aboutsummaryrefslogtreecommitdiff
path: root/fs/logfs/segment.c
blob: 614d7a6fda2d823dc1eab2653109bab58f23fc5e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
/*
 * fs/logfs/segment.c	- Handling the Object Store
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
 *
 * Object store or ostore makes up the complete device with exception of
 * the superblock and journal areas.  Apart from its own metadata it stores
 * three kinds of objects: inodes, dentries and blocks, both data and indirect.
 */
#include "logfs.h"
#include <linux/slab.h>

static int logfs_mark_segment_bad(struct super_block *sb, u32 segno)
{
	struct logfs_super *super = logfs_super(sb);
	struct btree_head32 *head = &super->s_reserved_segments;
	int err;

	err = btree_insert32(head, segno, (void *)1, GFP_NOFS);
	if (err)
		return err;
	logfs_super(sb)->s_bad_segments++;
	/* FIXME: write to journal */
	return 0;
}

int logfs_erase_segment(struct super_block *sb, u32 segno, int ensure_erase)
{
	struct logfs_super *super = logfs_super(sb);

	super->s_gec++;

	return super->s_devops->erase(sb, (u64)segno << super->s_segshift,
			super->s_segsize, ensure_erase);
}

static s64 logfs_get_free_bytes(struct logfs_area *area, size_t bytes)
{
	s32 ofs;

	logfs_open_area(area, bytes);

	ofs = area->a_used_bytes;
	area->a_used_bytes += bytes;
	BUG_ON(area->a_used_bytes >= logfs_super(area->a_sb)->s_segsize);

	return dev_ofs(area->a_sb, area->a_segno, ofs);
}

static struct page *get_mapping_page(struct super_block *sb, pgoff_t index,
		int use_filler)
{
	struct logfs_super *super = logfs_super(sb);
	struct address_space *mapping = super->s_mapping_inode->i_mapping;
	filler_t *filler = super->s_devops->readpage;
	struct page *page;

	BUG_ON(mapping_gfp_mask(mapping) & __GFP_FS);
	if (use_filler)
		page = read_cache_page(mapping, index, filler, sb);
	else {
		page = find_or_create_page(mapping, index, GFP_NOFS);
		unlock_page(page);
	}
	return page;
}

void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
		int use_filler)
{
	pgoff_t index = ofs >> PAGE_SHIFT;
	struct page *page;
	long offset = ofs & (PAGE_SIZE-1);
	long copylen;

	/* Only logfs_wbuf_recover may use len==0 */
	BUG_ON(!len && !use_filler);
	do {
		copylen = min((ulong)len, PAGE_SIZE - offset);

		page = get_mapping_page(area->a_sb, index, use_filler);
		SetPageUptodate(page);
		BUG_ON(!page); /* FIXME: reserve a pool */
		memcpy(page_address(page) + offset, buf, copylen);
		SetPagePrivate(page);
		page_cache_release(page);

		buf += copylen;
		len -= copylen;
		offset = 0;
		index++;
	} while (len);
}

/*
 * bdev_writeseg will write full pages.  Memset the tail to prevent data leaks.
 */
static void pad_wbuf(struct logfs_area *area, int final)
{
	struct super_block *sb = area->a_sb;
	struct logfs_super *super = logfs_super(sb);
	struct page *page;
	u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes);
	pgoff_t index = ofs >> PAGE_SHIFT;
	long offset = ofs & (PAGE_SIZE-1);
	u32 len = PAGE_SIZE - offset;

	if (len == PAGE_SIZE) {
		/* The math in this function can surely use some love */
		len = 0;
	}
	if (len) {
		BUG_ON(area->a_used_bytes >= super->s_segsize);

		page = get_mapping_page(area->a_sb, index, 0);
		BUG_ON(!page); /* FIXME: reserve a pool */
		memset(page_address(page) + offset, 0xff, len);
		SetPagePrivate(page);
		page_cache_release(page);
	}

	if (!final)
		return;

	area->a_used_bytes += len;
	for ( ; area->a_used_bytes < super->s_segsize;
			area->a_used_bytes += PAGE_SIZE) {
		/* Memset another page */
		index++;
		page = get_mapping_page(area->a_sb, index, 0);
		BUG_ON(!page); /* FIXME: reserve a pool */
		memset(page_address(page), 0xff, PAGE_SIZE);
		SetPagePrivate(page);
		page_cache_release(page);
	}
}

