// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  linux/mm/memory_hotplug.c
   *
   *  Copyright (C)
   */

  #include <linux/stddef.h>
  #include <linux/mm.h>

  #include <linux/sched/signal.h>

  #include <linux/swap.h>
  #include <linux/interrupt.h>
  #include <linux/pagemap.h>

  #include <linux/compiler.h>

  #include <linux/export.h>

  #include <linux/pagevec.h>

  #include <linux/writeback.h>

  #include <linux/slab.h>
  #include <linux/sysctl.h>
  #include <linux/cpu.h>
  #include <linux/memory.h>

  #include <linux/memremap.h>

  #include <linux/memory_hotplug.h>
  #include <linux/highmem.h>
  #include <linux/vmalloc.h>

  #include <linux/ioport.h>

  #include <linux/delay.h>
  #include <linux/migrate.h>
  #include <linux/page-isolation.h>

  #include <linux/pfn.h>

  #include <linux/suspend.h>

  #include <linux/mm_inline.h>

  #include <linux/firmware-map.h>

  #include <linux/stop_machine.h>

  #include <linux/hugetlb.h>

  #include <linux/memblock.h>

  #include <linux/compaction.h>

  #include <linux/rmap.h>

  
  #include <asm/tlbflush.h>

  #include "internal.h"

  #include "shuffle.h"

  /*
   * online_page_callback contains pointer to current page onlining function.
   * Initially it is generic_online_page(). If it is required it could be
   * changed by calling set_online_page_callback() for callback registration
   * and restore_online_page_callback() for generic callback restore.
   */

  static void generic_online_page(struct page *page, unsigned int order);

  
  static online_page_callback_t online_page_callback = generic_online_page;

  static DEFINE_MUTEX(online_page_callback_lock);

  DEFINE_STATIC_PERCPU_RWSEM(mem_hotplug_lock);

  void get_online_mems(void)
  {
  	percpu_down_read(&mem_hotplug_lock);
  }

  void put_online_mems(void)
  {
  	percpu_up_read(&mem_hotplug_lock);
  }

  bool movable_node_enabled = false;

  #ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE

  bool memhp_auto_online;

  #else
  bool memhp_auto_online = true;
  #endif

  EXPORT_SYMBOL_GPL(memhp_auto_online);

  static int __init setup_memhp_default_state(char *str)
  {
  	if (!strcmp(str, "online"))
  		memhp_auto_online = true;
  	else if (!strcmp(str, "offline"))
  		memhp_auto_online = false;
  
  	return 1;
  }
  __setup("memhp_default_state=", setup_memhp_default_state);

  void mem_hotplug_begin(void)

  {

  	cpus_read_lock();
  	percpu_down_write(&mem_hotplug_lock);

  }

  void mem_hotplug_done(void)

  {

  	percpu_up_write(&mem_hotplug_lock);
  	cpus_read_unlock();

  }

  u64 max_mem_size = U64_MAX;

  /* add this memory to iomem resource */
  static struct resource *register_memory_resource(u64 start, u64 size)
  {

  	struct resource *res;
  	unsigned long flags =  IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
  	char *resource_name = "System RAM";

  
  	if (start + size > max_mem_size)
  		return ERR_PTR(-E2BIG);

  	/*
  	 * Request ownership of the new memory range.  This might be
  	 * a child of an existing resource that was present but
  	 * not marked as busy.
  	 */
  	res = __request_region(&iomem_resource, start, size,
  			       resource_name, flags);
  
  	if (!res) {
  		pr_debug("Unable to reserve System RAM region: %016llx->%016llx
  ",
  				start, start + size);

  		return ERR_PTR(-EEXIST);

  	}
  	return res;
  }
  
  static void release_memory_resource(struct resource *res)
  {
  	if (!res)
  		return;
  	release_resource(res);
  	kfree(res);

  }

  #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE

  void get_page_bootmem(unsigned long info,  struct page *page,
  		      unsigned long type)

  {

  	page->freelist = (void *)type;

  	SetPagePrivate(page);
  	set_page_private(page, info);

  	page_ref_inc(page);

  }

  void put_page_bootmem(struct page *page)

  {

  	unsigned long type;

  	type = (unsigned long) page->freelist;

  	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
  	       type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);

  	if (page_ref_dec_return(page) == 1) {

  		page->freelist = NULL;

  		ClearPagePrivate(page);
  		set_page_private(page, 0);

  		INIT_LIST_HEAD(&page->lru);

  		free_reserved_page(page);

  	}

  }

  #ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
  #ifndef CONFIG_SPARSEMEM_VMEMMAP

  static void register_page_bootmem_info_section(unsigned long start_pfn)

  {

  	unsigned long mapsize, section_nr, i;

  	struct mem_section *ms;
  	struct page *page, *memmap;

  	struct mem_section_usage *usage;

  	section_nr = pfn_to_section_nr(start_pfn);
  	ms = __nr_to_section(section_nr);
  
  	/* Get section's memmap address */
  	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
  
  	/*
  	 * Get page for the memmap's phys address
  	 * XXX: need more consideration for sparse_vmemmap...
  	 */
  	page = virt_to_page(memmap);
  	mapsize = sizeof(struct page) * PAGES_PER_SECTION;
  	mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
  
  	/* remember memmap's page */
  	for (i = 0; i < mapsize; i++, page++)
  		get_page_bootmem(section_nr, page, SECTION_INFO);

  	usage = ms->usage;
  	page = virt_to_page(usage);

  	mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT;

  
  	for (i = 0; i < mapsize; i++, page++)

  		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);

  
  }

  #else /* CONFIG_SPARSEMEM_VMEMMAP */
  static void register_page_bootmem_info_section(unsigned long start_pfn)
  {

  	unsigned long mapsize, section_nr, i;

  	struct mem_section *ms;
  	struct page *page, *memmap;

  	struct mem_section_usage *usage;

  	section_nr = pfn_to_section_nr(start_pfn);
  	ms = __nr_to_section(section_nr);
  
  	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
  
  	register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION);

  	usage = ms->usage;
  	page = virt_to_page(usage);

  	mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT;

  
  	for (i = 0; i < mapsize; i++, page++)
  		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
  }
  #endif /* !CONFIG_SPARSEMEM_VMEMMAP */

  void __init register_page_bootmem_info_node(struct pglist_data *pgdat)

  {
  	unsigned long i, pfn, end_pfn, nr_pages;
  	int node = pgdat->node_id;
  	struct page *page;

  
  	nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
  	page = virt_to_page(pgdat);
  
  	for (i = 0; i < nr_pages; i++, page++)
  		get_page_bootmem(node, page, NODE_INFO);

  	pfn = pgdat->node_start_pfn;

  	end_pfn = pgdat_end_pfn(pgdat);

  	/* register section info */

  	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
  		/*
  		 * Some platforms can assign the same pfn to multiple nodes - on
  		 * node0 as well as nodeN.  To avoid registering a pfn against
  		 * multiple nodes we check that this pfn does not already

  		 * reside in some other nodes.

