Re: [PATCH 9/9] io_uring: pass submission ref to async

[Pavel Begunkov]

On 01/03/2020 19:18, Pavel Begunkov wrote:
> Currenlty, every async work handler accepts a submission reference,
> which it should put. Also there is a reference grabbed in io_get_work()
> and dropped in io_put_work(). This patch merge them together.
> 
> - So, ownership of the submission reference passed to io-wq, and it'll
> be put in io_put_work().
> - io_get_put() doesn't take a ref now and so deleted.
> - async handlers don't put the submission ref anymore.
> - make cancellation bits of io-wq to call {get,put}_work() handlers

Hmm, it makes them more like {init,fini}_work() and unbalanced/unpaired. May be
no a desirable thing.

> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
>  fs/io-wq.c    | 17 +++++++++++++----
>  fs/io_uring.c | 32 +++++++++++++-------------------
>  2 files changed, 26 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/io-wq.c b/fs/io-wq.c
> index f9b18c16ebd8..686ad043c6ac 100644
> --- a/fs/io-wq.c
> +++ b/fs/io-wq.c
> @@ -751,14 +751,23 @@ static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
>  	return true;
>  }
>  
> -static void io_run_cancel(struct io_wq_work *work)
> +static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe)
>  {
> +	struct io_wq *wq = wqe->wq;
> +
>  	do {
>  		struct io_wq_work *old_work = work;
> +		bool is_internal = work->flags & IO_WQ_WORK_INTERNAL;
> +
> +		if (wq->get_work && !is_internal)
> +			wq->get_work(work);
>  
>  		work->flags |= IO_WQ_WORK_CANCEL;
>  		work->func(&work);
>  		work = (work == old_work) ? NULL : work;
> +
> +		if (wq->put_work && !is_internal)
> +			wq->put_work(old_work);
>  	} while (work);
>  }
>  
> @@ -775,7 +784,7 @@ static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
>  	 * It's close enough to not be an issue, fork() has the same delay.
>  	 */
>  	if (unlikely(!io_wq_can_queue(wqe, acct, work))) {
> -		io_run_cancel(work);
> +		io_run_cancel(work, wqe);
>  		return;
>  	}
>  
> @@ -914,7 +923,7 @@ static enum io_wq_cancel io_wqe_cancel_cb_work(struct io_wqe *wqe,
>  	spin_unlock_irqrestore(&wqe->lock, flags);
>  
>  	if (found) {
> -		io_run_cancel(work);
> +		io_run_cancel(work, wqe);
>  		return IO_WQ_CANCEL_OK;
>  	}
>  
> @@ -989,7 +998,7 @@ static enum io_wq_cancel io_wqe_cancel_work(struct io_wqe *wqe,
>  	spin_unlock_irqrestore(&wqe->lock, flags);
>  
>  	if (found) {
> -		io_run_cancel(work);
> +		io_run_cancel(work, wqe);
>  		return IO_WQ_CANCEL_OK;
>  	}
>  
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index d456b0ff6835..c6845a1e5aaa 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -1556,12 +1556,13 @@ static struct io_kiocb *io_put_req_submission(struct io_kiocb *req)
>  	return nxt;
>  }
>  
> -static void io_put_req_async_submission(struct io_kiocb *req,
> -					struct io_wq_work **workptr)
> +static void io_steal_work(struct io_kiocb *req,
> +			  struct io_wq_work **workptr)
>  {
> -	static struct io_kiocb *nxt;
> +	struct io_kiocb *nxt = NULL;
>  
> -	nxt = io_put_req_submission(req);
> +	if (!(req->flags & REQ_F_DONT_STEAL_NEXT))
> +		io_req_find_next(req, &nxt);
>  	if (nxt)
>  		io_wq_assign_next(workptr, nxt);
>  }
> @@ -2575,7 +2576,7 @@ static bool io_req_cancelled(struct io_kiocb *req)
>  	if (req->work.flags & IO_WQ_WORK_CANCEL) {
>  		req_set_fail_links(req);
>  		io_cqring_add_event(req, -ECANCELED);
> -		io_double_put_req(req);
> +		io_put_req(req);
>  		return true;
>  	}
>  
> @@ -2603,7 +2604,7 @@ static void io_fsync_finish(struct io_wq_work **workptr)
>  	if (io_req_cancelled(req))
>  		return;
>  	__io_fsync(req);
> -	io_put_req_async_submission(req, workptr);
> +	io_steal_work(req, workptr);
>  }
>  
>  static int io_fsync(struct io_kiocb *req, bool force_nonblock)
> @@ -2636,7 +2637,7 @@ static void io_fallocate_finish(struct io_wq_work **workptr)
>  	if (io_req_cancelled(req))
>  		return;
>  	__io_fallocate(req);
> -	io_put_req_async_submission(req, workptr);
> +	io_steal_work(req, workptr);
>  }
>  
>  static int io_fallocate_prep(struct io_kiocb *req,
> @@ -3003,7 +3004,7 @@ static void io_close_finish(struct io_wq_work **workptr)
>  
>  	/* not cancellable, don't do io_req_cancelled() */
>  	__io_close_finish(req);
> -	io_put_req_async_submission(req, workptr);
> +	io_steal_work(req, workptr);
>  }
>  
>  static int io_close(struct io_kiocb *req, bool force_nonblock)
> @@ -3076,7 +3077,7 @@ static void io_sync_file_range_finish(struct io_wq_work **workptr)
>  	if (io_req_cancelled(req))
>  		return;
>  	__io_sync_file_range(req);
> -	io_put_req_async_submission(req, workptr);
> +	io_steal_work(req, workptr);
>  }
>  
>  static int io_sync_file_range(struct io_kiocb *req, bool force_nonblock)
> @@ -3446,7 +3447,7 @@ static void io_accept_finish(struct io_wq_work **workptr)
>  	if (io_req_cancelled(req))
>  		return;
>  	__io_accept(req, false);
> -	io_put_req_async_submission(req, workptr);
> +	io_steal_work(req, workptr);
>  }
>  #endif
>  
> @@ -4716,7 +4717,7 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
>  		io_put_req(req);
>  	}
>  
> -	io_put_req_async_submission(req, workptr);
> +	io_steal_work(req, workptr);
>  }
>  
>  static int io_req_needs_file(struct io_kiocb *req, int fd)
> @@ -6107,13 +6108,6 @@ static void io_put_work(struct io_wq_work *work)
>  	io_put_req(req);
>  }
>  
> -static void io_get_work(struct io_wq_work *work)
> -{
> -	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
> -
> -	refcount_inc(&req->refs);
> -}
> -
>  static int io_init_wq_offload(struct io_ring_ctx *ctx,
>  			      struct io_uring_params *p)
>  {
> @@ -6124,7 +6118,7 @@ static int io_init_wq_offload(struct io_ring_ctx *ctx,
>  	int ret = 0;
>  
>  	data.user = ctx->user;
> -	data.get_work = io_get_work;
> +	data.get_work = NULL;
>  	data.put_work = io_put_work;
>  
>  	if (!(p->flags & IORING_SETUP_ATTACH_WQ)) {
> 

-- 
Pavel Begunkov