[PATCH v2 6/6] mm/mm_init: add zone mismatch warning during page init

For vmemmap-optimized sections, tail struct pages may be backed by
shared vmemmap pages. Those shared pages must carry the same page zone
ID as the struct pages initialized for the section.

Warn in __init_single_page() if the shared tail page has a different
page_zone_id(), which would indicate inconsistent initialization.

Signed-off-by: Muchun Song <redacted>
---
v2:
- New patch.
---
 mm/mm_init.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 1650d6bc1211..bd02e8d06965 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c

@@ -609,6 +609,9 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	if (!is_highmem_idx(zone))
 		set_page_address(page, __va(pfn << PAGE_SHIFT));
 #endif
+	VM_WARN_ON_ONCE(vmemmap_optimizable_order(pfn_to_section_compound_order(pfn)) &&
+			page_zone_id(page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) !=
+			page_zone_id(page));
 }
 
 #ifdef CONFIG_NUMA

-- 
2.54.0