/*
 * We have to be careful with the alias tree.  Since lookup is done by bix,
 * it needs to be normalized, so 14, 15, 16, etc. all match when dealing with
 * indirect blocks.  So always use it through accessor functions.
 */
static void *alias_tree_lookup(struct super_block *sb, u64 ino, u64 bix,
		level_t level)
{
	struct btree_head128 *head = &logfs_super(sb)->s_object_alias_tree;
	pgoff_t index = logfs_pack_index(bix, level);

	return btree_lookup128(head, ino, index);
}

static int alias_tree_insert(struct super_block *sb, u64 ino, u64 bix,
		level_t level, void *val)
{
	struct btree_head128 *head = &logfs_super(sb)->s_object_alias_tree;
	pgoff_t index = logfs_pack_index(bix, level);

	return btree_insert128(head, ino, index, val, GFP_NOFS);
}

static int btree_write_alias(struct super_block *sb, struct logfs_block *block,
		write_alias_t *write_one_alias)
{
	struct object_alias_item *item;
	int err;

	list_for_each_entry(item, &block->item_list, list) {
		err = write_alias_journal(sb, block->ino, block->bix,
				block->level, item->child_no, item->val);
		if (err)
			return err;
	}
	return 0;
}

static gc_level_t btree_block_level(struct logfs_block *block)
{
	return expand_level(block->ino, block->level);
}

static struct logfs_block_ops btree_block_ops = {
	.write_block	= btree_write_block,
	.block_level	= btree_block_level,
	.free_block	= __free_block,
	.write_alias	= btree_write_alias,
};

int logfs_load_object_aliases(struct super_block *sb,
		struct logfs_obj_alias *oa, int count)
{
	struct logfs_super *super = logfs_super(sb);
	struct logfs_block *block;
	struct object_alias_item *item;
	u64 ino, bix;
	level_t level;
	int i, err;

	super->s_flags |= LOGFS_SB_FLAG_OBJ_ALIAS;
	count /= sizeof(*oa);
	for (i = 0; i < count; i++) {
		item = mempool_alloc(super->s_alias_pool, GFP_NOFS);
		if (!item)
			return -ENOMEM;
		memset(item, 0, sizeof(*item));

		super->s_no_object_aliases++;
		item->val = oa[i].val;
		item->child_no = be16_to_cpu(oa[i].child_no);

		ino = be64_to_cpu(oa[i].ino);
		bix = be64_to_cpu(oa[i].bix);
		level = LEVEL(oa[i].level);

		log_aliases("logfs_load_object_aliases(%llx, %llx, %x, %x) %llx\n",
				ino, bix, level, item->child_no,
				be64_to_cpu(item->val));
		block = alias_tree_lookup(sb, ino, bix, level);
		if (!block) {
			block = __alloc_block(sb, ino, bix, level);
			block->ops = &btree_block_ops;
			err = alias_tree_insert(sb, ino, bix, level, block);
			BUG_ON(err); /* mempool empty */
		}
		if (test_and_set_bit(item->child_no, block->alias_map)) {
			printk(KERN_ERR"LogFS: Alias collision detected\n");
			return -EIO;
		}
		list_move_tail(&block->alias_list, &super->s_object_alias);
		list_add(&item->list, &block->item_list);
	}
	return 0;
}

static void kill_alias(void *_block, unsigned long ignore0,
		u64 ignore1, u64 ignore2, size_t ignore3)
{
	struct logfs_block *block = _block;
	struct super_block *sb = block->sb;
	struct logfs_super *super = logfs_super(sb);
	struct object_alias_item *item;

	while (!list_empty(&block->item_list)) {
		item = list_entry(block->item_list.next, typeof(*item), list);
		list_del(&item->list);
		mempool_free(item, super->s_alias_pool);
	}
	block->ops->free_block(sb, block);
}

static int obj_type(struct inode *inode, level_t level)
{
	if (level == 0) {
		if (S_ISDIR(inode->i_mode))
			return OBJ_DENTRY;
		if (inode->i_ino == LOGFS_INO_MASTER)
			return OBJ_INODE;
	}
	return OBJ_BLOCK;
}

static int obj_len(struct super_block *sb, int obj_type)
{
	switch (obj_type) {
	case OBJ_DENTRY:
		return sizeof(struct logfs_disk_dentry);
	case OBJ_INODE:
		return sizeof(struct logfs_disk_inode);
	case OBJ_BLOCK:
		return sb->s_blocksize;
	default:
		BUG();
	}
}

