xref: /include/linux/mmzone.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MMZONE_H
#define _LINUX_MMZONE_H

#ifndef __ASSEMBLY__
#ifndef __GENERATING_BOUNDS_H

#include <linux/android_kabi.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/list_nulls.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 <linux/mm_types.h>
#include <linux/page-flags.h>
#include <linux/local_lock.h>
#include <linux/zswap.h>
#include <linux/android_kabi.h>
#include <asm/page.h>

/* Free memory management - zoned buddy allocator.  */
#ifndef CONFIG_ARCH_FORCE_MAX_ORDER
#define MAX_PAGE_ORDER 10
#else
#define MAX_PAGE_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
#endif
#define MAX_ORDER_NR_PAGES (1 << MAX_PAGE_ORDER)

#define IS_MAX_ORDER_ALIGNED(pfn) IS_ALIGNED(pfn, MAX_ORDER_NR_PAGES)

#define NR_PAGE_ORDERS (MAX_PAGE_ORDER + 1)

/* Defines the order for the number of pages that have a migrate type. */
#ifndef CONFIG_PAGE_BLOCK_ORDER
#define PAGE_BLOCK_ORDER MAX_PAGE_ORDER
#else
#define PAGE_BLOCK_ORDER CONFIG_PAGE_BLOCK_ORDER
#endif /* CONFIG_PAGE_BLOCK_ORDER */

/*
 * The MAX_PAGE_ORDER, which defines the max order of pages to be allocated
 * by the buddy allocator, has to be larger or equal to the PAGE_BLOCK_ORDER,
 * which defines the order for the number of pages that can have a migrate type
 */
#if (PAGE_BLOCK_ORDER > MAX_PAGE_ORDER)
#error MAX_PAGE_ORDER must be >= PAGE_BLOCK_ORDER
#endif

/*
 * 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 migratetype {
	MIGRATE_UNMOVABLE,
	MIGRATE_MOVABLE,
	MIGRATE_RECLAIMABLE,
	/* the number of types that have fallbacks */
	MIGRATE_FALLBACKS,
#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.
	 */
	MIGRATE_CMA = MIGRATE_FALLBACKS,
	MIGRATE_PCPTYPES,
#else
	/* the number of types on the pcp lists */
	MIGRATE_PCPTYPES = MIGRATE_FALLBACKS,
#endif
	MIGRATE_HIGHATOMIC = MIGRATE_PCPTYPES,
#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 const 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)
#  define is_migrate_cma_folio(folio, pfn)	(MIGRATE_CMA ==		\
	get_pfnblock_flags_mask(&folio->page, pfn, MIGRATETYPE_MASK))
#  define get_cma_migrate_type() MIGRATE_CMA
#else
#  define is_migrate_cma(migratetype) false
#  define is_migrate_cma_page(_page) false
#  define is_migrate_cma_folio(folio, pfn) false
#  define get_cma_migrate_type() MIGRATE_MOVABLE
#endif

static inline bool is_migrate_movable(int mt)
{
	return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE;
}

/*
 * Check whether a migratetype can be merged with another migratetype.
 *
 * It is only mergeable when it can fall back to other migratetypes for
 * allocation. See fallbacks[MIGRATE_TYPES][3] in page_alloc.c.
 */
static inline bool migratetype_is_mergeable(int mt)
{
	return mt < MIGRATE_FALLBACKS;
}

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

extern int page_group_by_mobility_disabled;

#define MIGRATETYPE_MASK ((1UL << PB_migratetype_bits) - 1)

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

#define folio_migratetype(folio)				\
	get_pfnblock_flags_mask(&folio->page, folio_pfn(folio),		\
			MIGRATETYPE_MASK)
struct free_area {
	struct list_head	free_list[MIGRATE_TYPES];
	unsigned long		nr_free;
};

struct pglist_data;

#ifdef CONFIG_NUMA
enum numa_stat_item {
	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 */
	NR_VM_NUMA_EVENT_ITEMS
};
#else
#define NR_VM_NUMA_EVENT_ITEMS 0
#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 */
	/* Second 128 byte cacheline */
	NR_BOUNCE,
	NR_ZSPAGES,		/* allocated in zsmalloc */
	NR_FREE_CMA_PAGES,
#ifdef CONFIG_UNACCEPTED_MEMORY
	NR_UNACCEPTED,
#endif
	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_SLAB_RECLAIMABLE_B,
	NR_SLAB_UNRECLAIMABLE_B,
	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
	WORKINGSET_NODES,
	WORKINGSET_REFAULT_BASE,
	WORKINGSET_REFAULT_ANON = WORKINGSET_REFAULT_BASE,
	WORKINGSET_REFAULT_FILE,
	WORKINGSET_ACTIVATE_BASE,
	WORKINGSET_ACTIVATE_ANON = WORKINGSET_ACTIVATE_BASE,
	WORKINGSET_ACTIVATE_FILE,
	WORKINGSET_RESTORE_BASE,
	WORKINGSET_RESTORE_ANON = WORKINGSET_RESTORE_BASE,
	WORKINGSET_RESTORE_FILE,
	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_FILE_THPS,
	NR_FILE_PMDMAPPED,
	NR_ANON_THPS,
	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_THROTTLED_WRITTEN,	/* NR_WRITTEN while reclaim throttled */
	NR_KERNEL_MISC_RECLAIMABLE,	/* reclaimable non-slab kernel pages */
	NR_FOLL_PIN_ACQUIRED,	/* via: pin_user_page(), gup flag: FOLL_PIN */
	NR_FOLL_PIN_RELEASED,	/* pages returned via unpin_user_page() */
	NR_KERNEL_STACK_KB,	/* measured in KiB */
#if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
	NR_KERNEL_SCS_KB,	/* measured in KiB */
#endif
	NR_PAGETABLE,		/* used for pagetables */
	NR_SECONDARY_PAGETABLE, /* secondary pagetables, KVM & IOMMU */
#ifdef CONFIG_IOMMU_SUPPORT
	NR_IOMMU_PAGES,		/* # of pages allocated by IOMMU */
#endif
#ifdef CONFIG_SWAP
	NR_SWAPCACHE,
#endif
#ifdef CONFIG_NUMA_BALANCING
	PGPROMOTE_SUCCESS,	/* promote successfully */
	PGPROMOTE_CANDIDATE,	/* candidate pages to promote */
#endif
	/* PGDEMOTE_*: pages demoted */
	PGDEMOTE_KSWAPD,
	PGDEMOTE_DIRECT,
	PGDEMOTE_KHUGEPAGED,
	NR_VM_NODE_STAT_ITEMS
};

/*
 * Returns true if the item should be printed in THPs (/proc/vmstat
 * currently prints number of anon, file and shmem THPs. But the item
 * is charged in pages).
 */
static __always_inline bool vmstat_item_print_in_thp(enum node_stat_item item)
{
	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
		return false;

	return item == NR_ANON_THPS ||
	       item == NR_FILE_THPS ||
	       item == NR_SHMEM_THPS ||
	       item == NR_SHMEM_PMDMAPPED ||
	       item == NR_FILE_PMDMAPPED;
}

