/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/ldlm/interval_tree.c
 *
 * Interval tree library used by ldlm extent lock code
 *
 * Author: Huang Wei <huangwei@clusterfs.com>
 * Author: Jay Xiong <jinshan.xiong@sun.com>
 */
#include "../include/lustre_dlm.h"
#include "../include/obd_support.h"
#include "../include/interval_tree.h"

enum {
        INTERVAL_RED = 0,
        INTERVAL_BLACK = 1
};

static inline int node_is_left_child(struct interval_node *node)
{
        return node == node->in_parent->in_left;
}

static inline int node_is_right_child(struct interval_node *node)
{
        return node == node->in_parent->in_right;
}

static inline int node_is_red(struct interval_node *node)
{
        return node->in_color == INTERVAL_RED;
}

static inline int node_is_black(struct interval_node *node)
{
        return node->in_color == INTERVAL_BLACK;
}

static inline int extent_compare(struct interval_node_extent *e1,
                                 struct interval_node_extent *e2)
{
        int rc;

        if (e1->start == e2->start) {
                if (e1->end < e2->end)
                        rc = -1;
                else if (e1->end > e2->end)
                        rc = 1;
                else
                        rc = 0;
        } else {
                if (e1->start < e2->start)
                        rc = -1;
                else
                        rc = 1;
        }
        return rc;
}

static inline int extent_equal(struct interval_node_extent *e1,
                               struct interval_node_extent *e2)
{
        return (e1->start == e2->start) && (e1->end == e2->end);
}

static inline __u64 max_u64(__u64 x, __u64 y)
{
        return x > y ? x : y;
}

static struct interval_node *interval_first(struct interval_node *node)
{
        if (!node)
                return NULL;
        while (node->in_left)
                node = node->in_left;
        return node;
}

static struct interval_node *interval_next(struct interval_node *node)
{
        if (!node)
                return NULL;
        if (node->in_right)
                return interval_first(node->in_right);
        while (node->in_parent && node_is_right_child(node))
                node = node->in_parent;
        return node->in_parent;
}

static void __rotate_change_maxhigh(struct interval_node *node,
                                    struct interval_node *rotate)
{
        __u64 left_max, right_max;

        rotate->in_max_high = node->in_max_high;
        left_max = node->in_left ? node->in_left->in_max_high : 0;
        right_max = node->in_right ? node->in_right->in_max_high : 0;
        node->in_max_high  = max_u64(interval_high(node),
                                     max_u64(left_max, right_max));
}

/* The left rotation "pivots" around the link from node to node->right, and
 * - node will be linked to node->right's left child, and
 * - node->right's left child will be linked to node's right child.
 */
static void __rotate_left(struct interval_node *node,
                          struct interval_node **root)
{
        struct interval_node *right = node->in_right;
        struct interval_node *parent = node->in_parent;

        node->in_right = right->in_left;
        if (node->in_right)
                right->in_left->in_parent = node;

        right->in_left = node;
        right->in_parent = parent;
        if (parent) {
                if (node_is_left_child(node))
                        parent->in_left = right;
                else
                        parent->in_right = right;
        } else {
                *root = right;
        }
        node->in_parent = right;

        /* update max_high for node and right */
        __rotate_change_maxhigh(node, right);
}

/* The right rotation "pivots" around the link from node to node->left, and
 * - node will be linked to node->left's right child, and
 * - node->left's right child will be linked to node's left child.
 */
static void __rotate_right(struct interval_node *node,
                           struct interval_node **root)
{
        struct interval_node *left = node->in_left;
        struct interval_node *parent = node->in_parent;

        node->in_left = left->in_right;
        if (node->in_left)
                left->in_right->in_parent = node;
        left->in_right = node;

        left->in_parent = parent;
        if (parent) {
                if (node_is_right_child(node))
                        parent->in_right = left;
                else
                        parent->in_left = left;
        } else {
                *root = left;
        }
        node->in_parent = left;

        /* update max_high for node and left */
        __rotate_change_maxhigh(node, left);
}

