// 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 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

  int memhp_default_online_type = MMOP_OFFLINE;

  #else

  int memhp_default_online_type = MMOP_ONLINE;

  #endif

  static int __init setup_memhp_default_state(char *str)
  {

  	const int online_type = memhp_online_type_from_str(str);
  
  	if (online_type >= 0)
  		memhp_default_online_type = online_type;

  
  	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,
  						 const char *resource_name)

  {

  	struct resource *res;
  	unsigned long flags =  IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;

  
  	if (strcmp(resource_name, "System RAM"))

  		flags |= IORESOURCE_SYSRAM_DRIVER_MANAGED;

  	/*
  	 * Make sure value parsed from 'mem=' only restricts memory adding
  	 * while booting, so that memory hotplug won't be impacted. Please
  	 * refer to document of 'mem=' in kernel-parameters.txt for more
  	 * details.
  	 */
  	if (start + size > max_mem_size && system_state < SYSTEM_RUNNING)

  		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;
  }

  static int check_hotplug_memory_addressable(unsigned long pfn,
  					    unsigned long nr_pages)
  {
  	const u64 max_addr = PFN_PHYS(pfn + nr_pages) - 1;
  
  	if (max_addr >> MAX_PHYSMEM_BITS) {
  		const u64 max_allowed = (1ull << (MAX_PHYSMEM_BITS + 1)) - 1;
  		WARN(1,
  		     "Hotplugged memory exceeds maximum addressable address, range=%#llx-%#llx, maximum=%#llx
  ",
  		     (u64)PFN_PHYS(pfn), max_addr, max_allowed);
  		return -E2BIG;
  	}
  
  	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_params *params)

  {

  	const unsigned long end_pfn = pfn + nr_pages;
  	unsigned long cur_nr_pages;

  	int err;

  	struct vmem_altmap *altmap = params->altmap;

  	if (WARN_ON_ONCE(!params->pgprot.pgprot))
  		return -EINVAL;

  	err = check_hotplug_memory_addressable(pfn, nr_pages);
  	if (err)
  		return err;

  	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;

  	for (; pfn < end_pfn; pfn += cur_nr_pages) {
  		/* Select all remaining pages up to the next section boundary */
  		cur_nr_pages = min(end_pfn - pfn,
  				   SECTION_ALIGN_UP(pfn + 1) - pfn);
  		err = sparse_add_section(nid, pfn, cur_nr_pages, altmap);

  		if (err)
  			break;

  		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 != 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 != 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 pfn;

  	int nid = zone_to_nid(zone);
  
  	zone_span_writelock(zone);

  	if (zone->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(zone));

  		if (pfn) {

  			zone->spanned_pages = zone_end_pfn(zone) - pfn;

  			zone->zone_start_pfn = pfn;

  		} else {
  			zone->zone_start_pfn = 0;
  			zone->spanned_pages = 0;

  		}

  	} else if (zone_end_pfn(zone) == 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->zone_start_pfn,

  					       start_pfn);
  		if (pfn)

  			zone->spanned_pages = pfn - zone->zone_start_pfn + 1;

  		else {
  			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)

  {

  	const unsigned long end_pfn = start_pfn + nr_pages;

  	struct pglist_data *pgdat = zone->zone_pgdat;

  	unsigned long pfn, cur_nr_pages, flags;

  	/* Poison struct pages because they are now uninitialized again. */

  	for (pfn = start_pfn; pfn < end_pfn; pfn += cur_nr_pages) {
  		cond_resched();
  
  		/* Select all remaining pages up to the next section boundary */
  		cur_nr_pages =
  			min(end_pfn - pfn, SECTION_ALIGN_UP(pfn + 1) - pfn);
  		page_init_poison(pfn_to_page(pfn),
  				 sizeof(struct page) * cur_nr_pages);
  	}

  #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 = __pfn_to_section(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)

  {

  	const unsigned long end_pfn = pfn + nr_pages;
  	unsigned long cur_nr_pages;

  	unsigned long map_offset = 0;

  	map_offset = vmem_altmap_offset(altmap);

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

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

  		cond_resched();

  		/* Select all remaining pages up to the next section boundary */

  		cur_nr_pages = min(end_pfn - pfn,
  				   SECTION_ALIGN_UP(pfn + 1) - pfn);

  		__remove_section(pfn, cur_nr_pages, map_offset, altmap);

  		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 generic_online_page(struct page *page, unsigned int order)

  {

  	/*
  	 * Freeing the page with debug_pagealloc enabled will try to unmap it,
  	 * so we should map it first. This is better than introducing a special
  	 * case in page freeing fast path.
  	 */
  	if (debug_pagealloc_enabled_static())
  		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
  }

  EXPORT_SYMBOL_GPL(generic_online_page);

  static void online_pages_range(unsigned long start_pfn, unsigned long nr_pages)

  {

  	const unsigned long end_pfn = start_pfn + nr_pages;
  	unsigned long pfn;

  
  	/*

  	 * Online the pages in MAX_ORDER - 1 aligned chunks. The callback might
  	 * decide to not expose all pages to the buddy (e.g., expose them
  	 * later). We account all pages as being online and belonging to this
  	 * zone ("present").

