[$] The "rnull" Rust block driver

Thenull blockdriver (null_blk)is a small driver that is mostly useful for benchmarking block-layerimplementations. It accepts all requests and marks them complete as quickly aspossible, doing as little work as possible. In June2026, Andreas Hindborg shareda patch set implementing the same functionality in Rust, in order to showthat a simple block driver is now possible to write using the kernel'sRust APIs and to enable comparisons between the C and Rustimplementations.A minimal version of the "rnull" driver is already present in the mainlinekernel, but Hindborg's patch set brings it up to feature parity with the Cversion.