summaryrefslogtreecommitdiffstats
path: root/fs/nilfs2/recovery.c
blob: 2f11f0868d877e4898bbd3e7e0a93ec73e5926e2 (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
/*
 * recovery.c - NILFS recovery logic
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Written by Ryusuke Konishi <ryusuke@osrg.net>
 */

#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/crc32.h>
#include "nilfs.h"
#include "segment.h"
#include "sufile.h"
#include "page.h"
#include "segbuf.h"

/*
 * Segment check result
 */
enum {
	NILFS_SEG_VALID,
	NILFS_SEG_NO_SUPER_ROOT,
	NILFS_SEG_FAIL_IO,
	NILFS_SEG_FAIL_MAGIC,
	NILFS_SEG_FAIL_SEQ,
	NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT,
	NILFS_SEG_FAIL_CHECKSUM_FULL,
	NILFS_SEG_FAIL_CONSISTENCY,
};

/* work structure for recovery */
struct nilfs_recovery_block {
	ino_t ino;		/* Inode number of the file that this block
				   belongs to */
	sector_t blocknr;	/* block number */
	__u64 vblocknr;		/* virtual block number */
	unsigned long blkoff;	/* File offset of the data block (per block) */
	struct list_head list;
};


static int nilfs_warn_segment_error(int err)
{
	switch (err) {
	case NILFS_SEG_FAIL_IO:
		printk(KERN_WARNING
		       "NILFS warning: I/O error on loading last segment\n");
		return -EIO;
	case NILFS_SEG_FAIL_MAGIC:
		printk(KERN_WARNING
		       "NILFS warning: Segment magic number invalid\n");
		break;
	case NILFS_SEG_FAIL_SEQ:
		printk(KERN_WARNING
		       "NILFS warning: Sequence number mismatch\n");
		break;
	case NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT:
		printk(KERN_WARNING
		       "NILFS warning: Checksum error in super root\n");
		break;
	case NILFS_SEG_FAIL_CHECKSUM_FULL:
		printk(KERN_WARNING
		       "NILFS warning: Checksum error in segment payload\n");
		break;
	case NILFS_SEG_FAIL_CONSISTENCY:
		printk(KERN_WARNING
		       "NILFS warning: Inconsistent segment\n");
		break;
	case NILFS_SEG_NO_SUPER_ROOT:
		printk(KERN_WARNING
		       "NILFS warning: No super root in the last segment\n");
		break;
	}
	return -EINVAL;
}

static void store_segsum_info(struct nilfs_segsum_info *ssi,
			      struct nilfs_segment_summary *sum,
			      unsigned int blocksize)
{
	ssi->flags = le16_to_cpu(sum->ss_flags);
	ssi->seg_seq = le64_to_cpu(sum->ss_seq);
	ssi->ctime = le64_to_cpu(sum->ss_create);
	ssi->next = le64_to_cpu(sum->ss_next);
	ssi->nblocks = le32_to_cpu(sum->ss_nblocks);
	ssi->nfinfo = le32_to_cpu(sum->ss_nfinfo);
	ssi->sumbytes = le32_to_cpu(sum->ss_sumbytes);

	ssi->nsumblk = DIV_ROUND_UP(ssi->sumbytes, blocksize);
	ssi->nfileblk = ssi->nblocks - ssi->nsumblk - !!NILFS_SEG_HAS_SR(ssi);

	/* need to verify ->ss_bytes field if read ->ss_cno */
}

/**
 * calc_crc_cont - check CRC of blocks continuously
 * @sbi: nilfs_sb_info
 * @bhs: buffer head of start block
 * @sum: place to store result
 * @offset: offset bytes in the first block
 * @check_bytes: number of bytes to be checked
 * @start: DBN of start block
 * @nblock: number of blocks to be checked
 */
static int calc_crc_cont(struct nilfs_sb_info *sbi, struct buffer_head *bhs,
			 u32 *sum, unsigned long offset, u64 check_bytes,
			 sector_t start, unsigned long nblock)
{
	unsigned long blocksize = sbi->s_super->s_blocksize;
	unsigned long size;
	u32 crc;

