aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/pagemap.h
blob: 20225b067583ab552a0fc22a22c6bad81cabd12a (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
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
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_PAGEMAP_H
#define _LINUX_PAGEMAP_H

/*
 * Copyright 1995 Linus Torvalds
 */
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/compiler.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/bitops.h>
#include <linux/hardirq.h> /* for in_interrupt() */
#include <linux/hugetlb_inline.h>

struct pagevec;

/*
 * Bits in mapping->flags.
 */
enum mapping_flags {
	AS_EIO		= 0,	/* IO error on async write */
	AS_ENOSPC	= 1,	/* ENOSPC on async write */
	AS_MM_ALL_LOCKS	= 2,	/* under mm_take_all_locks() */
	AS_UNEVICTABLE	= 3,	/* e.g., ramdisk, SHM_LOCK */
	AS_EXITING	= 4, 	/* final truncate in progress */
	/* writeback related tags are not used */
	AS_NO_WRITEBACK_TAGS = 5,
	AS_THP_SUPPORT = 6,	/* THPs supported */
};

/**
 * mapping_set_error - record a writeback error in the address_space
 * @mapping: the mapping in which an error should be set
 * @error: the error to set in the mapping
 *
 * When writeback fails in some way, we must record that error so that
 * userspace can be informed when fsync and the like are called.  We endeavor
 * to report errors on any file that was open at the time of the error.  Some
 * internal callers also need to know when writeback errors have occurred.
 *
 * When a writeback error occurs, most filesystems will want to call
 * mapping_set_error to record the error in the mapping so that it can be
 * reported when the application calls fsync(2).
 */
static inline void mapping_set_error(struct address_space *mapping, int error)
{
	if (likely(!error))
		return;

	/* Record in wb_err for checkers using errseq_t based tracking */
	__filemap_set_wb_err(mapping, error);

	/* Record it in superblock */
	if (mapping->host)
		errseq_set(&mapping->host->i_sb->s_wb_err, error);

	/* Record it in flags for now, for legacy callers */
	if (error == -ENOSPC)
		set_bit(AS_ENOSPC, &mapping->flags);
	else
		set_bit(AS_EIO, &mapping->flags);
}

static inline void mapping_set_unevictable(struct address_space *mapping)
{
	set_bit(AS_UNEVICTABLE, &mapping->flags);
}

static inline void mapping_clear_unevictable(struct address_space *mapping)
{
	clear_bit(AS_UNEVICTABLE, &mapping->flags);
}

static inline bool mapping_unevictable(struct address_space *mapping)
{
	return mapping && test_bit(AS_UNEVICTABLE, &mapping->flags);
}

static inline void mapping_set_exiting(struct address_space *mapping)
{
	set_bit(AS_EXITING, &mapping->flags);
}

static inline int mapping_exiting(struct address_space *mapping)
{
	return test_bit(AS_EXITING, &mapping->flags);
}

static inline void mapping_set_no_writeback_tags(struct address_space *mapping)
{
	set_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
}

static inline int mapping_use_writeback_tags(struct address_space *mapping)
{
	return !test_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
}

static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
{
	return mapping->gfp_mask;
}

/* Restricts the given gfp_mask to what the mapping allows. */
static inline gfp_t mapping_gfp_constraint(struct address_space *mapping,
		gfp_t gfp_mask)
{
	return mapping_gfp_mask(mapping) & gfp_mask;
}

/*
 * This is non-atomic.  Only to be used before the mapping is activated.
 * Probably needs a barrier...
 */
static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
{
	m->gfp_mask = mask;
}

static inline bool mapping_thp_support(struct address_space *mapping)
{
	return test_bit(AS_THP_SUPPORT, &mapping->flags);
}

static inline int filemap_nr_thps(struct address_space *mapping)
{
#ifdef CONFIG_READ_ONLY_THP_FOR_FS
	return atomic_read(&mapping->nr_thps);
#else
	return 0;
#endif
}

static inline void filemap_nr_thps_inc(struct address_space *mapping)
{
#ifdef CONFIG_READ_ONLY_THP_FOR_FS
	if (!mapping_thp_support(mapping))
		atomic_inc(&mapping->nr_thps);
#else
	WARN_ON_ONCE(1);
#endif
}

static inline void filemap_nr_thps_dec(struct address_space *mapping)
{
#ifdef CONFIG_READ_ONLY_THP_FOR_FS
	if (!mapping_thp_support(mapping))
		atomic_dec(&mapping->nr_thps);
#else
	WARN_ON_ONCE(1);
#endif
}

void release_pages(struct page **pages, int nr);

