Re: [PATCH v2 5/5] mm/sparse-vmemmap: drop @pgmap from vmemmap population APIs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] mm: undeclared vmemmap in section_vmemmap_optimization_disable()
--

commit b9ce7eece3f26dd29a5fe079915770aa843f9257
Author: Muchun Song <muchun.song@linux.dev>

mm/sparse-vmemmap: drop @pgmap from vmemmap population APIs

This commit removes the @pgmap parameter from the vmemmap population
helpers and related memory hotplug interfaces, relying instead on
mem_section state and internal architecture-specific checks.

> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 71a927d67a9f9..5777f2e296845 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -462,8 +462,7 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
>  }
>  
>  struct page * __meminit __populate_section_memmap(unsigned long pfn,
> -		unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
> -		struct dev_pagemap *pgmap)
> +		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>  {
>  	unsigned long start = (unsigned long) pfn_to_page(pfn);
>  	unsigned long end = start + nr_pages * sizeof(struct page);

[Severity: Low]
Does section_vmemmap_optimization_disable() (called right below here in
__populate_section_memmap()) cause a build failure on 64-bit LoongArch
when CONFIG_VMEMMAP_OPTIMIZATION is enabled?

In include/linux/vmemmap-optimization.h,
section_vmemmap_optimization_disable() is a static inline function that
calls page_to_pfn():

include/linux/vmemmap-optimization.h:
static inline void section_vmemmap_optimization_disable(unsigned long start,
		unsigned long end)
{
	unsigned long pfn = page_to_pfn((struct page *)start);

Under CONFIG_SPARSEMEM_VMEMMAP, page_to_pfn() expands via
include/asm-generic/memory_model.h to ((unsigned long)((page) - vmemmap)).
However, include/linux/vmemmap-optimization.h does not include
linux/pgtable.h or asm/pgtable.h where vmemmap is defined.

On 64-bit LoongArch, arch/loongarch/include/asm/pgtable.h includes
linux/vmemmap-optimization.h before defining the vmemmap macro:

arch/loongarch/include/asm/pgtable.h:
#include <linux/mm_types.h>
#include <linux/mmzone.h>
#include <linux/vmemmap-optimization.h>
...
#define VMEMMAP_ALIGN	max(PMD_SIZE, MAX_FOLIO_VMEMMAP_ALIGN)
#define vmemmap		((struct page *)(ALIGN(VMALLOC_END, VMEMMAP_ALIGN)))

Because section_vmemmap_optimization_disable() is a static inline
function, the preprocessor expands page_to_pfn() inside
linux/vmemmap-optimization.h before vmemmap is defined, leaving vmemmap as
an undeclared identifier when compiling any translation unit that includes
asm/pgtable.h with CONFIG_VMEMMAP_OPTIMIZATION=y.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261105061217.13302-1-songmuchun@bytedance.com?part=5