memory_hotplug.c

/*
 *  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/compiler.h>
#include <linux/export.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/memory.h>
#include <linux/memremap.h>
#include <linux/memory_hotplug.h>
#include <linux/highmem.h>
#include <linux/vmalloc.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/migrate.h>
#include <linux/page-isolation.h>
#include <linux/pfn.h>
#include <linux/suspend.h>
#include <linux/mm_inline.h>
#include <linux/firmware-map.h>
#include <linux/stop_machine.h>
#include <linux/hugetlb.h>
#include <linux/memblock.h>
#include <linux/bootmem.h>
#include <linux/compaction.h>

#include <asm/tlbflush.h>

#include "internal.h"

/*
 * online_page_callback contains pointer to current page onlining function.
 * Initially it is generic_online_page(). If it is required it could be
 * changed by calling set_online_page_callback() for callback registration
 * and restore_online_page_callback() for generic callback restore.
 */

static void generic_online_page(struct page *page);

static online_page_callback_t online_page_callback = generic_online_page;
static DEFINE_MUTEX(online_page_callback_lock);

/* The same as the cpu_hotplug lock, but for memory hotplug. */
static struct {
	struct task_struct *active_writer;
	struct mutex lock; /* Synchronizes accesses to refcount, */
	/*
	 * Also blocks the new readers during
	 * an ongoing mem hotplug operation.
	 */
	int refcount;

#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map dep_map;
#endif
} mem_hotplug = {
	.active_writer = NULL,
	.lock = __MUTEX_INITIALIZER(mem_hotplug.lock),
	.refcount = 0,
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	.dep_map = {.name = "mem_hotplug.lock" },
#endif
};

/* Lockdep annotations for get/put_online_mems() and mem_hotplug_begin/end() */
#define memhp_lock_acquire_read() lock_map_acquire_read(&mem_hotplug.dep_map)
#define memhp_lock_acquire()      lock_map_acquire(&mem_hotplug.dep_map)
#define memhp_lock_release()      lock_map_release(&mem_hotplug.dep_map)

#ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE
bool memhp_auto_online;
#else
bool memhp_auto_online = true;
#endif
EXPORT_SYMBOL_GPL(memhp_auto_online);

static int __init setup_memhp_default_state(char *str)
{
	if (!strcmp(str, "online"))
		memhp_auto_online = true;
	else if (!strcmp(str, "offline"))
		memhp_auto_online = false;

	return 1;
}
__setup("memhp_default_state=", setup_memhp_default_state);

void get_online_mems(void)
{
	might_sleep();
	if (mem_hotplug.active_writer == current)
		return;
	memhp_lock_acquire_read();
	mutex_lock(&mem_hotplug.lock);
	mem_hotplug.refcount++;
	mutex_unlock(&mem_hotplug.lock);

}

void put_online_mems(void)
{
	if (mem_hotplug.active_writer == current)
		return;
	mutex_lock(&mem_hotplug.lock);

	if (WARN_ON(!mem_hotplug.refcount))
		mem_hotplug.refcount++; /* try to fix things up */

	if (!--mem_hotplug.refcount && unlikely(mem_hotplug.active_writer))
		wake_up_process(mem_hotplug.active_writer);
	mutex_unlock(&mem_hotplug.lock);
	memhp_lock_release();

}

void mem_hotplug_begin(void)
{
	mem_hotplug.active_writer = current;

	memhp_lock_acquire();
	for (;;) {
		mutex_lock(&mem_hotplug.lock);
		if (likely(!mem_hotplug.refcount))
			break;
		__set_current_state(TASK_UNINTERRUPTIBLE);
		mutex_unlock(&mem_hotplug.lock);
		schedule();
	}
}

void mem_hotplug_done(void)
{
	mem_hotplug.active_writer = NULL;
	mutex_unlock(&mem_hotplug.lock);
	memhp_lock_release();
}

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

	res->name = "System RAM";
	res->start = start;
	res->end = start + size - 1;
	res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
	if (request_resource(&iomem_resource, res) < 0) {
		pr_debug("System RAM resource %pR cannot be added\n", res);
		kfree(res);
		return ERR_PTR(-EEXIST);
	}
	return res;
}

