[PATCH v2 62/69] mm/hugetlb: Simplify hugetlb_folio_init_vmemmap()

[Muchun Song <songmuchun@bytedance.com>]

hugetlb_folio_init_vmemmap() currently splits the open-coded
compound-page setup across two helpers even though the tail-page
initialization is only used here.

Fold the tail-page initialization into the main helper and pass
the precomputed page metadata in from the caller. This makes
the initialization flow easier to follow.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/hugetlb.c | 50 +++++++++++++++++---------------------------------
 1 file changed, 17 insertions(+), 33 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3cb8fffb9e3e..950b0fa3bc27 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3126,33 +3126,8 @@ static bool __init alloc_bootmem_huge_page(struct hstate *h, int nid)
 	return true;
 }
 
-/* Initialize [start_page:end_page_number] tail struct pages of a hugepage */
-static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
-					struct hstate *h,
-					unsigned long start_page_number,
-					unsigned long end_page_number)
-{
-	enum zone_type zone = folio_zonenum(folio);
-	int nid = folio_nid(folio);
-	struct page *page = folio_page(folio, start_page_number);
-	unsigned long head_pfn = folio_pfn(folio);
-	unsigned long pfn, end_pfn = head_pfn + end_page_number;
-	unsigned int order = huge_page_order(h);
-
-	/*
-	 * As we marked all tail pages with memblock_reserved_mark_noinit(),
-	 * we must initialize them ourselves here.
-	 */
-	for (pfn = head_pfn + start_page_number; pfn < end_pfn; page++, pfn++) {
-		__init_single_page(page, pfn, zone, nid);
-		prep_compound_tail(page, &folio->page, order);
-		set_page_count(page, 0);
-	}
-}
-
-static void __init hugetlb_folio_init_vmemmap(struct folio *folio,
-					      struct hstate *h,
-					      unsigned long nr_pages)
+static void __init hugetlb_folio_init_vmemmap(struct page *head, unsigned long pfn,
+		enum zone_type zone, int nid, unsigned int order, unsigned int nr_pages)
 {
 	int ret;
 
@@ -3161,12 +3136,19 @@ static void __init hugetlb_folio_init_vmemmap(struct folio *folio,
 	 * walking pages twice by initializing/preparing+freezing them in the
 	 * same go.
 	 */
-	__folio_clear_reserved(folio);
-	__folio_set_head(folio);
-	ret = folio_ref_freeze(folio, 1);
+	__ClearPageReserved(head);
+	ret = page_ref_freeze(head, 1);
 	VM_BUG_ON(!ret);
-	hugetlb_folio_init_tail_vmemmap(folio, h, 1, nr_pages);
-	prep_compound_head(&folio->page, huge_page_order(h));
+
+	__SetPageHead(head);
+	for (int i = 1; i < nr_pages; i++) {
+		struct page *page = head + i;
+
+		__init_single_page(page, pfn + i, zone, nid);
+		prep_compound_tail(page, head, order);
+		set_page_count(page, 0);
+	}
+	prep_compound_head(head, order);
 }
 
 /*
@@ -3226,6 +3208,7 @@ static void __init gather_bootmem_prealloc_node(unsigned long nid)
 		struct folio *folio = (void *)page;
 		unsigned long pfn = PHYS_PFN(__pa(m));
 		unsigned long nr_pages = pages_per_huge_page(m->hstate);
+		enum zone_type zone = folio_zonenum(folio);
 
 		h = m->hstate;
 		/*
@@ -3239,7 +3222,8 @@ static void __init gather_bootmem_prealloc_node(unsigned long nid)
 		VM_BUG_ON(!hstate_is_gigantic(h));
 		WARN_ON(folio_ref_count(folio) != 1);
 
-		hugetlb_folio_init_vmemmap(folio, h, vmemmap_nr_struct_pages(pfn, nr_pages));
+		hugetlb_folio_init_vmemmap(page, pfn, zone, nid, huge_page_order(h),
+					   vmemmap_nr_struct_pages(pfn, nr_pages));
 		init_new_hugetlb_folio(folio);
 
 		if (order_vmemmap_optimizable(pfn_to_section_order(pfn))) {
-- 
2.54.0