Re: io_uring_prep_openat_direct() and link/drain

[Miklos Szeredi <miklos@szeredi.hu>]

On Tue, 29 Mar 2022 at 22:03, Jens Axboe <axboe@kernel.dk> wrote:

> Can you try and repull the branch? I rebased the top two, so reset to
> v5.17 first and then pull it.

This one works in all cases, except if there's a link flag on the
read.  In that case the read itself will succeed but following
requests on the link chain will fail with -ECANCELED.

> BTW, I would not recommend using DRAIN, it's very expensive compared to
> just a link. Particularly, using just a single link between the
> open+read makes sense, and should be efficient. Don't link between all
> of them, that's creating a more expensive dependency that doesn't make
> any sense for your use case either. Should they both work? Of course,
> and I think they will in the current branch. Merely stating that they
> make no sense other than as an exercise-the-logic test case.

Understood.   Once all of these cases work, it should be possible to
compare the performance of parallel vs. serial execution.

Thanks,
Miklos