Linux 4.10-rc3

[linux/fpc-iii.git] / mm / 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 __init register_page_bootmem_info_node(struct pglist_data *pgdat)
{
        unsigned long i, pfn, end_pfn, nr_pages;
        int node = pgdat->node_id;
        struct page *page;

        nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
        page = virt_to_page(pgdat);

        for (i = 0; i < nr_pages; i++, page++)
                get_page_bootmem(node, page, NODE_INFO);

        pfn = pgdat->node_start_pfn;
        end_pfn = pgdat_end_pfn(pgdat);

        /* register section info */
        for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
                /*
                 * Some platforms can assign the same pfn to multiple nodes - on
                 * node0 as well as nodeN.  To avoid registering a pfn against
                 * multiple nodes we check that this pfn does not already
                 * reside in some other nodes.
                 */
                if (pfn_valid(pfn) && (early_pfn_to_nid(pfn) == node))
                        register_page_bootmem_info_section(pfn);
        }
}
#endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */

static 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 struct zone * __meminit move_pfn_range(int zone_shift,
                unsigned long start_pfn, unsigned long end_pfn)
{
        struct zone *zone = page_zone(pfn_to_page(start_pfn));
        int ret = 0;

        if (zone_shift < 0)
                ret = move_pfn_range_left(zone + zone_shift, zone,
                                          start_pfn, end_pfn);
        else if (zone_shift)
                ret = move_pfn_range_right(zone, zone + zone_shift,
                                           start_pfn, end_pfn);

        if (ret)
                return NULL;

        return zone + zone_shift;
}

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;

        if (zone_idx(zone) <= zone_last && !node_state(nid, N_HIGH_MEMORY))
                arg->status_change_nid_high = nid;
        else
                arg->status_change_nid_high = -1;
#else
        arg->status_change_nid_high = arg->status_change_nid_normal;
#endif

        /*
         * if the node don't have memory befor online, we will need to
         * set the node to node_states[N_MEMORY] after the memory
         * is online.
         */
        if (!node_state(nid, N_MEMORY))
                arg->status_change_nid = nid;
        else
                arg->status_change_nid = -1;
}

static void node_states_set_node(int node, struct memory_notify *arg)
{
        if (arg->status_change_nid_normal >= 0)
                node_set_state(node, N_NORMAL_MEMORY);

        if (arg->status_change_nid_high >= 0)
                node_set_state(node, N_HIGH_MEMORY);

        node_set_state(node, N_MEMORY);
}

int zone_can_shift(unsigned long pfn, unsigned long nr_pages,
                   enum zone_type target)
{
        struct zone *zone = page_zone(pfn_to_page(pfn));
        enum zone_type idx = zone_idx(zone);
        int i;

        if (idx < target) {
                /* pages must be at end of current zone */
                if (pfn + nr_pages != zone_end_pfn(zone))
                        return 0;

                /* no zones in use between current zone and target */
                for (i = idx + 1; i < target; i++)
                        if (zone_is_initialized(zone - idx + i))
                                return 0;
        }

        if (target < idx) {
                /* pages must be at beginning of current zone */
                if (pfn != zone->zone_start_pfn)
                        return 0;

                /* no zones in use between current zone and target */
                for (i = target + 1; i < idx; i++)
                        if (zone_is_initialized(zone - idx + i))
                                return 0;
        }

        return target - idx;
}

/* Must be protected by mem_hotplug_begin() */
int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)
{
        unsigned long flags;
        unsigned long onlined_pages = 0;
        struct zone *zone;
        int need_zonelists_rebuild = 0;
        int nid;
        int ret;
        struct memory_notify arg;
        int zone_shift = 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_mutex.
         */
        zone = page_zone(pfn_to_page(pfn));

        if ((zone_idx(zone) > ZONE_NORMAL ||
            online_type == MMOP_ONLINE_MOVABLE) &&
            !can_online_high_movable(zone))
                return -EINVAL;

