grub-1.99 and btrfs-only

I have a btrfs-only system, using grub2 (1.99), and have /boot on btrfs as well...

When I first boot, grub first complains it cannot find files, then apparently successfully finds them, loading the menu..

After I select the option I want, grub again complains of unable to find a file, and seconds later begins to properly boot..

This is my boot.cfg
---
set timeout=5

insmod gpt
insmod btrfs
set root=(hd0,gpt3)
search --no-floppy --fs-uuid --set a549b032-017c-4a96-ae28-5dffe61cff1d
if loadfont /boot/grub/unifont.pf2; then
set gfxmode=1680x1050
insmod gfxterm
insmod vbe
terminal_output gfxterm
fi

set menu_color_normal=cyan/black
set menu_color_highlight=black/cyan

menuentry "Linux 3.1.0" {
insmod gpt
insmod btrfs
set root=(hd0,gpt3)
search --no-floppy --fs-uuid --set a549b032-017c-4a96-ae28-5dffe61cff1d linux /boot/bzImage-3.1.0 root=/dev/sda3 rootfstype=btrfs initrd /boot/initframfs-3.1.0
set gfxpayload=keep
}
set default=0
---

These are my current subvolumes:

# btrfs sub list /
ID 256 top level 5 path mainroot
ID 257 top level 5 path home

I have sub 256 set as default, and then home is mounted onto mainroot.

I'm assuming that since I have my boot inside that subvolume, that is why grub, at first, has issues locating the files, but then manages to find it.

My question is this: Is anyone aware of any grub.cfg magic I can use to specify a specific subvolume to look for /boot/grub ? my plan is to eventually move boot into it's -own- subvolume, and create more subvolumes for different distros.

I advise against using set-default at all. The setup Ubuntu seems to be going for ( and is working well for me so far ) creates two subvolumes under the default root, named @ and @home, and intended to be mounted in / and /home respectively. The /@ subvolume is then mounted as the root via rootflags=subvol=@ argument, and grub is configured to use /@/boot/grub as its prefix directory.

I'm still getting a "sparse file not allowed" error during boot, and have to press enter to continue though. Still not tracked that one down.

https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/736743

Missing feature in GRUB, see Colin Watson's comments in partucular.