text: /*
   *  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/swap.h>
  #include <linux/interrupt.h>
  #include <linux/pagemap.h>
  #include <linux/jiffies.h>
  #include <linux/bootmem.h>
  #include <linux/memblock.h>
  #include <linux/compiler.h>
  #include <linux/kernel.h>
  #include <linux/kmemcheck.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/notifier.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/sort.h>
  #include <linux/pfn.h>
  #include <linux/backing-dev.h>
  #include <linux/fault-inject.h>
  #include <linux/page-isolation.h>
  #include <linux/page_ext.h>
  #include <linux/debugobjects.h>
  #include <linux/kmemleak.h>
  #include <linux/compaction.h>
  #include <trace/events/kmem.h>
  #include <linux/prefetch.h>
  #include <linux/mm_inline.h>
  #include <linux/migrate.h>
  #include <linux/page_ext.h>
  #include <linux/hugetlb.h>
  #include <linux/sched/rt.h>
  #include <linux/page_owner.h>
  #include <linux/kthread.h>
  #include <linux/memcontrol.h>
  #include <linux/show_mem_notifier.h>
  #include <linux/psi.h>
  
  #include <asm/sections.h>
  #include <asm/tlbflush.h>
  #include <asm/div64.h>
  #include "internal.h"
  
  atomic_long_t kswapd_waiters = ATOMIC_LONG_INIT(0);
  
  /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
  static DEFINE_MUTEX(pcp_batch_high_lock);
  #define MIN_PERCPU_PAGELIST_FRACTION	(8)
  
  #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
  DEFINE_PER_CPU(int, numa_node);
  EXPORT_PER_CPU_SYMBOL(numa_node);
  #endif
  
  #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_);
  int _node_numa_mem_[MAX_NUMNODES];
  #endif
  
  #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
  #ifdef CONFIG_MOVABLE_NODE
  	[N_MEMORY] = { { [0] = 1UL } },
  #endif
  	[N_CPU] = { { [0] = 1UL } },
  #endif	/* NUMA */
  };
  EXPORT_SYMBOL(node_states);
  
  /* Protect totalram_pages and zone->managed_pages */
  static DEFINE_SPINLOCK(managed_page_count_lock);
  
  unsigned long totalram_pages __read_mostly;
  unsigned long totalreserve_pages __read_mostly;
  unsigned long totalcma_pages __read_mostly;
  
  int percpu_pagelist_fraction;
  gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
  
  /*
   * 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 pm_mutex held (gfp_allowed_mask also should
   * only be modified with pm_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(&pm_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(&pm_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);
  
  /*
   * 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-1] = {
  #ifdef CONFIG_ZONE_DMA
  	 256,
  #endif
  #ifdef CONFIG_ZONE_DMA32
  	 256,
  #endif
  #ifdef CONFIG_HIGHMEM
  	 32,
  #endif
  	 32,
  };
  
  EXPORT_SYMBOL(totalram_pages);
  
  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
  };
  
  char * const migratetype_names[MIGRATE_TYPES] = {
  	"Unmovable",
  	"Movable",
  	"Reclaimable",
  #ifdef CONFIG_CMA
  	"CMA",
  #endif
  	"HighAtomic",
  #ifdef CONFIG_MEMORY_ISOLATION
  	"Isolate",
  #endif
  };
  
  compound_page_dtor * const compound_page_dtors[] = {
  	NULL,
  	free_compound_page,
  #ifdef CONFIG_HUGETLB_PAGE
  	free_huge_page,
  #endif
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	free_transhuge_page,
  #endif
  };
  
  /*
   * Try to keep at least this much lowmem free.  Do not allow normal
   * allocations below this point, only high priority ones. Automatically
   * tuned according to the amount of memory in the system.
   */
  int min_free_kbytes = 1024;
  int user_min_free_kbytes = -1;
  int watermark_scale_factor;
  
  /*
   * Extra memory for the system to try freeing. Used to temporarily
   * free memory, to make space for new workloads. Anyone can allocate
   * down to the min watermarks controlled by min_free_kbytes above.
   */
  int extra_free_kbytes;
  
  static unsigned long __meminitdata nr_kernel_pages;
  static unsigned long __meminitdata nr_all_pages;
  static unsigned long __meminitdata dma_reserve;
  
  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
  static unsigned long __meminitdata arch_zone_lowest_possible_pfn[MAX_NR_ZONES];
  static unsigned long __meminitdata arch_zone_highest_possible_pfn[MAX_NR_ZONES];
  static unsigned long __initdata required_kernelcore;
  static unsigned long __initdata required_movablecore;
  static unsigned long __meminitdata zone_movable_pfn[MAX_NUMNODES];
  static bool mirrored_kernelcore;
  
  /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
  int movable_zone;
  EXPORT_SYMBOL(movable_zone);
  #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
  
  #if MAX_NUMNODES > 1
  int nr_node_ids __read_mostly = MAX_NUMNODES;
  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
  
  /*
   * Determine how many pages need to be initialized durig early boot
   * (non-deferred initialization).
   * The value of first_deferred_pfn will be set later, once non-deferred pages
   * are initialized, but for now set it ULONG_MAX.
   */
  static inline void reset_deferred_meminit(pg_data_t *pgdat)
  {
  	phys_addr_t start_addr, end_addr;
  	unsigned long max_pgcnt;
  	unsigned long reserved;
  
  	/*
  	 * Initialise at least 2G of a node but also take into account that
  	 * two large system hashes that can take up 1GB for 0.25TB/node.
  	 */
  	max_pgcnt = max(2UL << (30 - PAGE_SHIFT),
  			(pgdat->node_spanned_pages >> 8));
  
  	/*
  	 * Compensate the all the memblock reservations (e.g. crash kernel)
  	 * from the initial estimation to make sure we will initialize enough
  	 * memory to boot.
  	 */
  	start_addr = PFN_PHYS(pgdat->node_start_pfn);
  	end_addr = PFN_PHYS(pgdat->node_start_pfn + max_pgcnt);
  	reserved = memblock_reserved_memory_within(start_addr, end_addr);
  	max_pgcnt += PHYS_PFN(reserved);
  
  	pgdat->static_init_pgcnt = min(max_pgcnt, pgdat->node_spanned_pages);
  	pgdat->first_deferred_pfn = ULONG_MAX;
  }
  
  /* 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 false when the remaining initialisation should be deferred until
   * later in the boot cycle when it can be parallelised.
   */
  static inline bool update_defer_init(pg_data_t *pgdat,
  				unsigned long pfn, unsigned long zone_end,
  				unsigned long *nr_initialised)
  {
  	/* Always populate low zones for address-contrained allocations */
  	if (zone_end < pgdat_end_pfn(pgdat))
  		return true;
  	(*nr_initialised)++;
  	if ((*nr_initialised > pgdat->static_init_pgcnt) &&
  	    (pfn & (PAGES_PER_SECTION - 1)) == 0) {
  		pgdat->first_deferred_pfn = pfn;
  		return false;
  	}
  
  	return true;
  }
  #else
  static inline void reset_deferred_meminit(pg_data_t *pgdat)
  {
  }
  
  static inline bool early_page_uninitialised(unsigned long pfn)
  {
  	return false;
  }
  
  static inline bool update_defer_init(pg_data_t *pgdat,
  				unsigned long pfn, unsigned long zone_end,
  				unsigned long *nr_initialised)
  {
  	return true;
  }
  #endif
  
  /* Return a pointer to the bitmap storing bits affecting a block of pages */
  static inline unsigned long *get_pageblock_bitmap(struct page *page,
  							unsigned long pfn)
  {
  #ifdef CONFIG_SPARSEMEM
  	return __pfn_to_section(pfn)->pageblock_flags;
  #else
  	return page_zone(page)->pageblock_flags;
  #endif /* CONFIG_SPARSEMEM */
  }
  
  static inline int pfn_to_bitidx(struct page *page, unsigned long pfn)
  {
  #ifdef CONFIG_SPARSEMEM
  	pfn &= (PAGES_PER_SECTION-1);
  	return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
  #else
  	pfn = pfn - round_down(page_zone(page)->zone_start_pfn, pageblock_nr_pages);
  	return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
  #endif /* CONFIG_SPARSEMEM */
  }
  
  /**
   * 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
   * @end_bitidx: The last bit of interest to retrieve
   * @mask: mask of bits that the caller is interested in
   *
   * Return: pageblock_bits flags
   */
  static __always_inline unsigned long __get_pfnblock_flags_mask(struct page *page,
  					unsigned long pfn,
  					unsigned long end_bitidx,
  					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];
  	bitidx += end_bitidx;
  	return (word >> (BITS_PER_LONG - bitidx - 1)) & mask;
  }
  
  unsigned long get_pfnblock_flags_mask(struct page *page, unsigned long pfn,
  					unsigned long end_bitidx,
  					unsigned long mask)
  {
  	return __get_pfnblock_flags_mask(page, pfn, end_bitidx, mask);
  }
  
  static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
  {
  	return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, 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
   * @end_bitidx: The last bit of interest
   * @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 end_bitidx,
  					unsigned long mask)
  {
  	unsigned long *bitmap;
  	unsigned long bitidx, word_bitidx;
  	unsigned long old_word, word;
  
  	BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
  
  	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);
  
  	bitidx += end_bitidx;
  	mask <<= (BITS_PER_LONG - bitidx - 1);
  	flags <<= (BITS_PER_LONG - bitidx - 1);
  
  	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_pageblock_flags_group(page, (unsigned long)migratetype,
  					PB_migrate, PB_migrate_end);
  }
  
  #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 (!pfn_valid_within(page_to_pfn(page)))
  		return 0;
  	if (zone != page_zone(page))
  		return 0;
  
  	return 1;
  }
  /*
   * Temporary debugging check for pages not lying within a given zone.
   */
  static int 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 bad_range(struct zone *zone, struct page *page)
  {
  	return 0;
  }
  #endif
  
  static void bad_page(struct page *page, const char *reason,
  		unsigned long bad_flags)
  {
  	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);
  	bad_flags &= page->flags;
  	if (bad_flags)
  		pr_alert("bad because of flags: %#lx(%pGp)\n",
  						bad_flags, &bad_flags);
  	dump_page_owner(page);
  
  	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);
  }
  
  /*
   * 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)
  {
  	__free_pages_ok(page, compound_order(page));
  }
  
  void prep_compound_page(struct page *page, unsigned int order)
  {
  	int i;
  	int nr_pages = 1 << order;
  
  	set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
  	set_compound_order(page, order);
  	__SetPageHead(page);
  	for (i = 1; i < nr_pages; i++) {
  		struct page *p = page + i;
  		set_page_count(p, 0);
  		p->mapping = TAIL_MAPPING;
  		set_compound_head(p, page);
  	}
  	atomic_set(compound_mapcount_ptr(page), -1);
  }
  
  #ifdef CONFIG_DEBUG_PAGEALLOC
  unsigned int _debug_guardpage_minorder;
  bool _debug_pagealloc_enabled __read_mostly
  			= IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
  EXPORT_SYMBOL(_debug_pagealloc_enabled);
  bool _debug_guardpage_enabled __read_mostly;
  
  static int __init early_debug_pagealloc(char *buf)
  {
  	if (!buf)
  		return -EINVAL;
  	return kstrtobool(buf, &_debug_pagealloc_enabled);
  }
  early_param("debug_pagealloc", early_debug_pagealloc);
  
  static bool need_debug_guardpage(void)
  {
  	/* If we don't use debug_pagealloc, we don't need guard page */
  	if (!debug_pagealloc_enabled())
  		return false;
  
  	if (!debug_guardpage_minorder())
  		return false;
  
  	return true;
  }
  
  static void init_debug_guardpage(void)
  {
  	if (!debug_pagealloc_enabled())
  		return;
  
  	if (!debug_guardpage_minorder())
  		return;
  
  	_debug_guardpage_enabled = true;
  }
  
  struct page_ext_operations debug_guardpage_ops = {
  	.need = need_debug_guardpage,
  	.init = init_debug_guardpage,
  };
  
  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)
  {
  	struct page_ext *page_ext;
  
  	if (!debug_guardpage_enabled())
  		return false;
  
  	if (order >= debug_guardpage_minorder())
  		return false;
  
  	page_ext = lookup_page_ext(page);
  	if (unlikely(!page_ext))
  		return false;
  
  	__set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
  
  	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)
  {
  	struct page_ext *page_ext;
  
  	if (!debug_guardpage_enabled())
  		return;
  
  	page_ext = lookup_page_ext(page);
  	if (unlikely(!page_ext))
  		return;
  
  	__clear_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
  
  	set_page_private(page, 0);
  	if (!is_migrate_isolate(migratetype))
  		__mod_zone_freepage_state(zone, (1 << order), migratetype);
  }
  #else
  struct page_ext_operations debug_guardpage_ops;
  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
  
  static inline void set_page_order(struct page *page, unsigned int order)
  {
  	set_page_private(page, order);
  	__SetPageBuddy(page);
  }
  
  static inline void rmv_page_order(struct page *page)
  {
  	__ClearPageBuddy(page);
  	set_page_private(page, 0);
  }
  
  /*
   * This function checks whether a page is free && is the buddy
   * we can do coalesce a page and its buddy if
   * (a) the buddy is not in a hole &&
   * (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 ->_mapcount
   * PAGE_BUDDY_MAPCOUNT_VALUE.
   * Setting, clearing, and testing _mapcount PAGE_BUDDY_MAPCOUNT_VALUE is
   * serialized by zone->lock.
   *
   * For recording page's order, we use page_private(page).
   */
  static inline int page_is_buddy(struct page *page, struct page *buddy,
  							unsigned int order)
  {
  	if (!pfn_valid_within(page_to_pfn(buddy)))
  		return 0;
  
  	if (page_is_guard(buddy) && page_order(buddy) == order) {
  		if (page_zone_id(page) != page_zone_id(buddy))
  			return 0;
  
  		VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
  
  		return 1;
  	}
  
  	if (PageBuddy(buddy) && page_order(buddy) == order) {
  		/*
  		 * 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 0;
  
  		VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
  
  		return 1;
  	}
  	return 0;
  }
  
  /*
   * 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 _mapcount
   * PAGE_BUDDY_MAPCOUNT_VALUE. 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)
  {
  	unsigned long page_idx;
  	unsigned long combined_idx;
  	unsigned long uninitialized_var(buddy_idx);
  	struct page *buddy;
  	unsigned int max_order;
  
  	max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1);
  
  	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);
  
  	page_idx = pfn & ((1 << MAX_ORDER) - 1);
  
  	VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page);
  	VM_BUG_ON_PAGE(bad_range(zone, page), page);
  
  continue_merging:
  	while (order < max_order - 1) {
  		buddy_idx = __find_buddy_index(page_idx, order);
  		buddy = page + (buddy_idx - page_idx);
  		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 {
  			list_del(&buddy->lru);
  			zone->free_area[order].nr_free--;
  			rmv_page_order(buddy);
  		}
  		combined_idx = buddy_idx & page_idx;
  		page = page + (combined_idx - page_idx);
  		page_idx = combined_idx;
  		order++;
  	}
  	if (max_order < MAX_ORDER) {
  		/* 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_idx = __find_buddy_index(page_idx, order);
  			buddy = page + (buddy_idx - page_idx);
  			buddy_mt = get_pageblock_migratetype(buddy);
  
  			if (migratetype != buddy_mt
  					&& (is_migrate_isolate(migratetype) ||
  						is_migrate_isolate(buddy_mt)))
  				goto done_merging;
  		}
  		max_order++;
  		goto continue_merging;
  	}
  
  done_merging:
  	set_page_order(page, order);
  
