1	// SPDX-License-Identifier: GPL-2.0-only
2	/*
3	* Copyright (C) 2011 Red Hat, Inc.
4	*
5	* This file is released under the GPL.
6	*/
7
8	#include "dm-btree-internal.h"
9	#include "dm-space-map.h"
10	#include "dm-transaction-manager.h"
11
12	#include <linux/export.h>
13	#include <linux/device-mapper.h>
14
15	#define DM_MSG_PREFIX "btree"
16
17	/*
18	*--------------------------------------------------------------
19	* Array manipulation
20	*--------------------------------------------------------------
21	*/
22	static void memcpy_disk(void *dest, const void *src, size_t len)
23	__dm_written_to_disk(src)
24	{
25	memcpy(dest, src, len);
26	__dm_unbless_for_disk(src);
27	}
28
29	static void array_insert(void *base, size_t elt_size, unsigned int nr_elts,
30	unsigned int index, void *elt)
31	__dm_written_to_disk(elt)
32	{
33	if (index < nr_elts)
34	memmove(base + (elt_size * (index + 1)),
35	base + (elt_size * index),
36	(nr_elts - index) * elt_size);
37
38	memcpy_disk(dest: base + (elt_size * index), src: elt, len: elt_size);
39	}
40
41	/*----------------------------------------------------------------*/
42
43	/* makes the assumption that no two keys are the same. */
44	static int bsearch(struct btree_node *n, uint64_t key, int want_hi)
45	{
46	int lo = -1, hi = le32_to_cpu(n->header.nr_entries);
47
48	while (hi - lo > 1) {
49	int mid = lo + ((hi - lo) / 2);
50	uint64_t mid_key = le64_to_cpu(n->keys[mid]);
51
52	if (mid_key == key)
53	return mid;
54
55	if (mid_key < key)
56	lo = mid;
57	else
58	hi = mid;
59	}
60
61	return want_hi ? hi : lo;
62	}
63
64	int lower_bound(struct btree_node *n, uint64_t key)
65	{
66	return bsearch(n, key, want_hi: 0);
67	}
68
69	static int upper_bound(struct btree_node *n, uint64_t key)
70	{
71	return bsearch(n, key, want_hi: 1);
72	}
73
74	void inc_children(struct dm_transaction_manager *tm, struct btree_node *n,
75	struct dm_btree_value_type *vt)
76	{
77	uint32_t nr_entries = le32_to_cpu(n->header.nr_entries);
78
79	if (le32_to_cpu(n->header.flags) & INTERNAL_NODE)
80	dm_tm_with_runs(tm, value_le: value_ptr(n, index: 0), count: nr_entries, fn: dm_tm_inc_range);
81
82	else if (vt->inc)
83	vt->inc(vt->context, value_ptr(n, index: 0), nr_entries);
84	}
85
86	static int insert_at(size_t value_size, struct btree_node *node, unsigned int index,
87	uint64_t key, void *value)
88	__dm_written_to_disk(value)
89	{
90	uint32_t nr_entries = le32_to_cpu(node->header.nr_entries);
91	uint32_t max_entries = le32_to_cpu(node->header.max_entries);
92	__le64 key_le = cpu_to_le64(key);
93
94	if (index > nr_entries ||
95	index >= max_entries ||
96	nr_entries >= max_entries) {
97	DMERR("too many entries in btree node for insert");
98	__dm_unbless_for_disk(value);
99	return -ENOMEM;
100	}
101
102	__dm_bless_for_disk(&key_le);
103
104	array_insert(base: node->keys, elt_size: sizeof(*node->keys), nr_elts: nr_entries, index, elt: &key_le);
105	array_insert(base: value_base(n: node), elt_size: value_size, nr_elts: nr_entries, index, elt: value);
106	node->header.nr_entries = cpu_to_le32(nr_entries + 1);
107
108	return 0;
109	}
110
111	/*----------------------------------------------------------------*/
112
113	/*
114	* We want 3n entries (for some n). This works more nicely for repeated
115	* insert remove loops than (2n + 1).
116	*/
117	static uint32_t calc_max_entries(size_t value_size, size_t block_size)
118	{
119	uint32_t total, n;
120	size_t elt_size = sizeof(uint64_t) + value_size; /* key + value */
121
122	block_size -= sizeof(struct node_header);
123	total = block_size / elt_size;
124	n = total / 3; /* rounds down */
125
126	return 3 * n;
127	}
128
129	int dm_btree_empty(struct dm_btree_info *info, dm_block_t *root)
130	{
131	int r;
132	struct dm_block *b;
133	struct btree_node *n;
134	size_t block_size;
135	uint32_t max_entries;
136
137	r = new_block(info, result: &b);
138	if (r < 0)
139	return r;
140
141	block_size = dm_bm_block_size(bm: dm_tm_get_bm(tm: info->tm));
142	max_entries = calc_max_entries(value_size: info->value_type.size, block_size);
143
144	n = dm_block_data(b);
145	memset(n, 0, block_size);
146	n->header.flags = cpu_to_le32(LEAF_NODE);
147	n->header.nr_entries = cpu_to_le32(0);
148	n->header.max_entries = cpu_to_le32(max_entries);
149	n->header.value_size = cpu_to_le32(info->value_type.size);
150
151	*root = dm_block_location(b);
152	unlock_block(info, b);
153
154	return 0;
155	}
156	EXPORT_SYMBOL_GPL(dm_btree_empty);
157
158	/*----------------------------------------------------------------*/
159
160	/*
161	* Deletion uses a recursive algorithm, since we have limited stack space
162	* we explicitly manage our own stack on the heap.
163	*/
164	#define MAX_SPINE_DEPTH 64
165	struct frame {
166	struct dm_block *b;
167	struct btree_node *n;
168	unsigned int level;
169	unsigned int nr_children;
170	unsigned int current_child;
171	};
172
173	struct del_stack {
174	struct dm_btree_info *info;
175	struct dm_transaction_manager *tm;
176	int top;
177	struct frame spine[MAX_SPINE_DEPTH];
178	};
179
180	static int top_frame(struct del_stack *s, struct frame **f)
181	{
182	if (s->top < 0) {
183	DMERR("btree deletion stack empty");
184	return -EINVAL;
185	}
186
187	*f = s->spine + s->top;
188
189	return 0;
190	}
191
192	static int unprocessed_frames(struct del_stack *s)
193	{
194	return s->top >= 0;
195	}
196
197	static void prefetch_children(struct del_stack *s, struct frame *f)
198	{
199	unsigned int i;
200	struct dm_block_manager *bm = dm_tm_get_bm(tm: s->tm);
201
202	for (i = 0; i < f->nr_children; i++)
203	dm_bm_prefetch(bm, b: value64(n: f->n, index: i));
204	}
205
206	static bool is_internal_level(struct dm_btree_info *info, struct frame *f)
207	{
208	return f->level < (info->levels - 1);
209	}
210
211	static int push_frame(struct del_stack *s, dm_block_t b, unsigned int level)
212	{
213	int r;
214	uint32_t ref_count;
215
216	if (s->top >= MAX_SPINE_DEPTH - 1) {
217	DMERR("btree deletion stack out of memory");
218	return -ENOMEM;
219	}
220
221	r = dm_tm_ref(tm: s->tm, b, result: &ref_count);
222	if (r)
223	return r;
224
225	if (ref_count > 1)
226	/*
227	* This is a shared node, so we can just decrement it's
228	* reference counter and leave the children.
