[PATCH v9 03/32] loongarch: mm: add PMD swap-exclusive helpers

[Usama Arif <usama.arif@linux.dev>]

Prepare for keeping a PMD-mapped anonymous THP mapped by a PMD across the
swap round-trip, which makes PG_anon_exclusive have to survive in a swap
PMD and not just in a swap PTE.

A LoongArch swap PMD is the swap PTE value plus _PAGE_HUGE, and
_PAGE_SWP_EXCLUSIVE sits outside both the type and the offset field, so the
PMD helpers can use the same bit.

Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: loongarch@lists.linux.dev
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
---
 arch/loongarch/include/asm/pgtable.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index f876031351319..30a256a99bfcf 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -352,6 +352,25 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 	return pte;
 }
 
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline bool pmd_swp_exclusive(pmd_t pmd)
+{
+	return pmd_val(pmd) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+	pmd_val(pmd) |= _PAGE_SWP_EXCLUSIVE;
+	return pmd;
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+	pmd_val(pmd) &= ~_PAGE_SWP_EXCLUSIVE;
+	return pmd;
+}
+#endif
+
 #define pte_none(pte)		(!(pte_val(pte) & ~_PAGE_GLOBAL))
 #define pte_present(pte)	(pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROTNONE))
 #define pte_no_exec(pte)	(pte_val(pte) & _PAGE_NO_EXEC)
-- 
2.53.0-Meta