Btrfs: Make defrag check nodes against the progress key to prevent repeating work

[deliverable/linux.git] / fs / btrfs / ctree.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "print-tree.h"

static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_path *path, int level);
static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_key *ins_key,
                      struct btrfs_path *path, int data_size, int extend);
static int push_node_left(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, struct extent_buffer *dst,
                          struct extent_buffer *src);
static int balance_node_right(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct extent_buffer *dst_buf,
                              struct extent_buffer *src_buf);
static int del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                   struct btrfs_path *path, int level, int slot);

inline void btrfs_init_path(struct btrfs_path *p)
{
        memset(p, 0, sizeof(*p));
}

struct btrfs_path *btrfs_alloc_path(void)
{
        struct btrfs_path *path;
        path = kmem_cache_alloc(btrfs_path_cachep, GFP_NOFS);
        if (path) {
                btrfs_init_path(path);
                path->reada = 1;
        }
        return path;
}

void btrfs_free_path(struct btrfs_path *p)
{
        btrfs_release_path(NULL, p);
        kmem_cache_free(btrfs_path_cachep, p);
}

void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
{
        int i;
        for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
                if (!p->nodes[i])
                        break;
                free_extent_buffer(p->nodes[i]);
        }
        memset(p, 0, sizeof(*p));
}

static int __btrfs_cow_block(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root,
                             struct extent_buffer *buf,
                             struct extent_buffer *parent, int parent_slot,
                             struct extent_buffer **cow_ret,
                             u64 search_start, u64 empty_size)
{
        struct extent_buffer *cow;
        int ret = 0;
        int different_trans = 0;

        WARN_ON(root->ref_cows && trans->transid != root->last_trans);

        cow = btrfs_alloc_free_block(trans, root, buf->len,
                                     search_start, empty_size);
        if (IS_ERR(cow))
                return PTR_ERR(cow);

        copy_extent_buffer(cow, buf, 0, 0, cow->len);
        btrfs_set_header_bytenr(cow, cow->start);
        btrfs_set_header_generation(cow, trans->transid);
        btrfs_set_header_owner(cow, root->root_key.objectid);

        WARN_ON(btrfs_header_generation(buf) > trans->transid);
        if (btrfs_header_generation(buf) != trans->transid) {
                different_trans = 1;
                ret = btrfs_inc_ref(trans, root, buf);
                if (ret)
                        return ret;
        } else {
                clean_tree_block(trans, root, buf);
        }

        if (buf == root->node) {
                root->node = cow;
                extent_buffer_get(cow);
                if (buf != root->commit_root) {
                        btrfs_free_extent(trans, root, buf->start,
                                          buf->len, 1);
                }
                free_extent_buffer(buf);
        } else {
                btrfs_set_node_blockptr(parent, parent_slot,
                                        cow->start);
                btrfs_mark_buffer_dirty(parent);
                WARN_ON(btrfs_header_generation(parent) != trans->transid);
                btrfs_free_extent(trans, root, buf->start, buf->len, 1);
        }
        free_extent_buffer(buf);
        btrfs_mark_buffer_dirty(cow);
        *cow_ret = cow;
        return 0;
}

int btrfs_cow_block(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root, struct extent_buffer *buf,
                    struct extent_buffer *parent, int parent_slot,
                    struct extent_buffer **cow_ret)
{
        u64 search_start;
        int ret;
        if (trans->transaction != root->fs_info->running_transaction) {
                printk(KERN_CRIT "trans %Lu running %Lu\n", trans->transid,
                       root->fs_info->running_transaction->transid);
                WARN_ON(1);
        }
        if (trans->transid != root->fs_info->generation) {
                printk(KERN_CRIT "trans %Lu running %Lu\n", trans->transid,
                       root->fs_info->generation);
                WARN_ON(1);
        }
        if (btrfs_header_generation(buf) == trans->transid) {
                *cow_ret = buf;
                return 0;
        }

        search_start = buf->start & ~((u64)BTRFS_BLOCK_GROUP_SIZE - 1);
        ret = __btrfs_cow_block(trans, root, buf, parent,
                                 parent_slot, cow_ret, search_start, 0);
        return ret;
}

static int close_blocks(u64 blocknr, u64 other, u32 blocksize)
{
        if (blocknr < other && other - (blocknr + blocksize) < 32768)
                return 1;
        if (blocknr > other && blocknr - (other + blocksize) < 32768)
                return 1;
        return 0;
}

/*
 * compare two keys in a memcmp fashion
 */
static int comp_keys(struct btrfs_disk_key *disk, struct btrfs_key *k2)
{
        struct btrfs_key k1;

        btrfs_disk_key_to_cpu(&k1, disk);

        if (k1.objectid > k2->objectid)
                return 1;
        if (k1.objectid < k2->objectid)
                return -1;
        if (k1.type > k2->type)
                return 1;
        if (k1.type < k2->type)
                return -1;
        if (k1.offset > k2->offset)
                return 1;
        if (k1.offset < k2->offset)
                return -1;
        return 0;
}


int btrfs_realloc_node(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root, struct extent_buffer *parent,
                       int start_slot, int cache_only, u64 *last_ret,
                       struct btrfs_key *progress)
{
        struct extent_buffer *cur;
        struct extent_buffer *tmp;
        u64 blocknr;
        u64 search_start = *last_ret;
        u64 last_block = 0;
        u64 other;
        u32 parent_nritems;
        int end_slot;
        int i;
        int err = 0;
        int parent_level;
        int uptodate;
        u32 blocksize;
        int progress_passed = 0;
        struct btrfs_disk_key disk_key;

        parent_level = btrfs_header_level(parent);
        if (cache_only && parent_level != 1)
                return 0;

        if (trans->transaction != root->fs_info->running_transaction) {
                printk(KERN_CRIT "trans %Lu running %Lu\n", trans->transid,
                       root->fs_info->running_transaction->transid);
                WARN_ON(1);
        }
        if (trans->transid != root->fs_info->generation) {
                printk(KERN_CRIT "trans %Lu running %Lu\n", trans->transid,
                       root->fs_info->generation);
                WARN_ON(1);
        }

        parent_nritems = btrfs_header_nritems(parent);
        blocksize = btrfs_level_size(root, parent_level - 1);
        end_slot = parent_nritems;

        if (parent_nritems == 1)
                return 0;

        for (i = start_slot; i < end_slot; i++) {
                int close = 1;

                if (!parent->map_token) {
                        map_extent_buffer(parent,
                                        btrfs_node_key_ptr_offset(i),
                                        sizeof(struct btrfs_key_ptr),
                                        &parent->map_token, &parent->kaddr,
                                        &parent->map_start, &parent->map_len,
                                        KM_USER1);
                }
                btrfs_node_key(parent, &disk_key, i);
                if (!progress_passed && comp_keys(&disk_key, progress) < 0)
                        continue;

                progress_passed = 1;
                blocknr = btrfs_node_blockptr(parent, i);
                if (last_block == 0)
                        last_block = blocknr;

                if (i > 0) {
                        other = btrfs_node_blockptr(parent, i - 1);
                        close = close_blocks(blocknr, other, blocksize);
                }
                if (close && i < end_slot - 2) {
                        other = btrfs_node_blockptr(parent, i + 1);
                        close = close_blocks(blocknr, other, blocksize);
                }
                if (close) {
                        last_block = blocknr;
                        continue;
                }
                if (parent->map_token) {
                        unmap_extent_buffer(parent, parent->map_token,
                                            KM_USER1);
                        parent->map_token = NULL;
                }

                cur = btrfs_find_tree_block(root, blocknr, blocksize);
                if (cur)
                        uptodate = btrfs_buffer_uptodate(cur);
                else
                        uptodate = 0;
                if (!cur || !uptodate) {
                        if (cache_only) {
                                free_extent_buffer(cur);
                                continue;
                        }
                        if (!cur) {
                                cur = read_tree_block(root, blocknr,
                                                         blocksize);
                        } else if (!uptodate) {
                                btrfs_read_buffer(cur);
                        }
                }
                if (search_start == 0)
                        search_start = last_block;

                err = __btrfs_cow_block(trans, root, cur, parent, i,
                                        &tmp, search_start,
                                        min(16 * blocksize,
                                            (end_slot - i) * blocksize));
                if (err) {
                        free_extent_buffer(cur);
                        break;
                }
                search_start = tmp->start;
                last_block = tmp->start;
                *last_ret = search_start;
                if (parent_level == 1)
                        btrfs_clear_buffer_defrag(tmp);
                free_extent_buffer(tmp);
        }
        if (parent->map_token) {
                unmap_extent_buffer(parent, parent->map_token,
                                    KM_USER1);
                parent->map_token = NULL;
        }
        return err;
}

