Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 6712 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
new file mode 100644
index 0000000000..afed33fd87
--- /dev/null
+++ b/mm/page_alloc.c
@@ -0,0 +1,6712 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/mm/page_alloc.c
+ *
+ *  Manages the free list, the system allocates free pages here.
+ *  Note that kmalloc() lives in slab.c
+ *
+ *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *  Swap reorganised 29.12.95, Stephen Tweedie
+ *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
+ *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
+ *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
+ *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
+ *  Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
+ *          (lots of bits borrowed from Ingo Molnar & Andrew Morton)
+ */
+
+#include <linux/stddef.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/interrupt.h>
+#include <linux/jiffies.h>
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/kasan.h>
+#include <linux/kmsan.h>
+#include <linux/module.h>
+#include <linux/suspend.h>
+#include <linux/ratelimit.h>
+#include <linux/oom.h>
+#include <linux/topology.h>
+#include <linux/sysctl.h>
+#include <linux/cpu.h>
+#include <linux/cpuset.h>
+#include <linux/memory_hotplug.h>
+#include <linux/nodemask.h>
+#include <linux/vmstat.h>
+#include <linux/fault-inject.h>
+#include <linux/compaction.h>
+#include <trace/events/kmem.h>
+#include <trace/events/oom.h>
+#include <linux/prefetch.h>
+#include <linux/mm_inline.h>
+#include <linux/mmu_notifier.h>
+#include <linux/migrate.h>
+#include <linux/sched/mm.h>
+#include <linux/page_owner.h>
+#include <linux/page_table_check.h>
+#include <linux/memcontrol.h>
+#include <linux/ftrace.h>
+#include <linux/lockdep.h>
+#include <linux/psi.h>
+#include <linux/khugepaged.h>
+#include <linux/delayacct.h>
+#include <asm/div64.h>
+#include "internal.h"
+#include "shuffle.h"
+#include "page_reporting.h"
+
+/* Free Page Internal flags: for internal, non-pcp variants of free_pages(). */
+typedef int __bitwise fpi_t;
+
+/* No special request */
+#define FPI_NONE		((__force fpi_t)0)
+
+/*
+ * Skip free page reporting notification for the (possibly merged) page.
+ * This does not hinder free page reporting from grabbing the page,
+ * reporting it and marking it "reported" -  it only skips notifying
+ * the free page reporting infrastructure about a newly freed page. For
+ * example, used when temporarily pulling a page from a freelist and
+ * putting it back unmodified.
+ */
+#define FPI_SKIP_REPORT_NOTIFY	((__force fpi_t)BIT(0))
+
+/*
+ * Place the (possibly merged) page to the tail of the freelist. Will ignore
+ * page shuffling (relevant code - e.g., memory onlining - is expected to
+ * shuffle the whole zone).
+ *
+ * Note: No code should rely on this flag for correctness - it's purely
+ *       to allow for optimizations when handing back either fresh pages
+ *       (memory onlining) or untouched pages (page isolation, free page
+ *       reporting).
+ */
+#define FPI_TO_TAIL		((__force fpi_t)BIT(1))
+
+/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
+static DEFINE_MUTEX(pcp_batch_high_lock);
+#define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
+
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
+/*
+ * On SMP, spin_trylock is sufficient protection.
+ * On PREEMPT_RT, spin_trylock is equivalent on both SMP and UP.
+ */
+#define pcp_trylock_prepare(flags)	do { } while (0)
+#define pcp_trylock_finish(flag)	do { } while (0)
+#else
+
+/* UP spin_trylock always succeeds so disable IRQs to prevent re-entrancy. */
+#define pcp_trylock_prepare(flags)	local_irq_save(flags)
+#define pcp_trylock_finish(flags)	local_irq_restore(flags)
+#endif
+
+/*
+ * Locking a pcp requires a PCP lookup followed by a spinlock. To avoid
+ * a migration causing the wrong PCP to be locked and remote memory being
+ * potentially allocated, pin the task to the CPU for the lookup+lock.
+ * preempt_disable is used on !RT because it is faster than migrate_disable.
+ * migrate_disable is used on RT because otherwise RT spinlock usage is
+ * interfered with and a high priority task cannot preempt the allocator.
+ */
+#ifndef CONFIG_PREEMPT_RT
+#define pcpu_task_pin()		preempt_disable()
+#define pcpu_task_unpin()	preempt_enable()
+#else
+#define pcpu_task_pin()		migrate_disable()
+#define pcpu_task_unpin()	migrate_enable()
+#endif
+
+/*
+ * Generic helper to lookup and a per-cpu variable with an embedded spinlock.
+ * Return value should be used with equivalent unlock helper.
+ */
+#define pcpu_spin_lock(type, member, ptr)				\
+({									\
+	type *_ret;							\
+	pcpu_task_pin();						\
+	_ret = this_cpu_ptr(ptr);					\
+	spin_lock(&_ret->member);					\
+	_ret;								\
+})
+
+#define pcpu_spin_trylock(type, member, ptr)				\
+({									\
+	type *_ret;							\
+	pcpu_task_pin();						\
+	_ret = this_cpu_ptr(ptr);					\
+	if (!spin_trylock(&_ret->member)) {				\
+		pcpu_task_unpin();					\
+		_ret = NULL;						\
+	}								\
+	_ret;								\
+})
+
+#define pcpu_spin_unlock(member, ptr)					\
+({									\
+	spin_unlock(&ptr->member);					\
+	pcpu_task_unpin();						\
+})
+
+/* struct per_cpu_pages specific helpers. */
+#define pcp_spin_lock(ptr)						\
+	pcpu_spin_lock(struct per_cpu_pages, lock, ptr)
+
+#define pcp_spin_trylock(ptr)						\
+	pcpu_spin_trylock(struct per_cpu_pages, lock, ptr)
+
+#define pcp_spin_unlock(ptr)						\
+	pcpu_spin_unlock(lock, ptr)
+
+#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
+DEFINE_PER_CPU(int, numa_node);
+EXPORT_PER_CPU_SYMBOL(numa_node);
+#endif
+
+DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);
+
+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+/*
+ * N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
+ * It will not be defined when CONFIG_HAVE_MEMORYLESS_NODES is not defined.
+ * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem()
+ * defined in <linux/topology.h>.
+ */
+DEFINE_PER_CPU(int, _numa_mem_);		/* Kernel "local memory" node */
+EXPORT_PER_CPU_SYMBOL(_numa_mem_);
+#endif
+
+static DEFINE_MUTEX(pcpu_drain_mutex);
+
+#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
+volatile unsigned long latent_entropy __latent_entropy;
+EXPORT_SYMBOL(latent_entropy);
+#endif
+
+/*
+ * Array of node states.
+ */
+nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
+	[N_POSSIBLE] = NODE_MASK_ALL,
+	[N_ONLINE] = { { [0] = 1UL } },
+#ifndef CONFIG_NUMA
+	[N_NORMAL_MEMORY] = { { [0] = 1UL } },
+#ifdef CONFIG_HIGHMEM
+	[N_HIGH_MEMORY] = { { [0] = 1UL } },
+#endif
+	[N_MEMORY] = { { [0] = 1UL } },
+	[N_CPU] = { { [0] = 1UL } },
+#endif	/* NUMA */
+};
+EXPORT_SYMBOL(node_states);
+
+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_HUGETLB_PAGE_SIZE_VARIABLE
+unsigned int pageblock_order __read_mostly;
+#endif
+
+static void __free_pages_ok(struct page *page, unsigned int order,
+			    fpi_t fpi_flags);
+
+/*
+ * results with 256, 32 in the lowmem_reserve sysctl:
+ *	1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
+ *	1G machine -> (16M dma, 784M normal, 224M high)
+ *	NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
+ *	HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
+ *	HIGHMEM allocation will leave (224M+784M)/256 of ram reserved in ZONE_DMA
+ *
+ * TBD: should special case ZONE_DMA32 machines here - in those we normally
+ * don't need any ZONE_NORMAL reservation
+ */
+static int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {
+#ifdef CONFIG_ZONE_DMA
+	[ZONE_DMA] = 256,
+#endif
+#ifdef CONFIG_ZONE_DMA32
+	[ZONE_DMA32] = 256,
+#endif
+	[ZONE_NORMAL] = 32,
+#ifdef CONFIG_HIGHMEM
+	[ZONE_HIGHMEM] = 0,
+#endif
+	[ZONE_MOVABLE] = 0,
+};
+
+char * const zone_names[MAX_NR_ZONES] = {
+#ifdef CONFIG_ZONE_DMA
+	 "DMA",
+#endif
+#ifdef CONFIG_ZONE_DMA32
+	 "DMA32",
+#endif
+	 "Normal",
+#ifdef CONFIG_HIGHMEM
+	 "HighMem",
+#endif
+	 "Movable",
+#ifdef CONFIG_ZONE_DEVICE
+	 "Device",
+#endif
+};
+
+const char * const migratetype_names[MIGRATE_TYPES] = {
+	"Unmovable",
+	"Movable",
+	"Reclaimable",
+	"HighAtomic",
+#ifdef CONFIG_CMA
+	"CMA",
+#endif
+#ifdef CONFIG_MEMORY_ISOLATION
+	"Isolate",
+#endif
+};
+
+int min_free_kbytes = 1024;
+int user_min_free_kbytes = -1;
+static int watermark_boost_factor __read_mostly = 15000;
+static int watermark_scale_factor = 10;
+
+/* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
+int movable_zone;
+EXPORT_SYMBOL(movable_zone);
+
+#if MAX_NUMNODES > 1
+unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;
+unsigned int nr_online_nodes __read_mostly = 1;
+EXPORT_SYMBOL(nr_node_ids);
+EXPORT_SYMBOL(nr_online_nodes);
+#endif
+
+static bool page_contains_unaccepted(struct page *page, unsigned int order);
+static void accept_page(struct page *page, unsigned int order);
+static bool try_to_accept_memory(struct zone *zone, unsigned int order);
+static inline bool has_unaccepted_memory(void);
+static bool __free_unaccepted(struct page *page);
+
+int page_group_by_mobility_disabled __read_mostly;
+
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+/*
+ * During boot we initialize deferred pages on-demand, as needed, but once
+ * page_alloc_init_late() has finished, the deferred pages are all initialized,
+ * and we can permanently disable that path.
+ */
+DEFINE_STATIC_KEY_TRUE(deferred_pages);
+
+static inline bool deferred_pages_enabled(void)
+{
+	return static_branch_unlikely(&deferred_pages);
+}
+
+/*
+ * deferred_grow_zone() is __init, but it is called from
+ * get_page_from_freelist() during early boot until deferred_pages permanently
+ * disables this call. This is why we have refdata wrapper to avoid warning,
+ * and to ensure that the function body gets unloaded.
+ */
+static bool __ref
+_deferred_grow_zone(struct zone *zone, unsigned int order)
+{
+       return deferred_grow_zone(zone, order);
+}
+#else
+static inline bool deferred_pages_enabled(void)
+{
+	return false;
+}
+#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
+
+/* Return a pointer to the bitmap storing bits affecting a block of pages */
+static inline unsigned long *get_pageblock_bitmap(const struct page *page,
+							unsigned long pfn)
+{
+#ifdef CONFIG_SPARSEMEM
+	return section_to_usemap(__pfn_to_section(pfn));
+#else
+	return page_zone(page)->pageblock_flags;
+#endif /* CONFIG_SPARSEMEM */
+}
+
+static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)
+{
+#ifdef CONFIG_SPARSEMEM
+	pfn &= (PAGES_PER_SECTION-1);
+#else
+	pfn = pfn - pageblock_start_pfn(page_zone(page)->zone_start_pfn);
+#endif /* CONFIG_SPARSEMEM */
+	return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
+}
+
+/**
+ * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages
+ * @page: The page within the block of interest
+ * @pfn: The target page frame number
+ * @mask: mask of bits that the caller is interested in
+ *
+ * Return: pageblock_bits flags
+ */
+unsigned long get_pfnblock_flags_mask(const struct page *page,
+					unsigned long pfn, unsigned long mask)
+{
+	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);
+	/*
+	 * This races, without locks, with set_pfnblock_flags_mask(). Ensure
+	 * a consistent read of the memory array, so that results, even though
+	 * racy, are not corrupted.
+	 */
+	word = READ_ONCE(bitmap[word_bitidx]);
+	return (word >> bitidx) & mask;
+}
+
+static __always_inline int get_pfnblock_migratetype(const struct page *page,
+					unsigned long pfn)
+{
+	return get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
+}
+
+/**
+ * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
+ * @page: The page within the block of interest
+ * @flags: The flags to set
+ * @pfn: The target page frame number
+ * @mask: mask of bits that the caller is interested in
+ */
+void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
+					unsigned long pfn,
+					unsigned long mask)
+{
+	unsigned long *bitmap;
+	unsigned long bitidx, word_bitidx;
+	unsigned long word;
+
+	BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
+	BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
+
+	bitmap = get_pageblock_bitmap(page, pfn);
+	bitidx = pfn_to_bitidx(page, pfn);
+	word_bitidx = bitidx / BITS_PER_LONG;
+	bitidx &= (BITS_PER_LONG-1);
+
+	VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
+
+	mask <<= bitidx;
+	flags <<= bitidx;
+
+	word = READ_ONCE(bitmap[word_bitidx]);
+	do {
+	} while (!try_cmpxchg(&bitmap[word_bitidx], &word, (word & ~mask) | flags));
+}
+
+void set_pageblock_migratetype(struct page *page, int migratetype)
+{
+	if (unlikely(page_group_by_mobility_disabled &&
+		     migratetype < MIGRATE_PCPTYPES))
+		migratetype = MIGRATE_UNMOVABLE;
+
+	set_pfnblock_flags_mask(page, (unsigned long)migratetype,
+				page_to_pfn(page), MIGRATETYPE_MASK);
+}
+
+#ifdef CONFIG_DEBUG_VM
+static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
+{
+	int ret;
+	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;
+		ret = !zone_spans_pfn(zone, pfn);
+	} 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;
+}
+
+/*
+ * Temporary debugging check for pages not lying within a given zone.
+ */
+static int __maybe_unused bad_range(struct zone *zone, struct page *page)
+{
+	if (page_outside_zone_boundaries(zone, page))
+		return 1;
+	if (zone != page_zone(page))
+		return 1;
+
+	return 0;
+}
+#else
+static inline int __maybe_unused bad_range(struct zone *zone, struct page *page)
+{
+	return 0;
+}
+#endif
+
+static void bad_page(struct page *page, const char *reason)
+{
+	static unsigned long resume;
+	static unsigned long nr_shown;
+	static unsigned long nr_unshown;
+
+	/*
+	 * Allow a burst of 60 reports, then keep quiet for that minute;
+	 * or allow a steady drip of one report per second.
+	 */
+	if (nr_shown == 60) {
+		if (time_before(jiffies, resume)) {
+			nr_unshown++;
+			goto out;
+		}
+		if (nr_unshown) {
+			pr_alert(
+			      "BUG: Bad page state: %lu messages suppressed\n",
+				nr_unshown);
+			nr_unshown = 0;
+		}
+		nr_shown = 0;
+	}
+	if (nr_shown++ == 0)
+		resume = jiffies + 60 * HZ;
+
+	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
+		current->comm, page_to_pfn(page));
+	dump_page(page, reason);
+
+	print_modules();
+	dump_stack();
+out:
+	/* Leave bad fields for debug, except PageBuddy could make trouble */
+	page_mapcount_reset(page); /* remove PageBuddy */
+	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
+}
+
+static inline unsigned int order_to_pindex(int migratetype, int order)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (order > PAGE_ALLOC_COSTLY_ORDER) {
+		VM_BUG_ON(order != pageblock_order);
+		return NR_LOWORDER_PCP_LISTS;
+	}
+#else
+	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
+#endif
+
+	return (MIGRATE_PCPTYPES * order) + migratetype;
+}
+
+static inline int pindex_to_order(unsigned int pindex)
+{
+	int order = pindex / MIGRATE_PCPTYPES;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (pindex == NR_LOWORDER_PCP_LISTS)
+		order = pageblock_order;
+#else
+	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
+#endif
+
+	return order;
+}
+
+static inline bool pcp_allowed_order(unsigned int order)
+{
+	if (order <= PAGE_ALLOC_COSTLY_ORDER)
+		return true;
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (order == pageblock_order)
+		return true;
+#endif
+	return false;
+}
+
+static inline void free_the_page(struct page *page, unsigned int order)
+{
+	if (pcp_allowed_order(order))		/* Via pcp? */
+		free_unref_page(page, order);
+	else
+		__free_pages_ok(page, order, FPI_NONE);
+}
+
+/*
+ * Higher-order pages are called "compound pages".  They are structured thusly:
+ *
+ * The first PAGE_SIZE page is called the "head page" and have PG_head set.
+ *
+ * The remaining PAGE_SIZE pages are called "tail pages". PageTail() is encoded
+ * in bit 0 of page->compound_head. The rest of bits is pointer to head page.
+ *
+ * The first tail page's ->compound_order holds the order of allocation.
+ * This usage means that zero-order pages may not be compound.
+ */
+
+void prep_compound_page(struct page *page, unsigned int order)
+{
+	int i;
+	int nr_pages = 1 << order;
+
+	__SetPageHead(page);
+	for (i = 1; i < nr_pages; i++)
+		prep_compound_tail(page, i);
+
+	prep_compound_head(page, order);
+}
+
+void destroy_large_folio(struct folio *folio)
+{
+	if (folio_test_hugetlb(folio)) {
+		free_huge_folio(folio);
+		return;
+	}
+
+	if (folio_test_large_rmappable(folio))
+		folio_undo_large_rmappable(folio);
+
+	mem_cgroup_uncharge(folio);
+	free_the_page(&folio->page, folio_order(folio));
+}
+
+static inline void set_buddy_order(struct page *page, unsigned int order)
+{
+	set_page_private(page, order);
+	__SetPageBuddy(page);
+}
+
+#ifdef CONFIG_COMPACTION
+static inline struct capture_control *task_capc(struct zone *zone)
+{
+	struct capture_control *capc = current->capture_control;
+
+	return unlikely(capc) &&
+		!(current->flags & PF_KTHREAD) &&
+		!capc->page &&
+		capc->cc->zone == zone ? capc : NULL;
+}
+
+static inline bool
+compaction_capture(struct capture_control *capc, struct page *page,
+		   int order, int migratetype)
+{
+	if (!capc || order != capc->cc->order)
+		return false;
+
+	/* Do not accidentally pollute CMA or isolated regions*/
+	if (is_migrate_cma(migratetype) ||
+	    is_migrate_isolate(migratetype))
+		return false;
+
+	/*
+	 * Do not let lower order allocations pollute a movable pageblock.
+	 * This might let an unmovable request use a reclaimable pageblock
+	 * and vice-versa but no more than normal fallback logic which can
+	 * have trouble finding a high-order free page.
+	 */
+	if (order < pageblock_order && migratetype == MIGRATE_MOVABLE)
+		return false;
+
+	capc->page = page;
+	return true;
+}
+
+#else
+static inline struct capture_control *task_capc(struct zone *zone)
+{
+	return NULL;
+}
+
+static inline bool
+compaction_capture(struct capture_control *capc, struct page *page,
+		   int order, int migratetype)
+{
+	return false;
+}
+#endif /* CONFIG_COMPACTION */
+
+/* Used for pages not on another list */
+static inline void add_to_free_list(struct page *page, struct zone *zone,
+				    unsigned int order, int migratetype)
+{
+	struct free_area *area = &zone->free_area[order];
+
+	list_add(&page->buddy_list, &area->free_list[migratetype]);
+	area->nr_free++;
+}
+
+/* Used for pages not on another list */
+static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
+					 unsigned int order, int migratetype)
+{
+	struct free_area *area = &zone->free_area[order];
+
+	list_add_tail(&page->buddy_list, &area->free_list[migratetype]);
+	area->nr_free++;
+}
+
+/*
+ * Used for pages which are on another list. Move the pages to the tail
+ * of the list - so the moved pages won't immediately be considered for
+ * allocation again (e.g., optimization for memory onlining).
+ */
+static inline void move_to_free_list(struct page *page, struct zone *zone,
+				     unsigned int order, int migratetype)
+{
+	struct free_area *area = &zone->free_area[order];
+
+	list_move_tail(&page->buddy_list, &area->free_list[migratetype]);
+}
+
+static inline void del_page_from_free_list(struct page *page, struct zone *zone,
+					   unsigned int order)
+{
+	/* clear reported state and update reported page count */
+	if (page_reported(page))
+		__ClearPageReported(page);
+
+	list_del(&page->buddy_list);
+	__ClearPageBuddy(page);
+	set_page_private(page, 0);
+	zone->free_area[order].nr_free--;
+}
+
+static inline struct page *get_page_from_free_area(struct free_area *area,
+					    int migratetype)
+{
+	return list_first_entry_or_null(&area->free_list[migratetype],
+					struct page, buddy_list);
+}
+
+/*
+ * If this is not the largest possible page, check if the buddy
+ * of the next-highest order is free. If it is, it's possible
+ * that pages are being freed that will coalesce soon. In case,
+ * that is happening, add the free page to the tail of the list
+ * so it's less likely to be used soon and more likely to be merged
+ * as a higher order page
+ */
+static inline bool
+buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
+		   struct page *page, unsigned int order)
+{
+	unsigned long higher_page_pfn;
+	struct page *higher_page;
+
+	if (order >= MAX_ORDER - 1)
+		return false;
+
+	higher_page_pfn = buddy_pfn & pfn;
+	higher_page = page + (higher_page_pfn - pfn);
+
+	return find_buddy_page_pfn(higher_page, higher_page_pfn, order + 1,
+			NULL) != NULL;
+}
+
+/*
+ * Freeing function for a buddy system allocator.
+ *
+ * The concept of a buddy system is to maintain direct-mapped table
+ * (containing bit values) for memory blocks of various "orders".
+ * The bottom level table contains the map for the smallest allocatable
+ * units of memory (here, pages), and each level above it describes
+ * pairs of units from the levels below, hence, "buddies".
+ * At a high level, all that happens here is marking the table entry
+ * at the bottom level available, and propagating the changes upward
+ * as necessary, plus some accounting needed to play nicely with other
+ * parts of the VM system.
+ * At each level, we keep a list of pages, which are heads of continuous
+ * free pages of length of (1 << order) and marked with PageBuddy.
+ * Page's order is recorded in page_private(page) field.
+ * So when we are allocating or freeing one, we can derive the state of the
+ * other.  That is, if we allocate a small block, and both were
+ * free, the remainder of the region must be split into blocks.
+ * If a block is freed, and its buddy is also free, then this
+ * triggers coalescing into a block of larger size.
+ *
+ * -- nyc
+ */
+
+static inline void __free_one_page(struct page *page,
+		unsigned long pfn,
+		struct zone *zone, unsigned int order,
+		int migratetype, fpi_t fpi_flags)
+{
+	struct capture_control *capc = task_capc(zone);
+	unsigned long buddy_pfn = 0;
+	unsigned long combined_pfn;
+	struct page *buddy;
+	bool to_tail;
+
+	VM_BUG_ON(!zone_is_initialized(zone));
+	VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
+
+	VM_BUG_ON(migratetype == -1);
+	if (likely(!is_migrate_isolate(migratetype)))
+		__mod_zone_freepage_state(zone, 1 << order, migratetype);
+
+	VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
+	VM_BUG_ON_PAGE(bad_range(zone, page), page);
+
+	while (order < MAX_ORDER) {
+		if (compaction_capture(capc, page, order, migratetype)) {
+			__mod_zone_freepage_state(zone, -(1 << order),
+								migratetype);
+			return;
+		}
+
+		buddy = find_buddy_page_pfn(page, pfn, order, &buddy_pfn);
+		if (!buddy)
+			goto done_merging;
+
+		if (unlikely(order >= pageblock_order)) {
+			/*
+			 * We want to prevent merge between freepages on pageblock
+			 * without fallbacks and normal pageblock. Without this,
+			 * pageblock isolation could cause incorrect freepage or CMA
+			 * accounting or HIGHATOMIC accounting.
+			 */
+			int buddy_mt = get_pfnblock_migratetype(buddy, buddy_pfn);
+
+			if (migratetype != buddy_mt
+					&& (!migratetype_is_mergeable(migratetype) ||
+						!migratetype_is_mergeable(buddy_mt)))
+				goto done_merging;
+		}
+
+		/*
+		 * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
+		 * merge with it and move up one order.
+		 */
+		if (page_is_guard(buddy))
+			clear_page_guard(zone, buddy, order, migratetype);
+		else
+			del_page_from_free_list(buddy, zone, order);
+		combined_pfn = buddy_pfn & pfn;
+		page = page + (combined_pfn - pfn);
+		pfn = combined_pfn;
+		order++;
+	}
+
+done_merging:
+	set_buddy_order(page, order);
+
+	if (fpi_flags & FPI_TO_TAIL)
+		to_tail = true;
+	else if (is_shuffle_order(order))
+		to_tail = shuffle_pick_tail();
+	else
+		to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order);
+
+	if (to_tail)
+		add_to_free_list_tail(page, zone, order, migratetype);
+	else
+		add_to_free_list(page, zone, order, migratetype);
+
+	/* Notify page reporting subsystem of freed page */
+	if (!(fpi_flags & FPI_SKIP_REPORT_NOTIFY))
+		page_reporting_notify_free(order);
+}
+
+/**
+ * split_free_page() -- split a free page at split_pfn_offset
+ * @free_page:		the original free page
+ * @order:		the order of the page
+ * @split_pfn_offset:	split offset within the page
+ *
+ * Return -ENOENT if the free page is changed, otherwise 0
+ *
+ * It is used when the free page crosses two pageblocks with different migratetypes
+ * at split_pfn_offset within the page. The split free page will be put into
+ * separate migratetype lists afterwards. Otherwise, the function achieves
+ * nothing.
