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

Reza Arbab
2016-06-23T19:37:51Z

On Thu, Jun 23, 2016 at 10:47:20PM +0530, Aneesh Kumar K.V wrote:
>Reza Arbab <arbab@linux.vnet.ibm.com> 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