229	*/
230	dm_tm_dec(tm: s->tm, b);
231
232	else {
233	uint32_t flags;
234	struct frame *f = s->spine + ++s->top;
235
236	r = dm_tm_read_lock(tm: s->tm, b, v: &btree_node_validator, result: &f->b);
237	if (r) {
238	s->top--;
239	return r;
240	}
241
242	f->n = dm_block_data(b: f->b);
243	f->level = level;
244	f->nr_children = le32_to_cpu(f->n->header.nr_entries);
245	f->current_child = 0;
246
247	flags = le32_to_cpu(f->n->header.flags);
248	if (flags & INTERNAL_NODE || is_internal_level(info: s->info, f))
249	prefetch_children(s, f);
250	}
251
252	return 0;
253	}
254
255	static void pop_frame(struct del_stack *s)
256	{
257	struct frame *f = s->spine + s->top--;
258
259	dm_tm_dec(tm: s->tm, b: dm_block_location(b: f->b));
260	dm_tm_unlock(tm: s->tm, b: f->b);
261	}
262
263	static void unlock_all_frames(struct del_stack *s)
264	{
265	struct frame *f;
266
267	while (unprocessed_frames(s)) {
268	f = s->spine + s->top--;
269	dm_tm_unlock(tm: s->tm, b: f->b);
270	}
271	}
272
273	int dm_btree_del(struct dm_btree_info *info, dm_block_t root)
274	{
275	int r;
276	struct del_stack *s;
277
278	/*
279	* dm_btree_del() is called via an ioctl, as such should be
280	* considered an FS op. We can't recurse back into the FS, so we
281	* allocate GFP_NOFS.
282	*/
283	s = kmalloc(size: sizeof(*s), GFP_NOFS);
284	if (!s)
285	return -ENOMEM;
286	s->info = info;
287	s->tm = info->tm;
288	s->top = -1;
289
290	r = push_frame(s, b: root, level: 0);
291	if (r)
292	goto out;
293
294	while (unprocessed_frames(s)) {
295	uint32_t flags;
296	struct frame *f;
297	dm_block_t b;
298
299	r = top_frame(s, f: &f);
300	if (r)
301	goto out;
302
303	if (f->current_child >= f->nr_children) {
304	pop_frame(s);
305	continue;
306	}
307
308	flags = le32_to_cpu(f->n->header.flags);
309	if (flags & INTERNAL_NODE) {
310	b = value64(n: f->n, index: f->current_child);
311	f->current_child++;
312	r = push_frame(s, b, level: f->level);
313	if (r)
314	goto out;
315
316	} else if (is_internal_level(info, f)) {
317	b = value64(n: f->n, index: f->current_child);
318	f->current_child++;
319	r = push_frame(s, b, level: f->level + 1);
320	if (r)
321	goto out;
322
323	} else {
324	if (info->value_type.dec)
325	info->value_type.dec(info->value_type.context,
326	value_ptr(n: f->n, index: 0), f->nr_children);
327	pop_frame(s);
328	}
329	}
330	out:
331	if (r) {
332	/* cleanup all frames of del_stack */
333	unlock_all_frames(s);
334	}
335	kfree(objp: s);
336
337	return r;
338	}
339	EXPORT_SYMBOL_GPL(dm_btree_del);
340
341	/*----------------------------------------------------------------*/
342
343	static int btree_lookup_raw(struct ro_spine *s, dm_block_t block, uint64_t key,
344	int (*search_fn)(struct btree_node *, uint64_t),
345	uint64_t *result_key, void *v, size_t value_size)
346	{
347	int i, r;
348	uint32_t flags, nr_entries;
349
350	do {
351	r = ro_step(s, new_child: block);
352	if (r < 0)
353	return r;
354
355	i = search_fn(ro_node(s), key);
356
357	flags = le32_to_cpu(ro_node(s)->header.flags);
358	nr_entries = le32_to_cpu(ro_node(s)->header.nr_entries);
359	if (i < 0 || i >= nr_entries)
360	return -ENODATA;
361
362	if (flags & INTERNAL_NODE)
363	block = value64(n: ro_node(s), index: i);
364
365	} while (!(flags & LEAF_NODE));
366
367	*result_key = le64_to_cpu(ro_node(s)->keys[i]);
368	if (v)
369	memcpy(v, value_ptr(ro_node(s), i), value_size);
370
371	return 0;
372	}
373
374	int dm_btree_lookup(struct dm_btree_info *info, dm_block_t root,
375	uint64_t *keys, void *value_le)
376	{
377	unsigned int level, last_level = info->levels - 1;
378	int r = -ENODATA;
379	uint64_t rkey;
380	__le64 internal_value_le;
381	struct ro_spine spine;
382
383	init_ro_spine(s: &spine, info);
384	for (level = 0; level < info->levels; level++) {
385	size_t size;
386	void *value_p;
387
388	if (level == last_level) {
389	value_p = value_le;
390	size = info->value_type.size;
391
392	} else {
393	value_p = &internal_value_le;
394	size = sizeof(uint64_t);
395	}
396
397	r = btree_lookup_raw(s: &spine, block: root, key: keys[level],
398	search_fn: lower_bound, result_key: &rkey,
399	v: value_p, value_size: size);
400
401	if (!r) {
402	if (rkey != keys[level]) {
403	exit_ro_spine(s: &spine);
404	return -ENODATA;
405	}
406	} else {
407	exit_ro_spine(s: &spine);
408	return r;
409	}
410
411	root = le64_to_cpu(internal_value_le);
412	}
413	exit_ro_spine(s: &spine);
414
415	return r;
416	}
417	EXPORT_SYMBOL_GPL(dm_btree_lookup);
418
419	static int dm_btree_lookup_next_single(struct dm_btree_info *info, dm_block_t root,
420	uint64_t key, uint64_t *rkey, void *value_le)
421	{
422	int r, i;
423	uint32_t flags, nr_entries;
424	struct dm_block *node;
425	struct btree_node *n;
426
427	r = bn_read_lock(info, b: root, result: &node);
428	if (r)
429	return r;
430
431	n = dm_block_data(b: node);
432	flags = le32_to_cpu(n->header.flags);
433	nr_entries = le32_to_cpu(n->header.nr_entries);
434
435	if (flags & INTERNAL_NODE) {
436	i = lower_bound(n, key);
437	if (i < 0) {
438	/*
439	* avoid early -ENODATA return when all entries are
440	* higher than the search @key.
