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? >>>> I do think the right thing to do is have a common helper that returns >>>> whatever value you want (or sets it), and split the ioctl parts into a >>>> wrapper around that that simply copies in/out as needed. Then >>>> ->uring_cmd() could call that, or you could some exported function that >>>> does supports that. >>>> >>>> This works for the basic cases, though I do suspect we'll want to go >>>> down the ->uring_cmd() at some point for more advanced cases or cases >>>> that cannot sanely be done in an ioctl fashion. >>> >>> Right now the two examples are ioctls that return an integer. Do you >>> already have other calls in mind? That would help estimate whether >>> ->uring_cmd() indeed will be needed and we might as well do it now. >> >> Right, it's a proof of concept. But we'd want to support anything that >> setsockopt/getsockopt would do. This is necessary so that direct >> descriptors (eg ones that describe a struct file that isn't in the >> process file table or have a regular fd) can be used for anything that a >> regular file can. Beyond that, perhaps various things necessary for >> efficient zero copy rx. >> >> I do think we can make the ->uring_cmd() hookup a bit more palatable in >> terms of API. It really should be just a sub-opcode and then arguments >> to support that. The grunt of the work is really refactoring the ioctl >> and set/getsockopt bits so that they can be called in-kernel rather than >> assuming copy in/out is needed. Once that is done, the actual uring_cmd >> hookup should be simple and trivial. > > That sounds like what I proposed above. That suggestion was only for > the narrow case where ioctls return an integer. The general approach > has to handle any put_user. Right > Though my initial skim of TCP, UDP and RAW did not bring up any other > forms. > > getsockopt indeed has plenty of examples, such as receive zerocopy. -- Jens Axboe
