/*
 * 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.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * 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>
 */
#ifdef __KERNEL__
# include <lustre_dlm.h>
#else
# include <libcfs/libcfs.h>
#endif
#include <obd_support.h>
#include <interval_tree.h>

enum {
        INTERVAL_RED = 0,
        INTERVAL_BLACK = 1
};

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

static inline int node_is_right_child(struct interval_node *node)
{
        LASSERT(node->in_parent != NULL);
        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 int extent_overlapped(struct interval_node_extent *e1, 
                                    struct interval_node_extent *e2)
{
        return (e1->start <= e2->end) && (e2->start <= e1->end);
}

static inline int node_compare(struct interval_node *n1,
                               struct interval_node *n2)
{
        return extent_compare(&n1->in_extent, &n2->in_extent);
}

static inline int node_equal(struct interval_node *n1,
                             struct interval_node *n2)
{
        return extent_equal(&n1->in_extent, &n2->in_extent);
}

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

static inline __u64 min_u64(__u64 x, __u64 y)
{
        return x < y ? x : y;
}

#define interval_for_each(node, root)                   \
for (node = interval_first(root); node != NULL;         \
     node = interval_next(node))

#define interval_for_each_reverse(node, root)           \
for (node = interval_last(root); node != NULL;          \
     node = interval_prev(node))

static struct interval_node *interval_first(struct interval_node *node)
{
        ENTRY;

        if (!node)
                RETURN(NULL);
        while (node->in_left)
                node = node->in_left;
        RETURN(node);
}

static struct interval_node *interval_last(struct interval_node *node)
{
        ENTRY;

        if (!node)
                RETURN(NULL);
        while (node->in_right)
                node = node->in_right;
        RETURN(node);
}

static struct interval_node *interval_next(struct interval_node *node)
{
        ENTRY;

        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 struct interval_node *interval_prev(struct interval_node *node)
{
        ENTRY;

        if (!node)
                RETURN(NULL);

        if (node->in_left)
                RETURN(interval_last(node->in_left));

        while (node->in_parent && node_is_left_child(node))
                node = node->in_parent;

        RETURN(node->in_parent);
}

enum interval_iter interval_iterate(struct interval_node *root,
                                    interval_callback_t func,
                                    void *data)
{
        struct interval_node *node;
        enum interval_iter rc = INTERVAL_ITER_CONT;
        ENTRY;
        
        interval_for_each(node, root) {
                rc = func(node, data);
                if (rc == INTERVAL_ITER_STOP)
                        break;
        }

        RETURN(rc);
}
EXPORT_SYMBOL(interval_iterate);

enum interval_iter interval_iterate_reverse(struct interval_node *root,
                                            interval_callback_t func,
                                            void *data)
{
        struct interval_node *node;
        enum interval_iter rc = INTERVAL_ITER_CONT;
        ENTRY;
        
        interval_for_each_reverse(node, root) {
                rc = func(node, data);
                if (rc == INTERVAL_ITER_STOP)
                        break;
        }

        RETURN(rc);
}
EXPORT_SYMBOL(interval_iterate_reverse);

/* try to find a node with same interval in the tree,
 * if found, return the pointer to the node, otherwise return NULL*/
struct interval_node *interval_find(struct interval_node *root,
                                    struct interval_node_extent *ex)
{
        struct interval_node *walk = root;
        int rc;
        ENTRY;

        while (walk) {
                rc = extent_compare(ex, &walk->in_extent);
                if (rc == 0)
                        break;
                else if (rc < 0)
                        walk = walk->in_left;
                else
                        walk = walk->in_right;
        }

        RETURN(walk);
}
EXPORT_SYMBOL(interval_find);

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;
        ENTRY;

        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;
        EXIT;
}

struct interval_node *interval_insert(struct interval_node *node,
                                      struct interval_node **root)
                     
{
        struct interval_node **p, *parent = NULL;
        ENTRY;

        LASSERT(!interval_is_intree(node));
        p = root;
        while (*p) {
                parent = *p;
                if (node_equal(parent, node))
                        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 (node_compare(node, parent) < 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 = 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;
        ENTRY;

        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;
                                        if ((o_left = tmp->in_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;
                                        if ((o_right = tmp->in_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;
        EXIT;
}

/* 
 * 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;
        ENTRY;

        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;
        }
        EXIT;
}

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

        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);
        EXIT;
}
EXPORT_SYMBOL(interval_erase);

static inline int interval_may_overlap(struct interval_node *node,
                                          struct interval_node_extent *ext)
{
        return (ext->start <= node->in_max_high &&
                ext->end >= interval_low(node));
}

