/*
 * Copyright 2000 by Hans Reiser, licensing governed by reiserfs/README
 */

#include <linux/time.h>
#include <linux/slab.h>
#include <linux/string.h>
#include "reiserfs.h"
#include <linux/buffer_head.h>

/*
 * To make any changes in the tree we find a node that contains item
 * to be changed/deleted or position in the node we insert a new item
 * to. We call this node S. To do balancing we need to decide what we
 * will shift to left/right neighbor, or to a new node, where new item
 * will be etc. To make this analysis simpler we build virtual
 * node. Virtual node is an array of items, that will replace items of
 * node S. (For instance if we are going to delete an item, virtual
 * node does not contain it). Virtual node keeps information about
 * item sizes and types, mergeability of first and last items, sizes
 * of all entries in directory item. We use this array of items when
 * calculating what we can shift to neighbors and how many nodes we
 * have to have if we do not any shiftings, if we shift to left/right
 * neighbor or to both.
 */

/*
 * Takes item number in virtual node, returns number of item
 * that it has in source buffer
 */
static inline int old_item_num(int new_num, int affected_item_num, int mode)
{
        if (mode == M_PASTE || mode == M_CUT || new_num < affected_item_num)
                return new_num;

        if (mode == M_INSERT) {

                RFALSE(new_num == 0,
                       "vs-8005: for INSERT mode and item number of inserted item");

                return new_num - 1;
        }

        RFALSE(mode != M_DELETE,
               "vs-8010: old_item_num: mode must be M_DELETE (mode = \'%c\'",
               mode);
        /* delete mode */
        return new_num + 1;
}

static void create_virtual_node(struct tree_balance *tb, int h)
{
        struct item_head *ih;
        struct virtual_node *vn = tb->tb_vn;
        int new_num;
        struct buffer_head *Sh; /* this comes from tb->S[h] */

        Sh = PATH_H_PBUFFER(tb->tb_path, h);

        /* size of changed node */
        vn->vn_size =
            MAX_CHILD_SIZE(Sh) - B_FREE_SPACE(Sh) + tb->insert_size[h];

        /* for internal nodes array if virtual items is not created */
        if (h) {
                vn->vn_nr_item = (vn->vn_size - DC_SIZE) / (DC_SIZE + KEY_SIZE);
                return;
        }

        /* number of items in virtual node  */
        vn->vn_nr_item =
            B_NR_ITEMS(Sh) + ((vn->vn_mode == M_INSERT) ? 1 : 0) -
            ((vn->vn_mode == M_DELETE) ? 1 : 0);

        /* first virtual item */
        vn->vn_vi = (struct virtual_item *)(tb->tb_vn + 1);
        memset(vn->vn_vi, 0, vn->vn_nr_item * sizeof(struct virtual_item));
        vn->vn_free_ptr += vn->vn_nr_item * sizeof(struct virtual_item);

        /* first item in the node */
        ih = item_head(Sh, 0);

        /* define the mergeability for 0-th item (if it is not being deleted) */
        if (op_is_left_mergeable(&ih->ih_key, Sh->b_size)
            && (vn->vn_mode != M_DELETE || vn->vn_affected_item_num))
                vn->vn_vi[0].vi_type |= VI_TYPE_LEFT_MERGEABLE;

        /*
         * go through all items that remain in the virtual
         * node (except for the new (inserted) one)
         */
        for (new_num = 0; new_num < vn->vn_nr_item; new_num++) {
                int j;
                struct virtual_item *vi = vn->vn_vi + new_num;
                int is_affected =
                    ((new_num != vn->vn_affected_item_num) ? 0 : 1);

                if (is_affected && vn->vn_mode == M_INSERT)
                        continue;

                /* get item number in source node */
                j = old_item_num(new_num, vn->vn_affected_item_num,
                                 vn->vn_mode);

                vi->vi_item_len += ih_item_len(ih + j) + IH_SIZE;
                vi->vi_ih = ih + j;
                vi->vi_item = ih_item_body(Sh, ih + j);
                vi->vi_uarea = vn->vn_free_ptr;

                /*
                 * FIXME: there is no check that item operation did not
                 * consume too much memory
                 */
                vn->vn_free_ptr +=
                    op_create_vi(vn, vi, is_affected, tb->insert_size[0]);
                if (tb->vn_buf + tb->vn_buf_size < vn->vn_free_ptr)
                        reiserfs_panic(tb->tb_sb, "vs-8030",
                                       "virtual node space consumed");

                if (!is_affected)
                        /* this is not being changed */
                        continue;

                if (vn->vn_mode == M_PASTE || vn->vn_mode == M_CUT) {
                        vn->vn_vi[new_num].vi_item_len += tb->insert_size[0];
                        /* pointer to data which is going to be pasted */
                        vi->vi_new_data = vn->vn_data;
                }
        }

        /* virtual inserted item is not defined yet */
        if (vn->vn_mode == M_INSERT) {
                struct virtual_item *vi = vn->vn_vi + vn->vn_affected_item_num;

                RFALSE(vn->vn_ins_ih == NULL,
                       "vs-8040: item header of inserted item is not specified");
                vi->vi_item_len = tb->insert_size[0];
                vi->vi_ih = vn->vn_ins_ih;
                vi->vi_item = vn->vn_data;
                vi->vi_uarea = vn->vn_free_ptr;

                op_create_vi(vn, vi, 0 /*not pasted or cut */ ,
                             tb->insert_size[0]);
        }

        /*
         * set right merge flag we take right delimiting key and
         * check whether it is a mergeable item
         */
        if (tb->CFR[0]) {
                struct reiserfs_key *key;

                key = internal_key(tb->CFR[0], tb->rkey[0]);
                if (op_is_left_mergeable(key, Sh->b_size)
                    && (vn->vn_mode != M_DELETE
                        || vn->vn_affected_item_num != B_NR_ITEMS(Sh) - 1))
                        vn->vn_vi[vn->vn_nr_item - 1].vi_type |=
                            VI_TYPE_RIGHT_MERGEABLE;

#ifdef CONFIG_REISERFS_CHECK
                if (op_is_left_mergeable(key, Sh->b_size) &&
                    !(vn->vn_mode != M_DELETE
                      || vn->vn_affected_item_num != B_NR_ITEMS(Sh) - 1)) {
                        /*
                         * we delete last item and it could be merged
                         * with right neighbor's first item
                         */
                        if (!
                            (B_NR_ITEMS(Sh) == 1
                             && is_direntry_le_ih(item_head(Sh, 0))
                             && ih_entry_count(item_head(Sh, 0)) == 1)) {
                                /*
                                 * node contains more than 1 item, or item
                                 * is not directory item, or this item
                                 * contains more than 1 entry
                                 */
                                print_block(Sh, 0, -1, -1);
                                reiserfs_panic(tb->tb_sb, "vs-8045",
                                               "rdkey %k, affected item==%d "
                                               "(mode==%c) Must be %c",
                                               key, vn->vn_affected_item_num,
                                               vn->vn_mode, M_DELETE);
                        }
                }
#endif

        }
}

/*
 * Using virtual node check, how many items can be
 * shifted to left neighbor
 */
static void check_left(struct tree_balance *tb, int h, int cur_free)
{
        int i;
        struct virtual_node *vn = tb->tb_vn;
        struct virtual_item *vi;
        int d_size, ih_size;

        RFALSE(cur_free < 0, "vs-8050: cur_free (%d) < 0", cur_free);

        /* internal level */
        if (h > 0) {
                tb->lnum[h] = cur_free / (DC_SIZE + KEY_SIZE);
                return;
        }

        /* leaf level */

        if (!cur_free || !vn->vn_nr_item) {
                /* no free space or nothing to move */
                tb->lnum[h] = 0;
                tb->lbytes = -1;
                return;
        }

        RFALSE(!PATH_H_PPARENT(tb->tb_path, 0),
               "vs-8055: parent does not exist or invalid");

        vi = vn->vn_vi;
        if ((unsigned int)cur_free >=
            (vn->vn_size -
             ((vi->vi_type & VI_TYPE_LEFT_MERGEABLE) ? IH_SIZE : 0))) {
                /* all contents of S[0] fits into L[0] */

                RFALSE(vn->vn_mode == M_INSERT || vn->vn_mode == M_PASTE,
                       "vs-8055: invalid mode or balance condition failed");

                tb->lnum[0] = vn->vn_nr_item;
                tb->lbytes = -1;
                return;
        }

        d_size = 0, ih_size = IH_SIZE;

        /* first item may be merge with last item in left neighbor */
        if (vi->vi_type & VI_TYPE_LEFT_MERGEABLE)
                d_size = -((int)IH_SIZE), ih_size = 0;

        tb->lnum[0] = 0;
        for (i = 0; i < vn->vn_nr_item;
             i++, ih_size = IH_SIZE, d_size = 0, vi++) {
                d_size += vi->vi_item_len;
                if (cur_free >= d_size) {
                        /* the item can be shifted entirely */
                        cur_free -= d_size;
                        tb->lnum[0]++;
                        continue;
                }

                /* the item cannot be shifted entirely, try to split it */
                /*
                 * check whether L[0] can hold ih and at least one byte
                 * of the item body
                 */

                /* cannot shift even a part of the current item */
                if (cur_free <= ih_size) {
                        tb->lbytes = -1;
                        return;
                }
                cur_free -= ih_size;

                tb->lbytes = op_check_left(vi, cur_free, 0, 0);
                if (tb->lbytes != -1)
                        /* count partially shifted item */
                        tb->lnum[0]++;

                break;
        }

        return;
}

/*
 * Using virtual node check, how many items can be
 * shifted to right neighbor
 */
static void check_right(struct tree_balance *tb, int h, int cur_free)
{
        int i;
        struct virtual_node *vn = tb->tb_vn;
        struct virtual_item *vi;
        int d_size, ih_size;

        RFALSE(cur_free < 0, "vs-8070: cur_free < 0");

        /* internal level */
        if (h > 0) {
                tb->rnum[h] = cur_free / (DC_SIZE + KEY_SIZE);
                return;
        }

        /* leaf level */

        if (!cur_free || !vn->vn_nr_item) {
                /* no free space  */
                tb->rnum[h] = 0;
                tb->rbytes = -1;
                return;
        }

        RFALSE(!PATH_H_PPARENT(tb->tb_path, 0),
               "vs-8075: parent does not exist or invalid");

        vi = vn->vn_vi + vn->vn_nr_item - 1;
        if ((unsigned int)cur_free >=
            (vn->vn_size -
             ((vi->vi_type & VI_TYPE_RIGHT_MERGEABLE) ? IH_SIZE : 0))) {
                /* all contents of S[0] fits into R[0] */

                RFALSE(vn->vn_mode == M_INSERT || vn->vn_mode == M_PASTE,
                       "vs-8080: invalid mode or balance condition failed");

                tb->rnum[h] = vn->vn_nr_item;
                tb->rbytes = -1;
                return;
        }

        d_size = 0, ih_size = IH_SIZE;

        /* last item may be merge with first item in right neighbor */
        if (vi->vi_type & VI_TYPE_RIGHT_MERGEABLE)
                d_size = -(int)IH_SIZE, ih_size = 0;

        tb->rnum[0] = 0;
        for (i = vn->vn_nr_item - 1; i >= 0;
             i--, d_size = 0, ih_size = IH_SIZE, vi--) {
                d_size += vi->vi_item_len;
                if (cur_free >= d_size) {
                        /* the item can be shifted entirely */
                        cur_free -= d_size;
                        tb->rnum[0]++;
                        continue;
                }

                /*
                 * check whether R[0] can hold ih and at least one
                 * byte of the item body
                 */

                /* cannot shift even a part of the current item */
                if (cur_free <= ih_size) {
                        tb->rbytes = -1;
                        return;
                }

                /*
                 * R[0] can hold the header of the item and at least
                 * one byte of its body
                 */
                cur_free -= ih_size;    /* cur_free is still > 0 */

                tb->rbytes = op_check_right(vi, cur_free);
                if (tb->rbytes != -1)
                        /* count partially shifted item */
                        tb->rnum[0]++;

                break;
        }

        return;
}

/*
 * from - number of items, which are shifted to left neighbor entirely
 * to - number of item, which are shifted to right neighbor entirely
 * from_bytes - number of bytes of boundary item (or directory entries)
 *              which are shifted to left neighbor
 * to_bytes - number of bytes of boundary item (or directory entries)
 *            which are shifted to right neighbor
 */
static int get_num_ver(int mode, struct tree_balance *tb, int h,
                       int from, int from_bytes,
                       int to, int to_bytes, short *snum012, int flow)
{
        int i;
        int units;
        struct virtual_node *vn = tb->tb_vn;
        int total_node_size, max_node_size, current_item_size;
        int needed_nodes;