/*
 * speculatively take a reference to a page.
 * If the page is free (_refcount == 0), then _refcount is untouched, and 0
 * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned.
 *
 * This function must be called inside the same rcu_read_lock() section as has
 * been used to lookup the page in the pagecache radix-tree (or page table):
 * this allows allocators to use a synchronize_rcu() to stabilize _refcount.
 *
 * Unless an RCU grace period has passed, the count of all pages coming out
 * of the allocator must be considered unstable. page_count may return higher
 * than expected, and put_page must be able to do the right thing when the
 * page has been finished with, no matter what it is subsequently allocated
 * for (because put_page is what is used here to drop an invalid speculative
 * reference).
 *
 * This is the interesting part of the lockless pagecache (and lockless
 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
 * has the following pattern:
 * 1. find page in radix tree
 * 2. conditionally increment refcount
 * 3. check the page is still in pagecache (if no, goto 1)
 *
 * Remove-side that cares about stability of _refcount (eg. reclaim) has the
 * following (with the i_pages lock held):
 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
 * B. remove page from pagecache
 * C. free the page
 *
 * There are 2 critical interleavings that matter:
 * - 2 runs before A: in this case, A sees elevated refcount and bails out
 * - A runs before 2: in this case, 2 sees zero refcount and retries;
 *   subsequently, B will complete and 1 will find no page, causing the
 *   lookup to return NULL.
 *
 * It is possible that between 1 and 2, the page is removed then the exact same
 * page is inserted into the same position in pagecache. That's OK: the
 * old find_get_page using a lock could equally have run before or after
 * such a re-insertion, depending on order that locks are granted.
 *
 * Lookups racing against pagecache insertion isn't a big problem: either 1
 * will find the page or it will not. Likewise, the old find_get_page could run
 * either before the insertion or afterwards, depending on timing.
 */
static inline int __page_cache_add_speculative(struct page *page, int count)
{
#ifdef CONFIG_TINY_RCU
# ifdef CONFIG_PREEMPT_COUNT
	VM_BUG_ON(!in_atomic() && !irqs_disabled());
# endif
	/*
	 * Preempt must be disabled here - we rely on rcu_read_lock doing
	 * this for us.
	 *
	 * Pagecache won't be truncated from interrupt context, so if we have
	 * found a page in the radix tree here, we have pinned its refcount by
	 * disabling preempt, and hence no need for the "speculative get" that
	 * SMP requires.
	 */
	VM_BUG_ON_PAGE(page_count(page) == 0, page);
	page_ref_add(page, count);

#else
	if (unlikely(!page_ref_add_unless(page, count, 0))) {
		/*
		 * Either the page has been freed, or will be freed.
		 * In either case, retry here and the caller should
		 * do the right thing (see comments above).
		 */
		return 0;
	}
#endif
	VM_BUG_ON_PAGE(PageTail(page), page);

	return 1;
}

static inline int page_cache_get_speculative(struct page *page)
{
	return __page_cache_add_speculative(page, 1);
}

static inline int page_cache_add_speculative(struct page *page, int count)
{
	return __page_cache_add_speculative(page, count);
}

/**
 * attach_page_private - Attach private data to a page.
 * @page: Page to attach data to.
 * @data: Data to attach to page.
 *
 * Attaching private data to a page increments the page's reference count.
 * The data must be detached before the page will be freed.
 */
static inline void attach_page_private(struct page *page, void *data)
{
	get_page(page);
	set_page_private(page, (unsigned long)data);
	SetPagePrivate(page);
}

