summaryrefslogtreecommitdiff
path: root/fs/iomap/buffered-io.c
blob: e25901ae3ff447712ec6d5635bb7d9ddfd180d3e (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
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
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2010 Red Hat, Inc.
 * Copyright (c) 2016-2018 Christoph Hellwig.
 */
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <linux/buffer_head.h>
#include <linux/dax.h>
#include <linux/writeback.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/sched/signal.h>
#include <linux/migrate.h>

#include "../internal.h"

static struct iomap_page *
iomap_page_create(struct inode *inode, struct page *page)
{
	struct iomap_page *iop = to_iomap_page(page);

	if (iop || i_blocksize(inode) == PAGE_SIZE)
		return iop;

	iop = kmalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL);
	atomic_set(&iop->read_count, 0);
	atomic_set(&iop->write_count, 0);
	bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);

	/*
	 * migrate_page_move_mapping() assumes that pages with private data have
	 * their count elevated by 1.
	 */
	get_page(page);
	set_page_private(page, (unsigned long)iop);
	SetPagePrivate(page);
	return iop;
}

static void
iomap_page_release(struct page *page)
{
	struct iomap_page *iop = to_iomap_page(page);

	if (!iop)
		return;
	WARN_ON_ONCE(atomic_read(&iop->read_count));
	WARN_ON_ONCE(atomic_read(&iop->write_count));
	ClearPagePrivate(page);
	set_page_private(page, 0);
	put_page(page);
	kfree(iop);
}

/*
 * Calculate the range inside the page that we actually need to read.
 */
static void
iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
		loff_t *pos, loff_t length, unsigned *offp, unsigned *lenp)
{
	loff_t orig_pos = *pos;
	loff_t isize = i_size_read(inode);
	unsigned block_bits = inode->i_blkbits;
	unsigned block_size = (1 << block_bits);
	unsigned poff = offset_in_page(*pos);
	unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
	unsigned first = poff >> block_bits;
	unsigned last = (poff + plen - 1) >> block_bits;

	/*
	 * If the block size is smaller than the page size we need to check the
	 * per-block uptodate status and adjust the offset and length if needed
	 * to avoid reading in already uptodate ranges.
	 */
	if (iop) {
		unsigned int i;

		/* move forward for each leading block marked uptodate */
		for (i = first; i <= last; i++) {
			if (!test_bit(i, iop->uptodate))
				break;
			*pos += block_size;
			poff += block_size;
			plen -= block_size;
			first++;
		}

		/* truncate len if we find any trailing uptodate block(s) */
		for ( ; i <= last; i++) {
			if (test_bit(i, iop->uptodate)) {
				plen -= (last - i + 1) * block_size;
				last = i - 1;
				break;
			}
		}
	}

	/*
	 * If the extent spans the block that contains the i_size we need to
	 * handle both halves separately so that we properly zero data in the
	 * page cache for blocks that are entirely outside of i_size.
	 */
	if (orig_pos <= isize && orig_pos + length > isize) {
		unsigned end = offset_in_page(isize - 1) >> block_bits;

		if (first <= end && last > end)
			plen -= (last - end) * block_size;
	}

	*offp = poff;
	*lenp = plen;
}

static void
iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len)
{
	struct iomap_page *iop = to_iomap_page(page);
	struct inode *inode = page->mapping->host;
	unsigned first = off >> inode->i_blkbits;
	unsigned last = (off + len - 1) >> inode->i_blkbits;
	unsigned int i;
	bool uptodate = true;

	if (iop) {
		for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) {
			if (i >= first && i <= last)
				set_bit(i, iop->uptodate);
			else if (!test_bit(i, iop->uptodate))
				uptodate = false;
		}
	}

	if (uptodate && !PageError(page))
		SetPageUptodate(page);
}

static void
iomap_read_finish(struct iomap_page *iop, struct page *page)
{
	if (!iop || atomic_dec_and_test(&iop->read_count))
		unlock_page(page);
}

