On Mon, Sep 1, 2025 at 3:03 AM Ming Lei <ming.lei@xxxxxxxxxx> wrote:
>
> batch io is designed to be independent of task context, and we will not
> track task context for batch io feature.
>
> So warn on non-batch-io code paths.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> drivers/block/ublk_drv.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index a0dfad8a56f0..46be5b656f22 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -261,6 +261,11 @@ static inline bool ublk_dev_support_batch_io(const struct ublk_device *ub)
> return false;
> }
>
> +static inline bool ublk_support_batch_io(const struct ublk_queue *ubq)
> +{
> + return false;
> +}
> +
> static inline struct ublksrv_io_desc *
> ublk_get_iod(const struct ublk_queue *ubq, unsigned tag)
> {
> @@ -1309,6 +1314,8 @@ static void ublk_dispatch_req(struct ublk_queue *ubq,
> __func__, ubq->q_id, req->tag, io->flags,
> ublk_get_iod(ubq, req->tag)->addr);
>
> + WARN_ON_ONCE(ublk_support_batch_io(ubq));
Hmm, not a huge fan of extra checks in the I/O path. It seems fairly
easy to verify from the code that these functions won't be called for
batch commands. Do we really need the assertion?
> +
> /*
> * Task is exiting if either:
> *
> @@ -1868,6 +1875,8 @@ static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd,
> if (WARN_ON_ONCE(pdu->tag >= ubq->q_depth))
> return;
>
> + WARN_ON_ONCE(ublk_support_batch_io(ubq));
> +
> task = io_uring_cmd_get_task(cmd);
> io = &ubq->ios[pdu->tag];
> if (WARN_ON_ONCE(task && task != io->task))
> @@ -2233,7 +2242,10 @@ static int __ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
>
> ublk_fill_io_cmd(io, cmd);
>
> - WRITE_ONCE(io->task, get_task_struct(current));
> + if (ublk_support_batch_io(ubq))
> + WRITE_ONCE(io->task, NULL);
Don't see a need to explicitly write NULL here since the ublk_io
memory is zero-initialized.
Best,
Caleb
> + else
> + WRITE_ONCE(io->task, get_task_struct(current));
> ublk_mark_io_ready(ub, ubq);
> out:
> return ret;
> @@ -2347,6 +2359,8 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
> if (tag >= ubq->q_depth)
> goto out;
>
> + WARN_ON_ONCE(ublk_support_batch_io(ubq));
> +
> io = &ubq->ios[tag];
> /* UBLK_IO_FETCH_REQ can be handled on any task, which sets io->task */
> if (unlikely(_IOC_NR(cmd_op) == UBLK_IO_FETCH_REQ)) {
> --
> 2.47.0
>
