Diskless APKOVL loading dosn't work on btrfs and xfs filesystems, or nvme-based devices

Hi,

I'm using the stock 3.11.6 ISO in conjunction with an APKOVL for a diskless-boot. The configuration works just fine when I place the APKOVL on an ext4-formatted partition on a SCSI-device. However, when I place the same APKOVL on any of the following, it's not loaded:

• A btrfs-formatted partition
• An xfs-formatted partition
• Any partition on an NVMe device (e.g. nvme0n1p1)
• Anywhere other than the root of a partition (e.g. in a subdirectory)

I can see the last item being by design, but as for the others, there's already native btrfs/xfs/nvme support, so I would expect them to be supported out-of-the-box.

Thanks!