[PATCHv6 09/17] mm/sparse: Check memmap alignment for compound_info_has_mask()

[Kiryl Shutsemau]

If page->compound_info encodes a mask, it is expected that vmemmap to be
naturally aligned to the maximum folio size.

Add a VM_BUG_ON() to check the alignment.

Signed-off-by: Kiryl Shutsemau <kas at kernel.org>
Acked-by: Zi Yan <ziy at nvidia.com>
---
 mm/sparse.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/sparse.c b/mm/sparse.c
index b5b2b6f7041b..6c9b62607f3f 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -600,6 +600,13 @@ void __init sparse_init(void)
 	BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section)));
 	memblocks_present();
 
+	if (compound_info_has_mask()) {
+		unsigned long alignment;
+
+		alignment = MAX_FOLIO_NR_PAGES * sizeof(struct page);
+		VM_BUG_ON(!IS_ALIGNED((unsigned long) pfn_to_page(0), alignment));
+	}
+
 	pnum_begin = first_present_section_nr();
 	nid_begin = sparse_early_nid(__nr_to_section(pnum_begin));
 
-- 
2.51.2