = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], tag);
> > +	enum auto_buf_reg_res res = AUTO_BUF_REG_FALLBACK;
> > +	struct io_uring_cmd *cmd = data->cmd;
> > +
> > +	if (!ublk_start_io(ubq, req, io))
> > +		return false;
> > +
> > +	if (ublk_support_auto_buf_reg(ubq) && ublk_rq_has_data(req)) {
> > +		res = __ublk_do_auto_buf_reg(ubq, req, io, cmd,
> > +				data->issue_flags);
> > +
> > +		if (res == AUTO_BUF_REG_FAIL)
> > +			return false;
> > +	}
> > +
> > +	ublk_io_lock(io);
> > +	ublk_prep_auto_buf_reg_io(ubq, req, io, cmd, res);
> > +	ublk_io_unlock(io);
> > +
> > +	return true;
> > +}
> 
> [ ... ]
> 
> > +#define MAX_NR_TAG 128
> > +static int __ublk_batch_dispatch(struct ublk_queue *ubq,
> > +				 const struct ublk_batch_io_data *data,
> > +				 struct ublk_batch_fetch_cmd *fcmd)
> > +{
> 
> [ ... ]
> 
> > +	sel.val = ublk_batch_copy_io_tags(fcmd, sel.addr, tag_buf, len * tag_sz);
> > +	ret = ublk_batch_fetch_post_cqe(fcmd, &sel, data->issue_flags);
> > +	if (unlikely(ret < 0)) {
> > +		int i, res;
> > +
> > +		/*
> > +		 * Undo prep state for all IOs since userspace never received them.
> > +		 * This restores IOs to pre-prepared state so they can be cleanly
> > +		 * re-prepared when tags are pulled from FIFO again.
> > +		 */
> > +		for (i = 0; i < len; i++) {
> > +			struct ublk_io *io = &ubq->ios[tag_buf[i]];
> > +			int index = -1;
> > +
> > +			ublk_io_lock(io);
> > +			if (io->flags & UBLK_IO_FLAG_AUTO_BUF_REG)
> > +				index = io->buf.auto_reg.index;
> > +			io->flags &= ~(UBLK_IO_FLAG_OWNED_BY_SRV | UBLK_IO_FLAG_AUTO_BUF_REG);
> > +			io->flags |= UBLK_IO_FLAG_ACTIVE;
> > +			ublk_io_unlock(io);
> > +
> > +			if (index != -1)
> > +				io_buffer_unregister_bvec(data->cmd, index,
> > +						data->issue_flags);
> > +		}
> 
> Should io->task_registered_buffers also be cleared here?

No, io_buffer_unregister_bvec() and the callback(ublk_io_release()) consumes
io->task_registered_buffers actually.



Thanks,
Ming