Training courses

Kernel and Embedded Linux

Bootlin training courses

Embedded Linux, kernel,
Yocto Project, Buildroot, real-time,
graphics, boot time, debugging...

Bootlin logo

Elixir Cross Referencer

   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
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/swap.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 */

/*
 * This file contains the default values for the operation of the
 * Linux VM subsystem. Fine-tuning documentation can be found in
 * Documentation/admin-guide/sysctl/vm.rst.
 * Started 18.12.91
 * Swap aging added 23.2.95, Stephen Tweedie.
 * Buffermem limits added 12.3.98, Rik van Riel.
 */

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/mm_inline.h>
#include <linux/percpu_counter.h>
#include <linux/memremap.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/backing-dev.h>
#include <linux/memcontrol.h>
#include <linux/gfp.h>
#include <linux/uio.h>
#include <linux/hugetlb.h>
#include <linux/page_idle.h>

#include "internal.h"

#define CREATE_TRACE_POINTS
#include <trace/events/pagemap.h>

/* How many pages do we try to swap or page in/out together? */
int page_cluster;

static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
static DEFINE_PER_CPU(struct pagevec, lru_deactivate_file_pvecs);
static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
static DEFINE_PER_CPU(struct pagevec, lru_lazyfree_pvecs);
#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
#endif

/*
 * This path almost never happens for VM activity - pages are normally
 * freed via pagevecs.  But it gets used by networking.
 */
static void __page_cache_release(struct page *page)
{
	if (PageLRU(page)) {
		pg_data_t *pgdat = page_pgdat(page);
		struct lruvec *lruvec;
		unsigned long flags;

		spin_lock_irqsave(&pgdat->lru_lock, flags);
		lruvec = mem_cgroup_page_lruvec(page, pgdat);
		VM_BUG_ON_PAGE(!PageLRU(page), page);
		__ClearPageLRU(page);
		del_page_from_lru_list(page, lruvec, page_off_lru(page));
		spin_unlock_irqrestore(&pgdat->lru_lock, flags);
	}
	__ClearPageWaiters(page);
}

static void __put_single_page(struct page *page)
{
	__page_cache_release(page);
	mem_cgroup_uncharge(page);
	free_unref_page(page);
}

static void __put_compound_page(struct page *page)
{
	compound_page_dtor *dtor;

	/*
	 * __page_cache_release() is supposed to be called for thp, not for
	 * hugetlb. This is because hugetlb page does never have PageLRU set
	 * (it's never listed to any LRU lists) and no memcg routines should
	 * be called for hugetlb (it has a separate hugetlb_cgroup.)
	 */
	if (!PageHuge(page))
		__page_cache_release(page);
	dtor = get_compound_page_dtor(page);
	(*dtor)(page);
}

void __put_page(struct page *page)
{
	if (is_zone_device_page(page)) {
		put_dev_pagemap(page->pgmap);

		/*
		 * The page belongs to the device that created pgmap. Do
		 * not return it to page allocator.
		 */
		return;
	}

	if (unlikely(PageCompound(page)))
		__put_compound_page(page);
	else
		__put_single_page(page);
}
EXPORT_SYMBOL(__put_page);

/**
 * put_pages_list() - release a list of pages
 * @pages: list of pages threaded on page->lru
 *
 * Release a list of pages which are strung together on page.lru.  Currently
 * used by read_cache_pages() and related error recovery code.
 */
void put_pages_list(struct list_head *pages)
{
	while (!list_empty(pages)) {
		struct page *victim;

		victim = lru_to_page(pages);
		list_del(&victim->lru);
		put_page(victim);
	}
}
EXPORT_SYMBOL(put_pages_list);

/*
 * get_kernel_pages() - pin kernel pages in memory
 * @kiov:	An array of struct kvec structures
 * @nr_segs:	number of segments to pin
 * @write:	pinning for read/write, currently ignored
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_segs long.
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno. Each page returned must be released
 * with a put_page() call when it is finished with.
 */
int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
		struct page **pages)
{
	int seg;

	for (seg = 0; seg < nr_segs; seg++) {
		if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
			return seg;

		pages[seg] = kmap_to_page(kiov[seg].iov_base);
		get_page(pages[seg]);
	}

	return seg;
}
EXPORT_SYMBOL_GPL(get_kernel_pages);