+ */
+int split_free_page(struct page *free_page,
+			unsigned int order, unsigned long split_pfn_offset)
+{
+	struct zone *zone = page_zone(free_page);
+	unsigned long free_page_pfn = page_to_pfn(free_page);
+	unsigned long pfn;
+	unsigned long flags;
+	int free_page_order;
+	int mt;
+	int ret = 0;
+
+	if (split_pfn_offset == 0)
+		return ret;
+
+	spin_lock_irqsave(&zone->lock, flags);
+
+	if (!PageBuddy(free_page) || buddy_order(free_page) != order) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	mt = get_pfnblock_migratetype(free_page, free_page_pfn);
+	if (likely(!is_migrate_isolate(mt)))
+		__mod_zone_freepage_state(zone, -(1UL << order), mt);
+
+	del_page_from_free_list(free_page, zone, order);
+	for (pfn = free_page_pfn;
+	     pfn < free_page_pfn + (1UL << order);) {
+		int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn);
+
+		free_page_order = min_t(unsigned int,
+					pfn ? __ffs(pfn) : order,
+					__fls(split_pfn_offset));
+		__free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
+				mt, FPI_NONE);
+		pfn += 1UL << free_page_order;
+		split_pfn_offset -= (1UL << free_page_order);
+		/* we have done the first part, now switch to second part */
+		if (split_pfn_offset == 0)
+			split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
+	}
+out:
+	spin_unlock_irqrestore(&zone->lock, flags);
+	return ret;
+}
+/*
+ * A bad page could be due to a number of fields. Instead of multiple branches,
+ * try and check multiple fields with one check. The caller must do a detailed
+ * check if necessary.
+ */
+static inline bool page_expected_state(struct page *page,
+					unsigned long check_flags)
+{
+	if (unlikely(atomic_read(&page->_mapcount) != -1))
+		return false;
+
+	if (unlikely((unsigned long)page->mapping |
+			page_ref_count(page) |
+#ifdef CONFIG_MEMCG
+			page->memcg_data |
+#endif
+			(page->flags & check_flags)))
+		return false;
+
+	return true;
+}
+
+static const char *page_bad_reason(struct page *page, unsigned long flags)
+{
+	const char *bad_reason = NULL;
+
+	if (unlikely(atomic_read(&page->_mapcount) != -1))
+		bad_reason = "nonzero mapcount";
+	if (unlikely(page->mapping != NULL))
+		bad_reason = "non-NULL mapping";
+	if (unlikely(page_ref_count(page) != 0))
+		bad_reason = "nonzero _refcount";
+	if (unlikely(page->flags & flags)) {
+		if (flags == PAGE_FLAGS_CHECK_AT_PREP)
+			bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag(s) set";
+		else
+			bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
+	}
+#ifdef CONFIG_MEMCG
+	if (unlikely(page->memcg_data))
+		bad_reason = "page still charged to cgroup";
+#endif
+	return bad_reason;
+}
+
+static void free_page_is_bad_report(struct page *page)
+{
+	bad_page(page,
+		 page_bad_reason(page, PAGE_FLAGS_CHECK_AT_FREE));
+}
+
+static inline bool free_page_is_bad(struct page *page)
+{
+	if (likely(page_expected_state(page, PAGE_FLAGS_CHECK_AT_FREE)))
+		return false;
+
+	/* Something has gone sideways, find it */
+	free_page_is_bad_report(page);
+	return true;
+}
+
+static inline bool is_check_pages_enabled(void)
+{
+	return static_branch_unlikely(&check_pages_enabled);
+}
+
+static int free_tail_page_prepare(struct page *head_page, struct page *page)
+{
+	struct folio *folio = (struct folio *)head_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_check_pages_enabled()) {
+		ret = 0;
+		goto out;
+	}
+	switch (page - head_page) {
+	case 1:
+		/* the first tail page: these may be in place of ->mapping */
+		if (unlikely(folio_entire_mapcount(folio))) {
+			bad_page(page, "nonzero entire_mapcount");
+			goto out;
+		}
+		if (unlikely(atomic_read(&folio->_nr_pages_mapped))) {
+			bad_page(page, "nonzero nr_pages_mapped");
+			goto out;
+		}
+		if (unlikely(atomic_read(&folio->_pincount))) {
+			bad_page(page, "nonzero pincount");
+			goto out;
+		}
+		break;
+	case 2:
+		/*
+		 * the second tail page: ->mapping is
+		 * deferred_list.next -- ignore value.
+		 */
+		break;
+	default:
+		if (page->mapping != TAIL_MAPPING) {
+			bad_page(page, "corrupted mapping in tail page");
+			goto out;
+		}
+		break;
+	}
+	if (unlikely(!PageTail(page))) {
+		bad_page(page, "PageTail not set");
+		goto out;
+	}
+	if (unlikely(compound_head(page) != head_page)) {
+		bad_page(page, "compound_head not consistent");
+		goto out;
+	}
+	ret = 0;
+out:
+	page->mapping = NULL;
+	clear_compound_head(page);
+	return ret;
+}
+
+/*
+ * Skip KASAN memory poisoning when either:
+ *
+ * 1. For generic KASAN: deferred memory initialization has not yet completed.
+ *    Tag-based KASAN modes skip pages freed via deferred memory initialization
+ *    using page tags instead (see below).
+ * 2. For tag-based KASAN modes: the page has a match-all KASAN tag, indicating
+ *    that error detection is disabled for accesses via the page address.
+ *
+ * Pages will have match-all tags in the following circumstances:
+ *
+ * 1. Pages are being initialized for the first time, including during deferred
+ *    memory init; see the call to page_kasan_tag_reset in __init_single_page.
+ * 2. The allocation was not unpoisoned due to __GFP_SKIP_KASAN, with the
+ *    exception of pages unpoisoned by kasan_unpoison_vmalloc.
+ * 3. The allocation was excluded from being checked due to sampling,
+ *    see the call to kasan_unpoison_pages.
+ *
+ * Poisoning pages during deferred memory init will greatly lengthen the
+ * process and cause problem in large memory systems as the deferred pages
+ * initialization is done with interrupt disabled.
+ *
+ * Assuming that there will be no reference to those newly initialized
+ * pages before they are ever allocated, this should have no effect on
+ * KASAN memory tracking as the poison will be properly inserted at page
+ * allocation time. The only corner case is when pages are allocated by
+ * on-demand allocation and then freed again before the deferred pages
+ * initialization is done, but this is not likely to happen.
+ */
+static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
+{
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		return deferred_pages_enabled();
+
+	return page_kasan_tag(page) == 0xff;
+}
+
+static void kernel_init_pages(struct page *page, int numpages)
+{
+	int i;
+
+	/* s390's use of memset() could override KASAN redzones. */
+	kasan_disable_current();
+	for (i = 0; i < numpages; i++)
+		clear_highpage_kasan_tagged(page + i);
+	kasan_enable_current();
+}
+
+static __always_inline bool free_pages_prepare(struct page *page,
+			unsigned int order, fpi_t fpi_flags)
+{
+	int bad = 0;
+	bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags);
+	bool init = want_init_on_free();
+
+	VM_BUG_ON_PAGE(PageTail(page), page);
+
+	trace_mm_page_free(page, order);
+	kmsan_free_page(page, order);
+
+	if (unlikely(PageHWPoison(page)) && !order) {
+		/*
+		 * Do not let hwpoison pages hit pcplists/buddy
+		 * Untie memcg state and reset page's owner
+		 */
+		if (memcg_kmem_online() && PageMemcgKmem(page))
+			__memcg_kmem_uncharge_page(page, order);
+		reset_page_owner(page, order);
+		page_table_check_free(page, order);
+		return false;
+	}
+
+	/*
+	 * Check tail pages before head page information is cleared to
+	 * avoid checking PageCompound for order-0 pages.
+	 */
+	if (unlikely(order)) {
+		bool compound = PageCompound(page);
+		int i;
+
+		VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
+
+		if (compound)
+			page[1].flags &= ~PAGE_FLAGS_SECOND;
+		for (i = 1; i < (1 << order); i++) {
+			if (compound)
+				bad += free_tail_page_prepare(page, page + i);
+			if (is_check_pages_enabled()) {
+				if (free_page_is_bad(page + i)) {
+					bad++;
+					continue;
+				}
+			}
+			(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+		}
+	}
+	if (PageMappingFlags(page))
+		page->mapping = NULL;
+	if (memcg_kmem_online() && PageMemcgKmem(page))
+		__memcg_kmem_uncharge_page(page, order);
+	if (is_check_pages_enabled()) {
+		if (free_page_is_bad(page))
+			bad++;
+		if (bad)
+			return false;
+	}
+
+	page_cpupid_reset_last(page);
+	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+	reset_page_owner(page, order);
+	page_table_check_free(page, order);
+
+	if (!PageHighMem(page)) {
+		debug_check_no_locks_freed(page_address(page),
+					   PAGE_SIZE << order);
+		debug_check_no_obj_freed(page_address(page),
+					   PAGE_SIZE << order);
+	}
+
+	kernel_poison_pages(page, 1 << order);
+
+	/*
+	 * As memory initialization might be integrated into KASAN,
+	 * KASAN poisoning and memory initialization code must be
+	 * kept together to avoid discrepancies in behavior.
+	 *
+	 * With hardware tag-based KASAN, memory tags must be set before the
+	 * page becomes unavailable via debug_pagealloc or arch_free_page.
+	 */
+	if (!skip_kasan_poison) {
+		kasan_poison_pages(page, order, init);
+
+		/* Memory is already initialized if KASAN did it internally. */
+		if (kasan_has_integrated_init())
+			init = false;
+	}
+	if (init)
+		kernel_init_pages(page, 1 << order);
+
+	/*
+	 * arch_free_page() can make the page's contents inaccessible.  s390
+	 * does this.  So nothing which can access the page's contents should
+	 * happen after this.
+	 */
+	arch_free_page(page, order);
+
+	debug_pagealloc_unmap_pages(page, 1 << order);
+
+	return true;
+}
+
+/*
+ * Frees a number of pages from the PCP lists
+ * Assumes all pages on list are in same zone.
+ * count is the number of pages to free.
+ */
+static void free_pcppages_bulk(struct zone *zone, int count,
+					struct per_cpu_pages *pcp,
+					int pindex)
+{
+	unsigned long flags;
+	unsigned int order;
+	bool isolated_pageblocks;
+	struct page *page;
+
+	/*
+	 * Ensure proper count is passed which otherwise would stuck in the
+	 * below while (list_empty(list)) loop.
+	 */
+	count = min(pcp->count, count);
+
+	/* Ensure requested pindex is drained first. */
+	pindex = pindex - 1;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	isolated_pageblocks = has_isolate_pageblock(zone);
+
+	while (count > 0) {
+		struct list_head *list;
+		int nr_pages;
+
+		/* Remove pages from lists in a round-robin fashion. */
+		do {
+			if (++pindex > NR_PCP_LISTS - 1)
+				pindex = 0;
+			list = &pcp->lists[pindex];
+		} while (list_empty(list));
+
+		order = pindex_to_order(pindex);
+		nr_pages = 1 << order;
+		do {
+			int mt;
+
+			page = list_last_entry(list, struct page, pcp_list);
+			mt = get_pcppage_migratetype(page);
+
+			/* must delete to avoid corrupting pcp list */
+			list_del(&page->pcp_list);
+			count -= nr_pages;
+			pcp->count -= nr_pages;
+
+			/* MIGRATE_ISOLATE page should not go to pcplists */
+			VM_BUG_ON_PAGE(is_migrate_isolate(mt), page);
+			/* Pageblock could have been isolated meanwhile */
+			if (unlikely(isolated_pageblocks))
+				mt = get_pageblock_migratetype(page);
+
+			__free_one_page(page, page_to_pfn(page), zone, order, mt, FPI_NONE);
+			trace_mm_page_pcpu_drain(page, order, mt);
+		} while (count > 0 && !list_empty(list));
+	}
+
+	spin_unlock_irqrestore(&zone->lock, flags);
+}
+
+static void free_one_page(struct zone *zone,
+				struct page *page, unsigned long pfn,
+				unsigned int order,
+				int migratetype, fpi_t fpi_flags)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	if (unlikely(has_isolate_pageblock(zone) ||
+		is_migrate_isolate(migratetype))) {
+		migratetype = get_pfnblock_migratetype(page, pfn);
+	}
+	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
+	spin_unlock_irqrestore(&zone->lock, flags);
+}
+
+static void __free_pages_ok(struct page *page, unsigned int order,
+			    fpi_t fpi_flags)
+{
+	unsigned long flags;
+	int migratetype;
+	unsigned long pfn = page_to_pfn(page);
+	struct zone *zone = page_zone(page);
+
+	if (!free_pages_prepare(page, order, fpi_flags))
+		return;
+
+	/*
+	 * Calling get_pfnblock_migratetype() without spin_lock_irqsave() here
+	 * is used to avoid calling get_pfnblock_migratetype() under the lock.
+	 * This will reduce the lock holding time.
+	 */
+	migratetype = get_pfnblock_migratetype(page, pfn);
+
+	spin_lock_irqsave(&zone->lock, flags);
+	if (unlikely(has_isolate_pageblock(zone) ||
+		is_migrate_isolate(migratetype))) {
+		migratetype = get_pfnblock_migratetype(page, pfn);
+	}
+	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	__count_vm_events(PGFREE, 1 << order);
+}
+
+void __free_pages_core(struct page *page, unsigned int order)
+{
+	unsigned int nr_pages = 1 << order;
+	struct page *p = page;
+	unsigned int loop;
+
+	/*
+	 * When initializing the memmap, __init_single_page() sets the refcount
+	 * of all pages to 1 ("allocated"/"not free"). We have to set the
+	 * refcount of all involved pages to 0.
+	 */
+	prefetchw(p);
+	for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
+		prefetchw(p + 1);
+		__ClearPageReserved(p);
+		set_page_count(p, 0);
+	}
+	__ClearPageReserved(p);
+	set_page_count(p, 0);
+
+	atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
+
+	if (page_contains_unaccepted(page, order)) {
+		if (order == MAX_ORDER && __free_unaccepted(page))
+			return;
+
+		accept_page(page, order);
+	}
+
+	/*
+	 * Bypass PCP and place fresh pages right to the tail, primarily
+	 * relevant for memory onlining.
+	 */
+	__free_pages_ok(page, order, FPI_TO_TAIL);
+}
+
+/*
+ * Check that the whole (or subset of) a pageblock given by the interval of
+ * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
+ * with the migration of free compaction scanner.
+ *
+ * Return struct page pointer of start_pfn, or NULL if checks were not passed.
+ *
+ * It's possible on some configurations to have a setup like node0 node1 node0
+ * i.e. it's possible that all pages within a zones range of pages do not
+ * belong to a single zone. We assume that a border between node0 and node1
+ * can occur within a single pageblock, but not a node0 node1 node0
+ * interleaving within a single pageblock. It is therefore sufficient to check
+ * the first and last page of a pageblock and avoid checking each individual
+ * page in a pageblock.
+ *
+ * Note: the function may return non-NULL struct page even for a page block
+ * which contains a memory hole (i.e. there is no physical memory for a subset
+ * of the pfn range). For example, if the pageblock order is MAX_ORDER, which
+ * will fall into 2 sub-sections, and the end pfn of the pageblock may be hole
+ * even though the start pfn is online and valid. This should be safe most of
+ * the time because struct pages are still initialized via init_unavailable_range()
+ * and pfn walkers shouldn't touch any physical memory range for which they do
+ * not recognize any specific metadata in struct pages.
+ */
+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(end_pfn))
+		return NULL;
+
+	start_page = pfn_to_online_page(start_pfn);
+	if (!start_page)
+		return NULL;
+
+	if (page_zone(start_page) != zone)
+		return NULL;
+
+	end_page = pfn_to_page(end_pfn);
+
+	/* This gives a shorter code than deriving page_zone(end_page) */
+	if (page_zone_id(start_page) != page_zone_id(end_page))
+		return NULL;
+
+	return start_page;
+}
+
+/*
+ * The order of subdivision here is critical for the IO subsystem.
+ * Please do not alter this order without good reasons and regression
+ * testing. Specifically, as large blocks of memory are subdivided,
+ * the order in which smaller blocks are delivered depends on the order
+ * they're subdivided in this function. This is the primary factor
+ * influencing the order in which pages are delivered to the IO
+ * subsystem according to empirical testing, and this is also justified
+ * by considering the behavior of a buddy system containing a single
+ * large block of memory acted on by a series of small allocations.
+ * This behavior is a critical factor in sglist merging's success.
+ *
+ * -- nyc
+ */
+static inline void expand(struct zone *zone, struct page *page,
+	int low, int high, int migratetype)
+{
+	unsigned long size = 1 << high;
+
+	while (high > low) {
+		high--;
+		size >>= 1;
+		VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
+
+		/*
+		 * Mark as guard pages (or page), that will allow to
+		 * merge back to allocator when buddy will be freed.
+		 * Corresponding page table entries will not be touched,
+		 * pages will stay not present in virtual address space
+		 */
+		if (set_page_guard(zone, &page[size], high, migratetype))
+			continue;
+
+		add_to_free_list(&page[size], zone, high, migratetype);
+		set_buddy_order(&page[size], high);
+	}
+}
+
+static void check_new_page_bad(struct page *page)
+{
+	if (unlikely(page->flags & __PG_HWPOISON)) {
+		/* Don't complain about hwpoisoned pages */
+		page_mapcount_reset(page); /* remove PageBuddy */
+		return;
+	}
+
+	bad_page(page,
+		 page_bad_reason(page, PAGE_FLAGS_CHECK_AT_PREP));
+}
+
+/*
+ * This page is about to be returned from the page allocator
+ */
+static 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 check_new_pages(struct page *page, unsigned int order)
+{
+	if (is_check_pages_enabled()) {
+		for (int i = 0; i < (1 << order); i++) {
+			struct page *p = page + i;
+
+			if (check_new_page(p))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+static inline bool should_skip_kasan_unpoison(gfp_t flags)
+{
+	/* Don't skip if a software KASAN mode is enabled. */
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+	    IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+		return false;
+
+	/* Skip, if hardware tag-based KASAN is not enabled. */
+	if (!kasan_hw_tags_enabled())
+		return true;
+
+	/*
+	 * With hardware tag-based KASAN enabled, skip if this has been
+	 * requested via __GFP_SKIP_KASAN.
+	 */
+	return flags & __GFP_SKIP_KASAN;
+}
+
+static inline bool should_skip_init(gfp_t flags)
+{
+	/* Don't skip, if hardware tag-based KASAN is not enabled. */
+	if (!kasan_hw_tags_enabled())
+		return false;
+
+	/* For hardware tag-based KASAN, skip if requested. */
+	return (flags & __GFP_SKIP_ZERO);
+}
+
+inline void post_alloc_hook(struct page *page, unsigned int order,
+				gfp_t gfp_flags)
+{
+	bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) &&
+			!should_skip_init(gfp_flags);
+	bool zero_tags = init && (gfp_flags & __GFP_ZEROTAGS);
+	int i;
+
+	set_page_private(page, 0);
+	set_page_refcounted(page);
+
+	arch_alloc_page(page, order);
+	debug_pagealloc_map_pages(page, 1 << order);
+
+	/*
+	 * Page unpoisoning must happen before memory initialization.
+	 * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
+	 * allocations and the page unpoisoning code will complain.
+	 */
+	kernel_unpoison_pages(page, 1 << order);
+
+	/*
+	 * As memory initialization might be integrated into KASAN,
+	 * KASAN unpoisoning and memory initializion code must be
+	 * kept together to avoid discrepancies in behavior.
+	 */
+
+	/*
+	 * If memory tags should be zeroed
+	 * (which happens only when memory should be initialized as well).
+	 */
+	if (zero_tags) {
+		/* Initialize both memory and memory tags. */
+		for (i = 0; i != 1 << order; ++i)
+			tag_clear_highpage(page + i);
+
+		/* Take note that memory was initialized by the loop above. */
+		init = false;
+	}
+	if (!should_skip_kasan_unpoison(gfp_flags) &&
+	    kasan_unpoison_pages(page, order, init)) {
+		/* Take note that memory was initialized by KASAN. */
+		if (kasan_has_integrated_init())
+			init = false;
+	} else {
+		/*
+		 * If memory tags have not been set by KASAN, reset the page
+		 * tags to ensure page_address() dereferencing does not fault.
+		 */
+		for (i = 0; i != 1 << order; ++i)
+			page_kasan_tag_reset(page + i);
+	}
+	/* If memory is still not initialized, initialize it now. */
+	if (init)
+		kernel_init_pages(page, 1 << order);
+
+	set_page_owner(page, order, gfp_flags);
+	page_table_check_alloc(page, order);
+}
+
+static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
+							unsigned int alloc_flags)
+{
+	post_alloc_hook(page, order, gfp_flags);
+
+	if (order && (gfp_flags & __GFP_COMP))
+		prep_compound_page(page, order);
+
+	/*
+	 * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to
+	 * allocate the page. The expectation is that the caller is taking
+	 * steps that will free more memory. The caller should avoid the page
+	 * being used for !PFMEMALLOC purposes.
+	 */
+	if (alloc_flags & ALLOC_NO_WATERMARKS)
+		set_page_pfmemalloc(page);
+	else
+		clear_page_pfmemalloc(page);
+}
+
+/*
+ * Go through the free lists for the given migratetype and remove
+ * the smallest available page from the freelists
+ */
+static __always_inline
+struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
+						int migratetype)
+{
+	unsigned int current_order;
+	struct free_area *area;
+	struct page *page;
+
+	/* Find a page of the appropriate size in the preferred list */
+	for (current_order = order; current_order <= MAX_ORDER; ++current_order) {
+		area = &(zone->free_area[current_order]);
+		page = get_page_from_free_area(area, migratetype);
+		if (!page)
+			continue;
+		del_page_from_free_list(page, zone, current_order);
+		expand(zone, page, order, current_order, migratetype);
+		set_pcppage_migratetype(page, migratetype);
+		trace_mm_page_alloc_zone_locked(page, order, migratetype,
+				pcp_allowed_order(order) &&
+				migratetype < MIGRATE_PCPTYPES);
+		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
+ *
+ * The other migratetypes do not have fallbacks.
+ */
+static int fallbacks[MIGRATE_TYPES][MIGRATE_PCPTYPES - 1] = {
+	[MIGRATE_UNMOVABLE]   = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE   },
+	[MIGRATE_MOVABLE]     = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE },
+	[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE,   MIGRATE_MOVABLE   },
+};
+
+#ifdef CONFIG_CMA
+static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,
+					unsigned int order)
+{
+	return __rmqueue_smallest(zone, order, MIGRATE_CMA);
+}
+#else
+static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
+					unsigned int order) { return NULL; }
+#endif
+
+/*
+ * Move the free pages in a range to the freelist tail of the requested type.
+ * Note that start_page and end_pages are not aligned on a pageblock
+ * boundary. If alignment is required, use move_freepages_block()
+ */
+static int move_freepages(struct zone *zone,
+			  unsigned long start_pfn, unsigned long end_pfn,
+			  int migratetype, int *num_movable)
+{
+	struct page *page;
+	unsigned long pfn;
+	unsigned int order;
+	int pages_moved = 0;
+
+	for (pfn = start_pfn; pfn <= end_pfn;) {
+		page = pfn_to_page(pfn);
+		if (!PageBuddy(page)) {
+			/*
+			 * We assume that pages that could be isolated for
+			 * migration are movable. But we don't actually try
+			 * isolating, as that would be expensive.
+			 */
+			if (num_movable &&
+					(PageLRU(page) || __PageMovable(page)))
+				(*num_movable)++;
+			pfn++;
+			continue;
+		}
+
+		/* Make sure we are not inadvertently changing nodes */
+		VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
+		VM_BUG_ON_PAGE(page_zone(page) != zone, page);
+
+		order = buddy_order(page);
+		move_to_free_list(page, zone, order, migratetype);
+		pfn += 1 << order;
+		pages_moved += 1 << order;
+	}
+
+	return pages_moved;
+}
+
+int move_freepages_block(struct zone *zone, struct page *page,
+				int migratetype, int *num_movable)
+{
+	unsigned long start_pfn, end_pfn, pfn;
+
+	if (num_movable)
+		*num_movable = 0;
+
+	pfn = page_to_pfn(page);
+	start_pfn = pageblock_start_pfn(pfn);
+	end_pfn = pageblock_end_pfn(pfn) - 1;
+
+	/* Do not cross zone boundaries */
+	if (!zone_spans_pfn(zone, start_pfn))
+		start_pfn = pfn;
+	if (!zone_spans_pfn(zone, end_pfn))
+		return 0;
+
+	return move_freepages(zone, start_pfn, end_pfn, migratetype,
+								num_movable);
+}
+
+static void change_pageblock_range(struct page *pageblock_page,
+					int start_order, int migratetype)
+{
+	int nr_pageblocks = 1 << (start_order - pageblock_order);
+
+	while (nr_pageblocks--) {
+		set_pageblock_migratetype(pageblock_page, migratetype);
+		pageblock_page += pageblock_nr_pages;
+	}
+}
+
+/*
+ * When we are falling back to another migratetype during allocation, try to
+ * steal extra free pages from the same pageblocks to satisfy further
+ * allocations, instead of polluting multiple pageblocks.
+ *
+ * If we are stealing a relatively large buddy page, it is likely there will
+ * be more free pages in the pageblock, so try to steal them all. For
+ * reclaimable and unmovable allocations, we steal regardless of page size,
+ * as fragmentation caused by those allocations polluting movable pageblocks
+ * is worse than movable allocations stealing from unmovable and reclaimable
+ * pageblocks.
