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

  #include <linux/stddef.h>
  #include <linux/mm.h>
  #include <linux/swap.h>
  #include <linux/interrupt.h>
  #include <linux/pagemap.h>
  #include <linux/bootmem.h>
  #include <linux/compiler.h>
  #include <linux/module.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/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 <asm/tlbflush.h>

  #include "internal.h"

  /* add this memory to iomem resource */
  static struct resource *register_memory_resource(u64 start, u64 size)
  {
  	struct resource *res;
  	res = kzalloc(sizeof(struct resource), GFP_KERNEL);
  	BUG_ON(!res);
  
  	res->name = "System RAM";
  	res->start = start;
  	res->end = start + size - 1;

  	res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;

  	if (request_resource(&iomem_resource, res) < 0) {
  		printk("System RAM resource %llx - %llx cannot be added
  ",
  		(unsigned long long)res->start, (unsigned long long)res->end);
  		kfree(res);
  		res = NULL;
  	}
  	return res;
  }
  
  static void release_memory_resource(struct resource *res)
  {
  	if (!res)
  		return;
  	release_resource(res);
  	kfree(res);
  	return;
  }

  #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE

  #ifndef CONFIG_SPARSEMEM_VMEMMAP

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

  {

  	atomic_set(&page->_mapcount, type);

  	SetPagePrivate(page);
  	set_page_private(page, info);
  	atomic_inc(&page->_count);
  }

  /* reference to __meminit __free_pages_bootmem is valid
   * so use __ref to tell modpost not to generate a warning */
  void __ref put_page_bootmem(struct page *page)

  {

  	int type;

  	type = atomic_read(&page->_mapcount);
  	BUG_ON(type >= -1);

  
  	if (atomic_dec_return(&page->_count) == 1) {
  		ClearPagePrivate(page);
  		set_page_private(page, 0);
  		reset_page_mapcount(page);
  		__free_pages_bootmem(page, 0);
  	}
  
  }

  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);
  
  	/* 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);

  
  }
  
  void 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;
  	struct zone *zone;
  
  	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);
  
  	zone = &pgdat->node_zones[0];
  	for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
  		if (zone->wait_table) {
  			nr_pages = zone->wait_table_hash_nr_entries
  				* sizeof(wait_queue_head_t);
  			nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
  			page = virt_to_page(zone->wait_table);
  
  			for (i = 0; i < nr_pages; i++, page++)
  				get_page_bootmem(node, page, NODE_INFO);
  		}
  	}
  
  	pfn = pgdat->node_start_pfn;
  	end_pfn = pfn + pgdat->node_spanned_pages;
  
  	/* register_section info */
  	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
  		register_page_bootmem_info_section(pfn);
  
  }
  #endif /* !CONFIG_SPARSEMEM_VMEMMAP */

  static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
  			   unsigned long end_pfn)
  {
  	unsigned long old_zone_end_pfn;
  
  	zone_span_writelock(zone);
  
  	old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
  	if (start_pfn < zone->zone_start_pfn)
  		zone->zone_start_pfn = start_pfn;
  
  	zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
  				zone->zone_start_pfn;
  
  	zone_span_writeunlock(zone);
  }
  
  static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
  			    unsigned long end_pfn)
  {
  	unsigned long old_pgdat_end_pfn =
  		pgdat->node_start_pfn + pgdat->node_spanned_pages;
  
  	if (start_pfn < pgdat->node_start_pfn)
  		pgdat->node_start_pfn = start_pfn;
  
  	pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
  					pgdat->node_start_pfn;
  }

  static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)

  {
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	int nr_pages = PAGES_PER_SECTION;
  	int nid = pgdat->node_id;
  	int zone_type;

  	unsigned long flags;

  
  	zone_type = zone - pgdat->node_zones;

  	if (!zone->wait_table) {
  		int ret;
  
  		ret = init_currently_empty_zone(zone, phys_start_pfn,
  						nr_pages, MEMMAP_HOTPLUG);
  		if (ret)
  			return ret;
  	}
  	pgdat_resize_lock(zone->zone_pgdat, &flags);
  	grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
  	grow_pgdat_span(zone->zone_pgdat, phys_start_pfn,
  			phys_start_pfn + nr_pages);
  	pgdat_resize_unlock(zone->zone_pgdat, &flags);

  	memmap_init_zone(nr_pages, nid, zone_type,
  			 phys_start_pfn, MEMMAP_HOTPLUG);

  	return 0;