/*
 * get_kernel_page() - pin a kernel page in memory
 * @start:	starting kernel address
 * @write:	pinning for read/write, currently ignored
 * @pages:	array that receives pointer to the page pinned.
 *		Must be at least nr_segs long.
 *
 * Returns 1 if page is pinned. If the page was not pinned, returns
 * -errno. The page returned must be released with a put_page() call
 * when it is finished with.
 */
int get_kernel_page(unsigned long start, int write, struct page **pages)
{
	const struct kvec kiov = {
		.iov_base = (void *)start,
		.iov_len = PAGE_SIZE
	};

	return get_kernel_pages(&kiov, 1, write, pages);
}
EXPORT_SYMBOL_GPL(get_kernel_page);

static void pagevec_lru_move_fn(struct pagevec *pvec,
	void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
	void *arg)
{
	int i;
	struct pglist_data *pgdat = NULL;
	struct lruvec *lruvec;
	unsigned long flags = 0;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct pglist_data *pagepgdat = page_pgdat(page);

		if (pagepgdat != pgdat) {
			if (pgdat)
				spin_unlock_irqrestore(&pgdat->lru_lock, flags);
			pgdat = pagepgdat;
			spin_lock_irqsave(&pgdat->lru_lock, flags);
		}

		lruvec = mem_cgroup_page_lruvec(page, pgdat);
		(*move_fn)(page, lruvec, arg);
	}
	if (pgdat)
		spin_unlock_irqrestore(&pgdat->lru_lock, flags);
	release_pages(pvec->pages, pvec->nr);
	pagevec_reinit(pvec);
}

static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
				 void *arg)
{
	int *pgmoved = arg;

	if (PageLRU(page) && !PageUnevictable(page)) {
		del_page_from_lru_list(page, lruvec, page_lru(page));
		ClearPageActive(page);
		add_page_to_lru_list_tail(page, lruvec, page_lru(page));
		(*pgmoved)++;
	}
}

/*
 * pagevec_move_tail() must be called with IRQ disabled.
 * Otherwise this may cause nasty races.
 */
static void pagevec_move_tail(struct pagevec *pvec)
{
	int pgmoved = 0;

	pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
	__count_vm_events(PGROTATED, pgmoved);
}

/*
 * Writeback is about to end against a page which has been marked for immediate
 * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 * inactive list.
 */
void rotate_reclaimable_page(struct page *page)
{
	if (!PageLocked(page) && !PageDirty(page) &&
	    !PageUnevictable(page) && PageLRU(page)) {
		struct pagevec *pvec;
		unsigned long flags;

		get_page(page);
		local_irq_save(flags);
		pvec = this_cpu_ptr(&lru_rotate_pvecs);
		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_move_tail(pvec);
		local_irq_restore(flags);
	}
}

static void update_page_reclaim_stat(struct lruvec *lruvec,
				     int file, int rotated)
{
	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;

	reclaim_stat->recent_scanned[file]++;
	if (rotated)
		reclaim_stat->recent_rotated[file]++;
}

static void __activate_page(struct page *page, struct lruvec *lruvec,
			    void *arg)
{
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		int file = page_is_file_cache(page);
		int lru = page_lru_base_type(page);

		del_page_from_lru_list(page, lruvec, lru);
		SetPageActive(page);
		lru += LRU_ACTIVE;
		add_page_to_lru_list(page, lruvec, lru);
		trace_mm_lru_activate(page);

		__count_vm_event(PGACTIVATE);
		update_page_reclaim_stat(lruvec, file, 1);
	}
}

#ifdef CONFIG_SMP
static void activate_page_drain(int cpu)
{
	struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);

	if (pagevec_count(pvec))
		pagevec_lru_move_fn(pvec, __activate_page, NULL);
}

static bool need_activate_page_drain(int cpu)
{
	return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
}

void activate_page(struct page *page)
{
	page = compound_head(page);
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);

		get_page(page);
		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_lru_move_fn(pvec, __activate_page, NULL);
		put_cpu_var(activate_page_pvecs);
	}
}

#else
static inline void activate_page_drain(int cpu)
{
}

void activate_page(struct page *page)
{
	pg_data_t *pgdat = page_pgdat(page);

	page = compound_head(page);
	spin_lock_irq(&pgdat->lru_lock);
	__activate_page(page, mem_cgroup_page_lruvec(page, pgdat), NULL);
	spin_unlock_irq(&pgdat->lru_lock);
}
#endif

static void __lru_cache_activate_page(struct page *page)
{
	struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
	int i;

