text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   *  linux/mm/page_alloc.c
   *
   *  Manages the free list, the system allocates free pages here.
   *  Note that kmalloc() lives in slab.c
   *
   *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   *  Swap reorganised 29.12.95, Stephen Tweedie
   *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
   *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
   *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
   *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
   *  Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
   *          (lots of bits borrowed from Ingo Molnar & Andrew Morton)
   */
  
  #include <linux/stddef.h>
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/interrupt.h>
  #include <linux/pagemap.h>
  #include <linux/jiffies.h>
  #include <linux/memblock.h>
  #include <linux/compiler.h>
  #include <linux/kernel.h>
  #include <linux/kasan.h>
  #include <linux/module.h>
  #include <linux/suspend.h>
  #include <linux/pagevec.h>
  #include <linux/blkdev.h>
  #include <linux/slab.h>
  #include <linux/ratelimit.h>
  #include <linux/oom.h>
  #include <linux/topology.h>
  #include <linux/sysctl.h>
  #include <linux/cpu.h>
  #include <linux/cpuset.h>
  #include <linux/memory_hotplug.h>
  #include <linux/nodemask.h>
  #include <linux/vmalloc.h>
  #include <linux/vmstat.h>
  #include <linux/mempolicy.h>
  #include <linux/memremap.h>
  #include <linux/stop_machine.h>
  #include <linux/random.h>
  #include <linux/sort.h>
  #include <linux/pfn.h>
  #include <linux/backing-dev.h>
  #include <linux/fault-inject.h>
  #include <linux/page-isolation.h>
  #include <linux/debugobjects.h>
  #include <linux/kmemleak.h>
  #include <linux/compaction.h>
  #include <trace/events/kmem.h>
  #include <trace/events/oom.h>
  #include <linux/prefetch.h>
  #include <linux/mm_inline.h>
  #include <linux/mmu_notifier.h>
  #include <linux/migrate.h>
  #include <linux/hugetlb.h>
  #include <linux/sched/rt.h>
  #include <linux/sched/mm.h>
  #include <linux/page_owner.h>
  #include <linux/page_table_check.h>
  #include <linux/kthread.h>
  #include <linux/memcontrol.h>
  #include <linux/ftrace.h>
  #include <linux/lockdep.h>
  #include <linux/nmi.h>
  #include <linux/psi.h>
  #include <linux/padata.h>
  #include <linux/khugepaged.h>
  #include <linux/buffer_head.h>
  #include <linux/delayacct.h>
  #include <asm/sections.h>
  #include <asm/tlbflush.h>
  #include <asm/div64.h>
  #include "internal.h"
  #include "shuffle.h"
  #include "page_reporting.h"
  
  /* Free Page Internal flags: for internal, non-pcp variants of free_pages(). */
  typedef int __bitwise fpi_t;
  
  /* No special request */
  #define FPI_NONE		((__force fpi_t)0)
  
  /*
   * Skip free page reporting notification for the (possibly merged) page.
   * This does not hinder free page reporting from grabbing the page,
   * reporting it and marking it "reported" -  it only skips notifying
   * the free page reporting infrastructure about a newly freed page. For
   * example, used when temporarily pulling a page from a freelist and
   * putting it back unmodified.
   */
  #define FPI_SKIP_REPORT_NOTIFY	((__force fpi_t)BIT(0))
  
  /*
   * Place the (possibly merged) page to the tail of the freelist. Will ignore
   * page shuffling (relevant code - e.g., memory onlining - is expected to
   * shuffle the whole zone).
   *
   * Note: No code should rely on this flag for correctness - it's purely
   *       to allow for optimizations when handing back either fresh pages
   *       (memory onlining) or untouched pages (page isolation, free page
   *       reporting).
   */
  #define FPI_TO_TAIL		((__force fpi_t)BIT(1))
  
  /*
   * Don't poison memory with KASAN (only for the tag-based modes).
   * During boot, all non-reserved memblock memory is exposed to page_alloc.
   * Poisoning all that memory lengthens boot time, especially on systems with
   * large amount of RAM. This flag is used to skip that poisoning.
   * This is only done for the tag-based KASAN modes, as those are able to
   * detect memory corruptions with the memory tags assigned by default.
   * All memory allocated normally after boot gets poisoned as usual.
   */
  #define FPI_SKIP_KASAN_POISON	((__force fpi_t)BIT(2))
  
  /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
  static DEFINE_MUTEX(pcp_batch_high_lock);
  #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
  
  struct pagesets {
  	local_lock_t lock;
  };
  static DEFINE_PER_CPU(struct pagesets, pagesets) = {
  	.lock = INIT_LOCAL_LOCK(lock),
  };
  
  #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
  DEFINE_PER_CPU(int, numa_node);
  EXPORT_PER_CPU_SYMBOL(numa_node);
  #endif
  
  DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);
  
  #ifdef CONFIG_HAVE_MEMORYLESS_NODES
  /*
   * N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
   * It will not be defined when CONFIG_HAVE_MEMORYLESS_NODES is not defined.
   * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem()
   * defined in <linux/topology.h>.
   */
  DEFINE_PER_CPU(int, _numa_mem_);		/* Kernel "local memory" node */
  EXPORT_PER_CPU_SYMBOL(_numa_mem_);
  #endif
  
  /* work_structs for global per-cpu drains */
  struct pcpu_drain {
  	struct zone *zone;
  	struct work_struct work;
  };
  static DEFINE_MUTEX(pcpu_drain_mutex);
  static DEFINE_PER_CPU(struct pcpu_drain, pcpu_drain);
  
  #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
  volatile unsigned long latent_entropy __latent_entropy;
  EXPORT_SYMBOL(latent_entropy);
  #endif
  
  /*
   * Array of node states.
   */
  nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
  	[N_POSSIBLE] = NODE_MASK_ALL,
  	[N_ONLINE] = { { [0] = 1UL } },
  #ifndef CONFIG_NUMA
  	[N_NORMAL_MEMORY] = { { [0] = 1UL } },
  #ifdef CONFIG_HIGHMEM
  	[N_HIGH_MEMORY] = { { [0] = 1UL } },
  #endif
  	[N_MEMORY] = { { [0] = 1UL } },
  	[N_CPU] = { { [0] = 1UL } },
  #endif	/* NUMA */
  };
  EXPORT_SYMBOL(node_states);
  
  atomic_long_t _totalram_pages __read_mostly;
  EXPORT_SYMBOL(_totalram_pages);
  unsigned long totalreserve_pages __read_mostly;
  unsigned long totalcma_pages __read_mostly;
  
  int percpu_pagelist_high_fraction;
  gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
  DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
  EXPORT_SYMBOL(init_on_alloc);
  
  DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
  EXPORT_SYMBOL(init_on_free);
  
  static bool _init_on_alloc_enabled_early __read_mostly
  				= IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);
  static int __init early_init_on_alloc(char *buf)
  {
  
  	return kstrtobool(buf, &_init_on_alloc_enabled_early);
  }
  early_param("init_on_alloc", early_init_on_alloc);
  
  static bool _init_on_free_enabled_early __read_mostly
  				= IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON);
  static int __init early_init_on_free(char *buf)
  {
  	return kstrtobool(buf, &_init_on_free_enabled_early);
  }
  early_param("init_on_free", early_init_on_free);
  
  /*
   * A cached value of the page's pageblock's migratetype, used when the page is
   * put on a pcplist. Used to avoid the pageblock migratetype lookup when
   * freeing from pcplists in most cases, at the cost of possibly becoming stale.
   * Also the migratetype set in the page does not necessarily match the pcplist
   * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any
   * other index - this ensures that it will be put on the correct CMA freelist.
   */
  static inline int get_pcppage_migratetype(struct page *page)
  {
  	return page->index;
  }
  
  static inline void set_pcppage_migratetype(struct page *page, int migratetype)
  {
  	page->index = migratetype;
  }
  
  #ifdef CONFIG_PM_SLEEP
  /*
   * The following functions are used by the suspend/hibernate code to temporarily
   * change gfp_allowed_mask in order to avoid using I/O during memory allocations
   * while devices are suspended.  To avoid races with the suspend/hibernate code,
   * they should always be called with system_transition_mutex held
   * (gfp_allowed_mask also should only be modified with system_transition_mutex
   * held, unless the suspend/hibernate code is guaranteed not to run in parallel
   * with that modification).
   */
  
  static gfp_t saved_gfp_mask;
  
  void pm_restore_gfp_mask(void)
  {
  	WARN_ON(!mutex_is_locked(&system_transition_mutex));
  	if (saved_gfp_mask) {
  		gfp_allowed_mask = saved_gfp_mask;
  		saved_gfp_mask = 0;
  	}
  }
  
  void pm_restrict_gfp_mask(void)
  {
  	WARN_ON(!mutex_is_locked(&system_transition_mutex));
  	WARN_ON(saved_gfp_mask);
  	saved_gfp_mask = gfp_allowed_mask;
  	gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);
  }
  
  bool pm_suspended_storage(void)
  {
  	if ((gfp_allowed_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
  		return false;
  	return true;
  }
  #endif /* CONFIG_PM_SLEEP */
  
  #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
  unsigned int pageblock_order __read_mostly;
  #endif
  
  static void __free_pages_ok(struct page *page, unsigned int order,
  			    fpi_t fpi_flags);
  
  /*
   * results with 256, 32 in the lowmem_reserve sysctl:
   *	1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
   *	1G machine -> (16M dma, 784M normal, 224M high)
   *	NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
   *	HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
   *	HIGHMEM allocation will leave (224M+784M)/256 of ram reserved in ZONE_DMA
   *
   * TBD: should special case ZONE_DMA32 machines here - in those we normally
   * don't need any ZONE_NORMAL reservation
   */
  int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {
  #ifdef CONFIG_ZONE_DMA
  	[ZONE_DMA] = 256,
  #endif
  #ifdef CONFIG_ZONE_DMA32
  	[ZONE_DMA32] = 256,
  #endif
  	[ZONE_NORMAL] = 32,
  #ifdef CONFIG_HIGHMEM
  	[ZONE_HIGHMEM] = 0,
  #endif
  	[ZONE_MOVABLE] = 0,
  };
  
  static char * const zone_names[MAX_NR_ZONES] = {
  #ifdef CONFIG_ZONE_DMA
  	 "DMA",
  #endif
  #ifdef CONFIG_ZONE_DMA32
  	 "DMA32",
  #endif
  	 "Normal",
  #ifdef CONFIG_HIGHMEM
  	 "HighMem",
  #endif
  	 "Movable",
  #ifdef CONFIG_ZONE_DEVICE
  	 "Device",
  #endif
  };
  
  const char * const migratetype_names[MIGRATE_TYPES] = {
  	"Unmovable",
  	"Movable",
  	"Reclaimable",
  	"HighAtomic",
  #ifdef CONFIG_CMA
  	"CMA",
  #endif
  #ifdef CONFIG_MEMORY_ISOLATION
  	"Isolate",
  #endif
  };
  
  compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
  	[NULL_COMPOUND_DTOR] = NULL,
  	[COMPOUND_PAGE_DTOR] = free_compound_page,
  #ifdef CONFIG_HUGETLB_PAGE
  	[HUGETLB_PAGE_DTOR] = free_huge_page,
  #endif
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	[TRANSHUGE_PAGE_DTOR] = free_transhuge_page,
  #endif
  };
  
  int min_free_kbytes = 1024;
  int user_min_free_kbytes = -1;
  int watermark_boost_factor __read_mostly = 15000;
  int watermark_scale_factor = 10;
  
  static unsigned long nr_kernel_pages __initdata;
  static unsigned long nr_all_pages __initdata;
  static unsigned long dma_reserve __initdata;
  
  static unsigned long arch_zone_lowest_possible_pfn[MAX_NR_ZONES] __initdata;
  static unsigned long arch_zone_highest_possible_pfn[MAX_NR_ZONES] __initdata;
  static unsigned long required_kernelcore __initdata;
  static unsigned long required_kernelcore_percent __initdata;
  static unsigned long required_movablecore __initdata;
  static unsigned long required_movablecore_percent __initdata;
  static unsigned long zone_movable_pfn[MAX_NUMNODES] __initdata;
  static bool mirrored_kernelcore __meminitdata;
  
  /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
  int movable_zone;
  EXPORT_SYMBOL(movable_zone);
  
  #if MAX_NUMNODES > 1
  unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;
  unsigned int nr_online_nodes __read_mostly = 1;
  EXPORT_SYMBOL(nr_node_ids);
  EXPORT_SYMBOL(nr_online_nodes);
  #endif
  
  int page_group_by_mobility_disabled __read_mostly;
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  /*
   * During boot we initialize deferred pages on-demand, as needed, but once
   * page_alloc_init_late() has finished, the deferred pages are all initialized,
   * and we can permanently disable that path.
   */
  static DEFINE_STATIC_KEY_TRUE(deferred_pages);
  
  /*
   * Calling kasan_poison_pages() only after deferred memory initialization
   * has completed. Poisoning pages during deferred memory init will greatly
   * lengthen the process and cause problem in large memory systems as the
   * deferred pages initialization is done with interrupt disabled.
   *
   * Assuming that there will be no reference to those newly initialized
   * pages before they are ever allocated, this should have no effect on
   * KASAN memory tracking as the poison will be properly inserted at page
   * allocation time. The only corner case is when pages are allocated by
   * on-demand allocation and then freed again before the deferred pages
   * initialization is done, but this is not likely to happen.
   */
  static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
  {
  	return static_branch_unlikely(&deferred_pages) ||
  	       (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
  		(fpi_flags & FPI_SKIP_KASAN_POISON)) ||
  	       PageSkipKASanPoison(page);
  }
  
  /* Returns true if the struct page for the pfn is uninitialised */
  static inline bool __meminit early_page_uninitialised(unsigned long pfn)
  {
  	int nid = early_pfn_to_nid(pfn);
  
  	if (node_online(nid) && pfn >= NODE_DATA(nid)->first_deferred_pfn)
  		return true;
  
  	return false;
  }
  
  /*
   * Returns true when the remaining initialisation should be deferred until
   * later in the boot cycle when it can be parallelised.
   */
  static bool __meminit
  defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
  {
  	static unsigned long prev_end_pfn, nr_initialised;
  
  	/*
  	 * prev_end_pfn static that contains the end of previous zone
  	 * No need to protect because called very early in boot before smp_init.
  	 */
  	if (prev_end_pfn != end_pfn) {
  		prev_end_pfn = end_pfn;
  		nr_initialised = 0;
  	}
  
  	/* Always populate low zones for address-constrained allocations */
  	if (end_pfn < pgdat_end_pfn(NODE_DATA(nid)))
  		return false;
  
  	if (NODE_DATA(nid)->first_deferred_pfn != ULONG_MAX)
  		return true;
  	/*
  	 * We start only with one section of pages, more pages are added as
  	 * needed until the rest of deferred pages are initialized.
  	 */
  	nr_initialised++;
  	if ((nr_initialised > PAGES_PER_SECTION) &&
  	    (pfn & (PAGES_PER_SECTION - 1)) == 0) {
  		NODE_DATA(nid)->first_deferred_pfn = pfn;
  		return true;
  	}
  	return false;
  }
  #else
  static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
  {
  	return (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
  		(fpi_flags & FPI_SKIP_KASAN_POISON)) ||
  	       PageSkipKASanPoison(page);
  }
  
  static inline bool early_page_uninitialised(unsigned long pfn)
  {
  	return false;
  }
  
  static inline bool defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
  {
  	return false;
  }
  #endif
  
  /* Return a pointer to the bitmap storing bits affecting a block of pages */
  static inline unsigned long *get_pageblock_bitmap(const struct page *page,
  							unsigned long pfn)
  {
  #ifdef CONFIG_SPARSEMEM
  	return section_to_usemap(__pfn_to_section(pfn));
  #else
  	return page_zone(page)->pageblock_flags;
  #endif /* CONFIG_SPARSEMEM */
  }
  
  static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)
  {
  #ifdef CONFIG_SPARSEMEM
  	pfn &= (PAGES_PER_SECTION-1);
  #else
  	pfn = pfn - round_down(page_zone(page)->zone_start_pfn, pageblock_nr_pages);
  #endif /* CONFIG_SPARSEMEM */
  	return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
  }
  
  static __always_inline
  unsigned long __get_pfnblock_flags_mask(const struct page *page,
  					unsigned long pfn,
  					unsigned long mask)
  {
  	unsigned long *bitmap;
  	unsigned long bitidx, word_bitidx;
  	unsigned long word;
  
  	bitmap = get_pageblock_bitmap(page, pfn);
  	bitidx = pfn_to_bitidx(page, pfn);
  	word_bitidx = bitidx / BITS_PER_LONG;
  	bitidx &= (BITS_PER_LONG-1);
  
  	word = bitmap[word_bitidx];
  	return (word >> bitidx) & mask;
  }
  
  /**
   * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages
   * @page: The page within the block of interest
   * @pfn: The target page frame number
   * @mask: mask of bits that the caller is interested in
   *
   * Return: pageblock_bits flags
   */
  unsigned long get_pfnblock_flags_mask(const struct page *page,
  					unsigned long pfn, unsigned long mask)
  {
  	return __get_pfnblock_flags_mask(page, pfn, mask);
  }
  
  static __always_inline int get_pfnblock_migratetype(const struct page *page,
  					unsigned long pfn)
  {
  	return __get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
  }
  
  /**
   * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
   * @page: The page within the block of interest
   * @flags: The flags to set
   * @pfn: The target page frame number
   * @mask: mask of bits that the caller is interested in
   */
  void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
  					unsigned long pfn,
  					unsigned long mask)
  {
  	unsigned long *bitmap;
  	unsigned long bitidx, word_bitidx;
  	unsigned long old_word, word;
  
  	BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
  	BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
  
  	bitmap = get_pageblock_bitmap(page, pfn);
  	bitidx = pfn_to_bitidx(page, pfn);
  	word_bitidx = bitidx / BITS_PER_LONG;
  	bitidx &= (BITS_PER_LONG-1);
  
  	VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
  
  	mask <<= bitidx;
  	flags <<= bitidx;
  
  	word = READ_ONCE(bitmap[word_bitidx]);
  	for (;;) {
  		old_word = cmpxchg(&bitmap[word_bitidx], word, (word & ~mask) | flags);
  		if (word == old_word)
  			break;
  		word = old_word;
  	}
  }
  
  void set_pageblock_migratetype(struct page *page, int migratetype)
  {
  	if (unlikely(page_group_by_mobility_disabled &&
  		     migratetype < MIGRATE_PCPTYPES))
  		migratetype = MIGRATE_UNMOVABLE;
  
  	set_pfnblock_flags_mask(page, (unsigned long)migratetype,
  				page_to_pfn(page), MIGRATETYPE_MASK);
  }
  
  #ifdef CONFIG_DEBUG_VM
  static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
  {
  	int ret = 0;
  	unsigned seq;
  	unsigned long pfn = page_to_pfn(page);
  	unsigned long sp, start_pfn;
  
  	do {
  		seq = zone_span_seqbegin(zone);
  		start_pfn = zone->zone_start_pfn;
  		sp = zone->spanned_pages;
  		if (!zone_spans_pfn(zone, pfn))
  			ret = 1;
  	} while (zone_span_seqretry(zone, seq));
  
  	if (ret)
  		pr_err("page 0x%lx outside node %d zone %s [ 0x%lx - 0x%lx ]\n",
  			pfn, zone_to_nid(zone), zone->name,
  			start_pfn, start_pfn + sp);
  
  	return ret;
  }
  
  static int page_is_consistent(struct zone *zone, struct page *page)
  {
  	if (zone != page_zone(page))
  		return 0;
  
  	return 1;
  }
  /*
   * Temporary debugging check for pages not lying within a given zone.
   */
  static int __maybe_unused bad_range(struct zone *zone, struct page *page)
  {
  	if (page_outside_zone_boundaries(zone, page))
  		return 1;
  	if (!page_is_consistent(zone, page))
  		return 1;
  
  	return 0;
  }
  #else
  static inline int __maybe_unused bad_range(struct zone *zone, struct page *page)
  {
  	return 0;
  }
  #endif
  
  static void bad_page(struct page *page, const char *reason)
  {
  	static unsigned long resume;
  	static unsigned long nr_shown;
  	static unsigned long nr_unshown;
  
  	/*
  	 * Allow a burst of 60 reports, then keep quiet for that minute;
  	 * or allow a steady drip of one report per second.
  	 */
  	if (nr_shown == 60) {
  		if (time_before(jiffies, resume)) {
  			nr_unshown++;
  			goto out;
  		}
  		if (nr_unshown) {
  			pr_alert(
  			      "BUG: Bad page state: %lu messages suppressed\n",
  				nr_unshown);
  			nr_unshown = 0;
  		}
  		nr_shown = 0;
  	}
  	if (nr_shown++ == 0)
  		resume = jiffies + 60 * HZ;
  
  	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
  		current->comm, page_to_pfn(page));
  	dump_page(page, reason);
  
  	print_modules();
  	dump_stack();
  out:
  	/* Leave bad fields for debug, except PageBuddy could make trouble */
  	page_mapcount_reset(page); /* remove PageBuddy */
  	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  }
  
  static inline unsigned int order_to_pindex(int migratetype, int order)
  {
  	int base = order;
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	if (order > PAGE_ALLOC_COSTLY_ORDER) {
  		VM_BUG_ON(order != pageblock_order);
  		base = PAGE_ALLOC_COSTLY_ORDER + 1;
  	}
  #else
  	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
  #endif
  
  	return (MIGRATE_PCPTYPES * base) + migratetype;
  }
  
  static inline int pindex_to_order(unsigned int pindex)
  {
  	int order = pindex / MIGRATE_PCPTYPES;
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	if (order > PAGE_ALLOC_COSTLY_ORDER)
  		order = pageblock_order;
  #else
  	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
  #endif
  
  	return order;
  }
  
  static inline bool pcp_allowed_order(unsigned int order)
  {
  	if (order <= PAGE_ALLOC_COSTLY_ORDER)
  		return true;
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	if (order == pageblock_order)
  		return true;
  #endif
  	return false;
  }
  
  static inline void free_the_page(struct page *page, unsigned int order)
  {
  	if (pcp_allowed_order(order))		/* Via pcp? */
  		free_unref_page(page, order);
  	else
  		__free_pages_ok(page, order, FPI_NONE);
  }
  
  /*
   * Higher-order pages are called "compound pages".  They are structured thusly:
   *
   * The first PAGE_SIZE page is called the "head page" and have PG_head set.
   *
   * The remaining PAGE_SIZE pages are called "tail pages". PageTail() is encoded
   * in bit 0 of page->compound_head. The rest of bits is pointer to head page.
   *
   * The first tail page's ->compound_dtor holds the offset in array of compound
   * page destructors. See compound_page_dtors.
   *
   * The first tail page's ->compound_order holds the order of allocation.
   * This usage means that zero-order pages may not be compound.
   */
  
  void free_compound_page(struct page *page)
  {
  	mem_cgroup_uncharge(page_folio(page));
  	free_the_page(page, compound_order(page));
  }
  
  static void prep_compound_head(struct page *page, unsigned int order)
  {
  	set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
  	set_compound_order(page, order);
  	atomic_set(compound_mapcount_ptr(page), -1);
  	if (hpage_pincount_available(page))
  		atomic_set(compound_pincount_ptr(page), 0);
  }
  
  static void prep_compound_tail(struct page *head, int tail_idx)
  {
  	struct page *p = head + tail_idx;
  
  	p->mapping = TAIL_MAPPING;
  	set_compound_head(p, head);
  }
  
  void prep_compound_page(struct page *page, unsigned int order)
  {
  	int i;
  	int nr_pages = 1 << order;
  
  	__SetPageHead(page);
  	for (i = 1; i < nr_pages; i++)
  		prep_compound_tail(page, i);
  
  	prep_compound_head(page, order);
  }
  
  #ifdef CONFIG_DEBUG_PAGEALLOC
  unsigned int _debug_guardpage_minorder;
  
  bool _debug_pagealloc_enabled_early __read_mostly
  			= IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
  EXPORT_SYMBOL(_debug_pagealloc_enabled_early);
  DEFINE_STATIC_KEY_FALSE(_debug_pagealloc_enabled);
  EXPORT_SYMBOL(_debug_pagealloc_enabled);
  
  DEFINE_STATIC_KEY_FALSE(_debug_guardpage_enabled);
  
  static int __init early_debug_pagealloc(char *buf)
  {
  	return kstrtobool(buf, &_debug_pagealloc_enabled_early);
  }
  early_param("debug_pagealloc", early_debug_pagealloc);
  
  static int __init debug_guardpage_minorder_setup(char *buf)
  {
  	unsigned long res;
  
  	if (kstrtoul(buf, 10, &res) < 0 ||  res > MAX_ORDER / 2) {
  		pr_err("Bad debug_guardpage_minorder value\n");
  		return 0;
  	}
  	_debug_guardpage_minorder = res;
  	pr_info("Setting debug_guardpage_minorder to %lu\n", res);
  	return 0;
  }
  early_param("debug_guardpage_minorder", debug_guardpage_minorder_setup);
  
  static inline bool set_page_guard(struct zone *zone, struct page *page,
  				unsigned int order, int migratetype)
  {
  	if (!debug_guardpage_enabled())
  		return false;
  
  	if (order >= debug_guardpage_minorder())
  		return false;
  
  	__SetPageGuard(page);
  	INIT_LIST_HEAD(&page->lru);
  	set_page_private(page, order);
  	/* Guard pages are not available for any usage */
  	__mod_zone_freepage_state(zone, -(1 << order), migratetype);
  
  	return true;
  }
  
  static inline void clear_page_guard(struct zone *zone, struct page *page,
  				unsigned int order, int migratetype)
  {
  	if (!debug_guardpage_enabled())
  		return;
  
  	__ClearPageGuard(page);
  
  	set_page_private(page, 0);
  	if (!is_migrate_isolate(migratetype))
  		__mod_zone_freepage_state(zone, (1 << order), migratetype);
  }
  #else
  static inline bool set_page_guard(struct zone *zone, struct page *page,
  			unsigned int order, int migratetype) { return false; }
  static inline void clear_page_guard(struct zone *zone, struct page *page,
  				unsigned int order, int migratetype) {}
  #endif
  
  /*
   * Enable static keys related to various memory debugging and hardening options.
   * Some override others, and depend on early params that are evaluated in the
   * order of appearance. So we need to first gather the full picture of what was
   * enabled, and then make decisions.
   */
  void init_mem_debugging_and_hardening(void)
  {
  	bool page_poisoning_requested = false;
  
  #ifdef CONFIG_PAGE_POISONING
  	/*
  	 * Page poisoning is debug page alloc for some arches. If
  	 * either of those options are enabled, enable poisoning.
  	 */
  	if (page_poisoning_enabled() ||
  	     (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
  	      debug_pagealloc_enabled())) {
  		static_branch_enable(&_page_poisoning_enabled);
  		page_poisoning_requested = true;
  	}
  #endif
  
  	if ((_init_on_alloc_enabled_early || _init_on_free_enabled_early) &&
  	    page_poisoning_requested) {
  		pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
  			"will take precedence over init_on_alloc and init_on_free\n");
  		_init_on_alloc_enabled_early = false;
  		_init_on_free_enabled_early = false;
  	}
  
  	if (_init_on_alloc_enabled_early)
  		static_branch_enable(&init_on_alloc);
  	else
  		static_branch_disable(&init_on_alloc);
  
  	if (_init_on_free_enabled_early)
  		static_branch_enable(&init_on_free);
  	else
  		static_branch_disable(&init_on_free);
  
  #ifdef CONFIG_DEBUG_PAGEALLOC
  	if (!debug_pagealloc_enabled())
  		return;
  
  	static_branch_enable(&_debug_pagealloc_enabled);
  
  	if (!debug_guardpage_minorder())
  		return;
  
  	static_branch_enable(&_debug_guardpage_enabled);
  #endif
  }
  
  static inline void set_buddy_order(struct page *page, unsigned int order)
  {
  	set_page_private(page, order);
  	__SetPageBuddy(page);
  }
  
  /*
   * This function checks whether a page is free && is the buddy
   * we can coalesce a page and its buddy if
   * (a) the buddy is not in a hole (check before calling!) &&
   * (b) the buddy is in the buddy system &&
   * (c) a page and its buddy have the same order &&
   * (d) a page and its buddy are in the same zone.
   *
   * For recording whether a page is in the buddy system, we set PageBuddy.
   * Setting, clearing, and testing PageBuddy is serialized by zone->lock.
   *
   * For recording page's order, we use page_private(page).
   */
  static inline bool page_is_buddy(struct page *page, struct page *buddy,
  							unsigned int order)
  {
  	if (!page_is_guard(buddy) && !PageBuddy(buddy))
  		return false;
  
  	if (buddy_order(buddy) != order)
  		return false;
  
  	/*
  	 * zone check is done late to avoid uselessly calculating
  	 * zone/node ids for pages that could never merge.
  	 */
  	if (page_zone_id(page) != page_zone_id(buddy))
  		return false;
  
  	VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
  
  	return true;
  }
  
  #ifdef CONFIG_COMPACTION
  static inline struct capture_control *task_capc(struct zone *zone)
  {
  	struct capture_control *capc = current->capture_control;
  
  	return unlikely(capc) &&
  		!(current->flags & PF_KTHREAD) &&
  		!capc->page &&
  		capc->cc->zone == zone ? capc : NULL;
  }
  
  static inline bool
  compaction_capture(struct capture_control *capc, struct page *page,
  		   int order, int migratetype)
  {
  	if (!capc || order != capc->cc->order)
  		return false;
  
  	/* Do not accidentally pollute CMA or isolated regions*/
  	if (is_migrate_cma(migratetype) ||
  	    is_migrate_isolate(migratetype))
  		return false;
  
  	/*
  	 * Do not let lower order allocations pollute a movable pageblock.
  	 * This might let an unmovable request use a reclaimable pageblock
  	 * and vice-versa but no more than normal fallback logic which can
  	 * have trouble finding a high-order free page.
  	 */
  	if (order < pageblock_order && migratetype == MIGRATE_MOVABLE)
  		return false;
  
  	capc->page = page;
  	return true;
  }
  
  #else
  static inline struct capture_control *task_capc(struct zone *zone)
  {
  	return NULL;
  }
  
  static inline bool
  compaction_capture(struct capture_control *capc, struct page *page,
  		   int order, int migratetype)
  {
  	return false;
  }
  #endif /* CONFIG_COMPACTION */
  
  /* Used for pages not on another list */
  static inline void add_to_free_list(struct page *page, struct zone *zone,
  				    unsigned int order, int migratetype)
  {
  	struct free_area *area = &zone->free_area[order];
  
  	list_add(&page->lru, &area->free_list[migratetype]);
  	area->nr_free++;
  }
  
  /* Used for pages not on another list */
  static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
  					 unsigned int order, int migratetype)
  {
  	struct free_area *area = &zone->free_area[order];
  
  	list_add_tail(&page->lru, &area->free_list[migratetype]);
  	area->nr_free++;
  }
  
  /*
   * Used for pages which are on another list. Move the pages to the tail
   * of the list - so the moved pages won't immediately be considered for
   * allocation again (e.g., optimization for memory onlining).
   */
  static inline void move_to_free_list(struct page *page, struct zone *zone,
  				     unsigned int order, int migratetype)
  {
  	struct free_area *area = &zone->free_area[order];
  
  	list_move_tail(&page->lru, &area->free_list[migratetype]);
  }
  
  static inline void del_page_from_free_list(struct page *page, struct zone *zone,
  					   unsigned int order)
  {
  	/* clear reported state and update reported page count */
  	if (page_reported(page))
  		__ClearPageReported(page);
  
  	list_del(&page->lru);
  	__ClearPageBuddy(page);
  	set_page_private(page, 0);
  	zone->free_area[order].nr_free--;
  }
  
  /*
   * If this is not the largest possible page, check if the buddy
   * of the next-highest order is free. If it is, it's possible
   * that pages are being freed that will coalesce soon. In case,
   * that is happening, add the free page to the tail of the list
   * so it's less likely to be used soon and more likely to be merged
   * as a higher order page
   */
  static inline bool
  buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
  		   struct page *page, unsigned int order)
  {
  	struct page *higher_page, *higher_buddy;
  	unsigned long combined_pfn;
  
  	if (order >= MAX_ORDER - 2)
  		return false;
  
  	combined_pfn = buddy_pfn & pfn;
  	higher_page = page + (combined_pfn - pfn);
  	buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1);
  	higher_buddy = higher_page + (buddy_pfn - combined_pfn);
  
  	return page_is_buddy(higher_page, higher_buddy, order + 1);
  }
  
  /*
   * Freeing function for a buddy system allocator.
   *
   * The concept of a buddy system is to maintain direct-mapped table
   * (containing bit values) for memory blocks of various "orders".
   * The bottom level table contains the map for the smallest allocatable
   * units of memory (here, pages), and each level above it describes
   * pairs of units from the levels below, hence, "buddies".
   * At a high level, all that happens here is marking the table entry
   * at the bottom level available, and propagating the changes upward
   * as necessary, plus some accounting needed to play nicely with other
   * parts of the VM system.
   * At each level, we keep a list of pages, which are heads of continuous
   * free pages of length of (1 << order) and marked with PageBuddy.
   * Page's order is recorded in page_private(page) field.
   * So when we are allocating or freeing one, we can derive the state of the
   * other.  That is, if we allocate a small block, and both were
   * free, the remainder of the region must be split into blocks.
   * If a block is freed, and its buddy is also free, then this
   * triggers coalescing into a block of larger size.
   *
   * -- nyc
   */
  
  static inline void __free_one_page(struct page *page,
  		unsigned long pfn,
  		struct zone *zone, unsigned int order,
  		int migratetype, fpi_t fpi_flags)
  {
  	struct capture_control *capc = task_capc(zone);
  	unsigned long buddy_pfn;
  	unsigned long combined_pfn;
  	unsigned int max_order;
  	struct page *buddy;
  	bool to_tail;
  
  	max_order = min_t(unsigned int, MAX_ORDER - 1, pageblock_order);
  
  	VM_BUG_ON(!zone_is_initialized(zone));
  	VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
  
  	VM_BUG_ON(migratetype == -1);
  	if (likely(!is_migrate_isolate(migratetype)))
  		__mod_zone_freepage_state(zone, 1 << order, migratetype);
  
  	VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
  	VM_BUG_ON_PAGE(bad_range(zone, page), page);
  
  continue_merging:
  	while (order < max_order) {
  		if (compaction_capture(capc, page, order, migratetype)) {
  			__mod_zone_freepage_state(zone, -(1 << order),
  								migratetype);
  			return;
  		}
  		buddy_pfn = __find_buddy_pfn(pfn, order);
  		buddy = page + (buddy_pfn - pfn);
  
  		if (!page_is_buddy(page, buddy, order))
  			goto done_merging;
  		/*
  		 * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
  		 * merge with it and move up one order.
  		 */
  		if (page_is_guard(buddy))
  			clear_page_guard(zone, buddy, order, migratetype);
  		else
  			del_page_from_free_list(buddy, zone, order);
  		combined_pfn = buddy_pfn & pfn;
  		page = page + (combined_pfn - pfn);
  		pfn = combined_pfn;
  		order++;
  	}
  	if (order < MAX_ORDER - 1) {
  		/* If we are here, it means order is >= pageblock_order.
  		 * We want to prevent merge between freepages on isolate
  		 * pageblock and normal pageblock. Without this, pageblock
  		 * isolation could cause incorrect freepage or CMA accounting.
  		 *
  		 * We don't want to hit this code for the more frequent
  		 * low-order merging.
  		 */
  		if (unlikely(has_isolate_pageblock(zone))) {
  			int buddy_mt;
  
  			buddy_pfn = __find_buddy_pfn(pfn, order);
  			buddy = page + (buddy_pfn - pfn);
  			buddy_mt = get_pageblock_migratetype(buddy);
  
  			if (migratetype != buddy_mt
  					&& (is_migrate_isolate(migratetype) ||
  						is_migrate_isolate(buddy_mt)))
  				goto done_merging;
  		}
  		max_order = order + 1;
  		goto continue_merging;
  	}
  
  done_merging:
  	set_buddy_order(page, order);
  
  	if (fpi_flags & FPI_TO_TAIL)
  		to_tail = true;
  	else if (is_shuffle_order(order))
  		to_tail = shuffle_pick_tail();
  	else
  		to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order);
  
  	if (to_tail)
  		add_to_free_list_tail(page, zone, order, migratetype);
  	else
  		add_to_free_list(page, zone, order, migratetype);
  
  	/* Notify page reporting subsystem of freed page */
  	if (!(fpi_flags & FPI_SKIP_REPORT_NOTIFY))
  		page_reporting_notify_free(order);
  }
  
  /*
   * A bad page could be due to a number of fields. Instead of multiple branches,
   * try and check multiple fields with one check. The caller must do a detailed
   * check if necessary.
   */
  static inline bool page_expected_state(struct page *page,
  					unsigned long check_flags)
  {
  	if (unlikely(atomic_read(&page->_mapcount) != -1))
  		return false;
  
  	if (unlikely((unsigned long)page->mapping |
  			page_ref_count(page) |
  #ifdef CONFIG_MEMCG
  			page->memcg_data |
  #endif
  			(page->flags & check_flags)))
  		return false;
  
  	return true;
  }
  
  static const char *page_bad_reason(struct page *page, unsigned long flags)
  {
  	const char *bad_reason = NULL;
  
  	if (unlikely(atomic_read(&page->_mapcount) != -1))
  		bad_reason = "nonzero mapcount";
  	if (unlikely(page->mapping != NULL))
  		bad_reason = "non-NULL mapping";
  	if (unlikely(page_ref_count(page) != 0))
  		bad_reason = "nonzero _refcount";
  	if (unlikely(page->flags & flags)) {
  		if (flags == PAGE_FLAGS_CHECK_AT_PREP)
  			bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag(s) set";
  		else
  			bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
  	}
  #ifdef CONFIG_MEMCG
  	if (unlikely(page->memcg_data))
  		bad_reason = "page still charged to cgroup";
  #endif
  	return bad_reason;
  }
  
  static void check_free_page_bad(struct page *page)
  {
  	bad_page(page,
  		 page_bad_reason(page, PAGE_FLAGS_CHECK_AT_FREE));
  }
  
  static inline int check_free_page(struct page *page)
  {
  	if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
  		return 0;
  
