Distros will work a bit at shipping the right toolchain the first time they ship a rust-written module, but otherwise, it can't break userspace. I guess they'll start by merging the close reimplementation to make regressions easy to track.

Happy happy joy! I've been using it for a year already, as it is simpler to manage than luks + lvm + bcache + whatever FS.

It has been entirely unproblematic through frequent kernel upgrades; caching, background compression and encryption just work.

I'm very glad it made it in; it deserves wider adoption.