1 /*
2  * Copyright (C) 2011 Red Hat, Inc.
3  *
4  * This file is released under the GPL.
5  */
6 
7 #include "dm-space-map.h"
8 #include "dm-space-map-common.h"
9 #include "dm-space-map-metadata.h"
10 
11 #include <linux/list.h>
12 #include <linux/slab.h>
13 #include <linux/device-mapper.h>
14 
15 #define DM_MSG_PREFIX "space map metadata"
16 
17 /*----------------------------------------------------------------*/
18 
19 /*
20  * An edge triggered threshold.
21  */
22 struct threshold {
23 	bool threshold_set;
24 	bool value_set;
25 	dm_block_t threshold;
26 	dm_block_t current_value;
27 	dm_sm_threshold_fn fn;
28 	void *context;
29 };
30 
31 static void threshold_init(struct threshold *t)
32 {
33 	t->threshold_set = false;
34 	t->value_set = false;
35 }
36 
37 static void set_threshold(struct threshold *t, dm_block_t value,
38 			  dm_sm_threshold_fn fn, void *context)
39 {
40 	t->threshold_set = true;
41 	t->threshold = value;
42 	t->fn = fn;
43 	t->context = context;
44 }
45 
46 static bool below_threshold(struct threshold *t, dm_block_t value)
47 {
48 	return t->threshold_set && value <= t->threshold;
49 }
50 
51 static bool threshold_already_triggered(struct threshold *t)
52 {
53 	return t->value_set && below_threshold(t, t->current_value);
54 }
55 
56 static void check_threshold(struct threshold *t, dm_block_t value)
57 {
58 	if (below_threshold(t, value) &&
59 	    !threshold_already_triggered(t))
60 		t->fn(t->context);
61 
62 	t->value_set = true;
63 	t->current_value = value;
64 }
65 
66 /*----------------------------------------------------------------*/
67 
68 /*
69  * Space map interface.
70  *
71  * The low level disk format is written using the standard btree and
72  * transaction manager.  This means that performing disk operations may
73  * cause us to recurse into the space map in order to allocate new blocks.
74  * For this reason we have a pool of pre-allocated blocks large enough to
75  * service any metadata_ll_disk operation.
76  */
77 
78 /*
79  * FIXME: we should calculate this based on the size of the device.
80  * Only the metadata space map needs this functionality.
81  */
82 #define MAX_RECURSIVE_ALLOCATIONS 1024
83 
84 enum block_op_type {
85 	BOP_INC,
86 	BOP_DEC
87 };
88 
89 struct block_op {
90 	enum block_op_type type;
91 	dm_block_t block;
92 };
93 
94 struct bop_ring_buffer {
95 	unsigned begin;
96 	unsigned end;
97 	struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
98 };
99 
100 static void brb_init(struct bop_ring_buffer *brb)
101 {
102 	brb->begin = 0;
103 	brb->end = 0;
104 }
105 
106 static bool brb_empty(struct bop_ring_buffer *brb)
107 {
108 	return brb->begin == brb->end;
109 }
110 
111 static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
112 {
113 	unsigned r = old + 1;
114 	return (r >= (sizeof(brb->bops) / sizeof(*brb->bops))) ? 0 : r;
115 }
116 
117 static int brb_push(struct bop_ring_buffer *brb,
118 		    enum block_op_type type, dm_block_t b)
119 {
120 	struct block_op *bop;
121 	unsigned next = brb_next(brb, brb->end);
122 
123 	/*
124 	 * We don't allow the last bop to be filled, this way we can
125 	 * differentiate between full and empty.