static void
iomap_read_page_end_io(struct bio_vec *bvec, int error)
{
	struct page *page = bvec->bv_page;
	struct iomap_page *iop = to_iomap_page(page);

	if (unlikely(error)) {
		ClearPageUptodate(page);
		SetPageError(page);
	} else {
		iomap_set_range_uptodate(page, bvec->bv_offset, bvec->bv_len);
	}

	iomap_read_finish(iop, page);
}

static void
iomap_read_end_io(struct bio *bio)
{
	int error = blk_status_to_errno(bio->bi_status);
	struct bio_vec *bvec;
	struct bvec_iter_all iter_all;

	bio_for_each_segment_all(bvec, bio, iter_all)
		iomap_read_page_end_io(bvec, error);
	bio_put(bio);
}

struct iomap_readpage_ctx {
	struct page		*cur_page;
	bool			cur_page_in_bio;
	bool			is_readahead;
	struct bio		*bio;
	struct list_head	*pages;
};

static void
iomap_read_inline_data(struct inode *inode, struct page *page,
		struct iomap *iomap)
{
	size_t size = i_size_read(inode);
	void *addr;

	if (PageUptodate(page))
		return;

	BUG_ON(page->index);
	BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));

	addr = kmap_atomic(page);
	memcpy(addr, iomap->inline_data, size);
	memset(addr + size, 0, PAGE_SIZE - size);
	kunmap_atomic(addr);
	SetPageUptodate(page);
}

static loff_t
iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	struct iomap_readpage_ctx *ctx = data;
	struct page *page = ctx->cur_page;
	struct iomap_page *iop = iomap_page_create(inode, page);
	bool same_page = false, is_contig = false;
	loff_t orig_pos = pos;
	unsigned poff, plen;
	sector_t sector;

	if (iomap->type == IOMAP_INLINE) {
		WARN_ON_ONCE(pos);
		iomap_read_inline_data(inode, page, iomap);
		return PAGE_SIZE;
	}

	/* zero post-eof blocks as the page may be mapped */
	iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
	if (plen == 0)
		goto done;

	if (iomap->type != IOMAP_MAPPED || pos >= i_size_read(inode)) {
		zero_user(page, poff, plen);
		iomap_set_range_uptodate(page, poff, plen);
		goto done;
	}

	ctx->cur_page_in_bio = true;

	/*
	 * Try to merge into a previous segment if we can.
	 */
	sector = iomap_sector(iomap, pos);
	if (ctx->bio && bio_end_sector(ctx->bio) == sector)
		is_contig = true;

	if (is_contig &&
	    __bio_try_merge_page(ctx->bio, page, plen, poff, &same_page)) {
		if (!same_page && iop)
			atomic_inc(&iop->read_count);
		goto done;
	}

	/*
	 * If we start a new segment we need to increase the read count, and we
	 * need to do so before submitting any previous full bio to make sure
	 * that we don't prematurely unlock the page.
	 */
	if (iop)
		atomic_inc(&iop->read_count);

	if (!ctx->bio || !is_contig || bio_full(ctx->bio, plen)) {
		gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
		int nr_vecs = (length + PAGE_SIZE - 1) >> PAGE_SHIFT;

		if (ctx->bio)
			submit_bio(ctx->bio);

		if (ctx->is_readahead) /* same as readahead_gfp_mask */
			gfp |= __GFP_NORETRY | __GFP_NOWARN;
		ctx->bio = bio_alloc(gfp, min(BIO_MAX_PAGES, nr_vecs));
		ctx->bio->bi_opf = REQ_OP_READ;
		if (ctx->is_readahead)
			ctx->bio->bi_opf |= REQ_RAHEAD;
		ctx->bio->bi_iter.bi_sector = sector;
		bio_set_dev(ctx->bio, iomap->bdev);
		ctx->bio->bi_end_io = iomap_read_end_io;
	}

	bio_add_page(ctx->bio, page, plen, poff);
done:
	/*
	 * Move the caller beyond our range so that it keeps making progress.
	 * For that we have to include any leading non-uptodate ranges, but
	 * we can skip trailing ones as they will be handled in the next
	 * iteration.
	 */
	return pos - orig_pos + plen;
}

