mmzone.h

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MMZONE_H
#define _LINUX_MMZONE_H
 
#ifndef __ASSEMBLY__
#ifndef __GENERATING_BOUNDS_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/sizes.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_MAX_ORDER
#define PAGE_BLOCK_MAX_ORDER MAX_PAGE_ORDER
#else
#define PAGE_BLOCK_MAX_ORDER CONFIG_PAGE_BLOCK_MAX_ORDER
#endif /* CONFIG_PAGE_BLOCK_MAX_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_MAX_ORDER,
 * which defines the order for the number of pages that can have a migrate type
 */
#if (PAGE_BLOCK_MAX_ORDER > MAX_PAGE_ORDER)
#error MAX_PAGE_ORDER must be >= PAGE_BLOCK_MAX_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
 
#if !defined(CONFIG_HAVE_GIGANTIC_FOLIOS)
/*
 * We don't expect any folios that exceed buddy sizes (and consequently
 * memory sections).
 */
#define MAX_FOLIO_ORDER     MAX_PAGE_ORDER
#elif defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
/*
 * Only pages within a single memory section are guaranteed to be
 * contiguous. By limiting folios to a single memory section, all folio
 * pages are guaranteed to be contiguous.
 */
#define MAX_FOLIO_ORDER     PFN_SECTION_SHIFT
#elif defined(CONFIG_HUGETLB_PAGE)
/*
 * There is no real limit on the folio size. We limit them to the maximum we
 * currently expect (see CONFIG_HAVE_GIGANTIC_FOLIOS): with hugetlb, we expect
 * no folios larger than 16 GiB on 64bit and 1 GiB on 32bit.
 */
#ifdef CONFIG_64BIT
#define MAX_FOLIO_ORDER     (ilog2(SZ_16G) - PAGE_SHIFT)
#else
#define MAX_FOLIO_ORDER     (ilog2(SZ_1G) - PAGE_SHIFT)
#endif
#else
/*
 * Without hugetlb, gigantic folios that are bigger than a single PUD are
 * currently impossible.
 */
#define MAX_FOLIO_ORDER     (PUD_SHIFT - PAGE_SHIFT)
#endif
 
#define MAX_FOLIO_NR_PAGES  (1UL << MAX_FOLIO_ORDER)
 
/*
 * HugeTLB Vmemmap Optimization (HVO) requires struct pages of the head page to
 * be naturally aligned with regard to the folio size.
 *
 * HVO which is only active if the size of struct page is a power of 2.
 */
#define MAX_FOLIO_VMEMMAP_ALIGN \
    (IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP) && \
     is_power_of_2(sizeof(struct page)) ? \
     MAX_FOLIO_NR_PAGES * sizeof(struct page) : 0)
 
/*
 * vmemmap optimization (like HVO) is only possible for page orders that fill
 * two or more pages with struct pages.
 */
#define VMEMMAP_TAIL_MIN_ORDER (ilog2(2 * PAGE_SIZE / sizeof(struct page)))
#define __NR_VMEMMAP_TAILS (MAX_FOLIO_ORDER - VMEMMAP_TAIL_MIN_ORDER + 1)
#define NR_VMEMMAP_TAILS (__NR_VMEMMAP_TAILS > 0 ? __NR_VMEMMAP_TAILS : 0)
 
enum migratetype {
    MIGRATE_UNMOVABLE,
    MIGRATE_MOVABLE,
    MIGRATE_RECLAIMABLE,
    MIGRATE_PCPTYPES,   /* the number of types on the pcp lists */
    MIGRATE_HIGHATOMIC = MIGRATE_PCPTYPES,
#ifdef CONFIG_CMA
    /*
     * MIGRATE_CMA migration type is designed to mimic the way
     * ZONE_MOVABLE works.  Only movable pages can be allocated
     * from MIGRATE_CMA pageblocks and page allocator never
     * implicitly change migration type of MIGRATE_CMA pageblock.
     *
     * The way to use it is to change migratetype of a range of
     * pageblocks to MIGRATE_CMA which can be done by
     * __free_pageblock_cma() function.
     */
    MIGRATE_CMA,
    __MIGRATE_TYPE_END = MIGRATE_CMA,
#else
    __MIGRATE_TYPE_END = MIGRATE_HIGHATOMIC,
#endif
#ifdef CONFIG_MEMORY_ISOLATION
    MIGRATE_ISOLATE,    /* can't allocate from here */
#endif
    MIGRATE_TYPES
};
 
