Cannot solve my VFS root issue (GPT, btrfs, grub2)

[SumDog]

I'm in kernel boot/panic hell. I got a new desktop and tried moving my gentoo install out of a VM and onto it. Also decided to try out GPT and Btrfs (desktop is BIOS, not EFI). I setup all the correct partition tables and with some fiddling, got grub2 to correctly load. But I kept getting kernel panics. My kernel is built with GPT support and Btrfs built in (not as modules), but when I try to boot I get this screen:

http://i.imgur.com/MpUzAMv.jpg

As you can see on the screen, it shows all four partitions (sda1 is the EFI boot partition that grub puts its core.img in, sda2 is /boot, sda3 is swap and sda4 is root). I double checked and btrfs is in there and I can mount /dev/sda4 from my LiveCD (also running 3.14.0-gentoo) no problems at all. I cannot for the life of me figure out why it can't load that root partition. I've tried root=/dev/sda4 and root=sda4 as kernel arguments. What is going on?

EDIT: wrong screenshot; added the one where I specified the root. Also I noticed it's trying to mount that partition as UDF-fs instead of btrfs. ??!

[SumDog]

Got it! Found this post: https://forums.gentoo.org/viewtopic-t-938502-start-0.html

that mentioned specifying rootfstype (so I set mine to rootfstype=btrfs). It booted!