  		 */

  		if (pfn_valid(pfn) && (early_pfn_to_nid(pfn) == node))

  			register_page_bootmem_info_section(pfn);
  	}

  }

  #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */

  static int check_pfn_span(unsigned long pfn, unsigned long nr_pages,
  		const char *reason)
  {
  	/*
  	 * Disallow all operations smaller than a sub-section and only
  	 * allow operations smaller than a section for
  	 * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
  	 * enforces a larger memory_block_size_bytes() granularity for
  	 * memory that will be marked online, so this check should only
  	 * fire for direct arch_{add,remove}_memory() users outside of
  	 * add_memory_resource().
  	 */
  	unsigned long min_align;
  
  	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
  		min_align = PAGES_PER_SUBSECTION;
  	else
  		min_align = PAGES_PER_SECTION;
  	if (!IS_ALIGNED(pfn, min_align)
  			|| !IS_ALIGNED(nr_pages, min_align)) {
  		WARN(1, "Misaligned __%s_pages start: %#lx end: #%lx
  ",
  				reason, pfn, pfn + nr_pages - 1);
  		return -EINVAL;
  	}
  	return 0;
  }

  /*
   * Reasonably generic function for adding memory.  It is
   * expected that archs that support memory hotplug will
   * call this function after deciding the zone to which to
   * add the new pages.
   */

  int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
  		struct mhp_restrictions *restrictions)

  {

  	int err;
  	unsigned long nr, start_sec, end_sec;

  	struct vmem_altmap *altmap = restrictions->altmap;

  	if (altmap) {
  		/*
  		 * Validate altmap is within bounds of the total request
  		 */

  		if (altmap->base_pfn != pfn

  				|| vmem_altmap_offset(altmap) > nr_pages) {
  			pr_warn_once("memory add fail, invalid altmap
  ");

  			return -EINVAL;

  		}
  		altmap->alloc = 0;
  	}

  	err = check_pfn_span(pfn, nr_pages, "add");
  	if (err)
  		return err;
  
  	start_sec = pfn_to_section_nr(pfn);
  	end_sec = pfn_to_section_nr(pfn + nr_pages - 1);

  	for (nr = start_sec; nr <= end_sec; nr++) {

  		unsigned long pfns;
  
  		pfns = min(nr_pages, PAGES_PER_SECTION
  				- (pfn & ~PAGE_SECTION_MASK));

  		err = sparse_add_section(nid, pfn, pfns, altmap);
  		if (err)
  			break;

  		pfn += pfns;
  		nr_pages -= pfns;

  		cond_resched();

  	}

  	vmemmap_populate_print_last();

  	return err;
  }

  /* find the smallest valid pfn in the range [start_pfn, end_pfn) */

  static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,

  				     unsigned long start_pfn,
  				     unsigned long end_pfn)
  {

  	for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUBSECTION) {

  		if (unlikely(!pfn_to_online_page(start_pfn)))

  			continue;
  
  		if (unlikely(pfn_to_nid(start_pfn) != nid))
  			continue;
  
  		if (zone && zone != page_zone(pfn_to_page(start_pfn)))
  			continue;
  
  		return start_pfn;
  	}
  
  	return 0;
  }
  
  /* find the biggest valid pfn in the range [start_pfn, end_pfn). */

  static unsigned long find_biggest_section_pfn(int nid, struct zone *zone,

  				    unsigned long start_pfn,
  				    unsigned long end_pfn)
  {

  	unsigned long pfn;
  
  	/* pfn is the end pfn of a memory section. */
  	pfn = end_pfn - 1;

  	for (; pfn >= start_pfn; pfn -= PAGES_PER_SUBSECTION) {

  		if (unlikely(!pfn_to_online_page(pfn)))

  			continue;
  
  		if (unlikely(pfn_to_nid(pfn) != nid))
  			continue;
  
  		if (zone && zone != page_zone(pfn_to_page(pfn)))
  			continue;
  
  		return pfn;
  	}
  
  	return 0;
  }
  
  static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
  			     unsigned long end_pfn)
  {

  	unsigned long zone_start_pfn = zone->zone_start_pfn;
  	unsigned long z = zone_end_pfn(zone); /* zone_end_pfn namespace clash */
  	unsigned long zone_end_pfn = z;

  	unsigned long pfn;

  	int nid = zone_to_nid(zone);
  
  	zone_span_writelock(zone);
  	if (zone_start_pfn == start_pfn) {
  		/*
  		 * If the section is smallest section in the zone, it need
  		 * shrink zone->zone_start_pfn and zone->zone_spanned_pages.
  		 * In this case, we find second smallest valid mem_section
  		 * for shrinking zone.
  		 */
  		pfn = find_smallest_section_pfn(nid, zone, end_pfn,
  						zone_end_pfn);
  		if (pfn) {
  			zone->zone_start_pfn = pfn;
  			zone->spanned_pages = zone_end_pfn - pfn;
  		}
  	} else if (zone_end_pfn == end_pfn) {
  		/*
  		 * If the section is biggest section in the zone, it need
  		 * shrink zone->spanned_pages.
  		 * In this case, we find second biggest valid mem_section for
  		 * shrinking zone.
  		 */
  		pfn = find_biggest_section_pfn(nid, zone, zone_start_pfn,
  					       start_pfn);
  		if (pfn)
  			zone->spanned_pages = pfn - zone_start_pfn + 1;
  	}
  