/*
 * Returns true if the value is measured in bytes (most vmstat values are
 * measured in pages). This defines the API part, the internal representation
 * might be different.
 */
static __always_inline bool vmstat_item_in_bytes(int idx)
{
	/*
	 * Global and per-node slab counters track slab pages.
	 * It's expected that changes are multiples of PAGE_SIZE.
	 * Internally values are stored in pages.
	 *
	 * Per-memcg and per-lruvec counters track memory, consumed
	 * by individual slab objects. These counters are actually
	 * byte-precise.
	 */
	return (idx == NR_SLAB_RECLAIMABLE_B ||
		idx == NR_SLAB_UNRECLAIMABLE_B);
}

/*
 * 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
};

enum vmscan_throttle_state {
	VMSCAN_THROTTLE_WRITEBACK,
	VMSCAN_THROTTLE_ISOLATED,
	VMSCAN_THROTTLE_NOPROGRESS,
	VMSCAN_THROTTLE_CONGESTED,
	NR_VMSCAN_THROTTLE,
};

#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 bool is_file_lru(enum lru_list lru)
{
	return (lru == LRU_INACTIVE_FILE || lru == LRU_ACTIVE_FILE);
}

static inline bool is_active_lru(enum lru_list lru)
{
	return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
}

#define WORKINGSET_ANON 0
#define WORKINGSET_FILE 1
#define ANON_AND_FILE 2

enum lruvec_flags {
	/*
	 * An lruvec has many dirty pages backed by a congested BDI:
	 * 1. LRUVEC_CGROUP_CONGESTED is set by cgroup-level reclaim.
	 *    It can be cleared by cgroup reclaim or kswapd.
	 * 2. LRUVEC_NODE_CONGESTED is set by kswapd node-level reclaim.
	 *    It can only be cleared by kswapd.
	 *
	 * Essentially, kswapd can unthrottle an lruvec throttled by cgroup
	 * reclaim, but not vice versa. This only applies to the root cgroup.
	 * The goal is to prevent cgroup reclaim on the root cgroup (e.g.
	 * memory.reclaim) to unthrottle an unbalanced node (that was throttled
	 * by kswapd).
	 */
	LRUVEC_CGROUP_CONGESTED,
	LRUVEC_NODE_CONGESTED,
};

#endif /* !__GENERATING_BOUNDS_H */

/*
 * Evictable folios are divided into multiple generations. The youngest and the
 * oldest generation numbers, max_seq and min_seq, are monotonically increasing.
 * They form a sliding window of a variable size [MIN_NR_GENS, MAX_NR_GENS]. An
 * offset within MAX_NR_GENS, i.e., gen, indexes the LRU list of the
 * corresponding generation. The gen counter in folio->flags stores gen+1 while
 * a folio is on one of lrugen->folios[]. Otherwise it stores 0.
 *
 * After a folio is faulted in, the aging needs to check the accessed bit at
 * least twice before handing this folio over to the eviction. The first check
 * clears the accessed bit from the initial fault; the second check makes sure
 * this folio hasn't been used since then. This process, AKA second chance,
 * requires a minimum of two generations, hence MIN_NR_GENS. And to maintain ABI
 * compatibility with the active/inactive LRU, e.g., /proc/vmstat, these two
 * generations are considered active; the rest of generations, if they exist,
 * are considered inactive. See lru_gen_is_active().
 *
 * PG_active is always cleared while a folio is on one of lrugen->folios[] so
 * that the sliding window needs not to worry about it. And it's set again when
 * a folio considered active is isolated for non-reclaiming purposes, e.g.,
 * migration. See lru_gen_add_folio() and lru_gen_del_folio().
 *
 * MAX_NR_GENS is set to 4 so that the multi-gen LRU can support twice the
 * number of categories of the active/inactive LRU when keeping track of
 * accesses through page tables. This requires order_base_2(MAX_NR_GENS+1) bits
 * in folio->flags, masked by LRU_GEN_MASK.
 */
#define MIN_NR_GENS		2U
#define MAX_NR_GENS		4U

/*
 * Each generation is divided into multiple tiers. A folio accessed N times
 * through file descriptors is in tier order_base_2(N). A folio in the first
 * tier (N=0,1) is marked by PG_referenced unless it was faulted in through page
 * tables or read ahead. A folio in the last tier (MAX_NR_TIERS-1) is marked by
 * PG_workingset. A folio in any other tier (1<N<5) between the first and last
 * is marked by additional bits of LRU_REFS_WIDTH in folio->flags.
 *
 * In contrast to moving across generations which requires the LRU lock, moving
 * across tiers only involves atomic operations on folio->flags and therefore
 * has a negligible cost in the buffered access path. In the eviction path,
 * comparisons of refaulted/(evicted+protected) from the first tier and the rest
 * infer whether folios accessed multiple times through file descriptors are
 * statistically hot and thus worth protecting.
 *
 * MAX_NR_TIERS is set to 4 so that the multi-gen LRU can support twice the
 * number of categories of the active/inactive LRU when keeping track of
 * accesses through file descriptors. This uses MAX_NR_TIERS-2 spare bits in
 * folio->flags, masked by LRU_REFS_MASK.
 */
#define MAX_NR_TIERS		4U

#ifndef __GENERATING_BOUNDS_H

#define LRU_GEN_MASK		((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF)
#define LRU_REFS_MASK		((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF)

/*
 * For folios accessed multiple times through file descriptors,
 * lru_gen_inc_refs() sets additional bits of LRU_REFS_WIDTH in folio->flags
 * after PG_referenced, then PG_workingset after LRU_REFS_WIDTH. After all its
 * bits are set, i.e., LRU_REFS_FLAGS|BIT(PG_workingset), a folio is lazily
 * promoted into the second oldest generation in the eviction path. And when
 * folio_inc_gen() does that, it clears LRU_REFS_FLAGS so that
 * lru_gen_inc_refs() can start over. Note that for this case, LRU_REFS_MASK is
 * only valid when PG_referenced is set.
 *
 * For folios accessed multiple times through page tables, folio_update_gen()
 * from a page table walk or lru_gen_set_refs() from a rmap walk sets
 * PG_referenced after the accessed bit is cleared for the first time.
 * Thereafter, those two paths set PG_workingset and promote folios to the
 * youngest generation. Like folio_inc_gen(), folio_update_gen() also clears
 * PG_referenced. Note that for this case, LRU_REFS_MASK is not used.
 *
 * For both cases above, after PG_workingset is set on a folio, it remains until
 * this folio is either reclaimed, or "deactivated" by lru_gen_clear_refs(). It
 * can be set again if lru_gen_test_recent() returns true upon a refault.
 */
#define LRU_REFS_FLAGS		(LRU_REFS_MASK | BIT(PG_referenced))

struct lruvec;
struct page_vma_mapped_walk;

