[kernel-hardening] Re: Conversion from atomic_t to refcount_t: summary of issues

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Nov 29, 2016 at 02:19:56PM +1100, Alexey Kardashevskiy wrote:
> On 28/11/16 23:13, Peter Zijlstra wrote:
> > On Mon, Nov 28, 2016 at 11:56:17AM +0000, Reshetova, Elena wrote:
> >> First, about the types. 
> >> We do have a number of instances of atomic_long_t used as refcounters, see below:
> > 
> > Right, those were expected. We could do long_refcount_t I suppose.
> > 
> >> And yes, we *do* have at least one instance (again not 100% finished,
> >> more might show up) of atomic64_t used as refcounter:
> >>
> >> arch/powerpc/mm/mmu_context_iommu.c:
> >> struct mm_iommu_table_group_mem_t {
> >> ...
> >>     atomic64_t mapped;
> >> ...
> >> }
> > 
> > *urgh*, Alexey does that really need to be atomic64_t ? Wouldn't
> > atomic_long_t work for you?
> 
> 
> It would, this code only works in 64bit where long==64bit anyway (in fact
> even 32bit variant would do).
> 

Thanks, we'll convert it to a 32bit refcount then.