[OpenAFS-devel] setgroups() fails to change pag under linux 2.6

[Roland Kuhn]

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Hi Chas!

On 9 Aug 2006, at 15:41, chas williams - CONTRACTOR wrote:

> In message  
> <17623.34774.671617.38354@khavrinen.csail.mit.edu>,Garrett Wollman w
> rites:
>> Doesn't matter, so long as each PAG gets a distinct memory location.
>> In a real implementation, it would probably be a pointer to a
>> reference count.
>
> negative.  it really should just be an indentifier that is used to  
> group
> together objects.  there should not be identifier reuse.  pointers to
> kernel memory are very likely to be reused (mostly due to the slab
> allocator).  since you might pass these identifiers to a user process
> you cant let them repeat since you have no idea how long a user  
> process
> might hold onto these things.

You got me curious. I should probably watched this thread more  
closely and maybe it would then be clear to me: Why should userspace  
ever see a PAG identifier? What should it be able to do with it?

 From my (very limited) understanding a PAG should behave essentially  
like a session: it is inherited by fork()/exec(), you can detach from  
it, you can create a new one and you can modify it (klog). For none  
of these operations you need to know how the kernel internally  
handles this...

Ciao,
                     Roland

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