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   1 #ifndef _LINUX_MM_TYPES_H
   2 #define _LINUX_MM_TYPES_H
   3
   4 #include <linux/types.h>
   5 #include <linux/threads.h>
   6 #include <linux/list.h>
   7 #include <linux/spinlock.h>
   8
   9 struct address_space;
  10
  11 /*
  12  * Each physical page in the system has a struct page associated with
  13  * it to keep track of whatever it is we are using the page for at the
  14  * moment. Note that we have no way to track which tasks are using
  15  * a page, though if it is a pagecache page, rmap structures can tell us
  16  * who is mapping it.
  17  */
  18 struct page {
  19         unsigned long flags;            /* Atomic flags, some possibly
  20                                          * updated asynchronously */
  21         atomic_t _count;                /* Usage count, see below. */
  22         atomic_t _mapcount;             /* Count of ptes mapped in mms,
  23                                          * to show when page is mapped
  24                                          * & limit reverse map searches.
  25                                          */
  26         union {
  27             struct {
  28                 unsigned long private;          /* Mapping-private opaque data:
  29                                                  * usually used for buffer_heads
  30                                                  * if PagePrivate set; used for
  31                                                  * swp_entry_t if PageSwapCache;
  32                                                  * indicates order in the buddy
  33                                                  * system if PG_buddy is set.
  34                                                  */
  35                 struct address_space *mapping;  /* If low bit clear, points to
  36                                                  * inode address_space, or NULL.
  37                                                  * If page mapped as anonymous
  38                                                  * memory, low bit is set, and
  39                                                  * it points to anon_vma object:
  40                                                  * see PAGE_MAPPING_ANON below.
  41                                                  */
  42             };
  43 #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
  44             spinlock_t ptl;
  45 #endif
  46         };
  47         pgoff_t index;                  /* Our offset within mapping. */
  48         struct list_head lru;           /* Pageout list, eg. active_list
  49                                          * protected by zone->lru_lock !
  50                                          */
  51         /*
  52          * On machines where all RAM is mapped into kernel address space,
  53          * we can simply calculate the virtual address. On machines with
  54          * highmem some memory is mapped into kernel virtual memory
  55          * dynamically, so we need a place to store that address.
  56          * Note that this field could be 16 bits on x86 ... ;)
  57          *
  58          * Architectures with slow multiplication can define
  59          * WANT_PAGE_VIRTUAL in asm/page.h
  60          */
  61 #if defined(WANT_PAGE_VIRTUAL)
  62         void *virtual;                  /* Kernel virtual address (NULL if
  63                                            not kmapped, ie. highmem) */
  64 #endif /* WANT_PAGE_VIRTUAL */
  65 };
  66
  67 #endif /* _LINUX_MM_TYPES_H */