Re: [RFC v2 3/5] io_uring/bpf: implement struct_ops registration

[Jens Axboe <axboe@kernel.dk>]

On 6/6/25 7:58 AM, Pavel Begunkov wrote:
> Add ring_fd to the struct_ops and implement [un]registration.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  io_uring/bpf.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  io_uring/bpf.h |  3 +++
>  2 files changed, 69 insertions(+), 1 deletion(-)
> 
> diff --git a/io_uring/bpf.c b/io_uring/bpf.c
> index 3096c54e4fb3..0f82acf09959 100644
> --- a/io_uring/bpf.c
> +++ b/io_uring/bpf.c
> @@ -3,6 +3,8 @@
>  #include "bpf.h"
>  #include "register.h"
>  
> +DEFINE_MUTEX(io_bpf_ctrl_mutex);
> +
>  static struct io_uring_ops io_bpf_ops_stubs = {
>  };
>  
> @@ -50,20 +52,83 @@ static int bpf_io_init_member(const struct btf_type *t,
>  			       const struct btf_member *member,
>  			       void *kdata, const void *udata)
>  {
> +	u32 moff = __btf_member_bit_offset(t, member) / 8;
> +	const struct io_uring_ops *uops = udata;
> +	struct io_uring_ops *ops = kdata;
> +
> +	switch (moff) {
> +	case offsetof(struct io_uring_ops, ring_fd):
> +		ops->ring_fd = uops->ring_fd;
> +		return 1;
> +	}
> +	return 0;

Possible to pass in here whether the ring fd is registered or not? Such
that it can be used in bpf_io_reg() as well.

> +static int io_register_bpf_ops(struct io_ring_ctx *ctx, struct io_uring_ops *ops)
> +{
> +	if (ctx->bpf_ops)
> +		return -EBUSY;
> +	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
> +		return -EOPNOTSUPP;
> +
> +	percpu_ref_get(&ctx->refs);
> +	ops->ctx = ctx;
> +	ctx->bpf_ops = ops;
>  	return 0;
>  }

Haven't looked too deeply yet, but what's the dependency with
DEFER_TASKRUN?

-- 
Jens Axboe