summaryrefslogtreecommitdiffstats
path: root/fs/nilfs2/the_nilfs.c
blob: 71400496ed36519d2524ab552efed3e150899a52 (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
// SPDX-License-Identifier: GPL-2.0+
/*
 * the_nilfs shared structure.
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * Written by Ryusuke Konishi.
 *
 */

#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/random.h>
#include <linux/log2.h>
#include <linux/crc32.h>
#include "nilfs.h"
#include "segment.h"
#include "alloc.h"
#include "cpfile.h"
#include "sufile.h"
#include "dat.h"
#include "segbuf.h"


static int nilfs_valid_sb(struct nilfs_super_block *sbp);

void nilfs_set_last_segment(struct the_nilfs *nilfs,
			    sector_t start_blocknr, u64 seq, __u64 cno)
{
	spin_lock(&nilfs->ns_last_segment_lock);
	nilfs->ns_last_pseg = start_blocknr;
	nilfs->ns_last_seq = seq;
	nilfs->ns_last_cno = cno;

	if (!nilfs_sb_dirty(nilfs)) {
		if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
			goto stay_cursor;

		set_nilfs_sb_dirty(nilfs);
	}
	nilfs->ns_prev_seq = nilfs->ns_last_seq;

 stay_cursor:
	spin_unlock(&nilfs->ns_last_segment_lock);
}

/**
 * alloc_nilfs - allocate a nilfs object
 * @sb: super block instance
 *
 * Return Value: On success, pointer to the_nilfs is returned.
 * On error, NULL is returned.
 */
struct the_nilfs *alloc_nilfs(struct super_block *sb)
{
	struct the_nilfs *nilfs;

	nilfs = kzalloc(sizeof(*nilfs), GFP_KERNEL);
	if (!nilfs)
		return NULL;

	nilfs->ns_sb = sb;
	nilfs->ns_bdev = sb->s_bdev;
	atomic_set(&nilfs->ns_ndirtyblks, 0);
	init_rwsem(&nilfs->ns_sem);
	mutex_init(&nilfs->ns_snapshot_mount_mutex);
	INIT_LIST_HEAD(&nilfs->ns_dirty_files);
	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
	spin_lock_init(&nilfs->ns_inode_lock);
	spin_lock_init(&nilfs->ns_next_gen_lock);
	spin_lock_init(&nilfs->ns_last_segment_lock);
	nilfs->ns_cptree = RB_ROOT;
	spin_lock_init(&nilfs->ns_cptree_lock);
	init_rwsem(&nilfs->ns_segctor_sem);
	nilfs->ns_sb_update_freq = NILFS_SB_FREQ;

	return nilfs;
}

/**
 * destroy_nilfs - destroy nilfs object
 * @nilfs: nilfs object to be released
 */
void destroy_nilfs(struct the_nilfs *nilfs)
{
	might_sleep();
	if (nilfs_init(nilfs)) {
		brelse(nilfs->ns_sbh[0]);
		brelse(nilfs->ns_sbh[1]);
	}
	kfree(nilfs);
}

static int nilfs_load_super_root(struct the_nilfs *nilfs,
				 struct super_block *sb, sector_t sr_block)
{
	struct buffer_head *bh_sr;
	struct nilfs_super_root *raw_sr;
	struct nilfs_super_block **sbp = nilfs->ns_sbp;
	struct nilfs_inode *rawi;
	unsigned int dat_entry_size, segment_usage_size, checkpoint_size;
	unsigned int inode_size;
	int err;

	err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);
	if (unlikely(err))
		return err;

	down_read(&nilfs->ns_sem);
	dat_entry_size = le16_to_cpu(sbp[0]->s_dat_entry_size);
	checkpoint_size = le16_to_cpu(sbp[0]->s_checkpoint_size);
	segment_usage_size = le16_to_cpu(sbp[0]->s_segment_usage_size);
	up_read(&nilfs->ns_sem);

	inode_size = nilfs->ns_inode_size;

	rawi = (void *)bh_sr->b_data + NILFS_SR_DAT_OFFSET(inode_size);
	err = nilfs_dat_read(sb, dat_entry_size, rawi, &nilfs->ns_dat);
	if (err)
		goto failed;

	rawi = (void *)bh_sr->b_data + NILFS_SR_CPFILE_OFFSET(inode_size);
	err = nilfs_cpfile_read(sb, checkpoint_size, rawi, &nilfs->ns_cpfile);
	if (err)
		goto failed_dat;

	rawi = (void *)bh_sr->b_data + NILFS_SR_SUFILE_OFFSET(inode_size);
	err = nilfs_sufile_read(sb, segment_usage_size, rawi,
				&nilfs->ns_sufile);
	if (err)
		goto failed_cpfile;

