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Date: Fri, 22 Aug 2008 17:46:31 +0200
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Brooks Davis <brooks@freebsd.org>
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Cc: Ivan Voras <ivoras@freebsd.org>, Christian Brueffer <brueffer@freebsd.org>,
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Subject: Re: Magic symlinks redux
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On Fri, Aug 22, 2008 at 10:07:29AM -0500, Brooks Davis wrote:
> On Fri, Aug 22, 2008 at 04:56:16PM +0200, Luigi Rizzo wrote:
> > On Fri, Aug 22, 2008 at 02:05:26PM +0200, Christian Brueffer wrote:
> > > On Fri, Aug 22, 2008 at 12:24:41PM +0200, Ivan Voras wrote:
> > ...
> > > > This patch is huge. As far as I can tell DragonflyBSD has a whole 
> > > > framework dedicated to varsyms, spread across a fair part of the kernel 
> > > > and with at least one special userland utility. It allows the operator 
> > > > to define his own variables that can be used in the substitutions, and I 
> > > > don't see that it predefines "special" variables like "uid" and 
> > > > "hostname". It's not necessarily a bad solution but I consider it overkill.
> > ...
> > > Brooks has a varsym port in p4, see //depot/user/brooks/varsym/
> > 
> > this also seems to be based on Dragonfly's code, quite intrusive.
> 
> This code adds one global symbol, one function call in the vfs code,
> and two pointers to struct proc.  For that we get a system which is
> significantly more flexible than the NetBSD code.
> 
> While the simplicity of the NetBSD code is somewhat attractive, the
> fact that variables can not be defined renders it useless for my
> purposes which are providing partial file system virtulization for
> computing job/sessions where I need to key off of externally derived job
> IDs or job specific temporary paths.

understood -- it's just that the difference in code size is impressive.

Do you know how much of it is used to implement the "varsym"
subsystem (user- or system-wide variables) and how much is the
core name translation ?

	cheers
	luigi