Re: [PATCH v1 2/5] io_uring/rsrc: split io_buffer_register_request() logic

[Joanne Koong <joannelkoong@gmail.com>]

On Mon, Mar 23, 2026 at 5:10 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Split the main initialization logic in io_buffer_register_request() into
> a helper function.
>
> This is a preparatory patch for supporting kernel-populated buffers in
> fuse io-uring, which will be reusing this logic.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
> ---
>  io_uring/rsrc.c | 84 ++++++++++++++++++++++++++++++-------------------
>  1 file changed, 51 insertions(+), 33 deletions(-)
>
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 7579f6992a25..1902ab7941ac 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -924,64 +924,82 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
>         return ret;
>  }
>
> -int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
> -                              void (*release)(void *), unsigned int index,
> -                              unsigned int issue_flags)
> +static struct io_mapped_ubuf *io_kernel_buffer_init(struct io_ring_ctx *ctx,
> +                                                   unsigned int nr_bvecs,
> +                                                   unsigned int total_bytes,
> +                                                   u8 dir,
> +                                                   void (*release)(void *),
> +                                                   void *priv,
> +                                                   unsigned int index)
>  {
> -       struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
>         struct io_rsrc_data *data = &ctx->buf_table;
> -       struct req_iterator rq_iter;
>         struct io_mapped_ubuf *imu;
>         struct io_rsrc_node *node;
> -       struct bio_vec bv;
> -       unsigned int nr_bvecs = 0;
> -       int ret = 0;
>
> -       io_ring_submit_lock(ctx, issue_flags);
> -       if (index >= data->nr) {
> -               ret = -EINVAL;
> -               goto unlock;
> -       }
> +       if (index >= data->nr)
> +               return ERR_PTR(-EINVAL);
>         index = array_index_nospec(index, data->nr);
>
> -       if (data->nodes[index]) {
> -               ret = -EBUSY;
> -               goto unlock;
> -       }
> +       if (data->nodes[index])
> +               return ERR_PTR(-EBUSY);
>
>         node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER);
> -       if (!node) {
> -               ret = -ENOMEM;
> -               goto unlock;
> -       }
> +       if (!node)
> +               return ERR_PTR(-ENOMEM);
>
> -       /*
> -        * blk_rq_nr_phys_segments() may overestimate the number of bvecs
> -        * but avoids needing to iterate over the bvecs
> -        */
> -       imu = io_alloc_imu(ctx, blk_rq_nr_phys_segments(rq));
> +       imu = io_alloc_imu(ctx, nr_bvecs);
>         if (!imu) {
>                 kfree(node);
> -               ret = -ENOMEM;
> -               goto unlock;
> +               return ERR_PTR(-ENOMEM);
>         }
>
>         imu->ubuf = 0;
> -       imu->len = blk_rq_bytes(rq);
> +       imu->len = total_bytes;
>         imu->acct_pages = 0;
>         imu->folio_shift = PAGE_SHIFT;
> +       imu->nr_bvecs = nr_bvecs;
>         refcount_set(&imu->refs, 1);
>         imu->release = release;
> -       imu->priv = rq;
> +       imu->priv = priv;
> +       imu->dir = 1 << dir;

I'm going to update this line to take a bitmasked dir directly so that
callers can set both dest and source if needed. I'll send out v2 with
this change.

Thanks,
Joanne

>         imu->flags = IO_REGBUF_F_KBUF;
> -       imu->dir = 1 << rq_data_dir(rq);
>
> +       node->buf = imu;
> +       data->nodes[index] = node;
> +
> +       return imu;
> +}
> +