include/linux/page_ext.h

   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
  59 static inline bool early_page_ext_enabled(void)
  60 {
  61         return early_page_ext;
  62 }
  63
  64 #ifdef CONFIG_SPARSEMEM
  65 static inline void page_ext_init_flatmem(void)
  66 {
  67 }
  68 extern void page_ext_init(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);
  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
  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
  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
  99 static inline bool early_page_ext_enabled(void)
 100 {
 101         return false;
 102 }
 103
 104 static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
 105 {
 106 }
 107
 108 static inline void page_ext_init(void)
 109 {
 110 }
 111
 112 static inline void page_ext_init_flatmem_late(void)
 113 {
 114 }
 115
 116 static inline void page_ext_init_flatmem(void)
 117 {
 118 }
 119
 120 static inline struct page_ext *page_ext_get(const struct page *page)
 121 {
 122         return NULL;
 123 }
 124
 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 */