Linux v4.1-rc1: Unable to handle kernel NULL pointer dereference

Hi,

btrfs fails to work on my rootfs, with a NULL pointer dereference:
http://sprunge.us/aIWe resulting in a panic on boot. This has also been happening with linux-next-2015042* at least.

It works on 3.8 and 3.18 kernels. The reason the FS is mounted rather late is because I drop to a shell from inside my initramfs and then mount it manually to get a trace; the rootfs is encrypted. Initially mounting the btrfs seems to work, but when actually accessing content it fails.

My kernel is "dirty" because I applied a single line patch to my device tree (ARM device): I have no local btrfs changes.

Cheers,
Merlijn