summaryrefslogtreecommitdiff
path: root/fs/nilfs2/sufile.c
blob: 8b2f93ca1e165a66837db5d9e58b79624ad5f83b (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
/*
 * sufile.c - NILFS segment usage file.
 *
 * Copyright (C) 2006-2008 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 Koji Sato <koji@osrg.net>.
 */

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/errno.h>
#include <linux/nilfs2_fs.h>
#include "mdt.h"
#include "sufile.h"


static inline unsigned long
nilfs_sufile_segment_usages_per_block(const struct inode *sufile)
{
	return NILFS_MDT(sufile)->mi_entries_per_block;
}

static unsigned long
nilfs_sufile_get_blkoff(const struct inode *sufile, __u64 segnum)
{
	__u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
	do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
	return (unsigned long)t;
}

static unsigned long
nilfs_sufile_get_offset(const struct inode *sufile, __u64 segnum)
{
	__u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
	return do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
}

static unsigned long
nilfs_sufile_segment_usages_in_block(const struct inode *sufile, __u64 curr,
				     __u64 max)
{
	return min_t(unsigned long,
		     nilfs_sufile_segment_usages_per_block(sufile) -
		     nilfs_sufile_get_offset(sufile, curr),
		     max - curr + 1);
}

static inline struct nilfs_sufile_header *
nilfs_sufile_block_get_header(const struct inode *sufile,
			      struct buffer_head *bh,
			      void *kaddr)
{
	return kaddr + bh_offset(bh);
}

static struct nilfs_segment_usage *
nilfs_sufile_block_get_segment_usage(const struct inode *sufile, __u64 segnum,
				     struct buffer_head *bh, void *kaddr)
{
	return kaddr + bh_offset(bh) +
		nilfs_sufile_get_offset(sufile, segnum) *
		NILFS_MDT(sufile)->mi_entry_size;
}

static inline int nilfs_sufile_get_header_block(struct inode *sufile,
						struct buffer_head **bhp)
{
	return nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);
}

static inline int
nilfs_sufile_get_segment_usage_block(struct inode *sufile, __u64 segnum,
				     int create, struct buffer_head **bhp)
{
	return nilfs_mdt_get_block(sufile,
				   nilfs_sufile_get_blkoff(sufile, segnum),
				   create, NULL, bhp);
}

/**
 * nilfs_sufile_alloc - allocate a segment
 * @sufile: inode of segment usage file
 * @segnump: pointer to segment number
 *
 * Description: nilfs_sufile_alloc() allocates a clean segment.
 *
 * Return Value: On success, 0 is returned and the segment number of the
 * allocated segment is stored in the place pointed by @segnump. On error, one
 * of the following negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 *
 * %-ENOSPC - No clean segment left.
 */
int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
{
	struct buffer_head *header_bh, *su_bh;
	struct the_nilfs *nilfs;
	struct nilfs_sufile_header *header;
	struct nilfs_segment_usage *su;
	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
	__u64 segnum, maxsegnum, last_alloc;
	void *kaddr;
	unsigned long nsegments, ncleansegs, nsus;
	int ret, i, j;

	down_write(&NILFS_MDT(sufile)->mi_sem);

	nilfs = NILFS_MDT(sufile)->mi_nilfs;

	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
	if (ret < 0)
		goto out_sem;
	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
	ncleansegs = le64_to_cpu(header->sh_ncleansegs);
	last_alloc = le64_to_cpu(header->sh_last_alloc);
	kunmap_atomic(kaddr, KM_USER0);

	nsegments = nilfs_sufile_get_nsegments(sufile);
	segnum = last_alloc + 1;
	maxsegnum = nsegments - 1;
	for (i = 0; i < nsegments; i += nsus) {
		if (segnum >= nsegments) {
			/* wrap around */
			segnum = 0;
			maxsegnum = last_alloc;
		}
		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1,
							   &su_bh);
		if (ret < 0)
			goto out_header;
		kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
		su = nilfs_sufile_block_get_segment_usage(
			sufile, segnum, su_bh, kaddr);

		nsus = nilfs_sufile_segment_usages_in_block(
			sufile, segnum, maxsegnum);
		for (j = 0; j < nsus; j++, su = (void *)su + susz, segnum++) {
			if (!nilfs_segment_usage_clean(su))
				continue;
			/* found a clean segment */
			nilfs_segment_usage_set_dirty(su);
			kunmap_atomic(kaddr, KM_USER0);

			kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
			header = nilfs_sufile_block_get_header(
				sufile, header_bh, kaddr);
			le64_add_cpu(&header->sh_ncleansegs, -1);
			le64_add_cpu(&header->sh_ndirtysegs, 1);
			header->sh_last_alloc = cpu_to_le64(segnum);
			kunmap_atomic(kaddr, KM_USER0);

