summaryrefslogtreecommitdiffstats
path: root/mm/memory_hotplug.c
blob: 93aba78dc8b6985f458a0f6d3811ee0c7162ae97 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
/*
 *  linux/mm/memory_hotplug.c
 *
 *  Copyright (C)
 */

#include <linux/stddef.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/bootmem.h>
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/memory.h>
#include <linux/memory_hotplug.h>
#include <linux/highmem.h>
#include <linux/vmalloc.h>
#include <linux/ioport.h>
#include <linux/cpuset.h>
#include <linux/delay.h>
#include <linux/migrate.h>
#include <linux/page-isolation.h>

#include <asm/tlbflush.h>

#include "internal.h"

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

	res->name = "System RAM";
	res->start = start;
	res->end = start + size - 1;
	res->flags = IORESOURCE_MEM | 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, int type)
{
	atomic_set(&page->_mapcount, type);
	SetPagePrivate(page);
	set_page_private(page, info);
	atomic_inc(&page->_count);
}

void put_page_bootmem(struct page *page)
{
	int type;

	type = atomic_read(&page->_mapcount);
	BUG_ON(type >= -1);

	if (atomic_dec_return(&page->_count) == 1) {
		ClearPagePrivate(page);
		set_page_private(page, 0);
		reset_page_mapcount(page);
		__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 __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 __add_section(struct zone *zone, unsigned long phys_start_pfn)
{
	int nr_pages = PAGES_PER_SECTION;
	int ret;

	if (pfn_valid(phys_start_pfn))
		return -EEXIST;

	ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);

	if (ret < 0)
		return ret;

	ret = __add_zone(zone, phys_start_pfn);

	if (ret < 0)
		return ret;

	return register_new_memory(__pfn_to_section(phys_start_pfn));
}

#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 __add_pages(struct zone *zone, unsigned long phys_start_pfn,
		 unsigned long nr_pages)
{
	unsigned long i;
	int err = 0;
	int start_sec, end_sec;
	/* during initialize mem_map, align hot-added range to section */
	start_sec = pfn_to_section_nr(phys_start_pfn);
	end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);

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

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

	return err;
}
EXPORT_SYMBOL_GPL(__add_pages);

/**
 * __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);

	release_mem_region(phys_start_pfn << PAGE_SHIFT, nr_pages * PAGE_SIZE);

	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));
		if (ret)
			break;
	}
	return ret;
}
EXPORT_SYMBOL_GPL(__remove_pages);

void online_page(struct page *page)
{
	totalram_pages++;
	num_physpages++;

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

#ifdef CONFIG_FLATMEM
	max_mapnr = max(page_to_pfn(page), max_mapnr);
#endif

	ClearPageReserved(page);
	init_page_count(page);
	__free_page(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(page);
			onlined_pages++;
		}
	*(unsigned long *)arg = onlined_pages;
	return 0;
}


int 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;

	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);
		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.
	 */
	if (!populated_zone(zone))
		need_zonelists_rebuild = 1;

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

	zone->present_pages += onlined_pages;
	zone->zone_pgdat->node_present_pages += onlined_pages;

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

	if (need_zonelists_rebuild)
		build_all_zonelists();
	else
		vm_total_pages = nr_free_pagecache_pages();

	writeback_set_ratelimit();

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

	return 0;
}
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

static pg_data_t *hotadd_new_pgdat(int nid, u64 start)
{
	struct pglist_data *pgdat;
	unsigned long zones_size[MAX_NR_ZONES] = {0};
	unsigned long zholes_size[MAX_NR_ZONES] = {0};
	unsigned long start_pfn = start >> PAGE_SHIFT;

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

	arch_refresh_nodedata(nid, pgdat);

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

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

	return pgdat;
}

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


int add_memory(int nid, u64 start, u64 size)
{
	pg_data_t *pgdat = NULL;
	int new_pgdat = 0;
	struct resource *res;
	int ret;

	res = register_memory_resource(start, size);
	if (!res)
		return -EEXIST;

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

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

	if (ret < 0)
		goto error;

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

	cpuset_track_online_nodes();

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

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

	return ret;
}
EXPORT_SYMBOL_GPL(add_memory);

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

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

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


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

	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
		if (!pfn_valid(pfn))
			continue;
		page = pfn_to_page(pfn);
		if (!page_count(page))
			continue;
		/*
		 * We can skip free pages. And we can only deal with pages on
		 * LRU.
		 */
		ret = isolate_lru_page(page, &source);
		if (!ret) { /* Success */
			move_pages--;
		} else {
			/* Becasue we don't have big zone->lock. we should
			   check this again here. */
			if (page_count(page))
				not_managed++;
#ifdef CONFIG_DEBUG_VM
			printk(KERN_INFO "removing from LRU failed"
					 " %lx/%d/%lx\n",
				pfn, page_count(page), page->flags);
#endif
		}
	}
	ret = -EBUSY;
	if (not_managed) {
		if (!list_empty(&source))
			putback_lru_pages(&source);
		goto out;
	}
	ret = 0;
	if (list_empty(&source))
		goto out;
	/* this function returns # of failed pages */
	ret = migrate_pages(&source, hotremove_migrate_alloc, 0);

out:
	return ret;
}

/*
 * remove from free_area[] and mark all as Reserved.
 */
static int
offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
			void *data)
{
	__offline_isolated_pages(start, start + nr_pages);
	return 0;
}

static void
offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
{
	walk_memory_resource(start_pfn, end_pfn - start_pfn, NULL,
				offline_isolated_pages_cb);
}

/*
 * Check all pages in range, recoreded as memory resource, are isolated.
 */
static int
check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
			void *data)
{
	int ret;
	long offlined = *(long *)data;
	ret = test_pages_isolated(start_pfn, start_pfn + nr_pages);
	offlined = nr_pages;
	if (!ret)
		*(long *)data += offlined;
	return ret;
}

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

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

int offline_pages(unsigned long start_pfn,
		  unsigned long end_pfn, unsigned long timeout)
{
	unsigned long pfn, nr_pages, expire;
	long offlined_pages;
	int ret, drain, retry_max, 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;

	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)
		return ret;

	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();
		flush_scheduled_work();
		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();
	flush_scheduled_work();
	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;
	num_physpages -= offlined_pages;

	vm_total_pages = nr_free_pagecache_pages();
	writeback_set_ratelimit();

	memory_notify(MEM_OFFLINE, &arg);
	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);

	return ret;
}
#else
int remove_memory(u64 start, u64 size)
{
	return -EINVAL;
}
EXPORT_SYMBOL_GPL(remove_memory);
#endif /* CONFIG_MEMORY_HOTREMOVE */