aboutsummaryrefslogtreecommitdiff
path: root/fs/ubifs/sb.c
blob: bf31b4729e51ce466560777a1e24bad90356311b (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
/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * 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
 *
 * Authors: Artem Bityutskiy (Битюцкий Артём)
 *          Adrian Hunter
 */

/*
 * This file implements UBIFS superblock. The superblock is stored at the first
 * LEB of the volume and is never changed by UBIFS. Only user-space tools may
 * change it. The superblock node mostly contains geometry information.
 */

#include "ubifs.h"
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/math64.h>

/*
 * Default journal size in logical eraseblocks as a percent of total
 * flash size.
 */
#define DEFAULT_JNL_PERCENT 5

/* Default maximum journal size in bytes */
#define DEFAULT_MAX_JNL (32*1024*1024)

/* Default indexing tree fanout */
#define DEFAULT_FANOUT 8

/* Default number of data journal heads */
#define DEFAULT_JHEADS_CNT 1

/* Default positions of different LEBs in the main area */
#define DEFAULT_IDX_LEB  0
#define DEFAULT_DATA_LEB 1
#define DEFAULT_GC_LEB   2

/* Default number of LEB numbers in LPT's save table */
#define DEFAULT_LSAVE_CNT 256

/* Default reserved pool size as a percent of maximum free space */
#define DEFAULT_RP_PERCENT 5

/* The default maximum size of reserved pool in bytes */
#define DEFAULT_MAX_RP_SIZE (5*1024*1024)

/* Default time granularity in nanoseconds */
#define DEFAULT_TIME_GRAN 1000000000

/**
 * create_default_filesystem - format empty UBI volume.
 * @c: UBIFS file-system description object
 *
 * This function creates default empty file-system. Returns zero in case of
 * success and a negative error code in case of failure.
 */
static int create_default_filesystem(struct ubifs_info *c)
{
	struct ubifs_sb_node *sup;
	struct ubifs_mst_node *mst;
	struct ubifs_idx_node *idx;
	struct ubifs_branch *br;
	struct ubifs_ino_node *ino;
	struct ubifs_cs_node *cs;
	union ubifs_key key;
	int err, tmp, jnl_lebs, log_lebs, max_buds, main_lebs, main_first;
	int lpt_lebs, lpt_first, orph_lebs, big_lpt, ino_waste, sup_flags = 0;
	int min_leb_cnt = UBIFS_MIN_LEB_CNT;
	long long tmp64, main_bytes;
	__le64 tmp_le64;

	/* Some functions called from here depend on the @c->key_len filed */
	c->key_len = UBIFS_SK_LEN;

	/*
	 * First of all, we have to calculate default file-system geometry -
	 * log size, journal size, etc.
	 */
	if (c->leb_cnt < 0x7FFFFFFF / DEFAULT_JNL_PERCENT)
		/* We can first multiply then divide and have no overflow */
		jnl_lebs = c->leb_cnt * DEFAULT_JNL_PERCENT / 100;
	else
		jnl_lebs = (c->leb_cnt / 100) * DEFAULT_JNL_PERCENT;

	if (jnl_lebs < UBIFS_MIN_JNL_LEBS)
		jnl_lebs = UBIFS_MIN_JNL_LEBS;
	if (jnl_lebs * c->leb_size > DEFAULT_MAX_JNL)
		jnl_lebs = DEFAULT_MAX_JNL / c->leb_size;

	/*
	 * The log should be large enough to fit reference nodes for all bud
	 * LEBs. Because buds do not have to start from the beginning of LEBs
	 * (half of the LEB may contain committed data), the log should
	 * generally be larger, make it twice as large.
	 */
	tmp = 2 * (c->ref_node_alsz * jnl_lebs) + c->leb_size - 1;
	log_lebs = tmp / c->leb_size;
	/* Plus one LEB reserved for commit */
	log_lebs += 1;
	if (c->leb_cnt - min_leb_cnt > 8) {
		/* And some extra space to allow writes while committing */
		log_lebs += 1;
		min_leb_cnt += 1;
	}

	max_buds = jnl_lebs - log_lebs;
	if (max_buds < UBIFS_MIN_BUD_LEBS)
		max_buds = UBIFS_MIN_BUD_LEBS;

