grub2-mkconfig generates wrong grub.cfg with multi-device btrfs root

[Juan Orti Alcaine]

Hello,

I ask for help in this mailing list after first reporting this bug to
Fedora bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1294532

The problem is that grub2-mkconfig generates wrong grub.cfg when the
root filesystem is a multidevice btrfs with mixed partitions and lvm
logical volumes. Instead of setting the kernel line with
root=UUID=xxx, I get the list of devices of the filesystem separated
by newlines, which, of course, breaks the config file.

I can easily reproduce this bug in a fully updated Fedora 23 VM with
this root filesystem:

address@hidden ~]# btrfs fi show
Label: 'fedora_fedora23w-btrfs'  uuid: 933ffc76-ecab-4779-9eab-7f8fcb234015
        Total devices 4 FS bytes used 4.02GiB
        devid    1 size 17.51GiB used 0.00B path /dev/vda3
        devid    2 size 20.00GiB used 2.03GiB path /dev/vdb1
        devid    3 size 20.00GiB used 2.03GiB path /dev/vdc1
        devid    4 size 20.00GiB used 2.00GiB path /dev/mapper/vg01-lv01

btrfs-progs v4.2.2

The versions I have:
grub2-efi-2.02-0.25.fc23.x86_64
grub2-2.02-0.25.fc23.x86_64
grub2-tools-2.02-0.25.fc23.x86_64
btrfs-progs-4.2.2-1.fc23.x86_64

I have "set -x" in /etc/grub.d/10_linux

Then I run:
grub2-mkconfig -o /tmp/grub.cfg 2>&1 | tee /tmp/grub2-mkconfig.out

The output of the grub2-mkconfig command is here:
https://bugzilla.redhat.com/attachment.cgi?id=1112455

The wrong grub.cfg generated:
https://bugzilla.redhat.com/attachment.cgi?id=1112456

-- 
Juan Orti
https://apuntesderootblog.wordpress.com/