441	*/
442	i = 0;
443	}
444	if (i >= nr_entries) {
445	r = -ENODATA;
446	goto out;
447	}
448
449	r = dm_btree_lookup_next_single(info, root: value64(n, index: i), key, rkey, value_le);
450	if (r == -ENODATA && i < (nr_entries - 1)) {
451	i++;
452	r = dm_btree_lookup_next_single(info, root: value64(n, index: i), key, rkey, value_le);
453	}
454
455	} else {
456	i = upper_bound(n, key);
457	if (i < 0 || i >= nr_entries) {
458	r = -ENODATA;
459	goto out;
460	}
461
462	*rkey = le64_to_cpu(n->keys[i]);
463	memcpy(value_le, value_ptr(n, i), info->value_type.size);
464	}
465	out:
466	dm_tm_unlock(tm: info->tm, b: node);
467	return r;
468	}
469
470	int dm_btree_lookup_next(struct dm_btree_info *info, dm_block_t root,
471	uint64_t *keys, uint64_t *rkey, void *value_le)
472	{
473	unsigned int level;
474	int r = -ENODATA;
475	__le64 internal_value_le;
476	struct ro_spine spine;
477
478	init_ro_spine(s: &spine, info);
479	for (level = 0; level < info->levels - 1u; level++) {
480	r = btree_lookup_raw(s: &spine, block: root, key: keys[level],
481	search_fn: lower_bound, result_key: rkey,
482	v: &internal_value_le, value_size: sizeof(uint64_t));
483	if (r)
484	goto out;
485
486	if (*rkey != keys[level]) {
487	r = -ENODATA;
488	goto out;
489	}
490
491	root = le64_to_cpu(internal_value_le);
492	}
493
494	r = dm_btree_lookup_next_single(info, root, key: keys[level], rkey, value_le);
495	out:
496	exit_ro_spine(s: &spine);
497	return r;
498	}
499	EXPORT_SYMBOL_GPL(dm_btree_lookup_next);
500
501	/*----------------------------------------------------------------*/
502
503	/*
504	* Copies entries from one region of a btree node to another. The regions
505	* must not overlap.
506	*/
507	static void copy_entries(struct btree_node *dest, unsigned int dest_offset,
508	struct btree_node *src, unsigned int src_offset,
509	unsigned int count)
510	{
511	size_t value_size = le32_to_cpu(dest->header.value_size);
512
513	memcpy(dest->keys + dest_offset, src->keys + src_offset, count * sizeof(uint64_t));
514	memcpy(value_ptr(dest, dest_offset), value_ptr(src, src_offset), count * value_size);
515	}
516
517	/*
518	* Moves entries from one region fo a btree node to another. The regions
519	* may overlap.
520	*/
521	static void move_entries(struct btree_node *dest, unsigned int dest_offset,
522	struct btree_node *src, unsigned int src_offset,
523	unsigned int count)
524	{
525	size_t value_size = le32_to_cpu(dest->header.value_size);
526
527	memmove(dest->keys + dest_offset, src->keys + src_offset, count * sizeof(uint64_t));
528	memmove(value_ptr(dest, dest_offset), value_ptr(src, src_offset), count * value_size);
529	}
530
531	/*
532	* Erases the first 'count' entries of a btree node, shifting following
533	* entries down into their place.
534	*/
535	static void shift_down(struct btree_node *n, unsigned int count)
536	{
537	move_entries(dest: n, dest_offset: 0, src: n, src_offset: count, le32_to_cpu(n->header.nr_entries) - count);
538	}
539
540	/*
541	* Moves entries in a btree node up 'count' places, making space for
542	* new entries at the start of the node.
543	*/
544	static void shift_up(struct btree_node *n, unsigned int count)
545	{
546	move_entries(dest: n, dest_offset: count, src: n, src_offset: 0, le32_to_cpu(n->header.nr_entries));
547	}
548
549	/*
550	* Redistributes entries between two btree nodes to make them
551	* have similar numbers of entries.
552	*/
553	static void redistribute2(struct btree_node *left, struct btree_node *right)
554	{
555	unsigned int nr_left = le32_to_cpu(left->header.nr_entries);
556	unsigned int nr_right = le32_to_cpu(right->header.nr_entries);
557	unsigned int total = nr_left + nr_right;
558	unsigned int target_left = total / 2;
559	unsigned int target_right = total - target_left;
560
561	if (nr_left < target_left) {
562	unsigned int delta = target_left - nr_left;
563
564	copy_entries(dest: left, dest_offset: nr_left, src: right, src_offset: 0, count: delta);
565	shift_down(n: right, count: delta);
566	} else if (nr_left > target_left) {
567	unsigned int delta = nr_left - target_left;
568
569	if (nr_right)
570	shift_up(n: right, count: delta);
571	copy_entries(dest: right, dest_offset: 0, src: left, src_offset: target_left, count: delta);
572	}
573
574	left->header.nr_entries = cpu_to_le32(target_left);
575	right->header.nr_entries = cpu_to_le32(target_right);
576	}
577
578	/*
579	* Redistribute entries between three nodes. Assumes the central
580	* node is empty.
581	*/
582	static void redistribute3(struct btree_node *left, struct btree_node *center,
583	struct btree_node *right)
584	{
585	unsigned int nr_left = le32_to_cpu(left->header.nr_entries);
586	unsigned int nr_center = le32_to_cpu(center->header.nr_entries);
587	unsigned int nr_right = le32_to_cpu(right->header.nr_entries);
588	unsigned int total, target_left, target_center, target_right;
589
590	BUG_ON(nr_center);
591
592	total = nr_left + nr_right;
593	target_left = total / 3;
594	target_center = (total - target_left) / 2;
595	target_right = (total - target_left - target_center);
596
597	if (nr_left < target_left) {
598	unsigned int left_short = target_left - nr_left;
599
600	copy_entries(dest: left, dest_offset: nr_left, src: right, src_offset: 0, count: left_short);
601	copy_entries(dest: center, dest_offset: 0, src: right, src_offset: left_short, count: target_center);
602	shift_down(n: right, count: nr_right - target_right);
603
604	} else if (nr_left < (target_left + target_center)) {
605	unsigned int left_to_center = nr_left - target_left;
606
607	copy_entries(dest: center, dest_offset: 0, src: left, src_offset: target_left, count: left_to_center);
608	copy_entries(dest: center, dest_offset: left_to_center, src: right, src_offset: 0, count: target_center - left_to_center);
609	shift_down(n: right, count: nr_right - target_right);
610
611	} else {
612	unsigned int right_short = target_right - nr_right;
613
614	shift_up(n: right, count: right_short);
615	copy_entries(dest: right, dest_offset: 0, src: left, src_offset: nr_left - right_short, count: right_short);
616	copy_entries(dest: center, dest_offset: 0, src: left, src_offset: target_left, count: nr_left - target_left);
617	}
618
619	left->header.nr_entries = cpu_to_le32(target_left);
620	center->header.nr_entries = cpu_to_le32(target_center);
621	right->header.nr_entries = cpu_to_le32(target_right);
622	}
623
624	/*
625	* Splits a node by creating a sibling node and shifting half the nodes
626	* contents across. Assumes there is a parent node, and it has room for
627	* another child.
