Missing dm-thin-pool Causes LXD LVM Failure

[Brett Holman]

Summary:
Missing dm-thin-pool.ko causes LXD failure.

1) Release
root@jammy-vm:~# lsb_release -rd
Description: Ubuntu Jammy Jellyfish (development branch)
Release: 22.04

2) Package
root@jammy-vm:~# apt-cache policy linux-modules-5.15.0-1002-kvm
linux-modules-5.15.0-1002-kvm:
  Installed: 5.15.0-1002.2
  Candidate: 5.15.0-1002.2
  Version table:
 *** 5.15.0-1002.2 500
        500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages
        100 /var/lib/dpkg/status

3) What I expect to happen

The following command should succeed.

lxd init --auto --storage-backend=lvm

4) What happened:

Lxd's default lvm storage backend fails on linux-kvm due to missing dm-thin-pool.ko.

Output:

root@jammy-vm:~# uname -a
Linux jammy-vm 5.15.0-1002-kvm #2-Ubuntu SMP Wed Feb 9 10:14:12 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

root@jammy-vm:~# modinfo dm-thin-pool
modinfo: ERROR: Module dm-thin-pool not found.

root@jammy-vm:~# lxd init --auto --storage-backend=lvm
Error: Failed to create storage pool 'default': Error creating LVM thin pool named "LXDThinPool": Failed to run: lvcreate --yes --wipesignatures y --poolmetadatasize 1G --thinpool default/LXDThinPool --extents 100%FREE: modprobe: FATAL: Module dm-thin-pool not found in directory /lib/modules/5.15.0-1002-kvm
  /sbin/modprobe failed: 1
  thin-pool: Required device-mapper target(s) not detected in your kernel.
  Run `lvcreate --help' for more information.

I haven't found any -kvm kernels yet that have this kmod, so I suspect a backport of the fix will be required to supported releases.