#ifndef _LINUX_MMZONE_H
  #define _LINUX_MMZONE_H
  
  #ifdef __KERNEL__
  #ifndef __ASSEMBLY__

  #include <linux/spinlock.h>
  #include <linux/list.h>
  #include <linux/wait.h>
  #include <linux/cache.h>
  #include <linux/threads.h>
  #include <linux/numa.h>
  #include <linux/init.h>

  #include <linux/seqlock.h>

  #include <linux/nodemask.h>

  #include <asm/atomic.h>

  #include <asm/page.h>

  
  /* Free memory management - zoned buddy allocator.  */
  #ifndef CONFIG_FORCE_MAX_ZONEORDER
  #define MAX_ORDER 11
  #else
  #define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER
  #endif

  #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))

  /*
   * PAGE_ALLOC_COSTLY_ORDER is the order at which allocations are deemed
   * costly to service.  That is between allocation orders which should
   * coelesce naturally under reasonable reclaim pressure and those which
   * will not.
   */
  #define PAGE_ALLOC_COSTLY_ORDER 3

  struct free_area {
  	struct list_head	free_list;
  	unsigned long		nr_free;
  };
  
  struct pglist_data;
  
  /*
   * zone->lock and zone->lru_lock are two of the hottest locks in the kernel.
   * So add a wild amount of padding here to ensure that they fall into separate
   * cachelines.  There are very few zone structures in the machine, so space
   * consumption is not a concern here.
   */
  #if defined(CONFIG_SMP)
  struct zone_padding {
  	char x[0];

  } ____cacheline_internodealigned_in_smp;

  #define ZONE_PADDING(name)	struct zone_padding name;
  #else
  #define ZONE_PADDING(name)
  #endif

  enum zone_stat_item {

  	/* First 128 byte cacheline (assuming 64 bit words) */

  	NR_FREE_PAGES,

  	NR_INACTIVE,
  	NR_ACTIVE,

  	NR_ANON_PAGES,	/* Mapped anonymous pages */
  	NR_FILE_MAPPED,	/* pagecache pages mapped into pagetables.

  			   only modified from process context */

  	NR_FILE_PAGES,

  	NR_FILE_DIRTY,

  	NR_WRITEBACK,

  	/* Second 128 byte cacheline */
  	NR_SLAB_RECLAIMABLE,
  	NR_SLAB_UNRECLAIMABLE,
  	NR_PAGETABLE,		/* used for pagetables */

  	NR_UNSTABLE_NFS,	/* NFS unstable pages */

  	NR_BOUNCE,

  	NR_VMSCAN_WRITE,

  #ifdef CONFIG_NUMA
  	NUMA_HIT,		/* allocated in intended node */
  	NUMA_MISS,		/* allocated in non intended node */
  	NUMA_FOREIGN,		/* was intended here, hit elsewhere */
  	NUMA_INTERLEAVE_HIT,	/* interleaver preferred this zone */
  	NUMA_LOCAL,		/* allocation from local node */
  	NUMA_OTHER,		/* allocation from other node */
  #endif

  	NR_VM_ZONE_STAT_ITEMS };

  struct per_cpu_pages {
  	int count;		/* number of pages in the list */

  	int high;		/* high watermark, emptying needed */
  	int batch;		/* chunk size for buddy add/remove */
  	struct list_head list;	/* the list of pages */
  };
  
  struct per_cpu_pageset {
  	struct per_cpu_pages pcp[2];	/* 0: hot.  1: cold */

  #ifdef CONFIG_NUMA
  	s8 expire;
  #endif

  #ifdef CONFIG_SMP

  	s8 stat_threshold;

  	s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
  #endif

  } ____cacheline_aligned_in_smp;

  #ifdef CONFIG_NUMA
  #define zone_pcp(__z, __cpu) ((__z)->pageset[(__cpu)])
  #else
  #define zone_pcp(__z, __cpu) (&(__z)->pageset[(__cpu)])
  #endif

  enum zone_type {

  #ifdef CONFIG_ZONE_DMA

  	/*
  	 * ZONE_DMA is used when there are devices that are not able
  	 * to do DMA to all of addressable memory (ZONE_NORMAL). Then we
  	 * carve out the portion of memory that is needed for these devices.
  	 * The range is arch specific.
  	 *
  	 * Some examples
  	 *
  	 * Architecture		Limit
  	 * ---------------------------
  	 * parisc, ia64, sparc	<4G
  	 * s390			<2G
  	 * arm26		<48M
  	 * arm			Various
  	 * alpha		Unlimited or 0-16MB.
  	 *
  	 * i386, x86_64 and multiple other arches
  	 * 			<16M.
  	 */
  	ZONE_DMA,

