It does do various things which the Linux kernel maintainers don't like (particularly how tightly integrated all the components are, something something "rampan

It does do various things which the Linux kernel maintainers don't like (particularly how tightly integrated all the components are, something something "rampant layering violation"). While getting ZFS in-tree would be a godsend, I don't mind building as an out-of-tree module, just that it would be nice if didn't duplicate so much functionality.