zte's code,first commit

Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/mm/memory_hotplug.c b/ap/os/linux/linux-3.4.x/mm/memory_hotplug.c
new file mode 100644
index 0000000..09d87b7
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/mm/memory_hotplug.c
@@ -0,0 +1,1010 @@
+/*
+ *  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;
+
+	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) {
+		/*
+		 * 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 node.
+		 */
+		if (pfn_valid(pfn) && (pfn_to_nid(pfn) == node))
+			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 (onlined_pages) {
+		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
+		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));
+
+	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);