/* In mm/page_alloc.c; keep in sync also with show_migration_types() there */
extern 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)
/*
 * __dump_folio() in mm/debug.c passes a folio pointer to on-stack struct folio,
 * so folio_pfn() cannot be used and pfn is needed.
 */
#  define is_migrate_cma_folio(folio, pfn) \
    (get_pfnblock_migratetype(&folio->page, pfn) == MIGRATE_CMA)
#else
#  define is_migrate_cma(migratetype) false
#  define is_migrate_cma_page(_page) false
#  define is_migrate_cma_folio(folio, pfn) false
#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_PCPTYPES;
}
 
#define for_each_free_list(list, zone, order)               \
    for (order = 0; order < NR_PAGE_ORDERS; order++)        \
        for (unsigned int __type = 0;               \
             __type < MIGRATE_TYPES &&              \
            (list = &(zone)->free_area[order].free_list[__type], 1); \
             __type++)
 
extern int page_group_by_mobility_disabled;
 
#define get_pageblock_migratetype(page) \
    get_pfnblock_migratetype(page, page_to_pfn(page))
 
#define folio_migratetype(folio) \
    get_pageblock_migratetype(&folio->page)
 
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 {
    NR_FREE_PAGES,
    NR_FREE_PAGES_BLOCKS,
    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 */
#if IS_ENABLED(CONFIG_ZSMALLOC)
    NR_ZSPAGES,     /* allocated in zsmalloc */
#endif
    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_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_VMALLOC,
    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,
    PGPROMOTE_CANDIDATE_NRL,
#endif
    /* PGDEMOTE_*: pages demoted */
    PGDEMOTE_KSWAPD,
    PGDEMOTE_DIRECT,
    PGDEMOTE_KHUGEPAGED,
    PGDEMOTE_PROACTIVE,
    PGSTEAL_KSWAPD,
    PGSTEAL_DIRECT,
    PGSTEAL_KHUGEPAGED,
    PGSTEAL_PROACTIVE,
    PGSTEAL_ANON,
    PGSTEAL_FILE,
    PGSCAN_KSWAPD,
    PGSCAN_DIRECT,
    PGSCAN_KHUGEPAGED,
    PGSCAN_PROACTIVE,
    PGSCAN_ANON,
    PGSCAN_FILE,
    PGREFILL,
#ifdef CONFIG_HUGETLB_PAGE
    NR_HUGETLB,
#endif
    NR_BALLOON_PAGES,
    NR_KERNEL_FILE_PAGES,
    NR_GPU_ACTIVE,  /* Pages assigned to GPU objects */
    NR_GPU_RECLAIM, /* Pages in shrinkable GPU pools */
    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;
};
 
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];
};
 
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;
};
 
/*
 * 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, unsigned int nr);
 
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);
void max_lru_gen_memcg(struct mem_cgroup *memcg, int nid);
bool recheck_lru_gen_max_memcg(struct mem_cgroup *memcg, int nid);
void lru_gen_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, 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,
        unsigned int nr)
{
    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)
{
}
 
static inline void max_lru_gen_memcg(struct mem_cgroup *memcg, int nid)
{
}
 
static inline bool recheck_lru_gen_max_memcg(struct mem_cgroup *memcg, int nid)
{
    return true;
}
 
static inline
void lru_gen_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, 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;
};
 
/* 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;
 
    /* To be called once the last page in the zone is accepted */
    struct work_struct  unaccepted_cleanup;
#endif
 
    /* zone flags, see below */
    unsigned long       flags;
 
    /* Primarily protects free_area */
    spinlock_t      lock;
 
    /* Pages to be freed when next trylock succeeds */
    struct llist_head   trylock_free_pages;
 
    /* 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];
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
    struct page *vmemmap_tails[NR_VMEMMAP_TAILS];
#endif
} ____cacheline_internodealigned_in_smp;
 
enum pgdat_flags {
    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(const 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(const struct zone *zone)
{
    return zone->initialized;
}
 
static inline bool zone_is_empty(const 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 memdesc_zonenum(memdesc_flags_t flags)
{
    ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT);
    return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK;
}
 
static inline enum zone_type page_zonenum(const struct page *page)
{
    return memdesc_zonenum(page->flags);
}
 
static inline enum zone_type folio_zonenum(const struct folio *folio)
{
    return memdesc_zonenum(folio->flags);
}
 