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

#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
void get_page_bootmem(unsigned long info,  struct page *page,
		      unsigned long type)
{
	page->lru.next = (struct list_head *) 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->lru.next;
	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
	       type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);

	if (page_ref_dec_return(page) == 1) {
		ClearPagePrivate(page);
		set_page_private(page, 0);
		INIT_LIST_HEAD(&page->lru);
		free_reserved_page(page);
	}
}

#ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
#ifndef CONFIG_SPARSEMEM_VMEMMAP
static void register_page_bootmem_info_section(unsigned long start_pfn)
{
	unsigned long *usemap, mapsize, section_nr, i;
	struct mem_section *ms;
	struct page *page, *memmap;

	section_nr = pfn_to_section_nr(start_pfn);
	ms = __nr_to_section(section_nr);

	/* Get section's memmap address */
	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);

	/*
	 * Get page for the memmap's phys address
	 * XXX: need more consideration for sparse_vmemmap...
	 */
	page = virt_to_page(memmap);
	mapsize = sizeof(struct page) * PAGES_PER_SECTION;
	mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;

	/* remember memmap's page */
	for (i = 0; i < mapsize; i++, page++)
		get_page_bootmem(section_nr, page, SECTION_INFO);

	usemap = __nr_to_section(section_nr)->pageblock_flags;
	page = virt_to_page(usemap);

	mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;

	for (i = 0; i < mapsize; i++, page++)
		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);

}
#else /* CONFIG_SPARSEMEM_VMEMMAP */
static void register_page_bootmem_info_section(unsigned long start_pfn)
{
	unsigned long *usemap, mapsize, section_nr, i;
	struct mem_section *ms;
	struct page *page, *memmap;

	if (!pfn_valid(start_pfn))
		return;

	section_nr = pfn_to_section_nr(start_pfn);
	ms = __nr_to_section(section_nr);

	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);

	register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION);

	usemap = __nr_to_section(section_nr)->pageblock_flags;
	page = virt_to_page(usemap);

	mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;

	for (i = 0; i < mapsize; i++, page++)
		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
}
#endif /* !CONFIG_SPARSEMEM_VMEMMAP */

void 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_is_initialized(zone)) {
			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 = 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) && (pfn_to_nid(pfn) == node))
			register_page_bootmem_info_section(pfn);
	}
}
#endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */

static void __meminit 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_end_pfn(zone);
	if (zone_is_empty(zone) || 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 resize_zone(struct zone *zone, unsigned long start_pfn,
		unsigned long end_pfn)
{
	zone_span_writelock(zone);

	if (end_pfn - start_pfn) {
		zone->zone_start_pfn = start_pfn;
		zone->spanned_pages = end_pfn - start_pfn;
	} else {
		/*
		 * make it consist as free_area_init_core(),
		 * if spanned_pages = 0, then keep start_pfn = 0
		 */
		zone->zone_start_pfn = 0;
		zone->spanned_pages = 0;
	}

	zone_span_writeunlock(zone);
}

static void fix_zone_id(struct zone *zone, unsigned long start_pfn,
		unsigned long end_pfn)
{
	enum zone_type zid = zone_idx(zone);
	int nid = zone->zone_pgdat->node_id;
	unsigned long pfn;

	for (pfn = start_pfn; pfn < end_pfn; pfn++)
		set_page_links(pfn_to_page(pfn), zid, nid, pfn);
}

/* Can fail with -ENOMEM from allocating a wait table with vmalloc() or
 * alloc_bootmem_node_nopanic()/memblock_virt_alloc_node_nopanic() */
static int __ref ensure_zone_is_initialized(struct zone *zone,
			unsigned long start_pfn, unsigned long num_pages)
{
	if (!zone_is_initialized(zone))
		return init_currently_empty_zone(zone, start_pfn, num_pages);

	return 0;
}

static int __meminit move_pfn_range_left(struct zone *z1, struct zone *z2,
		unsigned long start_pfn, unsigned long end_pfn)
{
	int ret;
	unsigned long flags;
	unsigned long z1_start_pfn;

	ret = ensure_zone_is_initialized(z1, start_pfn, end_pfn - start_pfn);
	if (ret)
		return ret;

	pgdat_resize_lock(z1->zone_pgdat, &flags);