  #endif

  #ifdef CONFIG_ZONE_DMA32

  	/*
  	 * x86_64 needs two ZONE_DMAs because it supports devices that are
  	 * only able to do DMA to the lower 16M but also 32 bit devices that
  	 * can only do DMA areas below 4G.
  	 */
  	ZONE_DMA32,

  #endif

  	/*
  	 * Normal addressable memory is in ZONE_NORMAL. DMA operations can be
  	 * performed on pages in ZONE_NORMAL if the DMA devices support
  	 * transfers to all addressable memory.
  	 */
  	ZONE_NORMAL,

  #ifdef CONFIG_HIGHMEM

  	/*
  	 * A memory area that is only addressable by the kernel through
  	 * mapping portions into its own address space. This is for example
  	 * used by i386 to allow the kernel to address the memory beyond
  	 * 900MB. The kernel will set up special mappings (page
  	 * table entries on i386) for each page that the kernel needs to
  	 * access.
  	 */
  	ZONE_HIGHMEM,

  #endif

  	ZONE_MOVABLE,

  	MAX_NR_ZONES
  };

  /*
   * When a memory allocation must conform to specific limitations (such
   * as being suitable for DMA) the caller will pass in hints to the
   * allocator in the gfp_mask, in the zone modifier bits.  These bits
   * are used to select a priority ordered list of memory zones which

   * match the requested limits. See gfp_zone() in include/linux/gfp.h

   */

  /*
   * Count the active zones.  Note that the use of defined(X) outside
   * #if and family is not necessarily defined so ensure we cannot use
   * it later.  Use __ZONE_COUNT to work out how many shift bits we need.
   */
  #define __ZONE_COUNT (			\
  	  defined(CONFIG_ZONE_DMA)	\
  	+ defined(CONFIG_ZONE_DMA32)	\
  	+ 1				\
  	+ defined(CONFIG_HIGHMEM)	\

  	+ 1				\

  )
  #if __ZONE_COUNT < 2
  #define ZONES_SHIFT 0
  #elif __ZONE_COUNT <= 2

  #define ZONES_SHIFT 1

  #elif __ZONE_COUNT <= 4

  #define ZONES_SHIFT 2

  #else
  #error ZONES_SHIFT -- too many zones configured adjust calculation

  #endif

  #undef __ZONE_COUNT

  struct zone {
  	/* Fields commonly accessed by the page allocator */

  	unsigned long		pages_min, pages_low, pages_high;
  	/*
  	 * We don't know if the memory that we're going to allocate will be freeable
  	 * or/and it will be released eventually, so to avoid totally wasting several
  	 * GB of ram we must reserve some of the lower zone memory (otherwise we risk
  	 * to run OOM on the lower zones despite there's tons of freeable ram
  	 * on the higher zones). This array is recalculated at runtime if the
  	 * sysctl_lowmem_reserve_ratio sysctl changes.
  	 */
  	unsigned long		lowmem_reserve[MAX_NR_ZONES];

  #ifdef CONFIG_NUMA

  	int node;

  	/*
  	 * zone reclaim becomes active if more unmapped pages exist.
  	 */

  	unsigned long		min_unmapped_pages;

  	unsigned long		min_slab_pages;

  	struct per_cpu_pageset	*pageset[NR_CPUS];
  #else

  	struct per_cpu_pageset	pageset[NR_CPUS];

  #endif

  	/*
  	 * free areas of different sizes
  	 */
  	spinlock_t		lock;

  #ifdef CONFIG_MEMORY_HOTPLUG
  	/* see spanned/present_pages for more description */
  	seqlock_t		span_seqlock;
  #endif

  	struct free_area	free_area[MAX_ORDER];
  
  
  	ZONE_PADDING(_pad1_)
  
  	/* Fields commonly accessed by the page reclaim scanner */
  	spinlock_t		lru_lock;	
  	struct list_head	active_list;
  	struct list_head	inactive_list;
  	unsigned long		nr_scan_active;
  	unsigned long		nr_scan_inactive;

  	unsigned long		pages_scanned;	   /* since last reclaim */
  	int			all_unreclaimable; /* All pages pinned */

