aboutsummaryrefslogtreecommitdiff
path: root/mm/sparse.c
blob: 950981fd07c5f2686b08cb864c2e0f3d548d4d95 (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
799
800
801
802
803
/*
 * sparse memory mappings.
 */
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/mmzone.h>
#include <linux/bootmem.h>
#include <linux/highmem.h>
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include "internal.h"
#include <asm/dma.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>

/*
 * Permanent SPARSEMEM data:
 *
 * 1) mem_section	- memory sections, mem_map's for valid memory
 */
#ifdef CONFIG_SPARSEMEM_EXTREME
struct mem_section *mem_section[NR_SECTION_ROOTS]
	____cacheline_internodealigned_in_smp;
#else
struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
	____cacheline_internodealigned_in_smp;
#endif
EXPORT_SYMBOL(mem_section);

#ifdef NODE_NOT_IN_PAGE_FLAGS
/*
 * If we did not store the node number in the page then we have to
 * do a lookup in the section_to_node_table in order to find which
 * node the page belongs to.
 */
#if MAX_NUMNODES <= 256
static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
#else
static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
#endif

int page_to_nid(const struct page *page)
{
	return section_to_node_table[page_to_section(page)];
}
EXPORT_SYMBOL(page_to_nid);

static void set_section_nid(unsigned long section_nr, int nid)
{
	section_to_node_table[section_nr] = nid;
}
#else /* !NODE_NOT_IN_PAGE_FLAGS */
static inline void set_section_nid(unsigned long section_nr, int nid)
{
}
#endif

#ifdef CONFIG_SPARSEMEM_EXTREME
static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
{
	struct mem_section *section = NULL;
	unsigned long array_size = SECTIONS_PER_ROOT *
				   sizeof(struct mem_section);

	if (slab_is_available()) {
		if (node_state(nid, N_HIGH_MEMORY))
			section = kmalloc_node(array_size, GFP_KERNEL, nid);
		else
			section = kmalloc(array_size, GFP_KERNEL);
	} else
		section = alloc_bootmem_node(NODE_DATA(nid), array_size);

	if (section)
		memset(section, 0, array_size);

	return section;
}

static int __meminit sparse_index_init(unsigned long section_nr, int nid)
{
	static DEFINE_SPINLOCK(index_init_lock);
	unsigned long root = SECTION_NR_TO_ROOT(section_nr);
	struct mem_section *section;
	int ret = 0;

	if (mem_section[root])
		return -EEXIST;

	section = sparse_index_alloc(nid);
	if (!section)
		return -ENOMEM;
	/*
	 * This lock keeps two different sections from
	 * reallocating for the same index
	 */
	spin_lock(&index_init_lock);

	if (mem_section[root]) {
		ret = -EEXIST;
		goto out;
	}

	mem_section[root] = section;
out:
	spin_unlock(&index_init_lock);
	return ret;
}
#else /* !SPARSEMEM_EXTREME */
static inline int sparse_index_init(unsigned long section_nr, int nid)
{
	return 0;
}
#endif

/*
 * Although written for the SPARSEMEM_EXTREME case, this happens
 * to also work for the flat array case because
 * NR_SECTION_ROOTS==NR_MEM_SECTIONS.
 */
int __section_nr(struct mem_section* ms)
{
	unsigned long root_nr;
	struct mem_section* root;

	for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) {
		root = __nr_to_section(root_nr * SECTIONS_PER_ROOT);
		if (!root)
			continue;

		if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT)))
		     break;
	}

	return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
}

/*
 * During early boot, before section_mem_map is used for an actual
 * mem_map, we use section_mem_map to store the section's NUMA
 * node.  This keeps us from having to use another data structure.  The
 * node information is cleared just before we store the real mem_map.
 */
static inline unsigned long sparse_encode_early_nid(int nid)
{
	return (nid << SECTION_NID_SHIFT);
}

static inline int sparse_early_nid(struct mem_section *section)
{
	return (section->section_mem_map >> SECTION_NID_SHIFT);
}

/* Validate the physical addressing limitations of the model */
void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
						unsigned long *end_pfn)
{
	unsigned long max_sparsemem_pfn = 1UL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);