	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
	nilfs->ns_nongc_ctime = le64_to_cpu(raw_sr->sr_nongc_ctime);

 failed:
	brelse(bh_sr);
	return err;

 failed_cpfile:
	iput(nilfs->ns_cpfile);

 failed_dat:
	iput(nilfs->ns_dat);
	goto failed;
}

static void nilfs_init_recovery_info(struct nilfs_recovery_info *ri)
{
	memset(ri, 0, sizeof(*ri));
	INIT_LIST_HEAD(&ri->ri_used_segments);
}

static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
{
	nilfs_dispose_segment_list(&ri->ri_used_segments);
}

/**
 * nilfs_store_log_cursor - load log cursor from a super block
 * @nilfs: nilfs object
 * @sbp: buffer storing super block to be read
 *
 * nilfs_store_log_cursor() reads the last position of the log
 * containing a super root from a given super block, and initializes
 * relevant information on the nilfs object preparatory for log
 * scanning and recovery.
 */
static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
				  struct nilfs_super_block *sbp)
{
	int ret = 0;

	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);

	nilfs->ns_prev_seq = nilfs->ns_last_seq;
	nilfs->ns_seg_seq = nilfs->ns_last_seq;
	nilfs->ns_segnum =
		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
	nilfs->ns_cno = nilfs->ns_last_cno + 1;
	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
		nilfs_err(nilfs->ns_sb,
			  "pointed segment number is out of range: segnum=%llu, nsegments=%lu",
			  (unsigned long long)nilfs->ns_segnum,
			  nilfs->ns_nsegments);
		ret = -EINVAL;
	}
	return ret;
}

/**
 * nilfs_get_blocksize - get block size from raw superblock data
 * @sb: super block instance
 * @sbp: superblock raw data buffer
 * @blocksize: place to store block size
 *
 * nilfs_get_blocksize() calculates the block size from the block size
 * exponent information written in @sbp and stores it in @blocksize,
 * or aborts with an error message if it's too large.
 *
 * Return Value: On success, 0 is returned. If the block size is too
 * large, -EINVAL is returned.
 */
static int nilfs_get_blocksize(struct super_block *sb,
			       struct nilfs_super_block *sbp, int *blocksize)
{
	unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size);

	if (unlikely(shift_bits >
		     ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)) {
		nilfs_err(sb, "too large filesystem blocksize: 2 ^ %u KiB",
			  shift_bits);
		return -EINVAL;
	}
	*blocksize = BLOCK_SIZE << shift_bits;
	return 0;
}

/**
 * load_nilfs - load and recover the nilfs
 * @nilfs: the_nilfs structure to be released
 * @sb: super block instance used to recover past segment
 *
 * load_nilfs() searches and load the latest super root,
 * attaches the last segment, and does recovery if needed.
 * The caller must call this exclusively for simultaneous mounts.
 */
int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
{
	struct nilfs_recovery_info ri;
	unsigned int s_flags = sb->s_flags;
	int really_read_only = bdev_read_only(nilfs->ns_bdev);
	int valid_fs = nilfs_valid_fs(nilfs);
	int err;

	if (!valid_fs) {
		nilfs_warn(sb, "mounting unchecked fs");
		if (s_flags & SB_RDONLY) {
			nilfs_info(sb,
				   "recovery required for readonly filesystem");
			nilfs_info(sb,
				   "write access will be enabled during recovery");
		}
	}

	nilfs_init_recovery_info(&ri);

	err = nilfs_search_super_root(nilfs, &ri);
	if (unlikely(err)) {
		struct nilfs_super_block **sbp = nilfs->ns_sbp;
		int blocksize;

		if (err != -EINVAL)
			goto scan_error;

		if (!nilfs_valid_sb(sbp[1])) {
			nilfs_warn(sb,
				   "unable to fall back to spare super block");
			goto scan_error;
		}
		nilfs_info(sb, "trying rollback from an earlier position");

