Re: [RFC PATCH 4/7] ublk: convert to refcount_t

[Caleb Sander Mateos <csander@purestorage.com>]

On Mon, Apr 28, 2025 at 2:45 AM Ming Lei <ming.lei@redhat.com> wrote:
>
> Convert to refcount_t and prepare for supporting to register bvec buffer
> automatically, which needs to initialize reference counter as 2, and
> kref doesn't provide this interface, so convert to refcount_t.
>
> Suggested-by: Caleb Sander Mateos <csander@purestorage.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/block/ublk_drv.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index ac56482b55f5..9cd331d12fa6 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -79,7 +79,7 @@
>          UBLK_PARAM_TYPE_DMA_ALIGN | UBLK_PARAM_TYPE_SEGMENT)
>
>  struct ublk_rq_data {
> -       struct kref ref;
> +       refcount_t ref;
>  };
>
>  struct ublk_uring_cmd_pdu {
> @@ -484,7 +484,6 @@ static blk_status_t ublk_setup_iod_zoned(struct ublk_queue *ubq,
>  #endif
>
>  static inline void __ublk_complete_rq(struct request *req);
> -static void ublk_complete_rq(struct kref *ref);
>
>  static dev_t ublk_chr_devt;
>  static const struct class ublk_chr_class = {
> @@ -644,7 +643,7 @@ static inline void ublk_init_req_ref(const struct ublk_queue *ubq,
>         if (ublk_need_req_ref(ubq)) {
>                 struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
>
> -               kref_init(&data->ref);
> +               refcount_set(&data->ref, 1);
>         }
>  }
>
> @@ -654,7 +653,7 @@ static inline bool ublk_get_req_ref(const struct ublk_queue *ubq,
>         if (ublk_need_req_ref(ubq)) {
>                 struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
>
> -               return kref_get_unless_zero(&data->ref);
> +               return refcount_inc_not_zero(&data->ref);
>         }
>
>         return true;
> @@ -666,7 +665,8 @@ static inline void ublk_put_req_ref(const struct ublk_queue *ubq,
>         if (ublk_need_req_ref(ubq)) {
>                 struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
>
> -               kref_put(&data->ref, ublk_complete_rq);
> +               if(refcount_dec_and_test(&data->ref))

nit: missing space after if

Other than that,

Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>

> +                       __ublk_complete_rq(req);
>         } else {
>                 __ublk_complete_rq(req);
>         }
> @@ -1124,15 +1124,6 @@ static inline void __ublk_complete_rq(struct request *req)
>         blk_mq_end_request(req, res);
>  }
>
> -static void ublk_complete_rq(struct kref *ref)
> -{
> -       struct ublk_rq_data *data = container_of(ref, struct ublk_rq_data,
> -                       ref);
> -       struct request *req = blk_mq_rq_from_pdu(data);
> -
> -       __ublk_complete_rq(req);
> -}
> -
>  static void ublk_complete_io_cmd(struct ublk_io *io, struct request *req,
>                                  int res, unsigned issue_flags)
>  {
> --
> 2.47.0
>