grubenv on md, Btrfs, LUKS, etc

[Chris Murphy]

Hi,

GRUB code can certainly read files that are on Btrfs, md devices,
LUKS, LVM, and so on. But GRUB code can also write to the physical
block for grubenv - but are there safe guards that prevent it from
doing so if grubenv is on something like Btrfs, mdadm raid5, LUKS?

And also what about XFS? This used to be safe, but now with reflink
support, grubenv could be reflink copied, meaning any overwrite is
disallowed and must be COW'd. How is that handled?

I'm pretty sure on Btrfs GRUB knows is can't write to grubenv, I'm
just curious about the other cases.

-- 
Chris Murphy