mm/memory_hotplug.c - kernel/msm - Gitiles

 /*
  *  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;
 	if (request_resource(&iomem_resource, res) < 0) {
 		printk("System RAM resource %llx - %llx cannot be added\n",
 		(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;

 	/*
 	 * 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();
 	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\n",
 				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;
 	struct zone *zone;

 	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;
 	/* set above range as isolated */
 	ret = start_isolate_page_range(start_pfn, end_pfn);
 	if (ret)
 		return ret;
 	nr_pages = end_pfn - start_pfn;
 	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\n", 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 */
 	start_isolate_page_range(start_pfn, end_pfn);
 	/* removal success */
 	zone = page_zone(pfn_to_page(start_pfn));
 	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();
 	return 0;

 failed_removal:
 	printk(KERN_INFO "memory offlining %lx to %lx failed\n",
 		start_pfn, end_pfn);
 	/* 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 */
	/*
	* 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;
	if (request_resource(&iomem_resource, res) < 0) {
	printk("System RAM resource %llx - %llx cannot be added\n",
	(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;

	/*
	* 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();
	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\n",
	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;
	struct zone *zone;

	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;
	/* set above range as isolated */
	ret = start_isolate_page_range(start_pfn, end_pfn);
	if (ret)
	return ret;
	nr_pages = end_pfn - start_pfn;
	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\n", 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 */
	start_isolate_page_range(start_pfn, end_pfn);
	/* removal success */
	zone = page_zone(pfn_to_page(start_pfn));
	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();
	return 0;

	failed_removal:
	printk(KERN_INFO "memory offlining %lx to %lx failed\n",
	start_pfn, end_pfn);
	/* 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 */