Re: [PATCH v5 2/3] fs: openat2: Extend open_how to allow userspace-selected fds

[Miklos Szeredi <miklos@szeredi.hu>]

On Thu, Apr 23, 2020 at 9:33 AM Josh Triplett <josh@joshtriplett.org> wrote:

> > What are the plans for those syscalls that don't easily lend
> > themselves to this modification (such as accept(2))?
>
> accept4 has a flags argument with more flags available, so it'd be
> entirely possible to cleanly extend it further without introducing a new
> version.

Variable argument syscalls, you are thinking?

> > I mean, you could open the file descriptor outside of io_uring in such
> > cases, no?
>
> I would prefer to not introduce that limitation in the first place, and
> instead open normal file descriptors.
>
> > The point of O_SPECIFIC_FD is to be able to perform short
> > sequences of open/dosomething/close without having to block and having
> > to issue separate syscalls.
>
> "close" is not a required component. It's entirely possible to use
> io_uring to open a file descriptor, do various things with it, and then
> leave it open for subsequent usage via either other io_uring chains or
> standalone syscalls.

If this use case arraises, we could add an op to dup/move a private
descriptor to a public one.  io_uring can return values, right?

Still not convinced...

Thanks,
Miklos