Re: [PATCH] io_uring: cancel all requests on task exit

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

On 17/01/2021 04:04, Jens Axboe wrote:
> We used to have task exit tied to canceling files_struct ownership, but we
> really should just simplify this and cancel any request that the task has
> pending when it exits. Instead of handling files ownership specially, we
> do the same regardless of request type.
> 
> This can be further simplified in the next major kernel release, unifying
> how we cancel across exec and exit.

Looks good in general. See a comment below, but otherwise
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

btw, I wonder if we can incite syzbot to try to break it.

> 
> Cc: stable@vger.kernel.org # 5.9+
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> ---
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 383ff6ed3734..1190296fc95f 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -9029,7 +9029,7 @@ static void io_uring_remove_task_files(struct io_uring_task *tctx)
>  		io_uring_del_task_file(file);
>  }
>  
> -void __io_uring_files_cancel(struct files_struct *files)
> +static void __io_uring_files_cancel(void)
>  {
>  	struct io_uring_task *tctx = current->io_uring;
>  	struct file *file;
> @@ -9038,11 +9038,10 @@ void __io_uring_files_cancel(struct files_struct *files)
>  	/* make sure overflow events are dropped */
>  	atomic_inc(&tctx->in_idle);
>  	xa_for_each(&tctx->xa, index, file)
> -		io_uring_cancel_task_requests(file->private_data, files);
> +		io_uring_cancel_task_requests(file->private_data, NULL);
>  	atomic_dec(&tctx->in_idle);
>  
> -	if (files)
> -		io_uring_remove_task_files(tctx);
> +	io_uring_remove_task_files(tctx);

This restricts cancellations to only one iteration. Just delete it,
__io_uring_task_cancel() calls it already.

-- 
Pavel Begunkov