vendor/illumos merges

[Mark Johnston]

Hi,

Now that FreeBSD uses OpenZFS as the upstream for ZFS, vendor/illumos is
mostly unused.  However, we still use illumos as an upstream for CTF
tools and DTrace, though there haven't been any imports in a while.

illumos has put a lot of work into their CTF toolchain, and I'd like to
import that.  There are a couple of snags that I'd appreciate some
guidance on.

First, I believe I should delete now-unused ZFS code from the vendor
branch and merge the result to main.  I did this locally and got an
empty merge, which is what I'd expect.  Is there any problem with this?

Second, with Subversion we had both vendor/illumos and
vendor-sys/illumos, and now we just have the former, seemingly with
sys/* bits imported from vendor-sys.  Some of the upstream commits touch
both userspace and kernel bits, but the merge targets for these in
FreeBSD are different: cddl/contrib/opensolaris vs.
sys/cddl/contrib/opensolaris.  How should I merge into main in this
case?  I don't really see any options other than to split each offending
upstream commit into two parts, one for userspace and one for the
kernel, and merge them separately.

If it helps to look at the branch where I staged the upstream commits,
I've pushed it to vendor/illumos2 in https://github.com/markjdb/freebsd
.