summaryrefslogtreecommitdiffstats
path: root/drivers/md/persistent-data/dm-space-map-metadata.c
blob: fca6dbcf9a4727f85d61f7d161094870f5db24d5 (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
/*
 * Copyright (C) 2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-space-map.h"
#include "dm-space-map-common.h"
#include "dm-space-map-metadata.h"

#include <linux/list.h>
#include <linux/slab.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "space map metadata"

/*----------------------------------------------------------------*/

/*
 * An edge triggered threshold.
 */
struct threshold {
	bool threshold_set;
	bool value_set;
	dm_block_t threshold;
	dm_block_t current_value;
	dm_sm_threshold_fn fn;
	void *context;
};

static void threshold_init(struct threshold *t)
{
	t->threshold_set = false;
	t->value_set = false;
}

static void set_threshold(struct threshold *t, dm_block_t value,
			  dm_sm_threshold_fn fn, void *context)
{
	t->threshold_set = true;
	t->threshold = value;
	t->fn = fn;
	t->context = context;
}

static bool below_threshold(struct threshold *t, dm_block_t value)
{
	return t->threshold_set && value <= t->threshold;
}

static bool threshold_already_triggered(struct threshold *t)
{
	return t->value_set && below_threshold(t, t->current_value);
}

static void check_threshold(struct threshold *t, dm_block_t value)
{
	if (below_threshold(t, value) &&
	    !threshold_already_triggered(t))
		t->fn(t->context);

	t->value_set = true;
	t->current_value = value;
}

/*----------------------------------------------------------------*/

/*
 * Space map interface.
 *
 * The low level disk format is written using the standard btree and
 * transaction manager.  This means that performing disk operations may
 * cause us to recurse into the space map in order to allocate new blocks.
 * For this reason we have a pool of pre-allocated blocks large enough to
 * service any metadata_ll_disk operation.
 */

/*
 * FIXME: we should calculate this based on the size of the device.
 * Only the metadata space map needs this functionality.
 */
#define MAX_RECURSIVE_ALLOCATIONS 1024

enum block_op_type {
	BOP_INC,
	BOP_DEC
};

struct block_op {
	enum block_op_type type;
	dm_block_t block;
};

struct bop_ring_buffer {
	unsigned begin;
	unsigned end;
	struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
};

static void brb_init(struct bop_ring_buffer *brb)
{
	brb->begin = 0;
	brb->end = 0;
}

static bool brb_empty(struct bop_ring_buffer *brb)
{
	return brb->begin == brb->end;
}

static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
{
	unsigned r = old + 1;
	return (r >= (sizeof(brb->bops) / sizeof(*brb->bops))) ? 0 : r;
}

static int brb_push(struct bop_ring_buffer *brb,
		    enum block_op_type type, dm_block_t b)
{
	struct block_op *bop;
	unsigned next = brb_next(brb, brb->end);

	/*
	 * We don't allow the last bop to be filled, this way we can
	 * differentiate between full and empty.
	 */
	if (next == brb->begin)
		return -ENOMEM;

	bop = brb->bops + brb->end;
	bop->type = type;
	bop->block = b;

	brb->end = next;

	return 0;
}

static int brb_peek(struct bop_ring_buffer *brb, struct block_op *result)
{
	struct block_op *bop;

	if (brb_empty(brb))
		return -ENODATA;

	bop = brb->bops + brb->begin;
	result->type = bop->type;
	result->block = bop->block;

	return 0;
}

static int brb_pop(struct bop_ring_buffer *brb)
{
	struct block_op *bop;

	if (brb_empty(brb))
		return -ENODATA;

	bop = brb->bops + brb->begin;
	brb->begin = brb_next(brb, brb->begin);

	return 0;
}

/*----------------------------------------------------------------*/

struct sm_metadata {
	struct dm_space_map sm;

	struct ll_disk ll;
	struct ll_disk old_ll;

	dm_block_t begin;

	unsigned recursion_count;
	unsigned allocated_this_transaction;
	struct bop_ring_buffer uncommitted;

	struct threshold threshold;
};

static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
{
	int r = brb_push(&smm->uncommitted, type, b);

	if (r) {
		DMERR("too many recursive allocations");
		return -ENOMEM;
	}

	return 0;
}

static int commit_bop(struct sm_metadata *smm, struct block_op *op)
{
	int r = 0;
	enum allocation_event ev;

	switch (op->type) {
	case BOP_INC:
		r = sm_ll_inc(&smm->ll, op->block, &ev);
		break;

	case BOP_DEC:
		r = sm_ll_dec(&smm->ll, op->block, &ev);
		break;
	}

	return r;
}

static void in(struct sm_metadata *smm)
{
	smm->recursion_count++;
}

static int apply_bops(struct sm_metadata *smm)
{
	int r = 0;

	while (!brb_empty(&smm->uncommitted)) {
		struct block_op bop;

		r = brb_peek(&smm->uncommitted, &bop);
		if (r) {
			DMERR("bug in bop ring buffer");
			break;
		}

		r = commit_bop(smm, &bop);
		if (r)
			break;

		brb_pop(&smm->uncommitted);
	}

	return r;
}

static int out(struct sm_metadata *smm)
{
	int r = 0;

