On Fri, Jun 23, 2006 at 10:26:00AM -0700, Bill Studenmund wrote:
> On Thu, Jun 22, 2006 at 05:55:52PM +0200, Juergen Hannken-Illjes wrote:
> > On Wed, Jun 21, 2006 at 02:24:53PM -0700, Bill Studenmund wrote:
> > > On Wed, Jun 21, 2006 at 01:34:38PM +0200, Juergen Hannken-Illjes wrote:
> > > > On Wed, Jun 21, 2006 at 08:02:56PM +0900, YAMAMOTO Takashi wrote:
> > [snip]
> > > > > well, i think neither syscalls or individual VOPs are appropriate
> > > > > for your purpose.  what you need is the intermediate.  ie. a set of VOPs.
> > > 
> > > Yeah, this is what I'm thinking we should do.
> > 
> > What if we add "critical regions" to vnodes?  This could look like
> > 
> >     vn_hold(vp, V_WAIT);
> >     VOP_XXX(...);
> >     VOP_XXX(...);
> >     ...
> >     vn_release(vp);
> > 
> > or
> > 
> >     NDINIT(..., ... | HOLDLEAF, ...);
> >     if (namei(...) == 0) {
> > 	VOP_XXX(nd->ni_vp, ...);
> > 	VOP_XXX(nd->ni_vp, ...);
> > 	...
> > 	vn_release(vp);
> >     }
> > 
> > vn_hold() would wait until suspension is over and the vnode is not held,
> > then set a flag VHOLD and increment a hold counter in vp->v_mount.
> 
> This is kinda what we are doing now, and what I think is a good idea.
[snip]

Correct me if I'm wrong... Could this simply replace vn_lock/VOP_UNLOCK
outside of file systems?  It looks like we would get always things like

    vn_hold(vp, V_WAIT);
    vn_lock(vp, LK_...);
    ...
    VOP_UNLOCK(vp);
    vn_release(vp);

What would we need to support layered file systems?

-- 
Juergen Hannken-Illjes - hannken@eis.cs.tu-bs.de - TU Braunschweig (Germany)