        /* position of item we start filling node from */
        int start_item;

        /* position of item we finish filling node by */
        int end_item;

        /*
         * number of first bytes (entries for directory) of start_item-th item
         * we do not include into node that is being filled
         */
        int start_bytes;

        /*
         * number of last bytes (entries for directory) of end_item-th item
         * we do node include into node that is being filled
         */
        int end_bytes;

        /*
         * these are positions in virtual item of items, that are split
         * between S[0] and S1new and S1new and S2new
         */
        int split_item_positions[2];

        split_item_positions[0] = -1;
        split_item_positions[1] = -1;

        /*
         * We only create additional nodes if we are in insert or paste mode
         * or we are in replace mode at the internal level. If h is 0 and
         * the mode is M_REPLACE then in fix_nodes we change the mode to
         * paste or insert before we get here in the code.
         */
        RFALSE(tb->insert_size[h] < 0 || (mode != M_INSERT && mode != M_PASTE),
               "vs-8100: insert_size < 0 in overflow");

        max_node_size = MAX_CHILD_SIZE(PATH_H_PBUFFER(tb->tb_path, h));

        /*
         * snum012 [0-2] - number of items, that lay
         * to S[0], first new node and second new node
         */
        snum012[3] = -1;        /* s1bytes */
        snum012[4] = -1;        /* s2bytes */

        /* internal level */
        if (h > 0) {
                i = ((to - from) * (KEY_SIZE + DC_SIZE) + DC_SIZE);
                if (i == max_node_size)
                        return 1;
                return (i / max_node_size + 1);
        }

        /* leaf level */
        needed_nodes = 1;
        total_node_size = 0;

        /* start from 'from'-th item */
        start_item = from;
        /* skip its first 'start_bytes' units */
        start_bytes = ((from_bytes != -1) ? from_bytes : 0);

        /* last included item is the 'end_item'-th one */
        end_item = vn->vn_nr_item - to - 1;
        /* do not count last 'end_bytes' units of 'end_item'-th item */
        end_bytes = (to_bytes != -1) ? to_bytes : 0;

        /*
         * go through all item beginning from the start_item-th item
         * and ending by the end_item-th item. Do not count first
         * 'start_bytes' units of 'start_item'-th item and last
         * 'end_bytes' of 'end_item'-th item
         */
        for (i = start_item; i <= end_item; i++) {
                struct virtual_item *vi = vn->vn_vi + i;
                int skip_from_end = ((i == end_item) ? end_bytes : 0);

                RFALSE(needed_nodes > 3, "vs-8105: too many nodes are needed");

                /* get size of current item */
                current_item_size = vi->vi_item_len;

                /*
                 * do not take in calculation head part (from_bytes)
                 * of from-th item
                 */
                current_item_size -=
                    op_part_size(vi, 0 /*from start */ , start_bytes);

                /* do not take in calculation tail part of last item */
                current_item_size -=
                    op_part_size(vi, 1 /*from end */ , skip_from_end);

                /* if item fits into current node entierly */
                if (total_node_size + current_item_size <= max_node_size) {
                        snum012[needed_nodes - 1]++;
                        total_node_size += current_item_size;
                        start_bytes = 0;
                        continue;
                }

                /*
                 * virtual item length is longer, than max size of item in
                 * a node. It is impossible for direct item
                 */
                if (current_item_size > max_node_size) {
                        RFALSE(is_direct_le_ih(vi->vi_ih),
                               "vs-8110: "
                               "direct item length is %d. It can not be longer than %d",
                               current_item_size, max_node_size);
                        /* we will try to split it */
                        flow = 1;
                }

                /* as we do not split items, take new node and continue */
                if (!flow) {
                        needed_nodes++;
                        i--;
                        total_node_size = 0;
                        continue;
                }

                /*
                 * calculate number of item units which fit into node being
                 * filled
                 */
                {
                        int free_space;

                        free_space = max_node_size - total_node_size - IH_SIZE;
                        units =
                            op_check_left(vi, free_space, start_bytes,
                                          skip_from_end);
                        /*
                         * nothing fits into current node, take new
                         * node and continue
                         */
                        if (units == -1) {
                                needed_nodes++, i--, total_node_size = 0;
                                continue;
                        }
                }

                /* something fits into the current node */
                start_bytes += units;
                snum012[needed_nodes - 1 + 3] = units;

                if (needed_nodes > 2)
                        reiserfs_warning(tb->tb_sb, "vs-8111",
                                         "split_item_position is out of range");
                snum012[needed_nodes - 1]++;
                split_item_positions[needed_nodes - 1] = i;
                needed_nodes++;
                /* continue from the same item with start_bytes != -1 */
                start_item = i;
                i--;
                total_node_size = 0;
        }

        /*
         * sum012[4] (if it is not -1) contains number of units of which
         * are to be in S1new, snum012[3] - to be in S0. They are supposed
         * to be S1bytes and S2bytes correspondingly, so recalculate
         */
        if (snum012[4] > 0) {
                int split_item_num;
                int bytes_to_r, bytes_to_l;
                int bytes_to_S1new;

                split_item_num = split_item_positions[1];
                bytes_to_l =
                    ((from == split_item_num
                      && from_bytes != -1) ? from_bytes : 0);
                bytes_to_r =
                    ((end_item == split_item_num
                      && end_bytes != -1) ? end_bytes : 0);
                bytes_to_S1new =
                    ((split_item_positions[0] ==
                      split_item_positions[1]) ? snum012[3] : 0);

                /* s2bytes */
                snum012[4] =
                    op_unit_num(&vn->vn_vi[split_item_num]) - snum012[4] -
                    bytes_to_r - bytes_to_l - bytes_to_S1new;

                if (vn->vn_vi[split_item_num].vi_index != TYPE_DIRENTRY &&
                    vn->vn_vi[split_item_num].vi_index != TYPE_INDIRECT)
                        reiserfs_warning(tb->tb_sb, "vs-8115",
                                         "not directory or indirect item");
        }

        /* now we know S2bytes, calculate S1bytes */
        if (snum012[3] > 0) {
                int split_item_num;
                int bytes_to_r, bytes_to_l;
                int bytes_to_S2new;

                split_item_num = split_item_positions[0];
                bytes_to_l =
                    ((from == split_item_num
                      && from_bytes != -1) ? from_bytes : 0);
                bytes_to_r =
                    ((end_item == split_item_num
                      && end_bytes != -1) ? end_bytes : 0);
                bytes_to_S2new =
                    ((split_item_positions[0] == split_item_positions[1]
                      && snum012[4] != -1) ? snum012[4] : 0);

                /* s1bytes */
                snum012[3] =
                    op_unit_num(&vn->vn_vi[split_item_num]) - snum012[3] -
                    bytes_to_r - bytes_to_l - bytes_to_S2new;
        }

        return needed_nodes;
}


/*
 * Set parameters for balancing.
 * Performs write of results of analysis of balancing into structure tb,
 * where it will later be used by the functions that actually do the balancing.
 * Parameters:
 *      tb      tree_balance structure;
 *      h       current level of the node;
 *      lnum    number of items from S[h] that must be shifted to L[h];
 *      rnum    number of items from S[h] that must be shifted to R[h];
 *      blk_num number of blocks that S[h] will be splitted into;
 *      s012    number of items that fall into splitted nodes.
 *      lbytes  number of bytes which flow to the left neighbor from the
 *              item that is not shifted entirely
 *      rbytes  number of bytes which flow to the right neighbor from the
 *              item that is not shifted entirely
 *      s1bytes number of bytes which flow to the first  new node when
 *              S[0] splits (this number is contained in s012 array)
 */

static void set_parameters(struct tree_balance *tb, int h, int lnum,
                           int rnum, int blk_num, short *s012, int lb, int rb)
{

        tb->lnum[h] = lnum;
        tb->rnum[h] = rnum;
        tb->blknum[h] = blk_num;

        /* only for leaf level */
        if (h == 0) {
                if (s012 != NULL) {
                        tb->s0num = *s012++;
                        tb->snum[0] = *s012++;
                        tb->snum[1] = *s012++;
                        tb->sbytes[0] = *s012++;
                        tb->sbytes[1] = *s012;
                }
                tb->lbytes = lb;
                tb->rbytes = rb;
        }
        PROC_INFO_ADD(tb->tb_sb, lnum[h], lnum);
        PROC_INFO_ADD(tb->tb_sb, rnum[h], rnum);

        PROC_INFO_ADD(tb->tb_sb, lbytes[h], lb);
        PROC_INFO_ADD(tb->tb_sb, rbytes[h], rb);
}

/*
 * check if node disappears if we shift tb->lnum[0] items to left
 * neighbor and tb->rnum[0] to the right one.
 */
static int is_leaf_removable(struct tree_balance *tb)
{
        struct virtual_node *vn = tb->tb_vn;
        int to_left, to_right;
        int size;
        int remain_items;

        /*
         * number of items that will be shifted to left (right) neighbor
         * entirely
         */
        to_left = tb->lnum[0] - ((tb->lbytes != -1) ? 1 : 0);
        to_right = tb->rnum[0] - ((tb->rbytes != -1) ? 1 : 0);
        remain_items = vn->vn_nr_item;

        /* how many items remain in S[0] after shiftings to neighbors */
        remain_items -= (to_left + to_right);

        /* all content of node can be shifted to neighbors */
        if (remain_items < 1) {
                set_parameters(tb, 0, to_left, vn->vn_nr_item - to_left, 0,
                               NULL, -1, -1);
                return 1;
        }

        /* S[0] is not removable */
        if (remain_items > 1 || tb->lbytes == -1 || tb->rbytes == -1)
                return 0;

        /* check whether we can divide 1 remaining item between neighbors */

        /* get size of remaining item (in item units) */
        size = op_unit_num(&vn->vn_vi[to_left]);

        if (tb->lbytes + tb->rbytes >= size) {
                set_parameters(tb, 0, to_left + 1, to_right + 1, 0, NULL,
                               tb->lbytes, -1);
                return 1;
        }

        return 0;
}

/* check whether L, S, R can be joined in one node */
static int are_leaves_removable(struct tree_balance *tb, int lfree, int rfree)
{
        struct virtual_node *vn = tb->tb_vn;
        int ih_size;
        struct buffer_head *S0;

        S0 = PATH_H_PBUFFER(tb->tb_path, 0);

        ih_size = 0;
        if (vn->vn_nr_item) {
                if (vn->vn_vi[0].vi_type & VI_TYPE_LEFT_MERGEABLE)
                        ih_size += IH_SIZE;

                if (vn->vn_vi[vn->vn_nr_item - 1].
                    vi_type & VI_TYPE_RIGHT_MERGEABLE)
                        ih_size += IH_SIZE;
        } else {
                /* there was only one item and it will be deleted */
                struct item_head *ih;

                RFALSE(B_NR_ITEMS(S0) != 1,
                       "vs-8125: item number must be 1: it is %d",
                       B_NR_ITEMS(S0));

                ih = item_head(S0, 0);
                if (tb->CFR[0]
                    && !comp_short_le_keys(&ih->ih_key,
                                           internal_key(tb->CFR[0],
                                                          tb->rkey[0])))
                        /*
                         * Directory must be in correct state here: that is
                         * somewhere at the left side should exist first
                         * directory item. But the item being deleted can
                         * not be that first one because its right neighbor
                         * is item of the same directory. (But first item
                         * always gets deleted in last turn). So, neighbors
                         * of deleted item can be merged, so we can save
                         * ih_size
                         */
                        if (is_direntry_le_ih(ih)) {
                                ih_size = IH_SIZE;

                                /*
                                 * we might check that left neighbor exists
                                 * and is of the same directory
                                 */
                                RFALSE(le_ih_k_offset(ih) == DOT_OFFSET,
                                       "vs-8130: first directory item can not be removed until directory is not empty");
                        }

        }

        if (MAX_CHILD_SIZE(S0) + vn->vn_size <= rfree + lfree + ih_size) {
                set_parameters(tb, 0, -1, -1, -1, NULL, -1, -1);
                PROC_INFO_INC(tb->tb_sb, leaves_removable);
                return 1;
        }
        return 0;