/*
 * The leaf data grows from end-to-front in the node.
 * this returns the address of the start of the last item,
 * which is the stop of the leaf data stack
 */
static inline unsigned int leaf_data_end(struct btrfs_root *root,
                                         struct extent_buffer *leaf)
{
        u32 nr = btrfs_header_nritems(leaf);
        if (nr == 0)
                return BTRFS_LEAF_DATA_SIZE(root);
        return btrfs_item_offset_nr(leaf, nr - 1);
}

static int check_node(struct btrfs_root *root, struct btrfs_path *path,
                      int level)
{
        struct extent_buffer *parent = NULL;
        struct extent_buffer *node = path->nodes[level];
        struct btrfs_disk_key parent_key;
        struct btrfs_disk_key node_key;
        int parent_slot;
        int slot;
        struct btrfs_key cpukey;
        u32 nritems = btrfs_header_nritems(node);

        if (path->nodes[level + 1])
                parent = path->nodes[level + 1];

        slot = path->slots[level];
        BUG_ON(nritems == 0);
        if (parent) {
                parent_slot = path->slots[level + 1];
                btrfs_node_key(parent, &parent_key, parent_slot);
                btrfs_node_key(node, &node_key, 0);
                BUG_ON(memcmp(&parent_key, &node_key,
                              sizeof(struct btrfs_disk_key)));
                BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
                       btrfs_header_bytenr(node));
        }
        BUG_ON(nritems > BTRFS_NODEPTRS_PER_BLOCK(root));
        if (slot != 0) {
                btrfs_node_key_to_cpu(node, &cpukey, slot - 1);
                btrfs_node_key(node, &node_key, slot);
                BUG_ON(comp_keys(&node_key, &cpukey) <= 0);
        }
        if (slot < nritems - 1) {
                btrfs_node_key_to_cpu(node, &cpukey, slot + 1);
                btrfs_node_key(node, &node_key, slot);
                BUG_ON(comp_keys(&node_key, &cpukey) >= 0);
        }
        return 0;
}

static int check_leaf(struct btrfs_root *root, struct btrfs_path *path,
                      int level)
{
        struct extent_buffer *leaf = path->nodes[level];
        struct extent_buffer *parent = NULL;
        int parent_slot;
        struct btrfs_key cpukey;
        struct btrfs_disk_key parent_key;
        struct btrfs_disk_key leaf_key;
        int slot = path->slots[0];

        u32 nritems = btrfs_header_nritems(leaf);

        if (path->nodes[level + 1])
                parent = path->nodes[level + 1];

        if (nritems == 0)
                return 0;

        if (parent) {
                parent_slot = path->slots[level + 1];
                btrfs_node_key(parent, &parent_key, parent_slot);
                btrfs_item_key(leaf, &leaf_key, 0);

                BUG_ON(memcmp(&parent_key, &leaf_key,
                       sizeof(struct btrfs_disk_key)));
                BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
                       btrfs_header_bytenr(leaf));
        }
#if 0
        for (i = 0; nritems > 1 && i < nritems - 2; i++) {
                btrfs_item_key_to_cpu(leaf, &cpukey, i + 1);
                btrfs_item_key(leaf, &leaf_key, i);
                if (comp_keys(&leaf_key, &cpukey) >= 0) {
                        btrfs_print_leaf(root, leaf);
                        printk("slot %d offset bad key\n", i);
                        BUG_ON(1);
                }
                if (btrfs_item_offset_nr(leaf, i) !=
                        btrfs_item_end_nr(leaf, i + 1)) {
                        btrfs_print_leaf(root, leaf);
                        printk("slot %d offset bad\n", i);
                        BUG_ON(1);
                }
                if (i == 0) {
                        if (btrfs_item_offset_nr(leaf, i) +
                               btrfs_item_size_nr(leaf, i) !=
                               BTRFS_LEAF_DATA_SIZE(root)) {
                                btrfs_print_leaf(root, leaf);
                                printk("slot %d first offset bad\n", i);
                                BUG_ON(1);
                        }
                }
        }
        if (nritems > 0) {
                if (btrfs_item_size_nr(leaf, nritems - 1) > 4096) {
                                btrfs_print_leaf(root, leaf);
                                printk("slot %d bad size \n", nritems - 1);
                                BUG_ON(1);
                }
        }
#endif
        if (slot != 0 && slot < nritems - 1) {
                btrfs_item_key(leaf, &leaf_key, slot);
                btrfs_item_key_to_cpu(leaf, &cpukey, slot - 1);
                if (comp_keys(&leaf_key, &cpukey) <= 0) {
                        btrfs_print_leaf(root, leaf);
                        printk("slot %d offset bad key\n", slot);
                        BUG_ON(1);
                }
                if (btrfs_item_offset_nr(leaf, slot - 1) !=
                       btrfs_item_end_nr(leaf, slot)) {
                        btrfs_print_leaf(root, leaf);
                        printk("slot %d offset bad\n", slot);
                        BUG_ON(1);
                }
        }
        if (slot < nritems - 1) {
                btrfs_item_key(leaf, &leaf_key, slot);
                btrfs_item_key_to_cpu(leaf, &cpukey, slot + 1);
                BUG_ON(comp_keys(&leaf_key, &cpukey) >= 0);
                if (btrfs_item_offset_nr(leaf, slot) !=
                        btrfs_item_end_nr(leaf, slot + 1)) {
                        btrfs_print_leaf(root, leaf);
                        printk("slot %d offset bad\n", slot);
                        BUG_ON(1);
                }
        }
        BUG_ON(btrfs_item_offset_nr(leaf, 0) +
               btrfs_item_size_nr(leaf, 0) != BTRFS_LEAF_DATA_SIZE(root));
        return 0;
}

static int check_block(struct btrfs_root *root, struct btrfs_path *path,
                        int level)
{
        return 0;
#if 0
        struct extent_buffer *buf = path->nodes[level];

        if (memcmp_extent_buffer(buf, root->fs_info->fsid,
                                 (unsigned long)btrfs_header_fsid(buf),
                                 BTRFS_FSID_SIZE)) {
                printk("warning bad block %Lu\n", buf->start);
                return 1;
        }
#endif
        if (level == 0)
                return check_leaf(root, path, level);
        return check_node(root, path, level);
}

/*
 * search for key in the extent_buffer.  The items start at offset p,
 * and they are item_size apart.  There are 'max' items in p.
 *
 * the slot in the array is returned via slot, and it points to
 * the place where you would insert key if it is not found in
 * the array.
 *
 * slot may point to max if the key is bigger than all of the keys
 */
static int generic_bin_search(struct extent_buffer *eb, unsigned long p,
                              int item_size, struct btrfs_key *key,
                              int max, int *slot)
{
        int low = 0;
        int high = max;
        int mid;
        int ret;
        struct btrfs_disk_key *tmp = NULL;
        struct btrfs_disk_key unaligned;
        unsigned long offset;
        char *map_token = NULL;
        char *kaddr = NULL;
        unsigned long map_start = 0;
        unsigned long map_len = 0;
        int err;

        while(low < high) {
                mid = (low + high) / 2;
                offset = p + mid * item_size;

                if (!map_token || offset < map_start ||
                    (offset + sizeof(struct btrfs_disk_key)) >
                    map_start + map_len) {
                        if (map_token) {
                                unmap_extent_buffer(eb, map_token, KM_USER0);
                                map_token = NULL;
                        }
                        err = map_extent_buffer(eb, offset,
                                                sizeof(struct btrfs_disk_key),
                                                &map_token, &kaddr,
                                                &map_start, &map_len, KM_USER0);

                        if (!err) {
                                tmp = (struct btrfs_disk_key *)(kaddr + offset -
                                                        map_start);
                        } else {
                                read_extent_buffer(eb, &unaligned,
                                                   offset, sizeof(unaligned));
                                tmp = &unaligned;
                        }

                } else {
                        tmp = (struct btrfs_disk_key *)(kaddr + offset -
                                                        map_start);
                }
                ret = comp_keys(tmp, key);

                if (ret < 0)
                        low = mid + 1;
                else if (ret > 0)
                        high = mid;
                else {
                        *slot = mid;
                        if (map_token)
                                unmap_extent_buffer(eb, map_token, KM_USER0);
                        return 0;
                }
        }
        *slot = low;
        if (map_token)
                unmap_extent_buffer(eb, map_token, KM_USER0);
        return 1;
}

/*
 * simple bin_search frontend that does the right thing for
 * leaves vs nodes
 */
static int bin_search(struct extent_buffer *eb, struct btrfs_key *key,
                      int level, int *slot)
{
        if (level == 0) {
                return generic_bin_search(eb,
                                          offsetof(struct btrfs_leaf, items),
                                          sizeof(struct btrfs_item),
                                          key, btrfs_header_nritems(eb),
                                          slot);
        } else {
                return generic_bin_search(eb,
                                          offsetof(struct btrfs_node, ptrs),
                                          sizeof(struct btrfs_key_ptr),
                                          key, btrfs_header_nritems(eb),
                                          slot);
        }
        return -1;
}

static struct extent_buffer *read_node_slot(struct btrfs_root *root,
                                   struct extent_buffer *parent, int slot)
{
        if (slot < 0)
                return NULL;
        if (slot >= btrfs_header_nritems(parent))
                return NULL;
        return read_tree_block(root, btrfs_node_blockptr(parent, slot),
                       btrfs_level_size(root, btrfs_header_level(parent) - 1));
}

static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                         *root, struct btrfs_path *path, int level)
{
        struct extent_buffer *right = NULL;
        struct extent_buffer *mid;
        struct extent_buffer *left = NULL;
        struct extent_buffer *parent = NULL;
        int ret = 0;
        int wret;
        int pslot;
        int orig_slot = path->slots[level];
        int err_on_enospc = 0;
        u64 orig_ptr;

        if (level == 0)
                return 0;

        mid = path->nodes[level];
        orig_ptr = btrfs_node_blockptr(mid, orig_slot);

        if (level < BTRFS_MAX_LEVEL - 1)
                parent = path->nodes[level + 1];
        pslot = path->slots[level + 1];

        /*
         * deal with the case where there is only one pointer in the root
         * by promoting the node below to a root
         */
        if (!parent) {
                struct extent_buffer *child;

                if (btrfs_header_nritems(mid) != 1)
                        return 0;

