[rbanffy]

Only the boot file system drivers need to be in the kernel. As long as there is a stable ABI, it's fine for everything else to be someplace else.

[skissane]

> As long as there is a stable ABI, it's fine for everything else to be someplace else.

Mainline Linux has a policy against in-kernel ABI stability guarantees. User-space is given ABI stability guarantees, in-kernel code by intention is not. That includes filesystems.