	/*
	 * Orphan nodes are stored in a separate area. One node can store a lot
	 * of orphan inode numbers, but when new orphan comes we just add a new
	 * orphan node. At some point the nodes are consolidated into one
	 * orphan node.
	 */
	orph_lebs = UBIFS_MIN_ORPH_LEBS;
#ifdef CONFIG_UBIFS_FS_DEBUG
	if (c->leb_cnt - min_leb_cnt > 1)
		/*
		 * For debugging purposes it is better to have at least 2
		 * orphan LEBs, because the orphan subsystem would need to do
		 * consolidations and would be stressed more.
		 */
		orph_lebs += 1;
#endif

	main_lebs = c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS - log_lebs;
	main_lebs -= orph_lebs;

	lpt_first = UBIFS_LOG_LNUM + log_lebs;
	c->lsave_cnt = DEFAULT_LSAVE_CNT;
	c->max_leb_cnt = c->leb_cnt;
	err = ubifs_create_dflt_lpt(c, &main_lebs, lpt_first, &lpt_lebs,
				    &big_lpt);
	if (err)
		return err;

	dbg_gen("LEB Properties Tree created (LEBs %d-%d)", lpt_first,
		lpt_first + lpt_lebs - 1);

	main_first = c->leb_cnt - main_lebs;

	/* Create default superblock */
	tmp = ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size);
	sup = kzalloc(tmp, GFP_KERNEL);
	if (!sup)
		return -ENOMEM;

	tmp64 = (long long)max_buds * c->leb_size;
	if (big_lpt)
		sup_flags |= UBIFS_FLG_BIGLPT;

	sup->ch.node_type  = UBIFS_SB_NODE;
	sup->key_hash      = UBIFS_KEY_HASH_R5;
	sup->flags         = cpu_to_le32(sup_flags);
	sup->min_io_size   = cpu_to_le32(c->min_io_size);
	sup->leb_size      = cpu_to_le32(c->leb_size);
	sup->leb_cnt       = cpu_to_le32(c->leb_cnt);
	sup->max_leb_cnt   = cpu_to_le32(c->max_leb_cnt);
	sup->max_bud_bytes = cpu_to_le64(tmp64);
	sup->log_lebs      = cpu_to_le32(log_lebs);
	sup->lpt_lebs      = cpu_to_le32(lpt_lebs);
	sup->orph_lebs     = cpu_to_le32(orph_lebs);
	sup->jhead_cnt     = cpu_to_le32(DEFAULT_JHEADS_CNT);
	sup->fanout        = cpu_to_le32(DEFAULT_FANOUT);
	sup->lsave_cnt     = cpu_to_le32(c->lsave_cnt);
	sup->fmt_version   = cpu_to_le32(UBIFS_FORMAT_VERSION);
	sup->time_gran     = cpu_to_le32(DEFAULT_TIME_GRAN);
	if (c->mount_opts.override_compr)
		sup->default_compr = cpu_to_le16(c->mount_opts.compr_type);
	else
		sup->default_compr = cpu_to_le16(UBIFS_COMPR_LZO);

	generate_random_uuid(sup->uuid);

	main_bytes = (long long)main_lebs * c->leb_size;
	tmp64 = div_u64(main_bytes * DEFAULT_RP_PERCENT, 100);
	if (tmp64 > DEFAULT_MAX_RP_SIZE)
		tmp64 = DEFAULT_MAX_RP_SIZE;
	sup->rp_size = cpu_to_le64(tmp64);
	sup->ro_compat_version = cpu_to_le32(UBIFS_RO_COMPAT_VERSION);

	err = ubifs_write_node(c, sup, UBIFS_SB_NODE_SZ, 0, 0, UBI_LONGTERM);
	kfree(sup);
	if (err)
		return err;

	dbg_gen("default superblock created at LEB 0:0");

	/* Create default master node */
	mst = kzalloc(c->mst_node_alsz, GFP_KERNEL);
	if (!mst)
		return -ENOMEM;