  	/* Something has gone sideways, find it */
  	check_free_page_bad(page);
  	return 1;
  }
  
  static int free_tail_pages_check(struct page *head_page, struct page *page)
  {
  	int ret = 1;
  
  	/*
  	 * We rely page->lru.next never has bit 0 set, unless the page
  	 * is PageTail(). Let's make sure that's true even for poisoned ->lru.
  	 */
  	BUILD_BUG_ON((unsigned long)LIST_POISON1 & 1);
  
  	if (!IS_ENABLED(CONFIG_DEBUG_VM)) {
  		ret = 0;
  		goto out;
  	}
  	switch (page - head_page) {
  	case 1:
  		/* the first tail page: ->mapping may be compound_mapcount() */
  		if (unlikely(compound_mapcount(page))) {
  			bad_page(page, "nonzero compound_mapcount");
  			goto out;
  		}
  		break;
  	case 2:
  		/*
  		 * the second tail page: ->mapping is
  		 * deferred_list.next -- ignore value.
  		 */
  		break;
  	default:
  		if (page->mapping != TAIL_MAPPING) {
  			bad_page(page, "corrupted mapping in tail page");
  			goto out;
  		}
  		break;
  	}
  	if (unlikely(!PageTail(page))) {
  		bad_page(page, "PageTail not set");
  		goto out;
  	}
  	if (unlikely(compound_head(page) != head_page)) {
  		bad_page(page, "compound_head not consistent");
  		goto out;
  	}
  	ret = 0;
  out:
  	page->mapping = NULL;
  	clear_compound_head(page);
  	return ret;
  }
  
  static void kernel_init_free_pages(struct page *page, int numpages, bool zero_tags)
  {
  	int i;
  
  	if (zero_tags) {
  		for (i = 0; i < numpages; i++)
  			tag_clear_highpage(page + i);
  		return;
  	}
  
  	/* s390's use of memset() could override KASAN redzones. */
  	kasan_disable_current();
  	for (i = 0; i < numpages; i++) {
  		u8 tag = page_kasan_tag(page + i);
  		page_kasan_tag_reset(page + i);
  		clear_highpage(page + i);
  		page_kasan_tag_set(page + i, tag);
  	}
  	kasan_enable_current();
  }
  
  static __always_inline bool free_pages_prepare(struct page *page,
  			unsigned int order, bool check_free, fpi_t fpi_flags)
  {
  	int bad = 0;
  	bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags);
  
  	VM_BUG_ON_PAGE(PageTail(page), page);
  
  	trace_mm_page_free(page, order);
  
  	if (unlikely(PageHWPoison(page)) && !order) {
  		/*
  		 * Do not let hwpoison pages hit pcplists/buddy
  		 * Untie memcg state and reset page's owner
  		 */
  		if (memcg_kmem_enabled() && PageMemcgKmem(page))
  			__memcg_kmem_uncharge_page(page, order);
  		reset_page_owner(page, order);
  		page_table_check_free(page, order);
  		return false;
  	}
  
  	/*
  	 * Check tail pages before head page information is cleared to
  	 * avoid checking PageCompound for order-0 pages.
  	 */
  	if (unlikely(order)) {
  		bool compound = PageCompound(page);
  		int i;
  
  		VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
  
  		if (compound) {
  			ClearPageDoubleMap(page);
  			ClearPageHasHWPoisoned(page);
  		}
  		for (i = 1; i < (1 << order); i++) {
  			if (compound)
  				bad += free_tail_pages_check(page, page + i);
  			if (unlikely(check_free_page(page + i))) {
  				bad++;
  				continue;
  			}
  			(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
  		}
  	}
  	if (PageMappingFlags(page))
  		page->mapping = NULL;
  	if (memcg_kmem_enabled() && PageMemcgKmem(page))
  		__memcg_kmem_uncharge_page(page, order);
  	if (check_free)
  		bad += check_free_page(page);
  	if (bad)
  		return false;
  
  	page_cpupid_reset_last(page);
  	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
  	reset_page_owner(page, order);
  	page_table_check_free(page, order);
  
  	if (!PageHighMem(page)) {
  		debug_check_no_locks_freed(page_address(page),
  					   PAGE_SIZE << order);
  		debug_check_no_obj_freed(page_address(page),
  					   PAGE_SIZE << order);
  	}
  
  	kernel_poison_pages(page, 1 << order);
  
  	/*
  	 * As memory initialization might be integrated into KASAN,
  	 * kasan_free_pages and kernel_init_free_pages must be
  	 * kept together to avoid discrepancies in behavior.
  	 *
  	 * With hardware tag-based KASAN, memory tags must be set before the
  	 * page becomes unavailable via debug_pagealloc or arch_free_page.
  	 */
  	if (kasan_has_integrated_init()) {
  		if (!skip_kasan_poison)
  			kasan_free_pages(page, order);
  	} else {
  		bool init = want_init_on_free();
  
  		if (init)
  			kernel_init_free_pages(page, 1 << order, false);
  		if (!skip_kasan_poison)
  			kasan_poison_pages(page, order, init);
  	}
  
  	/*
  	 * arch_free_page() can make the page's contents inaccessible.  s390
  	 * does this.  So nothing which can access the page's contents should
  	 * happen after this.
  	 */
  	arch_free_page(page, order);
  
  	debug_pagealloc_unmap_pages(page, 1 << order);
  
  	return true;
  }
  
  #ifdef CONFIG_DEBUG_VM
  /*
   * With DEBUG_VM enabled, order-0 pages are checked immediately when being freed
   * to pcp lists. With debug_pagealloc also enabled, they are also rechecked when
   * moved from pcp lists to free lists.
   */
  static bool free_pcp_prepare(struct page *page, unsigned int order)
  {
  	return free_pages_prepare(page, order, true, FPI_NONE);
  }
  
  static bool bulkfree_pcp_prepare(struct page *page)
  {
  	if (debug_pagealloc_enabled_static())
  		return check_free_page(page);
  	else
  		return false;
  }
  #else
  /*
   * With DEBUG_VM disabled, order-0 pages being freed are checked only when
   * moving from pcp lists to free list in order to reduce overhead. With
   * debug_pagealloc enabled, they are checked also immediately when being freed
   * to the pcp lists.
   */
  static bool free_pcp_prepare(struct page *page, unsigned int order)
  {
  	if (debug_pagealloc_enabled_static())
  		return free_pages_prepare(page, order, true, FPI_NONE);
  	else
  		return free_pages_prepare(page, order, false, FPI_NONE);
  }
  
  static bool bulkfree_pcp_prepare(struct page *page)
  {
  	return check_free_page(page);
  }
  #endif /* CONFIG_DEBUG_VM */
  
  static inline void prefetch_buddy(struct page *page)
  {
  	unsigned long pfn = page_to_pfn(page);
  	unsigned long buddy_pfn = __find_buddy_pfn(pfn, 0);
  	struct page *buddy = page + (buddy_pfn - pfn);
  
  	prefetch(buddy);
  }
  
  /*
   * Frees a number of pages from the PCP lists
   * Assumes all pages on list are in same zone.
   * count is the number of pages to free.
   */
  static void free_pcppages_bulk(struct zone *zone, int count,
  					struct per_cpu_pages *pcp)
  {
  	int pindex = 0;
  	int batch_free = 0;
  	int nr_freed = 0;
  	unsigned int order;
  	int prefetch_nr = READ_ONCE(pcp->batch);
  	bool isolated_pageblocks;
  	struct page *page, *tmp;
  	LIST_HEAD(head);
  
  	/*
  	 * Ensure proper count is passed which otherwise would stuck in the
  	 * below while (list_empty(list)) loop.
  	 */
  	count = min(pcp->count, count);
  	while (count > 0) {
  		struct list_head *list;
  
  		/*
  		 * Remove pages from lists in a round-robin fashion. A
  		 * batch_free count is maintained that is incremented when an
  		 * empty list is encountered.  This is so more pages are freed
  		 * off fuller lists instead of spinning excessively around empty
  		 * lists
  		 */
  		do {
  			batch_free++;
  			if (++pindex == NR_PCP_LISTS)
  				pindex = 0;
  			list = &pcp->lists[pindex];
  		} while (list_empty(list));
  
  		/* This is the only non-empty list. Free them all. */
  		if (batch_free == NR_PCP_LISTS)
  			batch_free = count;
  
  		order = pindex_to_order(pindex);
  		BUILD_BUG_ON(MAX_ORDER >= (1<<NR_PCP_ORDER_WIDTH));
  		do {
  			page = list_last_entry(list, struct page, lru);
  			/* must delete to avoid corrupting pcp list */
  			list_del(&page->lru);
  			nr_freed += 1 << order;
  			count -= 1 << order;
  
  			if (bulkfree_pcp_prepare(page))
  				continue;
  
  			/* Encode order with the migratetype */
  			page->index <<= NR_PCP_ORDER_WIDTH;
  			page->index |= order;
  
  			list_add_tail(&page->lru, &head);
  
  			/*
  			 * We are going to put the page back to the global
  			 * pool, prefetch its buddy to speed up later access
  			 * under zone->lock. It is believed the overhead of
  			 * an additional test and calculating buddy_pfn here
  			 * can be offset by reduced memory latency later. To
  			 * avoid excessive prefetching due to large count, only
  			 * prefetch buddy for the first pcp->batch nr of pages.
  			 */
  			if (prefetch_nr) {
  				prefetch_buddy(page);
  				prefetch_nr--;
  			}
  		} while (count > 0 && --batch_free && !list_empty(list));
  	}
  	pcp->count -= nr_freed;
  
  	/*
  	 * local_lock_irq held so equivalent to spin_lock_irqsave for
  	 * both PREEMPT_RT and non-PREEMPT_RT configurations.
  	 */
  	spin_lock(&zone->lock);
  	isolated_pageblocks = has_isolate_pageblock(zone);
  
  	/*
  	 * Use safe version since after __free_one_page(),
  	 * page->lru.next will not point to original list.
  	 */
  	list_for_each_entry_safe(page, tmp, &head, lru) {
  		int mt = get_pcppage_migratetype(page);
  
  		/* mt has been encoded with the order (see above) */
  		order = mt & NR_PCP_ORDER_MASK;
  		mt >>= NR_PCP_ORDER_WIDTH;
  
  		/* MIGRATE_ISOLATE page should not go to pcplists */
  		VM_BUG_ON_PAGE(is_migrate_isolate(mt), page);
  		/* Pageblock could have been isolated meanwhile */
  		if (unlikely(isolated_pageblocks))
  			mt = get_pageblock_migratetype(page);
  
  		__free_one_page(page, page_to_pfn(page), zone, order, mt, FPI_NONE);
  		trace_mm_page_pcpu_drain(page, order, mt);
  	}
  	spin_unlock(&zone->lock);
  }
  
  static void free_one_page(struct zone *zone,
  				struct page *page, unsigned long pfn,
  				unsigned int order,
  				int migratetype, fpi_t fpi_flags)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&zone->lock, flags);
  	if (unlikely(has_isolate_pageblock(zone) ||
  		is_migrate_isolate(migratetype))) {
  		migratetype = get_pfnblock_migratetype(page, pfn);
  	}
  	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  
  static void __meminit __init_single_page(struct page *page, unsigned long pfn,
  				unsigned long zone, int nid)
  {
  	mm_zero_struct_page(page);
  	set_page_links(page, zone, nid, pfn);
  	init_page_count(page);
  	page_mapcount_reset(page);
  	page_cpupid_reset_last(page);
  	page_kasan_tag_reset(page);
  
  	INIT_LIST_HEAD(&page->lru);
  #ifdef WANT_PAGE_VIRTUAL
  	/* The shift won't overflow because ZONE_NORMAL is below 4G. */
  	if (!is_highmem_idx(zone))
  		set_page_address(page, __va(pfn << PAGE_SHIFT));
  #endif
  }
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  static void __meminit init_reserved_page(unsigned long pfn)
  {
  	pg_data_t *pgdat;
  	int nid, zid;
  
  	if (!early_page_uninitialised(pfn))
  		return;
  
  	nid = early_pfn_to_nid(pfn);
  	pgdat = NODE_DATA(nid);
  
  	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
  		struct zone *zone = &pgdat->node_zones[zid];
  
  		if (zone_spans_pfn(zone, pfn))
  			break;
  	}
  	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
  }
  #else
  static inline void init_reserved_page(unsigned long pfn)
  {
  }
  #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
  
  /*
   * Initialised pages do not have PageReserved set. This function is
   * called for each range allocated by the bootmem allocator and
   * marks the pages PageReserved. The remaining valid pages are later
   * sent to the buddy page allocator.
   */
  void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
  {
  	unsigned long start_pfn = PFN_DOWN(start);
  	unsigned long end_pfn = PFN_UP(end);
  
  	for (; start_pfn < end_pfn; start_pfn++) {
  		if (pfn_valid(start_pfn)) {
  			struct page *page = pfn_to_page(start_pfn);
  
  			init_reserved_page(start_pfn);
  
  			/* Avoid false-positive PageTail() */
  			INIT_LIST_HEAD(&page->lru);
  
  			/*
  			 * no need for atomic set_bit because the struct
  			 * page is not visible yet so nobody should
  			 * access it yet.
  			 */
  			__SetPageReserved(page);
  		}
  	}
  }
  
  static void __free_pages_ok(struct page *page, unsigned int order,
  			    fpi_t fpi_flags)
  {
  	unsigned long flags;
  	int migratetype;
  	unsigned long pfn = page_to_pfn(page);
  	struct zone *zone = page_zone(page);
  
  	if (!free_pages_prepare(page, order, true, fpi_flags))
  		return;
  
  	migratetype = get_pfnblock_migratetype(page, pfn);
  
  	spin_lock_irqsave(&zone->lock, flags);
  	if (unlikely(has_isolate_pageblock(zone) ||
  		is_migrate_isolate(migratetype))) {
  		migratetype = get_pfnblock_migratetype(page, pfn);
  	}
  	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
  	spin_unlock_irqrestore(&zone->lock, flags);
  
  	__count_vm_events(PGFREE, 1 << order);
  }
  
  void __free_pages_core(struct page *page, unsigned int order)
  {
  	unsigned int nr_pages = 1 << order;
  	struct page *p = page;
  	unsigned int loop;
  
  	/*
  	 * When initializing the memmap, __init_single_page() sets the refcount
  	 * of all pages to 1 ("allocated"/"not free"). We have to set the
  	 * refcount of all involved pages to 0.
  	 */
  	prefetchw(p);
  	for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
  		prefetchw(p + 1);
  		__ClearPageReserved(p);
  		set_page_count(p, 0);
  	}
  	__ClearPageReserved(p);
  	set_page_count(p, 0);
  
  	atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
  
  	/*
  	 * Bypass PCP and place fresh pages right to the tail, primarily
  	 * relevant for memory onlining.
  	 */
  	__free_pages_ok(page, order, FPI_TO_TAIL | FPI_SKIP_KASAN_POISON);
  }
  
  #ifdef CONFIG_NUMA
  
  /*
   * During memory init memblocks map pfns to nids. The search is expensive and
   * this caches recent lookups. The implementation of __early_pfn_to_nid
   * treats start/end as pfns.
   */
  struct mminit_pfnnid_cache {
  	unsigned long last_start;
  	unsigned long last_end;
  	int last_nid;
  };
  
  static struct mminit_pfnnid_cache early_pfnnid_cache __meminitdata;
  
  /*
   * Required by SPARSEMEM. Given a PFN, return what node the PFN is on.
   */
  static int __meminit __early_pfn_to_nid(unsigned long pfn,
  					struct mminit_pfnnid_cache *state)
  {
  	unsigned long start_pfn, end_pfn;
  	int nid;
  
  	if (state->last_start <= pfn && pfn < state->last_end)
  		return state->last_nid;
  
  	nid = memblock_search_pfn_nid(pfn, &start_pfn, &end_pfn);
  	if (nid != NUMA_NO_NODE) {
  		state->last_start = start_pfn;
  		state->last_end = end_pfn;
  		state->last_nid = nid;
  	}
  
  	return nid;
  }
  
  int __meminit early_pfn_to_nid(unsigned long pfn)
  {
  	static DEFINE_SPINLOCK(early_pfn_lock);
  	int nid;
  
  	spin_lock(&early_pfn_lock);
  	nid = __early_pfn_to_nid(pfn, &early_pfnnid_cache);
  	if (nid < 0)
  		nid = first_online_node;
  	spin_unlock(&early_pfn_lock);
  
  	return nid;
  }
  #endif /* CONFIG_NUMA */
  
  void __init memblock_free_pages(struct page *page, unsigned long pfn,
  							unsigned int order)
  {
  	if (early_page_uninitialised(pfn))
  		return;
  	__free_pages_core(page, order);
  }
  
  /*
   * Check that the whole (or subset of) a pageblock given by the interval of
   * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
   * with the migration of free compaction scanner.
   *
   * Return struct page pointer of start_pfn, or NULL if checks were not passed.
   *
   * It's possible on some configurations to have a setup like node0 node1 node0
   * i.e. it's possible that all pages within a zones range of pages do not
   * belong to a single zone. We assume that a border between node0 and node1
   * can occur within a single pageblock, but not a node0 node1 node0
   * interleaving within a single pageblock. It is therefore sufficient to check
   * the first and last page of a pageblock and avoid checking each individual
   * page in a pageblock.
   */
  struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
  				     unsigned long end_pfn, struct zone *zone)
  {
  	struct page *start_page;
  	struct page *end_page;
  
  	/* end_pfn is one past the range we are checking */
  	end_pfn--;
  
  	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
  		return NULL;
  
  	start_page = pfn_to_online_page(start_pfn);
  	if (!start_page)
  		return NULL;
  
  	if (page_zone(start_page) != zone)
  		return NULL;
  
  	end_page = pfn_to_page(end_pfn);
  
  	/* This gives a shorter code than deriving page_zone(end_page) */
  	if (page_zone_id(start_page) != page_zone_id(end_page))
  		return NULL;
  
  	return start_page;
  }
  
  void set_zone_contiguous(struct zone *zone)
  {
  	unsigned long block_start_pfn = zone->zone_start_pfn;
  	unsigned long block_end_pfn;
  
  	block_end_pfn = ALIGN(block_start_pfn + 1, pageblock_nr_pages);
  	for (; block_start_pfn < zone_end_pfn(zone);
  			block_start_pfn = block_end_pfn,
  			 block_end_pfn += pageblock_nr_pages) {
  
  		block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));
  
  		if (!__pageblock_pfn_to_page(block_start_pfn,
  					     block_end_pfn, zone))
  			return;
  		cond_resched();
  	}
  
  	/* We confirm that there is no hole */
  	zone->contiguous = true;
  }
  
  void clear_zone_contiguous(struct zone *zone)
  {
  	zone->contiguous = false;
  }
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  static void __init deferred_free_range(unsigned long pfn,
  				       unsigned long nr_pages)
  {
  	struct page *page;
  	unsigned long i;
  
  	if (!nr_pages)
  		return;
  
  	page = pfn_to_page(pfn);
  
  	/* Free a large naturally-aligned chunk if possible */
  	if (nr_pages == pageblock_nr_pages &&
  	    (pfn & (pageblock_nr_pages - 1)) == 0) {
  		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
  		__free_pages_core(page, pageblock_order);
  		return;
  	}
  
  	for (i = 0; i < nr_pages; i++, page++, pfn++) {
  		if ((pfn & (pageblock_nr_pages - 1)) == 0)
  			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
  		__free_pages_core(page, 0);
  	}
  }
  
  /* Completion tracking for deferred_init_memmap() threads */
  static atomic_t pgdat_init_n_undone __initdata;
  static __initdata DECLARE_COMPLETION(pgdat_init_all_done_comp);
  
  static inline void __init pgdat_init_report_one_done(void)
  {
  	if (atomic_dec_and_test(&pgdat_init_n_undone))
  		complete(&pgdat_init_all_done_comp);
  }
  
  /*
   * Returns true if page needs to be initialized or freed to buddy allocator.
   *
   * First we check if pfn is valid on architectures where it is possible to have
   * holes within pageblock_nr_pages. On systems where it is not possible, this
   * function is optimized out.
   *
   * Then, we check if a current large page is valid by only checking the validity
   * of the head pfn.
   */
  static inline bool __init deferred_pfn_valid(unsigned long pfn)
  {
  	if (!(pfn & (pageblock_nr_pages - 1)) && !pfn_valid(pfn))
  		return false;
  	return true;
  }
  
  /*
   * Free pages to buddy allocator. Try to free aligned pages in
   * pageblock_nr_pages sizes.
   */
  static void __init deferred_free_pages(unsigned long pfn,
  				       unsigned long end_pfn)
  {
  	unsigned long nr_pgmask = pageblock_nr_pages - 1;
  	unsigned long nr_free = 0;
  
  	for (; pfn < end_pfn; pfn++) {
  		if (!deferred_pfn_valid(pfn)) {
  			deferred_free_range(pfn - nr_free, nr_free);
  			nr_free = 0;
  		} else if (!(pfn & nr_pgmask)) {
  			deferred_free_range(pfn - nr_free, nr_free);
  			nr_free = 1;
  		} else {
  			nr_free++;
  		}
  	}
  	/* Free the last block of pages to allocator */
  	deferred_free_range(pfn - nr_free, nr_free);
  }
  
  /*
   * Initialize struct pages.  We minimize pfn page lookups and scheduler checks
   * by performing it only once every pageblock_nr_pages.
   * Return number of pages initialized.
   */
  static unsigned long  __init deferred_init_pages(struct zone *zone,
  						 unsigned long pfn,
  						 unsigned long end_pfn)
  {
  	unsigned long nr_pgmask = pageblock_nr_pages - 1;
  	int nid = zone_to_nid(zone);
  	unsigned long nr_pages = 0;
  	int zid = zone_idx(zone);
  	struct page *page = NULL;
  
  	for (; pfn < end_pfn; pfn++) {
  		if (!deferred_pfn_valid(pfn)) {
  			page = NULL;
  			continue;
  		} else if (!page || !(pfn & nr_pgmask)) {
  			page = pfn_to_page(pfn);
  		} else {
  			page++;
  		}
  		__init_single_page(page, pfn, zid, nid);
  		nr_pages++;
  	}
  	return (nr_pages);
  }
  
  /*
   * This function is meant to pre-load the iterator for the zone init.
   * Specifically it walks through the ranges until we are caught up to the
   * first_init_pfn value and exits there. If we never encounter the value we
   * return false indicating there are no valid ranges left.
   */
  static bool __init
  deferred_init_mem_pfn_range_in_zone(u64 *i, struct zone *zone,
  				    unsigned long *spfn, unsigned long *epfn,
  				    unsigned long first_init_pfn)
  {
  	u64 j;
  
  	/*
  	 * Start out by walking through the ranges in this zone that have
  	 * already been initialized. We don't need to do anything with them
  	 * so we just need to flush them out of the system.
  	 */
  	for_each_free_mem_pfn_range_in_zone(j, zone, spfn, epfn) {
  		if (*epfn <= first_init_pfn)
  			continue;
  		if (*spfn < first_init_pfn)
  			*spfn = first_init_pfn;
  		*i = j;
  		return true;
  	}
  
  	return false;
  }
  
  /*
   * Initialize and free pages. We do it in two loops: first we initialize
   * struct page, then free to buddy allocator, because while we are
   * freeing pages we can access pages that are ahead (computing buddy
   * page in __free_one_page()).
   *
   * In order to try and keep some memory in the cache we have the loop
   * broken along max page order boundaries. This way we will not cause
   * any issues with the buddy page computation.
   */
  static unsigned long __init
  deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
  		       unsigned long *end_pfn)
  {
  	unsigned long mo_pfn = ALIGN(*start_pfn + 1, MAX_ORDER_NR_PAGES);
  	unsigned long spfn = *start_pfn, epfn = *end_pfn;
  	unsigned long nr_pages = 0;
  	u64 j = *i;
  
  	/* First we loop through and initialize the page values */
  	for_each_free_mem_pfn_range_in_zone_from(j, zone, start_pfn, end_pfn) {
  		unsigned long t;
  
  		if (mo_pfn <= *start_pfn)
  			break;
  
  		t = min(mo_pfn, *end_pfn);
  		nr_pages += deferred_init_pages(zone, *start_pfn, t);
  
  		if (mo_pfn < *end_pfn) {
  			*start_pfn = mo_pfn;
  			break;
  		}
  	}
  
  	/* Reset values and now loop through freeing pages as needed */
  	swap(j, *i);
  
  	for_each_free_mem_pfn_range_in_zone_from(j, zone, &spfn, &epfn) {
  		unsigned long t;
  
  		if (mo_pfn <= spfn)
  			break;
  
  		t = min(mo_pfn, epfn);
  		deferred_free_pages(spfn, t);
  
  		if (mo_pfn <= epfn)
  			break;
  	}
  
  	return nr_pages;
  }
  
  static void __init
  deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
  			   void *arg)
  {
  	unsigned long spfn, epfn;
  	struct zone *zone = arg;
  	u64 i;
  
  	deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, start_pfn);
  
  	/*
  	 * Initialize and free pages in MAX_ORDER sized increments so that we
  	 * can avoid introducing any issues with the buddy allocator.
  	 */
  	while (spfn < end_pfn) {
  		deferred_init_maxorder(&i, zone, &spfn, &epfn);
  		cond_resched();
  	}
  }
  
  /* An arch may override for more concurrency. */
  __weak int __init
  deferred_page_init_max_threads(const struct cpumask *node_cpumask)
  {
  	return 1;
  }
  
  /* Initialise remaining memory on a node */
  static int __init deferred_init_memmap(void *data)
  {
  	pg_data_t *pgdat = data;
  	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
  	unsigned long spfn = 0, epfn = 0;
  	unsigned long first_init_pfn, flags;
  	unsigned long start = jiffies;
  	struct zone *zone;
  	int zid, max_threads;
  	u64 i;
  
  	/* Bind memory initialisation thread to a local node if possible */
  	if (!cpumask_empty(cpumask))
  		set_cpus_allowed_ptr(current, cpumask);
  
  	pgdat_resize_lock(pgdat, &flags);
  	first_init_pfn = pgdat->first_deferred_pfn;
  	if (first_init_pfn == ULONG_MAX) {
  		pgdat_resize_unlock(pgdat, &flags);
  		pgdat_init_report_one_done();
  		return 0;
  	}
  
  	/* Sanity check boundaries */
  	BUG_ON(pgdat->first_deferred_pfn < pgdat->node_start_pfn);
  	BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
  	pgdat->first_deferred_pfn = ULONG_MAX;
  
  	/*
  	 * Once we unlock here, the zone cannot be grown anymore, thus if an
  	 * interrupt thread must allocate this early in boot, zone must be
  	 * pre-grown prior to start of deferred page initialization.
  	 */
  	pgdat_resize_unlock(pgdat, &flags);
  
  	/* Only the highest zone is deferred so find it */
  	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
  		zone = pgdat->node_zones + zid;
  		if (first_init_pfn < zone_end_pfn(zone))
  			break;
  	}
  
  	/* If the zone is empty somebody else may have cleared out the zone */
  	if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
  						 first_init_pfn))
  		goto zone_empty;
  
  	max_threads = deferred_page_init_max_threads(cpumask);
  
  	while (spfn < epfn) {
  		unsigned long epfn_align = ALIGN(epfn, PAGES_PER_SECTION);
  		struct padata_mt_job job = {
  			.thread_fn   = deferred_init_memmap_chunk,
  			.fn_arg      = zone,
  			.start       = spfn,
  			.size        = epfn_align - spfn,
  			.align       = PAGES_PER_SECTION,
  			.min_chunk   = PAGES_PER_SECTION,
  			.max_threads = max_threads,
  		};
  
  		padata_do_multithreaded(&job);
  		deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
  						    epfn_align);
  	}
  zone_empty:
  	/* Sanity check that the next zone really is unpopulated */
  	WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));
  
  	pr_info("node %d deferred pages initialised in %ums\n",
  		pgdat->node_id, jiffies_to_msecs(jiffies - start));
  
  	pgdat_init_report_one_done();
  	return 0;
  }
  
  /*
   * If this zone has deferred pages, try to grow it by initializing enough
   * deferred pages to satisfy the allocation specified by order, rounded up to
   * the nearest PAGES_PER_SECTION boundary.  So we're adding memory in increments
   * of SECTION_SIZE bytes by initializing struct pages in increments of
   * PAGES_PER_SECTION * sizeof(struct page) bytes.
   *
   * Return true when zone was grown, otherwise return false. We return true even
   * when we grow less than requested, to let the caller decide if there are
   * enough pages to satisfy the allocation.
   *
   * Note: We use noinline because this function is needed only during boot, and
   * it is called from a __ref function _deferred_grow_zone. This way we are
   * making sure that it is not inlined into permanent text section.
   */
  static noinline bool __init
  deferred_grow_zone(struct zone *zone, unsigned int order)
  {
  	unsigned long nr_pages_needed = ALIGN(1 << order, PAGES_PER_SECTION);
  	pg_data_t *pgdat = zone->zone_pgdat;
  	unsigned long first_deferred_pfn = pgdat->first_deferred_pfn;
  	unsigned long spfn, epfn, flags;
  	unsigned long nr_pages = 0;
  	u64 i;
  
  	/* Only the last zone may have deferred pages */
  	if (zone_end_pfn(zone) != pgdat_end_pfn(pgdat))
  		return false;
  
  	pgdat_resize_lock(pgdat, &flags);
  
  	/*
  	 * If someone grew this zone while we were waiting for spinlock, return
  	 * true, as there might be enough pages already.
  	 */
  	if (first_deferred_pfn != pgdat->first_deferred_pfn) {
  		pgdat_resize_unlock(pgdat, &flags);
  		return true;
  	}
  
  	/* If the zone is empty somebody else may have cleared out the zone */
  	if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
  						 first_deferred_pfn)) {
  		pgdat->first_deferred_pfn = ULONG_MAX;
  		pgdat_resize_unlock(pgdat, &flags);
  		/* Retry only once. */
  		return first_deferred_pfn != ULONG_MAX;
  	}
  
  	/*
  	 * Initialize and free pages in MAX_ORDER sized increments so
  	 * that we can avoid introducing any issues with the buddy
  	 * allocator.
  	 */
  	while (spfn < epfn) {
  		/* update our first deferred PFN for this section */
  		first_deferred_pfn = spfn;
  
  		nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
  		touch_nmi_watchdog();
  
  		/* We should only stop along section boundaries */
  		if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION)
  			continue;
  
  		/* If our quota has been met we can stop here */
  		if (nr_pages >= nr_pages_needed)
  			break;
  	}
  
  	pgdat->first_deferred_pfn = spfn;
  	pgdat_resize_unlock(pgdat, &flags);
  
  	return nr_pages > 0;
  }
  
  /*
   * deferred_grow_zone() is __init, but it is called from
   * get_page_from_freelist() during early boot until deferred_pages permanently
   * disables this call. This is why we have refdata wrapper to avoid warning,
   * and to ensure that the function body gets unloaded.
   */
  static bool __ref
  _deferred_grow_zone(struct zone *zone, unsigned int order)
  {
  	return deferred_grow_zone(zone, order);
  }
  
  #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
  
  void __init page_alloc_init_late(void)
  {
  	struct zone *zone;
  	int nid;
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  
  	/* There will be num_node_state(N_MEMORY) threads */
  	atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY));
  	for_each_node_state(nid, N_MEMORY) {
  		kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid);
  	}
  
  	/* Block until all are initialised */
  	wait_for_completion(&pgdat_init_all_done_comp);
  
  	/*
  	 * We initialized the rest of the deferred pages.  Permanently disable
  	 * on-demand struct page initialization.
  	 */
  	static_branch_disable(&deferred_pages);
  
  	/* Reinit limits that are based on free pages after the kernel is up */
  	files_maxfiles_init();
  #endif
  
  	buffer_init();
  
  	/* Discard memblock private memory */
  	memblock_discard();
  
  	for_each_node_state(nid, N_MEMORY)
  		shuffle_free_memory(NODE_DATA(nid));
  
  	for_each_populated_zone(zone)
  		set_zone_contiguous(zone);
  }
  
  #ifdef CONFIG_CMA
  /* Free whole pageblock and set its migration type to MIGRATE_CMA. */
  void __init init_cma_reserved_pageblock(struct page *page)
  {
  	unsigned i = pageblock_nr_pages;
  	struct page *p = page;
  
  	do {
  		__ClearPageReserved(p);
  		set_page_count(p, 0);
  	} while (++p, --i);
  
  	set_pageblock_migratetype(page, MIGRATE_CMA);
  
  	if (pageblock_order >= MAX_ORDER) {
  		i = pageblock_nr_pages;
  		p = page;
  		do {
  			set_page_refcounted(p);
  			__free_pages(p, MAX_ORDER - 1);
  			p += MAX_ORDER_NR_PAGES;
  		} while (i -= MAX_ORDER_NR_PAGES);
  	} else {
  		set_page_refcounted(page);
  		__free_pages(page, pageblock_order);
  	}
  
  	adjust_managed_page_count(page, pageblock_nr_pages);
  	page_zone(page)->cma_pages += pageblock_nr_pages;
  }
  #endif
  
  /*
   * The order of subdivision here is critical for the IO subsystem.
   * Please do not alter this order without good reasons and regression
   * testing. Specifically, as large blocks of memory are subdivided,
   * the order in which smaller blocks are delivered depends on the order
   * they're subdivided in this function. This is the primary factor
   * influencing the order in which pages are delivered to the IO
   * subsystem according to empirical testing, and this is also justified
   * by considering the behavior of a buddy system containing a single
   * large block of memory acted on by a series of small allocations.
   * This behavior is a critical factor in sglist merging's success.
   *
   * -- nyc
   */
  static inline void expand(struct zone *zone, struct page *page,
  	int low, int high, int migratetype)
  {
  	unsigned long size = 1 << high;
  
  	while (high > low) {
  		high--;
  		size >>= 1;
  		VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
  
  		/*
  		 * Mark as guard pages (or page), that will allow to
  		 * merge back to allocator when buddy will be freed.
  		 * Corresponding page table entries will not be touched,
  		 * pages will stay not present in virtual address space
  		 */
  		if (set_page_guard(zone, &page[size], high, migratetype))
  			continue;
  
  		add_to_free_list(&page[size], zone, high, migratetype);
  		set_buddy_order(&page[size], high);
  	}
  }
  
  static void check_new_page_bad(struct page *page)
  {
  	if (unlikely(page->flags & __PG_HWPOISON)) {
  		/* Don't complain about hwpoisoned pages */
  		page_mapcount_reset(page); /* remove PageBuddy */
  		return;
  	}
  
  	bad_page(page,
  		 page_bad_reason(page, PAGE_FLAGS_CHECK_AT_PREP));
  }
  
  /*
   * This page is about to be returned from the page allocator
   */
  static inline int check_new_page(struct page *page)
  {
  	if (likely(page_expected_state(page,
  				PAGE_FLAGS_CHECK_AT_PREP|__PG_HWPOISON)))
  		return 0;
  
  	check_new_page_bad(page);
  	return 1;
  }
  
  #ifdef CONFIG_DEBUG_VM
  /*
   * With DEBUG_VM enabled, order-0 pages are checked for expected state when
   * being allocated from pcp lists. With debug_pagealloc also enabled, they are
   * also checked when pcp lists are refilled from the free lists.
   */
  static inline bool check_pcp_refill(struct page *page)
  {
  	if (debug_pagealloc_enabled_static())
  		return check_new_page(page);
  	else
  		return false;
  }
  
  static inline bool check_new_pcp(struct page *page)
  {
  	return check_new_page(page);
  }
  #else
  /*
   * With DEBUG_VM disabled, free order-0 pages are checked for expected state
   * when pcp lists are being refilled from the free lists. With debug_pagealloc
   * enabled, they are also checked when being allocated from the pcp lists.
   */
  static inline bool check_pcp_refill(struct page *page)
  {
  	return check_new_page(page);
  }
  static inline bool check_new_pcp(struct page *page)
  {
  	if (debug_pagealloc_enabled_static())
  		return check_new_page(page);
  	else
  		return false;
  }
  #endif /* CONFIG_DEBUG_VM */
  
  static bool check_new_pages(struct page *page, unsigned int order)
  {
  	int i;
  	for (i = 0; i < (1 << order); i++) {
  		struct page *p = page + i;
  
  		if (unlikely(check_new_page(p)))
  			return true;
  	}
  
  	return false;
  }
  
  inline void post_alloc_hook(struct page *page, unsigned int order,
  				gfp_t gfp_flags)
  {
  	set_page_private(page, 0);
  	set_page_refcounted(page);
  
  	arch_alloc_page(page, order);
  	debug_pagealloc_map_pages(page, 1 << order);
  
  	/*
  	 * Page unpoisoning must happen before memory initialization.
  	 * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
  	 * allocations and the page unpoisoning code will complain.
  	 */
  	kernel_unpoison_pages(page, 1 << order);
  
  	/*
  	 * As memory initialization might be integrated into KASAN,
  	 * kasan_alloc_pages and kernel_init_free_pages must be
  	 * kept together to avoid discrepancies in behavior.
  	 */
  	if (kasan_has_integrated_init()) {
  		kasan_alloc_pages(page, order, gfp_flags);
  	} else {
  		bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags);
  
  		kasan_unpoison_pages(page, order, init);
  		if (init)
  			kernel_init_free_pages(page, 1 << order,
  					       gfp_flags & __GFP_ZEROTAGS);
  	}
  
  	set_page_owner(page, order, gfp_flags);
  	page_table_check_alloc(page, order);
  }
  
  static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
  							unsigned int alloc_flags)
  {
  	post_alloc_hook(page, order, gfp_flags);
  
  	if (order && (gfp_flags & __GFP_COMP))
  		prep_compound_page(page, order);
  