	/*
	 * Search backwards on the optimistic assumption that the page being
	 * activated has just been added to this pagevec. Note that only
	 * the local pagevec is examined as a !PageLRU page could be in the
	 * process of being released, reclaimed, migrated or on a remote
	 * pagevec that is currently being drained. Furthermore, marking
	 * a remote pagevec's page PageActive potentially hits a race where
	 * a page is marked PageActive just after it is added to the inactive
	 * list causing accounting errors and BUG_ON checks to trigger.
	 */
	for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
		struct page *pagevec_page = pvec->pages[i];

		if (pagevec_page == page) {
			SetPageActive(page);
			break;
		}
	}

	put_cpu_var(lru_add_pvec);
}

/*
 * Mark a page as having seen activity.
 *
 * inactive,unreferenced	->	inactive,referenced
 * inactive,referenced		->	active,unreferenced
 * active,unreferenced		->	active,referenced
 *
 * When a newly allocated page is not yet visible, so safe for non-atomic ops,
 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
 */
void mark_page_accessed(struct page *page)
{
	page = compound_head(page);
	if (!PageActive(page) && !PageUnevictable(page) &&
			PageReferenced(page)) {

		/*
		 * If the page is on the LRU, queue it for activation via
		 * activate_page_pvecs. Otherwise, assume the page is on a
		 * pagevec, mark it active and it'll be moved to the active
		 * LRU on the next drain.
		 */
		if (PageLRU(page))
			activate_page(page);
		else
			__lru_cache_activate_page(page);
		ClearPageReferenced(page);
		if (page_is_file_cache(page))
			workingset_activation(page);
	} else if (!PageReferenced(page)) {
		SetPageReferenced(page);
	}
	if (page_is_idle(page))
		clear_page_idle(page);
}
EXPORT_SYMBOL(mark_page_accessed);

static void __lru_cache_add(struct page *page)
{
	struct pagevec *pvec = &get_cpu_var(lru_add_pvec);

	get_page(page);
	if (!pagevec_add(pvec, page) || PageCompound(page))
		__pagevec_lru_add(pvec);
	put_cpu_var(lru_add_pvec);
}

/**
 * lru_cache_add_anon - add a page to the page lists
 * @page: the page to add
 */
void lru_cache_add_anon(struct page *page)
{
	if (PageActive(page))
		ClearPageActive(page);
	__lru_cache_add(page);
}

void lru_cache_add_file(struct page *page)
{
	if (PageActive(page))
		ClearPageActive(page);
	__lru_cache_add(page);
}
EXPORT_SYMBOL(lru_cache_add_file);

/**
 * lru_cache_add - add a page to a page list
 * @page: the page to be added to the LRU.
 *
 * Queue the page for addition to the LRU via pagevec. The decision on whether
 * to add the page to the [in]active [file|anon] list is deferred until the
 * pagevec is drained. This gives a chance for the caller of lru_cache_add()
 * have the page added to the active list using mark_page_accessed().
 */
void lru_cache_add(struct page *page)
{
	VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
	VM_BUG_ON_PAGE(PageLRU(page), page);
	__lru_cache_add(page);
}

/**
 * lru_cache_add_active_or_unevictable
 * @page:  the page to be added to LRU
 * @vma:   vma in which page is mapped for determining reclaimability
 *
 * Place @page on the active or unevictable LRU list, depending on its
 * evictability.  Note that if the page is not evictable, it goes
 * directly back onto it's zone's unevictable list, it does NOT use a
 * per cpu pagevec.
 */
void lru_cache_add_active_or_unevictable(struct page *page,
					 struct vm_area_struct *vma)
{
	VM_BUG_ON_PAGE(PageLRU(page), page);

	if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
		SetPageActive(page);
	else if (!TestSetPageMlocked(page)) {
		/*
		 * We use the irq-unsafe __mod_zone_page_stat because this
		 * counter is not modified from interrupt context, and the pte
		 * lock is held(spinlock), which implies preemption disabled.
		 */
		__mod_zone_page_state(page_zone(page), NR_MLOCK,
				    hpage_nr_pages(page));
		count_vm_event(UNEVICTABLE_PGMLOCKED);
	}
	lru_cache_add(page);
}

