1 files changed, 78 insertions, 0 deletions
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 82265b055a0d..bb70da461b7d 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -274,6 +274,84 @@ static inline int is_readable_migration_entry(swp_entry_t entry)
 
 #endif
 
+typedef unsigned long pte_marker;
+
+#define  PTE_MARKER_MASK     (0)
+
+#ifdef CONFIG_PTE_MARKER
+
+static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
+{
+	return swp_entry(SWP_PTE_MARKER, marker);
+}
+
+static inline bool is_pte_marker_entry(swp_entry_t entry)
+{
+	return swp_type(entry) == SWP_PTE_MARKER;
+}
+
+static inline pte_marker pte_marker_get(swp_entry_t entry)
+{
+	return swp_offset(entry) & PTE_MARKER_MASK;
+}
+
+static inline bool is_pte_marker(pte_t pte)
+{
+	return is_swap_pte(pte) && is_pte_marker_entry(pte_to_swp_entry(pte));
+}
+
+#else /* CONFIG_PTE_MARKER */
+
+static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
+{
+	/* This should never be called if !CONFIG_PTE_MARKER */
+	WARN_ON_ONCE(1);
+	return swp_entry(0, 0);
+}
+
+static inline bool is_pte_marker_entry(swp_entry_t entry)
+{
+	return false;
+}
+
+static inline pte_marker pte_marker_get(swp_entry_t entry)
+{
+	return 0;
+}
+
+static inline bool is_pte_marker(pte_t pte)
+{
+	return false;
+}
+
+#endif /* CONFIG_PTE_MARKER */
+
+static inline pte_t make_pte_marker(pte_marker marker)
+{
+	return swp_entry_to_pte(make_pte_marker_entry(marker));
+}
+
+/*
+ * This is a special version to check pte_none() just to cover the case when
+ * the pte is a pte marker.  It existed because in many cases the pte marker
+ * should be seen as a none pte; it's just that we have stored some information
+ * onto the none pte so it becomes not-none any more.
+ *
+ * It should be used when the pte is file-backed, ram-based and backing
+ * userspace pages, like shmem.  It is not needed upon pgtables that do not
+ * support pte markers at all.  For example, it's not needed on anonymous
+ * memory, kernel-only memory (including when the system is during-boot),
+ * non-ram based generic file-system.  It's fine to be used even there, but the
+ * extra pte marker check will be pure overhead.
+ *
+ * For systems configured with !CONFIG_PTE_MARKER this will be automatically
+ * optimized to pte_none().
+ */
+static inline int pte_none_mostly(pte_t pte)
+{
+	return pte_none(pte) || is_pte_marker(pte);
+}
+
 static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry)
 {
 	struct page *p = pfn_to_page(swp_offset(entry));