  }

  static int __meminit __add_section(int nid, struct zone *zone,
  					unsigned long phys_start_pfn)

  {

  	int nr_pages = PAGES_PER_SECTION;

  	int ret;

  	if (pfn_valid(phys_start_pfn))
  		return -EEXIST;

  	ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);

  
  	if (ret < 0)
  		return ret;

  	ret = __add_zone(zone, phys_start_pfn);
  
  	if (ret < 0)
  		return ret;

  	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));

  }

  #ifdef CONFIG_SPARSEMEM_VMEMMAP
  static int __remove_section(struct zone *zone, struct mem_section *ms)
  {
  	/*
  	 * XXX: Freeing memmap with vmemmap is not implement yet.
  	 *      This should be removed later.
  	 */
  	return -EBUSY;
  }
  #else

  static int __remove_section(struct zone *zone, struct mem_section *ms)
  {
  	unsigned long flags;
  	struct pglist_data *pgdat = zone->zone_pgdat;
  	int ret = -EINVAL;
  
  	if (!valid_section(ms))
  		return ret;
  
  	ret = unregister_memory_section(ms);
  	if (ret)
  		return ret;
  
  	pgdat_resize_lock(pgdat, &flags);
  	sparse_remove_one_section(zone, ms);
  	pgdat_resize_unlock(pgdat, &flags);
  	return 0;
  }

  #endif

  /*
   * 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, struct zone *zone, unsigned long phys_start_pfn,
  			unsigned long nr_pages)

  {
  	unsigned long i;
  	int err = 0;

  	int start_sec, end_sec;
  	/* 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);

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

  		err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);

  		/*

  		 * 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;

  	}
  
  	return err;
  }

  EXPORT_SYMBOL_GPL(__add_pages);

  /**
   * __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, ret = 0;
  	int sections_to_remove;
  
  	/*
  	 * 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;

  		release_mem_region(pfn << PAGE_SHIFT,
  				   PAGES_PER_SECTION << PAGE_SHIFT);

  		ret = __remove_section(zone, __pfn_to_section(pfn));
  		if (ret)
  			break;
  	}
  	return ret;
  }
  EXPORT_SYMBOL_GPL(__remove_pages);

  void online_page(struct page *page)
  {

  	unsigned long pfn = page_to_pfn(page);

  	totalram_pages++;

  	if (pfn >= num_physpages)
  		num_physpages = pfn + 1;

  
  #ifdef CONFIG_HIGHMEM
  	if (PageHighMem(page))
  		totalhigh_pages++;
  #endif
  
  #ifdef CONFIG_FLATMEM
  	max_mapnr = max(page_to_pfn(page), max_mapnr);
  #endif
  
  	ClearPageReserved(page);
  	init_page_count(page);
  	__free_page(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(page);
  			onlined_pages++;
  		}
  	*(unsigned long *)arg = onlined_pages;
  	return 0;
  }
  
  
  int online_pages(unsigned long pfn, unsigned long nr_pages)
  {

  	unsigned long onlined_pages = 0;
  	struct zone *zone;

  	int need_zonelists_rebuild = 0;

  	int nid;
  	int ret;
  	struct memory_notify arg;
  
  	arg.start_pfn = pfn;
  	arg.nr_pages = nr_pages;
  	arg.status_change_nid = -1;
  
  	nid = page_to_nid(pfn_to_page(pfn));
  	if (node_present_pages(nid) == 0)
  		arg.status_change_nid = nid;

  	ret = memory_notify(MEM_GOING_ONLINE, &arg);
  	ret = notifier_to_errno(ret);
  	if (ret) {
  		memory_notify(MEM_CANCEL_ONLINE, &arg);
  		return ret;
  	}

  	/*
  	 * This doesn't need a lock to do pfn_to_page().
  	 * The section can't be removed here because of the

  	 * memory_block->state_mutex.