int
iomap_readpage(struct page *page, const struct iomap_ops *ops)
{
	struct iomap_readpage_ctx ctx = { .cur_page = page };
	struct inode *inode = page->mapping->host;
	unsigned poff;
	loff_t ret;

	for (poff = 0; poff < PAGE_SIZE; poff += ret) {
		ret = iomap_apply(inode, page_offset(page) + poff,
				PAGE_SIZE - poff, 0, ops, &ctx,
				iomap_readpage_actor);
		if (ret <= 0) {
			WARN_ON_ONCE(ret == 0);
			SetPageError(page);
			break;
		}
	}

	if (ctx.bio) {
		submit_bio(ctx.bio);
		WARN_ON_ONCE(!ctx.cur_page_in_bio);
	} else {
		WARN_ON_ONCE(ctx.cur_page_in_bio);
		unlock_page(page);
	}

	/*
	 * Just like mpage_readpages and block_read_full_page we always
	 * return 0 and just mark the page as PageError on errors.  This
	 * should be cleaned up all through the stack eventually.
	 */
	return 0;
}
EXPORT_SYMBOL_GPL(iomap_readpage);

static struct page *
iomap_next_page(struct inode *inode, struct list_head *pages, loff_t pos,
		loff_t length, loff_t *done)
{
	while (!list_empty(pages)) {
		struct page *page = lru_to_page(pages);

		if (page_offset(page) >= (u64)pos + length)
			break;

		list_del(&page->lru);
		if (!add_to_page_cache_lru(page, inode->i_mapping, page->index,
				GFP_NOFS))
			return page;

		/*
		 * If we already have a page in the page cache at index we are
		 * done.  Upper layers don't care if it is uptodate after the
		 * readpages call itself as every page gets checked again once
		 * actually needed.
		 */
		*done += PAGE_SIZE;
		put_page(page);
	}

	return NULL;
}

static loff_t
iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
		void *data, struct iomap *iomap)
{
	struct iomap_readpage_ctx *ctx = data;
	loff_t done, ret;

	for (done = 0; done < length; done += ret) {
		if (ctx->cur_page && offset_in_page(pos + done) == 0) {
			if (!ctx->cur_page_in_bio)
				unlock_page(ctx->cur_page);
			put_page(ctx->cur_page);
			ctx->cur_page = NULL;
		}
		if (!ctx->cur_page) {
			ctx->cur_page = iomap_next_page(inode, ctx->pages,
					pos, length, &done);
			if (!ctx->cur_page)
				break;
			ctx->cur_page_in_bio = false;
		}
		ret = iomap_readpage_actor(inode, pos + done, length - done,
				ctx, iomap);
	}

	return done;
}

int
iomap_readpages(struct address_space *mapping, struct list_head *pages,
		unsigned nr_pages, const struct iomap_ops *ops)
{
	struct iomap_readpage_ctx ctx = {
		.pages		= pages,
		.is_readahead	= true,
	};
	loff_t pos = page_offset(list_entry(pages->prev, struct page, lru));
	loff_t last = page_offset(list_entry(pages->next, struct page, lru));
	loff_t length = last - pos + PAGE_SIZE, ret = 0;

	while (length > 0) {
		ret = iomap_apply(mapping->host, pos, length, 0, ops,
				&ctx, iomap_readpages_actor);
		if (ret <= 0) {
			WARN_ON_ONCE(ret == 0);
			goto done;
		}
		pos += ret;
		length -= ret;
	}
	ret = 0;
done:
	if (ctx.bio)
		submit_bio(ctx.bio);
	if (ctx.cur_page) {
		if (!ctx.cur_page_in_bio)
			unlock_page(ctx.cur_page);
		put_page(ctx.cur_page);
	}

	/*
	 * Check that we didn't lose a page due to the arcance calling
	 * conventions..
	 */
	WARN_ON_ONCE(!ret && !list_empty(ctx.pages));
	return ret;
}
EXPORT_SYMBOL_GPL(iomap_readpages);

