summaryrefslogtreecommitdiffstats
path: root/fs/nilfs2/the_nilfs.c
blob: 33871f7e4f013b2113547a4de2639685be007aae (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
/*
 * the_nilfs.c - the_nilfs shared structure.
 *
 * 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/slab.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.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 LIST_HEAD(nilfs_objects);
static DEFINE_SPINLOCK(nilfs_lock);

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;
	spin_unlock(&nilfs->ns_last_segment_lock);
}

/**
 * alloc_nilfs - allocate the_nilfs structure
 * @bdev: block device to which the_nilfs is related
 *
 * alloc_nilfs() allocates memory for the_nilfs and
 * initializes its reference count and locks.
 *
 * Return Value: On success, pointer to the_nilfs is returned.
 * On error, NULL is returned.
 */
static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
{
	struct the_nilfs *nilfs;

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

	nilfs->ns_bdev = bdev;
	atomic_set(&nilfs->ns_count, 1);
	atomic_set(&nilfs->ns_ndirtyblks, 0);
	init_rwsem(&nilfs->ns_sem);
	init_rwsem(&nilfs->ns_super_sem);
	mutex_init(&nilfs->ns_mount_mutex);
	init_rwsem(&nilfs->ns_writer_sem);
	INIT_LIST_HEAD(&nilfs->ns_list);
	INIT_LIST_HEAD(&nilfs->ns_supers);
	spin_lock_init(&nilfs->ns_last_segment_lock);
	nilfs->ns_gc_inodes_h = NULL;
	init_rwsem(&nilfs->ns_segctor_sem);

	return nilfs;
}

/**
 * find_or_create_nilfs - find or create nilfs object
 * @bdev: block device to which the_nilfs is related
 *
 * find_nilfs() looks up an existent nilfs object created on the
 * device and gets the reference count of the object.  If no nilfs object
 * is found on the device, a new nilfs object is allocated.
 *
 * Return Value: On success, pointer to the nilfs object is returned.
 * On error, NULL is returned.
 */
struct the_nilfs *find_or_create_nilfs(struct block_device *bdev)
{
	struct the_nilfs *nilfs, *new = NULL;

 retry:
	spin_lock(&nilfs_lock);
	list_for_each_entry(nilfs, &nilfs_objects, ns_list) {
		if (nilfs->ns_bdev == bdev) {
			get_nilfs(nilfs);
			spin_unlock(&nilfs_lock);
			if (new)
				put_nilfs(new);
			return nilfs; /* existing object */
		}
	}
	if (new) {
		list_add_tail(&new->ns_list, &nilfs_objects);
		spin_unlock(&nilfs_lock);
		return new; /* new object */
	}
	spin_unlock(&nilfs_lock);

	new = alloc_nilfs(bdev);
	if (new)
		goto retry;
	return NULL; /* insufficient memory */
}

/**
 * put_nilfs - release a reference to the_nilfs
 * @nilfs: the_nilfs structure to be released
 *
 * put_nilfs() decrements a reference counter of the_nilfs.
 * If the reference count reaches zero, the_nilfs is freed.
 */
void put_nilfs(struct the_nilfs *nilfs)
{
	spin_lock(&nilfs_lock);
	if (!atomic_dec_and_test(&nilfs->ns_count)) {
		spin_unlock(&nilfs_lock);
		return;
	}
	list_del_init(&nilfs->ns_list);
	spin_unlock(&nilfs_lock);

	/*
	 * Increment of ns_count never occurs below because the caller
	 * of get_nilfs() holds at least one reference to the_nilfs.
	 * Thus its exclusion control is not required here.
	 */

	might_sleep();
	if (nilfs_loaded(nilfs)) {
		nilfs_mdt_destroy(nilfs->ns_sufile);
		nilfs_mdt_destroy(nilfs->ns_cpfile);
		nilfs_mdt_destroy(nilfs->ns_dat);
		nilfs_mdt_destroy(nilfs->ns_gc_dat);
	}
	if (nilfs_init(nilfs)) {
		nilfs_destroy_gccache(nilfs);
		brelse(nilfs->ns_sbh[0]);
		brelse(nilfs->ns_sbh[1]);
	}
	kfree(nilfs);
}

