btrfs /target fails: install.py crashed with AssertionError in __init__(): Failed to mount the target: /target

[HuG]

Install crashed while creating file systems (with 32bit desktop 11.04 this works. I doubt it's the btrfs for root here (as also the the ubuntu 11.04 alternate 32bit CD install also fails to mount /target (btrfs root), while installing, which I haven't reported elsewhere as a bug):

sda6 ext4 /boot 80MB
sda7 btrfs / 12.5GB
sda8 ext4 /home >30GB
sda9 swap ~2GB

To enable compress=lzo ASAP for root, I loop (had no problem with 32bit) this in terminal window while installing:

while [ ! `mount | fgrep 'compress'` ]; do mount /target -o remount,compress=lzo; sleep .7; date; done

But the bug repeats even whithout this loop.

I think I have 64bit architecture hardware, as `cat /proc/cpuinfo | fgrep -c lm` returns 2.

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: ubiquity 2.6.10
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
Architecture: amd64
Date: Sun Sep 25 12:21:12 2011
ExecutablePath: /usr/share/ubiquity/install.py
InterpreterPath: /usr/bin/python2.7
LiveMediaBuild: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcCmdline: /usr/bin/python /usr/share/ubiquity/install.py
ProcEnviron:
 LANGUAGE=fi_FI.UTF-8
 PATH=(custom, no user)
 LANG=fi_FI.UTF-8
 SHELL=/bin/bash
 LC_COLLATE=C
PythonArgs: ['/usr/share/ubiquity/install.py']
SourcePackage: ubiquity
Title: install.py crashed with AssertionError in __init__(): Failed to mount the target: /target
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make Ubuntu better. This particular crash has already been reported and is a duplicate of bug #626775, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.