/*
 * iomap_is_partially_uptodate checks whether blocks within a page are
 * uptodate or not.
 *
 * Returns true if all blocks which correspond to a file portion
 * we want to read within the page are uptodate.
 */
int
iomap_is_partially_uptodate(struct page *page, unsigned long from,
		unsigned long count)
{
	struct iomap_page *iop = to_iomap_page(page);
	struct inode *inode = page->mapping->host;
	unsigned len, first, last;
	unsigned i;

	/* Limit range to one page */
	len = min_t(unsigned, PAGE_SIZE - from, count);

	/* First and last blocks in range within page */
	first = from >> inode->i_blkbits;
	last = (from + len - 1) >> inode->i_blkbits;

	if (iop) {
		for (i = first; i <= last; i++)
			if (!test_bit(i, iop->uptodate))
				return 0;
		return 1;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);

int
iomap_releasepage(struct page *page, gfp_t gfp_mask)
{
	/*
	 * mm accommodates an old ext3 case where clean pages might not have had
	 * the dirty bit cleared. Thus, it can send actual dirty pages to
	 * ->releasepage() via shrink_active_list(), skip those here.
	 */
	if (PageDirty(page) || PageWriteback(page))
		return 0;
	iomap_page_release(page);
	return 1;
}
EXPORT_SYMBOL_GPL(iomap_releasepage);

void
iomap_invalidatepage(struct page *page, unsigned int offset, unsigned int len)
{
	/*
	 * If we are invalidating the entire page, clear the dirty state from it
	 * and release it to avoid unnecessary buildup of the LRU.
	 */
	if (offset == 0 && len == PAGE_SIZE) {
		WARN_ON_ONCE(PageWriteback(page));
		cancel_dirty_page(page);
		iomap_page_release(page);
	}
}
EXPORT_SYMBOL_GPL(iomap_invalidatepage);

#ifdef CONFIG_MIGRATION
int
iomap_migrate_page(struct address_space *mapping, struct page *newpage,
		struct page *page, enum migrate_mode mode)
{
	int ret;

	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
	if (ret != MIGRATEPAGE_SUCCESS)
		return ret;

	if (page_has_private(page)) {
		ClearPagePrivate(page);
		get_page(newpage);
		set_page_private(newpage, page_private(page));
		set_page_private(page, 0);
		put_page(page);
		SetPagePrivate(newpage);
	}

	if (mode != MIGRATE_SYNC_NO_COPY)
		migrate_page_copy(newpage, page);
	else
		migrate_page_states(newpage, page);
	return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL_GPL(iomap_migrate_page);
#endif /* CONFIG_MIGRATION */

static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
	loff_t i_size = i_size_read(inode);

	/*
	 * Only truncate newly allocated pages beyoned EOF, even if the
	 * write started inside the existing inode size.
	 */
	if (pos + len > i_size)
		truncate_pagecache_range(inode, max(pos, i_size), pos + len);
}

static int
iomap_read_page_sync(struct inode *inode, loff_t block_start, struct page *page,
		unsigned poff, unsigned plen, unsigned from, unsigned to,
		struct iomap *iomap)
{
	struct bio_vec bvec;
	struct bio bio;

	if (iomap->type != IOMAP_MAPPED || block_start >= i_size_read(inode)) {
		zero_user_segments(page, poff, from, to, poff + plen);
		iomap_set_range_uptodate(page, poff, plen);
		return 0;
	}

	bio_init(&bio, &bvec, 1);
	bio.bi_opf = REQ_OP_READ;
	bio.bi_iter.bi_sector = iomap_sector(iomap, block_start);
	bio_set_dev(&bio, iomap->bdev);
	__bio_add_page(&bio, page, plen, poff);
	return submit_bio_wait(&bio);
}

