#ifndef _LINUX_MMZONE_H
  #define _LINUX_MMZONE_H

  #ifndef __ASSEMBLY__

  #ifndef __GENERATING_BOUNDS_H

  #include <linux/spinlock.h>
  #include <linux/list.h>
  #include <linux/wait.h>

  #include <linux/bitops.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 <linux/pageblock-flags.h>

  #include <linux/page-flags-layout.h>

  #include <linux/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

   * coalesce naturally under reasonable reclaim pressure and those which

   * will not.
   */
  #define PAGE_ALLOC_COSTLY_ORDER 3

  enum {
  	MIGRATE_UNMOVABLE,

  	MIGRATE_MOVABLE,

  	MIGRATE_RECLAIMABLE,

  	MIGRATE_PCPTYPES,	/* the number of types on the pcp lists */
  	MIGRATE_HIGHATOMIC = MIGRATE_PCPTYPES,

  #ifdef CONFIG_CMA
  	/*
  	 * MIGRATE_CMA migration type is designed to mimic the way
  	 * ZONE_MOVABLE works.  Only movable pages can be allocated
  	 * from MIGRATE_CMA pageblocks and page allocator never
  	 * implicitly change migration type of MIGRATE_CMA pageblock.
  	 *
  	 * The way to use it is to change migratetype of a range of
  	 * pageblocks to MIGRATE_CMA which can be done by
  	 * __free_pageblock_cma() function.  What is important though
  	 * is that a range of pageblocks must be aligned to
  	 * MAX_ORDER_NR_PAGES should biggest page be bigger then
  	 * a single pageblock.
  	 */
  	MIGRATE_CMA,
  #endif

  #ifdef CONFIG_MEMORY_ISOLATION

  	MIGRATE_ISOLATE,	/* can't allocate from here */

  #endif

  	MIGRATE_TYPES
  };

  /* In mm/page_alloc.c; keep in sync also with show_migration_types() there */
  extern char * const migratetype_names[MIGRATE_TYPES];

  #ifdef CONFIG_CMA
  #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)

  #  define is_migrate_cma_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_CMA)

  #else
  #  define is_migrate_cma(migratetype) false

  #  define is_migrate_cma_page(_page) false

  #endif

  
  #define for_each_migratetype_order(order, type) \
  	for (order = 0; order < MAX_ORDER; order++) \
  		for (type = 0; type < MIGRATE_TYPES; type++)

  extern int page_group_by_mobility_disabled;

  #define NR_MIGRATETYPE_BITS (PB_migrate_end - PB_migrate + 1)
  #define MIGRATETYPE_MASK ((1UL << NR_MIGRATETYPE_BITS) - 1)

  #define get_pageblock_migratetype(page)					\
  	get_pfnblock_flags_mask(page, page_to_pfn(page),		\
  			PB_migrate_end, MIGRATETYPE_MASK)

  struct free_area {

  	struct list_head	free_list[MIGRATE_TYPES];

  	unsigned long		nr_free;
  };
  
  struct pglist_data;
  
  /*

   * zone->lock and the 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_ZONE_LRU_BASE, /* Used only for compaction and reclaim retry */
  	NR_ZONE_INACTIVE_ANON = NR_ZONE_LRU_BASE,
  	NR_ZONE_ACTIVE_ANON,
  	NR_ZONE_INACTIVE_FILE,
  	NR_ZONE_ACTIVE_FILE,
  	NR_ZONE_UNEVICTABLE,

  	NR_ZONE_WRITE_PENDING,	/* Count of dirty, writeback and unstable pages */

  	NR_MLOCK,		/* mlock()ed pages found and moved off LRU */

  	NR_SLAB_RECLAIMABLE,
  	NR_SLAB_UNRECLAIMABLE,
  	NR_PAGETABLE,		/* used for pagetables */