  	/*
  	 * The section is not biggest or smallest mem_section in the zone, it
  	 * only creates a hole in the zone. So in this case, we need not
  	 * change the zone. But perhaps, the zone has only hole data. Thus
  	 * it check the zone has only hole or not.
  	 */
  	pfn = zone_start_pfn;

  	for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUBSECTION) {

  		if (unlikely(!pfn_to_online_page(pfn)))

  			continue;
  
  		if (page_zone(pfn_to_page(pfn)) != zone)
  			continue;

  		/* Skip range to be removed */
  		if (pfn >= start_pfn && pfn < end_pfn)

  			continue;
  
  		/* If we find valid section, we have nothing to do */
  		zone_span_writeunlock(zone);
  		return;
  	}
  
  	/* The zone has no valid section */
  	zone->zone_start_pfn = 0;
  	zone->spanned_pages = 0;
  	zone_span_writeunlock(zone);
  }

  static void update_pgdat_span(struct pglist_data *pgdat)

  {

  	unsigned long node_start_pfn = 0, node_end_pfn = 0;
  	struct zone *zone;
  
  	for (zone = pgdat->node_zones;
  	     zone < pgdat->node_zones + MAX_NR_ZONES; zone++) {
  		unsigned long zone_end_pfn = zone->zone_start_pfn +
  					     zone->spanned_pages;
  
  		/* No need to lock the zones, they can't change. */

  		if (!zone->spanned_pages)
  			continue;
  		if (!node_end_pfn) {
  			node_start_pfn = zone->zone_start_pfn;
  			node_end_pfn = zone_end_pfn;
  			continue;
  		}

  		if (zone_end_pfn > node_end_pfn)
  			node_end_pfn = zone_end_pfn;
  		if (zone->zone_start_pfn < node_start_pfn)
  			node_start_pfn = zone->zone_start_pfn;

  	}

  	pgdat->node_start_pfn = node_start_pfn;
  	pgdat->node_spanned_pages = node_end_pfn - node_start_pfn;

  }

  void __ref remove_pfn_range_from_zone(struct zone *zone,
  				      unsigned long start_pfn,
  				      unsigned long nr_pages)

  {
  	struct pglist_data *pgdat = zone->zone_pgdat;

  	unsigned long flags;

  #ifdef CONFIG_ZONE_DEVICE
  	/*
  	 * Zone shrinking code cannot properly deal with ZONE_DEVICE. So
  	 * we will not try to shrink the zones - which is okay as
  	 * set_zone_contiguous() cannot deal with ZONE_DEVICE either way.
  	 */
  	if (zone_idx(zone) == ZONE_DEVICE)
  		return;
  #endif

  	clear_zone_contiguous(zone);

  	pgdat_resize_lock(zone->zone_pgdat, &flags);
  	shrink_zone_span(zone, start_pfn, start_pfn + nr_pages);

  	update_pgdat_span(pgdat);

  	pgdat_resize_unlock(zone->zone_pgdat, &flags);

  
  	set_zone_contiguous(zone);

  }

  static void __remove_section(unsigned long pfn, unsigned long nr_pages,
  			     unsigned long map_offset,
  			     struct vmem_altmap *altmap)

  {

  	struct mem_section *ms = __nr_to_section(pfn_to_section_nr(pfn));

  	if (WARN_ON_ONCE(!valid_section(ms)))
  		return;

  	sparse_remove_section(ms, pfn, nr_pages, map_offset, altmap);

  }

  /**

   * __remove_pages() - remove sections of pages

   * @pfn: starting pageframe (must be aligned to start of a section)

   * @nr_pages: number of pages to remove (must be multiple of section size)

   * @altmap: alternative device page map or %NULL if default memmap is used

   *
   * Generic helper function to remove section mappings and sysfs entries
   * for the section of the memory we are removing. Caller needs to make
   * sure that pages are marked reserved and zones are adjust properly by
   * calling offline_pages().
   */

  void __remove_pages(unsigned long pfn, unsigned long nr_pages,
  		    struct vmem_altmap *altmap)

  {

  	unsigned long map_offset = 0;

  	unsigned long nr, start_sec, end_sec;

  	map_offset = vmem_altmap_offset(altmap);

  	if (check_pfn_span(pfn, nr_pages, "remove"))
  		return;

  	start_sec = pfn_to_section_nr(pfn);
  	end_sec = pfn_to_section_nr(pfn + nr_pages - 1);

  	for (nr = start_sec; nr <= end_sec; nr++) {

  		unsigned long pfns;

  		cond_resched();

  		pfns = min(nr_pages, PAGES_PER_SECTION
  				- (pfn & ~PAGE_SECTION_MASK));

  		__remove_section(pfn, pfns, map_offset, altmap);

  		pfn += pfns;
  		nr_pages -= pfns;

  		map_offset = 0;

  	}

  }

  int set_online_page_callback(online_page_callback_t callback)
  {
  	int rc = -EINVAL;

  	get_online_mems();
  	mutex_lock(&online_page_callback_lock);

  
  	if (online_page_callback == generic_online_page) {
  		online_page_callback = callback;
  		rc = 0;
  	}

  	mutex_unlock(&online_page_callback_lock);
  	put_online_mems();

  
  	return rc;
  }
  EXPORT_SYMBOL_GPL(set_online_page_callback);
  
  int restore_online_page_callback(online_page_callback_t callback)
  {
  	int rc = -EINVAL;

  	get_online_mems();
  	mutex_lock(&online_page_callback_lock);

  
  	if (online_page_callback == callback) {
  		online_page_callback = generic_online_page;
  		rc = 0;
  	}

  	mutex_unlock(&online_page_callback_lock);
  	put_online_mems();

  
  	return rc;
  }
  EXPORT_SYMBOL_GPL(restore_online_page_callback);
  
  void __online_page_set_limits(struct page *page)

  {

  }
  EXPORT_SYMBOL_GPL(__online_page_set_limits);
  
  void __online_page_increment_counters(struct page *page)
  {

  	adjust_managed_page_count(page, 1);