  	/*
  	 * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to
  	 * allocate the page. The expectation is that the caller is taking
  	 * steps that will free more memory. The caller should avoid the page
  	 * being used for !PFMEMALLOC purposes.
  	 */
  	if (alloc_flags & ALLOC_NO_WATERMARKS)
  		set_page_pfmemalloc(page);
  	else
  		clear_page_pfmemalloc(page);
  }
  
  /*
   * Go through the free lists for the given migratetype and remove
   * the smallest available page from the freelists
   */
  static __always_inline
  struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
  						int migratetype)
  {
  	unsigned int current_order;
  	struct free_area *area;
  	struct page *page;
  
  	/* Find a page of the appropriate size in the preferred list */
  	for (current_order = order; current_order < MAX_ORDER; ++current_order) {
  		area = &(zone->free_area[current_order]);
  		page = get_page_from_free_area(area, migratetype);
  		if (!page)
  			continue;
  		del_page_from_free_list(page, zone, current_order);
  		expand(zone, page, order, current_order, migratetype);
  		set_pcppage_migratetype(page, migratetype);
  		return page;
  	}
  
  	return NULL;
  }
  
  
  /*
   * This array describes the order lists are fallen back to when
   * the free lists for the desirable migrate type are depleted
   */
  static int fallbacks[MIGRATE_TYPES][3] = {
  	[MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
  	[MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
  	[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
  #ifdef CONFIG_CMA
  	[MIGRATE_CMA]         = { MIGRATE_TYPES }, /* Never used */
  #endif
  #ifdef CONFIG_MEMORY_ISOLATION
  	[MIGRATE_ISOLATE]     = { MIGRATE_TYPES }, /* Never used */
  #endif
  };
  
  #ifdef CONFIG_CMA
  static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,
  					unsigned int order)
  {
  	return __rmqueue_smallest(zone, order, MIGRATE_CMA);
  }
  #else
  static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
  					unsigned int order) { return NULL; }
  #endif
  
  /*
   * Move the free pages in a range to the freelist tail of the requested type.
   * Note that start_page and end_pages are not aligned on a pageblock
   * boundary. If alignment is required, use move_freepages_block()
   */
  static int move_freepages(struct zone *zone,
  			  unsigned long start_pfn, unsigned long end_pfn,
  			  int migratetype, int *num_movable)
  {
  	struct page *page;
  	unsigned long pfn;
  	unsigned int order;
  	int pages_moved = 0;
  
  	for (pfn = start_pfn; pfn <= end_pfn;) {
  		page = pfn_to_page(pfn);
  		if (!PageBuddy(page)) {
  			/*
  			 * We assume that pages that could be isolated for
  			 * migration are movable. But we don't actually try
  			 * isolating, as that would be expensive.
  			 */
  			if (num_movable &&
  					(PageLRU(page) || __PageMovable(page)))
  				(*num_movable)++;
  			pfn++;
  			continue;
  		}
  
  		/* Make sure we are not inadvertently changing nodes */
  		VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
  		VM_BUG_ON_PAGE(page_zone(page) != zone, page);
  
  		order = buddy_order(page);
  		move_to_free_list(page, zone, order, migratetype);
  		pfn += 1 << order;
  		pages_moved += 1 << order;
  	}
  
  	return pages_moved;
  }
  
  int move_freepages_block(struct zone *zone, struct page *page,
  				int migratetype, int *num_movable)
  {
  	unsigned long start_pfn, end_pfn, pfn;
  
  	if (num_movable)
  		*num_movable = 0;
  
  	pfn = page_to_pfn(page);
  	start_pfn = pfn & ~(pageblock_nr_pages - 1);
  	end_pfn = start_pfn + pageblock_nr_pages - 1;
  
  	/* Do not cross zone boundaries */
  	if (!zone_spans_pfn(zone, start_pfn))
  		start_pfn = pfn;
  	if (!zone_spans_pfn(zone, end_pfn))
  		return 0;
  
  	return move_freepages(zone, start_pfn, end_pfn, migratetype,
  								num_movable);
  }
  
  static void change_pageblock_range(struct page *pageblock_page,
  					int start_order, int migratetype)
  {
  	int nr_pageblocks = 1 << (start_order - pageblock_order);
  
  	while (nr_pageblocks--) {
  		set_pageblock_migratetype(pageblock_page, migratetype);
  		pageblock_page += pageblock_nr_pages;
  	}
  }
  
  /*
   * When we are falling back to another migratetype during allocation, try to
   * steal extra free pages from the same pageblocks to satisfy further
   * allocations, instead of polluting multiple pageblocks.
   *
   * If we are stealing a relatively large buddy page, it is likely there will
   * be more free pages in the pageblock, so try to steal them all. For
   * reclaimable and unmovable allocations, we steal regardless of page size,
   * as fragmentation caused by those allocations polluting movable pageblocks
   * is worse than movable allocations stealing from unmovable and reclaimable
   * pageblocks.
   */
  static bool can_steal_fallback(unsigned int order, int start_mt)
  {
  	/*
  	 * Leaving this order check is intended, although there is
  	 * relaxed order check in next check. The reason is that
  	 * we can actually steal whole pageblock if this condition met,
  	 * but, below check doesn't guarantee it and that is just heuristic
  	 * so could be changed anytime.
  	 */
  	if (order >= pageblock_order)
  		return true;
  
  	if (order >= pageblock_order / 2 ||
  		start_mt == MIGRATE_RECLAIMABLE ||
  		start_mt == MIGRATE_UNMOVABLE ||
  		page_group_by_mobility_disabled)
  		return true;
  
  	return false;
  }
  
  static inline bool boost_watermark(struct zone *zone)
  {
  	unsigned long max_boost;
  
  	if (!watermark_boost_factor)
  		return false;
  	/*
  	 * Don't bother in zones that are unlikely to produce results.
  	 * On small machines, including kdump capture kernels running
  	 * in a small area, boosting the watermark can cause an out of
  	 * memory situation immediately.
  	 */
  	if ((pageblock_nr_pages * 4) > zone_managed_pages(zone))
  		return false;
  
  	max_boost = mult_frac(zone->_watermark[WMARK_HIGH],
  			watermark_boost_factor, 10000);
  
  	/*
  	 * high watermark may be uninitialised if fragmentation occurs
  	 * very early in boot so do not boost. We do not fall
  	 * through and boost by pageblock_nr_pages as failing
  	 * allocations that early means that reclaim is not going
  	 * to help and it may even be impossible to reclaim the
  	 * boosted watermark resulting in a hang.
  	 */
  	if (!max_boost)
  		return false;
  
  	max_boost = max(pageblock_nr_pages, max_boost);
  
  	zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages,
  		max_boost);
  
  	return true;
  }
  
  /*
   * This function implements actual steal behaviour. If order is large enough,
   * we can steal whole pageblock. If not, we first move freepages in this
   * pageblock to our migratetype and determine how many already-allocated pages
   * are there in the pageblock with a compatible migratetype. If at least half
   * of pages are free or compatible, we can change migratetype of the pageblock
   * itself, so pages freed in the future will be put on the correct free list.
   */
  static void steal_suitable_fallback(struct zone *zone, struct page *page,
  		unsigned int alloc_flags, int start_type, bool whole_block)
  {
  	unsigned int current_order = buddy_order(page);
  	int free_pages, movable_pages, alike_pages;
  	int old_block_type;
  
  	old_block_type = get_pageblock_migratetype(page);
  
  	/*
  	 * This can happen due to races and we want to prevent broken
  	 * highatomic accounting.
  	 */
  	if (is_migrate_highatomic(old_block_type))
  		goto single_page;
  
  	/* Take ownership for orders >= pageblock_order */
  	if (current_order >= pageblock_order) {
  		change_pageblock_range(page, current_order, start_type);
  		goto single_page;
  	}
  
  	/*
  	 * Boost watermarks to increase reclaim pressure to reduce the
  	 * likelihood of future fallbacks. Wake kswapd now as the node
  	 * may be balanced overall and kswapd will not wake naturally.
  	 */
  	if (boost_watermark(zone) && (alloc_flags & ALLOC_KSWAPD))
  		set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
  
  	/* We are not allowed to try stealing from the whole block */
  	if (!whole_block)
  		goto single_page;
  
  	free_pages = move_freepages_block(zone, page, start_type,
  						&movable_pages);
  	/*
  	 * Determine how many pages are compatible with our allocation.
  	 * For movable allocation, it's the number of movable pages which
  	 * we just obtained. For other types it's a bit more tricky.
  	 */
  	if (start_type == MIGRATE_MOVABLE) {
  		alike_pages = movable_pages;
  	} else {
  		/*
  		 * If we are falling back a RECLAIMABLE or UNMOVABLE allocation
  		 * to MOVABLE pageblock, consider all non-movable pages as
  		 * compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
  		 * vice versa, be conservative since we can't distinguish the
  		 * exact migratetype of non-movable pages.
  		 */
  		if (old_block_type == MIGRATE_MOVABLE)
  			alike_pages = pageblock_nr_pages
  						- (free_pages + movable_pages);
  		else
  			alike_pages = 0;
  	}
  
  	/* moving whole block can fail due to zone boundary conditions */
  	if (!free_pages)
  		goto single_page;
  
  	/*
  	 * If a sufficient number of pages in the block are either free or of
  	 * comparable migratability as our allocation, claim the whole block.
  	 */
  	if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
  			page_group_by_mobility_disabled)
  		set_pageblock_migratetype(page, start_type);
  
  	return;
  
  single_page:
  	move_to_free_list(page, zone, current_order, start_type);
  }
  
  /*
   * Check whether there is a suitable fallback freepage with requested order.
   * If only_stealable is true, this function returns fallback_mt only if
   * we can steal other freepages all together. This would help to reduce
   * fragmentation due to mixed migratetype pages in one pageblock.
   */
  int find_suitable_fallback(struct free_area *area, unsigned int order,
  			int migratetype, bool only_stealable, bool *can_steal)
  {
  	int i;
  	int fallback_mt;
  
  	if (area->nr_free == 0)
  		return -1;
  
  	*can_steal = false;
  	for (i = 0;; i++) {
  		fallback_mt = fallbacks[migratetype][i];
  		if (fallback_mt == MIGRATE_TYPES)
  			break;
  
  		if (free_area_empty(area, fallback_mt))
  			continue;
  
  		if (can_steal_fallback(order, migratetype))
  			*can_steal = true;
  
  		if (!only_stealable)
  			return fallback_mt;
  
  		if (*can_steal)
  			return fallback_mt;
  	}
  
  	return -1;
  }
  
  /*
   * Reserve a pageblock for exclusive use of high-order atomic allocations if
   * there are no empty page blocks that contain a page with a suitable order
   */
  static void reserve_highatomic_pageblock(struct page *page, struct zone *zone,
  				unsigned int alloc_order)
  {
  	int mt;
  	unsigned long max_managed, flags;
  
  	/*
  	 * Limit the number reserved to 1 pageblock or roughly 1% of a zone.
  	 * Check is race-prone but harmless.
  	 */
  	max_managed = (zone_managed_pages(zone) / 100) + pageblock_nr_pages;
  	if (zone->nr_reserved_highatomic >= max_managed)
  		return;
  
  	spin_lock_irqsave(&zone->lock, flags);
  
  	/* Recheck the nr_reserved_highatomic limit under the lock */
  	if (zone->nr_reserved_highatomic >= max_managed)
  		goto out_unlock;
  
  	/* Yoink! */
  	mt = get_pageblock_migratetype(page);
  	if (!is_migrate_highatomic(mt) && !is_migrate_isolate(mt)
  	    && !is_migrate_cma(mt)) {
  		zone->nr_reserved_highatomic += pageblock_nr_pages;
  		set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
  		move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL);
  	}
  
  out_unlock:
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  
  /*
   * Used when an allocation is about to fail under memory pressure. This
   * potentially hurts the reliability of high-order allocations when under
   * intense memory pressure but failed atomic allocations should be easier
   * to recover from than an OOM.
   *
   * If @force is true, try to unreserve a pageblock even though highatomic
   * pageblock is exhausted.
   */
  static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
  						bool force)
  {
  	struct zonelist *zonelist = ac->zonelist;
  	unsigned long flags;
  	struct zoneref *z;
  	struct zone *zone;
  	struct page *page;
  	int order;
  	bool ret;
  
  	for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->highest_zoneidx,
  								ac->nodemask) {
  		/*
  		 * Preserve at least one pageblock unless memory pressure
  		 * is really high.
  		 */
  		if (!force && zone->nr_reserved_highatomic <=
  					pageblock_nr_pages)
  			continue;
  
  		spin_lock_irqsave(&zone->lock, flags);
  		for (order = 0; order < MAX_ORDER; order++) {
  			struct free_area *area = &(zone->free_area[order]);
  
  			page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
  			if (!page)
  				continue;
  
  			/*
  			 * In page freeing path, migratetype change is racy so
  			 * we can counter several free pages in a pageblock
  			 * in this loop although we changed the pageblock type
  			 * from highatomic to ac->migratetype. So we should
  			 * adjust the count once.
  			 */
  			if (is_migrate_highatomic_page(page)) {
  				/*
  				 * It should never happen but changes to
  				 * locking could inadvertently allow a per-cpu
  				 * drain to add pages to MIGRATE_HIGHATOMIC
  				 * while unreserving so be safe and watch for
  				 * underflows.
  				 */
  				zone->nr_reserved_highatomic -= min(
  						pageblock_nr_pages,
  						zone->nr_reserved_highatomic);
  			}
  
  			/*
  			 * Convert to ac->migratetype and avoid the normal
  			 * pageblock stealing heuristics. Minimally, the caller
  			 * is doing the work and needs the pages. More
  			 * importantly, if the block was always converted to
  			 * MIGRATE_UNMOVABLE or another type then the number
  			 * of pageblocks that cannot be completely freed
  			 * may increase.
  			 */
  			set_pageblock_migratetype(page, ac->migratetype);
  			ret = move_freepages_block(zone, page, ac->migratetype,
  									NULL);
  			if (ret) {
  				spin_unlock_irqrestore(&zone->lock, flags);
  				return ret;
  			}
  		}
  		spin_unlock_irqrestore(&zone->lock, flags);
  	}
  
  	return false;
  }
  
  /*
   * Try finding a free buddy page on the fallback list and put it on the free
   * list of requested migratetype, possibly along with other pages from the same
   * block, depending on fragmentation avoidance heuristics. Returns true if
   * fallback was found so that __rmqueue_smallest() can grab it.
   *
   * The use of signed ints for order and current_order is a deliberate
   * deviation from the rest of this file, to make the for loop
   * condition simpler.
   */
  static __always_inline bool
  __rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
  						unsigned int alloc_flags)
  {
  	struct free_area *area;
  	int current_order;
  	int min_order = order;
  	struct page *page;
  	int fallback_mt;
  	bool can_steal;
  
  	/*
  	 * Do not steal pages from freelists belonging to other pageblocks
  	 * i.e. orders < pageblock_order. If there are no local zones free,
  	 * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
  	 */
  	if (alloc_flags & ALLOC_NOFRAGMENT)
  		min_order = pageblock_order;
  
  	/*
  	 * Find the largest available free page in the other list. This roughly
  	 * approximates finding the pageblock with the most free pages, which
  	 * would be too costly to do exactly.
  	 */
  	for (current_order = MAX_ORDER - 1; current_order >= min_order;
  				--current_order) {
  		area = &(zone->free_area[current_order]);
  		fallback_mt = find_suitable_fallback(area, current_order,
  				start_migratetype, false, &can_steal);
  		if (fallback_mt == -1)
  			continue;
  
  		/*
  		 * We cannot steal all free pages from the pageblock and the
  		 * requested migratetype is movable. In that case it's better to
  		 * steal and split the smallest available page instead of the
  		 * largest available page, because even if the next movable
  		 * allocation falls back into a different pageblock than this
  		 * one, it won't cause permanent fragmentation.
  		 */
  		if (!can_steal && start_migratetype == MIGRATE_MOVABLE
  					&& current_order > order)
  			goto find_smallest;
  
  		goto do_steal;
  	}
  
  	return false;
  
  find_smallest:
  	for (current_order = order; current_order < MAX_ORDER;
  							current_order++) {
  		area = &(zone->free_area[current_order]);
  		fallback_mt = find_suitable_fallback(area, current_order,
  				start_migratetype, false, &can_steal);
  		if (fallback_mt != -1)
  			break;
  	}
  
  	/*
  	 * This should not happen - we already found a suitable fallback
  	 * when looking for the largest page.
  	 */
  	VM_BUG_ON(current_order == MAX_ORDER);
  
  do_steal:
  	page = get_page_from_free_area(area, fallback_mt);
  
  	steal_suitable_fallback(zone, page, alloc_flags, start_migratetype,
  								can_steal);
  
  	trace_mm_page_alloc_extfrag(page, order, current_order,
  		start_migratetype, fallback_mt);
  
  	return true;
  
  }
  
  /*
   * Do the hard work of removing an element from the buddy allocator.
   * Call me with the zone->lock already held.
   */
  static __always_inline struct page *
  __rmqueue(struct zone *zone, unsigned int order, int migratetype,
  						unsigned int alloc_flags)
  {
  	struct page *page;
  
  	if (IS_ENABLED(CONFIG_CMA)) {
  		/*
  		 * Balance movable allocations between regular and CMA areas by
  		 * allocating from CMA when over half of the zone's free memory
  		 * is in the CMA area.
  		 */
  		if (alloc_flags & ALLOC_CMA &&
  		    zone_page_state(zone, NR_FREE_CMA_PAGES) >
  		    zone_page_state(zone, NR_FREE_PAGES) / 2) {
  			page = __rmqueue_cma_fallback(zone, order);
  			if (page)
  				goto out;
  		}
  	}
  retry:
  	page = __rmqueue_smallest(zone, order, migratetype);
  	if (unlikely(!page)) {
  		if (alloc_flags & ALLOC_CMA)
  			page = __rmqueue_cma_fallback(zone, order);
  
  		if (!page && __rmqueue_fallback(zone, order, migratetype,
  								alloc_flags))
  			goto retry;
  	}
  out:
  	if (page)
  		trace_mm_page_alloc_zone_locked(page, order, migratetype);
  	return page;
  }
  
  /*
   * Obtain a specified number of elements from the buddy allocator, all under
   * a single hold of the lock, for efficiency.  Add them to the supplied list.
   * Returns the number of new pages which were placed at *list.
   */
  static int rmqueue_bulk(struct zone *zone, unsigned int order,
  			unsigned long count, struct list_head *list,
  			int migratetype, unsigned int alloc_flags)
  {
  	int i, allocated = 0;
  
  	/*
  	 * local_lock_irq held so equivalent to spin_lock_irqsave for
  	 * both PREEMPT_RT and non-PREEMPT_RT configurations.
  	 */
  	spin_lock(&zone->lock);
  	for (i = 0; i < count; ++i) {
  		struct page *page = __rmqueue(zone, order, migratetype,
  								alloc_flags);
  		if (unlikely(page == NULL))
  			break;
  
  		if (unlikely(check_pcp_refill(page)))
  			continue;
  
  		/*
  		 * Split buddy pages returned by expand() are received here in
  		 * physical page order. The page is added to the tail of
  		 * caller's list. From the callers perspective, the linked list
  		 * is ordered by page number under some conditions. This is
  		 * useful for IO devices that can forward direction from the
  		 * head, thus also in the physical page order. This is useful
  		 * for IO devices that can merge IO requests if the physical
  		 * pages are ordered properly.
  		 */
  		list_add_tail(&page->lru, list);
  		allocated++;
  		if (is_migrate_cma(get_pcppage_migratetype(page)))
  			__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
  					      -(1 << order));
  	}
  
  	/*
  	 * i pages were removed from the buddy list even if some leak due
  	 * to check_pcp_refill failing so adjust NR_FREE_PAGES based
  	 * on i. Do not confuse with 'allocated' which is the number of
  	 * pages added to the pcp list.
  	 */
  	__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
  	spin_unlock(&zone->lock);
  	return allocated;
  }
  
  #ifdef CONFIG_NUMA
  /*
   * Called from the vmstat counter updater to drain pagesets of this
   * currently executing processor on remote nodes after they have
   * expired.
   *
   * Note that this function must be called with the thread pinned to
   * a single processor.
   */
  void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
  {
  	unsigned long flags;
  	int to_drain, batch;
  
  	local_lock_irqsave(&pagesets.lock, flags);
  	batch = READ_ONCE(pcp->batch);
  	to_drain = min(pcp->count, batch);
  	if (to_drain > 0)
  		free_pcppages_bulk(zone, to_drain, pcp);
  	local_unlock_irqrestore(&pagesets.lock, flags);
  }
  #endif
  
  /*
   * Drain pcplists of the indicated processor and zone.
   *
   * The processor must either be the current processor and the
   * thread pinned to the current processor or a processor that
   * is not online.
   */
  static void drain_pages_zone(unsigned int cpu, struct zone *zone)
  {
  	unsigned long flags;
  	struct per_cpu_pages *pcp;
  
  	local_lock_irqsave(&pagesets.lock, flags);
  
  	pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
  	if (pcp->count)
  		free_pcppages_bulk(zone, pcp->count, pcp);
  
  	local_unlock_irqrestore(&pagesets.lock, flags);
  }
  
  /*
   * Drain pcplists of all zones on the indicated processor.
   *
   * The processor must either be the current processor and the
   * thread pinned to the current processor or a processor that
   * is not online.
   */
  static void drain_pages(unsigned int cpu)
  {
  	struct zone *zone;
  
  	for_each_populated_zone(zone) {
  		drain_pages_zone(cpu, zone);
  	}
  }
  
  /*
   * Spill all of this CPU's per-cpu pages back into the buddy allocator.
   *
   * The CPU has to be pinned. When zone parameter is non-NULL, spill just
   * the single zone's pages.
   */
  void drain_local_pages(struct zone *zone)
  {
  	int cpu = smp_processor_id();
  
  	if (zone)
  		drain_pages_zone(cpu, zone);
  	else
  		drain_pages(cpu);
  }
  
  static void drain_local_pages_wq(struct work_struct *work)
  {
  	struct pcpu_drain *drain;
  
  	drain = container_of(work, struct pcpu_drain, work);
  
  	/*
  	 * drain_all_pages doesn't use proper cpu hotplug protection so
  	 * we can race with cpu offline when the WQ can move this from
  	 * a cpu pinned worker to an unbound one. We can operate on a different
  	 * cpu which is alright but we also have to make sure to not move to
  	 * a different one.
  	 */
  	migrate_disable();
  	drain_local_pages(drain->zone);
  	migrate_enable();
  }
  
  /*
   * The implementation of drain_all_pages(), exposing an extra parameter to
   * drain on all cpus.
   *
   * drain_all_pages() is optimized to only execute on cpus where pcplists are
   * not empty. The check for non-emptiness can however race with a free to
   * pcplist that has not yet increased the pcp->count from 0 to 1. Callers
   * that need the guarantee that every CPU has drained can disable the
   * optimizing racy check.
   */
  static void __drain_all_pages(struct zone *zone, bool force_all_cpus)
  {
  	int cpu;
  
  	/*
  	 * Allocate in the BSS so we won't require allocation in
  	 * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
  	 */
  	static cpumask_t cpus_with_pcps;
  
  	/*
  	 * Make sure nobody triggers this path before mm_percpu_wq is fully
  	 * initialized.
  	 */
  	if (WARN_ON_ONCE(!mm_percpu_wq))
  		return;
  
  	/*
  	 * Do not drain if one is already in progress unless it's specific to
  	 * a zone. Such callers are primarily CMA and memory hotplug and need
  	 * the drain to be complete when the call returns.
  	 */
  	if (unlikely(!mutex_trylock(&pcpu_drain_mutex))) {
  		if (!zone)
  			return;
  		mutex_lock(&pcpu_drain_mutex);
  	}
  
  	/*
  	 * We don't care about racing with CPU hotplug event
  	 * as offline notification will cause the notified
  	 * cpu to drain that CPU pcps and on_each_cpu_mask
  	 * disables preemption as part of its processing
  	 */
  	for_each_online_cpu(cpu) {
  		struct per_cpu_pages *pcp;
  		struct zone *z;
  		bool has_pcps = false;
  
  		if (force_all_cpus) {
  			/*
  			 * The pcp.count check is racy, some callers need a
  			 * guarantee that no cpu is missed.
  			 */
  			has_pcps = true;
  		} else if (zone) {
  			pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
  			if (pcp->count)
  				has_pcps = true;
  		} else {
  			for_each_populated_zone(z) {
  				pcp = per_cpu_ptr(z->per_cpu_pageset, cpu);
  				if (pcp->count) {
  					has_pcps = true;
  					break;
  				}
  			}
  		}
  
  		if (has_pcps)
  			cpumask_set_cpu(cpu, &cpus_with_pcps);
  		else
  			cpumask_clear_cpu(cpu, &cpus_with_pcps);
  	}
  
  	for_each_cpu(cpu, &cpus_with_pcps) {
  		struct pcpu_drain *drain = per_cpu_ptr(&pcpu_drain, cpu);
  
  		drain->zone = zone;
  		INIT_WORK(&drain->work, drain_local_pages_wq);
  		queue_work_on(cpu, mm_percpu_wq, &drain->work);
  	}
  	for_each_cpu(cpu, &cpus_with_pcps)
  		flush_work(&per_cpu_ptr(&pcpu_drain, cpu)->work);
  
  	mutex_unlock(&pcpu_drain_mutex);
  }
  
  /*
   * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
   *
   * When zone parameter is non-NULL, spill just the single zone's pages.
   *
   * Note that this can be extremely slow as the draining happens in a workqueue.
   */
  void drain_all_pages(struct zone *zone)
  {
  	__drain_all_pages(zone, false);
  }
  
  #ifdef CONFIG_HIBERNATION
  
  /*
   * Touch the watchdog for every WD_PAGE_COUNT pages.
   */
  #define WD_PAGE_COUNT	(128*1024)
  
  void mark_free_pages(struct zone *zone)
  {
  	unsigned long pfn, max_zone_pfn, page_count = WD_PAGE_COUNT;
  	unsigned long flags;
  	unsigned int order, t;
  	struct page *page;
  
  	if (zone_is_empty(zone))
  		return;
  
  	spin_lock_irqsave(&zone->lock, flags);
  
  	max_zone_pfn = zone_end_pfn(zone);
  	for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
  		if (pfn_valid(pfn)) {
  			page = pfn_to_page(pfn);
  
  			if (!--page_count) {
  				touch_nmi_watchdog();
  				page_count = WD_PAGE_COUNT;
  			}
  
  			if (page_zone(page) != zone)
  				continue;
  
  			if (!swsusp_page_is_forbidden(page))
  				swsusp_unset_page_free(page);
  		}
  
  	for_each_migratetype_order(order, t) {
  		list_for_each_entry(page,
  				&zone->free_area[order].free_list[t], lru) {
  			unsigned long i;
  
  			pfn = page_to_pfn(page);
  			for (i = 0; i < (1UL << order); i++) {
  				if (!--page_count) {
  					touch_nmi_watchdog();
  					page_count = WD_PAGE_COUNT;
  				}
  				swsusp_set_page_free(pfn_to_page(pfn + i));
  			}
  		}
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  #endif /* CONFIG_PM */
  
  static bool free_unref_page_prepare(struct page *page, unsigned long pfn,
  							unsigned int order)
  {
  	int migratetype;
  
  	if (!free_pcp_prepare(page, order))
  		return false;
  
  	migratetype = get_pfnblock_migratetype(page, pfn);
  	set_pcppage_migratetype(page, migratetype);
  	return true;
  }
  
  static int nr_pcp_free(struct per_cpu_pages *pcp, int high, int batch)
  {
  	int min_nr_free, max_nr_free;
  
  	/* Check for PCP disabled or boot pageset */
  	if (unlikely(high < batch))
  		return 1;
  
  	/* Leave at least pcp->batch pages on the list */
  	min_nr_free = batch;
  	max_nr_free = high - batch;
  
  	/*
  	 * Double the number of pages freed each time there is subsequent
  	 * freeing of pages without any allocation.
  	 */
  	batch <<= pcp->free_factor;
  	if (batch < max_nr_free)
  		pcp->free_factor++;
  	batch = clamp(batch, min_nr_free, max_nr_free);
  
  	return batch;
  }
  
  static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone)
  {
  	int high = READ_ONCE(pcp->high);
  
  	if (unlikely(!high))
  		return 0;
  
  	if (!test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags))
  		return high;
  
  	/*
  	 * If reclaim is active, limit the number of pages that can be
  	 * stored on pcp lists
  	 */
  	return min(READ_ONCE(pcp->batch) << 2, high);
  }
  
  static void free_unref_page_commit(struct page *page, unsigned long pfn,
  				   int migratetype, unsigned int order)
  {
  	struct zone *zone = page_zone(page);
  	struct per_cpu_pages *pcp;
  	int high;
  	int pindex;
  
  	__count_vm_event(PGFREE);
  	pcp = this_cpu_ptr(zone->per_cpu_pageset);
  	pindex = order_to_pindex(migratetype, order);
  	list_add(&page->lru, &pcp->lists[pindex]);
  	pcp->count += 1 << order;
  	high = nr_pcp_high(pcp, zone);
  	if (pcp->count >= high) {
  		int batch = READ_ONCE(pcp->batch);
  
  		free_pcppages_bulk(zone, nr_pcp_free(pcp, high, batch), pcp);
  	}
  }
  
  /*
   * Free a pcp page
   */
  void free_unref_page(struct page *page, unsigned int order)
  {
  	unsigned long flags;
  	unsigned long pfn = page_to_pfn(page);
  	int migratetype;
  
  	if (!free_unref_page_prepare(page, pfn, order))
  		return;
  
  	/*
  	 * We only track unmovable, reclaimable and movable on pcp lists.
  	 * Place ISOLATE pages on the isolated list because they are being
  	 * offlined but treat HIGHATOMIC as movable pages so we can get those
  	 * areas back if necessary. Otherwise, we may have to free
  	 * excessively into the page allocator
  	 */
  	migratetype = get_pcppage_migratetype(page);
  	if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
  		if (unlikely(is_migrate_isolate(migratetype))) {
  			free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE);
  			return;
  		}
  		migratetype = MIGRATE_MOVABLE;
  	}
  
  	local_lock_irqsave(&pagesets.lock, flags);
  	free_unref_page_commit(page, pfn, migratetype, order);
  	local_unlock_irqrestore(&pagesets.lock, flags);
  }
  
  /*
   * Free a list of 0-order pages
   */
  void free_unref_page_list(struct list_head *list)
  {
  	struct page *page, *next;
  	unsigned long flags, pfn;
  	int batch_count = 0;
  	int migratetype;
  
  	/* Prepare pages for freeing */
  	list_for_each_entry_safe(page, next, list, lru) {
  		pfn = page_to_pfn(page);
  		if (!free_unref_page_prepare(page, pfn, 0)) {
  			list_del(&page->lru);
  			continue;
  		}
  
  		/*
  		 * Free isolated pages directly to the allocator, see
  		 * comment in free_unref_page.
  		 */
  		migratetype = get_pcppage_migratetype(page);
  		if (unlikely(is_migrate_isolate(migratetype))) {
  			list_del(&page->lru);
  			free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE);
  			continue;
  		}
  
  		set_page_private(page, pfn);
  	}
  
  	local_lock_irqsave(&pagesets.lock, flags);
  	list_for_each_entry_safe(page, next, list, lru) {
  		pfn = page_private(page);
  		set_page_private(page, 0);
  
  		/*
  		 * Non-isolated types over MIGRATE_PCPTYPES get added
  		 * to the MIGRATE_MOVABLE pcp list.
  		 */
  		migratetype = get_pcppage_migratetype(page);
  		if (unlikely(migratetype >= MIGRATE_PCPTYPES))
  			migratetype = MIGRATE_MOVABLE;
  
  		trace_mm_page_free_batched(page);
  		free_unref_page_commit(page, pfn, migratetype, 0);
  
  		/*
  		 * Guard against excessive IRQ disabled times when we get
  		 * a large list of pages to free.
  		 */
  		if (++batch_count == SWAP_CLUSTER_MAX) {
  			local_unlock_irqrestore(&pagesets.lock, flags);
  			batch_count = 0;
  			local_lock_irqsave(&pagesets.lock, flags);
  		}
  	}
  	local_unlock_irqrestore(&pagesets.lock, flags);
  }
  
  /*
   * split_page takes a non-compound higher-order page, and splits it into
   * n (1<<order) sub-pages: page[0..n]
   * Each sub-page must be freed individually.
   *
   * Note: this is probably too low level an operation for use in drivers.
   * Please consult with lkml before using this in your driver.
   */
  void split_page(struct page *page, unsigned int order)
  {
  	int i;
  
  	VM_BUG_ON_PAGE(PageCompound(page), page);
  	VM_BUG_ON_PAGE(!page_count(page), page);
  
  	for (i = 1; i < (1 << order); i++)
  		set_page_refcounted(page + i);
  	split_page_owner(page, 1 << order);
  	split_page_memcg(page, 1 << order);
  }
  EXPORT_SYMBOL_GPL(split_page);
  
  int __isolate_free_page(struct page *page, unsigned int order)
  {
  	unsigned long watermark;
  	struct zone *zone;
  	int mt;
  
  	BUG_ON(!PageBuddy(page));
  
  	zone = page_zone(page);
  	mt = get_pageblock_migratetype(page);
  
  	if (!is_migrate_isolate(mt)) {
  		/*
  		 * Obey watermarks as if the page was being allocated. We can
  		 * emulate a high-order watermark check with a raised order-0
  		 * watermark, because we already know our high-order page
  		 * exists.
  		 */
  		watermark = zone->_watermark[WMARK_MIN] + (1UL << order);
  		if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
  			return 0;
  
  		__mod_zone_freepage_state(zone, -(1UL << order), mt);
  	}
  
  	/* Remove page from free list */
  
  	del_page_from_free_list(page, zone, order);
  
  	/*
  	 * Set the pageblock if the isolated page is at least half of a
  	 * pageblock
  	 */
  	if (order >= pageblock_order - 1) {
  		struct page *endpage = page + (1 << order) - 1;
  		for (; page < endpage; page += pageblock_nr_pages) {
  			int mt = get_pageblock_migratetype(page);
  			if (!is_migrate_isolate(mt) && !is_migrate_cma(mt)
  			    && !is_migrate_highatomic(mt))
  				set_pageblock_migratetype(page,
  							  MIGRATE_MOVABLE);
  		}
  	}
  
  
  	return 1UL << order;
  }
  
  /**
   * __putback_isolated_page - Return a now-isolated page back where we got it
   * @page: Page that was isolated
   * @order: Order of the isolated page
   * @mt: The page's pageblock's migratetype
   *
   * This function is meant to return a page pulled from the free lists via
   * __isolate_free_page back to the free lists they were pulled from.
   */
  void __putback_isolated_page(struct page *page, unsigned int order, int mt)
  {
  	struct zone *zone = page_zone(page);
  
  	/* zone lock should be held when this function is called */
  	lockdep_assert_held(&zone->lock);
  
  	/* Return isolated page to tail of freelist. */
  	__free_one_page(page, page_to_pfn(page), zone, order, mt,
  			FPI_SKIP_REPORT_NOTIFY | FPI_TO_TAIL);
  }
  
  /*
   * Update NUMA hit/miss statistics
   *
   * Must be called with interrupts disabled.
   */
  static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
  				   long nr_account)
  {
  #ifdef CONFIG_NUMA
  	enum numa_stat_item local_stat = NUMA_LOCAL;
  
  	/* skip numa counters update if numa stats is disabled */
  	if (!static_branch_likely(&vm_numa_stat_key))
  		return;
  
  	if (zone_to_nid(z) != numa_node_id())
  		local_stat = NUMA_OTHER;
  
  	if (zone_to_nid(z) == zone_to_nid(preferred_zone))
  		__count_numa_events(z, NUMA_HIT, nr_account);
  	else {
  		__count_numa_events(z, NUMA_MISS, nr_account);
  		__count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
  	}
  	__count_numa_events(z, local_stat, nr_account);
  #endif
  }
  
  /* Remove page from the per-cpu list, caller must protect the list */
  static inline
  struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
  			int migratetype,
  			unsigned int alloc_flags,
  			struct per_cpu_pages *pcp,
  			struct list_head *list)
  {
  	struct page *page;
  
  	do {
  		if (list_empty(list)) {
  			int batch = READ_ONCE(pcp->batch);
  			int alloced;
  
  			/*
  			 * Scale batch relative to order if batch implies
  			 * free pages can be stored on the PCP. Batch can
  			 * be 1 for small zones or for boot pagesets which
  			 * should never store free pages as the pages may
  			 * belong to arbitrary zones.
  			 */
  			if (batch > 1)
  				batch = max(batch >> order, 2);
  			alloced = rmqueue_bulk(zone, order,
  					batch, list,
  					migratetype, alloc_flags);
  
  			pcp->count += alloced << order;
  			if (unlikely(list_empty(list)))
  				return NULL;
  		}
  
  		page = list_first_entry(list, struct page, lru);
  		list_del(&page->lru);
  		pcp->count -= 1 << order;
  	} while (check_new_pcp(page));
  
  	return page;
  }
  
  /* Lock and remove page from the per-cpu list */
  static struct page *rmqueue_pcplist(struct zone *preferred_zone,
  			struct zone *zone, unsigned int order,
  			gfp_t gfp_flags, int migratetype,
  			unsigned int alloc_flags)
  {
  	struct per_cpu_pages *pcp;
  	struct list_head *list;
  	struct page *page;
  	unsigned long flags;
  
  	local_lock_irqsave(&pagesets.lock, flags);
  