	BUG_ON(offset >= blocksize);
	check_bytes -= offset;
	size = min_t(u64, check_bytes, blocksize - offset);
	crc = crc32_le(sbi->s_nilfs->ns_crc_seed,
		       (unsigned char *)bhs->b_data + offset, size);
	if (--nblock > 0) {
		do {
			struct buffer_head *bh
				= sb_bread(sbi->s_super, ++start);
			if (!bh)
				return -EIO;
			check_bytes -= size;
			size = min_t(u64, check_bytes, blocksize);
			crc = crc32_le(crc, bh->b_data, size);
			brelse(bh);
		} while (--nblock > 0);
	}
	*sum = crc;
	return 0;
}

/**
 * nilfs_read_super_root_block - read super root block
 * @sb: super_block
 * @sr_block: disk block number of the super root block
 * @pbh: address of a buffer_head pointer to return super root buffer
 * @check: CRC check flag
 */
int nilfs_read_super_root_block(struct super_block *sb, sector_t sr_block,
				struct buffer_head **pbh, int check)
{
	struct buffer_head *bh_sr;
	struct nilfs_super_root *sr;
	u32 crc;
	int ret;

	*pbh = NULL;
	bh_sr = sb_bread(sb, sr_block);
	if (unlikely(!bh_sr)) {
		ret = NILFS_SEG_FAIL_IO;
		goto failed;
	}

	sr = (struct nilfs_super_root *)bh_sr->b_data;
	if (check) {
		unsigned bytes = le16_to_cpu(sr->sr_bytes);

		if (bytes == 0 || bytes > sb->s_blocksize) {
			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
			goto failed_bh;
		}
		if (calc_crc_cont(NILFS_SB(sb), bh_sr, &crc,
				  sizeof(sr->sr_sum), bytes, sr_block, 1)) {
			ret = NILFS_SEG_FAIL_IO;
			goto failed_bh;
		}
		if (crc != le32_to_cpu(sr->sr_sum)) {
			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
			goto failed_bh;
		}
	}
	*pbh = bh_sr;
	return 0;

 failed_bh:
	brelse(bh_sr);

 failed:
	return nilfs_warn_segment_error(ret);
}

/**
 * load_segment_summary - read segment summary of the specified partial segment
 * @sbi: nilfs_sb_info
 * @pseg_start: start disk block number of partial segment
 * @seg_seq: sequence number requested
 * @ssi: pointer to nilfs_segsum_info struct to store information
 */
static int
load_segment_summary(struct nilfs_sb_info *sbi, sector_t pseg_start,
		     u64 seg_seq, struct nilfs_segsum_info *ssi)
{
	struct buffer_head *bh_sum;
	struct nilfs_segment_summary *sum;
	unsigned long nblock;
	u32 crc;
	int ret = NILFS_SEG_FAIL_IO;

	bh_sum = sb_bread(sbi->s_super, pseg_start);
	if (!bh_sum)
		goto out;

	sum = (struct nilfs_segment_summary *)bh_sum->b_data;

	/* Check consistency of segment summary */
	if (le32_to_cpu(sum->ss_magic) != NILFS_SEGSUM_MAGIC) {
		ret = NILFS_SEG_FAIL_MAGIC;
		goto failed;
	}
	store_segsum_info(ssi, sum, sbi->s_super->s_blocksize);
	if (seg_seq != ssi->seg_seq) {
		ret = NILFS_SEG_FAIL_SEQ;
		goto failed;
	}

	nblock = ssi->nblocks;
	if (unlikely(nblock == 0 ||
		     nblock > sbi->s_nilfs->ns_blocks_per_segment)) {
		/* This limits the number of blocks read in the CRC check */
		ret = NILFS_SEG_FAIL_CONSISTENCY;
		goto failed;
	}
	if (calc_crc_cont(sbi, bh_sum, &crc, sizeof(sum->ss_datasum),
			  ((u64)nblock << sbi->s_super->s_blocksize_bits),
			  pseg_start, nblock)) {
		ret = NILFS_SEG_FAIL_IO;
		goto failed;
	}
	if (crc == le32_to_cpu(sum->ss_datasum))
		ret = 0;
	else
		ret = NILFS_SEG_FAIL_CHECKSUM_FULL;
 failed:
	brelse(bh_sum);
 out:
	return ret;
}

static void *segsum_get(struct super_block *sb, struct buffer_head **pbh,
			unsigned int *offset, unsigned int bytes)
{
	void *ptr;
	sector_t blocknr;

