/*
   *  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/bootmem.h>

  #include <linux/compaction.h>

  
  #include <asm/tlbflush.h>

  #include "internal.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);
  
  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();

  }

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

  	struct resource *res, *conflict;

  	res = kzalloc(sizeof(struct resource), GFP_KERNEL);

  	if (!res)
  		return ERR_PTR(-ENOMEM);

  
  	res->name = "System RAM";
  	res->start = start;
  	res->end = start + size - 1;

  	res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;

  	conflict =  request_resource_conflict(&iomem_resource, res);
  	if (conflict) {
  		if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
  			pr_debug("Device unaddressable memory block "
  				 "memory hotplug at %#010llx !
  ",
  				 (unsigned long long)start);
  		}

  		pr_debug("System RAM resource %pR cannot be added
  ", res);

  		kfree(res);

  		return ERR_PTR(-EEXIST);

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

  #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 *usemap, mapsize, section_nr, i;
  	struct mem_section *ms;
  	struct page *page, *memmap;

  	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);
  
  	usemap = __nr_to_section(section_nr)->pageblock_flags;
  	page = virt_to_page(usemap);
  
  	mapsize = PAGE_ALIGN(usemap_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 *usemap, mapsize, section_nr, i;
  	struct mem_section *ms;
  	struct page *page, *memmap;
  
  	if (!pfn_valid(start_pfn))
  		return;
  
  	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);
  
  	usemap = __nr_to_section(section_nr)->pageblock_flags;
  	page = virt_to_page(usemap);
  
  	mapsize = PAGE_ALIGN(usemap_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 __meminit __add_section(int nid, unsigned long phys_start_pfn,
  		bool want_memblock)

  {

  	int ret;

  	int i;

  	if (pfn_valid(phys_start_pfn))
  		return -EEXIST;

  	ret = sparse_add_one_section(NODE_DATA(nid), phys_start_pfn);

  	if (ret < 0)
  		return ret;

  	/*
  	 * Make all the pages reserved so that nobody will stumble over half
  	 * initialized state.
  	 * FIXME: We also have to associate it with a node because pfn_to_node
  	 * relies on having page with the proper node.
  	 */
  	for (i = 0; i < PAGES_PER_SECTION; i++) {
  		unsigned long pfn = phys_start_pfn + i;
  		struct page *page;
  		if (!pfn_valid(pfn))
  			continue;

  		page = pfn_to_page(pfn);
  		set_page_node(page, nid);
  		SetPageReserved(page);
  	}

  	if (!want_memblock)
  		return 0;

  	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));

  }

  /*
   * 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 phys_start_pfn,

  			unsigned long nr_pages, bool want_memblock)

  {
  	unsigned long i;
  	int err = 0;
  	int start_sec, end_sec;

  	struct vmem_altmap *altmap;

  	/* during initialize mem_map, align hot-added range to section */
  	start_sec = pfn_to_section_nr(phys_start_pfn);
  	end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);

  	altmap = to_vmem_altmap((unsigned long) pfn_to_page(phys_start_pfn));
  	if (altmap) {
  		/*
  		 * Validate altmap is within bounds of the total request
  		 */
  		if (altmap->base_pfn != phys_start_pfn
  				|| vmem_altmap_offset(altmap) > nr_pages) {
  			pr_warn_once("memory add fail, invalid altmap
  ");

  			err = -EINVAL;
  			goto out;

  		}
  		altmap->alloc = 0;
  	}

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

  		err = __add_section(nid, section_nr_to_pfn(i), want_memblock);

  
  		/*
  		 * EEXIST is finally dealt with by ioresource collision
  		 * check. see add_memory() => register_memory_resource()
  		 * Warning will be printed if there is collision.
  		 */
  		if (err && (err != -EEXIST))
  			break;
  		err = 0;

  		cond_resched();

  	}

  	vmemmap_populate_print_last();

  out:

  	return err;
  }
  EXPORT_SYMBOL_GPL(__add_pages);
  
  #ifdef CONFIG_MEMORY_HOTREMOVE

  /* 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)
  {
  	struct mem_section *ms;
  
  	for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SECTION) {
  		ms = __pfn_to_section(start_pfn);
  
  		if (unlikely(!valid_section(ms)))
  			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)
  {
  	struct mem_section *ms;
  	unsigned long pfn;
  
