Never break userspace

Where?

Okay, I know Linus says "never break user-space", and he is very strict about it. But at the end of the day, shit happens.

And there's plenty of kernel developers who *haven't* signed up to it. They just know that trying to get it past Linus is not a battle worth fighting most of the time.

There's one big example I can think of, that had a rather nasty fall-out, in the raid world. So bad, in fact, that kernels were modified to have an explicit "fail to boot" config, iirc!

Something to do with the fact that raid layout was accidentally changed. So you have pre-change kernels that will trash post-change arrays, pre-discovery kernels that will trash pre-change arrays, and post-discovery kernels that will refuse to access arrays without a "this is a pre/post-layout flag".

Sometimes that's all you can do :-(

Cheers,
Wol