Re: [PATCH 07/11] io_uring: add new api to register fixed workers

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/9/23 13:20, Hao Xu wrote:
> From: Hao Xu <howeyxu@tencent.com>
> 
> Add a new api to register fixed workers. The api is designed to register
> fixed workers for the current task. For simplicity, it doesn't allow
> worker number update. We have a separate unregister api to uninstall all
> the fixed workers. And then we can register different number of fixed
> workers again.
> 
> Signed-off-by: Hao Xu <howeyxu@tencent.com>
> ---
>   include/uapi/linux/io_uring.h |  9 ++++
>   io_uring/io-wq.c              | 85 +++++++++++++++++++++++++++++++++++
>   io_uring/io-wq.h              |  1 +
>   io_uring/io_uring.c           | 71 +++++++++++++++++++++++++++++
>   4 files changed, 166 insertions(+)
> 
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index f222d263bc55..6dc43be5009d 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
[...]
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index c99a7a0c3f21..bb8342b4a2c6 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -4351,6 +4351,71 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
>   	return ret;
>   }
>   
> +/*
> + * note: this function sets fixed workers for a single task, so every
> + * task which wants to set the fixed workers has to call this function
> + */
> +static __cold int io_register_iowq_fixed_workers(struct io_ring_ctx *ctx,
> +					       void __user *arg, int nr_args)
> +	__must_hold(&ctx->uring_lock)
> +{
> +	struct io_uring_task *tctx = NULL;
> +	struct io_sq_data *sqd = NULL;
> +	struct io_uring_fixed_worker_arg *res;
> +	size_t size;
> +	int i, ret;
> +	bool zero = true;
> +
> +	size = array_size(nr_args, sizeof(*res));
> +	if (size == SIZE_MAX)
> +		return -EOVERFLOW;

I don't think the number of accounting classes is going to
change, just move nr_args check from below here and have
on-stack array of size 2.


struct io_uring_fixed_worker_arg res[IO_WQ_ACCT_NR];

if (nr_args != IO_WQ_ACCT_NR)
	return -EINVAL;

...


> +
> +	res = memdup_user(arg, size);
> +	if (IS_ERR(res))
> +		return PTR_ERR(res);
> +
> +	for (i = 0; i < nr_args; i++) {
> +		if (res[i].nr_workers) {
> +			zero = false;
> +			break;
> +		}
> +	}
> +

-- 
Pavel Begunkov