/**
 * detach_page_private - Detach private data from a page.
 * @page: Page to detach data from.
 *
 * Removes the data that was previously attached to the page and decrements
 * the refcount on the page.
 *
 * Return: Data that was attached to the page.
 */
static inline void *detach_page_private(struct page *page)
{
	void *data = (void *)page_private(page);

	if (!PagePrivate(page))
		return NULL;
	ClearPagePrivate(page);
	set_page_private(page, 0);
	put_page(page);

	return data;
}

#ifdef CONFIG_NUMA
extern struct page *__page_cache_alloc(gfp_t gfp);
#else
static inline struct page *__page_cache_alloc(gfp_t gfp)
{
	return alloc_pages(gfp, 0);
}
#endif

static inline struct page *page_cache_alloc(struct address_space *x)
{
	return __page_cache_alloc(mapping_gfp_mask(x));
}

static inline gfp_t readahead_gfp_mask(struct address_space *x)
{
	return mapping_gfp_mask(x) | __GFP_NORETRY | __GFP_NOWARN;
}

typedef int filler_t(void *, struct page *);

pgoff_t page_cache_next_miss(struct address_space *mapping,
			     pgoff_t index, unsigned long max_scan);
pgoff_t page_cache_prev_miss(struct address_space *mapping,
			     pgoff_t index, unsigned long max_scan);

#define FGP_ACCESSED		0x00000001
#define FGP_LOCK		0x00000002
#define FGP_CREAT		0x00000004
#define FGP_WRITE		0x00000008
#define FGP_NOFS		0x00000010
#define FGP_NOWAIT		0x00000020
#define FGP_FOR_MMAP		0x00000040
#define FGP_HEAD		0x00000080
#define FGP_ENTRY		0x00000100

struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
		int fgp_flags, gfp_t cache_gfp_mask);

/**
 * find_get_page - find and get a page reference
 * @mapping: the address_space to search
 * @offset: the page index
 *
 * Looks up the page cache slot at @mapping & @offset.  If there is a
 * page cache page, it is returned with an increased refcount.
 *
 * Otherwise, %NULL is returned.
 */
static inline struct page *find_get_page(struct address_space *mapping,
					pgoff_t offset)
{
	return pagecache_get_page(mapping, offset, 0, 0);
}

static inline struct page *find_get_page_flags(struct address_space *mapping,
					pgoff_t offset, int fgp_flags)
{
	return pagecache_get_page(mapping, offset, fgp_flags, 0);
}

/**
 * find_lock_page - locate, pin and lock a pagecache page
 * @mapping: the address_space to search
 * @index: the page index
 *
 * Looks up the page cache entry at @mapping & @index.  If there is a
 * page cache page, it is returned locked and with an increased
 * refcount.
 *
 * Context: May sleep.
 * Return: A struct page or %NULL if there is no page in the cache for this
 * index.
 */
static inline struct page *find_lock_page(struct address_space *mapping,
					pgoff_t index)
{
	return pagecache_get_page(mapping, index, FGP_LOCK, 0);
}

/**
 * find_lock_head - Locate, pin and lock a pagecache page.
 * @mapping: The address_space to search.
 * @index: The page index.
 *
 * Looks up the page cache entry at @mapping & @index.  If there is a
 * page cache page, its head page is returned locked and with an increased
 * refcount.
 *
 * Context: May sleep.
 * Return: A struct page which is !PageTail, or %NULL if there is no page
 * in the cache for this index.
 */
static inline struct page *find_lock_head(struct address_space *mapping,
					pgoff_t index)
{
	return pagecache_get_page(mapping, index, FGP_LOCK | FGP_HEAD, 0);
}

/**
 * find_or_create_page - locate or add a pagecache page
 * @mapping: the page's address_space
 * @index: the page's index into the mapping
 * @gfp_mask: page allocation mode
 *
 * Looks up the page cache slot at @mapping & @offset.  If there is a
 * page cache page, it is returned locked and with an increased
 * refcount.
 *
 * If the page is not present, a new page is allocated using @gfp_mask
 * and added to the page cache and the VM's LRU list.  The page is
 * returned locked and with an increased refcount.
 *
 * On memory exhaustion, %NULL is returned.
 *
 * find_or_create_page() may sleep, even if @gfp_flags specifies an
 * atomic allocation!
 */
static inline struct page *find_or_create_page(struct address_space *mapping,
					pgoff_t index, gfp_t gfp_mask)
{
	return pagecache_get_page(mapping, index,
					FGP_LOCK|FGP_ACCESSED|FGP_CREAT,
					gfp_mask);
}

/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
 * This is intended for speculative data generators, where the data can
 * be regenerated if the page couldn't be grabbed.  This routine should
 * be safe to call while holding the lock for another page.
 *
 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
 * and deadlock against the caller's locked page.
 */
static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
				pgoff_t index)
{
	return pagecache_get_page(mapping, index,
			FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
			mapping_gfp_mask(mapping));
}