#ifdef CONFIG_LRU_GEN

enum {
	LRU_GEN_ANON,
	LRU_GEN_FILE,
};

enum {
	LRU_GEN_CORE,
	LRU_GEN_MM_WALK,
	LRU_GEN_NONLEAF_YOUNG,
	NR_LRU_GEN_CAPS
};

#define MIN_LRU_BATCH		BITS_PER_LONG
#define MAX_LRU_BATCH		(MIN_LRU_BATCH * 64)

/* whether to keep historical stats from evicted generations */
#ifdef CONFIG_LRU_GEN_STATS
#define NR_HIST_GENS		MAX_NR_GENS
#else
#define NR_HIST_GENS		1U
#endif

/*
 * The youngest generation number is stored in max_seq for both anon and file
 * types as they are aged on an equal footing. The oldest generation numbers are
 * stored in min_seq[] separately for anon and file types so that they can be
 * incremented independently. Ideally min_seq[] are kept in sync when both anon
 * and file types are evictable. However, to adapt to situations like extreme
 * swappiness, they are allowed to be out of sync by at most
 * MAX_NR_GENS-MIN_NR_GENS-1.
 *
 * The number of pages in each generation is eventually consistent and therefore
 * can be transiently negative when reset_batch_size() is pending.
 */
struct lru_gen_folio {
	/* the aging increments the youngest generation number */
	unsigned long max_seq;
	/* the eviction increments the oldest generation numbers */
	unsigned long min_seq[ANON_AND_FILE];
	/* the birth time of each generation in jiffies */
	unsigned long timestamps[MAX_NR_GENS];
	/* the multi-gen LRU lists, lazily sorted on eviction */
	struct list_head folios[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES];
	/* the multi-gen LRU sizes, eventually consistent */
	long nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES];
	/* the exponential moving average of refaulted */
	unsigned long avg_refaulted[ANON_AND_FILE][MAX_NR_TIERS];
	/* the exponential moving average of evicted+protected */
	unsigned long avg_total[ANON_AND_FILE][MAX_NR_TIERS];
	/* can only be modified under the LRU lock */
	unsigned long protected[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS];
	/* can be modified without holding the LRU lock */
	atomic_long_t evicted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS];
	atomic_long_t refaulted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS];
	/* whether the multi-gen LRU is enabled */
	bool enabled;
	/* the memcg generation this lru_gen_folio belongs to */
	u8 gen;
	/* the list segment this lru_gen_folio belongs to */
	u8 seg;
	/* per-node lru_gen_folio list for global reclaim */
	struct hlist_nulls_node list;

	ANDROID_KABI_RESERVE(1);
	ANDROID_KABI_RESERVE(2);
	ANDROID_OEM_DATA_ARRAY(1, 6);
};

enum {
	MM_LEAF_TOTAL,		/* total leaf entries */
	MM_LEAF_YOUNG,		/* young leaf entries */
	MM_NONLEAF_FOUND,	/* non-leaf entries found in Bloom filters */
	MM_NONLEAF_ADDED,	/* non-leaf entries added to Bloom filters */
	NR_MM_STATS
};

/* double-buffering Bloom filters */
#define NR_BLOOM_FILTERS	2

struct lru_gen_mm_state {
	/* synced with max_seq after each iteration */
	unsigned long seq;
	/* where the current iteration continues after */
	struct list_head *head;
	/* where the last iteration ended before */
	struct list_head *tail;
	/* Bloom filters flip after each iteration */
	unsigned long *filters[NR_BLOOM_FILTERS];
	/* the mm stats for debugging */
	unsigned long stats[NR_HIST_GENS][NR_MM_STATS];

	ANDROID_KABI_RESERVE(1);
};

struct lru_gen_mm_walk {
	/* the lruvec under reclaim */
	struct lruvec *lruvec;
	/* max_seq from lru_gen_folio: can be out of date */
	unsigned long seq;
	/* the next address within an mm to scan */
	unsigned long next_addr;
	/* to batch promoted pages */
	int nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES];
	/* to batch the mm stats */
	int mm_stats[NR_MM_STATS];
	/* total batched items */
	int batched;
	int swappiness;
	bool force_scan;

	ANDROID_KABI_RESERVE(1);
};

/*
 * For each node, memcgs are divided into two generations: the old and the
 * young. For each generation, memcgs are randomly sharded into multiple bins
 * to improve scalability. For each bin, the hlist_nulls is virtually divided
 * into three segments: the head, the tail and the default.
 *
 * An onlining memcg is added to the tail of a random bin in the old generation.
 * The eviction starts at the head of a random bin in the old generation. The
 * per-node memcg generation counter, whose reminder (mod MEMCG_NR_GENS) indexes
 * the old generation, is incremented when all its bins become empty.
 *
 * There are four operations:
 * 1. MEMCG_LRU_HEAD, which moves a memcg to the head of a random bin in its
 *    current generation (old or young) and updates its "seg" to "head";
 * 2. MEMCG_LRU_TAIL, which moves a memcg to the tail of a random bin in its
 *    current generation (old or young) and updates its "seg" to "tail";
 * 3. MEMCG_LRU_OLD, which moves a memcg to the head of a random bin in the old
 *    generation, updates its "gen" to "old" and resets its "seg" to "default";
 * 4. MEMCG_LRU_YOUNG, which moves a memcg to the tail of a random bin in the
 *    young generation, updates its "gen" to "young" and resets its "seg" to
 *    "default".
 *
 * The events that trigger the above operations are:
 * 1. Exceeding the soft limit, which triggers MEMCG_LRU_HEAD;
 * 2. The first attempt to reclaim a memcg below low, which triggers
 *    MEMCG_LRU_TAIL;
 * 3. The first attempt to reclaim a memcg offlined or below reclaimable size
 *    threshold, which triggers MEMCG_LRU_TAIL;
 * 4. The second attempt to reclaim a memcg offlined or below reclaimable size
 *    threshold, which triggers MEMCG_LRU_YOUNG;
 * 5. Attempting to reclaim a memcg below min, which triggers MEMCG_LRU_YOUNG;
 * 6. Finishing the aging on the eviction path, which triggers MEMCG_LRU_YOUNG;
 * 7. Offlining a memcg, which triggers MEMCG_LRU_OLD.
 *
 * Notes:
 * 1. Memcg LRU only applies to global reclaim, and the round-robin incrementing
 *    of their max_seq counters ensures the eventual fairness to all eligible
 *    memcgs. For memcg reclaim, it still relies on mem_cgroup_iter().
 * 2. There are only two valid generations: old (seq) and young (seq+1).
 *    MEMCG_NR_GENS is set to three so that when reading the generation counter
 *    locklessly, a stale value (seq-1) does not wraparound to young.
 */
#define MEMCG_NR_GENS	3
#define MEMCG_NR_BINS	8

struct lru_gen_memcg {
	/* the per-node memcg generation counter */
	unsigned long seq;
	/* each memcg has one lru_gen_folio per node */
	unsigned long nr_memcgs[MEMCG_NR_GENS];
	/* per-node lru_gen_folio list for global reclaim */
	struct hlist_nulls_head	fifo[MEMCG_NR_GENS][MEMCG_NR_BINS];
	/* protects the above */
	spinlock_t lock;
};

void lru_gen_init_pgdat(struct pglist_data *pgdat);
void lru_gen_init_lruvec(struct lruvec *lruvec);
bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw);

void lru_gen_init_memcg(struct mem_cgroup *memcg);
void lru_gen_exit_memcg(struct mem_cgroup *memcg);
void lru_gen_online_memcg(struct mem_cgroup *memcg);
void lru_gen_offline_memcg(struct mem_cgroup *memcg);
void lru_gen_release_memcg(struct mem_cgroup *memcg);
void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid);

