hi,

> I agre with the overall goal of simlpifying the VFS layer.
> But please, can we also ensure that the VFS layer still exports all
> the vnode operations necessary to support virtualizing a filesystem --
> as done, for example, for FreeBSD-4 by Erez Zadok's FiST tool?
> 
> (If I ever find time, I intend to write a wrapfs for NetBSD-3 or
> -current, assuming the FreeBSD-4 wrapfs is a useful starting point).

i don't know much about FiST.
in the vfs pov, it isn't different from arbitrary filesystems, is it?

> >afaik there is no point to export them.
> 
> I have a dim memory that the Solaris vnode interface uses VOP_TRUNCATE
> between stackable filesystems, though I don't recall if Solaris has
> a VOP_SETATTR, or (if so) why they use VOP_TRUNCATE also.
> 
> If (dim) memory serves, the FICUS work from UCLA was the source of
> support for stackable filesystems and was the motivating factor
> whereby CSRG put the "message-passing" VOP interface in 4.4BSD.  It'd
> be nice not to lose that functionality.

if they need redundant VOPs like VOP_TRUNCATE,
i'd say their design is broken.

YAMAMOTO Takashi