/* Does this page contain this index? */
static inline bool thp_contains(struct page *head, pgoff_t index)
{
	/* HugeTLBfs indexes the page cache in units of hpage_size */
	if (PageHuge(head))
		return head->index == index;
	return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL));
}

/*
 * Given the page we found in the page cache, return the page corresponding
 * to this index in the file
 */
static inline struct page *find_subpage(struct page *head, pgoff_t index)
{
	/* HugeTLBfs wants the head page regardless */
	if (PageHuge(head))
		return head;

	return head + (index & (thp_nr_pages(head) - 1));
}

unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
		pgoff_t end, struct pagevec *pvec, pgoff_t *indices);
unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
			pgoff_t end, unsigned int nr_pages,
			struct page **pages);
static inline unsigned find_get_pages(struct address_space *mapping,
			pgoff_t *start, unsigned int nr_pages,
			struct page **pages)
{
	return find_get_pages_range(mapping, start, (pgoff_t)-1, nr_pages,
				    pages);
}
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
			       unsigned int nr_pages, struct page **pages);
unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
			pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
			struct page **pages);
static inline unsigned find_get_pages_tag(struct address_space *mapping,
			pgoff_t *index, xa_mark_t tag, unsigned int nr_pages,
			struct page **pages)
{
	return find_get_pages_range_tag(mapping, index, (pgoff_t)-1, tag,
					nr_pages, pages);
}

struct page *grab_cache_page_write_begin(struct address_space *mapping,
			pgoff_t index, unsigned flags);

/*
 * Returns locked page at given index in given cache, creating it if needed.
 */
static inline struct page *grab_cache_page(struct address_space *mapping,
								pgoff_t index)
{
	return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
}

extern struct page * read_cache_page(struct address_space *mapping,
				pgoff_t index, filler_t *filler, void *data);
extern struct page * read_cache_page_gfp(struct address_space *mapping,
				pgoff_t index, gfp_t gfp_mask);
extern int read_cache_pages(struct address_space *mapping,
		struct list_head *pages, filler_t *filler, void *data);

static inline struct page *read_mapping_page(struct address_space *mapping,
				pgoff_t index, void *data)
{
	return read_cache_page(mapping, index, NULL, data);
}

/*
 * Get index of the page with in radix-tree
 * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
 */
static inline pgoff_t page_to_index(struct page *page)
{
	pgoff_t pgoff;

	if (likely(!PageTransTail(page)))
		return page->index;

	/*
	 *  We don't initialize ->index for tail pages: calculate based on
	 *  head page
	 */
	pgoff = compound_head(page)->index;
	pgoff += page - compound_head(page);
	return pgoff;
}

/*
 * Get the offset in PAGE_SIZE.
 * (TODO: hugepage should have ->index in PAGE_SIZE)
 */
static inline pgoff_t page_to_pgoff(struct page *page)
{
	if (unlikely(PageHeadHuge(page)))
		return page->index << compound_order(page);

	return page_to_index(page);
}

/*
 * Return byte-offset into filesystem object for page.
 */
static inline loff_t page_offset(struct page *page)
{
	return ((loff_t)page->index) << PAGE_SHIFT;
}

static inline loff_t page_file_offset(struct page *page)
{
	return ((loff_t)page_index(page)) << PAGE_SHIFT;
}

extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
				     unsigned long address);

static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
					unsigned long address)
{
	pgoff_t pgoff;
	if (unlikely(is_vm_hugetlb_page(vma)))
		return linear_hugepage_index(vma, address);
	pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
	pgoff += vma->vm_pgoff;
	return pgoff;
}

/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
struct wait_page_key {
	struct page *page;
	int bit_nr;
	int page_match;
};

struct wait_page_queue {
	struct page *page;
	int bit_nr;
	wait_queue_entry_t wait;
};

static inline bool wake_page_match(struct wait_page_queue *wait_page,
				  struct wait_page_key *key)
{
	if (wait_page->page != key->page)
	       return false;
	key->page_match = 1;

	if (wait_page->bit_nr != key->bit_nr)
		return false;

	return true;
}

extern void __lock_page(struct page *page);
extern int __lock_page_killable(struct page *page);
extern int __lock_page_async(struct page *page, struct wait_page_queue *wait);
extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
				unsigned int flags);
extern void unlock_page(struct page *page);