	/* can't move pfns which are higher than @z2 */
	if (end_pfn > zone_end_pfn(z2))
		goto out_fail;
	/* the move out part must be at the left most of @z2 */
	if (start_pfn > z2->zone_start_pfn)
		goto out_fail;
	/* must included/overlap */
	if (end_pfn <= z2->zone_start_pfn)
		goto out_fail;

	/* use start_pfn for z1's start_pfn if z1 is empty */
	if (!zone_is_empty(z1))
		z1_start_pfn = z1->zone_start_pfn;
	else
		z1_start_pfn = start_pfn;

	resize_zone(z1, z1_start_pfn, end_pfn);
	resize_zone(z2, end_pfn, zone_end_pfn(z2));

	pgdat_resize_unlock(z1->zone_pgdat, &flags);

	fix_zone_id(z1, start_pfn, end_pfn);

	return 0;
out_fail:
	pgdat_resize_unlock(z1->zone_pgdat, &flags);
	return -1;
}

static int __meminit move_pfn_range_right(struct zone *z1, struct zone *z2,
		unsigned long start_pfn, unsigned long end_pfn)
{
	int ret;
	unsigned long flags;
	unsigned long z2_end_pfn;

	ret = ensure_zone_is_initialized(z2, start_pfn, end_pfn - start_pfn);
	if (ret)
		return ret;

	pgdat_resize_lock(z1->zone_pgdat, &flags);

	/* can't move pfns which are lower than @z1 */
	if (z1->zone_start_pfn > start_pfn)
		goto out_fail;
	/* the move out part mast at the right most of @z1 */
	if (zone_end_pfn(z1) >  end_pfn)
		goto out_fail;
	/* must included/overlap */
	if (start_pfn >= zone_end_pfn(z1))
		goto out_fail;

	/* use end_pfn for z2's end_pfn if z2 is empty */
	if (!zone_is_empty(z2))
		z2_end_pfn = zone_end_pfn(z2);
	else
		z2_end_pfn = end_pfn;

	resize_zone(z1, z1->zone_start_pfn, start_pfn);
	resize_zone(z2, start_pfn, z2_end_pfn);

	pgdat_resize_unlock(z1->zone_pgdat, &flags);

	fix_zone_id(z2, start_pfn, end_pfn);

	return 0;
out_fail:
	pgdat_resize_unlock(z1->zone_pgdat, &flags);
	return -1;
}

static void __meminit grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
				      unsigned long end_pfn)
{
	unsigned long old_pgdat_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(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, pfn;
	int ret;

	zone_type = zone - pgdat->node_zones;
	ret = ensure_zone_is_initialized(zone, phys_start_pfn, nr_pages);
	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);

	/* online_page_range is called later and expects pages reserved */
	for (pfn = phys_start_pfn; pfn < phys_start_pfn + nr_pages; pfn++) {
		if (!pfn_valid(pfn))
			continue;

		SetPageReserved(pfn_to_page(pfn));
	}
	return 0;
}

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

	if (pfn_valid(phys_start_pfn))
		return -EEXIST;

	ret = sparse_add_one_section(zone, phys_start_pfn);

	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));
}

/*
 * 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;
	struct vmem_altmap *altmap;

	clear_zone_contiguous(zone);

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

	altmap = to_vmem_altmap((unsigned long) pfn_to_page(phys_start_pfn));
	if (altmap) {
		/*
		 * Validate altmap is within bounds of the total request
		 */
		if (altmap->base_pfn != phys_start_pfn
				|| vmem_altmap_offset(altmap) > nr_pages) {
			pr_warn_once("memory add fail, invalid altmap\n");
			err = -EINVAL;
			goto out;
		}
		altmap->alloc = 0;
	}

	for (i = start_sec; i <= end_sec; i++) {
		err = __add_section(nid, zone, section_nr_to_pfn(i));

		/*
		 * 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;
	}
	vmemmap_populate_print_last();
out:
	set_zone_contiguous(zone);
	return err;
}
EXPORT_SYMBOL_GPL(__add_pages);