  	/* A count of how many reclaimers are scanning this zone */
  	atomic_t		reclaim_in_progress;

  	/* Zone statistics */
  	atomic_long_t		vm_stat[NR_VM_ZONE_STAT_ITEMS];

  
  	/*

  	 * prev_priority holds the scanning priority for this zone.  It is
  	 * defined as the scanning priority at which we achieved our reclaim
  	 * target at the previous try_to_free_pages() or balance_pgdat()
  	 * invokation.
  	 *
  	 * We use prev_priority as a measure of how much stress page reclaim is
  	 * under - it drives the swappiness decision: whether to unmap mapped
  	 * pages.
  	 *

  	 * Access to both this field is quite racy even on uniprocessor.  But

  	 * it is expected to average out OK.
  	 */

  	int prev_priority;
  
  
  	ZONE_PADDING(_pad2_)
  	/* Rarely used or read-mostly fields */
  
  	/*
  	 * wait_table		-- the array holding the hash table

  	 * wait_table_hash_nr_entries	-- the size of the hash table array

  	 * wait_table_bits	-- wait_table_size == (1 << wait_table_bits)
  	 *
  	 * The purpose of all these is to keep track of the people
  	 * waiting for a page to become available and make them
  	 * runnable again when possible. The trouble is that this
  	 * consumes a lot of space, especially when so few things
  	 * wait on pages at a given time. So instead of using
  	 * per-page waitqueues, we use a waitqueue hash table.
  	 *
  	 * The bucket discipline is to sleep on the same queue when
  	 * colliding and wake all in that wait queue when removing.
  	 * When something wakes, it must check to be sure its page is
  	 * truly available, a la thundering herd. The cost of a
  	 * collision is great, but given the expected load of the
  	 * table, they should be so rare as to be outweighed by the
  	 * benefits from the saved space.
  	 *
  	 * __wait_on_page_locked() and unlock_page() in mm/filemap.c, are the
  	 * primary users of these fields, and in mm/page_alloc.c
  	 * free_area_init_core() performs the initialization of them.
  	 */
  	wait_queue_head_t	* wait_table;

  	unsigned long		wait_table_hash_nr_entries;

  	unsigned long		wait_table_bits;
  
  	/*
  	 * Discontig memory support fields.
  	 */
  	struct pglist_data	*zone_pgdat;

  	/* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
  	unsigned long		zone_start_pfn;

  	/*
  	 * zone_start_pfn, spanned_pages and present_pages are all
  	 * protected by span_seqlock.  It is a seqlock because it has
  	 * to be read outside of zone->lock, and it is done in the main
  	 * allocator path.  But, it is written quite infrequently.
  	 *
  	 * The lock is declared along with zone->lock because it is
  	 * frequently read in proximity to zone->lock.  It's good to
  	 * give them a chance of being in the same cacheline.
  	 */

  	unsigned long		spanned_pages;	/* total size, including holes */
  	unsigned long		present_pages;	/* amount of memory (excluding holes) */
  
  	/*
  	 * rarely used fields:
  	 */

  	const char		*name;

  } ____cacheline_internodealigned_in_smp;

  /*
   * The "priority" of VM scanning is how much of the queues we will scan in one
   * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
   * queues ("queue_length >> 12") during an aging round.
   */
  #define DEF_PRIORITY 12

  /* Maximum number of zones on a zonelist */
  #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
  