628	*
629	* Before:
630	* +--------+
631	* | Parent |
632	* +--------+
633	* |
634	* v
635	* +----------+
636	* | A ++++++ |
637	* +----------+
638	*
639	*
640	* After:
641	* +--------+
642	* | Parent |
643	* +--------+
644	* | |
645	* v +------+
646	* +---------+ |
647	* | A* +++ | v
648	* +---------+ +-------+
649	* | B +++ |
650	* +-------+
651	*
652	* Where A* is a shadow of A.
653	*/
654	static int split_one_into_two(struct shadow_spine *s, unsigned int parent_index,
655	struct dm_btree_value_type *vt, uint64_t key)
656	{
657	int r;
658	struct dm_block *left, *right, *parent;
659	struct btree_node *ln, *rn, *pn;
660	__le64 location;
661
662	left = shadow_current(s);
663
664	r = new_block(info: s->info, result: &right);
665	if (r < 0)
666	return r;
667
668	ln = dm_block_data(b: left);
669	rn = dm_block_data(b: right);
670
671	rn->header.flags = ln->header.flags;
672	rn->header.nr_entries = cpu_to_le32(0);
673	rn->header.max_entries = ln->header.max_entries;
674	rn->header.value_size = ln->header.value_size;
675	redistribute2(left: ln, right: rn);
676
677	/* patch up the parent */
678	parent = shadow_parent(s);
679	pn = dm_block_data(b: parent);
680
681	location = cpu_to_le64(dm_block_location(right));
682	__dm_bless_for_disk(&location);
683	r = insert_at(value_size: sizeof(__le64), node: pn, index: parent_index + 1,
684	le64_to_cpu(rn->keys[0]), value: &location);
685	if (r) {
686	unlock_block(info: s->info, b: right);
687	return r;
688	}
689
690	/* patch up the spine */
691	if (key < le64_to_cpu(rn->keys[0])) {
692	unlock_block(info: s->info, b: right);
693	s->nodes[1] = left;
694	} else {
695	unlock_block(info: s->info, b: left);
696	s->nodes[1] = right;
697	}
698
699	return 0;
700	}
701
702	/*
703	* We often need to modify a sibling node. This function shadows a particular
704	* child of the given parent node. Making sure to update the parent to point
705	* to the new shadow.
706	*/
707	static int shadow_child(struct dm_btree_info *info, struct dm_btree_value_type *vt,
708	struct btree_node *parent, unsigned int index,
709	struct dm_block **result)
710	{
711	int r, inc;
712	dm_block_t root;
713	struct btree_node *node;
714
715	root = value64(n: parent, index);
716
717	r = dm_tm_shadow_block(tm: info->tm, orig: root, v: &btree_node_validator,
718	result, inc_children: &inc);
719	if (r)
720	return r;
721
722	node = dm_block_data(b: *result);
723
724	if (inc)
725	inc_children(tm: info->tm, n: node, vt);
726
727	*((__le64 *) value_ptr(n: parent, index)) =
728	cpu_to_le64(dm_block_location(*result));
729
730	return 0;
731	}
732
733	/*
734	* Splits two nodes into three. This is more work, but results in fuller
735	* nodes, so saves metadata space.
736	*/
737	static int split_two_into_three(struct shadow_spine *s, unsigned int parent_index,
738	struct dm_btree_value_type *vt, uint64_t key)
739	{
740	int r;
741	unsigned int middle_index;
742	struct dm_block *left, *middle, *right, *parent;
743	struct btree_node *ln, *rn, *mn, *pn;
744	__le64 location;
745
746	parent = shadow_parent(s);
747	pn = dm_block_data(b: parent);
748
749	if (parent_index == 0) {
750	middle_index = 1;
751	left = shadow_current(s);
752	r = shadow_child(info: s->info, vt, parent: pn, index: parent_index + 1, result: &right);
753	if (r)
754	return r;
755	} else {
756	middle_index = parent_index;
757	right = shadow_current(s);
758	r = shadow_child(info: s->info, vt, parent: pn, index: parent_index - 1, result: &left);
759	if (r)
760	return r;
761	}
762
763	r = new_block(info: s->info, result: &middle);
764	if (r < 0)
765	return r;
766
767	ln = dm_block_data(b: left);
768	mn = dm_block_data(b: middle);
769	rn = dm_block_data(b: right);
770
771	mn->header.nr_entries = cpu_to_le32(0);
772	mn->header.flags = ln->header.flags;
773	mn->header.max_entries = ln->header.max_entries;
774	mn->header.value_size = ln->header.value_size;
775
776	redistribute3(left: ln, center: mn, right: rn);
777
778	/* patch up the parent */
779	pn->keys[middle_index] = rn->keys[0];
780	location = cpu_to_le64(dm_block_location(middle));
781	__dm_bless_for_disk(&location);
782	r = insert_at(value_size: sizeof(__le64), node: pn, index: middle_index,
783	le64_to_cpu(mn->keys[0]), value: &location);
784	if (r) {
785	if (shadow_current(s) != left)
786	unlock_block(info: s->info, b: left);
787
788	unlock_block(info: s->info, b: middle);
789
790	if (shadow_current(s) != right)
791	unlock_block(info: s->info, b: right);
792
793	return r;
794	}
795
796
797	/* patch up the spine */
798	if (key < le64_to_cpu(mn->keys[0])) {
799	unlock_block(info: s->info, b: middle);
800	unlock_block(info: s->info, b: right);
801	s->nodes[1] = left;
802	} else if (key < le64_to_cpu(rn->keys[0])) {
803	unlock_block(info: s->info, b: left);
804	unlock_block(info: s->info, b: right);
805	s->nodes[1] = middle;
806	} else {
807	unlock_block(info: s->info, b: left);
808	unlock_block(info: s->info, b: middle);
809	s->nodes[1] = right;
810	}
811
812	return 0;
813	}
814
815	/*----------------------------------------------------------------*/
816
817	/*
818	* Splits a node by creating two new children beneath the given node.
819	*
820	* Before:
821	* +----------+
822	* | A ++++++ |
823	* +----------+
824	*
825	*
826	* After:
827	* +------------+
828	* | A (shadow) |
829	* +------------+
830	* | |
831	* +------+ +----+
832	* | |
833	* v v
834	* +-------+ +-------+
835	* | B +++ | | C +++ |
836	* +-------+ +-------+
837	*/
838	static int btree_split_beneath(struct shadow_spine *s, uint64_t key)
839	{
840	int r;
841	size_t size;
842	unsigned int nr_left, nr_right;
843	struct dm_block *left, *right, *new_parent;
844	struct btree_node *pn, *ln, *rn;
845	__le64 val;
846
847	new_parent = shadow_current(s);
848
849	pn = dm_block_data(b: new_parent);
850	size = le32_to_cpu(pn->header.flags) & INTERNAL_NODE ?
