summaryrefslogtreecommitdiffstats
path: root/fs/erofs/zmap.c
blob: 0337b70b2dac40622a84bc18553cc75b62bd9c50 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2018-2019 HUAWEI, Inc.
 *             https://www.huawei.com/
 */
#include "internal.h"
#include <asm/unaligned.h>
#include <trace/events/erofs.h>

static int z_erofs_do_map_blocks(struct inode *inode,
				 struct erofs_map_blocks *map,
				 int flags);

int z_erofs_fill_inode(struct inode *inode)
{
	struct erofs_inode *const vi = EROFS_I(inode);
	struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb);

	if (!erofs_sb_has_big_pcluster(sbi) &&
	    !erofs_sb_has_ztailpacking(sbi) && !erofs_sb_has_fragments(sbi) &&
	    vi->datalayout == EROFS_INODE_FLAT_COMPRESSION_LEGACY) {
		vi->z_advise = 0;
		vi->z_algorithmtype[0] = 0;
		vi->z_algorithmtype[1] = 0;
		vi->z_logical_clusterbits = LOG_BLOCK_SIZE;
		set_bit(EROFS_I_Z_INITED_BIT, &vi->flags);
	}
	inode->i_mapping->a_ops = &z_erofs_aops;
	return 0;
}

static int z_erofs_fill_inode_lazy(struct inode *inode)
{
	struct erofs_inode *const vi = EROFS_I(inode);
	struct super_block *const sb = inode->i_sb;
	int err, headnr;
	erofs_off_t pos;
	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
	void *kaddr;
	struct z_erofs_map_header *h;

	if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) {
		/*
		 * paired with smp_mb() at the end of the function to ensure
		 * fields will only be observed after the bit is set.
		 */
		smp_mb();
		return 0;
	}

	if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_Z_BIT, TASK_KILLABLE))
		return -ERESTARTSYS;

	err = 0;
	if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags))
		goto out_unlock;

	pos = ALIGN(erofs_iloc(inode) + vi->inode_isize + vi->xattr_isize, 8);
	kaddr = erofs_read_metabuf(&buf, sb, erofs_blknr(pos), EROFS_KMAP);
	if (IS_ERR(kaddr)) {
		err = PTR_ERR(kaddr);
		goto out_unlock;
	}

	h = kaddr + erofs_blkoff(pos);
	/*
	 * if the highest bit of the 8-byte map header is set, the whole file
	 * is stored in the packed inode. The rest bits keeps z_fragmentoff.
	 */
	if (h->h_clusterbits >> Z_EROFS_FRAGMENT_INODE_BIT) {
		vi->z_advise = Z_EROFS_ADVISE_FRAGMENT_PCLUSTER;
		vi->z_fragmentoff = le64_to_cpu(*(__le64 *)h) ^ (1ULL << 63);
		vi->z_tailextent_headlcn = 0;
		goto done;
	}
	vi->z_advise = le16_to_cpu(h->h_advise);
	vi->z_algorithmtype[0] = h->h_algorithmtype & 15;
	vi->z_algorithmtype[1] = h->h_algorithmtype >> 4;

	headnr = 0;
	if (vi->z_algorithmtype[0] >= Z_EROFS_COMPRESSION_MAX ||
	    vi->z_algorithmtype[++headnr] >= Z_EROFS_COMPRESSION_MAX) {
		erofs_err(sb, "unknown HEAD%u format %u for nid %llu, please upgrade kernel",
			  headnr + 1, vi->z_algorithmtype[headnr], vi->nid);
		err = -EOPNOTSUPP;
		goto out_put_metabuf;
	}

	vi->z_logical_clusterbits = LOG_BLOCK_SIZE + (h->h_clusterbits & 7);
	if (!erofs_sb_has_big_pcluster(EROFS_SB(sb)) &&
	    vi->z_advise & (Z_EROFS_ADVISE_BIG_PCLUSTER_1 |
			    Z_EROFS_ADVISE_BIG_PCLUSTER_2)) {
		erofs_err(sb, "per-inode big pcluster without sb feature for nid %llu",
			  vi->nid);
		err = -EFSCORRUPTED;
		goto out_put_metabuf;
	}
	if (vi->datalayout == EROFS_INODE_FLAT_COMPRESSION &&
	    !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1) ^
	    !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_2)) {
		erofs_err(sb, "big pcluster head1/2 of compact indexes should be consistent for nid %llu",
			  vi->nid);
		err = -EFSCORRUPTED;
		goto out_put_metabuf;
	}