/*
 * If the page can not be invalidated, it is moved to the
 * inactive list to speed up its reclaim.  It is moved to the
 * head of the list, rather than the tail, to give the flusher
 * threads some time to write it out, as this is much more
 * effective than the single-page writeout from reclaim.
 *
 * If the page isn't page_mapped and dirty/writeback, the page
 * could reclaim asap using PG_reclaim.
 *
 * 1. active, mapped page -> none
 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
 * 3. inactive, mapped page -> none
 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
 * 5. inactive, clean -> inactive, tail
 * 6. Others -> none
 *
 * In 4, why it moves inactive's head, the VM expects the page would
 * be write it out by flusher threads as this is much more effective
 * than the single-page writeout from reclaim.
 */
static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
			      void *arg)
{
	int lru, file;
	bool active;

	if (!PageLRU(page))
		return;

	if (PageUnevictable(page))
		return;

	/* Some processes are using the page */
	if (page_mapped(page))
		return;

	active = PageActive(page);
	file = page_is_file_cache(page);
	lru = page_lru_base_type(page);

	del_page_from_lru_list(page, lruvec, lru + active);
	ClearPageActive(page);
	ClearPageReferenced(page);

	if (PageWriteback(page) || PageDirty(page)) {
		/*
		 * PG_reclaim could be raced with end_page_writeback
		 * It can make readahead confusing.  But race window
		 * is _really_ small and  it's non-critical problem.
		 */
		add_page_to_lru_list(page, lruvec, lru);
		SetPageReclaim(page);
	} else {
		/*
		 * The page's writeback ends up during pagevec
		 * We moves tha page into tail of inactive.
		 */
		add_page_to_lru_list_tail(page, lruvec, lru);
		__count_vm_event(PGROTATED);
	}

	if (active)
		__count_vm_event(PGDEACTIVATE);
	update_page_reclaim_stat(lruvec, file, 0);
}

static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
			    void *arg)
{
	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
		int file = page_is_file_cache(page);
		int lru = page_lru_base_type(page);

		del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
		ClearPageActive(page);
		ClearPageReferenced(page);
		add_page_to_lru_list(page, lruvec, lru);

		__count_vm_events(PGDEACTIVATE, hpage_nr_pages(page));
		update_page_reclaim_stat(lruvec, file, 0);
	}
}

static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
			    void *arg)
{
	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
	    !PageSwapCache(page) && !PageUnevictable(page)) {
		bool active = PageActive(page);

		del_page_from_lru_list(page, lruvec,
				       LRU_INACTIVE_ANON + active);
		ClearPageActive(page);
		ClearPageReferenced(page);
		/*
		 * lazyfree pages are clean anonymous pages. They have
		 * SwapBacked flag cleared to distinguish normal anonymous
		 * pages
		 */
		ClearPageSwapBacked(page);
		add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);

		__count_vm_events(PGLAZYFREE, hpage_nr_pages(page));
		count_memcg_page_event(page, PGLAZYFREE);
		update_page_reclaim_stat(lruvec, 1, 0);
	}
}

/*
 * Drain pages out of the cpu's pagevecs.
 * Either "cpu" is the current CPU, and preemption has already been
 * disabled; or "cpu" is being hot-unplugged, and is already dead.
 */
void lru_add_drain_cpu(int cpu)
{
	struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);

	if (pagevec_count(pvec))
		__pagevec_lru_add(pvec);

	pvec = &per_cpu(lru_rotate_pvecs, cpu);
	if (pagevec_count(pvec)) {
		unsigned long flags;

		/* No harm done if a racing interrupt already did this */
		local_irq_save(flags);
		pagevec_move_tail(pvec);
		local_irq_restore(flags);
	}

	pvec = &per_cpu(lru_deactivate_file_pvecs, cpu);
	if (pagevec_count(pvec))
		pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);

	pvec = &per_cpu(lru_deactivate_pvecs, cpu);
	if (pagevec_count(pvec))
		pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);

	pvec = &per_cpu(lru_lazyfree_pvecs, cpu);
	if (pagevec_count(pvec))
		pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);

	activate_page_drain(cpu);
}

/**
 * deactivate_file_page - forcefully deactivate a file page
 * @page: page to deactivate
 *
 * This function hints the VM that @page is a good reclaim candidate,
 * for example if its invalidation fails due to the page being dirty
 * or under writeback.
 */
void deactivate_file_page(struct page *page)
{
	/*
	 * In a workload with many unevictable page such as mprotect,
	 * unevictable page deactivation for accelerating reclaim is pointless.
	 */
	if (PageUnevictable(page))
		return;

	if (likely(get_page_unless_zero(page))) {
		struct pagevec *pvec = &get_cpu_var(lru_deactivate_file_pvecs);

