diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 44a1a699b5ad..6b0009e7d4ae 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -68,7 +68,7 @@ struct mem_cgroup;
 #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
 #define _struct_page_alignment	__aligned(2 * sizeof(unsigned long))
 #else
-#define _struct_page_alignment
+#define _struct_page_alignment	__aligned(sizeof(unsigned long))
 #endif
 
 struct page {
@@ -251,6 +251,38 @@ struct page {
 #endif
 } _struct_page_alignment;
 
+/*
+ * struct encoded_page - a nonexistent type marking this pointer
+ *
+ * An 'encoded_page' pointer is a pointer to a regular 'struct page', but
+ * with the low bits of the pointer indicating extra context-dependent
+ * information. Not super-common, but happens in mmu_gather and mlock
+ * handling, and this acts as a type system check on that use.
+ *
+ * We only really have two guaranteed bits in general, although you could
+ * play with 'struct page' alignment (see CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
+ * for more.
+ *
+ * Use the supplied helper functions to endcode/decode the pointer and bits.
+ */
+struct encoded_page;
+#define ENCODE_PAGE_BITS 3ul
+static __always_inline struct encoded_page *encode_page(struct page *page, unsigned long flags)
+{
+	BUILD_BUG_ON(flags > ENCODE_PAGE_BITS);
+	return (struct encoded_page *)(flags | (unsigned long)page);
+}
+
+static inline unsigned long encoded_page_flags(struct encoded_page *page)
+{
+	return ENCODE_PAGE_BITS & (unsigned long)page;
+}
+
+static inline struct page *encoded_page_ptr(struct encoded_page *page)
+{
+	return (struct page *)(~ENCODE_PAGE_BITS & (unsigned long)page);
+}
+
 /**
  * struct folio - Represents a contiguous set of bytes.
  * @flags: Identical to the page flags.