> Wouldn't this problem pretty much go away if, as you suggested, that
> the current cloud of vnodes (each layer allocates [its] own vnode and
> tracks that) [were] collapsed into a single entity that could be
> referenced by all the layers?

Perhaps, but then you have the problem that a single vnode can refer to
a whole wack of things, not just one per layer.  Consider, for example,
a layer which does name remapping a la Eunice - you will often have at
least two lower-layer entities for one upper-layer entity.  And such a
thing would be very useful to layer atop, for example, msdosfs.

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