https://bugzilla.redhat.com/show_bug.cgi?id=2429501

On Fedora Rawhide, grub2-install fails in BIOS mode when the root filesystem is XFS, causing bootc and Anaconda installations to fail with:

grub_fs_probe: unknown filesystem

This is a regression compared to Fedora 43. The same workflow succeeds when using btrfs or when booting in UEFI mode.

This breaks:
bootc install to-disk
Anaconda installer (BootloaderInstallationError)

Environment:
Fedora Rawhide (current)
grub2 >= 2.12-49.fc44 (Rawhide)
Boot mode: BIOS (i386-pc)
Root filesystem: XFS
Target disk: loopback device (/dev/loop0)
Tooling: bootc + bootupd

Reproducible: Always

Steps to Reproduce:
bootc install to-disk \
--disable-selinux \
--via-loopback \
--filesystem xfs \
--source-imgref docker://quay.io/centos-bootc/centos-bootc:stream10 \
./disk.img

bootc automatically enables --generic-image.

Partitioning created by bootc:

/dev/loop0p1 BIOS boot 1 MiB
/dev/loop0p2 EFI System 512 MiB (vfat)
/dev/loop0p3 Linux root 9.5 GiB (XFS)

Filesystem creation:

mkfs.xfs /dev/loop0p3
mkfs.fat /dev/loop0p2

Actual Results:
Bootloader installation fails:
Installing for i386-pc platform.
/usr/sbin/grub2-install: error: ../grub-core/kern/fs.c:grub_fs_probe:123:unknown filesystem.

bootc then aborts:
error: boot data installation failed: installing component BIOS
Failed to run "/usr/sbin/grub2-install" ... "/dev/loop0"

Full command:
grub2-install --target i386-pc \
--boot-directory /run/bootc/mounts/rootfs/boot \
--modules "mdraid1x part_gpt" \
/dev/loop0

Final failure:
BootloaderInstallationError / Installing bootloader failed

Expected Results:
Installation should succeed and GRUB should be installed to the disk as it does on early Fedora rawhide or Fedora 43.

Additional Information:
This appears to be caused by recent GRUB changes in Rawhide (possibly related to stricter filesystem probing introduced by the GRUB OOM-fix series).

Possibly related to
Bug 2427945
(GRUB regression in Rawhide), but this issue affects BIOS + XFS during installation rather than UEFI boot at runtime.