On 3/3/22 1:09 AM, Hannes Reinecke wrote: > On 3/2/22 17:52, Mike Christie wrote: >> On 2/21/22 1:59 PM, Gabriel Krisman Bertazi wrote: >>> I'd like to discuss an interface to implement user space block devices, >>> while avoiding local network NBD solutions. There has been reiterated >> >> Besides the tcmu approach, I've also worked on the local nbd based >> solution like here: >> >> https://urldefense.com/v3/__https://github.com/gluster/nbd-runner__;!!ACWV5N9M2RV99hQ!YY39rbV9MpaNUtr7ElzgcG1TyPznVEt1yppLwAGkq32-Fw9rQkqB6FzcaHiwIdgXp00K$ >> Have you looked into a modern take that uses io_uring's socket features >> with the zero copy work that's being worked on for it? If so, what are >> the issues you have hit with that? Was it mostly issues with the zero >> copy part of it? >> >> > Problem is that we'd need an _inverse_ io_uring interface. > The current io_uring interface writes submission queue elements, > and waits for completion queue elements. I'm not sure what you meant here. io_uring can do recvs right? So userspace nbd would do IORING_OP_RECVMSG to wait for drivers/block/nbd.c to send userspace cmds via the local socket. Userspace nbd would do IORING_OP_SENDMSG to send drivers/block/nbd.c the cmd response. drivers/block/nbd doesn't know/care what userspace did. It's just reading/writing from/to the socket.