static int __logfs_segment_write(struct inode *inode, void *buf,
		struct logfs_shadow *shadow, int type, int len, int compr)
{
	struct logfs_area *area;
	struct super_block *sb = inode->i_sb;
	s64 ofs;
	struct logfs_object_header h;
	int acc_len;

	if (shadow->gc_level == 0)
		acc_len = len;
	else
		acc_len = obj_len(sb, type);

	area = get_area(sb, shadow->gc_level);
	ofs = logfs_get_free_bytes(area, len + LOGFS_OBJECT_HEADERSIZE);
	LOGFS_BUG_ON(ofs <= 0, sb);
	/*
	 * Order is important.  logfs_get_free_bytes(), by modifying the
	 * segment file, may modify the content of the very page we're about
	 * to write now.  Which is fine, as long as the calculated crc and
	 * written data still match.  So do the modifications _before_
	 * calculating the crc.
	 */

	h.len	= cpu_to_be16(len);
	h.type	= type;
	h.compr	= compr;
	h.ino	= cpu_to_be64(inode->i_ino);
	h.bix	= cpu_to_be64(shadow->bix);
	h.crc	= logfs_crc32(&h, sizeof(h) - 4, 4);
	h.data_crc = logfs_crc32(buf, len, 0);

	logfs_buf_write(area, ofs, &h, sizeof(h));
	logfs_buf_write(area, ofs + LOGFS_OBJECT_HEADERSIZE, buf, len);

	shadow->new_ofs = ofs;
	shadow->new_len = acc_len + LOGFS_OBJECT_HEADERSIZE;

	return 0;
}

static s64 logfs_segment_write_compress(struct inode *inode, void *buf,
		struct logfs_shadow *shadow, int type, int len)
{
	struct super_block *sb = inode->i_sb;
	void *compressor_buf = logfs_super(sb)->s_compressed_je;
	ssize_t compr_len;
	int ret;

	mutex_lock(&logfs_super(sb)->s_journal_mutex);
	compr_len = logfs_compress(buf, compressor_buf, len, len);

	if (compr_len >= 0) {
		ret = __logfs_segment_write(inode, compressor_buf, shadow,
				type, compr_len, COMPR_ZLIB);
	} else {
		ret = __logfs_segment_write(inode, buf, shadow, type, len,
				COMPR_NONE);
	}
	mutex_unlock(&logfs_super(sb)->s_journal_mutex);
	return ret;
}

/**
 * logfs_segment_write - write data block to object store
 * @inode:		inode containing data
 *
 * Returns an errno or zero.
 */
int logfs_segment_write(struct inode *inode, struct page *page,
		struct logfs_shadow *shadow)
{
	struct super_block *sb = inode->i_sb;
	struct logfs_super *super = logfs_super(sb);
	int do_compress, type, len;
	int ret;
	void *buf;

	super->s_flags |= LOGFS_SB_FLAG_DIRTY;
	BUG_ON(super->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
	do_compress = logfs_inode(inode)->li_flags & LOGFS_IF_COMPRESSED;
	if (shadow->gc_level != 0) {
		/* temporarily disable compression for indirect blocks */
		do_compress = 0;
	}

	type = obj_type(inode, shrink_level(shadow->gc_level));
	len = obj_len(sb, type);
	buf = kmap(page);
	if (do_compress)
		ret = logfs_segment_write_compress(inode, buf, shadow, type,
				len);
	else
		ret = __logfs_segment_write(inode, buf, shadow, type, len,
				COMPR_NONE);
	kunmap(page);

	log_segment("logfs_segment_write(%llx, %llx, %x) %llx->%llx %x->%x\n",
			shadow->ino, shadow->bix, shadow->gc_level,
			shadow->old_ofs, shadow->new_ofs,
			shadow->old_len, shadow->new_len);
	/* this BUG_ON did catch a locking bug.  useful */
	BUG_ON(!(shadow->new_ofs & (super->s_segsize - 1)));
	return ret;
}

int wbuf_read(struct super_block *sb, u64 ofs, size_t len, void *buf)
{
	pgoff_t index = ofs >> PAGE_SHIFT;
	struct page *page;
	long offset = ofs & (PAGE_SIZE-1);
	long copylen;