#else /* !CONFIG_LRU_GEN */

static inline void lru_gen_init_pgdat(struct pglist_data *pgdat)
{
}

static inline void lru_gen_init_lruvec(struct lruvec *lruvec)
{
}

static inline bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
{
	return false;
}

static inline void lru_gen_init_memcg(struct mem_cgroup *memcg)
{
}

static inline void lru_gen_exit_memcg(struct mem_cgroup *memcg)
{
}

static inline void lru_gen_online_memcg(struct mem_cgroup *memcg)
{
}

static inline void lru_gen_offline_memcg(struct mem_cgroup *memcg)
{
}

static inline void lru_gen_release_memcg(struct mem_cgroup *memcg)
{
}

static inline void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid)
{
}

#endif /* CONFIG_LRU_GEN */

struct lruvec {
	struct list_head		lists[NR_LRU_LISTS];
	/* per lruvec lru_lock for memcg */
	spinlock_t			lru_lock;
	/*
	 * These track the cost of reclaiming one LRU - file or anon -
	 * over the other. As the observed cost of reclaiming one LRU
	 * increases, the reclaim scan balance tips toward the other.
	 */
	unsigned long			anon_cost;
	unsigned long			file_cost;
	/* Non-resident age, driven by LRU movement */
	atomic_long_t			nonresident_age;
	/* Refaults at the time of last reclaim cycle */
	unsigned long			refaults[ANON_AND_FILE];
	/* Various lruvec state flags (enum lruvec_flags) */
	unsigned long			flags;
#ifdef CONFIG_LRU_GEN
	/* evictable pages divided into generations */
	struct lru_gen_folio		lrugen;
#ifdef CONFIG_LRU_GEN_WALKS_MMU
	/* to concurrently iterate lru_gen_mm_list */
	struct lru_gen_mm_state		mm_state;
#endif
#endif /* CONFIG_LRU_GEN */
#ifdef CONFIG_MEMCG
	struct pglist_data *pgdat;
#endif
	struct zswap_lruvec_state zswap_lruvec_state;

	ANDROID_BACKPORT_RESERVE(1);
};

/* 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,
	WMARK_PROMO,
	NR_WMARK
};

/*
 * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. Two additional lists
 * are added for THP. One PCP list is used by GPF_MOVABLE, and the other PCP list
 * is used by GFP_UNMOVABLE and GFP_RECLAIMABLE.
 */
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define NR_PCP_THP 2
#else
#define NR_PCP_THP 0
#endif
#define NR_LOWORDER_PCP_LISTS (MIGRATE_PCPTYPES * (PAGE_ALLOC_COSTLY_ORDER + 1))
#define NR_PCP_LISTS (NR_LOWORDER_PCP_LISTS + NR_PCP_THP)

/*
 * Flags used in pcp->flags field.
 *
 * PCPF_PREV_FREE_HIGH_ORDER: a high-order page is freed in the
 * previous page freeing.  To avoid to drain PCP for an accident
 * high-order page freeing.
 *
 * PCPF_FREE_HIGH_BATCH: preserve "pcp->batch" pages in PCP before
 * draining PCP for consecutive high-order pages freeing without
 * allocation if data cache slice of CPU is large enough.  To reduce
 * zone lock contention and keep cache-hot pages reusing.
 */
#define	PCPF_PREV_FREE_HIGH_ORDER	BIT(0)
#define	PCPF_FREE_HIGH_BATCH		BIT(1)

struct per_cpu_pages {
	spinlock_t lock;	/* Protects lists field */
	int count;		/* number of pages in the list */
	int high;		/* high watermark, emptying needed */
	int high_min;		/* min high watermark */
	int high_max;		/* max high watermark */
	int batch;		/* chunk size for buddy add/remove */
	u8 flags;		/* protected by pcp->lock */
	u8 alloc_factor;	/* batch scaling factor during allocate */
#ifdef CONFIG_NUMA
	u8 expire;		/* When 0, remote pagesets are drained */
#endif
	short free_count;	/* consecutive free count */

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

struct per_cpu_zonestat {
#ifdef CONFIG_SMP
	s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
	s8 stat_threshold;
#endif
#ifdef CONFIG_NUMA
	/*
	 * Low priority inaccurate counters that are only folded
	 * on demand. Use a large type to avoid the overhead of
	 * folding during refresh_cpu_vm_stats.
	 */
	unsigned long vm_numa_event[NR_VM_NUMA_EVENT_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 {
	/*
	 * ZONE_DMA and ZONE_DMA32 are used when there are peripherals not able
	 * to DMA to all of the addressable memory (ZONE_NORMAL).
	 * On architectures where this area covers the whole 32 bit address
	 * space ZONE_DMA32 is used. ZONE_DMA is left for the ones with smaller
	 * DMA addressing constraints. This distinction is important as a 32bit
	 * DMA mask is assumed when ZONE_DMA32 is defined. Some 64-bit
	 * platforms may need both zones as they support peripherals with
	 * different DMA addressing limitations.
	 */
#ifdef CONFIG_ZONE_DMA
	ZONE_DMA,
#endif
#ifdef CONFIG_ZONE_DMA32
	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 is similar to ZONE_NORMAL, except that it contains
	 * movable pages with few exceptional cases described below. Main use
	 * cases for ZONE_MOVABLE are to make memory offlining/unplug more
	 * likely to succeed, and to locally limit unmovable allocations - e.g.,
	 * to increase the number of THP/huge pages. Notable special cases are:
	 *
	 * 1. Pinned pages: (long-term) pinning of movable pages might
	 *    essentially turn such pages unmovable. Therefore, we do not allow
	 *    pinning long-term pages in ZONE_MOVABLE. When pages are pinned and
	 *    faulted, they come from the right zone right away. However, it is
	 *    still possible that address space already has pages in
	 *    ZONE_MOVABLE at the time when pages are pinned (i.e. user has
	 *    touches that memory before pinning). In such case we migrate them
	 *    to a different zone. When migration fails - pinning fails.
	 * 2. memblock allocations: kernelcore/movablecore setups might create
	 *    situations where ZONE_MOVABLE contains unmovable allocations
	 *    after boot. Memory offlining and allocations fail early.
	 * 3. Memory holes: kernelcore/movablecore setups might create very rare
	 *    situations where ZONE_MOVABLE contains memory holes after boot,
	 *    for example, if we have sections that are only partially
	 *    populated. Memory offlining and allocations fail early.
	 * 4. PG_hwpoison pages: while poisoned pages can be skipped during
	 *    memory offlining, such pages cannot be allocated.
	 * 5. Unmovable PG_offline pages: in paravirtualized environments,
	 *    hotplugged memory blocks might only partially be managed by the
	 *    buddy (e.g., via XEN-balloon, Hyper-V balloon, virtio-mem). The
	 *    parts not manged by the buddy are unmovable PG_offline pages. In
	 *    some cases (virtio-mem), such pages can be skipped during
	 *    memory offlining, however, cannot be moved/allocated. These
	 *    techniques might use alloc_contig_range() to hide previously
	 *    exposed pages from the buddy again (e.g., to implement some sort
	 *    of memory unplug in virtio-mem).
	 * 6. ZERO_PAGE(0), kernelcore/movablecore setups might create
	 *    situations where ZERO_PAGE(0) which is allocated differently
	 *    on different platforms may end up in a movable zone. ZERO_PAGE(0)
	 *    cannot be migrated.
	 * 7. Memory-hotplug: when using memmap_on_memory and onlining the
	 *    memory to the MOVABLE zone, the vmemmap pages are also placed in
	 *    such zone. Such pages cannot be really moved around as they are
	 *    self-stored in the range, but they are treated as movable when
	 *    the range they describe is about to be offlined.
	 *
	 * In general, no unmovable allocations that degrade memory offlining
	 * should end up in ZONE_MOVABLE. Allocators (like alloc_contig_range())
	 * have to expect that migrating pages in ZONE_MOVABLE can fail (even
	 * if has_unmovable_pages() states that there are no unmovable pages,
	 * there can be false negatives).
	 */
	ZONE_MOVABLE,
#ifdef CONFIG_ZONE_DEVICE
	ZONE_DEVICE,
#endif
	__MAX_NR_ZONES

