[PATCH v3 1/2] mm/mm_init: factor out memmap_init_refresh_pfn_fields()

["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 refresh into memmap_init_refresh_pfn_fields() so other
boot-time memmap initialization paths can reuse the PFN-dependent part
while keeping their own copy primitive.

Define the helper as static inline in mm/mm_init.h, since it is small
and only shared by mm/ initialization code.

No functional change intended.

Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
---
 mm/mm_init.c | 11 ++++++-----
 mm/mm_init.h | 11 +++++++++++
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index d99af80ec752..33a9d8dd044c 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1076,11 +1076,12 @@ 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
+	/*
+	 * Refresh PFN-dependent fields in the template before the
+	 * non-temporal copy, so the destination page does not need cached
+	 * stores after memcpy_nontemporal().
+	 */
+	memmap_init_refresh_pfn_fields(template, pfn, ZONE_DEVICE);
 	memcpy_nontemporal(page, template, sizeof(*page));
 }
 
diff --git a/mm/mm_init.h b/mm/mm_init.h
index 0034e37dbabd..7e1d6897b844 100644
--- a/mm/mm_init.h
+++ b/mm/mm_init.h
@@ -112,4 +112,15 @@ void memblock_free_all(void);
 void __meminit __init_single_page(struct page *page, unsigned long pfn,
 				unsigned long zone, int nid);
 
+static inline void memmap_init_refresh_pfn_fields(struct page *page,
+						  unsigned long pfn,
+						  unsigned long zone)
+{
+	set_page_section_from_pfn(page, pfn);
+#ifdef WANT_PAGE_VIRTUAL
+	if (!is_highmem_idx(zone))
+		set_page_address(page, __va(pfn << PAGE_SHIFT));
+#endif
+}
+
 #endif /* __MM_MM_INIT_H */
-- 
2.20.1