		/*
		 * restore super block with its spare and reconfigure
		 * relevant states of the nilfs object.
		 */
		memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
		nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);

		/* verify consistency between two super blocks */
		err = nilfs_get_blocksize(sb, sbp[0], &blocksize);
		if (err)
			goto scan_error;

		if (blocksize != nilfs->ns_blocksize) {
			nilfs_warn(sb,
				   "blocksize differs between two super blocks (%d != %d)",
				   blocksize, nilfs->ns_blocksize);
			err = -EINVAL;
			goto scan_error;
		}

		err = nilfs_store_log_cursor(nilfs, sbp[0]);
		if (err)
			goto scan_error;

		/* drop clean flag to allow roll-forward and recovery */
		nilfs->ns_mount_state &= ~NILFS_VALID_FS;
		valid_fs = 0;

		err = nilfs_search_super_root(nilfs, &ri);
		if (err)
			goto scan_error;
	}

	err = nilfs_load_super_root(nilfs, sb, ri.ri_super_root);
	if (unlikely(err)) {
		nilfs_err(sb, "error %d while loading super root", err);
		goto failed;
	}

	err = nilfs_sysfs_create_device_group(sb);
	if (unlikely(err))
		goto sysfs_error;

	if (valid_fs)
		goto skip_recovery;

	if (s_flags & SB_RDONLY) {
		__u64 features;

		if (nilfs_test_opt(nilfs, NORECOVERY)) {
			nilfs_info(sb,
				   "norecovery option specified, skipping roll-forward recovery");
			goto skip_recovery;
		}
		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
			~NILFS_FEATURE_COMPAT_RO_SUPP;
		if (features) {
			nilfs_err(sb,
				  "couldn't proceed with recovery because of unsupported optional features (%llx)",
				  (unsigned long long)features);
			err = -EROFS;
			goto failed_unload;
		}
		if (really_read_only) {
			nilfs_err(sb,
				  "write access unavailable, cannot proceed");
			err = -EROFS;
			goto failed_unload;
		}
		sb->s_flags &= ~SB_RDONLY;
	} else if (nilfs_test_opt(nilfs, NORECOVERY)) {
		nilfs_err(sb,
			  "recovery cancelled because norecovery option was specified for a read/write mount");
		err = -EINVAL;
		goto failed_unload;
	}

	err = nilfs_salvage_orphan_logs(nilfs, sb, &ri);
	if (err)
		goto failed_unload;

	down_write(&nilfs->ns_sem);
	nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */
	err = nilfs_cleanup_super(sb);
	up_write(&nilfs->ns_sem);

	if (err) {
		nilfs_err(sb,
			  "error %d updating super block. recovery unfinished.",
			  err);
		goto failed_unload;
	}
	nilfs_info(sb, "recovery complete");

 skip_recovery:
	nilfs_clear_recovery_info(&ri);
	sb->s_flags = s_flags;
	return 0;

 scan_error:
	nilfs_err(sb, "error %d while searching super root", err);
	goto failed;

 failed_unload:
	nilfs_sysfs_delete_device_group(nilfs);

 sysfs_error:
	iput(nilfs->ns_cpfile);
	iput(nilfs->ns_sufile);
	iput(nilfs->ns_dat);

 failed:
	nilfs_clear_recovery_info(&ri);
	sb->s_flags = s_flags;
	return err;
}

static unsigned long long nilfs_max_size(unsigned int blkbits)
{
	unsigned int max_bits;
	unsigned long long res = MAX_LFS_FILESIZE; /* page cache limit */

	max_bits = blkbits + NILFS_BMAP_KEY_BIT; /* bmap size limit */
	if (max_bits < 64)
		res = min_t(unsigned long long, res, (1ULL << max_bits) - 1);
	return res;
}