}

/* when we do not split item, lnum and rnum are numbers of entire items */
#define SET_PAR_SHIFT_LEFT \
if (h)\
{\
   int to_l;\
   \
   to_l = (MAX_NR_KEY(Sh)+1 - lpar + vn->vn_nr_item + 1) / 2 -\
              (MAX_NR_KEY(Sh) + 1 - lpar);\
              \
              set_parameters (tb, h, to_l, 0, lnver, NULL, -1, -1);\
}\
else \
{\
   if (lset==LEFT_SHIFT_FLOW)\
     set_parameters (tb, h, lpar, 0, lnver, snum012+lset,\
                     tb->lbytes, -1);\
   else\
     set_parameters (tb, h, lpar - (tb->lbytes!=-1), 0, lnver, snum012+lset,\
                     -1, -1);\
}

#define SET_PAR_SHIFT_RIGHT \
if (h)\
{\
   int to_r;\
   \
   to_r = (MAX_NR_KEY(Sh)+1 - rpar + vn->vn_nr_item + 1) / 2 - (MAX_NR_KEY(Sh) + 1 - rpar);\
   \
   set_parameters (tb, h, 0, to_r, rnver, NULL, -1, -1);\
}\
else \
{\
   if (rset==RIGHT_SHIFT_FLOW)\
     set_parameters (tb, h, 0, rpar, rnver, snum012+rset,\
                  -1, tb->rbytes);\
   else\
     set_parameters (tb, h, 0, rpar - (tb->rbytes!=-1), rnver, snum012+rset,\
                  -1, -1);\
}

static void free_buffers_in_tb(struct tree_balance *tb)
{
        int i;

        pathrelse(tb->tb_path);

        for (i = 0; i < MAX_HEIGHT; i++) {
                brelse(tb->L[i]);
                brelse(tb->R[i]);
                brelse(tb->FL[i]);
                brelse(tb->FR[i]);
                brelse(tb->CFL[i]);
                brelse(tb->CFR[i]);

                tb->L[i] = NULL;
                tb->R[i] = NULL;
                tb->FL[i] = NULL;
                tb->FR[i] = NULL;
                tb->CFL[i] = NULL;
                tb->CFR[i] = NULL;
        }
}

/*
 * Get new buffers for storing new nodes that are created while balancing.
 * Returns:     SCHEDULE_OCCURRED - schedule occurred while the function worked;
 *              CARRY_ON - schedule didn't occur while the function worked;
 *              NO_DISK_SPACE - no disk space.
 */
/* The function is NOT SCHEDULE-SAFE! */
static int get_empty_nodes(struct tree_balance *tb, int h)
{
        struct buffer_head *new_bh, *Sh = PATH_H_PBUFFER(tb->tb_path, h);
        b_blocknr_t *blocknr, blocknrs[MAX_AMOUNT_NEEDED] = { 0, };
        int counter, number_of_freeblk;
        int  amount_needed;     /* number of needed empty blocks */
        int  retval = CARRY_ON;
        struct super_block *sb = tb->tb_sb;

        /*
         * number_of_freeblk is the number of empty blocks which have been
         * acquired for use by the balancing algorithm minus the number of
         * empty blocks used in the previous levels of the analysis,
         * number_of_freeblk = tb->cur_blknum can be non-zero if a schedule
         * occurs after empty blocks are acquired, and the balancing analysis
         * is then restarted, amount_needed is the number needed by this
         * level (h) of the balancing analysis.
         *
         * Note that for systems with many processes writing, it would be
         * more layout optimal to calculate the total number needed by all
         * levels and then to run reiserfs_new_blocks to get all of them at
         * once.
         */

        /*
         * Initiate number_of_freeblk to the amount acquired prior to the
         * restart of the analysis or 0 if not restarted, then subtract the
         * amount needed by all of the levels of the tree below h.
         */
        /* blknum includes S[h], so we subtract 1 in this calculation */
        for (counter = 0, number_of_freeblk = tb->cur_blknum;
             counter < h; counter++)
                number_of_freeblk -=
                    (tb->blknum[counter]) ? (tb->blknum[counter] -
                                                   1) : 0;

        /* Allocate missing empty blocks. */
        /* if Sh == 0  then we are getting a new root */
        amount_needed = (Sh) ? (tb->blknum[h] - 1) : 1;
        /*
         * Amount_needed = the amount that we need more than the
         * amount that we have.
         */
        if (amount_needed > number_of_freeblk)
                amount_needed -= number_of_freeblk;
        else    /* If we have enough already then there is nothing to do. */
                return CARRY_ON;

        /*
         * No need to check quota - is not allocated for blocks used
         * for formatted nodes
         */
        if (reiserfs_new_form_blocknrs(tb, blocknrs,
                                       amount_needed) == NO_DISK_SPACE)
                return NO_DISK_SPACE;

        /* for each blocknumber we just got, get a buffer and stick it on FEB */
        for (blocknr = blocknrs, counter = 0;
             counter < amount_needed; blocknr++, counter++) {

                RFALSE(!*blocknr,
                       "PAP-8135: reiserfs_new_blocknrs failed when got new blocks");

                new_bh = sb_getblk(sb, *blocknr);
                RFALSE(buffer_dirty(new_bh) ||
                       buffer_journaled(new_bh) ||
                       buffer_journal_dirty(new_bh),
                       "PAP-8140: journaled or dirty buffer %b for the new block",
                       new_bh);

                /* Put empty buffers into the array. */
                RFALSE(tb->FEB[tb->cur_blknum],
                       "PAP-8141: busy slot for new buffer");

                set_buffer_journal_new(new_bh);
                tb->FEB[tb->cur_blknum++] = new_bh;
        }

        if (retval == CARRY_ON && FILESYSTEM_CHANGED_TB(tb))
                retval = REPEAT_SEARCH;

        return retval;
}

/*
 * Get free space of the left neighbor, which is stored in the parent
 * node of the left neighbor.
 */
static int get_lfree(struct tree_balance *tb, int h)
{
        struct buffer_head *l, *f;
        int order;

        if ((f = PATH_H_PPARENT(tb->tb_path, h)) == NULL ||
            (l = tb->FL[h]) == NULL)
                return 0;

        if (f == l)
                order = PATH_H_B_ITEM_ORDER(tb->tb_path, h) - 1;
        else {
                order = B_NR_ITEMS(l);
                f = l;
        }

        return (MAX_CHILD_SIZE(f) - dc_size(B_N_CHILD(f, order)));
}

/*
 * Get free space of the right neighbor,
 * which is stored in the parent node of the right neighbor.
 */
static int get_rfree(struct tree_balance *tb, int h)
{
        struct buffer_head *r, *f;
        int order;

        if ((f = PATH_H_PPARENT(tb->tb_path, h)) == NULL ||
            (r = tb->FR[h]) == NULL)
                return 0;

        if (f == r)
                order = PATH_H_B_ITEM_ORDER(tb->tb_path, h) + 1;
        else {
                order = 0;
                f = r;
        }

        return (MAX_CHILD_SIZE(f) - dc_size(B_N_CHILD(f, order)));

}

/* Check whether left neighbor is in memory. */
static int is_left_neighbor_in_cache(struct tree_balance *tb, int h)
{
        struct buffer_head *father, *left;
        struct super_block *sb = tb->tb_sb;
        b_blocknr_t left_neighbor_blocknr;
        int left_neighbor_position;

        /* Father of the left neighbor does not exist. */
        if (!tb->FL[h])
                return 0;

        /* Calculate father of the node to be balanced. */
        father = PATH_H_PBUFFER(tb->tb_path, h + 1);

        RFALSE(!father ||
               !B_IS_IN_TREE(father) ||
               !B_IS_IN_TREE(tb->FL[h]) ||
               !buffer_uptodate(father) ||
               !buffer_uptodate(tb->FL[h]),
               "vs-8165: F[h] (%b) or FL[h] (%b) is invalid",
               father, tb->FL[h]);

        /*
         * Get position of the pointer to the left neighbor
         * into the left father.
         */
        left_neighbor_position = (father == tb->FL[h]) ?
            tb->lkey[h] : B_NR_ITEMS(tb->FL[h]);
        /* Get left neighbor block number. */
        left_neighbor_blocknr =
            B_N_CHILD_NUM(tb->FL[h], left_neighbor_position);
        /* Look for the left neighbor in the cache. */
        if ((left = sb_find_get_block(sb, left_neighbor_blocknr))) {

                RFALSE(buffer_uptodate(left) && !B_IS_IN_TREE(left),
                       "vs-8170: left neighbor (%b %z) is not in the tree",
                       left, left);
                put_bh(left);
                return 1;
        }

        return 0;

}

#define LEFT_PARENTS  'l'
#define RIGHT_PARENTS 'r'

static void decrement_key(struct cpu_key *key)
{
        /* call item specific function for this key */
        item_ops[cpu_key_k_type(key)]->decrement_key(key);
}

/*
 * Calculate far left/right parent of the left/right neighbor of the
 * current node, that is calculate the left/right (FL[h]/FR[h]) neighbor
 * of the parent F[h].
 * Calculate left/right common parent of the current node and L[h]/R[h].
 * Calculate left/right delimiting key position.
 * Returns:     PATH_INCORRECT    - path in the tree is not correct
 *              SCHEDULE_OCCURRED - schedule occurred while the function worked
 *              CARRY_ON          - schedule didn't occur while the function
 *                                  worked
 */
static int get_far_parent(struct tree_balance *tb,
                          int h,
                          struct buffer_head **pfather,
                          struct buffer_head **pcom_father, char c_lr_par)
{
        struct buffer_head *parent;
        INITIALIZE_PATH(s_path_to_neighbor_father);
        struct treepath *path = tb->tb_path;
        struct cpu_key s_lr_father_key;
        int counter,
            position = INT_MAX,
            first_last_position = 0,
            path_offset = PATH_H_PATH_OFFSET(path, h);

        /*
         * Starting from F[h] go upwards in the tree, and look for the common
         * ancestor of F[h], and its neighbor l/r, that should be obtained.
         */

        counter = path_offset;

        RFALSE(counter < FIRST_PATH_ELEMENT_OFFSET,
               "PAP-8180: invalid path length");

        for (; counter > FIRST_PATH_ELEMENT_OFFSET; counter--) {
                /*
                 * Check whether parent of the current buffer in the path
                 * is really parent in the tree.
                 */
                if (!B_IS_IN_TREE
                    (parent = PATH_OFFSET_PBUFFER(path, counter - 1)))
                        return REPEAT_SEARCH;

                /* Check whether position in the parent is correct. */
                if ((position =
                     PATH_OFFSET_POSITION(path,
                                          counter - 1)) >
                    B_NR_ITEMS(parent))
                        return REPEAT_SEARCH;

                /*
                 * Check whether parent at the path really points
                 * to the child.
                 */
                if (B_N_CHILD_NUM(parent, position) !=
                    PATH_OFFSET_PBUFFER(path, counter)->b_blocknr)
                        return REPEAT_SEARCH;

                /*
                 * Return delimiting key if position in the parent is not
                 * equal to first/last one.
                 */
                if (c_lr_par == RIGHT_PARENTS)
                        first_last_position = B_NR_ITEMS(parent);
                if (position != first_last_position) {
                        *pcom_father = parent;
                        get_bh(*pcom_father);
                        /*(*pcom_father = parent)->b_count++; */
                        break;
                }
        }

        /* if we are in the root of the tree, then there is no common father */
        if (counter == FIRST_PATH_ELEMENT_OFFSET) {
                /*
                 * Check whether first buffer in the path is the
                 * root of the tree.
                 */
                if (PATH_OFFSET_PBUFFER
                    (tb->tb_path,
                     FIRST_PATH_ELEMENT_OFFSET)->b_blocknr ==
                    SB_ROOT_BLOCK(tb->tb_sb)) {
                        *pfather = *pcom_father = NULL;
                        return CARRY_ON;
                }
                return REPEAT_SEARCH;
        }

        RFALSE(B_LEVEL(*pcom_father) <= DISK_LEAF_NODE_LEVEL,
               "PAP-8185: (%b %z) level too small",
               *pcom_father, *pcom_father);