126 	 */
127 	if (next == brb->begin)
128 		return -ENOMEM;
129 
130 	bop = brb->bops + brb->end;
131 	bop->type = type;
132 	bop->block = b;
133 
134 	brb->end = next;
135 
136 	return 0;
137 }
138 
139 static int brb_pop(struct bop_ring_buffer *brb, struct block_op *result)
140 {
141 	struct block_op *bop;
142 
143 	if (brb_empty(brb))
144 		return -ENODATA;
145 
146 	bop = brb->bops + brb->begin;
147 	result->type = bop->type;
148 	result->block = bop->block;
149 
150 	brb->begin = brb_next(brb, brb->begin);
151 
152 	return 0;
153 }
154 
155 /*----------------------------------------------------------------*/
156 
157 struct sm_metadata {
158 	struct dm_space_map sm;
159 
160 	struct ll_disk ll;
161 	struct ll_disk old_ll;
162 
163 	dm_block_t begin;
164 
165 	unsigned recursion_count;
166 	unsigned allocated_this_transaction;
167 	struct bop_ring_buffer uncommitted;
168 
169 	struct threshold threshold;
170 };
171 
172 static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
173 {
174 	int r = brb_push(&smm->uncommitted, type, b);
175 
176 	if (r) {
177 		DMERR("too many recursive allocations");
178 		return -ENOMEM;
179 	}
180 
181 	return 0;
182 }
183 
184 static int commit_bop(struct sm_metadata *smm, struct block_op *op)
185 {
186 	int r = 0;
187 	enum allocation_event ev;
188 
189 	switch (op->type) {
190 	case BOP_INC:
191 		r = sm_ll_inc(&smm->ll, op->block, &ev);
192 		break;
193 
194 	case BOP_DEC:
195 		r = sm_ll_dec(&smm->ll, op->block, &ev);
196 		break;
197 	}
198 
199 	return r;
200 }
201 
202 static void in(struct sm_metadata *smm)
203 {
204 	smm->recursion_count++;
205 }
206 
207 static int apply_bops(struct sm_metadata *smm)
208 {
209 	int r = 0;
210 
211 	while (!brb_empty(&smm->uncommitted)) {
212 		struct block_op bop;
213 
214 		r = brb_pop(&smm->uncommitted, &bop);
215 		if (r) {
216 			DMERR("bug in bop ring buffer");
217 			break;
218 		}
219 
220 		r = commit_bop(smm, &bop);
221 		if (r)
222 			break;
223 	}
224 
225 	return r;
226 }
227 
228 static int out(struct sm_metadata *smm)
229 {
230 	int r = 0;
231 
232 	/*
233 	 * If we're not recursing then very bad things are happening.
234 	 */
235 	if (!smm->recursion_count) {
236 		DMERR("lost track of recursion depth");
237 		return -ENOMEM;
238 	}
239 
240 	if (smm->recursion_count == 1)
241 		apply_bops(smm);
242 
243 	smm->recursion_count--;
244 
245 	return r;
246 }
247 
248 /*
249  * When using the out() function above, we often want to combine an error
250  * code for the operation run in the recursive context with that from
251  * out().
252  */
253 static int combine_errors(int r1, int r2)
254 {
255 	return r1 ? r1 : r2;
256 }
257 
258 static int recursing(struct sm_metadata *smm)
259 {
260 	return smm->recursion_count;
261 }
262 
263 static void sm_metadata_destroy(struct dm_space_map *sm)
264 {
265 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
266 
267 	kfree(smm);
268 }
269 
270 static int sm_metadata_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
271 {
272 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
273 
274 	*count = smm->ll.nr_blocks;
275 
276 	return 0;
277 }
278 
279 static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
280 {
281 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
282 
283 	*count = smm->old_ll.nr_blocks - smm->old_ll.nr_allocated -
284 		 smm->allocated_this_transaction;
285 
286 	return 0;
287 }
288 
289 static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
290 				 uint32_t *result)
291 {
292 	int r;
293 	unsigned i;
294 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
295 	unsigned adjustment = 0;
296 
297 	/*
298 	 * We may have some uncommitted adjustments to add.  This list
299 	 * should always be really short.
300 	 */
301 	for (i = smm->uncommitted.begin;
302 	     i != smm->uncommitted.end;
303 	     i = brb_next(&smm->uncommitted, i)) {
304 		struct block_op *op = smm->uncommitted.bops + i;
305 
306 		if (op->block != b)
307 			continue;
308 
309 		switch (op->type) {
310 		case BOP_INC:
311 			adjustment++;
312 			break;
313 
314 		case BOP_DEC:
315 			adjustment--;
316 			break;
317 		}
318 	}
319 
320 	r = sm_ll_lookup(&smm->ll, b, result);
321 	if (r)
322 		return r;
323 
324 	*result += adjustment;
325 
326 	return 0;
327 }
328 
329 static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
330 					      dm_block_t b, int *result)
331 {
332 	int r, adjustment = 0;
333 	unsigned i;
334 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
335 	uint32_t rc;
336 
337 	/*
338 	 * We may have some uncommitted adjustments to add.  This list
339 	 * should always be really short.
