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 #include <linux/kernel.h>
15 
16 #define DM_MSG_PREFIX "space map metadata"
17 
18 /*----------------------------------------------------------------*/
19 
20 /*
21  * An edge triggered threshold.
22  */
23 struct threshold {
24 	bool threshold_set;
25 	bool value_set;
26 	dm_block_t threshold;
27 	dm_block_t current_value;
28 	dm_sm_threshold_fn fn;
29 	void *context;
30 };
31 
32 static void threshold_init(struct threshold *t)
33 {
34 	t->threshold_set = false;
35 	t->value_set = false;
36 }
37 
38 static void set_threshold(struct threshold *t, dm_block_t value,
39 			  dm_sm_threshold_fn fn, void *context)
40 {
41 	t->threshold_set = true;
42 	t->threshold = value;
43 	t->fn = fn;
44 	t->context = context;
45 }
46 
47 static bool below_threshold(struct threshold *t, dm_block_t value)
48 {
49 	return t->threshold_set && value <= t->threshold;
50 }
51 
52 static bool threshold_already_triggered(struct threshold *t)
53 {
54 	return t->value_set && below_threshold(t, t->current_value);
55 }
56 
57 static void check_threshold(struct threshold *t, dm_block_t value)
58 {
59 	if (below_threshold(t, value) &&
60 	    !threshold_already_triggered(t))
61 		t->fn(t->context);
62 
63 	t->value_set = true;
64 	t->current_value = value;
65 }
66 
67 /*----------------------------------------------------------------*/
68 
69 /*
70  * Space map interface.
71  *
72  * The low level disk format is written using the standard btree and
73  * transaction manager.  This means that performing disk operations may
74  * cause us to recurse into the space map in order to allocate new blocks.
75  * For this reason we have a pool of pre-allocated blocks large enough to
76  * service any metadata_ll_disk operation.
77  */
78 
79 /*
80  * FIXME: we should calculate this based on the size of the device.
81  * Only the metadata space map needs this functionality.
82  */
83 #define MAX_RECURSIVE_ALLOCATIONS 1024
84 
85 enum block_op_type {
86 	BOP_INC,
87 	BOP_DEC
88 };
89 
90 struct block_op {
91 	enum block_op_type type;
92 	dm_block_t block;
93 };
94 
95 struct bop_ring_buffer {
96 	unsigned begin;
97 	unsigned end;
98 	struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
99 };
100 
101 static void brb_init(struct bop_ring_buffer *brb)
102 {
103 	brb->begin = 0;
104 	brb->end = 0;
105 }
106 
107 static bool brb_empty(struct bop_ring_buffer *brb)
108 {
109 	return brb->begin == brb->end;
110 }
111 
112 static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
113 {
114 	unsigned r = old + 1;
115 	return r >= ARRAY_SIZE(brb->bops) ? 0 : r;
116 }
117 
118 static int brb_push(struct bop_ring_buffer *brb,
119 		    enum block_op_type type, dm_block_t b)
120 {
121 	struct block_op *bop;
122 	unsigned next = brb_next(brb, brb->end);
123 
124 	/*
125 	 * We don't allow the last bop to be filled, this way we can
126 	 * differentiate between full and empty.