851	sizeof(__le64) : s->info->value_type.size;
852
853	/* create & init the left block */
854	r = new_block(info: s->info, result: &left);
855	if (r < 0)
856	return r;
857
858	ln = dm_block_data(b: left);
859	nr_left = le32_to_cpu(pn->header.nr_entries) / 2;
860
861	ln->header.flags = pn->header.flags;
862	ln->header.nr_entries = cpu_to_le32(nr_left);
863	ln->header.max_entries = pn->header.max_entries;
864	ln->header.value_size = pn->header.value_size;
865	memcpy(ln->keys, pn->keys, nr_left * sizeof(pn->keys[0]));
866	memcpy(value_ptr(ln, 0), value_ptr(pn, 0), nr_left * size);
867
868	/* create & init the right block */
869	r = new_block(info: s->info, result: &right);
870	if (r < 0) {
871	unlock_block(info: s->info, b: left);
872	return r;
873	}
874
875	rn = dm_block_data(b: right);
876	nr_right = le32_to_cpu(pn->header.nr_entries) - nr_left;
877
878	rn->header.flags = pn->header.flags;
879	rn->header.nr_entries = cpu_to_le32(nr_right);
880	rn->header.max_entries = pn->header.max_entries;
881	rn->header.value_size = pn->header.value_size;
882	memcpy(rn->keys, pn->keys + nr_left, nr_right * sizeof(pn->keys[0]));
883	memcpy(value_ptr(rn, 0), value_ptr(pn, nr_left),
884	nr_right * size);
885
886	/* new_parent should just point to l and r now */
887	pn->header.flags = cpu_to_le32(INTERNAL_NODE);
888	pn->header.nr_entries = cpu_to_le32(2);
889	pn->header.max_entries = cpu_to_le32(
890	calc_max_entries(sizeof(__le64),
891	dm_bm_block_size(
892	dm_tm_get_bm(s->info->tm))));
893	pn->header.value_size = cpu_to_le32(sizeof(__le64));
894
895	val = cpu_to_le64(dm_block_location(left));
896	__dm_bless_for_disk(&val);
897	pn->keys[0] = ln->keys[0];
898	memcpy_disk(dest: value_ptr(n: pn, index: 0), src: &val, len: sizeof(__le64));
899
900	val = cpu_to_le64(dm_block_location(right));
901	__dm_bless_for_disk(&val);
902	pn->keys[1] = rn->keys[0];
903	memcpy_disk(dest: value_ptr(n: pn, index: 1), src: &val, len: sizeof(__le64));
904
905	unlock_block(info: s->info, b: left);
906	unlock_block(info: s->info, b: right);
907	return 0;
908	}
909
910	/*----------------------------------------------------------------*/
911
912	/*
913	* Redistributes a node's entries with its left sibling.
914	*/
915	static int rebalance_left(struct shadow_spine *s, struct dm_btree_value_type *vt,
916	unsigned int parent_index, uint64_t key)
917	{
918	int r;
919	struct dm_block *sib;
920	struct btree_node *left, *right, *parent = dm_block_data(b: shadow_parent(s));
921
922	r = shadow_child(info: s->info, vt, parent, index: parent_index - 1, result: &sib);
923	if (r)
924	return r;
925
926	left = dm_block_data(b: sib);
927	right = dm_block_data(b: shadow_current(s));
928	redistribute2(left, right);
929	*key_ptr(n: parent, index: parent_index) = right->keys[0];
930
931	if (key < le64_to_cpu(right->keys[0])) {
932	unlock_block(info: s->info, b: s->nodes[1]);
933	s->nodes[1] = sib;
934	} else {
935	unlock_block(info: s->info, b: sib);
936	}
937
938	return 0;
939	}
940
941	/*
942	* Redistributes a nodes entries with its right sibling.
943	*/
944	static int rebalance_right(struct shadow_spine *s, struct dm_btree_value_type *vt,
945	unsigned int parent_index, uint64_t key)
946	{
947	int r;
948	struct dm_block *sib;
949	struct btree_node *left, *right, *parent = dm_block_data(b: shadow_parent(s));
950
951	r = shadow_child(info: s->info, vt, parent, index: parent_index + 1, result: &sib);
952	if (r)
953	return r;
954
955	left = dm_block_data(b: shadow_current(s));
956	right = dm_block_data(b: sib);
957	redistribute2(left, right);
958	*key_ptr(n: parent, index: parent_index + 1) = right->keys[0];
959
960	if (key < le64_to_cpu(right->keys[0])) {
961	unlock_block(info: s->info, b: sib);
962	} else {
963	unlock_block(info: s->info, b: s->nodes[1]);
964	s->nodes[1] = sib;
965	}
966
967	return 0;
968	}
969
970	/*
971	* Returns the number of spare entries in a node.
972	*/
973	static int get_node_free_space(struct dm_btree_info *info, dm_block_t b, unsigned int *space)
974	{
975	int r;
976	unsigned int nr_entries;
977	struct dm_block *block;
978	struct btree_node *node;
979
980	r = bn_read_lock(info, b, result: &block);
981	if (r)
982	return r;
983
984	node = dm_block_data(b: block);
985	nr_entries = le32_to_cpu(node->header.nr_entries);
986	*space = le32_to_cpu(node->header.max_entries) - nr_entries;
987
988	unlock_block(info, b: block);
989	return 0;
990	}
991
992	/*
993	* Make space in a node, either by moving some entries to a sibling,
994	* or creating a new sibling node. SPACE_THRESHOLD defines the minimum
995	* number of free entries that must be in the sibling to make the move
996	* worth while. If the siblings are shared (eg, part of a snapshot),
997	* then they are not touched, since this break sharing and so consume
998	* more space than we save.
999	*/
1000	#define SPACE_THRESHOLD 8
1001	static int rebalance_or_split(struct shadow_spine *s, struct dm_btree_value_type *vt,
1002	unsigned int parent_index, uint64_t key)
1003	{
1004	int r;
1005	struct btree_node *parent = dm_block_data(b: shadow_parent(s));
1006	unsigned int nr_parent = le32_to_cpu(parent->header.nr_entries);
1007	unsigned int free_space;
1008	int left_shared = 0, right_shared = 0;
1009
1010	/* Should we move entries to the left sibling? */
1011	if (parent_index > 0) {
1012	dm_block_t left_b = value64(n: parent, index: parent_index - 1);
1013
1014	r = dm_tm_block_is_shared(tm: s->info->tm, b: left_b, result: &left_shared);
1015	if (r)
1016	return r;
1017
1018	if (!left_shared) {
1019	r = get_node_free_space(info: s->info, b: left_b, space: &free_space);
1020	if (r)
1021	return r;
1022
1023	if (free_space >= SPACE_THRESHOLD)
1024	return rebalance_left(s, vt, parent_index, key);
1025	}
1026	}
1027
1028	/* Should we move entries to the right sibling? */
1029	if (parent_index < (nr_parent - 1)) {
1030	dm_block_t right_b = value64(n: parent, index: parent_index + 1);
1031
1032	r = dm_tm_block_is_shared(tm: s->info->tm, b: right_b, result: &right_shared);
1033	if (r)
1034	return r;
1035
1036	if (!right_shared) {
1037	r = get_node_free_space(info: s->info, b: right_b, space: &free_space);
1038	if (r)
1039	return r;
1040
1041	if (free_space >= SPACE_THRESHOLD)
1042	return rebalance_right(s, vt, parent_index, key);
1043	}
1044	}
1045
1046	/*
1047	* We need to split the node, normally we split two nodes
1048	* into three. But when inserting a sequence that is either
1049	* monotonically increasing or decreasing it's better to split
1050	* a single node into two.
