1 files changed, 3892 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
new file mode 100644
index 000000000000..71ef0a2e2daa
--- /dev/null
+++ b/fs/btrfs/ctree.c
@@ -0,0 +1,3892 @@
+/*
+ * Copyright (C) 2007,2008 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"
+#include "locking.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, int empty);
+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;
+}
+
+/* this also releases the path */
+void btrfs_free_path(struct btrfs_path *p)
+{
+        btrfs_release_path(NULL, p);
+        kmem_cache_free(btrfs_path_cachep, p);
+}
+
+/*
+ * path release drops references on the extent buffers in the path
+ * and it drops any locks held by this path
+ *
+ * It is safe to call this on paths that no locks or extent buffers held.
+ */
+void noinline btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
+{
+        int i;
+
+        for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
+                p->slots[i] = 0;
+                if (!p->nodes[i])
+                        continue;
+                if (p->locks[i]) {
+                        btrfs_tree_unlock(p->nodes[i]);
+                        p->locks[i] = 0;
+                }
+                free_extent_buffer(p->nodes[i]);
+                p->nodes[i] = NULL;
+        }
+}
+
+/*
+ * safely gets a reference on the root node of a tree.  A lock
+ * is not taken, so a concurrent writer may put a different node
+ * at the root of the tree.  See btrfs_lock_root_node for the
+ * looping required.
+ *
+ * The extent buffer returned by this has a reference taken, so
+ * it won't disappear.  It may stop being the root of the tree
+ * at any time because there are no locks held.
+ */
+struct extent_buffer *btrfs_root_node(struct btrfs_root *root)
+{
+        struct extent_buffer *eb;
+        spin_lock(&root->node_lock);
+        eb = root->node;
+        extent_buffer_get(eb);
+        spin_unlock(&root->node_lock);
+        return eb;
+}
+
+/* loop around taking references on and locking the root node of the
+ * tree until you end up with a lock on the root.  A locked buffer
+ * is returned, with a reference held.
+ */
+struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root)
+{
+        struct extent_buffer *eb;
+
+        while(1) {
+                eb = btrfs_root_node(root);
+                btrfs_tree_lock(eb);
+
+                spin_lock(&root->node_lock);
+                if (eb == root->node) {
+                        spin_unlock(&root->node_lock);
+                        break;
+                }
+                spin_unlock(&root->node_lock);
+
+                btrfs_tree_unlock(eb);
+                free_extent_buffer(eb);
+        }
+        return eb;
+}
+
+/* cowonly root (everything not a reference counted cow subvolume), just get
+ * put onto a simple dirty list.  transaction.c walks this to make sure they
+ * get properly updated on disk.
+ */
+static void add_root_to_dirty_list(struct btrfs_root *root)
+{
+        if (root->track_dirty && list_empty(&root->dirty_list)) {
+                list_add(&root->dirty_list,
+                         &root->fs_info->dirty_cowonly_roots);
+        }
+}
+
+/*
+ * used by snapshot creation to make a copy of a root for a tree with
+ * a given objectid.  The buffer with the new root node is returned in
+ * cow_ret, and this func returns zero on success or a negative error code.
+ */
+int btrfs_copy_root(struct btrfs_trans_handle *trans,
+                      struct btrfs_root *root,
+                      struct extent_buffer *buf,
+                      struct extent_buffer **cow_ret, u64 new_root_objectid)
+{
+        struct extent_buffer *cow;
+        u32 nritems;
+        int ret = 0;
+        int level;
+        struct btrfs_root *new_root;
+
+        new_root = kmalloc(sizeof(*new_root), GFP_NOFS);
+        if (!new_root)
+                return -ENOMEM;
+
+        memcpy(new_root, root, sizeof(*new_root));
+        new_root->root_key.objectid = new_root_objectid;
+
+        WARN_ON(root->ref_cows && trans->transid !=
+                root->fs_info->running_transaction->transid);
+        WARN_ON(root->ref_cows && trans->transid != root->last_trans);
+
+        level = btrfs_header_level(buf);
+        nritems = btrfs_header_nritems(buf);
+
+        cow = btrfs_alloc_free_block(trans, new_root, buf->len, 0,
+                                     new_root_objectid, trans->transid,
+                                     level, buf->start, 0);
+        if (IS_ERR(cow)) {
+                kfree(new_root);
+                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, new_root_objectid);
+        btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN);
+
+        write_extent_buffer(cow, root->fs_info->fsid,
+                            (unsigned long)btrfs_header_fsid(cow),
+                            BTRFS_FSID_SIZE);
+
+        WARN_ON(btrfs_header_generation(buf) > trans->transid);
+        ret = btrfs_inc_ref(trans, new_root, buf, cow, NULL);
+        kfree(new_root);
+
+        if (ret)
+                return ret;
+
+        btrfs_mark_buffer_dirty(cow);
+        *cow_ret = cow;
+        return 0;
+}
+
+/*
+ * does the dirty work in cow of a single block.  The parent block
+ * (if supplied) is updated to point to the new cow copy.  The new
+ * buffer is marked dirty and returned locked.  If you modify the block
+ * it needs to be marked dirty again.