/**
 * nilfs_nrsvsegs - calculate the number of reserved segments
 * @nilfs: nilfs object
 * @nsegs: total number of segments
 */
unsigned long nilfs_nrsvsegs(struct the_nilfs *nilfs, unsigned long nsegs)
{
	return max_t(unsigned long, NILFS_MIN_NRSVSEGS,
		     DIV_ROUND_UP(nsegs * nilfs->ns_r_segments_percentage,
				  100));
}

/**
 * nilfs_max_segment_count - calculate the maximum number of segments
 * @nilfs: nilfs object
 */
static u64 nilfs_max_segment_count(struct the_nilfs *nilfs)
{
	u64 max_count = U64_MAX;

	do_div(max_count, nilfs->ns_blocks_per_segment);
	return min_t(u64, max_count, ULONG_MAX);
}

void nilfs_set_nsegments(struct the_nilfs *nilfs, unsigned long nsegs)
{
	nilfs->ns_nsegments = nsegs;
	nilfs->ns_nrsvsegs = nilfs_nrsvsegs(nilfs, nsegs);
}

static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
				   struct nilfs_super_block *sbp)
{
	u64 nsegments, nblocks;

	if (le32_to_cpu(sbp->s_rev_level) < NILFS_MIN_SUPP_REV) {
		nilfs_err(nilfs->ns_sb,
			  "unsupported revision (superblock rev.=%d.%d, current rev.=%d.%d). Please check the version of mkfs.nilfs(2).",
			  le32_to_cpu(sbp->s_rev_level),
			  le16_to_cpu(sbp->s_minor_rev_level),
			  NILFS_CURRENT_REV, NILFS_MINOR_REV);
		return -EINVAL;
	}
	nilfs->ns_sbsize = le16_to_cpu(sbp->s_bytes);
	if (nilfs->ns_sbsize > BLOCK_SIZE)
		return -EINVAL;

	nilfs->ns_inode_size = le16_to_cpu(sbp->s_inode_size);
	if (nilfs->ns_inode_size > nilfs->ns_blocksize) {
		nilfs_err(nilfs->ns_sb, "too large inode size: %d bytes",
			  nilfs->ns_inode_size);
		return -EINVAL;
	} else if (nilfs->ns_inode_size < NILFS_MIN_INODE_SIZE) {
		nilfs_err(nilfs->ns_sb, "too small inode size: %d bytes",
			  nilfs->ns_inode_size);
		return -EINVAL;
	}

	nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);

	nilfs->ns_blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
	if (nilfs->ns_blocks_per_segment < NILFS_SEG_MIN_BLOCKS) {
		nilfs_err(nilfs->ns_sb, "too short segment: %lu blocks",
			  nilfs->ns_blocks_per_segment);
		return -EINVAL;
	}

	nilfs->ns_first_data_block = le64_to_cpu(sbp->s_first_data_block);
	nilfs->ns_r_segments_percentage =
		le32_to_cpu(sbp->s_r_segments_percentage);
	if (nilfs->ns_r_segments_percentage < 1 ||
	    nilfs->ns_r_segments_percentage > 99) {
		nilfs_err(nilfs->ns_sb,
			  "invalid reserved segments percentage: %lu",
			  nilfs->ns_r_segments_percentage);
		return -EINVAL;
	}

	nsegments = le64_to_cpu(sbp->s_nsegments);
	if (nsegments > nilfs_max_segment_count(nilfs)) {
		nilfs_err(nilfs->ns_sb,
			  "segment count %llu exceeds upper limit (%llu segments)",
			  (unsigned long long)nsegments,
			  (unsigned long long)nilfs_max_segment_count(nilfs));
		return -EINVAL;
	}

	nblocks = sb_bdev_nr_blocks(nilfs->ns_sb);
	if (nblocks) {
		u64 min_block_count = nsegments * nilfs->ns_blocks_per_segment;
		/*
		 * To avoid failing to mount early device images without a
		 * second superblock, exclude that block count from the
		 * "min_block_count" calculation.
		 */

		if (nblocks < min_block_count) {
			nilfs_err(nilfs->ns_sb,
				  "total number of segment blocks %llu exceeds device size (%llu blocks)",
				  (unsigned long long)min_block_count,
				  (unsigned long long)nblocks);
			return -EINVAL;
		}
	}