};

#ifndef __GENERATING_BOUNDS_H

#define ASYNC_AND_SYNC 2

struct zone {
	/* Read-mostly fields */

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

	unsigned long nr_reserved_highatomic;
	unsigned long nr_free_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_pages	__percpu *per_cpu_pageset;
	struct per_cpu_zonestat	__percpu *per_cpu_zonestats;
	/*
	 * the high and batch values are copied to individual pagesets for
	 * faster access
	 */
	int pageset_high_min;
	int pageset_high_max;
	int pageset_batch;

#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);
	 *
	 * present_early_pages is present pages existing within the zone
	 * located on memory available since early boot, excluding hotplugged
	 * memory.
	 *
	 * 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;
	 *
	 * cma pages is present pages that are assigned for CMA use
	 * (MIGRATE_CMA).
	 *
	 * 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/done(). Any reader who can't tolerant drift of
	 * present_pages should use get_online_mems() to get a stable value.
	 */
	atomic_long_t		managed_pages;
	unsigned long		spanned_pages;
	unsigned long		present_pages;
#if defined(CONFIG_MEMORY_HOTPLUG)
	unsigned long		present_early_pages;
#endif
#ifdef CONFIG_CMA
	unsigned long		cma_pages;
#endif

	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 */
	CACHELINE_PADDING(_pad1_);

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

#ifdef CONFIG_UNACCEPTED_MEMORY
	/* Pages to be accepted. All pages on the list are MAX_PAGE_ORDER */
	struct list_head	unaccepted_pages;
#endif

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

	/* Primarily protects free_area */
	spinlock_t		lock;

	/* Write-intensive fields used by compaction and vmstats. */
	CACHELINE_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 compaction migration scanner should start */
	unsigned long		compact_cached_migrate_pfn[ASYNC_AND_SYNC];
	unsigned long		compact_init_migrate_pfn;
	unsigned long		compact_init_free_pfn;
#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.
	 * compact_order_failed is the minimum compaction failed order.
	 */
	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;

	CACHELINE_PADDING(_pad3_);
	/* Zone statistics */
	atomic_long_t		vm_stat[NR_VM_ZONE_STAT_ITEMS];
	atomic_long_t		vm_numa_event[NR_VM_NUMA_EVENT_ITEMS];
} ____cacheline_internodealigned_in_smp;

enum pgdat_flags {
	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 */
};

enum zone_flags {
	ZONE_BOOSTED_WATERMARK,		/* zone recently boosted watermarks.
					 * Cleared when kswapd is woken.
					 */
	ZONE_RECLAIM_ACTIVE,		/* kswapd may be scanning the zone. */
	ZONE_BELOW_HIGH,		/* zone is below high watermark. */
};

static inline unsigned long wmark_pages(const struct zone *z,
					enum zone_watermarks w)
{
	return z->_watermark[w] + z->watermark_boost;
}

static inline unsigned long min_wmark_pages(const struct zone *z)
{
	return wmark_pages(z, WMARK_MIN);
}

static inline unsigned long low_wmark_pages(const struct zone *z)
{
	return wmark_pages(z, WMARK_LOW);
}

static inline unsigned long high_wmark_pages(const struct zone *z)
{
	return wmark_pages(z, WMARK_HIGH);
}

static inline unsigned long promo_wmark_pages(const struct zone *z)
{
	return wmark_pages(z, WMARK_PROMO);
}

static inline unsigned long zone_managed_pages(struct zone *zone)
{
	return (unsigned long)atomic_long_read(&zone->managed_pages);
}

static inline unsigned long zone_cma_pages(struct zone *zone)
{
#ifdef CONFIG_CMA
	return zone->cma_pages;
#else
	return 0;
#endif
}

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;
}

#ifndef BUILD_VDSO32_64
/*
 * The zone field is never updated after free_area_init_core()
 * sets it, so none of the operations on it need to be atomic.
 */

/* Page flags: | [SECTION] | [NODE] | ZONE | [LAST_CPUPID] | ... | FLAGS | */
#define SECTIONS_PGOFF		((sizeof(unsigned long)*8) - SECTIONS_WIDTH)
#define NODES_PGOFF		(SECTIONS_PGOFF - NODES_WIDTH)
#define ZONES_PGOFF		(NODES_PGOFF - ZONES_WIDTH)
#define LAST_CPUPID_PGOFF	(ZONES_PGOFF - LAST_CPUPID_WIDTH)
#define KASAN_TAG_PGOFF		(LAST_CPUPID_PGOFF - KASAN_TAG_WIDTH)
#define LRU_GEN_PGOFF		(KASAN_TAG_PGOFF - LRU_GEN_WIDTH)
#define LRU_REFS_PGOFF		(LRU_GEN_PGOFF - LRU_REFS_WIDTH)