  	/*
  	 * 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
  	 */
  	if ((order < MAX_ORDER-2) && pfn_valid_within(page_to_pfn(buddy))) {
  		struct page *higher_page, *higher_buddy;
  		combined_idx = buddy_idx & page_idx;
  		higher_page = page + (combined_idx - page_idx);
  		buddy_idx = __find_buddy_index(combined_idx, order + 1);
  		higher_buddy = higher_page + (buddy_idx - combined_idx);
  		if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
  			list_add_tail(&page->lru,
  				&zone->free_area[order].free_list[migratetype]);
  			goto out;
  		}
  	}
  
  	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
  out:
  	zone->free_area[order].nr_free++;
  }
  
  /*
   * 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
  			(unsigned long)page->mem_cgroup |
  #endif
  			(page->flags & check_flags)))
  		return false;
  
  	return true;
  }
  
  static void free_pages_check_bad(struct page *page)
  {
  	const char *bad_reason;
  	unsigned long bad_flags;
  
  	bad_reason = NULL;
  	bad_flags = 0;
  
  	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 & PAGE_FLAGS_CHECK_AT_FREE)) {
  		bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
  		bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
  	}
  #ifdef CONFIG_MEMCG
  	if (unlikely(page->mem_cgroup))
  		bad_reason = "page still charged to cgroup";
  #endif
  	bad_page(page, bad_reason, bad_flags);
  }
  
  static inline int free_pages_check(struct page *page)
  {
  	if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
  		return 0;
  
  	/* Something has gone sideways, find it */
  	free_pages_check_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 is compound_mapcount() */
  		if (unlikely(compound_mapcount(page))) {
  			bad_page(page, "nonzero compound_mapcount", 0);
  			goto out;
  		}
  		break;
  	case 2:
  		/*
  		 * the second tail page: ->mapping is
  		 * page_deferred_list().next -- ignore value.
  		 */
  		break;
  	default:
  		if (page->mapping != TAIL_MAPPING) {
  			bad_page(page, "corrupted mapping in tail page", 0);
  			goto out;
  		}
  		break;
  	}
  	if (unlikely(!PageTail(page))) {
  		bad_page(page, "PageTail not set", 0);
  		goto out;
  	}
  	if (unlikely(compound_head(page) != head_page)) {
  		bad_page(page, "compound_head not consistent", 0);
  		goto out;
  	}
  	ret = 0;
  out:
  	page->mapping = NULL;
  	clear_compound_head(page);
  	return ret;
  }
  
  static __always_inline bool free_pages_prepare(struct page *page,
  					unsigned int order, bool check_free)
  {
  	int bad = 0;
  
  	VM_BUG_ON_PAGE(PageTail(page), page);
  
  	trace_mm_page_free(page, order);
  	kmemcheck_free_shadow(page, order);
  
  	/*
  	 * 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);
  		for (i = 1; i < (1 << order); i++) {
  			if (compound)
  				bad += free_tail_pages_check(page, page + i);
  			if (unlikely(free_pages_check(page + i))) {
  				bad++;
  				continue;
  			}
  			(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
  		}
  	}
  	if (PageMappingFlags(page))
  		page->mapping = NULL;
  	if (memcg_kmem_enabled() && PageKmemcg(page))
  		memcg_kmem_uncharge(page, order);
  	if (check_free)
  		bad += free_pages_check(page);
  	if (bad)
  		return false;
  
  	page_cpupid_reset_last(page);
  	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
  	reset_page_owner(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);
  	}
  	arch_free_page(page, order);
  	kernel_poison_pages(page, 1 << order, 0);
  	kernel_map_pages(page, 1 << order, 0);
  	kasan_free_pages(page, order);
  
  	return true;
  }
  
  #ifdef CONFIG_DEBUG_VM
  static inline bool free_pcp_prepare(struct page *page)
  {
  	return free_pages_prepare(page, 0, true);
  }
  
  static inline bool bulkfree_pcp_prepare(struct page *page)
  {
  	return false;
  }
  #else
  static bool free_pcp_prepare(struct page *page)
  {
  	return free_pages_prepare(page, 0, false);
  }
  
  static bool bulkfree_pcp_prepare(struct page *page)
  {
  	return free_pages_check(page);
  }
  #endif /* CONFIG_DEBUG_VM */
  
  /*
   * Frees a number of pages from the PCP lists
   * Assumes all pages on list are in same zone, and of same order.
   * count is the number of pages to free.
   *
   * If the zone was previously in an "all pages pinned" state then look to
   * see if this freeing clears that state.
   *
   * And clear the zone's pages_scanned counter, to hold off the "all pages are
   * pinned" detection logic.
   */
  static void free_pcppages_bulk(struct zone *zone, int count,
  					struct per_cpu_pages *pcp)
  {
  	int migratetype = 0;
  	int batch_free = 0;
  	bool isolated_pageblocks;
  
  	spin_lock(&zone->lock);
  	isolated_pageblocks = has_isolate_pageblock(zone);
  
  	while (count) {
  		struct page *page;
  		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 (++migratetype == MIGRATE_PCPTYPES)
  				migratetype = 0;
  			list = &pcp->lists[migratetype];
  		} while (list_empty(list));
  
  		/* This is the only non-empty list. Free them all. */
  		if (batch_free == MIGRATE_PCPTYPES)
  			batch_free = count;
  
  		do {
  			int mt;	/* migratetype of the to-be-freed page */
  
  			page = list_last_entry(list, struct page, lru);
  			/* must delete as __free_one_page list manipulates */
  			list_del(&page->lru);
  
  			mt = get_pcppage_migratetype(page);
  			/* 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);
  
  			if (bulkfree_pcp_prepare(page))
  				continue;
  
  			__free_one_page(page, page_to_pfn(page), zone, 0, mt);
  			trace_mm_page_pcpu_drain(page, 0, mt);
  		} while (--count && --batch_free && !list_empty(list));
  	}
  	spin_unlock(&zone->lock);
  }
  
  static void free_one_page(struct zone *zone,
  				struct page *page, unsigned long pfn,
  				unsigned int order,
  				int migratetype)
  {
  	spin_lock(&zone->lock);
  	if (unlikely(has_isolate_pageblock(zone) ||
  		is_migrate_isolate(migratetype))) {
  		migratetype = get_pfnblock_migratetype(page, pfn);
  	}
  	__free_one_page(page, pfn, zone, order, migratetype);
  	spin_unlock(&zone->lock);
  }
  
  static void __meminit __init_single_page(struct page *page, unsigned long pfn,
  				unsigned long zone, int nid)
  {
  	set_page_links(page, zone, nid, pfn);
  	init_page_count(page);
  	page_mapcount_reset(page);
  	page_cpupid_reset_last(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
  }
  
  static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
  					int nid)
  {
  	return __init_single_page(pfn_to_page(pfn), pfn, zone, nid);
  }
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  static void 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 (pfn >= zone->zone_start_pfn && pfn < zone_end_pfn(zone))
  			break;
  	}
  	__init_single_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);
  
  			SetPageReserved(page);
  		}
  	}
  }
  
  static void __free_pages_ok(struct page *page, unsigned int order)
  {
  	unsigned long flags;
  	int migratetype;
  	unsigned long pfn = page_to_pfn(page);
  
  	if (!free_pages_prepare(page, order, true))
  		return;
  
  	migratetype = get_pfnblock_migratetype(page, pfn);
  	local_irq_save(flags);
  	__count_vm_events(PGFREE, 1 << order);
  	free_one_page(page_zone(page), page, pfn, order, migratetype);
  	local_irq_restore(flags);
  }
  
  static void __free_pages_boot_core(struct page *page, unsigned int order)
  {
  	unsigned int nr_pages = 1 << order;
  	struct page *p = page;
  	unsigned int loop;
  
  	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);
  
  	page_zone(page)->managed_pages += nr_pages;
  	set_page_refcounted(page);
  	__free_pages(page, order);
  }
  
  #if defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) || \
  	defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP)
  
  static struct mminit_pfnnid_cache early_pfnnid_cache __meminitdata;
  
  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
  
  #ifdef CONFIG_NODES_SPAN_OTHER_NODES
  static inline bool __meminit meminit_pfn_in_nid(unsigned long pfn, int node,
  					struct mminit_pfnnid_cache *state)
  {
  	int nid;
  
  	nid = __early_pfn_to_nid(pfn, state);
  	if (nid >= 0 && nid != node)
  		return false;
  	return true;
  }
  
  /* Only safe to use early in boot when initialisation is single-threaded */
  static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
  {
  	return meminit_pfn_in_nid(pfn, node, &early_pfnnid_cache);
  }
  
  #else
  
  static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
  {
  	return true;
  }
  static inline bool __meminit meminit_pfn_in_nid(unsigned long pfn, int node,
  					struct mminit_pfnnid_cache *state)
  {
  	return true;
  }
  #endif
  
  
  void __free_pages_bootmem(struct page *page, unsigned long pfn,
  							unsigned int order)
  {
  	if (early_page_uninitialised(pfn))
  		return;
  	return __free_pages_boot_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. The scanners then need to
   * use only pfn_valid_within() check for arches that allow holes within
   * pageblocks.
   *
   * 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_page(start_pfn);
  
  	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(struct page *page,
  					unsigned long pfn, int nr_pages)
  {
  	int i;
  
  	if (!page)
  		return;
  
  	/* 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_boot_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_boot_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);
  }
  
  /* Initialise remaining memory on a node */
  static int __init deferred_init_memmap(void *data)
  {
  	pg_data_t *pgdat = data;
  	int nid = pgdat->node_id;
  	struct mminit_pfnnid_cache nid_init_state = { };
  	unsigned long start = jiffies;
  	unsigned long nr_pages = 0;
  	unsigned long walk_start, walk_end;
  	int i, zid;
  	struct zone *zone;
  	unsigned long first_init_pfn = pgdat->first_deferred_pfn;
  	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
  
  	if (first_init_pfn == ULONG_MAX) {
  		pgdat_init_report_one_done();
  		return 0;
  	}
  
  	/* Bind memory initialisation thread to a local node if possible */
  	if (!cpumask_empty(cpumask))
  		set_cpus_allowed_ptr(current, cpumask);
  
  	/* 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;
  
  	/* 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;
  	}
  
  	for_each_mem_pfn_range(i, nid, &walk_start, &walk_end, NULL) {
  		unsigned long pfn, end_pfn;
  		struct page *page = NULL;
  		struct page *free_base_page = NULL;
  		unsigned long free_base_pfn = 0;
  		int nr_to_free = 0;
  
  		end_pfn = min(walk_end, zone_end_pfn(zone));
  		pfn = first_init_pfn;
  		if (pfn < walk_start)
  			pfn = walk_start;
  		if (pfn < zone->zone_start_pfn)
  			pfn = zone->zone_start_pfn;
  
  		for (; pfn < end_pfn; pfn++) {
  			if (!pfn_valid_within(pfn))
  				goto free_range;
  
  			/*
  			 * Ensure pfn_valid is checked every
  			 * pageblock_nr_pages for memory holes
  			 */
  			if ((pfn & (pageblock_nr_pages - 1)) == 0) {
  				if (!pfn_valid(pfn)) {
  					page = NULL;
  					goto free_range;
  				}
  			}
  
  			if (!meminit_pfn_in_nid(pfn, nid, &nid_init_state)) {
  				page = NULL;
  				goto free_range;
  			}
  
  			/* Minimise pfn page lookups and scheduler checks */
  			if (page && (pfn & (pageblock_nr_pages - 1)) != 0) {
  				page++;
  			} else {
  				nr_pages += nr_to_free;
  				deferred_free_range(free_base_page,
  						free_base_pfn, nr_to_free);
  				free_base_page = NULL;
  				free_base_pfn = nr_to_free = 0;
  
  				page = pfn_to_page(pfn);
  				cond_resched();
  			}
  
  			if (page->flags) {
  				VM_BUG_ON(page_zone(page) != zone);
  				goto free_range;
  			}
  
  			__init_single_page(page, pfn, zid, nid);
  			if (!free_base_page) {
  				free_base_page = page;
  				free_base_pfn = pfn;
  				nr_to_free = 0;
  			}
  			nr_to_free++;
  
  			/* Where possible, batch up pages for a single free */
  			continue;
  free_range:
  			/* Free the current block of pages to allocator */
  			nr_pages += nr_to_free;
  			deferred_free_range(free_base_page, free_base_pfn,
  								nr_to_free);
  			free_base_page = NULL;
  			free_base_pfn = nr_to_free = 0;
  		}
  		/* Free the last block of pages to allocator */
  		nr_pages += nr_to_free;
  		deferred_free_range(free_base_page, free_base_pfn, nr_to_free);
  
  		first_init_pfn = max(end_pfn, first_init_pfn);
  	}
  
  	/* Sanity check that the next zone really is unpopulated */
  	WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));
  
  	pr_info("node %d initialised, %lu pages in %ums\n", nid, nr_pages,
  					jiffies_to_msecs(jiffies - start));
  
  	pgdat_init_report_one_done();
  	return 0;
  }
  #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
  
  void __init page_alloc_init_late(void)
  {
  	struct zone *zone;
  
  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
  	int nid;
  
  	/* 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);
  
  	/* Reinit limits that are based on free pages after the kernel is up */
  	files_maxfiles_init();
  #endif
  #ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
  	/* Discard memblock private memory */
  	memblock_discard();
  #endif
  
  	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);
  }
  #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, struct free_area *area,
  	int migratetype)
  {
  	unsigned long size = 1 << high;
  
  	while (high > low) {
  		area--;
  		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;
  
  		list_add(&page[size].lru, &area->free_list[migratetype]);
  		area->nr_free++;
  		set_page_order(&page[size], high);
  	}
  }
  
  static void check_new_page_bad(struct page *page)
  {
  	const char *bad_reason = NULL;
  	unsigned long bad_flags = 0;
  
  	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 _count";
  	if (unlikely(page->flags & __PG_HWPOISON)) {
  		bad_reason = "HWPoisoned (hardware-corrupted)";
  		bad_flags = __PG_HWPOISON;
  		/* Don't complain about hwpoisoned pages */
  		page_mapcount_reset(page); /* remove PageBuddy */
  		return;
  	}
  	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
  		bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
  		bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
  	}
  #ifdef CONFIG_MEMCG
  	if (unlikely(page->mem_cgroup))
  		bad_reason = "page still charged to cgroup";
  #endif
  	bad_page(page, bad_reason, bad_flags);
  }
  
  /*
   * 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;
  }
  
  static inline bool free_pages_prezeroed(void)
  {
  	return IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) &&
  		page_poisoning_enabled();
  }
  