		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
		put_cpu_var(lru_deactivate_file_pvecs);
	}
}

/*
 * deactivate_page - deactivate a page
 * @page: page to deactivate
 *
 * deactivate_page() moves @page to the inactive list if @page was on the active
 * list and was not an unevictable page.  This is done to accelerate the reclaim
 * of @page.
 */
void deactivate_page(struct page *page)
{
	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);

		get_page(page);
		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
		put_cpu_var(lru_deactivate_pvecs);
	}
}

/**
 * mark_page_lazyfree - make an anon page lazyfree
 * @page: page to deactivate
 *
 * mark_page_lazyfree() moves @page to the inactive file list.
 * This is done to accelerate the reclaim of @page.
 */
void mark_page_lazyfree(struct page *page)
{
	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
	    !PageSwapCache(page) && !PageUnevictable(page)) {
		struct pagevec *pvec = &get_cpu_var(lru_lazyfree_pvecs);

		get_page(page);
		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
		put_cpu_var(lru_lazyfree_pvecs);
	}
}

void lru_add_drain(void)
{
	lru_add_drain_cpu(get_cpu());
	put_cpu();
}

#ifdef CONFIG_SMP

static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);

static void lru_add_drain_per_cpu(struct work_struct *dummy)
{
	lru_add_drain();
}

/*
 * Doesn't need any cpu hotplug locking because we do rely on per-cpu
 * kworkers being shut down before our page_alloc_cpu_dead callback is
 * executed on the offlined cpu.
 * Calling this function with cpu hotplug locks held can actually lead
 * to obscure indirect dependencies via WQ context.
 */
void lru_add_drain_all(void)
{
	static DEFINE_MUTEX(lock);
	static struct cpumask has_work;
	int cpu;

	/*
	 * Make sure nobody triggers this path before mm_percpu_wq is fully
	 * initialized.
	 */
	if (WARN_ON(!mm_percpu_wq))
		return;

	mutex_lock(&lock);
	cpumask_clear(&has_work);

	for_each_online_cpu(cpu) {
		struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);

		if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
		    pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
		    pagevec_count(&per_cpu(lru_deactivate_file_pvecs, cpu)) ||
		    pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
		    pagevec_count(&per_cpu(lru_lazyfree_pvecs, cpu)) ||
		    need_activate_page_drain(cpu)) {
			INIT_WORK(work, lru_add_drain_per_cpu);
			queue_work_on(cpu, mm_percpu_wq, work);
			cpumask_set_cpu(cpu, &has_work);
		}
	}

	for_each_cpu(cpu, &has_work)
		flush_work(&per_cpu(lru_add_drain_work, cpu));

	mutex_unlock(&lock);
}
#else
void lru_add_drain_all(void)
{
	lru_add_drain();
}
#endif

/**
 * release_pages - batched put_page()
 * @pages: array of pages to release
 * @nr: number of pages
 *
 * Decrement the reference count on all the pages in @pages.  If it
 * fell to zero, remove the page from the LRU and free it.
 */
void release_pages(struct page **pages, int nr)
{
	int i;
	LIST_HEAD(pages_to_free);
	struct pglist_data *locked_pgdat = NULL;
	struct lruvec *lruvec;
	unsigned long uninitialized_var(flags);
	unsigned int uninitialized_var(lock_batch);

	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		/*
		 * Make sure the IRQ-safe lock-holding time does not get
		 * excessive with a continuous string of pages from the
		 * same pgdat. The lock is held only if pgdat != NULL.
		 */
		if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
			spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
			locked_pgdat = NULL;
		}

		if (is_huge_zero_page(page))
			continue;

		if (is_zone_device_page(page)) {
			if (locked_pgdat) {
				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
						       flags);
				locked_pgdat = NULL;
			}
			/*
			 * ZONE_DEVICE pages that return 'false' from
			 * put_devmap_managed_page() do not require special
			 * processing, and instead, expect a call to
			 * put_page_testzero().
			 */
			if (put_devmap_managed_page(page))
				continue;
		}

