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_peek(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 	return 0;
151 }
152 
153 static int brb_pop(struct bop_ring_buffer *brb)
154 {
155 	if (brb_empty(brb))
156 		return -ENODATA;
157 
158 	brb->begin = brb_next(brb, brb->begin);
159 
160 	return 0;
161 }
162 
163 /*----------------------------------------------------------------*/
164 
165 struct sm_metadata {
166 	struct dm_space_map sm;
167 
168 	struct ll_disk ll;
169 	struct ll_disk old_ll;
170 
171 	dm_block_t begin;
172 
173 	unsigned recursion_count;
174 	unsigned allocated_this_transaction;
175 	struct bop_ring_buffer uncommitted;
176 
177 	struct threshold threshold;
178 };
179 
180 static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
181 {
182 	int r = brb_push(&smm->uncommitted, type, b);
183 
184 	if (r) {
185 		DMERR("too many recursive allocations");
186 		return -ENOMEM;
187 	}
188 
189 	return 0;
190 }
191 
192 static int commit_bop(struct sm_metadata *smm, struct block_op *op)
193 {
194 	int r = 0;
195 	enum allocation_event ev;
196 
197 	switch (op->type) {
198 	case BOP_INC:
199 		r = sm_ll_inc(&smm->ll, op->block, &ev);
200 		break;
201 
202 	case BOP_DEC:
203 		r = sm_ll_dec(&smm->ll, op->block, &ev);
204 		break;
205 	}
206 
207 	return r;
208 }
209 
210 static void in(struct sm_metadata *smm)
211 {
212 	smm->recursion_count++;
213 }
214 
215 static int apply_bops(struct sm_metadata *smm)
216 {
217 	int r = 0;
218 
219 	while (!brb_empty(&smm->uncommitted)) {
220 		struct block_op bop;
221 
222 		r = brb_peek(&smm->uncommitted, &bop);
223 		if (r) {
224 			DMERR("bug in bop ring buffer");
225 			break;
226 		}
227 
228 		r = commit_bop(smm, &bop);
229 		if (r)
230 			break;
231 
232 		brb_pop(&smm->uncommitted);
233 	}
234 
235 	return r;
236 }
237 
238 static int out(struct sm_metadata *smm)
239 {
240 	int r = 0;
241 
242 	/*
243 	 * If we're not recursing then very bad things are happening.
244 	 */
245 	if (!smm->recursion_count) {
246 		DMERR("lost track of recursion depth");
247 		return -ENOMEM;
248 	}
249 
250 	if (smm->recursion_count == 1)
251 		apply_bops(smm);
252 
253 	smm->recursion_count--;
254 
255 	return r;
256 }
257 
258 /*
259  * When using the out() function above, we often want to combine an error
260  * code for the operation run in the recursive context with that from
261  * out().
262  */
263 static int combine_errors(int r1, int r2)
264 {
265 	return r1 ? r1 : r2;
266 }
267 
268 static int recursing(struct sm_metadata *smm)
269 {
270 	return smm->recursion_count;
271 }
272 
273 static void sm_metadata_destroy(struct dm_space_map *sm)
274 {
275 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
276 
277 	kfree(smm);
278 }
279 
280 static int sm_metadata_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
281 {
282 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
283 
284 	*count = smm->ll.nr_blocks;
285 
286 	return 0;
287 }
288 
289 static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
290 {
291 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
292 
293 	*count = smm->old_ll.nr_blocks - smm->old_ll.nr_allocated -
294 		 smm->allocated_this_transaction;
295 
296 	return 0;
297 }
298 
299 static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
300 				 uint32_t *result)
301 {
302 	int r;
303 	unsigned i;
304 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
305 	unsigned adjustment = 0;
306 
307 	/*
308 	 * We may have some uncommitted adjustments to add.  This list
309 	 * should always be really short.
310 	 */
311 	for (i = smm->uncommitted.begin;
312 	     i != smm->uncommitted.end;
313 	     i = brb_next(&smm->uncommitted, i)) {
314 		struct block_op *op = smm->uncommitted.bops + i;
315 
316 		if (op->block != b)
317 			continue;
318 
319 		switch (op->type) {
320 		case BOP_INC:
321 			adjustment++;
322 			break;
323 
324 		case BOP_DEC:
325 			adjustment--;
326 			break;
327 		}
328 	}
329 
330 	r = sm_ll_lookup(&smm->ll, b, result);
331 	if (r)
332 		return r;
333 
334 	*result += adjustment;
335 
336 	return 0;
337 }
338 
339 static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
340 					      dm_block_t b, int *result)
341 {
342 	int r, adjustment = 0;
343 	unsigned i;
344 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
345 	uint32_t rc;
346 
347 	/*
348 	 * We may have some uncommitted adjustments to add.  This list
349 	 * should always be really short.