  #ifdef CONFIG_DEBUG_VM
  static bool check_pcp_refill(struct page *page)
  {
  	return false;
  }
  
  static bool check_new_pcp(struct page *page)
  {
  	return check_new_page(page);
  }
  #else
  static bool check_pcp_refill(struct page *page)
  {
  	return check_new_page(page);
  }
  static bool check_new_pcp(struct page *page)
  {
  	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);
  	kasan_alloc_pages(page, order);
  	kernel_map_pages(page, 1 << order, 1);
  	kernel_poison_pages(page, 1 << order, 1);
  	set_page_owner(page, order, gfp_flags);
  }
  
  static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
  							unsigned int alloc_flags)
  {
  	int i;
  
  	post_alloc_hook(page, order, gfp_flags);
  
  	if (!free_pages_prezeroed() && (gfp_flags & __GFP_ZERO))
  		for (i = 0; i < (1 << order); i++)
  			clear_highpage(page + i);
  
  	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 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 = list_first_entry_or_null(&area->free_list[migratetype],
  							struct page, lru);
  		if (!page)
  			continue;
  		list_del(&page->lru);
  		rmv_page_order(page);
  		area->nr_free--;
  		expand(zone, page, order, current_order, area, 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][4] = {
  	[MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,   MIGRATE_TYPES },
  	[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE,   MIGRATE_TYPES },
  	[MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
  #ifdef CONFIG_CMA
  	[MIGRATE_CMA]         = { MIGRATE_TYPES }, /* Never used */
  #endif
  #ifdef CONFIG_MEMORY_ISOLATION
  	[MIGRATE_ISOLATE]     = { MIGRATE_TYPES }, /* Never used */
  #endif
  };
  
  int *get_migratetype_fallbacks(int mtype)
  {
  	return fallbacks[mtype];
  }
  
  #ifdef CONFIG_CMA
  static 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 free lists 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()
   */
  int move_freepages(struct zone *zone,
  			  struct page *start_page, struct page *end_page,
  			  int migratetype)
  {
  	struct page *page;
  	unsigned int order;
  	int pages_moved = 0;
  
  #ifndef CONFIG_HOLES_IN_ZONE
  	/*
  	 * page_zone is not safe to call in this context when
  	 * CONFIG_HOLES_IN_ZONE is set. This bug check is probably redundant
  	 * anyway as we check zone boundaries in move_freepages_block().
  	 * Remove at a later date when no bug reports exist related to
  	 * grouping pages by mobility
  	 */
  	VM_BUG_ON(page_zone(start_page) != page_zone(end_page));
  #endif
  
  	for (page = start_page; page <= end_page;) {
  		if (!pfn_valid_within(page_to_pfn(page))) {
  			page++;
  			continue;
  		}
  
  		/* Make sure we are not inadvertently changing nodes */
  		VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
  
  		if (!PageBuddy(page)) {
  			page++;
  			continue;
  		}
  
  		order = page_order(page);
  		list_move(&page->lru,
  			  &zone->free_area[order].free_list[migratetype]);
  		page += 1 << order;
  		pages_moved += 1 << order;
  	}
  
  	return pages_moved;
  }
  
  int move_freepages_block(struct zone *zone, struct page *page,
  				int migratetype)
  {
  	unsigned long start_pfn, end_pfn;
  	struct page *start_page, *end_page;
  
  	start_pfn = page_to_pfn(page);
  	start_pfn = start_pfn & ~(pageblock_nr_pages-1);
  	start_page = pfn_to_page(start_pfn);
  	end_page = start_page + 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_page = page;
  	if (!zone_spans_pfn(zone, end_pfn))
  		return 0;
  
  	return move_freepages(zone, start_page, end_page, migratetype);
  }
  
  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;
  }
  
  /*
   * 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 and check whether half of pages are moved or not. If half of
   * pages are moved, we can change migratetype of pageblock and permanently
   * use it's pages as requested migratetype in the future.
   */
  static void steal_suitable_fallback(struct zone *zone, struct page *page,
  							  int start_type)
  {
  	unsigned int current_order = page_order(page);
  	int pages;
  
  	/* Take ownership for orders >= pageblock_order */
  	if (current_order >= pageblock_order) {
  		change_pageblock_range(page, current_order, start_type);
  		return;
  	}
  
  	pages = move_freepages_block(zone, page, start_type);
  
  	/* Claim the whole block if over half of it is free */
  	if (pages >= (1 << (pageblock_order-1)) ||
  			page_group_by_mobility_disabled)
  		set_pageblock_migratetype(page, 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 (list_empty(&area->free_list[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 / 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 (mt != MIGRATE_HIGHATOMIC &&
  			!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);
  	}
  
  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->high_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 = list_first_entry_or_null(
  					&area->free_list[MIGRATE_HIGHATOMIC],
  					struct page, lru);
  			if (!page)
  				continue;
  
  			/*
  			 * In page freeing path, migratetype change is racy so
  			 * we can counter several free pages in a pageblock
  			 * in this loop althoug we changed the pageblock type
  			 * from highatomic to ac->migratetype. So we should
  			 * adjust the count once.
  			 */
  			if (get_pageblock_migratetype(page) ==
  							MIGRATE_HIGHATOMIC) {
  				/*
  				 * 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);
  			if (ret) {
  				spin_unlock_irqrestore(&zone->lock, flags);
  				return ret;
  			}
  		}
  		spin_unlock_irqrestore(&zone->lock, flags);
  	}
  
  	return false;
  }
  
  /* Remove an element from the buddy allocator from the fallback list */
  static inline struct page *
  __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
  {
  	struct free_area *area;
  	unsigned int current_order;
  	struct page *page;
  	int fallback_mt;
  	bool can_steal;
  
  	/* Find the largest possible block of pages in the other list */
  	for (current_order = MAX_ORDER-1;
  				current_order >= order && current_order <= MAX_ORDER-1;
  				--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;
  
  		page = list_first_entry(&area->free_list[fallback_mt],
  						struct page, lru);
  		if (can_steal &&
  			get_pageblock_migratetype(page) != MIGRATE_HIGHATOMIC)
  			steal_suitable_fallback(zone, page, start_migratetype);
  
  		/* Remove the page from the freelists */
  		area->nr_free--;
  		list_del(&page->lru);
  		rmv_page_order(page);
  
  		expand(zone, page, order, current_order, area,
  					start_migratetype);
  		/*
  		 * The pcppage_migratetype may differ from pageblock's
  		 * migratetype depending on the decisions in
  		 * find_suitable_fallback(). This is OK as long as it does not
  		 * differ for MIGRATE_CMA pageblocks. Those can be used as
  		 * fallback only via special __rmqueue_cma_fallback() function
  		 */
  		set_pcppage_migratetype(page, start_migratetype);
  
  		trace_mm_page_alloc_extfrag(page, order, current_order,
  			start_migratetype, fallback_mt);
  
  		return page;
  	}
  
  	return NULL;
  }
  
  /*
   * Do the hard work of removing an element from the buddy allocator.
   * Call me with the zone->lock already held.
   */
  static struct page *__rmqueue(struct zone *zone, unsigned int order,
  				int migratetype)
  {
  	struct page *page;
  
  	page = __rmqueue_smallest(zone, order, migratetype);
  	if (unlikely(!page)) {
  		page = __rmqueue_fallback(zone, order, migratetype);
  	}
  
  	trace_mm_page_alloc_zone_locked(page, order, migratetype);
  	return page;
  }
  
  #ifdef CONFIG_CMA
  static struct page *__rmqueue_cma(struct zone *zone, unsigned int order)
  {
  	struct page *page = 0;
  	if (IS_ENABLED(CONFIG_CMA))
  		if (!zone->cma_alloc)
  			page = __rmqueue_cma_fallback(zone, order);
  	trace_mm_page_alloc_zone_locked(page, order, MIGRATE_CMA);
  	return page;
  }
  #else
  static inline struct page *__rmqueue_cma(struct zone *zone, unsigned int order)
  {
  	return NULL;
  }
  #endif
  
  /*
   * 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, bool cold)
  {
  	int i, alloced = 0;
  
  	spin_lock(&zone->lock);
  	for (i = 0; i < count; ++i) {
  		struct page *page;
  
  		/*
  		 * If migrate type CMA is being requested only try to
  		 * satisfy the request with CMA pages to try and increase
  		 * CMA utlization.
  		 */
  		if (is_migrate_cma(migratetype))
  			page = __rmqueue_cma(zone, order);
  		else
  			page = __rmqueue(zone, order, migratetype);
  		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 callers and
  		 * list and the list head then moves forward. From the callers
  		 * perspective, the linked list is ordered by page number in
  		 * some conditions. This is useful for IO devices that can
  		 * merge IO requests if the physical pages are ordered
  		 * properly.
  		 */
  		if (likely(!cold))
  			list_add(&page->lru, list);
  		else
  			list_add_tail(&page->lru, list);
  		list = &page->lru;
  		alloced++;
  		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 'alloced' 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 alloced;
  }
  
  /*
   * Return the pcp list that corresponds to the migrate type if that list isn't
   * empty.
   * If the list is empty return NULL.
   */
  static struct list_head *get_populated_pcp_list(struct zone *zone,
  			unsigned int order, struct per_cpu_pages *pcp,
  			int migratetype, int cold)
  {
  	struct list_head *list = &pcp->lists[migratetype];
  
  	if (list_empty(list)) {
  		pcp->count += rmqueue_bulk(zone, order,
  				pcp->batch, list,
  				migratetype, cold);
  
  		if (list_empty(list))
  			list = NULL;
  	}
  	return list;
  }
  
  #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_irq_save(flags);
  	batch = READ_ONCE(pcp->batch);
  	to_drain = min(pcp->count, batch);
  	if (to_drain > 0) {
  		free_pcppages_bulk(zone, to_drain, pcp);
  		pcp->count -= to_drain;
  	}
  	local_irq_restore(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_pageset *pset;
  	struct per_cpu_pages *pcp;
  
  	local_irq_save(flags);
  	pset = per_cpu_ptr(zone->pageset, cpu);
  
  	pcp = &pset->pcp;
  	if (pcp->count) {
  		free_pcppages_bulk(zone, pcp->count, pcp);
  		pcp->count = 0;
  	}
  	local_irq_restore(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(void *z)
  {
  	struct zone *zone = (struct zone *)z;
  	int cpu = smp_processor_id();
  
  	if (zone)
  		drain_pages_zone(cpu, zone);
  	else
  		drain_pages(cpu);
  }
  
  /*
   * 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 code is protected against sending an IPI to an offline
   * CPU but does not guarantee sending an IPI to newly hotplugged CPUs:
   * on_each_cpu_mask() blocks hotplug and won't talk to offlined CPUs but
   * nothing keeps CPUs from showing up after we populated the cpumask and
   * before the call to on_each_cpu_mask().
   */
  void drain_all_pages(struct zone *zone)
  {
  	int cpu;
  
  	/*
  	 * Allocate in the BSS so we wont require allocation in
  	 * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
  	 */
  	static cpumask_t cpus_with_pcps;
  
  	/*
  	 * 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_pageset *pcp;
  		struct zone *z;
  		bool has_pcps = false;
  
  		if (zone) {
  			pcp = per_cpu_ptr(zone->pageset, cpu);
  			if (pcp->pcp.count)
  				has_pcps = true;
  		} else {
  			for_each_populated_zone(z) {
  				pcp = per_cpu_ptr(z->pageset, cpu);
  				if (pcp->pcp.count) {
  					has_pcps = true;
  					break;
  				}
  			}
  		}
  
  		if (has_pcps)
  			cpumask_set_cpu(cpu, &cpus_with_pcps);
  		else
  			cpumask_clear_cpu(cpu, &cpus_with_pcps);
  	}
  	on_each_cpu_mask(&cpus_with_pcps, drain_local_pages, zone, 1);
  }
  
  #ifdef CONFIG_HIBERNATION
  
  void mark_free_pages(struct zone *zone)
  {
  	unsigned long pfn, max_zone_pfn;
  	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_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++)
  				swsusp_set_page_free(pfn_to_page(pfn + i));
  		}
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  #endif /* CONFIG_PM */
  
  /*
   * Free a 0-order page
   * cold == true ? free a cold page : free a hot page
   */
  void free_hot_cold_page(struct page *page, bool cold)
  {
  	struct zone *zone = page_zone(page);
  	struct per_cpu_pages *pcp;
  	unsigned long flags;
  	unsigned long pfn = page_to_pfn(page);
  	int migratetype;
  
  	if (!free_pcp_prepare(page))
  		return;
  
  	migratetype = get_pfnblock_migratetype(page, pfn);
  	set_pcppage_migratetype(page, migratetype);
  	local_irq_save(flags);
  	__count_vm_event(PGFREE);
  
  	/*
  	 * We only track unmovable, reclaimable and movable on pcp lists.
  	 * Free ISOLATE pages back to the allocator because they are being
  	 * offlined but treat RESERVE as movable pages so we can get those
  	 * areas back if necessary. Otherwise, we may have to free
  	 * excessively into the page allocator
  	 */
  	if (migratetype >= MIGRATE_PCPTYPES) {
  		if (unlikely(is_migrate_isolate(migratetype))) {
  			free_one_page(zone, page, pfn, 0, migratetype);
  			goto out;
  		}
  		migratetype = MIGRATE_MOVABLE;
  	}
  
  	pcp = &this_cpu_ptr(zone->pageset)->pcp;
  	if (!cold)
  		list_add(&page->lru, &pcp->lists[migratetype]);
  	else
  		list_add_tail(&page->lru, &pcp->lists[migratetype]);
  	pcp->count++;
  	if (pcp->count >= pcp->high) {
  		unsigned long batch = READ_ONCE(pcp->batch);
  		free_pcppages_bulk(zone, batch, pcp);
  		pcp->count -= batch;
  	}
  
  out:
  	local_irq_restore(flags);
  }
  
  /*
   * Free a list of 0-order pages
   */
  void free_hot_cold_page_list(struct list_head *list, bool cold)
  {
  	struct page *page, *next;
  
  	list_for_each_entry_safe(page, next, list, lru) {
  		trace_mm_page_free_batched(page, cold);
  		free_hot_cold_page(page, cold);
  	}
  }
  
  /*
   * 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);
  
  #ifdef CONFIG_KMEMCHECK
  	/*
  	 * Split shadow pages too, because free(page[0]) would
  	 * otherwise free the whole shadow.
  	 */
  	if (kmemcheck_page_is_tracked(page))
  		split_page(virt_to_page(page[0].shadow), order);
  #endif
  
  	for (i = 1; i < (1 << order); i++)
  		set_page_refcounted(page + i);
  	split_page_owner(page, 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 = min_wmark_pages(zone) + (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 */
  	list_del(&page->lru);
  	zone->free_area[order].nr_free--;
  	rmv_page_order(page);
  
  	/*
  	 * 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)
  				&& mt != MIGRATE_HIGHATOMIC)
  				set_pageblock_migratetype(page,
  							  MIGRATE_MOVABLE);
  		}
  	}
  
  
  	return 1UL << order;
  }
  
  /*
   * Update NUMA hit/miss statistics
   *
   * Must be called with interrupts disabled.
   */
  static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
  								gfp_t flags)
  {
  #ifdef CONFIG_NUMA
  	enum zone_stat_item local_stat = NUMA_LOCAL;
  
  	if (z->node != numa_node_id())
  		local_stat = NUMA_OTHER;
  
  	if (z->node == preferred_zone->node)
  		__inc_zone_state(z, NUMA_HIT);
  	else {
  		__inc_zone_state(z, NUMA_MISS);
  		__inc_zone_state(preferred_zone, NUMA_FOREIGN);
  	}
  	__inc_zone_state(z, local_stat);
  #endif
  }
  
