The intended semantics of this is that the filesystem lookup code calls
cache_lookup very early in its code path.  During the start of this
function (in the part you cited) you may notice this:

> int
> cache_lookup(dvp, vpp, cnp)
>         struct vnode *dvp;
>         struct vnode **vpp;
>         struct componentname *cnp;
> {
>         register struct namecache *ncp;
>         register struct nchashhead *ncpp;
> 
>         if (!doingcache) {
>                 cnp->cn_flags &= ~MAKEENTRY;
		  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                 return (0);
>         }
>         if (cnp->cn_namelen > NCHNAMLEN) {
>                 nchstats.ncs_long++;
>                 cnp->cn_flags &= ~MAKEENTRY;
		  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                 return (0);
>         }

This turns off the MAKEENTRY bit in the cn_flags.  This means that the caller
of cache_lookup is not meant to call cache_enter later on (this is not the
only reason that might result in MAKEENTRY being not set in cn_flags).

So this shouldn't be a problem.

For a double check however it might be appropriate to include a check for the
MAKEENTRY bit in cache_enter, at least #if DIAGNOSTIC.

Hope it helps,
Wolfgang
-- 
ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800