	mst->ch.node_type = UBIFS_MST_NODE;
	mst->log_lnum     = cpu_to_le32(UBIFS_LOG_LNUM);
	mst->highest_inum = cpu_to_le64(UBIFS_FIRST_INO);
	mst->cmt_no       = 0;
	mst->root_lnum    = cpu_to_le32(main_first + DEFAULT_IDX_LEB);
	mst->root_offs    = 0;
	tmp = ubifs_idx_node_sz(c, 1);
	mst->root_len     = cpu_to_le32(tmp);
	mst->gc_lnum      = cpu_to_le32(main_first + DEFAULT_GC_LEB);
	mst->ihead_lnum   = cpu_to_le32(main_first + DEFAULT_IDX_LEB);
	mst->ihead_offs   = cpu_to_le32(ALIGN(tmp, c->min_io_size));
	mst->index_size   = cpu_to_le64(ALIGN(tmp, 8));
	mst->lpt_lnum     = cpu_to_le32(c->lpt_lnum);
	mst->lpt_offs     = cpu_to_le32(c->lpt_offs);
	mst->nhead_lnum   = cpu_to_le32(c->nhead_lnum);
	mst->nhead_offs   = cpu_to_le32(c->nhead_offs);
	mst->ltab_lnum    = cpu_to_le32(c->ltab_lnum);
	mst->ltab_offs    = cpu_to_le32(c->ltab_offs);
	mst->lsave_lnum   = cpu_to_le32(c->lsave_lnum);
	mst->lsave_offs   = cpu_to_le32(c->lsave_offs);
	mst->lscan_lnum   = cpu_to_le32(main_first);
	mst->empty_lebs   = cpu_to_le32(main_lebs - 2);
	mst->idx_lebs     = cpu_to_le32(1);
	mst->leb_cnt      = cpu_to_le32(c->leb_cnt);

	/* Calculate lprops statistics */
	tmp64 = main_bytes;
	tmp64 -= ALIGN(ubifs_idx_node_sz(c, 1), c->min_io_size);
	tmp64 -= ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size);
	mst->total_free = cpu_to_le64(tmp64);

	tmp64 = ALIGN(ubifs_idx_node_sz(c, 1), c->min_io_size);
	ino_waste = ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size) -
			  UBIFS_INO_NODE_SZ;
	tmp64 += ino_waste;
	tmp64 -= ALIGN(ubifs_idx_node_sz(c, 1), 8);
	mst->total_dirty = cpu_to_le64(tmp64);

	/*  The indexing LEB does not contribute to dark space */
	tmp64 = (c->main_lebs - 1) * c->dark_wm;
	mst->total_dark = cpu_to_le64(tmp64);

	mst->total_used = cpu_to_le64(UBIFS_INO_NODE_SZ);

	err = ubifs_write_node(c, mst, UBIFS_MST_NODE_SZ, UBIFS_MST_LNUM, 0,
			       UBI_UNKNOWN);
	if (err) {
		kfree(mst);
		return err;
	}
	err = ubifs_write_node(c, mst, UBIFS_MST_NODE_SZ, UBIFS_MST_LNUM + 1, 0,
			       UBI_UNKNOWN);
	kfree(mst);
	if (err)
		return err;

	dbg_gen("default master node created at LEB %d:0", UBIFS_MST_LNUM);

	/* Create the root indexing node */
	tmp = ubifs_idx_node_sz(c, 1);
	idx = kzalloc(ALIGN(tmp, c->min_io_size), GFP_KERNEL);
	if (!idx)
		return -ENOMEM;

	c->key_fmt = UBIFS_SIMPLE_KEY_FMT;
	c->key_hash = key_r5_hash;

	idx->ch.node_type = UBIFS_IDX_NODE;
	idx->child_cnt = cpu_to_le16(1);
	ino_key_init(c, &key, UBIFS_ROOT_INO);
	br = ubifs_idx_branch(c, idx, 0);
	key_write_idx(c, &key, &br->key);
	br->lnum = cpu_to_le32(main_first + DEFAULT_DATA_LEB);
	br->len  = cpu_to_le32(UBIFS_INO_NODE_SZ);
	err = ubifs_write_node(c, idx, tmp, main_first + DEFAULT_IDX_LEB, 0,
			       UBI_UNKNOWN);
	kfree(idx);
	if (err)
		return err;

	dbg_gen("default root indexing node created LEB %d:0",
		main_first + DEFAULT_IDX_LEB);

	/* Create default root inode */
	tmp = ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size);
	ino = kzalloc(tmp, GFP_KERNEL);
	if (!ino)
		return -ENOMEM;

	ino_key_init_flash(c, &ino->key, UBIFS_ROOT_INO);
	ino->ch.node_type = UBIFS_INO_NODE;
	ino->creat_sqnum = cpu_to_le64(++c->max_sqnum);
	ino->nlink = cpu_to_le32(2);
	tmp_le64 = cpu_to_le64(CURRENT_TIME_SEC.tv_sec);
	ino->atime_sec   = tmp_le64;
	ino->ctime_sec   = tmp_le64;
	ino->mtime_sec   = tmp_le64;
	ino->atime_nsec  = 0;
	ino->ctime_nsec  = 0;
	ino->mtime_nsec  = 0;
	ino->mode = cpu_to_le32(S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO);
	ino->size = cpu_to_le64(UBIFS_INO_NODE_SZ);