                /* promote the child to a root */
                child = read_node_slot(root, mid, 0);
                BUG_ON(!child);
                root->node = child;
                path->nodes[level] = NULL;
                clean_tree_block(trans, root, mid);
                wait_on_tree_block_writeback(root, mid);
                /* once for the path */
                free_extent_buffer(mid);
                ret = btrfs_free_extent(trans, root, mid->start, mid->len, 1);
                /* once for the root ptr */
                free_extent_buffer(mid);
                return ret;
        }
        if (btrfs_header_nritems(mid) >
            BTRFS_NODEPTRS_PER_BLOCK(root) / 4)
                return 0;

        if (btrfs_header_nritems(mid) < 2)
                err_on_enospc = 1;

        left = read_node_slot(root, parent, pslot - 1);
        if (left) {
                wret = btrfs_cow_block(trans, root, left,
                                       parent, pslot - 1, &left);
                if (wret) {
                        ret = wret;
                        goto enospc;
                }
        }
        right = read_node_slot(root, parent, pslot + 1);
        if (right) {
                wret = btrfs_cow_block(trans, root, right,
                                       parent, pslot + 1, &right);
                if (wret) {
                        ret = wret;
                        goto enospc;
                }
        }

        /* first, try to make some room in the middle buffer */
        if (left) {
                orig_slot += btrfs_header_nritems(left);
                wret = push_node_left(trans, root, left, mid);
                if (wret < 0)
                        ret = wret;
                if (btrfs_header_nritems(mid) < 2)
                        err_on_enospc = 1;
        }

        /*
         * then try to empty the right most buffer into the middle
         */
        if (right) {
                wret = push_node_left(trans, root, mid, right);
                if (wret < 0 && wret != -ENOSPC)
                        ret = wret;
                if (btrfs_header_nritems(right) == 0) {
                        u64 bytenr = right->start;
                        u32 blocksize = right->len;

                        clean_tree_block(trans, root, right);
                        wait_on_tree_block_writeback(root, right);
                        free_extent_buffer(right);
                        right = NULL;
                        wret = del_ptr(trans, root, path, level + 1, pslot +
                                       1);
                        if (wret)
                                ret = wret;
                        wret = btrfs_free_extent(trans, root, bytenr,
                                                 blocksize, 1);
                        if (wret)
                                ret = wret;
                } else {
                        struct btrfs_disk_key right_key;
                        btrfs_node_key(right, &right_key, 0);
                        btrfs_set_node_key(parent, &right_key, pslot + 1);
                        btrfs_mark_buffer_dirty(parent);
                }
        }
        if (btrfs_header_nritems(mid) == 1) {
                /*
                 * we're not allowed to leave a node with one item in the
                 * tree during a delete.  A deletion from lower in the tree
                 * could try to delete the only pointer in this node.
                 * So, pull some keys from the left.
                 * There has to be a left pointer at this point because
                 * otherwise we would have pulled some pointers from the
                 * right
                 */
                BUG_ON(!left);
                wret = balance_node_right(trans, root, mid, left);
                if (wret < 0) {
                        ret = wret;
                        goto enospc;
                }
                BUG_ON(wret == 1);
        }
        if (btrfs_header_nritems(mid) == 0) {
                /* we've managed to empty the middle node, drop it */
                u64 bytenr = mid->start;
                u32 blocksize = mid->len;
                clean_tree_block(trans, root, mid);
                wait_on_tree_block_writeback(root, mid);
                free_extent_buffer(mid);
                mid = NULL;
                wret = del_ptr(trans, root, path, level + 1, pslot);
                if (wret)
                        ret = wret;
                wret = btrfs_free_extent(trans, root, bytenr, blocksize, 1);
                if (wret)
                        ret = wret;
        } else {
                /* update the parent key to reflect our changes */
                struct btrfs_disk_key mid_key;
                btrfs_node_key(mid, &mid_key, 0);
                btrfs_set_node_key(parent, &mid_key, pslot);
                btrfs_mark_buffer_dirty(parent);
        }

        /* update the path */
        if (left) {
                if (btrfs_header_nritems(left) > orig_slot) {
                        extent_buffer_get(left);
                        path->nodes[level] = left;
                        path->slots[level + 1] -= 1;
                        path->slots[level] = orig_slot;
                        if (mid)
                                free_extent_buffer(mid);
                } else {
                        orig_slot -= btrfs_header_nritems(left);
                        path->slots[level] = orig_slot;
                }
        }
        /* double check we haven't messed things up */
        check_block(root, path, level);
        if (orig_ptr !=
            btrfs_node_blockptr(path->nodes[level], path->slots[level]))
                BUG();
enospc:
        if (right)
                free_extent_buffer(right);
        if (left)
                free_extent_buffer(left);
        return ret;
}

/* returns zero if the push worked, non-zero otherwise */
static int push_nodes_for_insert(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_path *path, int level)
{
        struct extent_buffer *right = NULL;
        struct extent_buffer *mid;
        struct extent_buffer *left = NULL;
        struct extent_buffer *parent = NULL;
        int ret = 0;
        int wret;
        int pslot;
        int orig_slot = path->slots[level];
        u64 orig_ptr;

        if (level == 0)
                return 1;

        mid = path->nodes[level];
        orig_ptr = btrfs_node_blockptr(mid, orig_slot);

        if (level < BTRFS_MAX_LEVEL - 1)
                parent = path->nodes[level + 1];
        pslot = path->slots[level + 1];

        if (!parent)
                return 1;

        left = read_node_slot(root, parent, pslot - 1);

        /* first, try to make some room in the middle buffer */
        if (left) {
                u32 left_nr;
                left_nr = btrfs_header_nritems(left);
                if (left_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
                        wret = 1;
                } else {
                        ret = btrfs_cow_block(trans, root, left, parent,
                                              pslot - 1, &left);
                        if (ret)
                                wret = 1;
                        else {
                                wret = push_node_left(trans, root,
                                                      left, mid);
                        }
                }
                if (wret < 0)
                        ret = wret;
                if (wret == 0) {
                        struct btrfs_disk_key disk_key;
                        orig_slot += left_nr;
                        btrfs_node_key(mid, &disk_key, 0);
                        btrfs_set_node_key(parent, &disk_key, pslot);
                        btrfs_mark_buffer_dirty(parent);
                        if (btrfs_header_nritems(left) > orig_slot) {
                                path->nodes[level] = left;
                                path->slots[level + 1] -= 1;
                                path->slots[level] = orig_slot;
                                free_extent_buffer(mid);
                        } else {
                                orig_slot -=
                                        btrfs_header_nritems(left);
                                path->slots[level] = orig_slot;
                                free_extent_buffer(left);
                        }
                        return 0;
                }
                free_extent_buffer(left);
        }
        right= read_node_slot(root, parent, pslot + 1);

        /*
         * then try to empty the right most buffer into the middle
         */
        if (right) {
                u32 right_nr;
                right_nr = btrfs_header_nritems(right);
                if (right_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
                        wret = 1;
                } else {
                        ret = btrfs_cow_block(trans, root, right,
                                              parent, pslot + 1,
                                              &right);
                        if (ret)
                                wret = 1;
                        else {
                                wret = balance_node_right(trans, root,
                                                          right, mid);
                        }
                }
                if (wret < 0)
                        ret = wret;
                if (wret == 0) {
                        struct btrfs_disk_key disk_key;

                        btrfs_node_key(right, &disk_key, 0);
                        btrfs_set_node_key(parent, &disk_key, pslot + 1);
                        btrfs_mark_buffer_dirty(parent);

                        if (btrfs_header_nritems(mid) <= orig_slot) {
                                path->nodes[level] = right;
                                path->slots[level + 1] += 1;
                                path->slots[level] = orig_slot -
                                        btrfs_header_nritems(mid);
                                free_extent_buffer(mid);
                        } else {
                                free_extent_buffer(right);
                        }
                        return 0;
                }
                free_extent_buffer(right);
        }
        return 1;
}

/*
 * readahead one full node of leaves
 */
static void reada_for_search(struct btrfs_root *root, struct btrfs_path *path,
                             int level, int slot)
{
        struct extent_buffer *node;
        u32 nritems;
        u64 search;
        u64 lowest_read;
        u64 highest_read;
        u64 nread = 0;
        int direction = path->reada;
        struct extent_buffer *eb;
        u32 nr;
        u32 blocksize;
        u32 nscan = 0;

        if (level != 1)
                return;

        if (!path->nodes[level])
                return;

        node = path->nodes[level];
        search = btrfs_node_blockptr(node, slot);
        blocksize = btrfs_level_size(root, level - 1);
        eb = btrfs_find_tree_block(root, search, blocksize);
        if (eb) {
                free_extent_buffer(eb);
                return;
        }

        highest_read = search;
        lowest_read = search;

        nritems = btrfs_header_nritems(node);
        nr = slot;
        while(1) {
                if (direction < 0) {
                        if (nr == 0)
                                break;
                        nr--;
                } else if (direction > 0) {
                        nr++;
                        if (nr >= nritems)
                                break;
                }
                search = btrfs_node_blockptr(node, nr);
                if ((search >= lowest_read && search <= highest_read) ||
                    (search < lowest_read && lowest_read - search <= 32768) ||
                    (search > highest_read && search - highest_read <= 32768)) {
                        readahead_tree_block(root, search, blocksize);
                        nread += blocksize;
                }
                nscan++;
                if (path->reada < 2 && (nread > (256 * 1024) || nscan > 32))
                        break;
                if(nread > (1024 * 1024) || nscan > 128)
                        break;