  /*
   * Allocate a page from the given zone. Use pcplists for order-0 allocations.
   */
  static inline
  struct page *buffered_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 = NULL;
  	bool cold = ((gfp_flags & __GFP_COLD) != 0);
  
  	if (likely(order == 0)) {
  		struct per_cpu_pages *pcp;
  		struct list_head *list = NULL;
  
  		local_irq_save(flags);
  		do {
  			pcp = &this_cpu_ptr(zone->pageset)->pcp;
  
  			/* First try to get CMA pages */
  			if (migratetype == MIGRATE_MOVABLE &&
  				gfp_flags & __GFP_CMA) {
  				list = get_populated_pcp_list(zone, 0, pcp,
  						get_cma_migrate_type(), cold);
  			}
  
  			if (list == NULL) {
  				/*
  				 * Either CMA is not suitable or there are no
  				 * free CMA pages.
  				 */
  				list = get_populated_pcp_list(zone, 0, pcp,
  					migratetype, cold);
  				if (unlikely(list == NULL) ||
  					unlikely(list_empty(list)))
  					goto failed;
  			}
  
  			if (cold)
  				page = list_last_entry(list, struct page, lru);
  			else
  				page = list_first_entry(list, struct page, lru);
  
  			list_del(&page->lru);
  			pcp->count--;
  
  		} while (check_new_pcp(page));
  	} else {
  		/*
  		 * 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;
  			if (alloc_flags & ALLOC_HARDER) {
  				page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
  				if (page)
  					trace_mm_page_alloc_zone_locked(page, order, migratetype);
  			}
  			if (!page && migratetype == MIGRATE_MOVABLE &&
  					gfp_flags & __GFP_CMA)
  				page = __rmqueue_cma(zone, order);
  
  			if (!page)
  				page = __rmqueue(zone, order, migratetype);
  		} while (page && check_new_pages(page, order));
  
  		spin_unlock(&zone->lock);
  		if (!page)
  			goto failed;
  		__mod_zone_freepage_state(zone, -(1 << order),
  					  get_pcppage_migratetype(page));
  	}
  
  	__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
  	zone_statistics(preferred_zone, zone, gfp_flags);
  	local_irq_restore(flags);
  
  	VM_BUG_ON_PAGE(bad_range(zone, page), page);
  	return page;
  
  failed:
  	local_irq_restore(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 | S_IRUSR | S_IWUSR;
  	struct dentry *dir;
  
  	dir = fault_create_debugfs_attr("fail_page_alloc", NULL,
  					&fail_page_alloc.attr);
  	if (IS_ERR(dir))
  		return PTR_ERR(dir);
  
  	if (!debugfs_create_bool("ignore-gfp-wait", mode, dir,
  				&fail_page_alloc.ignore_gfp_reclaim))
  		goto fail;
  	if (!debugfs_create_bool("ignore-gfp-highmem", mode, dir,
  				&fail_page_alloc.ignore_gfp_highmem))
  		goto fail;
  	if (!debugfs_create_u32("min-order", mode, dir,
  				&fail_page_alloc.min_order))
  		goto fail;
  
  	return 0;
  fail:
  	debugfs_remove_recursive(dir);
  
  	return -ENOMEM;
  }
  
  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 */
  
  /*
   * 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 classzone_idx, unsigned int alloc_flags,
  			 long free_pages)
  {
  	long min = mark;
  	int o;
  	const bool alloc_harder = (alloc_flags & ALLOC_HARDER);
  
  	/* free_pages may go negative - that's OK */
  	free_pages -= (1 << order) - 1;
  
  	if (alloc_flags & ALLOC_HIGH)
  		min -= min / 2;
  
  	/*
  	 * 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))
  		free_pages -= z->nr_reserved_highatomic;
  	else
  		min -= min / 4;
  
  #ifdef CONFIG_CMA
  	/* If allocation can't use CMA areas don't use free CMA pages */
  	if (!(alloc_flags & ALLOC_CMA))
  		free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES);
  #endif
  
  	/*
  	 * 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[classzone_idx])
  		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++) {
  #ifdef CONFIG_CMA
  			/*
  			 * Note that this check is needed only
  			 * when MIGRATE_CMA < MIGRATE_PCPTYPES.
  			 */
  			if (mt == MIGRATE_CMA)
  				continue;
  #endif
  			if (!list_empty(&area->free_list[mt]))
  				return true;
  		}
  
  #ifdef CONFIG_CMA
  		if ((alloc_flags & ALLOC_CMA) &&
  		    !list_empty(&area->free_list[MIGRATE_CMA])) {
  			return true;
  		}
  #endif
  		if (alloc_harder &&
  			!list_empty(&area->free_list[MIGRATE_HIGHATOMIC]))
  			return true;
  	}
  	return false;
  }
  
  bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
  		      int classzone_idx, unsigned int alloc_flags)
  {
  	return __zone_watermark_ok(z, order, mark, classzone_idx, 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 classzone_idx, unsigned int alloc_flags)
  {
  	long free_pages = zone_page_state(z, NR_FREE_PAGES);
  	long cma_pages = 0;
  
  #ifdef CONFIG_CMA
  	/* If allocation can't use CMA areas don't use free CMA pages */
  	if (!(alloc_flags & ALLOC_CMA))
  		cma_pages = zone_page_state(z, NR_FREE_CMA_PAGES);
  #endif
  
  	/*
  	 * Fast check for order-0 only. If this fails then the reserves
  	 * need to be calculated. There is a corner case where the check
  	 * passes but only the high-order atomic reserve are free. If
  	 * the caller is !atomic then it'll uselessly search the free
  	 * list. That corner case is then slower but it is harmless.
  	 */
  	if (!order && (free_pages - cma_pages) > mark + z->lowmem_reserve[classzone_idx])
  		return true;
  
  	return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags,
  					free_pages);
  }
  
  bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
  			unsigned long mark, int classzone_idx)
  {
  	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, classzone_idx, 0,
  								free_pages);
  }
  
  #ifdef CONFIG_NUMA
  static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
  {
  	return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
  				RECLAIM_DISTANCE;
  }
  #else	/* CONFIG_NUMA */
  static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
  {
  	return true;
  }
  #endif	/* CONFIG_NUMA */
  
  /*
   * 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 = ac->preferred_zoneref;
  	struct zone *zone;
  	struct pglist_data *last_pgdat_dirty_limit = NULL;
  
  	/*
  	 * Scan zonelist, looking for a zone with enough free.
  	 * See also __cpuset_node_allowed() comment in kernel/cpuset.c.
  	 */
  	for_next_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_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;
  			}
  		}
  
  		mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
  		if (!zone_watermark_fast(zone, order, mark,
  				       ac_classzone_idx(ac), alloc_flags)) {
  			int ret;
  
  			/* 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_mode == 0 ||
  			    !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_classzone_idx(ac), alloc_flags))
  					goto try_this_zone;
  
  				continue;
  			}
  		}
  
  try_this_zone:
  		page = buffered_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;
  		}
  	}
  
  	return NULL;
  }
  
  /*
   * Large machines with many possible nodes should not always dump per-node
   * meminfo in irq context.
   */
  static inline bool should_suppress_show_mem(void)
  {
  	bool ret = false;
  
  #if NODES_SHIFT > 8
  	ret = in_interrupt();
  #endif
  	return ret;
  }
  
  static void warn_alloc_show_mem(gfp_t gfp_mask)
  {
  	unsigned int filter = SHOW_MEM_FILTER_NODES;
  	static DEFINE_RATELIMIT_STATE(show_mem_rs, HZ, 1);
  
  	if (should_suppress_show_mem() || !__ratelimit(&show_mem_rs))
  		return;
  
  	/*
  	 * 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 (test_thread_flag(TIF_MEMDIE) ||
  		    (current->flags & (PF_MEMALLOC | PF_EXITING)))
  			filter &= ~SHOW_MEM_FILTER_NODES;
  	if (in_interrupt() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
  		filter &= ~SHOW_MEM_FILTER_NODES;
  
  	show_mem(filter);
  }
  
  void warn_alloc(gfp_t gfp_mask, const char *fmt, ...)
  {
  	struct va_format vaf;
  	va_list args;
  	static DEFINE_RATELIMIT_STATE(nopage_rs, DEFAULT_RATELIMIT_INTERVAL,
  				      DEFAULT_RATELIMIT_BURST);
  
  	if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) ||
  	    debug_guardpage_minorder() > 0)
  		return;
  
  	pr_warn("%s: ", current->comm);
  
  	va_start(args, fmt);
  	vaf.fmt = fmt;
  	vaf.va = &args;
  	pr_cont("%pV", &vaf);
  	va_end(args);
  
  	pr_cont(", mode:%#x(%pGg)\n", gfp_mask, &gfp_mask);
  
  	dump_stack();
  	warn_alloc_show_mem(gfp_mask);
  }
  
  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.
  	 */
  	page = get_page_from_freelist(gfp_mask | __GFP_HARDWALL, order,
  					ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
  	if (page)
  		goto out;
  
  	if (!(gfp_mask & __GFP_NOFAIL)) {
  		/* 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;
  		/* The OOM killer does not needlessly kill tasks for lowmem */
  		if (ac->high_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.
  		 */
  
  		/* The OOM killer may not free memory on a specific node */
  		if (gfp_mask & __GFP_THISNODE)
  			goto out;
  	}
  	/* Exhausted what can be done so it's blamo time */
  	if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
  		*did_some_progress = 1;
  
  		if (gfp_mask & __GFP_NOFAIL) {
  			page = get_page_from_freelist(gfp_mask, order,
  					ALLOC_NO_WATERMARKS|ALLOC_CPUSET, ac);
  			/*
  			 * fallback to ignore cpuset restriction if our nodes
  			 * are depleted
  			 */
  			if (!page)
  				page = get_page_from_freelist(gfp_mask, order,
  					ALLOC_NO_WATERMARKS, ac);
  		}
  	}
  out:
  	mutex_unlock(&oom_lock);
  	return page;
  }
  
  /*
   * Maximum number of compaction retries wit 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;
  	unsigned long pflags;
  	unsigned int noreclaim_flag = current->flags & PF_MEMALLOC;
  
  	if (!order)
  		return NULL;
  
  	psi_memstall_enter(&pflags);
  	current->flags |= PF_MEMALLOC;
  
  	*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
  									prio);
  
  	current->flags = (current->flags & ~PF_MEMALLOC) | noreclaim_flag;
  	psi_memstall_leave(&pflags);
  
  	if (*compact_result <= COMPACT_INACTIVE)
  		return NULL;
  
  	/*
  	 * At least in one zone compaction wasn't deferred or skipped, so let's
  	 * count a compaction stall
  	 */
  	count_vm_event(COMPACTSTALL);
  
  	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;
  }
  
  #ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER
  static inline bool
  should_compact_lmk_retry(struct alloc_context *ac, int order, int alloc_flags)
  {
  	struct zone *zone;
  	struct zoneref *z;
  
  	/* Let costly order requests check for compaction progress */
  	if (order > PAGE_ALLOC_COSTLY_ORDER)
  		return false;
  
  	/*
  	 * For (0 < order < PAGE_ALLOC_COSTLY_ORDER) allow the shrinkers
  	 * to run and free up memory. Do not let these allocations fail
  	 * if shrinkers can free up memory. This is similar to
  	 * should_compact_retry implementation for !CONFIG_COMPACTION.
  	 */
  	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
  				ac->high_zoneidx, ac->nodemask) {
  		unsigned long available;
  
  		available = zone_reclaimable_pages(zone);
  		available +=
  			zone_page_state_snapshot(zone, NR_FREE_PAGES);
  
  		if (__zone_watermark_ok(zone, 0, min_wmark_pages(zone),
  			ac_classzone_idx(ac), alloc_flags, available))
  			return true;
  	}
  
  	return false;
  }
  #else
  static inline bool
  should_compact_lmk_retry(struct alloc_context *ac, int order, int alloc_flags)
  {
  	return false;
  }
  #endif
  
  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;
  
  	if (!order)
  		return false;
  
  	if (should_compact_lmk_retry(ac, order, alloc_flags))
  		return true;
  
  	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;
  
  	/*
  	 * 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 do not retry if the given zonelist is not suitable for
  	 * compaction.
  	 */
  	if (compaction_withdrawn(compact_result))
  		return compaction_zonelist_suitable(ac, order, alloc_flags);
  
  	/*
  	 * !costly requests are much more important than __GFP_REPEAT
  	 * 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)
  		return true;
  
  	/*
  	 * 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;
  		return true;
  	}
  	return false;
  }
  #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->high_zoneidx,
  					ac->nodemask) {
  		if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
  					ac_classzone_idx(ac), alloc_flags))
  			return true;
  	}
  	return false;
  }
  #endif /* CONFIG_COMPACTION */
  
  /* Perform direct synchronous page reclaim */
  static int
  __perform_reclaim(gfp_t gfp_mask, unsigned int order,
  					const struct alloc_context *ac)
  {
  	struct reclaim_state reclaim_state;
  	int progress;
  	unsigned long pflags;
  
  	cond_resched();
  
  	/* We now go into synchronous reclaim */
  	cpuset_memory_pressure_bump();
  	psi_memstall_enter(&pflags);
  	current->flags |= PF_MEMALLOC;
  	lockdep_set_current_reclaim_state(gfp_mask);
  	reclaim_state.reclaimed_slab = 0;
  	current->reclaim_state = &reclaim_state;
  
  	progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
  								ac->nodemask);
  
  	current->reclaim_state = NULL;
  	lockdep_clear_current_reclaim_state();
  	current->flags &= ~PF_MEMALLOC;
  	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 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, const struct alloc_context *ac)
  {
  	struct zoneref *z;
  	struct zone *zone;
  	pg_data_t *last_pgdat = NULL;
  
  	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
  					ac->high_zoneidx, ac->nodemask) {
  		if (last_pgdat != zone->zone_pgdat)
  			wakeup_kswapd(zone, order, ac->high_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 to save a branch. */
  	BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);
  
  	/*
  	 * 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);
  
  	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_interrupt())
  		alloc_flags |= ALLOC_HARDER;
  
  #ifdef CONFIG_CMA
  	if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
  		alloc_flags |= ALLOC_CMA;
  #endif
  	return alloc_flags;
  }
  
  bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
  {
  	if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
  		return false;
  
  	if (gfp_mask & __GFP_MEMALLOC)
  		return true;
  	if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
  		return true;
  	if (!in_interrupt() &&
  			((current->flags & PF_MEMALLOC) ||
  			 unlikely(test_thread_flag(TIF_MEMDIE))))
  		return true;
  
  	return false;
  }
  
  /*
   * 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;
  
  	/*
  	 * 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) ||
  			IS_ENABLED(CONFIG_ANDROID_LOW_MEMORY_KILLER))
  		*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->high_zoneidx,
  					ac->nodemask) {
  		unsigned long available;
  		unsigned long reclaimable;
  
  		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?
  		 */
  		if (__zone_watermark_ok(zone, order, min_wmark_pages(zone),
  				ac_classzone_idx(ac), alloc_flags, available)) {
  			/*
  			 * If we didn't make any progress and have a lot of
  			 * dirty + writeback pages then we should wait for
  			 * an IO to complete to slow down the reclaim and
  			 * prevent from pre mature OOM
  			 */
  			if (!did_some_progress) {
  				unsigned long write_pending;
  
  				write_pending = zone_page_state_snapshot(zone,
  							NR_ZONE_WRITE_PENDING);
  
  				if (2 * write_pending > reclaimable) {
  					congestion_wait(BLK_RW_ASYNC, HZ/10);
  					return true;
  				}
  			}
  