        if (online_type == MMOP_ONLINE_KERNEL)
                zone_shift = zone_can_shift(pfn, nr_pages, ZONE_NORMAL);
        else if (online_type == MMOP_ONLINE_MOVABLE)
                zone_shift = zone_can_shift(pfn, nr_pages, ZONE_MOVABLE);

        zone = move_pfn_range(zone_shift, pfn, pfn + nr_pages);
        if (!zone)
                return -EINVAL;

        arg.start_pfn = pfn;
        arg.nr_pages = nr_pages;
        node_states_check_changes_online(nr_pages, zone, &arg);

        nid = zone_to_nid(zone);

        ret = memory_notify(MEM_GOING_ONLINE, &arg);
        ret = notifier_to_errno(ret);
        if (ret)
                goto failed_addition;

        /*
         * 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;
                build_all_zonelists(NULL, zone);
        }

        ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
                online_pages_range);
        if (ret) {
                if (need_zonelists_rebuild)
                        zone_pcp_reset(zone);
                mutex_unlock(&zonelists_mutex);
                goto failed_addition;
        }

        zone->present_pages += onlined_pages;

        pgdat_resize_lock(zone->zone_pgdat, &flags);
        zone->zone_pgdat->node_present_pages += onlined_pages;
        pgdat_resize_unlock(zone->zone_pgdat, &flags);

        if (onlined_pages) {
                node_states_set_node(nid, &arg);
                if (need_zonelists_rebuild)
                        build_all_zonelists(NULL, NULL);
                else
                        zone_pcp_update(zone);
        }

        mutex_unlock(&zonelists_mutex);

        init_per_zone_wmark_min();

        if (onlined_pages) {
                kswapd_run(nid);
                kcompactd_run(nid);
        }

        vm_total_pages = nr_free_pagecache_pages();

        writeback_set_ratelimit();

        if (onlined_pages)
                memory_notify(MEM_ONLINE, &arg);
        return 0;

failed_addition:
        pr_debug("online_pages [mem %#010llx-%#010llx] failed\n",
                 (unsigned long long) pfn << PAGE_SHIFT,
                 (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
        memory_notify(MEM_CANCEL_ONLINE, &arg);
        return ret;
}
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

static void reset_node_present_pages(pg_data_t *pgdat)
{
        struct zone *z;

        for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
                z->present_pages = 0;

        pgdat->node_present_pages = 0;
}

/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
static pg_data_t __ref *hotadd_new_pgdat(int nid, 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 = PFN_DOWN(start);

        pgdat = NODE_DATA(nid);
        if (!pgdat) {
                pgdat = arch_alloc_nodedata(nid);
                if (!pgdat)
                        return NULL;

                arch_refresh_nodedata(nid, pgdat);
        } else {
                /* Reset the nr_zones, order and classzone_idx before reuse */
                pgdat->nr_zones = 0;
                pgdat->kswapd_order = 0;
                pgdat->kswapd_classzone_idx = 0;
        }

        /* 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);
        pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat);

        /*
         * The node we allocated has no zone fallback lists. For avoiding
         * to access not-initialized zonelist, build here.
         */
        mutex_lock(&zonelists_mutex);
        build_all_zonelists(pgdat, NULL);
        mutex_unlock(&zonelists_mutex);

        /*
         * zone->managed_pages is set to an approximate value in
         * free_area_init_core(), which will cause
         * /sys/device/system/node/nodeX/meminfo has wrong data.
         * So reset it to 0 before any memory is onlined.
         */
        reset_node_managed_pages(pgdat);