			nilfs_mdt_mark_buffer_dirty(header_bh);
			nilfs_mdt_mark_buffer_dirty(su_bh);
			nilfs_mdt_mark_dirty(sufile);
			brelse(su_bh);
			*segnump = segnum;
			goto out_header;
		}

		kunmap_atomic(kaddr, KM_USER0);
		brelse(su_bh);
	}

	/* no segments left */
	ret = -ENOSPC;

 out_header:
	brelse(header_bh);

 out_sem:
	up_write(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}

/**
 * nilfs_sufile_cancel_free -
 * @sufile: inode of segment usage file
 * @segnum: segment number
 *
 * Description:
 *
 * Return Value: On success, 0 is returned. On error, one of the following
 * negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 */
int nilfs_sufile_cancel_free(struct inode *sufile, __u64 segnum)
{
	struct buffer_head *header_bh, *su_bh;
	struct the_nilfs *nilfs;
	struct nilfs_sufile_header *header;
	struct nilfs_segment_usage *su;
	void *kaddr;
	int ret;

	down_write(&NILFS_MDT(sufile)->mi_sem);

	nilfs = NILFS_MDT(sufile)->mi_nilfs;

	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
	if (ret < 0)
		goto out_sem;

	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &su_bh);
	if (ret < 0)
		goto out_header;

	kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
	su = nilfs_sufile_block_get_segment_usage(
		sufile, segnum, su_bh, kaddr);
	if (unlikely(!nilfs_segment_usage_clean(su))) {
		printk(KERN_WARNING "%s: segment %llu must be clean\n",
		       __func__, (unsigned long long)segnum);
		kunmap_atomic(kaddr, KM_USER0);
		goto out_su_bh;
	}
	nilfs_segment_usage_set_dirty(su);
	kunmap_atomic(kaddr, KM_USER0);

	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
	le64_add_cpu(&header->sh_ncleansegs, -1);
	le64_add_cpu(&header->sh_ndirtysegs, 1);
	kunmap_atomic(kaddr, KM_USER0);

	nilfs_mdt_mark_buffer_dirty(header_bh);
	nilfs_mdt_mark_buffer_dirty(su_bh);
	nilfs_mdt_mark_dirty(sufile);

 out_su_bh:
	brelse(su_bh);
 out_header:
	brelse(header_bh);
 out_sem:
	up_write(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}

/**
 * nilfs_sufile_freev - free segments
 * @sufile: inode of segment usage file
 * @segnum: array of segment numbers
 * @nsegs: number of segments
 *
 * Description: nilfs_sufile_freev() frees segments specified by @segnum and
 * @nsegs, which must have been returned by a previous call to
 * nilfs_sufile_alloc().
 *
 * Return Value: On success, 0 is returned. On error, one of the following
 * negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 */
#define NILFS_SUFILE_FREEV_PREALLOC	16
int nilfs_sufile_freev(struct inode *sufile, __u64 *segnum, size_t nsegs)
{
	struct buffer_head *header_bh, **su_bh,
		*su_bh_prealloc[NILFS_SUFILE_FREEV_PREALLOC];
	struct the_nilfs *nilfs;
	struct nilfs_sufile_header *header;
	struct nilfs_segment_usage *su;
	void *kaddr;
	int ret, i;

	down_write(&NILFS_MDT(sufile)->mi_sem);

	nilfs = NILFS_MDT(sufile)->mi_nilfs;

	/* prepare resources */
	if (nsegs <= NILFS_SUFILE_FREEV_PREALLOC)
		su_bh = su_bh_prealloc;
	else {
		su_bh = kmalloc(sizeof(*su_bh) * nsegs, GFP_NOFS);
		if (su_bh == NULL) {
			ret = -ENOMEM;
			goto out_sem;
		}
	}

	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
	if (ret < 0)
		goto out_su_bh;
	for (i = 0; i < nsegs; i++) {
		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum[i],
							   0, &su_bh[i]);
		if (ret < 0)
			goto out_bh;
	}

