SquirrelFS: using the Rust compiler to check file-system crash consistency

This work introduces a new approach to building crash-safe file systems for persistent memory. We exploit the fact that Rust’s typestate pattern allows compile-time enforcement of a specific order of operations. We introduce a novel crash-consistency mechanism, Synchronous Soft Updates, that boils down crash safety to enforcing ordering among updates to file-system metadata. We employ this approach to build SquirrelFS, a new file system with crash-consistency guarantees that are checked at compile time. SquirrelFS avoids the need for separate proofs, instead incorporating correctness guarantees into the typestate itself. Compiling SquirrelFS only takes tens of seconds; successful compilation indicates crash consistency, while an error provides a starting point for fixing the bug. We evaluate SquirrelFS against state-of-the-art file systems such as NOVA and WineFS, and find that SquirrelFS achieves similar or better performance on a wide range of benchmarks and applications.