                if (search < lowest_read)
                        lowest_read = search;
                if (search > highest_read)
                        highest_read = search;
        }
}
/*
 * look for key in the tree.  path is filled in with nodes along the way
 * if key is found, we return zero and you can find the item in the leaf
 * level of the path (level 0)
 *
 * If the key isn't found, the path points to the slot where it should
 * be inserted, and 1 is returned.  If there are other errors during the
 * search a negative error number is returned.
 *
 * if ins_len > 0, nodes and leaves will be split as we walk down the
 * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
 * possible)
 */
int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_key *key, struct btrfs_path *p, int
                      ins_len, int cow)
{
        struct extent_buffer *b;
        u64 bytenr;
        int slot;
        int ret;
        int level;
        int should_reada = p->reada;
        u8 lowest_level = 0;

        lowest_level = p->lowest_level;
        WARN_ON(lowest_level && ins_len);
        WARN_ON(p->nodes[0] != NULL);
        WARN_ON(!mutex_is_locked(&root->fs_info->fs_mutex));
again:
        b = root->node;
        extent_buffer_get(b);
        while (b) {
                level = btrfs_header_level(b);
                if (cow) {
                        int wret;
                        wret = btrfs_cow_block(trans, root, b,
                                               p->nodes[level + 1],
                                               p->slots[level + 1],
                                               &b);
                        if (wret) {
                                free_extent_buffer(b);
                                return wret;
                        }
                }
                BUG_ON(!cow && ins_len);
                if (level != btrfs_header_level(b))
                        WARN_ON(1);
                level = btrfs_header_level(b);
                p->nodes[level] = b;
                ret = check_block(root, p, level);
                if (ret)
                        return -1;
                ret = bin_search(b, key, level, &slot);
                if (level != 0) {
                        if (ret && slot > 0)
                                slot -= 1;
                        p->slots[level] = slot;
                        if (ins_len > 0 && btrfs_header_nritems(b) >=
                            BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
                                int sret = split_node(trans, root, p, level);
                                BUG_ON(sret > 0);
                                if (sret)
                                        return sret;
                                b = p->nodes[level];
                                slot = p->slots[level];
                        } else if (ins_len < 0) {
                                int sret = balance_level(trans, root, p,
                                                         level);
                                if (sret)
                                        return sret;
                                b = p->nodes[level];
                                if (!b) {
                                        btrfs_release_path(NULL, p);
                                        goto again;
                                }
                                slot = p->slots[level];
                                BUG_ON(btrfs_header_nritems(b) == 1);
                        }
                        /* this is only true while dropping a snapshot */
                        if (level == lowest_level)
                                break;
                        bytenr = btrfs_node_blockptr(b, slot);
                        if (should_reada)
                                reada_for_search(root, p, level, slot);
                        b = read_tree_block(root, bytenr,
                                            btrfs_level_size(root, level - 1));
                } else {
                        p->slots[level] = slot;
                        if (ins_len > 0 && btrfs_leaf_free_space(root, b) <
                            sizeof(struct btrfs_item) + ins_len) {
                                int sret = split_leaf(trans, root, key,
                                                      p, ins_len, ret == 0);
                                BUG_ON(sret > 0);
                                if (sret)
                                        return sret;
                        }
                        return ret;
                }
        }
        return 1;
}

/*
 * adjust the pointers going up the tree, starting at level
 * making sure the right key of each node is points to 'key'.
 * This is used after shifting pointers to the left, so it stops
 * fixing up pointers when a given leaf/node is not in slot 0 of the
 * higher levels
 *
 * If this fails to write a tree block, it returns -1, but continues
 * fixing up the blocks in ram so the tree is consistent.
 */
static int fixup_low_keys(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, struct btrfs_path *path,
                          struct btrfs_disk_key *key, int level)
{
        int i;
        int ret = 0;
        struct extent_buffer *t;

        for (i = level; i < BTRFS_MAX_LEVEL; i++) {
                int tslot = path->slots[i];
                if (!path->nodes[i])
                        break;
                t = path->nodes[i];
                btrfs_set_node_key(t, key, tslot);
                btrfs_mark_buffer_dirty(path->nodes[i]);
                if (tslot != 0)
                        break;
        }
        return ret;
}

/*
 * try to push data from one node into the next node left in the
 * tree.
 *
 * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
 * error, and > 0 if there was no room in the left hand block.
 */
static int push_node_left(struct btrfs_trans_handle *trans, struct btrfs_root
                          *root, struct extent_buffer *dst,
                          struct extent_buffer *src)
{
        int push_items = 0;
        int src_nritems;
        int dst_nritems;
        int ret = 0;

        src_nritems = btrfs_header_nritems(src);
        dst_nritems = btrfs_header_nritems(dst);
        push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;

        if (push_items <= 0) {
                return 1;
        }

        if (src_nritems < push_items)
                push_items = src_nritems;

        copy_extent_buffer(dst, src,
                           btrfs_node_key_ptr_offset(dst_nritems),
                           btrfs_node_key_ptr_offset(0),
                           push_items * sizeof(struct btrfs_key_ptr));

        if (push_items < src_nritems) {
                memmove_extent_buffer(src, btrfs_node_key_ptr_offset(0),
                                      btrfs_node_key_ptr_offset(push_items),
                                      (src_nritems - push_items) *
                                      sizeof(struct btrfs_key_ptr));
        }
        btrfs_set_header_nritems(src, src_nritems - push_items);
        btrfs_set_header_nritems(dst, dst_nritems + push_items);
        btrfs_mark_buffer_dirty(src);
        btrfs_mark_buffer_dirty(dst);
        return ret;
}

/*
 * try to push data from one node into the next node right in the
 * tree.
 *
 * returns 0 if some ptrs were pushed, < 0 if there was some horrible
 * error, and > 0 if there was no room in the right hand block.
 *
 * this will  only push up to 1/2 the contents of the left node over
 */
static int balance_node_right(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct extent_buffer *dst,
                              struct extent_buffer *src)
{
        int push_items = 0;
        int max_push;
        int src_nritems;
        int dst_nritems;
        int ret = 0;

        src_nritems = btrfs_header_nritems(src);
        dst_nritems = btrfs_header_nritems(dst);
        push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
        if (push_items <= 0)
                return 1;

        max_push = src_nritems / 2 + 1;
        /* don't try to empty the node */
        if (max_push >= src_nritems)
                return 1;

        if (max_push < push_items)
                push_items = max_push;

        memmove_extent_buffer(dst, btrfs_node_key_ptr_offset(push_items),
                                      btrfs_node_key_ptr_offset(0),
                                      (dst_nritems) *
                                      sizeof(struct btrfs_key_ptr));

        copy_extent_buffer(dst, src,
                           btrfs_node_key_ptr_offset(0),
                           btrfs_node_key_ptr_offset(src_nritems - push_items),
                           push_items * sizeof(struct btrfs_key_ptr));

        btrfs_set_header_nritems(src, src_nritems - push_items);
        btrfs_set_header_nritems(dst, dst_nritems + push_items);

        btrfs_mark_buffer_dirty(src);
        btrfs_mark_buffer_dirty(dst);
        return ret;
}

/*
 * helper function to insert a new root level in the tree.
 * A new node is allocated, and a single item is inserted to
 * point to the existing root
 *
 * returns zero on success or < 0 on failure.
 */
static int insert_new_root(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root,
                           struct btrfs_path *path, int level)
{
        struct extent_buffer *lower;
        struct extent_buffer *c;
        struct btrfs_disk_key lower_key;

        BUG_ON(path->nodes[level]);
        BUG_ON(path->nodes[level-1] != root->node);

        c = btrfs_alloc_free_block(trans, root, root->nodesize,
                                   root->node->start, 0);
        if (IS_ERR(c))
                return PTR_ERR(c);
        memset_extent_buffer(c, 0, 0, root->nodesize);
        btrfs_set_header_nritems(c, 1);
        btrfs_set_header_level(c, level);
        btrfs_set_header_bytenr(c, c->start);
        btrfs_set_header_generation(c, trans->transid);
        btrfs_set_header_owner(c, root->root_key.objectid);
        lower = path->nodes[level-1];

        write_extent_buffer(c, root->fs_info->fsid,
                            (unsigned long)btrfs_header_fsid(c),
                            BTRFS_FSID_SIZE);
        if (level == 1)
                btrfs_item_key(lower, &lower_key, 0);
        else
                btrfs_node_key(lower, &lower_key, 0);
        btrfs_set_node_key(c, &lower_key, 0);
        btrfs_set_node_blockptr(c, 0, lower->start);

        btrfs_mark_buffer_dirty(c);

        /* the super has an extra ref to root->node */
        free_extent_buffer(root->node);
        root->node = c;
        extent_buffer_get(c);
        path->nodes[level] = c;
        path->slots[level] = 0;
        return 0;
}

/*
 * worker function to insert a single pointer in a node.
 * the node should have enough room for the pointer already
 *
 * slot and level indicate where you want the key to go, and
 * blocknr is the block the key points to.
 *
 * returns zero on success and < 0 on any error
 */
static int insert_ptr(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_path *path, struct btrfs_disk_key
                      *key, u64 bytenr, int slot, int level)
{
        struct extent_buffer *lower;
        int nritems;

