[PATCH v2 1/6] mm/arm64: constify pte_get*() and contpte get logic

[Pedro Falcato <pfalcato@suse.de>]

None of the contpte code needs write access to the PTEs.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 arch/arm64/include/asm/pgtable.h | 10 +++++-----
 arch/arm64/mm/contpte.c          | 11 ++++++++---
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index a2681d755358..043bc0649cee 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -378,7 +378,7 @@ static inline void __set_pte(pte_t *ptep, pte_t pte)
 	__set_pte_complete(pte);
 }
 
-static inline pte_t __ptep_get(pte_t *ptep)
+static inline pte_t __ptep_get(const pte_t *ptep)
 {
 	return READ_ONCE(*ptep);
 }
@@ -1652,8 +1652,8 @@ extern void __contpte_try_fold(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte);
 extern void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte);
-extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte);
-extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep);
+extern pte_t contpte_ptep_get(const pte_t *ptep, pte_t orig_pte);
+extern pte_t contpte_ptep_get_lockless(const pte_t *orig_ptep);
 extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte, unsigned int nr);
 extern void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr,
@@ -1732,7 +1732,7 @@ static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte)
  */
 
 #define ptep_get ptep_get
-static inline pte_t ptep_get(pte_t *ptep)
+static inline pte_t ptep_get(const pte_t *ptep)
 {
 	pte_t pte = __ptep_get(ptep);
 
@@ -1743,7 +1743,7 @@ static inline pte_t ptep_get(pte_t *ptep)
 }
 
 #define ptep_get_lockless ptep_get_lockless
-static inline pte_t ptep_get_lockless(pte_t *ptep)
+static inline pte_t ptep_get_lockless(const pte_t *ptep)
 {
 	pte_t pte = __ptep_get(ptep);
 
diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 2de12656b4d8..3a5d6937fb51 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -26,6 +26,11 @@ static inline pte_t *contpte_align_down(pte_t *ptep)
 	return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES);
 }
 
+#define contpte_align_down(ptep)                                                       \
+	_Generic((ptep),                                                               \
+		 const pte_t *: (const pte_t *) contpte_align_down((pte_t *) (ptep)),  \
+		 pte_t *: contpte_align_down((pte_t *) ptep))
+
 static inline pte_t *contpte_align_addr_ptep(unsigned long *start,
 					     unsigned long *end, pte_t *ptep,
 					     unsigned int nr)
@@ -310,7 +315,7 @@ void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
 }
 EXPORT_SYMBOL_GPL(__contpte_try_unfold);
 
-pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
+pte_t contpte_ptep_get(const pte_t *ptep, pte_t orig_pte)
 {
 	/*
 	 * Gather access/dirty bits, which may be populated in any of the ptes
@@ -367,7 +372,7 @@ static inline bool contpte_is_consistent(pte_t pte, unsigned long pfn,
 			pgprot_val(prot) == pgprot_val(orig_prot);
 }
 
-pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
+pte_t contpte_ptep_get_lockless(const pte_t *orig_ptep)
 {
 	/*
 	 * The ptep_get_lockless() API requires us to read and return *orig_ptep
@@ -386,10 +391,10 @@ pte_t contpte_ptep_get_lockless(pte_t *orig_ptep)
 	 * because it is not part of a contpte range.
 	 */
 
+	const pte_t *ptep;
 	pgprot_t orig_prot;
 	unsigned long pfn;
 	pte_t orig_pte;
-	pte_t *ptep;
 	pte_t pte;
 	int i;
 
-- 
2.55.0