During triage of https://bugs.launchpad.net/bugs/1619918 it was found out today that apparently commit https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4c63c2454eff996 introduces a regression when running an amd64 kernel with a system that is otherwise mostly i386.
I opened a ticket on launchpad in September since I was unable to use lsattr when having an amd64 kernel and i386 e2fsprogs. The proposed and committed fix 4c63c2454eff996 was backported and introduced regressions into the Ubuntu trusty 3.13.0-97 kernel, one of which was confirmed to be present in last week's mainline as well.
With kernel 4.9.0 I can no longer take a btrfs snapshot of my system. The error message is "Inappropriate ioctl for device", very similar to the original problem with lsattr before 4c63c2454eff996.
I believe this problem was fixed (I have come across a number of other issues, though, when running i386-userland with an amd64-kernel)