  	 */

  	for (pfn = start_pfn; pfn < end_pfn; pfn += MAX_ORDER_NR_PAGES)
  		(*online_page_callback)(pfn_to_page(pfn), MAX_ORDER - 1);

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

  }

  /* 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.

   *
   * All aligned pageblocks are initialized to the specified migratetype
   * (usually MIGRATE_MOVABLE). Besides setting the migratetype, no related
   * zone stats (e.g., nr_isolate_pageblock) are touched.

   */

  void __ref move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,

  				  unsigned long nr_pages,
  				  struct vmem_altmap *altmap, int migratetype)

  {
  	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, 0,

  			 MEMINIT_HOTPLUG, altmap, migratetype);

  
  	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, int nid)

  {

  	unsigned long flags;

  	struct zone *zone;

  	int need_zonelists_rebuild = 0;

  	int ret;
  	struct memory_notify arg;

  	/* We can only online full sections (e.g., SECTION_IS_ONLINE) */
  	if (WARN_ON_ONCE(!nr_pages ||
  			 !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
  		return -EINVAL;

  	mem_hotplug_begin();

  	/* 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, MIGRATE_ISOLATE);

  	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;

  	/*

  	 * Fixup the number of isolated pageblocks before marking the sections
  	 * onlining, such that undo_isolate_page_range() works correctly.
  	 */
  	spin_lock_irqsave(&zone->lock, flags);
  	zone->nr_isolate_pageblock += nr_pages / pageblock_nr_pages;
  	spin_unlock_irqrestore(&zone->lock, flags);
  
  	/*

  	 * 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);

  	}

  	online_pages_range(pfn, nr_pages);
  	zone->present_pages += nr_pages;

  
  	pgdat_resize_lock(zone->zone_pgdat, &flags);

  	zone->zone_pgdat->node_present_pages += nr_pages;

  	pgdat_resize_unlock(zone->zone_pgdat, &flags);

  	node_states_set_node(nid, &arg);
  	if (need_zonelists_rebuild)
  		build_all_zonelists(NULL);
  	zone_pcp_update(zone);
  
  	/* Basic onlining is complete, allow allocation of onlined pages. */
  	undo_isolate_page_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE);

  	/*

  	 * Freshly onlined pages aren't shuffled (e.g., all pages are placed to
  	 * the tail of the freelist when undoing isolation). Shuffle the whole
  	 * zone to make sure the just onlined pages are properly distributed
  	 * across the whole freelist - to create an initial shuffle.

  	 */

  	shuffle_zone(zone);

  	init_per_zone_wmark_min();

  	kswapd_run(nid);
  	kcompactd_run(nid);

  	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)

  {
  	struct pglist_data *pgdat;

  	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 highest_zoneidx before reuse.
  		 * Note that kswapd will init kswapd_highest_zoneidx properly

  		 * when it starts in the near future.
  		 */

  		pgdat->nr_zones = 0;

  		pgdat->kswapd_order = 0;

  		pgdat->kswapd_highest_zoneidx = 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 = 0;

  	/* 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

   * @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, bool set_node_online)

  {

  	pg_data_t *pgdat;
  	int ret = 1;

  	if (node_online(nid))
  		return 0;

  	pgdat = hotadd_new_pgdat(nid);

  	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, 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)
  {

  	mem->online_type = memhp_default_online_type;

  	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, mhp_t mhp_flags)

  {

  	struct mhp_params params = { .pgprot = PAGE_KERNEL };

  	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;

  	if (!node_possible(nid)) {
  		WARN(1, "node %d was absent from the node_possible_map
  ", nid);
  		return -EINVAL;
  	}

  	mem_hotplug_begin();

  	if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
  		memblock_add_node(start, size, nid);

  	ret = __try_online_node(nid, false);

  	if (ret < 0)
  		goto error;
  	new_node = ret;

  	/* call arch's memory hotadd */

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

  	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.*/

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

  	/* create new memmap entry */

  	if (!strcmp(res->name, "System RAM"))
  		firmware_map_add_hotplug(start, start + size, "System RAM");

