Merge branch 'for-3.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj...

[deliverable/linux.git] / include / linux / mmzone.h

#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_RECLAIMABLE,
        MIGRATE_MOVABLE,
        MIGRATE_PCPTYPES,       /* the number of types on the pcp lists */
        MIGRATE_RESERVE = 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
};

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

static inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
{
        BUILD_BUG_ON(PB_migrate_end - PB_migrate != 2);
        return get_pfnblock_flags_mask(page, pfn, 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 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_ALLOC_BATCH,
        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_VMSCAN_IMMEDIATE,    /* Prioritise for reclaim when writeback ends */
        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) */
        NR_DIRTIED,             /* page dirtyings since bootup */
        NR_WRITTEN,             /* page writings since bootup */
        NR_PAGES_SCANNED,       /* pages scanned since last reclaim */
#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
        WORKINGSET_REFAULT,
        WORKINGSET_ACTIVATE,
        WORKINGSET_NODERECLAIM,
        NR_ANON_TRANSPARENT_HUGEPAGES,
        NR_FREE_CMA_PAGES,
        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(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);
}

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

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;
#ifdef CONFIG_MEMCG
        struct zone *zone;
#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
};

#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

struct zone {
        /* Read-mostly fields */

        /* 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.
         */
        long lowmem_reserve[MAX_NR_ZONES];

#ifdef CONFIG_NUMA
        int node;
#endif

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

        struct pglist_data      *zone_pgdat;
        struct per_cpu_pageset __percpu *pageset;

        /*
         * This is a per-zone reserve of pages that should not be
         * considered dirtyable memory.
         */
        unsigned long           dirty_balance_reserve;

#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 */

#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 */

        /* 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;

        /*
         * Number of MIGRATE_RESEVE page block. To maintain for just
         * optimization. Protected by zone->lock.
         */
        int                     nr_migrate_reserve_block;

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

        /*
         * 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;

        ZONE_PADDING(_pad1_)

        /* Write-intensive fields used from the page allocator */
        spinlock_t              lock;

        /* free areas of different sizes */
        struct free_area        free_area[MAX_ORDER];

        /* zone flags, see below */
        unsigned long           flags;

        ZONE_PADDING(_pad2_)

        /* Write-intensive fields used by page reclaim */

        /* Fields commonly accessed by the page reclaim scanner */
        spinlock_t              lru_lock;
        struct lruvec           lruvec;

        /* Evictions & activations on the inactive file list */
        atomic_long_t           inactive_age;

        /*
         * 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

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

typedef enum {
        ZONE_RECLAIM_LOCKED,            /* prevents concurrent reclaim */
        ZONE_OOM_LOCKED,                /* zone is in OOM killer zonelist */
        ZONE_CONGESTED,                 /* zone has many dirty pages backed by
                                         * a congested BDI
                                         */
        ZONE_TAIL_LRU_DIRTY,            /* reclaim scanning has recently found
                                         * many dirty file pages at the tail
                                         * of the LRU.
                                         */
        ZONE_WRITEBACK,                 /* reclaim scanning has recently found
                                         * many pages under writeback
                                         */
        ZONE_FAIR_DEPLETED,             /* fair zone policy batch depleted */
} 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_congested(const struct zone *zone)
{
        return test_bit(ZONE_CONGESTED, &zone->flags);
}

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

static inline int zone_is_reclaim_writeback(const struct zone *zone)
{
        return test_bit(ZONE_WRITEBACK, &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_fair_depleted(const struct zone *zone)
{
        return test_bit(ZONE_FAIR_DEPLETED, &zone->flags);
}

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

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->wait_table;
}

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)

#ifdef CONFIG_NUMA

/*
 * The NUMA zonelists are doubled because 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_HAVE_MEMBLOCK_NODE_MAP
struct node_active_region {
        unsigned long start_pfn;
        unsigned long end_pfn;
        int nid;
};
#endif /* CONFIG_HAVE_MEMBLOCK_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_MEMCG
        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.
         *
         * 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_max_order;
        enum zone_type classzone_idx;
#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
} 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 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;
}

#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, int alloc_flags);
bool zone_watermark_ok_safe(struct zone *z, unsigned 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);

extern void lruvec_init(struct lruvec *lruvec);

static inline struct zone *lruvec_zone(struct lruvec *lruvec)
{
#ifdef CONFIG_MEMCG
        return lruvec->zone;
#else
        return container_of(lruvec, struct zone, lruvec);
#endif
}

#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)

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_HAVE_MEMBLOCK_NODE_MAP)
        return movable_zone == ZONE_HIGHMEM;
#elif defined(CONFIG_HIGHMEM)
        return (ZONE_MOVABLE - 1) == 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
}

/**
 * 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;
        return zone_off == ZONE_HIGHMEM * sizeof(*zone) ||
               (zone_off == ZONE_MOVABLE * sizeof(*zone) &&
                zone_movable_is_highmem());
#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 *);
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 */
}

/**
 * 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
 * @zone - The first suitable zone found is returned via this parameter
 *
 * 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.
 */
struct zoneref *next_zones_zonelist(struct zoneref *z,
                                        enum zone_type highest_zoneidx,
                                        nodemask_t *nodes,
                                        struct zone **zone);

/**
 * 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,
                                        struct zone **zone)
{
        return next_zones_zonelist(zonelist->_zonerefs, highest_zoneidx, nodes,
                                                                zone);
}

/**
 * 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); \
                zone;                                                   \
                z = next_zones_zonelist(++z, highidx, nodemask, &zone)) \

/**
 * 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_cgroup;
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_MEMCG
        /*
         * If !SPARSEMEM, pgdat doesn't have page_cgroup pointer. We use
         * section. (see memcontrol.h/page_cgroup.h about this.)
         */
        struct page_cgroup *page_cgroup;
        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 */

#ifdef CONFIG_NODES_SPAN_OTHER_NODES
bool early_pfn_in_nid(unsigned long pfn, int 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

#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.
 */
int memmap_valid_within(unsigned long pfn,
                                        struct page *page, struct zone *zone);
#else
static inline int memmap_valid_within(unsigned long pfn,
                                        struct page *page, struct zone *zone)
{
        return 1;
}
#endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */

#endif /* !__GENERATING_BOUNDS.H */
#endif /* !__ASSEMBLY__ */
#endif /* _LINUX_MMZONE_H */