include ext4

[Jason Newton]

Hello,

I'd also like to put my vote in on it being turned on - it is only a few 
changes to the kernel:
CONFIG_EXT4DEV_FS=m
CONFIG_EXT4DEV_FS_XATTR=y
CONFIG_EXT4DEV_FS_POSIX_ACL=y
CONFIG_EXT4DEV_FS_SECURITY=y
CONFIG_JBD2=m
CONFIG_JBD2_DEBUG=y

And with 2.6.27 ext4 is nearly good to go already, but it has itself put 
in checks to make sure only prepared people use it - marking the 
superblock with test_fs and using ext4dev as the mounting fs type .  It 
would also seem that everything else on ubuntu already supports it 
(namely e2fprogs) so long as the installer doesn't by default pick this 
fs, there is no problem support yet another option in the myriad of 
options ubuntu already supports.  Ubuntu wouldn't be alone in this 
either, fedora has had it enabled and even allowed installing (with 
appropriate warnings )on it since fedora 9 with 2.6.25

I've also been using it for a month on a 1 tb volume and my laptop's 
root (fedora rawhide) with some violent testing and can attest to its 
bit integrity and performance during that time.

Regarding it being a no problem endeavour to compile from the mainline 
subdir, it is a bit of a problem because atm there is a forced 
dependency on JBD2 which makes it quite a bit more work to build unless 
I'm doing it wrong.  Also requires getting source code + a recompilation 
every kernel update.  It would be much easier and make more sense to 
just enable it in the distros builds - especially so drives could be 
plugged into one up-to-date os/machine to any other with a minimal of 
overhead.