+ */
+static bool can_steal_fallback(unsigned int order, int start_mt)
+{
+	/*
+	 * Leaving this order check is intended, although there is
+	 * relaxed order check in next check. The reason is that
+	 * we can actually steal whole pageblock if this condition met,
+	 * but, below check doesn't guarantee it and that is just heuristic
+	 * so could be changed anytime.
+	 */
+	if (order >= pageblock_order)
+		return true;
+
+	if (order >= pageblock_order / 2 ||
+		start_mt == MIGRATE_RECLAIMABLE ||
+		start_mt == MIGRATE_UNMOVABLE ||
+		page_group_by_mobility_disabled)
+		return true;
+
+	return false;
+}
+
+static inline bool boost_watermark(struct zone *zone)
+{
+	unsigned long max_boost;
+
+	if (!watermark_boost_factor)
+		return false;
+	/*
+	 * Don't bother in zones that are unlikely to produce results.
+	 * On small machines, including kdump capture kernels running
+	 * in a small area, boosting the watermark can cause an out of
+	 * memory situation immediately.
+	 */
+	if ((pageblock_nr_pages * 4) > zone_managed_pages(zone))
+		return false;
+
+	max_boost = mult_frac(zone->_watermark[WMARK_HIGH],
+			watermark_boost_factor, 10000);
+
+	/*
+	 * high watermark may be uninitialised if fragmentation occurs
+	 * very early in boot so do not boost. We do not fall
+	 * through and boost by pageblock_nr_pages as failing
+	 * allocations that early means that reclaim is not going
+	 * to help and it may even be impossible to reclaim the
+	 * boosted watermark resulting in a hang.
+	 */
+	if (!max_boost)
+		return false;
+
+	max_boost = max(pageblock_nr_pages, max_boost);
+
+	zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages,
+		max_boost);
+
+	return true;
+}
+
+/*
+ * This function implements actual steal behaviour. If order is large enough,
+ * we can steal whole pageblock. If not, we first move freepages in this
+ * pageblock to our migratetype and determine how many already-allocated pages
+ * are there in the pageblock with a compatible migratetype. If at least half
+ * of pages are free or compatible, we can change migratetype of the pageblock
+ * itself, so pages freed in the future will be put on the correct free list.
+ */
+static void steal_suitable_fallback(struct zone *zone, struct page *page,
+		unsigned int alloc_flags, int start_type, bool whole_block)
+{
+	unsigned int current_order = buddy_order(page);
+	int free_pages, movable_pages, alike_pages;
+	int old_block_type;
+
+	old_block_type = get_pageblock_migratetype(page);
+
+	/*
+	 * This can happen due to races and we want to prevent broken
+	 * highatomic accounting.
+	 */
+	if (is_migrate_highatomic(old_block_type))
+		goto single_page;
+
+	/* Take ownership for orders >= pageblock_order */
+	if (current_order >= pageblock_order) {
+		change_pageblock_range(page, current_order, start_type);
+		goto single_page;
+	}
+
+	/*
+	 * Boost watermarks to increase reclaim pressure to reduce the
+	 * likelihood of future fallbacks. Wake kswapd now as the node
+	 * may be balanced overall and kswapd will not wake naturally.
+	 */
+	if (boost_watermark(zone) && (alloc_flags & ALLOC_KSWAPD))
+		set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
+
+	/* We are not allowed to try stealing from the whole block */
+	if (!whole_block)
+		goto single_page;
+
+	free_pages = move_freepages_block(zone, page, start_type,
+						&movable_pages);
+	/* moving whole block can fail due to zone boundary conditions */
+	if (!free_pages)
+		goto single_page;
+
+	/*
+	 * Determine how many pages are compatible with our allocation.
+	 * For movable allocation, it's the number of movable pages which
+	 * we just obtained. For other types it's a bit more tricky.
+	 */
+	if (start_type == MIGRATE_MOVABLE) {
+		alike_pages = movable_pages;
+	} else {
+		/*
+		 * If we are falling back a RECLAIMABLE or UNMOVABLE allocation
+		 * to MOVABLE pageblock, consider all non-movable pages as
+		 * compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
+		 * vice versa, be conservative since we can't distinguish the
+		 * exact migratetype of non-movable pages.
+		 */
+		if (old_block_type == MIGRATE_MOVABLE)
+			alike_pages = pageblock_nr_pages
+						- (free_pages + movable_pages);
+		else
+			alike_pages = 0;
+	}
+	/*
+	 * If a sufficient number of pages in the block are either free or of
+	 * compatible migratability as our allocation, claim the whole block.
+	 */
+	if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
+			page_group_by_mobility_disabled)
+		set_pageblock_migratetype(page, start_type);
+
+	return;
+
+single_page:
+	move_to_free_list(page, zone, current_order, start_type);
+}
+
+/*
+ * Check whether there is a suitable fallback freepage with requested order.
+ * If only_stealable is true, this function returns fallback_mt only if
+ * we can steal other freepages all together. This would help to reduce
+ * fragmentation due to mixed migratetype pages in one pageblock.
+ */
+int find_suitable_fallback(struct free_area *area, unsigned int order,
+			int migratetype, bool only_stealable, bool *can_steal)
+{
+	int i;
+	int fallback_mt;
+
+	if (area->nr_free == 0)
+		return -1;
+
+	*can_steal = false;
+	for (i = 0; i < MIGRATE_PCPTYPES - 1 ; i++) {
+		fallback_mt = fallbacks[migratetype][i];
+		if (free_area_empty(area, fallback_mt))
+			continue;
+
+		if (can_steal_fallback(order, migratetype))
+			*can_steal = true;
+
+		if (!only_stealable)
+			return fallback_mt;
+
+		if (*can_steal)
+			return fallback_mt;
+	}
+
+	return -1;
+}
+
+/*
+ * Reserve a pageblock for exclusive use of high-order atomic allocations if
+ * there are no empty page blocks that contain a page with a suitable order
+ */
+static void reserve_highatomic_pageblock(struct page *page, struct zone *zone)
+{
+	int mt;
+	unsigned long max_managed, flags;
+
+	/*
+	 * Limit the number reserved to 1 pageblock or roughly 1% of a zone.
+	 * Check is race-prone but harmless.
+	 */
+	max_managed = (zone_managed_pages(zone) / 100) + pageblock_nr_pages;
+	if (zone->nr_reserved_highatomic >= max_managed)
+		return;
+
+	spin_lock_irqsave(&zone->lock, flags);
+
+	/* Recheck the nr_reserved_highatomic limit under the lock */
+	if (zone->nr_reserved_highatomic >= max_managed)
+		goto out_unlock;
+
+	/* Yoink! */
+	mt = get_pageblock_migratetype(page);
+	/* Only reserve normal pageblocks (i.e., they can merge with others) */
+	if (migratetype_is_mergeable(mt)) {
+		zone->nr_reserved_highatomic += pageblock_nr_pages;
+		set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
+		move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL);
+	}
+
+out_unlock:
+	spin_unlock_irqrestore(&zone->lock, flags);
+}
+
+/*
+ * Used when an allocation is about to fail under memory pressure. This
+ * potentially hurts the reliability of high-order allocations when under
+ * intense memory pressure but failed atomic allocations should be easier
+ * to recover from than an OOM.
+ *
+ * If @force is true, try to unreserve a pageblock even though highatomic
+ * pageblock is exhausted.
+ */
+static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
+						bool force)
+{
+	struct zonelist *zonelist = ac->zonelist;
+	unsigned long flags;
+	struct zoneref *z;
+	struct zone *zone;
+	struct page *page;
+	int order;
+	bool ret;
+
+	for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->highest_zoneidx,
+								ac->nodemask) {
+		/*
+		 * Preserve at least one pageblock unless memory pressure
+		 * is really high.
+		 */
+		if (!force && zone->nr_reserved_highatomic <=
+					pageblock_nr_pages)
+			continue;
+
+		spin_lock_irqsave(&zone->lock, flags);
+		for (order = 0; order <= MAX_ORDER; order++) {
+			struct free_area *area = &(zone->free_area[order]);
+
+			page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
+			if (!page)
+				continue;
+
+			/*
+			 * In page freeing path, migratetype change is racy so
+			 * we can counter several free pages in a pageblock
+			 * in this loop although we changed the pageblock type
+			 * from highatomic to ac->migratetype. So we should
+			 * adjust the count once.
+			 */
+			if (is_migrate_highatomic_page(page)) {
+				/*
+				 * It should never happen but changes to
+				 * locking could inadvertently allow a per-cpu
+				 * drain to add pages to MIGRATE_HIGHATOMIC
+				 * while unreserving so be safe and watch for
+				 * underflows.
+				 */
+				zone->nr_reserved_highatomic -= min(
+						pageblock_nr_pages,
+						zone->nr_reserved_highatomic);
+			}
+
+			/*
+			 * Convert to ac->migratetype and avoid the normal
+			 * pageblock stealing heuristics. Minimally, the caller
+			 * is doing the work and needs the pages. More
+			 * importantly, if the block was always converted to
+			 * MIGRATE_UNMOVABLE or another type then the number
+			 * of pageblocks that cannot be completely freed
+			 * may increase.
+			 */
+			set_pageblock_migratetype(page, ac->migratetype);
+			ret = move_freepages_block(zone, page, ac->migratetype,
+									NULL);
+			if (ret) {
+				spin_unlock_irqrestore(&zone->lock, flags);
+				return ret;
+			}
+		}
+		spin_unlock_irqrestore(&zone->lock, flags);
+	}
+
+	return false;
+}
+
+/*
+ * Try finding a free buddy page on the fallback list and put it on the free
+ * list of requested migratetype, possibly along with other pages from the same
+ * block, depending on fragmentation avoidance heuristics. Returns true if
+ * fallback was found so that __rmqueue_smallest() can grab it.
+ *
+ * The use of signed ints for order and current_order is a deliberate
+ * deviation from the rest of this file, to make the for loop
+ * condition simpler.
+ */
+static __always_inline bool
+__rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
+						unsigned int alloc_flags)
+{
+	struct free_area *area;
+	int current_order;
+	int min_order = order;
+	struct page *page;
+	int fallback_mt;
+	bool can_steal;
+
+	/*
+	 * Do not steal pages from freelists belonging to other pageblocks
+	 * i.e. orders < pageblock_order. If there are no local zones free,
+	 * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
+	 */
+	if (order < pageblock_order && alloc_flags & ALLOC_NOFRAGMENT)
+		min_order = pageblock_order;
+
+	/*
+	 * Find the largest available free page in the other list. This roughly
+	 * approximates finding the pageblock with the most free pages, which
+	 * would be too costly to do exactly.
+	 */
+	for (current_order = MAX_ORDER; current_order >= min_order;
+				--current_order) {
+		area = &(zone->free_area[current_order]);
+		fallback_mt = find_suitable_fallback(area, current_order,
+				start_migratetype, false, &can_steal);
+		if (fallback_mt == -1)
+			continue;
+
+		/*
+		 * We cannot steal all free pages from the pageblock and the
+		 * requested migratetype is movable. In that case it's better to
+		 * steal and split the smallest available page instead of the
+		 * largest available page, because even if the next movable
+		 * allocation falls back into a different pageblock than this
+		 * one, it won't cause permanent fragmentation.
+		 */
+		if (!can_steal && start_migratetype == MIGRATE_MOVABLE
+					&& current_order > order)
+			goto find_smallest;
+
+		goto do_steal;
+	}
+
+	return false;
+
+find_smallest:
+	for (current_order = order; current_order <= MAX_ORDER;
+							current_order++) {
+		area = &(zone->free_area[current_order]);
+		fallback_mt = find_suitable_fallback(area, current_order,
+				start_migratetype, false, &can_steal);
+		if (fallback_mt != -1)
+			break;
+	}
+
+	/*
+	 * This should not happen - we already found a suitable fallback
+	 * when looking for the largest page.
+	 */
+	VM_BUG_ON(current_order > MAX_ORDER);
+
+do_steal:
+	page = get_page_from_free_area(area, fallback_mt);
+
+	steal_suitable_fallback(zone, page, alloc_flags, start_migratetype,
+								can_steal);
+
+	trace_mm_page_alloc_extfrag(page, order, current_order,
+		start_migratetype, fallback_mt);
+
+	return true;
+
+}
+
+/*
+ * Do the hard work of removing an element from the buddy allocator.
+ * Call me with the zone->lock already held.
+ */
+static __always_inline struct page *
+__rmqueue(struct zone *zone, unsigned int order, int migratetype,
+						unsigned int alloc_flags)
+{
+	struct page *page;
+
+	if (IS_ENABLED(CONFIG_CMA)) {
+		/*
+		 * Balance movable allocations between regular and CMA areas by
+		 * allocating from CMA when over half of the zone's free memory
+		 * is in the CMA area.
+		 */
+		if (alloc_flags & ALLOC_CMA &&
+		    zone_page_state(zone, NR_FREE_CMA_PAGES) >
+		    zone_page_state(zone, NR_FREE_PAGES) / 2) {
+			page = __rmqueue_cma_fallback(zone, order);
+			if (page)
+				return page;
+		}
+	}
+retry:
+	page = __rmqueue_smallest(zone, order, migratetype);
+	if (unlikely(!page)) {
+		if (alloc_flags & ALLOC_CMA)
+			page = __rmqueue_cma_fallback(zone, order);
+
+		if (!page && __rmqueue_fallback(zone, order, migratetype,
+								alloc_flags))
+			goto retry;
+	}
+	return page;
+}
+
+/*
+ * Obtain a specified number of elements from the buddy allocator, all under
+ * a single hold of the lock, for efficiency.  Add them to the supplied list.
+ * Returns the number of new pages which were placed at *list.
+ */
+static int rmqueue_bulk(struct zone *zone, unsigned int order,
+			unsigned long count, struct list_head *list,
+			int migratetype, unsigned int alloc_flags)
+{
+	unsigned long flags;
+	int i;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	for (i = 0; i < count; ++i) {
+		struct page *page = __rmqueue(zone, order, migratetype,
+								alloc_flags);
+		if (unlikely(page == NULL))
+			break;
+
+		/*
+		 * Split buddy pages returned by expand() are received here in
+		 * physical page order. The page is added to the tail of
+		 * caller's list. From the callers perspective, the linked list
+		 * is ordered by page number under some conditions. This is
+		 * useful for IO devices that can forward direction from the
+		 * head, thus also in the physical page order. This is useful
+		 * for IO devices that can merge IO requests if the physical
+		 * pages are ordered properly.
+		 */
+		list_add_tail(&page->pcp_list, list);
+		if (is_migrate_cma(get_pcppage_migratetype(page)))
+			__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
+					      -(1 << order));
+	}
+
+	__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	return i;
+}
+
+#ifdef CONFIG_NUMA
+/*
+ * Called from the vmstat counter updater to drain pagesets of this
+ * currently executing processor on remote nodes after they have
+ * expired.
+ */
+void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
+{
+	int to_drain, batch;
+
+	batch = READ_ONCE(pcp->batch);
+	to_drain = min(pcp->count, batch);
+	if (to_drain > 0) {
+		spin_lock(&pcp->lock);
+		free_pcppages_bulk(zone, to_drain, pcp, 0);
+		spin_unlock(&pcp->lock);
+	}
+}
+#endif
+
+/*
+ * Drain pcplists of the indicated processor and zone.
+ */
+static void drain_pages_zone(unsigned int cpu, struct zone *zone)
+{
+	struct per_cpu_pages *pcp;
+
+	pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
+	if (pcp->count) {
+		spin_lock(&pcp->lock);
+		free_pcppages_bulk(zone, pcp->count, pcp, 0);
+		spin_unlock(&pcp->lock);
+	}
+}
+
+/*
+ * Drain pcplists of all zones on the indicated processor.
+ */
+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.
+ */
+void drain_local_pages(struct zone *zone)
+{
+	int cpu = smp_processor_id();
+
+	if (zone)
+		drain_pages_zone(cpu, zone);
+	else
+		drain_pages(cpu);
+}
+
+/*
+ * The implementation of drain_all_pages(), exposing an extra parameter to
+ * drain on all cpus.
+ *
+ * drain_all_pages() is optimized to only execute on cpus where pcplists are
+ * not empty. The check for non-emptiness can however race with a free to
+ * pcplist that has not yet increased the pcp->count from 0 to 1. Callers
+ * that need the guarantee that every CPU has drained can disable the
+ * optimizing racy check.
+ */
+static void __drain_all_pages(struct zone *zone, bool force_all_cpus)
+{
+	int cpu;
+
+	/*
+	 * Allocate in the BSS so we won't require allocation in
+	 * direct reclaim path for CONFIG_CPUMASK_OFFSTACK=y
+	 */
+	static cpumask_t cpus_with_pcps;
+
+	/*
+	 * Do not drain if one is already in progress unless it's specific to
+	 * a zone. Such callers are primarily CMA and memory hotplug and need
+	 * the drain to be complete when the call returns.
+	 */
+	if (unlikely(!mutex_trylock(&pcpu_drain_mutex))) {
+		if (!zone)
+			return;
+		mutex_lock(&pcpu_drain_mutex);
+	}
+
+	/*
+	 * We don't care about racing with CPU hotplug event
+	 * as offline notification will cause the notified
+	 * cpu to drain that CPU pcps and on_each_cpu_mask
+	 * disables preemption as part of its processing
+	 */
+	for_each_online_cpu(cpu) {
+		struct per_cpu_pages *pcp;
+		struct zone *z;
+		bool has_pcps = false;
+
+		if (force_all_cpus) {
+			/*
+			 * The pcp.count check is racy, some callers need a
+			 * guarantee that no cpu is missed.
+			 */
+			has_pcps = true;
+		} else if (zone) {
+			pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
+			if (pcp->count)
+				has_pcps = true;
+		} else {
+			for_each_populated_zone(z) {
+				pcp = per_cpu_ptr(z->per_cpu_pageset, cpu);
+				if (pcp->count) {
+					has_pcps = true;
+					break;
+				}
+			}
+		}
+
+		if (has_pcps)
+			cpumask_set_cpu(cpu, &cpus_with_pcps);
+		else
+			cpumask_clear_cpu(cpu, &cpus_with_pcps);
+	}
+
+	for_each_cpu(cpu, &cpus_with_pcps) {
+		if (zone)
+			drain_pages_zone(cpu, zone);
+		else
+			drain_pages(cpu);
+	}
+
+	mutex_unlock(&pcpu_drain_mutex);
+}
+
+/*
+ * Spill all the per-cpu pages from all CPUs back into the buddy allocator.
+ *
+ * When zone parameter is non-NULL, spill just the single zone's pages.
+ */
+void drain_all_pages(struct zone *zone)
+{
+	__drain_all_pages(zone, false);
+}
+
+static bool free_unref_page_prepare(struct page *page, unsigned long pfn,
+							unsigned int order)
+{
+	int migratetype;
+
+	if (!free_pages_prepare(page, order, FPI_NONE))
+		return false;
+
+	migratetype = get_pfnblock_migratetype(page, pfn);
+	set_pcppage_migratetype(page, migratetype);
+	return true;
+}
+
+static int nr_pcp_free(struct per_cpu_pages *pcp, int high, bool free_high)
+{
+	int min_nr_free, max_nr_free;
+	int batch = READ_ONCE(pcp->batch);
+
+	/* Free everything if batch freeing high-order pages. */
+	if (unlikely(free_high))
+		return pcp->count;
+
+	/* Check for PCP disabled or boot pageset */
+	if (unlikely(high < batch))
+		return 1;
+
+	/* Leave at least pcp->batch pages on the list */
+	min_nr_free = batch;
+	max_nr_free = high - batch;
+
+	/*
+	 * Double the number of pages freed each time there is subsequent
+	 * freeing of pages without any allocation.
+	 */
+	batch <<= pcp->free_factor;
+	if (batch < max_nr_free)
+		pcp->free_factor++;
+	batch = clamp(batch, min_nr_free, max_nr_free);
+
+	return batch;
+}
+
+static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone,
+		       bool free_high)
+{
+	int high = READ_ONCE(pcp->high);
+
+	if (unlikely(!high || free_high))
+		return 0;
+
+	if (!test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags))
+		return high;
+
+	/*
+	 * If reclaim is active, limit the number of pages that can be
+	 * stored on pcp lists
+	 */
+	return min(READ_ONCE(pcp->batch) << 2, high);
+}
+
+static void free_unref_page_commit(struct zone *zone, struct per_cpu_pages *pcp,
+				   struct page *page, int migratetype,
+				   unsigned int order)
+{
+	int high;
+	int pindex;
+	bool free_high;
+
+	__count_vm_events(PGFREE, 1 << order);
+	pindex = order_to_pindex(migratetype, order);
+	list_add(&page->pcp_list, &pcp->lists[pindex]);
+	pcp->count += 1 << order;
+
+	/*
+	 * As high-order pages other than THP's stored on PCP can contribute
+	 * to fragmentation, limit the number stored when PCP is heavily
+	 * freeing without allocation. The remainder after bulk freeing
+	 * stops will be drained from vmstat refresh context.
+	 */
+	free_high = (pcp->free_factor && order && order <= PAGE_ALLOC_COSTLY_ORDER);
+
+	high = nr_pcp_high(pcp, zone, free_high);
+	if (pcp->count >= high) {
+		free_pcppages_bulk(zone, nr_pcp_free(pcp, high, free_high), pcp, pindex);
+	}
+}
+
+/*
+ * Free a pcp page
+ */
+void free_unref_page(struct page *page, unsigned int order)
+{
+	unsigned long __maybe_unused UP_flags;
+	struct per_cpu_pages *pcp;
+	struct zone *zone;
+	unsigned long pfn = page_to_pfn(page);
+	int migratetype, pcpmigratetype;
+
+	if (!free_unref_page_prepare(page, pfn, order))
+		return;
+
+	/*
+	 * We only track unmovable, reclaimable and movable on pcp lists.
+	 * Place ISOLATE pages on the isolated list because they are being
+	 * offlined but treat HIGHATOMIC and CMA as movable pages so we can
+	 * get those areas back if necessary. Otherwise, we may have to free
+	 * excessively into the page allocator
+	 */
+	migratetype = pcpmigratetype = get_pcppage_migratetype(page);
+	if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
+		if (unlikely(is_migrate_isolate(migratetype))) {
+			free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE);
+			return;
+		}
+		pcpmigratetype = MIGRATE_MOVABLE;
+	}
+
+	zone = page_zone(page);
+	pcp_trylock_prepare(UP_flags);
+	pcp = pcp_spin_trylock(zone->per_cpu_pageset);
+	if (pcp) {
+		free_unref_page_commit(zone, pcp, page, pcpmigratetype, order);
+		pcp_spin_unlock(pcp);
+	} else {
+		free_one_page(zone, page, pfn, order, migratetype, FPI_NONE);
+	}
+	pcp_trylock_finish(UP_flags);
+}
+
+/*
+ * Free a list of 0-order pages
+ */
+void free_unref_page_list(struct list_head *list)
+{
+	unsigned long __maybe_unused UP_flags;
+	struct page *page, *next;
+	struct per_cpu_pages *pcp = NULL;
+	struct zone *locked_zone = NULL;
+	int batch_count = 0;
+	int migratetype;
+
+	/* Prepare pages for freeing */
+	list_for_each_entry_safe(page, next, list, lru) {
+		unsigned long pfn = page_to_pfn(page);
+		if (!free_unref_page_prepare(page, pfn, 0)) {
+			list_del(&page->lru);
+			continue;
+		}
+
+		/*
+		 * Free isolated pages directly to the allocator, see
+		 * comment in free_unref_page.
+		 */
+		migratetype = get_pcppage_migratetype(page);
+		if (unlikely(is_migrate_isolate(migratetype))) {
+			list_del(&page->lru);
+			free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE);
+			continue;
+		}
+	}
+
+	list_for_each_entry_safe(page, next, list, lru) {
+		struct zone *zone = page_zone(page);
+
+		list_del(&page->lru);
+		migratetype = get_pcppage_migratetype(page);
+
+		/*
+		 * Either different zone requiring a different pcp lock or
+		 * excessive lock hold times when freeing a large list of
+		 * pages.
+		 */
+		if (zone != locked_zone || batch_count == SWAP_CLUSTER_MAX) {
+			if (pcp) {
+				pcp_spin_unlock(pcp);
+				pcp_trylock_finish(UP_flags);
+			}
+
+			batch_count = 0;
+
+			/*
+			 * trylock is necessary as pages may be getting freed
+			 * from IRQ or SoftIRQ context after an IO completion.
+			 */
+			pcp_trylock_prepare(UP_flags);
+			pcp = pcp_spin_trylock(zone->per_cpu_pageset);
+			if (unlikely(!pcp)) {
+				pcp_trylock_finish(UP_flags);
+				free_one_page(zone, page, page_to_pfn(page),
+					      0, migratetype, FPI_NONE);
+				locked_zone = NULL;
+				continue;
+			}
+			locked_zone = zone;
+		}
+
+		/*
+		 * Non-isolated types over MIGRATE_PCPTYPES get added
+		 * to the MIGRATE_MOVABLE pcp list.
+		 */
+		if (unlikely(migratetype >= MIGRATE_PCPTYPES))
+			migratetype = MIGRATE_MOVABLE;
+
+		trace_mm_page_free_batched(page);
+		free_unref_page_commit(zone, pcp, page, migratetype, 0);
+		batch_count++;
+	}
+
+	if (pcp) {
+		pcp_spin_unlock(pcp);
+		pcp_trylock_finish(UP_flags);
+	}
+}
+
+/*
+ * split_page takes a non-compound higher-order page, and splits it into
+ * n (1<<order) sub-pages: page[0..n]
+ * Each sub-page must be freed individually.
+ *
+ * Note: this is probably too low level an operation for use in drivers.