	/* free segments */
	for (i = 0; i < nsegs; i++) {
		kaddr = kmap_atomic(su_bh[i]->b_page, KM_USER0);
		su = nilfs_sufile_block_get_segment_usage(
			sufile, segnum[i], su_bh[i], kaddr);
		WARN_ON(nilfs_segment_usage_error(su));
		nilfs_segment_usage_set_clean(su);
		kunmap_atomic(kaddr, KM_USER0);
		nilfs_mdt_mark_buffer_dirty(su_bh[i]);
	}
	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
	le64_add_cpu(&header->sh_ncleansegs, nsegs);
	le64_add_cpu(&header->sh_ndirtysegs, -(u64)nsegs);
	kunmap_atomic(kaddr, KM_USER0);
	nilfs_mdt_mark_buffer_dirty(header_bh);
	nilfs_mdt_mark_dirty(sufile);

 out_bh:
	for (i--; i >= 0; i--)
		brelse(su_bh[i]);
	brelse(header_bh);

 out_su_bh:
	if (su_bh != su_bh_prealloc)
		kfree(su_bh);

 out_sem:
	up_write(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}

/**
 * nilfs_sufile_free -
 * @sufile:
 * @segnum:
 */
int nilfs_sufile_free(struct inode *sufile, __u64 segnum)
{
	return nilfs_sufile_freev(sufile, &segnum, 1);
}

/**
 * nilfs_sufile_get_segment_usage - get a segment usage
 * @sufile: inode of segment usage file
 * @segnum: segment number
 * @sup: pointer to segment usage
 * @bhp: pointer to buffer head
 *
 * Description: nilfs_sufile_get_segment_usage() acquires the segment usage
 * specified by @segnum.
 *
 * Return Value: On success, 0 is returned, and the segment usage and the
 * buffer head of the buffer on which the segment usage is located are stored
 * in the place pointed by @sup and @bhp, respectively. On error, one of the
 * following negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 *
 * %-EINVAL - Invalid segment usage number.
 */
int nilfs_sufile_get_segment_usage(struct inode *sufile, __u64 segnum,
				   struct nilfs_segment_usage **sup,
				   struct buffer_head **bhp)
{
	struct buffer_head *bh;
	struct nilfs_segment_usage *su;
	void *kaddr;
	int ret;

	/* segnum is 0 origin */
	if (segnum >= nilfs_sufile_get_nsegments(sufile))
		return -EINVAL;
	down_write(&NILFS_MDT(sufile)->mi_sem);
	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1, &bh);
	if (ret < 0)
		goto out_sem;
	kaddr = kmap(bh->b_page);
	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
	if (nilfs_segment_usage_error(su)) {
		kunmap(bh->b_page);
		brelse(bh);
		ret = -EINVAL;
		goto out_sem;
	}

	if (sup != NULL)
		*sup = su;
	*bhp = bh;

 out_sem:
	up_write(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}

/**
 * nilfs_sufile_put_segment_usage - put a segment usage
 * @sufile: inode of segment usage file
 * @segnum: segment number
 * @bh: buffer head
 *
 * Description: nilfs_sufile_put_segment_usage() releases the segment usage
 * specified by @segnum. @bh must be the buffer head which have been returned
 * by a previous call to nilfs_sufile_get_segment_usage() with @segnum.
 */
void nilfs_sufile_put_segment_usage(struct inode *sufile, __u64 segnum,
				    struct buffer_head *bh)
{
	kunmap(bh->b_page);
	brelse(bh);
}

/**
 * nilfs_sufile_get_stat - get segment usage statistics
 * @sufile: inode of segment usage file
 * @stat: pointer to a structure of segment usage statistics
 *
 * Description: nilfs_sufile_get_stat() returns information about segment
 * usage.
 *
 * Return Value: On success, 0 is returned, and segment usage information is
 * stored in the place pointed by @stat. On error, one of the following
 * negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 */
int nilfs_sufile_get_stat(struct inode *sufile, struct nilfs_sustat *sustat)
{
	struct buffer_head *header_bh;
	struct nilfs_sufile_header *header;
	struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
	void *kaddr;
	int ret;

	down_read(&NILFS_MDT(sufile)->mi_sem);

	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
	if (ret < 0)
		goto out_sem;

	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
	header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
	sustat->ss_nsegs = nilfs_sufile_get_nsegments(sufile);
	sustat->ss_ncleansegs = le64_to_cpu(header->sh_ncleansegs);
	sustat->ss_ndirtysegs = le64_to_cpu(header->sh_ndirtysegs);
	sustat->ss_ctime = nilfs->ns_ctime;
	sustat->ss_nongc_ctime = nilfs->ns_nongc_ctime;
	spin_lock(&nilfs->ns_last_segment_lock);
	sustat->ss_prot_seq = nilfs->ns_prot_seq;
	spin_unlock(&nilfs->ns_last_segment_lock);
	kunmap_atomic(kaddr, KM_USER0);
	brelse(header_bh);

 out_sem:
	up_read(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}

/**
 * nilfs_sufile_get_ncleansegs - get the number of clean segments
 * @sufile: inode of segment usage file
 * @nsegsp: pointer to the number of clean segments
 *
 * Description: nilfs_sufile_get_ncleansegs() acquires the number of clean
 * segments.
 *
 * Return Value: On success, 0 is returned and the number of clean segments is
 * stored in the place pointed by @nsegsp. On error, one of the following
 * negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 */
int nilfs_sufile_get_ncleansegs(struct inode *sufile, unsigned long *nsegsp)
{
	struct nilfs_sustat sustat;
	int ret;

	ret = nilfs_sufile_get_stat(sufile, &sustat);
	if (ret == 0)
		*nsegsp = sustat.ss_ncleansegs;
	return ret;
}

