Re: Replace lockmgr for vnodes

[Andrew Doran <ad%netbsd.org@localhost>]

On Fri, Jan 25, 2008 at 04:05:57PM -0800, Bill Stouder-Studenmund wrote:

> 2) How do/did we handle the issues that lead to us wanting LK_DRAIN?

It's not needed now for vnodes, the vnode reference count, XLOCK and
VOP_INACTIVE being made 'restartable' conspire to replace it. There
are problems with forced reclaim but those are not new.
 
> 3) I think it'd be nice if we could retain something akin to 
> lockmgr_printinfo(). I realize that our locking is now such that we need 
> to print more than just one big heavy lock. However being able to figure 
> out what's up/broken with locks can help. :-)

We have 'show lock' from ddb. I'll see about providing a replacement.
 
> 4) I think we can rip out the "UPPER LOCK" stuff in layerfs. It dated from 
> when lower file systems didn't do locking. The only thing now that doesn't 
> export a vn_lock is unionfs, which does do correct locking. Sorry, I've 
> been meaning to kill it but haven't gotten to it.

Sounds like union-over-union should be prevented? I'll see about removing
it.

Thanks,
Andrew