kernel: TCMU support

[cvlc]

Issue number:
N/A (See AmazonLinux issue)

Description of changes:
Added the TCMU (LinuxIO user subsystem) feature support as a module to the Bottlerocket kernel. TCMU is a feature of the Linux kernel that exposes block devices (eg. virtual/physical disks) to user space via LinuxIO (LIO) - for storage fabric solutions, eg. Ceph iSCSI Gateway and Ondat. This enables those solutions to run on Bottlerocket.

Testing done:
Standard cargo build.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[bcressey]

Looks reasonable to me. Just to confirm - the userspace solutions you have in mind would all be deployed via containers?

Is there a getting started guide focused on Kubernetes deployments for either of the solutions you mentioned? Ideally we'd add some smoke testing to our test clusters for this functionality.

[cvlc]

Whoops, apologies for the close-reopen!

Yes, indeed, it is aimed at containers:

There are a few options for testing

• https://docs.ondat.io/docs/install/ is the install guide for Ondat using a kubectl plugin
• https://github.com/storageos/init is an init container that runs some basic checks for TCMU module availability
• https://docs.ceph.com/en/latest/rbd/iscsi-overview/ covers the Ceph feature, though it's a little more involved, I think that Red Hat has an operator and that Rook supports this configuration.

[arnaldo2792]

I checked how the init container works, and it will attempt to load various kernel modules. I think the simple smoke test will be to attempt to do the same (load the kernel modules), and a more complete test could be to attempt to run the ondat-operator in Bottlerocket, which under the hood uses the referenced init container. Anyhow, looks good! Thanks @cvlc!

[zmrow]

Thanks! 🎉