		page = compound_head(page);
		if (!put_page_testzero(page))
			continue;

		if (PageCompound(page)) {
			if (locked_pgdat) {
				spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
				locked_pgdat = NULL;
			}
			__put_compound_page(page);
			continue;
		}

		if (PageLRU(page)) {
			struct pglist_data *pgdat = page_pgdat(page);

			if (pgdat != locked_pgdat) {
				if (locked_pgdat)
					spin_unlock_irqrestore(&locked_pgdat->lru_lock,
									flags);
				lock_batch = 0;
				locked_pgdat = pgdat;
				spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
			}

			lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
			VM_BUG_ON_PAGE(!PageLRU(page), page);
			__ClearPageLRU(page);
			del_page_from_lru_list(page, lruvec, page_off_lru(page));
		}

		/* Clear Active bit in case of parallel mark_page_accessed */
		__ClearPageActive(page);
		__ClearPageWaiters(page);

		list_add(&page->lru, &pages_to_free);
	}
	if (locked_pgdat)
		spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);

	mem_cgroup_uncharge_list(&pages_to_free);
	free_unref_page_list(&pages_to_free);
}
EXPORT_SYMBOL(release_pages);

/*
 * The pages which we're about to release may be in the deferred lru-addition
 * queues.  That would prevent them from really being freed right now.  That's
 * OK from a correctness point of view but is inefficient - those pages may be
 * cache-warm and we want to give them back to the page allocator ASAP.
 *
 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 * and __pagevec_lru_add_active() call release_pages() directly to avoid
 * mutual recursion.
 */
void __pagevec_release(struct pagevec *pvec)
{
	if (!pvec->percpu_pvec_drained) {
		lru_add_drain();
		pvec->percpu_pvec_drained = true;
	}
	release_pages(pvec->pages, pagevec_count(pvec));
	pagevec_reinit(pvec);
}
EXPORT_SYMBOL(__pagevec_release);

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/* used by __split_huge_page_refcount() */
void lru_add_page_tail(struct page *page, struct page *page_tail,
		       struct lruvec *lruvec, struct list_head *list)
{
	const int file = 0;

	VM_BUG_ON_PAGE(!PageHead(page), page);
	VM_BUG_ON_PAGE(PageCompound(page_tail), page);
	VM_BUG_ON_PAGE(PageLRU(page_tail), page);
	lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);

	if (!list)
		SetPageLRU(page_tail);

	if (likely(PageLRU(page)))
		list_add_tail(&page_tail->lru, &page->lru);
	else if (list) {
		/* page reclaim is reclaiming a huge page */
		get_page(page_tail);
		list_add_tail(&page_tail->lru, list);
	} else {
		/*
		 * Head page has not yet been counted, as an hpage,
		 * so we must account for each subpage individually.
		 *
		 * Put page_tail on the list at the correct position
		 * so they all end up in order.
		 */
		add_page_to_lru_list_tail(page_tail, lruvec,
					  page_lru(page_tail));
	}

	if (!PageUnevictable(page))
		update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
				 void *arg)
{
	enum lru_list lru;
	int was_unevictable = TestClearPageUnevictable(page);

	VM_BUG_ON_PAGE(PageLRU(page), page);

	SetPageLRU(page);
	/*
	 * Page becomes evictable in two ways:
	 * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
	 * 2) Before acquiring LRU lock to put the page to correct LRU and then
	 *   a) do PageLRU check with lock [check_move_unevictable_pages]
	 *   b) do PageLRU check before lock [clear_page_mlock]
	 *
	 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
	 * following strict ordering:
	 *
	 * #0: __pagevec_lru_add_fn		#1: clear_page_mlock
	 *
	 * SetPageLRU()				TestClearPageMlocked()
	 * smp_mb() // explicit ordering	// above provides strict
	 *					// ordering
	 * PageMlocked()			PageLRU()
	 *
	 *
	 * if '#1' does not observe setting of PG_lru by '#0' and fails
	 * isolation, the explicit barrier will make sure that page_evictable
	 * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
	 * can be reordered after PageMlocked check and can make '#1' to fail
	 * the isolation of the page whose Mlocked bit is cleared (#0 is also
	 * looking at the same page) and the evictable page will be stranded
	 * in an unevictable LRU.
	 */
	smp_mb();

