From: Steve Capper <redacted>

This patch adds a WARN_ON to set_huge_pte_at as the accessor assumes
that entries to be written down are all present. (There are separate
accessors to clear huge ptes).

We will need to handle the !pte_present case where memory offlining
is used on hugetlb pages. swap and migration entries will be supplied
to set_huge_pte_at in this case.

Cc: David Woods <redacted>
Signed-off-by: Steve Capper <redacted>
Signed-off-by: Punit Agrawal <redacted>
---
 arch/arm64/mm/hugetlbpage.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 425a8fcd3d38..0389e2ed51f1 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c

@@ -69,6 +69,12 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 	unsigned long pfn;
 	pgprot_t hugeprot;
 
+	/*
+	 * Code needs to be expanded to handle huge swap and migration
+	 * entries. Needed for HUGETLB and MEMORY_FAILURE.
+	 */
+	WARN_ON(!pte_present(pte));
+
 	if (ncontig == 1) {
 		set_pte_at(mm, addr, ptep, pte);
 		return;

-- 
2.11.0