350 	 */
351 	for (i = smm->uncommitted.begin;
352 	     i != smm->uncommitted.end;
353 	     i = brb_next(&smm->uncommitted, i)) {
354 
355 		struct block_op *op = smm->uncommitted.bops + i;
356 
357 		if (op->block != b)
358 			continue;
359 
360 		switch (op->type) {
361 		case BOP_INC:
362 			adjustment++;
363 			break;
364 
365 		case BOP_DEC:
366 			adjustment--;
367 			break;
368 		}
369 	}
370 
371 	if (adjustment > 1) {
372 		*result = 1;
373 		return 0;
374 	}
375 
376 	r = sm_ll_lookup_bitmap(&smm->ll, b, &rc);
377 	if (r)
378 		return r;
379 
380 	if (rc == 3)
381 		/*
382 		 * We err on the side of caution, and always return true.
383 		 */
384 		*result = 1;
385 	else
386 		*result = rc + adjustment > 1;
387 
388 	return 0;
389 }
390 
391 static int sm_metadata_set_count(struct dm_space_map *sm, dm_block_t b,
392 				 uint32_t count)
393 {
394 	int r, r2;
395 	enum allocation_event ev;
396 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
397 
398 	if (smm->recursion_count) {
399 		DMERR("cannot recurse set_count()");
400 		return -EINVAL;
401 	}
402 
403 	in(smm);
404 	r = sm_ll_insert(&smm->ll, b, count, &ev);
405 	r2 = out(smm);
406 
407 	return combine_errors(r, r2);
408 }
409 
410 static int sm_metadata_inc_block(struct dm_space_map *sm, dm_block_t b)
411 {
412 	int r, r2 = 0;
413 	enum allocation_event ev;
414 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
415 
416 	if (recursing(smm))
417 		r = add_bop(smm, BOP_INC, b);
418 	else {
419 		in(smm);
420 		r = sm_ll_inc(&smm->ll, b, &ev);
421 		r2 = out(smm);
422 	}
423 
424 	return combine_errors(r, r2);
425 }
426 
427 static int sm_metadata_dec_block(struct dm_space_map *sm, dm_block_t b)
428 {
429 	int r, r2 = 0;
430 	enum allocation_event ev;
431 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
432 
433 	if (recursing(smm))
434 		r = add_bop(smm, BOP_DEC, b);
435 	else {
436 		in(smm);
437 		r = sm_ll_dec(&smm->ll, b, &ev);
438 		r2 = out(smm);
439 	}
440 
441 	return combine_errors(r, r2);
442 }
443 
444 static int sm_metadata_new_block_(struct dm_space_map *sm, dm_block_t *b)
445 {
446 	int r, r2 = 0;
447 	enum allocation_event ev;
448 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
449 
450 	r = sm_ll_find_free_block(&smm->old_ll, smm->begin, smm->old_ll.nr_blocks, b);
451 	if (r)
452 		return r;
453 
454 	smm->begin = *b + 1;
455 
456 	if (recursing(smm))
457 		r = add_bop(smm, BOP_INC, *b);
458 	else {
459 		in(smm);
460 		r = sm_ll_inc(&smm->ll, *b, &ev);
461 		r2 = out(smm);
462 	}
463 
464 	if (!r)
465 		smm->allocated_this_transaction++;
466 
467 	return combine_errors(r, r2);
468 }
469 
470 static int sm_metadata_new_block(struct dm_space_map *sm, dm_block_t *b)
471 {
472 	dm_block_t count;
473 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
474 
475 	int r = sm_metadata_new_block_(sm, b);
476 	if (r) {
477 		DMERR_LIMIT("unable to allocate new metadata block");
478 		return r;
479 	}
480 
481 	r = sm_metadata_get_nr_free(sm, &count);
482 	if (r) {
483 		DMERR_LIMIT("couldn't get free block count");
484 		return r;
485 	}
486 
487 	check_threshold(&smm->threshold, count);
488 
489 	return r;
490 }
491 
492 static int sm_metadata_commit(struct dm_space_map *sm)
493 {
494 	int r;
495 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
496 
497 	r = sm_ll_commit(&smm->ll);
498 	if (r)
499 		return r;
500 
501 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
502 	smm->begin = 0;
503 	smm->allocated_this_transaction = 0;
504 
505 	return 0;
506 }
507 
508 static int sm_metadata_register_threshold_callback(struct dm_space_map *sm,
509 						   dm_block_t threshold,
510 						   dm_sm_threshold_fn fn,
511 						   void *context)
512 {
513 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
514 
515 	set_threshold(&smm->threshold, threshold, fn, context);
516 
517 	return 0;
518 }
519 
520 static int sm_metadata_root_size(struct dm_space_map *sm, size_t *result)
521 {
522 	*result = sizeof(struct disk_sm_root);
523 
524 	return 0;
525 }
526 
527 static int sm_metadata_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
528 {
529 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
530 	struct disk_sm_root root_le;
531 
532 	root_le.nr_blocks = cpu_to_le64(smm->ll.nr_blocks);
533 	root_le.nr_allocated = cpu_to_le64(smm->ll.nr_allocated);
534 	root_le.bitmap_root = cpu_to_le64(smm->ll.bitmap_root);
535 	root_le.ref_count_root = cpu_to_le64(smm->ll.ref_count_root);
536 
537 	if (max < sizeof(root_le))
538 		return -ENOSPC;
539 