/**
 * nilfs_sufile_set_error - mark a segment as erroneous
 * @sufile: inode of segment usage file
 * @segnum: segment number
 *
 * Description: nilfs_sufile_set_error() marks the segment specified by
 * @segnum as erroneous. The error segment will never be used again.
 *
 * Return Value: On success, 0 is returned. On error, one of the following
 * negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 *
 * %-EINVAL - Invalid segment usage number.
 */
int nilfs_sufile_set_error(struct inode *sufile, __u64 segnum)
{
	struct buffer_head *header_bh, *su_bh;
	struct nilfs_segment_usage *su;
	struct nilfs_sufile_header *header;
	void *kaddr;
	int suclean, ret;

	if (unlikely(segnum >= nilfs_sufile_get_nsegments(sufile))) {
		printk(KERN_WARNING "%s: invalid segment number: %llu\n",
		       __func__, (unsigned long long)segnum);
		return -EINVAL;
	}
	down_write(&NILFS_MDT(sufile)->mi_sem);

	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
	if (ret < 0)
		goto out_sem;
	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &su_bh);
	if (ret < 0)
		goto out_header;

	kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
	if (nilfs_segment_usage_error(su)) {
		kunmap_atomic(kaddr, KM_USER0);
		brelse(su_bh);
		goto out_header;
	}
	suclean = nilfs_segment_usage_clean(su);

	nilfs_segment_usage_set_error(su);
	kunmap_atomic(kaddr, KM_USER0);

	if (suclean) {
		kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
		header = nilfs_sufile_block_get_header(sufile, header_bh,
						       kaddr);
		le64_add_cpu(&header->sh_ncleansegs, -1);
		kunmap_atomic(kaddr, KM_USER0);
		nilfs_mdt_mark_buffer_dirty(header_bh);
	}
	nilfs_mdt_mark_buffer_dirty(su_bh);
	nilfs_mdt_mark_dirty(sufile);
	brelse(su_bh);

 out_header:
	brelse(header_bh);

 out_sem:
	up_write(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}

/**
 * nilfs_sufile_get_suinfo -
 * @sufile: inode of segment usage file
 * @segnum: segment number to start looking
 * @si: array of suinfo
 * @nsi: size of suinfo array
 *
 * Description:
 *
 * Return Value: On success, 0 is returned and .... On error, one of the
 * following negative error codes is returned.
 *
 * %-EIO - I/O error.
 *
 * %-ENOMEM - Insufficient amount of memory available.
 */
ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum,
				struct nilfs_suinfo *si, size_t nsi)
{
	struct buffer_head *su_bh;
	struct nilfs_segment_usage *su;
	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
	struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
	void *kaddr;
	unsigned long nsegs, segusages_per_block;
	ssize_t n;
	int ret, i, j;

	down_read(&NILFS_MDT(sufile)->mi_sem);

	segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
	nsegs = min_t(unsigned long,
		      nilfs_sufile_get_nsegments(sufile) - segnum,
		      nsi);
	for (i = 0; i < nsegs; i += n, segnum += n) {
		n = min_t(unsigned long,
			  segusages_per_block -
				  nilfs_sufile_get_offset(sufile, segnum),
			  nsegs - i);
		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
							   &su_bh);
		if (ret < 0) {
			if (ret != -ENOENT)
				goto out;
			/* hole */
			memset(&si[i], 0, sizeof(struct nilfs_suinfo) * n);
			continue;
		}

		kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
		su = nilfs_sufile_block_get_segment_usage(
			sufile, segnum, su_bh, kaddr);
		for (j = 0; j < n; j++, su = (void *)su + susz) {
			si[i + j].sui_lastmod = le64_to_cpu(su->su_lastmod);
			si[i + j].sui_nblocks = le32_to_cpu(su->su_nblocks);
			si[i + j].sui_flags = le32_to_cpu(su->su_flags) &
				~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
			if (nilfs_segment_is_active(nilfs, segnum + j))
				si[i + j].sui_flags |=
					(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
		}
		kunmap_atomic(kaddr, KM_USER0);
		brelse(su_bh);
	}
	ret = nsegs;

 out:
	up_read(&NILFS_MDT(sufile)->mi_sem);
	return ret;
}