#ifdef CONFIG_MEMORY_HOTREMOVE
/* find the smallest valid pfn in the range [start_pfn, end_pfn) */
static int find_smallest_section_pfn(int nid, struct zone *zone,
				     unsigned long start_pfn,
				     unsigned long end_pfn)
{
	struct mem_section *ms;

	for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SECTION) {
		ms = __pfn_to_section(start_pfn);

		if (unlikely(!valid_section(ms)))
			continue;

		if (unlikely(pfn_to_nid(start_pfn) != nid))
			continue;

		if (zone && zone != page_zone(pfn_to_page(start_pfn)))
			continue;

		return start_pfn;
	}

	return 0;
}

/* find the biggest valid pfn in the range [start_pfn, end_pfn). */
static int find_biggest_section_pfn(int nid, struct zone *zone,
				    unsigned long start_pfn,
				    unsigned long end_pfn)
{
	struct mem_section *ms;
	unsigned long pfn;

	/* pfn is the end pfn of a memory section. */
	pfn = end_pfn - 1;
	for (; pfn >= start_pfn; pfn -= PAGES_PER_SECTION) {
		ms = __pfn_to_section(pfn);

		if (unlikely(!valid_section(ms)))
			continue;

		if (unlikely(pfn_to_nid(pfn) != nid))
			continue;

		if (zone && zone != page_zone(pfn_to_page(pfn)))
			continue;

		return pfn;
	}

	return 0;
}

static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
			     unsigned long end_pfn)
{
	unsigned long zone_start_pfn = zone->zone_start_pfn;
	unsigned long z = zone_end_pfn(zone); /* zone_end_pfn namespace clash */
	unsigned long zone_end_pfn = z;
	unsigned long pfn;
	struct mem_section *ms;
	int nid = zone_to_nid(zone);

	zone_span_writelock(zone);
	if (zone_start_pfn == start_pfn) {
		/*
		 * If the section is smallest section in the zone, it need
		 * shrink zone->zone_start_pfn and zone->zone_spanned_pages.
		 * In this case, we find second smallest valid mem_section
		 * for shrinking zone.
		 */
		pfn = find_smallest_section_pfn(nid, zone, end_pfn,
						zone_end_pfn);
		if (pfn) {
			zone->zone_start_pfn = pfn;
			zone->spanned_pages = zone_end_pfn - pfn;
		}
	} else if (zone_end_pfn == end_pfn) {
		/*
		 * If the section is biggest section in the zone, it need
		 * shrink zone->spanned_pages.
		 * In this case, we find second biggest valid mem_section for
		 * shrinking zone.
		 */
		pfn = find_biggest_section_pfn(nid, zone, zone_start_pfn,
					       start_pfn);
		if (pfn)
			zone->spanned_pages = pfn - zone_start_pfn + 1;
	}

	/*
	 * The section is not biggest or smallest mem_section in the zone, it
	 * only creates a hole in the zone. So in this case, we need not
	 * change the zone. But perhaps, the zone has only hole data. Thus
	 * it check the zone has only hole or not.
	 */
	pfn = zone_start_pfn;
	for (; pfn < zone_end_pfn; pfn += PAGES_PER_SECTION) {
		ms = __pfn_to_section(pfn);

		if (unlikely(!valid_section(ms)))
			continue;

		if (page_zone(pfn_to_page(pfn)) != zone)
			continue;

		 /* If the section is current section, it continues the loop */
		if (start_pfn == pfn)
			continue;

		/* If we find valid section, we have nothing to do */
		zone_span_writeunlock(zone);
		return;
	}