127 	 */
128 	if (next == brb->begin)
129 		return -ENOMEM;
130 
131 	bop = brb->bops + brb->end;
132 	bop->type = type;
133 	bop->block = b;
134 
135 	brb->end = next;
136 
137 	return 0;
138 }
139 
140 static int brb_peek(struct bop_ring_buffer *brb, struct block_op *result)
141 {
142 	struct block_op *bop;
143 
144 	if (brb_empty(brb))
145 		return -ENODATA;
146 
147 	bop = brb->bops + brb->begin;
148 	result->type = bop->type;
149 	result->block = bop->block;
150 
151 	return 0;
152 }
153 
154 static int brb_pop(struct bop_ring_buffer *brb)
155 {
156 	if (brb_empty(brb))
157 		return -ENODATA;
158 
159 	brb->begin = brb_next(brb, brb->begin);
160 
161 	return 0;
162 }
163 
164 /*----------------------------------------------------------------*/
165 
166 struct sm_metadata {
167 	struct dm_space_map sm;
168 
169 	struct ll_disk ll;
170 	struct ll_disk old_ll;
171 
172 	dm_block_t begin;
173 
174 	unsigned recursion_count;
175 	unsigned allocated_this_transaction;
176 	struct bop_ring_buffer uncommitted;
177 
178 	struct threshold threshold;
179 };
180 
181 static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
182 {
183 	int r = brb_push(&smm->uncommitted, type, b);
184 
185 	if (r) {
186 		DMERR("too many recursive allocations");
187 		return -ENOMEM;
188 	}
189 
190 	return 0;
191 }
192 
193 static int commit_bop(struct sm_metadata *smm, struct block_op *op)
194 {
195 	int r = 0;
196 	enum allocation_event ev;
197 
198 	switch (op->type) {
199 	case BOP_INC:
200 		r = sm_ll_inc(&smm->ll, op->block, &ev);
201 		break;
202 
203 	case BOP_DEC:
204 		r = sm_ll_dec(&smm->ll, op->block, &ev);
205 		break;
206 	}
207 
208 	return r;
209 }
210 
211 static void in(struct sm_metadata *smm)
212 {
213 	smm->recursion_count++;
214 }
215 
216 static int apply_bops(struct sm_metadata *smm)
217 {
218 	int r = 0;
219 
220 	while (!brb_empty(&smm->uncommitted)) {
221 		struct block_op bop;
222 
223 		r = brb_peek(&smm->uncommitted, &bop);
224 		if (r) {
225 			DMERR("bug in bop ring buffer");
226 			break;
227 		}
228 
229 		r = commit_bop(smm, &bop);
230 		if (r)
231 			break;
232 
233 		brb_pop(&smm->uncommitted);
234 	}
235 
236 	return r;
237 }
238 
239 static int out(struct sm_metadata *smm)
240 {
241 	int r = 0;
242 
243 	/*
244 	 * If we're not recursing then very bad things are happening.
245 	 */
246 	if (!smm->recursion_count) {
247 		DMERR("lost track of recursion depth");
248 		return -ENOMEM;
249 	}
250 
251 	if (smm->recursion_count == 1)
252 		apply_bops(smm);
253 
254 	smm->recursion_count--;
255 
256 	return r;
257 }
258 
259 /*
260  * When using the out() function above, we often want to combine an error
261  * code for the operation run in the recursive context with that from
262  * out().
263  */
264 static int combine_errors(int r1, int r2)
265 {
266 	return r1 ? r1 : r2;
267 }
268 
269 static int recursing(struct sm_metadata *smm)
270 {
271 	return smm->recursion_count;
272 }
273 
274 static void sm_metadata_destroy(struct dm_space_map *sm)
275 {
276 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
277 
278 	kfree(smm);
279 }
280 
281 static int sm_metadata_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
282 {
283 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
284 
285 	*count = smm->ll.nr_blocks;
286 
287 	return 0;
288 }
289 
290 static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
291 {
292 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
293 
294 	*count = smm->old_ll.nr_blocks - smm->old_ll.nr_allocated -
295 		 smm->allocated_this_transaction;
296 
297 	return 0;
298 }
299 
300 static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
301 				 uint32_t *result)
302 {
303 	int r;
304 	unsigned i;
305 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
306 	unsigned adjustment = 0;
307 
308 	/*
309 	 * We may have some uncommitted adjustments to add.  This list
310 	 * should always be really short.
311 	 */
312 	for (i = smm->uncommitted.begin;
313 	     i != smm->uncommitted.end;
314 	     i = brb_next(&smm->uncommitted, i)) {
315 		struct block_op *op = smm->uncommitted.bops + i;
316 
317 		if (op->block != b)
318 			continue;
319 
320 		switch (op->type) {
321 		case BOP_INC:
322 			adjustment++;
323 			break;
324 
325 		case BOP_DEC:
326 			adjustment--;
327 			break;
328 		}
329 	}
330 
331 	r = sm_ll_lookup(&smm->ll, b, result);
332 	if (r)
333 		return r;
334 
335 	*result += adjustment;
336 
337 	return 0;
338 }
339 
340 static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
341 					      dm_block_t b, int *result)
342 {
343 	int r, adjustment = 0;
344 	unsigned i;
345 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
346 	uint32_t rc;
347 
348 	/*
349 	 * We may have some uncommitted adjustments to add.  This list
350 	 * should always be really short.