	/*
	 * Sanity checks - do not allow an architecture to pass
	 * in larger pfns than the maximum scope of sparsemem:
	 */
	if (*start_pfn > max_sparsemem_pfn) {
		mminit_dprintk(MMINIT_WARNING, "pfnvalidation",
			"Start of range %lu -> %lu exceeds SPARSEMEM max %lu\n",
			*start_pfn, *end_pfn, max_sparsemem_pfn);
		WARN_ON_ONCE(1);
		*start_pfn = max_sparsemem_pfn;
		*end_pfn = max_sparsemem_pfn;
	} else if (*end_pfn > max_sparsemem_pfn) {
		mminit_dprintk(MMINIT_WARNING, "pfnvalidation",
			"End of range %lu -> %lu exceeds SPARSEMEM max %lu\n",
			*start_pfn, *end_pfn, max_sparsemem_pfn);
		WARN_ON_ONCE(1);
		*end_pfn = max_sparsemem_pfn;
	}
}

/* Record a memory area against a node. */
void __init memory_present(int nid, unsigned long start, unsigned long end)
{
	unsigned long pfn;

	start &= PAGE_SECTION_MASK;
	mminit_validate_memmodel_limits(&start, &end);
	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
		unsigned long section = pfn_to_section_nr(pfn);
		struct mem_section *ms;

		sparse_index_init(section, nid);
		set_section_nid(section, nid);

		ms = __nr_to_section(section);
		if (!ms->section_mem_map)
			ms->section_mem_map = sparse_encode_early_nid(nid) |
							SECTION_MARKED_PRESENT;
	}
}

/*
 * Only used by the i386 NUMA architecures, but relatively
 * generic code.
 */
unsigned long __init node_memmap_size_bytes(int nid, unsigned long start_pfn,
						     unsigned long end_pfn)
{
	unsigned long pfn;
	unsigned long nr_pages = 0;

	mminit_validate_memmodel_limits(&start_pfn, &end_pfn);
	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
		if (nid != early_pfn_to_nid(pfn))
			continue;

		if (pfn_present(pfn))
			nr_pages += PAGES_PER_SECTION;
	}

	return nr_pages * sizeof(struct page);
}

/*
 * Subtle, we encode the real pfn into the mem_map such that
 * the identity pfn - section_mem_map will return the actual
 * physical page frame number.
 */
static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long pnum)
{
	return (unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
}

/*
 * Decode mem_map from the coded memmap
 */
struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
{
	/* mask off the extra low bits of information */
	coded_mem_map &= SECTION_MAP_MASK;
	return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
}

static int __meminit sparse_init_one_section(struct mem_section *ms,
		unsigned long pnum, struct page *mem_map,
		unsigned long *pageblock_bitmap)
{
	if (!present_section(ms))
		return -EINVAL;

	ms->section_mem_map &= ~SECTION_MAP_MASK;
	ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) |
							SECTION_HAS_MEM_MAP;
 	ms->pageblock_flags = pageblock_bitmap;

	return 1;
}

unsigned long usemap_size(void)
{
	unsigned long size_bytes;
	size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
	size_bytes = roundup(size_bytes, sizeof(unsigned long));
	return size_bytes;
}

#ifdef CONFIG_MEMORY_HOTPLUG
static unsigned long *__kmalloc_section_usemap(void)
{
	return kmalloc(usemap_size(), GFP_KERNEL);
}
#endif /* CONFIG_MEMORY_HOTPLUG */

#ifdef CONFIG_MEMORY_HOTREMOVE
static unsigned long * __init
sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
					 unsigned long size)
{
	unsigned long goal, limit;
	unsigned long *p;
	int nid;
	/*
	 * A page may contain usemaps for other sections preventing the
	 * page being freed and making a section unremovable while
	 * other sections referencing the usemap retmain active. Similarly,
	 * a pgdat can prevent a section being removed. If section A
	 * contains a pgdat and section B contains the usemap, both
	 * sections become inter-dependent. This allocates usemaps
	 * from the same section as the pgdat where possible to avoid
	 * this problem.
	 */
	goal = __pa(pgdat) & (PAGE_SECTION_MASK << PAGE_SHIFT);
	limit = goal + (1UL << PA_SECTION_SHIFT);
	nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
again:
	p = ___alloc_bootmem_node_nopanic(NODE_DATA(nid), size,
					  SMP_CACHE_BYTES, goal, limit);
	if (!p && limit) {
		limit = 0;
		goto again;
	}
	return p;
}

static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
{
	unsigned long usemap_snr, pgdat_snr;
	static unsigned long old_usemap_snr = NR_MEM_SECTIONS;
	static unsigned long old_pgdat_snr = NR_MEM_SECTIONS;
	struct pglist_data *pgdat = NODE_DATA(nid);
	int usemap_nid;

	usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT);
	pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
	if (usemap_snr == pgdat_snr)
		return;

	if (old_usemap_snr == usemap_snr && old_pgdat_snr == pgdat_snr)
		/* skip redundant message */
		return;

	old_usemap_snr = usemap_snr;
	old_pgdat_snr = pgdat_snr;

	usemap_nid = sparse_early_nid(__nr_to_section(usemap_snr));
	if (usemap_nid != nid) {
		printk(KERN_INFO
		       "node %d must be removed before remove section %ld\n",
		       nid, usemap_snr);
		return;
	}
	/*
	 * There is a circular dependency.
	 * Some platforms allow un-removable section because they will just
	 * gather other removable sections for dynamic partitioning.
	 * Just notify un-removable section's number here.
	 */
	printk(KERN_INFO "Section %ld and %ld (node %d)", usemap_snr,
	       pgdat_snr, nid);
	printk(KERN_CONT
	       " have a circular dependency on usemap and pgdat allocations\n");
}
#else
static unsigned long * __init
sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
					 unsigned long size)
{
	return alloc_bootmem_node_nopanic(pgdat, size);
}

static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
{
}
#endif /* CONFIG_MEMORY_HOTREMOVE */

static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map,
				 unsigned long pnum_begin,
				 unsigned long pnum_end,
				 unsigned long usemap_count, int nodeid)
{
	void *usemap;
	unsigned long pnum;
	int size = usemap_size();

	usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid),
							  size * usemap_count);
	if (!usemap) {
		printk(KERN_WARNING "%s: allocation failed\n", __func__);
		return;
	}

	for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
		if (!present_section_nr(pnum))
			continue;
		usemap_map[pnum] = usemap;
		usemap += size;
		check_usemap_section_nr(nodeid, usemap_map[pnum]);
	}
}

#ifndef CONFIG_SPARSEMEM_VMEMMAP
struct page __init *sparse_mem_map_populate(unsigned long pnum, int nid)
{
	struct page *map;
	unsigned long size;

	map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
	if (map)
		return map;

	size = PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
	map = __alloc_bootmem_node_high(NODE_DATA(nid), size,
					 PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
	return map;
}
void __init sparse_mem_maps_populate_node(struct page **map_map,
					  unsigned long pnum_begin,
					  unsigned long pnum_end,
					  unsigned long map_count, int nodeid)
{
	void *map;
	unsigned long pnum;
	unsigned long size = sizeof(struct page) * PAGES_PER_SECTION;

	map = alloc_remap(nodeid, size * map_count);
	if (map) {
		for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
			if (!present_section_nr(pnum))
				continue;
			map_map[pnum] = map;
			map += size;
		}
		return;
	}

	size = PAGE_ALIGN(size);
	map = __alloc_bootmem_node_high(NODE_DATA(nodeid), size * map_count,
					 PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
	if (map) {
		for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
			if (!present_section_nr(pnum))
				continue;
			map_map[pnum] = map;
			map += size;
		}
		return;
	}

	/* fallback */
	for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
		struct mem_section *ms;

		if (!present_section_nr(pnum))
			continue;
		map_map[pnum] = sparse_mem_map_populate(pnum, nodeid);
		if (map_map[pnum])
			continue;
		ms = __nr_to_section(pnum);
		printk(KERN_ERR "%s: sparsemem memory map backing failed "
			"some memory will not be available.\n", __func__);
		ms->section_mem_map = 0;
	}
}
#endif /* !CONFIG_SPARSEMEM_VMEMMAP */

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
static void __init sparse_early_mem_maps_alloc_node(struct page **map_map,
				 unsigned long pnum_begin,
				 unsigned long pnum_end,
				 unsigned long map_count, int nodeid)
{
	sparse_mem_maps_populate_node(map_map, pnum_begin, pnum_end,
					 map_count, nodeid);
}
#else
static struct page __init *sparse_early_mem_map_alloc(unsigned long pnum)
{
	struct page *map;
	struct mem_section *ms = __nr_to_section(pnum);
	int nid = sparse_early_nid(ms);

	map = sparse_mem_map_populate(pnum, nid);
	if (map)
		return map;

	printk(KERN_ERR "%s: sparsemem memory map backing failed "
			"some memory will not be available.\n", __func__);
	ms->section_mem_map = 0;
	return NULL;
}
#endif

void __attribute__((weak)) __meminit vmemmap_populate_print_last(void)
{
}

/*
 * Allocate the accumulated non-linear sections, allocate a mem_map
 * for each and record the physical to section mapping.
 */
void __init sparse_init(void)
{
	unsigned long pnum;
	struct page *map;
	unsigned long *usemap;
	unsigned long **usemap_map;
	int size;
	int nodeid_begin = 0;
	unsigned long pnum_begin = 0;
	unsigned long usemap_count;
#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
	unsigned long map_count;
	int size2;
	struct page **map_map;
#endif