        BUG_ON(!path->nodes[level]);
        lower = path->nodes[level];
        nritems = btrfs_header_nritems(lower);
        if (slot > nritems)
                BUG();
        if (nritems == BTRFS_NODEPTRS_PER_BLOCK(root))
                BUG();
        if (slot != nritems) {
                memmove_extent_buffer(lower,
                              btrfs_node_key_ptr_offset(slot + 1),
                              btrfs_node_key_ptr_offset(slot),
                              (nritems - slot) * sizeof(struct btrfs_key_ptr));
        }
        btrfs_set_node_key(lower, key, slot);
        btrfs_set_node_blockptr(lower, slot, bytenr);
        btrfs_set_header_nritems(lower, nritems + 1);
        btrfs_mark_buffer_dirty(lower);
        return 0;
}

/*
 * split the node at the specified level in path in two.
 * The path is corrected to point to the appropriate node after the split
 *
 * Before splitting this tries to make some room in the node by pushing
 * left and right, if either one works, it returns right away.
 *
 * returns 0 on success and < 0 on failure
 */
static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_path *path, int level)
{
        struct extent_buffer *c;
        struct extent_buffer *split;
        struct btrfs_disk_key disk_key;
        int mid;
        int ret;
        int wret;
        u32 c_nritems;

        c = path->nodes[level];
        if (c == root->node) {
                /* trying to split the root, lets make a new one */
                ret = insert_new_root(trans, root, path, level + 1);
                if (ret)
                        return ret;
        } else {
                ret = push_nodes_for_insert(trans, root, path, level);
                c = path->nodes[level];
                if (!ret && btrfs_header_nritems(c) <
                    BTRFS_NODEPTRS_PER_BLOCK(root) - 1)
                        return 0;
                if (ret < 0)
                        return ret;
        }

        c_nritems = btrfs_header_nritems(c);
        split = btrfs_alloc_free_block(trans, root, root->nodesize,
                                       c->start, 0);
        if (IS_ERR(split))
                return PTR_ERR(split);

        btrfs_set_header_flags(split, btrfs_header_flags(c));
        btrfs_set_header_level(split, btrfs_header_level(c));
        btrfs_set_header_bytenr(split, split->start);
        btrfs_set_header_generation(split, trans->transid);
        btrfs_set_header_owner(split, root->root_key.objectid);
        write_extent_buffer(split, root->fs_info->fsid,
                            (unsigned long)btrfs_header_fsid(split),
                            BTRFS_FSID_SIZE);

        mid = (c_nritems + 1) / 2;

        copy_extent_buffer(split, c,
                           btrfs_node_key_ptr_offset(0),
                           btrfs_node_key_ptr_offset(mid),
                           (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
        btrfs_set_header_nritems(split, c_nritems - mid);
        btrfs_set_header_nritems(c, mid);
        ret = 0;

        btrfs_mark_buffer_dirty(c);
        btrfs_mark_buffer_dirty(split);

        btrfs_node_key(split, &disk_key, 0);
        wret = insert_ptr(trans, root, path, &disk_key, split->start,
                          path->slots[level + 1] + 1,
                          level + 1);
        if (wret)
                ret = wret;

        if (path->slots[level] >= mid) {
                path->slots[level] -= mid;
                free_extent_buffer(c);
                path->nodes[level] = split;
                path->slots[level + 1] += 1;
        } else {
                free_extent_buffer(split);
        }
        return ret;
}

/*
 * how many bytes are required to store the items in a leaf.  start
 * and nr indicate which items in the leaf to check.  This totals up the
 * space used both by the item structs and the item data
 */
static int leaf_space_used(struct extent_buffer *l, int start, int nr)
{
        int data_len;
        int nritems = btrfs_header_nritems(l);
        int end = min(nritems, start + nr) - 1;

        if (!nr)
                return 0;
        data_len = btrfs_item_end_nr(l, start);
        data_len = data_len - btrfs_item_offset_nr(l, end);
        data_len += sizeof(struct btrfs_item) * nr;
        WARN_ON(data_len < 0);
        return data_len;
}

/*
 * The space between the end of the leaf items and
 * the start of the leaf data.  IOW, how much room
 * the leaf has left for both items and data
 */
int btrfs_leaf_free_space(struct btrfs_root *root, struct extent_buffer *leaf)
{
        int nritems = btrfs_header_nritems(leaf);
        int ret;
        ret = BTRFS_LEAF_DATA_SIZE(root) - leaf_space_used(leaf, 0, nritems);
        if (ret < 0) {
                printk("leaf free space ret %d, leaf data size %lu, used %d nritems %d\n",
                       ret, (unsigned long) BTRFS_LEAF_DATA_SIZE(root),
                       leaf_space_used(leaf, 0, nritems), nritems);
        }
        return ret;
}

/*
 * push some data in the path leaf to the right, trying to free up at
 * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 *
 * returns 1 if the push failed because the other node didn't have enough
 * room, 0 if everything worked out and < 0 if there were major errors.
 */
static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
                           *root, struct btrfs_path *path, int data_size)
{
        struct extent_buffer *left = path->nodes[0];
        struct extent_buffer *right;
        struct extent_buffer *upper;
        struct btrfs_disk_key disk_key;
        int slot;
        int i;
        int free_space;
        int push_space = 0;
        int push_items = 0;
        struct btrfs_item *item;
        u32 left_nritems;
        u32 right_nritems;
        u32 data_end;
        u32 this_item_size;
        int ret;

        slot = path->slots[1];
        if (!path->nodes[1]) {
                return 1;
        }
        upper = path->nodes[1];
        if (slot >= btrfs_header_nritems(upper) - 1)
                return 1;

        right = read_tree_block(root, btrfs_node_blockptr(upper, slot + 1),
                                root->leafsize);
        free_space = btrfs_leaf_free_space(root, right);
        if (free_space < data_size + sizeof(struct btrfs_item)) {
                free_extent_buffer(right);
                return 1;
        }

        /* cow and double check */
        ret = btrfs_cow_block(trans, root, right, upper,
                              slot + 1, &right);
        if (ret) {
                free_extent_buffer(right);
                return 1;
        }
        free_space = btrfs_leaf_free_space(root, right);
        if (free_space < data_size + sizeof(struct btrfs_item)) {
                free_extent_buffer(right);
                return 1;
        }

        left_nritems = btrfs_header_nritems(left);
        if (left_nritems == 0) {
                free_extent_buffer(right);
                return 1;
        }

        for (i = left_nritems - 1; i >= 1; i--) {
                item = btrfs_item_nr(left, i);

                if (path->slots[0] == i)
                        push_space += data_size + sizeof(*item);

                if (!left->map_token) {
                        map_extent_buffer(left, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &left->map_token, &left->kaddr,
                                        &left->map_start, &left->map_len,
                                        KM_USER1);
                }

                this_item_size = btrfs_item_size(left, item);
                if (this_item_size + sizeof(*item) + push_space > free_space)
                        break;
                push_items++;
                push_space += this_item_size + sizeof(*item);
        }
        if (left->map_token) {
                unmap_extent_buffer(left, left->map_token, KM_USER1);
                left->map_token = NULL;
        }

        if (push_items == 0) {
                free_extent_buffer(right);
                return 1;
        }

        if (push_items == left_nritems)
                WARN_ON(1);

        /* push left to right */
        right_nritems = btrfs_header_nritems(right);
        push_space = btrfs_item_end_nr(left, left_nritems - push_items);
        push_space -= leaf_data_end(root, left);

        /* make room in the right data area */
        data_end = leaf_data_end(root, right);
        memmove_extent_buffer(right,
                              btrfs_leaf_data(right) + data_end - push_space,
                              btrfs_leaf_data(right) + data_end,
                              BTRFS_LEAF_DATA_SIZE(root) - data_end);

        /* copy from the left data area */
        copy_extent_buffer(right, left, btrfs_leaf_data(right) +
                     BTRFS_LEAF_DATA_SIZE(root) - push_space,
                     btrfs_leaf_data(left) + leaf_data_end(root, left),
                     push_space);

        memmove_extent_buffer(right, btrfs_item_nr_offset(push_items),
                              btrfs_item_nr_offset(0),
                              right_nritems * sizeof(struct btrfs_item));

        /* copy the items from left to right */
        copy_extent_buffer(right, left, btrfs_item_nr_offset(0),
                   btrfs_item_nr_offset(left_nritems - push_items),
                   push_items * sizeof(struct btrfs_item));

        /* update the item pointers */
        right_nritems += push_items;
        btrfs_set_header_nritems(right, right_nritems);
        push_space = BTRFS_LEAF_DATA_SIZE(root);

        for (i = 0; i < right_nritems; i++) {
                item = btrfs_item_nr(right, i);
                if (!right->map_token) {
                        map_extent_buffer(right, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &right->map_token, &right->kaddr,
                                        &right->map_start, &right->map_len,
                                        KM_USER1);
                }
                push_space -= btrfs_item_size(right, item);
                btrfs_set_item_offset(right, item, push_space);
        }

        if (right->map_token) {
                unmap_extent_buffer(right, right->map_token, KM_USER1);
                right->map_token = NULL;
        }
        left_nritems -= push_items;
        btrfs_set_header_nritems(left, left_nritems);

        btrfs_mark_buffer_dirty(left);
        btrfs_mark_buffer_dirty(right);

        btrfs_item_key(right, &disk_key, 0);
        btrfs_set_node_key(upper, &disk_key, slot + 1);
        btrfs_mark_buffer_dirty(upper);