/*
 * Return true if the page was successfully locked
 */
static inline int trylock_page(struct page *page)
{
	page = compound_head(page);
	return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
}

/*
 * lock_page may only be called if we have the page's inode pinned.
 */
static inline void lock_page(struct page *page)
{
	might_sleep();
	if (!trylock_page(page))
		__lock_page(page);
}

/*
 * lock_page_killable is like lock_page but can be interrupted by fatal
 * signals.  It returns 0 if it locked the page and -EINTR if it was
 * killed while waiting.
 */
static inline int lock_page_killable(struct page *page)
{
	might_sleep();
	if (!trylock_page(page))
		return __lock_page_killable(page);
	return 0;
}

/*
 * lock_page_async - Lock the page, unless this would block. If the page
 * is already locked, then queue a callback when the page becomes unlocked.
 * This callback can then retry the operation.
 *
 * Returns 0 if the page is locked successfully, or -EIOCBQUEUED if the page
 * was already locked and the callback defined in 'wait' was queued.
 */
static inline int lock_page_async(struct page *page,
				  struct wait_page_queue *wait)
{
	if (!trylock_page(page))
		return __lock_page_async(page, wait);
	return 0;
}

/*
 * lock_page_or_retry - Lock the page, unless this would block and the
 * caller indicated that it can handle a retry.
 *
 * Return value and mmap_lock implications depend on flags; see
 * __lock_page_or_retry().
 */
static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
				     unsigned int flags)
{
	might_sleep();
	return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
}

/*
 * This is exported only for wait_on_page_locked/wait_on_page_writeback, etc.,
 * and should not be used directly.
 */
extern void wait_on_page_bit(struct page *page, int bit_nr);
extern int wait_on_page_bit_killable(struct page *page, int bit_nr);

/* 
 * Wait for a page to be unlocked.
 *
 * This must be called with the caller "holding" the page,
 * ie with increased "page->count" so that the page won't
 * go away during the wait..
 */
static inline void wait_on_page_locked(struct page *page)
{
	if (PageLocked(page))
		wait_on_page_bit(compound_head(page), PG_locked);
}

static inline int wait_on_page_locked_killable(struct page *page)
{
	if (!PageLocked(page))
		return 0;
	return wait_on_page_bit_killable(compound_head(page), PG_locked);
}

int put_and_wait_on_page_locked(struct page *page, int state);
void wait_on_page_writeback(struct page *page);
extern void end_page_writeback(struct page *page);
void wait_for_stable_page(struct page *page);

void page_endio(struct page *page, bool is_write, int err);

/*
 * Add an arbitrary waiter to a page's wait queue
 */
extern void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter);

/*
 * Fault everything in given userspace address range in.
 */
static inline int fault_in_pages_writeable(char __user *uaddr, int size)
{
	char __user *end = uaddr + size - 1;

	if (unlikely(size == 0))
		return 0;

	if (unlikely(uaddr > end))
		return -EFAULT;
	/*
	 * Writing zeroes into userspace here is OK, because we know that if
	 * the zero gets there, we'll be overwriting it.
	 */
	do {
		if (unlikely(__put_user(0, uaddr) != 0))
			return -EFAULT;
		uaddr += PAGE_SIZE;
	} while (uaddr <= end);

	/* Check whether the range spilled into the next page. */
	if (((unsigned long)uaddr & PAGE_MASK) ==
			((unsigned long)end & PAGE_MASK))
		return __put_user(0, end);

	return 0;
}

static inline int fault_in_pages_readable(const char __user *uaddr, int size)
{
	volatile char c;
	const char __user *end = uaddr + size - 1;

	if (unlikely(size == 0))
		return 0;

	if (unlikely(uaddr > end))
		return -EFAULT;

	do {
		if (unlikely(__get_user(c, uaddr) != 0))
			return -EFAULT;
		uaddr += PAGE_SIZE;
	} while (uaddr <= end);

	/* Check whether the range spilled into the next page. */
	if (((unsigned long)uaddr & PAGE_MASK) ==
			((unsigned long)end & PAGE_MASK)) {
		return __get_user(c, end);
	}

	(void)c;
	return 0;
}

int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
				pgoff_t index, gfp_t gfp_mask);
int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
				pgoff_t index, gfp_t gfp_mask);
extern void delete_from_page_cache(struct page *page);
extern void __delete_from_page_cache(struct page *page, void *shadow);
void replace_page_cache_page(struct page *old, struct page *new);
void delete_from_page_cache_batch(struct address_space *mapping,
				  struct pagevec *pvec);
loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
		int whence);