340 	 */
341 	for (i = smm->uncommitted.begin;
342 	     i != smm->uncommitted.end;
343 	     i = brb_next(&smm->uncommitted, i)) {
344 
345 		struct block_op *op = smm->uncommitted.bops + i;
346 
347 		if (op->block != b)
348 			continue;
349 
350 		switch (op->type) {
351 		case BOP_INC:
352 			adjustment++;
353 			break;
354 
355 		case BOP_DEC:
356 			adjustment--;
357 			break;
358 		}
359 	}
360 
361 	if (adjustment > 1) {
362 		*result = 1;
363 		return 0;
364 	}
365 
366 	r = sm_ll_lookup_bitmap(&smm->ll, b, &rc);
367 	if (r)
368 		return r;
369 
370 	if (rc == 3)
371 		/*
372 		 * We err on the side of caution, and always return true.
373 		 */
374 		*result = 1;
375 	else
376 		*result = rc + adjustment > 1;
377 
378 	return 0;
379 }
380 
381 static int sm_metadata_set_count(struct dm_space_map *sm, dm_block_t b,
382 				 uint32_t count)
383 {
384 	int r, r2;
385 	enum allocation_event ev;
386 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
387 
388 	if (smm->recursion_count) {
389 		DMERR("cannot recurse set_count()");
390 		return -EINVAL;
391 	}
392 
393 	in(smm);
394 	r = sm_ll_insert(&smm->ll, b, count, &ev);
395 	r2 = out(smm);
396 
397 	return combine_errors(r, r2);
398 }
399 
400 static int sm_metadata_inc_block(struct dm_space_map *sm, dm_block_t b)
401 {
402 	int r, r2 = 0;
403 	enum allocation_event ev;
404 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
405 
406 	if (recursing(smm))
407 		r = add_bop(smm, BOP_INC, b);
408 	else {
409 		in(smm);
410 		r = sm_ll_inc(&smm->ll, b, &ev);
411 		r2 = out(smm);
412 	}
413 
414 	return combine_errors(r, r2);
415 }
416 
417 static int sm_metadata_dec_block(struct dm_space_map *sm, dm_block_t b)
418 {
419 	int r, r2 = 0;
420 	enum allocation_event ev;
421 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
422 
423 	if (recursing(smm))
424 		r = add_bop(smm, BOP_DEC, b);
425 	else {
426 		in(smm);
427 		r = sm_ll_dec(&smm->ll, b, &ev);
428 		r2 = out(smm);
429 	}
430 
431 	return combine_errors(r, r2);
432 }
433 
434 static int sm_metadata_new_block_(struct dm_space_map *sm, dm_block_t *b)
435 {
436 	int r, r2 = 0;
437 	enum allocation_event ev;
438 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
439 
440 	r = sm_ll_find_free_block(&smm->old_ll, smm->begin, smm->old_ll.nr_blocks, b);
441 	if (r)
442 		return r;
443 
444 	smm->begin = *b + 1;
445 
446 	if (recursing(smm))
447 		r = add_bop(smm, BOP_INC, *b);
448 	else {
449 		in(smm);
450 		r = sm_ll_inc(&smm->ll, *b, &ev);
451 		r2 = out(smm);
452 	}
453 
454 	if (!r)
455 		smm->allocated_this_transaction++;
456 
457 	return combine_errors(r, r2);
458 }
459 
460 static int sm_metadata_new_block(struct dm_space_map *sm, dm_block_t *b)
461 {
462 	dm_block_t count;
463 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
464 
465 	int r = sm_metadata_new_block_(sm, b);
466 	if (r) {
467 		DMERR_LIMIT("unable to allocate new metadata block");
468 		return r;
469 	}
470 
471 	r = sm_metadata_get_nr_free(sm, &count);
472 	if (r) {
473 		DMERR_LIMIT("couldn't get free block count");
474 		return r;
475 	}
476 
477 	check_threshold(&smm->threshold, count);
478 
479 	return r;
480 }
481 
482 static int sm_metadata_commit(struct dm_space_map *sm)
483 {
484 	int r;
485 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
486 
487 	r = sm_ll_commit(&smm->ll);
488 	if (r)
489 		return r;
490 
491 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
492 	smm->begin = 0;
493 	smm->allocated_this_transaction = 0;
494 
495 	return 0;
496 }
497 
498 static int sm_metadata_register_threshold_callback(struct dm_space_map *sm,
499 						   dm_block_t threshold,
500 						   dm_sm_threshold_fn fn,
501 						   void *context)
502 {
503 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
504 
505 	set_threshold(&smm->threshold, threshold, fn, context);
506 
507 	return 0;
508 }
509 
510 static int sm_metadata_root_size(struct dm_space_map *sm, size_t *result)
511 {
512 	*result = sizeof(struct disk_sm_root);
513 
514 	return 0;
515 }
516 
517 static int sm_metadata_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
518 {
519 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
520 	struct disk_sm_root root_le;
521 
522 	root_le.nr_blocks = cpu_to_le64(smm->ll.nr_blocks);
523 	root_le.nr_allocated = cpu_to_le64(smm->ll.nr_allocated);
524 	root_le.bitmap_root = cpu_to_le64(smm->ll.bitmap_root);
525 	root_le.ref_count_root = cpu_to_le64(smm->ll.ref_count_root);
526 
527 	if (max < sizeof(root_le))
528 		return -ENOSPC;
529 