  	/*
  	 * On allocation, reduce the number of pages that are batch freed.
  	 * See nr_pcp_free() where free_factor is increased for subsequent
  	 * frees.
  	 */
  	pcp = this_cpu_ptr(zone->per_cpu_pageset);
  	pcp->free_factor >>= 1;
  	list = &pcp->lists[order_to_pindex(migratetype, order)];
  	page = __rmqueue_pcplist(zone, order, migratetype, alloc_flags, pcp, list);
  	local_unlock_irqrestore(&pagesets.lock, flags);
  	if (page) {
  		__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
  		zone_statistics(preferred_zone, zone, 1);
  	}
  	return page;
  }
  
  /*
   * Allocate a page from the given zone. Use pcplists for order-0 allocations.
   */
  static inline
  struct page *rmqueue(struct zone *preferred_zone,
  			struct zone *zone, unsigned int order,
  			gfp_t gfp_flags, unsigned int alloc_flags,
  			int migratetype)
  {
  	unsigned long flags;
  	struct page *page;
  
  	if (likely(pcp_allowed_order(order))) {
  		/*
  		 * MIGRATE_MOVABLE pcplist could have the pages on CMA area and
  		 * we need to skip it when CMA area isn't allowed.
  		 */
  		if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA ||
  				migratetype != MIGRATE_MOVABLE) {
  			page = rmqueue_pcplist(preferred_zone, zone, order,
  					gfp_flags, migratetype, alloc_flags);
  			goto out;
  		}
  	}
  
  	/*
  	 * We most definitely don't want callers attempting to
  	 * allocate greater than order-1 page units with __GFP_NOFAIL.
  	 */
  	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
  	spin_lock_irqsave(&zone->lock, flags);
  
  	do {
  		page = NULL;
  		/*
  		 * order-0 request can reach here when the pcplist is skipped
  		 * due to non-CMA allocation context. HIGHATOMIC area is
  		 * reserved for high-order atomic allocation, so order-0
  		 * request should skip it.
  		 */
  		if (order > 0 && alloc_flags & ALLOC_HARDER) {
  			page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
  			if (page)
  				trace_mm_page_alloc_zone_locked(page, order, migratetype);
  		}
  		if (!page)
  			page = __rmqueue(zone, order, migratetype, alloc_flags);
  	} while (page && check_new_pages(page, order));
  	if (!page)
  		goto failed;
  
  	__mod_zone_freepage_state(zone, -(1 << order),
  				  get_pcppage_migratetype(page));
  	spin_unlock_irqrestore(&zone->lock, flags);
  
  	__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
  	zone_statistics(preferred_zone, zone, 1);
  
  out:
  	/* Separate test+clear to avoid unnecessary atomics */
  	if (test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags)) {
  		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
  		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
  	}
  
  	VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
  	return page;
  
  failed:
  	spin_unlock_irqrestore(&zone->lock, flags);
  	return NULL;
  }
  
  #ifdef CONFIG_FAIL_PAGE_ALLOC
  
  static struct {
  	struct fault_attr attr;
  
  	bool ignore_gfp_highmem;
  	bool ignore_gfp_reclaim;
  	u32 min_order;
  } fail_page_alloc = {
  	.attr = FAULT_ATTR_INITIALIZER,
  	.ignore_gfp_reclaim = true,
  	.ignore_gfp_highmem = true,
  	.min_order = 1,
  };
  
  static int __init setup_fail_page_alloc(char *str)
  {
  	return setup_fault_attr(&fail_page_alloc.attr, str);
  }
  __setup("fail_page_alloc=", setup_fail_page_alloc);
  
  static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
  {
  	if (order < fail_page_alloc.min_order)
  		return false;
  	if (gfp_mask & __GFP_NOFAIL)
  		return false;
  	if (fail_page_alloc.ignore_gfp_highmem && (gfp_mask & __GFP_HIGHMEM))
  		return false;
  	if (fail_page_alloc.ignore_gfp_reclaim &&
  			(gfp_mask & __GFP_DIRECT_RECLAIM))
  		return false;
  
  	return should_fail(&fail_page_alloc.attr, 1 << order);
  }
  
  #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
  
  static int __init fail_page_alloc_debugfs(void)
  {
  	umode_t mode = S_IFREG | 0600;
  	struct dentry *dir;
  
  	dir = fault_create_debugfs_attr("fail_page_alloc", NULL,
  					&fail_page_alloc.attr);
  
  	debugfs_create_bool("ignore-gfp-wait", mode, dir,
  			    &fail_page_alloc.ignore_gfp_reclaim);
  	debugfs_create_bool("ignore-gfp-highmem", mode, dir,
  			    &fail_page_alloc.ignore_gfp_highmem);
  	debugfs_create_u32("min-order", mode, dir, &fail_page_alloc.min_order);
  
  	return 0;
  }
  
  late_initcall(fail_page_alloc_debugfs);
  
  #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
  
  #else /* CONFIG_FAIL_PAGE_ALLOC */
  
  static inline bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
  {
  	return false;
  }
  
  #endif /* CONFIG_FAIL_PAGE_ALLOC */
  
  noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
  {
  	return __should_fail_alloc_page(gfp_mask, order);
  }
  ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE);
  
  static inline long __zone_watermark_unusable_free(struct zone *z,
  				unsigned int order, unsigned int alloc_flags)
  {
  	const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
  	long unusable_free = (1 << order) - 1;
  
  	/*
  	 * If the caller does not have rights to ALLOC_HARDER then subtract
  	 * the high-atomic reserves. This will over-estimate the size of the
  	 * atomic reserve but it avoids a search.
  	 */
  	if (likely(!alloc_harder))
  		unusable_free += z->nr_reserved_highatomic;
  
  #ifdef CONFIG_CMA
  	/* If allocation can't use CMA areas don't use free CMA pages */
  	if (!(alloc_flags & ALLOC_CMA))
  		unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
  #endif
  
  	return unusable_free;
  }
  
  /*
   * Return true if free base pages are above 'mark'. For high-order checks it
   * will return true of the order-0 watermark is reached and there is at least
   * one free page of a suitable size. Checking now avoids taking the zone lock
   * to check in the allocation paths if no pages are free.
   */
  bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
  			 int highest_zoneidx, unsigned int alloc_flags,
  			 long free_pages)
  {
  	long min = mark;
  	int o;
  	const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
  
  	/* free_pages may go negative - that's OK */
  	free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
  
  	if (alloc_flags & ALLOC_HIGH)
  		min -= min / 2;
  
  	if (unlikely(alloc_harder)) {
  		/*
  		 * OOM victims can try even harder than normal ALLOC_HARDER
  		 * users on the grounds that it's definitely going to be in
  		 * the exit path shortly and free memory. Any allocation it
  		 * makes during the free path will be small and short-lived.
  		 */
  		if (alloc_flags & ALLOC_OOM)
  			min -= min / 2;
  		else
  			min -= min / 4;
  	}
  
  	/*
  	 * Check watermarks for an order-0 allocation request. If these
  	 * are not met, then a high-order request also cannot go ahead
  	 * even if a suitable page happened to be free.
  	 */
  	if (free_pages <= min + z->lowmem_reserve[highest_zoneidx])
  		return false;
  
  	/* If this is an order-0 request then the watermark is fine */
  	if (!order)
  		return true;
  
  	/* For a high-order request, check at least one suitable page is free */
  	for (o = order; o < MAX_ORDER; o++) {
  		struct free_area *area = &z->free_area[o];
  		int mt;
  
  		if (!area->nr_free)
  			continue;
  
  		for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
  			if (!free_area_empty(area, mt))
  				return true;
  		}
  
  #ifdef CONFIG_CMA
  		if ((alloc_flags & ALLOC_CMA) &&
  		    !free_area_empty(area, MIGRATE_CMA)) {
  			return true;
  		}
  #endif
  		if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC))
  			return true;
  	}
  	return false;
  }
  
  bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
  		      int highest_zoneidx, unsigned int alloc_flags)
  {
  	return __zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
  					zone_page_state(z, NR_FREE_PAGES));
  }
  
  static inline bool zone_watermark_fast(struct zone *z, unsigned int order,
  				unsigned long mark, int highest_zoneidx,
  				unsigned int alloc_flags, gfp_t gfp_mask)
  {
  	long free_pages;
  
  	free_pages = zone_page_state(z, NR_FREE_PAGES);
  
  	/*
  	 * Fast check for order-0 only. If this fails then the reserves
  	 * need to be calculated.
  	 */
  	if (!order) {
  		long fast_free;
  
  		fast_free = free_pages;
  		fast_free -= __zone_watermark_unusable_free(z, 0, alloc_flags);
  		if (fast_free > mark + z->lowmem_reserve[highest_zoneidx])
  			return true;
  	}
  
  	if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
  					free_pages))
  		return true;
  	/*
  	 * Ignore watermark boosting for GFP_ATOMIC order-0 allocations
  	 * when checking the min watermark. The min watermark is the
  	 * point where boosting is ignored so that kswapd is woken up
  	 * when below the low watermark.
  	 */
  	if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost
  		&& ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) {
  		mark = z->_watermark[WMARK_MIN];
  		return __zone_watermark_ok(z, order, mark, highest_zoneidx,
  					alloc_flags, free_pages);
  	}
  
  	return false;
  }
  
  bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
  			unsigned long mark, int highest_zoneidx)
  {
  	long free_pages = zone_page_state(z, NR_FREE_PAGES);
  
  	if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
  		free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);
  
  	return __zone_watermark_ok(z, order, mark, highest_zoneidx, 0,
  								free_pages);
  }
  
  #ifdef CONFIG_NUMA
  int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;
  
  static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
  {
  	return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
  				node_reclaim_distance;
  }
  #else	/* CONFIG_NUMA */
  static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
  {
  	return true;
  }
  #endif	/* CONFIG_NUMA */
  
  /*
   * The restriction on ZONE_DMA32 as being a suitable zone to use to avoid
   * fragmentation is subtle. If the preferred zone was HIGHMEM then
   * premature use of a lower zone may cause lowmem pressure problems that
   * are worse than fragmentation. If the next zone is ZONE_DMA then it is
   * probably too small. It only makes sense to spread allocations to avoid
   * fragmentation between the Normal and DMA32 zones.
   */
  static inline unsigned int
  alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
  {
  	unsigned int alloc_flags;
  
  	/*
  	 * __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
  	 * to save a branch.
  	 */
  	alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);
  
  #ifdef CONFIG_ZONE_DMA32
  	if (!zone)
  		return alloc_flags;
  
  	if (zone_idx(zone) != ZONE_NORMAL)
  		return alloc_flags;
  
  	/*
  	 * If ZONE_DMA32 exists, assume it is the one after ZONE_NORMAL and
  	 * the pointer is within zone->zone_pgdat->node_zones[]. Also assume
  	 * on UMA that if Normal is populated then so is DMA32.
  	 */
  	BUILD_BUG_ON(ZONE_NORMAL - ZONE_DMA32 != 1);
  	if (nr_online_nodes > 1 && !populated_zone(--zone))
  		return alloc_flags;
  
  	alloc_flags |= ALLOC_NOFRAGMENT;
  #endif /* CONFIG_ZONE_DMA32 */
  	return alloc_flags;
  }
  
  /* Must be called after current_gfp_context() which can change gfp_mask */
  static inline unsigned int gfp_to_alloc_flags_cma(gfp_t gfp_mask,
  						  unsigned int alloc_flags)
  {
  #ifdef CONFIG_CMA
  	if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
  		alloc_flags |= ALLOC_CMA;
  #endif
  	return alloc_flags;
  }
  
  /*
   * get_page_from_freelist goes through the zonelist trying to allocate
   * a page.
   */
  static struct page *
  get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
  						const struct alloc_context *ac)
  {
  	struct zoneref *z;
  	struct zone *zone;
  	struct pglist_data *last_pgdat_dirty_limit = NULL;
  	bool no_fallback;
  
  retry:
  	/*
  	 * Scan zonelist, looking for a zone with enough free.
  	 * See also __cpuset_node_allowed() comment in kernel/cpuset.c.
  	 */
  	no_fallback = alloc_flags & ALLOC_NOFRAGMENT;
  	z = ac->preferred_zoneref;
  	for_next_zone_zonelist_nodemask(zone, z, ac->highest_zoneidx,
  					ac->nodemask) {
  		struct page *page;
  		unsigned long mark;
  
  		if (cpusets_enabled() &&
  			(alloc_flags & ALLOC_CPUSET) &&
  			!__cpuset_zone_allowed(zone, gfp_mask))
  				continue;
  		/*
  		 * When allocating a page cache page for writing, we
  		 * want to get it from a node that is within its dirty
  		 * limit, such that no single node holds more than its
  		 * proportional share of globally allowed dirty pages.
  		 * The dirty limits take into account the node's
  		 * lowmem reserves and high watermark so that kswapd
  		 * should be able to balance it without having to
  		 * write pages from its LRU list.
  		 *
  		 * XXX: For now, allow allocations to potentially
  		 * exceed the per-node dirty limit in the slowpath
  		 * (spread_dirty_pages unset) before going into reclaim,
  		 * which is important when on a NUMA setup the allowed
  		 * nodes are together not big enough to reach the
  		 * global limit.  The proper fix for these situations
  		 * will require awareness of nodes in the
  		 * dirty-throttling and the flusher threads.
  		 */
  		if (ac->spread_dirty_pages) {
  			if (last_pgdat_dirty_limit == zone->zone_pgdat)
  				continue;
  
  			if (!node_dirty_ok(zone->zone_pgdat)) {
  				last_pgdat_dirty_limit = zone->zone_pgdat;
  				continue;
  			}
  		}
  
  		if (no_fallback && nr_online_nodes > 1 &&
  		    zone != ac->preferred_zoneref->zone) {
  			int local_nid;
  
  			/*
  			 * If moving to a remote node, retry but allow
  			 * fragmenting fallbacks. Locality is more important
  			 * than fragmentation avoidance.
  			 */
  			local_nid = zone_to_nid(ac->preferred_zoneref->zone);
  			if (zone_to_nid(zone) != local_nid) {
  				alloc_flags &= ~ALLOC_NOFRAGMENT;
  				goto retry;
  			}
  		}
  
  		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
  		if (!zone_watermark_fast(zone, order, mark,
  				       ac->highest_zoneidx, alloc_flags,
  				       gfp_mask)) {
  			int ret;
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  			/*
  			 * Watermark failed for this zone, but see if we can
  			 * grow this zone if it contains deferred pages.
  			 */
  			if (static_branch_unlikely(&deferred_pages)) {
  				if (_deferred_grow_zone(zone, order))
  					goto try_this_zone;
  			}
  #endif
  			/* Checked here to keep the fast path fast */
  			BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
  			if (alloc_flags & ALLOC_NO_WATERMARKS)
  				goto try_this_zone;
  
  			if (!node_reclaim_enabled() ||
  			    !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
  				continue;
  
  			ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
  			switch (ret) {
  			case NODE_RECLAIM_NOSCAN:
  				/* did not scan */
  				continue;
  			case NODE_RECLAIM_FULL:
  				/* scanned but unreclaimable */
  				continue;
  			default:
  				/* did we reclaim enough */
  				if (zone_watermark_ok(zone, order, mark,
  					ac->highest_zoneidx, alloc_flags))
  					goto try_this_zone;
  
  				continue;
  			}
  		}
  
  try_this_zone:
  		page = rmqueue(ac->preferred_zoneref->zone, zone, order,
  				gfp_mask, alloc_flags, ac->migratetype);
  		if (page) {
  			prep_new_page(page, order, gfp_mask, alloc_flags);
  
  			/*
  			 * If this is a high-order atomic allocation then check
  			 * if the pageblock should be reserved for the future
  			 */
  			if (unlikely(order && (alloc_flags & ALLOC_HARDER)))
  				reserve_highatomic_pageblock(page, zone, order);
  
  			return page;
  		} else {
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  			/* Try again if zone has deferred pages */
  			if (static_branch_unlikely(&deferred_pages)) {
  				if (_deferred_grow_zone(zone, order))
  					goto try_this_zone;
  			}
  #endif
  		}
  	}
  
  	/*
  	 * It's possible on a UMA machine to get through all zones that are
  	 * fragmented. If avoiding fragmentation, reset and try again.
  	 */
  	if (no_fallback) {
  		alloc_flags &= ~ALLOC_NOFRAGMENT;
  		goto retry;
  	}
  
  	return NULL;
  }
  
  static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
  {
  	unsigned int filter = SHOW_MEM_FILTER_NODES;
  
  	/*
  	 * This documents exceptions given to allocations in certain
  	 * contexts that are allowed to allocate outside current's set
  	 * of allowed nodes.
  	 */
  	if (!(gfp_mask & __GFP_NOMEMALLOC))
  		if (tsk_is_oom_victim(current) ||
  		    (current->flags & (PF_MEMALLOC | PF_EXITING)))
  			filter &= ~SHOW_MEM_FILTER_NODES;
  	if (!in_task() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
  		filter &= ~SHOW_MEM_FILTER_NODES;
  
  	show_mem(filter, nodemask);
  }
  
  void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
  {
  	struct va_format vaf;
  	va_list args;
  	static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);
  
  	if ((gfp_mask & __GFP_NOWARN) ||
  	     !__ratelimit(&nopage_rs) ||
  	     ((gfp_mask & __GFP_DMA) && !has_managed_dma()))
  		return;
  
  	va_start(args, fmt);
  	vaf.fmt = fmt;
  	vaf.va = &args;
  	pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl",
  			current->comm, &vaf, gfp_mask, &gfp_mask,
  			nodemask_pr_args(nodemask));
  	va_end(args);
  
  	cpuset_print_current_mems_allowed();
  	pr_cont("\n");
  	dump_stack();
  	warn_alloc_show_mem(gfp_mask, nodemask);
  }
  
  static inline struct page *
  __alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,
  			      unsigned int alloc_flags,
  			      const struct alloc_context *ac)
  {
  	struct page *page;
  
  	page = get_page_from_freelist(gfp_mask, order,
  			alloc_flags|ALLOC_CPUSET, ac);
  	/*
  	 * fallback to ignore cpuset restriction if our nodes
  	 * are depleted
  	 */
  	if (!page)
  		page = get_page_from_freelist(gfp_mask, order,
  				alloc_flags, ac);
  
  	return page;
  }
  
  static inline struct page *
  __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
  	const struct alloc_context *ac, unsigned long *did_some_progress)
  {
  	struct oom_control oc = {
  		.zonelist = ac->zonelist,
  		.nodemask = ac->nodemask,
  		.memcg = NULL,
  		.gfp_mask = gfp_mask,
  		.order = order,
  	};
  	struct page *page;
  
  	*did_some_progress = 0;
  
  	/*
  	 * Acquire the oom lock.  If that fails, somebody else is
  	 * making progress for us.
  	 */
  	if (!mutex_trylock(&oom_lock)) {
  		*did_some_progress = 1;
  		schedule_timeout_uninterruptible(1);
  		return NULL;
  	}
  
  	/*
  	 * Go through the zonelist yet one more time, keep very high watermark
  	 * here, this is only to catch a parallel oom killing, we must fail if
  	 * we're still under heavy pressure. But make sure that this reclaim
  	 * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
  	 * allocation which will never fail due to oom_lock already held.
  	 */
  	page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) &
  				      ~__GFP_DIRECT_RECLAIM, order,
  				      ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
  	if (page)
  		goto out;
  
  	/* Coredumps can quickly deplete all memory reserves */
  	if (current->flags & PF_DUMPCORE)
  		goto out;
  	/* The OOM killer will not help higher order allocs */
  	if (order > PAGE_ALLOC_COSTLY_ORDER)
  		goto out;
  	/*
  	 * We have already exhausted all our reclaim opportunities without any
  	 * success so it is time to admit defeat. We will skip the OOM killer
  	 * because it is very likely that the caller has a more reasonable
  	 * fallback than shooting a random task.
  	 *
  	 * The OOM killer may not free memory on a specific node.
  	 */
  	if (gfp_mask & (__GFP_RETRY_MAYFAIL | __GFP_THISNODE))
  		goto out;
  	/* The OOM killer does not needlessly kill tasks for lowmem */
  	if (ac->highest_zoneidx < ZONE_NORMAL)
  		goto out;
  	if (pm_suspended_storage())
  		goto out;
  	/*
  	 * XXX: GFP_NOFS allocations should rather fail than rely on
  	 * other request to make a forward progress.
  	 * We are in an unfortunate situation where out_of_memory cannot
  	 * do much for this context but let's try it to at least get
  	 * access to memory reserved if the current task is killed (see
  	 * out_of_memory). Once filesystems are ready to handle allocation
  	 * failures more gracefully we should just bail out here.
  	 */
  
  	/* Exhausted what can be done so it's blame time */
  	if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
  		*did_some_progress = 1;
  
  		/*
  		 * Help non-failing allocations by giving them access to memory
  		 * reserves
  		 */
  		if (gfp_mask & __GFP_NOFAIL)
  			page = __alloc_pages_cpuset_fallback(gfp_mask, order,
  					ALLOC_NO_WATERMARKS, ac);
  	}
  out:
  	mutex_unlock(&oom_lock);
  	return page;
  }
  
  /*
   * Maximum number of compaction retries with a progress before OOM
   * killer is consider as the only way to move forward.
   */
  #define MAX_COMPACT_RETRIES 16
  
  #ifdef CONFIG_COMPACTION
  /* Try memory compaction for high-order allocations before reclaim */
  static struct page *
  __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
  		unsigned int alloc_flags, const struct alloc_context *ac,
  		enum compact_priority prio, enum compact_result *compact_result)
  {
  	struct page *page = NULL;
  	unsigned long pflags;
  	unsigned int noreclaim_flag;
  
  	if (!order)
  		return NULL;
  
  	psi_memstall_enter(&pflags);
  	delayacct_compact_start();
  	noreclaim_flag = memalloc_noreclaim_save();
  
  	*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
  								prio, &page);
  
  	memalloc_noreclaim_restore(noreclaim_flag);
  	psi_memstall_leave(&pflags);
  	delayacct_compact_end();
  
  	if (*compact_result == COMPACT_SKIPPED)
  		return NULL;
  	/*
  	 * At least in one zone compaction wasn't deferred or skipped, so let's
  	 * count a compaction stall
  	 */
  	count_vm_event(COMPACTSTALL);
  
  	/* Prep a captured page if available */
  	if (page)
  		prep_new_page(page, order, gfp_mask, alloc_flags);
  
  	/* Try get a page from the freelist if available */
  	if (!page)
  		page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
  
  	if (page) {
  		struct zone *zone = page_zone(page);
  
  		zone->compact_blockskip_flush = false;
  		compaction_defer_reset(zone, order, true);
  		count_vm_event(COMPACTSUCCESS);
  		return page;
  	}
  
  	/*
  	 * It's bad if compaction run occurs and fails. The most likely reason
  	 * is that pages exist, but not enough to satisfy watermarks.
  	 */
  	count_vm_event(COMPACTFAIL);
  
  	cond_resched();
  
  	return NULL;
  }
  
  static inline bool
  should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
  		     enum compact_result compact_result,
  		     enum compact_priority *compact_priority,
  		     int *compaction_retries)
  {
  	int max_retries = MAX_COMPACT_RETRIES;
  	int min_priority;
  	bool ret = false;
  	int retries = *compaction_retries;
  	enum compact_priority priority = *compact_priority;
  
  	if (!order)
  		return false;
  
  	if (fatal_signal_pending(current))
  		return false;
  
  	if (compaction_made_progress(compact_result))
  		(*compaction_retries)++;
  
  	/*
  	 * compaction considers all the zone as desperately out of memory
  	 * so it doesn't really make much sense to retry except when the
  	 * failure could be caused by insufficient priority
  	 */
  	if (compaction_failed(compact_result))
  		goto check_priority;
  
  	/*
  	 * compaction was skipped because there are not enough order-0 pages
  	 * to work with, so we retry only if it looks like reclaim can help.
  	 */
  	if (compaction_needs_reclaim(compact_result)) {
  		ret = compaction_zonelist_suitable(ac, order, alloc_flags);
  		goto out;
  	}
  
  	/*
  	 * make sure the compaction wasn't deferred or didn't bail out early
  	 * due to locks contention before we declare that we should give up.
  	 * But the next retry should use a higher priority if allowed, so
  	 * we don't just keep bailing out endlessly.
  	 */
  	if (compaction_withdrawn(compact_result)) {
  		goto check_priority;
  	}
  
  	/*
  	 * !costly requests are much more important than __GFP_RETRY_MAYFAIL
  	 * costly ones because they are de facto nofail and invoke OOM
  	 * killer to move on while costly can fail and users are ready
  	 * to cope with that. 1/4 retries is rather arbitrary but we
  	 * would need much more detailed feedback from compaction to
  	 * make a better decision.
  	 */
  	if (order > PAGE_ALLOC_COSTLY_ORDER)
  		max_retries /= 4;
  	if (*compaction_retries <= max_retries) {
  		ret = true;
  		goto out;
  	}
  
  	/*
  	 * Make sure there are attempts at the highest priority if we exhausted
  	 * all retries or failed at the lower priorities.
  	 */
  check_priority:
  	min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
  			MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
  
  	if (*compact_priority > min_priority) {
  		(*compact_priority)--;
  		*compaction_retries = 0;
  		ret = true;
  	}
  out:
  	trace_compact_retry(order, priority, compact_result, retries, max_retries, ret);
  	return ret;
  }
  #else
  static inline struct page *
  __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
  		unsigned int alloc_flags, const struct alloc_context *ac,
  		enum compact_priority prio, enum compact_result *compact_result)
  {
  	*compact_result = COMPACT_SKIPPED;
  	return NULL;
  }
  
  static inline bool
  should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
  		     enum compact_result compact_result,
  		     enum compact_priority *compact_priority,
  		     int *compaction_retries)
  {
  	struct zone *zone;
  	struct zoneref *z;
  
  	if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
  		return false;
  
  	/*
  	 * There are setups with compaction disabled which would prefer to loop
  	 * inside the allocator rather than hit the oom killer prematurely.
  	 * Let's give them a good hope and keep retrying while the order-0
  	 * watermarks are OK.
  	 */
  	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
  				ac->highest_zoneidx, ac->nodemask) {
  		if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
  					ac->highest_zoneidx, alloc_flags))
  			return true;
  	}
  	return false;
  }
  #endif /* CONFIG_COMPACTION */
  
  #ifdef CONFIG_LOCKDEP
  static struct lockdep_map __fs_reclaim_map =
  	STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
  
  static bool __need_reclaim(gfp_t gfp_mask)
  {
  	/* no reclaim without waiting on it */
  	if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
  		return false;
  
  	/* this guy won't enter reclaim */
  	if (current->flags & PF_MEMALLOC)
  		return false;
  
  	if (gfp_mask & __GFP_NOLOCKDEP)
  		return false;
  
  	return true;
  }
  
  void __fs_reclaim_acquire(unsigned long ip)
  {
  	lock_acquire_exclusive(&__fs_reclaim_map, 0, 0, NULL, ip);
  }
  
  void __fs_reclaim_release(unsigned long ip)
  {
  	lock_release(&__fs_reclaim_map, ip);
  }
  
  void fs_reclaim_acquire(gfp_t gfp_mask)
  {
  	gfp_mask = current_gfp_context(gfp_mask);
  
  	if (__need_reclaim(gfp_mask)) {
  		if (gfp_mask & __GFP_FS)
  			__fs_reclaim_acquire(_RET_IP_);
  
  #ifdef CONFIG_MMU_NOTIFIER
  		lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
  		lock_map_release(&__mmu_notifier_invalidate_range_start_map);
  #endif
  
  	}
  }
  EXPORT_SYMBOL_GPL(fs_reclaim_acquire);
  
  void fs_reclaim_release(gfp_t gfp_mask)
  {
  	gfp_mask = current_gfp_context(gfp_mask);
  
  	if (__need_reclaim(gfp_mask)) {
  		if (gfp_mask & __GFP_FS)
  			__fs_reclaim_release(_RET_IP_);
  	}
  }
  EXPORT_SYMBOL_GPL(fs_reclaim_release);
  #endif
  
  /* Perform direct synchronous page reclaim */
  static unsigned long
  __perform_reclaim(gfp_t gfp_mask, unsigned int order,
  					const struct alloc_context *ac)
  {
  	unsigned int noreclaim_flag;
  	unsigned long pflags, progress;
  
  	cond_resched();
  
  	/* We now go into synchronous reclaim */
  	cpuset_memory_pressure_bump();
  	psi_memstall_enter(&pflags);
  	fs_reclaim_acquire(gfp_mask);
  	noreclaim_flag = memalloc_noreclaim_save();
  
  	progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
  								ac->nodemask);
  
  	memalloc_noreclaim_restore(noreclaim_flag);
  	fs_reclaim_release(gfp_mask);
  	psi_memstall_leave(&pflags);
  
  	cond_resched();
  
  	return progress;
  }
  
  /* The really slow allocator path where we enter direct reclaim */
  static inline struct page *
  __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
  		unsigned int alloc_flags, const struct alloc_context *ac,
  		unsigned long *did_some_progress)
  {
  	struct page *page = NULL;
  	bool drained = false;
  
  	*did_some_progress = __perform_reclaim(gfp_mask, order, ac);
  	if (unlikely(!(*did_some_progress)))
  		return NULL;
  
  retry:
  	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
  
  	/*
  	 * If an allocation failed after direct reclaim, it could be because
  	 * pages are pinned on the per-cpu lists or in high alloc reserves.
  	 * Shrink them and try again
  	 */
  	if (!page && !drained) {
  		unreserve_highatomic_pageblock(ac, false);
  		drain_all_pages(NULL);
  		drained = true;
  		goto retry;
  	}
  
  	return page;
  }
  
  static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
  			     const struct alloc_context *ac)
  {
  	struct zoneref *z;
  	struct zone *zone;
  	pg_data_t *last_pgdat = NULL;
  	enum zone_type highest_zoneidx = ac->highest_zoneidx;
  
  	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
  					ac->nodemask) {
  		if (last_pgdat != zone->zone_pgdat)
  			wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
  		last_pgdat = zone->zone_pgdat;
  	}
  }
  
  static inline unsigned int
  gfp_to_alloc_flags(gfp_t gfp_mask)
  {
  	unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
  
  	/*
  	 * __GFP_HIGH is assumed to be the same as ALLOC_HIGH
  	 * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
  	 * to save two branches.
  	 */
  	BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);
  	BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
  
  	/*
  	 * The caller may dip into page reserves a bit more if the caller
  	 * cannot run direct reclaim, or if the caller has realtime scheduling
  	 * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
  	 * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_HIGH (__GFP_HIGH).
  	 */
  	alloc_flags |= (__force int)
  		(gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
  
  	if (gfp_mask & __GFP_ATOMIC) {
  		/*
  		 * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
  		 * if it can't schedule.
  		 */
  		if (!(gfp_mask & __GFP_NOMEMALLOC))
  			alloc_flags |= ALLOC_HARDER;
  		/*
  		 * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
  		 * comment for __cpuset_node_allowed().
  		 */
  		alloc_flags &= ~ALLOC_CPUSET;
  	} else if (unlikely(rt_task(current)) && in_task())
  		alloc_flags |= ALLOC_HARDER;
  
  	alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, alloc_flags);
  
  	return alloc_flags;
  }
  
  static bool oom_reserves_allowed(struct task_struct *tsk)
  {
  	if (!tsk_is_oom_victim(tsk))
  		return false;
  
  	/*
  	 * !MMU doesn't have oom reaper so give access to memory reserves
  	 * only to the thread with TIF_MEMDIE set
  	 */
  	if (!IS_ENABLED(CONFIG_MMU) && !test_thread_flag(TIF_MEMDIE))
  		return false;
  
  	return true;
  }
  
  /*
   * Distinguish requests which really need access to full memory
   * reserves from oom victims which can live with a portion of it
   */
  static inline int __gfp_pfmemalloc_flags(gfp_t gfp_mask)
  {
  	if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
  		return 0;
  	if (gfp_mask & __GFP_MEMALLOC)
  		return ALLOC_NO_WATERMARKS;
  	if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
  		return ALLOC_NO_WATERMARKS;
  	if (!in_interrupt()) {
  		if (current->flags & PF_MEMALLOC)
  			return ALLOC_NO_WATERMARKS;
  		else if (oom_reserves_allowed(current))
  			return ALLOC_OOM;
  	}
  
  	return 0;
  }
  
  bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
  {
  	return !!__gfp_pfmemalloc_flags(gfp_mask);
  }
  
  /*
   * Checks whether it makes sense to retry the reclaim to make a forward progress
   * for the given allocation request.
   *
   * We give up when we either have tried MAX_RECLAIM_RETRIES in a row
   * without success, or when we couldn't even meet the watermark if we
   * reclaimed all remaining pages on the LRU lists.
   *
   * Returns true if a retry is viable or false to enter the oom path.
   */
  static inline bool
  should_reclaim_retry(gfp_t gfp_mask, unsigned order,
  		     struct alloc_context *ac, int alloc_flags,
  		     bool did_some_progress, int *no_progress_loops)
  {
  	struct zone *zone;
  	struct zoneref *z;
  	bool ret = false;
  
  	/*
  	 * Costly allocations might have made a progress but this doesn't mean
  	 * their order will become available due to high fragmentation so
  	 * always increment the no progress counter for them
  	 */
  	if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
  		*no_progress_loops = 0;
  	else
  		(*no_progress_loops)++;
  
  	/*
  	 * Make sure we converge to OOM if we cannot make any progress
  	 * several times in the row.
  	 */
  	if (*no_progress_loops > MAX_RECLAIM_RETRIES) {
  		/* Before OOM, exhaust highatomic_reserve */
  		return unreserve_highatomic_pageblock(ac, true);
  	}
  
  	/*
  	 * Keep reclaiming pages while there is a chance this will lead
  	 * somewhere.  If none of the target zones can satisfy our allocation
  	 * request even if all reclaimable pages are considered then we are
  	 * screwed and have to go OOM.
  	 */
  	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
  				ac->highest_zoneidx, ac->nodemask) {
  		unsigned long available;
  		unsigned long reclaimable;
  		unsigned long min_wmark = min_wmark_pages(zone);
  		bool wmark;
  
  		available = reclaimable = zone_reclaimable_pages(zone);
  		available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
  
  		/*
  		 * Would the allocation succeed if we reclaimed all
  		 * reclaimable pages?
  		 */
  		wmark = __zone_watermark_ok(zone, order, min_wmark,
  				ac->highest_zoneidx, alloc_flags, available);
  		trace_reclaim_retry_zone(z, order, reclaimable,
  				available, min_wmark, *no_progress_loops, wmark);
  		if (wmark) {
  			ret = true;
  			break;
  		}
  	}
  
  	/*
  	 * Memory allocation/reclaim might be called from a WQ context and the
  	 * current implementation of the WQ concurrency control doesn't
  	 * recognize that a particular WQ is congested if the worker thread is
  	 * looping without ever sleeping. Therefore we have to do a short sleep
  	 * here rather than calling cond_resched().
  	 */
  	if (current->flags & PF_WQ_WORKER)
  		schedule_timeout_uninterruptible(1);
  	else
  		cond_resched();
  	return ret;
  }
  
  static inline bool
  check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)
  {
  	/*
  	 * It's possible that cpuset's mems_allowed and the nodemask from
  	 * mempolicy don't intersect. This should be normally dealt with by
  	 * policy_nodemask(), but it's possible to race with cpuset update in
  	 * such a way the check therein was true, and then it became false
  	 * before we got our cpuset_mems_cookie here.
  	 * This assumes that for all allocations, ac->nodemask can come only
  	 * from MPOL_BIND mempolicy (whose documented semantics is to be ignored
  	 * when it does not intersect with the cpuset restrictions) or the
  	 * caller can deal with a violated nodemask.
  	 */
  	if (cpusets_enabled() && ac->nodemask &&
  			!cpuset_nodemask_valid_mems_allowed(ac->nodemask)) {
  		ac->nodemask = NULL;
  		return true;
  	}
  
  	/*
  	 * When updating a task's mems_allowed or mempolicy nodemask, it is
  	 * possible to race with parallel threads in such a way that our
  	 * allocation can fail while the mask is being updated. If we are about
  	 * to fail, check if the cpuset changed during allocation and if so,
  	 * retry.
  	 */
  	if (read_mems_allowed_retry(cpuset_mems_cookie))
  		return true;
  
  	return false;
  }
  
  static inline struct page *
  __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
  						struct alloc_context *ac)
  {
  	bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
  	const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
  	struct page *page = NULL;
  	unsigned int alloc_flags;
  	unsigned long did_some_progress;
  	enum compact_priority compact_priority;
  	enum compact_result compact_result;
  	int compaction_retries;
  	int no_progress_loops;
  	unsigned int cpuset_mems_cookie;
  	int reserve_flags;
  
  	/*
  	 * We also sanity check to catch abuse of atomic reserves being used by
  	 * callers that are not in atomic context.
  	 */
  	if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
  				(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
  		gfp_mask &= ~__GFP_ATOMIC;
  
  retry_cpuset:
  	compaction_retries = 0;
  	no_progress_loops = 0;
  	compact_priority = DEF_COMPACT_PRIORITY;
  	cpuset_mems_cookie = read_mems_allowed_begin();
  
  	/*
  	 * The fast path uses conservative alloc_flags to succeed only until
  	 * kswapd needs to be woken up, and to avoid the cost of setting up
  	 * alloc_flags precisely. So we do that now.
  	 */
  	alloc_flags = gfp_to_alloc_flags(gfp_mask);
  
