[Natty] [BTRFS] grub 2 won't install if /boot is BTRFS

Binary package hint: grub2

After converting a whole system from ext3 to BTRFS, trying to reinstall grub2 with a BTRFS /boot results in :

root@tethys:/# grub-install /dev/sda
/usr/sbin/grub-setup: warn: Your core.img is unusually large. It won't fit in the embedding area..
/usr/sbin/grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists. However, blocklists are UNRELIABLE and their use is discouraged..
/usr/sbin/grub-setup: error: will not proceed with blocklists.

Only solution found so far : Convert /boot back to ext2, and proceed with the rest of the system on BTRFS, except for /boot.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: grub-pc 1.99~rc1-13ubuntu3
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
Architecture: i386
CheckboxSubmission: 1ea6109db29b53f721a523a77b7f3abf
CheckboxSystem: d00f84de8a555815fa1c4660280da308
Date: Wed May 11 11:40:05 2011
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
 LANGUAGE=fr_FR:en
 PATH=(custom, user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: grub2
UpgradeStatus: Upgraded to natty on 2011-04-03 (38 days ago)