540 	memcpy(where_le, &root_le, sizeof(root_le));
541 
542 	return 0;
543 }
544 
545 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks);
546 
547 static struct dm_space_map ops = {
548 	.destroy = sm_metadata_destroy,
549 	.extend = sm_metadata_extend,
550 	.get_nr_blocks = sm_metadata_get_nr_blocks,
551 	.get_nr_free = sm_metadata_get_nr_free,
552 	.get_count = sm_metadata_get_count,
553 	.count_is_more_than_one = sm_metadata_count_is_more_than_one,
554 	.set_count = sm_metadata_set_count,
555 	.inc_block = sm_metadata_inc_block,
556 	.dec_block = sm_metadata_dec_block,
557 	.new_block = sm_metadata_new_block,
558 	.commit = sm_metadata_commit,
559 	.root_size = sm_metadata_root_size,
560 	.copy_root = sm_metadata_copy_root,
561 	.register_threshold_callback = sm_metadata_register_threshold_callback
562 };
563 
564 /*----------------------------------------------------------------*/
565 
566 /*
567  * When a new space map is created that manages its own space.  We use
568  * this tiny bootstrap allocator.
569  */
570 static void sm_bootstrap_destroy(struct dm_space_map *sm)
571 {
572 }
573 
574 static int sm_bootstrap_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
575 {
576 	DMERR("bootstrap doesn't support extend");
577 
578 	return -EINVAL;
579 }
580 
581 static int sm_bootstrap_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
582 {
583 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
584 
585 	*count = smm->ll.nr_blocks;
586 
587 	return 0;
588 }
589 
590 static int sm_bootstrap_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
591 {
592 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
593 
594 	*count = smm->ll.nr_blocks - smm->begin;
595 
596 	return 0;
597 }
598 
599 static int sm_bootstrap_get_count(struct dm_space_map *sm, dm_block_t b,
600 				  uint32_t *result)
601 {
602 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
603 
604 	*result = (b < smm->begin) ? 1 : 0;
605 
606 	return 0;
607 }
608 
609 static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
610 					       dm_block_t b, int *result)
611 {
612 	*result = 0;
613 
614 	return 0;
615 }
616 
617 static int sm_bootstrap_set_count(struct dm_space_map *sm, dm_block_t b,
618 				  uint32_t count)
619 {
620 	DMERR("bootstrap doesn't support set_count");
621 
622 	return -EINVAL;
623 }
624 
625 static int sm_bootstrap_new_block(struct dm_space_map *sm, dm_block_t *b)
626 {
627 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
628 
629 	/*
630 	 * We know the entire device is unused.
631 	 */
632 	if (smm->begin == smm->ll.nr_blocks)
633 		return -ENOSPC;
634 
635 	*b = smm->begin++;
636 
637 	return 0;
638 }
639 
640 static int sm_bootstrap_inc_block(struct dm_space_map *sm, dm_block_t b)
641 {
642 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
643 
644 	return add_bop(smm, BOP_INC, b);
645 }
646 
647 static int sm_bootstrap_dec_block(struct dm_space_map *sm, dm_block_t b)
648 {
649 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
650 
651 	return add_bop(smm, BOP_DEC, b);
652 }
653 
654 static int sm_bootstrap_commit(struct dm_space_map *sm)
655 {
656 	return 0;
657 }
658 
659 static int sm_bootstrap_root_size(struct dm_space_map *sm, size_t *result)
660 {
661 	DMERR("bootstrap doesn't support root_size");
662 
663 	return -EINVAL;
664 }
665 
666 static int sm_bootstrap_copy_root(struct dm_space_map *sm, void *where,
667 				  size_t max)
668 {
669 	DMERR("bootstrap doesn't support copy_root");
670 
671 	return -EINVAL;
672 }
673 
674 static struct dm_space_map bootstrap_ops = {
675 	.destroy = sm_bootstrap_destroy,
676 	.extend = sm_bootstrap_extend,
677 	.get_nr_blocks = sm_bootstrap_get_nr_blocks,
678 	.get_nr_free = sm_bootstrap_get_nr_free,
679 	.get_count = sm_bootstrap_get_count,
680 	.count_is_more_than_one = sm_bootstrap_count_is_more_than_one,
681 	.set_count = sm_bootstrap_set_count,
682 	.inc_block = sm_bootstrap_inc_block,
683 	.dec_block = sm_bootstrap_dec_block,
684 	.new_block = sm_bootstrap_new_block,
685 	.commit = sm_bootstrap_commit,
686 	.root_size = sm_bootstrap_root_size,
687 	.copy_root = sm_bootstrap_copy_root,
688 	.register_threshold_callback = NULL
689 };
690 
691 /*----------------------------------------------------------------*/
692 
693 static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
694 {
695 	int r, i;
696 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
697 	dm_block_t old_len = smm->ll.nr_blocks;
698 
699 	/*
700 	 * Flick into a mode where all blocks get allocated in the new area.