	if (vi->z_advise & Z_EROFS_ADVISE_INLINE_PCLUSTER) {
		struct erofs_map_blocks map = {
			.buf = __EROFS_BUF_INITIALIZER
		};

		vi->z_idata_size = le16_to_cpu(h->h_idata_size);
		err = z_erofs_do_map_blocks(inode, &map,
					    EROFS_GET_BLOCKS_FINDTAIL);
		erofs_put_metabuf(&map.buf);

		if (!map.m_plen ||
		    erofs_blkoff(map.m_pa) + map.m_plen > EROFS_BLKSIZ) {
			erofs_err(sb, "invalid tail-packing pclustersize %llu",
				  map.m_plen);
			err = -EFSCORRUPTED;
		}
		if (err < 0)
			goto out_put_metabuf;
	}

	if (vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER &&
	    !(h->h_clusterbits >> Z_EROFS_FRAGMENT_INODE_BIT)) {
		struct erofs_map_blocks map = {
			.buf = __EROFS_BUF_INITIALIZER
		};

		vi->z_fragmentoff = le32_to_cpu(h->h_fragmentoff);
		err = z_erofs_do_map_blocks(inode, &map,
					    EROFS_GET_BLOCKS_FINDTAIL);
		erofs_put_metabuf(&map.buf);
		if (err < 0)
			goto out_put_metabuf;
	}
done:
	/* paired with smp_mb() at the beginning of the function */
	smp_mb();
	set_bit(EROFS_I_Z_INITED_BIT, &vi->flags);
out_put_metabuf:
	erofs_put_metabuf(&buf);
out_unlock:
	clear_and_wake_up_bit(EROFS_I_BL_Z_BIT, &vi->flags);
	return err;
}

struct z_erofs_maprecorder {
	struct inode *inode;
	struct erofs_map_blocks *map;
	void *kaddr;

	unsigned long lcn;
	/* compression extent information gathered */
	u8  type, headtype;
	u16 clusterofs;
	u16 delta[2];
	erofs_blk_t pblk, compressedblks;
	erofs_off_t nextpackoff;
	bool partialref;
};

static int legacy_load_cluster_from_disk(struct z_erofs_maprecorder *m,
					 unsigned long lcn)
{
	struct inode *const inode = m->inode;
	struct erofs_inode *const vi = EROFS_I(inode);
	const erofs_off_t pos =
		Z_EROFS_VLE_LEGACY_INDEX_ALIGN(erofs_iloc(inode) +
				vi->inode_isize + vi->xattr_isize) +
		lcn * sizeof(struct z_erofs_vle_decompressed_index);
	struct z_erofs_vle_decompressed_index *di;
	unsigned int advise, type;

	m->kaddr = erofs_read_metabuf(&m->map->buf, inode->i_sb,
				      erofs_blknr(pos), EROFS_KMAP_ATOMIC);
	if (IS_ERR(m->kaddr))
		return PTR_ERR(m->kaddr);

	m->nextpackoff = pos + sizeof(struct z_erofs_vle_decompressed_index);
	m->lcn = lcn;
	di = m->kaddr + erofs_blkoff(pos);

	advise = le16_to_cpu(di->di_advise);
	type = (advise >> Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT) &
		((1 << Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) - 1);
	switch (type) {
	case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
		m->clusterofs = 1 << vi->z_logical_clusterbits;
		m->delta[0] = le16_to_cpu(di->di_u.delta[0]);
		if (m->delta[0] & Z_EROFS_VLE_DI_D0_CBLKCNT) {
			if (!(vi->z_advise & (Z_EROFS_ADVISE_BIG_PCLUSTER_1 |
					Z_EROFS_ADVISE_BIG_PCLUSTER_2))) {
				DBG_BUGON(1);
				return -EFSCORRUPTED;
			}
			m->compressedblks = m->delta[0] &
				~Z_EROFS_VLE_DI_D0_CBLKCNT;
			m->delta[0] = 1;
		}
		m->delta[1] = le16_to_cpu(di->di_u.delta[1]);
		break;
	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
		if (advise & Z_EROFS_VLE_DI_PARTIAL_REF)
			m->partialref = true;
		m->clusterofs = le16_to_cpu(di->di_clusterofs);
		if (m->clusterofs >= 1 << vi->z_logical_clusterbits) {
			DBG_BUGON(1);
			return -EFSCORRUPTED;
		}
		m->pblk = le32_to_cpu(di->di_u.blkaddr);
		break;
	default:
		DBG_BUGON(1);
		return -EOPNOTSUPP;
	}
	m->type = type;
	return 0;
}

