"Reverse union" mount possible?

[Erez Zadok]

In message <20031121124549.44895c7c.tarkhil at over.ru>, Alex Povolotsky writes:
> On Thu, 20 Nov 2003 21:01:31 -0500
> Erez Zadok <ezk at cs.sunysb.edu> wrote:
> 
> EZ> > > Right now, I'm readonly mount_null'ing /bin, /sbin, /usr/bin,
> EZ> > > /usr/sbin,/usr/lib, /usr/include, /usr/libexec, /usr/share. With
> EZ> > > a dozen jails, there are too many mounts to my liking, and about
> EZ> > > twice a week I experience panic. Probabily it's nullfs-related.
> EZ> > 
> EZ> > Nullfs is known to be buggy in -stable. In particular, it seems to
> EZ> > deadlock under load / when vnodes start getting recycled.
> EZ> 
> EZ> My fist stackable templates were ported to fbsd 4.x and 5.0 not too
> EZ> long ago.  We ran extensive tests to ensure that the code is stable.
> EZ>  While it's
> EZ> possible we missed stuff, it might help if someone checked what is
> EZ> different about my "wrapfs" vs. Nullfs.  We may have fixed bugs in
> EZ> wrapfs not realizing that they originally came from the base Nullfs
> EZ> we started with.
> 
> Sounds cool. Where can I get the source?

FiST home page: http://www1.cs.columbia.edu/~ezk/research/fist/

> BTW, I've heard that nullfs/unionfs doesn't allow code sharing. Does wrapfs do it?

What do you mean by "code sharing"?  Licensing?  All of the freebsd fist
templates use the BSD license.

> Alex.

Erez.