  	NR_KERNEL_STACK_KB,	/* measured in KiB */

  	/* Second 128 byte cacheline */

  	NR_BOUNCE,

  #if IS_ENABLED(CONFIG_ZSMALLOC)
  	NR_ZSPAGES,		/* allocated in zsmalloc */
  #endif

  #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_FREE_CMA_PAGES,

  	NR_VM_ZONE_STAT_ITEMS };

  enum node_stat_item {

  	NR_LRU_BASE,
  	NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
  	NR_ACTIVE_ANON,		/*  "     "     "   "       "         */
  	NR_INACTIVE_FILE,	/*  "     "     "   "       "         */
  	NR_ACTIVE_FILE,		/*  "     "     "   "       "         */
  	NR_UNEVICTABLE,		/*  "     "     "   "       "         */
  	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
  	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
  	NR_PAGES_SCANNED,	/* pages scanned since last reclaim */

  	WORKINGSET_REFAULT,
  	WORKINGSET_ACTIVATE,
  	WORKINGSET_NODERECLAIM,

  	NR_ANON_MAPPED,	/* Mapped anonymous pages */

  	NR_FILE_MAPPED,	/* pagecache pages mapped into pagetables.
  			   only modified from process context */

  	NR_FILE_PAGES,
  	NR_FILE_DIRTY,
  	NR_WRITEBACK,
  	NR_WRITEBACK_TEMP,	/* Writeback using temporary buffers */
  	NR_SHMEM,		/* shmem pages (included tmpfs/GEM pages) */
  	NR_SHMEM_THPS,
  	NR_SHMEM_PMDMAPPED,
  	NR_ANON_THPS,
  	NR_UNSTABLE_NFS,	/* NFS unstable pages */

  	NR_VMSCAN_WRITE,
  	NR_VMSCAN_IMMEDIATE,	/* Prioritise for reclaim when writeback ends */
  	NR_DIRTIED,		/* page dirtyings since bootup */
  	NR_WRITTEN,		/* page writings since bootup */

  	NR_VM_NODE_STAT_ITEMS
  };

  /*
   * We do arithmetic on the LRU lists in various places in the code,
   * so it is important to keep the active lists LRU_ACTIVE higher in
   * the array than the corresponding inactive lists, and to keep
   * the *_FILE lists LRU_FILE higher than the corresponding _ANON lists.
   *
   * This has to be kept in sync with the statistics in zone_stat_item
   * above and the descriptions in vmstat_text in mm/vmstat.c
   */
  #define LRU_BASE 0
  #define LRU_ACTIVE 1
  #define LRU_FILE 2

  enum lru_list {

  	LRU_INACTIVE_ANON = LRU_BASE,
  	LRU_ACTIVE_ANON = LRU_BASE + LRU_ACTIVE,
  	LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
  	LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,

  	LRU_UNEVICTABLE,

  	NR_LRU_LISTS
  };

  #define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)

  #define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)

  static inline int is_file_lru(enum lru_list lru)

  {

  	return (lru == LRU_INACTIVE_FILE || lru == LRU_ACTIVE_FILE);

  }

  static inline int is_active_lru(enum lru_list lru)

  {

  	return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);

  }

  struct zone_reclaim_stat {
  	/*
  	 * The pageout code in vmscan.c keeps track of how many of the

  	 * mem/swap backed and file backed pages are referenced.

  	 * The higher the rotated/scanned ratio, the more valuable
  	 * that cache is.
  	 *
  	 * The anon LRU stats live in [0], file LRU stats in [1]
  	 */
  	unsigned long		recent_rotated[2];
  	unsigned long		recent_scanned[2];
  };

  struct lruvec {

  	struct list_head		lists[NR_LRU_LISTS];
  	struct zone_reclaim_stat	reclaim_stat;
  	/* Evictions & activations on the inactive file list */
  	atomic_long_t			inactive_age;

  #ifdef CONFIG_MEMCG

  	struct pglist_data *pgdat;

  #endif

  };