  #ifdef CONFIG_NUMA
  /*
   * We cache key information from each zonelist for smaller cache
   * footprint when scanning for free pages in get_page_from_freelist().
   *
   * 1) The BITMAP fullzones tracks which zones in a zonelist have come
   *    up short of free memory since the last time (last_fullzone_zap)
   *    we zero'd fullzones.
   * 2) The array z_to_n[] maps each zone in the zonelist to its node
   *    id, so that we can efficiently evaluate whether that node is
   *    set in the current tasks mems_allowed.
   *
   * Both fullzones and z_to_n[] are one-to-one with the zonelist,
   * indexed by a zones offset in the zonelist zones[] array.
   *
   * The get_page_from_freelist() routine does two scans.  During the
   * first scan, we skip zones whose corresponding bit in 'fullzones'
   * is set or whose corresponding node in current->mems_allowed (which
   * comes from cpusets) is not set.  During the second scan, we bypass
   * this zonelist_cache, to ensure we look methodically at each zone.
   *
   * Once per second, we zero out (zap) fullzones, forcing us to
   * reconsider nodes that might have regained more free memory.
   * The field last_full_zap is the time we last zapped fullzones.
   *
   * This mechanism reduces the amount of time we waste repeatedly
   * reexaming zones for free memory when they just came up low on
   * memory momentarilly ago.
   *
   * The zonelist_cache struct members logically belong in struct
   * zonelist.  However, the mempolicy zonelists constructed for
   * MPOL_BIND are intentionally variable length (and usually much
   * shorter).  A general purpose mechanism for handling structs with
   * multiple variable length members is more mechanism than we want
   * here.  We resort to some special case hackery instead.
   *
   * The MPOL_BIND zonelists don't need this zonelist_cache (in good
   * part because they are shorter), so we put the fixed length stuff
   * at the front of the zonelist struct, ending in a variable length
   * zones[], as is needed by MPOL_BIND.
   *
   * Then we put the optional zonelist cache on the end of the zonelist
   * struct.  This optional stuff is found by a 'zlcache_ptr' pointer in
   * the fixed length portion at the front of the struct.  This pointer
   * both enables us to find the zonelist cache, and in the case of
   * MPOL_BIND zonelists, (which will just set the zlcache_ptr to NULL)
   * to know that the zonelist cache is not there.
   *
   * The end result is that struct zonelists come in two flavors:
   *  1) The full, fixed length version, shown below, and
   *  2) The custom zonelists for MPOL_BIND.
   * The custom MPOL_BIND zonelists have a NULL zlcache_ptr and no zlcache.
   *
   * Even though there may be multiple CPU cores on a node modifying
   * fullzones or last_full_zap in the same zonelist_cache at the same
   * time, we don't lock it.  This is just hint data - if it is wrong now
   * and then, the allocator will still function, perhaps a bit slower.
   */
  
  
  struct zonelist_cache {

  	unsigned short z_to_n[MAX_ZONES_PER_ZONELIST];		/* zone->nid */

  	DECLARE_BITMAP(fullzones, MAX_ZONES_PER_ZONELIST);	/* zone full? */

  	unsigned long last_full_zap;		/* when last zap'd (jiffies) */
  };
  #else
  struct zonelist_cache;
  #endif

  /*
   * One allocation request operates on a zonelist. A zonelist
   * is a list of zones, the first one is the 'goal' of the
   * allocation, the other zones are fallback zones, in decreasing
   * priority.
   *

   * If zlcache_ptr is not NULL, then it is just the address of zlcache,
   * as explained above.  If zlcache_ptr is NULL, there is no zlcache.

   */

  struct zonelist {

  	struct zonelist_cache *zlcache_ptr;		     // NULL or &zlcache
  	struct zone *zones[MAX_ZONES_PER_ZONELIST + 1];      // NULL delimited
  #ifdef CONFIG_NUMA
  	struct zonelist_cache zlcache;			     // optional ...
  #endif

  };

  #ifdef CONFIG_ARCH_POPULATES_NODE_MAP
  struct node_active_region {
  	unsigned long start_pfn;
  	unsigned long end_pfn;
  	int nid;
  };
  #endif /* CONFIG_ARCH_POPULATES_NODE_MAP */

  #ifndef CONFIG_DISCONTIGMEM
  /* The array of struct pages - for discontigmem use pgdat->lmem_map */
  extern struct page *mem_map;
  #endif

  /*
   * The pg_data_t structure is used in machines with CONFIG_DISCONTIGMEM
   * (mostly NUMA machines?) to denote a higher-level memory zone than the
   * zone denotes.
   *
   * On NUMA machines, each NUMA node would have a pg_data_t to describe
   * it's memory layout.
   *
   * Memory statistics and page replacement data structures are maintained on a
   * per-zone basis.
   */
  struct bootmem_data;
  typedef struct pglist_data {
  	struct zone node_zones[MAX_NR_ZONES];

  	struct zonelist node_zonelists[MAX_NR_ZONES];

  	int nr_zones;

  #ifdef CONFIG_FLAT_NODE_MEM_MAP

  	struct page *node_mem_map;

  #endif

  	struct bootmem_data *bdata;

