[PATCH v4 1/9] arm64: hugetlb: set_huge_pte_at Add WARN_ON on !pte_present

[Punit Agrawal]

From: Steve Capper <steve.capper at arm.com>

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 <dwoods at mellanox.com>
Signed-off-by: Steve Capper <steve.capper at arm.com>
Signed-off-by: Punit Agrawal <punit.agrawal at arm.com>
---
 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 656e0ece2289..7b61e4833432 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -67,6 +67,12 @@ 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 (!pte_cont(pte)) {
 		set_pte_at(mm, addr, ptep, pte);
 		return;
-- 
2.11.0