Re: [PATCH 0/5] add initial io_uring_cmd support for sockets

Willem de Bruijn
2023-04-11T15:24:41Z

Jens Axboe wrote:
> On 4/11/23 9:00?AM, Willem de Bruijn wrote:
> > Jens Axboe wrote:
> >> On 4/11/23 8:51?AM, Willem de Bruijn wrote:
> >>> Jens Axboe wrote:
> >>>> On 4/11/23 8:36?AM, David Ahern wrote:
> >>>>> On 4/11/23 6:00 AM, Breno Leitao wrote:
> >>>>>> I am not sure if avoiding io_uring details in network code is possible.
> >>>>>>
> >>>>>> The "struct proto"->uring_cmd callback implementation (tcp_uring_cmd()
> >>>>>> in the TCP case) could be somewhere else, such as in the io_uring/
> >>>>>> directory, but, I think it might be cleaner if these implementations are
> >>>>>> closer to function assignment (in the network subsystem).
> >>>>>>
> >>>>>> And this function (tcp_uring_cmd() for instance) is the one that I am
> >>>>>> planning to map io_uring CMDs to ioctls. Such as SOCKET_URING_OP_SIOCINQ
> >>>>>> -> SIOCINQ.
> >>>>>>
> >>>>>> Please let me know if you have any other idea in mind.
> >>>>>
> >>>>> I am not convinced that this io_uring_cmd is needed. This is one
> >>>>> in-kernel subsystem calling into another, and there are APIs for that.
> >>>>> All of this set is ioctl based and as Willem noted a little refactoring
> >>>>> separates the get_user/put_user out so that in-kernel can call can be
> >>>>> made with existing ops.
> >>>>
> >>>> How do you want to wire it up then? We can't use fops->unlocked_ioctl()
> >>>> obviously, and we already have ->uring_cmd() for this purpose.
> >>>
> >>> Does this suggestion not work?
> >>
> >> Not sure I follow, what suggestion?
> >>
> >
> > This quote from earlier in the thread:
> >
> > I was thinking just having sock_uring_cmd call sock->ops->ioctl, like
> > sock_do_ioctl.
>
> But that doesn't work, because sock->ops->ioctl() assumes the arg is
> memory in userspace. Or do you mean change all of the sock->ops->ioctl()
> to pass in on-stack memory (or similar) and have it work with a kernel
> address?

That was what I suggested indeed.

It's about as much code change as this patch series. But it avoids
the code duplication.