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