	BUG_ON((*pbh)->b_size < *offset);
	if (bytes > (*pbh)->b_size - *offset) {
		blocknr = (*pbh)->b_blocknr;
		brelse(*pbh);
		*pbh = sb_bread(sb, blocknr + 1);
		if (unlikely(!*pbh))
			return NULL;
		*offset = 0;
	}
	ptr = (*pbh)->b_data + *offset;
	*offset += bytes;
	return ptr;
}

static void segsum_skip(struct super_block *sb, struct buffer_head **pbh,
			unsigned int *offset, unsigned int bytes,
			unsigned long count)
{
	unsigned int rest_item_in_current_block
		= ((*pbh)->b_size - *offset) / bytes;

	if (count <= rest_item_in_current_block) {
		*offset += bytes * count;
	} else {
		sector_t blocknr = (*pbh)->b_blocknr;
		unsigned int nitem_per_block = (*pbh)->b_size / bytes;
		unsigned int bcnt;

		count -= rest_item_in_current_block;
		bcnt = DIV_ROUND_UP(count, nitem_per_block);
		*offset = bytes * (count - (bcnt - 1) * nitem_per_block);

		brelse(*pbh);
		*pbh = sb_bread(sb, blocknr + bcnt);
	}
}

static int
collect_blocks_from_segsum(struct nilfs_sb_info *sbi, sector_t sum_blocknr,
			   struct nilfs_segsum_info *ssi,
			   struct list_head *head)
{
	struct buffer_head *bh;
	unsigned int offset;
	unsigned long nfinfo = ssi->nfinfo;
	sector_t blocknr = sum_blocknr + ssi->nsumblk;
	ino_t ino;
	int err = -EIO;

	if (!nfinfo)
		return 0;

	bh = sb_bread(sbi->s_super, sum_blocknr);
	if (unlikely(!bh))
		goto out;

	offset = le16_to_cpu(
		((struct nilfs_segment_summary *)bh->b_data)->ss_bytes);
	for (;;) {
		unsigned long nblocks, ndatablk, nnodeblk;
		struct nilfs_finfo *finfo;

		finfo = segsum_get(sbi->s_super, &bh, &offset, sizeof(*finfo));
		if (unlikely(!finfo))
			goto out;

		ino = le64_to_cpu(finfo->fi_ino);
		nblocks = le32_to_cpu(finfo->fi_nblocks);
		ndatablk = le32_to_cpu(finfo->fi_ndatablk);
		nnodeblk = nblocks - ndatablk;

		while (ndatablk-- > 0) {
			struct nilfs_recovery_block *rb;
			struct nilfs_binfo_v *binfo;

			binfo = segsum_get(sbi->s_super, &bh, &offset,
					   sizeof(*binfo));
			if (unlikely(!binfo))
				goto out;

			rb = kmalloc(sizeof(*rb), GFP_NOFS);
			if (unlikely(!rb)) {
				err = -ENOMEM;
				goto out;
			}
			rb->ino = ino;
			rb->blocknr = blocknr++;
			rb->vblocknr = le64_to_cpu(binfo->bi_vblocknr);
			rb->blkoff = le64_to_cpu(binfo->bi_blkoff);
			/* INIT_LIST_HEAD(&rb->list); */
			list_add_tail(&rb->list, head);
		}
		if (--nfinfo == 0)
			break;
		blocknr += nnodeblk; /* always 0 for the data sync segments */
		segsum_skip(sbi->s_super, &bh, &offset, sizeof(__le64),
			    nnodeblk);
		if (unlikely(!bh))
			goto out;
	}
	err = 0;
 out:
	brelse(bh);   /* brelse(NULL) is just ignored */
	return err;
}

static void dispose_recovery_list(struct list_head *head)
{
	while (!list_empty(head)) {
		struct nilfs_recovery_block *rb
			= list_entry(head->next,
				     struct nilfs_recovery_block, list);
		list_del(&rb->list);
		kfree(rb);
	}
}

struct nilfs_segment_entry {
	struct list_head	list;
	__u64			segnum;
};

static int nilfs_segment_list_add(struct list_head *head, __u64 segnum)
{
	struct nilfs_segment_entry *ent = kmalloc(sizeof(*ent), GFP_NOFS);

	if (unlikely(!ent))
		return -ENOMEM;

	ent->segnum = segnum;
	INIT_LIST_HEAD(&ent->list);
	list_add_tail(&ent->list, head);
	return 0;
}