  }
  EXPORT_SYMBOL_GPL(__online_page_increment_counters);

  void __online_page_free(struct page *page)
  {

  	__free_reserved_page(page);

  }

  EXPORT_SYMBOL_GPL(__online_page_free);

  static void generic_online_page(struct page *page, unsigned int order)

  {

  	kernel_map_pages(page, 1 << order, 1);

  	__free_pages_core(page, order);
  	totalram_pages_add(1UL << order);
  #ifdef CONFIG_HIGHMEM
  	if (PageHighMem(page))
  		totalhigh_pages_add(1UL << order);
  #endif
  }

  static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
  			void *arg)

  {

  	const unsigned long end_pfn = start_pfn + nr_pages;
  	unsigned long pfn;
  	int order;
  
  	/*
  	 * Online the pages. The callback might decide to keep some pages
  	 * PG_reserved (to add them to the buddy later), but we still account
  	 * them as being online/belonging to this zone ("present").
  	 */
  	for (pfn = start_pfn; pfn < end_pfn; pfn += 1ul << order) {
  		order = min(MAX_ORDER - 1, get_order(PFN_PHYS(end_pfn - pfn)));

  		/* __free_pages_core() wants pfns to be aligned to the order */
  		if (WARN_ON_ONCE(!IS_ALIGNED(pfn, 1ul << order)))
  			order = 0;

  		(*online_page_callback)(pfn_to_page(pfn), order);
  	}

  	/* mark all involved sections as online */
  	online_mem_sections(start_pfn, end_pfn);

  	*(unsigned long *)arg += nr_pages;

  	return 0;
  }

  /* check which state of node_states will be changed when online memory */
  static void node_states_check_changes_online(unsigned long nr_pages,
  	struct zone *zone, struct memory_notify *arg)
  {
  	int nid = zone_to_nid(zone);

  	arg->status_change_nid = NUMA_NO_NODE;
  	arg->status_change_nid_normal = NUMA_NO_NODE;
  	arg->status_change_nid_high = NUMA_NO_NODE;

  	if (!node_state(nid, N_MEMORY))
  		arg->status_change_nid = nid;
  	if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))

  		arg->status_change_nid_normal = nid;

  #ifdef CONFIG_HIGHMEM

  	if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))

  		arg->status_change_nid_high = nid;

  #endif

  }
  
  static void node_states_set_node(int node, struct memory_notify *arg)
  {
  	if (arg->status_change_nid_normal >= 0)
  		node_set_state(node, N_NORMAL_MEMORY);

  	if (arg->status_change_nid_high >= 0)
  		node_set_state(node, N_HIGH_MEMORY);

  	if (arg->status_change_nid >= 0)
  		node_set_state(node, N_MEMORY);

  }

  static void __meminit resize_zone_range(struct zone *zone, unsigned long start_pfn,
  		unsigned long nr_pages)
  {
  	unsigned long old_end_pfn = zone_end_pfn(zone);
  
  	if (zone_is_empty(zone) || start_pfn < zone->zone_start_pfn)
  		zone->zone_start_pfn = start_pfn;
  
  	zone->spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - zone->zone_start_pfn;
  }
  
  static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned long start_pfn,
                                       unsigned long nr_pages)
  {
  	unsigned long old_end_pfn = pgdat_end_pfn(pgdat);
  
  	if (!pgdat->node_spanned_pages || start_pfn < pgdat->node_start_pfn)
  		pgdat->node_start_pfn = start_pfn;
  
  	pgdat->node_spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - pgdat->node_start_pfn;

  }
  /*
   * Associate the pfn range with the given zone, initializing the memmaps
   * and resizing the pgdat/zone data to span the added pages. After this
   * call, all affected pages are PG_reserved.
   */

  void __ref move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
  		unsigned long nr_pages, struct vmem_altmap *altmap)

  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	int nid = pgdat->node_id;
  	unsigned long flags;

  	clear_zone_contiguous(zone);
  
  	/* TODO Huh pgdat is irqsave while zone is not. It used to be like that before */
  	pgdat_resize_lock(pgdat, &flags);
  	zone_span_writelock(zone);

  	if (zone_is_empty(zone))
  		init_currently_empty_zone(zone, start_pfn, nr_pages);

  	resize_zone_range(zone, start_pfn, nr_pages);
  	zone_span_writeunlock(zone);
  	resize_pgdat_range(pgdat, start_pfn, nr_pages);
  	pgdat_resize_unlock(pgdat, &flags);
  
  	/*
  	 * TODO now we have a visible range of pages which are not associated
  	 * with their zone properly. Not nice but set_pfnblock_flags_mask
  	 * expects the zone spans the pfn range. All the pages in the range
  	 * are reserved so nobody should be touching them so we should be safe
  	 */

  	memmap_init_zone(nr_pages, nid, zone_idx(zone), start_pfn,
  			MEMMAP_HOTPLUG, altmap);

  
  	set_zone_contiguous(zone);
  }
  
  /*

   * Returns a default kernel memory zone for the given pfn range.
   * If no kernel zone covers this pfn range it will automatically go
   * to the ZONE_NORMAL.
   */

  static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn,

  		unsigned long nr_pages)
  {
  	struct pglist_data *pgdat = NODE_DATA(nid);
  	int zid;
  
  	for (zid = 0; zid <= ZONE_NORMAL; zid++) {
  		struct zone *zone = &pgdat->node_zones[zid];
  
  		if (zone_intersects(zone, start_pfn, nr_pages))
  			return zone;
  	}
  
  	return &pgdat->node_zones[ZONE_NORMAL];
  }

  static inline struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn,
  		unsigned long nr_pages)

  {

  	struct zone *kernel_zone = default_kernel_zone_for_pfn(nid, start_pfn,
  			nr_pages);
  	struct zone *movable_zone = &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
  	bool in_kernel = zone_intersects(kernel_zone, start_pfn, nr_pages);
  	bool in_movable = zone_intersects(movable_zone, start_pfn, nr_pages);

  
  	/*

  	 * We inherit the existing zone in a simple case where zones do not
  	 * overlap in the given range

  	 */

  	if (in_kernel ^ in_movable)
  		return (in_kernel) ? kernel_zone : movable_zone;