  /* Mask used at gathering information at once (see memcontrol.c) */
  #define LRU_ALL_FILE (BIT(LRU_INACTIVE_FILE) | BIT(LRU_ACTIVE_FILE))
  #define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))

  #define LRU_ALL	     ((1 << NR_LRU_LISTS) - 1)

  /* Isolate clean file */

  #define ISOLATE_CLEAN		((__force isolate_mode_t)0x1)

  /* Isolate unmapped file */

  #define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x2)

  /* Isolate for asynchronous migration */

  #define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x4)

  /* Isolate unevictable pages */
  #define ISOLATE_UNEVICTABLE	((__force isolate_mode_t)0x8)

  
  /* LRU Isolation modes. */
  typedef unsigned __bitwise__ isolate_mode_t;

  enum zone_watermarks {
  	WMARK_MIN,
  	WMARK_LOW,
  	WMARK_HIGH,
  	NR_WMARK
  };
  
  #define min_wmark_pages(z) (z->watermark[WMARK_MIN])
  #define low_wmark_pages(z) (z->watermark[WMARK_LOW])
  #define high_wmark_pages(z) (z->watermark[WMARK_HIGH])

  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 */

  
  	/* Lists of pages, one per migrate type stored on the pcp-lists */
  	struct list_head lists[MIGRATE_PCPTYPES];

  };
  
  struct per_cpu_pageset {

  	struct per_cpu_pages pcp;

  #ifdef CONFIG_NUMA
  	s8 expire;
  #endif

  #ifdef CONFIG_SMP

  	s8 stat_threshold;

  	s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
  #endif

  };

  struct per_cpu_nodestat {
  	s8 stat_threshold;
  	s8 vm_node_stat_diff[NR_VM_NODE_STAT_ITEMS];
  };

  #endif /* !__GENERATING_BOUNDS.H */

  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

  	 * 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,

  #ifdef CONFIG_ZONE_DEVICE
  	ZONE_DEVICE,
  #endif

  	__MAX_NR_ZONES

  };

  #ifndef __GENERATING_BOUNDS_H

  struct zone {

  	/* Read-mostly fields */

  
  	/* zone watermarks, access with *_wmark_pages(zone) macros */
  	unsigned long watermark[NR_WMARK];

  	unsigned long nr_reserved_highatomic;

  	/*

  	 * 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 being tons of freeable ram on the higher zones).  This array is
  	 * recalculated at runtime if the sysctl_lowmem_reserve_ratio sysctl
  	 * changes.

  	 */

  	long lowmem_reserve[MAX_NR_ZONES];

  #ifdef CONFIG_NUMA

  	int node;

  #endif

  	struct pglist_data	*zone_pgdat;

  	struct per_cpu_pageset __percpu *pageset;

  #ifndef CONFIG_SPARSEMEM
  	/*

  	 * Flags for a pageblock_nr_pages block. See pageblock-flags.h.

  	 * In SPARSEMEM, this map is stored in struct mem_section
  	 */
  	unsigned long		*pageblock_flags;
  #endif /* CONFIG_SPARSEMEM */

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

  	/*

  	 * spanned_pages is the total pages spanned by the zone, including
  	 * holes, which is calculated as:
  	 * 	spanned_pages = zone_end_pfn - zone_start_pfn;

  	 *

  	 * present_pages is physical pages existing within the zone, which
  	 * is calculated as:

  	 *	present_pages = spanned_pages - absent_pages(pages in holes);

  	 *
  	 * managed_pages is present pages managed by the buddy system, which
  	 * is calculated as (reserved_pages includes pages allocated by the
  	 * bootmem allocator):
  	 *	managed_pages = present_pages - reserved_pages;
  	 *
  	 * So present_pages may be used by memory hotplug or memory power
  	 * management logic to figure out unmanaged pages by checking
  	 * (present_pages - managed_pages). And managed_pages should be used
  	 * by page allocator and vm scanner to calculate all kinds of watermarks
  	 * and thresholds.
  	 *
  	 * Locking rules:
  	 *
  	 * zone_start_pfn and spanned_pages are 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 span_seq 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.

