Re: [PATCH v3 23/25] io_uring/rsrc: add io_buffer_register_bvec()

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

On Mon, Dec 22, 2025 at 4:37 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Add io_buffer_register_bvec() for registering a bvec array.
>
> This is a preparatory patch for fuse-over-io-uring zero-copy.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  include/linux/io_uring/cmd.h | 12 ++++++++++++
>  io_uring/rsrc.c              | 27 +++++++++++++++++++++++++++
>  2 files changed, 39 insertions(+)
>
> diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
> index 06e4cfadb344..f5094eb1206a 100644
> --- a/include/linux/io_uring/cmd.h
> +++ b/include/linux/io_uring/cmd.h
> @@ -106,6 +106,9 @@ int io_uring_cmd_is_kmbuf_ring(struct io_uring_cmd *ioucmd,
>  int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
>                                void (*release)(void *), unsigned int index,
>                                unsigned int issue_flags);
> +int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct bio_vec *bvs,

Could take const struct bio_vec *? Might also be helpful to document
that this internally makes a copy of the bio_vec array, so the memory
bvs points to can be deallocated as soon as io_buffer_register_bvec()
returns.

> +                           unsigned int nr_bvecs, unsigned int total_bytes,
> +                           u8 dir, unsigned int index, unsigned int issue_flags);
>  int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
>                          unsigned int issue_flags);
>  #else
> @@ -199,6 +202,15 @@ static inline int io_buffer_register_request(struct io_uring_cmd *cmd,
>  {
>         return -EOPNOTSUPP;
>  }
> +static inline int io_buffer_register_bvec(struct io_uring_cmd *cmd,
> +                                         struct bio_vec *bvs,
> +                                         unsigned int nr_bvecs,
> +                                         unsigned int total_bytes, u8 dir,
> +                                         unsigned int index,
> +                                         unsigned int issue_flags)
> +{
> +       return -EOPNOTSUPP;
> +}
>  static inline int io_buffer_unregister(struct io_uring_cmd *cmd,
>                                        unsigned int index,
>                                        unsigned int issue_flags)
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 5a708cecba4a..32126c06f4c9 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -1020,6 +1020,33 @@ int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
>  }
>  EXPORT_SYMBOL_GPL(io_buffer_register_request);
>
> +int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct bio_vec *bvs,
> +                           unsigned int nr_bvecs, unsigned int total_bytes,
> +                           u8 dir, unsigned int index,
> +                           unsigned int issue_flags)
> +{
> +       struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
> +       struct io_mapped_ubuf *imu;
> +       struct bio_vec *bvec;
> +       int i;

unsigned?

Other than that,
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>

> +
> +       io_ring_submit_lock(ctx, issue_flags);
> +       imu = io_kernel_buffer_init(ctx, nr_bvecs, total_bytes, dir, NULL,
> +                                   NULL, index);
> +       if (IS_ERR(imu)) {
> +               io_ring_submit_unlock(ctx, issue_flags);
> +               return PTR_ERR(imu);
> +       }
> +
> +       bvec = imu->bvec;
> +       for (i = 0; i < nr_bvecs; i++)
> +               bvec[i] = bvs[i];
> +
> +       io_ring_submit_unlock(ctx, issue_flags);
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(io_buffer_register_bvec);
> +
>  int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
>                          unsigned int issue_flags)
>  {
> --
> 2.47.3
>