  	 */
  	zone = page_zone(pfn_to_page(pfn));

  	/*
  	 * 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.
  	 */

  	mutex_lock(&zonelists_mutex);

  	if (!populated_zone(zone))
  		need_zonelists_rebuild = 1;

  	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,

  		online_pages_range);

  	if (ret) {

  		mutex_unlock(&zonelists_mutex);

  		printk(KERN_DEBUG "online_pages %lx at %lx failed
  ",
  			nr_pages, pfn);
  		memory_notify(MEM_CANCEL_ONLINE, &arg);
  		return ret;
  	}

  	zone->present_pages += onlined_pages;

  	zone->zone_pgdat->node_present_pages += onlined_pages;

  	if (need_zonelists_rebuild)
  		build_all_zonelists(zone);
  	else
  		zone_pcp_update(zone);

  	mutex_unlock(&zonelists_mutex);

  	setup_per_zone_wmarks();

  	calculate_zone_inactive_ratio(zone);

  	if (onlined_pages) {
  		kswapd_run(zone_to_nid(zone));
  		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
  	}

  	vm_total_pages = nr_free_pagecache_pages();

  	writeback_set_ratelimit();

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

  	return 0;
  }

  #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

  /* 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 = start >> PAGE_SHIFT;
  
  	pgdat = arch_alloc_nodedata(nid);
  	if (!pgdat)
  		return NULL;
  
  	arch_refresh_nodedata(nid, pgdat);
  
  	/* 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);

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

  /*
   * called by cpu_up() to online a node without onlined memory.
   */
  int mem_online_node(int nid)
  {
  	pg_data_t	*pgdat;
  	int	ret;
  
  	lock_system_sleep();
  	pgdat = hotadd_new_pgdat(nid, 0);
  	if (pgdat) {
  		ret = -ENOMEM;
  		goto out;
  	}
  	node_set_online(nid);
  	ret = register_one_node(nid);
  	BUG_ON(ret);
  
  out:
  	unlock_system_sleep();
  	return ret;
  }

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

  {

  	pg_data_t *pgdat = NULL;
  	int new_pgdat = 0;

  	struct resource *res;

  	int ret;

  	lock_system_sleep();

  	res = register_memory_resource(start, size);

  	ret = -EEXIST;

  	if (!res)

  		goto out;

  	if (!node_online(nid)) {
  		pgdat = hotadd_new_pgdat(nid, start);

  		ret = -ENOMEM;

  		if (!pgdat)

  			goto out;

  		new_pgdat = 1;

  	}

  	/* call arch's memory hotadd */
  	ret = arch_add_memory(nid, start, size);

  	if (ret < 0)
  		goto error;

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

  	node_set_online(nid);

  	if (new_pgdat) {
  		ret = register_one_node(nid);
  		/*
  		 * 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");

  	goto out;

  error:
  	/* rollback pgdat allocation and others */
  	if (new_pgdat)
  		rollback_node_hotadd(nid, pgdat);

  	if (res)
  		release_memory_resource(res);

  out:
  	unlock_system_sleep();

  	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. */
  int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
  {
  	int type;
  	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)) {
  		type = get_pageblock_migratetype(page);
  
  		/*
  		 * A pageblock containing MOVABLE or free pages is considered
  		 * removable
  		 */
  		if (type != MIGRATE_MOVABLE && !pageblock_free(page))
  			return 0;
  
  		/*
  		 * A pageblock starting with a PageReserved page is not
  		 * considered removable.
  		 */
  		if (PageReserved(page))
  			return 0;
  	}
  
  	/* All pageblocks in the memory block are likely to be hot-removable */
  	return 1;
  }
  
  /*

   * Confirm all pages in a range [start, end) is belongs to the same zone.
   */
  static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn;
  	struct zone *zone = NULL;
  	struct page *page;
  	int i;
  	for (pfn = start_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)
  			continue;
  		page = pfn_to_page(pfn + i);
  		if (zone && page_zone(page) != zone)
  			return 0;
  		zone = page_zone(page);
  	}
  	return 1;
  }
  
  /*
   * Scanning pfn is much easier than scanning lru list.
   * Scan pfn from start to end and Find LRU page.
   */
  int scan_lru_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;
  		}
  	}
  	return 0;
  }
  
  static struct page *

  hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)