	nilfs_set_nsegments(nilfs, nsegments);
	nilfs->ns_crc_seed = le32_to_cpu(sbp->s_crc_seed);
	return 0;
}

static int nilfs_valid_sb(struct nilfs_super_block *sbp)
{
	static unsigned char sum[4];
	const int sumoff = offsetof(struct nilfs_super_block, s_sum);
	size_t bytes;
	u32 crc;

	if (!sbp || le16_to_cpu(sbp->s_magic) != NILFS_SUPER_MAGIC)
		return 0;
	bytes = le16_to_cpu(sbp->s_bytes);
	if (bytes < sumoff + 4 || bytes > BLOCK_SIZE)
		return 0;
	crc = crc32_le(le32_to_cpu(sbp->s_crc_seed), (unsigned char *)sbp,
		       sumoff);
	crc = crc32_le(crc, sum, 4);
	crc = crc32_le(crc, (unsigned char *)sbp + sumoff + 4,
		       bytes - sumoff - 4);
	return crc == le32_to_cpu(sbp->s_sum);
}

/**
 * nilfs_sb2_bad_offset - check the location of the second superblock
 * @sbp: superblock raw data buffer
 * @offset: byte offset of second superblock calculated from device size
 *
 * nilfs_sb2_bad_offset() checks if the position on the second
 * superblock is valid or not based on the filesystem parameters
 * stored in @sbp.  If @offset points to a location within the segment
 * area, or if the parameters themselves are not normal, it is
 * determined to be invalid.
 *
 * Return Value: true if invalid, false if valid.
 */
static bool nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
{
	unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size);
	u32 blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
	u64 nsegments = le64_to_cpu(sbp->s_nsegments);
	u64 index;

	if (blocks_per_segment < NILFS_SEG_MIN_BLOCKS ||
	    shift_bits > ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)
		return true;

	index = offset >> (shift_bits + BLOCK_SIZE_BITS);
	do_div(index, blocks_per_segment);
	return index < nsegments;
}

static void nilfs_release_super_block(struct the_nilfs *nilfs)
{
	int i;

	for (i = 0; i < 2; i++) {
		if (nilfs->ns_sbp[i]) {
			brelse(nilfs->ns_sbh[i]);
			nilfs->ns_sbh[i] = NULL;
			nilfs->ns_sbp[i] = NULL;
		}
	}
}

void nilfs_fall_back_super_block(struct the_nilfs *nilfs)
{
	brelse(nilfs->ns_sbh[0]);
	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
	nilfs->ns_sbh[1] = NULL;
	nilfs->ns_sbp[1] = NULL;
}

void nilfs_swap_super_block(struct the_nilfs *nilfs)
{
	struct buffer_head *tsbh = nilfs->ns_sbh[0];
	struct nilfs_super_block *tsbp = nilfs->ns_sbp[0];

	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
	nilfs->ns_sbh[1] = tsbh;
	nilfs->ns_sbp[1] = tsbp;
}

static int nilfs_load_super_block(struct the_nilfs *nilfs,
				  struct super_block *sb, int blocksize,
				  struct nilfs_super_block **sbpp)
{
	struct nilfs_super_block **sbp = nilfs->ns_sbp;
	struct buffer_head **sbh = nilfs->ns_sbh;
	u64 sb2off, devsize = bdev_nr_bytes(nilfs->ns_bdev);
	int valid[2], swp = 0;

	if (devsize < NILFS_SEG_MIN_BLOCKS * NILFS_MIN_BLOCK_SIZE + 4096) {
		nilfs_err(sb, "device size too small");
		return -EINVAL;
	}
	sb2off = NILFS_SB2_OFFSET_BYTES(devsize);

	sbp[0] = nilfs_read_super_block(sb, NILFS_SB_OFFSET_BYTES, blocksize,
					&sbh[0]);
	sbp[1] = nilfs_read_super_block(sb, sb2off, blocksize, &sbh[1]);

	if (!sbp[0]) {
		if (!sbp[1]) {
			nilfs_err(sb, "unable to read superblock");
			return -EIO;
		}
		nilfs_warn(sb,
			   "unable to read primary superblock (blocksize = %d)",
			   blocksize);
	} else if (!sbp[1]) {
		nilfs_warn(sb,
			   "unable to read secondary superblock (blocksize = %d)",
			   blocksize);
	}