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

	err = nilfs_read_super_root_block(sbi->s_super, 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;

	err = -ENOMEM;
	nilfs->ns_dat = nilfs_dat_new(nilfs, dat_entry_size);
	if (unlikely(!nilfs->ns_dat))
		goto failed;

	nilfs->ns_gc_dat = nilfs_dat_new(nilfs, dat_entry_size);
	if (unlikely(!nilfs->ns_gc_dat))
		goto failed_dat;

	nilfs->ns_cpfile = nilfs_cpfile_new(nilfs, checkpoint_size);
	if (unlikely(!nilfs->ns_cpfile))
		goto failed_gc_dat;

	nilfs->ns_sufile = nilfs_sufile_new(nilfs, segment_usage_size);
	if (unlikely(!nilfs->ns_sufile))
		goto failed_cpfile;

	nilfs_mdt_set_shadow(nilfs->ns_dat, nilfs->ns_gc_dat);

	err = nilfs_dat_read(nilfs->ns_dat, (void *)bh_sr->b_data +
			     NILFS_SR_DAT_OFFSET(inode_size));
	if (unlikely(err))
		goto failed_sufile;

	err = nilfs_cpfile_read(nilfs->ns_cpfile, (void *)bh_sr->b_data +
				NILFS_SR_CPFILE_OFFSET(inode_size));
	if (unlikely(err))
		goto failed_sufile;

	err = nilfs_sufile_read(nilfs->ns_sufile, (void *)bh_sr->b_data +
				NILFS_SR_SUFILE_OFFSET(inode_size));
	if (unlikely(err))
		goto failed_sufile;

	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_sufile:
	nilfs_mdt_destroy(nilfs->ns_sufile);

 failed_cpfile:
	nilfs_mdt_destroy(nilfs->ns_cpfile);

 failed_gc_dat:
	nilfs_mdt_destroy(nilfs->ns_gc_dat);

 failed_dat:
	nilfs_mdt_destroy(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);
}

/**
 * load_nilfs - load and recover the nilfs
 * @nilfs: the_nilfs structure to be released
 * @sbi: nilfs_sb_info 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 nilfs_sb_info *sbi)
{
	struct nilfs_recovery_info ri;
	unsigned int s_flags = sbi->s_super->s_flags;
	int really_read_only = bdev_read_only(nilfs->ns_bdev);
	int valid_fs = nilfs_valid_fs(nilfs);
	int err;

	if (nilfs_loaded(nilfs)) {
		if (valid_fs ||
		    ((s_flags & MS_RDONLY) && nilfs_test_opt(sbi, NORECOVERY)))
			return 0;
		printk(KERN_ERR "NILFS: the filesystem is in an incomplete "
		       "recovery state.\n");
		return -EINVAL;
	}

	if (!valid_fs) {
		printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
		if (s_flags & MS_RDONLY) {
			printk(KERN_INFO "NILFS: INFO: recovery "
			       "required for readonly filesystem.\n");
			printk(KERN_INFO "NILFS: write access will "
			       "be enabled during recovery.\n");
		}
	}

	nilfs_init_recovery_info(&ri);

	err = nilfs_search_super_root(nilfs, sbi, &ri);
	if (unlikely(err)) {
		printk(KERN_ERR "NILFS: error searching super root.\n");
		goto failed;
	}

	err = nilfs_load_super_root(nilfs, sbi, ri.ri_super_root);
	if (unlikely(err)) {
		printk(KERN_ERR "NILFS: error loading super root.\n");
		goto failed;
	}

	if (valid_fs)
		goto skip_recovery;

	if (s_flags & MS_RDONLY) {
		if (nilfs_test_opt(sbi, NORECOVERY)) {
			printk(KERN_INFO "NILFS: norecovery option specified. "
			       "skipping roll-forward recovery\n");
			goto skip_recovery;
		}
		if (really_read_only) {
			printk(KERN_ERR "NILFS: write access "
			       "unavailable, cannot proceed.\n");
			err = -EROFS;
			goto failed_unload;
		}
		sbi->s_super->s_flags &= ~MS_RDONLY;
	} else if (nilfs_test_opt(sbi, NORECOVERY)) {
		printk(KERN_ERR "NILFS: recovery cancelled because norecovery "
		       "option was specified for a read/write mount\n");
		err = -EINVAL;
		goto failed_unload;
	}

	err = nilfs_recover_logical_segments(nilfs, sbi, &ri);
	if (err)
		goto failed_unload;

