Magic symlinks redux

[Julian Elischer]

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.

then this needs to be put on the virtualisation mailing list (CC'd)
as Jamie and Vereo have another implementationt eh yare getting ready
I thing..
(with considerably different proporties especially designed for
use with virtualisation)  Verio have thsi in production.



> 
> -- Brooks
> 
>> I am playing with a rewrite (attached below) of the original patch,
>> which fixes at least one memory leak and addresses some of the
>> issues that i mentioned in this thread (abuse of macros, performance,
>> behaviour on errors, etc.).
>>
>> (i haven't looked up yet the original copyright but i guess it
>> is from netbsd...)
>>
>> 	cheers
>>