351 	 */
352 	for (i = smm->uncommitted.begin;
353 	     i != smm->uncommitted.end;
354 	     i = brb_next(&smm->uncommitted, i)) {
355 
356 		struct block_op *op = smm->uncommitted.bops + i;
357 
358 		if (op->block != b)
359 			continue;
360 
361 		switch (op->type) {
362 		case BOP_INC:
363 			adjustment++;
364 			break;
365 
366 		case BOP_DEC:
367 			adjustment--;
368 			break;
369 		}
370 	}
371 
372 	if (adjustment > 1) {
373 		*result = 1;
374 		return 0;
375 	}
376 
377 	r = sm_ll_lookup_bitmap(&smm->ll, b, &rc);
378 	if (r)
379 		return r;
380 
381 	if (rc == 3)
382 		/*
383 		 * We err on the side of caution, and always return true.
384 		 */
385 		*result = 1;
386 	else
387 		*result = rc + adjustment > 1;
388 
389 	return 0;
390 }
391 
392 static int sm_metadata_set_count(struct dm_space_map *sm, dm_block_t b,
393 				 uint32_t count)
394 {
395 	int r, r2;
396 	enum allocation_event ev;
397 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
398 
399 	if (smm->recursion_count) {
400 		DMERR("cannot recurse set_count()");
401 		return -EINVAL;
402 	}
403 
404 	in(smm);
405 	r = sm_ll_insert(&smm->ll, b, count, &ev);
406 	r2 = out(smm);
407 
408 	return combine_errors(r, r2);
409 }
410 
411 static int sm_metadata_inc_block(struct dm_space_map *sm, dm_block_t b)
412 {
413 	int r, r2 = 0;
414 	enum allocation_event ev;
415 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
416 
417 	if (recursing(smm))
418 		r = add_bop(smm, BOP_INC, b);
419 	else {
420 		in(smm);
421 		r = sm_ll_inc(&smm->ll, b, &ev);
422 		r2 = out(smm);
423 	}
424 
425 	return combine_errors(r, r2);
426 }
427 
428 static int sm_metadata_dec_block(struct dm_space_map *sm, dm_block_t b)
429 {
430 	int r, r2 = 0;
431 	enum allocation_event ev;
432 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
433 
434 	if (recursing(smm))
435 		r = add_bop(smm, BOP_DEC, b);
436 	else {
437 		in(smm);
438 		r = sm_ll_dec(&smm->ll, b, &ev);
439 		r2 = out(smm);
440 	}
441 
442 	return combine_errors(r, r2);
443 }
444 
445 static int sm_metadata_new_block_(struct dm_space_map *sm, dm_block_t *b)
446 {
447 	int r, r2 = 0;
448 	enum allocation_event ev;
449 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
450 
451 	r = sm_ll_find_free_block(&smm->old_ll, smm->begin, smm->old_ll.nr_blocks, b);
452 	if (r)
453 		return r;
454 
455 	smm->begin = *b + 1;
456 
457 	if (recursing(smm))
458 		r = add_bop(smm, BOP_INC, *b);
459 	else {
460 		in(smm);
461 		r = sm_ll_inc(&smm->ll, *b, &ev);
462 		r2 = out(smm);
463 	}
464 
465 	if (!r)
466 		smm->allocated_this_transaction++;
467 
468 	return combine_errors(r, r2);
469 }
470 
471 static int sm_metadata_new_block(struct dm_space_map *sm, dm_block_t *b)
472 {
473 	dm_block_t count;
474 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
475 
476 	int r = sm_metadata_new_block_(sm, b);
477 	if (r) {
478 		DMERR_LIMIT("unable to allocate new metadata block");
479 		return r;
480 	}
481 
482 	r = sm_metadata_get_nr_free(sm, &count);
483 	if (r) {
484 		DMERR_LIMIT("couldn't get free block count");
485 		return r;
486 	}
487 
488 	check_threshold(&smm->threshold, count);
489 
490 	return r;
491 }
492 
493 static int sm_metadata_commit(struct dm_space_map *sm)
494 {
495 	int r;
496 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
497 
498 	r = sm_ll_commit(&smm->ll);
499 	if (r)
500 		return r;
501 
502 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
503 	smm->begin = 0;
504 	smm->allocated_this_transaction = 0;
505 
506 	return 0;
507 }
508 
509 static int sm_metadata_register_threshold_callback(struct dm_space_map *sm,
510 						   dm_block_t threshold,
511 						   dm_sm_threshold_fn fn,
512 						   void *context)
513 {
514 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
515 
516 	set_threshold(&smm->threshold, threshold, fn, context);
517 
518 	return 0;
519 }
520 
521 static int sm_metadata_root_size(struct dm_space_map *sm, size_t *result)
522 {
523 	*result = sizeof(struct disk_sm_root);
524 
525 	return 0;
526 }
527 
528 static int sm_metadata_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
529 {
530 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
531 	struct disk_sm_root root_le;
532 
533 	root_le.nr_blocks = cpu_to_le64(smm->ll.nr_blocks);
534 	root_le.nr_allocated = cpu_to_le64(smm->ll.nr_allocated);
535 	root_le.bitmap_root = cpu_to_le64(smm->ll.bitmap_root);
536 	root_le.ref_count_root = cpu_to_le64(smm->ll.ref_count_root);
537 
538 	if (max < sizeof(root_le))
539 		return -ENOSPC;
540 