  	/* pfn is the end pfn of a memory section. */
  	pfn = end_pfn - 1;
  	for (; pfn >= start_pfn; pfn -= PAGES_PER_SECTION) {
  		ms = __pfn_to_section(pfn);
  
  		if (unlikely(!valid_section(ms)))
  			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;
  	struct mem_section *ms;
  	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_SECTION) {
  		ms = __pfn_to_section(pfn);
  
  		if (unlikely(!valid_section(ms)))
  			continue;
  
  		if (page_zone(pfn_to_page(pfn)) != zone)
  			continue;
  
  		 /* If the section is current section, it continues the loop */
  		if (start_pfn == 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 shrink_pgdat_span(struct pglist_data *pgdat,
  			      unsigned long start_pfn, unsigned long end_pfn)
  {

  	unsigned long pgdat_start_pfn = pgdat->node_start_pfn;
  	unsigned long p = pgdat_end_pfn(pgdat); /* pgdat_end_pfn namespace clash */
  	unsigned long pgdat_end_pfn = p;

  	unsigned long pfn;
  	struct mem_section *ms;
  	int nid = pgdat->node_id;
  
  	if (pgdat_start_pfn == start_pfn) {
  		/*
  		 * If the section is smallest section in the pgdat, it need
  		 * shrink pgdat->node_start_pfn and pgdat->node_spanned_pages.
  		 * In this case, we find second smallest valid mem_section
  		 * for shrinking zone.
  		 */
  		pfn = find_smallest_section_pfn(nid, NULL, end_pfn,
  						pgdat_end_pfn);
  		if (pfn) {
  			pgdat->node_start_pfn = pfn;
  			pgdat->node_spanned_pages = pgdat_end_pfn - pfn;
  		}
  	} else if (pgdat_end_pfn == end_pfn) {
  		/*
  		 * If the section is biggest section in the pgdat, it need
  		 * shrink pgdat->node_spanned_pages.
  		 * In this case, we find second biggest valid mem_section for
  		 * shrinking zone.
  		 */
  		pfn = find_biggest_section_pfn(nid, NULL, pgdat_start_pfn,
  					       start_pfn);
  		if (pfn)
  			pgdat->node_spanned_pages = pfn - pgdat_start_pfn + 1;
  	}
  
  	/*
  	 * If the section is not biggest or smallest mem_section in the pgdat,
  	 * it only creates a hole in the pgdat. So in this case, we need not
  	 * change the pgdat.
  	 * But perhaps, the pgdat has only hole data. Thus it check the pgdat
  	 * has only hole or not.
  	 */
  	pfn = pgdat_start_pfn;
  	for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SECTION) {
  		ms = __pfn_to_section(pfn);
  
  		if (unlikely(!valid_section(ms)))
  			continue;
  
  		if (pfn_to_nid(pfn) != nid)
  			continue;
  
  		 /* If the section is current section, it continues the loop */
  		if (start_pfn == pfn)
  			continue;
  
  		/* If we find valid section, we have nothing to do */
  		return;
  	}
  
  	/* The pgdat has no valid section */
  	pgdat->node_start_pfn = 0;
  	pgdat->node_spanned_pages = 0;
  }
  
  static void __remove_zone(struct zone *zone, unsigned long start_pfn)
  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	int nr_pages = PAGES_PER_SECTION;

  	unsigned long flags;

  	pgdat_resize_lock(zone->zone_pgdat, &flags);
  	shrink_zone_span(zone, start_pfn, start_pfn + nr_pages);
  	shrink_pgdat_span(pgdat, start_pfn, start_pfn + nr_pages);
  	pgdat_resize_unlock(zone->zone_pgdat, &flags);
  }

  static int __remove_section(struct zone *zone, struct mem_section *ms,
  		unsigned long map_offset)

  {

  	unsigned long start_pfn;
  	int scn_nr;

  	int ret = -EINVAL;
  
  	if (!valid_section(ms))
  		return ret;
  
  	ret = unregister_memory_section(ms);
  	if (ret)
  		return ret;

  	scn_nr = __section_nr(ms);

  	start_pfn = section_nr_to_pfn((unsigned long)scn_nr);

  	__remove_zone(zone, start_pfn);

  	sparse_remove_one_section(zone, ms, map_offset);

  	return 0;
  }

  /**
   * __remove_pages() - remove sections of pages from a zone
   * @zone: zone from which pages need to be removed
   * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
   * @nr_pages: number of pages to remove (must be multiple of section size)
   *
   * 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().
   */
  int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
  		 unsigned long nr_pages)
  {

  	unsigned long i;

  	unsigned long map_offset = 0;
  	int sections_to_remove, ret = 0;
  