  	/*
  	 * If the range doesn't belong to any zone or two zones overlap in the
  	 * given range then we use movable zone only if movable_node is
  	 * enabled because we always online to a kernel zone by default.
  	 */
  	return movable_node_enabled ? movable_zone : kernel_zone;

  }

  struct zone * zone_for_pfn_range(int online_type, int nid, unsigned start_pfn,
  		unsigned long nr_pages)

  {

  	if (online_type == MMOP_ONLINE_KERNEL)
  		return default_kernel_zone_for_pfn(nid, start_pfn, nr_pages);

  	if (online_type == MMOP_ONLINE_MOVABLE)
  		return &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];

  	return default_zone_for_pfn(nid, start_pfn, nr_pages);

  }

  int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)

  {

  	unsigned long flags;

  	unsigned long onlined_pages = 0;
  	struct zone *zone;

  	int need_zonelists_rebuild = 0;

  	int nid;
  	int ret;
  	struct memory_notify arg;

  	struct memory_block *mem;

  	mem_hotplug_begin();

  	/*
  	 * We can't use pfn_to_nid() because nid might be stored in struct page
  	 * which is not yet initialized. Instead, we find nid from memory block.
  	 */
  	mem = find_memory_block(__pfn_to_section(pfn));
  	nid = mem->nid;

  	put_device(&mem->dev);

  	/* associate pfn range with the zone */

  	zone = zone_for_pfn_range(online_type, nid, pfn, nr_pages);
  	move_pfn_range_to_zone(zone, pfn, nr_pages, NULL);

  	arg.start_pfn = pfn;
  	arg.nr_pages = nr_pages;

  	node_states_check_changes_online(nr_pages, zone, &arg);

  	ret = memory_notify(MEM_GOING_ONLINE, &arg);
  	ret = notifier_to_errno(ret);

  	if (ret)
  		goto failed_addition;

  	/*

  	 * If this zone is not populated, then it is not in zonelist.
  	 * This means the page allocator ignores this zone.
  	 * So, zonelist must be updated after online.
  	 */

  	if (!populated_zone(zone)) {

  		need_zonelists_rebuild = 1;

  		setup_zone_pageset(zone);

  	}

  	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,

  		online_pages_range);

  	if (ret) {

  		/* not a single memory resource was applicable */

  		if (need_zonelists_rebuild)
  			zone_pcp_reset(zone);

  		goto failed_addition;

  	}

  	zone->present_pages += onlined_pages;

  
  	pgdat_resize_lock(zone->zone_pgdat, &flags);

  	zone->zone_pgdat->node_present_pages += onlined_pages;

  	pgdat_resize_unlock(zone->zone_pgdat, &flags);

  	shuffle_zone(zone);

  	node_states_set_node(nid, &arg);
  	if (need_zonelists_rebuild)
  		build_all_zonelists(NULL);
  	else
  		zone_pcp_update(zone);

  	init_per_zone_wmark_min();

  	kswapd_run(nid);
  	kcompactd_run(nid);

  	vm_total_pages = nr_free_pagecache_pages();

  	writeback_set_ratelimit();

  	memory_notify(MEM_ONLINE, &arg);

  	mem_hotplug_done();

  	return 0;

  
  failed_addition:
  	pr_debug("online_pages [mem %#010llx-%#010llx] failed
  ",
  		 (unsigned long long) pfn << PAGE_SHIFT,
  		 (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
  	memory_notify(MEM_CANCEL_ONLINE, &arg);

  	remove_pfn_range_from_zone(zone, pfn, nr_pages);

  	mem_hotplug_done();

  	return ret;

  }

  #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

  static void reset_node_present_pages(pg_data_t *pgdat)
  {
  	struct zone *z;
  
  	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
  		z->present_pages = 0;
  
  	pgdat->node_present_pages = 0;
  }

  /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
  static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)

  {
  	struct pglist_data *pgdat;

  	unsigned long start_pfn = PFN_DOWN(start);

  	pgdat = NODE_DATA(nid);
  	if (!pgdat) {
  		pgdat = arch_alloc_nodedata(nid);
  		if (!pgdat)
  			return NULL;

  		pgdat->per_cpu_nodestats =
  			alloc_percpu(struct per_cpu_nodestat);

  		arch_refresh_nodedata(nid, pgdat);

  	} else {

  		int cpu;

  		/*
  		 * Reset the nr_zones, order and classzone_idx before reuse.
  		 * Note that kswapd will init kswapd_classzone_idx properly
  		 * when it starts in the near future.
  		 */

  		pgdat->nr_zones = 0;

  		pgdat->kswapd_order = 0;
  		pgdat->kswapd_classzone_idx = 0;

  		for_each_online_cpu(cpu) {
  			struct per_cpu_nodestat *p;
  
  			p = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu);
  			memset(p, 0, sizeof(*p));
  		}

  	}

  
  	/* we can use NODE_DATA(nid) from here */

  	pgdat->node_id = nid;
  	pgdat->node_start_pfn = start_pfn;

  	/* init node's zones as empty zones, we don't have any present pages.*/

  	free_area_init_core_hotplug(nid);

  	/*
  	 * The node we allocated has no zone fallback lists. For avoiding
  	 * to access not-initialized zonelist, build here.
  	 */

  	build_all_zonelists(pgdat);

  	/*

  	 * When memory is hot-added, all the memory is in offline state. So
  	 * clear all zones' present_pages because they will be updated in
  	 * online_pages() and offline_pages().
  	 */

  	reset_node_managed_pages(pgdat);

  	reset_node_present_pages(pgdat);

  	return pgdat;
  }

  static void rollback_node_hotadd(int nid)

  {

  	pg_data_t *pgdat = NODE_DATA(nid);

  	arch_refresh_nodedata(nid, NULL);

  	free_percpu(pgdat->per_cpu_nodestats);

  	arch_free_nodedata(pgdat);

  }

  /**
   * try_online_node - online a node if offlined

   * @nid: the node ID

   * @start: start addr of the node
   * @set_node_online: Whether we want to online the node

   * called by cpu_up() to online a node without onlined memory.