void nilfs_dispose_segment_list(struct list_head *head)
{
	while (!list_empty(head)) {
		struct nilfs_segment_entry *ent
			= list_entry(head->next,
				     struct nilfs_segment_entry, list);
		list_del(&ent->list);
		kfree(ent);
	}
}

static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,
					      struct nilfs_sb_info *sbi,
					      struct nilfs_recovery_info *ri)
{
	struct list_head *head = &ri->ri_used_segments;
	struct nilfs_segment_entry *ent, *n;
	struct inode *sufile = nilfs->ns_sufile;
	__u64 segnum[4];
	int err;
	int i;

	segnum[0] = nilfs->ns_segnum;
	segnum[1] = nilfs->ns_nextnum;
	segnum[2] = ri->ri_segnum;
	segnum[3] = ri->ri_nextnum;

	nilfs_attach_writer(nilfs, sbi);
	/*
	 * Releasing the next segment of the latest super root.
	 * The next segment is invalidated by this recovery.
	 */
	err = nilfs_sufile_free(sufile, segnum[1]);
	if (unlikely(err))
		goto failed;

	for (i = 1; i < 4; i++) {
		err = nilfs_segment_list_add(head, segnum[i]);
		if (unlikely(err))
			goto failed;
	}

	/*
	 * Collecting segments written after the latest super root.
	 * These are marked dirty to avoid being reallocated in the next write.
	 */
	list_for_each_entry_safe(ent, n, head, list) {
		if (ent->segnum != segnum[0]) {
			err = nilfs_sufile_scrap(sufile, ent->segnum);
			if (unlikely(err))
				goto failed;
		}
		list_del(&ent->list);
		kfree(ent);
	}

	/* Allocate new segments for recovery */
	err = nilfs_sufile_alloc(sufile, &segnum[0]);
	if (unlikely(err))
		goto failed;

	nilfs->ns_pseg_offset = 0;
	nilfs->ns_seg_seq = ri->ri_seq + 2;
	nilfs->ns_nextnum = nilfs->ns_segnum = segnum[0];

 failed:
	/* No need to recover sufile because it will be destroyed on error */
	nilfs_detach_writer(nilfs, sbi);
	return err;
}

static int nilfs_recovery_copy_block(struct nilfs_sb_info *sbi,
				     struct nilfs_recovery_block *rb,
				     struct page *page)
{
	struct buffer_head *bh_org;
	void *kaddr;

	bh_org = sb_bread(sbi->s_super, rb->blocknr);
	if (unlikely(!bh_org))
		return -EIO;

	kaddr = kmap_atomic(page, KM_USER0);
	memcpy(kaddr + bh_offset(bh_org), bh_org->b_data, bh_org->b_size);
	kunmap_atomic(kaddr, KM_USER0);
	brelse(bh_org);
	return 0;
}

static int recover_dsync_blocks(struct nilfs_sb_info *sbi,
				struct list_head *head,
				unsigned long *nr_salvaged_blocks)
{
	struct inode *inode;
	struct nilfs_recovery_block *rb, *n;
	unsigned blocksize = sbi->s_super->s_blocksize;
	struct page *page;
	loff_t pos;
	int err = 0, err2 = 0;

	list_for_each_entry_safe(rb, n, head, list) {
		inode = nilfs_iget(sbi->s_super, rb->ino);
		if (IS_ERR(inode)) {
			err = PTR_ERR(inode);
			inode = NULL;
			goto failed_inode;
		}

		pos = rb->blkoff << inode->i_blkbits;
		err = block_write_begin(inode->i_mapping, pos, blocksize,
					0, &page, nilfs_get_block);
		if (unlikely(err)) {
			loff_t isize = inode->i_size;
			if (pos + blocksize > isize)
				vmtruncate(inode, isize);
			goto failed_inode;
		}

		err = nilfs_recovery_copy_block(sbi, rb, page);
		if (unlikely(err))
			goto failed_page;

		err = nilfs_set_file_dirty(sbi, inode, 1);
		if (unlikely(err))
			goto failed_page;

		block_write_end(NULL, inode->i_mapping, pos, blocksize,
				blocksize, page, NULL);

		unlock_page(page);
		page_cache_release(page);