	while (len) {
		copylen = min((ulong)len, PAGE_SIZE - offset);

		page = get_mapping_page(sb, index, 1);
		if (IS_ERR(page))
			return PTR_ERR(page);
		memcpy(buf, page_address(page) + offset, copylen);
		page_cache_release(page);

		buf += copylen;
		len -= copylen;
		offset = 0;
		index++;
	}
	return 0;
}

/*
 * The "position" of indirect blocks is ambiguous.  It can be the position
 * of any data block somewhere behind this indirect block.  So we need to
 * normalize the positions through logfs_block_mask() before comparing.
 */
static int check_pos(struct super_block *sb, u64 pos1, u64 pos2, level_t level)
{
	return	(pos1 & logfs_block_mask(sb, level)) !=
		(pos2 & logfs_block_mask(sb, level));
}

#if 0
static int read_seg_header(struct super_block *sb, u64 ofs,
		struct logfs_segment_header *sh)
{
	__be32 crc;
	int err;

	err = wbuf_read(sb, ofs, sizeof(*sh), sh);
	if (err)
		return err;
	crc = logfs_crc32(sh, sizeof(*sh), 4);
	if (crc != sh->crc) {
		printk(KERN_ERR"LOGFS: header crc error at %llx: expected %x, "
				"got %x\n", ofs, be32_to_cpu(sh->crc),
				be32_to_cpu(crc));
		return -EIO;
	}
	return 0;
}
#endif

static int read_obj_header(struct super_block *sb, u64 ofs,
		struct logfs_object_header *oh)
{
	__be32 crc;
	int err;

	err = wbuf_read(sb, ofs, sizeof(*oh), oh);
	if (err)
		return err;
	crc = logfs_crc32(oh, sizeof(*oh) - 4, 4);
	if (crc != oh->crc) {
		printk(KERN_ERR"LOGFS: header crc error at %llx: expected %x, "
				"got %x\n", ofs, be32_to_cpu(oh->crc),
				be32_to_cpu(crc));
		return -EIO;
	}
	return 0;
}

static void move_btree_to_page(struct inode *inode, struct page *page,
		__be64 *data)
{
	struct super_block *sb = inode->i_sb;
	struct logfs_super *super = logfs_super(sb);
	struct btree_head128 *head = &super->s_object_alias_tree;
	struct logfs_block *block;
	struct object_alias_item *item, *next;

	if (!(super->s_flags & LOGFS_SB_FLAG_OBJ_ALIAS))
		return;

	block = btree_remove128(head, inode->i_ino, page->index);
	if (!block)
		return;

	log_blockmove("move_btree_to_page(%llx, %llx, %x)\n",
			block->ino, block->bix, block->level);
	list_for_each_entry_safe(item, next, &block->item_list, list) {
		data[item->child_no] = item->val;
		list_del(&item->list);
		mempool_free(item, super->s_alias_pool);
	}
	block->page = page;
	SetPagePrivate(page);
	page->private = (unsigned long)block;
	block->ops = &indirect_block_ops;
	initialize_block_counters(page, block, data, 0);
}

/*
 * This silences a false, yet annoying gcc warning.  I hate it when my editor
 * jumps into bitops.h each time I recompile this file.
 * TODO: Complain to gcc folks about this and upgrade compiler.
 */
static unsigned long fnb(const unsigned long *addr,
		unsigned long size, unsigned long offset)
{
	return find_next_bit(addr, size, offset);
}

void move_page_to_btree(struct page *page)
{
	struct logfs_block *block = logfs_block(page);
	struct super_block *sb = block->sb;
	struct logfs_super *super = logfs_super(sb);
	struct object_alias_item *item;
	unsigned long pos;
	__be64 *child;
	int err;

	if (super->s_flags & LOGFS_SB_FLAG_SHUTDOWN) {
		block->ops->free_block(sb, block);
		return;
	}
	log_blockmove("move_page_to_btree(%llx, %llx, %x)\n",
			block->ino, block->bix, block->level);
	super->s_flags |= LOGFS_SB_FLAG_OBJ_ALIAS;

	for (pos = 0; ; pos++) {
		pos = fnb(block->alias_map, LOGFS_BLOCK_FACTOR, pos);
		if (pos >= LOGFS_BLOCK_FACTOR)
			break;

		item = mempool_alloc(super->s_alias_pool, GFP_NOFS);
		BUG_ON(!item); /* mempool empty */
		memset(item, 0, sizeof(*item));