static int
__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
		struct page *page, struct iomap *iomap)
{
	struct iomap_page *iop = iomap_page_create(inode, page);
	loff_t block_size = i_blocksize(inode);
	loff_t block_start = pos & ~(block_size - 1);
	loff_t block_end = (pos + len + block_size - 1) & ~(block_size - 1);
	unsigned from = offset_in_page(pos), to = from + len, poff, plen;
	int status = 0;

	if (PageUptodate(page))
		return 0;

	do {
		iomap_adjust_read_range(inode, iop, &block_start,
				block_end - block_start, &poff, &plen);
		if (plen == 0)
			break;

		if ((from > poff && from < poff + plen) ||
		    (to > poff && to < poff + plen)) {
			status = iomap_read_page_sync(inode, block_start, page,
					poff, plen, from, to, iomap);
			if (status)
				break;
		}

	} while ((block_start += plen) < block_end);

	return status;
}

static int
iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
		struct page **pagep, struct iomap *iomap)
{
	const struct iomap_page_ops *page_ops = iomap->page_ops;
	pgoff_t index = pos >> PAGE_SHIFT;
	struct page *page;
	int status = 0;

	BUG_ON(pos + len > iomap->offset + iomap->length);

	if (fatal_signal_pending(current))
		return -EINTR;

	if (page_ops && page_ops->page_prepare) {
		status = page_ops->page_prepare(inode, pos, len, iomap);
		if (status)
			return status;
	}

	page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
	if (!page) {
		status = -ENOMEM;
		goto out_no_page;
	}

	if (iomap->type == IOMAP_INLINE)
		iomap_read_inline_data(inode, page, iomap);
	else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
		status = __block_write_begin_int(page, pos, len, NULL, iomap);
	else
		status = __iomap_write_begin(inode, pos, len, page, iomap);

	if (unlikely(status))
		goto out_unlock;

	*pagep = page;
	return 0;

out_unlock:
	unlock_page(page);
	put_page(page);
	iomap_write_failed(inode, pos, len);

out_no_page:
	if (page_ops && page_ops->page_done)
		page_ops->page_done(inode, pos, 0, NULL, iomap);
	return status;
}

int
iomap_set_page_dirty(struct page *page)
{
	struct address_space *mapping = page_mapping(page);
	int newly_dirty;

	if (unlikely(!mapping))
		return !TestSetPageDirty(page);

	/*
	 * Lock out page->mem_cgroup migration to keep PageDirty
	 * synchronized with per-memcg dirty page counters.
	 */
	lock_page_memcg(page);
	newly_dirty = !TestSetPageDirty(page);
	if (newly_dirty)
		__set_page_dirty(page, mapping, 0);
	unlock_page_memcg(page);

	if (newly_dirty)
		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
	return newly_dirty;
}
EXPORT_SYMBOL_GPL(iomap_set_page_dirty);

static int
__iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
		unsigned copied, struct page *page, struct iomap *iomap)
{
	flush_dcache_page(page);

	/*
	 * The blocks that were entirely written will now be uptodate, so we
	 * don't have to worry about a readpage reading them and overwriting a
	 * partial write.  However if we have encountered a short write and only
	 * partially written into a block, it will not be marked uptodate, so a
	 * readpage might come in and destroy our partial write.
	 *
	 * Do the simplest thing, and just treat any short write to a non
	 * uptodate page as a zero-length write, and force the caller to redo
	 * the whole thing.
	 */
	if (unlikely(copied < len && !PageUptodate(page)))
		return 0;
	iomap_set_range_uptodate(page, offset_in_page(pos), len);
	iomap_set_page_dirty(page);
	return copied;
}

static int
iomap_write_end_inline(struct inode *inode, struct page *page,
		struct iomap *iomap, loff_t pos, unsigned copied)
{
	void *addr;

