Re: [PATCH] powerpc/mm: update arch_{add,remove}_memory() for radix

[Reza Arbab]

On Thu, Jun 23, 2016 at 10:47:20PM +0530, Aneesh Kumar K.V wrote:
> Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx> writes:
> > These functions are making direct calls to the hash table APIs,
> > leading to a BUG() on systems using radix.
> >
> > Switch them to the vmemmap_{create,remove}_mapping() wrappers, and
> > move to the __meminit section.
>
> They are really not the same. They can possibly end up using different
> base page size. Also vmemmap is available only with SPARSEMEM_VMEMMAP
> enabled. Does hotplug depend on sparsemem vmemmap ?

I'm not sure. Maybe it's best if I back up a step and explain what lead 
me to this patch. During hotplug, you get

...
	arch_add_memory
		create_section_mapping
			htab_bolt_mapping
				BUG_ON(!ppc_md.hpte_insert);

So it seemed to me that I needed a radix equivalent of 
create_section_mapping().

After some digging, I found hash__vmemmap_create_mapping() and 
radix__vmemmap_create_mapping() did what I needed. I did not notice the 
#ifdef SPARSEMEM_VMEMMAP around them.

Hotplug/remove are now working for me as far as I can tell, so I think
the functional change in itself was correct. Hotplug may not depend on 
sparsemem vmemmap, but we seem to need a radix create_section_mapping() 
regardless.

Could it be that the functions just need to be renamed 
hash__create_mapping()/radix__create_mapping() and moved out of #ifdef 
SPARSEMEM_VMEMMAP?

--
Reza Arbab