Apparently /proc needs it; it's normally implemented using get_link if
readlink isn't implemented but proc's get_link crashes the kernel in
this case (because nameidata is only defined for open* paths)
Change-Id: I1864d6c948db879d33ea29b1b281bf84ff8eeec6
rhel8 is a 4.18 kernel but they've already backported some later fixes.
Instead of relying on the kernel version, the changes removed some defines so
we can check for the define presence to make the code more robust to kernel
version wilderness instead
Change-Id: I6cf5548a7b73a7394405daf850f715a1e20ab0b4
This newer version is much simpler than the old ones:
- the options are noop, this lets the code simplify all the allocating
of a new option struct and passing it around
- ovl_reset_ovl_entry was added and called all the time, but the
mechanism that made this required is gone in this kernel version
On the other hand, one new thing in this version:
- newer kernel check the stacking depth of filesystems now, and we are
reaching the default limit of two with our setup. Bump it to three here.
Also, while we are here, make make fail if requested directory does not
exist, instead of infinitely recurse into make modules in the mcoverlayfs
directory...
Change-Id: I45050d693a0aa6fd3027deaf417c29876ef6a1ea