#define interval_swap(a, b) do {                        \
        struct interval_node *c = a; a = b; b = c;      \
} while (0)

/*
 * Operations INSERT and DELETE, when run on a tree with n keys,
 * take O(logN) time.Because they modify the tree, the result
 * may violate the red-black properties.To restore these properties,
 * we must change the colors of some of the nodes in the tree
 * and also change the pointer structure.
 */
static void interval_insert_color(struct interval_node *node,
                                  struct interval_node **root)
{
        struct interval_node *parent, *gparent;

        while ((parent = node->in_parent) && node_is_red(parent)) {
                gparent = parent->in_parent;
                /* Parent is RED, so gparent must not be NULL */
                if (node_is_left_child(parent)) {
                        struct interval_node *uncle;

                        uncle = gparent->in_right;
                        if (uncle && node_is_red(uncle)) {
                                uncle->in_color = INTERVAL_BLACK;
                                parent->in_color = INTERVAL_BLACK;
                                gparent->in_color = INTERVAL_RED;
                                node = gparent;
                                continue;
                        }

                        if (parent->in_right == node) {
                                __rotate_left(parent, root);
                                interval_swap(node, parent);
                        }

                        parent->in_color = INTERVAL_BLACK;
                        gparent->in_color = INTERVAL_RED;
                        __rotate_right(gparent, root);
                } else {
                        struct interval_node *uncle;

                        uncle = gparent->in_left;
                        if (uncle && node_is_red(uncle)) {
                                uncle->in_color = INTERVAL_BLACK;
                                parent->in_color = INTERVAL_BLACK;
                                gparent->in_color = INTERVAL_RED;
                                node = gparent;
                                continue;
                        }

                        if (node_is_left_child(node)) {
                                __rotate_right(parent, root);
                                interval_swap(node, parent);
                        }

                        parent->in_color = INTERVAL_BLACK;
                        gparent->in_color = INTERVAL_RED;
                        __rotate_left(gparent, root);
                }
        }

        (*root)->in_color = INTERVAL_BLACK;
}

struct interval_node *interval_insert(struct interval_node *node,
                                      struct interval_node **root)

{
        struct interval_node **p, *parent = NULL;

        LASSERT(!interval_is_intree(node));
        p = root;
        while (*p) {
                parent = *p;
                if (extent_equal(&parent->in_extent, &node->in_extent))
                        return parent;

                /* max_high field must be updated after each iteration */
                if (parent->in_max_high < interval_high(node))
                        parent->in_max_high = interval_high(node);

                if (extent_compare(&node->in_extent, &parent->in_extent) < 0)
                        p = &parent->in_left;
                else
                        p = &parent->in_right;
        }

        /* link node into the tree */
        node->in_parent = parent;
        node->in_color = INTERVAL_RED;
        node->in_left = NULL;
        node->in_right = NULL;
        *p = node;

        interval_insert_color(node, root);
        node->in_intree = 1;

        return NULL;
}
EXPORT_SYMBOL(interval_insert);

static inline int node_is_black_or_0(struct interval_node *node)
{
        return !node || node_is_black(node);
}

static void interval_erase_color(struct interval_node *node,
                                 struct interval_node *parent,
                                 struct interval_node **root)
{
        struct interval_node *tmp;

        while (node_is_black_or_0(node) && node != *root) {
                if (parent->in_left == node) {
                        tmp = parent->in_right;
                        if (node_is_red(tmp)) {
                                tmp->in_color = INTERVAL_BLACK;
                                parent->in_color = INTERVAL_RED;
                                __rotate_left(parent, root);
                                tmp = parent->in_right;
                        }
                        if (node_is_black_or_0(tmp->in_left) &&
                            node_is_black_or_0(tmp->in_right)) {
                                tmp->in_color = INTERVAL_RED;
                                node = parent;
                                parent = node->in_parent;
                        } else {
                                if (node_is_black_or_0(tmp->in_right)) {
                                        struct interval_node *o_left;