	down_write(&nilfs->ns_sem);
	nilfs->ns_mount_state |= NILFS_VALID_FS;
	nilfs->ns_sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
	err = nilfs_commit_super(sbi, 1);
	up_write(&nilfs->ns_sem);

	if (err) {
		printk(KERN_ERR "NILFS: failed to update super block. "
		       "recovery unfinished.\n");
		goto failed_unload;
	}
	printk(KERN_INFO "NILFS: recovery complete.\n");

 skip_recovery:
	set_nilfs_loaded(nilfs);
	nilfs_clear_recovery_info(&ri);
	sbi->s_super->s_flags = s_flags;
	return 0;

 failed_unload:
	nilfs_mdt_destroy(nilfs->ns_cpfile);
	nilfs_mdt_destroy(nilfs->ns_sufile);
	nilfs_mdt_destroy(nilfs->ns_dat);

 failed:
	nilfs_clear_recovery_info(&ri);
	sbi->s_super->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;
}

static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
				   struct nilfs_super_block *sbp)
{
	if (le32_to_cpu(sbp->s_rev_level) != NILFS_CURRENT_REV) {
		printk(KERN_ERR "NILFS: revision mismatch "
		       "(superblock rev.=%d.%d, current rev.=%d.%d). "
		       "Please check the version of mkfs.nilfs.\n",
		       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);
	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) {
		printk(KERN_ERR "NILFS: too short segment.\n");
		return -EINVAL;
	}

	nilfs->ns_first_data_block = le64_to_cpu(sbp->s_first_data_block);
	nilfs->ns_nsegments = le64_to_cpu(sbp->s_nsegments);
	nilfs->ns_r_segments_percentage =
		le32_to_cpu(sbp->s_r_segments_percentage);
	nilfs->ns_nrsvsegs =
		max_t(unsigned long, NILFS_MIN_NRSVSEGS,
		      DIV_ROUND_UP(nilfs->ns_nsegments *
				   nilfs->ns_r_segments_percentage, 100));
	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 > 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);
}

static int nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
{
	return offset < ((le64_to_cpu(sbp->s_nsegments) *
			  le32_to_cpu(sbp->s_blocks_per_segment)) <<
			 (le32_to_cpu(sbp->s_log_block_size) + 10));
}

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 = NILFS_SB2_OFFSET_BYTES(nilfs->ns_bdev->bd_inode->i_size);
	int valid[2], swp = 0;

	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]) {
			printk(KERN_ERR "NILFS: unable to read superblock\n");
			return -EIO;
		}
		printk(KERN_WARNING
		       "NILFS warning: unable to read primary superblock\n");
	} else if (!sbp[1])
		printk(KERN_WARNING
		       "NILFS warning: unable to read secondary superblock\n");

	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_wtime) > le64_to_cpu(sbp[0]->s_wtime));

	if (valid[swp] && nilfs_sb2_bad_offset(sbp[swp], sb2off)) {
		brelse(sbh[1]);
		sbh[1] = NULL;
		sbp[1] = NULL;
		swp = 0;
	}
	if (!valid[swp]) {
		nilfs_release_super_block(nilfs);
		printk(KERN_ERR "NILFS: Can't find nilfs on dev %s.\n",
		       sb->s_id);
		return -EINVAL;
	}

	if (swp) {
		printk(KERN_WARNING "NILFS warning: broken superblock. "
		       "using spare superblock.\n");
		nilfs_swap_super_block(nilfs);
	}

	nilfs->ns_sbwtime[0] = le64_to_cpu(sbp[0]->s_wtime);
	nilfs->ns_sbwtime[1] = valid[!swp] ? le64_to_cpu(sbp[1]->s_wtime) : 0;
	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
 * @sbi: nilfs_sb_info
 * @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). It takes on some portion of the jobs
 * typically done by a fill_super() routine. This division arises from
 * the nature that multiple NILFS instances may be simultaneously
 * mounted on a device.
 * For multiple mounts on the same device, only the first mount
 * invokes these tasks.
 *
 * Return Value: On success, 0 is returned. On error, a negative error
 * code is returned.
 */
int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
{
	struct super_block *sb = sbi->s_super;
	struct nilfs_super_block *sbp;
	struct backing_dev_info *bdi;
	int blocksize;
	int err;

	down_write(&nilfs->ns_sem);
	if (nilfs_init(nilfs)) {
		/* Load values from existing the_nilfs */
		sbp = nilfs->ns_sbp[0];
		err = nilfs_store_magic_and_option(sb, sbp, data);
		if (err)
			goto out;

		blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
		if (sb->s_blocksize != blocksize &&
		    !sb_set_blocksize(sb, blocksize)) {
			printk(KERN_ERR "NILFS: blocksize %d unfit to device\n",
			       blocksize);
			err = -EINVAL;
		}
		sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
		goto out;
	}