	WARN_ON_ONCE(!PageUptodate(page));
	BUG_ON(pos + copied > PAGE_SIZE - offset_in_page(iomap->inline_data));

	addr = kmap_atomic(page);
	memcpy(iomap->inline_data + pos, addr + pos, copied);
	kunmap_atomic(addr);

	mark_inode_dirty(inode);
	return copied;
}

static int
iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
		unsigned copied, struct page *page, struct iomap *iomap)
{
	const struct iomap_page_ops *page_ops = iomap->page_ops;
	loff_t old_size = inode->i_size;
	int ret;

	if (iomap->type == IOMAP_INLINE) {
		ret = iomap_write_end_inline(inode, page, iomap, pos, copied);
	} else if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
		ret = block_write_end(NULL, inode->i_mapping, pos, len, copied,
				page, NULL);
	} else {
		ret = __iomap_write_end(inode, pos, len, copied, page, iomap);
	}

	/*
	 * Update the in-memory inode size after copying the data into the page
	 * cache.  It's up to the file system to write the updated size to disk,
	 * preferably after I/O completion so that no stale data is exposed.
	 */
	if (pos + ret > old_size) {
		i_size_write(inode, pos + ret);
		iomap->flags |= IOMAP_F_SIZE_CHANGED;
	}
	unlock_page(page);

	if (old_size < pos)
		pagecache_isize_extended(inode, old_size, pos);
	if (page_ops && page_ops->page_done)
		page_ops->page_done(inode, pos, ret, page, iomap);
	put_page(page);

	if (ret < len)
		iomap_write_failed(inode, pos, len);
	return ret;
}

static loff_t
iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	struct iov_iter *i = data;
	long status = 0;
	ssize_t written = 0;
	unsigned int flags = AOP_FLAG_NOFS;

	do {
		struct page *page;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */
		size_t copied;		/* Bytes copied from user */

		offset = offset_in_page(pos);
		bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_count(i));
again:
		if (bytes > length)
			bytes = length;

		/*
		 * Bring in the user page that we will copy from _first_.
		 * Otherwise there's a nasty deadlock on copying from the
		 * same page as we're writing to, without it being marked
		 * up-to-date.
		 *
		 * Not only is this an optimisation, but it is also required
		 * to check that the address is actually valid, when atomic
		 * usercopies are used, below.
		 */
		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
			status = -EFAULT;
			break;
		}

		status = iomap_write_begin(inode, pos, bytes, flags, &page,
				iomap);
		if (unlikely(status))
			break;

		if (mapping_writably_mapped(inode->i_mapping))
			flush_dcache_page(page);

		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);

		flush_dcache_page(page);

		status = iomap_write_end(inode, pos, bytes, copied, page,
				iomap);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

		iov_iter_advance(i, copied);
		if (unlikely(copied == 0)) {
			/*
			 * If we were unable to copy any data at all, we must
			 * fall back to a single segment length write.
			 *
			 * If we didn't fallback here, we could livelock
			 * because not all segments in the iov can be copied at
			 * once without a pagefault.
			 */
			bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_single_seg_count(i));
			goto again;
		}
		pos += copied;
		written += copied;
		length -= copied;

		balance_dirty_pages_ratelimited(inode->i_mapping);
	} while (iov_iter_count(i) && length);

	return written ? written : status;
}

ssize_t
iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
		const struct iomap_ops *ops)
{
	struct inode *inode = iocb->ki_filp->f_mapping->host;
	loff_t pos = iocb->ki_pos, ret = 0, written = 0;

	while (iov_iter_count(iter)) {
		ret = iomap_apply(inode, pos, iov_iter_count(iter),
				IOMAP_WRITE, ops, iter, iomap_write_actor);
		if (ret <= 0)
			break;
		pos += ret;
		written += ret;
	}

	return written ? written : ret;
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write);

static struct page *
__iomap_read_page(struct inode *inode, loff_t offset)
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;

	page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
	if (IS_ERR(page))
		return page;
	if (!PageUptodate(page)) {
		put_page(page);
		return ERR_PTR(-EIO);
	}
	return page;
}

static loff_t
iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	long status = 0;
	ssize_t written = 0;

	do {
		struct page *page, *rpage;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */

		offset = offset_in_page(pos);
		bytes = min_t(loff_t, PAGE_SIZE - offset, length);

		rpage = __iomap_read_page(inode, pos);
		if (IS_ERR(rpage))
			return PTR_ERR(rpage);

		status = iomap_write_begin(inode, pos, bytes,
					   AOP_FLAG_NOFS, &page, iomap);
		put_page(rpage);
		if (unlikely(status))
			return status;