  	/*
  	 * We need to recalculate the starting point for the zonelist iterator
  	 * because we might have used different nodemask in the fast path, or
  	 * there was a cpuset modification and we are retrying - otherwise we
  	 * could end up iterating over non-eligible zones endlessly.
  	 */
  	ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
  					ac->highest_zoneidx, ac->nodemask);
  	if (!ac->preferred_zoneref->zone)
  		goto nopage;
  
  	/*
  	 * Check for insane configurations where the cpuset doesn't contain
  	 * any suitable zone to satisfy the request - e.g. non-movable
  	 * GFP_HIGHUSER allocations from MOVABLE nodes only.
  	 */
  	if (cpusets_insane_config() && (gfp_mask & __GFP_HARDWALL)) {
  		struct zoneref *z = first_zones_zonelist(ac->zonelist,
  					ac->highest_zoneidx,
  					&cpuset_current_mems_allowed);
  		if (!z->zone)
  			goto nopage;
  	}
  
  	if (alloc_flags & ALLOC_KSWAPD)
  		wake_all_kswapds(order, gfp_mask, ac);
  
  	/*
  	 * The adjusted alloc_flags might result in immediate success, so try
  	 * that first
  	 */
  	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
  	if (page)
  		goto got_pg;
  
  	/*
  	 * For costly allocations, try direct compaction first, as it's likely
  	 * that we have enough base pages and don't need to reclaim. For non-
  	 * movable high-order allocations, do that as well, as compaction will
  	 * try prevent permanent fragmentation by migrating from blocks of the
  	 * same migratetype.
  	 * Don't try this for allocations that are allowed to ignore
  	 * watermarks, as the ALLOC_NO_WATERMARKS attempt didn't yet happen.
  	 */
  	if (can_direct_reclaim &&
  			(costly_order ||
  			   (order > 0 && ac->migratetype != MIGRATE_MOVABLE))
  			&& !gfp_pfmemalloc_allowed(gfp_mask)) {
  		page = __alloc_pages_direct_compact(gfp_mask, order,
  						alloc_flags, ac,
  						INIT_COMPACT_PRIORITY,
  						&compact_result);
  		if (page)
  			goto got_pg;
  
  		/*
  		 * Checks for costly allocations with __GFP_NORETRY, which
  		 * includes some THP page fault allocations
  		 */
  		if (costly_order && (gfp_mask & __GFP_NORETRY)) {
  			/*
  			 * If allocating entire pageblock(s) and compaction
  			 * failed because all zones are below low watermarks
  			 * or is prohibited because it recently failed at this
  			 * order, fail immediately unless the allocator has
  			 * requested compaction and reclaim retry.
  			 *
  			 * Reclaim is
  			 *  - potentially very expensive because zones are far
  			 *    below their low watermarks or this is part of very
  			 *    bursty high order allocations,
  			 *  - not guaranteed to help because isolate_freepages()
  			 *    may not iterate over freed pages as part of its
  			 *    linear scan, and
  			 *  - unlikely to make entire pageblocks free on its
  			 *    own.
  			 */
  			if (compact_result == COMPACT_SKIPPED ||
  			    compact_result == COMPACT_DEFERRED)
  				goto nopage;
  
  			/*
  			 * Looks like reclaim/compaction is worth trying, but
  			 * sync compaction could be very expensive, so keep
  			 * using async compaction.
  			 */
  			compact_priority = INIT_COMPACT_PRIORITY;
  		}
  	}
  
  retry:
  	/* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
  	if (alloc_flags & ALLOC_KSWAPD)
  		wake_all_kswapds(order, gfp_mask, ac);
  
  	reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
  	if (reserve_flags)
  		alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags);
  
  	/*
  	 * Reset the nodemask and zonelist iterators if memory policies can be
  	 * ignored. These allocations are high priority and system rather than
  	 * user oriented.
  	 */
  	if (!(alloc_flags & ALLOC_CPUSET) || reserve_flags) {
  		ac->nodemask = NULL;
  		ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
  					ac->highest_zoneidx, ac->nodemask);
  	}
  
  	/* Attempt with potentially adjusted zonelist and alloc_flags */
  	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
  	if (page)
  		goto got_pg;
  
  	/* Caller is not willing to reclaim, we can't balance anything */
  	if (!can_direct_reclaim)
  		goto nopage;
  
  	/* Avoid recursion of direct reclaim */
  	if (current->flags & PF_MEMALLOC)
  		goto nopage;
  
  	/* Try direct reclaim and then allocating */
  	page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
  							&did_some_progress);
  	if (page)
  		goto got_pg;
  
  	/* Try direct compaction and then allocating */
  	page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,
  					compact_priority, &compact_result);
  	if (page)
  		goto got_pg;
  
  	/* Do not loop if specifically requested */
  	if (gfp_mask & __GFP_NORETRY)
  		goto nopage;
  
  	/*
  	 * Do not retry costly high order allocations unless they are
  	 * __GFP_RETRY_MAYFAIL
  	 */
  	if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL))
  		goto nopage;
  
  	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
  				 did_some_progress > 0, &no_progress_loops))
  		goto retry;
  
  	/*
  	 * It doesn't make any sense to retry for the compaction if the order-0
  	 * reclaim is not able to make any progress because the current
  	 * implementation of the compaction depends on the sufficient amount
  	 * of free memory (see __compaction_suitable)
  	 */
  	if (did_some_progress > 0 &&
  			should_compact_retry(ac, order, alloc_flags,
  				compact_result, &compact_priority,
  				&compaction_retries))
  		goto retry;
  
  
  	/* Deal with possible cpuset update races before we start OOM killing */
  	if (check_retry_cpuset(cpuset_mems_cookie, ac))
  		goto retry_cpuset;
  
  	/* Reclaim has failed us, start killing things */
  	page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
  	if (page)
  		goto got_pg;
  
  	/* Avoid allocations with no watermarks from looping endlessly */
  	if (tsk_is_oom_victim(current) &&
  	    (alloc_flags & ALLOC_OOM ||
  	     (gfp_mask & __GFP_NOMEMALLOC)))
  		goto nopage;
  
  	/* Retry as long as the OOM killer is making progress */
  	if (did_some_progress) {
  		no_progress_loops = 0;
  		goto retry;
  	}
  
  nopage:
  	/* Deal with possible cpuset update races before we fail */
  	if (check_retry_cpuset(cpuset_mems_cookie, ac))
  		goto retry_cpuset;
  
  	/*
  	 * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
  	 * we always retry
  	 */
  	if (gfp_mask & __GFP_NOFAIL) {
  		/*
  		 * All existing users of the __GFP_NOFAIL are blockable, so warn
  		 * of any new users that actually require GFP_NOWAIT
  		 */
  		if (WARN_ON_ONCE(!can_direct_reclaim))
  			goto fail;
  
  		/*
  		 * PF_MEMALLOC request from this context is rather bizarre
  		 * because we cannot reclaim anything and only can loop waiting
  		 * for somebody to do a work for us
  		 */
  		WARN_ON_ONCE(current->flags & PF_MEMALLOC);
  
  		/*
  		 * non failing costly orders are a hard requirement which we
  		 * are not prepared for much so let's warn about these users
  		 * so that we can identify them and convert them to something
  		 * else.
  		 */
  		WARN_ON_ONCE(order > PAGE_ALLOC_COSTLY_ORDER);
  
  		/*
  		 * Help non-failing allocations by giving them access to memory
  		 * reserves but do not use ALLOC_NO_WATERMARKS because this
  		 * could deplete whole memory reserves which would just make
  		 * the situation worse
  		 */
  		page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_HARDER, ac);
  		if (page)
  			goto got_pg;
  
  		cond_resched();
  		goto retry;
  	}
  fail:
  	warn_alloc(gfp_mask, ac->nodemask,
  			"page allocation failure: order:%u", order);
  got_pg:
  	return page;
  }
  
  static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
  		int preferred_nid, nodemask_t *nodemask,
  		struct alloc_context *ac, gfp_t *alloc_gfp,
  		unsigned int *alloc_flags)
  {
  	ac->highest_zoneidx = gfp_zone(gfp_mask);
  	ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
  	ac->nodemask = nodemask;
  	ac->migratetype = gfp_migratetype(gfp_mask);
  
  	if (cpusets_enabled()) {
  		*alloc_gfp |= __GFP_HARDWALL;
  		/*
  		 * When we are in the interrupt context, it is irrelevant
  		 * to the current task context. It means that any node ok.
  		 */
  		if (in_task() && !ac->nodemask)
  			ac->nodemask = &cpuset_current_mems_allowed;
  		else
  			*alloc_flags |= ALLOC_CPUSET;
  	}
  
  	fs_reclaim_acquire(gfp_mask);
  	fs_reclaim_release(gfp_mask);
  
  	might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
  
  	if (should_fail_alloc_page(gfp_mask, order))
  		return false;
  
  	*alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, *alloc_flags);
  
  	/* Dirty zone balancing only done in the fast path */
  	ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
  
  	/*
  	 * The preferred zone is used for statistics but crucially it is
  	 * also used as the starting point for the zonelist iterator. It
  	 * may get reset for allocations that ignore memory policies.
  	 */
  	ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
  					ac->highest_zoneidx, ac->nodemask);
  
  	return true;
  }
  
  /*
   * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
   * @gfp: GFP flags for the allocation
   * @preferred_nid: The preferred NUMA node ID to allocate from
   * @nodemask: Set of nodes to allocate from, may be NULL
   * @nr_pages: The number of pages desired on the list or array
   * @page_list: Optional list to store the allocated pages
   * @page_array: Optional array to store the pages
   *
   * This is a batched version of the page allocator that attempts to
   * allocate nr_pages quickly. Pages are added to page_list if page_list
   * is not NULL, otherwise it is assumed that the page_array is valid.
   *
   * For lists, nr_pages is the number of pages that should be allocated.
   *
   * For arrays, only NULL elements are populated with pages and nr_pages
   * is the maximum number of pages that will be stored in the array.
   *
   * Returns the number of pages on the list or array.
   */
  unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
  			nodemask_t *nodemask, int nr_pages,
  			struct list_head *page_list,
  			struct page **page_array)
  {
  	struct page *page;
  	unsigned long flags;
  	struct zone *zone;
  	struct zoneref *z;
  	struct per_cpu_pages *pcp;
  	struct list_head *pcp_list;
  	struct alloc_context ac;
  	gfp_t alloc_gfp;
  	unsigned int alloc_flags = ALLOC_WMARK_LOW;
  	int nr_populated = 0, nr_account = 0;
  
  	/*
  	 * Skip populated array elements to determine if any pages need
  	 * to be allocated before disabling IRQs.
  	 */
  	while (page_array && nr_populated < nr_pages && page_array[nr_populated])
  		nr_populated++;
  
  	/* No pages requested? */
  	if (unlikely(nr_pages <= 0))
  		goto out;
  
  	/* Already populated array? */
  	if (unlikely(page_array && nr_pages - nr_populated == 0))
  		goto out;
  
  	/* Bulk allocator does not support memcg accounting. */
  	if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT))
  		goto failed;
  
  	/* Use the single page allocator for one page. */
  	if (nr_pages - nr_populated == 1)
  		goto failed;
  
  #ifdef CONFIG_PAGE_OWNER
  	/*
  	 * PAGE_OWNER may recurse into the allocator to allocate space to
  	 * save the stack with pagesets.lock held. Releasing/reacquiring
  	 * removes much of the performance benefit of bulk allocation so
  	 * force the caller to allocate one page at a time as it'll have
  	 * similar performance to added complexity to the bulk allocator.
  	 */
  	if (static_branch_unlikely(&page_owner_inited))
  		goto failed;
  #endif
  
  	/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
  	gfp &= gfp_allowed_mask;
  	alloc_gfp = gfp;
  	if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags))
  		goto out;
  	gfp = alloc_gfp;
  
  	/* Find an allowed local zone that meets the low watermark. */
  	for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) {
  		unsigned long mark;
  
  		if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
  		    !__cpuset_zone_allowed(zone, gfp)) {
  			continue;
  		}
  
  		if (nr_online_nodes > 1 && zone != ac.preferred_zoneref->zone &&
  		    zone_to_nid(zone) != zone_to_nid(ac.preferred_zoneref->zone)) {
  			goto failed;
  		}
  
  		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
  		if (zone_watermark_fast(zone, 0,  mark,
  				zonelist_zone_idx(ac.preferred_zoneref),
  				alloc_flags, gfp)) {
  			break;
  		}
  	}
  
  	/*
  	 * If there are no allowed local zones that meets the watermarks then
  	 * try to allocate a single page and reclaim if necessary.
  	 */
  	if (unlikely(!zone))
  		goto failed;
  
  	/* Attempt the batch allocation */
  	local_lock_irqsave(&pagesets.lock, flags);
  	pcp = this_cpu_ptr(zone->per_cpu_pageset);
  	pcp_list = &pcp->lists[order_to_pindex(ac.migratetype, 0)];
  
  	while (nr_populated < nr_pages) {
  
  		/* Skip existing pages */
  		if (page_array && page_array[nr_populated]) {
  			nr_populated++;
  			continue;
  		}
  
  		page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
  								pcp, pcp_list);
  		if (unlikely(!page)) {
  			/* Try and get at least one page */
  			if (!nr_populated)
  				goto failed_irq;
  			break;
  		}
  		nr_account++;
  
  		prep_new_page(page, 0, gfp, 0);
  		if (page_list)
  			list_add(&page->lru, page_list);
  		else
  			page_array[nr_populated] = page;
  		nr_populated++;
  	}
  
  	local_unlock_irqrestore(&pagesets.lock, flags);
  
  	__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
  	zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
  
  out:
  	return nr_populated;
  
  failed_irq:
  	local_unlock_irqrestore(&pagesets.lock, flags);
  
  failed:
  	page = __alloc_pages(gfp, 0, preferred_nid, nodemask);
  	if (page) {
  		if (page_list)
  			list_add(&page->lru, page_list);
  		else
  			page_array[nr_populated] = page;
  		nr_populated++;
  	}
  
  	goto out;
  }
  EXPORT_SYMBOL_GPL(__alloc_pages_bulk);
  
  /*
   * This is the 'heart' of the zoned buddy allocator.
   */
  struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
  							nodemask_t *nodemask)
  {
  	struct page *page;
  	unsigned int alloc_flags = ALLOC_WMARK_LOW;
  	gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */
  	struct alloc_context ac = { };
  
  	/*
  	 * There are several places where we assume that the order value is sane
  	 * so bail out early if the request is out of bound.
  	 */
  	if (unlikely(order >= MAX_ORDER)) {
  		WARN_ON_ONCE(!(gfp & __GFP_NOWARN));
  		return NULL;
  	}
  
  	gfp &= gfp_allowed_mask;
  	/*
  	 * Apply scoped allocation constraints. This is mainly about GFP_NOFS
  	 * resp. GFP_NOIO which has to be inherited for all allocation requests
  	 * from a particular context which has been marked by
  	 * memalloc_no{fs,io}_{save,restore}. And PF_MEMALLOC_PIN which ensures
  	 * movable zones are not used during allocation.
  	 */
  	gfp = current_gfp_context(gfp);
  	alloc_gfp = gfp;
  	if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, &ac,
  			&alloc_gfp, &alloc_flags))
  		return NULL;
  
  	/*
  	 * Forbid the first pass from falling back to types that fragment
  	 * memory until all local zones are considered.
  	 */
  	alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone, gfp);
  
  	/* First allocation attempt */
  	page = get_page_from_freelist(alloc_gfp, order, alloc_flags, &ac);
  	if (likely(page))
  		goto out;
  
  	alloc_gfp = gfp;
  	ac.spread_dirty_pages = false;
  
  	/*
  	 * Restore the original nodemask if it was potentially replaced with
  	 * &cpuset_current_mems_allowed to optimize the fast-path attempt.
  	 */
  	ac.nodemask = nodemask;
  
  	page = __alloc_pages_slowpath(alloc_gfp, order, &ac);
  
  out:
  	if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT) && page &&
  	    unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
  		__free_pages(page, order);
  		page = NULL;
  	}
  
  	trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);
  
  	return page;
  }
  EXPORT_SYMBOL(__alloc_pages);
  
  struct folio *__folio_alloc(gfp_t gfp, unsigned int order, int preferred_nid,
  		nodemask_t *nodemask)
  {
  	struct page *page = __alloc_pages(gfp | __GFP_COMP, order,
  			preferred_nid, nodemask);
  
  	if (page && order > 1)
  		prep_transhuge_page(page);
  	return (struct folio *)page;
  }
  EXPORT_SYMBOL(__folio_alloc);
  
  /*
   * Common helper functions. Never use with __GFP_HIGHMEM because the returned
   * address cannot represent highmem pages. Use alloc_pages and then kmap if
   * you need to access high mem.
   */
  unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
  {
  	struct page *page;
  
  	page = alloc_pages(gfp_mask & ~__GFP_HIGHMEM, order);
  	if (!page)
  		return 0;
  	return (unsigned long) page_address(page);
  }
  EXPORT_SYMBOL(__get_free_pages);
  
  unsigned long get_zeroed_page(gfp_t gfp_mask)
  {
  	return __get_free_pages(gfp_mask | __GFP_ZERO, 0);
  }
  EXPORT_SYMBOL(get_zeroed_page);
  
  /**
   * __free_pages - Free pages allocated with alloc_pages().
   * @page: The page pointer returned from alloc_pages().
   * @order: The order of the allocation.
   *
   * This function can free multi-page allocations that are not compound
   * pages.  It does not check that the @order passed in matches that of
   * the allocation, so it is easy to leak memory.  Freeing more memory
   * than was allocated will probably emit a warning.
   *
   * If the last reference to this page is speculative, it will be released
   * by put_page() which only frees the first page of a non-compound
   * allocation.  To prevent the remaining pages from being leaked, we free
   * the subsequent pages here.  If you want to use the page's reference
   * count to decide when to free the allocation, you should allocate a
   * compound page, and use put_page() instead of __free_pages().
   *
   * Context: May be called in interrupt context or while holding a normal
   * spinlock, but not in NMI context or while holding a raw spinlock.
   */
  void __free_pages(struct page *page, unsigned int order)
  {
  	if (put_page_testzero(page))
  		free_the_page(page, order);
  	else if (!PageHead(page))
  		while (order-- > 0)
  			free_the_page(page + (1 << order), order);
  }
  EXPORT_SYMBOL(__free_pages);
  
  void free_pages(unsigned long addr, unsigned int order)
  {
  	if (addr != 0) {
  		VM_BUG_ON(!virt_addr_valid((void *)addr));
  		__free_pages(virt_to_page((void *)addr), order);
  	}
  }
  
  EXPORT_SYMBOL(free_pages);
  
  /*
   * Page Fragment:
   *  An arbitrary-length arbitrary-offset area of memory which resides
   *  within a 0 or higher order page.  Multiple fragments within that page
   *  are individually refcounted, in the page's reference counter.
   *
   * The page_frag functions below provide a simple allocation framework for
   * page fragments.  This is used by the network stack and network device
   * drivers to provide a backing region of memory for use as either an
   * sk_buff->head, or to be used in the "frags" portion of skb_shared_info.
   */
  static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
  					     gfp_t gfp_mask)
  {
  	struct page *page = NULL;
  	gfp_t gfp = gfp_mask;
  
  #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
  	gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
  		    __GFP_NOMEMALLOC;
  	page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
  				PAGE_FRAG_CACHE_MAX_ORDER);
  	nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
  #endif
  	if (unlikely(!page))
  		page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
  
  	nc->va = page ? page_address(page) : NULL;
  
  	return page;
  }
  
  void __page_frag_cache_drain(struct page *page, unsigned int count)
  {
  	VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
  
  	if (page_ref_sub_and_test(page, count))
  		free_the_page(page, compound_order(page));
  }
  EXPORT_SYMBOL(__page_frag_cache_drain);
  
  void *page_frag_alloc_align(struct page_frag_cache *nc,
  		      unsigned int fragsz, gfp_t gfp_mask,
  		      unsigned int align_mask)
  {
  	unsigned int size = PAGE_SIZE;
  	struct page *page;
  	int offset;
  
  	if (unlikely(!nc->va)) {
  refill:
  		page = __page_frag_cache_refill(nc, gfp_mask);
  		if (!page)
  			return NULL;
  
  #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
  		/* if size can vary use size else just use PAGE_SIZE */
  		size = nc->size;
  #endif
  		/* Even if we own the page, we do not use atomic_set().
  		 * This would break get_page_unless_zero() users.
  		 */
  		page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
  
  		/* reset page count bias and offset to start of new frag */
  		nc->pfmemalloc = page_is_pfmemalloc(page);
  		nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
  		nc->offset = size;
  	}
  
  	offset = nc->offset - fragsz;
  	if (unlikely(offset < 0)) {
  		page = virt_to_page(nc->va);
  
  		if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
  			goto refill;
  
  		if (unlikely(nc->pfmemalloc)) {
  			free_the_page(page, compound_order(page));
  			goto refill;
  		}
  
  #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
  		/* if size can vary use size else just use PAGE_SIZE */
  		size = nc->size;
  #endif
  		/* OK, page count is 0, we can safely set it */
  		set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
  
  		/* reset page count bias and offset to start of new frag */
  		nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
  		offset = size - fragsz;
  	}
  
  	nc->pagecnt_bias--;
  	offset &= align_mask;
  	nc->offset = offset;
  
  	return nc->va + offset;
  }
  EXPORT_SYMBOL(page_frag_alloc_align);
  
  /*
   * Frees a page fragment allocated out of either a compound or order 0 page.
   */
  void page_frag_free(void *addr)
  {
  	struct page *page = virt_to_head_page(addr);
  
  	if (unlikely(put_page_testzero(page)))
  		free_the_page(page, compound_order(page));
  }
  EXPORT_SYMBOL(page_frag_free);
  
  static void *make_alloc_exact(unsigned long addr, unsigned int order,
  		size_t size)
  {
  	if (addr) {
  		unsigned long alloc_end = addr + (PAGE_SIZE << order);
  		unsigned long used = addr + PAGE_ALIGN(size);
  
  		split_page(virt_to_page((void *)addr), order);
  		while (used < alloc_end) {
  			free_page(used);
  			used += PAGE_SIZE;
  		}
  	}
  	return (void *)addr;
  }
  
  /**
   * alloc_pages_exact - allocate an exact number physically-contiguous pages.
   * @size: the number of bytes to allocate
   * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
   *
   * This function is similar to alloc_pages(), except that it allocates the
   * minimum number of pages to satisfy the request.  alloc_pages() can only
   * allocate memory in power-of-two pages.
   *
   * This function is also limited by MAX_ORDER.
   *
   * Memory allocated by this function must be released by free_pages_exact().
   *
   * Return: pointer to the allocated area or %NULL in case of error.
   */
  void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
  {
  	unsigned int order = get_order(size);
  	unsigned long addr;
  
  	if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
  		gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
  
  	addr = __get_free_pages(gfp_mask, order);
  	return make_alloc_exact(addr, order, size);
  }
  EXPORT_SYMBOL(alloc_pages_exact);
  
  /**
   * alloc_pages_exact_nid - allocate an exact number of physically-contiguous
   *			   pages on a node.
   * @nid: the preferred node ID where memory should be allocated
   * @size: the number of bytes to allocate
   * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
   *
   * Like alloc_pages_exact(), but try to allocate on node nid first before falling
   * back.
   *
   * Return: pointer to the allocated area or %NULL in case of error.
   */
  void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
  {
  	unsigned int order = get_order(size);
  	struct page *p;
  
  	if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
  		gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
  
  	p = alloc_pages_node(nid, gfp_mask, order);
  	if (!p)
  		return NULL;
  	return make_alloc_exact((unsigned long)page_address(p), order, size);
  }
  
  /**
   * free_pages_exact - release memory allocated via alloc_pages_exact()
   * @virt: the value returned by alloc_pages_exact.
   * @size: size of allocation, same value as passed to alloc_pages_exact().
   *
   * Release the memory allocated by a previous call to alloc_pages_exact.
   */
  void free_pages_exact(void *virt, size_t size)
  {
  	unsigned long addr = (unsigned long)virt;
  	unsigned long end = addr + PAGE_ALIGN(size);
  
  	while (addr < end) {
  		free_page(addr);
  		addr += PAGE_SIZE;
  	}
  }
  EXPORT_SYMBOL(free_pages_exact);
  
  /**
   * nr_free_zone_pages - count number of pages beyond high watermark
   * @offset: The zone index of the highest zone
   *
   * nr_free_zone_pages() counts the number of pages which are beyond the
   * high watermark within all zones at or below a given zone index.  For each
   * zone, the number of pages is calculated as:
   *
   *     nr_free_zone_pages = managed_pages - high_pages
   *
   * Return: number of pages beyond high watermark.
   */
  static unsigned long nr_free_zone_pages(int offset)
  {
  	struct zoneref *z;
  	struct zone *zone;
  
  	/* Just pick one node, since fallback list is circular */
  	unsigned long sum = 0;
  
  	struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL);
  
  	for_each_zone_zonelist(zone, z, zonelist, offset) {
  		unsigned long size = zone_managed_pages(zone);
  		unsigned long high = high_wmark_pages(zone);
  		if (size > high)
  			sum += size - high;
  	}
  
  	return sum;
  }
  
  /**
   * nr_free_buffer_pages - count number of pages beyond high watermark
   *
   * nr_free_buffer_pages() counts the number of pages which are beyond the high
   * watermark within ZONE_DMA and ZONE_NORMAL.
   *
   * Return: number of pages beyond high watermark within ZONE_DMA and
   * ZONE_NORMAL.
   */
  unsigned long nr_free_buffer_pages(void)
  {
  	return nr_free_zone_pages(gfp_zone(GFP_USER));
  }
  EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
  
  static inline void show_node(struct zone *zone)
  {
  	if (IS_ENABLED(CONFIG_NUMA))
  		printk("Node %d ", zone_to_nid(zone));
  }
  
  long si_mem_available(void)
  {
  	long available;
  	unsigned long pagecache;
  	unsigned long wmark_low = 0;
  	unsigned long pages[NR_LRU_LISTS];
  	unsigned long reclaimable;
  	struct zone *zone;
  	int lru;
  
  	for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
  		pages[lru] = global_node_page_state(NR_LRU_BASE + lru);
  
  	for_each_zone(zone)
  		wmark_low += low_wmark_pages(zone);
  
  	/*
  	 * Estimate the amount of memory available for userspace allocations,
  	 * without causing swapping.
  	 */
  	available = global_zone_page_state(NR_FREE_PAGES) - totalreserve_pages;
  
  	/*
  	 * Not all the page cache can be freed, otherwise the system will
  	 * start swapping. Assume at least half of the page cache, or the
  	 * low watermark worth of cache, needs to stay.
  	 */
  	pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
  	pagecache -= min(pagecache / 2, wmark_low);
  	available += pagecache;
  
  	/*
  	 * Part of the reclaimable slab and other kernel memory consists of
  	 * items that are in use, and cannot be freed. Cap this estimate at the
  	 * low watermark.
  	 */
  	reclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B) +
  		global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE);
  	available += reclaimable - min(reclaimable / 2, wmark_low);
  
  	if (available < 0)
  		available = 0;
  	return available;
  }
  EXPORT_SYMBOL_GPL(si_mem_available);
  
  void si_meminfo(struct sysinfo *val)
  {
  	val->totalram = totalram_pages();
  	val->sharedram = global_node_page_state(NR_SHMEM);
  	val->freeram = global_zone_page_state(NR_FREE_PAGES);
  	val->bufferram = nr_blockdev_pages();
  	val->totalhigh = totalhigh_pages();
  	val->freehigh = nr_free_highpages();
  	val->mem_unit = PAGE_SIZE;
  }
  
  EXPORT_SYMBOL(si_meminfo);
  
  #ifdef CONFIG_NUMA
  void si_meminfo_node(struct sysinfo *val, int nid)
  {
  	int zone_type;		/* needs to be signed */
  	unsigned long managed_pages = 0;
  	unsigned long managed_highpages = 0;
  	unsigned long free_highpages = 0;
  	pg_data_t *pgdat = NODE_DATA(nid);
  
  	for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++)
  		managed_pages += zone_managed_pages(&pgdat->node_zones[zone_type]);
  	val->totalram = managed_pages;
  	val->sharedram = node_page_state(pgdat, NR_SHMEM);
  	val->freeram = sum_zone_node_page_state(nid, NR_FREE_PAGES);
  #ifdef CONFIG_HIGHMEM
  	for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
  		struct zone *zone = &pgdat->node_zones[zone_type];
  
  		if (is_highmem(zone)) {
  			managed_highpages += zone_managed_pages(zone);
  			free_highpages += zone_page_state(zone, NR_FREE_PAGES);
  		}
  	}
  	val->totalhigh = managed_highpages;
  	val->freehigh = free_highpages;
  #else
  	val->totalhigh = managed_highpages;
  	val->freehigh = free_highpages;
  #endif
  	val->mem_unit = PAGE_SIZE;
  }
  #endif
  
  /*
   * Determine whether the node should be displayed or not, depending on whether
   * SHOW_MEM_FILTER_NODES was passed to show_free_areas().
   */
  static bool show_mem_node_skip(unsigned int flags, int nid, nodemask_t *nodemask)
  {
  	if (!(flags & SHOW_MEM_FILTER_NODES))
  		return false;
  
  	/*
  	 * no node mask - aka implicit memory numa policy. Do not bother with
  	 * the synchronization - read_mems_allowed_begin - because we do not
  	 * have to be precise here.
  	 */
  	if (!nodemask)
  		nodemask = &cpuset_current_mems_allowed;
  
  	return !node_isset(nid, *nodemask);
  }
  
  #define K(x) ((x) << (PAGE_SHIFT-10))
  
  static void show_migration_types(unsigned char type)
  {
  	static const char types[MIGRATE_TYPES] = {
  		[MIGRATE_UNMOVABLE]	= 'U',
  		[MIGRATE_MOVABLE]	= 'M',
  		[MIGRATE_RECLAIMABLE]	= 'E',
  		[MIGRATE_HIGHATOMIC]	= 'H',
  #ifdef CONFIG_CMA
  		[MIGRATE_CMA]		= 'C',
  #endif
  #ifdef CONFIG_MEMORY_ISOLATION
  		[MIGRATE_ISOLATE]	= 'I',
  #endif
  	};
  	char tmp[MIGRATE_TYPES + 1];
  	char *p = tmp;
  	int i;
  
  	for (i = 0; i < MIGRATE_TYPES; i++) {
  		if (type & (1 << i))
  			*p++ = types[i];
  	}
  
  	*p = '\0';
  	printk(KERN_CONT "(%s) ", tmp);
  }
  
  /*
   * Show free area list (used inside shift_scroll-lock stuff)
   * We also calculate the percentage fragmentation. We do this by counting the
   * memory on each free list with the exception of the first item on the list.
   *
   * Bits in @filter:
   * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's
   *   cpuset.
   */
  void show_free_areas(unsigned int filter, nodemask_t *nodemask)
  {
  	unsigned long free_pcp = 0;
  	int cpu;
  	struct zone *zone;
  	pg_data_t *pgdat;
  
  	for_each_populated_zone(zone) {
  		if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
  			continue;
  
  		for_each_online_cpu(cpu)
  			free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
  	}
  
  	printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
  		" active_file:%lu inactive_file:%lu isolated_file:%lu\n"
  		" unevictable:%lu dirty:%lu writeback:%lu\n"
  		" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
  		" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
  		" kernel_misc_reclaimable:%lu\n"
  		" free:%lu free_pcp:%lu free_cma:%lu\n",
  		global_node_page_state(NR_ACTIVE_ANON),
  		global_node_page_state(NR_INACTIVE_ANON),
  		global_node_page_state(NR_ISOLATED_ANON),
  		global_node_page_state(NR_ACTIVE_FILE),
  		global_node_page_state(NR_INACTIVE_FILE),
  		global_node_page_state(NR_ISOLATED_FILE),
  		global_node_page_state(NR_UNEVICTABLE),
  		global_node_page_state(NR_FILE_DIRTY),
  		global_node_page_state(NR_WRITEBACK),
  		global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B),
  		global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B),
  		global_node_page_state(NR_FILE_MAPPED),
  		global_node_page_state(NR_SHMEM),
  		global_node_page_state(NR_PAGETABLE),
  		global_zone_page_state(NR_BOUNCE),
  		global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE),
  		global_zone_page_state(NR_FREE_PAGES),
  		free_pcp,
  		global_zone_page_state(NR_FREE_CMA_PAGES));
  
  	for_each_online_pgdat(pgdat) {
  		if (show_mem_node_skip(filter, pgdat->node_id, nodemask))
  			continue;
  
  		printk("Node %d"
  			" active_anon:%lukB"
  			" inactive_anon:%lukB"
  			" active_file:%lukB"
  			" inactive_file:%lukB"
  			" unevictable:%lukB"
  			" isolated(anon):%lukB"
  			" isolated(file):%lukB"
  			" mapped:%lukB"
  			" dirty:%lukB"
  			" writeback:%lukB"
  			" shmem:%lukB"
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  			" shmem_thp: %lukB"
  			" shmem_pmdmapped: %lukB"
  			" anon_thp: %lukB"
  #endif
  			" writeback_tmp:%lukB"
  			" kernel_stack:%lukB"
  #ifdef CONFIG_SHADOW_CALL_STACK
  			" shadow_call_stack:%lukB"
  #endif
  			" pagetables:%lukB"
  			" all_unreclaimable? %s"
  			"\n",
  			pgdat->node_id,
  			K(node_page_state(pgdat, NR_ACTIVE_ANON)),
  			K(node_page_state(pgdat, NR_INACTIVE_ANON)),
  			K(node_page_state(pgdat, NR_ACTIVE_FILE)),
  			K(node_page_state(pgdat, NR_INACTIVE_FILE)),
  			K(node_page_state(pgdat, NR_UNEVICTABLE)),
  			K(node_page_state(pgdat, NR_ISOLATED_ANON)),
  			K(node_page_state(pgdat, NR_ISOLATED_FILE)),
  			K(node_page_state(pgdat, NR_FILE_MAPPED)),
  			K(node_page_state(pgdat, NR_FILE_DIRTY)),
  			K(node_page_state(pgdat, NR_WRITEBACK)),
  			K(node_page_state(pgdat, NR_SHMEM)),
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  			K(node_page_state(pgdat, NR_SHMEM_THPS)),
  			K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)),
  			K(node_page_state(pgdat, NR_ANON_THPS)),
  #endif
  			K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
  			node_page_state(pgdat, NR_KERNEL_STACK_KB),
  #ifdef CONFIG_SHADOW_CALL_STACK
  			node_page_state(pgdat, NR_KERNEL_SCS_KB),
  #endif
  			K(node_page_state(pgdat, NR_PAGETABLE)),
  			pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
  				"yes" : "no");
  	}
  
  	for_each_populated_zone(zone) {
  		int i;
  
  		if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
  			continue;
  
  		free_pcp = 0;
  		for_each_online_cpu(cpu)
  			free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
  
  		show_node(zone);
  		printk(KERN_CONT
  			"%s"
  			" free:%lukB"
  			" boost:%lukB"
  			" min:%lukB"
  			" low:%lukB"
  			" high:%lukB"
  			" reserved_highatomic:%luKB"
  			" active_anon:%lukB"
  			" inactive_anon:%lukB"
  			" active_file:%lukB"
  			" inactive_file:%lukB"
  			" unevictable:%lukB"
  			" writepending:%lukB"
  			" present:%lukB"
  			" managed:%lukB"
  			" mlocked:%lukB"
  			" bounce:%lukB"
  			" free_pcp:%lukB"
  			" local_pcp:%ukB"
  			" free_cma:%lukB"
  			"\n",
  			zone->name,
  			K(zone_page_state(zone, NR_FREE_PAGES)),
  			K(zone->watermark_boost),
  			K(min_wmark_pages(zone)),
  			K(low_wmark_pages(zone)),
  			K(high_wmark_pages(zone)),
  			K(zone->nr_reserved_highatomic),
  			K(zone_page_state(zone, NR_ZONE_ACTIVE_ANON)),
  			K(zone_page_state(zone, NR_ZONE_INACTIVE_ANON)),
  			K(zone_page_state(zone, NR_ZONE_ACTIVE_FILE)),
  			K(zone_page_state(zone, NR_ZONE_INACTIVE_FILE)),
  			K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)),
  			K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)),
  			K(zone->present_pages),
  			K(zone_managed_pages(zone)),
  			K(zone_page_state(zone, NR_MLOCK)),
  			K(zone_page_state(zone, NR_BOUNCE)),
  			K(free_pcp),
  			K(this_cpu_read(zone->per_cpu_pageset->count)),
  			K(zone_page_state(zone, NR_FREE_CMA_PAGES)));
  		printk("lowmem_reserve[]:");
  		for (i = 0; i < MAX_NR_ZONES; i++)
  			printk(KERN_CONT " %ld", zone->lowmem_reserve[i]);
  		printk(KERN_CONT "\n");
  	}
  
  	for_each_populated_zone(zone) {
  		unsigned int order;
  		unsigned long nr[MAX_ORDER], flags, total = 0;
  		unsigned char types[MAX_ORDER];
  
  		if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask))
  			continue;
  		show_node(zone);
  		printk(KERN_CONT "%s: ", zone->name);
  
  		spin_lock_irqsave(&zone->lock, flags);
  		for (order = 0; order < MAX_ORDER; order++) {
  			struct free_area *area = &zone->free_area[order];
  			int type;
  
  			nr[order] = area->nr_free;
  			total += nr[order] << order;
  
  			types[order] = 0;
  			for (type = 0; type < MIGRATE_TYPES; type++) {
  				if (!free_area_empty(area, type))
  					types[order] |= 1 << type;
  			}
  		}
  		spin_unlock_irqrestore(&zone->lock, flags);
  		for (order = 0; order < MAX_ORDER; order++) {
  			printk(KERN_CONT "%lu*%lukB ",
  			       nr[order], K(1UL) << order);
  			if (nr[order])
  				show_migration_types(types[order]);
  		}
  		printk(KERN_CONT "= %lukB\n", K(total));
  	}
  
  	hugetlb_show_meminfo();
  
  	printk("%ld total pagecache pages\n", global_node_page_state(NR_FILE_PAGES));
  
  	show_swap_cache_info();
  }
  
  static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
  {
  	zoneref->zone = zone;
  	zoneref->zone_idx = zone_idx(zone);
  }
  