  	 *

  	 * Write access to present_pages at runtime should be protected by

  	 * mem_hotplug_begin/end(). Any reader who can't tolerant drift of
  	 * present_pages should get_online_mems() to get a stable value.

  	 *
  	 * Read access to managed_pages should be safe because it's unsigned
  	 * long. Write access to zone->managed_pages and totalram_pages are
  	 * protected by managed_page_count_lock at runtime. Idealy only
  	 * adjust_managed_page_count() should be used instead of directly
  	 * touching zone->managed_pages and totalram_pages.

  	 */

  	unsigned long		managed_pages;

  	unsigned long		spanned_pages;
  	unsigned long		present_pages;

  
  	const char		*name;

  #ifdef CONFIG_MEMORY_ISOLATION
  	/*
  	 * Number of isolated pageblock. It is used to solve incorrect
  	 * freepage counting problem due to racy retrieving migratetype
  	 * of pageblock. Protected by zone->lock.
  	 */
  	unsigned long		nr_isolate_pageblock;
  #endif

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

  	int initialized;

  	/* Write-intensive fields used from the page allocator */

  	ZONE_PADDING(_pad1_)

  	/* free areas of different sizes */
  	struct free_area	free_area[MAX_ORDER];
  
  	/* zone flags, see below */
  	unsigned long		flags;

  	/* Primarily protects free_area */

  	spinlock_t		lock;

  	/* Write-intensive fields used by compaction and vmstats. */

  	ZONE_PADDING(_pad2_)

  	/*
  	 * When free pages are below this point, additional steps are taken
  	 * when reading the number of free pages to avoid per-cpu counter
  	 * drift allowing watermarks to be breached
  	 */
  	unsigned long percpu_drift_mark;
  
  #if defined CONFIG_COMPACTION || defined CONFIG_CMA
  	/* pfn where compaction free scanner should start */
  	unsigned long		compact_cached_free_pfn;
  	/* pfn where async and sync compaction migration scanner should start */
  	unsigned long		compact_cached_migrate_pfn[2];
  #endif
  
  #ifdef CONFIG_COMPACTION
  	/*
  	 * On compaction failure, 1<<compact_defer_shift compactions
  	 * are skipped before trying again. The number attempted since
  	 * last failure is tracked with compact_considered.
  	 */
  	unsigned int		compact_considered;
  	unsigned int		compact_defer_shift;
  	int			compact_order_failed;
  #endif
  
  #if defined CONFIG_COMPACTION || defined CONFIG_CMA
  	/* Set to true when the PG_migrate_skip bits should be cleared */
  	bool			compact_blockskip_flush;
  #endif

  	bool			contiguous;

  	ZONE_PADDING(_pad3_)
  	/* Zone statistics */
  	atomic_long_t		vm_stat[NR_VM_ZONE_STAT_ITEMS];

  } ____cacheline_internodealigned_in_smp;

  enum pgdat_flags {
  	PGDAT_CONGESTED,		/* pgdat has many dirty pages backed by

  					 * a congested BDI
  					 */

  	PGDAT_DIRTY,			/* reclaim scanning has recently found

  					 * many dirty file pages at the tail
  					 * of the LRU.
  					 */

  	PGDAT_WRITEBACK,		/* reclaim scanning has recently found

  					 * many pages under writeback
  					 */

  	PGDAT_RECLAIM_LOCKED,		/* prevents concurrent reclaim */

  };

  static inline unsigned long zone_end_pfn(const struct zone *zone)

  {
  	return zone->zone_start_pfn + zone->spanned_pages;
  }
  
  static inline bool zone_spans_pfn(const struct zone *zone, unsigned long pfn)
  {
  	return zone->zone_start_pfn <= pfn && pfn < zone_end_pfn(zone);
  }

  static inline bool zone_is_initialized(struct zone *zone)
  {

  	return zone->initialized;

