What were you trying to do that didn't work?

Build and boot RHCOS 9.6 on ppc64le with composefs enabled. The boot fails with

[    9.443308] ostree-prepare-root[1107]: sysroot.readonly configuration value: 1 (fs writable: 1)
[    9.443630] systemd[1]: Starting OSTree Prepare OS/...
[    9.453410] loop: module loaded
[    9.454551] loop0: detected capacity change from 0 to 10888
[    9.474449] erofs: (device loop0): erofs_read_superblock: blkszbits 12 isn't supported on this platform
[    9.474952] ostree-prepare-root[1107]: ostree-prepare-root: composefs: failed to mount: Invalid argument 

What is the impact of this issue to you?

Can't enable composefs in RHCOS 9.6.

Please provide the package NVR for which the bug is seen:

composefs-1.0.5-1.el9.ppc64le
composefs-libs-1.0.5-1.el9.ppc64le
kernel-5.14.0-537.el9.ppc64le
ostree-2024.9-1.el9.ppc64le

I filed this against composefs, but possibly it's the kernel or ostree.

How reproducible is this bug?:

100%

Steps to reproduce

1. Build RHCOS 9.6 on ppc64le (see https://github.com/openshift/os/blob/master/docs/development-rhcos.md, use `cosa init --variant rhel-9.6`)
2. Run any kola test (e.g. `kola run basic`) and look at the failure logs. It should also reproduce more directly with `cosa run -c`, though I haven't tried it yet.

Expected results

No boot failure.

Actual results

Boot failure.