   *
   * Returns:
   * 1 -> a new node has been allocated
   * 0 -> the node is already online
   * -ENOMEM -> the node could not be allocated

   */

  static int __try_online_node(int nid, u64 start, bool set_node_online)

  {

  	pg_data_t *pgdat;
  	int ret = 1;

  	if (node_online(nid))
  		return 0;

  	pgdat = hotadd_new_pgdat(nid, start);

  	if (!pgdat) {

  		pr_err("Cannot online node %d due to NULL pgdat
  ", nid);

  		ret = -ENOMEM;
  		goto out;
  	}

  
  	if (set_node_online) {
  		node_set_online(nid);
  		ret = register_one_node(nid);
  		BUG_ON(ret);
  	}

  out:

  	return ret;
  }
  
  /*
   * Users of this function always want to online/register the node
   */
  int try_online_node(int nid)
  {
  	int ret;
  
  	mem_hotplug_begin();
  	ret =  __try_online_node(nid, 0, true);

  	mem_hotplug_done();

  	return ret;
  }

  static int check_hotplug_memory_range(u64 start, u64 size)
  {

  	/* memory range must be block size aligned */

  	if (!size || !IS_ALIGNED(start, memory_block_size_bytes()) ||
  	    !IS_ALIGNED(size, memory_block_size_bytes())) {

  		pr_err("Block size [%#lx] unaligned hotplug range: start %#llx, size %#llx",

  		       memory_block_size_bytes(), start, size);

  		return -EINVAL;
  	}
  
  	return 0;
  }

  static int online_memory_block(struct memory_block *mem, void *arg)
  {

  	return device_online(&mem->dev);

  }

  /*
   * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
   * and online/offline operations (triggered e.g. by sysfs).
   *
   * we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG
   */

  int __ref add_memory_resource(int nid, struct resource *res)

  {

  	struct mhp_restrictions restrictions = {};

  	u64 start, size;

  	bool new_node = false;

  	int ret;

  	start = res->start;
  	size = resource_size(res);

  	ret = check_hotplug_memory_range(start, size);
  	if (ret)
  		return ret;

  	mem_hotplug_begin();

  	/*
  	 * Add new range to memblock so that when hotadd_new_pgdat() is called
  	 * to allocate new pgdat, get_pfn_range_for_nid() will be able to find
  	 * this new range and calculate total pages correctly.  The range will
  	 * be removed at hot-remove time.
  	 */
  	memblock_add_node(start, size, nid);

  	ret = __try_online_node(nid, start, false);
  	if (ret < 0)
  		goto error;
  	new_node = ret;

  	/* call arch's memory hotadd */

  	ret = arch_add_memory(nid, start, size, &restrictions);

  	if (ret < 0)
  		goto error;

  	/* create memory block devices after memory was added */
  	ret = create_memory_block_devices(start, size);
  	if (ret) {
  		arch_remove_memory(nid, start, size, NULL);
  		goto error;
  	}

  	if (new_node) {

  		/* If sysfs file of new node can't be created, cpu on the node

  		 * can't be hot-added. There is no rollback way now.
  		 * So, check by BUG_ON() to catch it reluctantly..

  		 * We online node here. We can't roll back from here.

  		 */

  		node_set_online(nid);
  		ret = __register_one_node(nid);

  		BUG_ON(ret);
  	}

  	/* link memory sections under this node.*/

  	ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1));

  	BUG_ON(ret);

  	/* create new memmap entry */
  	firmware_map_add_hotplug(start, start + size, "System RAM");

  	/* device_online() will take the lock when calling online_pages() */
  	mem_hotplug_done();

  	/* online pages if requested */

  	if (memhp_auto_online)

  		walk_memory_blocks(start, size, NULL, online_memory_block);

  	return ret;

  error:
  	/* rollback pgdat allocation and others */

  	if (new_node)
  		rollback_node_hotadd(nid);

  	memblock_remove(start, size);

  	mem_hotplug_done();

  	return ret;
  }

  /* requires device_hotplug_lock, see add_memory_resource() */
  int __ref __add_memory(int nid, u64 start, u64 size)

  {
  	struct resource *res;
  	int ret;
  
  	res = register_memory_resource(start, size);

  	if (IS_ERR(res))
  		return PTR_ERR(res);

  	ret = add_memory_resource(nid, res);

  	if (ret < 0)
  		release_memory_resource(res);
  	return ret;
  }

  
  int add_memory(int nid, u64 start, u64 size)
  {
  	int rc;
  
  	lock_device_hotplug();
  	rc = __add_memory(nid, start, size);
  	unlock_device_hotplug();
  
  	return rc;
  }

  EXPORT_SYMBOL_GPL(add_memory);

  
  #ifdef CONFIG_MEMORY_HOTREMOVE
  /*

   * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
   * set and the size of the free page is given by page_order(). Using this,
   * the function determines if the pageblock contains only free pages.
   * Due to buddy contraints, a free page at least the size of a pageblock will
   * be located at the start of the pageblock
   */
  static inline int pageblock_free(struct page *page)
  {
  	return PageBuddy(page) && page_order(page) >= pageblock_order;
  }

  /* Return the pfn of the start of the next active pageblock after a given pfn */
  static unsigned long next_active_pageblock(unsigned long pfn)

  {

  	struct page *page = pfn_to_page(pfn);

  	/* Ensure the starting page is pageblock-aligned */

  	BUG_ON(pfn & (pageblock_nr_pages - 1));

  	/* If the entire pageblock is free, move to the end of free page */

  	if (pageblock_free(page)) {
  		int order;
  		/* be careful. we don't have locks, page_order can be changed.*/
  		order = page_order(page);
  		if ((order < MAX_ORDER) && (order >= pageblock_order))

  			return pfn + (1 << order);

  	}

  	return pfn + pageblock_nr_pages;

  }

  static bool is_pageblock_removable_nolock(unsigned long pfn)

  {

  	struct page *page = pfn_to_page(pfn);

  	struct zone *zone;