  			/*
  			 * 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 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;
  	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;
  	bool woke_kswapd = false;
  
  	/*
  	 * In the slowpath, we sanity check order to avoid ever trying to
  	 * reclaim >= MAX_ORDER areas which will never succeed. Callers may
  	 * be using allocators in order of preference for an area that is
  	 * too large.
  	 */
  	if (order >= MAX_ORDER) {
  		WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
  		return NULL;
  	}
  
  	/*
  	 * 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();
  	/*
  	 * 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->high_zoneidx, ac->nodemask);
  	if (!ac->preferred_zoneref->zone)
  		goto nopage;
  
  
  	/*
  	 * 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);
  
  	if (gfp_mask & __GFP_KSWAPD_RECLAIM) {
  		if (!woke_kswapd) {
  			atomic_long_inc(&kswapd_waiters);
  			woke_kswapd = true;
  		}
  		wake_all_kswapds(order, 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. Don't try
  	 * that for allocations that are allowed to ignore watermarks, as the
  	 * ALLOC_NO_WATERMARKS attempt didn't yet happen.
  	 */
  	if (can_direct_reclaim && order > PAGE_ALLOC_COSTLY_ORDER &&
  		!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 THP page fault allocations
  		 */
  		if (gfp_mask & __GFP_NORETRY) {
  			/*
  			 * If compaction is deferred for high-order allocations,
  			 * it is because sync compaction recently failed. If
  			 * this is the case and the caller requested a THP
  			 * allocation, we do not want to heavily disrupt the
  			 * system, so we fail the allocation instead of entering
  			 * direct reclaim.
  			 */
  			if (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 (gfp_mask & __GFP_KSWAPD_RECLAIM)
  		wake_all_kswapds(order, ac);
  
  	if (gfp_pfmemalloc_allowed(gfp_mask))
  		alloc_flags = ALLOC_NO_WATERMARKS;
  
  	/*
  	 * Reset the zonelist iterators if memory policies can be ignored.
  	 * These allocations are high priority and system rather than user
  	 * orientated.
  	 */
  	if (!(alloc_flags & ALLOC_CPUSET) || (alloc_flags & ALLOC_NO_WATERMARKS)) {
  		ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
  					ac->high_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) {
  		/*
  		 * All existing users of the __GFP_NOFAIL are blockable, so warn
  		 * of any new users that actually allow this type of allocation
  		 * to fail.
  		 */
  		WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
  		goto nopage;
  	}
  
  	/* Avoid recursion of direct reclaim */
  	if (current->flags & PF_MEMALLOC) {
  		/*
  		 * __GFP_NOFAIL 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.
  		 */
  		if (WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
  			cond_resched();
  			goto retry;
  		}
  		goto nopage;
  	}
  
  	/* Avoid allocations with no watermarks from looping endlessly */
  	if (test_thread_flag(TIF_MEMDIE) && !(gfp_mask & __GFP_NOFAIL)) {
  		gfp_mask |= __GFP_NOWARN;
  		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_REPEAT
  	 */
  	if (order > PAGE_ALLOC_COSTLY_ORDER && !(gfp_mask & __GFP_REPEAT))
  		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 ||
  			IS_ENABLED(CONFIG_ANDROID_LOW_MEMORY_KILLER)) &&
  			should_compact_retry(ac, order, alloc_flags,
  				compact_result, &compact_priority,
  				&compaction_retries))
  		goto retry;
  
  	/*
  	 * It's possible we raced with cpuset update so the OOM would be
  	 * premature (see below the nopage: label for full explanation).
  	 */
  	if (read_mems_allowed_retry(cpuset_mems_cookie))
  		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;
  
  	/* Retry as long as the OOM killer is making progress */
  	if (did_some_progress) {
  		no_progress_loops = 0;
  		goto retry;
  	}
  
  nopage:
  	/*
  	 * 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))
  		goto retry_cpuset;
  
  got_pg:
  	if (woke_kswapd)
  		atomic_long_dec(&kswapd_waiters);
  	if (!page)
  		warn_alloc(gfp_mask,
  				"page allocation failure: order:%u", order);
  	return page;
  }
  
  /*
   * This is the 'heart' of the zoned buddy allocator.
   */
  struct page *
  __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
  			struct zonelist *zonelist, nodemask_t *nodemask)
  {
  	struct page *page;
  	unsigned int alloc_flags = ALLOC_WMARK_LOW;
  	gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
  	struct alloc_context ac = {
  		.high_zoneidx = gfp_zone(gfp_mask),
  		.zonelist = zonelist,
  		.nodemask = nodemask,
  		.migratetype = gfpflags_to_migratetype(gfp_mask),
  	};
  
  	if (cpusets_enabled()) {
  		alloc_mask |= __GFP_HARDWALL;
  		alloc_flags |= ALLOC_CPUSET;
  		if (!ac.nodemask)
  			ac.nodemask = &cpuset_current_mems_allowed;
  	}
  
  	gfp_mask &= gfp_allowed_mask;
  
  	lockdep_trace_alloc(gfp_mask);
  
  	might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
  
  	if (should_fail_alloc_page(gfp_mask, order))
  		return NULL;
  
  	/*
  	 * Check the zones suitable for the gfp_mask contain at least one
  	 * valid zone. It's possible to have an empty zonelist as a result
  	 * of __GFP_THISNODE and a memoryless node
  	 */
  	if (unlikely(!zonelist->_zonerefs->zone))
  		return NULL;
  
  	if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)
  		alloc_flags |= ALLOC_CMA;
  
  	/* 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.high_zoneidx, ac.nodemask);
  	if (!ac.preferred_zoneref->zone) {
  		page = NULL;
  		/*
  		 * This might be due to race with cpuset_current_mems_allowed
  		 * update, so make sure we retry with original nodemask in the
  		 * slow path.
  		 */
  		goto no_zone;
  	}
  
  	/* First allocation attempt */
  	page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);
  	if (likely(page))
  		goto out;
  
  no_zone:
  	/*
  	 * Runtime PM, block IO and its error handling path can deadlock
  	 * because I/O on the device might not complete.
  	 */
  	alloc_mask = memalloc_noio_flags(gfp_mask);
  	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.
  	 */
  	if (unlikely(ac.nodemask != nodemask))
  		ac.nodemask = nodemask;
  
  	page = __alloc_pages_slowpath(alloc_mask, order, &ac);
  
  out:
  	if (memcg_kmem_enabled() && (gfp_mask & __GFP_ACCOUNT) && page &&
  	    unlikely(memcg_kmem_charge(page, gfp_mask, order) != 0)) {
  		__free_pages(page, order);
  		page = NULL;
  	}
  
  	if (kmemcheck_enabled && page)
  		kmemcheck_pagealloc_alloc(page, order, gfp_mask);
  
  	trace_mm_page_alloc(page, order, alloc_mask, ac.migratetype);
  
  	return page;
  }
  EXPORT_SYMBOL(__alloc_pages_nodemask);
  
  /*
   * Common helper functions.
   */
  unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
  {
  	struct page *page;
  
  	/*
  	 * __get_free_pages() returns a 32-bit address, which cannot represent
  	 * a highmem page
  	 */
  	VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
  
  	page = alloc_pages(gfp_mask, 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);
  
  void __free_pages(struct page *page, unsigned int order)
  {
  	if (put_page_testzero(page)) {
  		if (order == 0)
  			free_hot_cold_page(page, false);
  		else
  			__free_pages_ok(page, 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_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 *__alloc_page_frag(struct page_frag_cache *nc,
  			unsigned int fragsz, gfp_t gfp_mask)
  {
  	unsigned int size = PAGE_SIZE;
  	struct page *page;
  	int offset;
  
  	if (unlikely(!nc->va)) {
  refill:
  		page = __page_frag_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 (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--;
  	nc->offset = offset;
  
  	return nc->va + offset;
  }
  EXPORT_SYMBOL(__alloc_page_frag);
  
  /*
   * Frees a page fragment allocated out of either a compound or order 0 page.
   */
  void __free_page_frag(void *addr)
  {
  	struct page *page = virt_to_head_page(addr);
  
  	if (unlikely(put_page_testzero(page)))
  		__free_pages_ok(page, compound_order(page));
  }
  EXPORT_SYMBOL(__free_page_frag);
  
  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
   *
   * 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().
   */
  void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
  {
  	unsigned int order = get_order(size);
  	unsigned long addr;
  
  	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
   *
   * Like alloc_pages_exact(), but try to allocate on node nid first before falling
   * back.
   */
  void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
  {
  	unsigned int order = get_order(size);
  	struct page *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 counts 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:
   *     managed_pages - high_pages
   */
  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;
  		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.
   */
  unsigned long nr_free_buffer_pages(void)
  {
  	return nr_free_zone_pages(gfp_zone(GFP_USER));
  }
  EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
  
  /**
   * nr_free_pagecache_pages - count number of pages beyond high watermark
   *
   * nr_free_pagecache_pages() counts the number of pages which are beyond the
   * high watermark within all zones.
   */
  unsigned long nr_free_pagecache_pages(void)
  {
  	return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
  }
  
  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];
  	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 += zone->watermark[WMARK_LOW];
  
  	/*
  	 * Estimate the amount of memory available for userspace allocations,
  	 * without causing swapping.
  	 */
  	available = global_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 consists of items that are in use,
  	 * and cannot be freed. Cap this estimate at the low watermark.
  	 */
  	available += global_page_state(NR_SLAB_RECLAIMABLE) -
  		     min(global_page_state(NR_SLAB_RECLAIMABLE) / 2, wmark_low);
  
  	/*
  	 * Part of the kernel memory, which can be released under memory
  	 * pressure.
  	 */
  	available += global_node_page_state(NR_INDIRECTLY_RECLAIMABLE_BYTES) >>
  		PAGE_SHIFT;
  
  	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_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 += pgdat->node_zones[zone_type].managed_pages;
  	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;
  			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().
   */
  bool skip_free_areas_node(unsigned int flags, int nid)
  {
  	bool ret = false;
  	unsigned int cpuset_mems_cookie;
  
  	if (!(flags & SHOW_MEM_FILTER_NODES))
  		goto out;
  
  	do {
  		cpuset_mems_cookie = read_mems_allowed_begin();
  		ret = !node_isset(nid, cpuset_current_mems_allowed);
  	} while (read_mems_allowed_retry(cpuset_mems_cookie));
  out:
  	return ret;
  }
  
  #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)
  {
  	unsigned long free_pcp = 0;
  	int cpu;
  	struct zone *zone;
  	pg_data_t *pgdat;
  
  	for_each_populated_zone(zone) {
  		if (skip_free_areas_node(filter, zone_to_nid(zone)))
  			continue;
  
  		for_each_online_cpu(cpu)
  			free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.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 unstable:%lu\n"
  		" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
  		" mapped:%lu shmem:%lu pagetables:%lu bounce:%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(NR_UNSTABLE_NFS),
  		global_page_state(NR_SLAB_RECLAIMABLE),
  		global_page_state(NR_SLAB_UNRECLAIMABLE),
  		global_node_page_state(NR_FILE_MAPPED),
  		global_node_page_state(NR_SHMEM),
  		global_page_state(NR_PAGETABLE),
  		global_page_state(NR_BOUNCE),
  		global_page_state(NR_FREE_PAGES),
  		free_pcp,
  		global_page_state(NR_FREE_CMA_PAGES));
  
  	for_each_online_pgdat(pgdat) {
  		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"
  			" unstable:%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) * HPAGE_PMD_NR),
  			K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)
  					* HPAGE_PMD_NR),
  			K(node_page_state(pgdat, NR_ANON_THPS) * HPAGE_PMD_NR),
  #endif
  			K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
  			K(node_page_state(pgdat, NR_UNSTABLE_NFS)),
  			pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
  				"yes" : "no");
  	}
  
  	for_each_populated_zone(zone) {
  		int i;
  
  		if (skip_free_areas_node(filter, zone_to_nid(zone)))
  			continue;
  
  		free_pcp = 0;
  		for_each_online_cpu(cpu)
  			free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;
  
  		show_node(zone);
  		printk(KERN_CONT
  			"%s"
  			" free:%lukB"
  			" min:%lukB"
  			" low:%lukB"
  			" high:%lukB"
  			" active_anon:%lukB"
  			" inactive_anon:%lukB"
  			" active_file:%lukB"
  			" inactive_file:%lukB"
  			" unevictable:%lukB"
  			" writepending:%lukB"
  			" present:%lukB"
  			" managed:%lukB"
  			" mlocked:%lukB"
  			" slab_reclaimable:%lukB"
  			" slab_unreclaimable:%lukB"
  			" kernel_stack:%lukB"
  #ifdef CONFIG_SHADOW_CALL_STACK
  			" shadow_call_stack:%lukB"
  #endif
  			" pagetables:%lukB"
  			" bounce:%lukB"
  			" free_pcp:%lukB"
  			" local_pcp:%ukB"
  			" free_cma:%lukB"
  			"\n",
  			zone->name,
  			K(zone_page_state(zone, NR_FREE_PAGES)),
  			K(min_wmark_pages(zone)),
  			K(low_wmark_pages(zone)),
  			K(high_wmark_pages(zone)),
  			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),
  			K(zone_page_state(zone, NR_MLOCK)),
  			K(zone_page_state(zone, NR_SLAB_RECLAIMABLE)),
  			K(zone_page_state(zone, NR_SLAB_UNRECLAIMABLE)),
  			zone_page_state(zone, NR_KERNEL_STACK_KB),
  #ifdef CONFIG_SHADOW_CALL_STACK
  			zone_page_state(zone, NR_KERNEL_SCS_BYTES) / 1024,
  #endif
  			K(zone_page_state(zone, NR_PAGETABLE)),
  			K(zone_page_state(zone, NR_BOUNCE)),
  			K(free_pcp),
  			K(this_cpu_read(zone->pageset->pcp.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 (skip_free_areas_node(filter, zone_to_nid(zone)))
  			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 (!list_empty(&area->free_list[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_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist,
  				int nr_zones)
  {
  	struct zone *zone;
  	enum zone_type zone_type = MAX_NR_ZONES;
  
  	do {
  		zone_type--;
  		zone = pgdat->node_zones + zone_type;
  		if (managed_zone(zone)) {
  			zoneref_set_zone(zone,
  				&zonelist->_zonerefs[nr_zones++]);
  			check_highest_zone(zone_type);
  		}
  	} while (zone_type);
  
  	return nr_zones;
  }
  
  
  /*
   *  zonelist_order:
   *  0 = automatic detection of better ordering.
   *  1 = order by ([node] distance, -zonetype)
   *  2 = order by (-zonetype, [node] distance)
   *
   *  If not NUMA, ZONELIST_ORDER_ZONE and ZONELIST_ORDER_NODE will create
   *  the same zonelist. So only NUMA can configure this param.
   */
  #define ZONELIST_ORDER_DEFAULT  0
  #define ZONELIST_ORDER_NODE     1
  #define ZONELIST_ORDER_ZONE     2
  