1051	*/
1052	if (left_shared || right_shared || (nr_parent <= 2) ||
1053	(parent_index == 0) || (parent_index + 1 == nr_parent)) {
1054	return split_one_into_two(s, parent_index, vt, key);
1055	} else {
1056	return split_two_into_three(s, parent_index, vt, key);
1057	}
1058	}
1059
1060	/*
1061	* Does the node contain a particular key?
1062	*/
1063	static bool contains_key(struct btree_node *node, uint64_t key)
1064	{
1065	int i = lower_bound(n: node, key);
1066
1067	if (i >= 0 && le64_to_cpu(node->keys[i]) == key)
1068	return true;
1069
1070	return false;
1071	}
1072
1073	/*
1074	* In general we preemptively make sure there's a free entry in every
1075	* node on the spine when doing an insert. But we can avoid that with
1076	* leaf nodes if we know it's an overwrite.
1077	*/
1078	static bool has_space_for_insert(struct btree_node *node, uint64_t key)
1079	{
1080	if (node->header.nr_entries == node->header.max_entries) {
1081	if (le32_to_cpu(node->header.flags) & LEAF_NODE) {
1082	/* we don't need space if it's an overwrite */
1083	return contains_key(node, key);
1084	}
1085
1086	return false;
1087	}
1088
1089	return true;
1090	}
1091
1092	static int btree_insert_raw(struct shadow_spine *s, dm_block_t root,
1093	struct dm_btree_value_type *vt,
1094	uint64_t key, unsigned int *index)
1095	{
1096	int r, i = *index, top = 1;
1097	struct btree_node *node;
1098
1099	for (;;) {
1100	r = shadow_step(s, b: root, vt);
1101	if (r < 0)
1102	return r;
1103
1104	node = dm_block_data(b: shadow_current(s));
1105
1106	/*
1107	* We have to patch up the parent node, ugly, but I don't
1108	* see a way to do this automatically as part of the spine
1109	* op.
1110	*/
1111	if (shadow_has_parent(s) && i >= 0) { /* FIXME: second clause unness. */
1112	__le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
1113
1114	__dm_bless_for_disk(&location);
1115	memcpy_disk(dest: value_ptr(n: dm_block_data(b: shadow_parent(s)), index: i),
1116	src: &location, len: sizeof(__le64));
1117	}
1118
1119	node = dm_block_data(b: shadow_current(s));
1120
1121	if (!has_space_for_insert(node, key)) {
1122	if (top)
1123	r = btree_split_beneath(s, key);
1124	else
1125	r = rebalance_or_split(s, vt, parent_index: i, key);
1126
1127	if (r < 0)
1128	return r;
1129
1130	/* making space can cause the current node to change */
1131	node = dm_block_data(b: shadow_current(s));
1132	}
1133
1134	i = lower_bound(n: node, key);
1135
1136	if (le32_to_cpu(node->header.flags) & LEAF_NODE)
1137	break;
1138
1139	if (i < 0) {
1140	/* change the bounds on the lowest key */
1141	node->keys[0] = cpu_to_le64(key);
1142	i = 0;
1143	}
1144
1145	root = value64(n: node, index: i);
1146	top = 0;
1147	}
1148
1149	if (i < 0 || le64_to_cpu(node->keys[i]) != key)
1150	i++;
1151
1152	*index = i;
1153	return 0;
1154	}
1155
1156	static int __btree_get_overwrite_leaf(struct shadow_spine *s, dm_block_t root,
1157	uint64_t key, int *index)
1158	{
1159	int r, i = -1;
1160	struct btree_node *node;
1161
1162	*index = 0;
1163	for (;;) {
1164	r = shadow_step(s, b: root, vt: &s->info->value_type);
1165	if (r < 0)
1166	return r;
1167
1168	node = dm_block_data(b: shadow_current(s));
1169
1170	/*
1171	* We have to patch up the parent node, ugly, but I don't
1172	* see a way to do this automatically as part of the spine
1173	* op.
1174	*/
1175	if (shadow_has_parent(s) && i >= 0) {
1176	__le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
1177
1178	__dm_bless_for_disk(&location);
1179	memcpy_disk(dest: value_ptr(n: dm_block_data(b: shadow_parent(s)), index: i),
1180	src: &location, len: sizeof(__le64));
1181	}
1182
1183	node = dm_block_data(b: shadow_current(s));
1184	i = lower_bound(n: node, key);
1185
1186	BUG_ON(i < 0);
1187	BUG_ON(i >= le32_to_cpu(node->header.nr_entries));
1188
1189	if (le32_to_cpu(node->header.flags) & LEAF_NODE) {
1190	if (key != le64_to_cpu(node->keys[i]))
1191	return -EINVAL;
1192	break;
1193	}
1194
1195	root = value64(n: node, index: i);
1196	}
1197
1198	*index = i;
1199	return 0;
1200	}
1201
1202	int btree_get_overwrite_leaf(struct dm_btree_info *info, dm_block_t root,
1203	uint64_t key, int *index,
1204	dm_block_t *new_root, struct dm_block **leaf)
1205	{
1206	int r;
1207	struct shadow_spine spine;
1208
1209	BUG_ON(info->levels > 1);
1210	init_shadow_spine(s: &spine, info);
1211	r = __btree_get_overwrite_leaf(s: &spine, root, key, index);
1212	if (!r) {
1213	*new_root = shadow_root(s: &spine);
1214	*leaf = shadow_current(s: &spine);
1215
1216	/*
1217	* Decrement the count so exit_shadow_spine() doesn't
1218	* unlock the leaf.