static unsigned int decode_compactedbits(unsigned int lobits,
					 unsigned int lomask,
					 u8 *in, unsigned int pos, u8 *type)
{
	const unsigned int v = get_unaligned_le32(in + pos / 8) >> (pos & 7);
	const unsigned int lo = v & lomask;

	*type = (v >> lobits) & 3;
	return lo;
}

static int get_compacted_la_distance(unsigned int lclusterbits,
				     unsigned int encodebits,
				     unsigned int vcnt, u8 *in, int i)
{
	const unsigned int lomask = (1 << lclusterbits) - 1;
	unsigned int lo, d1 = 0;
	u8 type;

	DBG_BUGON(i >= vcnt);

	do {
		lo = decode_compactedbits(lclusterbits, lomask,
					  in, encodebits * i, &type);

		if (type != Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD)
			return d1;
		++d1;
	} while (++i < vcnt);

	/* vcnt - 1 (Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD) item */
	if (!(lo & Z_EROFS_VLE_DI_D0_CBLKCNT))
		d1 += lo - 1;
	return d1;
}

static int unpack_compacted_index(struct z_erofs_maprecorder *m,
				  unsigned int amortizedshift,
				  erofs_off_t pos, bool lookahead)
{
	struct erofs_inode *const vi = EROFS_I(m->inode);
	const unsigned int lclusterbits = vi->z_logical_clusterbits;
	const unsigned int lomask = (1 << lclusterbits) - 1;
	unsigned int vcnt, base, lo, encodebits, nblk, eofs;
	int i;
	u8 *in, type;
	bool big_pcluster;

	if (1 << amortizedshift == 4 && lclusterbits <= 14)
		vcnt = 2;
	else if (1 << amortizedshift == 2 && lclusterbits == 12)
		vcnt = 16;
	else
		return -EOPNOTSUPP;

	/* it doesn't equal to round_up(..) */
	m->nextpackoff = round_down(pos, vcnt << amortizedshift) +
			 (vcnt << amortizedshift);
	big_pcluster = vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1;
	encodebits = ((vcnt << amortizedshift) - sizeof(__le32)) * 8 / vcnt;
	eofs = erofs_blkoff(pos);
	base = round_down(eofs, vcnt << amortizedshift);
	in = m->kaddr + base;

	i = (eofs - base) >> amortizedshift;

	lo = decode_compactedbits(lclusterbits, lomask,
				  in, encodebits * i, &type);
	m->type = type;
	if (type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD) {
		m->clusterofs = 1 << lclusterbits;

		/* figure out lookahead_distance: delta[1] if needed */
		if (lookahead)
			m->delta[1] = get_compacted_la_distance(lclusterbits,
						encodebits, vcnt, in, i);
		if (lo & Z_EROFS_VLE_DI_D0_CBLKCNT) {
			if (!big_pcluster) {
				DBG_BUGON(1);
				return -EFSCORRUPTED;
			}
			m->compressedblks = lo & ~Z_EROFS_VLE_DI_D0_CBLKCNT;
			m->delta[0] = 1;
			return 0;
		} else if (i + 1 != (int)vcnt) {
			m->delta[0] = lo;
			return 0;
		}
		/*
		 * since the last lcluster in the pack is special,
		 * of which lo saves delta[1] rather than delta[0].
		 * Hence, get delta[0] by the previous lcluster indirectly.
		 */
		lo = decode_compactedbits(lclusterbits, lomask,
					  in, encodebits * (i - 1), &type);
		if (type != Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD)
			lo = 0;
		else if (lo & Z_EROFS_VLE_DI_D0_CBLKCNT)
			lo = 1;
		m->delta[0] = lo + 1;
		return 0;
	}
	m->clusterofs = lo;
	m->delta[0] = 0;
	/* figout out blkaddr (pblk) for HEAD lclusters */
	if (!big_pcluster) {
		nblk = 1;
		while (i > 0) {
			--i;
			lo = decode_compactedbits(lclusterbits, lomask,
						  in, encodebits * i, &type);
			if (type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD)
				i -= lo;

