Comment 0 for bug 2046059

I've been using zswap without any issues for a while, but on upgrading from 18.04 to 22.04 (via 20.04) the kernel starting failing to find the modules for lz4hc compression and the z3fold zpool.

$ sudo dmesg | grep -E 'z3fold|lz4hc'
[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-6.2.0-37-generic root=PARTUUID=948a082e-cfd1-43af-bc7b-3e0b9b20370e ro console=tty1 console=ttyS0 zswap.enabled=1 zswap.compressor=lz4hc zswap.max_pool_percent=60 zswap.zpool=z3fold transparent_hugepage=always panic=-1
[ 0.021736] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-6.2.0-37-generic root=PARTUUID=948a082e-cfd1-43af-bc7b-3e0b9b20370e ro console=tty1 console=ttyS0 zswap.enabled=1 zswap.compressor=lz4hc zswap.max_pool_percent=60 zswap.zpool=z3fold transparent_hugepage=always panic=-1
[ 1.099655] zswap: compressor lz4hc not available, using default lzo
[ 1.101349] zswap: zpool z3fold not available, using default zbud

But the modules are in the initrd (as they always have been):

$ lsinitramfs /boot/initrd.img | grep -E 'lz4hc|z3fold'
usr/lib/modules/6.2.0-37-generic/kernel/crypto/lz4hc.ko
usr/lib/modules/6.2.0-37-generic/kernel/lib/lz4/lz4hc_compress.ko
usr/lib/modules/6.2.0-37-generic/kernel/mm/z3fold.ko

I'm at a complete loss. If the modules are there, why can't the kernel find them?

Both modules can be loaded (obviously from a different location – not the initrd) and the relevant parameters changed with startup scripts but this is a workaround not a solution.

From: https://askubuntu.com/q/1234721/170177

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: linux-image-6.2.0-37-generic 6.2.0-37.38~22.04.1
ProcVersionSignature: Ubuntu 6.2.0-37.38~22.04.1-generic 6.2.16
Uname: Linux 6.2.0-37-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckResult: unknown
CloudArchitecture: x86_64
CloudID: openstack
CloudName: openstack
CloudPlatform: openstack
CloudSubPlatform: metadata (http://169.254.169.254)
Date: Sun Dec 10 11:22:41 2023
Ec2AMI: ami-0008be8e
Ec2AMIManifest: FIXME
Ec2AvailabilityZone: nova
Ec2InstanceType: vps2020-starter-1-2-20
Ec2Kernel: unavailable
Ec2Ramdisk: unavailable
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: linux-signed-hwe-6.2
UpgradeStatus: Upgraded to jammy on 2022-08-15 (482 days ago)