701 	 */
702 	smm->begin = old_len;
703 	memcpy(sm, &bootstrap_ops, sizeof(*sm));
704 
705 	/*
706 	 * Extend.
707 	 */
708 	r = sm_ll_extend(&smm->ll, extra_blocks);
709 	if (r)
710 		goto out;
711 
712 	/*
713 	 * We repeatedly increment then commit until the commit doesn't
714 	 * allocate any new blocks.
715 	 */
716 	do {
717 		for (i = old_len; !r && i < smm->begin; i++)
718 			r = add_bop(smm, BOP_INC, i);
719 
720 		if (r)
721 			goto out;
722 
723 		old_len = smm->begin;
724 
725 		r = apply_bops(smm);
726 		if (r) {
727 			DMERR("%s: apply_bops failed", __func__);
728 			goto out;
729 		}
730 
731 		r = sm_ll_commit(&smm->ll);
732 		if (r)
733 			goto out;
734 
735 	} while (old_len != smm->begin);
736 
737 out:
738 	/*
739 	 * Switch back to normal behaviour.
740 	 */
741 	memcpy(sm, &ops, sizeof(*sm));
742 	return r;
743 }
744 
745 /*----------------------------------------------------------------*/
746 
747 struct dm_space_map *dm_sm_metadata_init(void)
748 {
749 	struct sm_metadata *smm;
750 
751 	smm = kmalloc(sizeof(*smm), GFP_KERNEL);
752 	if (!smm)
753 		return ERR_PTR(-ENOMEM);
754 
755 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
756 
757 	return &smm->sm;
758 }
759 
760 int dm_sm_metadata_create(struct dm_space_map *sm,
761 			  struct dm_transaction_manager *tm,
762 			  dm_block_t nr_blocks,
763 			  dm_block_t superblock)
764 {
765 	int r;
766 	dm_block_t i;
767 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
768 
769 	smm->begin = superblock + 1;
770 	smm->recursion_count = 0;
771 	smm->allocated_this_transaction = 0;
772 	brb_init(&smm->uncommitted);
773 	threshold_init(&smm->threshold);
774 
775 	memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
776 
777 	r = sm_ll_new_metadata(&smm->ll, tm);
778 	if (r)
779 		return r;
780 
781 	if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
782 		nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
783 	r = sm_ll_extend(&smm->ll, nr_blocks);
784 	if (r)
785 		return r;
786 
787 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
788 
789 	/*
790 	 * Now we need to update the newly created data structures with the
791 	 * allocated blocks that they were built from.
792 	 */
793 	for (i = superblock; !r && i < smm->begin; i++)
794 		r = add_bop(smm, BOP_INC, i);
795 
796 	if (r)
797 		return r;
798 
799 	r = apply_bops(smm);
800 	if (r) {
801 		DMERR("%s: apply_bops failed", __func__);
802 		return r;
803 	}
804 
805 	return sm_metadata_commit(sm);
806 }
807 
808 int dm_sm_metadata_open(struct dm_space_map *sm,
809 			struct dm_transaction_manager *tm,
810 			void *root_le, size_t len)
811 {
812 	int r;
813 	struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
814 
815 	r = sm_ll_open_metadata(&smm->ll, tm, root_le, len);
816 	if (r)
817 		return r;
818 
819 	smm->begin = 0;
820 	smm->recursion_count = 0;
821 	smm->allocated_this_transaction = 0;
822 	brb_init(&smm->uncommitted);
823 	threshold_init(&smm->threshold);
824 
825 	memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
826 	return 0;
827 }
828