  	/* In the ZONE_DEVICE case device driver owns the memory region */
  	if (is_dev_zone(zone)) {
  		struct page *page = pfn_to_page(phys_start_pfn);
  		struct vmem_altmap *altmap;
  
  		altmap = to_vmem_altmap((unsigned long) page);
  		if (altmap)
  			map_offset = vmem_altmap_offset(altmap);
  	} else {
  		resource_size_t start, size;
  
  		start = phys_start_pfn << PAGE_SHIFT;
  		size = nr_pages * PAGE_SIZE;
  
  		ret = release_mem_region_adjustable(&iomem_resource, start,
  					size);
  		if (ret) {
  			resource_size_t endres = start + size - 1;
  
  			pr_warn("Unable to release resource <%pa-%pa> (%d)
  ",
  					&start, &endres, ret);
  		}
  	}

  	clear_zone_contiguous(zone);

  	/*
  	 * We can only remove entire sections
  	 */
  	BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
  	BUG_ON(nr_pages % PAGES_PER_SECTION);

  	sections_to_remove = nr_pages / PAGES_PER_SECTION;
  	for (i = 0; i < sections_to_remove; i++) {
  		unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;

  
  		ret = __remove_section(zone, __pfn_to_section(pfn), map_offset);
  		map_offset = 0;

  		if (ret)
  			break;
  	}

  
  	set_zone_contiguous(zone);

  	return ret;
  }

  #endif /* CONFIG_MEMORY_HOTREMOVE */

  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)
  {
  	__online_page_set_limits(page);
  	__online_page_increment_counters(page);
  	__online_page_free(page);
  }

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

  {
  	unsigned long i;

  	unsigned long onlined_pages = *(unsigned long *)arg;
  	struct page *page;

  	if (PageReserved(pfn_to_page(start_pfn)))
  		for (i = 0; i < nr_pages; i++) {
  			page = pfn_to_page(start_pfn + i);

  			(*online_page_callback)(page);

  			onlined_pages++;
  		}

  
  	online_mem_sections(start_pfn, start_pfn + nr_pages);

  	*(unsigned long *)arg = onlined_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);
  	enum zone_type zone_last = ZONE_NORMAL;
  
  	/*

  	 * If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
  	 * contains nodes which have zones of 0...ZONE_NORMAL,
  	 * set zone_last to ZONE_NORMAL.

  	 *

  	 * If we don't have HIGHMEM nor movable node,
  	 * node_states[N_NORMAL_MEMORY] contains nodes which have zones of
  	 * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.

  	 */

  	if (N_MEMORY == N_NORMAL_MEMORY)

  		zone_last = ZONE_MOVABLE;
  
  	/*
  	 * if the memory to be online is in a zone of 0...zone_last, and
  	 * the zones of 0...zone_last don't have memory before online, we will
  	 * need to set the node to node_states[N_NORMAL_MEMORY] after
  	 * the memory is online.
  	 */
  	if (zone_idx(zone) <= zone_last && !node_state(nid, N_NORMAL_MEMORY))
  		arg->status_change_nid_normal = nid;
  	else
  		arg->status_change_nid_normal = -1;

  #ifdef CONFIG_HIGHMEM
  	/*
  	 * If we have movable node, node_states[N_HIGH_MEMORY]
  	 * contains nodes which have zones of 0...ZONE_HIGHMEM,
  	 * set zone_last to ZONE_HIGHMEM.
  	 *
  	 * If we don't have movable node, node_states[N_NORMAL_MEMORY]
  	 * contains nodes which have zones of 0...ZONE_MOVABLE,
  	 * set zone_last to ZONE_MOVABLE.
  	 */
  	zone_last = ZONE_HIGHMEM;
  	if (N_MEMORY == N_HIGH_MEMORY)
  		zone_last = ZONE_MOVABLE;
  
  	if (zone_idx(zone) <= zone_last && !node_state(nid, N_HIGH_MEMORY))
  		arg->status_change_nid_high = nid;
  	else
  		arg->status_change_nid_high = -1;
  #else
  	arg->status_change_nid_high = arg->status_change_nid_normal;
  #endif