1219	*/
1220	spine.count--;
1221	}
1222	exit_shadow_spine(s: &spine);
1223
1224	return r;
1225	}
1226
1227	static bool need_insert(struct btree_node *node, uint64_t *keys,
1228	unsigned int level, unsigned int index)
1229	{
1230	return ((index >= le32_to_cpu(node->header.nr_entries)) ||
1231	(le64_to_cpu(node->keys[index]) != keys[level]));
1232	}
1233
1234	static int insert(struct dm_btree_info *info, dm_block_t root,
1235	uint64_t *keys, void *value, dm_block_t *new_root,
1236	int *inserted)
1237	__dm_written_to_disk(value)
1238	{
1239	int r;
1240	unsigned int level, index = -1, last_level = info->levels - 1;
1241	dm_block_t block = root;
1242	struct shadow_spine spine;
1243	struct btree_node *n;
1244	struct dm_btree_value_type le64_type;
1245
1246	init_le64_type(tm: info->tm, vt: &le64_type);
1247	init_shadow_spine(s: &spine, info);
1248
1249	for (level = 0; level < (info->levels - 1); level++) {
1250	r = btree_insert_raw(s: &spine, root: block, vt: &le64_type, key: keys[level], index: &index);
1251	if (r < 0)
1252	goto bad;
1253
1254	n = dm_block_data(b: shadow_current(s: &spine));
1255
1256	if (need_insert(node: n, keys, level, index)) {
1257	dm_block_t new_tree;
1258	__le64 new_le;
1259
1260	r = dm_btree_empty(info, &new_tree);
1261	if (r < 0)
1262	goto bad;
1263
1264	new_le = cpu_to_le64(new_tree);
1265	__dm_bless_for_disk(&new_le);
1266
1267	r = insert_at(value_size: sizeof(uint64_t), node: n, index,
1268	key: keys[level], value: &new_le);
1269	if (r)
1270	goto bad;
1271	}
1272
1273	if (level < last_level)
1274	block = value64(n, index);
1275	}
1276
1277	r = btree_insert_raw(s: &spine, root: block, vt: &info->value_type,
1278	key: keys[level], index: &index);
1279	if (r < 0)
1280	goto bad;
1281
1282	n = dm_block_data(b: shadow_current(s: &spine));
1283
1284	if (need_insert(node: n, keys, level, index)) {
1285	if (inserted)
1286	*inserted = 1;
1287
1288	r = insert_at(value_size: info->value_type.size, node: n, index,
1289	key: keys[level], value);
1290	if (r)
1291	goto bad_unblessed;
1292	} else {
1293	if (inserted)
1294	*inserted = 0;
1295
1296	if (info->value_type.dec &&
1297	(!info->value_type.equal ||
1298	!info->value_type.equal(
1299	info->value_type.context,
1300	value_ptr(n, index),
1301	value))) {
1302	info->value_type.dec(info->value_type.context,
1303	value_ptr(n, index), 1);
1304	}
1305	memcpy_disk(dest: value_ptr(n, index),
1306	src: value, len: info->value_type.size);
1307	}
1308
1309	*new_root = shadow_root(s: &spine);
1310	exit_shadow_spine(s: &spine);
1311
1312	return 0;
1313
1314	bad:
1315	__dm_unbless_for_disk(value);
1316	bad_unblessed:
1317	exit_shadow_spine(s: &spine);
1318	return r;
1319	}
1320
1321	int dm_btree_insert(struct dm_btree_info *info, dm_block_t root,
1322	uint64_t *keys, void *value, dm_block_t *new_root)
1323	__dm_written_to_disk(value)
1324	{
1325	return insert(info, root, keys, value, new_root, NULL);
1326	}
1327	EXPORT_SYMBOL_GPL(dm_btree_insert);
1328
1329	int dm_btree_insert_notify(struct dm_btree_info *info, dm_block_t root,
1330	uint64_t *keys, void *value, dm_block_t *new_root,
1331	int *inserted)
1332	__dm_written_to_disk(value)
1333	{
1334	return insert(info, root, keys, value, new_root, inserted);
1335	}
1336	EXPORT_SYMBOL_GPL(dm_btree_insert_notify);
1337
1338	/*----------------------------------------------------------------*/
1339
1340	static int find_key(struct ro_spine *s, dm_block_t block, bool find_highest,
1341	uint64_t *result_key, dm_block_t *next_block)
1342	{
1343	int i, r;
1344	uint32_t flags;
1345
1346	do {
1347	r = ro_step(s, new_child: block);
1348	if (r < 0)
1349	return r;
1350
1351	flags = le32_to_cpu(ro_node(s)->header.flags);
1352	i = le32_to_cpu(ro_node(s)->header.nr_entries);
1353	if (!i)
1354	return -ENODATA;
1355
1356	i--;
1357
1358	if (find_highest)
1359	*result_key = le64_to_cpu(ro_node(s)->keys[i]);
1360	else
1361	*result_key = le64_to_cpu(ro_node(s)->keys[0]);
1362
1363	if (next_block || flags & INTERNAL_NODE) {
1364	if (find_highest)
1365	block = value64(n: ro_node(s), index: i);
1366	else
1367	block = value64(n: ro_node(s), index: 0);
1368	}
1369
1370	} while (flags & INTERNAL_NODE);
1371
1372	if (next_block)
1373	*next_block = block;
1374	return 0;
1375	}
1376
1377	static int dm_btree_find_key(struct dm_btree_info *info, dm_block_t root,
1378	bool find_highest, uint64_t *result_keys)
1379	{
1380	int r = 0, count = 0, level;
1381	struct ro_spine spine;
1382
1383	init_ro_spine(s: &spine, info);
1384	for (level = 0; level < info->levels; level++) {
1385	r = find_key(s: &spine, block: root, find_highest, result_key: result_keys + level,
1386	next_block: level == info->levels - 1 ? NULL : &root);
1387	if (r == -ENODATA) {
1388	r = 0;
1389	break;
1390
1391	} else if (r)
1392	break;
1393
1394	count++;
1395	}
1396	exit_ro_spine(s: &spine);
1397
1398	return r ? r : count;
1399	}
1400
1401	int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
1402	uint64_t *result_keys)
1403	{
1404	return dm_btree_find_key(info, root, find_highest: true, result_keys);
1405	}
1406	EXPORT_SYMBOL_GPL(dm_btree_find_highest_key);
1407
1408	int dm_btree_find_lowest_key(struct dm_btree_info *info, dm_block_t root,
1409	uint64_t *result_keys)
1410	{
1411	return dm_btree_find_key(info, root, find_highest: false, result_keys);
1412	}
1413	EXPORT_SYMBOL_GPL(dm_btree_find_lowest_key);
1414
1415	/*----------------------------------------------------------------*/
1416
1417	/*
1418	* FIXME: We shouldn't use a recursive algorithm when we have limited stack
1419	* space. Also this only works for single level trees.