		child = kmap_atomic(page, KM_USER0);
		item->val = child[pos];
		kunmap_atomic(child, KM_USER0);
		item->child_no = pos;
		list_add(&item->list, &block->item_list);
	}
	block->page = NULL;
	ClearPagePrivate(page);
	page->private = 0;
	block->ops = &btree_block_ops;
	err = alias_tree_insert(block->sb, block->ino, block->bix, block->level,
			block);
	BUG_ON(err); /* mempool empty */
	ClearPageUptodate(page);
}

static int __logfs_segment_read(struct inode *inode, void *buf,
		u64 ofs, u64 bix, level_t level)
{
	struct super_block *sb = inode->i_sb;
	void *compressor_buf = logfs_super(sb)->s_compressed_je;
	struct logfs_object_header oh;
	__be32 crc;
	u16 len;
	int err, block_len;

	block_len = obj_len(sb, obj_type(inode, level));
	err = read_obj_header(sb, ofs, &oh);
	if (err)
		goto out_err;

	err = -EIO;
	if (be64_to_cpu(oh.ino) != inode->i_ino
			|| check_pos(sb, be64_to_cpu(oh.bix), bix, level)) {
		printk(KERN_ERR"LOGFS: (ino, bix) don't match at %llx: "
				"expected (%lx, %llx), got (%llx, %llx)\n",
				ofs, inode->i_ino, bix,
				be64_to_cpu(oh.ino), be64_to_cpu(oh.bix));
		goto out_err;
	}

	len = be16_to_cpu(oh.len);

	switch (oh.compr) {
	case COMPR_NONE:
		err = wbuf_read(sb, ofs + LOGFS_OBJECT_HEADERSIZE, len, buf);
		if (err)
			goto out_err;
		crc = logfs_crc32(buf, len, 0);
		if (crc != oh.data_crc) {
			printk(KERN_ERR"LOGFS: uncompressed data crc error at "
					"%llx: expected %x, got %x\n", ofs,
					be32_to_cpu(oh.data_crc),
					be32_to_cpu(crc));
			goto out_err;
		}
		break;
	case COMPR_ZLIB:
		mutex_lock(&logfs_super(sb)->s_journal_mutex);
		err = wbuf_read(sb, ofs + LOGFS_OBJECT_HEADERSIZE, len,
				compressor_buf);
		if (err) {
			mutex_unlock(&logfs_super(sb)->s_journal_mutex);
			goto out_err;
		}
		crc = logfs_crc32(compressor_buf, len, 0);
		if (crc != oh.data_crc) {
			printk(KERN_ERR"LOGFS: compressed data crc error at "
					"%llx: expected %x, got %x\n", ofs,
					be32_to_cpu(oh.data_crc),
					be32_to_cpu(crc));
			mutex_unlock(&logfs_super(sb)->s_journal_mutex);
			goto out_err;
		}
		err = logfs_uncompress(compressor_buf, buf, len, block_len);
		mutex_unlock(&logfs_super(sb)->s_journal_mutex);
		if (err) {
			printk(KERN_ERR"LOGFS: uncompress error at %llx\n", ofs);
			goto out_err;
		}
		break;
	default:
		LOGFS_BUG(sb);
		err = -EIO;
		goto out_err;
	}
	return 0;

out_err:
	logfs_set_ro(sb);
	printk(KERN_ERR"LOGFS: device is read-only now\n");
	LOGFS_BUG(sb);
	return err;
}

/**
 * logfs_segment_read - read data block from object store
 * @inode:		inode containing data
 * @buf:		data buffer
 * @ofs:		physical data offset
 * @bix:		block index
 * @level:		block level
 *
 * Returns 0 on success or a negative errno.
 */
int logfs_segment_read(struct inode *inode, struct page *page,
		u64 ofs, u64 bix, level_t level)
{
	int err;
	void *buf;

	if (PageUptodate(page))
		return 0;

	ofs &= ~LOGFS_FULLY_POPULATED;

	buf = kmap(page);
	err = __logfs_segment_read(inode, buf, ofs, bix, level);
	if (!err) {
		move_btree_to_page(inode, page, buf);
		SetPageUptodate(page);
	}
	kunmap(page);
	log_segment("logfs_segment_read(%lx, %llx, %x) %llx (%d)\n",
			inode->i_ino, bix, level, ofs, err);
	return err;
}