        /* then fixup the leaf pointer in the path */
        if (path->slots[0] >= left_nritems) {
                path->slots[0] -= left_nritems;
                free_extent_buffer(path->nodes[0]);
                path->nodes[0] = right;
                path->slots[1] += 1;
        } else {
                free_extent_buffer(right);
        }
        return 0;
}
/*
 * push some data in the path leaf to the left, trying to free up at
 * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 */
static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
                          *root, struct btrfs_path *path, int data_size)
{
        struct btrfs_disk_key disk_key;
        struct extent_buffer *right = path->nodes[0];
        struct extent_buffer *left;
        int slot;
        int i;
        int free_space;
        int push_space = 0;
        int push_items = 0;
        struct btrfs_item *item;
        u32 old_left_nritems;
        u32 right_nritems;
        int ret = 0;
        int wret;
        u32 this_item_size;
        u32 old_left_item_size;

        slot = path->slots[1];
        if (slot == 0)
                return 1;
        if (!path->nodes[1])
                return 1;

        right_nritems = btrfs_header_nritems(right);
        if (right_nritems == 0) {
                return 1;
        }

        left = read_tree_block(root, btrfs_node_blockptr(path->nodes[1],
                               slot - 1), root->leafsize);
        free_space = btrfs_leaf_free_space(root, left);
        if (free_space < data_size + sizeof(struct btrfs_item)) {
                free_extent_buffer(left);
                return 1;
        }

        /* cow and double check */
        ret = btrfs_cow_block(trans, root, left,
                              path->nodes[1], slot - 1, &left);
        if (ret) {
                /* we hit -ENOSPC, but it isn't fatal here */
                free_extent_buffer(left);
                return 1;
        }

        free_space = btrfs_leaf_free_space(root, left);
        if (free_space < data_size + sizeof(struct btrfs_item)) {
                free_extent_buffer(left);
                return 1;
        }

        for (i = 0; i < right_nritems - 1; i++) {
                item = btrfs_item_nr(right, i);
                if (!right->map_token) {
                        map_extent_buffer(right, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &right->map_token, &right->kaddr,
                                        &right->map_start, &right->map_len,
                                        KM_USER1);
                }

                if (path->slots[0] == i)
                        push_space += data_size + sizeof(*item);

                this_item_size = btrfs_item_size(right, item);
                if (this_item_size + sizeof(*item) + push_space > free_space)
                        break;

                push_items++;
                push_space += this_item_size + sizeof(*item);
        }

        if (right->map_token) {
                unmap_extent_buffer(right, right->map_token, KM_USER1);
                right->map_token = NULL;
        }

        if (push_items == 0) {
                free_extent_buffer(left);
                return 1;
        }
        if (push_items == btrfs_header_nritems(right))
                WARN_ON(1);

        /* push data from right to left */
        copy_extent_buffer(left, right,
                           btrfs_item_nr_offset(btrfs_header_nritems(left)),
                           btrfs_item_nr_offset(0),
                           push_items * sizeof(struct btrfs_item));

        push_space = BTRFS_LEAF_DATA_SIZE(root) -
                     btrfs_item_offset_nr(right, push_items -1);

        copy_extent_buffer(left, right, btrfs_leaf_data(left) +
                     leaf_data_end(root, left) - push_space,
                     btrfs_leaf_data(right) +
                     btrfs_item_offset_nr(right, push_items - 1),
                     push_space);
        old_left_nritems = btrfs_header_nritems(left);
        BUG_ON(old_left_nritems < 0);

        old_left_item_size = btrfs_item_offset_nr(left, old_left_nritems - 1);
        for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
                u32 ioff;

                item = btrfs_item_nr(left, i);
                if (!left->map_token) {
                        map_extent_buffer(left, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &left->map_token, &left->kaddr,
                                        &left->map_start, &left->map_len,
                                        KM_USER1);
                }

                ioff = btrfs_item_offset(left, item);
                btrfs_set_item_offset(left, item,
                      ioff - (BTRFS_LEAF_DATA_SIZE(root) - old_left_item_size));
        }
        btrfs_set_header_nritems(left, old_left_nritems + push_items);
        if (left->map_token) {
                unmap_extent_buffer(left, left->map_token, KM_USER1);
                left->map_token = NULL;
        }

        /* fixup right node */
        push_space = btrfs_item_offset_nr(right, push_items - 1) -
                                          leaf_data_end(root, right);
        memmove_extent_buffer(right, btrfs_leaf_data(right) +
                              BTRFS_LEAF_DATA_SIZE(root) - push_space,
                              btrfs_leaf_data(right) +
                              leaf_data_end(root, right), push_space);

        memmove_extent_buffer(right, btrfs_item_nr_offset(0),
                              btrfs_item_nr_offset(push_items),
                             (btrfs_header_nritems(right) - push_items) *
                             sizeof(struct btrfs_item));

        right_nritems = btrfs_header_nritems(right) - push_items;
        btrfs_set_header_nritems(right, right_nritems);
        push_space = BTRFS_LEAF_DATA_SIZE(root);

        for (i = 0; i < right_nritems; i++) {
                item = btrfs_item_nr(right, i);

                if (!right->map_token) {
                        map_extent_buffer(right, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &right->map_token, &right->kaddr,
                                        &right->map_start, &right->map_len,
                                        KM_USER1);
                }

                push_space = push_space - btrfs_item_size(right, item);
                btrfs_set_item_offset(right, item, push_space);
        }
        if (right->map_token) {
                unmap_extent_buffer(right, right->map_token, KM_USER1);
                right->map_token = NULL;
        }

        btrfs_mark_buffer_dirty(left);
        btrfs_mark_buffer_dirty(right);

        btrfs_item_key(right, &disk_key, 0);
        wret = fixup_low_keys(trans, root, path, &disk_key, 1);
        if (wret)
                ret = wret;

        /* then fixup the leaf pointer in the path */
        if (path->slots[0] < push_items) {
                path->slots[0] += old_left_nritems;
                free_extent_buffer(path->nodes[0]);
                path->nodes[0] = left;
                path->slots[1] -= 1;
        } else {
                free_extent_buffer(left);
                path->slots[0] -= push_items;
        }
        BUG_ON(path->slots[0] < 0);
        return ret;
}

/*
 * split the path's leaf in two, making sure there is at least data_size
 * available for the resulting leaf level of the path.
 *
 * returns 0 if all went well and < 0 on failure.
 */
static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_key *ins_key,
                      struct btrfs_path *path, int data_size, int extend)
{
        struct extent_buffer *l;
        u32 nritems;
        int mid;
        int slot;
        struct extent_buffer *right;
        int space_needed = data_size + sizeof(struct btrfs_item);
        int data_copy_size;
        int rt_data_off;
        int i;
        int ret = 0;
        int wret;
        int double_split;
        int num_doubles = 0;
        struct btrfs_disk_key disk_key;

        if (extend)
                space_needed = data_size;

        /* first try to make some room by pushing left and right */
        if (ins_key->type != BTRFS_DIR_ITEM_KEY) {
                wret = push_leaf_right(trans, root, path, data_size);
                if (wret < 0) {
                        return wret;
                }
                if (wret) {
                        wret = push_leaf_left(trans, root, path, data_size);
                        if (wret < 0)
                                return wret;
                }
                l = path->nodes[0];

                /* did the pushes work? */
                if (btrfs_leaf_free_space(root, l) >= space_needed)
                        return 0;
        }

        if (!path->nodes[1]) {
                ret = insert_new_root(trans, root, path, 1);
                if (ret)
                        return ret;
        }
again:
        double_split = 0;
        l = path->nodes[0];
        slot = path->slots[0];
        nritems = btrfs_header_nritems(l);
        mid = (nritems + 1)/ 2;

        right = btrfs_alloc_free_block(trans, root, root->leafsize,
                                       l->start, 0);
        if (IS_ERR(right))
                return PTR_ERR(right);

        memset_extent_buffer(right, 0, 0, sizeof(struct btrfs_header));
        btrfs_set_header_bytenr(right, right->start);
        btrfs_set_header_generation(right, trans->transid);
        btrfs_set_header_owner(right, root->root_key.objectid);
        btrfs_set_header_level(right, 0);
        write_extent_buffer(right, root->fs_info->fsid,
                            (unsigned long)btrfs_header_fsid(right),
                            BTRFS_FSID_SIZE);
        if (mid <= slot) {
                if (nritems == 1 ||
                    leaf_space_used(l, mid, nritems - mid) + space_needed >
                        BTRFS_LEAF_DATA_SIZE(root)) {
                        if (slot >= nritems) {
                                btrfs_cpu_key_to_disk(&disk_key, ins_key);
                                btrfs_set_header_nritems(right, 0);
                                wret = insert_ptr(trans, root, path,
                                                  &disk_key, right->start,
                                                  path->slots[1] + 1, 1);
                                if (wret)
                                        ret = wret;
                                free_extent_buffer(path->nodes[0]);
                                path->nodes[0] = right;
                                path->slots[0] = 0;
                                path->slots[1] += 1;
                                return ret;
                        }
                        mid = slot;
                        if (mid != nritems &&
                            leaf_space_used(l, mid, nritems - mid) +
                            space_needed > BTRFS_LEAF_DATA_SIZE(root)) {
                                double_split = 1;
                        }
                }
        } else {
                if (leaf_space_used(l, 0, mid + 1) + space_needed >
                        BTRFS_LEAF_DATA_SIZE(root)) {
                        if (!extend && slot == 0) {
                                btrfs_cpu_key_to_disk(&disk_key, ins_key);
                                btrfs_set_header_nritems(right, 0);
                                wret = insert_ptr(trans, root, path,
                                                  &disk_key,
                                                  right->start,
                                                  path->slots[1], 1);
                                if (wret)
                                        ret = wret;
                                free_extent_buffer(path->nodes[0]);
                                path->nodes[0] = right;
                                path->slots[0] = 0;
                                if (path->slots[1] == 0) {
                                        wret = fixup_low_keys(trans, root,
                                                   path, &disk_key, 1);
                                        if (wret)
                                                ret = wret;
                                }
                                return ret;
                        } else if (extend && slot == 0) {
                                mid = 1;
                        } else {
                                mid = slot;
                                if (mid != nritems &&
                                    leaf_space_used(l, mid, nritems - mid) +
                                    space_needed > BTRFS_LEAF_DATA_SIZE(root)) {
                                        double_split = 1;
                                }
                        }
                }
        }
        nritems = nritems - mid;
        btrfs_set_header_nritems(right, nritems);
        data_copy_size = btrfs_item_end_nr(l, mid) - leaf_data_end(root, l);