/*
 * Define the bit shifts to access each section.  For non-existent
 * sections we define the shift as 0; that plus a 0 mask ensures
 * the compiler will optimise away reference to them.
 */
#define SECTIONS_PGSHIFT	(SECTIONS_PGOFF * (SECTIONS_WIDTH != 0))
#define NODES_PGSHIFT		(NODES_PGOFF * (NODES_WIDTH != 0))
#define ZONES_PGSHIFT		(ZONES_PGOFF * (ZONES_WIDTH != 0))
#define LAST_CPUPID_PGSHIFT	(LAST_CPUPID_PGOFF * (LAST_CPUPID_WIDTH != 0))
#define KASAN_TAG_PGSHIFT	(KASAN_TAG_PGOFF * (KASAN_TAG_WIDTH != 0))

/* NODE:ZONE or SECTION:ZONE is used to ID a zone for the buddy allocator */
#ifdef NODE_NOT_IN_PAGE_FLAGS
#define ZONEID_SHIFT		(SECTIONS_SHIFT + ZONES_SHIFT)
#define ZONEID_PGOFF		((SECTIONS_PGOFF < ZONES_PGOFF) ? \
						SECTIONS_PGOFF : ZONES_PGOFF)
#else
#define ZONEID_SHIFT		(NODES_SHIFT + ZONES_SHIFT)
#define ZONEID_PGOFF		((NODES_PGOFF < ZONES_PGOFF) ? \
						NODES_PGOFF : ZONES_PGOFF)
#endif

#define ZONEID_PGSHIFT		(ZONEID_PGOFF * (ZONEID_SHIFT != 0))

#define ZONES_MASK		((1UL << ZONES_WIDTH) - 1)
#define NODES_MASK		((1UL << NODES_WIDTH) - 1)
#define SECTIONS_MASK		((1UL << SECTIONS_WIDTH) - 1)
#define LAST_CPUPID_MASK	((1UL << LAST_CPUPID_SHIFT) - 1)
#define KASAN_TAG_MASK		((1UL << KASAN_TAG_WIDTH) - 1)
#define ZONEID_MASK		((1UL << ZONEID_SHIFT) - 1)

static inline enum zone_type page_zonenum(const struct page *page)
{
	ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT);
	return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
}

static inline enum zone_type folio_zonenum(const struct folio *folio)
{
	return page_zonenum(&folio->page);
}

#ifdef CONFIG_ZONE_DEVICE
static inline bool is_zone_device_page(const struct page *page)
{
	return page_zonenum(page) == ZONE_DEVICE;
}

/*
 * Consecutive zone device pages should not be merged into the same sgl
 * or bvec segment with other types of pages or if they belong to different
 * pgmaps. Otherwise getting the pgmap of a given segment is not possible
 * without scanning the entire segment. This helper returns true either if
 * both pages are not zone device pages or both pages are zone device pages
 * with the same pgmap.
 */
static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
						     const struct page *b)
{
	if (is_zone_device_page(a) != is_zone_device_page(b))
		return false;
	if (!is_zone_device_page(a))
		return true;
	return a->pgmap == b->pgmap;
}

extern void memmap_init_zone_device(struct zone *, unsigned long,
				    unsigned long, struct dev_pagemap *);
#else
static inline bool is_zone_device_page(const struct page *page)
{
	return false;
}
static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
						     const struct page *b)
{
	return true;
}
#endif

static inline bool folio_is_zone_device(const struct folio *folio)
{
	return is_zone_device_page(&folio->page);
}

static inline bool is_zone_movable_page(const struct page *page)
{
	return page_zonenum(page) == ZONE_MOVABLE;
}

static inline bool folio_is_zone_movable(const struct folio *folio)
{
	return folio_zonenum(folio) == ZONE_MOVABLE;
}
#endif

/*
 * Return true if [start_pfn, start_pfn + nr_pages) range has a non-empty
 * intersection with the given zone
 */
static inline bool zone_intersects(struct zone *zone,
		unsigned long start_pfn, unsigned long nr_pages)
{
	if (zone_is_empty(zone))
		return false;
	if (start_pfn >= zone_end_pfn(zone) ||
	    start_pfn + nr_pages <= zone->zone_start_pfn)
		return false;

	return true;
}

/*
 * 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];
};

/*
 * The array of struct pages for flatmem.
 * It must be declared for SPARSEMEM as well because there are configurations
 * that rely on that.
 */
extern struct page *mem_map;

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

#ifdef CONFIG_MEMORY_FAILURE
/*
 * Per NUMA node memory failure handling statistics.
 */
struct memory_failure_stats {
	/*
	 * Number of raw pages poisoned.
	 * Cases not accounted: memory outside kernel control, offline page,
	 * arch-specific memory_failure (SGX), hwpoison_filter() filtered
	 * error events, and unpoison actions from hwpoison_unpoison.
	 */
	unsigned long total;
	/*
	 * Recovery results of poisoned raw pages handled by memory_failure,
	 * in sync with mf_result.
	 * total = ignored + failed + delayed + recovered.
	 * total * PAGE_SIZE * #nodes = /proc/meminfo/HardwareCorrupted.
	 */
	unsigned long ignored;
	unsigned long failed;
	unsigned long delayed;
	unsigned long recovered;
};
#endif

/*
 * On NUMA machines, each NUMA node would have a pg_data_t to describe
 * it's memory layout. On UMA machines there is a single pglist_data which
 * describes the whole memory.
 *
 * Memory statistics and page replacement data structures are maintained on a
 * per-zone basis.
 */
typedef struct pglist_data {
	/*
	 * node_zones contains just the zones for THIS node. Not all of the
	 * zones may be populated, but it is the full list. It is referenced by
	 * this node's node_zonelists as well as other node's node_zonelists.
	 */
	struct zone node_zones[MAX_NR_ZONES];

	/*
	 * node_zonelists contains references to all zones in all nodes.
	 * Generally the first zones will be references to this node's
	 * node_zones.
	 */
	struct zonelist node_zonelists[MAX_ZONELISTS];

	int nr_zones; /* number of populated zones in this node */
#ifdef CONFIG_FLATMEM	/* means !SPARSEMEM */
	struct page *node_mem_map;
#ifdef CONFIG_PAGE_EXTENSION
	struct page_ext *node_page_ext;
#endif
#endif
#if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT)
	/*
	 * Must be held any time you expect node_start_pfn,
	 * node_present_pages, node_spanned_pages or nr_zones to stay constant.
	 * Also synchronizes pgdat->first_deferred_pfn during deferred page
	 * init.
	 *
	 * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
	 * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG
	 * or CONFIG_DEFERRED_STRUCT_PAGE_INIT.
	 *
	 * 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;

	/* workqueues for throttling reclaim for different reasons. */
	wait_queue_head_t reclaim_wait[NR_VMSCAN_THROTTLE];

	atomic_t nr_writeback_throttled;/* nr of writeback-throttled tasks */
	unsigned long nr_reclaim_start;	/* nr pages written while throttled
					 * when throttling started. */
#ifdef CONFIG_MEMORY_HOTPLUG
	struct mutex kswapd_lock;
#endif
	struct task_struct *kswapd;	/* Protected by kswapd_lock */
	int kswapd_order;
	enum zone_type kswapd_highest_zoneidx;

	int kswapd_failures;		/* Number of 'reclaimed == 0' runs */

#ifdef CONFIG_COMPACTION
	int kcompactd_max_order;
	enum zone_type kcompactd_highest_zoneidx;
	wait_queue_head_t kcompactd_wait;
	struct task_struct *kcompactd;
	bool proactive_compact_trigger;
#endif
	/*
	 * This is a per-node reserve of pages that are not available
	 * to userspace allocations.
	 */
	unsigned long		totalreserve_pages;

