rbtree: Add support for augmented rbtrees (17d9ddc7) · Commits · e / devices / android_kernel_xiaomi_markw

Documentation/rbtree.txt

+58 −0

Original line number	Diff line number	Diff line
		@@ -190,3 +190,61 @@ Example:
		for (node = rb_first(&mytree); node; node = rb_next(node))
		printk("key=%s\n", rb_entry(node, struct mytype, node)->keystring);

		Support for Augmented rbtrees
		-----------------------------

		Augmented rbtree is an rbtree with "some" additional data stored in each node.
		This data can be used to augment some new functionality to rbtree.
		Augmented rbtree is an optional feature built on top of basic rbtree
		infrastructure. rbtree user who wants this feature will have an augment
		callback function in rb_root initialized.

		This callback function will be called from rbtree core routines whenever
		a node has a change in one or both of its children. It is the responsibility
		of the callback function to recalculate the additional data that is in the
		rb node using new children information. Note that if this new additional
		data affects the parent node's additional data, then callback function has
		to handle it and do the recursive updates.


		Interval tree is an example of augmented rb tree. Reference -
		"Introduction to Algorithms" by Cormen, Leiserson, Rivest and Stein.
		More details about interval trees:

		Classical rbtree has a single key and it cannot be directly used to store
		interval ranges like [lo:hi] and do a quick lookup for any overlap with a new
		lo:hi or to find whether there is an exact match for a new lo:hi.

		However, rbtree can be augmented to store such interval ranges in a structured
		way making it possible to do efficient lookup and exact match.

		This "extra information" stored in each node is the maximum hi
		(max_hi) value among all the nodes that are its descendents. This
		information can be maintained at each node just be looking at the node
		and its immediate children. And this will be used in O(log n) lookup
		for lowest match (lowest start address among all possible matches)
		with something like:

		find_lowest_match(lo, hi, node)
		{
		lowest_match = NULL;
		while (node) {
		if (max_hi(node->left) > lo) {
		// Lowest overlap if any must be on left side
		node = node->left;
		} else if (overlap(lo, hi, node)) {
		lowest_match = node;
		break;
		} else if (lo > node->lo) {
		// Lowest overlap if any must be on right side
		node = node->right;
		} else {
		break;
		}
		}
		return lowest_match;
		}

		Finding exact match will be to first find lowest match and then to follow
		successor nodes looking for exact match, until the start of a node is beyond
		the hi value we are looking for.

include/linux/rbtree.h

+4 −1

Original line number	Diff line number	Diff line
		@@ -110,6 +110,7 @@ struct rb_node
		struct rb_root
		{
		struct rb_node *rb_node;
		void (augment_cb)(struct rb_node node);
		};


		@@ -129,7 +130,9 @@ static inline void rb_set_color(struct rb_node *rb, int color)
		rb->rb_parent_color = (rb->rb_parent_color & ~1) \| color;
		}

		#define RB_ROOT (struct rb_root) { NULL, }
		#define RB_ROOT (struct rb_root) { NULL, NULL, }
		#define RB_AUGMENT_ROOT(x) (struct rb_root) { NULL, x}

		#define rb_entry(ptr, type, member) container_of(ptr, type, member)

		#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL)

lib/rbtree.c

+44 −4

Original line number	Diff line number	Diff line
		@@ -44,6 +44,11 @@ static void __rb_rotate_left(struct rb_node node, struct rb_root root)
		else
		root->rb_node = right;
		rb_set_parent(node, right);

		if (root->augment_cb) {
		root->augment_cb(node);
		root->augment_cb(right);
		}
		}

		static void __rb_rotate_right(struct rb_node node, struct rb_root root)
		@@ -67,12 +72,20 @@ static void __rb_rotate_right(struct rb_node node, struct rb_root root)
		else
		root->rb_node = left;
		rb_set_parent(node, left);

		if (root->augment_cb) {
		root->augment_cb(node);
		root->augment_cb(left);
		}
		}

		void rb_insert_color(struct rb_node node, struct rb_root root)
		{
		struct rb_node parent, gparent;

		if (root->augment_cb)
		root->augment_cb(node);

		while ((parent = rb_parent(node)) && rb_is_red(parent))
		{
		gparent = rb_parent(parent);
		@@ -227,12 +240,15 @@ void rb_erase(struct rb_node node, struct rb_root root)
		else
		{
		struct rb_node old = node, left;
		int old_parent_cb = 0;
		int successor_parent_cb = 0;

		node = node->rb_right;
		while ((left = node->rb_left) != NULL)
		node = left;

		if (rb_parent(old)) {
		old_parent_cb = 1;
		if (rb_parent(old)->rb_left == old)
		rb_parent(old)->rb_left = node;
		else
		@@ -247,8 +263,10 @@ void rb_erase(struct rb_node node, struct rb_root root)
		if (parent == old) {
		parent = node;
		} else {
		successor_parent_cb = 1;
		if (child)
		rb_set_parent(child, parent);

		parent->rb_left = child;

		node->rb_right = old->rb_right;
		@@ -259,6 +277,24 @@ void rb_erase(struct rb_node node, struct rb_root root)
		node->rb_left = old->rb_left;
		rb_set_parent(old->rb_left, node);

		if (root->augment_cb) {
		/*
		* Here, three different nodes can have new children.
		* The parent of the successor node that was selected
		* to replace the node to be erased.
		* The node that is getting erased and is now replaced
		* by its successor.
		* The parent of the node getting erased-replaced.
		*/
		if (successor_parent_cb)
		root->augment_cb(parent);

		root->augment_cb(node);

		if (old_parent_cb)
		root->augment_cb(rb_parent(old));
		}

		goto color;
		}

		@@ -267,15 +303,19 @@ void rb_erase(struct rb_node node, struct rb_root root)

		if (child)
		rb_set_parent(child, parent);
		if (parent)
		{

		if (parent) {
		if (parent->rb_left == node)
		parent->rb_left = child;
		else
		parent->rb_right = child;
		}
		else

		if (root->augment_cb)
		root->augment_cb(parent);

		} else {
		root->rb_node = child;
		}

		color:
		if (color == RB_BLACK)