Kernels since 5.1 have implemented the io_uring interface (https://kernel.dk/io_uring.pdf) for efficient asynchronous IO submission to storage. According to posted results, io_uring is on-par with SPDK doing all of the IO in userspace. The io_uring interface is intended to replace the older libaio interface.

With the recent performance improvements for libaio AIO/DIO, it should be possible to use the io_uring interfaces in a similar manner.

I don't think many applications are using this interface yet, but since it provides a significant improvement over libaio it will likely become used in performance-oriented applications.