Subject: Re: vnode locking procedure change to suport stacked fs's.
To: Bill Studenmund <>
From: Kevin P. Neal <>
List: tech-kern
Date: 05/25/1999 02:02:31
On Mon, May 24, 1999 at 04:12:17PM -0700, Bill Studenmund wrote:
> Rather than just change the VOP_LOCK protocol to lock bottom up, I'd
> rather we change the vnode lock interface so that all vnodes point to the
> relevant struct lock for the node. For stacked fs's, upper vnodes would
> point to the struct lock for the lower vnode. Thus if we have multiple
> layers stacked on each other, whenever any one node gets locked, they all
> are locked.

What about for fan-in and fan-out?

If you have one node up top that fans out to multiple nodes on the bottom
then where does the lock live? 

How would you handle, say, a mirroring layer or perhaps a generic 
(fs-independent) ACL layer?

What about cycles in the layering?
Kevin P. Neal                      

"You know, I think I can hear the machine screaming from here...  \
'help me! hellpp meeee!'"  - Heather Flanagan, 14:52:23 Wed Jun 10 1998