541 	memcpy(where_le, &root_le, sizeof(root_le));
542 
543 	return 0;
544 }
545 
546 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks);
547 
548 static const struct dm_space_map ops = {
549 	.destroy = sm_metadata_destroy,
550 	.extend = sm_metadata_extend,
551 	.get_nr_blocks = sm_metadata_get_nr_blocks,
552 	.get_nr_free = sm_metadata_get_nr_free,
553 	.get_count = sm_metadata_get_count,
554 	.count_is_more_than_one = sm_metadata_count_is_more_than_one,
555 	.set_count = sm_metadata_set_count,
556 	.inc_block = sm_metadata_inc_block,
557 	.dec_block = sm_metadata_dec_block,
558 	.new_block = sm_metadata_new_block,
559 	.commit = sm_metadata_commit,
560 	.root_size = sm_metadata_root_size,
561 	.copy_root = sm_metadata_copy_root,
562 	.register_threshold_callback = sm_metadata_register_threshold_callback
563 };
564 
565 /*----------------------------------------------------------------*/
566 
567 /*
568  * When a new space map is created that manages its own space.  We use
569  * this tiny bootstrap allocator.
570  */
571 static void sm_bootstrap_destroy(struct dm_space_map *sm)
572 {
573 }
574 
575 static int sm_bootstrap_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
576 {
577 	DMERR("bootstrap doesn't support extend");
578 
579 	return -EINVAL;
580 }
581 
582 static int sm_bootstrap_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
583 {
584 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
585 
586 	*count = smm->ll.nr_blocks;
587 
588 	return 0;
589 }
590 
591 static int sm_bootstrap_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
592 {
593 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
594 
595 	*count = smm->ll.nr_blocks - smm->begin;
596 
597 	return 0;
598 }
599 
600 static int sm_bootstrap_get_count(struct dm_space_map *sm, dm_block_t b,
601 				  uint32_t *result)
602 {
603 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
604 
605 	*result = (b < smm->begin) ? 1 : 0;
606 
607 	return 0;
608 }
609 
610 static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
611 					       dm_block_t b, int *result)
612 {
613 	*result = 0;
614 
615 	return 0;
616 }
617 
618 static int sm_bootstrap_set_count(struct dm_space_map *sm, dm_block_t b,
619 				  uint32_t count)
620 {
621 	DMERR("bootstrap doesn't support set_count");
622 
623 	return -EINVAL;
624 }
625 
626 static int sm_bootstrap_new_block(struct dm_space_map *sm, dm_block_t *b)
627 {
628 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
629 
630 	/*
631 	 * We know the entire device is unused.
632 	 */
633 	if (smm->begin == smm->ll.nr_blocks)
634 		return -ENOSPC;
635 
636 	*b = smm->begin++;
637 
638 	return 0;
639 }
640 
641 static int sm_bootstrap_inc_block(struct dm_space_map *sm, dm_block_t b)
642 {
643 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
644 
645 	return add_bop(smm, BOP_INC, b);
646 }
647 
648 static int sm_bootstrap_dec_block(struct dm_space_map *sm, dm_block_t b)
649 {
650 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
651 
652 	return add_bop(smm, BOP_DEC, b);
653 }
654 
655 static int sm_bootstrap_commit(struct dm_space_map *sm)
656 {
657 	return 0;
658 }
659 
660 static int sm_bootstrap_root_size(struct dm_space_map *sm, size_t *result)
661 {
662 	DMERR("bootstrap doesn't support root_size");
663 
664 	return -EINVAL;
665 }
666 
667 static int sm_bootstrap_copy_root(struct dm_space_map *sm, void *where,
668 				  size_t max)
669 {
670 	DMERR("bootstrap doesn't support copy_root");
671 
672 	return -EINVAL;
673 }
674 
675 static const struct dm_space_map bootstrap_ops = {
676 	.destroy = sm_bootstrap_destroy,
677 	.extend = sm_bootstrap_extend,
678 	.get_nr_blocks = sm_bootstrap_get_nr_blocks,
679 	.get_nr_free = sm_bootstrap_get_nr_free,
680 	.get_count = sm_bootstrap_get_count,
681 	.count_is_more_than_one = sm_bootstrap_count_is_more_than_one,
682 	.set_count = sm_bootstrap_set_count,
683 	.inc_block = sm_bootstrap_inc_block,
684 	.dec_block = sm_bootstrap_dec_block,
685 	.new_block = sm_bootstrap_new_block,
686 	.commit = sm_bootstrap_commit,
687 	.root_size = sm_bootstrap_root_size,
688 	.copy_root = sm_bootstrap_copy_root,
689 	.register_threshold_callback = NULL
690 };
691 
692 /*----------------------------------------------------------------*/
693 
694 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
695 {
696 	int r, i;
697 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
698 	dm_block_t old_len = smm->ll.nr_blocks;
699 
700 	/*
701 	 * Flick into a mode where all blocks get allocated in the new area.
