Chris Mason, the lead Btrfs developer and its creator when back at Oracle in 2007, joined Fusion-io last year and continued working on Btrfs and its upstream kernel support. Assisting Chris through the Btrfs endeavours has been Josef Bacik, who was also working at Fusion-io. Chris Mason and Josef Bacik are both now leaving Fusion-io for Facebook.
There was a patch sent out today on the kernel mailing list updating the Btrfs maintainership to their new email addresses at Facebook. At Facebook, Chris and Josef will continue working on Btrfs and the Linux kernel.
Chris Mason had also written in a Btrfs mailing list post last week, "I'll continue to focus on Linux kernel development. Facebook is also very interested in helping to improve Btrfs...From a Btrfs point of view, very little will change. All of my Btrfs contributions will remain open and I'll continue to do all of my development upstream."