  /*
   * Builds allocation fallback zone lists.
   *
   * Add all populated zones of a node to the zonelist.
   */
  static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)
  {
  	struct zone *zone;
  	enum zone_type zone_type = MAX_NR_ZONES;
  	int nr_zones = 0;
  
  	do {
  		zone_type--;
  		zone = pgdat->node_zones + zone_type;
  		if (managed_zone(zone)) {
  			zoneref_set_zone(zone, &zonerefs[nr_zones++]);
  			check_highest_zone(zone_type);
  		}
  	} while (zone_type);
  
  	return nr_zones;
  }
  
  #ifdef CONFIG_NUMA
  
  static int __parse_numa_zonelist_order(char *s)
  {
  	/*
  	 * We used to support different zonelists modes but they turned
  	 * out to be just not useful. Let's keep the warning in place
  	 * if somebody still use the cmd line parameter so that we do
  	 * not fail it silently
  	 */
  	if (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) {
  		pr_warn("Ignoring unsupported numa_zonelist_order value:  %s\n", s);
  		return -EINVAL;
  	}
  	return 0;
  }
  
  char numa_zonelist_order[] = "Node";
  
  /*
   * sysctl handler for numa_zonelist_order
   */
  int numa_zonelist_order_handler(struct ctl_table *table, int write,
  		void *buffer, size_t *length, loff_t *ppos)
  {
  	if (write)
  		return __parse_numa_zonelist_order(buffer);
  	return proc_dostring(table, write, buffer, length, ppos);
  }
  
  
  #define MAX_NODE_LOAD (nr_online_nodes)
  static int node_load[MAX_NUMNODES];
  
  /**
   * find_next_best_node - find the next node that should appear in a given node's fallback list
   * @node: node whose fallback list we're appending
   * @used_node_mask: nodemask_t of already used nodes
   *
   * We use a number of factors to determine which is the next node that should
   * appear on a given node's fallback list.  The node should not have appeared
   * already in @node's fallback list, and it should be the next closest node
   * according to the distance array (which contains arbitrary distance values
   * from each node to each node in the system), and should also prefer nodes
   * with no CPUs, since presumably they'll have very little allocation pressure
   * on them otherwise.
   *
   * Return: node id of the found node or %NUMA_NO_NODE if no node is found.
   */
  int find_next_best_node(int node, nodemask_t *used_node_mask)
  {
  	int n, val;
  	int min_val = INT_MAX;
  	int best_node = NUMA_NO_NODE;
  
  	/* Use the local node if we haven't already */
  	if (!node_isset(node, *used_node_mask)) {
  		node_set(node, *used_node_mask);
  		return node;
  	}
  
  	for_each_node_state(n, N_MEMORY) {
  
  		/* Don't want a node to appear more than once */
  		if (node_isset(n, *used_node_mask))
  			continue;
  
  		/* Use the distance array to find the distance */
  		val = node_distance(node, n);
  
  		/* Penalize nodes under us ("prefer the next node") */
  		val += (n < node);
  
  		/* Give preference to headless and unused nodes */
  		if (!cpumask_empty(cpumask_of_node(n)))
  			val += PENALTY_FOR_NODE_WITH_CPUS;
  
  		/* Slight preference for less loaded node */
  		val *= (MAX_NODE_LOAD*MAX_NUMNODES);
  		val += node_load[n];
  
  		if (val < min_val) {
  			min_val = val;
  			best_node = n;
  		}
  	}
  
  	if (best_node >= 0)
  		node_set(best_node, *used_node_mask);
  
  	return best_node;
  }
  
  
  /*
   * Build zonelists ordered by node and zones within node.
   * This results in maximum locality--normal zone overflows into local
   * DMA zone, if any--but risks exhausting DMA zone.
   */
  static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
  		unsigned nr_nodes)
  {
  	struct zoneref *zonerefs;
  	int i;
  
  	zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
  
  	for (i = 0; i < nr_nodes; i++) {
  		int nr_zones;
  
  		pg_data_t *node = NODE_DATA(node_order[i]);
  
  		nr_zones = build_zonerefs_node(node, zonerefs);
  		zonerefs += nr_zones;
  	}
  	zonerefs->zone = NULL;
  	zonerefs->zone_idx = 0;
  }
  
  /*
   * Build gfp_thisnode zonelists
   */
  static void build_thisnode_zonelists(pg_data_t *pgdat)
  {
  	struct zoneref *zonerefs;
  	int nr_zones;
  
  	zonerefs = pgdat->node_zonelists[ZONELIST_NOFALLBACK]._zonerefs;
  	nr_zones = build_zonerefs_node(pgdat, zonerefs);
  	zonerefs += nr_zones;
  	zonerefs->zone = NULL;
  	zonerefs->zone_idx = 0;
  }
  
  /*
   * Build zonelists ordered by zone and nodes within zones.
   * This results in conserving DMA zone[s] until all Normal memory is
   * exhausted, but results in overflowing to remote node while memory
   * may still exist in local DMA zone.
   */
  
  static void build_zonelists(pg_data_t *pgdat)
  {
  	static int node_order[MAX_NUMNODES];
  	int node, load, nr_nodes = 0;
  	nodemask_t used_mask = NODE_MASK_NONE;
  	int local_node, prev_node;
  
  	/* NUMA-aware ordering of nodes */
  	local_node = pgdat->node_id;
  	load = nr_online_nodes;
  	prev_node = local_node;
  
  	memset(node_order, 0, sizeof(node_order));
  	while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
  		/*
  		 * We don't want to pressure a particular node.
  		 * So adding penalty to the first node in same
  		 * distance group to make it round-robin.
  		 */
  		if (node_distance(local_node, node) !=
  		    node_distance(local_node, prev_node))
  			node_load[node] += load;
  
  		node_order[nr_nodes++] = node;
  		prev_node = node;
  		load--;
  	}
  
  	build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
  	build_thisnode_zonelists(pgdat);
  	pr_info("Fallback order for Node %d: ", local_node);
  	for (node = 0; node < nr_nodes; node++)
  		pr_cont("%d ", node_order[node]);
  	pr_cont("\n");
  }
  
  #ifdef CONFIG_HAVE_MEMORYLESS_NODES
  /*
   * Return node id of node used for "local" allocations.
   * I.e., first node id of first zone in arg node's generic zonelist.
   * Used for initializing percpu 'numa_mem', which is used primarily
   * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
   */
  int local_memory_node(int node)
  {
  	struct zoneref *z;
  
  	z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
  				   gfp_zone(GFP_KERNEL),
  				   NULL);
  	return zone_to_nid(z->zone);
  }
  #endif
  
  static void setup_min_unmapped_ratio(void);
  static void setup_min_slab_ratio(void);
  #else	/* CONFIG_NUMA */
  
  static void build_zonelists(pg_data_t *pgdat)
  {
  	int node, local_node;
  	struct zoneref *zonerefs;
  	int nr_zones;
  
  	local_node = pgdat->node_id;
  
  	zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
  	nr_zones = build_zonerefs_node(pgdat, zonerefs);
  	zonerefs += nr_zones;
  
  	/*
  	 * Now we build the zonelist so that it contains the zones
  	 * of all the other nodes.
  	 * We don't want to pressure a particular node, so when
  	 * building the zones for node N, we make sure that the
  	 * zones coming right after the local ones are those from
  	 * node N+1 (modulo N)
  	 */
  	for (node = local_node + 1; node < MAX_NUMNODES; node++) {
  		if (!node_online(node))
  			continue;
  		nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
  		zonerefs += nr_zones;
  	}
  	for (node = 0; node < local_node; node++) {
  		if (!node_online(node))
  			continue;
  		nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
  		zonerefs += nr_zones;
  	}
  
  	zonerefs->zone = NULL;
  	zonerefs->zone_idx = 0;
  }
  
  #endif	/* CONFIG_NUMA */
  
  /*
   * Boot pageset table. One per cpu which is going to be used for all
   * zones and all nodes. The parameters will be set in such a way
   * that an item put on a list will immediately be handed over to
   * the buddy list. This is safe since pageset manipulation is done
   * with interrupts disabled.
   *
   * The boot_pagesets must be kept even after bootup is complete for
   * unused processors and/or zones. They do play a role for bootstrapping
   * hotplugged processors.
   *
   * zoneinfo_show() and maybe other functions do
   * not check if the processor is online before following the pageset pointer.
   * Other parts of the kernel may not check if the zone is available.
   */
  static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats);
  /* These effectively disable the pcplists in the boot pageset completely */
  #define BOOT_PAGESET_HIGH	0
  #define BOOT_PAGESET_BATCH	1
  static DEFINE_PER_CPU(struct per_cpu_pages, boot_pageset);
  static DEFINE_PER_CPU(struct per_cpu_zonestat, boot_zonestats);
  static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
  
  static void __build_all_zonelists(void *data)
  {
  	int nid;
  	int __maybe_unused cpu;
  	pg_data_t *self = data;
  	static DEFINE_SPINLOCK(lock);
  
  	spin_lock(&lock);
  
  #ifdef CONFIG_NUMA
  	memset(node_load, 0, sizeof(node_load));
  #endif
  
  	/*
  	 * This node is hotadded and no memory is yet present.   So just
  	 * building zonelists is fine - no need to touch other nodes.
  	 */
  	if (self && !node_online(self->node_id)) {
  		build_zonelists(self);
  	} else {
  		for_each_online_node(nid) {
  			pg_data_t *pgdat = NODE_DATA(nid);
  
  			build_zonelists(pgdat);
  		}
  
  #ifdef CONFIG_HAVE_MEMORYLESS_NODES
  		/*
  		 * We now know the "local memory node" for each node--
  		 * i.e., the node of the first zone in the generic zonelist.
  		 * Set up numa_mem percpu variable for on-line cpus.  During
  		 * boot, only the boot cpu should be on-line;  we'll init the
  		 * secondary cpus' numa_mem as they come on-line.  During
  		 * node/memory hotplug, we'll fixup all on-line cpus.
  		 */
  		for_each_online_cpu(cpu)
  			set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
  #endif
  	}
  
  	spin_unlock(&lock);
  }
  
  static noinline void __init
  build_all_zonelists_init(void)
  {
  	int cpu;
  
  	__build_all_zonelists(NULL);
  
  	/*
  	 * Initialize the boot_pagesets that are going to be used
  	 * for bootstrapping processors. The real pagesets for
  	 * each zone will be allocated later when the per cpu
  	 * allocator is available.
  	 *
  	 * boot_pagesets are used also for bootstrapping offline
  	 * cpus if the system is already booted because the pagesets
  	 * are needed to initialize allocators on a specific cpu too.
  	 * F.e. the percpu allocator needs the page allocator which
  	 * needs the percpu allocator in order to allocate its pagesets
  	 * (a chicken-egg dilemma).
  	 */
  	for_each_possible_cpu(cpu)
  		per_cpu_pages_init(&per_cpu(boot_pageset, cpu), &per_cpu(boot_zonestats, cpu));
  
  	mminit_verify_zonelist();
  	cpuset_init_current_mems_allowed();
  }
  
  /*
   * unless system_state == SYSTEM_BOOTING.
   *
   * __ref due to call of __init annotated helper build_all_zonelists_init
   * [protected by SYSTEM_BOOTING].
   */
  void __ref build_all_zonelists(pg_data_t *pgdat)
  {
  	unsigned long vm_total_pages;
  
  	if (system_state == SYSTEM_BOOTING) {
  		build_all_zonelists_init();
  	} else {
  		__build_all_zonelists(pgdat);
  		/* cpuset refresh routine should be here */
  	}
  	/* Get the number of free pages beyond high watermark in all zones. */
  	vm_total_pages = nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
  	/*
  	 * Disable grouping by mobility if the number of pages in the
  	 * system is too low to allow the mechanism to work. It would be
  	 * more accurate, but expensive to check per-zone. This check is
  	 * made on memory-hotadd so a system can start with mobility
  	 * disabled and enable it later
  	 */
  	if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES))
  		page_group_by_mobility_disabled = 1;
  	else
  		page_group_by_mobility_disabled = 0;
  
  	pr_info("Built %u zonelists, mobility grouping %s.  Total pages: %ld\n",
  		nr_online_nodes,
  		page_group_by_mobility_disabled ? "off" : "on",
  		vm_total_pages);
  #ifdef CONFIG_NUMA
  	pr_info("Policy zone: %s\n", zone_names[policy_zone]);
  #endif
  }
  
  /* If zone is ZONE_MOVABLE but memory is mirrored, it is an overlapped init */
  static bool __meminit
  overlap_memmap_init(unsigned long zone, unsigned long *pfn)
  {
  	static struct memblock_region *r;
  
  	if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
  		if (!r || *pfn >= memblock_region_memory_end_pfn(r)) {
  			for_each_mem_region(r) {
  				if (*pfn < memblock_region_memory_end_pfn(r))
  					break;
  			}
  		}
  		if (*pfn >= memblock_region_memory_base_pfn(r) &&
  		    memblock_is_mirror(r)) {
  			*pfn = memblock_region_memory_end_pfn(r);
  			return true;
  		}
  	}
  	return false;
  }
  
  /*
   * Initially all pages are reserved - free ones are freed
   * up by memblock_free_all() once the early boot process is
   * done. Non-atomic initialization, single-pass.
   *
   * All aligned pageblocks are initialized to the specified migratetype
   * (usually MIGRATE_MOVABLE). Besides setting the migratetype, no related
   * zone stats (e.g., nr_isolate_pageblock) are touched.
   */
  void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone,
  		unsigned long start_pfn, unsigned long zone_end_pfn,
  		enum meminit_context context,
  		struct vmem_altmap *altmap, int migratetype)
  {
  	unsigned long pfn, end_pfn = start_pfn + size;
  	struct page *page;
  
  	if (highest_memmap_pfn < end_pfn - 1)
  		highest_memmap_pfn = end_pfn - 1;
  
  #ifdef CONFIG_ZONE_DEVICE
  	/*
  	 * Honor reservation requested by the driver for this ZONE_DEVICE
  	 * memory. We limit the total number of pages to initialize to just
  	 * those that might contain the memory mapping. We will defer the
  	 * ZONE_DEVICE page initialization until after we have released
  	 * the hotplug lock.
  	 */
  	if (zone == ZONE_DEVICE) {
  		if (!altmap)
  			return;
  
  		if (start_pfn == altmap->base_pfn)
  			start_pfn += altmap->reserve;
  		end_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
  	}
  #endif
  
  	for (pfn = start_pfn; pfn < end_pfn; ) {
  		/*
  		 * There can be holes in boot-time mem_map[]s handed to this
  		 * function.  They do not exist on hotplugged memory.
  		 */
  		if (context == MEMINIT_EARLY) {
  			if (overlap_memmap_init(zone, &pfn))
  				continue;
  			if (defer_init(nid, pfn, zone_end_pfn))
  				break;
  		}
  
  		page = pfn_to_page(pfn);
  		__init_single_page(page, pfn, zone, nid);
  		if (context == MEMINIT_HOTPLUG)
  			__SetPageReserved(page);
  
  		/*
  		 * Usually, we want to mark the pageblock MIGRATE_MOVABLE,
  		 * such that unmovable allocations won't be scattered all
  		 * over the place during system boot.
  		 */
  		if (IS_ALIGNED(pfn, pageblock_nr_pages)) {
  			set_pageblock_migratetype(page, migratetype);
  			cond_resched();
  		}
  		pfn++;
  	}
  }
  
  #ifdef CONFIG_ZONE_DEVICE
  static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
  					  unsigned long zone_idx, int nid,
  					  struct dev_pagemap *pgmap)
  {
  
  	__init_single_page(page, pfn, zone_idx, nid);
  
  	/*
  	 * Mark page reserved as it will need to wait for onlining
  	 * phase for it to be fully associated with a zone.
  	 *
  	 * We can use the non-atomic __set_bit operation for setting
  	 * the flag as we are still initializing the pages.
  	 */
  	__SetPageReserved(page);
  
  	/*
  	 * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
  	 * and zone_device_data.  It is a bug if a ZONE_DEVICE page is
  	 * ever freed or placed on a driver-private list.
  	 */
  	page->pgmap = pgmap;
  	page->zone_device_data = NULL;
  
  	/*
  	 * Mark the block movable so that blocks are reserved for
  	 * movable at startup. This will force kernel allocations
  	 * to reserve their blocks rather than leaking throughout
  	 * the address space during boot when many long-lived
  	 * kernel allocations are made.
  	 *
  	 * Please note that MEMINIT_HOTPLUG path doesn't clear memmap
  	 * because this is done early in section_activate()
  	 */
  	if (IS_ALIGNED(pfn, pageblock_nr_pages)) {
  		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
  		cond_resched();
  	}
  }
  
  static void __ref memmap_init_compound(struct page *head,
  				       unsigned long head_pfn,
  				       unsigned long zone_idx, int nid,
  				       struct dev_pagemap *pgmap,
  				       unsigned long nr_pages)
  {
  	unsigned long pfn, end_pfn = head_pfn + nr_pages;
  	unsigned int order = pgmap->vmemmap_shift;
  
  	__SetPageHead(head);
  	for (pfn = head_pfn + 1; pfn < end_pfn; pfn++) {
  		struct page *page = pfn_to_page(pfn);
  
  		__init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
  		prep_compound_tail(head, pfn - head_pfn);
  		set_page_count(page, 0);
  
  		/*
  		 * The first tail page stores compound_mapcount_ptr() and
  		 * compound_order() and the second tail page stores
  		 * compound_pincount_ptr(). Call prep_compound_head() after
  		 * the first and second tail pages have been initialized to
  		 * not have the data overwritten.
  		 */
  		if (pfn == head_pfn + 2)
  			prep_compound_head(head, order);
  	}
  }
  
  void __ref memmap_init_zone_device(struct zone *zone,
  				   unsigned long start_pfn,
  				   unsigned long nr_pages,
  				   struct dev_pagemap *pgmap)
  {
  	unsigned long pfn, end_pfn = start_pfn + nr_pages;
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	struct vmem_altmap *altmap = pgmap_altmap(pgmap);
  	unsigned int pfns_per_compound = pgmap_vmemmap_nr(pgmap);
  	unsigned long zone_idx = zone_idx(zone);
  	unsigned long start = jiffies;
  	int nid = pgdat->node_id;
  
  	if (WARN_ON_ONCE(!pgmap || zone_idx(zone) != ZONE_DEVICE))
  		return;
  
  	/*
  	 * The call to memmap_init should have already taken care
  	 * of the pages reserved for the memmap, so we can just jump to
  	 * the end of that region and start processing the device pages.
  	 */
  	if (altmap) {
  		start_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
  		nr_pages = end_pfn - start_pfn;
  	}
  
  	for (pfn = start_pfn; pfn < end_pfn; pfn += pfns_per_compound) {
  		struct page *page = pfn_to_page(pfn);
  
  		__init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
  
  		if (pfns_per_compound == 1)
  			continue;
  
  		memmap_init_compound(page, pfn, zone_idx, nid, pgmap,
  				     pfns_per_compound);
  	}
  
  	pr_info("%s initialised %lu pages in %ums\n", __func__,
  		nr_pages, jiffies_to_msecs(jiffies - start));
  }
  
  #endif
  static void __meminit zone_init_free_lists(struct zone *zone)
  {
  	unsigned int order, t;
  	for_each_migratetype_order(order, t) {
  		INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
  		zone->free_area[order].nr_free = 0;
  	}
  }
  
  /*
   * Only struct pages that correspond to ranges defined by memblock.memory
   * are zeroed and initialized by going through __init_single_page() during
   * memmap_init_zone_range().
   *
   * But, there could be struct pages that correspond to holes in
   * memblock.memory. This can happen because of the following reasons:
   * - physical memory bank size is not necessarily the exact multiple of the
   *   arbitrary section size
   * - early reserved memory may not be listed in memblock.memory
   * - memory layouts defined with memmap= kernel parameter may not align
   *   nicely with memmap sections
   *
   * Explicitly initialize those struct pages so that:
   * - PG_Reserved is set
   * - zone and node links point to zone and node that span the page if the
   *   hole is in the middle of a zone
   * - zone and node links point to adjacent zone/node if the hole falls on
   *   the zone boundary; the pages in such holes will be prepended to the
   *   zone/node above the hole except for the trailing pages in the last
   *   section that will be appended to the zone/node below.
   */
  static void __init init_unavailable_range(unsigned long spfn,
  					  unsigned long epfn,
  					  int zone, int node)
  {
  	unsigned long pfn;
  	u64 pgcnt = 0;
  
  	for (pfn = spfn; pfn < epfn; pfn++) {
  		if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) {
  			pfn = ALIGN_DOWN(pfn, pageblock_nr_pages)
  				+ pageblock_nr_pages - 1;
  			continue;
  		}
  		__init_single_page(pfn_to_page(pfn), pfn, zone, node);
  		__SetPageReserved(pfn_to_page(pfn));
  		pgcnt++;
  	}
  
  	if (pgcnt)
  		pr_info("On node %d, zone %s: %lld pages in unavailable ranges",
  			node, zone_names[zone], pgcnt);
  }
  
  static void __init memmap_init_zone_range(struct zone *zone,
  					  unsigned long start_pfn,
  					  unsigned long end_pfn,
  					  unsigned long *hole_pfn)
  {
  	unsigned long zone_start_pfn = zone->zone_start_pfn;
  	unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages;
  	int nid = zone_to_nid(zone), zone_id = zone_idx(zone);
  
  	start_pfn = clamp(start_pfn, zone_start_pfn, zone_end_pfn);
  	end_pfn = clamp(end_pfn, zone_start_pfn, zone_end_pfn);
  
  	if (start_pfn >= end_pfn)
  		return;
  
  	memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn,
  			  zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE);
  
  	if (*hole_pfn < start_pfn)
  		init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid);
  
  	*hole_pfn = end_pfn;
  }
  
  static void __init memmap_init(void)
  {
  	unsigned long start_pfn, end_pfn;
  	unsigned long hole_pfn = 0;
  	int i, j, zone_id = 0, nid;
  
  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
  		struct pglist_data *node = NODE_DATA(nid);
  
  		for (j = 0; j < MAX_NR_ZONES; j++) {
  			struct zone *zone = node->node_zones + j;
  
  			if (!populated_zone(zone))
  				continue;
  
  			memmap_init_zone_range(zone, start_pfn, end_pfn,
  					       &hole_pfn);
  			zone_id = j;
  		}
  	}
  
  #ifdef CONFIG_SPARSEMEM
  	/*
  	 * Initialize the memory map for hole in the range [memory_end,
  	 * section_end].
  	 * Append the pages in this hole to the highest zone in the last
  	 * node.
  	 * The call to init_unavailable_range() is outside the ifdef to
  	 * silence the compiler warining about zone_id set but not used;
  	 * for FLATMEM it is a nop anyway
  	 */
  	end_pfn = round_up(end_pfn, PAGES_PER_SECTION);
  	if (hole_pfn < end_pfn)
  #endif
  		init_unavailable_range(hole_pfn, end_pfn, zone_id, nid);
  }
  
  void __init *memmap_alloc(phys_addr_t size, phys_addr_t align,
  			  phys_addr_t min_addr, int nid, bool exact_nid)
  {
  	void *ptr;
  
  	if (exact_nid)
  		ptr = memblock_alloc_exact_nid_raw(size, align, min_addr,
  						   MEMBLOCK_ALLOC_ACCESSIBLE,
  						   nid);
  	else
  		ptr = memblock_alloc_try_nid_raw(size, align, min_addr,
  						 MEMBLOCK_ALLOC_ACCESSIBLE,
  						 nid);
  
  	if (ptr && size > 0)
  		page_init_poison(ptr, size);
  
  	return ptr;
  }
  
  static int zone_batchsize(struct zone *zone)
  {
  #ifdef CONFIG_MMU
  	int batch;
  
  	/*
  	 * The number of pages to batch allocate is either ~0.1%
  	 * of the zone or 1MB, whichever is smaller. The batch
  	 * size is striking a balance between allocation latency
  	 * and zone lock contention.
  	 */
  	batch = min(zone_managed_pages(zone) >> 10, (1024 * 1024) / PAGE_SIZE);
  	batch /= 4;		/* We effectively *= 4 below */
  	if (batch < 1)
  		batch = 1;
  
  	/*
  	 * Clamp the batch to a 2^n - 1 value. Having a power
  	 * of 2 value was found to be more likely to have
  	 * suboptimal cache aliasing properties in some cases.
  	 *
  	 * For example if 2 tasks are alternately allocating
  	 * batches of pages, one task can end up with a lot
  	 * of pages of one half of the possible page colors
  	 * and the other with pages of the other colors.
  	 */
  	batch = rounddown_pow_of_two(batch + batch/2) - 1;
  
  	return batch;
  
  #else
  	/* The deferral and batching of frees should be suppressed under NOMMU
  	 * conditions.
  	 *
  	 * The problem is that NOMMU needs to be able to allocate large chunks
  	 * of contiguous memory as there's no hardware page translation to
  	 * assemble apparent contiguous memory from discontiguous pages.
  	 *
  	 * Queueing large contiguous runs of pages for batching, however,
  	 * causes the pages to actually be freed in smaller chunks.  As there
  	 * can be a significant delay between the individual batches being
  	 * recycled, this leads to the once large chunks of space being
  	 * fragmented and becoming unavailable for high-order allocations.
  	 */
  	return 0;
  #endif
  }
  
  static int zone_highsize(struct zone *zone, int batch, int cpu_online)
  {
  #ifdef CONFIG_MMU
  	int high;
  	int nr_split_cpus;
  	unsigned long total_pages;
  
  	if (!percpu_pagelist_high_fraction) {
  		/*
  		 * By default, the high value of the pcp is based on the zone
  		 * low watermark so that if they are full then background
  		 * reclaim will not be started prematurely.
  		 */
  		total_pages = low_wmark_pages(zone);
  	} else {
  		/*
  		 * If percpu_pagelist_high_fraction is configured, the high
  		 * value is based on a fraction of the managed pages in the
  		 * zone.
  		 */
  		total_pages = zone_managed_pages(zone) / percpu_pagelist_high_fraction;
  	}
  
  	/*
  	 * Split the high value across all online CPUs local to the zone. Note
  	 * that early in boot that CPUs may not be online yet and that during
  	 * CPU hotplug that the cpumask is not yet updated when a CPU is being
  	 * onlined. For memory nodes that have no CPUs, split pcp->high across
  	 * all online CPUs to mitigate the risk that reclaim is triggered
  	 * prematurely due to pages stored on pcp lists.
  	 */
  	nr_split_cpus = cpumask_weight(cpumask_of_node(zone_to_nid(zone))) + cpu_online;
  	if (!nr_split_cpus)
  		nr_split_cpus = num_online_cpus();
  	high = total_pages / nr_split_cpus;
  
  	/*
  	 * Ensure high is at least batch*4. The multiple is based on the
  	 * historical relationship between high and batch.
  	 */
  	high = max(high, batch << 2);
  
  	return high;
  #else
  	return 0;
  #endif
  }
  
  /*
   * pcp->high and pcp->batch values are related and generally batch is lower
   * than high. They are also related to pcp->count such that count is lower
   * than high, and as soon as it reaches high, the pcplist is flushed.
   *
   * However, guaranteeing these relations at all times would require e.g. write
   * barriers here but also careful usage of read barriers at the read side, and
   * thus be prone to error and bad for performance. Thus the update only prevents
   * store tearing. Any new users of pcp->batch and pcp->high should ensure they
   * can cope with those fields changing asynchronously, and fully trust only the
   * pcp->count field on the local CPU with interrupts disabled.
   *
   * mutex_is_locked(&pcp_batch_high_lock) required when calling this function
   * outside of boot time (or some other assurance that no concurrent updaters
   * exist).
   */
  static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
  		unsigned long batch)
  {
  	WRITE_ONCE(pcp->batch, batch);
  	WRITE_ONCE(pcp->high, high);
  }
  
  static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats)
  {
  	int pindex;
  
  	memset(pcp, 0, sizeof(*pcp));
  	memset(pzstats, 0, sizeof(*pzstats));
  
  	for (pindex = 0; pindex < NR_PCP_LISTS; pindex++)
  		INIT_LIST_HEAD(&pcp->lists[pindex]);
  
  	/*
  	 * Set batch and high values safe for a boot pageset. A true percpu
  	 * pageset's initialization will update them subsequently. Here we don't
  	 * need to be as careful as pageset_update() as nobody can access the
  	 * pageset yet.
  	 */
  	pcp->high = BOOT_PAGESET_HIGH;
  	pcp->batch = BOOT_PAGESET_BATCH;
  	pcp->free_factor = 0;
  }
  
  static void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high,
  		unsigned long batch)
  {
  	struct per_cpu_pages *pcp;
  	int cpu;
  
  	for_each_possible_cpu(cpu) {
  		pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
  		pageset_update(pcp, high, batch);
  	}
  }
  
  /*
   * Calculate and set new high and batch values for all per-cpu pagesets of a
   * zone based on the zone's size.
   */
  static void zone_set_pageset_high_and_batch(struct zone *zone, int cpu_online)
  {
  	int new_high, new_batch;
  
  	new_batch = max(1, zone_batchsize(zone));
  	new_high = zone_highsize(zone, new_batch, cpu_online);
  
  	if (zone->pageset_high == new_high &&
  	    zone->pageset_batch == new_batch)
  		return;
  
  	zone->pageset_high = new_high;
  	zone->pageset_batch = new_batch;
  
  	__zone_set_pageset_high_and_batch(zone, new_high, new_batch);
  }
  
  void __meminit setup_zone_pageset(struct zone *zone)
  {
  	int cpu;
  
  	/* Size may be 0 on !SMP && !NUMA */
  	if (sizeof(struct per_cpu_zonestat) > 0)
  		zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
  
  	zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
  	for_each_possible_cpu(cpu) {
  		struct per_cpu_pages *pcp;
  		struct per_cpu_zonestat *pzstats;
  
  		pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
  		pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
  		per_cpu_pages_init(pcp, pzstats);
  	}
  
  	zone_set_pageset_high_and_batch(zone, 0);
  }
  
  /*
   * Allocate per cpu pagesets and initialize them.
   * Before this call only boot pagesets were available.
   */
  void __init setup_per_cpu_pageset(void)
  {
  	struct pglist_data *pgdat;
  	struct zone *zone;
  	int __maybe_unused cpu;
  
  	for_each_populated_zone(zone)
  		setup_zone_pageset(zone);
  
  #ifdef CONFIG_NUMA
  	/*
  	 * Unpopulated zones continue using the boot pagesets.
  	 * The numa stats for these pagesets need to be reset.
  	 * Otherwise, they will end up skewing the stats of
  	 * the nodes these zones are associated with.
  	 */
  	for_each_possible_cpu(cpu) {
  		struct per_cpu_zonestat *pzstats = &per_cpu(boot_zonestats, cpu);
  		memset(pzstats->vm_numa_event, 0,
  		       sizeof(pzstats->vm_numa_event));
  	}
  #endif
  
  	for_each_online_pgdat(pgdat)
  		pgdat->per_cpu_nodestats =
  			alloc_percpu(struct per_cpu_nodestat);
  }
  
  static __meminit void zone_pcp_init(struct zone *zone)
  {
  	/*
  	 * per cpu subsystem is not up at this point. The following code
  	 * relies on the ability of the linker to provide the
  	 * offset of a (static) per cpu variable into the per cpu area.
  	 */
  	zone->per_cpu_pageset = &boot_pageset;
  	zone->per_cpu_zonestats = &boot_zonestats;
  	zone->pageset_high = BOOT_PAGESET_HIGH;
  	zone->pageset_batch = BOOT_PAGESET_BATCH;
  
  	if (populated_zone(zone))
  		pr_debug("  %s zone: %lu pages, LIFO batch:%u\n", zone->name,
  			 zone->present_pages, zone_batchsize(zone));
  }
  
  void __meminit init_currently_empty_zone(struct zone *zone,
  					unsigned long zone_start_pfn,
  					unsigned long size)
  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	int zone_idx = zone_idx(zone) + 1;
  
  	if (zone_idx > pgdat->nr_zones)
  		pgdat->nr_zones = zone_idx;
  
  	zone->zone_start_pfn = zone_start_pfn;
  
  	mminit_dprintk(MMINIT_TRACE, "memmap_init",
  			"Initialising map node %d zone %lu pfns %lu -> %lu\n",
  			pgdat->node_id,
  			(unsigned long)zone_idx(zone),
  			zone_start_pfn, (zone_start_pfn + size));
  
  	zone_init_free_lists(zone);
  	zone->initialized = 1;
  }
  
  /**
   * get_pfn_range_for_nid - Return the start and end page frames for a node
   * @nid: The nid to return the range for. If MAX_NUMNODES, the min and max PFN are returned.
   * @start_pfn: Passed by reference. On return, it will have the node start_pfn.
   * @end_pfn: Passed by reference. On return, it will have the node end_pfn.
   *
   * It returns the start and end page frame of a node based on information
   * provided by memblock_set_node(). If called for a node
   * with no available memory, a warning is printed and the start and end
   * PFNs will be 0.
   */
  void __init get_pfn_range_for_nid(unsigned int nid,
  			unsigned long *start_pfn, unsigned long *end_pfn)
  {
  	unsigned long this_start_pfn, this_end_pfn;
  	int i;
  
  	*start_pfn = -1UL;
  	*end_pfn = 0;
  
  	for_each_mem_pfn_range(i, nid, &this_start_pfn, &this_end_pfn, NULL) {
  		*start_pfn = min(*start_pfn, this_start_pfn);
  		*end_pfn = max(*end_pfn, this_end_pfn);
  	}
  
  	if (*start_pfn == -1UL)
  		*start_pfn = 0;
  }
  
  /*
   * This finds a zone that can be used for ZONE_MOVABLE pages. The
   * assumption is made that zones within a node are ordered in monotonic
   * increasing memory addresses so that the "highest" populated zone is used
   */
  static void __init find_usable_zone_for_movable(void)
  {
  	int zone_index;
  	for (zone_index = MAX_NR_ZONES - 1; zone_index >= 0; zone_index--) {
  		if (zone_index == ZONE_MOVABLE)
  			continue;
  
  		if (arch_zone_highest_possible_pfn[zone_index] >
  				arch_zone_lowest_possible_pfn[zone_index])
  			break;
  	}
  
  	VM_BUG_ON(zone_index == -1);
  	movable_zone = zone_index;
  }
  
  /*
   * The zone ranges provided by the architecture do not include ZONE_MOVABLE
   * because it is sized independent of architecture. Unlike the other zones,
   * the starting point for ZONE_MOVABLE is not fixed. It may be different
   * in each node depending on the size of each node and how evenly kernelcore
   * is distributed. This helper function adjusts the zone ranges
   * provided by the architecture for a given node by using the end of the
   * highest usable zone for ZONE_MOVABLE. This preserves the assumption that
   * zones within a node are in order of monotonic increases memory addresses
   */
  static void __init adjust_zone_range_for_zone_movable(int nid,
  					unsigned long zone_type,
  					unsigned long node_start_pfn,
  					unsigned long node_end_pfn,
  					unsigned long *zone_start_pfn,
  					unsigned long *zone_end_pfn)
  {
  	/* Only adjust if ZONE_MOVABLE is on this node */
  	if (zone_movable_pfn[nid]) {
  		/* Size ZONE_MOVABLE */
  		if (zone_type == ZONE_MOVABLE) {
  			*zone_start_pfn = zone_movable_pfn[nid];
  			*zone_end_pfn = min(node_end_pfn,
  				arch_zone_highest_possible_pfn[movable_zone]);
  
  		/* Adjust for ZONE_MOVABLE starting within this range */
  		} else if (!mirrored_kernelcore &&
  			*zone_start_pfn < zone_movable_pfn[nid] &&
  			*zone_end_pfn > zone_movable_pfn[nid]) {
  			*zone_end_pfn = zone_movable_pfn[nid];
  
  		/* Check if this whole range is within ZONE_MOVABLE */
  		} else if (*zone_start_pfn >= zone_movable_pfn[nid])
  			*zone_start_pfn = *zone_end_pfn;
  	}
  }
  
  /*
   * Return the number of pages a zone spans in a node, including holes
   * present_pages = zone_spanned_pages_in_node() - zone_absent_pages_in_node()
   */
  static unsigned long __init zone_spanned_pages_in_node(int nid,
  					unsigned long zone_type,
  					unsigned long node_start_pfn,
  					unsigned long node_end_pfn,
  					unsigned long *zone_start_pfn,
  					unsigned long *zone_end_pfn)
  {
  	unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
  	unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
  	/* When hotadd a new node from cpu_up(), the node should be empty */
  	if (!node_start_pfn && !node_end_pfn)
  		return 0;
  
  	/* Get the start and end of the zone */
  	*zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
  	*zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
  	adjust_zone_range_for_zone_movable(nid, zone_type,
  				node_start_pfn, node_end_pfn,
  				zone_start_pfn, zone_end_pfn);
  
  	/* Check that this node has pages within the zone's required range */
  	if (*zone_end_pfn < node_start_pfn || *zone_start_pfn > node_end_pfn)
  		return 0;
  
  	/* Move the zone boundaries inside the node if necessary */
  	*zone_end_pfn = min(*zone_end_pfn, node_end_pfn);
  	*zone_start_pfn = max(*zone_start_pfn, node_start_pfn);
  