        /*
         * When memory is hot-added, all the memory is in offline state. So
         * clear all zones' present_pages because they will be updated in
         * online_pages() and offline_pages().
         */
        reset_node_present_pages(pgdat);

        return pgdat;
}

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


/**
 * try_online_node - online a node if offlined
 *
 * called by cpu_up() to online a node without onlined memory.
 */
int try_online_node(int nid)
{
        pg_data_t       *pgdat;
        int     ret;

        if (node_online(nid))
                return 0;

        mem_hotplug_begin();
        pgdat = hotadd_new_pgdat(nid, 0);
        if (!pgdat) {
                pr_err("Cannot online node %d due to NULL pgdat\n", nid);
                ret = -ENOMEM;
                goto out;
        }
        node_set_online(nid);
        ret = register_one_node(nid);
        BUG_ON(ret);

        if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
                mutex_lock(&zonelists_mutex);
                build_all_zonelists(NULL, NULL);
                mutex_unlock(&zonelists_mutex);
        }

out:
        mem_hotplug_done();
        return ret;
}

static int check_hotplug_memory_range(u64 start, u64 size)
{
        u64 start_pfn = PFN_DOWN(start);
        u64 nr_pages = size >> PAGE_SHIFT;

        /* Memory range must be aligned with section */
        if ((start_pfn & ~PAGE_SECTION_MASK) ||
            (nr_pages % PAGES_PER_SECTION) || (!nr_pages)) {
                pr_err("Section-unaligned hotplug range: start 0x%llx, size 0x%llx\n",
                                (unsigned long long)start,
                                (unsigned long long)size);
                return -EINVAL;
        }

        return 0;
}

/*
 * If movable zone has already been setup, newly added memory should be check.
 * If its address is higher than movable zone, it should be added as movable.
 * Without this check, movable zone may overlap with other zone.
 */
static int should_add_memory_movable(int nid, u64 start, u64 size)
{
        unsigned long start_pfn = start >> PAGE_SHIFT;
        pg_data_t *pgdat = NODE_DATA(nid);
        struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;

        if (zone_is_empty(movable_zone))
                return 0;

        if (movable_zone->zone_start_pfn <= start_pfn)
                return 1;

        return 0;
}

int zone_for_memory(int nid, u64 start, u64 size, int zone_default,
                bool for_device)
{
#ifdef CONFIG_ZONE_DEVICE
        if (for_device)
                return ZONE_DEVICE;
#endif
        if (should_add_memory_movable(nid, start, size))
                return ZONE_MOVABLE;

        return zone_default;
}

static int online_memory_block(struct memory_block *mem, void *arg)
{
        return memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
}

/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
int __ref add_memory_resource(int nid, struct resource *res, bool online)
{
        u64 start, size;
        pg_data_t *pgdat = NULL;
        bool new_pgdat;
        bool new_node;
        int ret;

        start = res->start;
        size = resource_size(res);

        ret = check_hotplug_memory_range(start, size);
        if (ret)
                return ret;

        {       /* Stupid hack to suppress address-never-null warning */
                void *p = NODE_DATA(nid);
                new_pgdat = !p;
        }

        mem_hotplug_begin();

        /*
         * Add new range to memblock so that when hotadd_new_pgdat() is called
         * to allocate new pgdat, get_pfn_range_for_nid() will be able to find
         * this new range and calculate total pages correctly.  The range will
         * be removed at hot-remove time.
         */
        memblock_add_node(start, size, nid);

        new_node = !node_online(nid);
        if (new_node) {
                pgdat = hotadd_new_pgdat(nid, start);
                ret = -ENOMEM;
                if (!pgdat)
                        goto error;
        }

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

        if (ret < 0)
                goto error;

        /* we online node here. we can't roll back from here. */
        node_set_online(nid);

        if (new_node) {
                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");

        /* online pages if requested */
        if (online)
                walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1),
                                  NULL, online_memory_block);

        goto out;

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

out:
        mem_hotplug_done();
        return ret;
}
EXPORT_SYMBOL_GPL(add_memory_resource);

int __ref add_memory(int nid, u64 start, u64 size)
{
        struct resource *res;
        int ret;

        res = register_memory_resource(start, size);
        if (IS_ERR(res))
                return PTR_ERR(res);

        ret = add_memory_resource(nid, res, memhp_auto_online);
        if (ret < 0)
                release_memory_resource(res);
        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. */
bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
{
        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)) {
                if (!is_pageblock_removable_nolock(page))
                        return false;
                cond_resched();
        }