        /* Check whether the common parent is locked. */

        if (buffer_locked(*pcom_father)) {

                /* Release the write lock while the buffer is busy */
                int depth = reiserfs_write_unlock_nested(tb->tb_sb);
                __wait_on_buffer(*pcom_father);
                reiserfs_write_lock_nested(tb->tb_sb, depth);
                if (FILESYSTEM_CHANGED_TB(tb)) {
                        brelse(*pcom_father);
                        return REPEAT_SEARCH;
                }
        }

        /*
         * So, we got common parent of the current node and its
         * left/right neighbor.  Now we are getting the parent of the
         * left/right neighbor.
         */

        /* Form key to get parent of the left/right neighbor. */
        le_key2cpu_key(&s_lr_father_key,
                       internal_key(*pcom_father,
                                      (c_lr_par ==
                                       LEFT_PARENTS) ? (tb->lkey[h - 1] =
                                                        position -
                                                        1) : (tb->rkey[h -
                                                                           1] =
                                                              position)));

        if (c_lr_par == LEFT_PARENTS)
                decrement_key(&s_lr_father_key);

        if (search_by_key
            (tb->tb_sb, &s_lr_father_key, &s_path_to_neighbor_father,
             h + 1) == IO_ERROR)
                /* path is released */
                return IO_ERROR;

        if (FILESYSTEM_CHANGED_TB(tb)) {
                pathrelse(&s_path_to_neighbor_father);
                brelse(*pcom_father);
                return REPEAT_SEARCH;
        }

        *pfather = PATH_PLAST_BUFFER(&s_path_to_neighbor_father);

        RFALSE(B_LEVEL(*pfather) != h + 1,
               "PAP-8190: (%b %z) level too small", *pfather, *pfather);
        RFALSE(s_path_to_neighbor_father.path_length <
               FIRST_PATH_ELEMENT_OFFSET, "PAP-8192: path length is too small");

        s_path_to_neighbor_father.path_length--;
        pathrelse(&s_path_to_neighbor_father);
        return CARRY_ON;
}

/*
 * Get parents of neighbors of node in the path(S[path_offset]) and
 * common parents of S[path_offset] and L[path_offset]/R[path_offset]:
 * F[path_offset], FL[path_offset], FR[path_offset], CFL[path_offset],
 * CFR[path_offset].
 * Calculate numbers of left and right delimiting keys position:
 * lkey[path_offset], rkey[path_offset].
 * Returns:     SCHEDULE_OCCURRED - schedule occurred while the function worked
 *              CARRY_ON - schedule didn't occur while the function worked
 */
static int get_parents(struct tree_balance *tb, int h)
{
        struct treepath *path = tb->tb_path;
        int position,
            ret,
            path_offset = PATH_H_PATH_OFFSET(tb->tb_path, h);
        struct buffer_head *curf, *curcf;

        /* Current node is the root of the tree or will be root of the tree */
        if (path_offset <= FIRST_PATH_ELEMENT_OFFSET) {
                /*
                 * The root can not have parents.
                 * Release nodes which previously were obtained as
                 * parents of the current node neighbors.
                 */
                brelse(tb->FL[h]);
                brelse(tb->CFL[h]);
                brelse(tb->FR[h]);
                brelse(tb->CFR[h]);
                tb->FL[h]  = NULL;
                tb->CFL[h] = NULL;
                tb->FR[h]  = NULL;
                tb->CFR[h] = NULL;
                return CARRY_ON;
        }

        /* Get parent FL[path_offset] of L[path_offset]. */
        position = PATH_OFFSET_POSITION(path, path_offset - 1);
        if (position) {
                /* Current node is not the first child of its parent. */
                curf = PATH_OFFSET_PBUFFER(path, path_offset - 1);
                curcf = PATH_OFFSET_PBUFFER(path, path_offset - 1);
                get_bh(curf);
                get_bh(curf);
                tb->lkey[h] = position - 1;
        } else {
                /*
                 * Calculate current parent of L[path_offset], which is the
                 * left neighbor of the current node.  Calculate current
                 * common parent of L[path_offset] and the current node.
                 * Note that CFL[path_offset] not equal FL[path_offset] and
                 * CFL[path_offset] not equal F[path_offset].
                 * Calculate lkey[path_offset].
                 */
                if ((ret = get_far_parent(tb, h + 1, &curf,
                                                  &curcf,
                                                  LEFT_PARENTS)) != CARRY_ON)
                        return ret;
        }

        brelse(tb->FL[h]);
        tb->FL[h] = curf;       /* New initialization of FL[h]. */
        brelse(tb->CFL[h]);
        tb->CFL[h] = curcf;     /* New initialization of CFL[h]. */

        RFALSE((curf && !B_IS_IN_TREE(curf)) ||
               (curcf && !B_IS_IN_TREE(curcf)),
               "PAP-8195: FL (%b) or CFL (%b) is invalid", curf, curcf);

        /* Get parent FR[h] of R[h]. */

        /* Current node is the last child of F[h]. FR[h] != F[h]. */
        if (position == B_NR_ITEMS(PATH_H_PBUFFER(path, h + 1))) {
                /*
                 * Calculate current parent of R[h], which is the right
                 * neighbor of F[h].  Calculate current common parent of
                 * R[h] and current node. Note that CFR[h] not equal
                 * FR[path_offset] and CFR[h] not equal F[h].
                 */
                if ((ret =
                     get_far_parent(tb, h + 1, &curf, &curcf,
                                    RIGHT_PARENTS)) != CARRY_ON)
                        return ret;
        } else {
                /* Current node is not the last child of its parent F[h]. */
                curf = PATH_OFFSET_PBUFFER(path, path_offset - 1);
                curcf = PATH_OFFSET_PBUFFER(path, path_offset - 1);
                get_bh(curf);
                get_bh(curf);
                tb->rkey[h] = position;
        }

        brelse(tb->FR[h]);
        /* New initialization of FR[path_offset]. */
        tb->FR[h] = curf;

        brelse(tb->CFR[h]);
        /* New initialization of CFR[path_offset]. */
        tb->CFR[h] = curcf;

        RFALSE((curf && !B_IS_IN_TREE(curf)) ||
               (curcf && !B_IS_IN_TREE(curcf)),
               "PAP-8205: FR (%b) or CFR (%b) is invalid", curf, curcf);

        return CARRY_ON;
}

/*
 * it is possible to remove node as result of shiftings to
 * neighbors even when we insert or paste item.
 */
static inline int can_node_be_removed(int mode, int lfree, int sfree, int rfree,
                                      struct tree_balance *tb, int h)
{
        struct buffer_head *Sh = PATH_H_PBUFFER(tb->tb_path, h);
        int levbytes = tb->insert_size[h];
        struct item_head *ih;
        struct reiserfs_key *r_key = NULL;

        ih = item_head(Sh, 0);
        if (tb->CFR[h])
                r_key = internal_key(tb->CFR[h], tb->rkey[h]);

        if (lfree + rfree + sfree < MAX_CHILD_SIZE(Sh) + levbytes
            /* shifting may merge items which might save space */
            -
            ((!h
              && op_is_left_mergeable(&ih->ih_key, Sh->b_size)) ? IH_SIZE : 0)
            -
            ((!h && r_key
              && op_is_left_mergeable(r_key, Sh->b_size)) ? IH_SIZE : 0)
            + ((h) ? KEY_SIZE : 0)) {
                /* node can not be removed */
                if (sfree >= levbytes) {
                        /* new item fits into node S[h] without any shifting */
                        if (!h)
                                tb->s0num =
                                    B_NR_ITEMS(Sh) +
                                    ((mode == M_INSERT) ? 1 : 0);
                        set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
                        return NO_BALANCING_NEEDED;
                }
        }
        PROC_INFO_INC(tb->tb_sb, can_node_be_removed[h]);
        return !NO_BALANCING_NEEDED;
}

/*
 * Check whether current node S[h] is balanced when increasing its size by
 * Inserting or Pasting.
 * Calculate parameters for balancing for current level h.
 * Parameters:
 *      tb      tree_balance structure;
 *      h       current level of the node;
 *      inum    item number in S[h];
 *      mode    i - insert, p - paste;
 * Returns:     1 - schedule occurred;
 *              0 - balancing for higher levels needed;
 *             -1 - no balancing for higher levels needed;
 *             -2 - no disk space.
 */
/* ip means Inserting or Pasting */
static int ip_check_balance(struct tree_balance *tb, int h)
{
        struct virtual_node *vn = tb->tb_vn;
        /*
         * Number of bytes that must be inserted into (value is negative
         * if bytes are deleted) buffer which contains node being balanced.
         * The mnemonic is that the attempted change in node space used
         * level is levbytes bytes.
         */
        int levbytes;
        int ret;

        int lfree, sfree, rfree /* free space in L, S and R */ ;

        /*
         * nver is short for number of vertixes, and lnver is the number if
         * we shift to the left, rnver is the number if we shift to the
         * right, and lrnver is the number if we shift in both directions.
         * The goal is to minimize first the number of vertixes, and second,
         * the number of vertixes whose contents are changed by shifting,
         * and third the number of uncached vertixes whose contents are
         * changed by shifting and must be read from disk.
         */
        int nver, lnver, rnver, lrnver;

        /*
         * used at leaf level only, S0 = S[0] is the node being balanced,
         * sInum [ I = 0,1,2 ] is the number of items that will
         * remain in node SI after balancing.  S1 and S2 are new
         * nodes that might be created.
         */

        /*
         * we perform 8 calls to get_num_ver().  For each call we
         * calculate five parameters.  where 4th parameter is s1bytes
         * and 5th - s2bytes
         *
         * s0num, s1num, s2num for 8 cases
         * 0,1 - do not shift and do not shift but bottle
         * 2   - shift only whole item to left
         * 3   - shift to left and bottle as much as possible
         * 4,5 - shift to right (whole items and as much as possible
         * 6,7 - shift to both directions (whole items and as much as possible)
         */
        short snum012[40] = { 0, };

        /* Sh is the node whose balance is currently being checked */
        struct buffer_head *Sh;

        Sh = PATH_H_PBUFFER(tb->tb_path, h);
        levbytes = tb->insert_size[h];

        /* Calculate balance parameters for creating new root. */
        if (!Sh) {
                if (!h)
                        reiserfs_panic(tb->tb_sb, "vs-8210",
                                       "S[0] can not be 0");
                switch (ret = get_empty_nodes(tb, h)) {
                /* no balancing for higher levels needed */
                case CARRY_ON:
                        set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
                        return NO_BALANCING_NEEDED;

                case NO_DISK_SPACE:
                case REPEAT_SEARCH:
                        return ret;
                default:
                        reiserfs_panic(tb->tb_sb, "vs-8215", "incorrect "
                                       "return value of get_empty_nodes");
                }
        }

        /* get parents of S[h] neighbors. */
        ret = get_parents(tb, h);
        if (ret != CARRY_ON)
                return ret;

        sfree = B_FREE_SPACE(Sh);

        /* get free space of neighbors */
        rfree = get_rfree(tb, h);
        lfree = get_lfree(tb, h);

        /* and new item fits into node S[h] without any shifting */
        if (can_node_be_removed(vn->vn_mode, lfree, sfree, rfree, tb, h) ==
            NO_BALANCING_NEEDED)
                return NO_BALANCING_NEEDED;

        create_virtual_node(tb, h);

        /*
         * determine maximal number of items we can shift to the left
         * neighbor (in tb structure) and the maximal number of bytes
         * that can flow to the left neighbor from the left most liquid
         * item that cannot be shifted from S[0] entirely (returned value)
         */
        check_left(tb, h, lfree);

        /*
         * determine maximal number of items we can shift to the right
         * neighbor (in tb structure) and the maximal number of bytes
         * that can flow to the right neighbor from the right most liquid
         * item that cannot be shifted from S[0] entirely (returned value)
         */
        check_right(tb, h, rfree);

        /*
         * all contents of internal node S[h] can be moved into its
         * neighbors, S[h] will be removed after balancing
         */
        if (h && (tb->rnum[h] + tb->lnum[h] >= vn->vn_nr_item + 1)) {
                int to_r;

                /*
                 * Since we are working on internal nodes, and our internal
                 * nodes have fixed size entries, then we can balance by the
                 * number of items rather than the space they consume.  In this
                 * routine we set the left node equal to the right node,
                 * allowing a difference of less than or equal to 1 child
                 * pointer.
                 */
                to_r =
                    ((MAX_NR_KEY(Sh) << 1) + 2 - tb->lnum[h] - tb->rnum[h] +
                     vn->vn_nr_item + 1) / 2 - (MAX_NR_KEY(Sh) + 1 -
                                                tb->rnum[h]);
                set_parameters(tb, h, vn->vn_nr_item + 1 - to_r, to_r, 0, NULL,
                               -1, -1);
                return CARRY_ON;
        }

