Re: [PATCH 06/11] io-wq: return io_worker after successful inline worker creation

[Pavel Begunkov <asml.silence@xxxxxxxxx>]

On 6/9/23 13:20, Hao Xu wrote:
> From: Hao Xu <howeyxu@xxxxxxxxxxx>
>
> After creating a io worker inline successfully, return the io_worker
> structure. This is used by fixed worker.
>
> Signed-off-by: Hao Xu <howeyxu@xxxxxxxxxxx>
> ---
>   io_uring/io-wq.c | 20 ++++++++++----------
>   1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
> index 048856eef4d4..4338e5b23b07 100644
> --- a/io_uring/io-wq.c
> +++ b/io_uring/io-wq.c
> @@ -137,7 +137,7 @@ struct io_cb_cancel_data {
>   	bool cancel_all;
>   };
>   
> -static bool create_io_worker(struct io_wq *wq, int index, bool fixed);
> +static struct io_worker *create_io_worker(struct io_wq *wq, int index, bool fixed);
>   static void io_wq_dec_running(struct io_worker *worker);
>   static bool io_acct_cancel_pending_work(struct io_wq *wq,
>   					struct io_wq_acct *acct,
> @@ -284,8 +284,8 @@ static bool io_wq_activate_free_worker(struct io_wq *wq,
>    * We need a worker. If we find a free one, we're good. If not, and we're
>    * below the max number of workers, create one.
>    */
> -static bool io_wq_create_worker(struct io_wq *wq, struct io_wq_acct *acct,
> -				bool fixed)
> +static struct io_worker *io_wq_create_worker(struct io_wq *wq,
> +					     struct io_wq_acct *acct, bool fixed)
>   {
>   	/*
>   	 * Most likely an attempt to queue unbounded work on an io_wq that
> @@ -297,7 +297,7 @@ static bool io_wq_create_worker(struct io_wq *wq, struct io_wq_acct *acct,
>   	raw_spin_lock(&wq->lock);
>   	if (acct->nr_workers >= acct->max_workers) {
>   		raw_spin_unlock(&wq->lock);
> -		return true;
> +		return NULL;

Something is not right here. The function could succeed even if it didn't
create a new worker. Now it's a failure.

>   	}
>   	acct->nr_workers++;
>   	raw_spin_unlock(&wq->lock);
> @@ -809,11 +809,11 @@ static void io_workqueue_create(struct work_struct *work)
>   		kfree(worker);
>   }
>   
> -static bool create_io_worker(struct io_wq *wq, int index, bool fixed)
> +static struct io_worker *create_io_worker(struct io_wq *wq, int index, bool fixed)
>   {
>   	struct io_wq_acct *acct = &wq->acct[index];
>   	struct io_worker *worker;
> -	struct task_struct *tsk;
> +	struct task_struct *tsk = NULL;
>   
>   	__set_current_state(TASK_RUNNING);
>   
> @@ -825,7 +825,7 @@ static bool create_io_worker(struct io_wq *wq, int index, bool fixed)
>   		acct->nr_workers--;
>   		raw_spin_unlock(&wq->lock);
>   		io_worker_ref_put(wq);
> -		return false;
> +		return tsk ? (struct io_worker *)tsk : ERR_PTR(-ENOMEM);

How it this conversion valid? I don't remember us overlaying struct
io_worker onto task_struct

>   	}
>   
>   	refcount_set(&worker->ref, 1);
> @@ -841,8 +841,8 @@ static bool create_io_worker(struct io_wq *wq, int index, bool fixed)
>   
>   	tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
>   	if (!IS_ERR(tsk)) {
> -		if (!fixed)
> -			io_init_new_worker(wq, worker, tsk);
> +		io_init_new_worker(wq, worker, tsk);
> +		return worker;
>   	} else if (fixed || !io_should_retry_thread(PTR_ERR(tsk))) {
>   		kfree(worker);
>   		goto fail;
> @@ -851,7 +851,7 @@ static bool create_io_worker(struct io_wq *wq, int index, bool fixed)
>   		schedule_work(&worker->work);
>   	}
>   
> -	return true;
> +	return (struct io_worker *)tsk;
>   }
>   
>   /*

--
Pavel Begunkov