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To: Jeff Roberson <jroberson@chesapeake.net>
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Date: Mon, 02 May 2005 15:19:42 +0300
From: Danny Braniss <danny@cs.huji.ac.il>
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cc: freebsd-current@freebsd.org
cc: Oleg Sharoiko <os@rsu.ru>
cc: Kris Kennaway <kris@obsecurity.org>
Subject: Re: diskless/unionfs panics 
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> On Sun, 1 May 2005, Oleg Sharoiko wrote:
> 
> >
> > On Sun, 1 May 2005, Jeff Roberson wrote:
> >
> > JR>Where is this patch?
> >
> > It was quoted by Danny in his mail http://docs.freebsd.org/cgi/mid.cgi?E1DRs0M-0006E4-9a
> > I sent it him privately, because I wasn't sure about the patch.
> 
> Yes, unfortunately this is only part of the problem.  The v_object can
> change on a unionfs vnode leading to inconsistent results for mmap/exec.
> This also causes problems for unionfs mounted on top of unionfs as the
> lower vp can also change v_object fields.  This was one advantage to the
> VOP based solution.  It would propagate all the way down the stack on each
> access.
> 
so can we partialy solve the problem :-)?

> >
> > Here it is:
> > -----
> > Index: union_vnops.c
> > ===================================================================
> > RCS file: /home/ncvs/src/sys/fs/unionfs/union_vnops.c,v
> > retrieving revision 1.131
> > diff -u -r1.131 union_vnops.c
> > --- union_vnops.c       13 Apr 2005 10:59:08 -0000      1.131
> > +++ union_vnops.c       1 May 2005 07:50:27 -0000
> > @@ -748,6 +748,9 @@
> >         if (error == 0)
> >                 error = VOP_OPEN(tvp, mode, cred, td, -1);
> >
> > +       if (error == 0)
> > +               ap->a_vp->v_object = tvp->v_object;
> > +
> >         /*
> >          * Release any locks held.
> >          */
> > -----
> >
> > I made it similar to the way it's done in nullfs. You can check my
> > explanaitons quoted by Danny.
> >
> > --
> > Oleg Sharoiko.
> > Software and Network Engineer
> > Computer Center of Rostov State University.
> >