Subject: Re: [PATCH 11/49] mm: defer sparse_init() until after zone initialization

From: Mike Rapoport <[email-masked]>
Date: Tue, 28 Apr 2026 09:15:48 +0200

On Sun, Apr 05, 2026 at 08:52:02PM +0800, Muchun Song wrote:
> According to the comment of free_area_init(), its main goal is to
> initialise all pg_data_t and zone data. However, sparse_init() and
> memmap_init() are aimed at allocating vmemmap pages and initializing
> struct page respectively, which differs from the goal of free_area_init().
> Therefore, it is reasonable to move them out of free_area_init().
> 
> Call sparse_init() after free_area_init() to guarantee that zone data
> structures are available when sparse_init() executes. This change is a
> prerequisite for integrating vmemmap initialization steps and allows
> sparse_init() to safely access zone information if needed (e.g. HVO case).
> 
> Also, move hugetlb reservation functions (hugetlb_cma_reserve() and
> hugetlb_bootmem_alloc()) to be after free_area_init(). This allows
> hugetlb reservation to access zone information to ensure that contiguous
> pages are not allocated across zone boundaries, which simplifies the
> hugetlb code. So this is a preparation for subsequent changes.
> 
> Signed-off-by: Muchun Song <[email-masked]>
> ---
>  mm/mm_init.c | 15 ++++++++-------
>  mm/sparse.c  |  3 ---
>  2 files changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index c7f91dc2e5b5..5fe0a7e66775 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -406,9 +406,6 @@ void __init sparse_init(void)
>  	pnum_begin = first_present_section_nr();
>  	nid_begin = sparse_early_nid(__nr_to_section(pnum_begin));
>  
> -	/* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
> -	set_pageblock_order();
> -

This does not seem related to this patch. Otherwise

Reviewed-by: Mike Rapoport (Microsoft) <[email-masked]>

>  	for_each_present_section_nr(pnum_begin + 1, pnum_end) {
>  		int nid = sparse_early_nid(__nr_to_section(pnum_end));
>  
> -- 
> 2.20.1
> 

-- 
Sincerely yours,
Mike.