        /* All pageblocks in the memory block are likely to be hot-removable */
        return true;
}

/*
 * Confirm all pages in a range [start, end) is belongs to the same zone.
 */
int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
{
        unsigned long pfn, sec_end_pfn;
        struct zone *zone = NULL;
        struct page *page;
        int i;
        for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn);
             pfn < end_pfn;
             pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) {
                /* Make sure the memory section is present first */
                if (!present_section_nr(pfn_to_section_nr(pfn)))
                        continue;
                for (; pfn < sec_end_pfn && pfn < end_pfn;
                     pfn += MAX_ORDER_NR_PAGES) {
                        i = 0;
                        /* This is just a CONFIG_HOLES_IN_ZONE check.*/
                        while ((i < MAX_ORDER_NR_PAGES) &&
                                !pfn_valid_within(pfn + i))
                                i++;
                        if (i == MAX_ORDER_NR_PAGES)
                                continue;
                        page = pfn_to_page(pfn + i);
                        if (zone && page_zone(page) != zone)
                                return 0;
                        zone = page_zone(page);
                }
        }
        return 1;
}

/*
 * Scan pfn range [start,end) to find movable/migratable pages (LRU pages
 * and hugepages). We scan pfn because it's much easier than scanning over
 * linked list. This function returns the pfn of the first found movable
 * page if it's found, otherwise 0.
 */
static unsigned long scan_movable_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;
                        if (PageHuge(page)) {
                                if (page_huge_active(page))
                                        return pfn;
                                else
                                        pfn = round_up(pfn + 1,
                                                1 << compound_order(page)) - 1;
                        }
                }
        }
        return 0;
}

static struct page *new_node_page(struct page *page, unsigned long private,
                int **result)
{
        gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
        int nid = page_to_nid(page);
        nodemask_t nmask = node_states[N_MEMORY];
        struct page *new_page = NULL;

        /*
         * TODO: allocate a destination hugepage from a nearest neighbor node,
         * accordance with memory policy of the user process if possible. For
         * now as a simple work-around, we use the next node for destination.
         */
        if (PageHuge(page))
                return alloc_huge_page_node(page_hstate(compound_head(page)),
                                        next_node_in(nid, nmask));

        node_clear(nid, nmask);

        if (PageHighMem(page)
            || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
                gfp_mask |= __GFP_HIGHMEM;

        if (!nodes_empty(nmask))
                new_page = __alloc_pages_nodemask(gfp_mask, 0,
                                        node_zonelist(nid, gfp_mask), &nmask);
        if (!new_page)
                new_page = __alloc_pages(gfp_mask, 0,
                                        node_zonelist(nid, gfp_mask));

        return new_page;
}

#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 (PageHuge(page)) {
                        struct page *head = compound_head(page);
                        pfn = page_to_pfn(head) + (1<<compound_order(head)) - 1;
                        if (compound_order(head) > PFN_SECTION_SHIFT) {
                                ret = -EBUSY;
                                break;
                        }
                        if (isolate_huge_page(page, &source))
                                move_pages -= 1 << compound_order(head);
                        continue;
                }

                if (!get_page_unless_zero(page))
                        continue;
                /*
                 * We can skip free pages. And we can only deal with pages on
                 * LRU.
                 */
                ret = isolate_lru_page(page);
                if (!ret) { /* Success */
                        put_page(page);
                        list_add_tail(&page->lru, &source);
                        move_pages--;
                        inc_node_page_state(page, NR_ISOLATED_ANON +
                                            page_is_file_cache(page));