		(*nr_salvaged_blocks)++;
		goto next;

 failed_page:
		unlock_page(page);
		page_cache_release(page);

 failed_inode:
		printk(KERN_WARNING
		       "NILFS warning: error recovering data block "
		       "(err=%d, ino=%lu, block-offset=%llu)\n",
		       err, (unsigned long)rb->ino,
		       (unsigned long long)rb->blkoff);
		if (!err2)
			err2 = err;
 next:
		iput(inode); /* iput(NULL) is just ignored */
		list_del_init(&rb->list);
		kfree(rb);
	}
	return err2;
}

/**
 * nilfs_do_roll_forward - salvage logical segments newer than the latest
 * checkpoint
 * @sbi: nilfs_sb_info
 * @nilfs: the_nilfs
 * @ri: pointer to a nilfs_recovery_info
 */
static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
				 struct nilfs_sb_info *sbi,
				 struct nilfs_recovery_info *ri)
{
	struct nilfs_segsum_info ssi;
	sector_t pseg_start;
	sector_t seg_start, seg_end;  /* Starting/ending DBN of full segment */
	unsigned long nsalvaged_blocks = 0;
	u64 seg_seq;
	__u64 segnum, nextnum = 0;
	int empty_seg = 0;
	int err = 0, ret;
	LIST_HEAD(dsync_blocks);  /* list of data blocks to be recovered */
	enum {
		RF_INIT_ST,
		RF_DSYNC_ST,   /* scanning data-sync segments */
	};
	int state = RF_INIT_ST;

	nilfs_attach_writer(nilfs, sbi);
	pseg_start = ri->ri_lsegs_start;
	seg_seq = ri->ri_lsegs_start_seq;
	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);

	while (segnum != ri->ri_segnum || pseg_start <= ri->ri_pseg_start) {

		ret = load_segment_summary(sbi, pseg_start, seg_seq, &ssi);
		if (ret) {
			if (ret == NILFS_SEG_FAIL_IO) {
				err = -EIO;
				goto failed;
			}
			goto strayed;
		}
		if (unlikely(NILFS_SEG_HAS_SR(&ssi)))
			goto confused;

		/* Found a valid partial segment; do recovery actions */
		nextnum = nilfs_get_segnum_of_block(nilfs, ssi.next);
		empty_seg = 0;
		nilfs->ns_ctime = ssi.ctime;
		if (!(ssi.flags & NILFS_SS_GC))
			nilfs->ns_nongc_ctime = ssi.ctime;

		switch (state) {
		case RF_INIT_ST:
			if (!NILFS_SEG_LOGBGN(&ssi) || !NILFS_SEG_DSYNC(&ssi))
				goto try_next_pseg;
			state = RF_DSYNC_ST;
			/* Fall through */
		case RF_DSYNC_ST:
			if (!NILFS_SEG_DSYNC(&ssi))
				goto confused;

			err = collect_blocks_from_segsum(
				sbi, pseg_start, &ssi, &dsync_blocks);
			if (unlikely(err))
				goto failed;
			if (NILFS_SEG_LOGEND(&ssi)) {
				err = recover_dsync_blocks(
					sbi, &dsync_blocks, &nsalvaged_blocks);
				if (unlikely(err))
					goto failed;
				state = RF_INIT_ST;
			}
			break; /* Fall through to try_next_pseg */
		}

 try_next_pseg:
		if (pseg_start == ri->ri_lsegs_end)
			break;
		pseg_start += ssi.nblocks;
		if (pseg_start < seg_end)
			continue;
		goto feed_segment;

 strayed:
		if (pseg_start == ri->ri_lsegs_end)
			break;

 feed_segment:
		/* Looking to the next full segment */
		if (empty_seg++)
			break;
		seg_seq++;
		segnum = nextnum;
		nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
		pseg_start = seg_start;
	}

	if (nsalvaged_blocks) {
		printk(KERN_INFO "NILFS (device %s): salvaged %lu blocks\n",
		       sbi->s_super->s_id, nsalvaged_blocks);
		ri->ri_need_recovery = NILFS_RECOVERY_ROLLFORWARD_DONE;
	}
 out:
	dispose_recovery_list(&dsync_blocks);
	nilfs_detach_writer(sbi->s_nilfs, sbi);
	return err;

 confused:
	err = -EINVAL;
 failed:
	printk(KERN_ERR
	       "NILFS (device %s): Error roll-forwarding "
	       "(err=%d, pseg block=%llu). ",
	       sbi->s_super->s_id, err, (unsigned long long)pseg_start);
	goto out;
}