			if (i >= 0)
				++nblk;
		}
	} else {
		nblk = 0;
		while (i > 0) {
			--i;
			lo = decode_compactedbits(lclusterbits, lomask,
						  in, encodebits * i, &type);
			if (type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD) {
				if (lo & Z_EROFS_VLE_DI_D0_CBLKCNT) {
					--i;
					nblk += lo & ~Z_EROFS_VLE_DI_D0_CBLKCNT;
					continue;
				}
				/* bigpcluster shouldn't have plain d0 == 1 */
				if (lo <= 1) {
					DBG_BUGON(1);
					return -EFSCORRUPTED;
				}
				i -= lo - 2;
				continue;
			}
			++nblk;
		}
	}
	in += (vcnt << amortizedshift) - sizeof(__le32);
	m->pblk = le32_to_cpu(*(__le32 *)in) + nblk;
	return 0;
}

static int compacted_load_cluster_from_disk(struct z_erofs_maprecorder *m,
					    unsigned long lcn, bool lookahead)
{
	struct inode *const inode = m->inode;
	struct erofs_inode *const vi = EROFS_I(inode);
	const erofs_off_t ebase = sizeof(struct z_erofs_map_header) +
		ALIGN(erofs_iloc(inode) + vi->inode_isize + vi->xattr_isize, 8);
	const unsigned int totalidx = DIV_ROUND_UP(inode->i_size, EROFS_BLKSIZ);
	unsigned int compacted_4b_initial, compacted_2b;
	unsigned int amortizedshift;
	erofs_off_t pos;

	if (lcn >= totalidx)
		return -EINVAL;

	m->lcn = lcn;
	/* used to align to 32-byte (compacted_2b) alignment */
	compacted_4b_initial = (32 - ebase % 32) / 4;
	if (compacted_4b_initial == 32 / 4)
		compacted_4b_initial = 0;

	if ((vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B) &&
	    compacted_4b_initial < totalidx)
		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
	else
		compacted_2b = 0;

	pos = ebase;
	if (lcn < compacted_4b_initial) {
		amortizedshift = 2;
		goto out;
	}
	pos += compacted_4b_initial * 4;
	lcn -= compacted_4b_initial;

	if (lcn < compacted_2b) {
		amortizedshift = 1;
		goto out;
	}
	pos += compacted_2b * 2;
	lcn -= compacted_2b;
	amortizedshift = 2;
out:
	pos += lcn * (1 << amortizedshift);
	m->kaddr = erofs_read_metabuf(&m->map->buf, inode->i_sb,
				      erofs_blknr(pos), EROFS_KMAP_ATOMIC);
	if (IS_ERR(m->kaddr))
		return PTR_ERR(m->kaddr);
	return unpack_compacted_index(m, amortizedshift, pos, lookahead);
}

static int z_erofs_load_cluster_from_disk(struct z_erofs_maprecorder *m,
					  unsigned int lcn, bool lookahead)
{
	const unsigned int datamode = EROFS_I(m->inode)->datalayout;

	if (datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY)
		return legacy_load_cluster_from_disk(m, lcn);

	if (datamode == EROFS_INODE_FLAT_COMPRESSION)
		return compacted_load_cluster_from_disk(m, lcn, lookahead);

	return -EINVAL;
}

static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
				   unsigned int lookback_distance)
{
	struct erofs_inode *const vi = EROFS_I(m->inode);
	const unsigned int lclusterbits = vi->z_logical_clusterbits;

	while (m->lcn >= lookback_distance) {
		unsigned long lcn = m->lcn - lookback_distance;
		int err;