  {

  	/* This should be improooooved!! */
  	return alloc_page(GFP_HIGHUSER_MOVABLE);

  }

  #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 (!page_count(page))
  			continue;
  		/*
  		 * We can skip free pages. And we can only deal with pages on
  		 * LRU.
  		 */

  		ret = isolate_lru_page(page);

  		if (!ret) { /* Success */

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

  			move_pages--;

  			inc_zone_page_state(page, NR_ISOLATED_ANON +
  					    page_is_file_cache(page));

  		} else {
  			/* Becasue we don't have big zone->lock. we should
  			   check this again here. */
  			if (page_count(page))
  				not_managed++;
  #ifdef CONFIG_DEBUG_VM

  			printk(KERN_ALERT "removing pfn %lx from LRU failed
  ",
  			       pfn);
  			dump_page(page);

  #endif
  		}
  	}
  	ret = -EBUSY;
  	if (not_managed) {
  		if (!list_empty(&source))
  			putback_lru_pages(&source);
  		goto out;
  	}
  	ret = 0;
  	if (list_empty(&source))
  		goto out;
  	/* this function returns # of failed pages */

  	ret = migrate_pages(&source, hotremove_migrate_alloc, 0, 1);

  
  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);
  	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 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;

  	struct zone *zone;

  	struct memory_notify arg;

  
  	BUG_ON(start_pfn >= end_pfn);
  	/* 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))
  		return -EINVAL;

  	lock_system_sleep();

  	zone = page_zone(pfn_to_page(start_pfn));
  	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);
  	if (ret)

  		goto out;

  
  	arg.start_pfn = start_pfn;
  	arg.nr_pages = nr_pages;
  	arg.status_change_nid = -1;
  	if (nr_pages >= node_present_pages(node))
  		arg.status_change_nid = node;
  
  	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();
  		flush_scheduled_work();
  		cond_resched();

  		drain_all_pages();

  	}
  
  	pfn = scan_lru_pages(start_pfn, end_pfn);
  	if (pfn) { /* We have page on LRU */
  		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 asyncronous... */
  	lru_add_drain_all();
  	flush_scheduled_work();
  	yield();
  	/* drain pcp pages , this is synchrouns. */

  	drain_all_pages();

  	/* check again */
  	offlined_pages = check_pages_isolated(start_pfn, end_pfn);
  	if (offlined_pages < 0) {
  		ret = -EBUSY;
  		goto failed_removal;
  	}
  	printk(KERN_INFO "Offlined Pages %ld
  ", offlined_pages);
  	/* Ok, all of our target is islaoted.
  	   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);

  	/* removal success */

  	zone->present_pages -= offlined_pages;
  	zone->zone_pgdat->node_present_pages -= offlined_pages;
  	totalram_pages -= offlined_pages;

  	setup_per_zone_wmarks();
  	calculate_zone_inactive_ratio(zone);

  	if (!node_present_pages(node)) {
  		node_clear_state(node, N_HIGH_MEMORY);
  		kswapd_stop(node);
  	}

  	vm_total_pages = nr_free_pagecache_pages();
  	writeback_set_ratelimit();

  
  	memory_notify(MEM_OFFLINE, &arg);

  	unlock_system_sleep();

  	return 0;
  
  failed_removal:
  	printk(KERN_INFO "memory offlining %lx to %lx failed
  ",
  		start_pfn, end_pfn);

  	memory_notify(MEM_CANCEL_OFFLINE, &arg);

  	/* pushback to free area */
  	undo_isolate_page_range(start_pfn, end_pfn);

  out:
  	unlock_system_sleep();

  	return ret;
  }

  
  int remove_memory(u64 start, u64 size)
  {
  	unsigned long start_pfn, end_pfn;
  
  	start_pfn = PFN_DOWN(start);
  	end_pfn = start_pfn + PFN_DOWN(size);
  	return offline_pages(start_pfn, end_pfn, 120 * HZ);
  }

  #else
  int remove_memory(u64 start, u64 size)
  {
  	return -EINVAL;
  }

  #endif /* CONFIG_MEMORY_HOTREMOVE */

  EXPORT_SYMBOL_GPL(remove_memory);