On Tue, Apr 15, 2025 at 6:00 PM Uday Shankar <ushankar@xxxxxxxxxxxxxxx> wrote:
>
> We now allow multiple tasks to operate on I/Os belonging to the same
> queue concurrently. This means that any writes to ublk_queue in the I/O
> path are potential sources of data races. Try to prevent these by
> marking ublk_queue pointers as const in ublk_handle_need_get_data. Also
> move a bit more of the NEED_GET_DATA-specific logic into
> ublk_handle_need_get_data, to make the pattern in __ublk_ch_uring_cmd
> more uniform.
>
> Suggested-by: Ming Lei <ming.lei@xxxxxxxxxx>
> Signed-off-by: Uday Shankar <ushankar@xxxxxxxxxxxxxxx>
> ---
> drivers/block/ublk_drv.c | 33 ++++++++++++++++++++-------------
> 1 file changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index e2cb54895481aebaa91ab23ba05cf26a950a642f..c8ce9349ca280b8b16040a1242a62b895ee01b5d 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1291,7 +1291,7 @@ static void ublk_cmd_tw_cb(struct io_uring_cmd *cmd,
> ublk_dispatch_req(ubq, pdu->req, issue_flags);
> }
>
> -static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq)
> +static void ublk_queue_cmd(const struct ublk_queue *ubq, struct request *rq)
> {
> struct io_uring_cmd *cmd = ubq->ios[rq->tag].cmd;
> struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
> @@ -1813,15 +1813,6 @@ static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
> mutex_unlock(&ub->mutex);
> }
>
> -static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id,
> - int tag)
> -{
> - struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
> - struct request *req = blk_mq_tag_to_rq(ub->tag_set.tags[q_id], tag);
> -
> - ublk_queue_cmd(ubq, req);
> -}
> -
> static inline int ublk_check_cmd_op(u32 cmd_op)
> {
> u32 ioc_type = _IOC_TYPE(cmd_op);
> @@ -1933,6 +1924,21 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
> return -EIOCBQUEUED;
> }
>
> +static int ublk_handle_need_get_data(const struct ublk_queue *ubq,
> + struct ublk_io *io,
> + struct io_uring_cmd *cmd,
> + const struct ublksrv_io_cmd *ub_cmd,
> + struct request *req)
nit: I see this is matching the name of the opcode (I am not sure why
it has "need" in its name) and there is already a function named
"ublk_need_get_data". But maybe naming this function "ublk_get_data"
would be clearer?
> +{
> + if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
> + return -EINVAL;
> +
> + ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
> + ublk_queue_cmd(ubq, req);
> +
> + return -EIOCBQUEUED;
Here too, I think a return value of 0 would be clearer.
Best,
Caleb