	/* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
	set_pageblock_order();

	/*
	 * map is using big page (aka 2M in x86 64 bit)
	 * usemap is less one page (aka 24 bytes)
	 * so alloc 2M (with 2M align) and 24 bytes in turn will
	 * make next 2M slip to one more 2M later.
	 * then in big system, the memory will have a lot of holes...
	 * here try to allocate 2M pages continuously.
	 *
	 * powerpc need to call sparse_init_one_section right after each
	 * sparse_early_mem_map_alloc, so allocate usemap_map at first.
	 */
	size = sizeof(unsigned long *) * NR_MEM_SECTIONS;
	usemap_map = alloc_bootmem(size);
	if (!usemap_map)
		panic("can not allocate usemap_map\n");

	for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
		struct mem_section *ms;

		if (!present_section_nr(pnum))
			continue;
		ms = __nr_to_section(pnum);
		nodeid_begin = sparse_early_nid(ms);
		pnum_begin = pnum;
		break;
	}
	usemap_count = 1;
	for (pnum = pnum_begin + 1; pnum < NR_MEM_SECTIONS; pnum++) {
		struct mem_section *ms;
		int nodeid;

		if (!present_section_nr(pnum))
			continue;
		ms = __nr_to_section(pnum);
		nodeid = sparse_early_nid(ms);
		if (nodeid == nodeid_begin) {
			usemap_count++;
			continue;
		}
		/* ok, we need to take cake of from pnum_begin to pnum - 1*/
		sparse_early_usemaps_alloc_node(usemap_map, pnum_begin, pnum,
						 usemap_count, nodeid_begin);
		/* new start, update count etc*/
		nodeid_begin = nodeid;
		pnum_begin = pnum;
		usemap_count = 1;
	}
	/* ok, last chunk */
	sparse_early_usemaps_alloc_node(usemap_map, pnum_begin, NR_MEM_SECTIONS,
					 usemap_count, nodeid_begin);

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
	size2 = sizeof(struct page *) * NR_MEM_SECTIONS;
	map_map = alloc_bootmem(size2);
	if (!map_map)
		panic("can not allocate map_map\n");

	for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
		struct mem_section *ms;

		if (!present_section_nr(pnum))
			continue;
		ms = __nr_to_section(pnum);
		nodeid_begin = sparse_early_nid(ms);
		pnum_begin = pnum;
		break;
	}
	map_count = 1;
	for (pnum = pnum_begin + 1; pnum < NR_MEM_SECTIONS; pnum++) {
		struct mem_section *ms;
		int nodeid;

		if (!present_section_nr(pnum))
			continue;
		ms = __nr_to_section(pnum);
		nodeid = sparse_early_nid(ms);
		if (nodeid == nodeid_begin) {
			map_count++;
			continue;
		}
		/* ok, we need to take cake of from pnum_begin to pnum - 1*/
		sparse_early_mem_maps_alloc_node(map_map, pnum_begin, pnum,
						 map_count, nodeid_begin);
		/* new start, update count etc*/
		nodeid_begin = nodeid;
		pnum_begin = pnum;
		map_count = 1;
	}
	/* ok, last chunk */
	sparse_early_mem_maps_alloc_node(map_map, pnum_begin, NR_MEM_SECTIONS,
					 map_count, nodeid_begin);
#endif

	for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
		if (!present_section_nr(pnum))
			continue;

		usemap = usemap_map[pnum];
		if (!usemap)
			continue;

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
		map = map_map[pnum];
#else
		map = sparse_early_mem_map_alloc(pnum);
#endif
		if (!map)
			continue;

		sparse_init_one_section(__nr_to_section(pnum), pnum, map,
								usemap);
	}

	vmemmap_populate_print_last();

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
	free_bootmem(__pa(map_map), size2);
#endif
	free_bootmem(__pa(usemap_map), size);
}