static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,
				      struct nilfs_sb_info *sbi,
				      struct nilfs_recovery_info *ri)
{
	struct buffer_head *bh;
	int err;

	if (nilfs_get_segnum_of_block(nilfs, ri->ri_lsegs_start) !=
	    nilfs_get_segnum_of_block(nilfs, ri->ri_super_root))
		return;

	bh = sb_getblk(sbi->s_super, ri->ri_lsegs_start);
	BUG_ON(!bh);
	memset(bh->b_data, 0, bh->b_size);
	set_buffer_dirty(bh);
	err = sync_dirty_buffer(bh);
	if (unlikely(err))
		printk(KERN_WARNING
		       "NILFS warning: buffer sync write failed during "
		       "post-cleaning of recovery.\n");
	brelse(bh);
}

/**
 * nilfs_recover_logical_segments - salvage logical segments written after
 * the latest super root
 * @nilfs: the_nilfs
 * @sbi: nilfs_sb_info
 * @ri: pointer to a nilfs_recovery_info struct to store search results.
 *
 * Return Value: On success, 0 is returned.  On error, one of the following
 * negative error code is returned.
 *
 * %-EINVAL - Inconsistent filesystem state.
 *
 * %-EIO - I/O error
 *
 * %-ENOSPC - No space left on device (only in a panic state).
 *
 * %-ERESTARTSYS - Interrupted.
 *
 * %-ENOMEM - Insufficient memory available.
 */
int nilfs_recover_logical_segments(struct the_nilfs *nilfs,
				   struct nilfs_sb_info *sbi,
				   struct nilfs_recovery_info *ri)
{
	int err;

	if (ri->ri_lsegs_start == 0 || ri->ri_lsegs_end == 0)
		return 0;

	err = nilfs_attach_checkpoint(sbi, ri->ri_cno);
	if (unlikely(err)) {
		printk(KERN_ERR
		       "NILFS: error loading the latest checkpoint.\n");
		return err;
	}

	err = nilfs_do_roll_forward(nilfs, sbi, ri);
	if (unlikely(err))
		goto failed;

	if (ri->ri_need_recovery == NILFS_RECOVERY_ROLLFORWARD_DONE) {
		err = nilfs_prepare_segment_for_recovery(nilfs, sbi, ri);
		if (unlikely(err)) {
			printk(KERN_ERR "NILFS: Error preparing segments for "
			       "recovery.\n");
			goto failed;
		}

		err = nilfs_attach_segment_constructor(sbi);
		if (unlikely(err))
			goto failed;

		set_nilfs_discontinued(nilfs);
		err = nilfs_construct_segment(sbi->s_super);
		nilfs_detach_segment_constructor(sbi);

		if (unlikely(err)) {
			printk(KERN_ERR "NILFS: Oops! recovery failed. "
			       "(err=%d)\n", err);
			goto failed;
		}

		nilfs_finish_roll_forward(nilfs, sbi, ri);
	}

 failed:
	nilfs_detach_checkpoint(sbi);
	return err;
}

/**
 * nilfs_search_super_root - search the latest valid super root
 * @nilfs: the_nilfs
 * @sbi: nilfs_sb_info
 * @ri: pointer to a nilfs_recovery_info struct to store search results.
 *
 * nilfs_search_super_root() looks for the latest super-root from a partial
 * segment pointed by the superblock.  It sets up struct the_nilfs through
 * this search. It fills nilfs_recovery_info (ri) required for recovery.
 *
 * Return Value: On success, 0 is returned.  On error, one of the following
 * negative error code is returned.
 *
 * %-EINVAL - No valid segment found
 *
 * %-EIO - I/O error
 */
int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
			    struct nilfs_recovery_info *ri)
{
	struct nilfs_segsum_info ssi;
	sector_t pseg_start, pseg_end, sr_pseg_start = 0;
	sector_t seg_start, seg_end; /* range of full segment (block number) */
	sector_t b, end;
	u64 seg_seq;
	__u64 segnum, nextnum = 0;
	__u64 cno;
	LIST_HEAD(segments);
	int empty_seg = 0, scan_newer = 0;
	int ret;

	pseg_start = nilfs->ns_last_pseg;
	seg_seq = nilfs->ns_last_seq;
	cno = nilfs->ns_last_cno;
	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);