  	/*
  	 * if the node don't have memory befor online, we will need to

  	 * set the node to node_states[N_MEMORY] after the memory

  	 * is online.
  	 */

  	if (!node_state(nid, N_MEMORY))

  		arg->status_change_nid = nid;
  	else
  		arg->status_change_nid = -1;
  }
  
  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);
  
  	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;
  }

  void __ref move_pfn_range_to_zone(struct zone *zone,

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

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

  	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);
  	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);
  
  	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);

  }
  
  /*
   * Associates the given pfn range with the given node and the zone appropriate
   * for the given online type.
   */
  static struct zone * __meminit move_pfn_range(int online_type, int nid,
  		unsigned long start_pfn, unsigned long nr_pages)
  {
  	struct zone *zone;
  
  	zone = zone_for_pfn_range(online_type, nid, start_pfn, nr_pages);

  	move_pfn_range_to_zone(zone, start_pfn, nr_pages);
  	return zone;

  }

  /* Must be protected by mem_hotplug_begin() or a device_lock */

  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;

  	nid = pfn_to_nid(pfn);

  	/* associate pfn range with the zone */
  	zone = move_pfn_range(online_type, nid, pfn, nr_pages);

  	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) {

  		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);

  	if (onlined_pages) {

  		node_states_set_node(nid, &arg);

  		if (need_zonelists_rebuild)

  			build_all_zonelists(NULL);

  		else
  			zone_pcp_update(zone);
  	}

  	init_per_zone_wmark_min();

  	if (onlined_pages) {

  		kswapd_run(nid);

  		kcompactd_run(nid);
  	}

  	vm_total_pages = nr_free_pagecache_pages();

  	writeback_set_ratelimit();

  
  	if (onlined_pages)
  		memory_notify(MEM_ONLINE, &arg);

  	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);
  	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 zones_size[MAX_NR_ZONES] = {0};
  	unsigned long zholes_size[MAX_NR_ZONES] = {0};

  	unsigned long start_pfn = PFN_DOWN(start);

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

  		arch_refresh_nodedata(nid, pgdat);

  	} else {

  		/*
  		 * 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;

  	}

  
  	/* we can use NODE_DATA(nid) from here */
  
  	/* init node's zones as empty zones, we don't have any present pages.*/

  	free_area_init_node(nid, zones_size, start_pfn, zholes_size);

  	pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat);

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

  	build_all_zonelists(pgdat);

  	/*
  	 * zone->managed_pages is set to an approximate value in
  	 * free_area_init_core(), which will cause
  	 * /sys/device/system/node/nodeX/meminfo has wrong data.
  	 * So reset it to 0 before any memory is onlined.
  	 */
  	reset_node_managed_pages(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_present_pages(pgdat);

  	return pgdat;
  }
  
  static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
  {
  	arch_refresh_nodedata(nid, NULL);

  	free_percpu(pgdat->per_cpu_nodestats);

  	arch_free_nodedata(pgdat);
  	return;
  }

  /**
   * try_online_node - online a node if offlined
   *

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

  int try_online_node(int nid)

  {
  	pg_data_t	*pgdat;
  	int	ret;

  	if (node_online(nid))
  		return 0;

  	mem_hotplug_begin();

  	pgdat = hotadd_new_pgdat(nid, 0);

  	if (!pgdat) {

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

  		ret = -ENOMEM;
  		goto out;
  	}
  	node_set_online(nid);
  	ret = register_one_node(nid);
  	BUG_ON(ret);

  out:

  	mem_hotplug_done();

  	return ret;
  }

  static int check_hotplug_memory_range(u64 start, u64 size)
  {

  	u64 start_pfn = PFN_DOWN(start);

  	u64 nr_pages = size >> PAGE_SHIFT;
  
  	/* Memory range must be aligned with section */
  	if ((start_pfn & ~PAGE_SECTION_MASK) ||
  	    (nr_pages % PAGES_PER_SECTION) || (!nr_pages)) {
  		pr_err("Section-unaligned hotplug range: start 0x%llx, size 0x%llx
  ",
  				(unsigned long long)start,
  				(unsigned long long)size);
  		return -EINVAL;
  	}
  
  	return 0;
  }

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

  	return device_online(&mem->dev);

  }

  /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */

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

  {

  	u64 start, size;

  	pg_data_t *pgdat = NULL;

  	bool new_pgdat;
  	bool new_node;

  	int ret;