#ifdef CONFIG_MEMORY_HOTPLUG
#ifdef CONFIG_SPARSEMEM_VMEMMAP
static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
						 unsigned long nr_pages)
{
	/* This will make the necessary allocations eventually. */
	return sparse_mem_map_populate(pnum, nid);
}
static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
{
	return; /* XXX: Not implemented yet */
}
static void free_map_bootmem(struct page *page, unsigned long nr_pages)
{
}
#else
static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
{
	struct page *page, *ret;
	unsigned long memmap_size = sizeof(struct page) * nr_pages;

	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
	if (page)
		goto got_map_page;

	ret = vmalloc(memmap_size);
	if (ret)
		goto got_map_ptr;

	return NULL;
got_map_page:
	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
got_map_ptr:
	memset(ret, 0, memmap_size);

	return ret;
}

static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
						  unsigned long nr_pages)
{
	return __kmalloc_section_memmap(nr_pages);
}

static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
{
	if (is_vmalloc_addr(memmap))
		vfree(memmap);
	else
		free_pages((unsigned long)memmap,
			   get_order(sizeof(struct page) * nr_pages));
}

static void free_map_bootmem(struct page *page, unsigned long nr_pages)
{
	unsigned long maps_section_nr, removing_section_nr, i;
	unsigned long magic;

	for (i = 0; i < nr_pages; i++, page++) {
		magic = (unsigned long) page->lru.next;

		BUG_ON(magic == NODE_INFO);

		maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
		removing_section_nr = page->private;

		/*
		 * When this function is called, the removing section is
		 * logical offlined state. This means all pages are isolated
		 * from page allocator. If removing section's memmap is placed
		 * on the same section, it must not be freed.
		 * If it is freed, page allocator may allocate it which will
		 * be removed physically soon.
		 */
		if (maps_section_nr != removing_section_nr)
			put_page_bootmem(page);
	}
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

static void free_section_usemap(struct page *memmap, unsigned long *usemap)
{
	struct page *usemap_page;
	unsigned long nr_pages;

	if (!usemap)
		return;

	usemap_page = virt_to_page(usemap);
	/*
	 * Check to see if allocation came from hot-plug-add
	 */
	if (PageSlab(usemap_page)) {
		kfree(usemap);
		if (memmap)
			__kfree_section_memmap(memmap, PAGES_PER_SECTION);
		return;
	}

	/*
	 * The usemap came from bootmem. This is packed with other usemaps
	 * on the section which has pgdat at boot time. Just keep it as is now.
	 */

	if (memmap) {
		struct page *memmap_page;
		memmap_page = virt_to_page(memmap);

		nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
			>> PAGE_SHIFT;

		free_map_bootmem(memmap_page, nr_pages);
	}
}

/*
 * returns the number of sections whose mem_maps were properly
 * set.  If this is <=0, then that means that the passed-in
 * map was not consumed and must be freed.
 */
int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
			   int nr_pages)
{
	unsigned long section_nr = pfn_to_section_nr(start_pfn);
	struct pglist_data *pgdat = zone->zone_pgdat;
	struct mem_section *ms;
	struct page *memmap;
	unsigned long *usemap;
	unsigned long flags;
	int ret;

	/*
	 * no locking for this, because it does its own
	 * plus, it does a kmalloc
	 */
	ret = sparse_index_init(section_nr, pgdat->node_id);
	if (ret < 0 && ret != -EEXIST)
		return ret;
	memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, nr_pages);
	if (!memmap)
		return -ENOMEM;
	usemap = __kmalloc_section_usemap();
	if (!usemap) {
		__kfree_section_memmap(memmap, nr_pages);
		return -ENOMEM;
	}

	pgdat_resize_lock(pgdat, &flags);

	ms = __pfn_to_section(start_pfn);
	if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
		ret = -EEXIST;
		goto out;
	}

	ms->section_mem_map |= SECTION_MARKED_PRESENT;

	ret = sparse_init_one_section(ms, section_nr, memmap, usemap);

out:
	pgdat_resize_unlock(pgdat, &flags);
	if (ret <= 0) {
		kfree(usemap);
		__kfree_section_memmap(memmap, nr_pages);
	}
	return ret;
}

void sparse_remove_one_section(struct zone *zone, struct mem_section *ms)
{
	struct page *memmap = NULL;
	unsigned long *usemap = NULL;

	if (ms->section_mem_map) {
		usemap = ms->pageblock_flags;
		memmap = sparse_decode_mem_map(ms->section_mem_map,
						__section_nr(ms));
		ms->section_mem_map = 0;
		ms->pageblock_flags = NULL;
	}

	free_section_usemap(memmap, usemap);
}
#endif