From: Li Youhong <liyouhong@kylinos.cn>

min_order_for_split() expects to be called with the folio locked,
but does not enforce this itself. Add a VM_WARN_ON_ONCE_FOLIO()
check to validate this assumption and document the locking requirement.

Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Li Youhong <liyouhong@kylinos.cn>
---
 mm/huge_memory.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 58cabe6af33d..e3f16dadc1d4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4300,6 +4300,8 @@ int folio_split(struct folio *folio, unsigned int new_order,
  */
 unsigned int min_order_for_split(struct folio *folio)
 {
+	VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
+
 	if (folio_test_anon(folio))
 		return 0;
 
-- 
2.25.1