	/*
	 * Compare two super blocks and set 1 in swp if the secondary
	 * super block is valid and newer.  Otherwise, set 0 in swp.
	 */
	valid[0] = nilfs_valid_sb(sbp[0]);
	valid[1] = nilfs_valid_sb(sbp[1]);
	swp = valid[1] && (!valid[0] ||
			   le64_to_cpu(sbp[1]->s_last_cno) >
			   le64_to_cpu(sbp[0]->s_last_cno));

	if (valid[swp] && nilfs_sb2_bad_offset(sbp[swp], sb2off)) {
		brelse(sbh[1]);
		sbh[1] = NULL;
		sbp[1] = NULL;
		valid[1] = 0;
		swp = 0;
	}
	if (!valid[swp]) {
		nilfs_release_super_block(nilfs);
		nilfs_err(sb, "couldn't find nilfs on the device");
		return -EINVAL;
	}

	if (!valid[!swp])
		nilfs_warn(sb,
			   "broken superblock, retrying with spare superblock (blocksize = %d)",
			   blocksize);
	if (swp)
		nilfs_swap_super_block(nilfs);

	nilfs->ns_sbwcount = 0;
	nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
	*sbpp = sbp[0];
	return 0;
}

/**
 * init_nilfs - initialize a NILFS instance.
 * @nilfs: the_nilfs structure
 * @sb: super block
 * @data: mount options
 *
 * init_nilfs() performs common initialization per block device (e.g.
 * reading the super block, getting disk layout information, initializing
 * shared fields in the_nilfs).
 *
 * Return Value: On success, 0 is returned. On error, a negative error
 * code is returned.
 */
int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data)
{
	struct nilfs_super_block *sbp;
	int blocksize;
	int err;

	down_write(&nilfs->ns_sem);

	blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
	if (!blocksize) {
		nilfs_err(sb, "unable to set blocksize");
		err = -EINVAL;
		goto out;
	}
	err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
	if (err)
		goto out;

	err = nilfs_store_magic_and_option(sb, sbp, data);
	if (err)
		goto failed_sbh;

	err = nilfs_check_feature_compatibility(sb, sbp);
	if (err)
		goto failed_sbh;

	err = nilfs_get_blocksize(sb, sbp, &blocksize);
	if (err)
		goto failed_sbh;

	if (blocksize < NILFS_MIN_BLOCK_SIZE) {
		nilfs_err(sb,
			  "couldn't mount because of unsupported filesystem blocksize %d",
			  blocksize);
		err = -EINVAL;
		goto failed_sbh;
	}
	if (sb->s_blocksize != blocksize) {
		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);

		if (blocksize < hw_blocksize) {
			nilfs_err(sb,
				  "blocksize %d too small for device (sector-size = %d)",
				  blocksize, hw_blocksize);
			err = -EINVAL;
			goto failed_sbh;
		}
		nilfs_release_super_block(nilfs);
		if (!sb_set_blocksize(sb, blocksize)) {
			nilfs_err(sb, "bad blocksize %d", blocksize);
			err = -EINVAL;
			goto out;
		}

		err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
		if (err)
			goto out;
			/*
			 * Not to failed_sbh; sbh is released automatically
			 * when reloading fails.
			 */
	}
	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
	nilfs->ns_blocksize = blocksize;

	get_random_bytes(&nilfs->ns_next_generation,
			 sizeof(nilfs->ns_next_generation));

	err = nilfs_store_disk_layout(nilfs, sbp);
	if (err)
		goto failed_sbh;

	sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);

	nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);

	err = nilfs_store_log_cursor(nilfs, sbp);
	if (err)
		goto failed_sbh;

	set_nilfs_init(nilfs);
	err = 0;
 out:
	up_write(&nilfs->ns_sem);
	return err;

 failed_sbh:
	nilfs_release_super_block(nilfs);
	goto out;
}

int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
			    size_t nsegs)
{
	sector_t seg_start, seg_end;
	sector_t start = 0, nblocks = 0;
	unsigned int sects_per_block;
	__u64 *sn;
	int ret = 0;