	if (page_evictable(page)) {
		lru = page_lru(page);
		update_page_reclaim_stat(lruvec, page_is_file_cache(page),
					 PageActive(page));
		if (was_unevictable)
			count_vm_event(UNEVICTABLE_PGRESCUED);
	} else {
		lru = LRU_UNEVICTABLE;
		ClearPageActive(page);
		SetPageUnevictable(page);
		if (!was_unevictable)
			count_vm_event(UNEVICTABLE_PGCULLED);
	}

	add_page_to_lru_list(page, lruvec, lru);
	trace_mm_lru_insertion(page, lru);
}

/*
 * Add the passed pages to the LRU, then drop the caller's refcount
 * on them.  Reinitialises the caller's pagevec.
 */
void __pagevec_lru_add(struct pagevec *pvec)
{
	pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
}
EXPORT_SYMBOL(__pagevec_lru_add);

/**
 * pagevec_lookup_entries - gang pagecache lookup
 * @pvec:	Where the resulting entries are placed
 * @mapping:	The address_space to search
 * @start:	The starting entry index
 * @nr_entries:	The maximum number of pages
 * @indices:	The cache indices corresponding to the entries in @pvec
 *
 * pagevec_lookup_entries() will search for and return a group of up
 * to @nr_pages pages and shadow entries in the mapping.  All
 * entries are placed in @pvec.  pagevec_lookup_entries() takes a
 * reference against actual pages in @pvec.
 *
 * The search returns a group of mapping-contiguous entries with
 * ascending indexes.  There may be holes in the indices due to
 * not-present entries.
 *
 * pagevec_lookup_entries() returns the number of entries which were
 * found.
 */
unsigned pagevec_lookup_entries(struct pagevec *pvec,
				struct address_space *mapping,
				pgoff_t start, unsigned nr_entries,
				pgoff_t *indices)
{
	pvec->nr = find_get_entries(mapping, start, nr_entries,
				    pvec->pages, indices);
	return pagevec_count(pvec);
}

/**
 * pagevec_remove_exceptionals - pagevec exceptionals pruning
 * @pvec:	The pagevec to prune
 *
 * pagevec_lookup_entries() fills both pages and exceptional radix
 * tree entries into the pagevec.  This function prunes all
 * exceptionals from @pvec without leaving holes, so that it can be
 * passed on to page-only pagevec operations.
 */
void pagevec_remove_exceptionals(struct pagevec *pvec)
{
	int i, j;

	for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		if (!xa_is_value(page))
			pvec->pages[j++] = page;
	}
	pvec->nr = j;
}

/**
 * pagevec_lookup_range - gang pagecache lookup
 * @pvec:	Where the resulting pages are placed
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @end:	The final page index
 *
 * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
 * pages in the mapping starting from index @start and upto index @end
 * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
 * reference against the pages in @pvec.
 *
 * The search returns a group of mapping-contiguous pages with ascending
 * indexes.  There may be holes in the indices due to not-present pages. We
 * also update @start to index the next page for the traversal.
 *
 * pagevec_lookup_range() returns the number of pages which were found. If this
 * number is smaller than PAGEVEC_SIZE, the end of specified range has been
 * reached.
 */
unsigned pagevec_lookup_range(struct pagevec *pvec,
		struct address_space *mapping, pgoff_t *start, pgoff_t end)
{
	pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
					pvec->pages);
	return pagevec_count(pvec);
}
EXPORT_SYMBOL(pagevec_lookup_range);

unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
		struct address_space *mapping, pgoff_t *index, pgoff_t end,
		xa_mark_t tag)
{
	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
					PAGEVEC_SIZE, pvec->pages);
	return pagevec_count(pvec);
}
EXPORT_SYMBOL(pagevec_lookup_range_tag);

unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
		struct address_space *mapping, pgoff_t *index, pgoff_t end,
		xa_mark_t tag, unsigned max_pages)
{
	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
		min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
	return pagevec_count(pvec);
}
EXPORT_SYMBOL(pagevec_lookup_range_nr_tag);
/*
 * Perform any setup for the swap system
 */
void __init swap_setup(void)
{
	unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);

	/* Use a smaller cluster for small-memory machines */
	if (megs < 16)
		page_cluster = 2;
	else
		page_cluster = 3;
	/*
	 * Right now other parts of the system means that we
	 * _really_ don't want to cluster much more
	 */
}