		/* load extent head logical cluster if needed */
		err = z_erofs_load_cluster_from_disk(m, lcn, false);
		if (err)
			return err;

		switch (m->type) {
		case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
			if (!m->delta[0]) {
				erofs_err(m->inode->i_sb,
					  "invalid lookback distance 0 @ nid %llu",
					  vi->nid);
				DBG_BUGON(1);
				return -EFSCORRUPTED;
			}
			lookback_distance = m->delta[0];
			continue;
		case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
		case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
		case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
			m->headtype = m->type;
			m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
			return 0;
		default:
			erofs_err(m->inode->i_sb,
				  "unknown type %u @ lcn %lu of nid %llu",
				  m->type, lcn, vi->nid);
			DBG_BUGON(1);
			return -EOPNOTSUPP;
		}
	}

	erofs_err(m->inode->i_sb, "bogus lookback distance @ nid %llu",
		  vi->nid);
	DBG_BUGON(1);
	return -EFSCORRUPTED;
}

static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
					    unsigned int initial_lcn)
{
	struct erofs_inode *const vi = EROFS_I(m->inode);
	struct erofs_map_blocks *const map = m->map;
	const unsigned int lclusterbits = vi->z_logical_clusterbits;
	unsigned long lcn;
	int err;

	DBG_BUGON(m->type != Z_EROFS_VLE_CLUSTER_TYPE_PLAIN &&
		  m->type != Z_EROFS_VLE_CLUSTER_TYPE_HEAD1 &&
		  m->type != Z_EROFS_VLE_CLUSTER_TYPE_HEAD2);
	DBG_BUGON(m->type != m->headtype);

	if (m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN ||
	    ((m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD1) &&
	     !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) ||
	    ((m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) &&
	     !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_2))) {
		map->m_plen = 1ULL << lclusterbits;
		return 0;
	}
	lcn = m->lcn + 1;
	if (m->compressedblks)
		goto out;

	err = z_erofs_load_cluster_from_disk(m, lcn, false);
	if (err)
		return err;

	/*
	 * If the 1st NONHEAD lcluster has already been handled initially w/o
	 * valid compressedblks, which means at least it mustn't be CBLKCNT, or
	 * an internal implemenatation error is detected.
	 *
	 * The following code can also handle it properly anyway, but let's
	 * BUG_ON in the debugging mode only for developers to notice that.
	 */
	DBG_BUGON(lcn == initial_lcn &&
		  m->type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD);

	switch (m->type) {
	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
		/*
		 * if the 1st NONHEAD lcluster is actually PLAIN or HEAD type
		 * rather than CBLKCNT, it's a 1 lcluster-sized pcluster.
		 */
		m->compressedblks = 1 << (lclusterbits - LOG_BLOCK_SIZE);
		break;
	case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
		if (m->delta[0] != 1)
			goto err_bonus_cblkcnt;
		if (m->compressedblks)
			break;
		fallthrough;
	default:
		erofs_err(m->inode->i_sb,
			  "cannot found CBLKCNT @ lcn %lu of nid %llu",
			  lcn, vi->nid);
		DBG_BUGON(1);
		return -EFSCORRUPTED;
	}
out:
	map->m_plen = (u64)m->compressedblks << LOG_BLOCK_SIZE;
	return 0;
err_bonus_cblkcnt:
	erofs_err(m->inode->i_sb,
		  "bogus CBLKCNT @ lcn %lu of nid %llu",
		  lcn, vi->nid);
	DBG_BUGON(1);
	return -EFSCORRUPTED;
}

static int z_erofs_get_extent_decompressedlen(struct z_erofs_maprecorder *m)
{
	struct inode *inode = m->inode;
	struct erofs_inode *vi = EROFS_I(inode);
	struct erofs_map_blocks *map = m->map;
	unsigned int lclusterbits = vi->z_logical_clusterbits;
	u64 lcn = m->lcn, headlcn = map->m_la >> lclusterbits;
	int err;

	do {
		/* handle the last EOF pcluster (no next HEAD lcluster) */
		if ((lcn << lclusterbits) >= inode->i_size) {
			map->m_llen = inode->i_size - map->m_la;
			return 0;
		}

		err = z_erofs_load_cluster_from_disk(m, lcn, true);
		if (err)
			return err;