	/* Set compression enabled by default */
	ino->flags = cpu_to_le32(UBIFS_COMPR_FL);

	err = ubifs_write_node(c, ino, UBIFS_INO_NODE_SZ,
			       main_first + DEFAULT_DATA_LEB, 0,
			       UBI_UNKNOWN);
	kfree(ino);
	if (err)
		return err;

	dbg_gen("root inode created at LEB %d:0",
		main_first + DEFAULT_DATA_LEB);

	/*
	 * The first node in the log has to be the commit start node. This is
	 * always the case during normal file-system operation. Write a fake
	 * commit start node to the log.
	 */
	tmp = ALIGN(UBIFS_CS_NODE_SZ, c->min_io_size);
	cs = kzalloc(tmp, GFP_KERNEL);
	if (!cs)
		return -ENOMEM;

	cs->ch.node_type = UBIFS_CS_NODE;
	err = ubifs_write_node(c, cs, UBIFS_CS_NODE_SZ, UBIFS_LOG_LNUM,
			       0, UBI_UNKNOWN);
	kfree(cs);

	ubifs_msg("default file-system created");
	return 0;
}

/**
 * validate_sb - validate superblock node.
 * @c: UBIFS file-system description object
 * @sup: superblock node
 *
 * This function validates superblock node @sup. Since most of data was read
 * from the superblock and stored in @c, the function validates fields in @c
 * instead. Returns zero in case of success and %-EINVAL in case of validation
 * failure.
 */
static int validate_sb(struct ubifs_info *c, struct ubifs_sb_node *sup)
{
	long long max_bytes;
	int err = 1, min_leb_cnt;

	if (!c->key_hash) {
		err = 2;
		goto failed;
	}

	if (sup->key_fmt != UBIFS_SIMPLE_KEY_FMT) {
		err = 3;
		goto failed;
	}

	if (le32_to_cpu(sup->min_io_size) != c->min_io_size) {
		ubifs_err("min. I/O unit mismatch: %d in superblock, %d real",
			  le32_to_cpu(sup->min_io_size), c->min_io_size);
		goto failed;
	}

	if (le32_to_cpu(sup->leb_size) != c->leb_size) {
		ubifs_err("LEB size mismatch: %d in superblock, %d real",
			  le32_to_cpu(sup->leb_size), c->leb_size);
		goto failed;
	}

	if (c->log_lebs < UBIFS_MIN_LOG_LEBS ||
	    c->lpt_lebs < UBIFS_MIN_LPT_LEBS ||
	    c->orph_lebs < UBIFS_MIN_ORPH_LEBS ||
	    c->main_lebs < UBIFS_MIN_MAIN_LEBS) {
		err = 4;
		goto failed;
	}

	/*
	 * Calculate minimum allowed amount of main area LEBs. This is very
	 * similar to %UBIFS_MIN_LEB_CNT, but we take into account real what we
	 * have just read from the superblock.
	 */
	min_leb_cnt = UBIFS_SB_LEBS + UBIFS_MST_LEBS + c->log_lebs;
	min_leb_cnt += c->lpt_lebs + c->orph_lebs + c->jhead_cnt + 6;

	if (c->leb_cnt < min_leb_cnt || c->leb_cnt > c->vi.size) {
		ubifs_err("bad LEB count: %d in superblock, %d on UBI volume, "
			  "%d minimum required", c->leb_cnt, c->vi.size,
			  min_leb_cnt);
		goto failed;
	}

	if (c->max_leb_cnt < c->leb_cnt) {
		ubifs_err("max. LEB count %d less than LEB count %d",
			  c->max_leb_cnt, c->leb_cnt);
		goto failed;
	}

	if (c->main_lebs < UBIFS_MIN_MAIN_LEBS) {
		err = 7;
		goto failed;
	}

	if (c->max_bud_bytes < (long long)c->leb_size * UBIFS_MIN_BUD_LEBS ||
	    c->max_bud_bytes > (long long)c->leb_size * c->main_lebs) {
		err = 8;
		goto failed;
	}

