On-disk format robustness requirements for new filesystems

$ git grep fuzz tests/xfs/group |wc -l
156
$

156 separate on-disk format fuzzing tests, quite a few (~40) of which also test the ability of the under-development online repair code to fix the fuzzing damage automatically. These fuzzers know the on-disk format, so they defeat all the CRC checking by recalculating the CRC after the structures have been corrupted. That's why we have our own fuzzers - at the time nobody had a fuzzer capable of defeating CRCs, so we extended our own tools to do it....

So the truth is that XFS developers have a very high standard for on-disk format robustness and we have both the toolchain and runtime verification in place to find and fix bugs and areas we don't validate as well as we should. It's an ongoing process of improvement....

-Dave.