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

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

  	{	/* Stupid hack to suppress address-never-null warning */
  		void *p = NODE_DATA(nid);
  		new_pgdat = !p;
  	}

  	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);

  	new_node = !node_online(nid);
  	if (new_node) {

  		pgdat = hotadd_new_pgdat(nid, start);

  		ret = -ENOMEM;

  		if (!pgdat)

  			goto error;

  	}

  	/* call arch's memory hotadd */

  	ret = arch_add_memory(nid, start, size, true);

  	if (ret < 0)
  		goto error;

  	/* we online node here. we can't roll back from here. */

  	node_set_online(nid);

  	if (new_node) {

  		unsigned long start_pfn = start >> PAGE_SHIFT;
  		unsigned long nr_pages = size >> PAGE_SHIFT;
  
  		ret = __register_one_node(nid);
  		if (ret)
  			goto register_fail;
  
  		/*
  		 * link memory sections under this node. This is already
  		 * done when creatig memory section in register_new_memory
  		 * but that depends to have the node registered so offline
  		 * nodes have to go through register_node.
  		 * TODO clean up this mess.
  		 */
  		ret = link_mem_sections(nid, start_pfn, nr_pages);
  register_fail:

  		/*
  		 * If sysfs file of new node can't create, cpu on the node
  		 * can't be hot-added. There is no rollback way now.
  		 * So, check by BUG_ON() to catch it reluctantly..
  		 */
  		BUG_ON(ret);
  	}

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

  	/* online pages if requested */
  	if (online)
  		walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1),
  				  NULL, online_memory_block);

  	goto out;

  error:
  	/* rollback pgdat allocation and others */

  	if (new_pgdat && pgdat)

  		rollback_node_hotadd(nid, pgdat);

  	memblock_remove(start, size);

  out:

  	mem_hotplug_done();

  	return ret;
  }

  EXPORT_SYMBOL_GPL(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, memhp_auto_online);

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

  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 start of the next active pageblock after a given page */
  static struct page *next_active_pageblock(struct page *page)
  {

  	/* Ensure the starting page is pageblock-aligned */
  	BUG_ON(page_to_pfn(page) & (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 page + (1 << order);
  	}

  	return page + pageblock_nr_pages;

  }
  
  /* 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)

  {

  	struct page *page = pfn_to_page(start_pfn);
  	struct page *end_page = page + nr_pages;
  
  	/* Check the starting page of each pageblock within the range */
  	for (; page < end_page; page = next_active_pageblock(page)) {

  		if (!is_pageblock_removable_nolock(page))

  			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;
  			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;
  	struct page *page;
  	for (pfn = start; pfn < end; pfn++) {
  		if (pfn_valid(pfn)) {
  			page = pfn_to_page(pfn);
  			if (PageLRU(page))
  				return pfn;

  			if (__PageMovable(page))
  				return pfn;

  			if (PageHuge(page)) {

  				if (page_huge_active(page))

  					return pfn;
  				else
  					pfn = round_up(pfn + 1,
  						1 << compound_order(page)) - 1;
  			}

  		}
  	}
  	return 0;
  }

  static struct page *new_node_page(struct page *page, unsigned long private,
  		int **result)
  {

  	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);

  }

  #define NR_OFFLINE_AT_ONCE_PAGES	(256)
  static int
  do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn;
  	struct page *page;
  	int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
  	int not_managed = 0;
  	int ret = 0;
  	LIST_HEAD(source);
  
  	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; 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) + (1<<compound_order(head)) - 1;
  			if (compound_order(head) > PFN_SECTION_SHIFT) {
  				ret = -EBUSY;
  				break;
  			}
  			if (isolate_huge_page(page, &source))
  				move_pages -= 1 << compound_order(head);
  			continue;

  		} else if (thp_migration_supported() && PageTransHuge(page))
  			pfn = page_to_pfn(compound_head(page))
  				+ hpage_nr_pages(page) - 1;

  		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 */

  			put_page(page);

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

  			move_pages--;

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

  		} else {

  #ifdef CONFIG_DEBUG_VM

  			pr_alert("failed to isolate pfn %lx
  ", pfn);
  			dump_page(page, "isolation failed");

  #endif

  			put_page(page);

  			/* Because we don't have big zone->lock. we should

  			   check this again here. */
  			if (page_count(page)) {
  				not_managed++;

  				ret = -EBUSY;

  				break;
  			}

  		}
  	}

  	if (!list_empty(&source)) {
  		if (not_managed) {

  			putback_movable_pages(&source);

  			goto out;
  		}

  		/* 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)

  			putback_movable_pages(&source);