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

  	/*
  	 * In case we're allowed to merge the resource, flag it and trigger
  	 * merging now that adding succeeded.
  	 */
  	if (mhp_flags & MEMHP_MERGE_RESOURCE)
  		merge_system_ram_resource(res);

  	/* online pages if requested */

  	if (memhp_default_online_type != MMOP_OFFLINE)

  		walk_memory_blocks(start, size, NULL, online_memory_block);

  	return ret;

  error:
  	/* rollback pgdat allocation and others */

  	if (new_node)
  		rollback_node_hotadd(nid);

  	if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
  		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, mhp_t mhp_flags)

  {
  	struct resource *res;
  	int ret;

  	res = register_memory_resource(start, size, "System RAM");

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

  	ret = add_memory_resource(nid, res, mhp_flags);

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

  int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)

  {
  	int rc;
  
  	lock_device_hotplug();

  	rc = __add_memory(nid, start, size, mhp_flags);

  	unlock_device_hotplug();
  
  	return rc;
  }

  EXPORT_SYMBOL_GPL(add_memory);

  int add_memory_subsection(int nid, u64 start, u64 size)
  {
  	struct mhp_params params = { .pgprot = PAGE_KERNEL };
  	struct resource *res;
  	int ret;
  
  	if (size == memory_block_size_bytes())
  		return add_memory(nid, start, size, MHP_NONE);
  
  	if (!IS_ALIGNED(start, SUBSECTION_SIZE) ||
  	    !IS_ALIGNED(size, SUBSECTION_SIZE)) {
  		pr_err("%s: start 0x%lx size 0x%lx not aligned to subsection size
  ",
  			   __func__, start, size);
  		return -EINVAL;
  	}
  
  	res = register_memory_resource(start, size, "System RAM");
  	if (IS_ERR(res))
  		return PTR_ERR(res);
  
  	mem_hotplug_begin();
  
  	nid = memory_add_physaddr_to_nid(start);
  
  	if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
  		memblock_add_node(start, size, nid);
  
  	ret = arch_add_memory(nid, start, size, &params);
  	if (ret) {
  		if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
  			memblock_remove(start, size);
  		pr_err("%s failed to add subsection start 0x%lx size 0x%lx
  ",
  			   __func__, start, size);
  	}
  	mem_hotplug_done();
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(add_memory_subsection);

  /*
   * Add special, driver-managed memory to the system as system RAM. Such
   * memory is not exposed via the raw firmware-provided memmap as system
   * RAM, instead, it is detected and added by a driver - during cold boot,
   * after a reboot, and after kexec.
   *
   * Reasons why this memory should not be used for the initial memmap of a
   * kexec kernel or for placing kexec images:
   * - The booting kernel is in charge of determining how this memory will be
   *   used (e.g., use persistent memory as system RAM)
   * - Coordination with a hypervisor is required before this memory
   *   can be used (e.g., inaccessible parts).
   *
   * For this memory, no entries in /sys/firmware/memmap ("raw firmware-provided
   * memory map") are created. Also, the created memory resource is flagged

   * with IORESOURCE_SYSRAM_DRIVER_MANAGED, so in-kernel users can special-case

   * this memory as well (esp., not place kexec images onto it).
   *
   * The resource_name (visible via /proc/iomem) has to have the format
   * "System RAM ($DRIVER)".
   */
  int add_memory_driver_managed(int nid, u64 start, u64 size,

  			      const char *resource_name, mhp_t mhp_flags)

  {
  	struct resource *res;
  	int rc;
  
  	if (!resource_name ||
  	    strstr(resource_name, "System RAM (") != resource_name ||
  	    resource_name[strlen(resource_name) - 1] != ')')
  		return -EINVAL;
  
  	lock_device_hotplug();
  
  	res = register_memory_resource(start, size, resource_name);
  	if (IS_ERR(res)) {
  		rc = PTR_ERR(res);
  		goto out_unlock;
  	}

  	rc = add_memory_resource(nid, res, mhp_flags);

  	if (rc < 0)
  		release_memory_resource(res);
  
  out_unlock:
  	unlock_device_hotplug();
  	return rc;
  }
  EXPORT_SYMBOL_GPL(add_memory_driver_managed);

  #ifdef CONFIG_MEMORY_HOTREMOVE
  /*

   * Confirm all pages in a range [start, end) belong to the same zone (skipping
   * memory holes). When true, return the zone.