1420	*/
1421	static int walk_node(struct dm_btree_info *info, dm_block_t block,
1422	int (*fn)(void *context, uint64_t *keys, void *leaf),
1423	void *context)
1424	{
1425	int r;
1426	unsigned int i, nr;
1427	struct dm_block *node;
1428	struct btree_node *n;
1429	uint64_t keys;
1430
1431	r = bn_read_lock(info, b: block, result: &node);
1432	if (r)
1433	return r;
1434
1435	n = dm_block_data(b: node);
1436
1437	nr = le32_to_cpu(n->header.nr_entries);
1438	for (i = 0; i < nr; i++) {
1439	if (le32_to_cpu(n->header.flags) & INTERNAL_NODE) {
1440	r = walk_node(info, block: value64(n, index: i), fn, context);
1441	if (r)
1442	goto out;
1443	} else {
1444	keys = le64_to_cpu(*key_ptr(n, i));
1445	r = fn(context, &keys, value_ptr(n, index: i));
1446	if (r)
1447	goto out;
1448	}
1449	}
1450
1451	out:
1452	dm_tm_unlock(tm: info->tm, b: node);
1453	return r;
1454	}
1455
1456	int dm_btree_walk(struct dm_btree_info *info, dm_block_t root,
1457	int (*fn)(void *context, uint64_t *keys, void *leaf),
1458	void *context)
1459	{
1460	BUG_ON(info->levels > 1);
1461	return walk_node(info, block: root, fn, context);
1462	}
1463	EXPORT_SYMBOL_GPL(dm_btree_walk);
1464
1465	/*----------------------------------------------------------------*/
1466
1467	static void prefetch_values(struct dm_btree_cursor *c)
1468	{
1469	unsigned int i, nr;
1470	__le64 value_le;
1471	struct cursor_node *n = c->nodes + c->depth - 1;
1472	struct btree_node *bn = dm_block_data(b: n->b);
1473	struct dm_block_manager *bm = dm_tm_get_bm(tm: c->info->tm);
1474
1475	BUG_ON(c->info->value_type.size != sizeof(value_le));
1476
1477	nr = le32_to_cpu(bn->header.nr_entries);
1478	for (i = 0; i < nr; i++) {
1479	memcpy(&value_le, value_ptr(bn, i), sizeof(value_le));
1480	dm_bm_prefetch(bm, le64_to_cpu(value_le));
1481	}
1482	}
1483
1484	static bool leaf_node(struct dm_btree_cursor *c)
1485	{
1486	struct cursor_node *n = c->nodes + c->depth - 1;
1487	struct btree_node *bn = dm_block_data(b: n->b);
1488
1489	return le32_to_cpu(bn->header.flags) & LEAF_NODE;
1490	}
1491
1492	static int push_node(struct dm_btree_cursor *c, dm_block_t b)
1493	{
1494	int r;
1495	struct cursor_node *n = c->nodes + c->depth;
1496
1497	if (c->depth >= DM_BTREE_CURSOR_MAX_DEPTH - 1) {
1498	DMERR("couldn't push cursor node, stack depth too high");
1499	return -EINVAL;
1500	}
1501
1502	r = bn_read_lock(info: c->info, b, result: &n->b);
1503	if (r)
1504	return r;
1505
1506	n->index = 0;
1507	c->depth++;
1508
1509	if (c->prefetch_leaves || !leaf_node(c))
1510	prefetch_values(c);
1511
1512	return 0;
1513	}
1514
1515	static void pop_node(struct dm_btree_cursor *c)
1516	{
1517	c->depth--;
1518	unlock_block(info: c->info, b: c->nodes[c->depth].b);
1519	}
1520
1521	static int inc_or_backtrack(struct dm_btree_cursor *c)
1522	{
1523	struct cursor_node *n;
1524	struct btree_node *bn;
1525
1526	for (;;) {
1527	if (!c->depth)
1528	return -ENODATA;
1529
1530	n = c->nodes + c->depth - 1;
1531	bn = dm_block_data(b: n->b);
1532
1533	n->index++;
1534	if (n->index < le32_to_cpu(bn->header.nr_entries))
1535	break;
1536
1537	pop_node(c);
1538	}
1539
1540	return 0;
1541	}
1542
1543	static int find_leaf(struct dm_btree_cursor *c)
1544	{
1545	int r = 0;
1546	struct cursor_node *n;
1547	struct btree_node *bn;
1548	__le64 value_le;
1549
1550	for (;;) {
1551	n = c->nodes + c->depth - 1;
1552	bn = dm_block_data(b: n->b);
1553
1554	if (le32_to_cpu(bn->header.flags) & LEAF_NODE)
1555	break;
1556
1557	memcpy(&value_le, value_ptr(bn, n->index), sizeof(value_le));
1558	r = push_node(c, le64_to_cpu(value_le));
1559	if (r) {
1560	DMERR("push_node failed");
1561	break;
1562	}
1563	}
1564
1565	if (!r && (le32_to_cpu(bn->header.nr_entries) == 0))
1566	return -ENODATA;
1567
1568	return r;
1569	}
1570
1571	int dm_btree_cursor_begin(struct dm_btree_info *info, dm_block_t root,
1572	bool prefetch_leaves, struct dm_btree_cursor *c)
1573	{
1574	int r;
1575
1576	c->info = info;
1577	c->root = root;
1578	c->depth = 0;
1579	c->prefetch_leaves = prefetch_leaves;
1580
1581	r = push_node(c, b: root);
1582	if (r)
1583	return r;
1584
1585	return find_leaf(c);
1586	}
1587	EXPORT_SYMBOL_GPL(dm_btree_cursor_begin);
1588
1589	void dm_btree_cursor_end(struct dm_btree_cursor *c)
1590	{
1591	while (c->depth)
1592	pop_node(c);
1593	}
1594	EXPORT_SYMBOL_GPL(dm_btree_cursor_end);
1595
1596	int dm_btree_cursor_next(struct dm_btree_cursor *c)
1597	{
1598	int r = inc_or_backtrack(c);
1599
1600	if (!r) {
1601	r = find_leaf(c);
1602	if (r)
1603	DMERR("find_leaf failed");
1604	}
1605
1606	return r;
1607	}
1608	EXPORT_SYMBOL_GPL(dm_btree_cursor_next);
1609
1610	int dm_btree_cursor_skip(struct dm_btree_cursor *c, uint32_t count)
1611	{
1612	int r = 0;
1613
1614	while (count-- && !r)
1615	r = dm_btree_cursor_next(c);
1616
1617	return r;
1618	}
1619	EXPORT_SYMBOL_GPL(dm_btree_cursor_skip);
1620
1621	int dm_btree_cursor_get_value(struct dm_btree_cursor *c, uint64_t *key, void *value_le)
1622	{
1623	if (c->depth) {
1624	struct cursor_node *n = c->nodes + c->depth - 1;
1625	struct btree_node *bn = dm_block_data(b: n->b);
1626
1627	if (le32_to_cpu(bn->header.flags) & INTERNAL_NODE)
1628	return -EINVAL;
1629
1630	*key = le64_to_cpu(*key_ptr(bn, n->index));
1631	memcpy(value_le, value_ptr(bn, n->index), c->info->value_type.size);
1632	return 0;
1633
1634	} else
1635	return -ENODATA;
1636	}
1637	EXPORT_SYMBOL_GPL(dm_btree_cursor_get_value);
1638