  	}

  out:
  	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)
  {
  	__offline_isolated_pages(start, start + nr_pages);
  	return 0;
  }
  
  static void
  offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
  {

  	walk_system_ram_range(start_pfn, end_pfn - start_pfn, NULL,

  				offline_isolated_pages_cb);
  }
  
  /*
   * 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)
  {
  	int ret;
  	long offlined = *(long *)data;

  	ret = test_pages_isolated(start_pfn, start_pfn + nr_pages, true);

  	offlined = nr_pages;
  	if (!ret)
  		*(long *)data += offlined;
  	return ret;
  }
  
  static long
  check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
  {
  	long offlined = 0;
  	int ret;

  	ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, &offlined,

  			check_pages_isolated_cb);
  	if (ret < 0)
  		offlined = (long)ret;
  	return offlined;
  }

  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, zone_last = ZONE_NORMAL;
  
  	/*

  	 * If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
  	 * contains nodes which have zones of 0...ZONE_NORMAL,
  	 * set zone_last to ZONE_NORMAL.

  	 *

  	 * If we don't have HIGHMEM nor movable node,
  	 * node_states[N_NORMAL_MEMORY] contains nodes which have zones of
  	 * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.

  	 */

  	if (N_MEMORY == N_NORMAL_MEMORY)

  		zone_last = ZONE_MOVABLE;
  
  	/*
  	 * check whether node_states[N_NORMAL_MEMORY] will be changed.
  	 * If the memory to be offline is in a zone of 0...zone_last,
  	 * and it is the last present memory, 0...zone_last will
  	 * become empty after offline , thus we can determind we will
  	 * need to clear the node from node_states[N_NORMAL_MEMORY].
  	 */
  	for (zt = 0; zt <= zone_last; zt++)
  		present_pages += pgdat->node_zones[zt].present_pages;
  	if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
  		arg->status_change_nid_normal = zone_to_nid(zone);
  	else
  		arg->status_change_nid_normal = -1;

  #ifdef CONFIG_HIGHMEM
  	/*
  	 * If we have movable node, node_states[N_HIGH_MEMORY]
  	 * contains nodes which have zones of 0...ZONE_HIGHMEM,
  	 * set zone_last to ZONE_HIGHMEM.
  	 *
  	 * If we don't have movable node, node_states[N_NORMAL_MEMORY]
  	 * contains nodes which have zones of 0...ZONE_MOVABLE,
  	 * set zone_last to ZONE_MOVABLE.
  	 */
  	zone_last = ZONE_HIGHMEM;
  	if (N_MEMORY == N_HIGH_MEMORY)
  		zone_last = ZONE_MOVABLE;
  
  	for (; zt <= zone_last; zt++)
  		present_pages += pgdat->node_zones[zt].present_pages;
  	if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
  		arg->status_change_nid_high = zone_to_nid(zone);
  	else
  		arg->status_change_nid_high = -1;
  #else
  	arg->status_change_nid_high = arg->status_change_nid_normal;
  #endif

  	/*
  	 * node_states[N_HIGH_MEMORY] contains nodes which have 0...ZONE_MOVABLE
  	 */
  	zone_last = ZONE_MOVABLE;
  
  	/*
  	 * check whether node_states[N_HIGH_MEMORY] will be changed
  	 * If we try to offline the last present @nr_pages from the node,
  	 * we can determind we will need to clear the node from
  	 * node_states[N_HIGH_MEMORY].
  	 */
  	for (; zt <= zone_last; zt++)
  		present_pages += pgdat->node_zones[zt].present_pages;
  	if (nr_pages >= present_pages)
  		arg->status_change_nid = zone_to_nid(zone);
  	else
  		arg->status_change_nid = -1;
  }
  
  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 ((N_MEMORY != N_NORMAL_MEMORY) &&
  	    (arg->status_change_nid_high >= 0))

  		node_clear_state(node, N_HIGH_MEMORY);

  
  	if ((N_MEMORY != N_HIGH_MEMORY) &&
  	    (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 timeout)
  {
  	unsigned long pfn, nr_pages, expire;
  	long offlined_pages;

  	int ret, drain, retry_max, node;

  	unsigned long flags;

  	unsigned long valid_start, valid_end;

  	struct zone *zone;

  	struct memory_notify arg;

