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[zen-stable.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/bootmem.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/memory_hotplug.h>
#include <linux/highmem.h>
#include <linux/vmalloc.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/migrate.h>
#include <linux/page-isolation.h>
#include <linux/pfn.h>
#include <linux/suspend.h>
#include <linux/mm_inline.h>
#include <linux/firmware-map.h>

#include <asm/tlbflush.h>

#include "internal.h"

/*
 * 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;

DEFINE_MUTEX(mem_hotplug_mutex);

void lock_memory_hotplug(void)
{
        mutex_lock(&mem_hotplug_mutex);

        /* for exclusive hibernation if CONFIG_HIBERNATION=y */
        lock_system_sleep();
}

void unlock_memory_hotplug(void)
{
        unlock_system_sleep();
        mutex_unlock(&mem_hotplug_mutex);
}


/* add this memory to iomem resource */
static struct resource *register_memory_resource(u64 start, u64 size)
{
        struct resource *res;
        res = kzalloc(sizeof(struct resource), GFP_KERNEL);
        BUG_ON(!res);

        res->name = "System RAM";
        res->start = start;
        res->end = start + size - 1;
        res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
        if (request_resource(&iomem_resource, res) < 0) {
                printk("System RAM resource %llx - %llx cannot be added\n",
                (unsigned long long)res->start, (unsigned long long)res->end);
                kfree(res);
                res = NULL;
        }
        return res;
}

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

#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
#ifndef CONFIG_SPARSEMEM_VMEMMAP
static 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);
        atomic_inc(&page->_count);
}

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

        type = (unsigned long) page->lru.next;
        BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
               type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);

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

}

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

        if (!pfn_valid(start_pfn))
                return;

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

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

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

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

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

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

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

}

void register_page_bootmem_info_node(struct pglist_data *pgdat)
{
        unsigned long i, pfn, end_pfn, nr_pages;
        int node = pgdat->node_id;
        struct page *page;
        struct zone *zone;

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

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

        zone = &pgdat->node_zones[0];
        for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
                if (zone->wait_table) {
                        nr_pages = zone->wait_table_hash_nr_entries
                                * sizeof(wait_queue_head_t);
                        nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
                        page = virt_to_page(zone->wait_table);

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

        pfn = pgdat->node_start_pfn;
        end_pfn = pfn + pgdat->node_spanned_pages;

        /* register_section info */
        for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
                register_page_bootmem_info_section(pfn);

}
#endif /* !CONFIG_SPARSEMEM_VMEMMAP */

static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
                           unsigned long end_pfn)
{
        unsigned long old_zone_end_pfn;

        zone_span_writelock(zone);

        old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
        if (start_pfn < zone->zone_start_pfn)
                zone->zone_start_pfn = start_pfn;

        zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
                                zone->zone_start_pfn;

        zone_span_writeunlock(zone);
}

static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
                            unsigned long end_pfn)
{
        unsigned long old_pgdat_end_pfn =
                pgdat->node_start_pfn + pgdat->node_spanned_pages;

        if (start_pfn < pgdat->node_start_pfn)
                pgdat->node_start_pfn = start_pfn;

        pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
                                        pgdat->node_start_pfn;
}

static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
{
        struct pglist_data *pgdat = zone->zone_pgdat;
        int nr_pages = PAGES_PER_SECTION;
        int nid = pgdat->node_id;
        int zone_type;
        unsigned long flags;

        zone_type = zone - pgdat->node_zones;
        if (!zone->wait_table) {
                int ret;

                ret = init_currently_empty_zone(zone, phys_start_pfn,
                                                nr_pages, MEMMAP_HOTPLUG);
                if (ret)
                        return ret;
        }
        pgdat_resize_lock(zone->zone_pgdat, &flags);
        grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
        grow_pgdat_span(zone->zone_pgdat, phys_start_pfn,
                        phys_start_pfn + nr_pages);
        pgdat_resize_unlock(zone->zone_pgdat, &flags);
        memmap_init_zone(nr_pages, nid, zone_type,
                         phys_start_pfn, MEMMAP_HOTPLUG);
        return 0;
}

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

        if (pfn_valid(phys_start_pfn))
                return -EEXIST;

        ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);

        if (ret < 0)
                return ret;

        ret = __add_zone(zone, phys_start_pfn);

        if (ret < 0)
                return ret;

        return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
}

#ifdef CONFIG_SPARSEMEM_VMEMMAP
static int __remove_section(struct zone *zone, struct mem_section *ms)
{
        /*
         * XXX: Freeing memmap with vmemmap is not implement yet.
         *      This should be removed later.
         */
        return -EBUSY;
}
#else
static int __remove_section(struct zone *zone, struct mem_section *ms)
{
        unsigned long flags;
        struct pglist_data *pgdat = zone->zone_pgdat;
        int ret = -EINVAL;

        if (!valid_section(ms))
                return ret;

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

        pgdat_resize_lock(pgdat, &flags);
        sparse_remove_one_section(zone, ms);
        pgdat_resize_unlock(pgdat, &flags);
        return 0;
}
#endif

/*
 * Reasonably generic function for adding memory.  It is
 * expected that archs that support memory hotplug will
 * call this function after deciding the zone to which to
 * add the new pages.
 */
int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
                        unsigned long nr_pages)
{
        unsigned long i;
        int err = 0;
        int start_sec, end_sec;
        /* during initialize mem_map, align hot-added range to section */
        start_sec = pfn_to_section_nr(phys_start_pfn);
        end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);

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

                /*
                 * EEXIST is finally dealt with by ioresource collision
                 * check. see add_memory() => register_memory_resource()
                 * Warning will be printed if there is collision.
                 */
                if (err && (err != -EEXIST))
                        break;
                err = 0;
        }

        return err;
}
EXPORT_SYMBOL_GPL(__add_pages);

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

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

        sections_to_remove = nr_pages / PAGES_PER_SECTION;
        for (i = 0; i < sections_to_remove; i++) {
                unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
                release_mem_region(pfn << PAGE_SHIFT,
                                   PAGES_PER_SECTION << PAGE_SHIFT);
                ret = __remove_section(zone, __pfn_to_section(pfn));
                if (ret)
                        break;
        }
        return ret;
}
EXPORT_SYMBOL_GPL(__remove_pages);

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

        lock_memory_hotplug();

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

        unlock_memory_hotplug();

        return rc;
}
EXPORT_SYMBOL_GPL(set_online_page_callback);

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

        lock_memory_hotplug();

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

        unlock_memory_hotplug();

        return rc;
}
EXPORT_SYMBOL_GPL(restore_online_page_callback);

void __online_page_set_limits(struct page *page)
{
        unsigned long pfn = page_to_pfn(page);

        if (pfn >= num_physpages)
                num_physpages = pfn + 1;
}
EXPORT_SYMBOL_GPL(__online_page_set_limits);

void __online_page_increment_counters(struct page *page)
{
        totalram_pages++;

#ifdef CONFIG_HIGHMEM
        if (PageHighMem(page))
                totalhigh_pages++;
#endif
}
EXPORT_SYMBOL_GPL(__online_page_increment_counters);

void __online_page_free(struct page *page)
{
        ClearPageReserved(page);
        init_page_count(page);
        __free_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;
}


int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
{
        unsigned long onlined_pages = 0;
        struct zone *zone;
        int need_zonelists_rebuild = 0;
        int nid;
        int ret;
        struct memory_notify arg;

        lock_memory_hotplug();
        arg.start_pfn = pfn;
        arg.nr_pages = nr_pages;
        arg.status_change_nid = -1;

        nid = page_to_nid(pfn_to_page(pfn));
        if (node_present_pages(nid) == 0)
                arg.status_change_nid = nid;

        ret = memory_notify(MEM_GOING_ONLINE, &arg);
        ret = notifier_to_errno(ret);
        if (ret) {
                memory_notify(MEM_CANCEL_ONLINE, &arg);
                unlock_memory_hotplug();
                return ret;
        }
        /*
         * This doesn't need a lock to do pfn_to_page().
         * The section can't be removed here because of the
         * memory_block->state_mutex.
         */
        zone = page_zone(pfn_to_page(pfn));
        /*
         * If this zone is not populated, then it is not in zonelist.
         * This means the page allocator ignores this zone.
         * So, zonelist must be updated after online.
         */
        mutex_lock(&zonelists_mutex);
        if (!populated_zone(zone))
                need_zonelists_rebuild = 1;

        ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
                online_pages_range);
        if (ret) {
                mutex_unlock(&zonelists_mutex);
                printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
                        nr_pages, pfn);
                memory_notify(MEM_CANCEL_ONLINE, &arg);
                unlock_memory_hotplug();
                return ret;
        }

        zone->present_pages += onlined_pages;
        zone->zone_pgdat->node_present_pages += onlined_pages;
        if (need_zonelists_rebuild)
                build_all_zonelists(zone);
        else
                zone_pcp_update(zone);

        mutex_unlock(&zonelists_mutex);

        init_per_zone_wmark_min();