  
  	/*
  	 * We have to be careful here because we are iterating over memory
  	 * sections which are not zone aware so we might end up outside of
  	 * the zone but still within the section.
  	 * We have to take care about the node as well. If the node is offline
  	 * its NODE_DATA will be NULL - see page_zone.
  	 */
  	if (!node_online(page_to_nid(page)))
  		return false;
  
  	zone = page_zone(page);
  	pfn = page_to_pfn(page);
  	if (!zone_spans_pfn(zone, pfn))
  		return false;

  	return !has_unmovable_pages(zone, page, 0, MIGRATE_MOVABLE, SKIP_HWPOISON);

  }

  /* Checks if this range of memory is likely to be hot-removable. */

  bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)

  {

  	unsigned long end_pfn, pfn;
  
  	end_pfn = min(start_pfn + nr_pages,
  			zone_end_pfn(page_zone(pfn_to_page(start_pfn))));

  
  	/* Check the starting page of each pageblock within the range */

  	for (pfn = start_pfn; pfn < end_pfn; pfn = next_active_pageblock(pfn)) {
  		if (!is_pageblock_removable_nolock(pfn))

  			return false;

  		cond_resched();

  	}
  
  	/* All pageblocks in the memory block are likely to be hot-removable */

  	return true;

  }
  
  /*

   * Confirm all pages in a range [start, end) belong to the same zone.

   * When true, return its valid [start, end).

   */

  int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
  			 unsigned long *valid_start, unsigned long *valid_end)

  {

  	unsigned long pfn, sec_end_pfn;

  	unsigned long start, end;

  	struct zone *zone = NULL;
  	struct page *page;
  	int i;

  	for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn + 1);

  	     pfn < end_pfn;

  	     pfn = sec_end_pfn, sec_end_pfn += PAGES_PER_SECTION) {

  		/* Make sure the memory section is present first */
  		if (!present_section_nr(pfn_to_section_nr(pfn)))

  			continue;

  		for (; pfn < sec_end_pfn && pfn < end_pfn;
  		     pfn += MAX_ORDER_NR_PAGES) {
  			i = 0;
  			/* This is just a CONFIG_HOLES_IN_ZONE check.*/
  			while ((i < MAX_ORDER_NR_PAGES) &&
  				!pfn_valid_within(pfn + i))
  				i++;

  			if (i == MAX_ORDER_NR_PAGES || pfn + i >= end_pfn)

  				continue;

  			/* Check if we got outside of the zone */
  			if (zone && !zone_spans_pfn(zone, pfn + i))
  				return 0;

  			page = pfn_to_page(pfn + i);
  			if (zone && page_zone(page) != zone)
  				return 0;

  			if (!zone)
  				start = pfn + i;

  			zone = page_zone(page);

  			end = pfn + MAX_ORDER_NR_PAGES;

  		}

  	}

  	if (zone) {
  		*valid_start = start;

  		*valid_end = min(end, end_pfn);

  		return 1;

  	} else {

  		return 0;

  	}

  }
  
  /*

   * Scan pfn range [start,end) to find movable/migratable pages (LRU pages,
   * non-lru movable pages and hugepages). We scan pfn because it's much
   * easier than scanning over linked list. This function returns the pfn
   * of the first found movable page if it's found, otherwise 0.

   */

  static unsigned long scan_movable_pages(unsigned long start, unsigned long end)

  {
  	unsigned long pfn;

  	for (pfn = start; pfn < end; pfn++) {

  		struct page *page, *head;
  		unsigned long skip;
  
  		if (!pfn_valid(pfn))
  			continue;
  		page = pfn_to_page(pfn);
  		if (PageLRU(page))
  			return pfn;
  		if (__PageMovable(page))
  			return pfn;
  
  		if (!PageHuge(page))
  			continue;
  		head = compound_head(page);

  		if (page_huge_active(head))

  			return pfn;

  		skip = compound_nr(head) - (page - head);

  		pfn += skip - 1;

  	}
  	return 0;
  }

  static struct page *new_node_page(struct page *page, unsigned long private)

  {

  	int nid = page_to_nid(page);

  	nodemask_t nmask = node_states[N_MEMORY];

  
  	/*
  	 * try to allocate from a different node but reuse this node if there
  	 * are no other online nodes to be used (e.g. we are offlining a part
  	 * of the only existing node)
  	 */
  	node_clear(nid, nmask);
  	if (nodes_empty(nmask))
  		node_set(nid, nmask);

  	return new_page_nodemask(page, nid, &nmask);

  }

  static int
  do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn;
  	struct page *page;

  	int ret = 0;
  	LIST_HEAD(source);

  	for (pfn = start_pfn; pfn < end_pfn; pfn++) {

  		if (!pfn_valid(pfn))
  			continue;
  		page = pfn_to_page(pfn);

  
  		if (PageHuge(page)) {
  			struct page *head = compound_head(page);

  			pfn = page_to_pfn(head) + compound_nr(head) - 1;

  			isolate_huge_page(head, &source);

  			continue;

  		} else if (PageTransHuge(page))

  			pfn = page_to_pfn(compound_head(page))
  				+ hpage_nr_pages(page) - 1;

  		/*
  		 * HWPoison pages have elevated reference counts so the migration would
  		 * fail on them. It also doesn't make any sense to migrate them in the
  		 * first place. Still try to unmap such a page in case it is still mapped
  		 * (e.g. current hwpoison implementation doesn't unmap KSM pages but keep
  		 * the unmap as the catch all safety net).
  		 */
  		if (PageHWPoison(page)) {
  			if (WARN_ON(PageLRU(page)))
  				isolate_lru_page(page);
  			if (page_mapped(page))
  				try_to_unmap(page, TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS);
  			continue;
  		}

  		if (!get_page_unless_zero(page))

  			continue;
  		/*

  		 * We can skip free pages. And we can deal with pages on
  		 * LRU and non-lru movable pages.

