[PATCH v4 6/6] mm/mm_init: add zone mismatch warning during page init

[Muchun Song <songmuchun@bytedance.com>]

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 <songmuchun@bytedance.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
---
v4:
- Factor the zone check into a local helper (suggested by Mike Rapoport)
- Collect Reviewed-by from Lance Yang

v3:
- Collect Acked-by from Qi Zheng

v2:
- New patch.
---
 mm/mm_init.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 1650d6bc1211..6deae33db882 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -593,6 +593,15 @@ static void __init find_zone_movable_pfns_for_nodes(void)
 	node_states[N_MEMORY] = saved_node_state;
 }
 
+static inline void vmemmap_optimization_verify_zone(struct page *page)
+{
+	const unsigned int order = pfn_to_section_compound_order(page_to_pfn(page));
+
+	VM_WARN_ON_ONCE(vmemmap_optimizable_order(order) &&
+			page_zone_id(page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) !=
+			page_zone_id(page));
+}
+
 void __meminit __init_single_page(struct page *page, unsigned long pfn,
 				unsigned long zone, int nid)
 {
@@ -609,6 +618,7 @@ 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
+	vmemmap_optimization_verify_zone(page);
 }
 
 #ifdef CONFIG_NUMA
-- 
2.54.0