+ * Please consult with lkml before using this in your driver.
+ */
+void split_page(struct page *page, unsigned int order)
+{
+	int i;
+
+	VM_BUG_ON_PAGE(PageCompound(page), page);
+	VM_BUG_ON_PAGE(!page_count(page), page);
+
+	for (i = 1; i < (1 << order); i++)
+		set_page_refcounted(page + i);
+	split_page_owner(page, 1 << order);
+	split_page_memcg(page, 1 << order);
+}
+EXPORT_SYMBOL_GPL(split_page);
+
+int __isolate_free_page(struct page *page, unsigned int order)
+{
+	struct zone *zone = page_zone(page);
+	int mt = get_pageblock_migratetype(page);
+
+	if (!is_migrate_isolate(mt)) {
+		unsigned long watermark;
+		/*
+		 * Obey watermarks as if the page was being allocated. We can
+		 * emulate a high-order watermark check with a raised order-0
+		 * watermark, because we already know our high-order page
+		 * exists.
+		 */
+		watermark = zone->_watermark[WMARK_MIN] + (1UL << order);
+		if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
+			return 0;
+
+		__mod_zone_freepage_state(zone, -(1UL << order), mt);
+	}
+
+	del_page_from_free_list(page, zone, order);
+
+	/*
+	 * Set the pageblock if the isolated page is at least half of a
+	 * pageblock
+	 */
+	if (order >= pageblock_order - 1) {
+		struct page *endpage = page + (1 << order) - 1;
+		for (; page < endpage; page += pageblock_nr_pages) {
+			int mt = get_pageblock_migratetype(page);
+			/*
+			 * Only change normal pageblocks (i.e., they can merge
+			 * with others)
+			 */
+			if (migratetype_is_mergeable(mt))
+				set_pageblock_migratetype(page,
+							  MIGRATE_MOVABLE);
+		}
+	}
+
+	return 1UL << order;
+}
+
+/**
+ * __putback_isolated_page - Return a now-isolated page back where we got it
+ * @page: Page that was isolated
+ * @order: Order of the isolated page
+ * @mt: The page's pageblock's migratetype
+ *
+ * This function is meant to return a page pulled from the free lists via
+ * __isolate_free_page back to the free lists they were pulled from.
+ */
+void __putback_isolated_page(struct page *page, unsigned int order, int mt)
+{
+	struct zone *zone = page_zone(page);
+
+	/* zone lock should be held when this function is called */
+	lockdep_assert_held(&zone->lock);
+
+	/* Return isolated page to tail of freelist. */
+	__free_one_page(page, page_to_pfn(page), zone, order, mt,
+			FPI_SKIP_REPORT_NOTIFY | FPI_TO_TAIL);
+}
+
+/*
+ * Update NUMA hit/miss statistics
+ */
+static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
+				   long nr_account)
+{
+#ifdef CONFIG_NUMA
+	enum numa_stat_item local_stat = NUMA_LOCAL;
+
+	/* skip numa counters update if numa stats is disabled */
+	if (!static_branch_likely(&vm_numa_stat_key))
+		return;
+
+	if (zone_to_nid(z) != numa_node_id())
+		local_stat = NUMA_OTHER;
+
+	if (zone_to_nid(z) == zone_to_nid(preferred_zone))
+		__count_numa_events(z, NUMA_HIT, nr_account);
+	else {
+		__count_numa_events(z, NUMA_MISS, nr_account);
+		__count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
+	}
+	__count_numa_events(z, local_stat, nr_account);
+#endif
+}
+
+static __always_inline
+struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
+			   unsigned int order, unsigned int alloc_flags,
+			   int migratetype)
+{
+	struct page *page;
+	unsigned long flags;
+
+	do {
+		page = NULL;
+		spin_lock_irqsave(&zone->lock, flags);
+		if (alloc_flags & ALLOC_HIGHATOMIC)
+			page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+		if (!page) {
+			page = __rmqueue(zone, order, migratetype, alloc_flags);
+
+			/*
+			 * If the allocation fails, allow OOM handling access
+			 * to HIGHATOMIC reserves as failing now is worse than
+			 * failing a high-order atomic allocation in the
+			 * future.
+			 */
+			if (!page && (alloc_flags & ALLOC_OOM))
+				page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+
+			if (!page) {
+				spin_unlock_irqrestore(&zone->lock, flags);
+				return NULL;
+			}
+		}
+		__mod_zone_freepage_state(zone, -(1 << order),
+					  get_pcppage_migratetype(page));
+		spin_unlock_irqrestore(&zone->lock, flags);
+	} while (check_new_pages(page, order));
+
+	__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
+	zone_statistics(preferred_zone, zone, 1);
+
+	return page;
+}
+
+/* Remove page from the per-cpu list, caller must protect the list */
+static inline
+struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
+			int migratetype,
+			unsigned int alloc_flags,
+			struct per_cpu_pages *pcp,
+			struct list_head *list)
+{
+	struct page *page;
+
+	do {
+		if (list_empty(list)) {
+			int batch = READ_ONCE(pcp->batch);
+			int alloced;
+
+			/*
+			 * Scale batch relative to order if batch implies
+			 * free pages can be stored on the PCP. Batch can
+			 * be 1 for small zones or for boot pagesets which
+			 * should never store free pages as the pages may
+			 * belong to arbitrary zones.
+			 */
+			if (batch > 1)
+				batch = max(batch >> order, 2);
+			alloced = rmqueue_bulk(zone, order,
+					batch, list,
+					migratetype, alloc_flags);
+
+			pcp->count += alloced << order;
+			if (unlikely(list_empty(list)))
+				return NULL;
+		}
+
+		page = list_first_entry(list, struct page, pcp_list);
+		list_del(&page->pcp_list);
+		pcp->count -= 1 << order;
+	} while (check_new_pages(page, order));
+
+	return page;
+}
+
+/* Lock and remove page from the per-cpu list */
+static struct page *rmqueue_pcplist(struct zone *preferred_zone,
+			struct zone *zone, unsigned int order,
+			int migratetype, unsigned int alloc_flags)
+{
+	struct per_cpu_pages *pcp;
+	struct list_head *list;
+	struct page *page;
+	unsigned long __maybe_unused UP_flags;
+
+	/* spin_trylock may fail due to a parallel drain or IRQ reentrancy. */
+	pcp_trylock_prepare(UP_flags);
+	pcp = pcp_spin_trylock(zone->per_cpu_pageset);
+	if (!pcp) {
+		pcp_trylock_finish(UP_flags);
+		return NULL;
+	}
+
+	/*
+	 * On allocation, reduce the number of pages that are batch freed.
+	 * See nr_pcp_free() where free_factor is increased for subsequent
+	 * frees.
+	 */
+	pcp->free_factor >>= 1;
+	list = &pcp->lists[order_to_pindex(migratetype, order)];
+	page = __rmqueue_pcplist(zone, order, migratetype, alloc_flags, pcp, list);
+	pcp_spin_unlock(pcp);
+	pcp_trylock_finish(UP_flags);
+	if (page) {
+		__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
+		zone_statistics(preferred_zone, zone, 1);
+	}
+	return page;
+}
+
+/*
+ * Allocate a page from the given zone.
+ * Use pcplists for THP or "cheap" high-order allocations.
+ */
+
+/*
+ * Do not instrument rmqueue() with KMSAN. This function may call
+ * __msan_poison_alloca() through a call to set_pfnblock_flags_mask().
+ * If __msan_poison_alloca() attempts to allocate pages for the stack depot, it
+ * may call rmqueue() again, which will result in a deadlock.
+ */
+__no_sanitize_memory
+static inline
+struct page *rmqueue(struct zone *preferred_zone,
+			struct zone *zone, unsigned int order,
+			gfp_t gfp_flags, unsigned int alloc_flags,
+			int migratetype)
+{
+	struct page *page;
+
+	/*
+	 * 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));
+
+	if (likely(pcp_allowed_order(order))) {
+		page = rmqueue_pcplist(preferred_zone, zone, order,
+				       migratetype, alloc_flags);
+		if (likely(page))
+			goto out;
+	}
+
+	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
+							migratetype);
+
+out:
+	/* Separate test+clear to avoid unnecessary atomics */
+	if ((alloc_flags & ALLOC_KSWAPD) &&
+	    unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
+		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
+		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
+	}
+
+	VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
+	return page;
+}
+
+noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
+{
+	return __should_fail_alloc_page(gfp_mask, order);
+}
+ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE);
+
+static inline long __zone_watermark_unusable_free(struct zone *z,
+				unsigned int order, unsigned int alloc_flags)
+{
+	long unusable_free = (1 << order) - 1;
+
+	/*
+	 * If the caller does not have rights to reserves below the min
+	 * watermark then subtract the high-atomic reserves. This will
+	 * over-estimate the size of the atomic reserve but it avoids a search.
+	 */
+	if (likely(!(alloc_flags & ALLOC_RESERVES)))
+		unusable_free += z->nr_reserved_highatomic;
+
+#ifdef CONFIG_CMA
+	/* If allocation can't use CMA areas don't use free CMA pages */
+	if (!(alloc_flags & ALLOC_CMA))
+		unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
+#endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	unusable_free += zone_page_state(z, NR_UNACCEPTED);
+#endif
+
+	return unusable_free;
+}
+
+/*
+ * Return true if free base pages are above 'mark'. For high-order checks it
+ * will return true of the order-0 watermark is reached and there is at least
+ * one free page of a suitable size. Checking now avoids taking the zone lock
+ * to check in the allocation paths if no pages are free.
+ */
+bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
+			 int highest_zoneidx, unsigned int alloc_flags,
+			 long free_pages)
+{
+	long min = mark;
+	int o;
+
+	/* free_pages may go negative - that's OK */
+	free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
+
+	if (unlikely(alloc_flags & ALLOC_RESERVES)) {
+		/*
+		 * __GFP_HIGH allows access to 50% of the min reserve as well
+		 * as OOM.
+		 */
+		if (alloc_flags & ALLOC_MIN_RESERVE) {
+			min -= min / 2;
+
+			/*
+			 * Non-blocking allocations (e.g. GFP_ATOMIC) can
+			 * access more reserves than just __GFP_HIGH. Other
+			 * non-blocking allocations requests such as GFP_NOWAIT
+			 * or (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) do not get
+			 * access to the min reserve.
+			 */
+			if (alloc_flags & ALLOC_NON_BLOCK)
+				min -= min / 4;
+		}
+
+		/*
+		 * OOM victims can try even harder than the normal reserve
+		 * users on the grounds that it's definitely going to be in
+		 * the exit path shortly and free memory. Any allocation it
+		 * makes during the free path will be small and short-lived.
+		 */
+		if (alloc_flags & ALLOC_OOM)
+			min -= min / 2;
+	}
+
+	/*
+	 * Check watermarks for an order-0 allocation request. If these
+	 * are not met, then a high-order request also cannot go ahead
+	 * even if a suitable page happened to be free.
+	 */
+	if (free_pages <= min + z->lowmem_reserve[highest_zoneidx])
+		return false;
+
+	/* If this is an order-0 request then the watermark is fine */
+	if (!order)
+		return true;
+
+	/* For a high-order request, check at least one suitable page is free */
+	for (o = order; o <= MAX_ORDER; o++) {
+		struct free_area *area = &z->free_area[o];
+		int mt;
+
+		if (!area->nr_free)
+			continue;
+
+		for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
+			if (!free_area_empty(area, mt))
+				return true;
+		}
+
+#ifdef CONFIG_CMA
+		if ((alloc_flags & ALLOC_CMA) &&
+		    !free_area_empty(area, MIGRATE_CMA)) {
+			return true;
+		}
+#endif
+		if ((alloc_flags & (ALLOC_HIGHATOMIC|ALLOC_OOM)) &&
+		    !free_area_empty(area, MIGRATE_HIGHATOMIC)) {
+			return true;
+		}
+	}
+	return false;
+}
+
+bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
+		      int highest_zoneidx, unsigned int alloc_flags)
+{
+	return __zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
+					zone_page_state(z, NR_FREE_PAGES));
+}
+
+static inline bool zone_watermark_fast(struct zone *z, unsigned int order,
+				unsigned long mark, int highest_zoneidx,
+				unsigned int alloc_flags, gfp_t gfp_mask)
+{
+	long free_pages;
+
+	free_pages = zone_page_state(z, NR_FREE_PAGES);
+
+	/*
+	 * Fast check for order-0 only. If this fails then the reserves
+	 * need to be calculated.
+	 */
+	if (!order) {
+		long usable_free;
+		long reserved;
+
+		usable_free = free_pages;
+		reserved = __zone_watermark_unusable_free(z, 0, alloc_flags);
+
+		/* reserved may over estimate high-atomic reserves. */
+		usable_free -= min(usable_free, reserved);
+		if (usable_free > mark + z->lowmem_reserve[highest_zoneidx])
+			return true;
+	}
+
+	if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags,
+					free_pages))
+		return true;
+
+	/*
+	 * Ignore watermark boosting for __GFP_HIGH order-0 allocations
+	 * when checking the min watermark. The min watermark is the
+	 * point where boosting is ignored so that kswapd is woken up
+	 * when below the low watermark.
+	 */
+	if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost
+		&& ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) {
+		mark = z->_watermark[WMARK_MIN];
+		return __zone_watermark_ok(z, order, mark, highest_zoneidx,
+					alloc_flags, free_pages);
+	}
+
+	return false;
+}
+
+bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
+			unsigned long mark, int highest_zoneidx)
+{
+	long free_pages = zone_page_state(z, NR_FREE_PAGES);
+
+	if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
+		free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);
+
+	return __zone_watermark_ok(z, order, mark, highest_zoneidx, 0,
+								free_pages);
+}
+
+#ifdef CONFIG_NUMA
+int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;
+
+static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
+{
+	return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
+				node_reclaim_distance;
+}
+#else	/* CONFIG_NUMA */
+static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
+{
+	return true;
+}
+#endif	/* CONFIG_NUMA */
+
+/*
+ * The restriction on ZONE_DMA32 as being a suitable zone to use to avoid
+ * fragmentation is subtle. If the preferred zone was HIGHMEM then
+ * premature use of a lower zone may cause lowmem pressure problems that
+ * are worse than fragmentation. If the next zone is ZONE_DMA then it is
+ * probably too small. It only makes sense to spread allocations to avoid
+ * fragmentation between the Normal and DMA32 zones.
+ */
+static inline unsigned int
+alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
+{
+	unsigned int alloc_flags;
+
+	/*
+	 * __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
+	 * to save a branch.
+	 */
+	alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);
+
+#ifdef CONFIG_ZONE_DMA32
+	if (!zone)
+		return alloc_flags;
+
+	if (zone_idx(zone) != ZONE_NORMAL)
+		return alloc_flags;
+
+	/*
+	 * If ZONE_DMA32 exists, assume it is the one after ZONE_NORMAL and
+	 * the pointer is within zone->zone_pgdat->node_zones[]. Also assume
+	 * on UMA that if Normal is populated then so is DMA32.
+	 */
+	BUILD_BUG_ON(ZONE_NORMAL - ZONE_DMA32 != 1);
+	if (nr_online_nodes > 1 && !populated_zone(--zone))
+		return alloc_flags;
+
+	alloc_flags |= ALLOC_NOFRAGMENT;
+#endif /* CONFIG_ZONE_DMA32 */
+	return alloc_flags;
+}
+
+/* Must be called after current_gfp_context() which can change gfp_mask */
+static inline unsigned int gfp_to_alloc_flags_cma(gfp_t gfp_mask,
+						  unsigned int alloc_flags)
+{
+#ifdef CONFIG_CMA
+	if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
+		alloc_flags |= ALLOC_CMA;
+#endif
+	return alloc_flags;
+}
+
+/*
+ * get_page_from_freelist goes through the zonelist trying to allocate
+ * a page.
+ */
+static struct page *
+get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
+						const struct alloc_context *ac)
+{
+	struct zoneref *z;
+	struct zone *zone;
+	struct pglist_data *last_pgdat = NULL;
+	bool last_pgdat_dirty_ok = false;
+	bool no_fallback;
+
+retry:
+	/*
+	 * Scan zonelist, looking for a zone with enough free.
+	 * See also cpuset_node_allowed() comment in kernel/cgroup/cpuset.c.
+	 */
+	no_fallback = alloc_flags & ALLOC_NOFRAGMENT;
+	z = ac->preferred_zoneref;
+	for_next_zone_zonelist_nodemask(zone, z, ac->highest_zoneidx,
+					ac->nodemask) {
+		struct page *page;
+		unsigned long mark;
+
+		if (cpusets_enabled() &&
+			(alloc_flags & ALLOC_CPUSET) &&
+			!__cpuset_zone_allowed(zone, gfp_mask))
+				continue;
+		/*
+		 * When allocating a page cache page for writing, we
+		 * want to get it from a node that is within its dirty
+		 * limit, such that no single node holds more than its
+		 * proportional share of globally allowed dirty pages.
+		 * The dirty limits take into account the node's
+		 * lowmem reserves and high watermark so that kswapd
+		 * should be able to balance it without having to
+		 * write pages from its LRU list.
+		 *
+		 * XXX: For now, allow allocations to potentially
+		 * exceed the per-node dirty limit in the slowpath
+		 * (spread_dirty_pages unset) before going into reclaim,
+		 * which is important when on a NUMA setup the allowed
+		 * nodes are together not big enough to reach the
+		 * global limit.  The proper fix for these situations
+		 * will require awareness of nodes in the
+		 * dirty-throttling and the flusher threads.
+		 */
+		if (ac->spread_dirty_pages) {
+			if (last_pgdat != zone->zone_pgdat) {
+				last_pgdat = zone->zone_pgdat;
+				last_pgdat_dirty_ok = node_dirty_ok(zone->zone_pgdat);
+			}
+
+			if (!last_pgdat_dirty_ok)
+				continue;
+		}
+
+		if (no_fallback && nr_online_nodes > 1 &&
+		    zone != ac->preferred_zoneref->zone) {
+			int local_nid;
+
+			/*
+			 * If moving to a remote node, retry but allow
+			 * fragmenting fallbacks. Locality is more important
+			 * than fragmentation avoidance.
+			 */
+			local_nid = zone_to_nid(ac->preferred_zoneref->zone);
+			if (zone_to_nid(zone) != local_nid) {
+				alloc_flags &= ~ALLOC_NOFRAGMENT;
+				goto retry;
+			}
+		}
+
+		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
+		if (!zone_watermark_fast(zone, order, mark,
+				       ac->highest_zoneidx, alloc_flags,
+				       gfp_mask)) {
+			int ret;
+
+			if (has_unaccepted_memory()) {
+				if (try_to_accept_memory(zone, order))
+					goto try_this_zone;
+			}
+
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+			/*
+			 * Watermark failed for this zone, but see if we can
+			 * grow this zone if it contains deferred pages.
+			 */
+			if (deferred_pages_enabled()) {
+				if (_deferred_grow_zone(zone, order))
+					goto try_this_zone;
+			}
+#endif
+			/* Checked here to keep the fast path fast */
+			BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
+			if (alloc_flags & ALLOC_NO_WATERMARKS)
+				goto try_this_zone;
+
+			if (!node_reclaim_enabled() ||
+			    !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
+				continue;
+
+			ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
+			switch (ret) {
+			case NODE_RECLAIM_NOSCAN:
+				/* did not scan */
+				continue;
+			case NODE_RECLAIM_FULL:
+				/* scanned but unreclaimable */
+				continue;
+			default:
+				/* did we reclaim enough */
+				if (zone_watermark_ok(zone, order, mark,
+					ac->highest_zoneidx, alloc_flags))
+					goto try_this_zone;
+
+				continue;
+			}
+		}
+
+try_this_zone:
+		page = rmqueue(ac->preferred_zoneref->zone, zone, order,
+				gfp_mask, alloc_flags, ac->migratetype);
+		if (page) {
+			prep_new_page(page, order, gfp_mask, alloc_flags);
+
+			/*
+			 * If this is a high-order atomic allocation then check
+			 * if the pageblock should be reserved for the future
+			 */
+			if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
+				reserve_highatomic_pageblock(page, zone);
+
+			return page;
+		} else {
+			if (has_unaccepted_memory()) {
+				if (try_to_accept_memory(zone, order))
+					goto try_this_zone;
+			}
+
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+			/* Try again if zone has deferred pages */
+			if (deferred_pages_enabled()) {
+				if (_deferred_grow_zone(zone, order))
+					goto try_this_zone;
+			}
+#endif
+		}
+	}
+
+	/*
+	 * It's possible on a UMA machine to get through all zones that are
+	 * fragmented. If avoiding fragmentation, reset and try again.
+	 */
+	if (no_fallback) {
+		alloc_flags &= ~ALLOC_NOFRAGMENT;
+		goto retry;
+	}
+
+	return NULL;
+}
+
+static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
+{
+	unsigned int filter = SHOW_MEM_FILTER_NODES;
+
+	/*
+	 * This documents exceptions given to allocations in certain
+	 * contexts that are allowed to allocate outside current's set
+	 * of allowed nodes.
+	 */
+	if (!(gfp_mask & __GFP_NOMEMALLOC))
+		if (tsk_is_oom_victim(current) ||
+		    (current->flags & (PF_MEMALLOC | PF_EXITING)))
+			filter &= ~SHOW_MEM_FILTER_NODES;
+	if (!in_task() || !(gfp_mask & __GFP_DIRECT_RECLAIM))
+		filter &= ~SHOW_MEM_FILTER_NODES;
+
+	__show_mem(filter, nodemask, gfp_zone(gfp_mask));
+}
+
+void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);
+
+	if ((gfp_mask & __GFP_NOWARN) ||
+	     !__ratelimit(&nopage_rs) ||
+	     ((gfp_mask & __GFP_DMA) && !has_managed_dma()))
+		return;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl",
+			current->comm, &vaf, gfp_mask, &gfp_mask,
+			nodemask_pr_args(nodemask));
+	va_end(args);
+
+	cpuset_print_current_mems_allowed();
+	pr_cont("\n");
+	dump_stack();
+	warn_alloc_show_mem(gfp_mask, nodemask);
+}
+
+static inline struct page *
+__alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,
+			      unsigned int alloc_flags,
+			      const struct alloc_context *ac)
+{
+	struct page *page;
+
+	page = get_page_from_freelist(gfp_mask, order,
+			alloc_flags|ALLOC_CPUSET, ac);
+	/*
+	 * fallback to ignore cpuset restriction if our nodes
+	 * are depleted
+	 */
+	if (!page)
+		page = get_page_from_freelist(gfp_mask, order,
+				alloc_flags, ac);
+
+	return page;
+}
+
+static inline struct page *
+__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
+	const struct alloc_context *ac, unsigned long *did_some_progress)
+{
+	struct oom_control oc = {
+		.zonelist = ac->zonelist,
+		.nodemask = ac->nodemask,
+		.memcg = NULL,
+		.gfp_mask = gfp_mask,
+		.order = order,
+	};
+	struct page *page;
+
+	*did_some_progress = 0;
+
+	/*
+	 * Acquire the oom lock.  If that fails, somebody else is
+	 * making progress for us.
+	 */
+	if (!mutex_trylock(&oom_lock)) {
+		*did_some_progress = 1;
+		schedule_timeout_uninterruptible(1);
+		return NULL;
+	}
+
+	/*
+	 * Go through the zonelist yet one more time, keep very high watermark
+	 * here, this is only to catch a parallel oom killing, we must fail if
+	 * we're still under heavy pressure. But make sure that this reclaim
+	 * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY
+	 * allocation which will never fail due to oom_lock already held.
+	 */
+	page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) &
+				      ~__GFP_DIRECT_RECLAIM, order,
+				      ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac);
+	if (page)
+		goto out;
+
+	/* Coredumps can quickly deplete all memory reserves */
+	if (current->flags & PF_DUMPCORE)
+		goto out;
+	/* The OOM killer will not help higher order allocs */
+	if (order > PAGE_ALLOC_COSTLY_ORDER)
+		goto out;
+	/*
+	 * We have already exhausted all our reclaim opportunities without any
+	 * success so it is time to admit defeat. We will skip the OOM killer
+	 * because it is very likely that the caller has a more reasonable
+	 * fallback than shooting a random task.
+	 *
+	 * The OOM killer may not free memory on a specific node.
+	 */
+	if (gfp_mask & (__GFP_RETRY_MAYFAIL | __GFP_THISNODE))
+		goto out;
+	/* The OOM killer does not needlessly kill tasks for lowmem */
+	if (ac->highest_zoneidx < ZONE_NORMAL)
+		goto out;
+	if (pm_suspended_storage())
+		goto out;
+	/*
+	 * XXX: GFP_NOFS allocations should rather fail than rely on
+	 * other request to make a forward progress.
+	 * We are in an unfortunate situation where out_of_memory cannot
+	 * do much for this context but let's try it to at least get
+	 * access to memory reserved if the current task is killed (see
+	 * out_of_memory). Once filesystems are ready to handle allocation
+	 * failures more gracefully we should just bail out here.
+	 */
+
+	/* Exhausted what can be done so it's blame time */
+	if (out_of_memory(&oc) ||
+	    WARN_ON_ONCE_GFP(gfp_mask & __GFP_NOFAIL, gfp_mask)) {
+		*did_some_progress = 1;
+
+		/*
+		 * Help non-failing allocations by giving them access to memory
+		 * reserves
+		 */
+		if (gfp_mask & __GFP_NOFAIL)
+			page = __alloc_pages_cpuset_fallback(gfp_mask, order,
+					ALLOC_NO_WATERMARKS, ac);
+	}
+out:
+	mutex_unlock(&oom_lock);
+	return page;
+}
+
+/*
+ * Maximum number of compaction retries with a progress before OOM
+ * killer is consider as the only way to move forward.