  	/* at least, alignment against pageblock is necessary */
  	if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
  		return -EINVAL;
  	if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
  		return -EINVAL;
  	/* 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))

  		return -EINVAL;

  	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, true);

  	if (ret)

  		return 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)
  		goto failed_removal;

  	pfn = start_pfn;
  	expire = jiffies + timeout;
  	drain = 0;
  	retry_max = 5;
  repeat:
  	/* start memory hot removal */
  	ret = -EAGAIN;
  	if (time_after(jiffies, expire))
  		goto failed_removal;
  	ret = -EINTR;
  	if (signal_pending(current))
  		goto failed_removal;
  	ret = 0;
  	if (drain) {

  		lru_add_drain_all_cpuslocked();

  		cond_resched();

  		drain_all_pages(zone);

  	}

  	pfn = scan_movable_pages(start_pfn, end_pfn);
  	if (pfn) { /* We have movable pages */

  		ret = do_migrate_range(pfn, end_pfn);
  		if (!ret) {
  			drain = 1;
  			goto repeat;
  		} else {
  			if (ret < 0)
  				if (--retry_max == 0)
  					goto failed_removal;
  			yield();
  			drain = 1;
  			goto repeat;
  		}
  	}

  	/* drain all zone's lru pagevec, this is asynchronous... */

  	lru_add_drain_all_cpuslocked();

  	yield();

  	/* drain pcp pages, this is synchronous. */

  	drain_all_pages(zone);

  	/*
  	 * dissolve free hugepages in the memory block before doing offlining
  	 * actually in order to make hugetlbfs's object counting consistent.
  	 */

  	ret = dissolve_free_huge_pages(start_pfn, end_pfn);
  	if (ret)
  		goto failed_removal;

  	/* check again */
  	offlined_pages = check_pages_isolated(start_pfn, end_pfn);
  	if (offlined_pages < 0) {
  		ret = -EBUSY;
  		goto failed_removal;
  	}

  	pr_info("Offlined Pages %ld
  ", offlined_pages);

  	/* Ok, all of our target is isolated.

  	   We cannot do rollback at this point. */
  	offline_isolated_pages(start_pfn, end_pfn);

  	/* reset pagetype flags and makes migrate type to be MOVABLE */

  	undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);

  	/* removal success */

  	adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages);

  	zone->present_pages -= offlined_pages;

  
  	pgdat_resize_lock(zone->zone_pgdat, &flags);

  	zone->zone_pgdat->node_present_pages -= offlined_pages;

  	pgdat_resize_unlock(zone->zone_pgdat, &flags);

  	init_per_zone_wmark_min();

  	if (!populated_zone(zone)) {

  		zone_pcp_reset(zone);

  		build_all_zonelists(NULL);

  	} else
  		zone_pcp_update(zone);

  	node_states_clear_node(node, &arg);

  	if (arg.status_change_nid >= 0) {

  		kswapd_stop(node);

  		kcompactd_stop(node);
  	}

  	vm_total_pages = nr_free_pagecache_pages();
  	writeback_set_ratelimit();

  
  	memory_notify(MEM_OFFLINE, &arg);

  	return 0;
  
  failed_removal:

  	pr_debug("memory offlining [mem %#010llx-%#010llx] failed
  ",
  		 (unsigned long long) start_pfn << PAGE_SHIFT,
  		 ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);

  	memory_notify(MEM_CANCEL_OFFLINE, &arg);

  	/* pushback to free area */

  	undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);

  	return ret;
  }

  /* Must be protected by mem_hotplug_begin() or a device_lock */

  int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
  {
  	return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ);
  }

  #endif /* CONFIG_MEMORY_HOTREMOVE */

  /**
   * walk_memory_range - walks through all mem sections in [start_pfn, end_pfn)
   * @start_pfn: start pfn of the memory range

   * @end_pfn: end pfn of the memory range

   * @arg: argument passed to func
   * @func: callback for each memory section walked
   *
   * This function walks through all present mem sections in range
   * [start_pfn, end_pfn) and call func on each mem section.
   *
   * Returns the return value of func.
   */

  int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,

  		void *arg, int (*func)(struct memory_block *, void *))

  {

  	struct memory_block *mem = NULL;
  	struct mem_section *section;

  	unsigned long pfn, section_nr;
  	int ret;