        /*
         * this checks balance condition, that any two neighboring nodes
         * can not fit in one node
         */
        RFALSE(h &&
               (tb->lnum[h] >= vn->vn_nr_item + 1 ||
                tb->rnum[h] >= vn->vn_nr_item + 1),
               "vs-8220: tree is not balanced on internal level");
        RFALSE(!h && ((tb->lnum[h] >= vn->vn_nr_item && (tb->lbytes == -1)) ||
                      (tb->rnum[h] >= vn->vn_nr_item && (tb->rbytes == -1))),
               "vs-8225: tree is not balanced on leaf level");

        /*
         * all contents of S[0] can be moved into its neighbors
         * S[0] will be removed after balancing.
         */
        if (!h && is_leaf_removable(tb))
                return CARRY_ON;

        /*
         * why do we perform this check here rather than earlier??
         * Answer: we can win 1 node in some cases above. Moreover we
         * checked it above, when we checked, that S[0] is not removable
         * in principle
         */

         /* new item fits into node S[h] without any shifting */
        if (sfree >= levbytes) {
                if (!h)
                        tb->s0num = vn->vn_nr_item;
                set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
                return NO_BALANCING_NEEDED;
        }

        {
                int lpar, rpar, nset, lset, rset, lrset;
                /* regular overflowing of the node */

                /*
                 * get_num_ver works in 2 modes (FLOW & NO_FLOW)
                 * lpar, rpar - number of items we can shift to left/right
                 *              neighbor (including splitting item)
                 * nset, lset, rset, lrset - shows, whether flowing items
                 *                           give better packing
                 */
#define FLOW 1
#define NO_FLOW 0               /* do not any splitting */

                /* we choose one of the following */
#define NOTHING_SHIFT_NO_FLOW   0
#define NOTHING_SHIFT_FLOW      5
#define LEFT_SHIFT_NO_FLOW      10
#define LEFT_SHIFT_FLOW         15
#define RIGHT_SHIFT_NO_FLOW     20
#define RIGHT_SHIFT_FLOW        25
#define LR_SHIFT_NO_FLOW        30
#define LR_SHIFT_FLOW           35

                lpar = tb->lnum[h];
                rpar = tb->rnum[h];

                /*
                 * calculate number of blocks S[h] must be split into when
                 * nothing is shifted to the neighbors, as well as number of
                 * items in each part of the split node (s012 numbers),
                 * and number of bytes (s1bytes) of the shared drop which
                 * flow to S1 if any
                 */
                nset = NOTHING_SHIFT_NO_FLOW;
                nver = get_num_ver(vn->vn_mode, tb, h,
                                   0, -1, h ? vn->vn_nr_item : 0, -1,
                                   snum012, NO_FLOW);

                if (!h) {
                        int nver1;

                        /*
                         * note, that in this case we try to bottle
                         * between S[0] and S1 (S1 - the first new node)
                         */
                        nver1 = get_num_ver(vn->vn_mode, tb, h,
                                            0, -1, 0, -1,
                                            snum012 + NOTHING_SHIFT_FLOW, FLOW);
                        if (nver > nver1)
                                nset = NOTHING_SHIFT_FLOW, nver = nver1;
                }

                /*
                 * calculate number of blocks S[h] must be split into when
                 * l_shift_num first items and l_shift_bytes of the right
                 * most liquid item to be shifted are shifted to the left
                 * neighbor, as well as number of items in each part of the
                 * splitted node (s012 numbers), and number of bytes
                 * (s1bytes) of the shared drop which flow to S1 if any
                 */
                lset = LEFT_SHIFT_NO_FLOW;
                lnver = get_num_ver(vn->vn_mode, tb, h,
                                    lpar - ((h || tb->lbytes == -1) ? 0 : 1),
                                    -1, h ? vn->vn_nr_item : 0, -1,
                                    snum012 + LEFT_SHIFT_NO_FLOW, NO_FLOW);
                if (!h) {
                        int lnver1;

                        lnver1 = get_num_ver(vn->vn_mode, tb, h,
                                             lpar -
                                             ((tb->lbytes != -1) ? 1 : 0),
                                             tb->lbytes, 0, -1,
                                             snum012 + LEFT_SHIFT_FLOW, FLOW);
                        if (lnver > lnver1)
                                lset = LEFT_SHIFT_FLOW, lnver = lnver1;
                }

                /*
                 * calculate number of blocks S[h] must be split into when
                 * r_shift_num first items and r_shift_bytes of the left most
                 * liquid item to be shifted are shifted to the right neighbor,
                 * as well as number of items in each part of the splitted
                 * node (s012 numbers), and number of bytes (s1bytes) of the
                 * shared drop which flow to S1 if any
                 */
                rset = RIGHT_SHIFT_NO_FLOW;
                rnver = get_num_ver(vn->vn_mode, tb, h,
                                    0, -1,
                                    h ? (vn->vn_nr_item - rpar) : (rpar -
                                                                   ((tb->
                                                                     rbytes !=
                                                                     -1) ? 1 :
                                                                    0)), -1,
                                    snum012 + RIGHT_SHIFT_NO_FLOW, NO_FLOW);
                if (!h) {
                        int rnver1;

                        rnver1 = get_num_ver(vn->vn_mode, tb, h,
                                             0, -1,
                                             (rpar -
                                              ((tb->rbytes != -1) ? 1 : 0)),
                                             tb->rbytes,
                                             snum012 + RIGHT_SHIFT_FLOW, FLOW);

                        if (rnver > rnver1)
                                rset = RIGHT_SHIFT_FLOW, rnver = rnver1;
                }

                /*
                 * calculate number of blocks S[h] must be split into when
                 * items are shifted in both directions, as well as number
                 * of items in each part of the splitted node (s012 numbers),
                 * and number of bytes (s1bytes) of the shared drop which
                 * flow to S1 if any
                 */
                lrset = LR_SHIFT_NO_FLOW;
                lrnver = get_num_ver(vn->vn_mode, tb, h,
                                     lpar - ((h || tb->lbytes == -1) ? 0 : 1),
                                     -1,
                                     h ? (vn->vn_nr_item - rpar) : (rpar -
                                                                    ((tb->
                                                                      rbytes !=
                                                                      -1) ? 1 :
                                                                     0)), -1,
                                     snum012 + LR_SHIFT_NO_FLOW, NO_FLOW);
                if (!h) {
                        int lrnver1;

                        lrnver1 = get_num_ver(vn->vn_mode, tb, h,
                                              lpar -
                                              ((tb->lbytes != -1) ? 1 : 0),
                                              tb->lbytes,
                                              (rpar -
                                               ((tb->rbytes != -1) ? 1 : 0)),
                                              tb->rbytes,
                                              snum012 + LR_SHIFT_FLOW, FLOW);
                        if (lrnver > lrnver1)
                                lrset = LR_SHIFT_FLOW, lrnver = lrnver1;
                }

                /*
                 * Our general shifting strategy is:
                 * 1) to minimized number of new nodes;
                 * 2) to minimized number of neighbors involved in shifting;
                 * 3) to minimized number of disk reads;
                 */

                /* we can win TWO or ONE nodes by shifting in both directions */
                if (lrnver < lnver && lrnver < rnver) {
                        RFALSE(h &&
                               (tb->lnum[h] != 1 ||
                                tb->rnum[h] != 1 ||
                                lrnver != 1 || rnver != 2 || lnver != 2
                                || h != 1), "vs-8230: bad h");
                        if (lrset == LR_SHIFT_FLOW)
                                set_parameters(tb, h, tb->lnum[h], tb->rnum[h],
                                               lrnver, snum012 + lrset,
                                               tb->lbytes, tb->rbytes);
                        else
                                set_parameters(tb, h,
                                               tb->lnum[h] -
                                               ((tb->lbytes == -1) ? 0 : 1),
                                               tb->rnum[h] -
                                               ((tb->rbytes == -1) ? 0 : 1),
                                               lrnver, snum012 + lrset, -1, -1);

                        return CARRY_ON;
                }

                /*
                 * if shifting doesn't lead to better packing
                 * then don't shift
                 */
                if (nver == lrnver) {
                        set_parameters(tb, h, 0, 0, nver, snum012 + nset, -1,
                                       -1);
                        return CARRY_ON;
                }

                /*
                 * now we know that for better packing shifting in only one
                 * direction either to the left or to the right is required
                 */

                /*
                 * if shifting to the left is better than
                 * shifting to the right
                 */
                if (lnver < rnver) {
                        SET_PAR_SHIFT_LEFT;
                        return CARRY_ON;
                }

                /*
                 * if shifting to the right is better than
                 * shifting to the left
                 */
                if (lnver > rnver) {
                        SET_PAR_SHIFT_RIGHT;
                        return CARRY_ON;
                }

                /*
                 * now shifting in either direction gives the same number
                 * of nodes and we can make use of the cached neighbors
                 */
                if (is_left_neighbor_in_cache(tb, h)) {
                        SET_PAR_SHIFT_LEFT;
                        return CARRY_ON;
                }

                /*
                 * shift to the right independently on whether the
                 * right neighbor in cache or not
                 */
                SET_PAR_SHIFT_RIGHT;
                return CARRY_ON;
        }
}

/*
 * Check whether current node S[h] is balanced when Decreasing its size by
 * Deleting or Cutting for INTERNAL node of S+tree.
 * Calculate parameters for balancing for current level h.
 * Parameters:
 *      tb      tree_balance structure;
 *      h       current level of the node;
 *      inum    item number in S[h];
 *      mode    i - insert, p - paste;
 * Returns:     1 - schedule occurred;
 *              0 - balancing for higher levels needed;
 *             -1 - no balancing for higher levels needed;
 *             -2 - no disk space.
 *
 * Note: Items of internal nodes have fixed size, so the balance condition for
 * the internal part of S+tree is as for the B-trees.
 */
static int dc_check_balance_internal(struct tree_balance *tb, int h)
{
        struct virtual_node *vn = tb->tb_vn;

        /*
         * Sh is the node whose balance is currently being checked,
         * and Fh is its father.
         */
        struct buffer_head *Sh, *Fh;
        int ret;
        int lfree, rfree /* free space in L and R */ ;

        Sh = PATH_H_PBUFFER(tb->tb_path, h);
        Fh = PATH_H_PPARENT(tb->tb_path, h);

        /*
         * using tb->insert_size[h], which is negative in this case,
         * create_virtual_node calculates:
         * new_nr_item = number of items node would have if operation is
         * performed without balancing (new_nr_item);
         */
        create_virtual_node(tb, h);

        if (!Fh) {              /* S[h] is the root. */
                /* no balancing for higher levels needed */
                if (vn->vn_nr_item > 0) {
                        set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
                        return NO_BALANCING_NEEDED;
                }
                /*
                 * new_nr_item == 0.
                 * Current root will be deleted resulting in
                 * decrementing the tree height.
                 */
                set_parameters(tb, h, 0, 0, 0, NULL, -1, -1);
                return CARRY_ON;
        }

        if ((ret = get_parents(tb, h)) != CARRY_ON)
                return ret;

        /* get free space of neighbors */
        rfree = get_rfree(tb, h);
        lfree = get_lfree(tb, h);

        /* determine maximal number of items we can fit into neighbors */
        check_left(tb, h, lfree);
        check_right(tb, h, rfree);

        /*
         * Balance condition for the internal node is valid.
         * In this case we balance only if it leads to better packing.
         */
        if (vn->vn_nr_item >= MIN_NR_KEY(Sh)) {
                /*
                 * Here we join S[h] with one of its neighbors,
                 * which is impossible with greater values of new_nr_item.
                 */
                if (vn->vn_nr_item == MIN_NR_KEY(Sh)) {
                        /* All contents of S[h] can be moved to L[h]. */
                        if (tb->lnum[h] >= vn->vn_nr_item + 1) {
                                int n;
                                int order_L;

