Re: [PATCH v4 2/5] mm/sparse-vmemmap: Pass @pgmap argument to memory deactivation paths

[David Hildenbrand (Arm)]

On 4/22/26 10:14, Muchun Song wrote:
> Currently, the memory hot-remove call chain -- arch_remove_memory(),
> __remove_pages(), sparse_remove_section() and section_deactivate() --
> does not carry the struct dev_pagemap pointer. This prevents the lower
> levels from knowing whether the section was originally populated with
> vmemmap optimizations (e.g., DAX with vmemmap optimization enabled).
> 
> Without this information, we cannot call vmemmap_can_optimize() to
> determine if the vmemmap pages were optimized. As a result, the vmemmap
> page accounting during teardown will mistakenly assume a non-optimized
> allocation, leading to incorrect memmap statistics.
> 
> To lay the groundwork for fixing the vmemmap page accounting, we need
> to pass the @pgmap pointer down to the deactivation location. Plumb the
> @pgmap argument through the APIs of arch_remove_memory(), __remove_pages()
> and sparse_remove_section(), mirroring the corresponding *_activate()
> paths.
> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>


[...]

>  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
> -		struct vmem_altmap *altmap)
> +		struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
>  {
>  	unsigned long start = (unsigned long) pfn_to_page(pfn);
>  	unsigned long end = start + nr_pages * sizeof(struct page);
> @@ -746,7 +746,7 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>   * usage map, but still need to free the vmemmap range.
>   */
>  static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> -		struct vmem_altmap *altmap)
> +		struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
>  {
>  	struct mem_section *ms = __pfn_to_section(pfn);
>  	bool section_is_early = early_section(ms);
> @@ -784,7 +784,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>  	 * section_activate() and pfn_valid() .
>  	 */
>  	if (!section_is_early)
> -		depopulate_section_memmap(pfn, nr_pages, altmap);
> +		depopulate_section_memmap(pfn, nr_pages, altmap, pgmap);
>  	else if (memmap)
>  		free_map_bootmem(memmap);
>  
> @@ -828,7 +828,7 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
>  
>  	memmap = populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
>  	if (!memmap) {
> -		section_deactivate(pfn, nr_pages, altmap);
> +		section_deactivate(pfn, nr_pages, altmap, pgmap);
>  		return ERR_PTR(-ENOMEM);
>  	}
>  
> @@ -889,13 +889,13 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>  }
>  
>  void sparse_remove_section(unsigned long pfn, unsigned long nr_pages,
> -			   struct vmem_altmap *altmap)
> +			   struct vmem_altmap *altmap, struct dev_pagemap *pgmap)

While at it, could switch to two-tab indent here as well.

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David