drbd_interval.c revision e9f05b4cfed38d0e57b0a705a7f480cfbe0c3247 
1#include <asm/bug.h>
2#include <linux/rbtree_augmented.h>
3#include "drbd_interval.h"
4
5/**
6 * interval_end  -  return end of @node
7 */
8static inline
9sector_t interval_end(struct rb_node *node)
10{
11	struct drbd_interval *this = rb_entry(node, struct drbd_interval, rb);
12	return this->end;
13}
14
15/**
16 * compute_subtree_last  -  compute end of @node
17 *
18 * The end of an interval is the highest (start + (size >> 9)) value of this
19 * node and of its children.  Called for @node and its parents whenever the end
20 * may have changed.
21 */
22static inline sector_t
23compute_subtree_last(struct drbd_interval *node)
24{
25	sector_t max = node->sector + (node->size >> 9);
26
27	if (node->rb.rb_left) {
28		sector_t left = interval_end(node->rb.rb_left);
29		if (left > max)
30			max = left;
31	}
32	if (node->rb.rb_right) {
33		sector_t right = interval_end(node->rb.rb_right);
34		if (right > max)
35			max = right;
36	}
37	return max;
38}
39
40RB_DECLARE_CALLBACKS(static, augment_callbacks, struct drbd_interval, rb,
41		     sector_t, end, compute_subtree_last);
42
43/**
44 * drbd_insert_interval  -  insert a new interval into a tree
45 */
46bool
47drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
48{
49	struct rb_node **new = &root->rb_node, *parent = NULL;
50	sector_t this_end = this->sector + (this->size >> 9);
51
52	BUG_ON(!IS_ALIGNED(this->size, 512));
53
54	while (*new) {
55		struct drbd_interval *here =
56			rb_entry(*new, struct drbd_interval, rb);
57
58		parent = *new;
59		if (here->end < this_end)
60			here->end = this_end;
61		if (this->sector < here->sector)
62			new = &(*new)->rb_left;
63		else if (this->sector > here->sector)
64			new = &(*new)->rb_right;
65		else if (this < here)
66			new = &(*new)->rb_left;
67		else if (this > here)
68			new = &(*new)->rb_right;
69		else
70			return false;
71	}
72
73	this->end = this_end;
74	rb_link_node(&this->rb, parent, new);
75	rb_insert_augmented(&this->rb, root, &augment_callbacks);
76	return true;
77}
78
79/**
80 * drbd_contains_interval  -  check if a tree contains a given interval
81 * @sector:	start sector of @interval
82 * @interval:	may not be a valid pointer
83 *
84 * Returns if the tree contains the node @interval with start sector @start.
85 * Does not dereference @interval until @interval is known to be a valid object
86 * in @tree.  Returns %false if @interval is in the tree but with a different
87 * sector number.
88 */
89bool
90drbd_contains_interval(struct rb_root *root, sector_t sector,
91		       struct drbd_interval *interval)
92{
93	struct rb_node *node = root->rb_node;
94
95	while (node) {
96		struct drbd_interval *here =
97			rb_entry(node, struct drbd_interval, rb);
98
99		if (sector < here->sector)
100			node = node->rb_left;
101		else if (sector > here->sector)
102			node = node->rb_right;
103		else if (interval < here)
104			node = node->rb_left;
105		else if (interval > here)
106			node = node->rb_right;
107		else
108			return true;
109	}
110	return false;
111}
112
113/**
114 * drbd_remove_interval  -  remove an interval from a tree
115 */
116void
117drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
118{
119	rb_erase_augmented(&this->rb, root, &augment_callbacks);
120}
121
122/**
123 * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
124 * @sector:	start sector
125 * @size:	size, aligned to 512 bytes
126 *
127 * Returns an interval overlapping with [sector, sector + size), or NULL if
128 * there is none.  When there is more than one overlapping interval in the
129 * tree, the interval with the lowest start sector is returned, and all other
130 * overlapping intervals will be on the right side of the tree, reachable with
131 * rb_next().
132 */
133struct drbd_interval *
134drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
135{
136	struct rb_node *node = root->rb_node;
137	struct drbd_interval *overlap = NULL;
138	sector_t end = sector + (size >> 9);
139
140	BUG_ON(!IS_ALIGNED(size, 512));
141
142	while (node) {
143		struct drbd_interval *here =
144			rb_entry(node, struct drbd_interval, rb);
145
146		if (node->rb_left &&
147		    sector < interval_end(node->rb_left)) {
148			/* Overlap if any must be on left side */
149			node = node->rb_left;
150		} else if (here->sector < end &&
151			   sector < here->sector + (here->size >> 9)) {
152			overlap = here;
153			break;
154		} else if (sector >= here->sector) {
155			/* Overlap if any must be on right side */
156			node = node->rb_right;
157		} else
158			break;
159	}
160	return overlap;
161}
162
163struct drbd_interval *
164drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
165{
166	sector_t end = sector + (size >> 9);
167	struct rb_node *node;
168
169	for (;;) {
170		node = rb_next(&i->rb);
171		if (!node)
172			return NULL;
173		i = rb_entry(node, struct drbd_interval, rb);
174		if (i->sector >= end)
175			return NULL;
176		if (sector < i->sector + (i->size >> 9))
177			return i;
178	}
179}
180