Io_submit is part of the Linux aio subsystem. Thus patch is literally a extension to that subsystem to avoid doing a kernel call to submit aio requests and collect results.
Sure, but this patch is only useful for single-purpose, HFT-like workloads. Batched io_submit on sockets would be useful for any application sending many small packets to lots of clients, such as game servers.
For network io, an userspace accelerated network stack is probably better though.