530 	memcpy(where_le, &root_le, sizeof(root_le));
531 
532 	return 0;
533 }
534 
535 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks);
536 
537 static struct dm_space_map ops = {
538 	.destroy = sm_metadata_destroy,
539 	.extend = sm_metadata_extend,
540 	.get_nr_blocks = sm_metadata_get_nr_blocks,
541 	.get_nr_free = sm_metadata_get_nr_free,
542 	.get_count = sm_metadata_get_count,
543 	.count_is_more_than_one = sm_metadata_count_is_more_than_one,
544 	.set_count = sm_metadata_set_count,
545 	.inc_block = sm_metadata_inc_block,
546 	.dec_block = sm_metadata_dec_block,
547 	.new_block = sm_metadata_new_block,
548 	.commit = sm_metadata_commit,
549 	.root_size = sm_metadata_root_size,
550 	.copy_root = sm_metadata_copy_root,
551 	.register_threshold_callback = sm_metadata_register_threshold_callback
552 };
553 
554 /*----------------------------------------------------------------*/
555 
556 /*
557  * When a new space map is created that manages its own space.  We use
558  * this tiny bootstrap allocator.
559  */
560 static void sm_bootstrap_destroy(struct dm_space_map *sm)
561 {
562 }
563 
564 static int sm_bootstrap_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
565 {
566 	DMERR("bootstrap doesn't support extend");
567 
568 	return -EINVAL;
569 }
570 
571 static int sm_bootstrap_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
572 {
573 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
574 
575 	*count = smm->ll.nr_blocks;
576 
577 	return 0;
578 }
579 
580 static int sm_bootstrap_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
581 {
582 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
583 
584 	*count = smm->ll.nr_blocks - smm->begin;
585 
586 	return 0;
587 }
588 
589 static int sm_bootstrap_get_count(struct dm_space_map *sm, dm_block_t b,
590 				  uint32_t *result)
591 {
592 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
593 
594 	*result = (b < smm->begin) ? 1 : 0;
595 
596 	return 0;
597 }
598 
599 static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
600 					       dm_block_t b, int *result)
601 {
602 	*result = 0;
603 
604 	return 0;
605 }
606 
607 static int sm_bootstrap_set_count(struct dm_space_map *sm, dm_block_t b,
608 				  uint32_t count)
609 {
610 	DMERR("bootstrap doesn't support set_count");
611 
612 	return -EINVAL;
613 }
614 
615 static int sm_bootstrap_new_block(struct dm_space_map *sm, dm_block_t *b)
616 {
617 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
618 
619 	/*
620 	 * We know the entire device is unused.
621 	 */
622 	if (smm->begin == smm->ll.nr_blocks)
623 		return -ENOSPC;
624 
625 	*b = smm->begin++;
626 
627 	return 0;
628 }
629 
630 static int sm_bootstrap_inc_block(struct dm_space_map *sm, dm_block_t b)
631 {
632 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
633 
634 	return add_bop(smm, BOP_INC, b);
635 }
636 
637 static int sm_bootstrap_dec_block(struct dm_space_map *sm, dm_block_t b)
638 {
639 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
640 
641 	return add_bop(smm, BOP_DEC, b);
642 }
643 
644 static int sm_bootstrap_commit(struct dm_space_map *sm)
645 {
646 	return 0;
647 }
648 
649 static int sm_bootstrap_root_size(struct dm_space_map *sm, size_t *result)
650 {
651 	DMERR("bootstrap doesn't support root_size");
652 
653 	return -EINVAL;
654 }
655 
656 static int sm_bootstrap_copy_root(struct dm_space_map *sm, void *where,
657 				  size_t max)
658 {
659 	DMERR("bootstrap doesn't support copy_root");
660 
661 	return -EINVAL;
662 }
663 
664 static struct dm_space_map bootstrap_ops = {
665 	.destroy = sm_bootstrap_destroy,
666 	.extend = sm_bootstrap_extend,
667 	.get_nr_blocks = sm_bootstrap_get_nr_blocks,
668 	.get_nr_free = sm_bootstrap_get_nr_free,
669 	.get_count = sm_bootstrap_get_count,
670 	.count_is_more_than_one = sm_bootstrap_count_is_more_than_one,
671 	.set_count = sm_bootstrap_set_count,
672 	.inc_block = sm_bootstrap_inc_block,
673 	.dec_block = sm_bootstrap_dec_block,
674 	.new_block = sm_bootstrap_new_block,
675 	.commit = sm_bootstrap_commit,
676 	.root_size = sm_bootstrap_root_size,
677 	.copy_root = sm_bootstrap_copy_root,
678 	.register_threshold_callback = NULL
679 };
680 
681 /*----------------------------------------------------------------*/
682 
683 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
684 {
685 	int r, i;
686 	enum allocation_event ev;
687 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
688 	dm_block_t old_len = smm->ll.nr_blocks;
689 
690 	/*
691 	 * Flick into a mode where all blocks get allocated in the new area.