#ifdef CONFIG_NUMA
	/*
	 * node 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 */
	CACHELINE_PADDING(_pad1_);

#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
	struct deferred_split deferred_split_queue;
#endif

#ifdef CONFIG_NUMA_BALANCING
	/* start time in ms of current promote rate limit period */
	unsigned int nbp_rl_start;
	/* number of promote candidate pages at start time of current rate limit period */
	unsigned long nbp_rl_nr_cand;
	/* promote threshold in ms */
	unsigned int nbp_threshold;
	/* start time in ms of current promote threshold adjustment period */
	unsigned int nbp_th_start;
	/*
	 * number of promote candidate pages at start time of current promote
	 * threshold adjustment period
	 */
	unsigned long nbp_th_nr_cand;
#endif
	/* Fields commonly accessed by the page reclaim scanner */

	/*
	 * NOTE: THIS IS UNUSED IF MEMCG IS ENABLED.
	 *
	 * Use mem_cgroup_lruvec() to look up lruvecs.
	 */
	struct lruvec		__lruvec;

	unsigned long		flags;

#ifdef CONFIG_LRU_GEN
	/* kswap mm walk data */
	struct lru_gen_mm_walk mm_walk;
	/* lru_gen_folio list */
	struct lru_gen_memcg memcg_lru;
#endif

	CACHELINE_PADDING(_pad2_);

	/* Per-node vmstats */
	struct per_cpu_nodestat __percpu *per_cpu_nodestats;
	atomic_long_t		vm_stat[NR_VM_NODE_STAT_ITEMS];
#ifdef CONFIG_NUMA
	struct memory_tier __rcu *memtier;
#endif
#ifdef CONFIG_MEMORY_FAILURE
	struct memory_failure_stats mf_stats;
#endif

	ANDROID_KABI_RESERVE(1);
	ANDROID_BACKPORT_RESERVE(1);
	ANDROID_OEM_DATA(1);
} 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)

#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;
}

#include <linux/memory_hotplug.h>

void build_all_zonelists(pg_data_t *pgdat);
void wakeup_kswapd(struct zone *zone, gfp_t gfp_mask, int order,
		   enum zone_type highest_zoneidx);
bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
			 int highest_zoneidx, unsigned int alloc_flags,
			 long free_pages);
bool zone_watermark_ok(struct zone *z, unsigned int order,
		unsigned long mark, int highest_zoneidx,
		unsigned int alloc_flags);
bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
		unsigned long mark, int highest_zoneidx);
/*
 * Memory initialization context, use to differentiate memory added by
 * the platform statically or via memory hotplug interface.
 */
enum meminit_context {
	MEMINIT_EARLY,
	MEMINIT_HOTPLUG,
};

extern void 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
}

#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

/*
 * 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)

#ifdef CONFIG_ZONE_DEVICE
static inline bool zone_is_zone_device(struct zone *zone)
{
	return zone_idx(zone) == ZONE_DEVICE;
}
#else
static inline bool zone_is_zone_device(struct zone *zone)
{
	return false;
}
#endif

/*
 * 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(zone);
}

/* Returns true if a zone has memory */
static inline bool populated_zone(struct zone *zone)
{
	return zone->present_pages;
}

#ifdef CONFIG_NUMA
static inline int zone_to_nid(struct zone *zone)
{
	return zone->node;
}

static inline void zone_set_nid(struct zone *zone, int nid)
{
	zone->node = nid;
}
#else
static inline int zone_to_nid(struct zone *zone)
{
	return 0;
}

static inline void zone_set_nid(struct zone *zone, int nid) {}
#endif

extern int movable_zone;

static inline int is_highmem_idx(enum zone_type idx)
{
#ifdef CONFIG_HIGHMEM
	return (idx == ZONE_HIGHMEM ||
		(idx == ZONE_MOVABLE && movable_zone == ZONE_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
 * Return: 1 for a highmem zone, 0 otherwise
 */
static inline int is_highmem(struct zone *zone)
{
	return is_highmem_idx(zone_idx(zone));
}

#ifdef CONFIG_ZONE_DMA
bool has_managed_dma(void);
#else
static inline bool has_managed_dma(void)
{
	return false;
}
#endif


#ifndef CONFIG_NUMA

extern struct pglist_data contig_page_data;
static inline struct pglist_data *NODE_DATA(int nid)
{
	return &contig_page_data;
}

#else /* CONFIG_NUMA */

#include <asm/mmzone.h>

#endif /* !CONFIG_NUMA */

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);
extern int isolate_anon_lru_page(struct page *page);

#ifdef CONFIG_COMPACTION
extern unsigned long isolate_and_split_free_page(struct page *page,
			struct list_head *list);
#else
static inline unsigned long isolate_and_split_free_page(struct page *page,
				struct list_head *list)
{
	return 0;
}
#endif /* CONFIG_COMPACTION */

/**
 * 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)
{
	return zone_to_nid(zoneref->zone);
}

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.
 *
 * Return: the next zone at or below highest_zoneidx within the allowed
 * nodemask using a cursor within a zonelist as a starting point
 */
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
 *
 * 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.
 *
 * When no eligible zone is found, zoneref->zone is NULL (zoneref itself is
 * never NULL). This may happen either genuinely, or due to concurrent nodemask
 * update due to cpuset modification.
 *
 * Return: Zoneref pointer for the first suitable zone found
 */
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->_zonerefs 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, highidx, nodemask) \
	for (zone = zonelist_zone(z);	\
		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)

/* Whether the 'nodes' are all movable nodes */
static inline bool movable_only_nodes(nodemask_t *nodes)
{
	struct zonelist *zonelist;
	struct zoneref *z;
	int nid;

	if (nodes_empty(*nodes))
		return false;

	/*
	 * We can chose arbitrary node from the nodemask to get a
	 * zonelist as they are interlinked. We just need to find
	 * at least one zone that can satisfy kernel allocations.
	 */
	nid = first_node(*nodes);
	zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
	z = first_zones_zonelist(zonelist, ZONE_NORMAL,	nodes);
	return (!zonelist_zone(z)) ? true : false;
}


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

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

#ifdef CONFIG_SPARSEMEM

/*
 * 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_PAGE_ORDER + PAGE_SHIFT) > SECTION_SIZE_BITS
#error Allocator MAX_PAGE_ORDER exceeds SECTION_SIZE
#endif

static inline unsigned long pfn_to_section_nr(unsigned long pfn)
{
	return pfn >> PFN_SECTION_SHIFT;
}
static inline unsigned long section_nr_to_pfn(unsigned long sec)
{
	return 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)