  #ifdef CONFIG_MEMORY_HOTPLUG
  	/*
  	 * Must be held any time you expect node_start_pfn, node_present_pages
  	 * or node_spanned_pages stay constant.  Holding this will also
  	 * guarantee that any pfn_valid() stays that way.
  	 *
  	 * Nests above zone->lock and zone->size_seqlock.
  	 */
  	spinlock_t node_size_lock;
  #endif

  	unsigned long node_start_pfn;
  	unsigned long node_present_pages; /* total number of physical pages */
  	unsigned long node_spanned_pages; /* total size of physical page
  					     range, including holes */
  	int node_id;

  	wait_queue_head_t kswapd_wait;
  	struct task_struct *kswapd;
  	int kswapd_max_order;
  } pg_data_t;
  
  #define node_present_pages(nid)	(NODE_DATA(nid)->node_present_pages)
  #define node_spanned_pages(nid)	(NODE_DATA(nid)->node_spanned_pages)

  #ifdef CONFIG_FLAT_NODE_MEM_MAP

  #define pgdat_page_nr(pgdat, pagenr)	((pgdat)->node_mem_map + (pagenr))

  #else
  #define pgdat_page_nr(pgdat, pagenr)	pfn_to_page((pgdat)->node_start_pfn + (pagenr))
  #endif

  #define nid_page_nr(nid, pagenr) 	pgdat_page_nr(NODE_DATA(nid),(pagenr))

  #include <linux/memory_hotplug.h>

  void get_zone_counts(unsigned long *active, unsigned long *inactive,
  			unsigned long *free);
  void build_all_zonelists(void);
  void wakeup_kswapd(struct zone *zone, int order);
  int zone_watermark_ok(struct zone *z, int order, unsigned long mark,

  		int classzone_idx, int alloc_flags);

  enum memmap_context {
  	MEMMAP_EARLY,
  	MEMMAP_HOTPLUG,
  };

  extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,

  				     unsigned long size,
  				     enum memmap_context context);

  #ifdef CONFIG_HAVE_MEMORY_PRESENT
  void memory_present(int nid, unsigned long start, unsigned long end);
  #else
  static inline void memory_present(int nid, unsigned long start, unsigned long end) {}
  #endif
  
  #ifdef CONFIG_NEED_NODE_MEMMAP_SIZE
  unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
  #endif
  
  /*
   * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
   */
  #define zone_idx(zone)		((zone) - (zone)->zone_pgdat->node_zones)

  static inline int populated_zone(struct zone *zone)
  {
  	return (!!zone->present_pages);
  }

  extern int movable_zone;
  
  static inline int zone_movable_is_highmem(void)
  {
  #if defined(CONFIG_HIGHMEM) && defined(CONFIG_ARCH_POPULATES_NODE_MAP)
  	return movable_zone == ZONE_HIGHMEM;
  #else
  	return 0;
  #endif
  }

  static inline int is_highmem_idx(enum zone_type idx)

  {

  #ifdef CONFIG_HIGHMEM

  	return (idx == ZONE_HIGHMEM ||
  		(idx == ZONE_MOVABLE && zone_movable_is_highmem()));

  #else
  	return 0;
  #endif

  }

  static inline int is_normal_idx(enum zone_type idx)

  {
  	return (idx == ZONE_NORMAL);
  }

  /**
   * is_highmem - helper function to quickly check if a struct zone is a 
   *              highmem zone or not.  This is an attempt to keep references
   *              to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum.
   * @zone - pointer to struct zone variable
   */
  static inline int is_highmem(struct zone *zone)
  {

  #ifdef CONFIG_HIGHMEM

  	int zone_idx = zone - zone->zone_pgdat->node_zones;
  	return zone_idx == ZONE_HIGHMEM ||
  		(zone_idx == ZONE_MOVABLE && zone_movable_is_highmem());

  #else
  	return 0;
  #endif

  }
  
  static inline int is_normal(struct zone *zone)
  {
  	return zone == zone->zone_pgdat->node_zones + ZONE_NORMAL;
  }

  static inline int is_dma32(struct zone *zone)
  {

  #ifdef CONFIG_ZONE_DMA32

  	return zone == zone->zone_pgdat->node_zones + ZONE_DMA32;

  #else
  	return 0;
  #endif

  }
  
  static inline int is_dma(struct zone *zone)
  {

  #ifdef CONFIG_ZONE_DMA

  	return zone == zone->zone_pgdat->node_zones + ZONE_DMA;

