typedef struct pglist_data {

    zone_t node_zones[MAX_NR_ZONES];

    zonelist_t node_zonelists[NR_GFPINDEX];

    struct page *node_mem_map;

    unsigned long *valid_addr_bitmap;

    struct bootmem_data *bdata;

    unsigned long node_start_paddr;

    unsigned long node_start_mapnr;

    unsigned long node_size;

    int node_id;

    struct pglist_data *node_next;

} pg_data_t;

typedef struct zone_struct {

    /*

     * Commonly accessed fields:

     */

    spinlock_t        lock;

    unsigned long        offset;

    unsigned long        free_pages;

    unsigned long        inactive_clean_pages;

    unsigned long        inactive_dirty_pages;

    unsigned long        pages_min, pages_low, pages_high;

    /*

     * free areas of different sizes

     */

    struct list_head    inactive_clean_list;

    free_area_t        free_area[MAX_ORDER];

    /*

     * rarely used fields:

     */

    char            *name;

    unsigned long        size;

    /*

     * Discontig memory support fields.

     */

    struct pglist_data    *zone_pgdat;

    unsigned long        zone_start_paddr;

    unsigned long        zone_start_mapnr;

    struct page        *zone_mem_map;

} zone_t;

typedef struct page {

    struct list_head list;

    struct address_space *mapping;

    unsigned long index;

    struct page *next_hash;

    atomic_t count;

    unsigned long flags;    /* atomic flags, some possibly updated asynchronously */

    struct list_head lru;

    unsigned long age;

    wait_queue_head_t wait;

    struct page **pprev_hash;

    struct buffer_head * buffers;

    void *virtual; /* non-NULL if kmapped */

    struct zone_struct *zone;

} mem_map_t;