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Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH 0/5] add initial io_uring_cmd support for sockets Content-Language: en-US To: Willem de Bruijn , David Ahern , Breno Leitao Cc: Willem de Bruijn , io-uring@vger.kernel.org, netdev@vger.kernel.org, kuba@kernel.org, asml.silence@gmail.com, leit@fb.com, edumazet@google.com, pabeni@redhat.com, davem@davemloft.net, dccp@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, matthieu.baerts@tessares.net, marcelo.leitner@gmail.com References: <20230406144330.1932798-1-leitao@debian.org> <75e3c434-eb8b-66e5-5768-ca0f906979a1@kernel.org> <67831406-8d2f-feff-f56b-d0f002a95d96@kernel.dk> <643573df81e20_11117c2942@willemb.c.googlers.com.notmuch> <036c80e5-4844-5c84-304c-7e553fe17a9b@kernel.dk> <64357608c396d_113ebd294ba@willemb.c.googlers.com.notmuch> From: Jens Axboe In-Reply-To: <64357608c396d_113ebd294ba@willemb.c.googlers.com.notmuch> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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