  #else
  	return 0;
  #endif

  }

  /* These two functions are used to setup the per zone pages min values */
  struct ctl_table;
  struct file;
  int min_free_kbytes_sysctl_handler(struct ctl_table *, int, struct file *, 
  					void __user *, size_t *, loff_t *);
  extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
  int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, struct file *,
  					void __user *, size_t *, loff_t *);

  int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int, struct file *,
  					void __user *, size_t *, loff_t *);

  int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,
  			struct file *, void __user *, size_t *, loff_t *);

  int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
  			struct file *, void __user *, size_t *, loff_t *);

  extern int numa_zonelist_order_handler(struct ctl_table *, int,
  			struct file *, void __user *, size_t *, loff_t *);
  extern char numa_zonelist_order[];
  #define NUMA_ZONELIST_ORDER_LEN 16	/* string buffer size */

  #include <linux/topology.h>
  /* Returns the number of the current Node. */

  #ifndef numa_node_id

  #define numa_node_id()		(cpu_to_node(raw_smp_processor_id()))

  #endif

  #ifndef CONFIG_NEED_MULTIPLE_NODES

  
  extern struct pglist_data contig_page_data;
  #define NODE_DATA(nid)		(&contig_page_data)
  #define NODE_MEM_MAP(nid)	mem_map
  #define MAX_NODES_SHIFT		1

  #else /* CONFIG_NEED_MULTIPLE_NODES */

  
  #include <asm/mmzone.h>

  #endif /* !CONFIG_NEED_MULTIPLE_NODES */

  extern struct pglist_data *first_online_pgdat(void);
  extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
  extern struct zone *next_zone(struct zone *zone);

  
  /**
   * for_each_pgdat - helper macro to iterate over all nodes
   * @pgdat - pointer to a pg_data_t variable
   */
  #define for_each_online_pgdat(pgdat)			\
  	for (pgdat = first_online_pgdat();		\
  	     pgdat;					\
  	     pgdat = next_online_pgdat(pgdat))

  /**
   * for_each_zone - helper macro to iterate over all memory zones
   * @zone - pointer to struct zone variable
   *
   * The user only needs to declare the zone variable, for_each_zone
   * fills it in.
   */
  #define for_each_zone(zone)			        \
  	for (zone = (first_online_pgdat())->node_zones; \
  	     zone;					\
  	     zone = next_zone(zone))

  #ifdef CONFIG_SPARSEMEM
  #include <asm/sparsemem.h>
  #endif

  #if BITS_PER_LONG == 32

  /*

   * with 32 bit page->flags field, we reserve 9 bits for node/zone info.
   * there are 4 zones (3 bits) and this leaves 9-3=6 bits for nodes.

   */

  #define FLAGS_RESERVED		9

  #elif BITS_PER_LONG == 64
  /*
   * with 64 bit flags field, there's plenty of room.
   */

  #define FLAGS_RESERVED		32

  #else

  #error BITS_PER_LONG not defined

  #endif

  #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \
  	!defined(CONFIG_ARCH_POPULATES_NODE_MAP)

  #define early_pfn_to_nid(nid)  (0UL)
  #endif

  #ifdef CONFIG_FLATMEM
  #define pfn_to_nid(pfn)		(0)
  #endif

  #define pfn_to_section_nr(pfn) ((pfn) >> PFN_SECTION_SHIFT)
  #define section_nr_to_pfn(sec) ((sec) << PFN_SECTION_SHIFT)
  
  #ifdef CONFIG_SPARSEMEM
  
  /*
   * SECTION_SHIFT    		#bits space required to store a section #
   *
   * PA_SECTION_SHIFT		physical address to/from section number
   * PFN_SECTION_SHIFT		pfn to/from section number
   */
  #define SECTIONS_SHIFT		(MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
  
  #define PA_SECTION_SHIFT	(SECTION_SIZE_BITS)
  #define PFN_SECTION_SHIFT	(SECTION_SIZE_BITS - PAGE_SHIFT)
  
  #define NR_MEM_SECTIONS		(1UL << SECTIONS_SHIFT)
  
  #define PAGES_PER_SECTION       (1UL << PFN_SECTION_SHIFT)
  #define PAGE_SECTION_MASK	(~(PAGES_PER_SECTION-1))
  
  #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
  #error Allocator MAX_ORDER exceeds SECTION_SIZE
  #endif
  
  struct page;
  struct mem_section {

  	/*
  	 * This is, logically, a pointer to an array of struct
  	 * pages.  However, it is stored with some other magic.
  	 * (see sparse.c::sparse_init_one_section())
  	 *