	if (c->jhead_cnt < NONDATA_JHEADS_CNT + 1 ||
	    c->jhead_cnt > NONDATA_JHEADS_CNT + UBIFS_MAX_JHEADS) {
		err = 9;
		goto failed;
	}

	if (c->fanout < UBIFS_MIN_FANOUT ||
	    ubifs_idx_node_sz(c, c->fanout) > c->leb_size) {
		err = 10;
		goto failed;
	}

	if (c->lsave_cnt < 0 || (c->lsave_cnt > DEFAULT_LSAVE_CNT &&
	    c->lsave_cnt > c->max_leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS -
	    c->log_lebs - c->lpt_lebs - c->orph_lebs)) {
		err = 11;
		goto failed;
	}

	if (UBIFS_SB_LEBS + UBIFS_MST_LEBS + c->log_lebs + c->lpt_lebs +
	    c->orph_lebs + c->main_lebs != c->leb_cnt) {
		err = 12;
		goto failed;
	}

	if (c->default_compr < 0 || c->default_compr >= UBIFS_COMPR_TYPES_CNT) {
		err = 13;
		goto failed;
	}

	max_bytes = c->main_lebs * (long long)c->leb_size;
	if (c->rp_size < 0 || max_bytes < c->rp_size) {
		err = 14;
		goto failed;
	}

	if (le32_to_cpu(sup->time_gran) > 1000000000 ||
	    le32_to_cpu(sup->time_gran) < 1) {
		err = 15;
		goto failed;
	}

	return 0;

failed:
	ubifs_err("bad superblock, error %d", err);
	dbg_dump_node(c, sup);
	return -EINVAL;
}

/**
 * ubifs_read_sb_node - read superblock node.
 * @c: UBIFS file-system description object
 *
 * This function returns a pointer to the superblock node or a negative error
 * code.
 */
struct ubifs_sb_node *ubifs_read_sb_node(struct ubifs_info *c)
{
	struct ubifs_sb_node *sup;
	int err;

	sup = kmalloc(ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size), GFP_NOFS);
	if (!sup)
		return ERR_PTR(-ENOMEM);

	err = ubifs_read_node(c, sup, UBIFS_SB_NODE, UBIFS_SB_NODE_SZ,
			      UBIFS_SB_LNUM, 0);
	if (err) {
		kfree(sup);
		return ERR_PTR(err);
	}

	return sup;
}

/**
 * ubifs_write_sb_node - write superblock node.
 * @c: UBIFS file-system description object
 * @sup: superblock node read with 'ubifs_read_sb_node()'
 *
 * This function returns %0 on success and a negative error code on failure.
 */
int ubifs_write_sb_node(struct ubifs_info *c, struct ubifs_sb_node *sup)
{
	int len = ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size);

	ubifs_prepare_node(c, sup, UBIFS_SB_NODE_SZ, 1);
	return ubifs_leb_change(c, UBIFS_SB_LNUM, sup, len, UBI_LONGTERM);
}

/**
 * ubifs_read_superblock - read superblock.
 * @c: UBIFS file-system description object
 *
 * This function finds, reads and checks the superblock. If an empty UBI volume
 * is being mounted, this function creates default superblock. Returns zero in
 * case of success, and a negative error code in case of failure.
 */
int ubifs_read_superblock(struct ubifs_info *c)
{
	int err, sup_flags;
	struct ubifs_sb_node *sup;

	if (c->empty) {
		err = create_default_filesystem(c);
		if (err)
			return err;
	}

	sup = ubifs_read_sb_node(c);
	if (IS_ERR(sup))
		return PTR_ERR(sup);

	c->fmt_version = le32_to_cpu(sup->fmt_version);
	c->ro_compat_version = le32_to_cpu(sup->ro_compat_version);

	/*
	 * The software supports all previous versions but not future versions,
	 * due to the unavailability of time-travelling equipment.
	 */
	if (c->fmt_version > UBIFS_FORMAT_VERSION) {
		ubifs_assert(!c->ro_media || c->ro_mount);
		if (!c->ro_mount ||
		    c->ro_compat_version > UBIFS_RO_COMPAT_VERSION) {
			ubifs_err("on-flash format version is w%d/r%d, but "
				  "software only supports up to version "
				  "w%d/r%d", c->fmt_version,
				  c->ro_compat_version, UBIFS_FORMAT_VERSION,
				  UBIFS_RO_COMPAT_VERSION);
			if (c->ro_compat_version <= UBIFS_RO_COMPAT_VERSION) {
				ubifs_msg("only R/O mounting is possible");
				err = -EROFS;
			} else
				err = -EINVAL;
			goto out;
		}

