Re: [PATCH v2 1/8] io_uring/uring_cmd: add io_uring_cmd_import_fixed_full()

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

On Mon, Oct 27, 2025 at 3:29 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Add an API for fetching the registered buffer associated with a
> io_uring cmd. This is useful for callers who need access to the buffer
> but do not have prior knowledge of the buffer's user address or length.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  include/linux/io_uring/cmd.h |  3 +++
>  io_uring/rsrc.c              | 14 ++++++++++++++
>  io_uring/rsrc.h              |  2 ++
>  io_uring/uring_cmd.c         | 13 +++++++++++++
>  4 files changed, 32 insertions(+)
>
> diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
> index 7509025b4071..8c11d9a92733 100644
> --- a/include/linux/io_uring/cmd.h
> +++ b/include/linux/io_uring/cmd.h
> @@ -43,6 +43,9 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
>                               struct iov_iter *iter,
>                               struct io_uring_cmd *ioucmd,
>                               unsigned int issue_flags);
> +int io_uring_cmd_import_fixed_full(int rw, struct iov_iter *iter,
> +                                  struct io_uring_cmd *ioucmd,
> +                                  unsigned int issue_flags);
>  int io_uring_cmd_import_fixed_vec(struct io_uring_cmd *ioucmd,
>                                   const struct iovec __user *uvec,
>                                   size_t uvec_segs,
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index d787c16dc1c3..2c3d8489ae52 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -1147,6 +1147,20 @@ int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
>         return io_import_fixed(ddir, iter, node->buf, buf_addr, len);
>  }
>
> +int io_import_reg_buf_full(struct io_kiocb *req, struct iov_iter *iter,
> +                          int ddir, unsigned issue_flags)
> +{
> +       struct io_rsrc_node *node;
> +       struct io_mapped_ubuf *imu;
> +
> +       node = io_find_buf_node(req, issue_flags);
> +       if (!node)
> +               return -EFAULT;
> +
> +       imu = node->buf;
> +       return io_import_fixed(ddir, iter, imu, imu->ubuf, imu->len);

It's probably possible to avoid the logic in io_import_fixed() for
checking the user address range against the registered buffer's range
and offsetting the iov_iter, but that could always be done as future
optimization work.

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

> +}
> +
>  /* Lock two rings at once. The rings must be different! */
>  static void lock_two_rings(struct io_ring_ctx *ctx1, struct io_ring_ctx *ctx2)
>  {
> diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> index a3ca6ba66596..4e01eb0f277e 100644
> --- a/io_uring/rsrc.h
> +++ b/io_uring/rsrc.h
> @@ -64,6 +64,8 @@ struct io_rsrc_node *io_find_buf_node(struct io_kiocb *req,
>  int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
>                         u64 buf_addr, size_t len, int ddir,
>                         unsigned issue_flags);
> +int io_import_reg_buf_full(struct io_kiocb *req, struct iov_iter *iter,
> +                          int ddir, unsigned issue_flags);
>  int io_import_reg_vec(int ddir, struct iov_iter *iter,
>                         struct io_kiocb *req, struct iou_vec *vec,
>                         unsigned nr_iovs, unsigned issue_flags);
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index d1e3ba62ee8e..07730ced9449 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -292,6 +292,19 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
>  }
>  EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
>
> +int io_uring_cmd_import_fixed_full(int rw, struct iov_iter *iter,
> +                                  struct io_uring_cmd *ioucmd,
> +                                  unsigned int issue_flags)
> +{
> +       struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
> +
> +       if (WARN_ON_ONCE(!(ioucmd->flags & IORING_URING_CMD_FIXED)))
> +               return -EINVAL;
> +
> +       return io_import_reg_buf_full(req, iter, rw, issue_flags);
> +}
> +EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed_full);
> +
>  int io_uring_cmd_import_fixed_vec(struct io_uring_cmd *ioucmd,
>                                   const struct iovec __user *uvec,
>                                   size_t uvec_segs,
> --
> 2.47.3
>