+ */
+#define MAX_COMPACT_RETRIES 16
+
+#ifdef CONFIG_COMPACTION
+/* Try memory compaction for high-order allocations before reclaim */
+static struct page *
+__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
+		unsigned int alloc_flags, const struct alloc_context *ac,
+		enum compact_priority prio, enum compact_result *compact_result)
+{
+	struct page *page = NULL;
+	unsigned long pflags;
+	unsigned int noreclaim_flag;
+
+	if (!order)
+		return NULL;
+
+	psi_memstall_enter(&pflags);
+	delayacct_compact_start();
+	noreclaim_flag = memalloc_noreclaim_save();
+
+	*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
+								prio, &page);
+
+	memalloc_noreclaim_restore(noreclaim_flag);
+	psi_memstall_leave(&pflags);
+	delayacct_compact_end();
+
+	if (*compact_result == COMPACT_SKIPPED)
+		return NULL;
+	/*
+	 * At least in one zone compaction wasn't deferred or skipped, so let's
+	 * count a compaction stall
+	 */
+	count_vm_event(COMPACTSTALL);
+
+	/* Prep a captured page if available */
+	if (page)
+		prep_new_page(page, order, gfp_mask, alloc_flags);
+
+	/* Try get a page from the freelist if available */
+	if (!page)
+		page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
+
+	if (page) {
+		struct zone *zone = page_zone(page);
+
+		zone->compact_blockskip_flush = false;
+		compaction_defer_reset(zone, order, true);
+		count_vm_event(COMPACTSUCCESS);
+		return page;
+	}
+
+	/*
+	 * It's bad if compaction run occurs and fails. The most likely reason
+	 * is that pages exist, but not enough to satisfy watermarks.
+	 */
+	count_vm_event(COMPACTFAIL);
+
+	cond_resched();
+
+	return NULL;
+}
+
+static inline bool
+should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
+		     enum compact_result compact_result,
+		     enum compact_priority *compact_priority,
+		     int *compaction_retries)
+{
+	int max_retries = MAX_COMPACT_RETRIES;
+	int min_priority;
+	bool ret = false;
+	int retries = *compaction_retries;
+	enum compact_priority priority = *compact_priority;
+
+	if (!order)
+		return false;
+
+	if (fatal_signal_pending(current))
+		return false;
+
+	/*
+	 * Compaction was skipped due to a lack of free order-0
+	 * migration targets. Continue if reclaim can help.
+	 */
+	if (compact_result == COMPACT_SKIPPED) {
+		ret = compaction_zonelist_suitable(ac, order, alloc_flags);
+		goto out;
+	}
+
+	/*
+	 * Compaction managed to coalesce some page blocks, but the
+	 * allocation failed presumably due to a race. Retry some.
+	 */
+	if (compact_result == COMPACT_SUCCESS) {
+		/*
+		 * !costly requests are much more important than
+		 * __GFP_RETRY_MAYFAIL costly ones because they are de
+		 * facto nofail and invoke OOM killer to move on while
+		 * costly can fail and users are ready to cope with
+		 * that. 1/4 retries is rather arbitrary but we would
+		 * need much more detailed feedback from compaction to
+		 * make a better decision.
+		 */
+		if (order > PAGE_ALLOC_COSTLY_ORDER)
+			max_retries /= 4;
+
+		if (++(*compaction_retries) <= max_retries) {
+			ret = true;
+			goto out;
+		}
+	}
+
+	/*
+	 * Compaction failed. Retry with increasing priority.
+	 */
+	min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
+			MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
+
+	if (*compact_priority > min_priority) {
+		(*compact_priority)--;
+		*compaction_retries = 0;
+		ret = true;
+	}
+out:
+	trace_compact_retry(order, priority, compact_result, retries, max_retries, ret);
+	return ret;
+}
+#else
+static inline struct page *
+__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
+		unsigned int alloc_flags, const struct alloc_context *ac,
+		enum compact_priority prio, enum compact_result *compact_result)
+{
+	*compact_result = COMPACT_SKIPPED;
+	return NULL;
+}
+
+static inline bool
+should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
+		     enum compact_result compact_result,
+		     enum compact_priority *compact_priority,
+		     int *compaction_retries)
+{
+	struct zone *zone;
+	struct zoneref *z;
+
+	if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
+		return false;
+
+	/*
+	 * There are setups with compaction disabled which would prefer to loop
+	 * inside the allocator rather than hit the oom killer prematurely.
+	 * Let's give them a good hope and keep retrying while the order-0
+	 * watermarks are OK.
+	 */
+	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
+				ac->highest_zoneidx, ac->nodemask) {
+		if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
+					ac->highest_zoneidx, alloc_flags))
+			return true;
+	}
+	return false;
+}
+#endif /* CONFIG_COMPACTION */
+
+#ifdef CONFIG_LOCKDEP
+static struct lockdep_map __fs_reclaim_map =
+	STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
+
+static bool __need_reclaim(gfp_t gfp_mask)
+{
+	/* no reclaim without waiting on it */
+	if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
+		return false;
+
+	/* this guy won't enter reclaim */
+	if (current->flags & PF_MEMALLOC)
+		return false;
+
+	if (gfp_mask & __GFP_NOLOCKDEP)
+		return false;
+
+	return true;
+}
+
+void __fs_reclaim_acquire(unsigned long ip)
+{
+	lock_acquire_exclusive(&__fs_reclaim_map, 0, 0, NULL, ip);
+}
+
+void __fs_reclaim_release(unsigned long ip)
+{
+	lock_release(&__fs_reclaim_map, ip);
+}
+
+void fs_reclaim_acquire(gfp_t gfp_mask)
+{
+	gfp_mask = current_gfp_context(gfp_mask);
+
+	if (__need_reclaim(gfp_mask)) {
+		if (gfp_mask & __GFP_FS)
+			__fs_reclaim_acquire(_RET_IP_);
+
+#ifdef CONFIG_MMU_NOTIFIER
+		lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
+		lock_map_release(&__mmu_notifier_invalidate_range_start_map);
+#endif
+
+	}
+}
+EXPORT_SYMBOL_GPL(fs_reclaim_acquire);
+
+void fs_reclaim_release(gfp_t gfp_mask)
+{
+	gfp_mask = current_gfp_context(gfp_mask);
+
+	if (__need_reclaim(gfp_mask)) {
+		if (gfp_mask & __GFP_FS)
+			__fs_reclaim_release(_RET_IP_);
+	}
+}
+EXPORT_SYMBOL_GPL(fs_reclaim_release);
+#endif
+
+/*
+ * Zonelists may change due to hotplug during allocation. Detect when zonelists
+ * have been rebuilt so allocation retries. Reader side does not lock and
+ * retries the allocation if zonelist changes. Writer side is protected by the
+ * embedded spin_lock.
+ */
+static DEFINE_SEQLOCK(zonelist_update_seq);
+
+static unsigned int zonelist_iter_begin(void)
+{
+	if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
+		return read_seqbegin(&zonelist_update_seq);
+
+	return 0;
+}
+
+static unsigned int check_retry_zonelist(unsigned int seq)
+{
+	if (IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
+		return read_seqretry(&zonelist_update_seq, seq);
+
+	return seq;
+}
+
+/* Perform direct synchronous page reclaim */
+static unsigned long
+__perform_reclaim(gfp_t gfp_mask, unsigned int order,
+					const struct alloc_context *ac)
+{
+	unsigned int noreclaim_flag;
+	unsigned long progress;
+
+	cond_resched();
+
+	/* We now go into synchronous reclaim */
+	cpuset_memory_pressure_bump();
+	fs_reclaim_acquire(gfp_mask);
+	noreclaim_flag = memalloc_noreclaim_save();
+
+	progress = try_to_free_pages(ac->zonelist, order, gfp_mask,
+								ac->nodemask);
+
+	memalloc_noreclaim_restore(noreclaim_flag);
+	fs_reclaim_release(gfp_mask);
+
+	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;
+	unsigned long pflags;
+	bool drained = false;
+
+	psi_memstall_enter(&pflags);
+	*did_some_progress = __perform_reclaim(gfp_mask, order, ac);
+	if (unlikely(!(*did_some_progress)))
+		goto out;
+
+retry:
+	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
+
+	/*
+	 * If an allocation failed after direct reclaim, it could be because
+	 * pages are pinned on the per-cpu lists or in high alloc reserves.
+	 * Shrink them and try again
+	 */
+	if (!page && !drained) {
+		unreserve_highatomic_pageblock(ac, false);
+		drain_all_pages(NULL);
+		drained = true;
+		goto retry;
+	}
+out:
+	psi_memstall_leave(&pflags);
+
+	return page;
+}
+
+static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
+			     const struct alloc_context *ac)
+{
+	struct zoneref *z;
+	struct zone *zone;
+	pg_data_t *last_pgdat = NULL;
+	enum zone_type highest_zoneidx = ac->highest_zoneidx;
+
+	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
+					ac->nodemask) {
+		if (!managed_zone(zone))
+			continue;
+		if (last_pgdat != zone->zone_pgdat) {
+			wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
+			last_pgdat = zone->zone_pgdat;
+		}
+	}
+}
+
+static inline unsigned int
+gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order)
+{
+	unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
+
+	/*
+	 * __GFP_HIGH is assumed to be the same as ALLOC_MIN_RESERVE
+	 * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
+	 * to save two branches.
+	 */
+	BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_MIN_RESERVE);
+	BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
+
+	/*
+	 * The caller may dip into page reserves a bit more if the caller
+	 * cannot run direct reclaim, or if the caller has realtime scheduling
+	 * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
+	 * set both ALLOC_NON_BLOCK and ALLOC_MIN_RESERVE(__GFP_HIGH).
+	 */
+	alloc_flags |= (__force int)
+		(gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
+
+	if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {
+		/*
+		 * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
+		 * if it can't schedule.
+		 */
+		if (!(gfp_mask & __GFP_NOMEMALLOC)) {
+			alloc_flags |= ALLOC_NON_BLOCK;
+
+			if (order > 0)
+				alloc_flags |= ALLOC_HIGHATOMIC;
+		}
+
+		/*
+		 * Ignore cpuset mems for non-blocking __GFP_HIGH (probably
+		 * GFP_ATOMIC) rather than fail, see the comment for
+		 * cpuset_node_allowed().
+		 */
+		if (alloc_flags & ALLOC_MIN_RESERVE)
+			alloc_flags &= ~ALLOC_CPUSET;
+	} else if (unlikely(rt_task(current)) && in_task())
+		alloc_flags |= ALLOC_MIN_RESERVE;
+
+	alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, alloc_flags);
+
+	return alloc_flags;
+}
+
+static bool oom_reserves_allowed(struct task_struct *tsk)
+{
+	if (!tsk_is_oom_victim(tsk))
+		return false;
+
+	/*
+	 * !MMU doesn't have oom reaper so give access to memory reserves
+	 * only to the thread with TIF_MEMDIE set
+	 */
+	if (!IS_ENABLED(CONFIG_MMU) && !test_thread_flag(TIF_MEMDIE))
+		return false;
+
+	return true;
+}
+
+/*
+ * Distinguish requests which really need access to full memory
+ * reserves from oom victims which can live with a portion of it
+ */
+static inline int __gfp_pfmemalloc_flags(gfp_t gfp_mask)
+{
+	if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
+		return 0;
+	if (gfp_mask & __GFP_MEMALLOC)
+		return ALLOC_NO_WATERMARKS;
+	if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
+		return ALLOC_NO_WATERMARKS;
+	if (!in_interrupt()) {
+		if (current->flags & PF_MEMALLOC)
+			return ALLOC_NO_WATERMARKS;
+		else if (oom_reserves_allowed(current))
+			return ALLOC_OOM;
+	}
+
+	return 0;
+}
+
+bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
+{
+	return !!__gfp_pfmemalloc_flags(gfp_mask);
+}
+
+/*
+ * Checks whether it makes sense to retry the reclaim to make a forward progress
+ * for the given allocation request.
+ *
+ * We give up when we either have tried MAX_RECLAIM_RETRIES in a row
+ * without success, or when we couldn't even meet the watermark if we
+ * reclaimed all remaining pages on the LRU lists.
+ *
+ * Returns true if a retry is viable or false to enter the oom path.
+ */
+static inline bool
+should_reclaim_retry(gfp_t gfp_mask, unsigned order,
+		     struct alloc_context *ac, int alloc_flags,
+		     bool did_some_progress, int *no_progress_loops)
+{
+	struct zone *zone;
+	struct zoneref *z;
+	bool ret = false;
+
+	/*
+	 * Costly allocations might have made a progress but this doesn't mean
+	 * their order will become available due to high fragmentation so
+	 * always increment the no progress counter for them
+	 */
+	if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
+		*no_progress_loops = 0;
+	else
+		(*no_progress_loops)++;
+
+	if (*no_progress_loops > MAX_RECLAIM_RETRIES)
+		goto out;
+
+
+	/*
+	 * Keep reclaiming pages while there is a chance this will lead
+	 * somewhere.  If none of the target zones can satisfy our allocation
+	 * request even if all reclaimable pages are considered then we are
+	 * screwed and have to go OOM.
+	 */
+	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
+				ac->highest_zoneidx, ac->nodemask) {
+		unsigned long available;
+		unsigned long reclaimable;
+		unsigned long min_wmark = min_wmark_pages(zone);
+		bool wmark;
+
+		available = reclaimable = zone_reclaimable_pages(zone);
+		available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
+
+		/*
+		 * Would the allocation succeed if we reclaimed all
+		 * reclaimable pages?
+		 */
+		wmark = __zone_watermark_ok(zone, order, min_wmark,
+				ac->highest_zoneidx, alloc_flags, available);
+		trace_reclaim_retry_zone(z, order, reclaimable,
+				available, min_wmark, *no_progress_loops, wmark);
+		if (wmark) {
+			ret = true;
+			break;
+		}
+	}
+
+	/*
+	 * Memory allocation/reclaim might be called from a WQ context and the
+	 * current implementation of the WQ concurrency control doesn't
+	 * recognize that a particular WQ is congested if the worker thread is
+	 * looping without ever sleeping. Therefore we have to do a short sleep
+	 * here rather than calling cond_resched().
+	 */
+	if (current->flags & PF_WQ_WORKER)
+		schedule_timeout_uninterruptible(1);
+	else
+		cond_resched();
+out:
+	/* Before OOM, exhaust highatomic_reserve */
+	if (!ret)
+		return unreserve_highatomic_pageblock(ac, true);
+
+	return ret;
+}
+
+static inline bool
+check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)
+{
+	/*
+	 * It's possible that cpuset's mems_allowed and the nodemask from
+	 * mempolicy don't intersect. This should be normally dealt with by
+	 * policy_nodemask(), but it's possible to race with cpuset update in
+	 * such a way the check therein was true, and then it became false
+	 * before we got our cpuset_mems_cookie here.
+	 * This assumes that for all allocations, ac->nodemask can come only
+	 * from MPOL_BIND mempolicy (whose documented semantics is to be ignored
+	 * when it does not intersect with the cpuset restrictions) or the
+	 * caller can deal with a violated nodemask.
+	 */
+	if (cpusets_enabled() && ac->nodemask &&
+			!cpuset_nodemask_valid_mems_allowed(ac->nodemask)) {
+		ac->nodemask = NULL;
+		return true;
+	}
+
+	/*
+	 * When updating a task's mems_allowed or mempolicy nodemask, it is
+	 * possible to race with parallel threads in such a way that our
+	 * allocation can fail while the mask is being updated. If we are about
+	 * to fail, check if the cpuset changed during allocation and if so,
+	 * retry.
+	 */
+	if (read_mems_allowed_retry(cpuset_mems_cookie))
+		return true;
+
+	return false;
+}
+
+static inline struct page *
+__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
+						struct alloc_context *ac)
+{
+	bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
+	const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
+	struct page *page = NULL;
+	unsigned int alloc_flags;
+	unsigned long did_some_progress;
+	enum compact_priority compact_priority;
+	enum compact_result compact_result;
+	int compaction_retries;
+	int no_progress_loops;
+	unsigned int cpuset_mems_cookie;
+	unsigned int zonelist_iter_cookie;
+	int reserve_flags;
+
+restart:
+	compaction_retries = 0;
+	no_progress_loops = 0;
+	compact_priority = DEF_COMPACT_PRIORITY;
+	cpuset_mems_cookie = read_mems_allowed_begin();
+	zonelist_iter_cookie = zonelist_iter_begin();
+
+	/*
+	 * The fast path uses conservative alloc_flags to succeed only until
+	 * kswapd needs to be woken up, and to avoid the cost of setting up
+	 * alloc_flags precisely. So we do that now.
+	 */
+	alloc_flags = gfp_to_alloc_flags(gfp_mask, order);
+
+	/*
+	 * We need to recalculate the starting point for the zonelist iterator
+	 * because we might have used different nodemask in the fast path, or
+	 * there was a cpuset modification and we are retrying - otherwise we
+	 * could end up iterating over non-eligible zones endlessly.
+	 */
+	ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
+					ac->highest_zoneidx, ac->nodemask);
+	if (!ac->preferred_zoneref->zone)
+		goto nopage;
+
+	/*
+	 * Check for insane configurations where the cpuset doesn't contain
+	 * any suitable zone to satisfy the request - e.g. non-movable
+	 * GFP_HIGHUSER allocations from MOVABLE nodes only.
+	 */
+	if (cpusets_insane_config() && (gfp_mask & __GFP_HARDWALL)) {
+		struct zoneref *z = first_zones_zonelist(ac->zonelist,
+					ac->highest_zoneidx,
+					&cpuset_current_mems_allowed);
+		if (!z->zone)
+			goto nopage;
+	}
+
+	if (alloc_flags & ALLOC_KSWAPD)
+		wake_all_kswapds(order, gfp_mask, ac);
+
+	/*
+	 * The adjusted alloc_flags might result in immediate success, so try
+	 * that first
+	 */
+	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
+	if (page)
+		goto got_pg;
+
+	/*
+	 * For costly allocations, try direct compaction first, as it's likely
+	 * that we have enough base pages and don't need to reclaim. For non-
+	 * movable high-order allocations, do that as well, as compaction will
+	 * try prevent permanent fragmentation by migrating from blocks of the
+	 * same migratetype.
+	 * Don't try this for allocations that are allowed to ignore
+	 * watermarks, as the ALLOC_NO_WATERMARKS attempt didn't yet happen.
+	 */
+	if (can_direct_reclaim &&
+			(costly_order ||
+			   (order > 0 && ac->migratetype != MIGRATE_MOVABLE))
+			&& !gfp_pfmemalloc_allowed(gfp_mask)) {
+		page = __alloc_pages_direct_compact(gfp_mask, order,
+						alloc_flags, ac,
+						INIT_COMPACT_PRIORITY,
+						&compact_result);
+		if (page)
+			goto got_pg;
+
+		/*
+		 * Checks for costly allocations with __GFP_NORETRY, which
+		 * includes some THP page fault allocations
+		 */
+		if (costly_order && (gfp_mask & __GFP_NORETRY)) {
+			/*
+			 * If allocating entire pageblock(s) and compaction
+			 * failed because all zones are below low watermarks
+			 * or is prohibited because it recently failed at this
+			 * order, fail immediately unless the allocator has
+			 * requested compaction and reclaim retry.
+			 *
+			 * Reclaim is
+			 *  - potentially very expensive because zones are far
+			 *    below their low watermarks or this is part of very
+			 *    bursty high order allocations,
+			 *  - not guaranteed to help because isolate_freepages()
+			 *    may not iterate over freed pages as part of its
+			 *    linear scan, and
+			 *  - unlikely to make entire pageblocks free on its
+			 *    own.
+			 */
+			if (compact_result == COMPACT_SKIPPED ||
+			    compact_result == COMPACT_DEFERRED)
+				goto nopage;
+
+			/*
+			 * Looks like reclaim/compaction is worth trying, but
+			 * sync compaction could be very expensive, so keep
+			 * using async compaction.
+			 */
+			compact_priority = INIT_COMPACT_PRIORITY;
+		}
+	}
+
+retry:
+	/* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
+	if (alloc_flags & ALLOC_KSWAPD)
+		wake_all_kswapds(order, gfp_mask, ac);
+
+	reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
+	if (reserve_flags)
+		alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags) |
+					  (alloc_flags & ALLOC_KSWAPD);
+
+	/*
+	 * Reset the nodemask and zonelist iterators if memory policies can be
+	 * ignored. These allocations are high priority and system rather than
+	 * user oriented.
+	 */
+	if (!(alloc_flags & ALLOC_CPUSET) || reserve_flags) {
+		ac->nodemask = NULL;
+		ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
+					ac->highest_zoneidx, ac->nodemask);
+	}
+
+	/* Attempt with potentially adjusted zonelist and alloc_flags */
+	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
+	if (page)
+		goto got_pg;
+
+	/* Caller is not willing to reclaim, we can't balance anything */
+	if (!can_direct_reclaim)
+		goto nopage;
+
+	/* Avoid recursion of direct reclaim */
+	if (current->flags & PF_MEMALLOC)
+		goto nopage;
+
+	/* Try direct reclaim and then allocating */
+	page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
+							&did_some_progress);
+	if (page)
+		goto got_pg;
+
+	/* Try direct compaction and then allocating */
+	page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,
+					compact_priority, &compact_result);
+	if (page)
+		goto got_pg;
+
+	/* Do not loop if specifically requested */
+	if (gfp_mask & __GFP_NORETRY)
+		goto nopage;
+
+	/*
+	 * Do not retry costly high order allocations unless they are
+	 * __GFP_RETRY_MAYFAIL
+	 */
+	if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL))
+		goto nopage;
+
+	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
+				 did_some_progress > 0, &no_progress_loops))
+		goto retry;
+
+	/*
+	 * It doesn't make any sense to retry for the compaction if the order-0
+	 * reclaim is not able to make any progress because the current
+	 * implementation of the compaction depends on the sufficient amount
+	 * of free memory (see __compaction_suitable)
+	 */
+	if (did_some_progress > 0 &&
+			should_compact_retry(ac, order, alloc_flags,
+				compact_result, &compact_priority,
+				&compaction_retries))
+		goto retry;
+
+
+	/*
+	 * Deal with possible cpuset update races or zonelist updates to avoid
+	 * a unnecessary OOM kill.
+	 */
+	if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
+	    check_retry_zonelist(zonelist_iter_cookie))
+		goto restart;
+
+	/* Reclaim has failed us, start killing things */
+	page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
+	if (page)
+		goto got_pg;
+
+	/* Avoid allocations with no watermarks from looping endlessly */
+	if (tsk_is_oom_victim(current) &&
+	    (alloc_flags & ALLOC_OOM ||
+	     (gfp_mask & __GFP_NOMEMALLOC)))
+		goto nopage;
+
+	/* Retry as long as the OOM killer is making progress */
+	if (did_some_progress) {
+		no_progress_loops = 0;
+		goto retry;
+	}
+
+nopage:
+	/*
+	 * Deal with possible cpuset update races or zonelist updates to avoid
+	 * a unnecessary OOM kill.
+	 */
+	if (check_retry_cpuset(cpuset_mems_cookie, ac) ||
+	    check_retry_zonelist(zonelist_iter_cookie))
+		goto restart;
+
+	/*
+	 * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
+	 * we always retry
+	 */
+	if (gfp_mask & __GFP_NOFAIL) {
+		/*
+		 * All existing users of the __GFP_NOFAIL are blockable, so warn
+		 * of any new users that actually require GFP_NOWAIT
+		 */
+		if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
+			goto fail;
+
+		/*
+		 * PF_MEMALLOC request from this context is rather bizarre
+		 * because we cannot reclaim anything and only can loop waiting
+		 * for somebody to do a work for us
+		 */
+		WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
+
+		/*
+		 * non failing costly orders are a hard requirement which we
+		 * are not prepared for much so let's warn about these users
+		 * so that we can identify them and convert them to something
+		 * else.
+		 */
+		WARN_ON_ONCE_GFP(costly_order, gfp_mask);
+
+		/*
+		 * Help non-failing allocations by giving some access to memory
+		 * reserves normally used for high priority non-blocking
+		 * allocations but do not use ALLOC_NO_WATERMARKS because this
+		 * could deplete whole memory reserves which would just make
+		 * the situation worse.
+		 */
+		page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE, ac);
+		if (page)
+			goto got_pg;
+
+		cond_resched();
+		goto retry;
+	}
+fail:
+	warn_alloc(gfp_mask, ac->nodemask,
+			"page allocation failure: order:%u", order);
+got_pg:
+	return page;
+}
+
+static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
+		int preferred_nid, nodemask_t *nodemask,
+		struct alloc_context *ac, gfp_t *alloc_gfp,
+		unsigned int *alloc_flags)
+{
+	ac->highest_zoneidx = gfp_zone(gfp_mask);
+	ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
+	ac->nodemask = nodemask;
+	ac->migratetype = gfp_migratetype(gfp_mask);
+
+	if (cpusets_enabled()) {
+		*alloc_gfp |= __GFP_HARDWALL;
+		/*
+		 * When we are in the interrupt context, it is irrelevant
+		 * to the current task context. It means that any node ok.
+		 */
+		if (in_task() && !ac->nodemask)
+			ac->nodemask = &cpuset_current_mems_allowed;
+		else
+			*alloc_flags |= ALLOC_CPUSET;
+	}
+
+	might_alloc(gfp_mask);
+
+	if (should_fail_alloc_page(gfp_mask, order))
+		return false;
+
+	*alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, *alloc_flags);
+
+	/* Dirty zone balancing only done in the fast path */
+	ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
+
+	/*
+	 * The preferred zone is used for statistics but crucially it is
+	 * also used as the starting point for the zonelist iterator. It
+	 * may get reset for allocations that ignore memory policies.
