diff --git a/mm/memory.c b/mm/memory.c
index e119a8bf7b05a3..09e2cd0d7feedf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2970,6 +2970,8 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	int dirtied = 0;
 	int ret, tmp;
 
+	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+
 	ret = __do_fault(vma, address, pgoff, flags, &fault_page);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
 		return ret;