692 	 */
693 	smm->begin = old_len;
694 	memcpy(sm, &bootstrap_ops, sizeof(*sm));
695 
696 	/*
697 	 * Extend.
698 	 */
699 	r = sm_ll_extend(&smm->ll, extra_blocks);
700 	if (r)
701 		goto out;
702 
703 	/*
704 	 * We repeatedly increment then commit until the commit doesn't
705 	 * allocate any new blocks.
706 	 */
707 	do {
708 		for (i = old_len; !r && i < smm->begin; i++) {
709 			r = sm_ll_inc(&smm->ll, i, &ev);
710 			if (r)
711 				goto out;
712 		}
713 		old_len = smm->begin;
714 
715 		r = apply_bops(smm);
716 		if (r) {
717 			DMERR("%s: apply_bops failed", __func__);
718 			goto out;
719 		}
720 
721 		r = sm_ll_commit(&smm->ll);
722 		if (r)
723 			goto out;
724 
725 	} while (old_len != smm->begin);
726 
727 out:
728 	/*
729 	 * Switch back to normal behaviour.
730 	 */
731 	memcpy(sm, &ops, sizeof(*sm));
732 	return r;
733 }
734 
735 /*----------------------------------------------------------------*/
736 
737 struct dm_space_map *dm_sm_metadata_init(void)
738 {
739 	struct sm_metadata *smm;
740 
741 	smm = kmalloc(sizeof(*smm), GFP_KERNEL);
742 	if (!smm)
743 		return ERR_PTR(-ENOMEM);
744 
745 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
746 
747 	return &smm->sm;
748 }
749 
750 int dm_sm_metadata_create(struct dm_space_map *sm,
751 			  struct dm_transaction_manager *tm,
752 			  dm_block_t nr_blocks,
753 			  dm_block_t superblock)
754 {
755 	int r;
756 	dm_block_t i;
757 	enum allocation_event ev;
758 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
759 
760 	smm->begin = superblock + 1;
761 	smm->recursion_count = 0;
762 	smm->allocated_this_transaction = 0;
763 	brb_init(&smm->uncommitted);
764 	threshold_init(&smm->threshold);
765 
766 	memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
767 
768 	r = sm_ll_new_metadata(&smm->ll, tm);
769 	if (r)
770 		return r;
771 
772 	if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
773 		nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
774 	r = sm_ll_extend(&smm->ll, nr_blocks);
775 	if (r)
776 		return r;
777 
778 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
779 
780 	/*
781 	 * Now we need to update the newly created data structures with the
782 	 * allocated blocks that they were built from.
783 	 */
784 	for (i = superblock; !r && i < smm->begin; i++)
785 		r = sm_ll_inc(&smm->ll, i, &ev);
786 
787 	if (r)
788 		return r;
789 
790 	r = apply_bops(smm);
791 	if (r) {
792 		DMERR("%s: apply_bops failed", __func__);
793 		return r;
794 	}
795 
796 	return sm_metadata_commit(sm);
797 }
798 
799 int dm_sm_metadata_open(struct dm_space_map *sm,
800 			struct dm_transaction_manager *tm,
801 			void *root_le, size_t len)
802 {
803 	int r;
804 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
805 
806 	r = sm_ll_open_metadata(&smm->ll, tm, root_le, len);
807 	if (r)
808 		return r;
809 
810 	smm->begin = 0;
811 	smm->recursion_count = 0;
812 	smm->allocated_this_transaction = 0;
813 	brb_init(&smm->uncommitted);
814 	threshold_init(&smm->threshold);
815 
816 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
817 	return 0;
818 }
819