Description of problem: when attempting to Live-boot via grub2 m8-plasma.iso, the boot fails and drops to a dracut prompt.
some investigation finds a FATAL at about 3.5 sec into the boot:
dracut: modprobe: FATAL: Module btrfs not found in directory /lib/modules/5.10.16-desktop-1.mga8.
this failure seems to cause  the "loop" mount to fail.


Version-Release number of selected component (if applicable):


How reproducible:every time


Steps to Reproduce:
1.download a Live Mageia.iso
2.set up a btrfs HDD partition labelled the same as the downloaded .iso (eg: Mageia-8-Live-Plasma-x86_64)
3. create a suitable /etc/grub.d/40_custom grub2 menu entry ie:
menuentry "Liveboot" {

         insmod gzio
         insmod part_msdos
         insmod btrfs
         insmod ext2
         insmod xfs
         insmod loopback
         insmod iso9660
         insmod udf
    
    loopback loop (hd0,7)/Mageia-8-Live-Plasma-x86_64.iso 
    linux (loop)/boot/vmlinuz root=mgalive:LABEL=Mageia-8-Live-Plasma-x86_64 noiswmd vga=788
    initrd (loop)/boot/initrd.img

}
4: reboot and choose the custom grub2 menu entry
5: note error

6: should you extract the "loopbacks" directory from the .iso and place it with the .iso, boot is successful.