Several struct page fields have the same initial values for every page in
a zone. __init_single_page() initializes this state as part of its
per-page setup, while the shared vmemmap tail path open-codes only a
subset.

Factor the PFN-independent state into memmap_init_page_common() and use
it for both regular and shared tail struct pages. Keep section-, PFN-
and instance-specific initialization in __init_single_page().

This also initializes the last cpupid and KASAN tag for shared tail
struct pages consistently with regular struct pages.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 include/linux/mm.h  |  8 --------
 mm/mm_init.c        | 23 ++++++++++++++++++-----
 mm/mm_init.h        |  2 ++
 mm/sparse-vmemmap.c |  7 +------
 4 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 77b5d450fe45..2e182498898e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3022,14 +3022,6 @@ static inline void set_page_node(struct page *page, unsigned long node)
 	page->flags.f |= (node & NODES_MASK) << NODES_PGSHIFT;
 }
 
-static inline void set_page_links(struct page *page, enum zone_type zone,
-	unsigned long node, unsigned long pfn)
-{
-	set_page_zone(page, zone);
-	set_page_node(page, node);
-	set_page_section_from_pfn(page, pfn);
-}
-
 /**
  * folio_nr_pages - The number of pages in the folio.
  * @folio: The folio.
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 0129152b74d8..9677698f30d3 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -602,15 +602,28 @@ static inline void vmemmap_optimization_verify_zone(struct page *page)
 			page_zone_id(page));
 }
 
-void __meminit __init_single_page(struct page *page, unsigned long pfn,
-				unsigned long zone, int nid)
+/* Initialize PFN-independent fields common to pages in the same zone. */
+void __meminit memmap_init_page_common(struct page *page,
+		enum zone_type zone, int nid)
 {
 	mm_zero_struct_page(page);
-	set_page_links(page, zone, nid, pfn);
-	init_page_count(page);
-	atomic_set(&page->_mapcount, -1);
+	set_page_zone(page, zone);
+	set_page_node(page, nid);
 	page_cpupid_reset_last(page);
 	page_kasan_tag_reset(page);
+	atomic_set(&page->_mapcount, -1);
+#ifdef CONFIG_ZONE_DEVICE
+	if (zone == ZONE_DEVICE)
+		__SetPageReserved(page);
+#endif
+}
+
+void __meminit __init_single_page(struct page *page, unsigned long pfn,
+		unsigned long zone, int nid)
+{
+	memmap_init_page_common(page, zone, nid);
+	set_page_section_from_pfn(page, pfn);
+	init_page_count(page);
 
 	INIT_LIST_HEAD(&page->lru);
 #ifdef WANT_PAGE_VIRTUAL
diff --git a/mm/mm_init.h b/mm/mm_init.h
index 0034e37dbabd..0df0644c703c 100644
--- a/mm/mm_init.h
+++ b/mm/mm_init.h
@@ -109,6 +109,8 @@ extern bool mirrored_kernelcore;
 bool memblock_has_mirror(void);
 void memblock_free_all(void);
 
+void __meminit memmap_init_page_common(struct page *page, enum zone_type zone,
+		int nid);
 void __meminit __init_single_page(struct page *page, unsigned long pfn,
 				unsigned long zone, int nid);
 
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 9b80dd7326f7..fd869617423a 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -212,12 +212,7 @@ struct page __ref *vmemmap_shared_tail_page(unsigned int order, struct zone *zon
 
 	for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++) {
 		page = (struct page *)addr + i;
-		mm_zero_struct_page(page);
-		atomic_set(&page->_mapcount, -1);
-		set_page_node(page, zone_to_nid(zone));
-		set_page_zone(page, zone_idx(zone));
-		if (zone_is_zone_device(zone))
-			__SetPageReserved(page);
+		memmap_init_page_common(page, zone_idx(zone), zone_to_nid(zone));
 		prep_compound_tail(page, NULL, order);
 	}
 
-- 
2.54.0