+/*
+ * Returns whether the host has large enough swap offset field to support
+ * carrying over pgtable A/D bits for page migrations. The result is
+ * pretty much arch specific.
+ */
+static inline bool migration_entry_supports_ad(void)
+{
+ /*
+ * max_swapfile_size() returns the max supported swp-offset plus 1.
+ * We can support the migration A/D bits iff the pfn swap entry has
+ * the offset large enough to cover all of them (PFN, A & D bits).
+ */
+#ifdef CONFIG_SWAP
+ return max_swapfile_size() >= (1UL << SWP_MIG_TOTAL_BITS);
+#else /* CONFIG_SWAP */
+ return false;
+#endif /* CONFIG_SWAP */
+}
+
+static inline swp_entry_t make_migration_entry_young(swp_entry_t entry)
+{
+ if (migration_entry_supports_ad())
+ return swp_entry(swp_type(entry),
+ swp_offset(entry) | SWP_MIG_YOUNG);
+ return entry;
+}
+
+static inline bool is_migration_entry_young(swp_entry_t entry)
+{
+ if (migration_entry_supports_ad())
+ return swp_offset(entry) & SWP_MIG_YOUNG;
+ /* Keep the old behavior of aging page after migration */
+ return false;
+}
+
+static inline swp_entry_t make_migration_entry_dirty(swp_entry_t entry)
+{
+ if (migration_entry_supports_ad())
+ return swp_entry(swp_type(entry),
+ swp_offset(entry) | SWP_MIG_DIRTY);
+ return entry;
+}
+
+static inline bool is_migration_entry_dirty(swp_entry_t entry)
+{
+ if (migration_entry_supports_ad())
+ return swp_offset(entry) & SWP_MIG_DIRTY;
+ /* Keep the old behavior of clean page after migration */
+ return false;
+}
+