+ *
+ * search_start -- an allocation hint for the new block
+ *
+ * empty_size -- a hint that you plan on doing more cow.  This is the size in bytes
+ * the allocator should try to find free next to the block it returns.  This is
+ * just a hint and may be ignored by the allocator.
+ *
+ * prealloc_dest -- if you have already reserved a destination for the cow,
+ * this uses that block instead of allocating a new one.  btrfs_alloc_reserved_extent
+ * is used to finish the allocation.
+ */
+int noinline __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,
+                             u64 prealloc_dest)
+{
+        u64 parent_start;
+        struct extent_buffer *cow;
+        u32 nritems;
+        int ret = 0;
+        int level;
+        int unlock_orig = 0;
+
+        if (*cow_ret == buf)
+                unlock_orig = 1;
+
+        WARN_ON(!btrfs_tree_locked(buf));
+
+        if (parent)
+                parent_start = parent->start;
+        else
+                parent_start = 0;
+
+        WARN_ON(root->ref_cows && trans->transid !=
+                root->fs_info->running_transaction->transid);
+        WARN_ON(root->ref_cows && trans->transid != root->last_trans);
+
+        level = btrfs_header_level(buf);
+        nritems = btrfs_header_nritems(buf);
+
+        if (prealloc_dest) {
+                struct btrfs_key ins;
+
+                ins.objectid = prealloc_dest;
+                ins.offset = buf->len;
+                ins.type = BTRFS_EXTENT_ITEM_KEY;
+
+                ret = btrfs_alloc_reserved_extent(trans, root, parent_start,
+                                                  root->root_key.objectid,
+                                                  trans->transid, level, &ins);
+                BUG_ON(ret);
+                cow = btrfs_init_new_buffer(trans, root, prealloc_dest,
+                                            buf->len);
+        } else {
+                cow = btrfs_alloc_free_block(trans, root, buf->len,
+                                             parent_start,
+                                             root->root_key.objectid,
+                                             trans->transid, level,
+                                             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);
+        btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN);
+
+        write_extent_buffer(cow, root->fs_info->fsid,
+                            (unsigned long)btrfs_header_fsid(cow),
+                            BTRFS_FSID_SIZE);
+
+        WARN_ON(btrfs_header_generation(buf) > trans->transid);
+        if (btrfs_header_generation(buf) != trans->transid) {
+                u32 nr_extents;
+                ret = btrfs_inc_ref(trans, root, buf, cow, &nr_extents);
+                if (ret)
+                        return ret;
+
+                ret = btrfs_cache_ref(trans, root, buf, nr_extents);
+                WARN_ON(ret);
+        } else if (btrfs_header_owner(buf) == BTRFS_TREE_RELOC_OBJECTID) {
+                /*
+                 * There are only two places that can drop reference to
+                 * tree blocks owned by living reloc trees, one is here,
+                 * the other place is btrfs_drop_subtree. In both places,
+                 * we check reference count while tree block is locked.
+                 * Furthermore, if reference count is one, it won't get
+                 * increased by someone else.
