90dmsquash-live: cannot handle overlayfs module built into kernel

[AdrianVovk]

Describe the bug
As of kmod 28, modprobe fails and spits out an error code if the kernel module you're trying to load is already built into the kernel. I'm not super sure if this is a kmod bug (I cross-opened an issue there too, just in case), but this is currently breaking dracut. Dracut runs modprobe overlay, which fails because this module cannot be found (it's built-in) and then dracut stops and refuses to continue booting.

Distribution used
carbonOS 2021.1 (my own in-development distro)

Dracut version
53

Init system
systemd

To Reproduce
Build Linux with CONFIG_OVERLAY_FS as y instead of m. Ensure running on kmod 28. System will fail to boot into a live OS.

[haraldh]

Hmm, I can't reproduce this with kmod 28.

# modprobe --version
kmod version 28
+ZSTD +XZ +ZLIB +LIBCRYPTO -EXPERIMENTAL

# modinfo sg
name:           sg
filename:       (builtin)
[…]

# modprobe sg; echo $?
0

# lsinitrd /lib/modules/5.11.16-300.fc34.x86_64/initrd -f usr/lib/modules/5.11.16-300.fc34.x86_64/modules.builtin  | grep sg.ko
kernel/block/bsg.ko
kernel/drivers/scsi/sg.ko

[haraldh]

This is likely the culprit: #1436