io_uring based userspace block driver. Together with ublk server, ublk
has been working well, but interface with userspace or command data
definition isn't finalized yet, and might change according to future
requirement, so mark is as experimental now.

Say Y if you want to get better performance because task_work_add()
can be used in IO path for replacing io_uring cmd, which will become
shared between IO tasks and ubq daemon, meantime task_work_add() can
can handle batch more effectively, but task_work_add() isn't exported
for module, so ublk has to be built to kernel.

source code:

drivers/block//ublk_drv.c