[PATCH v2 1/2] mm/mm_init: factor out memmap_init_page_from_template()

["Li Zhe" <lizhe.67@bytedance.com>]

ZONE_DEVICE memmap initialization already uses a reusable struct page
template when initializing compound tail pages.  The template mostly
contains invariant state, but a few fields still depend on the target PFN
and must be refreshed before copying the template into each destination
struct page.

Factor that operation into memmap_init_page_from_template() so other
boot-time memmap initialization paths can reuse the same helper.

No functional change intended.

Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
---
 mm/mm_init.c | 34 ++++++++++++++++++++--------------
 mm/mm_init.h |  2 ++
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index d99af80ec752..905222772548 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -625,6 +625,22 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	vmemmap_optimization_verify_zone(page);
 }
 
+void __meminit memmap_init_page_from_template(struct page *page,
+		unsigned long pfn, unsigned long zone, struct page *template)
+{
+	/*
+	 * Refresh PFN-dependent fields in the template before the
+	 * non-temporal copy, so the destination page does not need cached
+	 * stores after memcpy_nontemporal().
+	 */
+	set_page_section_from_pfn(template, pfn);
+#ifdef WANT_PAGE_VIRTUAL
+	if (!is_highmem_idx(zone))
+		set_page_address(template, __va(pfn << PAGE_SHIFT));
+#endif
+	memcpy_nontemporal(page, template, sizeof(*page));
+}
+
 #ifdef CONFIG_NUMA
 /*
  * During memory init memblocks map pfns to nids. The search is expensive and
@@ -1073,17 +1089,6 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
 	}
 }
 
-static void zone_device_page_init_from_template(struct page *page,
-		unsigned long pfn, struct page *template)
-{
-	set_page_section_from_pfn(template, pfn);
-#ifdef WANT_PAGE_VIRTUAL
-	if (!is_highmem_idx(ZONE_DEVICE))
-		set_page_address(template, __va(pfn << PAGE_SHIFT));
-#endif
-	memcpy_nontemporal(page, template, sizeof(*page));
-}
-
 /*
  * With compound page geometry and when struct pages are stored in ram most
  * tail pages are reused. Consequently, the amount of unique struct pages to
@@ -1136,8 +1141,8 @@ static void __ref memmap_init_compound(struct page *head,
 
 	/* Initialize the remaining tail pages from template. */
 	for (pfn = head_pfn + 2; pfn < end_pfn; pfn++)
-		zone_device_page_init_from_template(pfn_to_page(pfn), pfn,
-						    &template);
+		memmap_init_page_from_template(pfn_to_page(pfn), pfn,
+					       ZONE_DEVICE, &template);
 	prep_compound_head(head, order);
 }
 
@@ -1192,7 +1197,8 @@ void __ref memmap_init_zone_device(struct zone *zone,
 	for (; pfn < end_pfn; pfn += pfns_per_compound) {
 		page = pfn_to_page(pfn);
 
-		zone_device_page_init_from_template(page, pfn, &template);
+		memmap_init_page_from_template(page, pfn, ZONE_DEVICE,
+					       &template);
 
 		if (IS_ALIGNED(pfn, PAGES_PER_SECTION))
 			cond_resched();
diff --git a/mm/mm_init.h b/mm/mm_init.h
index 0034e37dbabd..22c465122b47 100644
--- a/mm/mm_init.h
+++ b/mm/mm_init.h
@@ -111,5 +111,7 @@ void memblock_free_all(void);
 
 void __meminit __init_single_page(struct page *page, unsigned long pfn,
 				unsigned long zone, int nid);
+void __meminit memmap_init_page_from_template(struct page *page,
+		unsigned long pfn, unsigned long zone, struct page *template);
 
 #endif /* __MM_MM_INIT_H */
-- 
2.20.1