/*
 * Like add_to_page_cache_locked, but used to add newly allocated pages:
 * the page is new, so we can just run __SetPageLocked() against it.
 */
static inline int add_to_page_cache(struct page *page,
		struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
{
	int error;

	__SetPageLocked(page);
	error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
	if (unlikely(error))
		__ClearPageLocked(page);
	return error;
}

/**
 * struct readahead_control - Describes a readahead request.
 *
 * A readahead request is for consecutive pages.  Filesystems which
 * implement the ->readahead method should call readahead_page() or
 * readahead_page_batch() in a loop and attempt to start I/O against
 * each page in the request.
 *
 * Most of the fields in this struct are private and should be accessed
 * by the functions below.
 *
 * @file: The file, used primarily by network filesystems for authentication.
 *	  May be NULL if invoked internally by the filesystem.
 * @mapping: Readahead this filesystem object.
 */
struct readahead_control {
	struct file *file;
	struct address_space *mapping;
/* private: use the readahead_* accessors instead */
	pgoff_t _index;
	unsigned int _nr_pages;
	unsigned int _batch_count;
};

#define DEFINE_READAHEAD(rac, f, m, i)					\
	struct readahead_control rac = {				\
		.file = f,						\
		.mapping = m,						\
		._index = i,						\
	}

#define VM_READAHEAD_PAGES	(SZ_128K / PAGE_SIZE)

void page_cache_ra_unbounded(struct readahead_control *,
		unsigned long nr_to_read, unsigned long lookahead_count);
void page_cache_sync_ra(struct readahead_control *, struct file_ra_state *,
		unsigned long req_count);
void page_cache_async_ra(struct readahead_control *, struct file_ra_state *,
		struct page *, unsigned long req_count);

/**
 * page_cache_sync_readahead - generic file readahead
 * @mapping: address_space which holds the pagecache and I/O vectors
 * @ra: file_ra_state which holds the readahead state
 * @file: Used by the filesystem for authentication.
 * @index: Index of first page to be read.
 * @req_count: Total number of pages being read by the caller.
 *
 * page_cache_sync_readahead() should be called when a cache miss happened:
 * it will submit the read.  The readahead logic may decide to piggyback more
 * pages onto the read request if access patterns suggest it will improve
 * performance.
 */
static inline
void page_cache_sync_readahead(struct address_space *mapping,
		struct file_ra_state *ra, struct file *file, pgoff_t index,
		unsigned long req_count)
{
	DEFINE_READAHEAD(ractl, file, mapping, index);
	page_cache_sync_ra(&ractl, ra, req_count);
}

/**
 * page_cache_async_readahead - file readahead for marked pages
 * @mapping: address_space which holds the pagecache and I/O vectors
 * @ra: file_ra_state which holds the readahead state
 * @file: Used by the filesystem for authentication.
 * @page: The page at @index which triggered the readahead call.
 * @index: Index of first page to be read.
 * @req_count: Total number of pages being read by the caller.
 *
 * page_cache_async_readahead() should be called when a page is used which
 * is marked as PageReadahead; this is a marker to suggest that the application
 * has used up enough of the readahead window that we should start pulling in
 * more pages.
 */
static inline
void page_cache_async_readahead(struct address_space *mapping,
		struct file_ra_state *ra, struct file *file,
		struct page *page, pgoff_t index, unsigned long req_count)
{
	DEFINE_READAHEAD(ractl, file, mapping, index);
	page_cache_async_ra(&ractl, ra, page, req_count);
}

/**
 * readahead_page - Get the next page to read.
 * @rac: The current readahead request.
 *
 * Context: The page is locked and has an elevated refcount.  The caller
 * should decreases the refcount once the page has been submitted for I/O
 * and unlock the page once all I/O to that page has completed.
 * Return: A pointer to the next page, or %NULL if we are done.
 */
static inline struct page *readahead_page(struct readahead_control *rac)
{
	struct page *page;