/*
 * This function finds all intervals that overlap interval ext,
 * and calls func to handle resulted intervals one by one.
 * in lustre, this function will find all conflicting locks in
 * the granted queue and add these locks to the ast work list.
 *
 * {
 *       if (node == NULL)
 *               return 0;
 *       if (ext->end < interval_low(node)) {
 *               interval_search(node->in_left, ext, func, data);
 *       } else if (interval_may_overlap(node, ext)) {
 *               if (extent_overlapped(ext, &node->in_extent))
 *                       func(node, data);
 *               interval_search(node->in_left, ext, func, data);
 *               interval_search(node->in_right, ext, func, data);
 *       }
 *       return 0;
 * }
 *
 */
enum interval_iter interval_search(struct interval_node *node,
                                   struct interval_node_extent *ext,
                                   interval_callback_t func,
                                   void *data)
{
        struct interval_node *parent;
        enum interval_iter rc = INTERVAL_ITER_CONT;

        LASSERT(ext != NULL);
        LASSERT(func != NULL);

        while (node) {
                if (ext->end < interval_low(node)) {
                        if (node->in_left) {
                                node = node->in_left;
                                continue;
                        }
                } else if (interval_may_overlap(node, ext)) {
                        if (extent_overlapped(ext, &node->in_extent)) {
                                rc = func(node, data);
                                if (rc == INTERVAL_ITER_STOP)
                                        break;
                        }

                        if (node->in_left) {
                                node = node->in_left;
                                continue;
                        }
                        if (node->in_right) {
                                node = node->in_right;
                                continue;
                        }
                } 

                parent = node->in_parent;
                while (parent) {
                        if (node_is_left_child(node) &&
                            parent->in_right) {
                                /* If we ever got the left, it means that the 
                                 * parent met ext->end<interval_low(parent), or
                                 * may_overlap(parent). If the former is true,
                                 * we needn't go back. So stop early and check
                                 * may_overlap(parent) after this loop.  */
                                node = parent->in_right;
                                break;
                        }
                        node = parent;
                        parent = parent->in_parent;
                }
                if (parent == NULL || !interval_may_overlap(parent, ext))
                        break;
        }

        return rc;
}
EXPORT_SYMBOL(interval_search);

static enum interval_iter interval_overlap_cb(struct interval_node *n,
                                              void *args)
{
        *(int *)args = 1;
        return INTERVAL_ITER_STOP;
}

int interval_is_overlapped(struct interval_node *root,
                           struct interval_node_extent *ext)
{
        int has = 0;
        (void)interval_search(root, ext, interval_overlap_cb, &has);
        return has;
}
EXPORT_SYMBOL(interval_is_overlapped);

/* Don't expand to low. Expanding downwards is expensive, and meaningless to
 * some extents, because programs seldom do IO backward.
 *
 * The recursive algorithm of expanding low:
 * expand_low {
 *        struct interval_node *tmp;
 *        static __u64 res = 0;
 *
 *        if (root == NULL)
 *                return res;
 *        if (root->in_max_high < low) {
 *                res = max_u64(root->in_max_high + 1, res);
 *                return res;
 *        } else if (low < interval_low(root)) {
 *                interval_expand_low(root->in_left, low);
 *                return res;
 *        }
 *
 *        if (interval_high(root) < low)
 *                res = max_u64(interval_high(root) + 1, res);
 *        interval_expand_low(root->in_left, low);
 *        interval_expand_low(root->in_right, low);
 *
 *        return res;
 * }
 *
 * It's much easy to eliminate the recursion, see interval_search for 
 * an example. -jay
 */
static inline __u64 interval_expand_low(struct interval_node *root, __u64 low)
{
        /* we only concern the empty tree right now. */
        if (root == NULL)
                return 0;
        return low;
}

static inline __u64 interval_expand_high(struct interval_node *node, __u64 high)
{
        __u64 result = ~0;

        while (node != NULL) {
                if (node->in_max_high < high)
                        break;
                        
                if (interval_low(node) > high) {
                        result = interval_low(node) - 1;
                        node = node->in_left;
                } else {
                        node = node->in_right;
                }
        }

        return result;
}

/* expanding the extent based on @ext. */
void interval_expand(struct interval_node *root,
                     struct interval_node_extent *ext,
                     struct interval_node_extent *limiter)
{
        /* The assertion of interval_is_overlapped is expensive because we may
         * travel many nodes to find the overlapped node. */
        LASSERT(interval_is_overlapped(root, ext) == 0);
        if (!limiter || limiter->start < ext->start)
                ext->start = interval_expand_low(root, ext->start);
        if (!limiter || limiter->end > ext->end)
                ext->end = interval_expand_high(root, ext->end);
        LASSERT(interval_is_overlapped(root, ext) == 0);
}
EXPORT_SYMBOL(interval_expand);