	/*
	 * If we're not recursing then very bad things are happening.
	 */
	if (!smm->recursion_count) {
		DMERR("lost track of recursion depth");
		return -ENOMEM;
	}

	if (smm->recursion_count == 1)
		apply_bops(smm);

	smm->recursion_count--;

	return r;
}

/*
 * When using the out() function above, we often want to combine an error
 * code for the operation run in the recursive context with that from
 * out().
 */
static int combine_errors(int r1, int r2)
{
	return r1 ? r1 : r2;
}

static int recursing(struct sm_metadata *smm)
{
	return smm->recursion_count;
}

static void sm_metadata_destroy(struct dm_space_map *sm)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	kfree(smm);
}

static int sm_metadata_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	*count = smm->ll.nr_blocks;

	return 0;
}

static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	*count = smm->old_ll.nr_blocks - smm->old_ll.nr_allocated -
		 smm->allocated_this_transaction;

	return 0;
}

static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
				 uint32_t *result)
{
	int r;
	unsigned i;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
	unsigned adjustment = 0;

	/*
	 * We may have some uncommitted adjustments to add.  This list
	 * should always be really short.
	 */
	for (i = smm->uncommitted.begin;
	     i != smm->uncommitted.end;
	     i = brb_next(&smm->uncommitted, i)) {
		struct block_op *op = smm->uncommitted.bops + i;

		if (op->block != b)
			continue;

		switch (op->type) {
		case BOP_INC:
			adjustment++;
			break;

		case BOP_DEC:
			adjustment--;
			break;
		}
	}

	r = sm_ll_lookup(&smm->ll, b, result);
	if (r)
		return r;

	*result += adjustment;

	return 0;
}

static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
					      dm_block_t b, int *result)
{
	int r, adjustment = 0;
	unsigned i;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
	uint32_t rc;

	/*
	 * We may have some uncommitted adjustments to add.  This list
	 * should always be really short.
	 */
	for (i = smm->uncommitted.begin;
	     i != smm->uncommitted.end;
	     i = brb_next(&smm->uncommitted, i)) {

		struct block_op *op = smm->uncommitted.bops + i;

		if (op->block != b)
			continue;

		switch (op->type) {
		case BOP_INC:
			adjustment++;
			break;

		case BOP_DEC:
			adjustment--;
			break;
		}
	}

	if (adjustment > 1) {
		*result = 1;
		return 0;
	}

	r = sm_ll_lookup_bitmap(&smm->ll, b, &rc);
	if (r)
		return r;

	if (rc == 3)
		/*
		 * We err on the side of caution, and always return true.
		 */
		*result = 1;
	else
		*result = rc + adjustment > 1;

	return 0;
}

static int sm_metadata_set_count(struct dm_space_map *sm, dm_block_t b,
				 uint32_t count)
{
	int r, r2;
	enum allocation_event ev;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	if (smm->recursion_count) {
		DMERR("cannot recurse set_count()");
		return -EINVAL;
	}

	in(smm);
	r = sm_ll_insert(&smm->ll, b, count, &ev);
	r2 = out(smm);

	return combine_errors(r, r2);
}

static int sm_metadata_inc_block(struct dm_space_map *sm, dm_block_t b)
{
	int r, r2 = 0;
	enum allocation_event ev;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	if (recursing(smm))
		r = add_bop(smm, BOP_INC, b);
	else {
		in(smm);
		r = sm_ll_inc(&smm->ll, b, &ev);
		r2 = out(smm);
	}

	return combine_errors(r, r2);
}

static int sm_metadata_dec_block(struct dm_space_map *sm, dm_block_t b)
{
	int r, r2 = 0;
	enum allocation_event ev;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	if (recursing(smm))
		r = add_bop(smm, BOP_DEC, b);
	else {
		in(smm);
		r = sm_ll_dec(&smm->ll, b, &ev);
		r2 = out(smm);
	}