  /* zonelist order in the kernel.
   * set_zonelist_order() will set this to NODE or ZONE.
   */
  static int current_zonelist_order = ZONELIST_ORDER_DEFAULT;
  static char zonelist_order_name[3][8] = {"Default", "Node", "Zone"};
  
  
  #ifdef CONFIG_NUMA
  /* The value user specified ....changed by config */
  static int user_zonelist_order = ZONELIST_ORDER_DEFAULT;
  /* string for sysctl */
  #define NUMA_ZONELIST_ORDER_LEN	16
  char numa_zonelist_order[16] = "default";
  
  /*
   * interface for configure zonelist ordering.
   * command line option "numa_zonelist_order"
   *	= "[dD]efault	- default, automatic configuration.
   *	= "[nN]ode 	- order by node locality, then by zone within node
   *	= "[zZ]one      - order by zone, then by locality within zone
   */
  
  static int __parse_numa_zonelist_order(char *s)
  {
  	if (*s == 'd' || *s == 'D') {
  		user_zonelist_order = ZONELIST_ORDER_DEFAULT;
  	} else if (*s == 'n' || *s == 'N') {
  		user_zonelist_order = ZONELIST_ORDER_NODE;
  	} else if (*s == 'z' || *s == 'Z') {
  		user_zonelist_order = ZONELIST_ORDER_ZONE;
  	} else {
  		pr_warn("Ignoring invalid numa_zonelist_order value:  %s\n", s);
  		return -EINVAL;
  	}
  	return 0;
  }
  
  static __init int setup_numa_zonelist_order(char *s)
  {
  	int ret;
  
  	if (!s)
  		return 0;
  
  	ret = __parse_numa_zonelist_order(s);
  	if (ret == 0)
  		strlcpy(numa_zonelist_order, s, NUMA_ZONELIST_ORDER_LEN);
  
  	return ret;
  }
  early_param("numa_zonelist_order", setup_numa_zonelist_order);
  
  /*
   * sysctl handler for numa_zonelist_order
   */
  int numa_zonelist_order_handler(struct ctl_table *table, int write,
  		void __user *buffer, size_t *length,
  		loff_t *ppos)
  {
  	char saved_string[NUMA_ZONELIST_ORDER_LEN];
  	int ret;
  	static DEFINE_MUTEX(zl_order_mutex);
  
  	mutex_lock(&zl_order_mutex);
  	if (write) {
  		if (strlen((char *)table->data) >= NUMA_ZONELIST_ORDER_LEN) {
  			ret = -EINVAL;
  			goto out;
  		}
  		strcpy(saved_string, (char *)table->data);
  	}
  	ret = proc_dostring(table, write, buffer, length, ppos);
  	if (ret)
  		goto out;
  	if (write) {
  		int oldval = user_zonelist_order;
  
  		ret = __parse_numa_zonelist_order((char *)table->data);
  		if (ret) {
  			/*
  			 * bogus value.  restore saved string
  			 */
  			strncpy((char *)table->data, saved_string,
  				NUMA_ZONELIST_ORDER_LEN);
  			user_zonelist_order = oldval;
  		} else if (oldval != user_zonelist_order) {
  			mutex_lock(&zonelists_mutex);
  			build_all_zonelists(NULL, NULL);
  			mutex_unlock(&zonelists_mutex);
  		}
  	}
  out:
  	mutex_unlock(&zl_order_mutex);
  	return ret;
  }
  
  
  #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.
   * It returns -1 if no node is found.
   */
  static 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;
  	const struct cpumask *tmp = cpumask_of_node(0);
  
  	/* 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 */
  		tmp = cpumask_of_node(n);
  		if (!cpumask_empty(tmp))
  			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)
  {
  	int j;
  	struct zonelist *zonelist;
  
  	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
  	for (j = 0; zonelist->_zonerefs[j].zone != NULL; j++)
  		;
  	j = build_zonelists_node(NODE_DATA(node), zonelist, j);
  	zonelist->_zonerefs[j].zone = NULL;
  	zonelist->_zonerefs[j].zone_idx = 0;
  }
  
  /*
   * Build gfp_thisnode zonelists
   */
  static void build_thisnode_zonelists(pg_data_t *pgdat)
  {
  	int j;
  	struct zonelist *zonelist;
  
  	zonelist = &pgdat->node_zonelists[ZONELIST_NOFALLBACK];
  	j = build_zonelists_node(pgdat, zonelist, 0);
  	zonelist->_zonerefs[j].zone = NULL;
  	zonelist->_zonerefs[j].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 int node_order[MAX_NUMNODES];
  
  static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
  {
  	int pos, j, node;
  	int zone_type;		/* needs to be signed */
  	struct zone *z;
  	struct zonelist *zonelist;
  
  	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
  	pos = 0;
  	for (zone_type = MAX_NR_ZONES - 1; zone_type >= 0; zone_type--) {
  		for (j = 0; j < nr_nodes; j++) {
  			node = node_order[j];
  			z = &NODE_DATA(node)->node_zones[zone_type];
  			if (managed_zone(z)) {
  				zoneref_set_zone(z,
  					&zonelist->_zonerefs[pos++]);
  				check_highest_zone(zone_type);
  			}
  		}
  	}
  	zonelist->_zonerefs[pos].zone = NULL;
  	zonelist->_zonerefs[pos].zone_idx = 0;
  }
  
  #if defined(CONFIG_64BIT)
  /*
   * Devices that require DMA32/DMA are relatively rare and do not justify a
   * penalty to every machine in case the specialised case applies. Default
   * to Node-ordering on 64-bit NUMA machines
   */
  static int default_zonelist_order(void)
  {
  	return ZONELIST_ORDER_NODE;
  }
  #else
  /*
   * On 32-bit, the Normal zone needs to be preserved for allocations accessible
   * by the kernel. If processes running on node 0 deplete the low memory zone
   * then reclaim will occur more frequency increasing stalls and potentially
   * be easier to OOM if a large percentage of the zone is under writeback or
   * dirty. The problem is significantly worse if CONFIG_HIGHPTE is not set.
   * Hence, default to zone ordering on 32-bit.
   */
  static int default_zonelist_order(void)
  {
  	return ZONELIST_ORDER_ZONE;
  }
  #endif /* CONFIG_64BIT */
  
  static void set_zonelist_order(void)
  {
  	if (user_zonelist_order == ZONELIST_ORDER_DEFAULT)
  		current_zonelist_order = default_zonelist_order();
  	else
  		current_zonelist_order = user_zonelist_order;
  }
  
  static void build_zonelists(pg_data_t *pgdat)
  {
  	int i, node, load;
  	nodemask_t used_mask;
  	int local_node, prev_node;
  	struct zonelist *zonelist;
  	unsigned int order = current_zonelist_order;
  
  	/* initialize zonelists */
  	for (i = 0; i < MAX_ZONELISTS; i++) {
  		zonelist = pgdat->node_zonelists + i;
  		zonelist->_zonerefs[0].zone = NULL;
  		zonelist->_zonerefs[0].zone_idx = 0;
  	}
  
  	/* NUMA-aware ordering of nodes */
  	local_node = pgdat->node_id;
  	load = nr_online_nodes;
  	prev_node = local_node;
  	nodes_clear(used_mask);
  
  	memset(node_order, 0, sizeof(node_order));
  	i = 0;
  
  	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;
  
  		prev_node = node;
  		load--;
  		if (order == ZONELIST_ORDER_NODE)
  			build_zonelists_in_node_order(pgdat, node);
  		else
  			node_order[i++] = node;	/* remember order */
  	}
  
  	if (order == ZONELIST_ORDER_ZONE) {
  		/* calculate node order -- i.e., DMA last! */
  		build_zonelists_in_zone_order(pgdat, i);
  	}
  
  	build_thisnode_zonelists(pgdat);
  }
  
  #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 z->zone->node;
  }
  #endif
  
  static void setup_min_unmapped_ratio(void);
  static void setup_min_slab_ratio(void);
  #else	/* CONFIG_NUMA */
  
  static void set_zonelist_order(void)
  {
  	current_zonelist_order = ZONELIST_ORDER_ZONE;
  }
  
  static void build_zonelists(pg_data_t *pgdat)
  {
  	int node, local_node;
  	enum zone_type j;
  	struct zonelist *zonelist;
  
  	local_node = pgdat->node_id;
  
  	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
  	j = build_zonelists_node(pgdat, zonelist, 0);
  
  	/*
  	 * 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;
  		j = build_zonelists_node(NODE_DATA(node), zonelist, j);
  	}
  	for (node = 0; node < local_node; node++) {
  		if (!node_online(node))
  			continue;
  		j = build_zonelists_node(NODE_DATA(node), zonelist, j);
  	}
  
  	zonelist->_zonerefs[j].zone = NULL;
  	zonelist->_zonerefs[j].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 setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
  static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
  static void setup_zone_pageset(struct zone *zone);
  
  /*
   * Global mutex to protect against size modification of zonelists
   * as well as to serialize pageset setup for the new populated zone.
   */
  DEFINE_MUTEX(zonelists_mutex);
  
  /* return values int ....just for stop_machine() */
  static int __build_all_zonelists(void *data)
  {
  	int nid;
  	int cpu;
  	pg_data_t *self = data;
  
  #ifdef CONFIG_NUMA
  	memset(node_load, 0, sizeof(node_load));
  #endif
  
  	if (self && !node_online(self->node_id)) {
  		build_zonelists(self);
  	}
  
  	for_each_online_node(nid) {
  		pg_data_t *pgdat = NODE_DATA(nid);
  
  		build_zonelists(pgdat);
  	}
  
  	/*
  	 * 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) {
  		setup_pageset(&per_cpu(boot_pageset, cpu), 0);
  
  #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.
  		 */
  		if (cpu_online(cpu))
  			set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
  #endif
  	}
  
  	return 0;
  }
  
  static noinline void __init
  build_all_zonelists_init(void)
  {
  	__build_all_zonelists(NULL);
  	mminit_verify_zonelist();
  	cpuset_init_current_mems_allowed();
  }
  
  /*
   * Called with zonelists_mutex held always
   * unless system_state == SYSTEM_BOOTING.
   *
   * __ref due to (1) call of __meminit annotated setup_zone_pageset
   * [we're only called with non-NULL zone through __meminit paths] and
   * (2) call of __init annotated helper build_all_zonelists_init
   * [protected by SYSTEM_BOOTING].
   */
  void __ref build_all_zonelists(pg_data_t *pgdat, struct zone *zone)
  {
  	set_zonelist_order();
  
  	if (system_state == SYSTEM_BOOTING) {
  		build_all_zonelists_init();
  	} else {
  #ifdef CONFIG_MEMORY_HOTPLUG
  		if (zone)
  			setup_zone_pageset(zone);
  #endif
  		/* we have to stop all cpus to guarantee there is no user
  		   of zonelist */
  		stop_machine(__build_all_zonelists, pgdat, NULL);
  		/* cpuset refresh routine should be here */
  	}
  	vm_total_pages = nr_free_pagecache_pages();
  	/*
  	 * 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 %i zonelists in %s order, mobility grouping %s.  Total pages: %ld\n",
  		nr_online_nodes,
  		zonelist_order_name[current_zonelist_order],
  		page_group_by_mobility_disabled ? "off" : "on",
  		vm_total_pages);
  #ifdef CONFIG_NUMA
  	pr_info("Policy zone: %s\n", zone_names[policy_zone]);
  #endif
  }
  
  /*
   * Initially all pages are reserved - free ones are freed
   * up by free_all_bootmem() once the early boot process is
   * done. Non-atomic initialization, single-pass.
   */
  void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
  		unsigned long start_pfn, enum memmap_context context)
  {
  	struct vmem_altmap *altmap = to_vmem_altmap(__pfn_to_phys(start_pfn));
  	unsigned long end_pfn = start_pfn + size;
  	pg_data_t *pgdat = NODE_DATA(nid);
  	unsigned long pfn;
  	unsigned long nr_initialised = 0;
  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
  	struct memblock_region *r = NULL, *tmp;
  #endif
  
  	if (highest_memmap_pfn < end_pfn - 1)
  		highest_memmap_pfn = end_pfn - 1;
  
  	/*
  	 * Honor reservation requested by the driver for this ZONE_DEVICE
  	 * memory
  	 */
  	if (altmap && start_pfn == altmap->base_pfn)
  		start_pfn += altmap->reserve;
  
  	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
  		/*
  		 * There can be holes in boot-time mem_map[]s handed to this
  		 * function.  They do not exist on hotplugged memory.
  		 */
  		if (context != MEMMAP_EARLY)
  			goto not_early;
  
  		if (!early_pfn_valid(pfn))
  			continue;
  		if (!early_pfn_in_nid(pfn, nid))
  			continue;
  		if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
  			break;
  
  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
  		/*
  		 * Check given memblock attribute by firmware which can affect
  		 * kernel memory layout.  If zone==ZONE_MOVABLE but memory is
  		 * mirrored, it's an overlapped memmap init. skip it.
  		 */
  		if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
  			if (!r || pfn >= memblock_region_memory_end_pfn(r)) {
  				for_each_memblock(memory, tmp)
  					if (pfn < memblock_region_memory_end_pfn(tmp))
  						break;
  				r = tmp;
  			}
  			if (pfn >= memblock_region_memory_base_pfn(r) &&
  			    memblock_is_mirror(r)) {
  				/* already initialized as NORMAL */
  				pfn = memblock_region_memory_end_pfn(r);
  				continue;
  			}
  		}
  #endif
  
  not_early:
  		/*
  		 * 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.
  		 *
  		 * bitmap is created for zone's valid pfn range. but memmap
  		 * can be created for invalid pages (for alignment)
  		 * check here not to call set_pageblock_migratetype() against
  		 * pfn out of zone.
  		 */
  		if (!(pfn & (pageblock_nr_pages - 1))) {
  			struct page *page = pfn_to_page(pfn);
  
  			__init_single_page(page, pfn, zone, nid);
  			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
  		} else {
  			__init_single_pfn(pfn, zone, nid);
  		}
  	}
  }
  
  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;
  	}
  }
  
  #ifndef __HAVE_ARCH_MEMMAP_INIT
  #define memmap_init(size, nid, zone, start_pfn) \
  	memmap_init_zone((size), (nid), (zone), (start_pfn), MEMMAP_EARLY)
  #endif
  
  static int zone_batchsize(struct zone *zone)
  {
  #ifdef CONFIG_MMU
  	int batch;
  
  	/*
  	 * The per-cpu-pages pools are set to around 1000th of the
  	 * size of the zone.  But no more than 1/2 of a meg.
  	 *
  	 * OK, so we don't know how big the cache is.  So guess.
  	 */
  	batch = zone->managed_pages / 1024;
  	if (batch * PAGE_SIZE > 512 * 1024)
  		batch = (512 * 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
  }
  
  /*
   * pcp->high and pcp->batch values are related and dependent on one another:
   * ->batch must never be higher then ->high.
   * The following function updates them in a safe manner without read side
   * locking.
   *
   * Any new users of pcp->batch and pcp->high should ensure they can cope with
   * those fields changing asynchronously (acording the the above rule).
   *
   * 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)
  {
         /* start with a fail safe value for batch */
  	pcp->batch = 1;
  	smp_wmb();
  
