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/mmzone.h>
7#include <linux/stacktrace.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
74static inline bool page_ext_iter_next_fast_possible(unsigned long next_pfn)
75{
76 /*
77 * page_ext is allocated per memory section. Once we cross a
78 * memory section, we have to fetch the new pointer.
79 */
80 return next_pfn % PAGES_PER_SECTION;
81}
82#else
83extern void page_ext_init_flatmem(void);
84extern void page_ext_init_flatmem_late(void);
85static inline void page_ext_init(void)
86{
87}
88
89static inline bool page_ext_iter_next_fast_possible(unsigned long next_pfn)
90{
91 return true;
92}
93#endif
94
95extern struct page_ext *page_ext_get(const struct page *page);
96extern void page_ext_put(struct page_ext *page_ext);
97extern struct page_ext *page_ext_lookup(unsigned long pfn);
98
99static inline void *page_ext_data(struct page_ext *page_ext,
100 struct page_ext_operations *ops)
101{
102 return (void *)(page_ext) + ops->offset;
103}
104
105static inline struct page_ext *page_ext_next(struct page_ext *curr)
106{
107 void *next = curr;
108 next += page_ext_size;
109 return next;
110}
111
112struct page_ext_iter {
113 unsigned long index;
114 unsigned long start_pfn;
115 struct page_ext *page_ext;
116};
117
118/**
119 * page_ext_iter_begin() - Prepare for iterating through page extensions.
120 * @iter: page extension iterator.
121 * @pfn: PFN of the page we're interested in.
122 *
123 * Must be called with RCU read lock taken.
124 *
125 * Return: NULL if no page_ext exists for this page.
126 */
127static inline struct page_ext *page_ext_iter_begin(struct page_ext_iter *iter,
128 unsigned long pfn)
129{
130 iter->index = 0;
131 iter->start_pfn = pfn;
132 iter->page_ext = page_ext_lookup(pfn);
133
134 return iter->page_ext;
135}
136
137/**
138 * page_ext_iter_next() - Get next page extension
139 * @iter: page extension iterator.
140 *
141 * Must be called with RCU read lock taken.
142 *
143 * Return: NULL if no next page_ext exists.
144 */
145static inline struct page_ext *page_ext_iter_next(struct page_ext_iter *iter)
146{
147 unsigned long pfn;
148
149 if (WARN_ON_ONCE(!iter->page_ext))
150 return NULL;
151
152 iter->index++;
153 pfn = iter->start_pfn + iter->index;
154
155 if (page_ext_iter_next_fast_possible(pfn))
156 iter->page_ext = page_ext_next(iter->page_ext);
157 else
158 iter->page_ext = page_ext_lookup(pfn);
159
160 return iter->page_ext;
161}
162
163/**
164 * page_ext_iter_get() - Get current page extension
165 * @iter: page extension iterator.
166 *
167 * Return: NULL if no page_ext exists for this iterator.
168 */
169static inline struct page_ext *page_ext_iter_get(const struct page_ext_iter *iter)
170{
171 return iter->page_ext;
172}
173
174/**
175 * for_each_page_ext(): iterate through page_ext objects.
176 * @__page: the page we're interested in
177 * @__pgcount: how many pages to iterate through
178 * @__page_ext: struct page_ext pointer where the current page_ext
179 * object is returned
180 * @__iter: struct page_ext_iter object (defined in the stack)
181 *
182 * IMPORTANT: must be called with RCU read lock taken.
183 */
184#define for_each_page_ext(__page, __pgcount, __page_ext, __iter) \
185 for (__page_ext = page_ext_iter_begin(&__iter, page_to_pfn(__page));\
186 __page_ext && __iter.index < __pgcount; \
187 __page_ext = page_ext_iter_next(&__iter))
188
189#else /* !CONFIG_PAGE_EXTENSION */
190struct page_ext;
191
192static inline bool early_page_ext_enabled(void)
193{
194 return false;
195}
196
197static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
198{
199}
200
201static inline void page_ext_init(void)
202{
203}
204
205static inline void page_ext_init_flatmem_late(void)
206{
207}
208
209static inline void page_ext_init_flatmem(void)
210{
211}
212
213static inline struct page_ext *page_ext_get(const struct page *page)
214{
215 return NULL;
216}
217
218static inline void page_ext_put(struct page_ext *page_ext)
219{
220}
221#endif /* CONFIG_PAGE_EXTENSION */
222#endif /* __LINUX_PAGE_EXT_H */
223