Freeing vnodes.

[David Schultz]

On Mon, Mar 28, 2005, Jeff Roberson wrote:
> > > I am worried about the v_dd,v_ddid fields of a directory B that has the
> > > to be released vnode A as parent. (Obviously in this case there is no
> > > namecache entry with the vnode A as the directory (nc_dvp))
> > >
> > > Right now A is type stable - but if A is released, access to B->v_dd
> > > may cause a page fault.
> > >
> > > Stephan
> >
> > Jeff,
> >
> > Do you plan to address the problem now that the code is checked in?
> 
> Vnodes with children in the name cache are held with vhold() and not
> recycled.

Yes, but cache_purge() is called directly in a number of places
where the vnode may have children, e.g. in mount.  So dangling
references might still be possible unless cache_purge() fixes up
the children's v_dd pointers appropriately.