        copy_extent_buffer(right, l, btrfs_item_nr_offset(0),
                           btrfs_item_nr_offset(mid),
                           nritems * sizeof(struct btrfs_item));

        copy_extent_buffer(right, l,
                     btrfs_leaf_data(right) + BTRFS_LEAF_DATA_SIZE(root) -
                     data_copy_size, btrfs_leaf_data(l) +
                     leaf_data_end(root, l), data_copy_size);

        rt_data_off = BTRFS_LEAF_DATA_SIZE(root) -
                      btrfs_item_end_nr(l, mid);

        for (i = 0; i < nritems; i++) {
                struct btrfs_item *item = btrfs_item_nr(right, i);
                u32 ioff;

                if (!right->map_token) {
                        map_extent_buffer(right, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &right->map_token, &right->kaddr,
                                        &right->map_start, &right->map_len,
                                        KM_USER1);
                }

                ioff = btrfs_item_offset(right, item);
                btrfs_set_item_offset(right, item, ioff + rt_data_off);
        }

        if (right->map_token) {
                unmap_extent_buffer(right, right->map_token, KM_USER1);
                right->map_token = NULL;
        }

        btrfs_set_header_nritems(l, mid);
        ret = 0;
        btrfs_item_key(right, &disk_key, 0);
        wret = insert_ptr(trans, root, path, &disk_key, right->start,
                          path->slots[1] + 1, 1);
        if (wret)
                ret = wret;

        btrfs_mark_buffer_dirty(right);
        btrfs_mark_buffer_dirty(l);
        BUG_ON(path->slots[0] != slot);

        if (mid <= slot) {
                free_extent_buffer(path->nodes[0]);
                path->nodes[0] = right;
                path->slots[0] -= mid;
                path->slots[1] += 1;
        } else
                free_extent_buffer(right);

        BUG_ON(path->slots[0] < 0);

        if (double_split) {
                BUG_ON(num_doubles != 0);
                num_doubles++;
                goto again;
        }
        return ret;
}

int btrfs_truncate_item(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
                        struct btrfs_path *path,
                        u32 new_size, int from_end)
{
        int ret = 0;
        int slot;
        int slot_orig;
        struct extent_buffer *leaf;
        struct btrfs_item *item;
        u32 nritems;
        unsigned int data_end;
        unsigned int old_data_start;
        unsigned int old_size;
        unsigned int size_diff;
        int i;

        slot_orig = path->slots[0];
        leaf = path->nodes[0];
        slot = path->slots[0];

        old_size = btrfs_item_size_nr(leaf, slot);
        if (old_size == new_size)
                return 0;

        nritems = btrfs_header_nritems(leaf);
        data_end = leaf_data_end(root, leaf);

        old_data_start = btrfs_item_offset_nr(leaf, slot);

        size_diff = old_size - new_size;

        BUG_ON(slot < 0);
        BUG_ON(slot >= nritems);

        /*
         * item0..itemN ... dataN.offset..dataN.size .. data0.size
         */
        /* first correct the data pointers */
        for (i = slot; i < nritems; i++) {
                u32 ioff;
                item = btrfs_item_nr(leaf, i);

                if (!leaf->map_token) {
                        map_extent_buffer(leaf, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &leaf->map_token, &leaf->kaddr,
                                        &leaf->map_start, &leaf->map_len,
                                        KM_USER1);
                }

                ioff = btrfs_item_offset(leaf, item);
                btrfs_set_item_offset(leaf, item, ioff + size_diff);
        }

        if (leaf->map_token) {
                unmap_extent_buffer(leaf, leaf->map_token, KM_USER1);
                leaf->map_token = NULL;
        }

        /* shift the data */
        if (from_end) {
                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
                              data_end + size_diff, btrfs_leaf_data(leaf) +
                              data_end, old_data_start + new_size - data_end);
        } else {
                struct btrfs_disk_key disk_key;
                u64 offset;

                btrfs_item_key(leaf, &disk_key, slot);

                if (btrfs_disk_key_type(&disk_key) == BTRFS_EXTENT_DATA_KEY) {
                        unsigned long ptr;
                        struct btrfs_file_extent_item *fi;

                        fi = btrfs_item_ptr(leaf, slot,
                                            struct btrfs_file_extent_item);
                        fi = (struct btrfs_file_extent_item *)(
                             (unsigned long)fi - size_diff);

                        if (btrfs_file_extent_type(leaf, fi) ==
                            BTRFS_FILE_EXTENT_INLINE) {
                                ptr = btrfs_item_ptr_offset(leaf, slot);
                                memmove_extent_buffer(leaf, ptr,
                                        (unsigned long)fi,
                                        offsetof(struct btrfs_file_extent_item,
                                                 disk_bytenr));
                        }
                }

                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
                              data_end + size_diff, btrfs_leaf_data(leaf) +
                              data_end, old_data_start - data_end);

                offset = btrfs_disk_key_offset(&disk_key);
                btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
                btrfs_set_item_key(leaf, &disk_key, slot);
                if (slot == 0)
                        fixup_low_keys(trans, root, path, &disk_key, 1);
        }

        item = btrfs_item_nr(leaf, slot);
        btrfs_set_item_size(leaf, item, new_size);
        btrfs_mark_buffer_dirty(leaf);

        ret = 0;
        if (btrfs_leaf_free_space(root, leaf) < 0) {
                btrfs_print_leaf(root, leaf);
                BUG();
        }
        return ret;
}

int btrfs_extend_item(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root, struct btrfs_path *path,
                      u32 data_size)
{
        int ret = 0;
        int slot;
        int slot_orig;
        struct extent_buffer *leaf;
        struct btrfs_item *item;
        u32 nritems;
        unsigned int data_end;
        unsigned int old_data;
        unsigned int old_size;
        int i;

        slot_orig = path->slots[0];
        leaf = path->nodes[0];

        nritems = btrfs_header_nritems(leaf);
        data_end = leaf_data_end(root, leaf);

        if (btrfs_leaf_free_space(root, leaf) < data_size) {
                btrfs_print_leaf(root, leaf);
                BUG();
        }
        slot = path->slots[0];
        old_data = btrfs_item_end_nr(leaf, slot);

        BUG_ON(slot < 0);
        if (slot >= nritems) {
                btrfs_print_leaf(root, leaf);
                printk("slot %d too large, nritems %d\n", slot, nritems);
                BUG_ON(1);
        }

        /*
         * item0..itemN ... dataN.offset..dataN.size .. data0.size
         */
        /* first correct the data pointers */
        for (i = slot; i < nritems; i++) {
                u32 ioff;
                item = btrfs_item_nr(leaf, i);

                if (!leaf->map_token) {
                        map_extent_buffer(leaf, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &leaf->map_token, &leaf->kaddr,
                                        &leaf->map_start, &leaf->map_len,
                                        KM_USER1);
                }
                ioff = btrfs_item_offset(leaf, item);
                btrfs_set_item_offset(leaf, item, ioff - data_size);
        }

        if (leaf->map_token) {
                unmap_extent_buffer(leaf, leaf->map_token, KM_USER1);
                leaf->map_token = NULL;
        }

        /* shift the data */
        memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
                      data_end - data_size, btrfs_leaf_data(leaf) +
                      data_end, old_data - data_end);

        data_end = old_data;
        old_size = btrfs_item_size_nr(leaf, slot);
        item = btrfs_item_nr(leaf, slot);
        btrfs_set_item_size(leaf, item, old_size + data_size);
        btrfs_mark_buffer_dirty(leaf);

        ret = 0;
        if (btrfs_leaf_free_space(root, leaf) < 0) {
                btrfs_print_leaf(root, leaf);
                BUG();
        }
        return ret;
}

/*
 * Given a key and some data, insert an item into the tree.
 * This does all the path init required, making room in the tree if needed.
 */
int btrfs_insert_empty_item(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            struct btrfs_path *path,
                            struct btrfs_key *cpu_key, u32 data_size)
{
        struct extent_buffer *leaf;
        struct btrfs_item *item;
        int ret = 0;
        int slot;
        int slot_orig;
        u32 nritems;
        unsigned int data_end;
        struct btrfs_disk_key disk_key;

        btrfs_cpu_key_to_disk(&disk_key, cpu_key);

