1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_PAGE_EXT_H
3#define __LINUX_PAGE_EXT_H
4
5#include <linux/types.h>
6#include <linux/stacktrace.h>
7#include <linux/stackdepot.h>
8
9struct pglist_data;
10
11#ifdef CONFIG_PAGE_EXTENSION
12/**
13 * struct page_ext_operations - per page_ext client operations
14 * @offset: Offset to the client's data within page_ext. Offset is returned to
15 *          the client by page_ext_init.
16 * @size: The size of the client data within page_ext.
17 * @need: Function that returns true if client requires page_ext.
18 * @init: (optional) Called to initialize client once page_exts are allocated.
19 * @need_shared_flags: True when client is using shared page_ext->flags
20 *                     field.
21 *
22 * Each Page Extension client must define page_ext_operations in
23 * page_ext_ops array.
24 */
25struct page_ext_operations {
26	size_t offset;
27	size_t size;
28	bool (*need)(void);
29	void (*init)(void);
30	bool need_shared_flags;
31};
32
33/*
34 * The page_ext_flags users must set need_shared_flags to true.
35 */
36enum page_ext_flags {
37	PAGE_EXT_OWNER,
38	PAGE_EXT_OWNER_ALLOCATED,
39#if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
40	PAGE_EXT_YOUNG,
41	PAGE_EXT_IDLE,
42#endif
43};
44
45/*
46 * Page Extension can be considered as an extended mem_map.
47 * A page_ext page is associated with every page descriptor. The
48 * page_ext helps us add more information about the page.
49 * All page_ext are allocated at boot or memory hotplug event,
50 * then the page_ext for pfn always exists.
51 */
52struct page_ext {
53	unsigned long flags;
54};
55
56extern bool early_page_ext;
57extern unsigned long page_ext_size;
58extern void pgdat_page_ext_init(struct pglist_data *pgdat);
59
60static inline bool early_page_ext_enabled(void)
61{
62	return early_page_ext;
63}
64
65#ifdef CONFIG_SPARSEMEM
66static inline void page_ext_init_flatmem(void)
67{
68}
69extern void page_ext_init(void);
70static inline void page_ext_init_flatmem_late(void)
71{
72}
73#else
74extern void page_ext_init_flatmem(void);
75extern void page_ext_init_flatmem_late(void);
76static inline void page_ext_init(void)
77{
78}
79#endif
80
81extern struct page_ext *page_ext_get(struct page *page);
82extern void page_ext_put(struct page_ext *page_ext);
83
84static inline void *page_ext_data(struct page_ext *page_ext,
85				  struct page_ext_operations *ops)
86{
87	return (void *)(page_ext) + ops->offset;
88}
89
90static inline struct page_ext *page_ext_next(struct page_ext *curr)
91{
92	void *next = curr;
93	next += page_ext_size;
94	return next;
95}
96
97#else /* !CONFIG_PAGE_EXTENSION */
98struct page_ext;
99
100static inline bool early_page_ext_enabled(void)
101{
102	return false;
103}
104
105static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
106{
107}
108
109static inline void page_ext_init(void)
110{
111}
112
113static inline void page_ext_init_flatmem_late(void)
114{
115}
116
117static inline void page_ext_init_flatmem(void)
118{
119}
120
121static inline struct page_ext *page_ext_get(struct page *page)
122{
123	return NULL;
124}
125
126static inline void page_ext_put(struct page_ext *page_ext)
127{
128}
129#endif /* CONFIG_PAGE_EXTENSION */
130#endif /* __LINUX_PAGE_EXT_H */
131