   */

  struct zone *test_pages_in_a_zone(unsigned long start_pfn,
  				  unsigned long end_pfn)

  {

  	unsigned long pfn, sec_end_pfn;

  	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 NULL;

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

  				return NULL;

  			zone = page_zone(page);
  		}

  	}

  	return zone;

  }
  
  /*

   * Scan pfn range [start,end) to find movable/migratable pages (LRU pages,

   * non-lru movable pages and hugepages). Will skip over most unmovable
   * pages (esp., pages that can be skipped when offlining), but bail out on
   * definitely unmovable pages.
   *
   * Returns:
   *	0 in case a movable page is found and movable_pfn was updated.
   *	-ENOENT in case no movable page was found.
   *	-EBUSY in case a definitely unmovable page was found.

   */

  static int scan_movable_pages(unsigned long start, unsigned long end,
  			      unsigned long *movable_pfn)

  {
  	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))

  			goto found;

  		if (__PageMovable(page))

  			goto found;
  
  		/*
  		 * PageOffline() pages that are not marked __PageMovable() and
  		 * have a reference count > 0 (after MEM_GOING_OFFLINE) are
  		 * definitely unmovable. If their reference count would be 0,
  		 * they could at least be skipped when offlining memory.
  		 */
  		if (PageOffline(page) && page_count(page))
  			return -EBUSY;

  
  		if (!PageHuge(page))
  			continue;
  		head = compound_head(page);

  		if (page_huge_active(head))

  			goto found;

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

  		pfn += skip - 1;

  	}

  	return -ENOENT;
  found:
  	*movable_pfn = pfn;

  	return 0;
  }

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

  	struct page *page, *head;

  	int ret = 0;
  	LIST_HEAD(source);

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

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

  		head = compound_head(page);

  
  		if (PageHuge(page)) {

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

  			isolate_huge_page(head, &source);

  			continue;

  		} else if (PageTransHuge(page))

  			pfn = page_to_pfn(head) + thp_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);

  			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_lru(page));

  		} else {

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

  			dump_page(page, "isolation failed");

  		}

  		put_page(page);

  	}

  	if (!list_empty(&source)) {

  		nodemask_t nmask = node_states[N_MEMORY];
  		struct migration_target_control mtc = {
  			.nmask = &nmask,
  			.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
  		};
  
  		/*
  		 * We have checked that migration range is on a single zone so
  		 * we can use the nid of the first page to all the others.
  		 */
  		mtc.nid = page_to_nid(list_first_entry(&source, struct page, lru));
  
  		/*
  		 * 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(mtc.nid, nmask);
  		if (nodes_empty(nmask))
  			node_set(mtc.nid, nmask);
  		ret = migrate_pages(&source, alloc_migration_target, NULL,
  			(unsigned long)&mtc, 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;
  }

  static int __init cmdline_parse_movable_node(char *p)
  {

  	movable_node_enabled = true;

  	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 count_system_ram_pages_cb(unsigned long start_pfn,
  				     unsigned long nr_pages, void *data)
  {
  	unsigned long *nr_system_ram_pages = data;
  
  	*nr_system_ram_pages += nr_pages;
  	return 0;
  }

  int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)

  {

  	const unsigned long end_pfn = start_pfn + nr_pages;

  	unsigned long pfn, system_ram_pages = 0;

  	unsigned long flags;

  	struct zone *zone;

  	struct memory_notify arg;

  	int ret, node;

  	char *reason;

  	/* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
  	if (WARN_ON_ONCE(!nr_pages ||
  			 !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
  		return -EINVAL;

  	mem_hotplug_begin();

  	/*
  	 * Don't allow to offline memory blocks that contain holes.
  	 * Consequently, memory blocks with holes can never get onlined
  	 * via the hotplug path - online_pages() - as hotplugged memory has
  	 * no holes. This way, we e.g., don't have to worry about marking
  	 * memory holes PG_reserved, don't need pfn_valid() checks, and can
  	 * avoid using walk_system_ram_range() later.
  	 */

  	walk_system_ram_range(start_pfn, nr_pages, &system_ram_pages,

  			      count_system_ram_pages_cb);

  	if (system_ram_pages != nr_pages) {

  		ret = -EINVAL;
  		reason = "memory holes";
  		goto failed_removal;
  	}

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

  	zone = test_pages_in_a_zone(start_pfn, end_pfn);
  	if (!zone) {

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

  	}

  	node = zone_to_nid(zone);

  	/* set above range as isolated */

  	ret = start_isolate_page_range(start_pfn, end_pfn,

  				       MIGRATE_MOVABLE,

  				       MEMORY_OFFLINE | REPORT_FAILURE);

  	if (ret) {

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

  	}

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