Re: [RFC PATCH 2/3] fs: support tasks with a null root or cwd

A task's root directory (`fs->root`) and current working directory
(`fs->pwd`) are normally established by `chroot(2)`/`pivot_root(2)` and
`chdir(2)`/`fchdir(2)` (or inherited across `fork(2)`). Allow either to
instead be the null path, as documented in `struct fs_struct`. The two
are independent: a task may opt out of one, the other, or both.

No, absolutely we're not going to have tasks with struct path's in their
struct fs_struct that have NULL members in them. struct path is used
insanely widely in the kernel this is just an an open invitation for a
slew of security bugs. Not going to happen.

-- 
Christian Brauner [off-list ref]