  		 */

  		if (PageLRU(page))
  			ret = isolate_lru_page(page);
  		else
  			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);

  		if (!ret) { /* Success */

  			list_add_tail(&page->lru, &source);

  			if (!__PageMovable(page))
  				inc_node_page_state(page, NR_ISOLATED_ANON +
  						    page_is_file_cache(page));

  		} else {

  			pr_warn("failed to isolate pfn %lx
  ", pfn);

  			dump_page(page, "isolation failed");

  		}

  		put_page(page);

  	}

  	if (!list_empty(&source)) {

  		/* Allocate a new page from the nearest neighbor node */
  		ret = migrate_pages(&source, new_node_page, NULL, 0,

  					MIGRATE_SYNC, MR_MEMORY_HOTPLUG);

  		if (ret) {
  			list_for_each_entry(page, &source, lru) {
  				pr_warn("migrating pfn %lx failed ret:%d ",
  				       page_to_pfn(page), ret);
  				dump_page(page, "migration failure");
  			}

  			putback_movable_pages(&source);

  		}

  	}

  	return ret;
  }
  
  /*
   * remove from free_area[] and mark all as Reserved.
   */
  static int
  offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
  			void *data)
  {

  	unsigned long *offlined_pages = (unsigned long *)data;

  	*offlined_pages += __offline_isolated_pages(start, start + nr_pages);
  	return 0;

  }
  
  /*
   * Check all pages in range, recoreded as memory resource, are isolated.
   */
  static int
  check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
  			void *data)
  {

  	return test_pages_isolated(start_pfn, start_pfn + nr_pages, true);

  }

  static int __init cmdline_parse_movable_node(char *p)
  {

  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP

  	movable_node_enabled = true;

  #else
  	pr_warn("movable_node parameter depends on CONFIG_HAVE_MEMBLOCK_NODE_MAP to work properly
  ");
  #endif

  	return 0;
  }
  early_param("movable_node", cmdline_parse_movable_node);

  /* check which state of node_states will be changed when offline memory */
  static void node_states_check_changes_offline(unsigned long nr_pages,
  		struct zone *zone, struct memory_notify *arg)
  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	unsigned long present_pages = 0;

  	enum zone_type zt;

  	arg->status_change_nid = NUMA_NO_NODE;
  	arg->status_change_nid_normal = NUMA_NO_NODE;
  	arg->status_change_nid_high = NUMA_NO_NODE;

  
  	/*

  	 * Check whether node_states[N_NORMAL_MEMORY] will be changed.
  	 * If the memory to be offline is within the range
  	 * [0..ZONE_NORMAL], and it is the last present memory there,
  	 * the zones in that range will become empty after the offlining,
  	 * thus we can determine that we need to clear the node from
  	 * node_states[N_NORMAL_MEMORY].

  	 */

  	for (zt = 0; zt <= ZONE_NORMAL; zt++)

  		present_pages += pgdat->node_zones[zt].present_pages;

  	if (zone_idx(zone) <= ZONE_NORMAL && nr_pages >= present_pages)

  		arg->status_change_nid_normal = zone_to_nid(zone);

  #ifdef CONFIG_HIGHMEM
  	/*

  	 * node_states[N_HIGH_MEMORY] contains nodes which
  	 * have normal memory or high memory.
  	 * Here we add the present_pages belonging to ZONE_HIGHMEM.
  	 * If the zone is within the range of [0..ZONE_HIGHMEM), and
  	 * we determine that the zones in that range become empty,
  	 * we need to clear the node for N_HIGH_MEMORY.

  	 */

  	present_pages += pgdat->node_zones[ZONE_HIGHMEM].present_pages;
  	if (zone_idx(zone) <= ZONE_HIGHMEM && nr_pages >= present_pages)

  		arg->status_change_nid_high = zone_to_nid(zone);

  #endif

  	/*

  	 * We have accounted the pages from [0..ZONE_NORMAL), and
  	 * in case of CONFIG_HIGHMEM the pages from ZONE_HIGHMEM
  	 * as well.
  	 * Here we count the possible pages from ZONE_MOVABLE.
  	 * If after having accounted all the pages, we see that the nr_pages
  	 * to be offlined is over or equal to the accounted pages,
  	 * we know that the node will become empty, and so, we can clear
  	 * it for N_MEMORY as well.

  	 */

  	present_pages += pgdat->node_zones[ZONE_MOVABLE].present_pages;

  	if (nr_pages >= present_pages)
  		arg->status_change_nid = zone_to_nid(zone);

  }
  
  static void node_states_clear_node(int node, struct memory_notify *arg)
  {
  	if (arg->status_change_nid_normal >= 0)
  		node_clear_state(node, N_NORMAL_MEMORY);

  	if (arg->status_change_nid_high >= 0)

  		node_clear_state(node, N_HIGH_MEMORY);

  	if (arg->status_change_nid >= 0)

  		node_clear_state(node, N_MEMORY);

  }

  static int __ref __offline_pages(unsigned long start_pfn,

  		  unsigned long end_pfn)

  {

  	unsigned long pfn, nr_pages;

  	unsigned long offlined_pages = 0;

  	int ret, node, nr_isolate_pageblock;

  	unsigned long flags;

  	unsigned long valid_start, valid_end;

  	struct zone *zone;

  	struct memory_notify arg;

  	char *reason;

  	mem_hotplug_begin();

  	/* This makes hotplug much easier...and readable.
  	   we assume this for now. .*/

  	if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start,
  				  &valid_end)) {

  		ret = -EINVAL;
  		reason = "multizone range";
  		goto failed_removal;

  	}

  	zone = page_zone(pfn_to_page(valid_start));

  	node = zone_to_nid(zone);
  	nr_pages = end_pfn - start_pfn;

  	/* set above range as isolated */

  	ret = start_isolate_page_range(start_pfn, end_pfn,

  				       MIGRATE_MOVABLE,
  				       SKIP_HWPOISON | REPORT_FAILURE);

  	if (ret < 0) {

  		reason = "failure to isolate range";
  		goto failed_removal;

  	}

  	nr_isolate_pageblock = ret;

  
  	arg.start_pfn = start_pfn;
  	arg.nr_pages = nr_pages;

  	node_states_check_changes_offline(nr_pages, zone, &arg);

  
  	ret = memory_notify(MEM_GOING_OFFLINE, &arg);
  	ret = notifier_to_errno(ret);

  	if (ret) {
  		reason = "notifier failure";
  		goto failed_removal_isolated;
  	}

  	do {
  		for (pfn = start_pfn; pfn;) {
  			if (signal_pending(current)) {
  				ret = -EINTR;
  				reason = "signal backoff";
  				goto failed_removal_isolated;
  			}