Re: [PATCH for-5.10] io_uring: remove req cancel in ->flush()

[Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>]

hi,

> Every close(io_uring) causes cancellation of all inflight requests
> carrying ->files. That's not nice but was neccessary up until recently.
> Now task->files removal is handled in the core code, so that part of
> flush can be removed.
I don't catch up with newest io_uring codes yet, but have one question about
the initial implementation "io_uring: io_uring: add support for async work
inheriting files": https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fcb323cc53e29d9cc696d606bb42736b32dd9825
There was such comments:
+static int io_grab_files(struct io_ring_ctx *ctx, struct io_kiocb *req)
+{
+       int ret = -EBADF;
+
+       rcu_read_lock();
+       spin_lock_irq(&ctx->inflight_lock);
+       /*
+        * We use the f_ops->flush() handler to ensure that we can flush
+        * out work accessing these files if the fd is closed. Check if
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I wonder why we only need to flush reqs specifically when they access current->files, are there
any special reasons?

Regards,
Xiaoguang Wang

+        * the fd has changed since we started down this path, and disallow
+        * this operation if it has.
+        */
+       if (fcheck(req->submit.ring_fd) == req->submit.ring_file) {
+               list_add(&req->inflight_entry, &ctx->inflight_list);
+               req->flags |= REQ_F_INFLIGHT;
+               req->work.files = current->files;
+               ret = 0;
+       }
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>   fs/io_uring.c | 10 +++-------
>   1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 95d2bb7069c6..6536e24eb44e 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8748,16 +8748,12 @@ void __io_uring_task_cancel(void)
>   
>   static int io_uring_flush(struct file *file, void *data)
>   {
> -	struct io_ring_ctx *ctx = file->private_data;
> +	bool exiting = !data;
>   
> -	/*
> -	 * If the task is going away, cancel work it may have pending
> -	 */
>   	if (fatal_signal_pending(current) || (current->flags & PF_EXITING))
> -		data = NULL;
> +		exiting = true;
>   
> -	io_uring_cancel_task_requests(ctx, data);
> -	io_uring_attempt_task_drop(file, !data);
> +	io_uring_attempt_task_drop(file, exiting);
>   	return 0;
>   }
>   
>