		if (m->type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD) {
			DBG_BUGON(!m->delta[1] &&
				  m->clusterofs != 1 << lclusterbits);
		} else if (m->type == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN ||
			   m->type == Z_EROFS_VLE_CLUSTER_TYPE_HEAD1 ||
			   m->type == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) {
			/* go on until the next HEAD lcluster */
			if (lcn != headlcn)
				break;
			m->delta[1] = 1;
		} else {
			erofs_err(inode->i_sb, "unknown type %u @ lcn %llu of nid %llu",
				  m->type, lcn, vi->nid);
			DBG_BUGON(1);
			return -EOPNOTSUPP;
		}
		lcn += m->delta[1];
	} while (m->delta[1]);

	map->m_llen = (lcn << lclusterbits) + m->clusterofs - map->m_la;
	return 0;
}

static int z_erofs_do_map_blocks(struct inode *inode,
				 struct erofs_map_blocks *map,
				 int flags)
{
	struct erofs_inode *const vi = EROFS_I(inode);
	bool ztailpacking = vi->z_advise & Z_EROFS_ADVISE_INLINE_PCLUSTER;
	bool fragment = vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER;
	struct z_erofs_maprecorder m = {
		.inode = inode,
		.map = map,
	};
	int err = 0;
	unsigned int lclusterbits, endoff;
	unsigned long initial_lcn;
	unsigned long long ofs, end;

	lclusterbits = vi->z_logical_clusterbits;
	ofs = flags & EROFS_GET_BLOCKS_FINDTAIL ? inode->i_size - 1 : map->m_la;
	initial_lcn = ofs >> lclusterbits;
	endoff = ofs & ((1 << lclusterbits) - 1);

	err = z_erofs_load_cluster_from_disk(&m, initial_lcn, false);
	if (err)
		goto unmap_out;

	if (ztailpacking && (flags & EROFS_GET_BLOCKS_FINDTAIL))
		vi->z_idataoff = m.nextpackoff;

	map->m_flags = EROFS_MAP_MAPPED | EROFS_MAP_ENCODED;
	end = (m.lcn + 1ULL) << lclusterbits;

	switch (m.type) {
	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
		if (endoff >= m.clusterofs) {
			m.headtype = m.type;
			map->m_la = (m.lcn << lclusterbits) | m.clusterofs;
			/*
			 * For ztailpacking files, in order to inline data more
			 * effectively, special EOF lclusters are now supported
			 * which can have three parts at most.
			 */
			if (ztailpacking && end > inode->i_size)
				end = inode->i_size;
			break;
		}
		/* m.lcn should be >= 1 if endoff < m.clusterofs */
		if (!m.lcn) {
			erofs_err(inode->i_sb,
				  "invalid logical cluster 0 at nid %llu",
				  vi->nid);
			err = -EFSCORRUPTED;
			goto unmap_out;
		}
		end = (m.lcn << lclusterbits) | m.clusterofs;
		map->m_flags |= EROFS_MAP_FULL_MAPPED;
		m.delta[0] = 1;
		fallthrough;
	case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
		/* get the corresponding first chunk */
		err = z_erofs_extent_lookback(&m, m.delta[0]);
		if (err)
			goto unmap_out;
		break;
	default:
		erofs_err(inode->i_sb,
			  "unknown type %u @ offset %llu of nid %llu",
			  m.type, ofs, vi->nid);
		err = -EOPNOTSUPP;
		goto unmap_out;
	}
	if (m.partialref)
		map->m_flags |= EROFS_MAP_PARTIAL_REF;
	map->m_llen = end - map->m_la;

	if (flags & EROFS_GET_BLOCKS_FINDTAIL) {
		vi->z_tailextent_headlcn = m.lcn;
		/* for non-compact indexes, fragmentoff is 64 bits */
		if (fragment &&
		    vi->datalayout == EROFS_INODE_FLAT_COMPRESSION_LEGACY)
			vi->z_fragmentoff |= (u64)m.pblk << 32;
	}
	if (ztailpacking && m.lcn == vi->z_tailextent_headlcn) {
		map->m_flags |= EROFS_MAP_META;
		map->m_pa = vi->z_idataoff;
		map->m_plen = vi->z_idata_size;
	} else if (fragment && m.lcn == vi->z_tailextent_headlcn) {
		map->m_flags |= EROFS_MAP_FRAGMENT;
	} else {
		map->m_pa = blknr_to_addr(m.pblk);
		err = z_erofs_get_extent_compressedlen(&m, initial_lcn);
		if (err)
			goto unmap_out;
	}