702 	 */
703 	smm->begin = old_len;
704 	memcpy(sm, &bootstrap_ops, sizeof(*sm));
705 
706 	/*
707 	 * Extend.
708 	 */
709 	r = sm_ll_extend(&smm->ll, extra_blocks);
710 	if (r)
711 		goto out;
712 
713 	/*
714 	 * We repeatedly increment then commit until the commit doesn't
715 	 * allocate any new blocks.
716 	 */
717 	do {
718 		for (i = old_len; !r && i < smm->begin; i++)
719 			r = add_bop(smm, BOP_INC, i);
720 
721 		if (r)
722 			goto out;
723 
724 		old_len = smm->begin;
725 
726 		r = apply_bops(smm);
727 		if (r) {
728 			DMERR("%s: apply_bops failed", __func__);
729 			goto out;
730 		}
731 
732 		r = sm_ll_commit(&smm->ll);
733 		if (r)
734 			goto out;
735 
736 	} while (old_len != smm->begin);
737 
738 out:
739 	/*
740 	 * Switch back to normal behaviour.
741 	 */
742 	memcpy(sm, &ops, sizeof(*sm));
743 	return r;
744 }
745 
746 /*----------------------------------------------------------------*/
747 
748 struct dm_space_map *dm_sm_metadata_init(void)
749 {
750 	struct sm_metadata *smm;
751 
752 	smm = kmalloc(sizeof(*smm), GFP_KERNEL);
753 	if (!smm)
754 		return ERR_PTR(-ENOMEM);
755 
756 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
757 
758 	return &smm->sm;
759 }
760 
761 int dm_sm_metadata_create(struct dm_space_map *sm,
762 			  struct dm_transaction_manager *tm,
763 			  dm_block_t nr_blocks,
764 			  dm_block_t superblock)
765 {
766 	int r;
767 	dm_block_t i;
768 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
769 
770 	smm->begin = superblock + 1;
771 	smm->recursion_count = 0;
772 	smm->allocated_this_transaction = 0;
773 	brb_init(&smm->uncommitted);
774 	threshold_init(&smm->threshold);
775 
776 	memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
777 
778 	r = sm_ll_new_metadata(&smm->ll, tm);
779 	if (!r) {
780 		if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
781 			nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
782 		r = sm_ll_extend(&smm->ll, nr_blocks);
783 	}
784 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
785 	if (r)
786 		return r;
787 
788 	/*
789 	 * Now we need to update the newly created data structures with the
790 	 * allocated blocks that they were built from.
791 	 */
792 	for (i = superblock; !r && i < smm->begin; i++)
793 		r = add_bop(smm, BOP_INC, i);
794 
795 	if (r)
796 		return r;
797 
798 	r = apply_bops(smm);
799 	if (r) {
800 		DMERR("%s: apply_bops failed", __func__);
801 		return r;
802 	}
803 
804 	return sm_metadata_commit(sm);
805 }
806 
807 int dm_sm_metadata_open(struct dm_space_map *sm,
808 			struct dm_transaction_manager *tm,
809 			void *root_le, size_t len)
810 {
811 	int r;
812 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
813 
814 	r = sm_ll_open_metadata(&smm->ll, tm, root_le, len);
815 	if (r)
816 		return r;
817 
818 	smm->begin = 0;
819 	smm->recursion_count = 0;
820 	smm->allocated_this_transaction = 0;
821 	brb_init(&smm->uncommitted);
822 	threshold_init(&smm->threshold);
823 
824 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
825 	return 0;
826 }
827