	BUG_ON(rac->_batch_count > rac->_nr_pages);
	rac->_nr_pages -= rac->_batch_count;
	rac->_index += rac->_batch_count;

	if (!rac->_nr_pages) {
		rac->_batch_count = 0;
		return NULL;
	}

	page = xa_load(&rac->mapping->i_pages, rac->_index);
	VM_BUG_ON_PAGE(!PageLocked(page), page);
	rac->_batch_count = thp_nr_pages(page);

	return page;
}

static inline unsigned int __readahead_batch(struct readahead_control *rac,
		struct page **array, unsigned int array_sz)
{
	unsigned int i = 0;
	XA_STATE(xas, &rac->mapping->i_pages, 0);
	struct page *page;

	BUG_ON(rac->_batch_count > rac->_nr_pages);
	rac->_nr_pages -= rac->_batch_count;
	rac->_index += rac->_batch_count;
	rac->_batch_count = 0;

	xas_set(&xas, rac->_index);
	rcu_read_lock();
	xas_for_each(&xas, page, rac->_index + rac->_nr_pages - 1) {
		if (xas_retry(&xas, page))
			continue;
		VM_BUG_ON_PAGE(!PageLocked(page), page);
		VM_BUG_ON_PAGE(PageTail(page), page);
		array[i++] = page;
		rac->_batch_count += thp_nr_pages(page);

		/*
		 * The page cache isn't using multi-index entries yet,
		 * so the xas cursor needs to be manually moved to the
		 * next index.  This can be removed once the page cache
		 * is converted.
		 */
		if (PageHead(page))
			xas_set(&xas, rac->_index + rac->_batch_count);

		if (i == array_sz)
			break;
	}
	rcu_read_unlock();

	return i;
}

/**
 * readahead_page_batch - Get a batch of pages to read.
 * @rac: The current readahead request.
 * @array: An array of pointers to struct page.
 *
 * Context: The pages are locked and have an elevated refcount.  The caller
 * should decreases the refcount once the page has been submitted for I/O
 * and unlock the page once all I/O to that page has completed.
 * Return: The number of pages placed in the array.  0 indicates the request
 * is complete.
 */
#define readahead_page_batch(rac, array)				\
	__readahead_batch(rac, array, ARRAY_SIZE(array))

/**
 * readahead_pos - The byte offset into the file of this readahead request.
 * @rac: The readahead request.
 */
static inline loff_t readahead_pos(struct readahead_control *rac)
{
	return (loff_t)rac->_index * PAGE_SIZE;
}

/**
 * readahead_length - The number of bytes in this readahead request.
 * @rac: The readahead request.
 */
static inline loff_t readahead_length(struct readahead_control *rac)
{
	return (loff_t)rac->_nr_pages * PAGE_SIZE;
}

/**
 * readahead_index - The index of the first page in this readahead request.
 * @rac: The readahead request.
 */
static inline pgoff_t readahead_index(struct readahead_control *rac)
{
	return rac->_index;
}

/**
 * readahead_count - The number of pages in this readahead request.
 * @rac: The readahead request.
 */
static inline unsigned int readahead_count(struct readahead_control *rac)
{
	return rac->_nr_pages;
}

static inline unsigned long dir_pages(struct inode *inode)
{
	return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
			       PAGE_SHIFT;
}

/**
 * page_mkwrite_check_truncate - check if page was truncated
 * @page: the page to check
 * @inode: the inode to check the page against
 *
 * Returns the number of bytes in the page up to EOF,
 * or -EFAULT if the page was truncated.
 */
static inline int page_mkwrite_check_truncate(struct page *page,
					      struct inode *inode)
{
	loff_t size = i_size_read(inode);
	pgoff_t index = size >> PAGE_SHIFT;
	int offset = offset_in_page(size);

	if (page->mapping != inode->i_mapping)
		return -EFAULT;

	/* page is wholly inside EOF */
	if (page->index < index)
		return PAGE_SIZE;
	/* page is wholly past EOF */
	if (page->index > index || !offset)
		return -EFAULT;
	/* page is partially inside EOF */
	return offset;
}

/**
 * i_blocks_per_page - How many blocks fit in this page.
 * @inode: The inode which contains the blocks.
 * @page: The page (head page if the page is a THP).
 *
 * If the block size is larger than the size of this page, return zero.
 *
 * Context: The caller should hold a refcount on the page to prevent it
 * from being split.
 * Return: The number of filesystem blocks covered by this page.
 */
static inline
unsigned int i_blocks_per_page(struct inode *inode, struct page *page)
{
	return thp_size(page) >> inode->i_blkbits;
}
#endif /* _LINUX_PAGEMAP_H */