int logfs_segment_delete(struct inode *inode, struct logfs_shadow *shadow)
{
	struct super_block *sb = inode->i_sb;
	struct logfs_super *super = logfs_super(sb);
	struct logfs_object_header h;
	u16 len;
	int err;

	super->s_flags |= LOGFS_SB_FLAG_DIRTY;
	BUG_ON(super->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
	BUG_ON(shadow->old_ofs & LOGFS_FULLY_POPULATED);
	if (!shadow->old_ofs)
		return 0;

	log_segment("logfs_segment_delete(%llx, %llx, %x) %llx->%llx %x->%x\n",
			shadow->ino, shadow->bix, shadow->gc_level,
			shadow->old_ofs, shadow->new_ofs,
			shadow->old_len, shadow->new_len);
	err = read_obj_header(sb, shadow->old_ofs, &h);
	LOGFS_BUG_ON(err, sb);
	LOGFS_BUG_ON(be64_to_cpu(h.ino) != inode->i_ino, sb);
	LOGFS_BUG_ON(check_pos(sb, shadow->bix, be64_to_cpu(h.bix),
				shrink_level(shadow->gc_level)), sb);

	if (shadow->gc_level == 0)
		len = be16_to_cpu(h.len);
	else
		len = obj_len(sb, h.type);
	shadow->old_len = len + sizeof(h);
	return 0;
}

static void freeseg(struct super_block *sb, u32 segno)
{
	struct logfs_super *super = logfs_super(sb);
	struct address_space *mapping = super->s_mapping_inode->i_mapping;
	struct page *page;
	u64 ofs, start, end;

	start = dev_ofs(sb, segno, 0);
	end = dev_ofs(sb, segno + 1, 0);
	for (ofs = start; ofs < end; ofs += PAGE_SIZE) {
		page = find_get_page(mapping, ofs >> PAGE_SHIFT);
		if (!page)
			continue;
		ClearPagePrivate(page);
		page_cache_release(page);
	}
}

int logfs_open_area(struct logfs_area *area, size_t bytes)
{
	struct super_block *sb = area->a_sb;
	struct logfs_super *super = logfs_super(sb);
	int err, closed = 0;

	if (area->a_is_open && area->a_used_bytes + bytes <= super->s_segsize)
		return 0;

	if (area->a_is_open) {
		u64 ofs = dev_ofs(sb, area->a_segno, area->a_written_bytes);
		u32 len = super->s_segsize - area->a_written_bytes;

		log_gc("logfs_close_area(%x)\n", area->a_segno);
		pad_wbuf(area, 1);
		super->s_devops->writeseg(area->a_sb, ofs, len);
		freeseg(sb, area->a_segno);
		closed = 1;
	}

	area->a_used_bytes = 0;
	area->a_written_bytes = 0;
again:
	area->a_ops->get_free_segment(area);
	area->a_ops->get_erase_count(area);

	log_gc("logfs_open_area(%x, %x)\n", area->a_segno, area->a_level);
	err = area->a_ops->erase_segment(area);
	if (err) {
		printk(KERN_WARNING "LogFS: Error erasing segment %x\n",
				area->a_segno);
		logfs_mark_segment_bad(sb, area->a_segno);
		goto again;
	}
	area->a_is_open = 1;
	return closed;
}

void logfs_sync_area(struct logfs_area *area)
{
	struct super_block *sb = area->a_sb;
	struct logfs_super *super = logfs_super(sb);
	u64 ofs = dev_ofs(sb, area->a_segno, area->a_written_bytes);
	u32 len = (area->a_used_bytes - area->a_written_bytes);

	if (super->s_writesize)
		len &= ~(super->s_writesize - 1);
	if (len == 0)
		return;
	pad_wbuf(area, 0);
	super->s_devops->writeseg(sb, ofs, len);
	area->a_written_bytes += len;
}

void logfs_sync_segments(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	int i;

	for_each_area(i)
		logfs_sync_area(super->s_area[i]);
}

/*
 * Pick a free segment to be used for this area.  Effectively takes a
 * candidate from the free list (not really a candidate anymore).
 */
static void ostore_get_free_segment(struct logfs_area *area)
{
	struct super_block *sb = area->a_sb;
	struct logfs_super *super = logfs_super(sb);

