Re: [PATCH] io_uring: pick up link work on submit reference drop

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

On 25/02/2020 23:27, Jens Axboe wrote:
> If work completes inline, then we should pick up a dependent link item
> in __io_queue_sqe() as well. If we don't do so, we're forced to go async
> with that item, which is suboptimal.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> ---
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index ffd9bfa84d86..160cf1b0f478 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -4531,8 +4531,15 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
>  		} while (1);
>  	}
>  
> -	/* drop submission reference */
> -	io_put_req(req);
> +	/*
> +	 * Drop submission reference. In case the handler already dropped the
> +	 * completion reference, then it didn't pick up any potential link
> +	 * work. If 'nxt' isn't set, try and do that here.
> +	 */
> +	if (nxt)

It can't even get here, because of the submission ref, isn't it? would the
following do?

-	io_put_req(req);
+	io_put_req_find_next(req, &nxt);

BTW, as I mentioned before, it appears to me, we don't even need completion ref
as it always pinned by the submission ref. I'll resurrect the patches doing
that, but after your poll work will land.


> +		io_put_req(req);
> +	else
> +		io_put_req_find_next(req, &nxt);
>  
>  	if (ret) {
>  		req_set_fail_links(req);
> 

-- 
Pavel Begunkov