	/* The zone has no valid section */
	zone->zone_start_pfn = 0;
	zone->spanned_pages = 0;
	zone_span_writeunlock(zone);
}

static void shrink_pgdat_span(struct pglist_data *pgdat,
			      unsigned long start_pfn, unsigned long end_pfn)
{
	unsigned long pgdat_start_pfn = pgdat->node_start_pfn;
	unsigned long p = pgdat_end_pfn(pgdat); /* pgdat_end_pfn namespace clash */
	unsigned long pgdat_end_pfn = p;
	unsigned long pfn;
	struct mem_section *ms;
	int nid = pgdat->node_id;

	if (pgdat_start_pfn == start_pfn) {
		/*
		 * If the section is smallest section in the pgdat, it need
		 * shrink pgdat->node_start_pfn and pgdat->node_spanned_pages.
		 * In this case, we find second smallest valid mem_section
		 * for shrinking zone.
		 */
		pfn = find_smallest_section_pfn(nid, NULL, end_pfn,
						pgdat_end_pfn);
		if (pfn) {
			pgdat->node_start_pfn = pfn;
			pgdat->node_spanned_pages = pgdat_end_pfn - pfn;
		}
	} else if (pgdat_end_pfn == end_pfn) {
		/*
		 * If the section is biggest section in the pgdat, it need
		 * shrink pgdat->node_spanned_pages.
		 * In this case, we find second biggest valid mem_section for
		 * shrinking zone.
		 */
		pfn = find_biggest_section_pfn(nid, NULL, pgdat_start_pfn,
					       start_pfn);
		if (pfn)
			pgdat->node_spanned_pages = pfn - pgdat_start_pfn + 1;
	}

	/*
	 * If the section is not biggest or smallest mem_section in the pgdat,
	 * it only creates a hole in the pgdat. So in this case, we need not
	 * change the pgdat.
	 * But perhaps, the pgdat has only hole data. Thus it check the pgdat
	 * has only hole or not.
	 */
	pfn = pgdat_start_pfn;
	for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SECTION) {
		ms = __pfn_to_section(pfn);

		if (unlikely(!valid_section(ms)))
			continue;

		if (pfn_to_nid(pfn) != nid)
			continue;

		 /* If the section is current section, it continues the loop */
		if (start_pfn == pfn)
			continue;

		/* If we find valid section, we have nothing to do */
		return;
	}

	/* The pgdat has no valid section */
	pgdat->node_start_pfn = 0;
	pgdat->node_spanned_pages = 0;
}

static void __remove_zone(struct zone *zone, unsigned long start_pfn)
{
	struct pglist_data *pgdat = zone->zone_pgdat;
	int nr_pages = PAGES_PER_SECTION;
	int zone_type;
	unsigned long flags;

	zone_type = zone - pgdat->node_zones;

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

static int __remove_section(struct zone *zone, struct mem_section *ms,
		unsigned long map_offset)
{
	unsigned long start_pfn;
	int scn_nr;
	int ret = -EINVAL;

	if (!valid_section(ms))
		return ret;

	ret = unregister_memory_section(ms);
	if (ret)
		return ret;

	scn_nr = __section_nr(ms);
	start_pfn = section_nr_to_pfn(scn_nr);
	__remove_zone(zone, start_pfn);

	sparse_remove_one_section(zone, ms, map_offset);
	return 0;
}

/**
 * __remove_pages() - remove sections of pages from a zone
 * @zone: zone from which pages need to be removed
 * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
 * @nr_pages: number of pages to remove (must be multiple of section size)
 *
 * Generic helper function to remove section mappings and sysfs entries
 * for the section of the memory we are removing. Caller needs to make
 * sure that pages are marked reserved and zones are adjust properly by
 * calling offline_pages().
 */
int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
		 unsigned long nr_pages)
{
	unsigned long i;
	unsigned long map_offset = 0;
	int sections_to_remove, ret = 0;

	/* In the ZONE_DEVICE case device driver owns the memory region */
	if (is_dev_zone(zone)) {
		struct page *page = pfn_to_page(phys_start_pfn);
		struct vmem_altmap *altmap;

		altmap = to_vmem_altmap((unsigned long) page);
		if (altmap)
			map_offset = vmem_altmap_offset(altmap);
	} else {
		resource_size_t start, size;

		start = phys_start_pfn << PAGE_SHIFT;
		size = nr_pages * PAGE_SIZE;

		ret = release_mem_region_adjustable(&iomem_resource, start,
					size);
		if (ret) {
			resource_size_t endres = start + size - 1;

			pr_warn("Unable to release resource <%pa-%pa> (%d)\n",
					&start, &endres, ret);
		}
	}

	clear_zone_contiguous(zone);