  }
  
  static inline bool zone_is_empty(struct zone *zone)
  {
  	return zone->spanned_pages == 0;
  }

  /*
   * 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)

  enum {
  	ZONELIST_FALLBACK,	/* zonelist with fallback */

  #ifdef CONFIG_NUMA

  	/*
  	 * The NUMA zonelists are doubled because we need zonelists that
  	 * restrict the allocations to a single node for __GFP_THISNODE.
  	 */
  	ZONELIST_NOFALLBACK,	/* zonelist without fallback (__GFP_THISNODE) */

  #endif

  	MAX_ZONELISTS
  };

  /*

   * This struct contains information about a zone in a zonelist. It is stored
   * here to avoid dereferences into large structures and lookups of tables
   */
  struct zoneref {
  	struct zone *zone;	/* Pointer to actual zone */
  	int zone_idx;		/* zone_idx(zoneref->zone) */
  };
  
  /*

   * 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.
   *

   * To speed the reading of the zonelist, the zonerefs contain the zone index
   * of the entry being read. Helper functions to access information given
   * a struct zoneref are
   *
   * zonelist_zone()	- Return the struct zone * for an entry in _zonerefs
   * zonelist_zone_idx()	- Return the index of the zone for an entry
   * zonelist_node_idx()	- Return the index of the node for an entry

   */
  struct zonelist {

  	struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];

  };

  #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_ZONELISTS];

  	int nr_zones;

  #ifdef CONFIG_FLAT_NODE_MEM_MAP	/* means !SPARSEMEM */

  	struct page *node_mem_map;

  #ifdef CONFIG_PAGE_EXTENSION
  	struct page_ext *node_page_ext;
  #endif

  #endif

  #ifndef CONFIG_NO_BOOTMEM

  	struct bootmem_data *bdata;

  #endif

  #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.
  	 *

  	 * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
  	 * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
  	 *

  	 * Nests above zone->lock and zone->span_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;

  	wait_queue_head_t pfmemalloc_wait;

  	struct task_struct *kswapd;	/* Protected by
  					   mem_hotplug_begin/end() */

  	int kswapd_order;
  	enum zone_type kswapd_classzone_idx;

  #ifdef CONFIG_COMPACTION
  	int kcompactd_max_order;
  	enum zone_type kcompactd_classzone_idx;
  	wait_queue_head_t kcompactd_wait;
  	struct task_struct *kcompactd;
  #endif

  #ifdef CONFIG_NUMA_BALANCING

  	/* Lock serializing the migrate rate limiting window */

  	spinlock_t numabalancing_migrate_lock;
  
  	/* Rate limiting time interval */
  	unsigned long numabalancing_migrate_next_window;
  
  	/* Number of pages migrated during the rate limiting time interval */
  	unsigned long numabalancing_migrate_nr_pages;
  #endif

  	/*
  	 * This is a per-node reserve of pages that are not available
  	 * to userspace allocations.
  	 */
  	unsigned long		totalreserve_pages;

  #ifdef CONFIG_NUMA
  	/*
  	 * zone reclaim becomes active if more unmapped pages exist.
  	 */
  	unsigned long		min_unmapped_pages;
  	unsigned long		min_slab_pages;
  #endif /* CONFIG_NUMA */

  	/* Write-intensive fields used by page reclaim */
  	ZONE_PADDING(_pad1_)
  	spinlock_t		lru_lock;

  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  	/*
  	 * If memory initialisation on large machines is deferred then this
  	 * is the first PFN that needs to be initialised.
  	 */
  	unsigned long first_deferred_pfn;
  #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */

  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	spinlock_t split_queue_lock;
  	struct list_head split_queue;
  	unsigned long split_queue_len;
  #endif

  	/* Fields commonly accessed by the page reclaim scanner */
  	struct lruvec		lruvec;
  
  	/*
  	 * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
  	 * this node's LRU.  Maintained by the pageout code.
  	 */
  	unsigned int inactive_ratio;
  
  	unsigned long		flags;
  