                                order_L =
                                    ((n =
                                      PATH_H_B_ITEM_ORDER(tb->tb_path,
                                                          h)) ==
                                     0) ? B_NR_ITEMS(tb->FL[h]) : n - 1;
                                n = dc_size(B_N_CHILD(tb->FL[h], order_L)) /
                                    (DC_SIZE + KEY_SIZE);
                                set_parameters(tb, h, -n - 1, 0, 0, NULL, -1,
                                               -1);
                                return CARRY_ON;
                        }

                        /* All contents of S[h] can be moved to R[h]. */
                        if (tb->rnum[h] >= vn->vn_nr_item + 1) {
                                int n;
                                int order_R;

                                order_R =
                                    ((n =
                                      PATH_H_B_ITEM_ORDER(tb->tb_path,
                                                          h)) ==
                                     B_NR_ITEMS(Fh)) ? 0 : n + 1;
                                n = dc_size(B_N_CHILD(tb->FR[h], order_R)) /
                                    (DC_SIZE + KEY_SIZE);
                                set_parameters(tb, h, 0, -n - 1, 0, NULL, -1,
                                               -1);
                                return CARRY_ON;
                        }
                }

                /*
                 * All contents of S[h] can be moved to the neighbors
                 * (L[h] & R[h]).
                 */
                if (tb->rnum[h] + tb->lnum[h] >= vn->vn_nr_item + 1) {
                        int to_r;

                        to_r =
                            ((MAX_NR_KEY(Sh) << 1) + 2 - tb->lnum[h] -
                             tb->rnum[h] + vn->vn_nr_item + 1) / 2 -
                            (MAX_NR_KEY(Sh) + 1 - tb->rnum[h]);
                        set_parameters(tb, h, vn->vn_nr_item + 1 - to_r, to_r,
                                       0, NULL, -1, -1);
                        return CARRY_ON;
                }

                /* Balancing does not lead to better packing. */
                set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
                return NO_BALANCING_NEEDED;
        }

        /*
         * Current node contain insufficient number of items.
         * Balancing is required.
         */
        /* Check whether we can merge S[h] with left neighbor. */
        if (tb->lnum[h] >= vn->vn_nr_item + 1)
                if (is_left_neighbor_in_cache(tb, h)
                    || tb->rnum[h] < vn->vn_nr_item + 1 || !tb->FR[h]) {
                        int n;
                        int order_L;

                        order_L =
                            ((n =
                              PATH_H_B_ITEM_ORDER(tb->tb_path,
                                                  h)) ==
                             0) ? B_NR_ITEMS(tb->FL[h]) : n - 1;
                        n = dc_size(B_N_CHILD(tb->FL[h], order_L)) / (DC_SIZE +
                                                                      KEY_SIZE);
                        set_parameters(tb, h, -n - 1, 0, 0, NULL, -1, -1);
                        return CARRY_ON;
                }

        /* Check whether we can merge S[h] with right neighbor. */
        if (tb->rnum[h] >= vn->vn_nr_item + 1) {
                int n;
                int order_R;

                order_R =
                    ((n =
                      PATH_H_B_ITEM_ORDER(tb->tb_path,
                                          h)) == B_NR_ITEMS(Fh)) ? 0 : (n + 1);
                n = dc_size(B_N_CHILD(tb->FR[h], order_R)) / (DC_SIZE +
                                                              KEY_SIZE);
                set_parameters(tb, h, 0, -n - 1, 0, NULL, -1, -1);
                return CARRY_ON;
        }

        /* All contents of S[h] can be moved to the neighbors (L[h] & R[h]). */
        if (tb->rnum[h] + tb->lnum[h] >= vn->vn_nr_item + 1) {
                int to_r;

                to_r =
                    ((MAX_NR_KEY(Sh) << 1) + 2 - tb->lnum[h] - tb->rnum[h] +
                     vn->vn_nr_item + 1) / 2 - (MAX_NR_KEY(Sh) + 1 -
                                                tb->rnum[h]);
                set_parameters(tb, h, vn->vn_nr_item + 1 - to_r, to_r, 0, NULL,
                               -1, -1);
                return CARRY_ON;
        }

        /* For internal nodes try to borrow item from a neighbor */
        RFALSE(!tb->FL[h] && !tb->FR[h], "vs-8235: trying to borrow for root");

        /* Borrow one or two items from caching neighbor */
        if (is_left_neighbor_in_cache(tb, h) || !tb->FR[h]) {
                int from_l;

                from_l =
                    (MAX_NR_KEY(Sh) + 1 - tb->lnum[h] + vn->vn_nr_item +
                     1) / 2 - (vn->vn_nr_item + 1);
                set_parameters(tb, h, -from_l, 0, 1, NULL, -1, -1);
                return CARRY_ON;
        }

        set_parameters(tb, h, 0,
                       -((MAX_NR_KEY(Sh) + 1 - tb->rnum[h] + vn->vn_nr_item +
                          1) / 2 - (vn->vn_nr_item + 1)), 1, NULL, -1, -1);
        return CARRY_ON;
}

/*
 * Check whether current node S[h] is balanced when Decreasing its size by
 * Deleting or Truncating for LEAF node of S+tree.
 * Calculate parameters for balancing for current level h.
 * Parameters:
 *      tb      tree_balance structure;
 *      h       current level of the node;
 *      inum    item number in S[h];
 *      mode    i - insert, p - paste;
 * Returns:     1 - schedule occurred;
 *              0 - balancing for higher levels needed;
 *             -1 - no balancing for higher levels needed;
 *             -2 - no disk space.
 */
static int dc_check_balance_leaf(struct tree_balance *tb, int h)
{
        struct virtual_node *vn = tb->tb_vn;

        /*
         * Number of bytes that must be deleted from
         * (value is negative if bytes are deleted) buffer which
         * contains node being balanced.  The mnemonic is that the
         * attempted change in node space used level is levbytes bytes.
         */
        int levbytes;

        /* the maximal item size */
        int maxsize, ret;

        /*
         * S0 is the node whose balance is currently being checked,
         * and F0 is its father.
         */
        struct buffer_head *S0, *F0;
        int lfree, rfree /* free space in L and R */ ;

        S0 = PATH_H_PBUFFER(tb->tb_path, 0);
        F0 = PATH_H_PPARENT(tb->tb_path, 0);

        levbytes = tb->insert_size[h];

        maxsize = MAX_CHILD_SIZE(S0);   /* maximal possible size of an item */

        if (!F0) {              /* S[0] is the root now. */

                RFALSE(-levbytes >= maxsize - B_FREE_SPACE(S0),
                       "vs-8240: attempt to create empty buffer tree");

                set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
                return NO_BALANCING_NEEDED;
        }

        if ((ret = get_parents(tb, h)) != CARRY_ON)
                return ret;

        /* get free space of neighbors */
        rfree = get_rfree(tb, h);
        lfree = get_lfree(tb, h);

        create_virtual_node(tb, h);

        /* if 3 leaves can be merge to one, set parameters and return */
        if (are_leaves_removable(tb, lfree, rfree))
                return CARRY_ON;

        /*
         * determine maximal number of items we can shift to the left/right
         * neighbor and the maximal number of bytes that can flow to the
         * left/right neighbor from the left/right most liquid item that
         * cannot be shifted from S[0] entirely
         */
        check_left(tb, h, lfree);
        check_right(tb, h, rfree);

        /* check whether we can merge S with left neighbor. */
        if (tb->lnum[0] >= vn->vn_nr_item && tb->lbytes == -1)
                if (is_left_neighbor_in_cache(tb, h) || ((tb->rnum[0] - ((tb->rbytes == -1) ? 0 : 1)) < vn->vn_nr_item) ||      /* S can not be merged with R */
                    !tb->FR[h]) {

                        RFALSE(!tb->FL[h],
                               "vs-8245: dc_check_balance_leaf: FL[h] must exist");

                        /* set parameter to merge S[0] with its left neighbor */
                        set_parameters(tb, h, -1, 0, 0, NULL, -1, -1);
                        return CARRY_ON;
                }

        /* check whether we can merge S[0] with right neighbor. */
        if (tb->rnum[0] >= vn->vn_nr_item && tb->rbytes == -1) {
                set_parameters(tb, h, 0, -1, 0, NULL, -1, -1);

                return CARRY_ON;
        }

        /*
         * All contents of S[0] can be moved to the neighbors (L[0] & R[0]).
         * Set parameters and return
         */
        if (is_leaf_removable(tb))
                return CARRY_ON;

        /* Balancing is not required. */
        tb->s0num = vn->vn_nr_item;
        set_parameters(tb, h, 0, 0, 1, NULL, -1, -1);
        return NO_BALANCING_NEEDED;
}

/*
 * Check whether current node S[h] is balanced when Decreasing its size by
 * Deleting or Cutting.
 * Calculate parameters for balancing for current level h.
 * Parameters:
 *      tb      tree_balance structure;
 *      h       current level of the node;
 *      inum    item number in S[h];
 *      mode    d - delete, c - cut.
 * Returns:     1 - schedule occurred;
 *              0 - balancing for higher levels needed;
 *             -1 - no balancing for higher levels needed;
 *             -2 - no disk space.
 */
static int dc_check_balance(struct tree_balance *tb, int h)
{
        RFALSE(!(PATH_H_PBUFFER(tb->tb_path, h)),
               "vs-8250: S is not initialized");

        if (h)
                return dc_check_balance_internal(tb, h);
        else
                return dc_check_balance_leaf(tb, h);
}

/*
 * Check whether current node S[h] is balanced.
 * Calculate parameters for balancing for current level h.
 * Parameters:
 *
 *      tb      tree_balance structure:
 *
 *              tb is a large structure that must be read about in the header
 *              file at the same time as this procedure if the reader is
 *              to successfully understand this procedure
 *
 *      h       current level of the node;
 *      inum    item number in S[h];
 *      mode    i - insert, p - paste, d - delete, c - cut.
 * Returns:     1 - schedule occurred;
 *              0 - balancing for higher levels needed;
 *             -1 - no balancing for higher levels needed;
 *             -2 - no disk space.
 */
static int check_balance(int mode,
                         struct tree_balance *tb,
                         int h,
                         int inum,
                         int pos_in_item,
                         struct item_head *ins_ih, const void *data)
{
        struct virtual_node *vn;

        vn = tb->tb_vn = (struct virtual_node *)(tb->vn_buf);
        vn->vn_free_ptr = (char *)(tb->tb_vn + 1);
        vn->vn_mode = mode;
        vn->vn_affected_item_num = inum;
        vn->vn_pos_in_item = pos_in_item;
        vn->vn_ins_ih = ins_ih;
        vn->vn_data = data;

        RFALSE(mode == M_INSERT && !vn->vn_ins_ih,
               "vs-8255: ins_ih can not be 0 in insert mode");

        /* Calculate balance parameters when size of node is increasing. */
        if (tb->insert_size[h] > 0)
                return ip_check_balance(tb, h);

        /* Calculate balance parameters when  size of node is decreasing. */
        return dc_check_balance(tb, h);
}

/* Check whether parent at the path is the really parent of the current node.*/
static int get_direct_parent(struct tree_balance *tb, int h)
{
        struct buffer_head *bh;
        struct treepath *path = tb->tb_path;
        int position,
            path_offset = PATH_H_PATH_OFFSET(tb->tb_path, h);

        /* We are in the root or in the new root. */
        if (path_offset <= FIRST_PATH_ELEMENT_OFFSET) {

                RFALSE(path_offset < FIRST_PATH_ELEMENT_OFFSET - 1,
                       "PAP-8260: invalid offset in the path");

                if (PATH_OFFSET_PBUFFER(path, FIRST_PATH_ELEMENT_OFFSET)->
                    b_blocknr == SB_ROOT_BLOCK(tb->tb_sb)) {
                        /* Root is not changed. */
                        PATH_OFFSET_PBUFFER(path, path_offset - 1) = NULL;
                        PATH_OFFSET_POSITION(path, path_offset - 1) = 0;
                        return CARRY_ON;
                }
                /* Root is changed and we must recalculate the path. */
                return REPEAT_SEARCH;
        }

        /* Parent in the path is not in the tree. */
        if (!B_IS_IN_TREE
            (bh = PATH_OFFSET_PBUFFER(path, path_offset - 1)))
                return REPEAT_SEARCH;

        if ((position =
             PATH_OFFSET_POSITION(path,
                                  path_offset - 1)) > B_NR_ITEMS(bh))
                return REPEAT_SEARCH;

