This will be committed in two parts. Flag field resizing and renumbering prevents the vnode from growing with later addition of v_nchash and will be committed first.
This significantly speeds up path lookup, Cascade Lake doing access(2) on ufs on /usr/obj/usr/src/amd64.amd64/sys/GENERIC/vnode_if.c, ops/s:
That is +10%.
The reversed order of computation here does not seem to matter. I dumped the namecache populated with > 7 mln and recomputed chain placement with both methods, almost no differences.
I tried to lump this in with v_hash, but unfortunately that one has many testicles elsewhere and in particular is not constant for the lifetime of the vnode.