  	ZONE_PADDING(_pad2_)

  	/* Per-node vmstats */
  	struct per_cpu_nodestat __percpu *per_cpu_nodestats;
  	atomic_long_t		vm_stat[NR_VM_NODE_STAT_ITEMS];

  } 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))

  #define node_start_pfn(nid)	(NODE_DATA(nid)->node_start_pfn)

  #define node_end_pfn(nid) pgdat_end_pfn(NODE_DATA(nid))

  static inline spinlock_t *zone_lru_lock(struct zone *zone)
  {
  	return &zone->zone_pgdat->lru_lock;
  }

  static inline struct lruvec *node_lruvec(struct pglist_data *pgdat)

  {

  	return &pgdat->lruvec;

  }

  static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
  {
  	return pgdat->node_start_pfn + pgdat->node_spanned_pages;
  }
  
  static inline bool pgdat_is_empty(pg_data_t *pgdat)
  {
  	return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
  }

  static inline int zone_id(const struct zone *zone)
  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  
  	return zone - pgdat->node_zones;
  }
  
  #ifdef CONFIG_ZONE_DEVICE
  static inline bool is_dev_zone(const struct zone *zone)
  {
  	return zone_id(zone) == ZONE_DEVICE;
  }
  #else
  static inline bool is_dev_zone(const struct zone *zone)
  {
  	return false;
  }
  #endif

  #include <linux/memory_hotplug.h>

  extern struct mutex zonelists_mutex;

  void build_all_zonelists(pg_data_t *pgdat, struct zone *zone);

  void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx);

  bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
  			 int classzone_idx, unsigned int alloc_flags,
  			 long free_pages);

  bool zone_watermark_ok(struct zone *z, unsigned int order,

  		unsigned long mark, int classzone_idx,
  		unsigned int alloc_flags);

  bool zone_watermark_ok_safe(struct zone *z, unsigned int order,

  		unsigned long mark, int classzone_idx);

  enum memmap_context {
  	MEMMAP_EARLY,
  	MEMMAP_HOTPLUG,
  };

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

  				     unsigned long size);

  extern void lruvec_init(struct lruvec *lruvec);

  static inline struct pglist_data *lruvec_pgdat(struct lruvec *lruvec)

  {

  #ifdef CONFIG_MEMCG

  	return lruvec->pgdat;

  #else

  	return container_of(lruvec, struct pglist_data, lruvec);

  #endif
  }

  extern unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru);

  #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_HAVE_MEMORYLESS_NODES
  int local_memory_node(int node_id);
  #else
  static inline int local_memory_node(int node_id) { return node_id; };
  #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)

  /*
   * Returns true if a zone has pages managed by the buddy allocator.
   * All the reclaim decisions have to use this function rather than
   * populated_zone(). If the whole zone is reserved then we can easily
   * end up with populated_zone() && !managed_zone().
   */
  static inline bool managed_zone(struct zone *zone)
  {
  	return zone->managed_pages;
  }
  
  /* Returns true if a zone has memory */
  static inline bool populated_zone(struct zone *zone)

  {

  	return zone->present_pages;

  }

  extern int movable_zone;

  #ifdef CONFIG_HIGHMEM

  static inline int zone_movable_is_highmem(void)
  {

  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP

  	return movable_zone == ZONE_HIGHMEM;
  #else

  	return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;

  #endif
  }

  #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

  }

  /**
   * 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

  	return is_highmem_idx(zone_idx(zone));

