Subject: Re: diffs for UVM/UBC improvements available
To: Chuck Silvers <>
From: Bill Studenmund <>
List: tech-kern
Date: 05/23/2001 16:59:16
On Tue, 22 May 2001, Chuck Silvers wrote:

> On Tue, May 22, 2001 at 08:32:29PM -0700, Bill Studenmund wrote:
> > Hmmm... I should look at the diff. My thought was we'd keep the struct
> > vnode *, which would just point into the fs-private data.
> actually, here's a reason why this isn't preferable:  it means that
> a filesystem which does not use a struct lock to implement VOP_LOCK()
> would not work with the layered filesystems.  an example of such a
> filesystem would be a cluster filesystem which would need to use a
> cluster-wide vnode lock.

That was already covered - if the exported struct lock * was NULL, then
layer_{,un}lock() called the underlying VOP_LOCK(). This idea already came
up so we could support a layered fs over a unionfs system (which has to do
its own lock gyrations).

Any other reason?

Take care,