         /* Update high, then batch, in order */
  	pcp->high = high;
  	smp_wmb();
  
  	pcp->batch = batch;
  }
  
  /* a companion to pageset_set_high() */
  static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
  {
  	pageset_update(&p->pcp, 6 * batch, max(1UL, 1 * batch));
  }
  
  static void pageset_init(struct per_cpu_pageset *p)
  {
  	struct per_cpu_pages *pcp;
  	int migratetype;
  
  	memset(p, 0, sizeof(*p));
  
  	pcp = &p->pcp;
  	pcp->count = 0;
  	for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
  		INIT_LIST_HEAD(&pcp->lists[migratetype]);
  }
  
  static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
  {
  	pageset_init(p);
  	pageset_set_batch(p, batch);
  }
  
  /*
   * pageset_set_high() sets the high water mark for hot per_cpu_pagelist
   * to the value high for the pageset p.
   */
  static void pageset_set_high(struct per_cpu_pageset *p,
  				unsigned long high)
  {
  	unsigned long batch = max(1UL, high / 4);
  	if ((high / 4) > (PAGE_SHIFT * 8))
  		batch = PAGE_SHIFT * 8;
  
  	pageset_update(&p->pcp, high, batch);
  }
  
  static void pageset_set_high_and_batch(struct zone *zone,
  				       struct per_cpu_pageset *pcp)
  {
  	if (percpu_pagelist_fraction)
  		pageset_set_high(pcp,
  			(zone->managed_pages /
  				percpu_pagelist_fraction));
  	else
  		pageset_set_batch(pcp, zone_batchsize(zone));
  }
  
  static void __meminit zone_pageset_init(struct zone *zone, int cpu)
  {
  	struct per_cpu_pageset *pcp = per_cpu_ptr(zone->pageset, cpu);
  
  	pageset_init(pcp);
  	pageset_set_high_and_batch(zone, pcp);
  }
  
  static void __meminit setup_zone_pageset(struct zone *zone)
  {
  	int cpu;
  	zone->pageset = alloc_percpu(struct per_cpu_pageset);
  	for_each_possible_cpu(cpu)
  		zone_pageset_init(zone, cpu);
  }
  
  /*
   * 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;
  
  	for_each_populated_zone(zone)
  		setup_zone_pageset(zone);
  
  	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->pageset = &boot_pageset;
  
  	if (populated_zone(zone))
  		printk(KERN_DEBUG "  %s zone: %lu pages, LIFO batch:%u\n",
  			zone->name, zone->present_pages,
  					 zone_batchsize(zone));
  }
  
  int __meminit init_currently_empty_zone(struct zone *zone,
  					unsigned long zone_start_pfn,
  					unsigned long size)
  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  
  	pgdat->nr_zones = zone_idx(zone) + 1;
  
  	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;
  
  	return 0;
  }
  
  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
  #ifndef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
  
  /*
   * Required by SPARSEMEM. Given a PFN, return what node the PFN is on.
   */
  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 != -1) {
  		state->last_start = start_pfn;
  		state->last_end = end_pfn;
  		state->last_nid = nid;
  	}
  
  	return nid;
  }
  #endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */
  
  /**
   * free_bootmem_with_active_regions - Call memblock_free_early_nid for each active range
   * @nid: The node to free memory on. If MAX_NUMNODES, all nodes are freed.
   * @max_low_pfn: The highest PFN that will be passed to memblock_free_early_nid
   *
   * If an architecture guarantees that all ranges registered contain no holes
   * and may be freed, this this function may be used instead of calling
   * memblock_free_early_nid() manually.
   */
  void __init free_bootmem_with_active_regions(int nid, unsigned long max_low_pfn)
  {
  	unsigned long start_pfn, end_pfn;
  	int i, this_nid;
  
  	for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid) {
  		start_pfn = min(start_pfn, max_low_pfn);
  		end_pfn = min(end_pfn, max_low_pfn);
  
  		if (start_pfn < end_pfn)
  			memblock_free_early_nid(PFN_PHYS(start_pfn),
  					(end_pfn - start_pfn) << PAGE_SHIFT,
  					this_nid);
  	}
  }
  
  /**
   * sparse_memory_present_with_active_regions - Call memory_present for each active range
   * @nid: The node to call memory_present for. If MAX_NUMNODES, all nodes will be used.
   *
   * If an architecture guarantees that all ranges registered contain no holes and may
   * be freed, this function may be used instead of calling memory_present() manually.
   */
  void __init sparse_memory_present_with_active_regions(int nid)
  {
  	unsigned long start_pfn, end_pfn;
  	int i, this_nid;
  
  	for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid)
  		memory_present(this_nid, start_pfn, end_pfn);
  }
  
  /**
   * 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 __meminit 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 __meminit 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 __meminit 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 *ignored)
  {
  	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 __meminit __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
   *
   * It returns 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 __meminit zone_absent_pages_in_node(int nid,
  					unsigned long zone_type,
  					unsigned long node_start_pfn,
  					unsigned long node_end_pfn,
  					unsigned long *ignored)
  {
  	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_memblock(memory, 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;
  }
  
  #else /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
  static inline unsigned long __meminit 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 *zones_size)
  {
  	unsigned int zone;
  
  	*zone_start_pfn = node_start_pfn;
  	for (zone = 0; zone < zone_type; zone++)
  		*zone_start_pfn += zones_size[zone];
  
  	*zone_end_pfn = *zone_start_pfn + zones_size[zone_type];
  
  	return zones_size[zone_type];
  }
  
  static inline unsigned long __meminit zone_absent_pages_in_node(int nid,
  						unsigned long zone_type,
  						unsigned long node_start_pfn,
  						unsigned long node_end_pfn,
  						unsigned long *zholes_size)
  {
  	if (!zholes_size)
  		return 0;
  
  	return zholes_size[zone_type];
  }
  
  #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
  
  static void __meminit calculate_node_totalpages(struct pglist_data *pgdat,
  						unsigned long node_start_pfn,
  						unsigned long node_end_pfn,
  						unsigned long *zones_size,
  						unsigned long *zholes_size)
  {
  	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 size, real_size;
  
  		size = zone_spanned_pages_in_node(pgdat->node_id, i,
  						  node_start_pfn,
  						  node_end_pfn,
  						  &zone_start_pfn,
  						  &zone_end_pfn,
  						  zones_size);
  		real_size = size - zone_absent_pages_in_node(pgdat->node_id, i,
  						  node_start_pfn, node_end_pfn,
  						  zholes_size);
  		if (size)
  			zone->zone_start_pfn = zone_start_pfn;
  		else
  			zone->zone_start_pfn = 0;
  		zone->spanned_pages = size;
  		zone->present_pages = real_size;
  
  		totalpages += size;
  		realtotalpages += real_size;
  	}
  
  	pgdat->node_spanned_pages = totalpages;
  	pgdat->node_present_pages = realtotalpages;
  	printk(KERN_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 __init setup_usemap(struct pglist_data *pgdat,
  				struct zone *zone,
  				unsigned long zone_start_pfn,
  				unsigned long zonesize)
  {
  	unsigned long usemapsize = usemap_size(zone_start_pfn, zonesize);
  	zone->pageblock_flags = NULL;
  	if (usemapsize)
  		zone->pageblock_flags =
  			memblock_virt_alloc_node_nopanic(usemapsize,
  							 pgdat->node_id);
  }
  #else
  static inline void setup_usemap(struct pglist_data *pgdat, struct zone *zone,
  				unsigned long zone_start_pfn, unsigned long zonesize) {}
  #endif /* CONFIG_SPARSEMEM */
  
  #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
  
  /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
  void __paginginit 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 __paginginit set_pageblock_order(void)
  {
  }
  
  #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
  
  static unsigned long __paginginit 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 naturally algined 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;
  }
  
  /*
   * 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.
   */
  static void __paginginit free_area_init_core(struct pglist_data *pgdat)
  {
  	enum zone_type j;
  	int nid = pgdat->node_id;
  	int ret;
  
  	pgdat_resize_init(pgdat);
  #ifdef CONFIG_NUMA_BALANCING
  	spin_lock_init(&pgdat->numabalancing_migrate_lock);
  	pgdat->numabalancing_migrate_nr_pages = 0;
  	pgdat->numabalancing_migrate_next_window = jiffies;
  #endif
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	spin_lock_init(&pgdat->split_queue_lock);
  	INIT_LIST_HEAD(&pgdat->split_queue);
  	pgdat->split_queue_len = 0;
  #endif
  	init_waitqueue_head(&pgdat->kswapd_wait);
  	init_waitqueue_head(&pgdat->pfmemalloc_wait);
  #ifdef CONFIG_COMPACTION
  	init_waitqueue_head(&pgdat->kcompactd_wait);
  #endif
  	pgdat_page_ext_init(pgdat);
  	spin_lock_init(&pgdat->lru_lock);
  	lruvec_init(node_lruvec(pgdat));
  
  	for (j = 0; j < MAX_NR_ZONES; j++) {
  		struct zone *zone = pgdat->node_zones + j;
  		unsigned long size, realsize, freesize, memmap_pages;
  		unsigned long zone_start_pfn = zone->zone_start_pfn;
  
  		size = zone->spanned_pages;
  		realsize = 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, realsize);
  		if (!is_highmem_idx(j)) {
  			if (freesize >= memmap_pages) {
  				freesize -= memmap_pages;
  				if (memmap_pages)
  					printk(KERN_DEBUG
  					       "  %s zone: %lu pages used for memmap\n",
  					       zone_names[j], memmap_pages);
  			} else
  				pr_warn("  %s zone: %lu pages exceeds freesize %lu\n",
  					zone_names[j], memmap_pages, freesize);
  		}
  
  		/* Account for reserved pages */
  		if (j == 0 && freesize > dma_reserve) {
  			freesize -= dma_reserve;
  			printk(KERN_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->managed_pages = is_highmem_idx(j) ? realsize : freesize;
  #ifdef CONFIG_NUMA
  		zone->node = nid;
  #endif
  		zone->name = zone_names[j];
  		zone->zone_pgdat = pgdat;
  		spin_lock_init(&zone->lock);
  		zone_seqlock_init(zone);
  		zone_pcp_init(zone);
  
  		if (!size)
  			continue;
  
  		set_pageblock_order();
  		setup_usemap(pgdat, zone, zone_start_pfn, size);
  		ret = init_currently_empty_zone(zone, zone_start_pfn, size);
  		BUG_ON(ret);
  		memmap_init(size, nid, j, zone_start_pfn);
  	}
  }
  
  static void __ref 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;
  
  #ifdef CONFIG_FLAT_NODE_MEM_MAP
  	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 = alloc_remap(pgdat->node_id, size);
  		if (!map)
  			map = memblock_virt_alloc_node_nopanic(size,
  							       pgdat->node_id);
  		pgdat->node_mem_map = map + offset;
  	}
  #ifndef CONFIG_NEED_MULTIPLE_NODES
  	/*
  	 * 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 defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) || defined(CONFIG_FLATMEM)
  		if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
  			mem_map -= offset;
  #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
  	}
  #endif
  #endif /* CONFIG_FLAT_NODE_MEM_MAP */
  }
  
  void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
  		unsigned long node_start_pfn, unsigned long *zholes_size)
  {
  	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_classzone_idx);
  
  	pgdat->node_id = nid;
  	pgdat->node_start_pfn = node_start_pfn;
  	pgdat->per_cpu_nodestats = NULL;
  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
  	get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
  	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);
  #else
  	start_pfn = node_start_pfn;
  #endif
  	calculate_node_totalpages(pgdat, start_pfn, end_pfn,
  				  zones_size, zholes_size);
  
  	alloc_node_mem_map(pgdat);
  #ifdef CONFIG_FLAT_NODE_MEM_MAP
  	printk(KERN_DEBUG "free_area_init_node: node %d, pgdat %08lx, node_mem_map %08lx\n",
  		nid, (unsigned long)pgdat,
  		(unsigned long)pgdat->node_mem_map);
  #endif
  
  	reset_deferred_meminit(pgdat);
  	free_area_init_core(pgdat);
  }
  
  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
  
  #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.
   *
   * Returns 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 = -1;
  	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 the lowest pfn for a node */
  static unsigned long __init find_min_pfn_for_node(int nid)
  {
  	unsigned long min_pfn = ULONG_MAX;
  	unsigned long start_pfn;
  	int i;
  
  	for_each_mem_pfn_range(i, nid, &start_pfn, NULL, NULL)
  		min_pfn = min(min_pfn, start_pfn);
  
  	if (min_pfn == ULONG_MAX) {
  		pr_warn("Could not find start_pfn for node %d\n", nid);
  		return 0;
  	}
  
  	return min_pfn;
  }
  
  /**
   * find_min_pfn_with_active_regions - Find the minimum PFN registered
   *
   * It returns the minimum PFN based on information provided via
   * memblock_set_node().
   */
  unsigned long __init find_min_pfn_with_active_regions(void)
  {
  	return find_min_pfn_for_node(MAX_NUMNODES);
  }
  
  /*
   * 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_memblock(memory, r) {
  			if (!memblock_is_hotpluggable(r))
  				continue;
  
  			nid = r->nid;
  
  			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_memblock(memory, r) {
  			if (memblock_is_mirror(r))
  				continue;
  
  			nid = r->nid;
  
  			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.");
  
  		goto out2;
  	}
  
  	/*
  	 * If movablecore=nn[KMG] 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;
  
  	if (N_MEMORY == N_NORMAL_MEMORY)
  		return;
  
  	for (zone_type = 0; zone_type <= ZONE_MOVABLE - 1; zone_type++) {
  		struct zone *zone = &pgdat->node_zones[zone_type];
  		if (populated_zone(zone)) {
  			node_set_state(nid, N_HIGH_MEMORY);
  			if (N_NORMAL_MEMORY != N_HIGH_MEMORY &&
  			    zone_type <= ZONE_NORMAL)
  				node_set_state(nid, N_NORMAL_MEMORY);
  			break;
  		}
  	}
  }
  
  /**
   * free_area_init_nodes - 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_nodes(unsigned long *max_zone_pfn)
  {
  	unsigned long start_pfn, end_pfn;
  	int i, nid;
  
  	/* 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();
  
  	for (i = 0; i < MAX_NR_ZONES; i++) {
  		if (i == ZONE_MOVABLE)
  			continue;
  
  		end_pfn = max(max_zone_pfn[i], start_pfn);
  		arch_zone_lowest_possible_pfn[i] = start_pfn;
  		arch_zone_highest_possible_pfn[i] = end_pfn;
  
  		start_pfn = end_pfn;
  	}
  	arch_zone_lowest_possible_pfn[ZONE_MOVABLE] = 0;
  	arch_zone_highest_possible_pfn[ZONE_MOVABLE] = 0;
  
  	/* 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 */
  	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);
  
  	/* 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, NULL,
  				find_min_pfn_for_node(nid), NULL);
  
  		/* Any memory on that node */
  		if (pgdat->node_present_pages)
  			node_set_state(nid, N_MEMORY);
  		check_for_memory(pgdat, nid);
  	}
  }
  
  static int __init cmdline_parse_core(char *p, unsigned long *core)
  {
  	unsigned long long coremem;
  	if (!p)
  		return -EINVAL;
  
  	coremem = memparse(p, &p);
  	*core = coremem >> PAGE_SHIFT;
  
  	/* Paranoid check that UL is enough for the coremem value */
  	WARN_ON((coremem >> PAGE_SHIFT) > ULONG_MAX);
  
