The ABI status of filesystem formats

The problem is that we don't care about a spec, we care about "User space used to work and now it doesn't." So the fix is to program a lot of validation into the kernel so that Josh's filesystem never works from square one. If it never worked to begin with then it can never be broken. It's a lot of work to code this and it doesn't necessarily make Josh any happier.

So probably that approach is a waste of time.