		/*
		 * The FS is mounted R/O, and the media format is
		 * R/O-compatible with the UBIFS implementation, so we can
		 * mount.
		 */
		c->rw_incompat = 1;
	}

	if (c->fmt_version < 3) {
		ubifs_err("on-flash format version %d is not supported",
			  c->fmt_version);
		err = -EINVAL;
		goto out;
	}

	switch (sup->key_hash) {
	case UBIFS_KEY_HASH_R5:
		c->key_hash = key_r5_hash;
		c->key_hash_type = UBIFS_KEY_HASH_R5;
		break;

	case UBIFS_KEY_HASH_TEST:
		c->key_hash = key_test_hash;
		c->key_hash_type = UBIFS_KEY_HASH_TEST;
		break;
	};

	c->key_fmt = sup->key_fmt;

	switch (c->key_fmt) {
	case UBIFS_SIMPLE_KEY_FMT:
		c->key_len = UBIFS_SK_LEN;
		break;
	default:
		ubifs_err("unsupported key format");
		err = -EINVAL;
		goto out;
	}

	c->leb_cnt       = le32_to_cpu(sup->leb_cnt);
	c->max_leb_cnt   = le32_to_cpu(sup->max_leb_cnt);
	c->max_bud_bytes = le64_to_cpu(sup->max_bud_bytes);
	c->log_lebs      = le32_to_cpu(sup->log_lebs);
	c->lpt_lebs      = le32_to_cpu(sup->lpt_lebs);
	c->orph_lebs     = le32_to_cpu(sup->orph_lebs);
	c->jhead_cnt     = le32_to_cpu(sup->jhead_cnt) + NONDATA_JHEADS_CNT;
	c->fanout        = le32_to_cpu(sup->fanout);
	c->lsave_cnt     = le32_to_cpu(sup->lsave_cnt);
	c->rp_size       = le64_to_cpu(sup->rp_size);
	c->rp_uid        = le32_to_cpu(sup->rp_uid);
	c->rp_gid        = le32_to_cpu(sup->rp_gid);
	sup_flags        = le32_to_cpu(sup->flags);
	if (!c->mount_opts.override_compr)
		c->default_compr = le16_to_cpu(sup->default_compr);

	c->vfs_sb->s_time_gran = le32_to_cpu(sup->time_gran);
	memcpy(&c->uuid, &sup->uuid, 16);
	c->big_lpt = !!(sup_flags & UBIFS_FLG_BIGLPT);

	/* Automatically increase file system size to the maximum size */
	c->old_leb_cnt = c->leb_cnt;
	if (c->leb_cnt < c->vi.size && c->leb_cnt < c->max_leb_cnt) {
		c->leb_cnt = min_t(int, c->max_leb_cnt, c->vi.size);
		if (c->ro_mount)
			dbg_mnt("Auto resizing (ro) from %d LEBs to %d LEBs",
				c->old_leb_cnt,	c->leb_cnt);
		else {
			dbg_mnt("Auto resizing (sb) from %d LEBs to %d LEBs",
				c->old_leb_cnt, c->leb_cnt);
			sup->leb_cnt = cpu_to_le32(c->leb_cnt);
			err = ubifs_write_sb_node(c, sup);
			if (err)
				goto out;
			c->old_leb_cnt = c->leb_cnt;
		}
	}

	c->log_bytes = (long long)c->log_lebs * c->leb_size;
	c->log_last = UBIFS_LOG_LNUM + c->log_lebs - 1;
	c->lpt_first = UBIFS_LOG_LNUM + c->log_lebs;
	c->lpt_last = c->lpt_first + c->lpt_lebs - 1;
	c->orph_first = c->lpt_last + 1;
	c->orph_last = c->orph_first + c->orph_lebs - 1;
	c->main_lebs = c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS;
	c->main_lebs -= c->log_lebs + c->lpt_lebs + c->orph_lebs;
	c->main_first = c->leb_cnt - c->main_lebs;

	err = validate_sb(c, sup);
out:
	kfree(sup);
	return err;
}