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

Abstract

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.