                } else {
#ifdef CONFIG_DEBUG_VM
                        pr_alert("removing pfn %lx from LRU failed\n", pfn);
                        dump_page(page, "failed to remove from LRU");
#endif
                        put_page(page);
                        /* Because we don't have big zone->lock. we should
                           check this again here. */
                        if (page_count(page)) {
                                not_managed++;
                                ret = -EBUSY;
                                break;
                        }
                }
        }
        if (!list_empty(&source)) {
                if (not_managed) {
                        putback_movable_pages(&source);
                        goto out;
                }

                /* Allocate a new page from the nearest neighbor node */
                ret = migrate_pages(&source, new_node_page, NULL, 0,
                                        MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
                if (ret)
                        putback_movable_pages(&source);
        }
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, true);
        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;
}

#ifdef CONFIG_MOVABLE_NODE
/*
 * When CONFIG_MOVABLE_NODE, we permit offlining of a node which doesn't have
 * normal memory.
 */
static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
{
        return true;
}
#else /* CONFIG_MOVABLE_NODE */
/* ensure the node has NORMAL memory if it is still online */
static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
{
        struct pglist_data *pgdat = zone->zone_pgdat;
        unsigned long present_pages = 0;
        enum zone_type zt;

        for (zt = 0; zt <= ZONE_NORMAL; zt++)
                present_pages += pgdat->node_zones[zt].present_pages;

        if (present_pages > nr_pages)
                return true;

        present_pages = 0;
        for (; zt <= ZONE_MOVABLE; zt++)
                present_pages += pgdat->node_zones[zt].present_pages;

        /*
         * we can't offline the last normal memory until all
         * higher memory is offlined.
         */
        return present_pages == 0;
}
#endif /* CONFIG_MOVABLE_NODE */

static int __init cmdline_parse_movable_node(char *p)
{
#ifdef CONFIG_MOVABLE_NODE
        movable_node_enabled = true;
#else
        pr_warn("movable_node option not supported\n");
#endif
        return 0;
}
early_param("movable_node", cmdline_parse_movable_node);

/* check which state of node_states will be changed when offline memory */
static void node_states_check_changes_offline(unsigned long nr_pages,
                struct zone *zone, struct memory_notify *arg)
{
        struct pglist_data *pgdat = zone->zone_pgdat;
        unsigned long present_pages = 0;
        enum zone_type zt, 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;

        /*
         * check whether node_states[N_NORMAL_MEMORY] will be changed.
         * If the memory to be offline is in a zone of 0...zone_last,
         * and it is the last present memory, 0...zone_last will
         * become empty after offline , thus we can determind we will
         * need to clear the node from node_states[N_NORMAL_MEMORY].
         */
        for (zt = 0; zt <= zone_last; zt++)
                present_pages += pgdat->node_zones[zt].present_pages;
        if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
                arg->status_change_nid_normal = zone_to_nid(zone);
        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;

        for (; zt <= zone_last; zt++)
                present_pages += pgdat->node_zones[zt].present_pages;
        if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
                arg->status_change_nid_high = zone_to_nid(zone);
        else
                arg->status_change_nid_high = -1;
#else
        arg->status_change_nid_high = arg->status_change_nid_normal;
#endif

        /*
         * node_states[N_HIGH_MEMORY] contains nodes which have 0...ZONE_MOVABLE
         */
        zone_last = ZONE_MOVABLE;

        /*
         * check whether node_states[N_HIGH_MEMORY] will be changed
         * If we try to offline the last present @nr_pages from the node,
         * we can determind we will need to clear the node from
         * node_states[N_HIGH_MEMORY].
         */
        for (; zt <= zone_last; zt++)
                present_pages += pgdat->node_zones[zt].present_pages;
        if (nr_pages >= present_pages)
                arg->status_change_nid = zone_to_nid(zone);
        else
                arg->status_change_nid = -1;
}

static void node_states_clear_node(int node, struct memory_notify *arg)
{
        if (arg->status_change_nid_normal >= 0)
                node_clear_state(node, N_NORMAL_MEMORY);

        if ((N_MEMORY != N_NORMAL_MEMORY) &&
            (arg->status_change_nid_high >= 0))
                node_clear_state(node, N_HIGH_MEMORY);

        if ((N_MEMORY != N_HIGH_MEMORY) &&
            (arg->status_change_nid >= 0))
                node_clear_state(node, N_MEMORY);
}

static int __ref __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;
        unsigned long flags;
        struct zone *zone;
        struct memory_notify arg;