#define SUBSECTION_SHIFT 21
#define SUBSECTION_SIZE (1UL << SUBSECTION_SHIFT)

#define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT)
#define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT)
#define PAGE_SUBSECTION_MASK (~(PAGES_PER_SUBSECTION-1))

#if SUBSECTION_SHIFT > SECTION_SIZE_BITS
#error Subsection size exceeds section size
#else
#define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT))
#endif

#define SUBSECTION_ALIGN_UP(pfn) ALIGN((pfn), PAGES_PER_SUBSECTION)
#define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)

struct mem_section_usage {
	struct rcu_head rcu;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
#endif
	/* See declaration of similar field in struct zone */
	unsigned long pageblock_flags[0];
};

void subsection_map_init(unsigned long pfn, unsigned long nr_pages);

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;

	struct mem_section_usage *usage;
#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;
#else
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
#endif

static inline unsigned long *section_to_usemap(struct mem_section *ms)
{
	return ms->usage->pageblock_flags;
}

static inline struct mem_section *__nr_to_section(unsigned long nr)
{
	unsigned long root = SECTION_NR_TO_ROOT(nr);

	if (unlikely(root >= NR_SECTION_ROOTS))
		return NULL;

#ifdef CONFIG_SPARSEMEM_EXTREME
	if (!mem_section || !mem_section[root])
		return NULL;
#endif
	return &mem_section[root][nr & SECTION_ROOT_MASK];
}
extern size_t mem_section_usage_size(void);

/*
 * We use the lower bits of the mem_map pointer to store
 * a little bit of information.  The pointer is calculated
 * as mem_map - section_nr_to_pfn(pnum).  The result is
 * aligned to the minimum alignment of the two values:
 *   1. All mem_map arrays are page-aligned.
 *   2. section_nr_to_pfn() always clears PFN_SECTION_SHIFT
 *      lowest bits.  PFN_SECTION_SHIFT is arch-specific
 *      (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the
 *      worst combination is powerpc with 256k pages,
 *      which results in PFN_SECTION_SHIFT equal 6.
 * To sum it up, at least 6 bits are available on all architectures.
 * However, we can exceed 6 bits on some other architectures except
 * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available
 * with the worst case of 64K pages on arm64) if we make sure the
 * exceeded bit is not applicable to powerpc.
 */
enum {
	SECTION_MARKED_PRESENT_BIT,
	SECTION_HAS_MEM_MAP_BIT,
	SECTION_IS_ONLINE_BIT,
	SECTION_IS_EARLY_BIT,
#ifdef CONFIG_ZONE_DEVICE
	SECTION_TAINT_ZONE_DEVICE_BIT,
#endif
	SECTION_MAP_LAST_BIT,
};

#define SECTION_MARKED_PRESENT		BIT(SECTION_MARKED_PRESENT_BIT)
#define SECTION_HAS_MEM_MAP		BIT(SECTION_HAS_MEM_MAP_BIT)
#define SECTION_IS_ONLINE		BIT(SECTION_IS_ONLINE_BIT)
#define SECTION_IS_EARLY		BIT(SECTION_IS_EARLY_BIT)
#ifdef CONFIG_ZONE_DEVICE
#define SECTION_TAINT_ZONE_DEVICE	BIT(SECTION_TAINT_ZONE_DEVICE_BIT)
#endif
#define SECTION_MAP_MASK		(~(BIT(SECTION_MAP_LAST_BIT) - 1))
#define SECTION_NID_SHIFT		SECTION_MAP_LAST_BIT

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 early_section(struct mem_section *section)
{
	return (section && (section->section_mem_map & SECTION_IS_EARLY));
}

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

static inline int online_section(struct mem_section *section)
{
	return (section && (section->section_mem_map & SECTION_IS_ONLINE));
}

#ifdef CONFIG_ZONE_DEVICE
static inline int online_device_section(struct mem_section *section)
{
	unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE;

	return section && ((section->section_mem_map & flags) == flags);
}
#else
static inline int online_device_section(struct mem_section *section)
{
	return 0;
}
#endif

static inline int online_section_nr(unsigned long nr)
{
	return online_section(__nr_to_section(nr));
}

#ifdef CONFIG_MEMORY_HOTPLUG
void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
#endif

static inline struct mem_section *__pfn_to_section(unsigned long pfn)
{
	return __nr_to_section(pfn_to_section_nr(pfn));
}

extern unsigned long __highest_present_section_nr;

static inline int subsection_map_index(unsigned long pfn)
{
	return (pfn & ~(PAGE_SECTION_MASK)) / PAGES_PER_SUBSECTION;
}

#ifdef CONFIG_SPARSEMEM_VMEMMAP
static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
{
	int idx = subsection_map_index(pfn);
	struct mem_section_usage *usage = READ_ONCE(ms->usage);

	return usage ? test_bit(idx, usage->subsection_map) : 0;
}
#else
static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
{
	return 1;
}
#endif

#ifndef CONFIG_HAVE_ARCH_PFN_VALID
/**
 * pfn_valid - check if there is a valid memory map entry for a PFN
 * @pfn: the page frame number to check
 *
 * Check if there is a valid memory map entry aka struct page for the @pfn.
 * Note, that availability of the memory map entry does not imply that
 * there is actual usable memory at that @pfn. The struct page may
 * represent a hole or an unusable page frame.
 *
 * Return: 1 for PFNs that have memory map entries and 0 otherwise
 */
static inline int pfn_valid(unsigned long pfn)
{
	struct mem_section *ms;
	int ret;

	/*
	 * Ensure the upper PAGE_SHIFT bits are clear in the
	 * pfn. Else it might lead to false positives when
	 * some of the upper bits are set, but the lower bits
	 * match a valid pfn.
	 */
	if (PHYS_PFN(PFN_PHYS(pfn)) != pfn)
		return 0;

	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
		return 0;
	ms = __pfn_to_section(pfn);
	rcu_read_lock_sched();
	if (!valid_section(ms)) {
		rcu_read_unlock_sched();
		return 0;
	}
	/*
	 * Traditionally early sections always returned pfn_valid() for
	 * the entire section-sized span.
	 */
	ret = early_section(ms) || pfn_section_valid(ms, pfn);
	rcu_read_unlock_sched();

	return ret;
}
#endif

static inline int pfn_in_present_section(unsigned long pfn)
{
	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
		return 0;
	return present_section(__pfn_to_section(pfn));
}

static inline unsigned long next_present_section_nr(unsigned long section_nr)
{
	while (++section_nr <= __highest_present_section_nr) {
		if (present_section_nr(section_nr))
			return section_nr;
	}

	return -1;
}

/*
 * 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

void sparse_init(void);
#else
#define sparse_init()	do {} while (0)
#define sparse_index_init(_sec, _nid)  do {} while (0)
#define pfn_in_present_section pfn_valid
#define subsection_map_init(_pfn, _nr_pages) do {} while (0)
#endif /* CONFIG_SPARSEMEM */

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