	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
		bdev_logical_block_size(nilfs->ns_bdev);
	for (sn = segnump; sn < segnump + nsegs; sn++) {
		nilfs_get_segment_range(nilfs, *sn, &seg_start, &seg_end);

		if (!nblocks) {
			start = seg_start;
			nblocks = seg_end - seg_start + 1;
		} else if (start + nblocks == seg_start) {
			nblocks += seg_end - seg_start + 1;
		} else {
			ret = blkdev_issue_discard(nilfs->ns_bdev,
						   start * sects_per_block,
						   nblocks * sects_per_block,
						   GFP_NOFS);
			if (ret < 0)
				return ret;
			nblocks = 0;
		}
	}
	if (nblocks)
		ret = blkdev_issue_discard(nilfs->ns_bdev,
					   start * sects_per_block,
					   nblocks * sects_per_block,
					   GFP_NOFS);
	return ret;
}

int nilfs_count_free_blocks(struct the_nilfs *nilfs, sector_t *nblocks)
{
	unsigned long ncleansegs;

	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
	*nblocks = (sector_t)ncleansegs * nilfs->ns_blocks_per_segment;
	return 0;
}

int nilfs_near_disk_full(struct the_nilfs *nilfs)
{
	unsigned long ncleansegs, nincsegs;

	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
	nincsegs = atomic_read(&nilfs->ns_ndirtyblks) /
		nilfs->ns_blocks_per_segment + 1;

	return ncleansegs <= nilfs->ns_nrsvsegs + nincsegs;
}

struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno)
{
	struct rb_node *n;
	struct nilfs_root *root;

	spin_lock(&nilfs->ns_cptree_lock);
	n = nilfs->ns_cptree.rb_node;
	while (n) {
		root = rb_entry(n, struct nilfs_root, rb_node);

		if (cno < root->cno) {
			n = n->rb_left;
		} else if (cno > root->cno) {
			n = n->rb_right;
		} else {
			refcount_inc(&root->count);
			spin_unlock(&nilfs->ns_cptree_lock);
			return root;
		}
	}
	spin_unlock(&nilfs->ns_cptree_lock);

	return NULL;
}

struct nilfs_root *
nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
{
	struct rb_node **p, *parent;
	struct nilfs_root *root, *new;
	int err;

	root = nilfs_lookup_root(nilfs, cno);
	if (root)
		return root;

	new = kzalloc(sizeof(*root), GFP_KERNEL);
	if (!new)
		return NULL;

	spin_lock(&nilfs->ns_cptree_lock);

	p = &nilfs->ns_cptree.rb_node;
	parent = NULL;

	while (*p) {
		parent = *p;
		root = rb_entry(parent, struct nilfs_root, rb_node);

		if (cno < root->cno) {
			p = &(*p)->rb_left;
		} else if (cno > root->cno) {
			p = &(*p)->rb_right;
		} else {
			refcount_inc(&root->count);
			spin_unlock(&nilfs->ns_cptree_lock);
			kfree(new);
			return root;
		}
	}

	new->cno = cno;
	new->ifile = NULL;
	new->nilfs = nilfs;
	refcount_set(&new->count, 1);
	atomic64_set(&new->inodes_count, 0);
	atomic64_set(&new->blocks_count, 0);

	rb_link_node(&new->rb_node, parent, p);
	rb_insert_color(&new->rb_node, &nilfs->ns_cptree);

	spin_unlock(&nilfs->ns_cptree_lock);

	err = nilfs_sysfs_create_snapshot_group(new);
	if (err) {
		kfree(new);
		new = NULL;
	}

	return new;
}

void nilfs_put_root(struct nilfs_root *root)
{
	struct the_nilfs *nilfs = root->nilfs;

	if (refcount_dec_and_lock(&root->count, &nilfs->ns_cptree_lock)) {
		rb_erase(&root->rb_node, &nilfs->ns_cptree);
		spin_unlock(&nilfs->ns_cptree_lock);

		nilfs_sysfs_delete_snapshot_group(root);
		iput(root->ifile);

		kfree(root);
	}
}