		WARN_ON_ONCE(!PageUptodate(page));

		status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
		if (unlikely(status <= 0)) {
			if (WARN_ON_ONCE(status == 0))
				return -EIO;
			return status;
		}

		cond_resched();

		pos += status;
		written += status;
		length -= status;

		balance_dirty_pages_ratelimited(inode->i_mapping);
	} while (length);

	return written;
}

int
iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
		const struct iomap_ops *ops)
{
	loff_t ret;

	while (len) {
		ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
				iomap_dirty_actor);
		if (ret <= 0)
			return ret;
		pos += ret;
		len -= ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(iomap_file_dirty);

static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
		unsigned bytes, struct iomap *iomap)
{
	struct page *page;
	int status;

	status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
				   iomap);
	if (status)
		return status;

	zero_user(page, offset, bytes);
	mark_page_accessed(page);

	return iomap_write_end(inode, pos, bytes, bytes, page, iomap);
}

static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
		struct iomap *iomap)
{
	return __dax_zero_page_range(iomap->bdev, iomap->dax_dev,
			iomap_sector(iomap, pos & PAGE_MASK), offset, bytes);
}

static loff_t
iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
		void *data, struct iomap *iomap)
{
	bool *did_zero = data;
	loff_t written = 0;
	int status;

	/* already zeroed?  we're done. */
	if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
		return count;

	do {
		unsigned offset, bytes;

		offset = offset_in_page(pos);
		bytes = min_t(loff_t, PAGE_SIZE - offset, count);

		if (IS_DAX(inode))
			status = iomap_dax_zero(pos, offset, bytes, iomap);
		else
			status = iomap_zero(inode, pos, offset, bytes, iomap);
		if (status < 0)
			return status;

		pos += bytes;
		count -= bytes;
		written += bytes;
		if (did_zero)
			*did_zero = true;
	} while (count > 0);

	return written;
}

int
iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
		const struct iomap_ops *ops)
{
	loff_t ret;

	while (len > 0) {
		ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
				ops, did_zero, iomap_zero_range_actor);
		if (ret <= 0)
			return ret;

		pos += ret;
		len -= ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(iomap_zero_range);

int
iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
		const struct iomap_ops *ops)
{
	unsigned int blocksize = i_blocksize(inode);
	unsigned int off = pos & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!off)
		return 0;
	return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
}
EXPORT_SYMBOL_GPL(iomap_truncate_page);

static loff_t
iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
		void *data, struct iomap *iomap)
{
	struct page *page = data;
	int ret;

	if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
		ret = __block_write_begin_int(page, pos, length, NULL, iomap);
		if (ret)
			return ret;
		block_commit_write(page, 0, length);
	} else {
		WARN_ON_ONCE(!PageUptodate(page));
		iomap_page_create(inode, page);
		set_page_dirty(page);
	}

	return length;
}

vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
{
	struct page *page = vmf->page;
	struct inode *inode = file_inode(vmf->vma->vm_file);
	unsigned long length;
	loff_t offset, size;
	ssize_t ret;

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
	    (page_offset(page) > size)) {
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
	}

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_SHIFT) > size)
		length = offset_in_page(size);
	else
		length = PAGE_SIZE;

	offset = page_offset(page);
	while (length > 0) {
		ret = iomap_apply(inode, offset, length,
				IOMAP_WRITE | IOMAP_FAULT, ops, page,
				iomap_page_mkwrite_actor);
		if (unlikely(ret <= 0))
			goto out_unlock;
		offset += ret;
		length -= ret;
	}

	wait_for_stable_page(page);
	return VM_FAULT_LOCKED;
out_unlock:
	unlock_page(page);
	return block_page_mkwrite_return(ret);
}
EXPORT_SYMBOL_GPL(iomap_page_mkwrite);