        /* create a root if there isn't one */
        if (!root->node)
                BUG();

        ret = btrfs_search_slot(trans, root, cpu_key, path, data_size, 1);
        if (ret == 0) {
                return -EEXIST;
        }
        if (ret < 0)
                goto out;

        slot_orig = path->slots[0];
        leaf = path->nodes[0];

        nritems = btrfs_header_nritems(leaf);
        data_end = leaf_data_end(root, leaf);

        if (btrfs_leaf_free_space(root, leaf) <
            sizeof(struct btrfs_item) + data_size) {
                btrfs_print_leaf(root, leaf);
                printk("not enough freespace need %u have %d\n",
                       data_size, btrfs_leaf_free_space(root, leaf));
                BUG();
        }

        slot = path->slots[0];
        BUG_ON(slot < 0);

        if (slot != nritems) {
                int i;
                unsigned int old_data = btrfs_item_end_nr(leaf, slot);

                if (old_data < data_end) {
                        btrfs_print_leaf(root, leaf);
                        printk("slot %d old_data %d data_end %d\n",
                               slot, old_data, data_end);
                        BUG_ON(1);
                }
                /*
                 * item0..itemN ... dataN.offset..dataN.size .. data0.size
                 */
                /* first correct the data pointers */
                WARN_ON(leaf->map_token);
                for (i = slot; i < nritems; i++) {
                        u32 ioff;

                        item = btrfs_item_nr(leaf, i);
                        if (!leaf->map_token) {
                                map_extent_buffer(leaf, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &leaf->map_token, &leaf->kaddr,
                                        &leaf->map_start, &leaf->map_len,
                                        KM_USER1);
                        }

                        ioff = btrfs_item_offset(leaf, item);
                        btrfs_set_item_offset(leaf, item, ioff - data_size);
                }
                if (leaf->map_token) {
                        unmap_extent_buffer(leaf, leaf->map_token, KM_USER1);
                        leaf->map_token = NULL;
                }

                /* shift the items */
                memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + 1),
                              btrfs_item_nr_offset(slot),
                              (nritems - slot) * sizeof(struct btrfs_item));

                /* shift the data */
                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
                              data_end - data_size, btrfs_leaf_data(leaf) +
                              data_end, old_data - data_end);
                data_end = old_data;
        }

        /* setup the item for the new data */
        btrfs_set_item_key(leaf, &disk_key, slot);
        item = btrfs_item_nr(leaf, slot);
        btrfs_set_item_offset(leaf, item, data_end - data_size);
        btrfs_set_item_size(leaf, item, data_size);
        btrfs_set_header_nritems(leaf, nritems + 1);
        btrfs_mark_buffer_dirty(leaf);

        ret = 0;
        if (slot == 0)
                ret = fixup_low_keys(trans, root, path, &disk_key, 1);

        if (btrfs_leaf_free_space(root, leaf) < 0) {
                btrfs_print_leaf(root, leaf);
                BUG();
        }
out:
        return ret;
}

/*
 * Given a key and some data, insert an item into the tree.
 * This does all the path init required, making room in the tree if needed.
 */
int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_key *cpu_key, void *data, u32
                      data_size)
{
        int ret = 0;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        unsigned long ptr;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
        if (!ret) {
                leaf = path->nodes[0];
                ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
                write_extent_buffer(leaf, data, ptr, data_size);
                btrfs_mark_buffer_dirty(leaf);
        }
        btrfs_free_path(path);
        return ret;
}

/*
 * delete the pointer from a given node.
 *
 * If the delete empties a node, the node is removed from the tree,
 * continuing all the way the root if required.  The root is converted into
 * a leaf if all the nodes are emptied.
 */
static int del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                   struct btrfs_path *path, int level, int slot)
{
        struct extent_buffer *parent = path->nodes[level];
        u32 nritems;
        int ret = 0;
        int wret;

        nritems = btrfs_header_nritems(parent);
        if (slot != nritems -1) {
                memmove_extent_buffer(parent,
                              btrfs_node_key_ptr_offset(slot),
                              btrfs_node_key_ptr_offset(slot + 1),
                              sizeof(struct btrfs_key_ptr) *
                              (nritems - slot - 1));
        }
        nritems--;
        btrfs_set_header_nritems(parent, nritems);
        if (nritems == 0 && parent == root->node) {
                BUG_ON(btrfs_header_level(root->node) != 1);
                /* just turn the root into a leaf and break */
                btrfs_set_header_level(root->node, 0);
        } else if (slot == 0) {
                struct btrfs_disk_key disk_key;

                btrfs_node_key(parent, &disk_key, 0);
                wret = fixup_low_keys(trans, root, path, &disk_key, level + 1);
                if (wret)
                        ret = wret;
        }
        btrfs_mark_buffer_dirty(parent);
        return ret;
}

/*
 * delete the item at the leaf level in path.  If that empties
 * the leaf, remove it from the tree
 */
int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                   struct btrfs_path *path)
{
        int slot;
        struct extent_buffer *leaf;
        struct btrfs_item *item;
        int doff;
        int dsize;
        int ret = 0;
        int wret;
        u32 nritems;

        leaf = path->nodes[0];
        slot = path->slots[0];
        doff = btrfs_item_offset_nr(leaf, slot);
        dsize = btrfs_item_size_nr(leaf, slot);
        nritems = btrfs_header_nritems(leaf);

        if (slot != nritems - 1) {
                int i;
                int data_end = leaf_data_end(root, leaf);

                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
                              data_end + dsize,
                              btrfs_leaf_data(leaf) + data_end,
                              doff - data_end);

                for (i = slot + 1; i < nritems; i++) {
                        u32 ioff;

                        item = btrfs_item_nr(leaf, i);
                        if (!leaf->map_token) {
                                map_extent_buffer(leaf, (unsigned long)item,
                                        sizeof(struct btrfs_item),
                                        &leaf->map_token, &leaf->kaddr,
                                        &leaf->map_start, &leaf->map_len,
                                        KM_USER1);
                        }
                        ioff = btrfs_item_offset(leaf, item);
                        btrfs_set_item_offset(leaf, item, ioff + dsize);
                }

                if (leaf->map_token) {
                        unmap_extent_buffer(leaf, leaf->map_token, KM_USER1);
                        leaf->map_token = NULL;
                }

                memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot),
                              btrfs_item_nr_offset(slot + 1),
                              sizeof(struct btrfs_item) *
                              (nritems - slot - 1));
        }
        btrfs_set_header_nritems(leaf, nritems - 1);
        nritems--;

        /* delete the leaf if we've emptied it */
        if (nritems == 0) {
                if (leaf == root->node) {
                        btrfs_set_header_level(leaf, 0);
                } else {
                        clean_tree_block(trans, root, leaf);
                        wait_on_tree_block_writeback(root, leaf);
                        wret = del_ptr(trans, root, path, 1, path->slots[1]);
                        if (wret)
                                ret = wret;
                        wret = btrfs_free_extent(trans, root,
                                                 leaf->start, leaf->len, 1);
                        if (wret)
                                ret = wret;
                }
        } else {
                int used = leaf_space_used(leaf, 0, nritems);
                if (slot == 0) {
                        struct btrfs_disk_key disk_key;

                        btrfs_item_key(leaf, &disk_key, 0);
                        wret = fixup_low_keys(trans, root, path,
                                              &disk_key, 1);
                        if (wret)
                                ret = wret;
                }

                /* delete the leaf if it is mostly empty */
                if (used < BTRFS_LEAF_DATA_SIZE(root) / 3) {
                        /* push_leaf_left fixes the path.
                         * make sure the path still points to our leaf
                         * for possible call to del_ptr below
                         */
                        slot = path->slots[1];
                        extent_buffer_get(leaf);

                        wret = push_leaf_right(trans, root, path, 1);
                        if (wret < 0 && wret != -ENOSPC)
                                ret = wret;

                        if (path->nodes[0] == leaf &&
                            btrfs_header_nritems(leaf)) {
                                wret = push_leaf_left(trans, root, path, 1);
                                if (wret < 0 && wret != -ENOSPC)
                                        ret = wret;
                        }

                        if (btrfs_header_nritems(leaf) == 0) {
                                u64 bytenr = leaf->start;
                                u32 blocksize = leaf->len;

                                clean_tree_block(trans, root, leaf);
                                wait_on_tree_block_writeback(root, leaf);

                                wret = del_ptr(trans, root, path, 1, slot);
                                if (wret)
                                        ret = wret;

                                free_extent_buffer(leaf);
                                wret = btrfs_free_extent(trans, root, bytenr,
                                                         blocksize, 1);
                                if (wret)
                                        ret = wret;
                        } else {
                                btrfs_mark_buffer_dirty(leaf);
                                free_extent_buffer(leaf);
                        }
                } else {
                        btrfs_mark_buffer_dirty(leaf);
                }
        }
        return ret;
}

/*
 * walk up the tree as far as required to find the next leaf.
 * returns 0 if it found something or 1 if there are no greater leaves.
 * returns < 0 on io errors.
 */
int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
{
        int slot;
        int level = 1;
        u64 bytenr;
        struct extent_buffer *c;
        struct extent_buffer *next = NULL;

        while(level < BTRFS_MAX_LEVEL) {
                if (!path->nodes[level])
                        return 1;

                slot = path->slots[level] + 1;
                c = path->nodes[level];
                if (slot >= btrfs_header_nritems(c)) {
                        level++;
                        continue;
                }

                bytenr = btrfs_node_blockptr(c, slot);
                if (next)
                        free_extent_buffer(next);

                if (path->reada)
                        reada_for_search(root, path, level, slot);

                next = read_tree_block(root, bytenr,
                                       btrfs_level_size(root, level -1));
                break;
        }
        path->slots[level] = slot;
        while(1) {
                level--;
                c = path->nodes[level];
                free_extent_buffer(c);
                path->nodes[level] = next;
                path->slots[level] = 0;
                if (!level)
                        break;
                if (path->reada)
                        reada_for_search(root, path, level, 0);
                next = read_tree_block(root, btrfs_node_blockptr(next, 0),
                                       btrfs_level_size(root, level - 1));
        }
        return 0;
}