#ifdef CONFIG_ZONE_DEVICE
static inline bool memdesc_is_zone_device(memdesc_flags_t mdf)
{
    return memdesc_zonenum(mdf) == ZONE_DEVICE;
}
 
static inline struct dev_pagemap *page_pgmap(const struct page *page)
{
    VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(page->flags), page);
    return page_folio(page)->pgmap;
}
 
/*
 * 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 (memdesc_is_zone_device(a->flags) != memdesc_is_zone_device(b->flags))
        return false;
    if (!memdesc_is_zone_device(a->flags))
        return true;
    return page_pgmap(a) == page_pgmap(b);
}
 
extern void memmap_init_zone_device(struct zone *, unsigned long,
                    unsigned long, struct dev_pagemap *);
#else
static inline bool memdesc_is_zone_device(memdesc_flags_t mdf)
{
    return false;
}
static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
                             const struct page *b)
{
    return true;
}
static inline struct dev_pagemap *page_pgmap(const struct page *page)
{
    return NULL;
}
#endif
 
static inline bool is_zone_device_page(const struct page *page)
{
    return memdesc_is_zone_device(page->flags);
}
 
static inline bool folio_is_zone_device(const struct folio *folio)
{
    return memdesc_is_zone_device(folio->flags);
}
 
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(const 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_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;
 
    atomic_t 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_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
} 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);
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);
 
enum kswapd_clear_hopeless_reason {
    KSWAPD_CLEAR_HOPELESS_OTHER = 0,
    KSWAPD_CLEAR_HOPELESS_KSWAPD,
    KSWAPD_CLEAR_HOPELESS_DIRECT,
    KSWAPD_CLEAR_HOPELESS_PCP,
};
 
void wakeup_kswapd(struct zone *zone, gfp_t gfp_mask, int order,
           enum zone_type highest_zoneidx);
void kswapd_try_clear_hopeless(struct pglist_data *pgdat,
                   unsigned int order, int highest_zoneidx);
void kswapd_clear_hopeless(pg_data_t *pgdat, enum kswapd_clear_hopeless_reason reason);
bool kswapd_test_hopeless(pg_data_t *pgdat);
 
/*
 * 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(const struct zone *zone)
{
    return zone_idx(zone) == ZONE_DEVICE;
}
#else
static inline bool zone_is_zone_device(const 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(const struct zone *zone)
{
    return zone_managed_pages(zone);
}
 
/* Returns true if a zone has memory */
static inline bool populated_zone(const struct zone *zone)
{
    return zone->present_pages;
}
 
#ifdef CONFIG_NUMA
static inline int zone_to_nid(const 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(const 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
}
 
static inline int is_highmem(const struct zone *zone)
{
    return is_highmem_idx(zone_idx(zone));
}
 
bool has_managed_zone(enum zone_type zone);
static inline bool has_managed_dma(void)
{
#ifdef CONFIG_ZONE_DMA
    return has_managed_zone(ZONE_DMA);
#else
    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);
 
#define for_each_online_pgdat(pgdat)            \
    for (pgdat = first_online_pgdat();      \
         pgdat;                 \
         pgdat = next_online_pgdat(pgdat))
#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(const struct zoneref *zoneref)
{
    return zoneref->zone_idx;
}
 
static inline int zonelist_node_idx(const 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);
 
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);
}
 
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);
}
 
#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))
 
 
#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];
};
 
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_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().
 * 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.
 *
 * We always expect a single section to cover full pages. Therefore,
 * we can safely assume that PFN_SECTION_SHIFT is large enough to
 * accommodate SECTION_MAP_LAST_BIT. We use BUILD_BUG_ON() to ensure this.
 */
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
#ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
    SECTION_IS_VMEMMAP_PREINIT_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
#ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
#define SECTION_IS_VMEMMAP_PREINIT  BIT(SECTION_IS_VMEMMAP_PREINIT_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(const 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(const struct mem_section *section)
{
    return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
}
 
static inline int early_section(const 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(const struct mem_section *section)
{
    return (section && (section->section_mem_map & SECTION_IS_ONLINE));
}
 
#ifdef CONFIG_ZONE_DEVICE
static inline int online_device_section(const 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(const struct mem_section *section)
{
    return 0;
}
#endif
 
#ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
static inline int preinited_vmemmap_section(const struct mem_section *section)
{
    return (section &&
        (section->section_mem_map & SECTION_IS_VMEMMAP_PREINIT));
}
 
void sparse_vmemmap_init_nid_early(int nid);
void sparse_vmemmap_init_nid_late(int nid);
 
