The kernel radar: folios, multi-generational LRU, and Rust

It's not really accurate that the language wasn't built with the Idea in mind. Just like C, Rust does not depend on any kind of allocator, fallible or not. All of the difficulties here are just from the desire to reuse a userspace library (alloc) in the kernel. They certainly could have just written their own allocator api, list types, etc. just like the kernel does, but since the standard library developers were willing to support their use case it was just more convenient to share.