	if (super->s_free_list.count == 0) {
		printk(KERN_ERR"LOGFS: ran out of free segments\n");
		LOGFS_BUG(sb);
	}

	area->a_segno = get_best_cand(sb, &super->s_free_list, NULL);
}

static void ostore_get_erase_count(struct logfs_area *area)
{
	struct logfs_segment_entry se;
	u32 ec_level;

	logfs_get_segment_entry(area->a_sb, area->a_segno, &se);
	BUG_ON(se.ec_level == cpu_to_be32(BADSEG) ||
			se.valid == cpu_to_be32(RESERVED));

	ec_level = be32_to_cpu(se.ec_level);
	area->a_erase_count = (ec_level >> 4) + 1;
}

static int ostore_erase_segment(struct logfs_area *area)
{
	struct super_block *sb = area->a_sb;
	struct logfs_segment_header sh;
	u64 ofs;
	int err;

	err = logfs_erase_segment(sb, area->a_segno, 0);
	if (err)
		return err;

	sh.pad = 0;
	sh.type = SEG_OSTORE;
	sh.level = (__force u8)area->a_level;
	sh.segno = cpu_to_be32(area->a_segno);
	sh.ec = cpu_to_be32(area->a_erase_count);
	sh.gec = cpu_to_be64(logfs_super(sb)->s_gec);
	sh.crc = logfs_crc32(&sh, sizeof(sh), 4);

	logfs_set_segment_erased(sb, area->a_segno, area->a_erase_count,
			area->a_level);

	ofs = dev_ofs(sb, area->a_segno, 0);
	area->a_used_bytes = sizeof(sh);
	logfs_buf_write(area, ofs, &sh, sizeof(sh));
	return 0;
}

static const struct logfs_area_ops ostore_area_ops = {
	.get_free_segment	= ostore_get_free_segment,
	.get_erase_count	= ostore_get_erase_count,
	.erase_segment		= ostore_erase_segment,
};

static void free_area(struct logfs_area *area)
{
	if (area)
		freeseg(area->a_sb, area->a_segno);
	kfree(area);
}

static struct logfs_area *alloc_area(struct super_block *sb)
{
	struct logfs_area *area;

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

	area->a_sb = sb;
	return area;
}

static void map_invalidatepage(struct page *page, unsigned long l)
{
	BUG();
}

static int map_releasepage(struct page *page, gfp_t g)
{
	/* Don't release these pages */
	return 0;
}

static const struct address_space_operations mapping_aops = {
	.invalidatepage = map_invalidatepage,
	.releasepage	= map_releasepage,
	.set_page_dirty = __set_page_dirty_nobuffers,
};

int logfs_init_mapping(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	struct address_space *mapping;
	struct inode *inode;

	inode = logfs_new_meta_inode(sb, LOGFS_INO_MAPPING);
	if (IS_ERR(inode))
		return PTR_ERR(inode);
	super->s_mapping_inode = inode;
	mapping = inode->i_mapping;
	mapping->a_ops = &mapping_aops;
	/* Would it be possible to use __GFP_HIGHMEM as well? */
	mapping_set_gfp_mask(mapping, GFP_NOFS);
	return 0;
}

int logfs_init_areas(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	int i = -1;

	super->s_alias_pool = mempool_create_kmalloc_pool(600,
			sizeof(struct object_alias_item));
	if (!super->s_alias_pool)
		return -ENOMEM;

	super->s_journal_area = alloc_area(sb);
	if (!super->s_journal_area)
		goto err;

	for_each_area(i) {
		super->s_area[i] = alloc_area(sb);
		if (!super->s_area[i])
			goto err;
		super->s_area[i]->a_level = GC_LEVEL(i);
		super->s_area[i]->a_ops = &ostore_area_ops;
	}
	btree_init_mempool128(&super->s_object_alias_tree,
			super->s_btree_pool);
	return 0;

err:
	for (i--; i >= 0; i--)
		free_area(super->s_area[i]);
	free_area(super->s_journal_area);
	mempool_destroy(super->s_alias_pool);
	return -ENOMEM;
}

void logfs_cleanup_areas(struct super_block *sb)
{
	struct logfs_super *super = logfs_super(sb);
	int i;

	btree_grim_visitor128(&super->s_object_alias_tree, 0, kill_alias);
	for_each_area(i)
		free_area(super->s_area[i]);
	free_area(super->s_journal_area);
	destroy_meta_inode(super->s_mapping_inode);
}