Re: [PATCH v4 1/2] io_uring: avoid whole io_wq_work copy for requests completed inline

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

On 31/05/2020 19:15, Xiaoguang Wang wrote:
> In the begin of __io_splice_prep or io_close_prep, current io_uring mainline codes will
> modify req->work.flags firstly, so we need to call io_req_init_async to initialize
> io_wq_work before the work.flags modification.
> For below codes:
> static inline void io_req_init_async(struct io_kiocb *req,
>                         void (*func)(struct io_wq_work **))
> {
>         if (req->flags & REQ_F_WORK_INITIALIZED) {
>                 if (!req->work.func)
>                         req->work.func = func;
>         } else {
>                 req->work = (struct io_wq_work){ .func = func };
>                 req->flags |= REQ_F_WORK_INITIALIZED;
>         }
> }
> 
> if we not pass NULL to parameter 'func', e.g. pass io_wq_submit_work, then
> we can not use io_req_init_async() to pass io_close_finish again.

It's not as bad, just the thing you poked is overused and don't have strict rules.
I have a feeling, that for it to be done right it'd need more fundamental refactoring
with putting everything related to ->work closer to io_queue_async_work().

> 
> Now I'm confused how to write better codes based on current io_uring mainline codes :)
> If you have some free time, please have a deeper look, thanks.

-- 
Pavel Begunkov