	return combine_errors(r, r2);
}

static int sm_metadata_new_block_(struct dm_space_map *sm, dm_block_t *b)
{
	int r, r2 = 0;
	enum allocation_event ev;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	r = sm_ll_find_free_block(&smm->old_ll, smm->begin, smm->old_ll.nr_blocks, b);
	if (r)
		return r;

	smm->begin = *b + 1;

	if (recursing(smm))
		r = add_bop(smm, BOP_INC, *b);
	else {
		in(smm);
		r = sm_ll_inc(&smm->ll, *b, &ev);
		r2 = out(smm);
	}

	if (!r)
		smm->allocated_this_transaction++;

	return combine_errors(r, r2);
}

static int sm_metadata_new_block(struct dm_space_map *sm, dm_block_t *b)
{
	dm_block_t count;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	int r = sm_metadata_new_block_(sm, b);
	if (r) {
		DMERR_LIMIT("unable to allocate new metadata block");
		return r;
	}

	r = sm_metadata_get_nr_free(sm, &count);
	if (r) {
		DMERR_LIMIT("couldn't get free block count");
		return r;
	}

	check_threshold(&smm->threshold, count);

	return r;
}

static int sm_metadata_commit(struct dm_space_map *sm)
{
	int r;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	r = sm_ll_commit(&smm->ll);
	if (r)
		return r;

	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
	smm->begin = 0;
	smm->allocated_this_transaction = 0;

	return 0;
}

static int sm_metadata_register_threshold_callback(struct dm_space_map *sm,
						   dm_block_t threshold,
						   dm_sm_threshold_fn fn,
						   void *context)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	set_threshold(&smm->threshold, threshold, fn, context);

	return 0;
}

static int sm_metadata_root_size(struct dm_space_map *sm, size_t *result)
{
	*result = sizeof(struct disk_sm_root);

	return 0;
}

static int sm_metadata_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
	struct disk_sm_root root_le;

	root_le.nr_blocks = cpu_to_le64(smm->ll.nr_blocks);
	root_le.nr_allocated = cpu_to_le64(smm->ll.nr_allocated);
	root_le.bitmap_root = cpu_to_le64(smm->ll.bitmap_root);
	root_le.ref_count_root = cpu_to_le64(smm->ll.ref_count_root);

	if (max < sizeof(root_le))
		return -ENOSPC;

	memcpy(where_le, &root_le, sizeof(root_le));

	return 0;
}

static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks);

static struct dm_space_map ops = {
	.destroy = sm_metadata_destroy,
	.extend = sm_metadata_extend,
	.get_nr_blocks = sm_metadata_get_nr_blocks,
	.get_nr_free = sm_metadata_get_nr_free,
	.get_count = sm_metadata_get_count,
	.count_is_more_than_one = sm_metadata_count_is_more_than_one,
	.set_count = sm_metadata_set_count,
	.inc_block = sm_metadata_inc_block,
	.dec_block = sm_metadata_dec_block,
	.new_block = sm_metadata_new_block,
	.commit = sm_metadata_commit,
	.root_size = sm_metadata_root_size,
	.copy_root = sm_metadata_copy_root,
	.register_threshold_callback = sm_metadata_register_threshold_callback
};

/*----------------------------------------------------------------*/

/*
 * When a new space map is created that manages its own space.  We use
 * this tiny bootstrap allocator.
 */
static void sm_bootstrap_destroy(struct dm_space_map *sm)
{
}

static int sm_bootstrap_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
{
	DMERR("bootstrap doesn't support extend");

	return -EINVAL;
}

static int sm_bootstrap_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	*count = smm->ll.nr_blocks;

	return 0;
}

static int sm_bootstrap_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	*count = smm->ll.nr_blocks - smm->begin;

	return 0;
}

static int sm_bootstrap_get_count(struct dm_space_map *sm, dm_block_t b,
				  uint32_t *result)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	*result = (b < smm->begin) ? 1 : 0;

	return 0;
}

static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
					       dm_block_t b, int *result)
{
	*result = 0;

	return 0;
}

static int sm_bootstrap_set_count(struct dm_space_map *sm, dm_block_t b,
				  uint32_t count)
{
	DMERR("bootstrap doesn't support set_count");

	return -EINVAL;
}

static int sm_bootstrap_new_block(struct dm_space_map *sm, dm_block_t *b)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	/*
	 * We know the entire device is unused.
	 */
	if (smm->begin == smm->ll.nr_blocks)
		return -ENOSPC;