  	/* Return the spanned pages */
  	return *zone_end_pfn - *zone_start_pfn;
  }
  
  /*
   * Return the number of holes in a range on a node. If nid is MAX_NUMNODES,
   * then all holes in the requested range will be accounted for.
   */
  unsigned long __init __absent_pages_in_range(int nid,
  				unsigned long range_start_pfn,
  				unsigned long range_end_pfn)
  {
  	unsigned long nr_absent = range_end_pfn - range_start_pfn;
  	unsigned long start_pfn, end_pfn;
  	int i;
  
  	for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
  		start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
  		end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
  		nr_absent -= end_pfn - start_pfn;
  	}
  	return nr_absent;
  }
  
  /**
   * absent_pages_in_range - Return number of page frames in holes within a range
   * @start_pfn: The start PFN to start searching for holes
   * @end_pfn: The end PFN to stop searching for holes
   *
   * Return: the number of pages frames in memory holes within a range.
   */
  unsigned long __init absent_pages_in_range(unsigned long start_pfn,
  							unsigned long end_pfn)
  {
  	return __absent_pages_in_range(MAX_NUMNODES, start_pfn, end_pfn);
  }
  
  /* Return the number of page frames in holes in a zone on a node */
  static unsigned long __init zone_absent_pages_in_node(int nid,
  					unsigned long zone_type,
  					unsigned long node_start_pfn,
  					unsigned long node_end_pfn)
  {
  	unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
  	unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
  	unsigned long zone_start_pfn, zone_end_pfn;
  	unsigned long nr_absent;
  
  	/* When hotadd a new node from cpu_up(), the node should be empty */
  	if (!node_start_pfn && !node_end_pfn)
  		return 0;
  
  	zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
  	zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
  
  	adjust_zone_range_for_zone_movable(nid, zone_type,
  			node_start_pfn, node_end_pfn,
  			&zone_start_pfn, &zone_end_pfn);
  	nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
  
  	/*
  	 * ZONE_MOVABLE handling.
  	 * Treat pages to be ZONE_MOVABLE in ZONE_NORMAL as absent pages
  	 * and vice versa.
  	 */
  	if (mirrored_kernelcore && zone_movable_pfn[nid]) {
  		unsigned long start_pfn, end_pfn;
  		struct memblock_region *r;
  
  		for_each_mem_region(r) {
  			start_pfn = clamp(memblock_region_memory_base_pfn(r),
  					  zone_start_pfn, zone_end_pfn);
  			end_pfn = clamp(memblock_region_memory_end_pfn(r),
  					zone_start_pfn, zone_end_pfn);
  
  			if (zone_type == ZONE_MOVABLE &&
  			    memblock_is_mirror(r))
  				nr_absent += end_pfn - start_pfn;
  
  			if (zone_type == ZONE_NORMAL &&
  			    !memblock_is_mirror(r))
  				nr_absent += end_pfn - start_pfn;
  		}
  	}
  
  	return nr_absent;
  }
  
  static void __init calculate_node_totalpages(struct pglist_data *pgdat,
  						unsigned long node_start_pfn,
  						unsigned long node_end_pfn)
  {
  	unsigned long realtotalpages = 0, totalpages = 0;
  	enum zone_type i;
  
  	for (i = 0; i < MAX_NR_ZONES; i++) {
  		struct zone *zone = pgdat->node_zones + i;
  		unsigned long zone_start_pfn, zone_end_pfn;
  		unsigned long spanned, absent;
  		unsigned long size, real_size;
  
  		spanned = zone_spanned_pages_in_node(pgdat->node_id, i,
  						     node_start_pfn,
  						     node_end_pfn,
  						     &zone_start_pfn,
  						     &zone_end_pfn);
  		absent = zone_absent_pages_in_node(pgdat->node_id, i,
  						   node_start_pfn,
  						   node_end_pfn);
  
  		size = spanned;
  		real_size = size - absent;
  
  		if (size)
  			zone->zone_start_pfn = zone_start_pfn;
  		else
  			zone->zone_start_pfn = 0;
  		zone->spanned_pages = size;
  		zone->present_pages = real_size;
  #if defined(CONFIG_MEMORY_HOTPLUG)
  		zone->present_early_pages = real_size;
  #endif
  
  		totalpages += size;
  		realtotalpages += real_size;
  	}
  
  	pgdat->node_spanned_pages = totalpages;
  	pgdat->node_present_pages = realtotalpages;
  	pr_debug("On node %d totalpages: %lu\n", pgdat->node_id, realtotalpages);
  }
  
  #ifndef CONFIG_SPARSEMEM
  /*
   * Calculate the size of the zone->blockflags rounded to an unsigned long
   * Start by making sure zonesize is a multiple of pageblock_order by rounding
   * up. Then use 1 NR_PAGEBLOCK_BITS worth of bits per pageblock, finally
   * round what is now in bits to nearest long in bits, then return it in
   * bytes.
   */
  static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned long zonesize)
  {
  	unsigned long usemapsize;
  
  	zonesize += zone_start_pfn & (pageblock_nr_pages-1);
  	usemapsize = roundup(zonesize, pageblock_nr_pages);
  	usemapsize = usemapsize >> pageblock_order;
  	usemapsize *= NR_PAGEBLOCK_BITS;
  	usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long));
  
  	return usemapsize / 8;
  }
  
  static void __ref setup_usemap(struct zone *zone)
  {
  	unsigned long usemapsize = usemap_size(zone->zone_start_pfn,
  					       zone->spanned_pages);
  	zone->pageblock_flags = NULL;
  	if (usemapsize) {
  		zone->pageblock_flags =
  			memblock_alloc_node(usemapsize, SMP_CACHE_BYTES,
  					    zone_to_nid(zone));
  		if (!zone->pageblock_flags)
  			panic("Failed to allocate %ld bytes for zone %s pageblock flags on node %d\n",
  			      usemapsize, zone->name, zone_to_nid(zone));
  	}
  }
  #else
  static inline void setup_usemap(struct zone *zone) {}
  #endif /* CONFIG_SPARSEMEM */
  
  #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
  
  /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
  void __init set_pageblock_order(void)
  {
  	unsigned int order;
  
  	/* Check that pageblock_nr_pages has not already been setup */
  	if (pageblock_order)
  		return;
  
  	if (HPAGE_SHIFT > PAGE_SHIFT)
  		order = HUGETLB_PAGE_ORDER;
  	else
  		order = MAX_ORDER - 1;
  
  	/*
  	 * Assume the largest contiguous order of interest is a huge page.
  	 * This value may be variable depending on boot parameters on IA64 and
  	 * powerpc.
  	 */
  	pageblock_order = order;
  }
  #else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
  
  /*
   * When CONFIG_HUGETLB_PAGE_SIZE_VARIABLE is not set, set_pageblock_order()
   * is unused as pageblock_order is set at compile-time. See
   * include/linux/pageblock-flags.h for the values of pageblock_order based on
   * the kernel config
   */
  void __init set_pageblock_order(void)
  {
  }
  
  #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
  
  static unsigned long __init calc_memmap_size(unsigned long spanned_pages,
  						unsigned long present_pages)
  {
  	unsigned long pages = spanned_pages;
  
  	/*
  	 * Provide a more accurate estimation if there are holes within
  	 * the zone and SPARSEMEM is in use. If there are holes within the
  	 * zone, each populated memory region may cost us one or two extra
  	 * memmap pages due to alignment because memmap pages for each
  	 * populated regions may not be naturally aligned on page boundary.
  	 * So the (present_pages >> 4) heuristic is a tradeoff for that.
  	 */
  	if (spanned_pages > present_pages + (present_pages >> 4) &&
  	    IS_ENABLED(CONFIG_SPARSEMEM))
  		pages = present_pages;
  
  	return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static void pgdat_init_split_queue(struct pglist_data *pgdat)
  {
  	struct deferred_split *ds_queue = &pgdat->deferred_split_queue;
  
  	spin_lock_init(&ds_queue->split_queue_lock);
  	INIT_LIST_HEAD(&ds_queue->split_queue);
  	ds_queue->split_queue_len = 0;
  }
  #else
  static void pgdat_init_split_queue(struct pglist_data *pgdat) {}
  #endif
  
  #ifdef CONFIG_COMPACTION
  static void pgdat_init_kcompactd(struct pglist_data *pgdat)
  {
  	init_waitqueue_head(&pgdat->kcompactd_wait);
  }
  #else
  static void pgdat_init_kcompactd(struct pglist_data *pgdat) {}
  #endif
  
  static void __meminit pgdat_init_internals(struct pglist_data *pgdat)
  {
  	int i;
  
  	pgdat_resize_init(pgdat);
  
  	pgdat_init_split_queue(pgdat);
  	pgdat_init_kcompactd(pgdat);
  
  	init_waitqueue_head(&pgdat->kswapd_wait);
  	init_waitqueue_head(&pgdat->pfmemalloc_wait);
  
  	for (i = 0; i < NR_VMSCAN_THROTTLE; i++)
  		init_waitqueue_head(&pgdat->reclaim_wait[i]);
  
  	pgdat_page_ext_init(pgdat);
  	lruvec_init(&pgdat->__lruvec);
  }
  
  static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx, int nid,
  							unsigned long remaining_pages)
  {
  	atomic_long_set(&zone->managed_pages, remaining_pages);
  	zone_set_nid(zone, nid);
  	zone->name = zone_names[idx];
  	zone->zone_pgdat = NODE_DATA(nid);
  	spin_lock_init(&zone->lock);
  	zone_seqlock_init(zone);
  	zone_pcp_init(zone);
  }
  
  /*
   * Set up the zone data structures
   * - init pgdat internals
   * - init all zones belonging to this node
   *
   * NOTE: this function is only called during memory hotplug
   */
  #ifdef CONFIG_MEMORY_HOTPLUG
  void __ref free_area_init_core_hotplug(int nid)
  {
  	enum zone_type z;
  	pg_data_t *pgdat = NODE_DATA(nid);
  
  	pgdat_init_internals(pgdat);
  	for (z = 0; z < MAX_NR_ZONES; z++)
  		zone_init_internals(&pgdat->node_zones[z], z, nid, 0);
  }
  #endif
  
  /*
   * Set up the zone data structures:
   *   - mark all pages reserved
   *   - mark all memory queues empty
   *   - clear the memory bitmaps
   *
   * NOTE: pgdat should get zeroed by caller.
   * NOTE: this function is only called during early init.
   */
  static void __init free_area_init_core(struct pglist_data *pgdat)
  {
  	enum zone_type j;
  	int nid = pgdat->node_id;
  
  	pgdat_init_internals(pgdat);
  	pgdat->per_cpu_nodestats = &boot_nodestats;
  
  	for (j = 0; j < MAX_NR_ZONES; j++) {
  		struct zone *zone = pgdat->node_zones + j;
  		unsigned long size, freesize, memmap_pages;
  
  		size = zone->spanned_pages;
  		freesize = zone->present_pages;
  
  		/*
  		 * Adjust freesize so that it accounts for how much memory
  		 * is used by this zone for memmap. This affects the watermark
  		 * and per-cpu initialisations
  		 */
  		memmap_pages = calc_memmap_size(size, freesize);
  		if (!is_highmem_idx(j)) {
  			if (freesize >= memmap_pages) {
  				freesize -= memmap_pages;
  				if (memmap_pages)
  					pr_debug("  %s zone: %lu pages used for memmap\n",
  						 zone_names[j], memmap_pages);
  			} else
  				pr_warn("  %s zone: %lu memmap pages exceeds freesize %lu\n",
  					zone_names[j], memmap_pages, freesize);
  		}
  
  		/* Account for reserved pages */
  		if (j == 0 && freesize > dma_reserve) {
  			freesize -= dma_reserve;
  			pr_debug("  %s zone: %lu pages reserved\n", zone_names[0], dma_reserve);
  		}
  
  		if (!is_highmem_idx(j))
  			nr_kernel_pages += freesize;
  		/* Charge for highmem memmap if there are enough kernel pages */
  		else if (nr_kernel_pages > memmap_pages * 2)
  			nr_kernel_pages -= memmap_pages;
  		nr_all_pages += freesize;
  
  		/*
  		 * Set an approximate value for lowmem here, it will be adjusted
  		 * when the bootmem allocator frees pages into the buddy system.
  		 * And all highmem pages will be managed by the buddy system.
  		 */
  		zone_init_internals(zone, j, nid, freesize);
  
  		if (!size)
  			continue;
  
  		set_pageblock_order();
  		setup_usemap(zone);
  		init_currently_empty_zone(zone, zone->zone_start_pfn, size);
  	}
  }
  
  #ifdef CONFIG_FLATMEM
  static void __init alloc_node_mem_map(struct pglist_data *pgdat)
  {
  	unsigned long __maybe_unused start = 0;
  	unsigned long __maybe_unused offset = 0;
  
  	/* Skip empty nodes */
  	if (!pgdat->node_spanned_pages)
  		return;
  
  	start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
  	offset = pgdat->node_start_pfn - start;
  	/* ia64 gets its own node_mem_map, before this, without bootmem */
  	if (!pgdat->node_mem_map) {
  		unsigned long size, end;
  		struct page *map;
  
  		/*
  		 * The zone's endpoints aren't required to be MAX_ORDER
  		 * aligned but the node_mem_map endpoints must be in order
  		 * for the buddy allocator to function correctly.
  		 */
  		end = pgdat_end_pfn(pgdat);
  		end = ALIGN(end, MAX_ORDER_NR_PAGES);
  		size =  (end - start) * sizeof(struct page);
  		map = memmap_alloc(size, SMP_CACHE_BYTES, MEMBLOCK_LOW_LIMIT,
  				   pgdat->node_id, false);
  		if (!map)
  			panic("Failed to allocate %ld bytes for node %d memory map\n",
  			      size, pgdat->node_id);
  		pgdat->node_mem_map = map + offset;
  	}
  	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
  				__func__, pgdat->node_id, (unsigned long)pgdat,
  				(unsigned long)pgdat->node_mem_map);
  #ifndef CONFIG_NUMA
  	/*
  	 * With no DISCONTIG, the global mem_map is just set as node 0's
  	 */
  	if (pgdat == NODE_DATA(0)) {
  		mem_map = NODE_DATA(0)->node_mem_map;
  		if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
  			mem_map -= offset;
  	}
  #endif
  }
  #else
  static inline void alloc_node_mem_map(struct pglist_data *pgdat) { }
  #endif /* CONFIG_FLATMEM */
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  static inline void pgdat_set_deferred_range(pg_data_t *pgdat)
  {
  	pgdat->first_deferred_pfn = ULONG_MAX;
  }
  #else
  static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
  #endif
  
  static void __init free_area_init_node(int nid)
  {
  	pg_data_t *pgdat = NODE_DATA(nid);
  	unsigned long start_pfn = 0;
  	unsigned long end_pfn = 0;
  
  	/* pg_data_t should be reset to zero when it's allocated */
  	WARN_ON(pgdat->nr_zones || pgdat->kswapd_highest_zoneidx);
  
  	get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
  
  	pgdat->node_id = nid;
  	pgdat->node_start_pfn = start_pfn;
  	pgdat->per_cpu_nodestats = NULL;
  
  	pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
  		(u64)start_pfn << PAGE_SHIFT,
  		end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
  	calculate_node_totalpages(pgdat, start_pfn, end_pfn);
  
  	alloc_node_mem_map(pgdat);
  	pgdat_set_deferred_range(pgdat);
  
  	free_area_init_core(pgdat);
  }
  
  void __init free_area_init_memoryless_node(int nid)
  {
  	free_area_init_node(nid);
  }
  
  #if MAX_NUMNODES > 1
  /*
   * Figure out the number of possible node ids.
   */
  void __init setup_nr_node_ids(void)
  {
  	unsigned int highest;
  
  	highest = find_last_bit(node_possible_map.bits, MAX_NUMNODES);
  	nr_node_ids = highest + 1;
  }
  #endif
  
  /**
   * node_map_pfn_alignment - determine the maximum internode alignment
   *
   * This function should be called after node map is populated and sorted.
   * It calculates the maximum power of two alignment which can distinguish
   * all the nodes.
   *
   * For example, if all nodes are 1GiB and aligned to 1GiB, the return value
   * would indicate 1GiB alignment with (1 << (30 - PAGE_SHIFT)).  If the
   * nodes are shifted by 256MiB, 256MiB.  Note that if only the last node is
   * shifted, 1GiB is enough and this function will indicate so.
   *
   * This is used to test whether pfn -> nid mapping of the chosen memory
   * model has fine enough granularity to avoid incorrect mapping for the
   * populated node map.
   *
   * Return: the determined alignment in pfn's.  0 if there is no alignment
   * requirement (single node).
   */
  unsigned long __init node_map_pfn_alignment(void)
  {
  	unsigned long accl_mask = 0, last_end = 0;
  	unsigned long start, end, mask;
  	int last_nid = NUMA_NO_NODE;
  	int i, nid;
  
  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid) {
  		if (!start || last_nid < 0 || last_nid == nid) {
  			last_nid = nid;
  			last_end = end;
  			continue;
  		}
  
  		/*
  		 * Start with a mask granular enough to pin-point to the
  		 * start pfn and tick off bits one-by-one until it becomes
  		 * too coarse to separate the current node from the last.
  		 */
  		mask = ~((1 << __ffs(start)) - 1);
  		while (mask && last_end <= (start & (mask << 1)))
  			mask <<= 1;
  
  		/* accumulate all internode masks */
  		accl_mask |= mask;
  	}
  
  	/* convert mask to number of pages */
  	return ~accl_mask + 1;
  }
  
  /**
   * find_min_pfn_with_active_regions - Find the minimum PFN registered
   *
   * Return: the minimum PFN based on information provided via
   * memblock_set_node().
   */
  unsigned long __init find_min_pfn_with_active_regions(void)
  {
  	return PHYS_PFN(memblock_start_of_DRAM());
  }
  
  /*
   * early_calculate_totalpages()
   * Sum pages in active regions for movable zone.
   * Populate N_MEMORY for calculating usable_nodes.
   */
  static unsigned long __init early_calculate_totalpages(void)
  {
  	unsigned long totalpages = 0;
  	unsigned long start_pfn, end_pfn;
  	int i, nid;
  
  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
  		unsigned long pages = end_pfn - start_pfn;
  
  		totalpages += pages;
  		if (pages)
  			node_set_state(nid, N_MEMORY);
  	}
  	return totalpages;
  }
  
  /*
   * Find the PFN the Movable zone begins in each node. Kernel memory
   * is spread evenly between nodes as long as the nodes have enough
   * memory. When they don't, some nodes will have more kernelcore than
   * others
   */
  static void __init find_zone_movable_pfns_for_nodes(void)
  {
  	int i, nid;
  	unsigned long usable_startpfn;
  	unsigned long kernelcore_node, kernelcore_remaining;
  	/* save the state before borrow the nodemask */
  	nodemask_t saved_node_state = node_states[N_MEMORY];
  	unsigned long totalpages = early_calculate_totalpages();
  	int usable_nodes = nodes_weight(node_states[N_MEMORY]);
  	struct memblock_region *r;
  
  	/* Need to find movable_zone earlier when movable_node is specified. */
  	find_usable_zone_for_movable();
  
  	/*
  	 * If movable_node is specified, ignore kernelcore and movablecore
  	 * options.
  	 */
  	if (movable_node_is_enabled()) {
  		for_each_mem_region(r) {
  			if (!memblock_is_hotpluggable(r))
  				continue;
  
  			nid = memblock_get_region_node(r);
  
  			usable_startpfn = PFN_DOWN(r->base);
  			zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
  				min(usable_startpfn, zone_movable_pfn[nid]) :
  				usable_startpfn;
  		}
  
  		goto out2;
  	}
  
  	/*
  	 * If kernelcore=mirror is specified, ignore movablecore option
  	 */
  	if (mirrored_kernelcore) {
  		bool mem_below_4gb_not_mirrored = false;
  
  		for_each_mem_region(r) {
  			if (memblock_is_mirror(r))
  				continue;
  
  			nid = memblock_get_region_node(r);
  
  			usable_startpfn = memblock_region_memory_base_pfn(r);
  
  			if (usable_startpfn < 0x100000) {
  				mem_below_4gb_not_mirrored = true;
  				continue;
  			}
  
  			zone_movable_pfn[nid] = zone_movable_pfn[nid] ?
  				min(usable_startpfn, zone_movable_pfn[nid]) :
  				usable_startpfn;
  		}
  
  		if (mem_below_4gb_not_mirrored)
  			pr_warn("This configuration results in unmirrored kernel memory.\n");
  
  		goto out2;
  	}
  
  	/*
  	 * If kernelcore=nn% or movablecore=nn% was specified, calculate the
  	 * amount of necessary memory.
  	 */
  	if (required_kernelcore_percent)
  		required_kernelcore = (totalpages * 100 * required_kernelcore_percent) /
  				       10000UL;
  	if (required_movablecore_percent)
  		required_movablecore = (totalpages * 100 * required_movablecore_percent) /
  					10000UL;
  
  	/*
  	 * If movablecore= was specified, calculate what size of
  	 * kernelcore that corresponds so that memory usable for
  	 * any allocation type is evenly spread. If both kernelcore
  	 * and movablecore are specified, then the value of kernelcore
  	 * will be used for required_kernelcore if it's greater than
  	 * what movablecore would have allowed.
  	 */
  	if (required_movablecore) {
  		unsigned long corepages;
  
  		/*
  		 * Round-up so that ZONE_MOVABLE is at least as large as what
  		 * was requested by the user
  		 */
  		required_movablecore =
  			roundup(required_movablecore, MAX_ORDER_NR_PAGES);
  		required_movablecore = min(totalpages, required_movablecore);
  		corepages = totalpages - required_movablecore;
  
  		required_kernelcore = max(required_kernelcore, corepages);
  	}
  
  	/*
  	 * If kernelcore was not specified or kernelcore size is larger
  	 * than totalpages, there is no ZONE_MOVABLE.
  	 */
  	if (!required_kernelcore || required_kernelcore >= totalpages)
  		goto out;
  
  	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
  	usable_startpfn = arch_zone_lowest_possible_pfn[movable_zone];
  
  restart:
  	/* Spread kernelcore memory as evenly as possible throughout nodes */
  	kernelcore_node = required_kernelcore / usable_nodes;
  	for_each_node_state(nid, N_MEMORY) {
  		unsigned long start_pfn, end_pfn;
  
  		/*
  		 * Recalculate kernelcore_node if the division per node
  		 * now exceeds what is necessary to satisfy the requested
  		 * amount of memory for the kernel
  		 */
  		if (required_kernelcore < kernelcore_node)
  			kernelcore_node = required_kernelcore / usable_nodes;
  
  		/*
  		 * As the map is walked, we track how much memory is usable
  		 * by the kernel using kernelcore_remaining. When it is
  		 * 0, the rest of the node is usable by ZONE_MOVABLE
  		 */
  		kernelcore_remaining = kernelcore_node;
  
  		/* Go through each range of PFNs within this node */
  		for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
  			unsigned long size_pages;
  
  			start_pfn = max(start_pfn, zone_movable_pfn[nid]);
  			if (start_pfn >= end_pfn)
  				continue;
  
  			/* Account for what is only usable for kernelcore */
  			if (start_pfn < usable_startpfn) {
  				unsigned long kernel_pages;
  				kernel_pages = min(end_pfn, usable_startpfn)
  								- start_pfn;
  
  				kernelcore_remaining -= min(kernel_pages,
  							kernelcore_remaining);
  				required_kernelcore -= min(kernel_pages,
  							required_kernelcore);
  
  				/* Continue if range is now fully accounted */
  				if (end_pfn <= usable_startpfn) {
  
  					/*
  					 * Push zone_movable_pfn to the end so
  					 * that if we have to rebalance
  					 * kernelcore across nodes, we will
  					 * not double account here
  					 */
  					zone_movable_pfn[nid] = end_pfn;
  					continue;
  				}
  				start_pfn = usable_startpfn;
  			}
  
  			/*
  			 * The usable PFN range for ZONE_MOVABLE is from
  			 * start_pfn->end_pfn. Calculate size_pages as the
  			 * number of pages used as kernelcore
  			 */
  			size_pages = end_pfn - start_pfn;
  			if (size_pages > kernelcore_remaining)
  				size_pages = kernelcore_remaining;
  			zone_movable_pfn[nid] = start_pfn + size_pages;
  
  			/*
  			 * Some kernelcore has been met, update counts and
  			 * break if the kernelcore for this node has been
  			 * satisfied
  			 */
  			required_kernelcore -= min(required_kernelcore,
  								size_pages);
  			kernelcore_remaining -= size_pages;
  			if (!kernelcore_remaining)
  				break;
  		}
  	}
  
  	/*
  	 * If there is still required_kernelcore, we do another pass with one
  	 * less node in the count. This will push zone_movable_pfn[nid] further
  	 * along on the nodes that still have memory until kernelcore is
  	 * satisfied
  	 */
  	usable_nodes--;
  	if (usable_nodes && required_kernelcore > usable_nodes)
  		goto restart;
  
  out2:
  	/* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */
  	for (nid = 0; nid < MAX_NUMNODES; nid++)
  		zone_movable_pfn[nid] =
  			roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES);
  
  out:
  	/* restore the node_state */
  	node_states[N_MEMORY] = saved_node_state;
  }
  
  /* Any regular or high memory on that node ? */
  static void check_for_memory(pg_data_t *pgdat, int nid)
  {
  	enum zone_type zone_type;
  
  	for (zone_type = 0; zone_type <= ZONE_MOVABLE - 1; zone_type++) {
  		struct zone *zone = &pgdat->node_zones[zone_type];
  		if (populated_zone(zone)) {
  			if (IS_ENABLED(CONFIG_HIGHMEM))
  				node_set_state(nid, N_HIGH_MEMORY);
  			if (zone_type <= ZONE_NORMAL)
  				node_set_state(nid, N_NORMAL_MEMORY);
  			break;
  		}
  	}
  }
  
  /*
   * Some architectures, e.g. ARC may have ZONE_HIGHMEM below ZONE_NORMAL. For
   * such cases we allow max_zone_pfn sorted in the descending order
   */
  bool __weak arch_has_descending_max_zone_pfns(void)
  {
  	return false;
  }
  
  /**
   * free_area_init - Initialise all pg_data_t and zone data
   * @max_zone_pfn: an array of max PFNs for each zone
   *
   * This will call free_area_init_node() for each active node in the system.
   * Using the page ranges provided by memblock_set_node(), the size of each
   * zone in each node and their holes is calculated. If the maximum PFN
   * between two adjacent zones match, it is assumed that the zone is empty.
   * For example, if arch_max_dma_pfn == arch_max_dma32_pfn, it is assumed
   * that arch_max_dma32_pfn has no pages. It is also assumed that a zone
   * starts where the previous one ended. For example, ZONE_DMA32 starts
   * at arch_max_dma_pfn.
   */
  void __init free_area_init(unsigned long *max_zone_pfn)
  {
  	unsigned long start_pfn, end_pfn;
  	int i, nid, zone;
  	bool descending;
  
  	/* Record where the zone boundaries are */
  	memset(arch_zone_lowest_possible_pfn, 0,
  				sizeof(arch_zone_lowest_possible_pfn));
  	memset(arch_zone_highest_possible_pfn, 0,
  				sizeof(arch_zone_highest_possible_pfn));
  
  	start_pfn = find_min_pfn_with_active_regions();
  	descending = arch_has_descending_max_zone_pfns();
  
  	for (i = 0; i < MAX_NR_ZONES; i++) {
  		if (descending)
  			zone = MAX_NR_ZONES - i - 1;
  		else
  			zone = i;
  
  		if (zone == ZONE_MOVABLE)
  			continue;
  
  		end_pfn = max(max_zone_pfn[zone], start_pfn);
  		arch_zone_lowest_possible_pfn[zone] = start_pfn;
  		arch_zone_highest_possible_pfn[zone] = end_pfn;
  
  		start_pfn = end_pfn;
  	}
  
  	/* Find the PFNs that ZONE_MOVABLE begins at in each node */
  	memset(zone_movable_pfn, 0, sizeof(zone_movable_pfn));
  	find_zone_movable_pfns_for_nodes();
  
  	/* Print out the zone ranges */
  	pr_info("Zone ranges:\n");
  	for (i = 0; i < MAX_NR_ZONES; i++) {
  		if (i == ZONE_MOVABLE)
  			continue;
  		pr_info("  %-8s ", zone_names[i]);
  		if (arch_zone_lowest_possible_pfn[i] ==
  				arch_zone_highest_possible_pfn[i])
  			pr_cont("empty\n");
  		else
  			pr_cont("[mem %#018Lx-%#018Lx]\n",
  				(u64)arch_zone_lowest_possible_pfn[i]
  					<< PAGE_SHIFT,
  				((u64)arch_zone_highest_possible_pfn[i]
  					<< PAGE_SHIFT) - 1);
  	}
  
  	/* Print out the PFNs ZONE_MOVABLE begins at in each node */
  	pr_info("Movable zone start for each node\n");
  	for (i = 0; i < MAX_NUMNODES; i++) {
  		if (zone_movable_pfn[i])
  			pr_info("  Node %d: %#018Lx\n", i,
  			       (u64)zone_movable_pfn[i] << PAGE_SHIFT);
  	}
  
  	/*
  	 * Print out the early node map, and initialize the
  	 * subsection-map relative to active online memory ranges to
  	 * enable future "sub-section" extensions of the memory map.
  	 */
  	pr_info("Early memory node ranges\n");
  	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
  		pr_info("  node %3d: [mem %#018Lx-%#018Lx]\n", nid,
  			(u64)start_pfn << PAGE_SHIFT,
  			((u64)end_pfn << PAGE_SHIFT) - 1);
  		subsection_map_init(start_pfn, end_pfn - start_pfn);
  	}
  
  	/* Initialise every node */
  	mminit_verify_pageflags_layout();
  	setup_nr_node_ids();
  	for_each_online_node(nid) {
  		pg_data_t *pgdat = NODE_DATA(nid);
  		free_area_init_node(nid);
  
  		/* Any memory on that node */
  		if (pgdat->node_present_pages)
  			node_set_state(nid, N_MEMORY);
  		check_for_memory(pgdat, nid);
  	}
  
  	memmap_init();
  }
  
  static int __init cmdline_parse_core(char *p, unsigned long *core,
  				     unsigned long *percent)
  {
  	unsigned long long coremem;
  	char *endptr;
  
  	if (!p)
  		return -EINVAL;
  
  	/* Value may be a percentage of total memory, otherwise bytes */
  	coremem = simple_strtoull(p, &endptr, 0);
  	if (*endptr == '%') {
  		/* Paranoid check for percent values greater than 100 */
  		WARN_ON(coremem > 100);
  
  		*percent = coremem;
  	} else {
  		coremem = memparse(p, &p);
  		/* Paranoid check that UL is enough for the coremem value */
  		WARN_ON((coremem >> PAGE_SHIFT) > ULONG_MAX);
  
  		*core = coremem >> PAGE_SHIFT;
  		*percent = 0UL;
  	}
  	return 0;
  }
  
  /*
   * kernelcore=size sets the amount of memory for use for allocations that
   * cannot be reclaimed or migrated.
   */
  static int __init cmdline_parse_kernelcore(char *p)
  {
  	/* parse kernelcore=mirror */
  	if (parse_option_str(p, "mirror")) {
  		mirrored_kernelcore = true;
  		return 0;
  	}
  
  	return cmdline_parse_core(p, &required_kernelcore,
  				  &required_kernelcore_percent);
  }
  
  /*
   * movablecore=size sets the amount of memory for use for allocations that
   * can be reclaimed or migrated.
   */
  static int __init cmdline_parse_movablecore(char *p)
  {
  	return cmdline_parse_core(p, &required_movablecore,
  				  &required_movablecore_percent);
  }
  
  early_param("kernelcore", cmdline_parse_kernelcore);
  early_param("movablecore", cmdline_parse_movablecore);
  
  void adjust_managed_page_count(struct page *page, long count)
  {
  	atomic_long_add(count, &page_zone(page)->managed_pages);
  	totalram_pages_add(count);
  #ifdef CONFIG_HIGHMEM
  	if (PageHighMem(page))
  		totalhigh_pages_add(count);
  #endif
  }
  EXPORT_SYMBOL(adjust_managed_page_count);
  
  unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
  {
  	void *pos;
  	unsigned long pages = 0;
  
  	start = (void *)PAGE_ALIGN((unsigned long)start);
  	end = (void *)((unsigned long)end & PAGE_MASK);
  	for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
  		struct page *page = virt_to_page(pos);
  		void *direct_map_addr;
  
  		/*
  		 * 'direct_map_addr' might be different from 'pos'
  		 * because some architectures' virt_to_page()
  		 * work with aliases.  Getting the direct map
  		 * address ensures that we get a _writeable_
  		 * alias for the memset().
  		 */
  		direct_map_addr = page_address(page);
  		/*
  		 * Perform a kasan-unchecked memset() since this memory
  		 * has not been initialized.
  		 */
  		direct_map_addr = kasan_reset_tag(direct_map_addr);
  		if ((unsigned int)poison <= 0xFF)
  			memset(direct_map_addr, poison, PAGE_SIZE);
  
  		free_reserved_page(page);
  	}
  
  	if (pages && s)
  		pr_info("Freeing %s memory: %ldK\n", s, K(pages));
  
  	return pages;
  }
  
  void __init mem_init_print_info(void)
  {
  	unsigned long physpages, codesize, datasize, rosize, bss_size;
  	unsigned long init_code_size, init_data_size;
  
  	physpages = get_num_physpages();
  	codesize = _etext - _stext;
  	datasize = _edata - _sdata;
  	rosize = __end_rodata - __start_rodata;
  	bss_size = __bss_stop - __bss_start;
  	init_data_size = __init_end - __init_begin;
  	init_code_size = _einittext - _sinittext;
  
  	/*
  	 * Detect special cases and adjust section sizes accordingly:
  	 * 1) .init.* may be embedded into .data sections
  	 * 2) .init.text.* may be out of [__init_begin, __init_end],
  	 *    please refer to arch/tile/kernel/vmlinux.lds.S.
  	 * 3) .rodata.* may be embedded into .text or .data sections.
  	 */
  #define adj_init_size(start, end, size, pos, adj) \
  	do { \
  		if (&start[0] <= &pos[0] && &pos[0] < &end[0] && size > adj) \
  			size -= adj; \
  	} while (0)
  
  	adj_init_size(__init_begin, __init_end, init_data_size,
  		     _sinittext, init_code_size);
  	adj_init_size(_stext, _etext, codesize, _sinittext, init_code_size);
  	adj_init_size(_sdata, _edata, datasize, __init_begin, init_data_size);
  	adj_init_size(_stext, _etext, codesize, __start_rodata, rosize);
  	adj_init_size(_sdata, _edata, datasize, __start_rodata, rosize);
  
  #undef	adj_init_size
  
  	pr_info("Memory: %luK/%luK available (%luK kernel code, %luK rwdata, %luK rodata, %luK init, %luK bss, %luK reserved, %luK cma-reserved"
  #ifdef	CONFIG_HIGHMEM
  		", %luK highmem"
  #endif
  		")\n",
  		K(nr_free_pages()), K(physpages),
  		codesize >> 10, datasize >> 10, rosize >> 10,
  		(init_data_size + init_code_size) >> 10, bss_size >> 10,
  		K(physpages - totalram_pages() - totalcma_pages),
  		K(totalcma_pages)
  #ifdef	CONFIG_HIGHMEM
  		, K(totalhigh_pages())
  #endif
  		);
  }
  
  /**
   * set_dma_reserve - set the specified number of pages reserved in the first zone
   * @new_dma_reserve: The number of pages to mark reserved
   *
   * The per-cpu batchsize and zone watermarks are determined by managed_pages.
   * In the DMA zone, a significant percentage may be consumed by kernel image
   * and other unfreeable allocations which can skew the watermarks badly. This
   * function may optionally be used to account for unfreeable pages in the
   * first zone (e.g., ZONE_DMA). The effect will be lower watermarks and
   * smaller per-cpu batchsize.
   */
  void __init set_dma_reserve(unsigned long new_dma_reserve)
  {
  	dma_reserve = new_dma_reserve;
  }
  
  static int page_alloc_cpu_dead(unsigned int cpu)
  {
  	struct zone *zone;
  
  	lru_add_drain_cpu(cpu);
  	drain_pages(cpu);
  
  	/*
  	 * Spill the event counters of the dead processor
  	 * into the current processors event counters.
  	 * This artificially elevates the count of the current
  	 * processor.
  	 */
  	vm_events_fold_cpu(cpu);
  
  	/*
  	 * Zero the differential counters of the dead processor
  	 * so that the vm statistics are consistent.
  	 *
  	 * This is only okay since the processor is dead and cannot
  	 * race with what we are doing.
  	 */
  	cpu_vm_stats_fold(cpu);
  
  	for_each_populated_zone(zone)
  		zone_pcp_update(zone, 0);
  
  	return 0;
  }
  
  static int page_alloc_cpu_online(unsigned int cpu)
  {
  	struct zone *zone;
  
  	for_each_populated_zone(zone)
  		zone_pcp_update(zone, 1);
  	return 0;
  }
  
  #ifdef CONFIG_NUMA
  int hashdist = HASHDIST_DEFAULT;
  
  static int __init set_hashdist(char *str)
  {
  	if (!str)
  		return 0;
  	hashdist = simple_strtoul(str, &str, 0);
  	return 1;
  }
  __setup("hashdist=", set_hashdist);
  #endif
  
  void __init page_alloc_init(void)
  {
  	int ret;
  
  #ifdef CONFIG_NUMA
  	if (num_node_state(N_MEMORY) == 1)
  		hashdist = 0;
  #endif
  
  	ret = cpuhp_setup_state_nocalls(CPUHP_PAGE_ALLOC,
  					"mm/page_alloc:pcp",
  					page_alloc_cpu_online,
  					page_alloc_cpu_dead);
  	WARN_ON(ret < 0);
  }
  
