Re: [PATCH v2 liburing] add helper functions to verify io_uring functionality

Glauber Costa
2020-01-31T13:52:17Z

On Thu, Jan 30, 2020 at 11:31 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 1/30/20 9:29 AM, Glauber Costa wrote:
> > On Thu, Jan 30, 2020 at 11:13 AM Jens Axboe <axboe@kernel.dk> wrote:
> >>
> >> On 1/30/20 9:00 AM, Glauber Costa wrote:
> >>> It is common for an application using an ever-evolving interface to want
> >>> to inquire about the presence of certain functionality it plans to use.
> >>>
> >>> Information about opcodes is stored in a io_uring_probe structure. There
> >>> is usually some boilerplate involved in initializing one, and then using
> >>> it to check if it is enabled.
> >>>
> >>> This patch adds two new helper functions: one that returns a pointer to
> >>> a io_uring_probe (or null if it probe is not available), and another one
> >>> that given a probe checks if the opcode is supported.
> >>
> >> This looks good, I committed it with minor changes.
> >>
> >> On top of this, we should have a helper that doesn't need a ring. So
> >> basically one that just sets up a ring, calls io_uring_get_probe(),
> >> then tears down the ring.
> >>
> > I'd be happy to follow up with that.
> >
> > Just to be sure, the information returned by probe should be able to outlive the
> > tear down of the ring, right ?
>
> Yeah, same lifetime as the helper you have now, caller must free it once
> done.

Well, in hindsight, I should have called that
io_uring_get_probe_ring() so io_uring_get_probe()
doesn't take a ring.

Alternatively, to keep things in a single function, I can change
io_uring_get_probe() so that if it
ring is NULL, we do our own allocation.

I actually kind of like that. Would that work for you ?

>
> --
> Jens Axboe
>