kvm tools: Add interval red-black tree helper

Interval rb-tree allows to directly store interval ranges
and quickly lookup an overlap with a single point or a range.

The helper is based on the kernel rb-tree implementation
(located in <linux/rbtree.h>) which alows for the augmention
of the classical rb-tree to be used as an interval tree.

Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

Makefile

@@ -42,6 +42,7 @@ OBJS    += mptable.o
 OBJS    += threadpool.o
 OBJS    += irq.o
 OBJS    += ../../lib/rbtree.o
+OBJS    += util/rbtree-interval.o
 
 DEPS	:= $(patsubst %.o,%.d,$(OBJS))
 

include/kvm/rbtree-interval.h

@@ -0,0 +1,27 @@
+#ifndef KVM__INTERVAL_RBTREE_H
+#define KVM__INTERVAL_RBTREE_H
+
+#include <linux/rbtree.h>
+#include <linux/types.h>
+
+#define RB_INT_INIT(l, h) (struct rb_int_node){.low = l, .high = h}
+
+struct rb_int_node {
+	struct rb_node	node;
+	u64		low;
+	u64		high;
+
+	/* max_high will store the highest high of it's 2 children. */
+	u64		max_high;
+};
+
+/* Return the rb_int_node interval in which 'point' is located. */
+struct rb_int_node *rb_int_search_single(struct rb_root *root, u64 point);
+
+/* Return the rb_int_node in which start:len is located. */
+struct rb_int_node *rb_int_search_range(struct rb_root *root, u64 low, u64 high);
+
+int rb_int_insert(struct rb_root *root, struct rb_int_node *data);
+void rb_int_erase(struct rb_root *root, struct rb_int_node *node);
+
+#endif

include/linux/kernel.h

@@ -1,3 +1,4 @@
+
 #ifndef KVM__LINUX_KERNEL_H_
 #define KVM__LINUX_KERNEL_H_
 
@@ -23,4 +24,16 @@
 	(type *)((char *)__mptr - offsetof(type, member)); })
 #endif
 
+#define min(x, y) ({				\
+	typeof(x) _min1 = (x);			\
+	typeof(y) _min2 = (y);			\
+	(void) (&_min1 == &_min2);		\
+	_min1 < _min2 ? _min1 : _min2; })
+
+#define max(x, y) ({				\
+	typeof(x) _max1 = (x);			\
+	typeof(y) _max2 = (y);			\
+	(void) (&_max1 == &_max2);		\
+	_max1 > _max2 ? _max1 : _max2; })
+
 #endif

util/rbtree-interval.c

@@ -0,0 +1,90 @@
+#include <kvm/rbtree-interval.h>
+#include <stddef.h>
+
+#define rb_int(n) rb_entry(n, struct rb_int_node, node)
+
+struct rb_int_node *rb_int_search_single(struct rb_root *root, u64 point)
+{
+	struct rb_node *node = root->rb_node;
+	struct rb_node *lowest = NULL;
+
+	while (node) {
+		struct rb_int_node *cur = rb_int(node);
+
+		if (node->rb_left && (rb_int(node->rb_left)->max_high > point)) {
+			node = node->rb_left;
+		} else if (cur->low <= point && cur->high > point) {
+			lowest = node;
+			break;
+		} else if (point > cur->low) {
+			node = node->rb_right;
+		} else {
+			break;
+		}
+	}
+
+	if (lowest == NULL)
+		return NULL;
+
+	return rb_int(lowest);
+}
+
+struct rb_int_node *rb_int_search_range(struct rb_root *root, u64 low, u64 high)
+{
+	struct rb_int_node *range;
+
+	range = rb_int_search_single(root, low);
+	if (range == NULL)
+		return NULL;
+
+	/* We simply verify that 'high' is smaller than the end of the range where 'low' is located */
+	if (range->high < high)
+		return NULL;
+
+	return range;
+}
+
+static void update_node_max_high(struct rb_node *node, void *arg)
+{
+	struct rb_int_node *i_node = rb_int(node);
+
+	i_node->max_high = i_node->high;
+
+	if (node->rb_left)
+		i_node->max_high = max(i_node->max_high, rb_int(node->rb_left)->high);
+	if (node->rb_right)
+		i_node->max_high = max(i_node->max_high, rb_int(node->rb_right)->high);
+}
+
+int rb_int_insert(struct rb_root *root, struct rb_int_node *i_node)
+{
+	struct rb_node **node	= &(root->rb_node), *parent = NULL;
+
+	while (*node) {
+		int result	= i_node->low - rb_int(*node)->low;
+
+		parent = *node;
+		if (result < 0)
+			node	= &((*node)->rb_left);
+		else if (result > 0)
+			node	= &((*node)->rb_right);
+		else
+			return 0;
+	}
+
+	rb_link_node(&i_node->node, parent, node);
+	rb_insert_color(&i_node->node, root);
+
+	rb_augment_insert(*node, update_node_max_high, NULL);
+	return 1;
+}
+
+void rb_int_erase(struct rb_root *root, struct rb_int_node *node)
+{
+	struct rb_node *deepest;
+
+	deepest = rb_augment_erase_begin(&node->node);
+	rb_erase(&node->node, root);
+	rb_augment_erase_end(deepest, update_node_max_high, NULL);
+
+}