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

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

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

	set_zone_contiguous(zone);

	return ret;
}
EXPORT_SYMBOL_GPL(__remove_pages);
#endif /* CONFIG_MEMORY_HOTREMOVE */

int set_online_page_callback(online_page_callback_t callback)
{
	int rc = -EINVAL;

	get_online_mems();
	mutex_lock(&online_page_callback_lock);

	if (online_page_callback == generic_online_page) {
		online_page_callback = callback;
		rc = 0;
	}

	mutex_unlock(&online_page_callback_lock);
	put_online_mems();

	return rc;
}
EXPORT_SYMBOL_GPL(set_online_page_callback);

int restore_online_page_callback(online_page_callback_t callback)
{
	int rc = -EINVAL;

	get_online_mems();
	mutex_lock(&online_page_callback_lock);

	if (online_page_callback == callback) {
		online_page_callback = generic_online_page;
		rc = 0;
	}

	mutex_unlock(&online_page_callback_lock);
	put_online_mems();

	return rc;
}
EXPORT_SYMBOL_GPL(restore_online_page_callback);

void __online_page_set_limits(struct page *page)
{
}
EXPORT_SYMBOL_GPL(__online_page_set_limits);

void __online_page_increment_counters(struct page *page)
{
	adjust_managed_page_count(page, 1);
}
EXPORT_SYMBOL_GPL(__online_page_increment_counters);

void __online_page_free(struct page *page)
{
	__free_reserved_page(page);
}
EXPORT_SYMBOL_GPL(__online_page_free);

static void generic_online_page(struct page *page)
{
	__online_page_set_limits(page);
	__online_page_increment_counters(page);
	__online_page_free(page);
}

static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
			void *arg)
{
	unsigned long i;
	unsigned long onlined_pages = *(unsigned long *)arg;
	struct page *page;
	if (PageReserved(pfn_to_page(start_pfn)))
		for (i = 0; i < nr_pages; i++) {
			page = pfn_to_page(start_pfn + i);
			(*online_page_callback)(page);
			onlined_pages++;
		}
	*(unsigned long *)arg = onlined_pages;
	return 0;
}

#ifdef CONFIG_MOVABLE_NODE
/*
 * When CONFIG_MOVABLE_NODE, we permit onlining of a node which doesn't have
 * normal memory.
 */
static bool can_online_high_movable(struct zone *zone)
{
	return true;
}
#else /* CONFIG_MOVABLE_NODE */
/* ensure every online node has NORMAL memory */
static bool can_online_high_movable(struct zone *zone)
{
	return node_state(zone_to_nid(zone), N_NORMAL_MEMORY);
}
#endif /* CONFIG_MOVABLE_NODE */

/* check which state of node_states will be changed when online memory */
static void node_states_check_changes_online(unsigned long nr_pages,
	struct zone *zone, struct memory_notify *arg)
{
	int nid = zone_to_nid(zone);
	enum zone_type zone_last = ZONE_NORMAL;

	/*
	 * If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
	 * contains nodes which have zones of 0...ZONE_NORMAL,
	 * set zone_last to ZONE_NORMAL.
	 *
	 * If we don't have HIGHMEM nor movable node,
	 * node_states[N_NORMAL_MEMORY] contains nodes which have zones of
	 * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.
	 */
	if (N_MEMORY == N_NORMAL_MEMORY)
		zone_last = ZONE_MOVABLE;

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

#ifdef CONFIG_HIGHMEM
	/*
	 * If we have movable node, node_states[N_HIGH_MEMORY]
	 * contains nodes which have zones of 0...ZONE_HIGHMEM,
	 * set zone_last to ZONE_HIGHMEM.
	 *
	 * If we don't have movable node, node_states[N_NORMAL_MEMORY]
	 * contains nodes which have zones of 0...ZONE_MOVABLE,
	 * set zone_last to ZONE_MOVABLE.
	 */
	zone_last = ZONE_HIGHMEM;
	if (N_MEMORY == N_HIGH_MEMORY)
		zone_last = ZONE_MOVABLE;