  #else
  	return 0;
  #endif

  }

  /* These two functions are used to setup the per zone pages min values */
  struct ctl_table;

  int min_free_kbytes_sysctl_handler(struct ctl_table *, int,

  					void __user *, size_t *, loff_t *);

  int watermark_scale_factor_sysctl_handler(struct ctl_table *, int,
  					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,

  					void __user *, size_t *, loff_t *);

  int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int,

  					void __user *, size_t *, loff_t *);

  int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,

  			void __user *, size_t *, loff_t *);

  int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,

  			void __user *, size_t *, loff_t *);

  extern int numa_zonelist_order_handler(struct ctl_table *, int,

  			void __user *, size_t *, loff_t *);

  extern char numa_zonelist_order[];
  #define NUMA_ZONELIST_ORDER_LEN 16	/* string buffer size */

  #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

  #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_online_pgdat - helper macro to iterate over all online 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))

  #define for_each_populated_zone(zone)		        \
  	for (zone = (first_online_pgdat())->node_zones; \
  	     zone;					\
  	     zone = next_zone(zone))			\
  		if (!populated_zone(zone))		\
  			; /* do nothing */		\
  		else

  static inline struct zone *zonelist_zone(struct zoneref *zoneref)
  {
  	return zoneref->zone;
  }
  
  static inline int zonelist_zone_idx(struct zoneref *zoneref)
  {
  	return zoneref->zone_idx;
  }
  
  static inline int zonelist_node_idx(struct zoneref *zoneref)
  {
  #ifdef CONFIG_NUMA
  	/* zone_to_nid not available in this context */
  	return zoneref->zone->node;
  #else
  	return 0;
  #endif /* CONFIG_NUMA */
  }

  struct zoneref *__next_zones_zonelist(struct zoneref *z,
  					enum zone_type highest_zoneidx,
  					nodemask_t *nodes);

  /**
   * next_zones_zonelist - Returns the next zone at or below highest_zoneidx within the allowed nodemask using a cursor within a zonelist as a starting point
   * @z - The cursor used as a starting point for the search
   * @highest_zoneidx - The zone index of the highest zone to return
   * @nodes - An optional nodemask to filter the zonelist with

   *
   * This function returns the next zone at or below a given zone index that is
   * within the allowed nodemask using a cursor as the starting point for the

   * search. The zoneref returned is a cursor that represents the current zone
   * being examined. It should be advanced by one before calling
   * next_zones_zonelist again.

   */

  static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,

  					enum zone_type highest_zoneidx,

  					nodemask_t *nodes)
  {
  	if (likely(!nodes && zonelist_zone_idx(z) <= highest_zoneidx))
  		return z;
  	return __next_zones_zonelist(z, highest_zoneidx, nodes);
  }

  /**
   * first_zones_zonelist - Returns the first zone at or below highest_zoneidx within the allowed nodemask in a zonelist
   * @zonelist - The zonelist to search for a suitable zone
   * @highest_zoneidx - The zone index of the highest zone to return
   * @nodes - An optional nodemask to filter the zonelist with
   * @zone - The first suitable zone found is returned via this parameter
   *
   * This function returns the first zone at or below a given zone index that is
   * within the allowed nodemask. The zoneref returned is a cursor that can be

   * used to iterate the zonelist with next_zones_zonelist by advancing it by
   * one before calling.

   */

  static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,

  					enum zone_type highest_zoneidx,

  					nodemask_t *nodes)

  {

  	return next_zones_zonelist(zonelist->_zonerefs,

  							highest_zoneidx, nodes);

  }

  /**
   * for_each_zone_zonelist_nodemask - helper macro to iterate over valid zones in a zonelist at or below a given zone index and within a nodemask
   * @zone - The current zone in the iterator
   * @z - The current pointer within zonelist->zones being iterated
   * @zlist - The zonelist being iterated
   * @highidx - The zone index of the highest zone to return
   * @nodemask - Nodemask allowed by the allocator
   *
   * This iterator iterates though all zones at or below a given zone index and
   * within a given nodemask
   */
  #define for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, nodemask) \

  	for (z = first_zones_zonelist(zlist, highidx, nodemask), zone = zonelist_zone(z);	\

  		zone;							\

  		z = next_zones_zonelist(++z, highidx, nodemask),	\

  			zone = zonelist_zone(z))
  
