> > What if the ubuf pool can be found from the sk, and the index in that > > pool is passed as a cmsg? > > It looks to me that ubufs are by nature is something that is not > tightly bound to a socket (at least for io_uring API in the patchset), > it'll be pretty ugly: > > 1) io_uring'd need to care to register the pool in the socket. Having > multiple rings using the same socket would be horrible. It may be that > it doesn't make much sense to send in parallel from multiple rings, but > a per thread io_uring is a popular solution, and then someone would > want to pass a socket from one thread to another and we'd need to support > it. > > 2) And io_uring would also need to unregister it, so the pool would > store a list of sockets where it's used, and so referencing sockets > and then we need to bind it somehow to io_uring fixed files or > register all that for tracking referencing circular dependencies. > > 3) IIRC, we can't add a cmsg entry from the kernel, right? May be wrong, > but if so I don't like exposing basically io_uring's referencing through > cmsg. And it sounds io_uring would need to parse cmsg then. > > > A lot of nuances :) I'd really prefer to pass it on per-request basis, Ok > it's much cleaner, but still haven't got what's up with msghdr > initialisation... And passing the struct through multiple layers of functions. > Maybe, it's better to add a flags field, which would include > "msg_control_is_user : 1" and whether msghdr includes msg_iocb, msg_ubuf, > and everything else that may be optional. Does it sound sane? If sendmsg takes the argument, it will just have to be initialized, I think. Other functions are not aware of its existence so it can remain uninitialized there.