        /* 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;

        if (zone_idx(zone) <= ZONE_NORMAL && !can_offline_normal(zone, nr_pages))
                return -EINVAL;

        /* set above range as isolated */
        ret = start_isolate_page_range(start_pfn, end_pfn,
                                       MIGRATE_MOVABLE, true);
        if (ret)
                return ret;

        arg.start_pfn = start_pfn;
        arg.nr_pages = nr_pages;
        node_states_check_changes_offline(nr_pages, zone, &arg);

        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();
                cond_resched();
                drain_all_pages(zone);
        }

        pfn = scan_movable_pages(start_pfn, end_pfn);
        if (pfn) { /* We have movable pages */
                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 asynchronous... */
        lru_add_drain_all();
        yield();
        /* drain pcp pages, this is synchronous. */
        drain_all_pages(zone);
        /*
         * dissolve free hugepages in the memory block before doing offlining
         * actually in order to make hugetlbfs's object counting consistent.
         */
        ret = dissolve_free_huge_pages(start_pfn, end_pfn);
        if (ret)
                goto failed_removal;
        /* check again */
        offlined_pages = check_pages_isolated(start_pfn, end_pfn);
        if (offlined_pages < 0) {
                ret = -EBUSY;
                goto failed_removal;
        }
        pr_info("Offlined Pages %ld\n", offlined_pages);
        /* Ok, all of our target is isolated.
           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, MIGRATE_MOVABLE);
        /* removal success */
        adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages);
        zone->present_pages -= offlined_pages;

        pgdat_resize_lock(zone->zone_pgdat, &flags);
        zone->zone_pgdat->node_present_pages -= offlined_pages;
        pgdat_resize_unlock(zone->zone_pgdat, &flags);

        init_per_zone_wmark_min();

        if (!populated_zone(zone)) {
                zone_pcp_reset(zone);
                mutex_lock(&zonelists_mutex);
                build_all_zonelists(NULL, NULL);
                mutex_unlock(&zonelists_mutex);
        } else
                zone_pcp_update(zone);

        node_states_clear_node(node, &arg);
        if (arg.status_change_nid >= 0) {
                kswapd_stop(node);
                kcompactd_stop(node);
        }

        vm_total_pages = nr_free_pagecache_pages();
        writeback_set_ratelimit();

        memory_notify(MEM_OFFLINE, &arg);
        return 0;

failed_removal:
        pr_debug("memory offlining [mem %#010llx-%#010llx] failed\n",
                 (unsigned long long) start_pfn << PAGE_SHIFT,
                 ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);
        memory_notify(MEM_CANCEL_OFFLINE, &arg);
        /* pushback to free area */
        undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
        return ret;
}

/* Must be protected by mem_hotplug_begin() */
int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
{
        return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ);
}
#endif /* CONFIG_MEMORY_HOTREMOVE */

/**
 * walk_memory_range - walks through all mem sections in [start_pfn, end_pfn)
 * @start_pfn: start pfn of the memory range
 * @end_pfn: end pfn of the memory range
 * @arg: argument passed to func
 * @func: callback for each memory section walked
 *
 * This function walks through all present mem sections in range
 * [start_pfn, end_pfn) and call func on each mem section.
 *
 * Returns the return value of func.
 */
int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
                void *arg, int (*func)(struct memory_block *, void *))
{
        struct memory_block *mem = NULL;
        struct mem_section *section;
        unsigned long pfn, section_nr;
        int ret;

