Subject: Re: [PATCH v4 04/13] mm/vmemmap: Allow architectures to override how vmemmap optimization works

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 11 Jul 2023 09:57:32 +0530

Christophe Leroy <[email-masked]> writes:

> Le 10/07/2023 à 18:08, Aneesh Kumar K.V a écrit :
>> Architectures like powerpc will like to use different page table allocators
>> and mapping mechanisms to implement vmemmap optimization. Similar to
>> vmemmap_populate allow architectures to implement
>> vmemap_populate_compound_pages
>> 
>> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>> ---
>>   mm/sparse-vmemmap.c | 3 +++
>>   1 file changed, 3 insertions(+)
>> 
>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>> index a044a130405b..541b3f69a481 100644
>> --- a/mm/sparse-vmemmap.c
>> +++ b/mm/sparse-vmemmap.c
>> @@ -141,6 +141,7 @@ void __meminit vmemmap_verify(pte_t *pte, int node,
>>   			start, end - 1);
>>   }
>>   
>> +#ifndef vmemmap_populate_compound_pages
>>   pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
>>   				       struct vmem_altmap *altmap,
>>   				       struct page *reuse)
>
> Should vmemmap_pte_populate() be static ?
>
> It looks odd to exclude a non-static function based on a non related macro.
>
> There are several such function in the block being excluded here. Can 
> you explain why it is correct to do that ?
>

Those functions can actually be made static. But I will do that as a
part of different patch. I will update this patch and make sure the
 #ifdef will only override the vmemmap_populate_compound_pages.

modified   mm/sparse-vmemmap.c
@@ -141,7 +141,6 @@ void __meminit vmemmap_verify(pte_t *pte, int node,
			start, end - 1);
 }

-#ifndef vmemmap_populate_compound_pages
 pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
				       struct vmem_altmap *altmap,
				       struct page *reuse)
@@ -359,6 +358,7 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
	return 0;
 }

+#ifndef vmemmap_populate_compound_pages
 /*
  * For compound pages bigger than section size (e.g. x86 1G compound
  * pages with 2M subsection size) fill the rest of sections as tail

-aneesh