        /* Parent in the path is not parent of the current node in the tree. */
        if (B_N_CHILD_NUM(bh, position) !=
            PATH_OFFSET_PBUFFER(path, path_offset)->b_blocknr)
                return REPEAT_SEARCH;

        if (buffer_locked(bh)) {
                int depth = reiserfs_write_unlock_nested(tb->tb_sb);
                __wait_on_buffer(bh);
                reiserfs_write_lock_nested(tb->tb_sb, depth);
                if (FILESYSTEM_CHANGED_TB(tb))
                        return REPEAT_SEARCH;
        }

        /*
         * Parent in the path is unlocked and really parent
         * of the current node.
         */
        return CARRY_ON;
}

/*
 * Using lnum[h] and rnum[h] we should determine what neighbors
 * of S[h] we
 * need in order to balance S[h], and get them if necessary.
 * Returns:     SCHEDULE_OCCURRED - schedule occurred while the function worked;
 *              CARRY_ON - schedule didn't occur while the function worked;
 */
static int get_neighbors(struct tree_balance *tb, int h)
{
        int child_position,
            path_offset = PATH_H_PATH_OFFSET(tb->tb_path, h + 1);
        unsigned long son_number;
        struct super_block *sb = tb->tb_sb;
        struct buffer_head *bh;
        int depth;

        PROC_INFO_INC(sb, get_neighbors[h]);

        if (tb->lnum[h]) {
                /* We need left neighbor to balance S[h]. */
                PROC_INFO_INC(sb, need_l_neighbor[h]);
                bh = PATH_OFFSET_PBUFFER(tb->tb_path, path_offset);

                RFALSE(bh == tb->FL[h] &&
                       !PATH_OFFSET_POSITION(tb->tb_path, path_offset),
                       "PAP-8270: invalid position in the parent");

                child_position =
                    (bh ==
                     tb->FL[h]) ? tb->lkey[h] : B_NR_ITEMS(tb->
                                                                       FL[h]);
                son_number = B_N_CHILD_NUM(tb->FL[h], child_position);
                depth = reiserfs_write_unlock_nested(tb->tb_sb);
                bh = sb_bread(sb, son_number);
                reiserfs_write_lock_nested(tb->tb_sb, depth);
                if (!bh)
                        return IO_ERROR;
                if (FILESYSTEM_CHANGED_TB(tb)) {
                        brelse(bh);
                        PROC_INFO_INC(sb, get_neighbors_restart[h]);
                        return REPEAT_SEARCH;
                }

                RFALSE(!B_IS_IN_TREE(tb->FL[h]) ||
                       child_position > B_NR_ITEMS(tb->FL[h]) ||
                       B_N_CHILD_NUM(tb->FL[h], child_position) !=
                       bh->b_blocknr, "PAP-8275: invalid parent");
                RFALSE(!B_IS_IN_TREE(bh), "PAP-8280: invalid child");
                RFALSE(!h &&
                       B_FREE_SPACE(bh) !=
                       MAX_CHILD_SIZE(bh) -
                       dc_size(B_N_CHILD(tb->FL[0], child_position)),
                       "PAP-8290: invalid child size of left neighbor");

                brelse(tb->L[h]);
                tb->L[h] = bh;
        }

        /* We need right neighbor to balance S[path_offset]. */
        if (tb->rnum[h]) {
                PROC_INFO_INC(sb, need_r_neighbor[h]);
                bh = PATH_OFFSET_PBUFFER(tb->tb_path, path_offset);

                RFALSE(bh == tb->FR[h] &&
                       PATH_OFFSET_POSITION(tb->tb_path,
                                            path_offset) >=
                       B_NR_ITEMS(bh),
                       "PAP-8295: invalid position in the parent");

                child_position =
                    (bh == tb->FR[h]) ? tb->rkey[h] + 1 : 0;
                son_number = B_N_CHILD_NUM(tb->FR[h], child_position);
                depth = reiserfs_write_unlock_nested(tb->tb_sb);
                bh = sb_bread(sb, son_number);
                reiserfs_write_lock_nested(tb->tb_sb, depth);
                if (!bh)
                        return IO_ERROR;
                if (FILESYSTEM_CHANGED_TB(tb)) {
                        brelse(bh);
                        PROC_INFO_INC(sb, get_neighbors_restart[h]);
                        return REPEAT_SEARCH;
                }
                brelse(tb->R[h]);
                tb->R[h] = bh;

                RFALSE(!h
                       && B_FREE_SPACE(bh) !=
                       MAX_CHILD_SIZE(bh) -
                       dc_size(B_N_CHILD(tb->FR[0], child_position)),
                       "PAP-8300: invalid child size of right neighbor (%d != %d - %d)",
                       B_FREE_SPACE(bh), MAX_CHILD_SIZE(bh),
                       dc_size(B_N_CHILD(tb->FR[0], child_position)));

        }
        return CARRY_ON;
}

static int get_virtual_node_size(struct super_block *sb, struct buffer_head *bh)
{
        int max_num_of_items;
        int max_num_of_entries;
        unsigned long blocksize = sb->s_blocksize;

#define MIN_NAME_LEN 1

        max_num_of_items = (blocksize - BLKH_SIZE) / (IH_SIZE + MIN_ITEM_LEN);
        max_num_of_entries = (blocksize - BLKH_SIZE - IH_SIZE) /
            (DEH_SIZE + MIN_NAME_LEN);

        return sizeof(struct virtual_node) +
            max(max_num_of_items * sizeof(struct virtual_item),
                sizeof(struct virtual_item) + sizeof(struct direntry_uarea) +
                (max_num_of_entries - 1) * sizeof(__u16));
}

/*
 * maybe we should fail balancing we are going to perform when kmalloc
 * fails several times. But now it will loop until kmalloc gets
 * required memory
 */
static int get_mem_for_virtual_node(struct tree_balance *tb)
{
        int check_fs = 0;
        int size;
        char *buf;

        size = get_virtual_node_size(tb->tb_sb, PATH_PLAST_BUFFER(tb->tb_path));

        /* we have to allocate more memory for virtual node */
        if (size > tb->vn_buf_size) {
                if (tb->vn_buf) {
                        /* free memory allocated before */
                        kfree(tb->vn_buf);
                        /* this is not needed if kfree is atomic */
                        check_fs = 1;
                }

                /* virtual node requires now more memory */
                tb->vn_buf_size = size;

                /* get memory for virtual item */
                buf = kmalloc(size, GFP_ATOMIC | __GFP_NOWARN);
                if (!buf) {
                        /*
                         * getting memory with GFP_KERNEL priority may involve
                         * balancing now (due to indirect_to_direct conversion
                         * on dcache shrinking). So, release path and collected
                         * resources here
                         */
                        free_buffers_in_tb(tb);
                        buf = kmalloc(size, GFP_NOFS);
                        if (!buf) {
                                tb->vn_buf_size = 0;
                        }
                        tb->vn_buf = buf;
                        schedule();
                        return REPEAT_SEARCH;
                }

                tb->vn_buf = buf;
        }

        if (check_fs && FILESYSTEM_CHANGED_TB(tb))
                return REPEAT_SEARCH;

        return CARRY_ON;
}

#ifdef CONFIG_REISERFS_CHECK
static void tb_buffer_sanity_check(struct super_block *sb,
                                   struct buffer_head *bh,
                                   const char *descr, int level)
{
        if (bh) {
                if (atomic_read(&(bh->b_count)) <= 0)

                        reiserfs_panic(sb, "jmacd-1", "negative or zero "
                                       "reference counter for buffer %s[%d] "
                                       "(%b)", descr, level, bh);

                if (!buffer_uptodate(bh))
                        reiserfs_panic(sb, "jmacd-2", "buffer is not up "
                                       "to date %s[%d] (%b)",
                                       descr, level, bh);

                if (!B_IS_IN_TREE(bh))
                        reiserfs_panic(sb, "jmacd-3", "buffer is not "
                                       "in tree %s[%d] (%b)",
                                       descr, level, bh);

                if (bh->b_bdev != sb->s_bdev)
                        reiserfs_panic(sb, "jmacd-4", "buffer has wrong "
                                       "device %s[%d] (%b)",
                                       descr, level, bh);

                if (bh->b_size != sb->s_blocksize)
                        reiserfs_panic(sb, "jmacd-5", "buffer has wrong "
                                       "blocksize %s[%d] (%b)",
                                       descr, level, bh);

                if (bh->b_blocknr > SB_BLOCK_COUNT(sb))
                        reiserfs_panic(sb, "jmacd-6", "buffer block "
                                       "number too high %s[%d] (%b)",
                                       descr, level, bh);
        }
}
#else
static void tb_buffer_sanity_check(struct super_block *sb,
                                   struct buffer_head *bh,
                                   const char *descr, int level)
{;
}
#endif

static int clear_all_dirty_bits(struct super_block *s, struct buffer_head *bh)
{
        return reiserfs_prepare_for_journal(s, bh, 0);
}

static int wait_tb_buffers_until_unlocked(struct tree_balance *tb)
{
        struct buffer_head *locked;
#ifdef CONFIG_REISERFS_CHECK
        int repeat_counter = 0;
#endif
        int i;

        do {

                locked = NULL;

                for (i = tb->tb_path->path_length;
                     !locked && i > ILLEGAL_PATH_ELEMENT_OFFSET; i--) {
                        if (PATH_OFFSET_PBUFFER(tb->tb_path, i)) {
                                /*
                                 * if I understand correctly, we can only
                                 * be sure the last buffer in the path is
                                 * in the tree --clm
                                 */
#ifdef CONFIG_REISERFS_CHECK
                                if (PATH_PLAST_BUFFER(tb->tb_path) ==
                                    PATH_OFFSET_PBUFFER(tb->tb_path, i))
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               PATH_OFFSET_PBUFFER
                                                               (tb->tb_path,
                                                                i), "S",
                                                               tb->tb_path->
                                                               path_length - i);
#endif
                                if (!clear_all_dirty_bits(tb->tb_sb,
                                                          PATH_OFFSET_PBUFFER
                                                          (tb->tb_path,
                                                           i))) {
                                        locked =
                                            PATH_OFFSET_PBUFFER(tb->tb_path,
                                                                i);
                                }
                        }
                }

                for (i = 0; !locked && i < MAX_HEIGHT && tb->insert_size[i];
                     i++) {

                        if (tb->lnum[i]) {

                                if (tb->L[i]) {
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               tb->L[i],
                                                               "L", i);
                                        if (!clear_all_dirty_bits
                                            (tb->tb_sb, tb->L[i]))
                                                locked = tb->L[i];
                                }

                                if (!locked && tb->FL[i]) {
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               tb->FL[i],
                                                               "FL", i);
                                        if (!clear_all_dirty_bits
                                            (tb->tb_sb, tb->FL[i]))
                                                locked = tb->FL[i];
                                }

                                if (!locked && tb->CFL[i]) {
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               tb->CFL[i],
                                                               "CFL", i);
                                        if (!clear_all_dirty_bits
                                            (tb->tb_sb, tb->CFL[i]))
                                                locked = tb->CFL[i];
                                }

                        }

                        if (!locked && (tb->rnum[i])) {

                                if (tb->R[i]) {
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               tb->R[i],
                                                               "R", i);
                                        if (!clear_all_dirty_bits
                                            (tb->tb_sb, tb->R[i]))
                                                locked = tb->R[i];
                                }

                                if (!locked && tb->FR[i]) {
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               tb->FR[i],
                                                               "FR", i);
                                        if (!clear_all_dirty_bits
                                            (tb->tb_sb, tb->FR[i]))
                                                locked = tb->FR[i];
                                }

                                if (!locked && tb->CFR[i]) {
                                        tb_buffer_sanity_check(tb->tb_sb,
                                                               tb->CFR[i],
                                                               "CFR", i);
                                        if (!clear_all_dirty_bits
                                            (tb->tb_sb, tb->CFR[i]))
                                                locked = tb->CFR[i];
                                }
                        }
                }