  	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);
  }
  
  /*
   * 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);
  }
  
  early_param("kernelcore", cmdline_parse_kernelcore);
  early_param("movablecore", cmdline_parse_movablecore);
  
  #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
  
  void adjust_managed_page_count(struct page *page, long count)
  {
  	spin_lock(&managed_page_count_lock);
  	page_zone(page)->managed_pages += count;
  	totalram_pages += count;
  #ifdef CONFIG_HIGHMEM
  	if (PageHighMem(page))
  		totalhigh_pages += count;
  #endif
  	spin_unlock(&managed_page_count_lock);
  }
  EXPORT_SYMBOL(adjust_managed_page_count);
  
  unsigned long free_reserved_area(void *start, void *end, int poison, 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++) {
  		if ((unsigned int)poison <= 0xFF)
  			memset(pos, poison, PAGE_SIZE);
  		free_reserved_page(virt_to_page(pos));
  	}
  
  	if (pages && s)
  		pr_info("Freeing %s memory: %ldK\n",
  			s, pages << (PAGE_SHIFT - 10));
  
  	return pages;
  }
  EXPORT_SYMBOL(free_reserved_area);
  
  #ifdef	CONFIG_HIGHMEM
  void free_highmem_page(struct page *page)
  {
  	__free_reserved_page(page);
  	totalram_pages++;
  	page_zone(page)->managed_pages++;
  	totalhigh_pages++;
  }
  #endif
  
  
  void __init mem_init_print_info(const char *str)
  {
  	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 <= pos && pos < end && 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
  		"%s%s)\n",
  		nr_free_pages() << (PAGE_SHIFT - 10),
  		physpages << (PAGE_SHIFT - 10),
  		codesize >> 10, datasize >> 10, rosize >> 10,
  		(init_data_size + init_code_size) >> 10, bss_size >> 10,
  		(physpages - totalram_pages - totalcma_pages) << (PAGE_SHIFT - 10),
  		totalcma_pages << (PAGE_SHIFT - 10),
  #ifdef	CONFIG_HIGHMEM
  		totalhigh_pages << (PAGE_SHIFT - 10),
  #endif
  		str ? ", " : "", str ? str : "");
  }
  
  /**
   * 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;
  }
  
  void __init free_area_init(unsigned long *zones_size)
  {
  	free_area_init_node(0, zones_size,
  			__pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL);
  }
  
  static int page_alloc_cpu_notify(struct notifier_block *self,
  				 unsigned long action, void *hcpu)
  {
  	int cpu = (unsigned long)hcpu;
  
  	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
  		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);
  	}
  	return NOTIFY_OK;
  }
  
  void __init page_alloc_init(void)
  {
  	hotcpu_notifier(page_alloc_cpu_notify, 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;
  
  			/* 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 > zone->managed_pages)
  				max = zone->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 j, idx;
  
  	for_each_online_pgdat(pgdat) {
  		for (j = 0; j < MAX_NR_ZONES; j++) {
  			struct zone *zone = pgdat->node_zones + j;
  			unsigned long managed_pages = zone->managed_pages;
  
  			zone->lowmem_reserve[j] = 0;
  
  			idx = j;
  			while (idx) {
  				struct zone *lower_zone;
  
  				idx--;
  
  				if (sysctl_lowmem_reserve_ratio[idx] < 1)
  					sysctl_lowmem_reserve_ratio[idx] = 1;
  
  				lower_zone = pgdat->node_zones + idx;
  				lower_zone->lowmem_reserve[j] = managed_pages /
  					sysctl_lowmem_reserve_ratio[idx];
  				managed_pages += lower_zone->managed_pages;
  			}
  		}
  	}
  
  	/* 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 pages_low = extra_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;
  	}
  
  	for_each_zone(zone) {
  		u64 min, low;
  
  		spin_lock_irqsave(&zone->lock, flags);
  		min = (u64)pages_min * zone->managed_pages;
  		do_div(min, lowmem_pages);
  		low = (u64)pages_low * zone->managed_pages;
  		do_div(low, vm_total_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 asynch page reclaim, and so should
  			 * not be capped for highmem.
  			 */
  			unsigned long min_pages;
  
  			min_pages = zone->managed_pages / 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] = min;
  		}
  
  		/*
  		 * Set the kswapd watermarks distance according to the
  		 * scale factor in proportion to available memory, but
  		 * ensure a minimum size on small systems.
  		 */
  		min = max_t(u64, min >> 2,
  			    mult_frac(zone->managed_pages,
  				      watermark_scale_factor, 10000));
  
  		zone->watermark[WMARK_LOW]  = min_wmark_pages(zone) +
  					low + min;
  		zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) +
  					low + min * 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)
  {
  	mutex_lock(&zonelists_mutex);
  	__setup_per_zone_wmarks();
  	mutex_unlock(&zonelists_mutex);
  }
  
  /*
   * Initialise min_free_kbytes.
   *
   * For small machines we want it small (128k min).  For large machines
   * we want it large (64MB 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
   */
  int __meminit init_per_zone_wmark_min(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 = new_min_free_kbytes;
  		if (min_free_kbytes < 128)
  			min_free_kbytes = 128;
  		if (min_free_kbytes > 65536)
  			min_free_kbytes = 65536;
  	} 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);
  	}
  	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
  
  	return 0;
  }
  core_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
   *	or extra_free_kbytes changes.
   */
  int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
  	void __user *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 __user *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 *
  				sysctl_min_unmapped_ratio) / 100;
  }
  
  
  int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
  	void __user *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 *
  				sysctl_min_slab_ratio) / 100;
  }
  
  int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
  	void __user *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 __user *buffer, size_t *length, loff_t *ppos)
  {
  	proc_dointvec_minmax(table, write, buffer, length, ppos);
  	setup_per_zone_lowmem_reserve();
  	return 0;
  }
  
  /*
   * percpu_pagelist_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_fraction_sysctl_handler(struct ctl_table *table, int write,
  	void __user *buffer, size_t *length, loff_t *ppos)
  {
  	struct zone *zone;
  	int old_percpu_pagelist_fraction;
  	int ret;
  
  	mutex_lock(&pcp_batch_high_lock);
  	old_percpu_pagelist_fraction = percpu_pagelist_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_fraction &&
  	    percpu_pagelist_fraction < MIN_PERCPU_PAGELIST_FRACTION) {
  		percpu_pagelist_fraction = old_percpu_pagelist_fraction;
  		ret = -EINVAL;
  		goto out;
  	}
  
  	/* No change? */
  	if (percpu_pagelist_fraction == old_percpu_pagelist_fraction)
  		goto out;
  
  	for_each_populated_zone(zone) {
  		unsigned int cpu;
  
  		for_each_possible_cpu(cpu)
  			pageset_set_high_and_batch(zone,
  					per_cpu_ptr(zone->pageset, cpu));
  	}
  out:
  	mutex_unlock(&pcp_batch_high_lock);
  	return ret;
  }
  
  #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
  
  #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
  
  /*
   * 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;
  
  	/* 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);
  
  		/* 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);
  
  	do {
  		size = bucketsize << log2qty;
  		if (flags & HASH_EARLY)
  			table = memblock_virt_alloc_nopanic(size, 0);
  		else if (hashdist)
  			table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);
  		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
  			 */
  			if (get_order(size) < MAX_ORDER) {
  				table = alloc_pages_exact(size, GFP_ATOMIC);
  				kmemleak_alloc(table, size, 1, GFP_ATOMIC);
  			}
  		}
  	} 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)\n",
  		tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size);
  
  	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.
   * If @count is not zero, it is okay to include less @count unmovable pages
   *
   * PageLRU check without isolation or lru_lock could race so that
   * MIGRATE_MOVABLE block might include unmovable pages. It means you can't
   * expect this function should be exact.
   */
  bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
  			 bool skip_hwpoisoned_pages)
  {
  	unsigned long pfn, iter, found;
  	int mt;
  
  	/*
  	 * For avoiding noise data, lru_add_drain_all() should be called
  	 * If ZONE_MOVABLE, the zone never contains unmovable pages
  	 */
  	if (zone_idx(zone) == ZONE_MOVABLE)
  		return false;
  	mt = get_pageblock_migratetype(page);
  	if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt))
  		return false;
  
  	pfn = page_to_pfn(page);
  	for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) {
  		unsigned long check = pfn + iter;
  
  		if (!pfn_valid_within(check))
  			continue;
  
  		page = pfn_to_page(check);
  
  		/*
  		 * Hugepages are not in LRU lists, but they're movable.
  		 * We need not scan over tail pages bacause we don't
  		 * handle each tail page individually in migration.
  		 */
  		if (PageHuge(page)) {
  			iter = round_up(iter + 1, 1<<compound_order(page)) - 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 << page_order(page)) - 1;
  			continue;
  		}
  
  		/*
  		 * The HWPoisoned page may be not in buddy system, and
  		 * page_count() is not 0.
  		 */
  		if (skip_hwpoisoned_pages && PageHWPoison(page))
  			continue;
  
  		if (!PageLRU(page))
  			found++;
  		/*
  		 * 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.
  		 */
  		/*
  		 * If the page is not RAM, page_count()should be 0.
  		 * we don't need more check. This is an _used_ not-movable page.
  		 *
  		 * The problematic thing here is PG_reserved pages. PG_reserved
  		 * is set to both of a memory hole page and a _used_ kernel
  		 * page at boot.
  		 */
  		if (found > count)
  			return true;
  	}
  	return false;
  }
  
  bool is_pageblock_removable_nolock(struct page *page)
  {
  	struct zone *zone;
  	unsigned long pfn;
  
  	/*
  	 * We have to be careful here because we are iterating over memory
  	 * sections which are not zone aware so we might end up outside of
  	 * the zone but still within the section.
  	 * We have to take care about the node as well. If the node is offline
  	 * its NODE_DATA will be NULL - see page_zone.
  	 */
  	if (!node_online(page_to_nid(page)))
  		return false;
  
  	zone = page_zone(page);
  	pfn = page_to_pfn(page);
  	if (!zone_spans_pfn(zone, pfn))
  		return false;
  
  	return !has_unmovable_pages(zone, page, 0, true);
  }
  
  #if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA)
  
  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));
  }
  
  /* [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 long nr_reclaimed;
  	unsigned long pfn = start;
  	unsigned int tries = 0;
  	int ret = 0;
  
  	migrate_prep();
  
  	while (pfn < end || !list_empty(&cc->migratepages)) {
  		if (fatal_signal_pending(current)) {
  			ret = -EINTR;
  			break;
  		}
  
  		if (list_empty(&cc->migratepages)) {
  			cc->nr_migratepages = 0;
  			pfn = isolate_migratepages_range(cc, pfn, end);
  			if (!pfn) {
  				ret = -EINTR;
  				break;
  			}
  			tries = 0;
  		} else if (++tries == 5) {
  			ret = ret < 0 ? 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_migrate_target,
  				    NULL, 0, cc->mode, MR_CMA);
  	}
  	if (ret < 0) {
  		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 underlaying pageblocks (either
   *			#MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
   *			in range must have the same migratetype and it must
   *			be either of the two.
   *
   * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
   * aligned, however it's the caller's responsibility to guarantee that
   * we are the only thread that changes migrate type of pageblocks the
   * pages fall in.
   *
   * The PFN range must belong to a single zone.
   *
   * Returns 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)
  {
  	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,
  	};
  	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,
  				       false);
  	if (ret)
  		return ret;
  
  	cc.zone->cma_alloc = 1;
  	/*
  	 * 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.
  	 */
  
  	lru_add_drain_all();
  	drain_all_pages(cc.zone);
  
  	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 = page_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. */
  	ret = test_pages_isolated(outer_start, end, false);
  	if (ret) {
  		pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n",
  			__func__, outer_start, end);
  		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);
  	cc.zone->cma_alloc = 0;
  	return ret;
  }
  
  void free_contig_range(unsigned long pfn, unsigned nr_pages)
  {
  	unsigned int count = 0;
  
  	for (; nr_pages--; pfn++) {
  		struct page *page = pfn_to_page(pfn);
  
  		count += page_count(page) != 1;
  		__free_page(page);
  	}
  	WARN(count != 0, "%d pages are still in use!\n", count);
  }
  #endif
  
  #ifdef CONFIG_MEMORY_HOTPLUG
  /*
   * The zone indicated has a new number of managed_pages; batch sizes and percpu
   * page high values need to be recalulated.
   */
  void __meminit zone_pcp_update(struct zone *zone)
  {
  	unsigned cpu;
  	mutex_lock(&pcp_batch_high_lock);
  	for_each_possible_cpu(cpu)
  		pageset_set_high_and_batch(zone,
  				per_cpu_ptr(zone->pageset, cpu));
  	mutex_unlock(&pcp_batch_high_lock);
  }
  #endif
  
  void zone_pcp_reset(struct zone *zone)
  {
  	unsigned long flags;
  	int cpu;
  	struct per_cpu_pageset *pset;
  
  	/* avoid races with drain_pages()  */
  	local_irq_save(flags);
  	if (zone->pageset != &boot_pageset) {
  		for_each_online_cpu(cpu) {
  			pset = per_cpu_ptr(zone->pageset, cpu);
  			drain_zonestat(zone, pset);
  		}
  		free_percpu(zone->pageset);
  		zone->pageset = &boot_pageset;
  	}
  	local_irq_restore(flags);
  }
  
  #ifdef CONFIG_MEMORY_HOTREMOVE
  /*
   * All pages in the range must be in a single zone and isolated
   * before calling this.
   */
  void
  __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
  {
  	struct page *page;
  	struct zone *zone;
  	unsigned int order, i;
  	unsigned long pfn;
  	unsigned long flags;
  	/* find the first valid pfn */
  	for (pfn = start_pfn; pfn < end_pfn; pfn++)
  		if (pfn_valid(pfn))
  			break;
  	if (pfn == end_pfn)
  		return;
  	zone = page_zone(pfn_to_page(pfn));
  	spin_lock_irqsave(&zone->lock, flags);
  	pfn = start_pfn;
  	while (pfn < end_pfn) {
  		if (!pfn_valid(pfn)) {
  			pfn++;
  			continue;
  		}
  		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++;
  			SetPageReserved(page);
  			continue;
  		}
  
  		BUG_ON(page_count(page));
  		BUG_ON(!PageBuddy(page));
  		order = page_order(page);
  #ifdef CONFIG_DEBUG_VM
  		pr_info("remove from free list %lx %d %lx\n",
  			pfn, 1 << order, end_pfn);
  #endif
  		list_del(&page->lru);
  		rmv_page_order(page);
  		zone->free_area[order].nr_free--;
  		for (i = 0; i < (1 << order); i++)
  			SetPageReserved((page+i));
  		pfn += (1 << order);
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  }
  #endif
  
  bool is_free_buddy_page(struct page *page)
  {
  	struct zone *zone = page_zone(page);
  	unsigned long pfn = page_to_pfn(page);
  	unsigned long flags;
  	unsigned int order;
  
  	spin_lock_irqsave(&zone->lock, flags);
  	for (order = 0; order < MAX_ORDER; order++) {
  		struct page *page_head = page - (pfn & ((1 << order) - 1));
  
  		if (PageBuddy(page_head) && page_order(page_head) >= order)
  			break;
  	}
  	spin_unlock_irqrestore(&zone->lock, flags);
  
  	return order < MAX_ORDER;
  }
  