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

        vm_total_pages = nr_free_pagecache_pages();

        writeback_set_ratelimit();

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

        return 0;
}
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
{
        struct pglist_data *pgdat;
        unsigned long zones_size[MAX_NR_ZONES] = {0};
        unsigned long zholes_size[MAX_NR_ZONES] = {0};
        unsigned long start_pfn = start >> PAGE_SHIFT;

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

        arch_refresh_nodedata(nid, pgdat);

        /* we can use NODE_DATA(nid) from here */

        /* init node's zones as empty zones, we don't have any present pages.*/
        free_area_init_node(nid, zones_size, start_pfn, zholes_size);

        /*
         * 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(NULL);
        mutex_unlock(&zonelists_mutex);

        return pgdat;
}

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


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

        lock_memory_hotplug();
        pgdat = hotadd_new_pgdat(nid, 0);
        if (!pgdat) {
                ret = -ENOMEM;
                goto out;
        }
        node_set_online(nid);
        ret = register_one_node(nid);
        BUG_ON(ret);

out:
        unlock_memory_hotplug();
        return ret;
}

/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
int __ref add_memory(int nid, u64 start, u64 size)
{
        pg_data_t *pgdat = NULL;
        int new_pgdat = 0;
        struct resource *res;
        int ret;

        lock_memory_hotplug();

        res = register_memory_resource(start, size);
        ret = -EEXIST;
        if (!res)
                goto out;

        if (!node_online(nid)) {
                pgdat = hotadd_new_pgdat(nid, start);
                ret = -ENOMEM;
                if (!pgdat)
                        goto out;
                new_pgdat = 1;
        }

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

        if (ret < 0)
                goto error;

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

        if (new_pgdat) {
                ret = register_one_node(nid);
                /*
                 * If sysfs file of new node can't create, cpu on the node
                 * can't be hot-added. There is no rollback way now.
                 * So, check by BUG_ON() to catch it reluctantly..
                 */
                BUG_ON(ret);
        }

        /* create new memmap entry */
        firmware_map_add_hotplug(start, start + size, "System RAM");

        goto out;

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

out:
        unlock_memory_hotplug();
        return ret;
}
EXPORT_SYMBOL_GPL(add_memory);

#ifdef CONFIG_MEMORY_HOTREMOVE
/*
 * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
 * set and the size of the free page is given by page_order(). Using this,
 * the function determines if the pageblock contains only free pages.
 * Due to buddy contraints, a free page at least the size of a pageblock will
 * be located at the start of the pageblock
 */
static inline int pageblock_free(struct page *page)
{
        return PageBuddy(page) && page_order(page) >= pageblock_order;
}

/* Return the start of the next active pageblock after a given page */
static struct page *next_active_pageblock(struct page *page)
{
        /* Ensure the starting page is pageblock-aligned */
        BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));

        /* If the entire pageblock is free, move to the end of free page */
        if (pageblock_free(page)) {
                int order;
                /* be careful. we don't have locks, page_order can be changed.*/
                order = page_order(page);
                if ((order < MAX_ORDER) && (order >= pageblock_order))
                        return page + (1 << order);
        }

        return page + pageblock_nr_pages;
}

/* Checks if this range of memory is likely to be hot-removable. */
int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
{
        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 0;
                cond_resched();
        }

        /* All pageblocks in the memory block are likely to be hot-removable */
        return 1;
}

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

/*
 * Scanning pfn is much easier than scanning lru list.
 * Scan pfn from start to end and Find LRU page.
 */
static unsigned long scan_lru_pages(unsigned long start, unsigned long end)
{
        unsigned long pfn;
        struct page *page;
        for (pfn = start; pfn < end; pfn++) {
                if (pfn_valid(pfn)) {
                        page = pfn_to_page(pfn);
                        if (PageLRU(page))
                                return pfn;
                }
        }
        return 0;
}

static struct page *
hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
{
        /* This should be improooooved!! */
        return alloc_page(GFP_HIGHUSER_MOVABLE);
}

#define NR_OFFLINE_AT_ONCE_PAGES        (256)
static int
do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
{
        unsigned long pfn;
        struct page *page;
        int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
        int not_managed = 0;
        int ret = 0;
        LIST_HEAD(source);

        for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
                if (!pfn_valid(pfn))
                        continue;
                page = pfn_to_page(pfn);
                if (!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_zone_page_state(page, NR_ISOLATED_ANON +
                                            page_is_file_cache(page));