                                        o_left = tmp->in_left;
                                        if (o_left)
                                                o_left->in_color = INTERVAL_BLACK;
                                        tmp->in_color = INTERVAL_RED;
                                        __rotate_right(tmp, root);
                                        tmp = parent->in_right;
                                }
                                tmp->in_color = parent->in_color;
                                parent->in_color = INTERVAL_BLACK;
                                if (tmp->in_right)
                                        tmp->in_right->in_color = INTERVAL_BLACK;
                                __rotate_left(parent, root);
                                node = *root;
                                break;
                        }
                } else {
                        tmp = parent->in_left;
                        if (node_is_red(tmp)) {
                                tmp->in_color = INTERVAL_BLACK;
                                parent->in_color = INTERVAL_RED;
                                __rotate_right(parent, root);
                                tmp = parent->in_left;
                        }
                        if (node_is_black_or_0(tmp->in_left) &&
                            node_is_black_or_0(tmp->in_right)) {
                                tmp->in_color = INTERVAL_RED;
                                node = parent;
                                parent = node->in_parent;
                        } else {
                                if (node_is_black_or_0(tmp->in_left)) {
                                        struct interval_node *o_right;

                                        o_right = tmp->in_right;
                                        if (o_right)
                                                o_right->in_color = INTERVAL_BLACK;
                                        tmp->in_color = INTERVAL_RED;
                                        __rotate_left(tmp, root);
                                        tmp = parent->in_left;
                                }
                                tmp->in_color = parent->in_color;
                                parent->in_color = INTERVAL_BLACK;
                                if (tmp->in_left)
                                        tmp->in_left->in_color = INTERVAL_BLACK;
                                __rotate_right(parent, root);
                                node = *root;
                                break;
                        }
                }
        }
        if (node)
                node->in_color = INTERVAL_BLACK;
}

/*
 * if the @max_high value of @node is changed, this function traverse  a path
 * from node  up to the root to update max_high for the whole tree.
 */
static void update_maxhigh(struct interval_node *node,
                           __u64  old_maxhigh)
{
        __u64 left_max, right_max;

        while (node) {
                left_max = node->in_left ? node->in_left->in_max_high : 0;
                right_max = node->in_right ? node->in_right->in_max_high : 0;
                node->in_max_high = max_u64(interval_high(node),
                                            max_u64(left_max, right_max));

                if (node->in_max_high >= old_maxhigh)
                        break;
                node = node->in_parent;
        }
}

void interval_erase(struct interval_node *node,
                    struct interval_node **root)
{
        struct interval_node *child, *parent;
        int color;

        LASSERT(interval_is_intree(node));
        node->in_intree = 0;
        if (!node->in_left) {
                child = node->in_right;
        } else if (!node->in_right) {
                child = node->in_left;
        } else { /* Both left and right child are not NULL */
                struct interval_node *old = node;

                node = interval_next(node);
                child = node->in_right;
                parent = node->in_parent;
                color = node->in_color;

                if (child)
                        child->in_parent = parent;
                if (parent == old)
                        parent->in_right = child;
                else
                        parent->in_left = child;

                node->in_color = old->in_color;
                node->in_right = old->in_right;
                node->in_left = old->in_left;
                node->in_parent = old->in_parent;

                if (old->in_parent) {
                        if (node_is_left_child(old))
                                old->in_parent->in_left = node;
                        else
                                old->in_parent->in_right = node;
                } else {
                        *root = node;
                }

                old->in_left->in_parent = node;
                if (old->in_right)
                        old->in_right->in_parent = node;
                update_maxhigh(child ? : parent, node->in_max_high);
                update_maxhigh(node, old->in_max_high);
                if (parent == old)
                        parent = node;
                goto color;
        }
        parent = node->in_parent;
        color = node->in_color;

        if (child)
                child->in_parent = parent;
        if (parent) {
                if (node_is_left_child(node))
                        parent->in_left = child;
                else
                        parent->in_right = child;
        } else {
                *root = child;
        }

        update_maxhigh(child ? : parent, node->in_max_high);

color:
        if (color == INTERVAL_BLACK)
                interval_erase_color(child, parent, root);
}
EXPORT_SYMBOL(interval_erase);