Re: [RFC PATCH v4 2/3] io_uring: add api to set / get napi configuration.

[Jens Axboe <axboe@kernel.dk>]

On 11/21/22 10:29?AM, Stefan Roesch wrote:
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 4f432694cbed..cf0e7cc8ad2e 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -4122,6 +4122,48 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
>  	return ret;
>  }
>  
> +static int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
> +{
> +#ifdef CONFIG_NET_RX_BUSY_POLL
> +	const struct io_uring_napi curr = {
> +		.busy_poll_to = ctx->napi_busy_poll_to,
> +	};
> +	struct io_uring_napi *napi;
> +
> +	napi = memdup_user(arg, sizeof(*napi));
> +	if (IS_ERR(napi))
> +		return PTR_ERR(napi);
> +
> +	WRITE_ONCE(ctx->napi_busy_poll_to, napi->busy_poll_to);
> +
> +	kfree(napi);
> +
> +	if (copy_to_user(arg, &curr, sizeof(curr)))
> +		return -EFAULT;
> +
> +	return 0;
> +#else
> +	return -EINVAL;
> +#endif
> +}

This should return -EINVAL if any of the padding or reserved fields are
non-zero. If you don't do that, then it's not expendable in the future.

-- 
Jens Axboe