#include <asm/bug.h>
#include <linux/rbtree_augmented.h>
#include "drbd_interval.h"

/**
 * interval_end  -  return end of @node
 */
static inline
sector_t interval_end(struct rb_node *node)
{
        struct drbd_interval *this = rb_entry(node, struct drbd_interval, rb);
        return this->end;
}

/**
 * compute_subtree_last  -  compute end of @node
 *
 * The end of an interval is the highest (start + (size >> 9)) value of this
 * node and of its children.  Called for @node and its parents whenever the end
 * may have changed.
 */
static inline sector_t
compute_subtree_last(struct drbd_interval *node)
{
        sector_t max = node->sector + (node->size >> 9);

        if (node->rb.rb_left) {
                sector_t left = interval_end(node->rb.rb_left);
                if (left > max)
                        max = left;
        }
        if (node->rb.rb_right) {
                sector_t right = interval_end(node->rb.rb_right);
                if (right > max)
                        max = right;
        }
        return max;
}

static void augment_propagate(struct rb_node *rb, struct rb_node *stop)
{
        while (rb != stop) {
                struct drbd_interval *node = rb_entry(rb, struct drbd_interval, rb);
                sector_t subtree_last = compute_subtree_last(node);
                if (node->end == subtree_last)
                        break;
                node->end = subtree_last;
                rb = rb_parent(&node->rb);
        }
}

static void augment_copy(struct rb_node *rb_old, struct rb_node *rb_new)
{
        struct drbd_interval *old = rb_entry(rb_old, struct drbd_interval, rb);
        struct drbd_interval *new = rb_entry(rb_new, struct drbd_interval, rb);

        new->end = old->end;
}

static void augment_rotate(struct rb_node *rb_old, struct rb_node *rb_new)
{
        struct drbd_interval *old = rb_entry(rb_old, struct drbd_interval, rb);
        struct drbd_interval *new = rb_entry(rb_new, struct drbd_interval, rb);

        new->end = old->end;
        old->end = compute_subtree_last(old);
}

static const struct rb_augment_callbacks augment_callbacks = {
        augment_propagate,
        augment_copy,
        augment_rotate,
};

/**
 * drbd_insert_interval  -  insert a new interval into a tree
 */
bool
drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
{
        struct rb_node **new = &root->rb_node, *parent = NULL;

        BUG_ON(!IS_ALIGNED(this->size, 512));

        while (*new) {
                struct drbd_interval *here =
                        rb_entry(*new, struct drbd_interval, rb);

                parent = *new;
                if (this->sector < here->sector)
                        new = &(*new)->rb_left;
                else if (this->sector > here->sector)
                        new = &(*new)->rb_right;
                else if (this < here)
                        new = &(*new)->rb_left;
                else if (this > here)
                        new = &(*new)->rb_right;
                else
                        return false;
        }

        rb_link_node(&this->rb, parent, new);
        rb_insert_augmented(&this->rb, root, &augment_callbacks);
        return true;
}

/**
 * drbd_contains_interval  -  check if a tree contains a given interval
 * @sector:     start sector of @interval
 * @interval:   may not be a valid pointer
 *
 * Returns if the tree contains the node @interval with start sector @start.
 * Does not dereference @interval until @interval is known to be a valid object
 * in @tree.  Returns %false if @interval is in the tree but with a different
 * sector number.
 */
bool
drbd_contains_interval(struct rb_root *root, sector_t sector,
                       struct drbd_interval *interval)
{
        struct rb_node *node = root->rb_node;

        while (node) {
                struct drbd_interval *here =
                        rb_entry(node, struct drbd_interval, rb);

                if (sector < here->sector)
                        node = node->rb_left;
                else if (sector > here->sector)
                        node = node->rb_right;
                else if (interval < here)
                        node = node->rb_left;
                else if (interval > here)
                        node = node->rb_right;
                else
                        return true;
        }
        return false;
}

/**
 * drbd_remove_interval  -  remove an interval from a tree
 */
void
drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
{
        rb_erase_augmented(&this->rb, root, &augment_callbacks);
}

/**
 * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
 * @sector:     start sector
 * @size:       size, aligned to 512 bytes
 *
 * Returns an interval overlapping with [sector, sector + size), or NULL if
 * there is none.  When there is more than one overlapping interval in the
 * tree, the interval with the lowest start sector is returned, and all other
 * overlapping intervals will be on the right side of the tree, reachable with
 * rb_next().
 */
struct drbd_interval *
drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
{
        struct rb_node *node = root->rb_node;
        struct drbd_interval *overlap = NULL;
        sector_t end = sector + (size >> 9);

        BUG_ON(!IS_ALIGNED(size, 512));

        while (node) {
                struct drbd_interval *here =
                        rb_entry(node, struct drbd_interval, rb);

                if (node->rb_left &&
                    sector < interval_end(node->rb_left)) {
                        /* Overlap if any must be on left side */
                        node = node->rb_left;
                } else if (here->sector < end &&
                           sector < here->sector + (here->size >> 9)) {
                        overlap = here;
                        break;
                } else if (sector >= here->sector) {
                        /* Overlap if any must be on right side */
                        node = node->rb_right;
                } else
                        break;
        }
        return overlap;
}

struct drbd_interval *
drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
{
        sector_t end = sector + (size >> 9);
        struct rb_node *node;

        for (;;) {
                node = rb_next(&i->rb);
                if (!node)
                        return NULL;
                i = rb_entry(node, struct drbd_interval, rb);
                if (i->sector >= end)
                        return NULL;
                if (sector < i->sector + (i->size >> 9))
                        return i;
        }
}