Re: [ckrm-tech] [RFC][PATCH] UBC: user resource beancounters

Chandra Seetharaman
2006-08-25T18:21:54Z

On Thu, 2006-08-24 at 19:55 -0400, Kyle Moffett wrote:
> On Aug 24, 2006, at 19:48:28, Chandra Seetharaman wrote:
> > On Thu, 2006-08-24 at 12:10 +0100, Alan Cox wrote:
> >> All you need is
> >>
> >> struct wombat_controller
> >> {
> >> struct user_beancounter counter;
> >> void (*wombat_pest_control)(struct wombat *w);
> >> atomic_t wombat_population;
> >> int (*wombat_destructor)(struct wombat *w);
> >> };
> >
> > This may not solve the problem, as
> > - we won't be able get the controller data structure given the
> > beancounter data structure.
>
> Of course you can! This is what we do for linked lists too. Here's
> an example of how to get a pointer to your wombat_controller given
> the user_beancounter pointer:
> struct wombat_controller *wombat = containerof
> (ptr_to_user_beancounter, struct wombat_controller, counter);
>
> The containerof(PTR, TYPE, MEMBER) returns a pointer to the parent
> object of type "TYPE" whose member "MEMBER" has address "PTR".

Yes, it would work nicely.

But, the problem is that the struct user_beancounter (part of
wombat_controller above) is a _copy_ of the original, not the original
itself. We cannot keep the original (in _each_ controller), as there may
be more than one controller in the system and user_beancounter structure
is created/owned/destroyed by the beancounter infrastructure and not the
controller.

> Cheers,
> Kyle Moffett
>
>
>
>
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Chandra Seetharaman | Be careful what you choose....
- sekharan@us.ibm.com | .......you may get it.
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