Re: [PATCH v4 1/2] mm/sparse.c: Use kvmalloc/kvfree to alloc/free memmap for the classic sparse

[Pankaj Gupta]

> This change makes populate_section_memmap()/depopulate_section_memmap
> much simpler.
>
> Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> v3->v4:
>   Split the old v3 into two patches, to carve out the using 'nid'
>   as preferred node to allocate memmap into a separate patch. This
>   is suggested by Michal, and the carving out is put in patch 2.
>
> v2->v3:
>   Remove __GFP_NOWARN and use array_size when calling kvmalloc_node()
>   per Matthew's comments.
> http://lkml.kernel.org/r/20200312141749.GL27711@MiWiFi-R3L-srv
>
>  mm/sparse.c | 27 +++------------------------
>  1 file changed, 3 insertions(+), 24 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index e747a238a860..d01d09cc7d99 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -719,35 +719,14 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>  struct page * __meminit populate_section_memmap(unsigned long pfn,
>                 unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>  {
> -       struct page *page, *ret;
> -       unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
> -
> -       page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
> -       if (page)
> -               goto got_map_page;
> -
> -       ret = vmalloc(memmap_size);
> -       if (ret)
> -               goto got_map_ptr;
> -
> -       return NULL;
> -got_map_page:
> -       ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
> -got_map_ptr:
> -
> -       return ret;
> +       return kvmalloc(array_size(sizeof(struct page),
> +                       PAGES_PER_SECTION), GFP_KERNEL);
>  }
>
>  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
>                 struct vmem_altmap *altmap)
>  {
> -       struct page *memmap = pfn_to_page(pfn);
> -
> -       if (is_vmalloc_addr(memmap))
> -               vfree(memmap);
> -       else
> -               free_pages((unsigned long)memmap,
> -                          get_order(sizeof(struct page) * PAGES_PER_SECTION));
> +       kvfree(pfn_to_page(pfn));
>  }
>
>  static void free_map_bootmem(struct page *memmap)
> --
> 2.17.2

With David's indentation suggestion:
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>

>
>