#else
static inline int preinited_vmemmap_section(const struct mem_section *section)
{
    return 0;
}
static inline void sparse_vmemmap_init_nid_early(int nid)
{
}
 
static inline void sparse_vmemmap_init_nid_late(int nid)
{
}
#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;
}
 
static inline bool pfn_section_first_valid(struct mem_section *ms, unsigned long *pfn)
{
    struct mem_section_usage *usage = READ_ONCE(ms->usage);
    int idx = subsection_map_index(*pfn);
    unsigned long bit;
 
    if (!usage)
        return false;
 
    if (test_bit(idx, usage->subsection_map))
        return true;
 
    /* Find the next subsection that exists */
    bit = find_next_bit(usage->subsection_map, SUBSECTIONS_PER_SECTION, idx);
    if (bit == SUBSECTIONS_PER_SECTION)
        return false;
 
    *pfn = (*pfn & PAGE_SECTION_MASK) + (bit * PAGES_PER_SUBSECTION);
    return true;
}
#else
static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
{
    return 1;
}
 
static inline bool pfn_section_first_valid(struct mem_section *ms, unsigned long *pfn)
{
    return true;
}
#endif
 
void sparse_init_early_section(int nid, struct page *map, unsigned long pnum,
                   unsigned long flags);
 
#ifndef CONFIG_HAVE_ARCH_PFN_VALID
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;
}
 
/* Returns end_pfn or higher if no valid PFN remaining in range */
static inline unsigned long first_valid_pfn(unsigned long pfn, unsigned long end_pfn)
{
    unsigned long nr = pfn_to_section_nr(pfn);
 
    rcu_read_lock_sched();
 
    while (nr <= __highest_present_section_nr && pfn < end_pfn) {
        struct mem_section *ms = __pfn_to_section(pfn);
 
        if (valid_section(ms) &&
            (early_section(ms) || pfn_section_first_valid(ms, &pfn))) {
            rcu_read_unlock_sched();
            return pfn;
        }
 
        /* Nothing left in this section? Skip to next section */
        nr++;
        pfn = section_nr_to_pfn(nr);
    }
 
    rcu_read_unlock_sched();
    return end_pfn;
}
 
static inline unsigned long next_valid_pfn(unsigned long pfn, unsigned long end_pfn)
{
    pfn++;
 
    if (pfn >= end_pfn)
        return end_pfn;
 
    /*
     * Either every PFN within the section (or subsection for VMEMMAP) is
     * valid, or none of them are. So there's no point repeating the check
     * for every PFN; only call first_valid_pfn() again when crossing a
     * (sub)section boundary (i.e. !(pfn & ~PAGE_{SUB,}SECTION_MASK)).
     */
    if (pfn & ~(IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) ?
           PAGE_SUBSECTION_MASK : PAGE_SECTION_MASK))
        return pfn;
 
    return first_valid_pfn(pfn, end_pfn);
}
 
 
#define for_each_valid_pfn(_pfn, _start_pfn, _end_pfn)          \
    for ((_pfn) = first_valid_pfn((_start_pfn), (_end_pfn));    \
         (_pfn) < (_end_pfn);                   \
         (_pfn) = next_valid_pfn((_pfn), (_end_pfn)))
 
#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;
}
 
#define for_each_present_section_nr(start, section_nr)      \
    for (section_nr = next_present_section_nr(start - 1);   \
         section_nr != -1;                  \
         section_nr = next_present_section_nr(section_nr))
 
/*
 * 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
 
#else
#define sparse_vmemmap_init_nid_early(_nid) do {} while (0)
#define sparse_vmemmap_init_nid_late(_nid) do {} while (0)
#define pfn_in_present_section pfn_valid
#endif /* CONFIG_SPARSEMEM */
 
/*
 * Fallback case for when the architecture provides its own pfn_valid() but
 * not a corresponding for_each_valid_pfn().
 */
#ifndef for_each_valid_pfn
#define for_each_valid_pfn(_pfn, _start_pfn, _end_pfn)          \
    for ((_pfn) = (_start_pfn); (_pfn) < (_end_pfn); (_pfn)++)  \
        if (pfn_valid(_pfn))
#endif
 
#endif /* !__GENERATING_BOUNDS.H */
#endif /* !__ASSEMBLY__ */
#endif /* _LINUX_MMZONE_H */