1 files changed, 130 insertions, 0 deletions
diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
new file mode 100644
index 000000000..be9856419
--- /dev/null
+++ b/include/linux/page_ext.h
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_PAGE_EXT_H
+#define __LINUX_PAGE_EXT_H
+
+#include <linux/types.h>
+#include <linux/stacktrace.h>
+#include <linux/stackdepot.h>
+
+struct pglist_data;
+
+#ifdef CONFIG_PAGE_EXTENSION
+/**
+ * struct page_ext_operations - per page_ext client operations
+ * @offset: Offset to the client's data within page_ext. Offset is returned to
+ *          the client by page_ext_init.
+ * @size: The size of the client data within page_ext.
+ * @need: Function that returns true if client requires page_ext.
+ * @init: (optional) Called to initialize client once page_exts are allocated.
+ * @need_shared_flags: True when client is using shared page_ext->flags
+ *                     field.
+ *
+ * Each Page Extension client must define page_ext_operations in
+ * page_ext_ops array.
+ */
+struct page_ext_operations {
+	size_t offset;
+	size_t size;
+	bool (*need)(void);
+	void (*init)(void);
+	bool need_shared_flags;
+};
+
+/*
+ * The page_ext_flags users must set need_shared_flags to true.
+ */
+enum page_ext_flags {
+	PAGE_EXT_OWNER,
+	PAGE_EXT_OWNER_ALLOCATED,
+#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
+	PAGE_EXT_YOUNG,
+	PAGE_EXT_IDLE,
+#endif
+};
+
+/*
+ * Page Extension can be considered as an extended mem_map.
+ * A page_ext page is associated with every page descriptor. The
+ * page_ext helps us add more information about the page.
+ * All page_ext are allocated at boot or memory hotplug event,
+ * then the page_ext for pfn always exists.
+ */
+struct page_ext {
+	unsigned long flags;
+};
+
+extern bool early_page_ext;
+extern unsigned long page_ext_size;
+extern void pgdat_page_ext_init(struct pglist_data *pgdat);
+
+static inline bool early_page_ext_enabled(void)
+{
+	return early_page_ext;
+}
+
+#ifdef CONFIG_SPARSEMEM
+static inline void page_ext_init_flatmem(void)
+{
+}
+extern void page_ext_init(void);
+static inline void page_ext_init_flatmem_late(void)
+{
+}
+#else
+extern void page_ext_init_flatmem(void);
+extern void page_ext_init_flatmem_late(void);
+static inline void page_ext_init(void)
+{
+}
+#endif
+
+extern struct page_ext *page_ext_get(struct page *page);
+extern void page_ext_put(struct page_ext *page_ext);
+
+static inline void *page_ext_data(struct page_ext *page_ext,
+				  struct page_ext_operations *ops)
+{
+	return (void *)(page_ext) + ops->offset;
+}
+
+static inline struct page_ext *page_ext_next(struct page_ext *curr)
+{
+	void *next = curr;
+	next += page_ext_size;
+	return next;
+}
+
+#else /* !CONFIG_PAGE_EXTENSION */
+struct page_ext;
+
+static inline bool early_page_ext_enabled(void)
+{
+	return false;
+}
+
+static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
+{
+}
+
+static inline void page_ext_init(void)
+{
+}
+
+static inline void page_ext_init_flatmem_late(void)
+{
+}
+
+static inline void page_ext_init_flatmem(void)
+{
+}
+
+static inline struct page_ext *page_ext_get(struct page *page)
+{
+	return NULL;
+}
+
+static inline void page_ext_put(struct page_ext *page_ext)
+{
+}
+#endif /* CONFIG_PAGE_EXTENSION */
+#endif /* __LINUX_PAGE_EXT_H */