Re: [PATCH 1/2] io-wq: fix bug of creating io-wokers unconditionally

[Jens Axboe <axboe@kernel.dk>]

On 8/8/21 7:54 AM, Hao Xu wrote:
> The former patch to add check between nr_workers and max_workers has a
> bug, which will cause unconditionally creating io-workers. That's
> because the result of the check doesn't affect the call of
> create_io_worker(), fix it by bringing in a boolean value for it.
> 
> Fixes: 21698274da5b ("io-wq: fix lack of acct->nr_workers < acct->max_workers judgement")
> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
> ---
>  fs/io-wq.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/io-wq.c b/fs/io-wq.c
> index 12fc19353bb0..5536b2a008d1 100644
> --- a/fs/io-wq.c
> +++ b/fs/io-wq.c
> @@ -252,14 +252,15 @@ static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct)
>  
>  		raw_spin_lock_irq(&wqe->lock);
>  		if (acct->nr_workers < acct->max_workers) {
> -			atomic_inc(&acct->nr_running);
> -			atomic_inc(&wqe->wq->worker_refs);
>  			acct->nr_workers++;
>  			do_create = true;
>  		}
>  		raw_spin_unlock_irq(&wqe->lock);
> -		if (do_create)
> +		if (do_create) {
> +			atomic_inc(&acct->nr_running);
> +			atomic_inc(&wqe->wq->worker_refs);
>  			create_io_worker(wqe->wq, wqe, acct->index);
> +		}
>  	}

I don't get this hunk - we already know we're creating a worker, what's the
point in moving the incs?

-- 
Jens Axboe