/*-
 * Copyright (c) 2010 Isilon Systems, Inc.
 * Copyright (c) 2010 iX Systems, Inc.
 * Copyright (c) 2010 Panasas, Inc.
 * Copyright (c) 2013-2018 Mellanox Technologies, Ltd.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/radix-tree.h>
#include <linux/err.h>

static inline unsigned long
radix_max(struct radix_tree_root *root)
{
        return ((1UL << (root->height * RADIX_TREE_MAP_SHIFT)) - 1UL);
}

static inline int
radix_pos(long id, int height)
{
        return (id >> (RADIX_TREE_MAP_SHIFT * height)) & RADIX_TREE_MAP_MASK;
}

void *
radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
        struct radix_tree_node *node;
        void *item;
        int height;

        item = NULL;
        node = root->rnode;
        height = root->height - 1;
        if (index > radix_max(root))
                goto out;
        while (height && node)
                node = node->slots[radix_pos(index, height--)];
        if (node)
                item = node->slots[radix_pos(index, 0)];

out:
        return (item);
}

bool
radix_tree_iter_find(struct radix_tree_root *root, struct radix_tree_iter *iter,
    void ***pppslot)
{
        struct radix_tree_node *node;
        unsigned long index = iter->index;
        int height;

restart:
        node = root->rnode;
        if (node == NULL)
                return (false);
        height = root->height - 1;
        if (height == -1 || index > radix_max(root))
                return (false);
        do {
                unsigned long mask = RADIX_TREE_MAP_MASK << (RADIX_TREE_MAP_SHIFT * height);
                unsigned long step = 1UL << (RADIX_TREE_MAP_SHIFT * height);
                int pos = radix_pos(index, height);
                struct radix_tree_node *next;

                /* track last slot */
                *pppslot = node->slots + pos;

                next = node->slots[pos];
                if (next == NULL) {
                        index += step;
                        index &= -step;
                        if ((index & mask) == 0)
                                goto restart;
                } else {
                        node = next;
                        height--;
                }
        } while (height != -1);
        iter->index = index;
        return (true);
}

void *
radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
        struct radix_tree_node *stack[RADIX_TREE_MAX_HEIGHT];
        struct radix_tree_node *node;
        void *item;
        int height;
        int idx;

        item = NULL;
        node = root->rnode;
        height = root->height - 1;
        if (index > radix_max(root))
                goto out;
        /*
         * Find the node and record the path in stack.
         */
        while (height && node) {
                stack[height] = node;
                node = node->slots[radix_pos(index, height--)];
        }
        idx = radix_pos(index, 0);
        if (node)
                item = node->slots[idx];
        /*
         * If we removed something reduce the height of the tree.
         */
        if (item)
                for (;;) {
                        node->slots[idx] = NULL;
                        node->count--;
                        if (node->count > 0)
                                break;
                        kfree(node);
                        if (node == root->rnode) {
                                root->rnode = NULL;
                                root->height = 0;
                                break;
                        }
                        height++;
                        node = stack[height];
                        idx = radix_pos(index, height);
                }
out:
        return (item);
}

void
radix_tree_iter_delete(struct radix_tree_root *root,
    struct radix_tree_iter *iter, void **slot)
{
        radix_tree_delete(root, iter->index);
}

int
radix_tree_insert(struct radix_tree_root *root, unsigned long index, void *item)
{
        struct radix_tree_node *node;
        struct radix_tree_node *temp[RADIX_TREE_MAX_HEIGHT - 1];
        int height;
        int idx;

        /* bail out upon insertion of a NULL item */
        if (item == NULL)
                return (-EINVAL);

        /* get root node, if any */
        node = root->rnode;

        /* allocate root node, if any */
        if (node == NULL) {
                node = kmalloc(sizeof(*node), M_DRM, root->gfp_mask | M_ZERO);
                if (node == NULL)
                        return (-ENOMEM);
                root->rnode = node;
                root->height++;
        }

        /* expand radix tree as needed */
        while (radix_max(root) < index) {

                /* check if the radix tree is getting too big */
                if (root->height == RADIX_TREE_MAX_HEIGHT)
                        return (-E2BIG);

                /*
                 * If the root radix level is not empty, we need to
                 * allocate a new radix level:
                 */
                if (node->count != 0) {
                        node = kmalloc(sizeof(*node), M_DRM, root->gfp_mask | M_ZERO);
                        if (node == NULL)
                                return (-ENOMEM);
                        node->slots[0] = root->rnode;
                        node->count++;
                        root->rnode = node;
                }
                root->height++;
        }

        /* get radix tree height index */
        height = root->height - 1;

        /* walk down the tree until the first missing node, if any */
        for ( ; height != 0; height--) {
                idx = radix_pos(index, height);
                if (node->slots[idx] == NULL)
                        break;
                node = node->slots[idx];
        }

        /* allocate the missing radix levels, if any */
        for (idx = 0; idx != height; idx++) {
                temp[idx] = kmalloc(sizeof(*node), M_DRM,
                    root->gfp_mask | M_ZERO);
                if (temp[idx] == NULL) {
                        while(idx--)
                                kfree(temp[idx]);
                        /* Check if we should free the root node as well. */
                        if (root->rnode->count == 0) {
                                kfree(root->rnode);
                                root->rnode = NULL;
                                root->height = 0;
                        }
                        return (-ENOMEM);
                }
        }

        /* setup new radix levels, if any */
        for ( ; height != 0; height--) {
                idx = radix_pos(index, height);
                node->slots[idx] = temp[height - 1];
                node->count++;
                node = node->slots[idx];
        }

        /*
         * Insert and adjust count if the item does not already exist.
         */
        idx = radix_pos(index, 0);
        if (node->slots[idx])
                return (-EEXIST);
        node->slots[idx] = item;
        node->count++;

        return (0);
}