I'd use io_uring in a heartbeat on a dedicated system where the job is only I/O and security isolation isn't a concern. But multiuser/multiapplication/networked? Not a chance.
1. know what io_uring is
2. are interested in performance enough to look at improvements based on new linux kernel system calls and talk about it in public
3. care about security in multitenant environments or the syscalls used by third party libraries
I think io_uring right now probably makes a lot of sense for HPC and highly technical, performance-sensitive financial stuff, but they can be kind of insular. I don't think most linux hobbyists really need the performance benefits enough t care about it, and most businesses are using a major cloud vendor/don't have the scale or expertise to be thinking about this kind of stuff. Which leaves major cloud providers and really big businesses like Meta with their own internal clouds as the ones that stand to benefit enough to care about performance while really caring about security
That someone with kernel IO dev experience may be able to relatively easily add such a fetaure in the future (though I would doubt that, given that it hasn't yet been implemented apparently) doesn't make it a small problem.
- io_uring initially was conceived without considering security or auditing tools
- io_uring later was changed to allow ioctl calls, even though security people do not like ioctl because what its arguments mean depends on the device being called (possibly even on the version of the driver), not on the type of device, and often is poorly documented, making it hard for a security filter to decide what to do with a command.
That also made them fear that similar security-breaking changes might be made in the future.
This would be useful if you want to boot with io_uring but deny it for some sensitive workloads.
Nowadays its mostly a combination of eBPF, SELinux and auditd plus namespaces in case of containers. Usually in the combination that some distro ships, so nothing really fancy.