Linux procfs combines features that we have split in kernfs and procfs.
I agree that we should not have our procfs have all this, that's
why I made it a mount option.

Currently, the amount of code added to support the few Linux features
optionally (there are 3, besides 'cmdline', which was also a Linux
feature but is now part of our procfs too) outweighs having to go
through the trouble of splitting it up. The code for both would
be very similar, but different enough that sharing it will not be
easy. You'll have 2 filesystems, with different mount structures
and private vnode data, but with almost identical ways to build
the directories and look up files.

Had I expected that many more Linux features would have to be added,
I'd have gone for a split fs, even though it would have meant an
uneasy sharing of some code, or a non-negligible amount
of code duplication.

However, I didn't and don't think that many more features will be
needed. Perhaps a couple more eventually (but I'm talking over the course
of years). Should I be wrong about this, and if it turns out that
more Linux features are needed, then I'm all for a split. For now,
it just wasn't worth it.

- Fran