+	 */
+	ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
+					ac->highest_zoneidx, ac->nodemask);
+
+	return true;
+}
+
+/*
+ * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
+ * @gfp: GFP flags for the allocation
+ * @preferred_nid: The preferred NUMA node ID to allocate from
+ * @nodemask: Set of nodes to allocate from, may be NULL
+ * @nr_pages: The number of pages desired on the list or array
+ * @page_list: Optional list to store the allocated pages
+ * @page_array: Optional array to store the pages
+ *
+ * This is a batched version of the page allocator that attempts to
+ * allocate nr_pages quickly. Pages are added to page_list if page_list
+ * is not NULL, otherwise it is assumed that the page_array is valid.
+ *
+ * For lists, nr_pages is the number of pages that should be allocated.
+ *
+ * For arrays, only NULL elements are populated with pages and nr_pages
+ * is the maximum number of pages that will be stored in the array.
+ *
+ * Returns the number of pages on the list or array.
+ */
+unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
+			nodemask_t *nodemask, int nr_pages,
+			struct list_head *page_list,
+			struct page **page_array)
+{
+	struct page *page;
+	unsigned long __maybe_unused UP_flags;
+	struct zone *zone;
+	struct zoneref *z;
+	struct per_cpu_pages *pcp;
+	struct list_head *pcp_list;
+	struct alloc_context ac;
+	gfp_t alloc_gfp;
+	unsigned int alloc_flags = ALLOC_WMARK_LOW;
+	int nr_populated = 0, nr_account = 0;
+
+	/*
+	 * Skip populated array elements to determine if any pages need
+	 * to be allocated before disabling IRQs.
+	 */
+	while (page_array && nr_populated < nr_pages && page_array[nr_populated])
+		nr_populated++;
+
+	/* No pages requested? */
+	if (unlikely(nr_pages <= 0))
+		goto out;
+
+	/* Already populated array? */
+	if (unlikely(page_array && nr_pages - nr_populated == 0))
+		goto out;
+
+	/* Bulk allocator does not support memcg accounting. */
+	if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT))
+		goto failed;
+
+	/* Use the single page allocator for one page. */
+	if (nr_pages - nr_populated == 1)
+		goto failed;
+
+#ifdef CONFIG_PAGE_OWNER
+	/*
+	 * PAGE_OWNER may recurse into the allocator to allocate space to
+	 * save the stack with pagesets.lock held. Releasing/reacquiring
+	 * removes much of the performance benefit of bulk allocation so
+	 * force the caller to allocate one page at a time as it'll have
+	 * similar performance to added complexity to the bulk allocator.
+	 */
+	if (static_branch_unlikely(&page_owner_inited))
+		goto failed;
+#endif
+
+	/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
+	gfp &= gfp_allowed_mask;
+	alloc_gfp = gfp;
+	if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags))
+		goto out;
+	gfp = alloc_gfp;
+
+	/* Find an allowed local zone that meets the low watermark. */
+	for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) {
+		unsigned long mark;
+
+		if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
+		    !__cpuset_zone_allowed(zone, gfp)) {
+			continue;
+		}
+
+		if (nr_online_nodes > 1 && zone != ac.preferred_zoneref->zone &&
+		    zone_to_nid(zone) != zone_to_nid(ac.preferred_zoneref->zone)) {
+			goto failed;
+		}
+
+		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
+		if (zone_watermark_fast(zone, 0,  mark,
+				zonelist_zone_idx(ac.preferred_zoneref),
+				alloc_flags, gfp)) {
+			break;
+		}
+	}
+
+	/*
+	 * If there are no allowed local zones that meets the watermarks then
+	 * try to allocate a single page and reclaim if necessary.
+	 */
+	if (unlikely(!zone))
+		goto failed;
+
+	/* spin_trylock may fail due to a parallel drain or IRQ reentrancy. */
+	pcp_trylock_prepare(UP_flags);
+	pcp = pcp_spin_trylock(zone->per_cpu_pageset);
+	if (!pcp)
+		goto failed_irq;
+
+	/* Attempt the batch allocation */
+	pcp_list = &pcp->lists[order_to_pindex(ac.migratetype, 0)];
+	while (nr_populated < nr_pages) {
+
+		/* Skip existing pages */
+		if (page_array && page_array[nr_populated]) {
+			nr_populated++;
+			continue;
+		}
+
+		page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
+								pcp, pcp_list);
+		if (unlikely(!page)) {
+			/* Try and allocate at least one page */
+			if (!nr_account) {
+				pcp_spin_unlock(pcp);
+				goto failed_irq;
+			}
+			break;
+		}
+		nr_account++;
+
+		prep_new_page(page, 0, gfp, 0);
+		if (page_list)
+			list_add(&page->lru, page_list);
+		else
+			page_array[nr_populated] = page;
+		nr_populated++;
+	}
+
+	pcp_spin_unlock(pcp);
+	pcp_trylock_finish(UP_flags);
+
+	__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
+	zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
+
+out:
+	return nr_populated;
+
+failed_irq:
+	pcp_trylock_finish(UP_flags);
+
+failed:
+	page = __alloc_pages(gfp, 0, preferred_nid, nodemask);
+	if (page) {
+		if (page_list)
+			list_add(&page->lru, page_list);
+		else
+			page_array[nr_populated] = page;
+		nr_populated++;
+	}
+
+	goto out;
+}
+EXPORT_SYMBOL_GPL(__alloc_pages_bulk);
+
+/*
+ * This is the 'heart' of the zoned buddy allocator.
+ */
+struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
+							nodemask_t *nodemask)
+{
+	struct page *page;
+	unsigned int alloc_flags = ALLOC_WMARK_LOW;
+	gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */
+	struct alloc_context ac = { };
+
+	/*
+	 * There are several places where we assume that the order value is sane
+	 * so bail out early if the request is out of bound.
+	 */
+	if (WARN_ON_ONCE_GFP(order > MAX_ORDER, gfp))
+		return NULL;
+
+	gfp &= gfp_allowed_mask;
+	/*
+	 * Apply scoped allocation constraints. This is mainly about GFP_NOFS
+	 * resp. GFP_NOIO which has to be inherited for all allocation requests
+	 * from a particular context which has been marked by
+	 * memalloc_no{fs,io}_{save,restore}. And PF_MEMALLOC_PIN which ensures
+	 * movable zones are not used during allocation.
+	 */
+	gfp = current_gfp_context(gfp);
+	alloc_gfp = gfp;
+	if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, &ac,
+			&alloc_gfp, &alloc_flags))
+		return NULL;
+
+	/*
+	 * Forbid the first pass from falling back to types that fragment
+	 * memory until all local zones are considered.
+	 */
+	alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone, gfp);
+
+	/* First allocation attempt */
+	page = get_page_from_freelist(alloc_gfp, order, alloc_flags, &ac);
+	if (likely(page))
+		goto out;
+
+	alloc_gfp = gfp;
+	ac.spread_dirty_pages = false;
+
+	/*
+	 * Restore the original nodemask if it was potentially replaced with
+	 * &cpuset_current_mems_allowed to optimize the fast-path attempt.
+	 */
+	ac.nodemask = nodemask;
+
+	page = __alloc_pages_slowpath(alloc_gfp, order, &ac);
+
+out:
+	if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT) && page &&
+	    unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
+		__free_pages(page, order);
+		page = NULL;
+	}
+
+	trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);
+	kmsan_alloc_page(page, order, alloc_gfp);
+
+	return page;
+}
+EXPORT_SYMBOL(__alloc_pages);
+
+struct folio *__folio_alloc(gfp_t gfp, unsigned int order, int preferred_nid,
+		nodemask_t *nodemask)
+{
+	struct page *page = __alloc_pages(gfp | __GFP_COMP, order,
+			preferred_nid, nodemask);
+	struct folio *folio = (struct folio *)page;
+
+	if (folio && order > 1)
+		folio_prep_large_rmappable(folio);
+	return folio;
+}
+EXPORT_SYMBOL(__folio_alloc);
+
+/*
+ * Common helper functions. Never use with __GFP_HIGHMEM because the returned
+ * address cannot represent highmem pages. Use alloc_pages and then kmap if
+ * you need to access high mem.
+ */
+unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
+{
+	struct page *page;
+
+	page = alloc_pages(gfp_mask & ~__GFP_HIGHMEM, order);
+	if (!page)
+		return 0;
+	return (unsigned long) page_address(page);
+}
+EXPORT_SYMBOL(__get_free_pages);
+
+unsigned long get_zeroed_page(gfp_t gfp_mask)
+{
+	return __get_free_page(gfp_mask | __GFP_ZERO);
+}
+EXPORT_SYMBOL(get_zeroed_page);
+
+/**
+ * __free_pages - Free pages allocated with alloc_pages().
+ * @page: The page pointer returned from alloc_pages().
+ * @order: The order of the allocation.
+ *
+ * This function can free multi-page allocations that are not compound
+ * pages.  It does not check that the @order passed in matches that of
+ * the allocation, so it is easy to leak memory.  Freeing more memory
+ * than was allocated will probably emit a warning.
+ *
+ * If the last reference to this page is speculative, it will be released
+ * by put_page() which only frees the first page of a non-compound
+ * allocation.  To prevent the remaining pages from being leaked, we free
+ * the subsequent pages here.  If you want to use the page's reference
+ * count to decide when to free the allocation, you should allocate a
+ * compound page, and use put_page() instead of __free_pages().
+ *
+ * Context: May be called in interrupt context or while holding a normal
+ * spinlock, but not in NMI context or while holding a raw spinlock.
+ */
+void __free_pages(struct page *page, unsigned int order)
+{
+	/* get PageHead before we drop reference */
+	int head = PageHead(page);
+
+	if (put_page_testzero(page))
+		free_the_page(page, order);
+	else if (!head)
+		while (order-- > 0)
+			free_the_page(page + (1 << order), order);
+}
+EXPORT_SYMBOL(__free_pages);
+
+void free_pages(unsigned long addr, unsigned int order)
+{
+	if (addr != 0) {
+		VM_BUG_ON(!virt_addr_valid((void *)addr));
+		__free_pages(virt_to_page((void *)addr), order);
+	}
+}
+
+EXPORT_SYMBOL(free_pages);
+
+/*
+ * Page Fragment:
+ *  An arbitrary-length arbitrary-offset area of memory which resides
+ *  within a 0 or higher order page.  Multiple fragments within that page
+ *  are individually refcounted, in the page's reference counter.
+ *
+ * The page_frag functions below provide a simple allocation framework for
+ * page fragments.  This is used by the network stack and network device
+ * drivers to provide a backing region of memory for use as either an
+ * sk_buff->head, or to be used in the "frags" portion of skb_shared_info.
+ */
+static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
+					     gfp_t gfp_mask)
+{
+	struct page *page = NULL;
+	gfp_t gfp = gfp_mask;
+
+#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
+	gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
+		    __GFP_NOMEMALLOC;
+	page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
+				PAGE_FRAG_CACHE_MAX_ORDER);
+	nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
+#endif
+	if (unlikely(!page))
+		page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
+
+	nc->va = page ? page_address(page) : NULL;
+
+	return page;
+}
+
+void __page_frag_cache_drain(struct page *page, unsigned int count)
+{
+	VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
+
+	if (page_ref_sub_and_test(page, count))
+		free_the_page(page, compound_order(page));
+}
+EXPORT_SYMBOL(__page_frag_cache_drain);
+
+void *page_frag_alloc_align(struct page_frag_cache *nc,
+		      unsigned int fragsz, gfp_t gfp_mask,
+		      unsigned int align_mask)
+{
+	unsigned int size = PAGE_SIZE;
+	struct page *page;
+	int offset;
+
+	if (unlikely(!nc->va)) {
+refill:
+		page = __page_frag_cache_refill(nc, gfp_mask);
+		if (!page)
+			return NULL;
+
+#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
+		/* if size can vary use size else just use PAGE_SIZE */
+		size = nc->size;
+#endif
+		/* Even if we own the page, we do not use atomic_set().
+		 * This would break get_page_unless_zero() users.
+		 */
+		page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
+
+		/* reset page count bias and offset to start of new frag */
+		nc->pfmemalloc = page_is_pfmemalloc(page);
+		nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
+		nc->offset = size;
+	}
+
+	offset = nc->offset - fragsz;
+	if (unlikely(offset < 0)) {
+		page = virt_to_page(nc->va);
+
+		if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
+			goto refill;
+
+		if (unlikely(nc->pfmemalloc)) {
+			free_the_page(page, compound_order(page));
+			goto refill;
+		}
+
+#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
+		/* if size can vary use size else just use PAGE_SIZE */
+		size = nc->size;
+#endif
+		/* OK, page count is 0, we can safely set it */
+		set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
+
+		/* reset page count bias and offset to start of new frag */
+		nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
+		offset = size - fragsz;
+		if (unlikely(offset < 0)) {
+			/*
+			 * The caller is trying to allocate a fragment
+			 * with fragsz > PAGE_SIZE but the cache isn't big
+			 * enough to satisfy the request, this may
+			 * happen in low memory conditions.
+			 * We don't release the cache page because
+			 * it could make memory pressure worse
+			 * so we simply return NULL here.
+			 */
+			return NULL;
+		}
+	}
+
+	nc->pagecnt_bias--;
+	offset &= align_mask;
+	nc->offset = offset;
+
+	return nc->va + offset;
+}
+EXPORT_SYMBOL(page_frag_alloc_align);
+
+/*
+ * Frees a page fragment allocated out of either a compound or order 0 page.
+ */
+void page_frag_free(void *addr)
+{
+	struct page *page = virt_to_head_page(addr);
+
+	if (unlikely(put_page_testzero(page)))
+		free_the_page(page, compound_order(page));
+}
+EXPORT_SYMBOL(page_frag_free);
+
+static void *make_alloc_exact(unsigned long addr, unsigned int order,
+		size_t size)
+{
+	if (addr) {
+		unsigned long nr = DIV_ROUND_UP(size, PAGE_SIZE);
+		struct page *page = virt_to_page((void *)addr);
+		struct page *last = page + nr;
+
+		split_page_owner(page, 1 << order);
+		split_page_memcg(page, 1 << order);
+		while (page < --last)
+			set_page_refcounted(last);
+
+		last = page + (1UL << order);
+		for (page += nr; page < last; page++)
+			__free_pages_ok(page, 0, FPI_TO_TAIL);
+	}
+	return (void *)addr;
+}
+
+/**
+ * alloc_pages_exact - allocate an exact number physically-contiguous pages.
+ * @size: the number of bytes to allocate
+ * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
+ *
+ * This function is similar to alloc_pages(), except that it allocates the
+ * minimum number of pages to satisfy the request.  alloc_pages() can only
+ * allocate memory in power-of-two pages.
+ *
+ * This function is also limited by MAX_ORDER.
+ *
+ * Memory allocated by this function must be released by free_pages_exact().
+ *
+ * Return: pointer to the allocated area or %NULL in case of error.
+ */
+void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
+{
+	unsigned int order = get_order(size);
+	unsigned long addr;
+
+	if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
+		gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
+
+	addr = __get_free_pages(gfp_mask, order);
+	return make_alloc_exact(addr, order, size);
+}
+EXPORT_SYMBOL(alloc_pages_exact);
+
+/**
+ * alloc_pages_exact_nid - allocate an exact number of physically-contiguous
+ *			   pages on a node.
+ * @nid: the preferred node ID where memory should be allocated
+ * @size: the number of bytes to allocate
+ * @gfp_mask: GFP flags for the allocation, must not contain __GFP_COMP
+ *
+ * Like alloc_pages_exact(), but try to allocate on node nid first before falling
+ * back.
+ *
+ * Return: pointer to the allocated area or %NULL in case of error.
+ */
+void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask)
+{
+	unsigned int order = get_order(size);
+	struct page *p;
+
+	if (WARN_ON_ONCE(gfp_mask & (__GFP_COMP | __GFP_HIGHMEM)))
+		gfp_mask &= ~(__GFP_COMP | __GFP_HIGHMEM);
+
+	p = alloc_pages_node(nid, gfp_mask, order);
+	if (!p)
+		return NULL;
+	return make_alloc_exact((unsigned long)page_address(p), order, size);
+}
+
+/**
+ * free_pages_exact - release memory allocated via alloc_pages_exact()
+ * @virt: the value returned by alloc_pages_exact.
+ * @size: size of allocation, same value as passed to alloc_pages_exact().
+ *
+ * Release the memory allocated by a previous call to alloc_pages_exact.
+ */
+void free_pages_exact(void *virt, size_t size)
+{
+	unsigned long addr = (unsigned long)virt;
+	unsigned long end = addr + PAGE_ALIGN(size);
+
+	while (addr < end) {
+		free_page(addr);
+		addr += PAGE_SIZE;
+	}
+}
+EXPORT_SYMBOL(free_pages_exact);
+
+/**
+ * nr_free_zone_pages - count number of pages beyond high watermark
+ * @offset: The zone index of the highest zone
+ *
+ * nr_free_zone_pages() counts the number of pages which are beyond the
+ * high watermark within all zones at or below a given zone index.  For each
+ * zone, the number of pages is calculated as:
+ *
+ *     nr_free_zone_pages = managed_pages - high_pages
+ *
+ * Return: number of pages beyond high watermark.
+ */
+static unsigned long nr_free_zone_pages(int offset)
+{
+	struct zoneref *z;
+	struct zone *zone;
+
+	/* Just pick one node, since fallback list is circular */
+	unsigned long sum = 0;
+
+	struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL);
+
+	for_each_zone_zonelist(zone, z, zonelist, offset) {
+		unsigned long size = zone_managed_pages(zone);
+		unsigned long high = high_wmark_pages(zone);
+		if (size > high)
+			sum += size - high;
+	}
+
+	return sum;
+}
+
+/**
+ * nr_free_buffer_pages - count number of pages beyond high watermark
+ *
+ * nr_free_buffer_pages() counts the number of pages which are beyond the high
+ * watermark within ZONE_DMA and ZONE_NORMAL.
+ *
+ * Return: number of pages beyond high watermark within ZONE_DMA and
+ * ZONE_NORMAL.
+ */
+unsigned long nr_free_buffer_pages(void)
+{
+	return nr_free_zone_pages(gfp_zone(GFP_USER));
+}
+EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
+
+static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
+{
+	zoneref->zone = zone;
+	zoneref->zone_idx = zone_idx(zone);
+}
+
+/*
+ * Builds allocation fallback zone lists.
+ *
+ * Add all populated zones of a node to the zonelist.
+ */
+static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)
+{
+	struct zone *zone;
+	enum zone_type zone_type = MAX_NR_ZONES;
+	int nr_zones = 0;
+
+	do {
+		zone_type--;
+		zone = pgdat->node_zones + zone_type;
+		if (populated_zone(zone)) {
+			zoneref_set_zone(zone, &zonerefs[nr_zones++]);
+			check_highest_zone(zone_type);
+		}
+	} while (zone_type);
+
+	return nr_zones;
+}
+
+#ifdef CONFIG_NUMA
+
+static int __parse_numa_zonelist_order(char *s)
+{
+	/*
+	 * We used to support different zonelists modes but they turned
+	 * out to be just not useful. Let's keep the warning in place
+	 * if somebody still use the cmd line parameter so that we do
+	 * not fail it silently
+	 */
+	if (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) {
+		pr_warn("Ignoring unsupported numa_zonelist_order value:  %s\n", s);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static char numa_zonelist_order[] = "Node";
+#define NUMA_ZONELIST_ORDER_LEN	16
+/*
+ * sysctl handler for numa_zonelist_order
+ */
+static int numa_zonelist_order_handler(struct ctl_table *table, int write,
+		void *buffer, size_t *length, loff_t *ppos)
+{
+	if (write)
+		return __parse_numa_zonelist_order(buffer);
+	return proc_dostring(table, write, buffer, length, ppos);
+}
+
+static int node_load[MAX_NUMNODES];
+
+/**
+ * find_next_best_node - find the next node that should appear in a given node's fallback list
+ * @node: node whose fallback list we're appending
+ * @used_node_mask: nodemask_t of already used nodes
+ *
+ * We use a number of factors to determine which is the next node that should
+ * appear on a given node's fallback list.  The node should not have appeared
+ * already in @node's fallback list, and it should be the next closest node
+ * according to the distance array (which contains arbitrary distance values
+ * from each node to each node in the system), and should also prefer nodes
+ * with no CPUs, since presumably they'll have very little allocation pressure
+ * on them otherwise.
+ *
+ * Return: node id of the found node or %NUMA_NO_NODE if no node is found.
+ */
+int find_next_best_node(int node, nodemask_t *used_node_mask)
+{
+	int n, val;
+	int min_val = INT_MAX;
+	int best_node = NUMA_NO_NODE;
+
+	/* Use the local node if we haven't already */
+	if (!node_isset(node, *used_node_mask)) {
+		node_set(node, *used_node_mask);
+		return node;
+	}
+
+	for_each_node_state(n, N_MEMORY) {
+
+		/* Don't want a node to appear more than once */
+		if (node_isset(n, *used_node_mask))
+			continue;
+
+		/* Use the distance array to find the distance */
+		val = node_distance(node, n);
+
+		/* Penalize nodes under us ("prefer the next node") */
+		val += (n < node);
+
+		/* Give preference to headless and unused nodes */
+		if (!cpumask_empty(cpumask_of_node(n)))
+			val += PENALTY_FOR_NODE_WITH_CPUS;
+
+		/* Slight preference for less loaded node */
+		val *= MAX_NUMNODES;
+		val += node_load[n];
+
+		if (val < min_val) {
+			min_val = val;
+			best_node = n;
+		}
+	}
+
+	if (best_node >= 0)
+		node_set(best_node, *used_node_mask);
+
+	return best_node;
+}
+
+
+/*
+ * Build zonelists ordered by node and zones within node.
+ * This results in maximum locality--normal zone overflows into local
+ * DMA zone, if any--but risks exhausting DMA zone.
+ */
+static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
+		unsigned nr_nodes)
+{
+	struct zoneref *zonerefs;
+	int i;
+
+	zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
+
+	for (i = 0; i < nr_nodes; i++) {
+		int nr_zones;
+
+		pg_data_t *node = NODE_DATA(node_order[i]);
+
+		nr_zones = build_zonerefs_node(node, zonerefs);
+		zonerefs += nr_zones;
+	}
+	zonerefs->zone = NULL;
+	zonerefs->zone_idx = 0;
+}
+
+/*
+ * Build gfp_thisnode zonelists
+ */
+static void build_thisnode_zonelists(pg_data_t *pgdat)
+{
+	struct zoneref *zonerefs;
+	int nr_zones;
+
+	zonerefs = pgdat->node_zonelists[ZONELIST_NOFALLBACK]._zonerefs;
+	nr_zones = build_zonerefs_node(pgdat, zonerefs);
+	zonerefs += nr_zones;
+	zonerefs->zone = NULL;
+	zonerefs->zone_idx = 0;
+}
+
+/*
+ * Build zonelists ordered by zone and nodes within zones.
+ * This results in conserving DMA zone[s] until all Normal memory is
+ * exhausted, but results in overflowing to remote node while memory
+ * may still exist in local DMA zone.
+ */
+
+static void build_zonelists(pg_data_t *pgdat)
+{
+	static int node_order[MAX_NUMNODES];
+	int node, nr_nodes = 0;
+	nodemask_t used_mask = NODE_MASK_NONE;
+	int local_node, prev_node;
+
+	/* NUMA-aware ordering of nodes */
+	local_node = pgdat->node_id;
+	prev_node = local_node;
+
+	memset(node_order, 0, sizeof(node_order));
+	while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
+		/*
+		 * We don't want to pressure a particular node.
+		 * So adding penalty to the first node in same
+		 * distance group to make it round-robin.
+		 */
+		if (node_distance(local_node, node) !=
+		    node_distance(local_node, prev_node))
+			node_load[node] += 1;
+
+		node_order[nr_nodes++] = node;
+		prev_node = node;
+	}
+
+	build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
+	build_thisnode_zonelists(pgdat);
+	pr_info("Fallback order for Node %d: ", local_node);
+	for (node = 0; node < nr_nodes; node++)
+		pr_cont("%d ", node_order[node]);
+	pr_cont("\n");
+}
+
+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+/*
+ * Return node id of node used for "local" allocations.
+ * I.e., first node id of first zone in arg node's generic zonelist.
+ * Used for initializing percpu 'numa_mem', which is used primarily
+ * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
+ */
+int local_memory_node(int node)
+{
+	struct zoneref *z;
+
+	z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
+				   gfp_zone(GFP_KERNEL),
+				   NULL);
+	return zone_to_nid(z->zone);
+}
+#endif
+
+static void setup_min_unmapped_ratio(void);
+static void setup_min_slab_ratio(void);
+#else	/* CONFIG_NUMA */
+
+static void build_zonelists(pg_data_t *pgdat)
+{
+	int node, local_node;
+	struct zoneref *zonerefs;
+	int nr_zones;
+
+	local_node = pgdat->node_id;
+
+	zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
+	nr_zones = build_zonerefs_node(pgdat, zonerefs);
+	zonerefs += nr_zones;
+
+	/*
+	 * Now we build the zonelist so that it contains the zones
+	 * of all the other nodes.
+	 * We don't want to pressure a particular node, so when
+	 * building the zones for node N, we make sure that the
+	 * zones coming right after the local ones are those from
+	 * node N+1 (modulo N)
+	 */
+	for (node = local_node + 1; node < MAX_NUMNODES; node++) {
+		if (!node_online(node))
+			continue;
+		nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
+		zonerefs += nr_zones;
+	}
+	for (node = 0; node < local_node; node++) {
+		if (!node_online(node))
+			continue;
+		nr_zones = build_zonerefs_node(NODE_DATA(node), zonerefs);
+		zonerefs += nr_zones;
+	}
+
+	zonerefs->zone = NULL;
+	zonerefs->zone_idx = 0;
+}
+
+#endif	/* CONFIG_NUMA */
+
+/*
+ * Boot pageset table. One per cpu which is going to be used for all
+ * zones and all nodes. The parameters will be set in such a way
+ * that an item put on a list will immediately be handed over to
+ * the buddy list. This is safe since pageset manipulation is done
+ * with interrupts disabled.