  	 * Additionally during early boot we encode node id of
  	 * the location of the section here to guide allocation.
  	 * (see sparse.c::memory_present())
  	 *

  	 * Making it a UL at least makes someone do a cast
  	 * before using it wrong.
  	 */
  	unsigned long section_mem_map;

  };

  #ifdef CONFIG_SPARSEMEM_EXTREME
  #define SECTIONS_PER_ROOT       (PAGE_SIZE / sizeof (struct mem_section))
  #else
  #define SECTIONS_PER_ROOT	1
  #endif

  #define SECTION_NR_TO_ROOT(sec)	((sec) / SECTIONS_PER_ROOT)
  #define NR_SECTION_ROOTS	(NR_MEM_SECTIONS / SECTIONS_PER_ROOT)
  #define SECTION_ROOT_MASK	(SECTIONS_PER_ROOT - 1)

  #ifdef CONFIG_SPARSEMEM_EXTREME
  extern struct mem_section *mem_section[NR_SECTION_ROOTS];

  #else

  extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
  #endif

  static inline struct mem_section *__nr_to_section(unsigned long nr)
  {

  	if (!mem_section[SECTION_NR_TO_ROOT(nr)])
  		return NULL;
  	return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];

  }

  extern int __section_nr(struct mem_section* ms);

  
  /*
   * We use the lower bits of the mem_map pointer to store
   * a little bit of information.  There should be at least
   * 3 bits here due to 32-bit alignment.
   */
  #define	SECTION_MARKED_PRESENT	(1UL<<0)
  #define SECTION_HAS_MEM_MAP	(1UL<<1)
  #define SECTION_MAP_LAST_BIT	(1UL<<2)
  #define SECTION_MAP_MASK	(~(SECTION_MAP_LAST_BIT-1))

  #define SECTION_NID_SHIFT	2

  
  static inline struct page *__section_mem_map_addr(struct mem_section *section)
  {
  	unsigned long map = section->section_mem_map;
  	map &= SECTION_MAP_MASK;
  	return (struct page *)map;
  }
  
  static inline int valid_section(struct mem_section *section)
  {

  	return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));

  }
  
  static inline int section_has_mem_map(struct mem_section *section)
  {

  	return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));

  }
  
  static inline int valid_section_nr(unsigned long nr)
  {
  	return valid_section(__nr_to_section(nr));
  }

  static inline struct mem_section *__pfn_to_section(unsigned long pfn)
  {

  	return __nr_to_section(pfn_to_section_nr(pfn));

  }

  static inline int pfn_valid(unsigned long pfn)
  {
  	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
  		return 0;

  	return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));

  }
  
  /*
   * These are _only_ used during initialisation, therefore they
   * can use __initdata ...  They could have names to indicate
   * this restriction.
   */
  #ifdef CONFIG_NUMA

  #define pfn_to_nid(pfn)							\
  ({									\
  	unsigned long __pfn_to_nid_pfn = (pfn);				\
  	page_to_nid(pfn_to_page(__pfn_to_nid_pfn));			\
  })

  #else
  #define pfn_to_nid(pfn)		(0)

  #endif

  #define early_pfn_valid(pfn)	pfn_valid(pfn)
  void sparse_init(void);
  #else
  #define sparse_init()	do {} while (0)

  #define sparse_index_init(_sec, _nid)  do {} while (0)

  #endif /* CONFIG_SPARSEMEM */

  #ifdef CONFIG_NODES_SPAN_OTHER_NODES
  #define early_pfn_in_nid(pfn, nid)	(early_pfn_to_nid(pfn) == (nid))
  #else
  #define early_pfn_in_nid(pfn, nid)	(1)
  #endif

  #ifndef early_pfn_valid
  #define early_pfn_valid(pfn)	(1)
  #endif
  
  void memory_present(int nid, unsigned long start, unsigned long end);
  unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);

  /*
   * If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
   * need to check pfn validility within that MAX_ORDER_NR_PAGES block.
   * pfn_valid_within() should be used in this case; we optimise this away
   * when we have no holes within a MAX_ORDER_NR_PAGES block.
   */
  #ifdef CONFIG_HOLES_IN_ZONE
  #define pfn_valid_within(pfn) pfn_valid(pfn)
  #else
  #define pfn_valid_within(pfn) (1)
  #endif

  #endif /* !__ASSEMBLY__ */
  #endif /* __KERNEL__ */
  #endif /* _LINUX_MMZONE_H */