[Devel] Re: [PATCH 11/11] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs

[David Rientjes]

On Tue, 26 Jun 2012, Glauber Costa wrote:

> > Right, because I'm sure that __GFP_KMEMCG will be used in additional
> > places outside of this patchset and it will be a shame if we have to
> > always add #ifdef's.  I see no reason why we would care if __GFP_KMEMCG
> > was used when CONFIG_CGROUP_MEM_RES_CTLR_KMEM=n with the semantics that it
> > as in this patchset.  It's much cleaner by making it 0x0 when disabled.
> > 
> 
> What I can do, instead, is to WARN_ON conditionally to the config option in
> the page allocator, and make sure no one is actually passing the flag in that
> case.
> 

I don't think adding a conditional to the page allocator's fastpath when 
CONFIG_CGROUP_MEM_RES_CTLR_KMEM=n is appropriate.  I don't understand why 
this can't be 0x0 for such a configuration, __GFP_KMEM certainly means 
nothing when we don't have it enabled so how is this different at all from 
kmemcheck?