+ *
+ * The boot_pagesets must be kept even after bootup is complete for
+ * unused processors and/or zones. They do play a role for bootstrapping
+ * hotplugged processors.
+ *
+ * zoneinfo_show() and maybe other functions do
+ * not check if the processor is online before following the pageset pointer.
+ * Other parts of the kernel may not check if the zone is available.
+ */
+static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats);
+/* These effectively disable the pcplists in the boot pageset completely */
+#define BOOT_PAGESET_HIGH	0
+#define BOOT_PAGESET_BATCH	1
+static DEFINE_PER_CPU(struct per_cpu_pages, boot_pageset);
+static DEFINE_PER_CPU(struct per_cpu_zonestat, boot_zonestats);
+
+static void __build_all_zonelists(void *data)
+{
+	int nid;
+	int __maybe_unused cpu;
+	pg_data_t *self = data;
+	unsigned long flags;
+
+	/*
+	 * The zonelist_update_seq must be acquired with irqsave because the
+	 * reader can be invoked from IRQ with GFP_ATOMIC.
+	 */
+	write_seqlock_irqsave(&zonelist_update_seq, flags);
+	/*
+	 * Also disable synchronous printk() to prevent any printk() from
+	 * trying to hold port->lock, for
+	 * tty_insert_flip_string_and_push_buffer() on other CPU might be
+	 * calling kmalloc(GFP_ATOMIC | __GFP_NOWARN) with port->lock held.
+	 */
+	printk_deferred_enter();
+
+#ifdef CONFIG_NUMA
+	memset(node_load, 0, sizeof(node_load));
+#endif
+
+	/*
+	 * This node is hotadded and no memory is yet present.   So just
+	 * building zonelists is fine - no need to touch other nodes.
+	 */
+	if (self && !node_online(self->node_id)) {
+		build_zonelists(self);
+	} else {
+		/*
+		 * All possible nodes have pgdat preallocated
+		 * in free_area_init
+		 */
+		for_each_node(nid) {
+			pg_data_t *pgdat = NODE_DATA(nid);
+
+			build_zonelists(pgdat);
+		}
+
+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+		/*
+		 * We now know the "local memory node" for each node--
+		 * i.e., the node of the first zone in the generic zonelist.
+		 * Set up numa_mem percpu variable for on-line cpus.  During
+		 * boot, only the boot cpu should be on-line;  we'll init the
+		 * secondary cpus' numa_mem as they come on-line.  During
+		 * node/memory hotplug, we'll fixup all on-line cpus.
+		 */
+		for_each_online_cpu(cpu)
+			set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
+#endif
+	}
+
+	printk_deferred_exit();
+	write_sequnlock_irqrestore(&zonelist_update_seq, flags);
+}
+
+static noinline void __init
+build_all_zonelists_init(void)
+{
+	int cpu;
+
+	__build_all_zonelists(NULL);
+
+	/*
+	 * Initialize the boot_pagesets that are going to be used
+	 * for bootstrapping processors. The real pagesets for
+	 * each zone will be allocated later when the per cpu
+	 * allocator is available.
+	 *
+	 * boot_pagesets are used also for bootstrapping offline
+	 * cpus if the system is already booted because the pagesets
+	 * are needed to initialize allocators on a specific cpu too.
+	 * F.e. the percpu allocator needs the page allocator which
+	 * needs the percpu allocator in order to allocate its pagesets
+	 * (a chicken-egg dilemma).
+	 */
+	for_each_possible_cpu(cpu)
+		per_cpu_pages_init(&per_cpu(boot_pageset, cpu), &per_cpu(boot_zonestats, cpu));
+
+	mminit_verify_zonelist();
+	cpuset_init_current_mems_allowed();
+}
+
+/*
+ * unless system_state == SYSTEM_BOOTING.
+ *
+ * __ref due to call of __init annotated helper build_all_zonelists_init
+ * [protected by SYSTEM_BOOTING].
+ */
+void __ref build_all_zonelists(pg_data_t *pgdat)
+{
+	unsigned long vm_total_pages;
+
+	if (system_state == SYSTEM_BOOTING) {
+		build_all_zonelists_init();
+	} else {
+		__build_all_zonelists(pgdat);
+		/* cpuset refresh routine should be here */
+	}
+	/* Get the number of free pages beyond high watermark in all zones. */
+	vm_total_pages = nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
+	/*
+	 * Disable grouping by mobility if the number of pages in the
+	 * system is too low to allow the mechanism to work. It would be
+	 * more accurate, but expensive to check per-zone. This check is
+	 * made on memory-hotadd so a system can start with mobility
+	 * disabled and enable it later
+	 */
+	if (vm_total_pages < (pageblock_nr_pages * MIGRATE_TYPES))
+		page_group_by_mobility_disabled = 1;
+	else
+		page_group_by_mobility_disabled = 0;
+
+	pr_info("Built %u zonelists, mobility grouping %s.  Total pages: %ld\n",
+		nr_online_nodes,
+		page_group_by_mobility_disabled ? "off" : "on",
+		vm_total_pages);
+#ifdef CONFIG_NUMA
+	pr_info("Policy zone: %s\n", zone_names[policy_zone]);
+#endif
+}
+
+static int zone_batchsize(struct zone *zone)
+{
+#ifdef CONFIG_MMU
+	int batch;
+
+	/*
+	 * The number of pages to batch allocate is either ~0.1%
+	 * of the zone or 1MB, whichever is smaller. The batch
+	 * size is striking a balance between allocation latency
+	 * and zone lock contention.
+	 */
+	batch = min(zone_managed_pages(zone) >> 10, SZ_1M / PAGE_SIZE);
+	batch /= 4;		/* We effectively *= 4 below */
+	if (batch < 1)
+		batch = 1;
+
+	/*
+	 * Clamp the batch to a 2^n - 1 value. Having a power
+	 * of 2 value was found to be more likely to have
+	 * suboptimal cache aliasing properties in some cases.
+	 *
+	 * For example if 2 tasks are alternately allocating
+	 * batches of pages, one task can end up with a lot
+	 * of pages of one half of the possible page colors
+	 * and the other with pages of the other colors.
+	 */
+	batch = rounddown_pow_of_two(batch + batch/2) - 1;
+
+	return batch;
+
+#else
+	/* The deferral and batching of frees should be suppressed under NOMMU
+	 * conditions.
+	 *
+	 * The problem is that NOMMU needs to be able to allocate large chunks
+	 * of contiguous memory as there's no hardware page translation to
+	 * assemble apparent contiguous memory from discontiguous pages.
+	 *
+	 * Queueing large contiguous runs of pages for batching, however,
+	 * causes the pages to actually be freed in smaller chunks.  As there
+	 * can be a significant delay between the individual batches being
+	 * recycled, this leads to the once large chunks of space being
+	 * fragmented and becoming unavailable for high-order allocations.
+	 */
+	return 0;
+#endif
+}
+
+static int percpu_pagelist_high_fraction;
+static int zone_highsize(struct zone *zone, int batch, int cpu_online)
+{
+#ifdef CONFIG_MMU
+	int high;
+	int nr_split_cpus;
+	unsigned long total_pages;
+
+	if (!percpu_pagelist_high_fraction) {
+		/*
+		 * By default, the high value of the pcp is based on the zone
+		 * low watermark so that if they are full then background
+		 * reclaim will not be started prematurely.
+		 */
+		total_pages = low_wmark_pages(zone);
+	} else {
+		/*
+		 * If percpu_pagelist_high_fraction is configured, the high
+		 * value is based on a fraction of the managed pages in the
+		 * zone.
+		 */
+		total_pages = zone_managed_pages(zone) / percpu_pagelist_high_fraction;
+	}
+
+	/*
+	 * Split the high value across all online CPUs local to the zone. Note
+	 * that early in boot that CPUs may not be online yet and that during
+	 * CPU hotplug that the cpumask is not yet updated when a CPU is being
+	 * onlined. For memory nodes that have no CPUs, split pcp->high across
+	 * all online CPUs to mitigate the risk that reclaim is triggered
+	 * prematurely due to pages stored on pcp lists.
+	 */
+	nr_split_cpus = cpumask_weight(cpumask_of_node(zone_to_nid(zone))) + cpu_online;
+	if (!nr_split_cpus)
+		nr_split_cpus = num_online_cpus();
+	high = total_pages / nr_split_cpus;
+
+	/*
+	 * Ensure high is at least batch*4. The multiple is based on the
+	 * historical relationship between high and batch.
+	 */
+	high = max(high, batch << 2);
+
+	return high;
+#else
+	return 0;
+#endif
+}
+
+/*
+ * pcp->high and pcp->batch values are related and generally batch is lower
+ * than high. They are also related to pcp->count such that count is lower
+ * than high, and as soon as it reaches high, the pcplist is flushed.
+ *
+ * However, guaranteeing these relations at all times would require e.g. write
+ * barriers here but also careful usage of read barriers at the read side, and
+ * thus be prone to error and bad for performance. Thus the update only prevents
+ * store tearing. Any new users of pcp->batch and pcp->high should ensure they
+ * can cope with those fields changing asynchronously, and fully trust only the
+ * pcp->count field on the local CPU with interrupts disabled.
+ *
+ * mutex_is_locked(&pcp_batch_high_lock) required when calling this function
+ * outside of boot time (or some other assurance that no concurrent updaters
+ * exist).
+ */
+static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
+		unsigned long batch)
+{
+	WRITE_ONCE(pcp->batch, batch);
+	WRITE_ONCE(pcp->high, high);
+}
+
+static void per_cpu_pages_init(struct per_cpu_pages *pcp, struct per_cpu_zonestat *pzstats)
+{
+	int pindex;
+
+	memset(pcp, 0, sizeof(*pcp));
+	memset(pzstats, 0, sizeof(*pzstats));
+
+	spin_lock_init(&pcp->lock);
+	for (pindex = 0; pindex < NR_PCP_LISTS; pindex++)
+		INIT_LIST_HEAD(&pcp->lists[pindex]);
+
+	/*
+	 * Set batch and high values safe for a boot pageset. A true percpu
+	 * pageset's initialization will update them subsequently. Here we don't
+	 * need to be as careful as pageset_update() as nobody can access the
+	 * pageset yet.
+	 */
+	pcp->high = BOOT_PAGESET_HIGH;
+	pcp->batch = BOOT_PAGESET_BATCH;
+	pcp->free_factor = 0;
+}
+
+static void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high,
+		unsigned long batch)
+{
+	struct per_cpu_pages *pcp;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
+		pageset_update(pcp, high, batch);
+	}
+}
+
+/*
+ * Calculate and set new high and batch values for all per-cpu pagesets of a
+ * zone based on the zone's size.
+ */
+static void zone_set_pageset_high_and_batch(struct zone *zone, int cpu_online)
+{
+	int new_high, new_batch;
+
+	new_batch = max(1, zone_batchsize(zone));
+	new_high = zone_highsize(zone, new_batch, cpu_online);
+
+	if (zone->pageset_high == new_high &&
+	    zone->pageset_batch == new_batch)
+		return;
+
+	zone->pageset_high = new_high;
+	zone->pageset_batch = new_batch;
+
+	__zone_set_pageset_high_and_batch(zone, new_high, new_batch);
+}
+
+void __meminit setup_zone_pageset(struct zone *zone)
+{
+	int cpu;
+
+	/* Size may be 0 on !SMP && !NUMA */
+	if (sizeof(struct per_cpu_zonestat) > 0)
+		zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
+
+	zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
+	for_each_possible_cpu(cpu) {
+		struct per_cpu_pages *pcp;
+		struct per_cpu_zonestat *pzstats;
+
+		pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
+		pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
+		per_cpu_pages_init(pcp, pzstats);
+	}
+
+	zone_set_pageset_high_and_batch(zone, 0);
+}
+
+/*
+ * The zone indicated has a new number of managed_pages; batch sizes and percpu
+ * page high values need to be recalculated.
+ */
+static void zone_pcp_update(struct zone *zone, int cpu_online)
+{
+	mutex_lock(&pcp_batch_high_lock);
+	zone_set_pageset_high_and_batch(zone, cpu_online);
+	mutex_unlock(&pcp_batch_high_lock);
+}
+
+/*
+ * Allocate per cpu pagesets and initialize them.
+ * Before this call only boot pagesets were available.
+ */
+void __init setup_per_cpu_pageset(void)
+{
+	struct pglist_data *pgdat;
+	struct zone *zone;
+	int __maybe_unused cpu;
+
+	for_each_populated_zone(zone)
+		setup_zone_pageset(zone);
+
+#ifdef CONFIG_NUMA
+	/*
+	 * Unpopulated zones continue using the boot pagesets.
+	 * The numa stats for these pagesets need to be reset.
+	 * Otherwise, they will end up skewing the stats of
+	 * the nodes these zones are associated with.
+	 */
+	for_each_possible_cpu(cpu) {
+		struct per_cpu_zonestat *pzstats = &per_cpu(boot_zonestats, cpu);
+		memset(pzstats->vm_numa_event, 0,
+		       sizeof(pzstats->vm_numa_event));
+	}
+#endif
+
+	for_each_online_pgdat(pgdat)
+		pgdat->per_cpu_nodestats =
+			alloc_percpu(struct per_cpu_nodestat);
+}
+
+__meminit void zone_pcp_init(struct zone *zone)
+{
+	/*
+	 * per cpu subsystem is not up at this point. The following code
+	 * relies on the ability of the linker to provide the
+	 * offset of a (static) per cpu variable into the per cpu area.
+	 */
+	zone->per_cpu_pageset = &boot_pageset;
+	zone->per_cpu_zonestats = &boot_zonestats;
+	zone->pageset_high = BOOT_PAGESET_HIGH;
+	zone->pageset_batch = BOOT_PAGESET_BATCH;
+
+	if (populated_zone(zone))
+		pr_debug("  %s zone: %lu pages, LIFO batch:%u\n", zone->name,
+			 zone->present_pages, zone_batchsize(zone));
+}
+
+void adjust_managed_page_count(struct page *page, long count)
+{
+	atomic_long_add(count, &page_zone(page)->managed_pages);
+	totalram_pages_add(count);
+#ifdef CONFIG_HIGHMEM
+	if (PageHighMem(page))
+		totalhigh_pages_add(count);
+#endif
+}
+EXPORT_SYMBOL(adjust_managed_page_count);
+
+unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
+{
+	void *pos;
+	unsigned long pages = 0;
+
+	start = (void *)PAGE_ALIGN((unsigned long)start);
+	end = (void *)((unsigned long)end & PAGE_MASK);
+	for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
+		struct page *page = virt_to_page(pos);
+		void *direct_map_addr;
+
+		/*
+		 * 'direct_map_addr' might be different from 'pos'
+		 * because some architectures' virt_to_page()
+		 * work with aliases.  Getting the direct map
+		 * address ensures that we get a _writeable_
+		 * alias for the memset().
+		 */
+		direct_map_addr = page_address(page);
+		/*
+		 * Perform a kasan-unchecked memset() since this memory
+		 * has not been initialized.
+		 */
+		direct_map_addr = kasan_reset_tag(direct_map_addr);
+		if ((unsigned int)poison <= 0xFF)
+			memset(direct_map_addr, poison, PAGE_SIZE);
+
+		free_reserved_page(page);
+	}
+
+	if (pages && s)
+		pr_info("Freeing %s memory: %ldK\n", s, K(pages));
+
+	return pages;
+}
+
+static int page_alloc_cpu_dead(unsigned int cpu)
+{
+	struct zone *zone;
+
+	lru_add_drain_cpu(cpu);
+	mlock_drain_remote(cpu);
+	drain_pages(cpu);
+
+	/*
+	 * Spill the event counters of the dead processor
+	 * into the current processors event counters.
+	 * This artificially elevates the count of the current
+	 * processor.
+	 */
+	vm_events_fold_cpu(cpu);
+
+	/*
+	 * Zero the differential counters of the dead processor
+	 * so that the vm statistics are consistent.
+	 *
+	 * This is only okay since the processor is dead and cannot
+	 * race with what we are doing.
+	 */
+	cpu_vm_stats_fold(cpu);
+
+	for_each_populated_zone(zone)
+		zone_pcp_update(zone, 0);
+
+	return 0;
+}
+
+static int page_alloc_cpu_online(unsigned int cpu)
+{
+	struct zone *zone;
+
+	for_each_populated_zone(zone)
+		zone_pcp_update(zone, 1);
+	return 0;
+}
+
+void __init page_alloc_init_cpuhp(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_PAGE_ALLOC,
+					"mm/page_alloc:pcp",
+					page_alloc_cpu_online,
+					page_alloc_cpu_dead);
+	WARN_ON(ret < 0);
+}
+
+/*
+ * calculate_totalreserve_pages - called when sysctl_lowmem_reserve_ratio
+ *	or min_free_kbytes changes.
+ */
+static void calculate_totalreserve_pages(void)
+{
+	struct pglist_data *pgdat;
+	unsigned long reserve_pages = 0;
+	enum zone_type i, j;
+
+	for_each_online_pgdat(pgdat) {
+
+		pgdat->totalreserve_pages = 0;
+
+		for (i = 0; i < MAX_NR_ZONES; i++) {
+			struct zone *zone = pgdat->node_zones + i;
+			long max = 0;
+			unsigned long managed_pages = zone_managed_pages(zone);
+
+			/* Find valid and maximum lowmem_reserve in the zone */
+			for (j = i; j < MAX_NR_ZONES; j++) {
+				if (zone->lowmem_reserve[j] > max)
+					max = zone->lowmem_reserve[j];
+			}
+
+			/* we treat the high watermark as reserved pages. */
+			max += high_wmark_pages(zone);
+
+			if (max > managed_pages)
+				max = managed_pages;
+
+			pgdat->totalreserve_pages += max;
+
+			reserve_pages += max;
+		}
+	}
+	totalreserve_pages = reserve_pages;
+}
+
+/*
+ * setup_per_zone_lowmem_reserve - called whenever
+ *	sysctl_lowmem_reserve_ratio changes.  Ensures that each zone
+ *	has a correct pages reserved value, so an adequate number of
+ *	pages are left in the zone after a successful __alloc_pages().
+ */
+static void setup_per_zone_lowmem_reserve(void)
+{
+	struct pglist_data *pgdat;
+	enum zone_type i, j;
+
+	for_each_online_pgdat(pgdat) {
+		for (i = 0; i < MAX_NR_ZONES - 1; i++) {
+			struct zone *zone = &pgdat->node_zones[i];
+			int ratio = sysctl_lowmem_reserve_ratio[i];
+			bool clear = !ratio || !zone_managed_pages(zone);
+			unsigned long managed_pages = 0;
+
+			for (j = i + 1; j < MAX_NR_ZONES; j++) {
+				struct zone *upper_zone = &pgdat->node_zones[j];
+
+				managed_pages += zone_managed_pages(upper_zone);
+
+				if (clear)
+					zone->lowmem_reserve[j] = 0;
+				else
+					zone->lowmem_reserve[j] = managed_pages / ratio;
+			}
+		}
+	}
+
+	/* update totalreserve_pages */
+	calculate_totalreserve_pages();
+}
+
+static void __setup_per_zone_wmarks(void)
+{
+	unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
+	unsigned long lowmem_pages = 0;
+	struct zone *zone;
+	unsigned long flags;
+
+	/* Calculate total number of !ZONE_HIGHMEM and !ZONE_MOVABLE pages */
+	for_each_zone(zone) {
+		if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE)
+			lowmem_pages += zone_managed_pages(zone);
+	}
+
+	for_each_zone(zone) {
+		u64 tmp;
+
+		spin_lock_irqsave(&zone->lock, flags);
+		tmp = (u64)pages_min * zone_managed_pages(zone);
+		do_div(tmp, lowmem_pages);
+		if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
+			/*
+			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
+			 * need highmem and movable zones pages, so cap pages_min
+			 * to a small  value here.
+			 *
+			 * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN)
+			 * deltas control async page reclaim, and so should
+			 * not be capped for highmem and movable zones.
+			 */
+			unsigned long min_pages;
+
+			min_pages = zone_managed_pages(zone) / 1024;
+			min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL);
+			zone->_watermark[WMARK_MIN] = min_pages;
+		} else {
+			/*
+			 * If it's a lowmem zone, reserve a number of pages
+			 * proportionate to the zone's size.
+			 */
+			zone->_watermark[WMARK_MIN] = tmp;
+		}
+
+		/*
+		 * Set the kswapd watermarks distance according to the
+		 * scale factor in proportion to available memory, but
+		 * ensure a minimum size on small systems.
+		 */
+		tmp = max_t(u64, tmp >> 2,
+			    mult_frac(zone_managed_pages(zone),
+				      watermark_scale_factor, 10000));
+
+		zone->watermark_boost = 0;
+		zone->_watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
+		zone->_watermark[WMARK_HIGH] = low_wmark_pages(zone) + tmp;
+		zone->_watermark[WMARK_PROMO] = high_wmark_pages(zone) + tmp;
+
+		spin_unlock_irqrestore(&zone->lock, flags);
+	}
+
+	/* update totalreserve_pages */
+	calculate_totalreserve_pages();
+}
+
+/**
+ * setup_per_zone_wmarks - called when min_free_kbytes changes
+ * or when memory is hot-{added|removed}
+ *
+ * Ensures that the watermark[min,low,high] values for each zone are set
+ * correctly with respect to min_free_kbytes.
+ */
+void setup_per_zone_wmarks(void)
+{
+	struct zone *zone;
+	static DEFINE_SPINLOCK(lock);
+
+	spin_lock(&lock);
+	__setup_per_zone_wmarks();
+	spin_unlock(&lock);
+
+	/*
+	 * The watermark size have changed so update the pcpu batch
+	 * and high limits or the limits may be inappropriate.
+	 */
+	for_each_zone(zone)
+		zone_pcp_update(zone, 0);
+}
+
+/*
+ * Initialise min_free_kbytes.
+ *
+ * For small machines we want it small (128k min).  For large machines
+ * we want it large (256MB max).  But it is not linear, because network
+ * bandwidth does not increase linearly with machine size.  We use
+ *
+ *	min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
+ *	min_free_kbytes = sqrt(lowmem_kbytes * 16)
+ *
+ * which yields
+ *
+ * 16MB:	512k
+ * 32MB:	724k
+ * 64MB:	1024k
+ * 128MB:	1448k
+ * 256MB:	2048k
+ * 512MB:	2896k
+ * 1024MB:	4096k
+ * 2048MB:	5792k
+ * 4096MB:	8192k
+ * 8192MB:	11584k
+ * 16384MB:	16384k
+ */
+void calculate_min_free_kbytes(void)
+{
+	unsigned long lowmem_kbytes;
+	int new_min_free_kbytes;
+
+	lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
+	new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
+
+	if (new_min_free_kbytes > user_min_free_kbytes)
+		min_free_kbytes = clamp(new_min_free_kbytes, 128, 262144);
+	else
+		pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
+				new_min_free_kbytes, user_min_free_kbytes);
+
+}
+
+int __meminit init_per_zone_wmark_min(void)
+{
+	calculate_min_free_kbytes();
+	setup_per_zone_wmarks();
+	refresh_zone_stat_thresholds();
+	setup_per_zone_lowmem_reserve();
+
+#ifdef CONFIG_NUMA
+	setup_min_unmapped_ratio();
+	setup_min_slab_ratio();
+#endif
+
+	khugepaged_min_free_kbytes_update();
+
+	return 0;
+}
+postcore_initcall(init_per_zone_wmark_min)
+
+/*
+ * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
+ *	that we can call two helper functions whenever min_free_kbytes
+ *	changes.
+ */
+static int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
+		void *buffer, size_t *length, loff_t *ppos)
+{
+	int rc;
+
+	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (rc)
+		return rc;
+
+	if (write) {
+		user_min_free_kbytes = min_free_kbytes;
+		setup_per_zone_wmarks();
+	}
+	return 0;
+}
+
+static int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
+		void *buffer, size_t *length, loff_t *ppos)
+{
+	int rc;
+
+	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (rc)
+		return rc;
+
+	if (write)
+		setup_per_zone_wmarks();
+
+	return 0;
+}
+
+#ifdef CONFIG_NUMA
+static void setup_min_unmapped_ratio(void)
+{
+	pg_data_t *pgdat;
+	struct zone *zone;
+
+	for_each_online_pgdat(pgdat)
+		pgdat->min_unmapped_pages = 0;
+
+	for_each_zone(zone)
+		zone->zone_pgdat->min_unmapped_pages += (zone_managed_pages(zone) *
+						         sysctl_min_unmapped_ratio) / 100;
+}
+
+
+static int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
+		void *buffer, size_t *length, loff_t *ppos)
+{
+	int rc;
+
+	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (rc)
+		return rc;
+
+	setup_min_unmapped_ratio();
+
+	return 0;
+}
+
+static void setup_min_slab_ratio(void)
+{
+	pg_data_t *pgdat;
+	struct zone *zone;
+
+	for_each_online_pgdat(pgdat)
+		pgdat->min_slab_pages = 0;
+
+	for_each_zone(zone)
+		zone->zone_pgdat->min_slab_pages += (zone_managed_pages(zone) *
+						     sysctl_min_slab_ratio) / 100;
+}
+
+static int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
+		void *buffer, size_t *length, loff_t *ppos)
+{
+	int rc;
+
+	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (rc)
+		return rc;
+
+	setup_min_slab_ratio();
+
+	return 0;
+}
+#endif
+
+/*
+ * lowmem_reserve_ratio_sysctl_handler - just a wrapper around
+ *	proc_dointvec() so that we can call setup_per_zone_lowmem_reserve()
+ *	whenever sysctl_lowmem_reserve_ratio changes.