	/* Calculate range of segment */
	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);

	/* Read ahead segment */
	b = seg_start;
	while (b <= seg_end)
		sb_breadahead(sbi->s_super, b++);

	for (;;) {
		/* Load segment summary */
		ret = load_segment_summary(sbi, pseg_start, seg_seq, &ssi);
		if (ret) {
			if (ret == NILFS_SEG_FAIL_IO)
				goto failed;
			goto strayed;
		}
		pseg_end = pseg_start + ssi.nblocks - 1;
		if (unlikely(pseg_end > seg_end)) {
			ret = NILFS_SEG_FAIL_CONSISTENCY;
			goto strayed;
		}

		/* A valid partial segment */
		ri->ri_pseg_start = pseg_start;
		ri->ri_seq = seg_seq;
		ri->ri_segnum = segnum;
		nextnum = nilfs_get_segnum_of_block(nilfs, ssi.next);
		ri->ri_nextnum = nextnum;
		empty_seg = 0;

		if (!NILFS_SEG_HAS_SR(&ssi) && !scan_newer) {
			/* This will never happen because a superblock
			   (last_segment) always points to a pseg
			   having a super root. */
			ret = NILFS_SEG_FAIL_CONSISTENCY;
			goto failed;
		}

		if (pseg_start == seg_start) {
			nilfs_get_segment_range(nilfs, nextnum, &b, &end);
			while (b <= end)
				sb_breadahead(sbi->s_super, b++);
		}
		if (!NILFS_SEG_HAS_SR(&ssi)) {
			if (!ri->ri_lsegs_start && NILFS_SEG_LOGBGN(&ssi)) {
				ri->ri_lsegs_start = pseg_start;
				ri->ri_lsegs_start_seq = seg_seq;
			}
			if (NILFS_SEG_LOGEND(&ssi))
				ri->ri_lsegs_end = pseg_start;
			goto try_next_pseg;
		}

		/* A valid super root was found. */
		ri->ri_cno = cno++;
		ri->ri_super_root = pseg_end;
		ri->ri_lsegs_start = ri->ri_lsegs_end = 0;

		nilfs_dispose_segment_list(&segments);
		nilfs->ns_pseg_offset = (sr_pseg_start = pseg_start)
			+ ssi.nblocks - seg_start;
		nilfs->ns_seg_seq = seg_seq;
		nilfs->ns_segnum = segnum;
		nilfs->ns_cno = cno;  /* nilfs->ns_cno = ri->ri_cno + 1 */
		nilfs->ns_ctime = ssi.ctime;
		nilfs->ns_nextnum = nextnum;

		if (scan_newer)
			ri->ri_need_recovery = NILFS_RECOVERY_SR_UPDATED;
		else {
			if (nilfs->ns_mount_state & NILFS_VALID_FS)
				goto super_root_found;
			scan_newer = 1;
		}

		/* reset region for roll-forward */
		pseg_start += ssi.nblocks;
		if (pseg_start < seg_end)
			continue;
		goto feed_segment;

 try_next_pseg:
		/* Standing on a course, or met an inconsistent state */
		pseg_start += ssi.nblocks;
		if (pseg_start < seg_end)
			continue;
		goto feed_segment;

 strayed:
		/* Off the trail */
		if (!scan_newer)
			/*
			 * This can happen if a checkpoint was written without
			 * barriers, or as a result of an I/O failure.
			 */
			goto failed;

 feed_segment:
		/* Looking to the next full segment */
		if (empty_seg++)
			goto super_root_found; /* found a valid super root */

		ret = nilfs_segment_list_add(&segments, segnum);
		if (unlikely(ret))
			goto failed;

		seg_seq++;
		segnum = nextnum;
		nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
		pseg_start = seg_start;
	}

 super_root_found:
	/* Updating pointers relating to the latest checkpoint */
	list_splice_tail(&segments, &ri->ri_used_segments);
	nilfs->ns_last_pseg = sr_pseg_start;
	nilfs->ns_last_seq = nilfs->ns_seg_seq;
	nilfs->ns_last_cno = ri->ri_cno;
	return 0;

 failed:
	nilfs_dispose_segment_list(&segments);
	return (ret < 0) ? ret : nilfs_warn_segment_error(ret);
}