/*
   *  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/cpuset.h>

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

  
  #include <asm/tlbflush.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

  static int __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;
  
  	zone_type = zone - pgdat->node_zones;

  	if (!zone->wait_table) {

  		int ret = 0;

  		ret = init_currently_empty_zone(zone, phys_start_pfn,
  						nr_pages, MEMMAP_HOTPLUG);

  		if (ret < 0)
  			return ret;
  	}

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

  	return 0;

  }

  static int __add_section(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(__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 __add_pages(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(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);

  
  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 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 flags;
  	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_sem.
  	 */
  	zone = page_zone(pfn_to_page(pfn));
  	pgdat_resize_lock(zone->zone_pgdat, &flags);
  	grow_zone_span(zone, pfn, pfn + nr_pages);
  	grow_pgdat_span(zone->zone_pgdat, pfn, pfn + nr_pages);
  	pgdat_resize_unlock(zone->zone_pgdat, &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;

  	walk_memory_resource(pfn, nr_pages, &onlined_pages,
  		online_pages_range);

  	zone->present_pages += onlined_pages;

  	zone->zone_pgdat->node_present_pages += onlined_pages;

  	setup_per_zone_pages_min();

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

  	if (need_zonelists_rebuild)
  		build_all_zonelists();

  	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 */

  static pg_data_t *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, pgdat, 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;
  }

  int add_memory(int nid, u64 start, u64 size)
  {

  	pg_data_t *pgdat = NULL;
  	int new_pgdat = 0;

  	struct resource *res;

  	int ret;

  	res = register_memory_resource(start, size);
  	if (!res)
  		return -EEXIST;

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

  	cpuset_track_online_nodes();

  	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);
  	}

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

  	if (res)
  		release_memory_resource(res);

  	return ret;
  }
  EXPORT_SYMBOL_GPL(add_memory);

  
  #ifdef CONFIG_MEMORY_HOTREMOVE
  /*
   * 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 improoooooved!! */
  	return alloc_page(GFP_HIGHUSER_PAGECACHE);
  }
  
  
  #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, &source);
  		if (!ret) { /* Success */
  			move_pages--;
  		} 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_INFO "removing from LRU failed"
  					 " %lx/%d/%lx
  ",
  				pfn, page_count(page), page->flags);
  #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);
  
  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_memory_resource(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_memory_resource(start_pfn, end_pfn - start_pfn, &offlined,
  			check_pages_isolated_cb);
  	if (ret < 0)
  		offlined = (long)ret;
  	return offlined;
  }
  
  extern void drain_all_local_pages(void);
  
  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;

  
  	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)
  		return ret;

  
  	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_local_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_local_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;
  	num_physpages -= offlined_pages;

  	vm_total_pages = nr_free_pagecache_pages();
  	writeback_set_ratelimit();

  
  	memory_notify(MEM_OFFLINE, &arg);

  	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);

  	return ret;
  }

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

  #endif /* CONFIG_MEMORY_HOTREMOVE */