Magic symlinks redux
Luigi Rizzo
rizzo at iet.unipi.it
Fri Aug 22 15:43:56 UTC 2008
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
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