There is a newly updated ext4 patchset available at:
Compared to 2.6.20-ext4-1, I've removed the the i_version patch, since
they had numerous issues, including not building on ia64. I've also
added the nanosecond timestamp patch.
Discussion will be happening on the linux-ext4 mailing list. I plan to
be pushing extent-overlap-bugfix to Linus soon; other patches still need
work before they will be ready.