  
  	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
  		section_nr = pfn_to_section_nr(pfn);
  		if (!present_section_nr(section_nr))
  			continue;
  
  		section = __nr_to_section(section_nr);
  		/* same memblock? */
  		if (mem)
  			if ((section_nr >= mem->start_section_nr) &&
  			    (section_nr <= mem->end_section_nr))
  				continue;
  
  		mem = find_memory_block_hinted(section, mem);
  		if (!mem)
  			continue;

  		ret = func(mem, arg);

  		if (ret) {

  			kobject_put(&mem->dev.kobj);
  			return ret;

  		}
  	}
  
  	if (mem)
  		kobject_put(&mem->dev.kobj);

  	return 0;
  }

  #ifdef CONFIG_MEMORY_HOTREMOVE

  static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)

  {
  	int ret = !is_memblock_offlined(mem);

  	if (unlikely(ret)) {
  		phys_addr_t beginpa, endpa;
  
  		beginpa = PFN_PHYS(section_nr_to_pfn(mem->start_section_nr));
  		endpa = PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1;

  		pr_warn("removing memory fails, because memory [%pa-%pa] is onlined
  ",

  			&beginpa, &endpa);
  	}

  
  	return ret;
  }

  static int check_cpu_on_node(pg_data_t *pgdat)

  {

  	int cpu;
  
  	for_each_present_cpu(cpu) {
  		if (cpu_to_node(cpu) == pgdat->node_id)
  			/*
  			 * the cpu on this node isn't removed, and we can't
  			 * offline this node.
  			 */
  			return -EBUSY;
  	}
  
  	return 0;
  }

  static void unmap_cpu_on_node(pg_data_t *pgdat)

  {
  #ifdef CONFIG_ACPI_NUMA

  	int cpu;
  
  	for_each_possible_cpu(cpu)
  		if (cpu_to_node(cpu) == pgdat->node_id)
  			numa_clear_node(cpu);
  #endif
  }

  static int check_and_unmap_cpu_on_node(pg_data_t *pgdat)

  {

  	int ret;

  	ret = check_cpu_on_node(pgdat);

  	if (ret)
  		return ret;
  
  	/*
  	 * the node will be offlined when we come here, so we can clear
  	 * the cpu_to_node() now.
  	 */

  	unmap_cpu_on_node(pgdat);

  	return 0;
  }

  /**
   * try_offline_node
   *
   * Offline a node if all memory sections and cpus of the node are removed.
   *
   * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
   * and online/offline operations before this call.
   */

  void try_offline_node(int nid)

  {

  	pg_data_t *pgdat = NODE_DATA(nid);
  	unsigned long start_pfn = pgdat->node_start_pfn;
  	unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;

  	unsigned long pfn;
  
  	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
  		unsigned long section_nr = pfn_to_section_nr(pfn);
  
  		if (!present_section_nr(section_nr))
  			continue;
  
  		if (pfn_to_nid(pfn) != nid)
  			continue;
  
  		/*
  		 * some memory sections of this node are not removed, and we
  		 * can't offline node now.
  		 */
  		return;
  	}

  	if (check_and_unmap_cpu_on_node(pgdat))

  		return;
  
  	/*
  	 * all memory/cpu of this node are removed, we can offline this
  	 * node now.
  	 */
  	node_set_offline(nid);
  	unregister_one_node(nid);
  }

  EXPORT_SYMBOL(try_offline_node);

  /**
   * remove_memory
   *
   * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
   * and online/offline operations before this call, as required by
   * try_offline_node().
   */

  void __ref remove_memory(int nid, u64 start, u64 size)

  {

  	int ret;

  	BUG_ON(check_hotplug_memory_range(start, size));

  	mem_hotplug_begin();

  
  	/*

  	 * All memory blocks must be offlined before removing memory.  Check
  	 * whether all memory blocks in question are offline and trigger a BUG()
  	 * if this is not the case.

  	 */

  	ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL,

  				check_memblock_offlined_cb);

  	if (ret)

  		BUG();

  	/* remove memmap entry */
  	firmware_map_remove(start, start + size, "System RAM");

  	memblock_free(start, size);
  	memblock_remove(start, size);

  	arch_remove_memory(start, size);

  	try_offline_node(nid);

  	mem_hotplug_done();

  }

  EXPORT_SYMBOL_GPL(remove_memory);

  #endif /* CONFIG_MEMORY_HOTREMOVE */