        for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
                section_nr = pfn_to_section_nr(pfn);
                if (!present_section_nr(section_nr))
                        continue;

                section = __nr_to_section(section_nr);
                /* same memblock? */
                if (mem)
                        if ((section_nr >= mem->start_section_nr) &&
                            (section_nr <= mem->end_section_nr))
                                continue;

                mem = find_memory_block_hinted(section, mem);
                if (!mem)
                        continue;

                ret = func(mem, arg);
                if (ret) {
                        kobject_put(&mem->dev.kobj);
                        return ret;
                }
        }

        if (mem)
                kobject_put(&mem->dev.kobj);

        return 0;
}

#ifdef CONFIG_MEMORY_HOTREMOVE
static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)
{
        int ret = !is_memblock_offlined(mem);

        if (unlikely(ret)) {
                phys_addr_t beginpa, endpa;

                beginpa = PFN_PHYS(section_nr_to_pfn(mem->start_section_nr));
                endpa = PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1;
                pr_warn("removing memory fails, because memory [%pa-%pa] is onlined\n",
                        &beginpa, &endpa);
        }

        return ret;
}

static int check_cpu_on_node(pg_data_t *pgdat)
{
        int cpu;

        for_each_present_cpu(cpu) {
                if (cpu_to_node(cpu) == pgdat->node_id)
                        /*
                         * the cpu on this node isn't removed, and we can't
                         * offline this node.
                         */
                        return -EBUSY;
        }

        return 0;
}

static void unmap_cpu_on_node(pg_data_t *pgdat)
{
#ifdef CONFIG_ACPI_NUMA
        int cpu;

        for_each_possible_cpu(cpu)
                if (cpu_to_node(cpu) == pgdat->node_id)
                        numa_clear_node(cpu);
#endif
}

static int check_and_unmap_cpu_on_node(pg_data_t *pgdat)
{
        int ret;

        ret = check_cpu_on_node(pgdat);
        if (ret)
                return ret;

        /*
         * the node will be offlined when we come here, so we can clear
         * the cpu_to_node() now.
         */

        unmap_cpu_on_node(pgdat);
        return 0;
}

/**
 * try_offline_node
 *
 * Offline a node if all memory sections and cpus of the node are removed.
 *
 * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
 * and online/offline operations before this call.
 */
void try_offline_node(int nid)
{
        pg_data_t *pgdat = NODE_DATA(nid);
        unsigned long start_pfn = pgdat->node_start_pfn;
        unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
        unsigned long pfn;

        for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
                unsigned long section_nr = pfn_to_section_nr(pfn);

                if (!present_section_nr(section_nr))
                        continue;

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

                /*
                 * some memory sections of this node are not removed, and we
                 * can't offline node now.
                 */
                return;
        }

        if (check_and_unmap_cpu_on_node(pgdat))
                return;

        /*
         * all memory/cpu of this node are removed, we can offline this
         * node now.
         */
        node_set_offline(nid);
        unregister_one_node(nid);
}
EXPORT_SYMBOL(try_offline_node);

/**
 * remove_memory
 *
 * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
 * and online/offline operations before this call, as required by
 * try_offline_node().
 */
void __ref remove_memory(int nid, u64 start, u64 size)
{
        int ret;

        BUG_ON(check_hotplug_memory_range(start, size));

        mem_hotplug_begin();

        /*
         * All memory blocks must be offlined before removing memory.  Check
         * whether all memory blocks in question are offline and trigger a BUG()
         * if this is not the case.
         */
        ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL,
                                check_memblock_offlined_cb);
        if (ret)
                BUG();

        /* remove memmap entry */
        firmware_map_remove(start, start + size, "System RAM");
        memblock_free(start, size);
        memblock_remove(start, size);

        arch_remove_memory(start, size);

        try_offline_node(nid);

        mem_hotplug_done();
}
EXPORT_SYMBOL_GPL(remove_memory);
#endif /* CONFIG_MEMORY_HOTREMOVE */