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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         union {
  23                 atomic_t _mapcount;     /* Count of ptes mapped in mms,
  24                                          * to show when page is mapped
  25                                          * & limit reverse map searches.
  26                                          */
  27                 struct {        /* SLUB uses */
  28                         short unsigned int inuse;
  29                         short unsigned int offset;
  30                 };
  31         };
  32         union {
  33             struct {
  34                 unsigned long private;          /* Mapping-private opaque data:
  35                                                  * usually used for buffer_heads
  36                                                  * if PagePrivate set; used for
  37                                                  * swp_entry_t if PageSwapCache;
  38                                                  * indicates order in the buddy
  39                                                  * system if PG_buddy is set.
  40                                                  */
  41                 struct address_space *mapping;  /* If low bit clear, points to
  42                                                  * inode address_space, or NULL.
  43                                                  * If page mapped as anonymous
  44                                                  * memory, low bit is set, and
  45                                                  * it points to anon_vma object:
  46                                                  * see PAGE_MAPPING_ANON below.
  47                                                  */
  48             };
  49 #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
  50             spinlock_t ptl;
  51 #endif
  52             struct {                    /* SLUB uses */
  53                 struct page *first_page;        /* Compound pages */
  54                 struct kmem_cache *slab;        /* Pointer to slab */
  55             };
  56         };
  57         union {
  58                 pgoff_t index;          /* Our offset within mapping. */
  59                 void *freelist;         /* SLUB: pointer to free object */
  60         };
  61         struct list_head lru;           /* Pageout list, eg. active_list
  62                                          * protected by zone->lru_lock !
  63                                          */
  64         /*
  65          * On machines where all RAM is mapped into kernel address space,
  66          * we can simply calculate the virtual address. On machines with
  67          * highmem some memory is mapped into kernel virtual memory
  68          * dynamically, so we need a place to store that address.
  69          * Note that this field could be 16 bits on x86 ... ;)
  70          *
  71          * Architectures with slow multiplication can define
  72          * WANT_PAGE_VIRTUAL in asm/page.h
  73          */
  74 #if defined(WANT_PAGE_VIRTUAL)
  75         void *virtual;                  /* Kernel virtual address (NULL if
  76                                            not kmapped, ie. highmem) */
  77 #endif /* WANT_PAGE_VIRTUAL */
  78 };
  79
  80 #endif /* _LINUX_MM_TYPES_H */