include/linux/mmzone.h



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#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 <generated/bounds.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

#define MIGRATE_UNMOVABLE     0
#define MIGRATE_RECLAIMABLE   1
#define MIGRATE_MOVABLE       2
#define MIGRATE_PCPTYPES      3 /* the number of types on the pcp lists */
#define MIGRATE_RESERVE       3
#define MIGRATE_ISOLATE       4 /* can't allocate from here */
#define MIGRATE_TYPES         5

#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;

static inline int get_pageblock_migratetype(struct page *page)
{
	return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
}

struct free_area {
	struct list_head	free_list[MIGRATE_TYPES];
	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_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_MLOCK,		/* mlock()ed pages found and moved off LRU */
	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,
	NR_SLAB_RECLAIMABLE,
	NR_SLAB_UNRECLAIMABLE,
	NR_PAGETABLE,		/* used for pagetables */
	NR_KERNEL_STACK,
	/* Second 128 byte cacheline */
	NR_UNSTABLE_NFS,	/* NFS unstable pages */
	NR_BOUNCE,
	NR_VMSCAN_WRITE,
	NR_WRITEBACK_TEMP,	/* Writeback using temporary buffers */
	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
	NR_SHMEM,		/* shmem pages (included tmpfs/GEM pages) */
#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 };

/*
 * 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(l) for (l = 0; l < NR_LRU_LISTS; l++)

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

static inline int is_file_lru(enum lru_list l)
{
	return (l == LRU_INACTIVE_FILE || l == LRU_ACTIVE_FILE);
}

static inline int is_active_lru(enum lru_list l)
{
	return (l == LRU_ACTIVE_ANON || l == LRU_ACTIVE_FILE);
}

static inline int is_unevictable_lru(enum lru_list l)
{
	return (l == LRU_UNEVICTABLE);
}

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
};

#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,
	__MAX_NR_ZONES
};

#ifndef __GENERATING_BOUNDS_H

/*
 * 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
 */

#if MAX_NR_ZONES < 2
#define ZONES_SHIFT 0
#elif MAX_NR_ZONES <= 2
#define ZONES_SHIFT 1
#elif MAX_NR_ZONES <= 4
#define ZONES_SHIFT 2
#else
#error ZONES_SHIFT -- too many zones configured adjust calculation
#endif

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 refeferenced.
	 * 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];

	/*
	 * accumulated for batching
	 */
	unsigned long		nr_saved_scan[NR_LRU_LISTS];
};

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

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

	/*
	 * 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;
#endif
	struct per_cpu_pageset __percpu *pageset;
	/*
	 * free areas of different sizes
	 */
	spinlock_t		lock;
	int                     all_unreclaimable; /* All pages pinned */
#ifdef CONFIG_MEMORY_HOTPLUG
	/* see spanned/present_pages for more description */
	seqlock_t		span_seqlock;
#endif
	struct free_area	free_area[MAX_ORDER];

#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_PADDING(_pad1_)

	/* Fields commonly accessed by the page reclaim scanner */
	spinlock_t		lru_lock;	
	struct zone_lru {
		struct list_head list;
	} lru[NR_LRU_LISTS];

	struct zone_reclaim_stat reclaim_stat;

	unsigned long		pages_scanned;	   /* since last reclaim */
	unsigned long		flags;		   /* zone flags, see below */

	/* 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()
	 * invocation.
	 *
	 * 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;

	/*
	 * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
	 * this zone's LRU.  Maintained by the pageout code.
	 */
	unsigned int inactive_ratio;


	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;

typedef enum {
	ZONE_RECLAIM_LOCKED,		/* prevents concurrent reclaim */
	ZONE_OOM_LOCKED,		/* zone is in OOM killer zonelist */
} zone_flags_t;

static inline void zone_set_flag(struct zone *zone, zone_flags_t flag)
{
	set_bit(flag, &zone->flags);
}

static inline int zone_test_and_set_flag(struct zone *zone, zone_flags_t flag)
{
	return test_and_set_bit(flag, &zone->flags);
}

static inline void zone_clear_flag(struct zone *zone, zone_flags_t flag)
{
	clear_bit(flag, &zone->flags);
}

static inline int zone_is_reclaim_locked(const struct zone *zone)
{
	return test_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
}

static inline int zone_is_oom_locked(const struct zone *zone)
{
	return test_bit(ZONE_OOM_LOCKED, &zone->flags);
}

/*
 * 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

/*
 * The NUMA zonelists are doubled becausse we need zonelists that restrict the
 * allocations to a single node for GFP_THISNODE.
 *
 * [0]	: Zonelist with fallback
 * [1]	: No fallback (GFP_THISNODE)
 */
#define MAX_ZONELISTS 2


/*
 * 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
#define MAX_ZONELISTS 1
struct zonelist_cache;
#endif

/*
 * 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.
 *
 * 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.
 * *
 * 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 zonelist_cache *zlcache_ptr;		     // NULL or &zlcache
	struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
#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_ZONELISTS];
	int nr_zones;
#ifdef CONFIG_FLAT_NODE_MEM_MAP	/* means !SPARSEMEM */
	struct page *node_mem_map;
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
	struct page_cgroup *node_page_cgroup;
#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.
	 *
	 * 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_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;