                } else {
#ifdef CONFIG_DEBUG_VM
                        printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
                               pfn);
                        dump_page(page);
#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_lru_pages(&source);
                        goto out;
                }
                /* this function returns # of failed pages */
                ret = migrate_pages(&source, hotremove_migrate_alloc, 0,
                                                        true, MIGRATE_SYNC);
                if (ret)
                        putback_lru_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);
        offlined = nr_pages;
        if (!ret)
                *(long *)data += offlined;
        return ret;
}

static long
check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
{
        long offlined = 0;
        int ret;

        ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, &offlined,
                        check_pages_isolated_cb);
        if (ret < 0)
                offlined = (long)ret;
        return offlined;
}

static int __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;
        struct zone *zone;
        struct memory_notify arg;

        BUG_ON(start_pfn >= end_pfn);
        /* at least, alignment against pageblock is necessary */
        if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
                return -EINVAL;
        if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
                return -EINVAL;
        /* This makes hotplug much easier...and readable.
           we assume this for now. .*/
        if (!test_pages_in_a_zone(start_pfn, end_pfn))
                return -EINVAL;

        lock_memory_hotplug();

        zone = page_zone(pfn_to_page(start_pfn));
        node = zone_to_nid(zone);
        nr_pages = end_pfn - start_pfn;

        /* set above range as isolated */
        ret = start_isolate_page_range(start_pfn, end_pfn);
        if (ret)
                goto out;

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

        ret = memory_notify(MEM_GOING_OFFLINE, &arg);
        ret = notifier_to_errno(ret);
        if (ret)
                goto failed_removal;

        pfn = start_pfn;
        expire = jiffies + timeout;
        drain = 0;
        retry_max = 5;
repeat:
        /* start memory hot removal */
        ret = -EAGAIN;
        if (time_after(jiffies, expire))
                goto failed_removal;
        ret = -EINTR;
        if (signal_pending(current))
                goto failed_removal;
        ret = 0;
        if (drain) {
                lru_add_drain_all();
                cond_resched();
                drain_all_pages();
        }

        pfn = scan_lru_pages(start_pfn, end_pfn);
        if (pfn) { /* We have page on LRU */
                ret = do_migrate_range(pfn, end_pfn);
                if (!ret) {
                        drain = 1;
                        goto repeat;
                } else {
                        if (ret < 0)
                                if (--retry_max == 0)
                                        goto failed_removal;
                        yield();
                        drain = 1;
                        goto repeat;
                }
        }
        /* drain all zone's lru pagevec, this is asyncronous... */
        lru_add_drain_all();
        yield();
        /* drain pcp pages , this is synchrouns. */
        drain_all_pages();
        /* check again */
        offlined_pages = check_pages_isolated(start_pfn, end_pfn);
        if (offlined_pages < 0) {
                ret = -EBUSY;
                goto failed_removal;
        }
        printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
        /* Ok, all of our target is islaoted.
           We cannot do rollback at this point. */
        offline_isolated_pages(start_pfn, end_pfn);
        /* reset pagetype flags and makes migrate type to be MOVABLE */
        undo_isolate_page_range(start_pfn, end_pfn);
        /* removal success */
        zone->present_pages -= offlined_pages;
        zone->zone_pgdat->node_present_pages -= offlined_pages;
        totalram_pages -= offlined_pages;

        init_per_zone_wmark_min();

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

        vm_total_pages = nr_free_pagecache_pages();
        writeback_set_ratelimit();

        memory_notify(MEM_OFFLINE, &arg);
        unlock_memory_hotplug();
        return 0;

failed_removal:
        printk(KERN_INFO "memory offlining %lx to %lx failed\n",
                start_pfn, end_pfn);
        memory_notify(MEM_CANCEL_OFFLINE, &arg);
        /* pushback to free area */
        undo_isolate_page_range(start_pfn, end_pfn);

out:
        unlock_memory_hotplug();
        return ret;
}

int remove_memory(u64 start, u64 size)
{
        unsigned long start_pfn, end_pfn;

        start_pfn = PFN_DOWN(start);
        end_pfn = start_pfn + PFN_DOWN(size);
        return offline_pages(start_pfn, end_pfn, 120 * HZ);
}
#else
int remove_memory(u64 start, u64 size)
{
        return -EINVAL;
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
EXPORT_SYMBOL_GPL(remove_memory);