+ *
+ * The reserve ratio obviously has absolutely no relation with the
+ * minimum watermarks. The lowmem reserve ratio can only make sense
+ * if in function of the boot time zone sizes.
+ */
+static int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table,
+		int write, void *buffer, size_t *length, loff_t *ppos)
+{
+	int i;
+
+	proc_dointvec_minmax(table, write, buffer, length, ppos);
+
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		if (sysctl_lowmem_reserve_ratio[i] < 1)
+			sysctl_lowmem_reserve_ratio[i] = 0;
+	}
+
+	setup_per_zone_lowmem_reserve();
+	return 0;
+}
+
+/*
+ * percpu_pagelist_high_fraction - changes the pcp->high for each zone on each
+ * cpu. It is the fraction of total pages in each zone that a hot per cpu
+ * pagelist can have before it gets flushed back to buddy allocator.
+ */
+static int percpu_pagelist_high_fraction_sysctl_handler(struct ctl_table *table,
+		int write, void *buffer, size_t *length, loff_t *ppos)
+{
+	struct zone *zone;
+	int old_percpu_pagelist_high_fraction;
+	int ret;
+
+	mutex_lock(&pcp_batch_high_lock);
+	old_percpu_pagelist_high_fraction = percpu_pagelist_high_fraction;
+
+	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (!write || ret < 0)
+		goto out;
+
+	/* Sanity checking to avoid pcp imbalance */
+	if (percpu_pagelist_high_fraction &&
+	    percpu_pagelist_high_fraction < MIN_PERCPU_PAGELIST_HIGH_FRACTION) {
+		percpu_pagelist_high_fraction = old_percpu_pagelist_high_fraction;
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* No change? */
+	if (percpu_pagelist_high_fraction == old_percpu_pagelist_high_fraction)
+		goto out;
+
+	for_each_populated_zone(zone)
+		zone_set_pageset_high_and_batch(zone, 0);
+out:
+	mutex_unlock(&pcp_batch_high_lock);
+	return ret;
+}
+
+static struct ctl_table page_alloc_sysctl_table[] = {
+	{
+		.procname	= "min_free_kbytes",
+		.data		= &min_free_kbytes,
+		.maxlen		= sizeof(min_free_kbytes),
+		.mode		= 0644,
+		.proc_handler	= min_free_kbytes_sysctl_handler,
+		.extra1		= SYSCTL_ZERO,
+	},
+	{
+		.procname	= "watermark_boost_factor",
+		.data		= &watermark_boost_factor,
+		.maxlen		= sizeof(watermark_boost_factor),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+	},
+	{
+		.procname	= "watermark_scale_factor",
+		.data		= &watermark_scale_factor,
+		.maxlen		= sizeof(watermark_scale_factor),
+		.mode		= 0644,
+		.proc_handler	= watermark_scale_factor_sysctl_handler,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_THREE_THOUSAND,
+	},
+	{
+		.procname	= "percpu_pagelist_high_fraction",
+		.data		= &percpu_pagelist_high_fraction,
+		.maxlen		= sizeof(percpu_pagelist_high_fraction),
+		.mode		= 0644,
+		.proc_handler	= percpu_pagelist_high_fraction_sysctl_handler,
+		.extra1		= SYSCTL_ZERO,
+	},
+	{
+		.procname	= "lowmem_reserve_ratio",
+		.data		= &sysctl_lowmem_reserve_ratio,
+		.maxlen		= sizeof(sysctl_lowmem_reserve_ratio),
+		.mode		= 0644,
+		.proc_handler	= lowmem_reserve_ratio_sysctl_handler,
+	},
+#ifdef CONFIG_NUMA
+	{
+		.procname	= "numa_zonelist_order",
+		.data		= &numa_zonelist_order,
+		.maxlen		= NUMA_ZONELIST_ORDER_LEN,
+		.mode		= 0644,
+		.proc_handler	= numa_zonelist_order_handler,
+	},
+	{
+		.procname	= "min_unmapped_ratio",
+		.data		= &sysctl_min_unmapped_ratio,
+		.maxlen		= sizeof(sysctl_min_unmapped_ratio),
+		.mode		= 0644,
+		.proc_handler	= sysctl_min_unmapped_ratio_sysctl_handler,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE_HUNDRED,
+	},
+	{
+		.procname	= "min_slab_ratio",
+		.data		= &sysctl_min_slab_ratio,
+		.maxlen		= sizeof(sysctl_min_slab_ratio),
+		.mode		= 0644,
+		.proc_handler	= sysctl_min_slab_ratio_sysctl_handler,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE_HUNDRED,
+	},
+#endif
+	{}
+};
+
+void __init page_alloc_sysctl_init(void)
+{
+	register_sysctl_init("vm", page_alloc_sysctl_table);
+}
+
+#ifdef CONFIG_CONTIG_ALLOC
+/* Usage: See admin-guide/dynamic-debug-howto.rst */
+static void alloc_contig_dump_pages(struct list_head *page_list)
+{
+	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, "migrate failure");
+
+	if (DYNAMIC_DEBUG_BRANCH(descriptor)) {
+		struct page *page;
+
+		dump_stack();
+		list_for_each_entry(page, page_list, lru)
+			dump_page(page, "migration failure");
+	}
+}
+
+/* [start, end) must belong to a single zone. */
+int __alloc_contig_migrate_range(struct compact_control *cc,
+					unsigned long start, unsigned long end)
+{
+	/* This function is based on compact_zone() from compaction.c. */
+	unsigned int nr_reclaimed;
+	unsigned long pfn = start;
+	unsigned int tries = 0;
+	int ret = 0;
+	struct migration_target_control mtc = {
+		.nid = zone_to_nid(cc->zone),
+		.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
+	};
+
+	lru_cache_disable();
+
+	while (pfn < end || !list_empty(&cc->migratepages)) {
+		if (fatal_signal_pending(current)) {
+			ret = -EINTR;
+			break;
+		}
+
+		if (list_empty(&cc->migratepages)) {
+			cc->nr_migratepages = 0;
+			ret = isolate_migratepages_range(cc, pfn, end);
+			if (ret && ret != -EAGAIN)
+				break;
+			pfn = cc->migrate_pfn;
+			tries = 0;
+		} else if (++tries == 5) {
+			ret = -EBUSY;
+			break;
+		}
+
+		nr_reclaimed = reclaim_clean_pages_from_list(cc->zone,
+							&cc->migratepages);
+		cc->nr_migratepages -= nr_reclaimed;
+
+		ret = migrate_pages(&cc->migratepages, alloc_migration_target,
+			NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE, NULL);
+
+		/*
+		 * On -ENOMEM, migrate_pages() bails out right away. It is pointless
+		 * to retry again over this error, so do the same here.
+		 */
+		if (ret == -ENOMEM)
+			break;
+	}
+
+	lru_cache_enable();
+	if (ret < 0) {
+		if (!(cc->gfp_mask & __GFP_NOWARN) && ret == -EBUSY)
+			alloc_contig_dump_pages(&cc->migratepages);
+		putback_movable_pages(&cc->migratepages);
+		return ret;
+	}
+	return 0;
+}
+
+/**
+ * alloc_contig_range() -- tries to allocate given range of pages
+ * @start:	start PFN to allocate
+ * @end:	one-past-the-last PFN to allocate
+ * @migratetype:	migratetype of the underlying pageblocks (either
+ *			#MIGRATE_MOVABLE or #MIGRATE_CMA).  All pageblocks
+ *			in range must have the same migratetype and it must
+ *			be either of the two.
+ * @gfp_mask:	GFP mask to use during compaction
+ *
+ * The PFN range does not have to be pageblock aligned. The PFN range must
+ * belong to a single zone.
+ *
+ * The first thing this routine does is attempt to MIGRATE_ISOLATE all
+ * pageblocks in the range.  Once isolated, the pageblocks should not
+ * be modified by others.
+ *
+ * Return: zero on success or negative error code.  On success all
+ * pages which PFN is in [start, end) are allocated for the caller and
+ * need to be freed with free_contig_range().
+ */
+int alloc_contig_range(unsigned long start, unsigned long end,
+		       unsigned migratetype, gfp_t gfp_mask)
+{
+	unsigned long outer_start, outer_end;
+	int order;
+	int ret = 0;
+
+	struct compact_control cc = {
+		.nr_migratepages = 0,
+		.order = -1,
+		.zone = page_zone(pfn_to_page(start)),
+		.mode = MIGRATE_SYNC,
+		.ignore_skip_hint = true,
+		.no_set_skip_hint = true,
+		.gfp_mask = current_gfp_context(gfp_mask),
+		.alloc_contig = true,
+	};
+	INIT_LIST_HEAD(&cc.migratepages);
+
+	/*
+	 * What we do here is we mark all pageblocks in range as
+	 * MIGRATE_ISOLATE.  Because pageblock and max order pages may
+	 * have different sizes, and due to the way page allocator
+	 * work, start_isolate_page_range() has special handlings for this.
+	 *
+	 * 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(start, end, migratetype, 0, gfp_mask);
+	if (ret)
+		goto done;
+
+	drain_all_pages(cc.zone);
+
+	/*
+	 * In case of -EBUSY, we'd like to know which page causes problem.
+	 * So, just fall through. test_pages_isolated() has a tracepoint
+	 * which will report the busy page.
+	 *
+	 * It is possible that busy pages could become available before
+	 * the call to test_pages_isolated, and the range will actually be
+	 * allocated.  So, if we fall through be sure to clear ret so that
+	 * -EBUSY is not accidentally used or returned to caller.
+	 */
+	ret = __alloc_contig_migrate_range(&cc, start, end);
+	if (ret && ret != -EBUSY)
+		goto done;
+	ret = 0;
+
+	/*
+	 * Pages from [start, end) are within a pageblock_nr_pages
+	 * aligned blocks that are marked as MIGRATE_ISOLATE.  What's
+	 * more, all pages in [start, end) are free in page allocator.
+	 * What we are going to do is to allocate all pages from
+	 * [start, end) (that is remove them from page allocator).
+	 *
+	 * The only problem is that pages at the beginning and at the
+	 * end of interesting range may be not aligned with pages that
+	 * page allocator holds, ie. they can be part of higher order
+	 * pages.  Because of this, we reserve the bigger range and
+	 * once this is done free the pages we are not interested in.
+	 *
+	 * We don't have to hold zone->lock here because the pages are
+	 * isolated thus they won't get removed from buddy.
+	 */
+
+	order = 0;
+	outer_start = start;
+	while (!PageBuddy(pfn_to_page(outer_start))) {
+		if (++order > MAX_ORDER) {
+			outer_start = start;
+			break;
+		}
+		outer_start &= ~0UL << order;
+	}
+
+	if (outer_start != start) {
+		order = buddy_order(pfn_to_page(outer_start));
+
+		/*
+		 * outer_start page could be small order buddy page and
+		 * it doesn't include start page. Adjust outer_start
+		 * in this case to report failed page properly
+		 * on tracepoint in test_pages_isolated()
+		 */
+		if (outer_start + (1UL << order) <= start)
+			outer_start = start;
+	}
+
+	/* Make sure the range is really isolated. */
+	if (test_pages_isolated(outer_start, end, 0)) {
+		ret = -EBUSY;
+		goto done;
+	}
+
+	/* Grab isolated pages from freelists. */
+	outer_end = isolate_freepages_range(&cc, outer_start, end);
+	if (!outer_end) {
+		ret = -EBUSY;
+		goto done;
+	}
+
+	/* Free head and tail (if any) */
+	if (start != outer_start)
+		free_contig_range(outer_start, start - outer_start);
+	if (end != outer_end)
+		free_contig_range(end, outer_end - end);
+
+done:
+	undo_isolate_page_range(start, end, migratetype);
+	return ret;
+}
+EXPORT_SYMBOL(alloc_contig_range);
+
+static int __alloc_contig_pages(unsigned long start_pfn,
+				unsigned long nr_pages, gfp_t gfp_mask)
+{
+	unsigned long end_pfn = start_pfn + nr_pages;
+
+	return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE,
+				  gfp_mask);
+}
+
+static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
+				   unsigned long nr_pages)
+{
+	unsigned long i, end_pfn = start_pfn + nr_pages;
+	struct page *page;
+
+	for (i = start_pfn; i < end_pfn; i++) {
+		page = pfn_to_online_page(i);
+		if (!page)
+			return false;
+
+		if (page_zone(page) != z)
+			return false;
+
+		if (PageReserved(page))
+			return false;
+
+		if (PageHuge(page))
+			return false;
+	}
+	return true;
+}
+
+static bool zone_spans_last_pfn(const struct zone *zone,
+				unsigned long start_pfn, unsigned long nr_pages)
+{
+	unsigned long last_pfn = start_pfn + nr_pages - 1;
+
+	return zone_spans_pfn(zone, last_pfn);
+}
+
+/**
+ * alloc_contig_pages() -- tries to find and allocate contiguous range of pages
+ * @nr_pages:	Number of contiguous pages to allocate
+ * @gfp_mask:	GFP mask to limit search and used during compaction
+ * @nid:	Target node
+ * @nodemask:	Mask for other possible nodes
+ *
+ * This routine is a wrapper around alloc_contig_range(). It scans over zones
+ * on an applicable zonelist to find a contiguous pfn range which can then be
+ * tried for allocation with alloc_contig_range(). This routine is intended
+ * for allocation requests which can not be fulfilled with the buddy allocator.
+ *
+ * The allocated memory is always aligned to a page boundary. If nr_pages is a
+ * power of two, then allocated range is also guaranteed to be aligned to same
+ * nr_pages (e.g. 1GB request would be aligned to 1GB).
+ *
+ * Allocated pages can be freed with free_contig_range() or by manually calling
+ * __free_page() on each allocated page.
+ *
+ * Return: pointer to contiguous pages on success, or NULL if not successful.
+ */
+struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
+				int nid, nodemask_t *nodemask)
+{
+	unsigned long ret, pfn, flags;
+	struct zonelist *zonelist;
+	struct zone *zone;
+	struct zoneref *z;
+
+	zonelist = node_zonelist(nid, gfp_mask);
+	for_each_zone_zonelist_nodemask(zone, z, zonelist,
+					gfp_zone(gfp_mask), nodemask) {
+		spin_lock_irqsave(&zone->lock, flags);
+
+		pfn = ALIGN(zone->zone_start_pfn, nr_pages);
+		while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
+			if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
+				/*
+				 * We release the zone lock here because
+				 * alloc_contig_range() will also lock the zone
+				 * at some point. If there's an allocation
+				 * spinning on this lock, it may win the race
+				 * and cause alloc_contig_range() to fail...
+				 */
+				spin_unlock_irqrestore(&zone->lock, flags);
+				ret = __alloc_contig_pages(pfn, nr_pages,
+							gfp_mask);
+				if (!ret)
+					return pfn_to_page(pfn);
+				spin_lock_irqsave(&zone->lock, flags);
+			}
+			pfn += nr_pages;
+		}
+		spin_unlock_irqrestore(&zone->lock, flags);
+	}
+	return NULL;
+}
+#endif /* CONFIG_CONTIG_ALLOC */
+
+void free_contig_range(unsigned long pfn, unsigned long nr_pages)
+{
+	unsigned long count = 0;
+
+	for (; nr_pages--; pfn++) {
+		struct page *page = pfn_to_page(pfn);
+
+		count += page_count(page) != 1;
+		__free_page(page);
+	}
+	WARN(count != 0, "%lu pages are still in use!\n", count);
+}
+EXPORT_SYMBOL(free_contig_range);
+
+/*
+ * Effectively disable pcplists for the zone by setting the high limit to 0
+ * and draining all cpus. A concurrent page freeing on another CPU that's about
+ * to put the page on pcplist will either finish before the drain and the page
+ * will be drained, or observe the new high limit and skip the pcplist.
+ *
+ * Must be paired with a call to zone_pcp_enable().
+ */
+void zone_pcp_disable(struct zone *zone)
+{
+	mutex_lock(&pcp_batch_high_lock);
+	__zone_set_pageset_high_and_batch(zone, 0, 1);
+	__drain_all_pages(zone, true);
+}
+
+void zone_pcp_enable(struct zone *zone)
+{
+	__zone_set_pageset_high_and_batch(zone, zone->pageset_high, zone->pageset_batch);
+	mutex_unlock(&pcp_batch_high_lock);
+}
+
+void zone_pcp_reset(struct zone *zone)
+{
+	int cpu;
+	struct per_cpu_zonestat *pzstats;
+
+	if (zone->per_cpu_pageset != &boot_pageset) {
+		for_each_online_cpu(cpu) {
+			pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
+			drain_zonestat(zone, pzstats);
+		}
+		free_percpu(zone->per_cpu_pageset);
+		zone->per_cpu_pageset = &boot_pageset;
+		if (zone->per_cpu_zonestats != &boot_zonestats) {
+			free_percpu(zone->per_cpu_zonestats);
+			zone->per_cpu_zonestats = &boot_zonestats;
+		}
+	}
+}
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+/*
+ * All pages in the range must be in a single zone, must not contain holes,
+ * must span full sections, and must be isolated before calling this function.
+ */
+void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
+{
+	unsigned long pfn = start_pfn;
+	struct page *page;
+	struct zone *zone;
+	unsigned int order;
+	unsigned long flags;
+
+	offline_mem_sections(pfn, end_pfn);
+	zone = page_zone(pfn_to_page(pfn));
+	spin_lock_irqsave(&zone->lock, flags);
+	while (pfn < end_pfn) {
+		page = pfn_to_page(pfn);
+		/*
+		 * The HWPoisoned page may be not in buddy system, and
+		 * page_count() is not 0.
+		 */
+		if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
+			pfn++;
+			continue;
+		}
+		/*
+		 * At this point all remaining PageOffline() pages have a
+		 * reference count of 0 and can simply be skipped.
+		 */
+		if (PageOffline(page)) {
+			BUG_ON(page_count(page));
+			BUG_ON(PageBuddy(page));
+			pfn++;
+			continue;
+		}
+
+		BUG_ON(page_count(page));
+		BUG_ON(!PageBuddy(page));
+		order = buddy_order(page);
+		del_page_from_free_list(page, zone, order);
+		pfn += (1 << order);
+	}
+	spin_unlock_irqrestore(&zone->lock, flags);
+}
+#endif
+
+/*
+ * This function returns a stable result only if called under zone lock.
+ */
+bool is_free_buddy_page(struct page *page)
+{
+	unsigned long pfn = page_to_pfn(page);
+	unsigned int order;
+
+	for (order = 0; order <= MAX_ORDER; order++) {
+		struct page *page_head = page - (pfn & ((1 << order) - 1));
+
+		if (PageBuddy(page_head) &&
+		    buddy_order_unsafe(page_head) >= order)
+			break;
+	}
+
+	return order <= MAX_ORDER;
+}
+EXPORT_SYMBOL(is_free_buddy_page);
+
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Break down a higher-order page in sub-pages, and keep our target out of
+ * buddy allocator.
+ */
+static void break_down_buddy_pages(struct zone *zone, struct page *page,
+				   struct page *target, int low, int high,
+				   int migratetype)
+{
+	unsigned long size = 1 << high;
+	struct page *current_buddy, *next_page;
+
+	while (high > low) {
+		high--;
+		size >>= 1;
+
+		if (target >= &page[size]) {
+			next_page = page + size;
+			current_buddy = page;
+		} else {
+			next_page = page;
+			current_buddy = page + size;
+		}
+		page = next_page;
+
+		if (set_page_guard(zone, current_buddy, high, migratetype))
+			continue;
+
+		if (current_buddy != target) {
+			add_to_free_list(current_buddy, zone, high, migratetype);
+			set_buddy_order(current_buddy, high);
+		}
+	}
+}
+
+/*
+ * Take a page that will be marked as poisoned off the buddy allocator.
+ */
+bool take_page_off_buddy(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long pfn = page_to_pfn(page);
+	unsigned long flags;
+	unsigned int order;
+	bool ret = false;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	for (order = 0; order <= MAX_ORDER; order++) {
+		struct page *page_head = page - (pfn & ((1 << order) - 1));
+		int page_order = buddy_order(page_head);
+
+		if (PageBuddy(page_head) && page_order >= order) {
+			unsigned long pfn_head = page_to_pfn(page_head);
+			int migratetype = get_pfnblock_migratetype(page_head,
+								   pfn_head);
+
+			del_page_from_free_list(page_head, zone, page_order);
+			break_down_buddy_pages(zone, page_head, page, 0,
+						page_order, migratetype);
+			SetPageHWPoisonTakenOff(page);
+			if (!is_migrate_isolate(migratetype))
+				__mod_zone_freepage_state(zone, -1, migratetype);
+			ret = true;
+			break;
+		}
+		if (page_count(page_head) > 0)
+			break;
+	}
+	spin_unlock_irqrestore(&zone->lock, flags);
+	return ret;
+}
+
+/*
+ * Cancel takeoff done by take_page_off_buddy().
+ */
+bool put_page_back_buddy(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long pfn = page_to_pfn(page);
+	unsigned long flags;
+	int migratetype = get_pfnblock_migratetype(page, pfn);
+	bool ret = false;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	if (put_page_testzero(page)) {
+		ClearPageHWPoisonTakenOff(page);
+		__free_one_page(page, pfn, zone, 0, migratetype, FPI_NONE);
+		if (TestClearPageHWPoison(page)) {
+			ret = true;
+		}
+	}
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	return ret;
+}
+#endif
+
+#ifdef CONFIG_ZONE_DMA
+bool has_managed_dma(void)
+{
+	struct pglist_data *pgdat;
+
+	for_each_online_pgdat(pgdat) {
+		struct zone *zone = &pgdat->node_zones[ZONE_DMA];
+
+		if (managed_zone(zone))
+			return true;
+	}
+	return false;
+}
+#endif /* CONFIG_ZONE_DMA */
+
+#ifdef CONFIG_UNACCEPTED_MEMORY
+
+/* Counts number of zones with unaccepted pages. */
+static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
+
+static bool lazy_accept = true;
+
+static int __init accept_memory_parse(char *p)
+{
+	if (!strcmp(p, "lazy")) {
+		lazy_accept = true;
+		return 0;
+	} else if (!strcmp(p, "eager")) {
+		lazy_accept = false;
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+}
+early_param("accept_memory", accept_memory_parse);
+
+static bool page_contains_unaccepted(struct page *page, unsigned int order)
+{
+	phys_addr_t start = page_to_phys(page);
+	phys_addr_t end = start + (PAGE_SIZE << order);
+
+	return range_contains_unaccepted_memory(start, end);
+}
+
+static void accept_page(struct page *page, unsigned int order)
+{
+	phys_addr_t start = page_to_phys(page);
+
+	accept_memory(start, start + (PAGE_SIZE << order));
+}
+
+static bool try_to_accept_memory_one(struct zone *zone)
+{
+	unsigned long flags;
+	struct page *page;
+	bool last;
+
+	if (list_empty(&zone->unaccepted_pages))
+		return false;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	page = list_first_entry_or_null(&zone->unaccepted_pages,
+					struct page, lru);
+	if (!page) {
+		spin_unlock_irqrestore(&zone->lock, flags);
+		return false;
+	}
+
+	list_del(&page->lru);
+	last = list_empty(&zone->unaccepted_pages);
+
+	__mod_zone_freepage_state(zone, -MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
+	__mod_zone_page_state(zone, NR_UNACCEPTED, -MAX_ORDER_NR_PAGES);
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	accept_page(page, MAX_ORDER);
+
+	__free_pages_ok(page, MAX_ORDER, FPI_TO_TAIL);
+
+	if (last)
+		static_branch_dec(&zones_with_unaccepted_pages);
+
+	return true;
+}
+
+static bool try_to_accept_memory(struct zone *zone, unsigned int order)
+{
+	long to_accept;
+	int ret = false;
+
+	/* How much to accept to get to high watermark? */
+	to_accept = high_wmark_pages(zone) -
+		    (zone_page_state(zone, NR_FREE_PAGES) -
+		    __zone_watermark_unusable_free(zone, order, 0));
+
+	/* Accept at least one page */
+	do {
+		if (!try_to_accept_memory_one(zone))
+			break;
+		ret = true;
+		to_accept -= MAX_ORDER_NR_PAGES;
+	} while (to_accept > 0);
+
+	return ret;
+}
+
+static inline bool has_unaccepted_memory(void)
+{
+	return static_branch_unlikely(&zones_with_unaccepted_pages);
+}
+
+static bool __free_unaccepted(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long flags;
+	bool first = false;
+
+	if (!lazy_accept)
+		return false;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	first = list_empty(&zone->unaccepted_pages);
+	list_add_tail(&page->lru, &zone->unaccepted_pages);
+	__mod_zone_freepage_state(zone, MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
+	__mod_zone_page_state(zone, NR_UNACCEPTED, MAX_ORDER_NR_PAGES);
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	if (first)
+		static_branch_inc(&zones_with_unaccepted_pages);
+
+	return true;
+}
+
+#else
+
+static bool page_contains_unaccepted(struct page *page, unsigned int order)
+{
+	return false;
+}
+
+static void accept_page(struct page *page, unsigned int order)
+{
+}
+
+static bool try_to_accept_memory(struct zone *zone, unsigned int order)
+{
+	return false;
+}
+
+static inline bool has_unaccepted_memory(void)
+{
+	return false;
+}
+
+static bool __free_unaccepted(struct page *page)
+{
+	BUILD_BUG();
+	return false;
+}
+
+#endif /* CONFIG_UNACCEPTED_MEMORY */