Trouble compiling module, sys/vnode_if.h does not exist.

[Denver]

When I try to compile a module I have written which includes <sys/vnode.h> I
get the following message.

@/sys/vnode.h:544:22: vnode_if.h: No such file or directory

This is on a 6.2 Release machine.

I took a look at sys/sys and it seems as though sys/vnode_if.h is not a part
of the sources, but a header which is generated at kernel compile time. If
this is true, what could be the reason that it is not generated on my
machine?

Thank you,
Denver Cox