	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
	if (!blocksize) {
		printk(KERN_ERR "NILFS: unable to set blocksize\n");
		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;

	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
	if (sb->s_blocksize != blocksize) {
		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);

		if (blocksize < hw_blocksize) {
			printk(KERN_ERR
			       "NILFS: blocksize %d too small for device "
			       "(sector-size = %d).\n",
			       blocksize, hw_blocksize);
			err = -EINVAL;
			goto failed_sbh;
		}
		nilfs_release_super_block(nilfs);
		sb_set_blocksize(sb, blocksize);

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

	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);

	bdi = nilfs->ns_bdev->bd_inode->i_mapping->backing_dev_info;
	nilfs->ns_bdi = bdi ? : &default_backing_dev_info;

	/* Finding last segment */
	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_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) {
		printk(KERN_ERR "NILFS invalid last segment number.\n");
		err = -EINVAL;
		goto failed_sbh;
	}
	/* Dummy values  */
	nilfs->ns_free_segments_count =
		nilfs->ns_nsegments - (nilfs->ns_segnum + 1);

	/* Initialize gcinode cache */
	err = nilfs_init_gccache(nilfs);
	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,
						   DISCARD_FL_BARRIER);
			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, DISCARD_FL_BARRIER);
	return ret;
}

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

	down_read(&NILFS_MDT(dat)->mi_sem);	/* XXX */
	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
	up_read(&NILFS_MDT(dat)->mi_sem);	/* XXX */
	*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;
}

/**
 * nilfs_find_sbinfo - find existing nilfs_sb_info structure
 * @nilfs: nilfs object
 * @rw_mount: mount type (non-zero value for read/write mount)
 * @cno: checkpoint number (zero for read-only mount)
 *
 * nilfs_find_sbinfo() returns the nilfs_sb_info structure which
 * @rw_mount and @cno (in case of snapshots) matched.  If no instance
 * was found, NULL is returned.  Although the super block instance can
 * be unmounted after this function returns, the nilfs_sb_info struct
 * is kept on memory until nilfs_put_sbinfo() is called.
 */
struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *nilfs,
					int rw_mount, __u64 cno)
{
	struct nilfs_sb_info *sbi;

	down_read(&nilfs->ns_super_sem);
	/*
	 * The SNAPSHOT flag and sb->s_flags are supposed to be
	 * protected with nilfs->ns_super_sem.
	 */
	sbi = nilfs->ns_current;
	if (rw_mount) {
		if (sbi && !(sbi->s_super->s_flags & MS_RDONLY))
			goto found; /* read/write mount */
		else
			goto out;
	} else if (cno == 0) {
		if (sbi && (sbi->s_super->s_flags & MS_RDONLY))
			goto found; /* read-only mount */
		else
			goto out;
	}

	list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
		if (nilfs_test_opt(sbi, SNAPSHOT) &&
		    sbi->s_snapshot_cno == cno)
			goto found; /* snapshot mount */
	}
 out:
	up_read(&nilfs->ns_super_sem);
	return NULL;

 found:
	atomic_inc(&sbi->s_count);
	up_read(&nilfs->ns_super_sem);
	return sbi;
}

int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno,
				int snapshot_mount)
{
	struct nilfs_sb_info *sbi;
	int ret = 0;

	down_read(&nilfs->ns_super_sem);
	if (cno == 0 || cno > nilfs->ns_cno)
		goto out_unlock;

	list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
		if (sbi->s_snapshot_cno == cno &&
		    (!snapshot_mount || nilfs_test_opt(sbi, SNAPSHOT))) {
					/* exclude read-only mounts */
			ret++;
			break;
		}
	}
	/* for protecting recent checkpoints */
	if (cno >= nilfs_last_cno(nilfs))
		ret++;

 out_unlock:
	up_read(&nilfs->ns_super_sem);
	return ret;
}