	*b = smm->begin++;

	return 0;
}

static int sm_bootstrap_inc_block(struct dm_space_map *sm, dm_block_t b)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	return add_bop(smm, BOP_INC, b);
}

static int sm_bootstrap_dec_block(struct dm_space_map *sm, dm_block_t b)
{
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	return add_bop(smm, BOP_DEC, b);
}

static int sm_bootstrap_commit(struct dm_space_map *sm)
{
	return 0;
}

static int sm_bootstrap_root_size(struct dm_space_map *sm, size_t *result)
{
	DMERR("bootstrap doesn't support root_size");

	return -EINVAL;
}

static int sm_bootstrap_copy_root(struct dm_space_map *sm, void *where,
				  size_t max)
{
	DMERR("bootstrap doesn't support copy_root");

	return -EINVAL;
}

static struct dm_space_map bootstrap_ops = {
	.destroy = sm_bootstrap_destroy,
	.extend = sm_bootstrap_extend,
	.get_nr_blocks = sm_bootstrap_get_nr_blocks,
	.get_nr_free = sm_bootstrap_get_nr_free,
	.get_count = sm_bootstrap_get_count,
	.count_is_more_than_one = sm_bootstrap_count_is_more_than_one,
	.set_count = sm_bootstrap_set_count,
	.inc_block = sm_bootstrap_inc_block,
	.dec_block = sm_bootstrap_dec_block,
	.new_block = sm_bootstrap_new_block,
	.commit = sm_bootstrap_commit,
	.root_size = sm_bootstrap_root_size,
	.copy_root = sm_bootstrap_copy_root,
	.register_threshold_callback = NULL
};

/*----------------------------------------------------------------*/

static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
{
	int r, i;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
	dm_block_t old_len = smm->ll.nr_blocks;

	/*
	 * Flick into a mode where all blocks get allocated in the new area.
	 */
	smm->begin = old_len;
	memcpy(sm, &bootstrap_ops, sizeof(*sm));

	/*
	 * Extend.
	 */
	r = sm_ll_extend(&smm->ll, extra_blocks);
	if (r)
		goto out;

	/*
	 * We repeatedly increment then commit until the commit doesn't
	 * allocate any new blocks.
	 */
	do {
		for (i = old_len; !r && i < smm->begin; i++)
			r = add_bop(smm, BOP_INC, i);

		if (r)
			goto out;

		old_len = smm->begin;

		r = apply_bops(smm);
		if (r) {
			DMERR("%s: apply_bops failed", __func__);
			goto out;
		}

		r = sm_ll_commit(&smm->ll);
		if (r)
			goto out;

	} while (old_len != smm->begin);

out:
	/*
	 * Switch back to normal behaviour.
	 */
	memcpy(sm, &ops, sizeof(*sm));
	return r;
}

/*----------------------------------------------------------------*/

struct dm_space_map *dm_sm_metadata_init(void)
{
	struct sm_metadata *smm;

	smm = kmalloc(sizeof(*smm), GFP_KERNEL);
	if (!smm)
		return ERR_PTR(-ENOMEM);

	memcpy(&smm->sm, &ops, sizeof(smm->sm));

	return &smm->sm;
}

int dm_sm_metadata_create(struct dm_space_map *sm,
			  struct dm_transaction_manager *tm,
			  dm_block_t nr_blocks,
			  dm_block_t superblock)
{
	int r;
	dm_block_t i;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	smm->begin = superblock + 1;
	smm->recursion_count = 0;
	smm->allocated_this_transaction = 0;
	brb_init(&smm->uncommitted);
	threshold_init(&smm->threshold);

	memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));

	r = sm_ll_new_metadata(&smm->ll, tm);
	if (r)
		return r;

	if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
		nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
	r = sm_ll_extend(&smm->ll, nr_blocks);
	if (r)
		return r;

	memcpy(&smm->sm, &ops, sizeof(smm->sm));

	/*
	 * Now we need to update the newly created data structures with the
	 * allocated blocks that they were built from.
	 */
	for (i = superblock; !r && i < smm->begin; i++)
		r = add_bop(smm, BOP_INC, i);

	if (r)
		return r;

	r = apply_bops(smm);
	if (r) {
		DMERR("%s: apply_bops failed", __func__);
		return r;
	}

	return sm_metadata_commit(sm);
}

int dm_sm_metadata_open(struct dm_space_map *sm,
			struct dm_transaction_manager *tm,
			void *root_le, size_t len)
{
	int r;
	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

	r = sm_ll_open_metadata(&smm->ll, tm, root_le, len);
	if (r)
		return r;

	smm->begin = 0;
	smm->recursion_count = 0;
	smm->allocated_this_transaction = 0;
	brb_init(&smm->uncommitted);
	threshold_init(&smm->threshold);

	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
	return 0;
}