  /*
   * calculate_totalreserve_pages - called when sysctl_lowmem_reserve_ratio
   *	or min_free_kbytes changes.
   */
  static void calculate_totalreserve_pages(void)
  {
  	struct pglist_data *pgdat;
  	unsigned long reserve_pages = 0;
  	enum zone_type i, j;
  
  	for_each_online_pgdat(pgdat) {
  
  		pgdat->totalreserve_pages = 0;
  
  		for (i = 0; i < MAX_NR_ZONES; i++) {
  			struct zone *zone = pgdat->node_zones + i;
  			long max = 0;
  			unsigned long managed_pages = zone_managed_pages(zone);
  
  			/* Find valid and maximum lowmem_reserve in the zone */
  			for (j = i; j < MAX_NR_ZONES; j++) {
  				if (zone->lowmem_reserve[j] > max)
  					max = zone->lowmem_reserve[j];
  			}
  
  			/* we treat the high watermark as reserved pages. */
  			max += high_wmark_pages(zone);
  
  			if (max > managed_pages)
  				max = managed_pages;
  
  			pgdat->totalreserve_pages += max;
  
  			reserve_pages += max;
  		}
  	}
  	totalreserve_pages = reserve_pages;
  }
  
  /*
   * setup_per_zone_lowmem_reserve - called whenever
   *	sysctl_lowmem_reserve_ratio changes.  Ensures that each zone
   *	has a correct pages reserved value, so an adequate number of
   *	pages are left in the zone after a successful __alloc_pages().
   */
  static void setup_per_zone_lowmem_reserve(void)
  {
  	struct pglist_data *pgdat;
  	enum zone_type i, j;
  
  	for_each_online_pgdat(pgdat) {
  		for (i = 0; i < MAX_NR_ZONES - 1; i++) {
  			struct zone *zone = &pgdat->node_zones[i];
  			int ratio = sysctl_lowmem_reserve_ratio[i];
  			bool clear = !ratio || !zone_managed_pages(zone);
  			unsigned long managed_pages = 0;
  
  			for (j = i + 1; j < MAX_NR_ZONES; j++) {
  				struct zone *upper_zone = &pgdat->node_zones[j];
  
  				managed_pages += zone_managed_pages(upper_zone);
  
  				if (clear)
  					zone->lowmem_reserve[j] = 0;
  				else
  					zone->lowmem_reserve[j] = managed_pages / ratio;
  			}
  		}
  	}
  
  	/* update totalreserve_pages */
  	calculate_totalreserve_pages();
  }
  
  static void __setup_per_zone_wmarks(void)
  {
  	unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
  	unsigned long lowmem_pages = 0;
  	struct zone *zone;
  	unsigned long flags;
  
  	/* Calculate total number of !ZONE_HIGHMEM pages */
  	for_each_zone(zone) {
  		if (!is_highmem(zone))
  			lowmem_pages += zone_managed_pages(zone);
  	}
  
  	for_each_zone(zone) {
  		u64 tmp;
  
  		spin_lock_irqsave(&zone->lock, flags);
  		tmp = (u64)pages_min * zone_managed_pages(zone);
  		do_div(tmp, lowmem_pages);
  		if (is_highmem(zone)) {
  			/*
  			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
  			 * need highmem pages, so cap pages_min to a small
  			 * value here.
  			 *
  			 * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
  			 * deltas control async page reclaim, and so should
  			 * not be capped for highmem.
  			 */
  			unsigned long min_pages;
  
  			min_pages = zone_managed_pages(zone) / 1024;
  			min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL);
  			zone->_watermark[WMARK_MIN] = min_pages;
  		} else {
  			/*
  			 * If it's a lowmem zone, reserve a number of pages
  			 * proportionate to the zone's size.
  			 */
  			zone->_watermark[WMARK_MIN] = tmp;
  		}
  
  		/*
  		 * Set the kswapd watermarks distance according to the
  		 * scale factor in proportion to available memory, but
  		 * ensure a minimum size on small systems.
  		 */
  		tmp = max_t(u64, tmp >> 2,
  			    mult_frac(zone_managed_pages(zone),
  				      watermark_scale_factor, 10000));
  
  		zone->watermark_boost = 0;
  		zone->_watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
  		zone->_watermark[WMARK_HIGH] = min_wmark_pages(zone) + tmp * 2;
  
  		spin_unlock_irqrestore(&zone->lock, flags);
  	}
  
  	/* update totalreserve_pages */
  	calculate_totalreserve_pages();
  }
  
  /**
   * setup_per_zone_wmarks - called when min_free_kbytes changes
   * or when memory is hot-{added|removed}
   *
   * Ensures that the watermark[min,low,high] values for each zone are set
   * correctly with respect to min_free_kbytes.
   */
  void setup_per_zone_wmarks(void)
  {
  	struct zone *zone;
  	static DEFINE_SPINLOCK(lock);
  
  	spin_lock(&lock);
  	__setup_per_zone_wmarks();
  	spin_unlock(&lock);
  
  	/*
  	 * The watermark size have changed so update the pcpu batch
  	 * and high limits or the limits may be inappropriate.
  	 */
  	for_each_zone(zone)
  		zone_pcp_update(zone, 0);
  }
  
  /*
   * Initialise min_free_kbytes.
   *
   * For small machines we want it small (128k min).  For large machines
   * we want it large (256MB max).  But it is not linear, because network
   * bandwidth does not increase linearly with machine size.  We use
   *
   *	min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
   *	min_free_kbytes = sqrt(lowmem_kbytes * 16)
   *
   * which yields
   *
   * 16MB:	512k
   * 32MB:	724k
   * 64MB:	1024k
   * 128MB:	1448k
   * 256MB:	2048k
   * 512MB:	2896k
   * 1024MB:	4096k
   * 2048MB:	5792k
   * 4096MB:	8192k
   * 8192MB:	11584k
   * 16384MB:	16384k
   */
  void calculate_min_free_kbytes(void)
  {
  	unsigned long lowmem_kbytes;
  	int new_min_free_kbytes;
  
  	lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
  	new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
  
  	if (new_min_free_kbytes > user_min_free_kbytes)
  		min_free_kbytes = clamp(new_min_free_kbytes, 128, 262144);
  	else
  		pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
  				new_min_free_kbytes, user_min_free_kbytes);
  
  }
  
  int __meminit init_per_zone_wmark_min(void)
  {
  	calculate_min_free_kbytes();
  	setup_per_zone_wmarks();
  	refresh_zone_stat_thresholds();
  	setup_per_zone_lowmem_reserve();
  
  #ifdef CONFIG_NUMA
  	setup_min_unmapped_ratio();
  	setup_min_slab_ratio();
  #endif
  
  	khugepaged_min_free_kbytes_update();
  
  	return 0;
  }
  postcore_initcall(init_per_zone_wmark_min)
  
  /*
   * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
   *	that we can call two helper functions whenever min_free_kbytes
   *	changes.
   */
  int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
  		void *buffer, size_t *length, loff_t *ppos)
  {
  	int rc;
  
  	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
  	if (rc)
  		return rc;
  
  	if (write) {
  		user_min_free_kbytes = min_free_kbytes;
  		setup_per_zone_wmarks();
  	}
  	return 0;
  }
  
  int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
  		void *buffer, size_t *length, loff_t *ppos)
  {
  	int rc;
  
  	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
  	if (rc)
  		return rc;
  
  	if (write)
  		setup_per_zone_wmarks();
  
  	return 0;
  }
  
  #ifdef CONFIG_NUMA
  static void setup_min_unmapped_ratio(void)
  {
  	pg_data_t *pgdat;
  	struct zone *zone;
  
  	for_each_online_pgdat(pgdat)
  		pgdat->min_unmapped_pages = 0;
  
  	for_each_zone(zone)
  		zone->zone_pgdat->min_unmapped_pages += (zone_managed_pages(zone) *
  						         sysctl_min_unmapped_ratio) / 100;
  }
  
  
  int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
  		void *buffer, size_t *length, loff_t *ppos)
  {
  	int rc;
  
  	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
  	if (rc)
  		return rc;
  
  	setup_min_unmapped_ratio();
  
  	return 0;
  }
  
  static void setup_min_slab_ratio(void)
  {
  	pg_data_t *pgdat;
  	struct zone *zone;
  
  	for_each_online_pgdat(pgdat)
  		pgdat->min_slab_pages = 0;
  
  	for_each_zone(zone)
  		zone->zone_pgdat->min_slab_pages += (zone_managed_pages(zone) *
  						     sysctl_min_slab_ratio) / 100;
  }
  
  int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
  		void *buffer, size_t *length, loff_t *ppos)
  {
  	int rc;
  
  	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
  	if (rc)
  		return rc;
  
  	setup_min_slab_ratio();
  
  	return 0;
  }
  #endif
  
  /*
   * lowmem_reserve_ratio_sysctl_handler - just a wrapper around
   *	proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()
   *	whenever sysctl_lowmem_reserve_ratio changes.
   *
   * The reserve ratio obviously has absolutely no relation with the
   * minimum watermarks. The lowmem reserve ratio can only make sense
   * if in function of the boot time zone sizes.
   */
  int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write,
  		void *buffer, size_t *length, loff_t *ppos)
  {
  	int i;
  
  	proc_dointvec_minmax(table, write, buffer, length, ppos);
  
  	for (i = 0; i < MAX_NR_ZONES; i++) {
  		if (sysctl_lowmem_reserve_ratio[i] < 1)
  			sysctl_lowmem_reserve_ratio[i] = 0;
  	}
  
  	setup_per_zone_lowmem_reserve();
  	return 0;
  }
  
  /*
   * percpu_pagelist_high_fraction - changes the pcp->high for each zone on each
   * cpu. It is the fraction of total pages in each zone that a hot per cpu
   * pagelist can have before it gets flushed back to buddy allocator.
   */
  int percpu_pagelist_high_fraction_sysctl_handler(struct ctl_table *table,
  		int write, void *buffer, size_t *length, loff_t *ppos)
  {
  	struct zone *zone;
  	int old_percpu_pagelist_high_fraction;
  	int ret;
  
  	mutex_lock(&pcp_batch_high_lock);
  	old_percpu_pagelist_high_fraction = percpu_pagelist_high_fraction;
  
  	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  	if (!write || ret < 0)
  		goto out;
  
  	/* Sanity checking to avoid pcp imbalance */
  	if (percpu_pagelist_high_fraction &&
  	    percpu_pagelist_high_fraction < MIN_PERCPU_PAGELIST_HIGH_FRACTION) {
  		percpu_pagelist_high_fraction = old_percpu_pagelist_high_fraction;
  		ret = -EINVAL;
  		goto out;
  	}
  
  	/* No change? */
  	if (percpu_pagelist_high_fraction == old_percpu_pagelist_high_fraction)
  		goto out;
  
  	for_each_populated_zone(zone)
  		zone_set_pageset_high_and_batch(zone, 0);
  out:
  	mutex_unlock(&pcp_batch_high_lock);
  	return ret;
  }
  
  #ifndef __HAVE_ARCH_RESERVED_KERNEL_PAGES
  /*
   * Returns the number of pages that arch has reserved but
   * is not known to alloc_large_system_hash().
   */
  static unsigned long __init arch_reserved_kernel_pages(void)
  {
  	return 0;
  }
  #endif
  
  /*
   * Adaptive scale is meant to reduce sizes of hash tables on large memory
   * machines. As memory size is increased the scale is also increased but at
   * slower pace.  Starting from ADAPT_SCALE_BASE (64G), every time memory
   * quadruples the scale is increased by one, which means the size of hash table
   * only doubles, instead of quadrupling as well.
   * Because 32-bit systems cannot have large physical memory, where this scaling
   * makes sense, it is disabled on such platforms.
   */
  #if __BITS_PER_LONG > 32
  #define ADAPT_SCALE_BASE	(64ul << 30)
  #define ADAPT_SCALE_SHIFT	2
  #define ADAPT_SCALE_NPAGES	(ADAPT_SCALE_BASE >> PAGE_SHIFT)
  #endif
  
  /*
   * allocate a large system hash table from bootmem
   * - it is assumed that the hash table must contain an exact power-of-2
   *   quantity of entries
   * - limit is the number of hash buckets, not the total allocation size
   */
  void *__init alloc_large_system_hash(const char *tablename,
  				     unsigned long bucketsize,
  				     unsigned long numentries,
  				     int scale,
  				     int flags,
  				     unsigned int *_hash_shift,
  				     unsigned int *_hash_mask,
  				     unsigned long low_limit,
  				     unsigned long high_limit)
  {
  	unsigned long long max = high_limit;
  	unsigned long log2qty, size;
  	void *table = NULL;
  	gfp_t gfp_flags;
  	bool virt;
  	bool huge;
  
  	/* allow the kernel cmdline to have a say */
  	if (!numentries) {
  		/* round applicable memory size up to nearest megabyte */
  		numentries = nr_kernel_pages;
  		numentries -= arch_reserved_kernel_pages();
  
  		/* It isn't necessary when PAGE_SIZE >= 1MB */
  		if (PAGE_SHIFT < 20)
  			numentries = round_up(numentries, (1<<20)/PAGE_SIZE);
  
  #if __BITS_PER_LONG > 32
  		if (!high_limit) {
  			unsigned long adapt;
  
  			for (adapt = ADAPT_SCALE_NPAGES; adapt < numentries;
  			     adapt <<= ADAPT_SCALE_SHIFT)
  				scale++;
  		}
  #endif
  
  		/* limit to 1 bucket per 2^scale bytes of low memory */
  		if (scale > PAGE_SHIFT)
  			numentries >>= (scale - PAGE_SHIFT);
  		else
  			numentries <<= (PAGE_SHIFT - scale);
  
  		/* Make sure we've got at least a 0-order allocation.. */
  		if (unlikely(flags & HASH_SMALL)) {
  			/* Makes no sense without HASH_EARLY */
  			WARN_ON(!(flags & HASH_EARLY));
  			if (!(numentries >> *_hash_shift)) {
  				numentries = 1UL << *_hash_shift;
  				BUG_ON(!numentries);
  			}
  		} else if (unlikely((numentries * bucketsize) < PAGE_SIZE))
  			numentries = PAGE_SIZE / bucketsize;
  	}
  	numentries = roundup_pow_of_two(numentries);
  
  	/* limit allocation size to 1/16 total memory by default */
  	if (max == 0) {
  		max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
  		do_div(max, bucketsize);
  	}
  	max = min(max, 0x80000000ULL);
  
  	if (numentries < low_limit)
  		numentries = low_limit;
  	if (numentries > max)
  		numentries = max;
  
  	log2qty = ilog2(numentries);
  
  	gfp_flags = (flags & HASH_ZERO) ? GFP_ATOMIC | __GFP_ZERO : GFP_ATOMIC;
  	do {
  		virt = false;
  		size = bucketsize << log2qty;
  		if (flags & HASH_EARLY) {
  			if (flags & HASH_ZERO)
  				table = memblock_alloc(size, SMP_CACHE_BYTES);
  			else
  				table = memblock_alloc_raw(size,
  							   SMP_CACHE_BYTES);
  		} else if (get_order(size) >= MAX_ORDER || hashdist) {
  			table = __vmalloc(size, gfp_flags);
  			virt = true;
  			if (table)
  				huge = is_vm_area_hugepages(table);
  		} else {
  			/*
  			 * If bucketsize is not a power-of-two, we may free
  			 * some pages at the end of hash table which
  			 * alloc_pages_exact() automatically does
  			 */
  			table = alloc_pages_exact(size, gfp_flags);
  			kmemleak_alloc(table, size, 1, gfp_flags);
  		}
  	} while (!table && size > PAGE_SIZE && --log2qty);
  
  	if (!table)
  		panic("Failed to allocate %s hash table\n", tablename);
  
  	pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
  		tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
  		virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");
  
  	if (_hash_shift)
  		*_hash_shift = log2qty;
  	if (_hash_mask)
  		*_hash_mask = (1 << log2qty) - 1;
  
  	return table;
  }
  
  /*
   * This function checks whether pageblock includes unmovable pages or not.
   *
   * PageLRU check without isolation or lru_lock could race so that
   * MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
   * check without lock_page also may miss some movable non-lru pages at
   * race condition. So you can't expect this function should be exact.
   *
   * Returns a page without holding a reference. If the caller wants to
   * dereference that page (e.g., dumping), it has to make sure that it
   * cannot get removed (e.g., via memory unplug) concurrently.
   *
   */
  struct page *has_unmovable_pages(struct zone *zone, struct page *page,
  				 int migratetype, int flags)
  {
  	unsigned long iter = 0;
  	unsigned long pfn = page_to_pfn(page);
  	unsigned long offset = pfn % pageblock_nr_pages;
  
  	if (is_migrate_cma_page(page)) {
  		/*
  		 * CMA allocations (alloc_contig_range) really need to mark
  		 * isolate CMA pageblocks even when they are not movable in fact
  		 * so consider them movable here.
  		 */
  		if (is_migrate_cma(migratetype))
  			return NULL;
  
  		return page;
  	}
  
  	for (; iter < pageblock_nr_pages - offset; iter++) {
  		page = pfn_to_page(pfn + iter);
  
  		/*
  		 * Both, bootmem allocations and memory holes are marked
  		 * PG_reserved and are unmovable. We can even have unmovable
  		 * allocations inside ZONE_MOVABLE, for example when
  		 * specifying "movablecore".
  		 */
  		if (PageReserved(page))
  			return page;
  
  		/*
  		 * If the zone is movable and we have ruled out all reserved
  		 * pages then it should be reasonably safe to assume the rest
  		 * is movable.
  		 */
  		if (zone_idx(zone) == ZONE_MOVABLE)
  			continue;
  
  		/*
  		 * Hugepages are not in LRU lists, but they're movable.
  		 * THPs are on the LRU, but need to be counted as #small pages.
  		 * We need not scan over tail pages because we don't
  		 * handle each tail page individually in migration.
  		 */
  		if (PageHuge(page) || PageTransCompound(page)) {
  			struct page *head = compound_head(page);
  			unsigned int skip_pages;
  
  			if (PageHuge(page)) {
  				if (!hugepage_migration_supported(page_hstate(head)))
  					return page;
  			} else if (!PageLRU(head) && !__PageMovable(head)) {
  				return page;
  			}
  
  			skip_pages = compound_nr(head) - (page - head);
  			iter += skip_pages - 1;
  			continue;
  		}
  
  		/*
  		 * We can't use page_count without pin a page
  		 * because another CPU can free compound page.
  		 * This check already skips compound tails of THP
  		 * because their page->_refcount is zero at all time.
  		 */
  		if (!page_ref_count(page)) {
  			if (PageBuddy(page))
  				iter += (1 << buddy_order(page)) - 1;
  			continue;
  		}
  
  		/*
  		 * The HWPoisoned page may be not in buddy system, and
  		 * page_count() is not 0.
  		 */
  		if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
  			continue;
  
  		/*
  		 * We treat all PageOffline() pages as movable when offlining
  		 * to give drivers a chance to decrement their reference count
  		 * in MEM_GOING_OFFLINE in order to indicate that these pages
  		 * can be offlined as there are no direct references anymore.
  		 * For actually unmovable PageOffline() where the driver does
  		 * not support this, we will fail later when trying to actually
  		 * move these pages that still have a reference count > 0.
  		 * (false negatives in this function only)
  		 */
  		if ((flags & MEMORY_OFFLINE) && PageOffline(page))
  			continue;
  
  		if (__PageMovable(page) || PageLRU(page))
  			continue;
  
  		/*
  		 * If there are RECLAIMABLE pages, we need to check
  		 * it.  But now, memory offline itself doesn't call
  		 * shrink_node_slabs() and it still to be fixed.
  		 */
  		return page;
  	}
  	return NULL;
  }
  
  #ifdef CONFIG_CONTIG_ALLOC
  static unsigned long pfn_max_align_down(unsigned long pfn)
  {
  	return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
  			     pageblock_nr_pages) - 1);
  }
  
  static unsigned long pfn_max_align_up(unsigned long pfn)
  {
  	return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
  				pageblock_nr_pages));
  }
  
  #if defined(CONFIG_DYNAMIC_DEBUG) || \
  	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
  /* Usage: See admin-guide/dynamic-debug-howto.rst */
  static void alloc_contig_dump_pages(struct list_head *page_list)
  {
  	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, "migrate failure");
  
  	if (DYNAMIC_DEBUG_BRANCH(descriptor)) {
  		struct page *page;
  
  		dump_stack();
  		list_for_each_entry(page, page_list, lru)
  			dump_page(page, "migration failure");
  	}
  }
  #else
  static inline void alloc_contig_dump_pages(struct list_head *page_list)
  {
  }
  #endif
  
  /* [start, end) must belong to a single zone. */
  static int __alloc_contig_migrate_range(struct compact_control *cc,
  					unsigned long start, unsigned long end)
  {
  	/* This function is based on compact_zone() from compaction.c. */
  	unsigned int nr_reclaimed;
  	unsigned long pfn = start;
  	unsigned int tries = 0;
  	int ret = 0;
  	struct migration_target_control mtc = {
  		.nid = zone_to_nid(cc->zone),
  		.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
  	};
  
  	lru_cache_disable();
  
  	while (pfn < end || !list_empty(&cc->migratepages)) {
  		if (fatal_signal_pending(current)) {
  			ret = -EINTR;
  			break;
  		}
  
  		if (list_empty(&cc->migratepages)) {
  			cc->nr_migratepages = 0;
  			ret = isolate_migratepages_range(cc, pfn, end);
  			if (ret && ret != -EAGAIN)
  				break;
  			pfn = cc->migrate_pfn;
  			tries = 0;
  		} else if (++tries == 5) {
  			ret = -EBUSY;
  			break;
  		}
  
  		nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
  							&cc->migratepages);
  		cc->nr_migratepages -= nr_reclaimed;
  
  		ret = migrate_pages(&cc->migratepages, alloc_migration_target,
  			NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE, NULL);
  
  		/*
  		 * On -ENOMEM, migrate_pages() bails out right away. It is pointless
  		 * to retry again over this error, so do the same here.
  		 */
  		if (ret == -ENOMEM)
  			break;
  	}
  
  	lru_cache_enable();
  	if (ret < 0) {
  		if (ret == -EBUSY)
  			alloc_contig_dump_pages(&cc->migratepages);
  		putback_movable_pages(&cc->migratepages);
  		return ret;
  	}
  	return 0;
  }
  
  /**
   * alloc_contig_range() -- tries to allocate given range of pages
   * @start:	start PFN to allocate
   * @end:	one-past-the-last PFN to allocate
   * @migratetype:	migratetype of the underlying pageblocks (either
   *			#MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
   *			in range must have the same migratetype and it must
   *			be either of the two.
   * @gfp_mask:	GFP mask to use during compaction
   *
   * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
   * aligned.  The PFN range must belong to a single zone.
   *
   * The first thing this routine does is attempt to MIGRATE_ISOLATE all
   * pageblocks in the range.  Once isolated, the pageblocks should not
   * be modified by others.
   *
   * Return: zero on success or negative error code.  On success all
   * pages which PFN is in [start, end) are allocated for the caller and
   * need to be freed with free_contig_range().
   */
  int alloc_contig_range(unsigned long start, unsigned long end,
  		       unsigned migratetype, gfp_t gfp_mask)
  {
  	unsigned long outer_start, outer_end;
  	unsigned int order;
  	int ret = 0;
  
  	struct compact_control cc = {
  		.nr_migratepages = 0,
  		.order = -1,
  		.zone = page_zone(pfn_to_page(start)),
  		.mode = MIGRATE_SYNC,
  		.ignore_skip_hint = true,
  		.no_set_skip_hint = true,
  		.gfp_mask = current_gfp_context(gfp_mask),
  		.alloc_contig = true,
  	};
  	INIT_LIST_HEAD(&cc.migratepages);
  
  	/*
  	 * What we do here is we mark all pageblocks in range as
  	 * MIGRATE_ISOLATE.  Because pageblock and max order pages may
  	 * have different sizes, and due to the way page allocator
  	 * work, we align the range to biggest of the two pages so
  	 * that page allocator won't try to merge buddies from
  	 * different pageblocks and change MIGRATE_ISOLATE to some
  	 * other migration type.
  	 *
  	 * Once the pageblocks are marked as MIGRATE_ISOLATE, we
  	 * migrate the pages from an unaligned range (ie. pages that
  	 * we are interested in).  This will put all the pages in
  	 * range back to page allocator as MIGRATE_ISOLATE.
  	 *
  	 * When this is done, we take the pages in range from page
  	 * allocator removing them from the buddy system.  This way
  	 * page allocator will never consider using them.
  	 *
  	 * This lets us mark the pageblocks back as
  	 * MIGRATE_CMA/MIGRATE_MOVABLE so that free pages in the
  	 * aligned range but not in the unaligned, original range are
  	 * put back to page allocator so that buddy can use them.
  	 */
  
  	ret = start_isolate_page_range(pfn_max_align_down(start),
  				       pfn_max_align_up(end), migratetype, 0);
  	if (ret)
  		return ret;
  
  	drain_all_pages(cc.zone);
  
  	/*
  	 * In case of -EBUSY, we'd like to know which page causes problem.
  	 * So, just fall through. test_pages_isolated() has a tracepoint
  	 * which will report the busy page.
  	 *
  	 * It is possible that busy pages could become available before
  	 * the call to test_pages_isolated, and the range will actually be
  	 * allocated.  So, if we fall through be sure to clear ret so that
  	 * -EBUSY is not accidentally used or returned to caller.
  	 */
  	ret = __alloc_contig_migrate_range(&cc, start, end);
  	if (ret && ret != -EBUSY)
  		goto done;
  	ret = 0;
  
  	/*
  	 * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
  	 * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
  	 * more, all pages in [start, end) are free in page allocator.
  	 * What we are going to do is to allocate all pages from
  	 * [start, end) (that is remove them from page allocator).
  	 *
  	 * The only problem is that pages at the beginning and at the
  	 * end of interesting range may be not aligned with pages that
  	 * page allocator holds, ie. they can be part of higher order
  	 * pages.  Because of this, we reserve the bigger range and
  	 * once this is done free the pages we are not interested in.
  	 *
  	 * We don't have to hold zone->lock here because the pages are
  	 * isolated thus they won't get removed from buddy.
  	 */
  
  	order = 0;
  	outer_start = start;
  	while (!PageBuddy(pfn_to_page(outer_start))) {
  		if (++order >= MAX_ORDER) {
  			outer_start = start;
  			break;
  		}
  		outer_start &= ~0UL << order;
  	}
  
  	if (outer_start != start) {
  		order = buddy_order(pfn_to_page(outer_start));
  
  		/*
  		 * outer_start page could be small order buddy page and
  		 * it doesn't include start page. Adjust outer_start
  		 * in this case to report failed page properly
  		 * on tracepoint in test_pages_isolated()
  		 */
  		if (outer_start + (1UL << order) <= start)
  			outer_start = start;
  	}
  
  	/* Make sure the range is really isolated. */
  	if (test_pages_isolated(outer_start, end, 0)) {
  		ret = -EBUSY;
  		goto done;
  	}
  
  	/* Grab isolated pages from freelists. */
  	outer_end = isolate_freepages_range(&cc, outer_start, end);
  	if (!outer_end) {
  		ret = -EBUSY;
  		goto done;
  	}
  
  	/* Free head and tail (if any) */
  	if (start != outer_start)
  		free_contig_range(outer_start, start - outer_start);
  	if (end != outer_end)
  		free_contig_range(end, outer_end - end);
  
  done:
  	undo_isolate_page_range(pfn_max_align_down(start),
  				pfn_max_align_up(end), migratetype);
  	return ret;
  }
  EXPORT_SYMBOL(alloc_contig_range);
  
  static int __alloc_contig_pages(unsigned long start_pfn,
  				unsigned long nr_pages, gfp_t gfp_mask)
  {
  	unsigned long end_pfn = start_pfn + nr_pages;
  
  	return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
  				  gfp_mask);
  }
  
  static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
  				   unsigned long nr_pages)
  {
  	unsigned long i, end_pfn = start_pfn + nr_pages;
  	struct page *page;
  
  	for (i = start_pfn; i < end_pfn; i++) {
  		page = pfn_to_online_page(i);
  		if (!page)
  			return false;
  
  		if (page_zone(page) != z)
  			return false;
  
  		if (PageReserved(page))
  			return false;
  	}
  	return true;
  }
  
  static bool zone_spans_last_pfn(const struct zone *zone,
  				unsigned long start_pfn, unsigned long nr_pages)
  {
  	unsigned long last_pfn = start_pfn + nr_pages - 1;
  
  	return zone_spans_pfn(zone, last_pfn);
  }
  
  /**
   * alloc_contig_pages() -- tries to find and allocate contiguous range of pages
   * @nr_pages:	Number of contiguous pages to allocate
   * @gfp_mask:	GFP mask to limit search and used during compaction
   * @nid:	Target node
   * @nodemask:	Mask for other possible nodes
   *
   * This routine is a wrapper around alloc_contig_range(). It scans over zones
   * on an applicable zonelist to find a contiguous pfn range which can then be
   * tried for allocation with alloc_contig_range(). This routine is intended
   * for allocation requests which can not be fulfilled with the buddy allocator.
   *
   * The allocated memory is always aligned to a page boundary. If nr_pages is a
   * power of two, then allocated range is also guaranteed to be aligned to same
   * nr_pages (e.g. 1GB request would be aligned to 1GB).
   *
   * Allocated pages can be freed with free_contig_range() or by manually calling
   * __free_page() on each allocated page.
   *
   * Return: pointer to contiguous pages on success, or NULL if not successful.
   */
  struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
  				int nid, nodemask_t *nodemask)
  {
  	unsigned long ret, pfn, flags;
  	struct zonelist *zonelist;
  	struct zone *zone;
  	struct zoneref *z;
  
  	zonelist = node_zonelist(nid, gfp_mask);
  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
  					gfp_zone(gfp_mask), nodemask) {
  		spin_lock_irqsave(&zone->lock, flags);
  
  		pfn = ALIGN(zone->zone_start_pfn, nr_pages);
  		while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
  			if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
  				/*
  				 * We release the zone lock here because
  				 * alloc_contig_range() will also lock the zone
  				 * at some point. If there's an allocation
  				 * spinning on this lock, it may win the race
  				 * and cause alloc_contig_range() to fail...
  				 */
  				spin_unlock_irqrestore(&zone->lock, flags);
  				ret = __alloc_contig_pages(pfn, nr_pages,
  							gfp_mask);
  				if (!ret)
  					return pfn_to_page(pfn);
  				spin_lock_irqsave(&zone->lock, flags);
  			}
  			pfn += nr_pages;
  		}
  		spin_unlock_irqrestore(&zone->lock, flags);
  	}
  	return NULL;
  }
  #endif /* CONFIG_CONTIG_ALLOC */
  
  void free_contig_range(unsigned long pfn, unsigned long nr_pages)
  {
  	unsigned long count = 0;
  
  	for (; nr_pages--; pfn++) {
  		struct page *page = pfn_to_page(pfn);
  
  		count += page_count(page) != 1;
  		__free_page(page);
  	}
  	WARN(count != 0, "%lu pages are still in use!\n", count);
  }
  EXPORT_SYMBOL(free_contig_range);
  
  /*
   * The zone indicated has a new number of managed_pages; batch sizes and percpu
   * page high values need to be recalculated.
   */
  void zone_pcp_update(struct zone *zone, int cpu_online)
  {
  	mutex_lock(&pcp_batch_high_lock);
  	zone_set_pageset_high_and_batch(zone, cpu_online);
  	mutex_unlock(&pcp_batch_high_lock);
  }
  
  /*
   * Effectively disable pcplists for the zone by setting the high limit to 0
   * and draining all cpus. A concurrent page freeing on another CPU that's about
   * to put the page on pcplist will either finish before the drain and the page
   * will be drained, or observe the new high limit and skip the pcplist.
   *
   * Must be paired with a call to zone_pcp_enable().
   */
  void zone_pcp_disable(struct zone *zone)
  {
  	mutex_lock(&pcp_batch_high_lock);
  	__zone_set_pageset_high_and_batch(zone, 0, 1);
  	__drain_all_pages(zone, true);
  }
  
  void zone_pcp_enable(struct zone *zone)
  {
  	__zone_set_pageset_high_and_batch(zone, zone->pageset_high, zone->pageset_batch);
  	mutex_unlock(&pcp_batch_high_lock);
  }
  
  void zone_pcp_reset(struct zone *zone)
  {
  	int cpu;
  	struct per_cpu_zonestat *pzstats;
  
  	if (zone->per_cpu_pageset != &boot_pageset) {
  		for_each_online_cpu(cpu) {
  			pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
  			drain_zonestat(zone, pzstats);
  		}
  		free_percpu(zone->per_cpu_pageset);
  		free_percpu(zone->per_cpu_zonestats);
  		zone->per_cpu_pageset = &boot_pageset;
  		zone->per_cpu_zonestats = &boot_zonestats;
  	}
  }
  
  #ifdef CONFIG_MEMORY_HOTREMOVE
  /*
   * All pages in the range must be in a single zone, must not contain holes,
   * must span full sections, and must be isolated before calling this function.
   */
  void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn = start_pfn;
  	struct page *page;
  	struct zone *zone;
  	unsigned int order;
  	unsigned long flags;
  
  	offline_mem_sections(pfn, end_pfn);
  	zone = page_zone(pfn_to_page(pfn));
  	spin_lock_irqsave(&zone->lock, flags);
  	while (pfn < end_pfn) {
  		page = pfn_to_page(pfn);
  		/*
  		 * The HWPoisoned page may be not in buddy system, and
  		 * page_count() is not 0.
  		 */
  		if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
  			pfn++;
  			continue;
  		}
  		/*
  		 * At this point all remaining PageOffline() pages have a
  		 * reference count of 0 and can simply be skipped.
  		 */
  		if (PageOffline(page)) {
  			BUG_ON(page_count(page));
  			BUG_ON(PageBuddy(page));
  			pfn++;
  			continue;
  		}
  
  		BUG_ON(page_count(page));
  		BUG_ON(!PageBuddy(page));
  		order = buddy_order(page);
  		del_page_from_free_list(page, zone, order);
  		pfn += (1 << order);
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  #endif
  
  /*
   * This function returns a stable result only if called under zone lock.
   */
  bool is_free_buddy_page(struct page *page)
  {
  	unsigned long pfn = page_to_pfn(page);
  	unsigned int order;
  
  	for (order = 0; order < MAX_ORDER; order++) {
  		struct page *page_head = page - (pfn & ((1 << order) - 1));
  
  		if (PageBuddy(page_head) &&
  		    buddy_order_unsafe(page_head) >= order)
  			break;
  	}
  
  	return order < MAX_ORDER;
  }
  
  #ifdef CONFIG_MEMORY_FAILURE
  /*
   * Break down a higher-order page in sub-pages, and keep our target out of
   * buddy allocator.
   */
  static void break_down_buddy_pages(struct zone *zone, struct page *page,
  				   struct page *target, int low, int high,
  				   int migratetype)
  {
  	unsigned long size = 1 << high;
  	struct page *current_buddy, *next_page;
  
  	while (high > low) {
  		high--;
  		size >>= 1;
  
  		if (target >= &page[size]) {
  			next_page = page + size;
  			current_buddy = page;
  		} else {
  			next_page = page;
  			current_buddy = page + size;
  		}
  
  		if (set_page_guard(zone, current_buddy, high, migratetype))
  			continue;
  
  		if (current_buddy != target) {
  			add_to_free_list(current_buddy, zone, high, migratetype);
  			set_buddy_order(current_buddy, high);
  			page = next_page;
  		}
  	}
  }
  
  /*
   * Take a page that will be marked as poisoned off the buddy allocator.
   */
  bool take_page_off_buddy(struct page *page)
  {
  	struct zone *zone = page_zone(page);
  	unsigned long pfn = page_to_pfn(page);
  	unsigned long flags;
  	unsigned int order;
  	bool ret = false;
  
  	spin_lock_irqsave(&zone->lock, flags);
  	for (order = 0; order < MAX_ORDER; order++) {
  		struct page *page_head = page - (pfn & ((1 << order) - 1));
  		int page_order = buddy_order(page_head);
  
  		if (PageBuddy(page_head) && page_order >= order) {
  			unsigned long pfn_head = page_to_pfn(page_head);
  			int migratetype = get_pfnblock_migratetype(page_head,
  								   pfn_head);
  
  			del_page_from_free_list(page_head, zone, page_order);
  			break_down_buddy_pages(zone, page_head, page, 0,
  						page_order, migratetype);
  			SetPageHWPoisonTakenOff(page);
  			if (!is_migrate_isolate(migratetype))
  				__mod_zone_freepage_state(zone, -1, migratetype);
  			ret = true;
  			break;
  		}
  		if (page_count(page_head) > 0)
  			break;
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  	return ret;
  }
  
  /*
   * Cancel takeoff done by take_page_off_buddy().
   */
  bool put_page_back_buddy(struct page *page)
  {
  	struct zone *zone = page_zone(page);
  	unsigned long pfn = page_to_pfn(page);
  	unsigned long flags;
  	int migratetype = get_pfnblock_migratetype(page, pfn);
  	bool ret = false;
  
  	spin_lock_irqsave(&zone->lock, flags);
  	if (put_page_testzero(page)) {
  		ClearPageHWPoisonTakenOff(page);
  		__free_one_page(page, pfn, zone, 0, migratetype, FPI_NONE);
  		if (TestClearPageHWPoison(page)) {
  			num_poisoned_pages_dec();
  			ret = true;
  		}
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  
  	return ret;
  }
  #endif
  
  #ifdef CONFIG_ZONE_DMA
  bool has_managed_dma(void)
  {
  	struct pglist_data *pgdat;
  
  	for_each_online_pgdat(pgdat) {
  		struct zone *zone = &pgdat->node_zones[ZONE_DMA];
  
  		if (managed_zone(zone))
  			return true;
  	}
  	return false;
  }
  #endif /* CONFIG_ZONE_DMA */
  