1 files changed, 88 insertions, 0 deletions
diff --git a/include/linux/interval_tree.h b/include/linux/interval_tree.h
new file mode 100644
index 000000000..2b8026a39
--- /dev/null
+++ b/include/linux/interval_tree.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_INTERVAL_TREE_H
+#define _LINUX_INTERVAL_TREE_H
+
+#include <linux/rbtree.h>
+
+struct interval_tree_node {
+	struct rb_node rb;
+	unsigned long start;	/* Start of interval */
+	unsigned long last;	/* Last location _in_ interval */
+	unsigned long __subtree_last;
+};
+
+extern void
+interval_tree_insert(struct interval_tree_node *node,
+		     struct rb_root_cached *root);
+
+extern void
+interval_tree_remove(struct interval_tree_node *node,
+		     struct rb_root_cached *root);
+
+extern struct interval_tree_node *
+interval_tree_iter_first(struct rb_root_cached *root,
+			 unsigned long start, unsigned long last);
+
+extern struct interval_tree_node *
+interval_tree_iter_next(struct interval_tree_node *node,
+			unsigned long start, unsigned long last);
+
+/**
+ * struct interval_tree_span_iter - Find used and unused spans.
+ * @start_hole: Start of an interval for a hole when is_hole == 1
+ * @last_hole: Inclusive end of an interval for a hole when is_hole == 1
+ * @start_used: Start of a used interval when is_hole == 0
+ * @last_used: Inclusive end of a used interval when is_hole == 0
+ * @is_hole: 0 == used, 1 == is_hole, -1 == done iteration
+ *
+ * This iterator travels over spans in an interval tree. It does not return
+ * nodes but classifies each span as either a hole, where no nodes intersect, or
+ * a used, which is fully covered by nodes. Each iteration step toggles between
+ * hole and used until the entire range is covered. The returned spans always
+ * fully cover the requested range.
+ *
+ * The iterator is greedy, it always returns the largest hole or used possible,
+ * consolidating all consecutive nodes.
+ *
+ * Use interval_tree_span_iter_done() to detect end of iteration.
+ */
+struct interval_tree_span_iter {
+	/* private: not for use by the caller */
+	struct interval_tree_node *nodes[2];
+	unsigned long first_index;
+	unsigned long last_index;
+
+	/* public: */
+	union {
+		unsigned long start_hole;
+		unsigned long start_used;
+	};
+	union {
+		unsigned long last_hole;
+		unsigned long last_used;
+	};
+	int is_hole;
+};
+
+void interval_tree_span_iter_first(struct interval_tree_span_iter *state,
+				   struct rb_root_cached *itree,
+				   unsigned long first_index,
+				   unsigned long last_index);
+void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter,
+				     struct rb_root_cached *itree,
+				     unsigned long new_index);
+void interval_tree_span_iter_next(struct interval_tree_span_iter *state);
+
+static inline bool
+interval_tree_span_iter_done(struct interval_tree_span_iter *state)
+{
+	return state->is_hole == -1;
+}
+
+#define interval_tree_for_each_span(span, itree, first_index, last_index)      \
+	for (interval_tree_span_iter_first(span, itree,                        \
+					   first_index, last_index);           \
+	     !interval_tree_span_iter_done(span);                              \
+	     interval_tree_span_iter_next(span))
+
+#endif	/* _LINUX_INTERVAL_TREE_H */