  #define for_next_zone_zonelist_nodemask(zone, z, zlist, highidx, nodemask) \
  	for (zone = z->zone;	\
  		zone;							\
  		z = next_zones_zonelist(++z, highidx, nodemask),	\
  			zone = zonelist_zone(z))

  
  /**
   * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
   * @zone - The current zone in the iterator
   * @z - The current pointer within zonelist->zones being iterated
   * @zlist - The zonelist being iterated
   * @highidx - The zone index of the highest zone to return
   *
   * This iterator iterates though all zones at or below a given zone index.
   */
  #define for_each_zone_zonelist(zone, z, zlist, highidx) \

  	for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, NULL)

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

  #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \

  	!defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP)

  static inline unsigned long early_pfn_to_nid(unsigned long pfn)
  {
  	return 0;
  }

  #endif

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

  #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 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))

  #define SECTION_BLOCKFLAGS_BITS \

  	((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)

  #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
  #error Allocator MAX_ORDER exceeds SECTION_SIZE
  #endif

  #define pfn_to_section_nr(pfn) ((pfn) >> PFN_SECTION_SHIFT)
  #define section_nr_to_pfn(sec) ((sec) << PFN_SECTION_SHIFT)

  #define SECTION_ALIGN_UP(pfn)	(((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
  #define SECTION_ALIGN_DOWN(pfn)	((pfn) & PAGE_SECTION_MASK)

  struct page;

  struct page_ext;

  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;

  
  	/* See declaration of similar field in struct zone */
  	unsigned long *pageblock_flags;

  #ifdef CONFIG_PAGE_EXTENSION
  	/*

  	 * If SPARSEMEM, pgdat doesn't have page_ext pointer. We use

  	 * section. (see page_ext.h about this.)
  	 */
  	struct page_ext *page_ext;
  	unsigned long pad;
  #endif

  	/*
  	 * WARNING: mem_section must be a power-of-2 in size for the
  	 * calculation and use of SECTION_ROOT_MASK to make sense.
  	 */

  };

  #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	DIV_ROUND_UP(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);

  extern unsigned long usemap_size(void);

  
  /*
   * 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 present_section(struct mem_section *section)

  {

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

  }

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

  }

  #ifndef CONFIG_HAVE_ARCH_PFN_VALID

  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)));

  }

  #endif

  static inline int pfn_present(unsigned long pfn)
  {
  	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
  		return 0;
  	return present_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 */

  /*
   * During memory init memblocks map pfns to nids. The search is expensive and
   * this caches recent lookups. The implementation of __early_pfn_to_nid
   * may treat start/end as pfns or sections.
   */
  struct mminit_pfnnid_cache {
  	unsigned long last_start;
  	unsigned long last_end;
  	int last_nid;
  };

  #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

  #ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
  /*
   * pfn_valid() is meant to be able to tell if a given PFN has valid memmap
   * associated with it or not. In FLATMEM, it is expected that holes always
   * have valid memmap as long as there is valid PFNs either side of the hole.
   * In SPARSEMEM, it is assumed that a valid section has a memmap for the
   * entire section.
   *
   * However, an ARM, and maybe other embedded architectures in the future
   * free memmap backing holes to save memory on the assumption the memmap is
   * never used. The page_zone linkages are then broken even though pfn_valid()
   * returns true. A walker of the full memmap must then do this additional
   * check to ensure the memmap they are looking at is sane by making sure
   * the zone and PFN linkages are still valid. This is expensive, but walkers
   * of the full memmap are extremely rare.
   */

  bool memmap_valid_within(unsigned long pfn,

  					struct page *page, struct zone *zone);
  #else

  static inline bool memmap_valid_within(unsigned long pfn,

  					struct page *page, struct zone *zone)
  {

  	return true;

  }
  #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */

  #endif /* !__GENERATING_BOUNDS.H */

  #endif /* !__ASSEMBLY__ */

  #endif /* _LINUX_MMZONE_H */