                /*
                 * as far as I can tell, this is not required.  The FEB list
                 * seems to be full of newly allocated nodes, which will
                 * never be locked, dirty, or anything else.
                 * To be safe, I'm putting in the checks and waits in.
                 * For the moment, they are needed to keep the code in
                 * journal.c from complaining about the buffer.
                 * That code is inside CONFIG_REISERFS_CHECK as well.  --clm
                 */
                for (i = 0; !locked && i < MAX_FEB_SIZE; i++) {
                        if (tb->FEB[i]) {
                                if (!clear_all_dirty_bits
                                    (tb->tb_sb, tb->FEB[i]))
                                        locked = tb->FEB[i];
                        }
                }

                if (locked) {
                        int depth;
#ifdef CONFIG_REISERFS_CHECK
                        repeat_counter++;
                        if ((repeat_counter % 10000) == 0) {
                                reiserfs_warning(tb->tb_sb, "reiserfs-8200",
                                                 "too many iterations waiting "
                                                 "for buffer to unlock "
                                                 "(%b)", locked);

                                /* Don't loop forever.  Try to recover from possible error. */

                                return (FILESYSTEM_CHANGED_TB(tb)) ?
                                    REPEAT_SEARCH : CARRY_ON;
                        }
#endif
                        depth = reiserfs_write_unlock_nested(tb->tb_sb);
                        __wait_on_buffer(locked);
                        reiserfs_write_lock_nested(tb->tb_sb, depth);
                        if (FILESYSTEM_CHANGED_TB(tb))
                                return REPEAT_SEARCH;
                }

        } while (locked);

        return CARRY_ON;
}

/*
 * Prepare for balancing, that is
 *      get all necessary parents, and neighbors;
 *      analyze what and where should be moved;
 *      get sufficient number of new nodes;
 * Balancing will start only after all resources will be collected at a time.
 *
 * When ported to SMP kernels, only at the last moment after all needed nodes
 * are collected in cache, will the resources be locked using the usual
 * textbook ordered lock acquisition algorithms.  Note that ensuring that
 * this code neither write locks what it does not need to write lock nor locks
 * out of order will be a pain in the butt that could have been avoided.
 * Grumble grumble. -Hans
 *
 * fix is meant in the sense of render unchanging
 *
 * Latency might be improved by first gathering a list of what buffers
 * are needed and then getting as many of them in parallel as possible? -Hans
 *
 * Parameters:
 *      op_mode i - insert, d - delete, c - cut (truncate), p - paste (append)
 *      tb      tree_balance structure;
 *      inum    item number in S[h];
 *      pos_in_item - comment this if you can
 *      ins_ih  item head of item being inserted
 *      data    inserted item or data to be pasted
 * Returns:     1 - schedule occurred while the function worked;
 *              0 - schedule didn't occur while the function worked;
 *             -1 - if no_disk_space
 */

int fix_nodes(int op_mode, struct tree_balance *tb,
              struct item_head *ins_ih, const void *data)
{
        int ret, h, item_num = PATH_LAST_POSITION(tb->tb_path);
        int pos_in_item;

        /*
         * we set wait_tb_buffers_run when we have to restore any dirty
         * bits cleared during wait_tb_buffers_run
         */
        int wait_tb_buffers_run = 0;
        struct buffer_head *tbS0 = PATH_PLAST_BUFFER(tb->tb_path);

        ++REISERFS_SB(tb->tb_sb)->s_fix_nodes;

        pos_in_item = tb->tb_path->pos_in_item;

        tb->fs_gen = get_generation(tb->tb_sb);

        /*
         * we prepare and log the super here so it will already be in the
         * transaction when do_balance needs to change it.
         * This way do_balance won't have to schedule when trying to prepare
         * the super for logging
         */
        reiserfs_prepare_for_journal(tb->tb_sb,
                                     SB_BUFFER_WITH_SB(tb->tb_sb), 1);
        journal_mark_dirty(tb->transaction_handle,
                           SB_BUFFER_WITH_SB(tb->tb_sb));
        if (FILESYSTEM_CHANGED_TB(tb))
                return REPEAT_SEARCH;

        /* if it possible in indirect_to_direct conversion */
        if (buffer_locked(tbS0)) {
                int depth = reiserfs_write_unlock_nested(tb->tb_sb);
                __wait_on_buffer(tbS0);
                reiserfs_write_lock_nested(tb->tb_sb, depth);
                if (FILESYSTEM_CHANGED_TB(tb))
                        return REPEAT_SEARCH;
        }
#ifdef CONFIG_REISERFS_CHECK
        if (REISERFS_SB(tb->tb_sb)->cur_tb) {
                print_cur_tb("fix_nodes");
                reiserfs_panic(tb->tb_sb, "PAP-8305",
                               "there is pending do_balance");
        }

        if (!buffer_uptodate(tbS0) || !B_IS_IN_TREE(tbS0))
                reiserfs_panic(tb->tb_sb, "PAP-8320", "S[0] (%b %z) is "
                               "not uptodate at the beginning of fix_nodes "
                               "or not in tree (mode %c)",
                               tbS0, tbS0, op_mode);

        /* Check parameters. */
        switch (op_mode) {
        case M_INSERT:
                if (item_num <= 0 || item_num > B_NR_ITEMS(tbS0))
                        reiserfs_panic(tb->tb_sb, "PAP-8330", "Incorrect "
                                       "item number %d (in S0 - %d) in case "
                                       "of insert", item_num,
                                       B_NR_ITEMS(tbS0));
                break;
        case M_PASTE:
        case M_DELETE:
        case M_CUT:
                if (item_num < 0 || item_num >= B_NR_ITEMS(tbS0)) {
                        print_block(tbS0, 0, -1, -1);
                        reiserfs_panic(tb->tb_sb, "PAP-8335", "Incorrect "
                                       "item number(%d); mode = %c "
                                       "insert_size = %d",
                                       item_num, op_mode,
                                       tb->insert_size[0]);
                }
                break;
        default:
                reiserfs_panic(tb->tb_sb, "PAP-8340", "Incorrect mode "
                               "of operation");
        }
#endif

        if (get_mem_for_virtual_node(tb) == REPEAT_SEARCH)
                /* FIXME: maybe -ENOMEM when tb->vn_buf == 0? Now just repeat */
                return REPEAT_SEARCH;

        /* Starting from the leaf level; for all levels h of the tree. */
        for (h = 0; h < MAX_HEIGHT && tb->insert_size[h]; h++) {
                ret = get_direct_parent(tb, h);
                if (ret != CARRY_ON)
                        goto repeat;

                ret = check_balance(op_mode, tb, h, item_num,
                                    pos_in_item, ins_ih, data);
                if (ret != CARRY_ON) {
                        if (ret == NO_BALANCING_NEEDED) {
                                /* No balancing for higher levels needed. */
                                ret = get_neighbors(tb, h);
                                if (ret != CARRY_ON)
                                        goto repeat;
                                if (h != MAX_HEIGHT - 1)
                                        tb->insert_size[h + 1] = 0;
                                /*
                                 * ok, analysis and resource gathering
                                 * are complete
                                 */
                                break;
                        }
                        goto repeat;
                }

                ret = get_neighbors(tb, h);
                if (ret != CARRY_ON)
                        goto repeat;

                /*
                 * No disk space, or schedule occurred and analysis may be
                 * invalid and needs to be redone.
                 */
                ret = get_empty_nodes(tb, h);
                if (ret != CARRY_ON)
                        goto repeat;

                /*
                 * We have a positive insert size but no nodes exist on this
                 * level, this means that we are creating a new root.
                 */
                if (!PATH_H_PBUFFER(tb->tb_path, h)) {

                        RFALSE(tb->blknum[h] != 1,
                               "PAP-8350: creating new empty root");

                        if (h < MAX_HEIGHT - 1)
                                tb->insert_size[h + 1] = 0;
                } else if (!PATH_H_PBUFFER(tb->tb_path, h + 1)) {
                        /*
                         * The tree needs to be grown, so this node S[h]
                         * which is the root node is split into two nodes,
                         * and a new node (S[h+1]) will be created to
                         * become the root node.
                         */
                        if (tb->blknum[h] > 1) {

                                RFALSE(h == MAX_HEIGHT - 1,
                                       "PAP-8355: attempt to create too high of a tree");

                                tb->insert_size[h + 1] =
                                    (DC_SIZE +
                                     KEY_SIZE) * (tb->blknum[h] - 1) +
                                    DC_SIZE;
                        } else if (h < MAX_HEIGHT - 1)
                                tb->insert_size[h + 1] = 0;
                } else
                        tb->insert_size[h + 1] =
                            (DC_SIZE + KEY_SIZE) * (tb->blknum[h] - 1);
        }

        ret = wait_tb_buffers_until_unlocked(tb);
        if (ret == CARRY_ON) {
                if (FILESYSTEM_CHANGED_TB(tb)) {
                        wait_tb_buffers_run = 1;
                        ret = REPEAT_SEARCH;
                        goto repeat;
                } else {
                        return CARRY_ON;
                }
        } else {
                wait_tb_buffers_run = 1;
                goto repeat;
        }

repeat:
        /*
         * fix_nodes was unable to perform its calculation due to
         * filesystem got changed under us, lack of free disk space or i/o
         * failure. If the first is the case - the search will be
         * repeated. For now - free all resources acquired so far except
         * for the new allocated nodes
         */
        {
                int i;

                /* Release path buffers. */
                if (wait_tb_buffers_run) {
                        pathrelse_and_restore(tb->tb_sb, tb->tb_path);
                } else {
                        pathrelse(tb->tb_path);
                }
                /* brelse all resources collected for balancing */
                for (i = 0; i < MAX_HEIGHT; i++) {
                        if (wait_tb_buffers_run) {
                                reiserfs_restore_prepared_buffer(tb->tb_sb,
                                                                 tb->L[i]);
                                reiserfs_restore_prepared_buffer(tb->tb_sb,
                                                                 tb->R[i]);
                                reiserfs_restore_prepared_buffer(tb->tb_sb,
                                                                 tb->FL[i]);
                                reiserfs_restore_prepared_buffer(tb->tb_sb,
                                                                 tb->FR[i]);
                                reiserfs_restore_prepared_buffer(tb->tb_sb,
                                                                 tb->
                                                                 CFL[i]);
                                reiserfs_restore_prepared_buffer(tb->tb_sb,
                                                                 tb->
                                                                 CFR[i]);
                        }

                        brelse(tb->L[i]);
                        brelse(tb->R[i]);
                        brelse(tb->FL[i]);
                        brelse(tb->FR[i]);
                        brelse(tb->CFL[i]);
                        brelse(tb->CFR[i]);

                        tb->L[i] = NULL;
                        tb->R[i] = NULL;
                        tb->FL[i] = NULL;
                        tb->FR[i] = NULL;
                        tb->CFL[i] = NULL;
                        tb->CFR[i] = NULL;
                }

                if (wait_tb_buffers_run) {
                        for (i = 0; i < MAX_FEB_SIZE; i++) {
                                if (tb->FEB[i])
                                        reiserfs_restore_prepared_buffer
                                            (tb->tb_sb, tb->FEB[i]);
                        }
                }
                return ret;
        }

}

void unfix_nodes(struct tree_balance *tb)
{
        int i;

        /* Release path buffers. */
        pathrelse_and_restore(tb->tb_sb, tb->tb_path);

        /* brelse all resources collected for balancing */
        for (i = 0; i < MAX_HEIGHT; i++) {
                reiserfs_restore_prepared_buffer(tb->tb_sb, tb->L[i]);
                reiserfs_restore_prepared_buffer(tb->tb_sb, tb->R[i]);
                reiserfs_restore_prepared_buffer(tb->tb_sb, tb->FL[i]);
                reiserfs_restore_prepared_buffer(tb->tb_sb, tb->FR[i]);
                reiserfs_restore_prepared_buffer(tb->tb_sb, tb->CFL[i]);
                reiserfs_restore_prepared_buffer(tb->tb_sb, tb->CFR[i]);

                brelse(tb->L[i]);
                brelse(tb->R[i]);
                brelse(tb->FL[i]);
                brelse(tb->FR[i]);
                brelse(tb->CFL[i]);
                brelse(tb->CFR[i]);
        }

        /* deal with list of allocated (used and unused) nodes */
        for (i = 0; i < MAX_FEB_SIZE; i++) {
                if (tb->FEB[i]) {
                        b_blocknr_t blocknr = tb->FEB[i]->b_blocknr;
                        /*
                         * de-allocated block which was not used by
                         * balancing and bforget about buffer for it
                         */
                        brelse(tb->FEB[i]);
                        reiserfs_free_block(tb->transaction_handle, NULL,
                                            blocknr, 0);
                }
                if (tb->used[i]) {
                        /* release used as new nodes including a new root */
                        brelse(tb->used[i]);
                }
        }

        kfree(tb->vn_buf);

}