This will conflict with my patch to remove a lot of this stuff. You can find it on this branch:
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit/?h=btrfs-mount-api
with the subject "security: Remove the set_mnt_opts and clone_mnt_opts ops".
Note that both nfs and btrfs need converting before this can be applied.
David