	if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN) {
		if (map->m_llen > map->m_plen) {
			DBG_BUGON(1);
			err = -EFSCORRUPTED;
			goto unmap_out;
		}
		if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)
			map->m_algorithmformat =
				Z_EROFS_COMPRESSION_INTERLACED;
		else
			map->m_algorithmformat =
				Z_EROFS_COMPRESSION_SHIFTED;
	} else if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) {
		map->m_algorithmformat = vi->z_algorithmtype[1];
	} else {
		map->m_algorithmformat = vi->z_algorithmtype[0];
	}

	if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
	    ((flags & EROFS_GET_BLOCKS_READMORE) &&
	     map->m_algorithmformat == Z_EROFS_COMPRESSION_LZMA &&
	     map->m_llen >= EROFS_BLKSIZ)) {
		err = z_erofs_get_extent_decompressedlen(&m);
		if (!err)
			map->m_flags |= EROFS_MAP_FULL_MAPPED;
	}

unmap_out:
	erofs_unmap_metabuf(&m.map->buf);
	erofs_dbg("%s, m_la %llu m_pa %llu m_llen %llu m_plen %llu m_flags 0%o",
		  __func__, map->m_la, map->m_pa,
		  map->m_llen, map->m_plen, map->m_flags);
	return err;
}

int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map,
			    int flags)
{
	struct erofs_inode *const vi = EROFS_I(inode);
	int err = 0;

	trace_z_erofs_map_blocks_iter_enter(inode, map, flags);

	/* when trying to read beyond EOF, leave it unmapped */
	if (map->m_la >= inode->i_size) {
		map->m_llen = map->m_la + 1 - inode->i_size;
		map->m_la = inode->i_size;
		map->m_flags = 0;
		goto out;
	}

	err = z_erofs_fill_inode_lazy(inode);
	if (err)
		goto out;

	if ((vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER) &&
	    !vi->z_tailextent_headlcn) {
		map->m_la = 0;
		map->m_llen = inode->i_size;
		map->m_flags = EROFS_MAP_MAPPED | EROFS_MAP_FULL_MAPPED |
				EROFS_MAP_FRAGMENT;
		goto out;
	}

	err = z_erofs_do_map_blocks(inode, map, flags);
out:
	trace_z_erofs_map_blocks_iter_exit(inode, map, flags, err);

	/* aggressively BUG_ON iff CONFIG_EROFS_FS_DEBUG is on */
	DBG_BUGON(err < 0 && err != -ENOMEM);
	return err;
}

static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset,
				loff_t length, unsigned int flags,
				struct iomap *iomap, struct iomap *srcmap)
{
	int ret;
	struct erofs_map_blocks map = { .m_la = offset };

	ret = z_erofs_map_blocks_iter(inode, &map, EROFS_GET_BLOCKS_FIEMAP);
	erofs_put_metabuf(&map.buf);
	if (ret < 0)
		return ret;

	iomap->bdev = inode->i_sb->s_bdev;
	iomap->offset = map.m_la;
	iomap->length = map.m_llen;
	if (map.m_flags & EROFS_MAP_MAPPED) {
		iomap->type = IOMAP_MAPPED;
		iomap->addr = map.m_flags & EROFS_MAP_FRAGMENT ?
			      IOMAP_NULL_ADDR : map.m_pa;
	} else {
		iomap->type = IOMAP_HOLE;
		iomap->addr = IOMAP_NULL_ADDR;
		/*
		 * No strict rule on how to describe extents for post EOF, yet
		 * we need to do like below. Otherwise, iomap itself will get
		 * into an endless loop on post EOF.
		 *
		 * Calculate the effective offset by subtracting extent start
		 * (map.m_la) from the requested offset, and add it to length.
		 * (NB: offset >= map.m_la always)
		 */
		if (iomap->offset >= inode->i_size)
			iomap->length = length + offset - map.m_la;
	}
	iomap->flags = 0;
	return 0;
}

const struct iomap_ops z_erofs_iomap_report_ops = {
	.iomap_begin = z_erofs_iomap_begin_report,
};