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 
9 struct pglist_data;
10 
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 extern bool deferred_struct_pages;
33 
34 #ifdef CONFIG_PAGE_EXTENSION
35 
36 /*
37  * The page_ext_flags users must set need_shared_flags to true.
38  */
39 enum page_ext_flags {
40 	PAGE_EXT_OWNER,
41 	PAGE_EXT_OWNER_ALLOCATED,
42 #if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
43 	PAGE_EXT_YOUNG,
44 	PAGE_EXT_IDLE,
45 #endif
46 };
47 
48 /*
49  * Page Extension can be considered as an extended mem_map.
50  * A page_ext page is associated with every page descriptor. The
51  * page_ext helps us add more information about the page.
52  * All page_ext are allocated at boot or memory hotplug event,
53  * then the page_ext for pfn always exists.
54  */
55 struct page_ext {
56 	unsigned long flags;
57 };
58 
59 extern bool early_page_ext;
60 extern unsigned long page_ext_size;
61 extern void pgdat_page_ext_init(struct pglist_data *pgdat);
62 
early_page_ext_enabled(void)63 static inline bool early_page_ext_enabled(void)
64 {
65 	return early_page_ext;
66 }
67 
68 #ifdef CONFIG_SPARSEMEM
page_ext_init_flatmem(void)69 static inline void page_ext_init_flatmem(void)
70 {
71 }
72 extern void page_ext_init(void);
page_ext_init_flatmem_late(void)73 static inline void page_ext_init_flatmem_late(void)
74 {
75 }
76 #else
77 extern void page_ext_init_flatmem(void);
78 extern void page_ext_init_flatmem_late(void);
page_ext_init(void)79 static inline void page_ext_init(void)
80 {
81 }
82 #endif
83 
84 extern struct page_ext *page_ext_get(struct page *page);
85 extern void page_ext_put(struct page_ext *page_ext);
86 
page_ext_next(struct page_ext * curr)87 static inline struct page_ext *page_ext_next(struct page_ext *curr)
88 {
89 	void *next = curr;
90 	next += page_ext_size;
91 	return next;
92 }
93 
94 #else /* !CONFIG_PAGE_EXTENSION */
95 struct page_ext;
96 
early_page_ext_enabled(void)97 static inline bool early_page_ext_enabled(void)
98 {
99 	return false;
100 }
101 
pgdat_page_ext_init(struct pglist_data * pgdat)102 static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
103 {
104 }
105 
page_ext_init(void)106 static inline void page_ext_init(void)
107 {
108 }
109 
page_ext_init_flatmem_late(void)110 static inline void page_ext_init_flatmem_late(void)
111 {
112 }
113 
page_ext_init_flatmem(void)114 static inline void page_ext_init_flatmem(void)
115 {
116 }
117 
page_ext_get(struct page * page)118 static inline struct page_ext *page_ext_get(struct page *page)
119 {
120 	return NULL;
121 }
122 
page_ext_put(struct page_ext * page_ext)123 static inline void page_ext_put(struct page_ext *page_ext)
124 {
125 }
126 #endif /* CONFIG_PAGE_EXTENSION */
127 #endif /* __LINUX_PAGE_EXT_H */
128