+                 */
+                u32 refs;
+                ret = btrfs_lookup_extent_ref(trans, root, buf->start,
+                                              buf->len, &refs);
+                BUG_ON(ret);
+                if (refs == 1) {
+                        ret = btrfs_update_ref(trans, root, buf, cow,
+                                               0, nritems);
+                        clean_tree_block(trans, root, buf);
+                } else {
+                        ret = btrfs_inc_ref(trans, root, buf, cow, NULL);
+                }
+                BUG_ON(ret);
+        } else {
+                ret = btrfs_update_ref(trans, root, buf, cow, 0, nritems);
+                if (ret)
+                        return ret;
+                clean_tree_block(trans, root, buf);
+        }
+
+        if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
+                ret = btrfs_reloc_tree_cache_ref(trans, root, cow, buf->start);
+                WARN_ON(ret);
+        }
+
+        if (buf == root->node) {
+                WARN_ON(parent && parent != buf);
+
+                spin_lock(&root->node_lock);
+                root->node = cow;
+                extent_buffer_get(cow);
+                spin_unlock(&root->node_lock);
+
+                if (buf != root->commit_root) {
+                        btrfs_free_extent(trans, root, buf->start,
+                                          buf->len, buf->start,
+                                          root->root_key.objectid,
+                                          btrfs_header_generation(buf),
+                                          level, 1);
+                }
+                free_extent_buffer(buf);
+                add_root_to_dirty_list(root);
+        } else {
+                btrfs_set_node_blockptr(parent, parent_slot,
+                                        cow->start);
+                WARN_ON(trans->transid == 0);
+                btrfs_set_node_ptr_generation(parent, parent_slot,
+                                              trans->transid);
+                btrfs_mark_buffer_dirty(parent);
+                WARN_ON(btrfs_header_generation(parent) != trans->transid);
+                btrfs_free_extent(trans, root, buf->start, buf->len,
+                                  parent_start, btrfs_header_owner(parent),
+                                  btrfs_header_generation(parent), level, 1);
+        }
+        if (unlock_orig)
+                btrfs_tree_unlock(buf);
+        free_extent_buffer(buf);
+        btrfs_mark_buffer_dirty(cow);
+        *cow_ret = cow;
+        return 0;
+}
+
+/*
+ * cows a single block, see __btrfs_cow_block for the real work.
+ * This version of it has extra checks so that a block isn't cow'd more than
+ * once per transaction, as long as it hasn't been written yet
+ */
+int noinline 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 prealloc_dest)
+{
+        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);
+        }
+
+        spin_lock(&root->fs_info->hash_lock);
+        if (btrfs_header_generation(buf) == trans->transid &&
+            btrfs_header_owner(buf) == root->root_key.objectid &&
+            !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
+                *cow_ret = buf;
+                spin_unlock(&root->fs_info->hash_lock);
+                WARN_ON(prealloc_dest);
+                return 0;
+        }
+        spin_unlock(&root->fs_info->hash_lock);
+        search_start = buf->start & ~((u64)(1024 * 1024 * 1024) - 1);
+        ret = __btrfs_cow_block(trans, root, buf, parent,
+                                 parent_slot, cow_ret, search_start, 0,
+                                 prealloc_dest);
+        return ret;
+}
+
+/*
+ * helper function for defrag to decide if two blocks pointed to by a
+ * node are actually close by
+ */
+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;
+}
+
+/*
+ * same as comp_keys only with two btrfs_key's
+ */
+static int comp_cpu_keys(struct btrfs_key *k1, struct btrfs_key *k2)
+{
+        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;
+}
+
+/*
+ * this is used by the defrag code to go through all the
+ * leaves pointed to by a node and reallocate them so that
+ * disk order is close to key order
+ */
+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;
+        u64 blocknr;
+        u64 gen;
+        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);
+                gen = btrfs_node_ptr_generation(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, gen);
+                else
+                        uptodate = 0;
+                if (!cur || !uptodate) {
+                        if (cache_only) {
+                                free_extent_buffer(cur);
+                                continue;
+                        }
+                        if (!cur) {
+                                cur = read_tree_block(root, blocknr,
+                                                         blocksize, gen);
+                        } else if (!uptodate) {
+                                btrfs_read_buffer(cur, gen);
+                        }
+                }
+                if (search_start == 0)
+                        search_start = last_block;
+
+                btrfs_tree_lock(cur);
+                err = __btrfs_cow_block(trans, root, cur, parent, i,
+                                        &cur, search_start,
+                                        min(16 * blocksize,
+                                            (end_slot - i) * blocksize), 0);
+                if (err) {
+                        btrfs_tree_unlock(cur);
+                        free_extent_buffer(cur);
+                        break;
+                }
+                search_start = cur->start;
+                last_block = cur->start;
+                *last_ret = search_start;
+                btrfs_tree_unlock(cur);
+                free_extent_buffer(cur);
+        }
+        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);
+}
+
+/*
+ * extra debugging checks to make sure all the items in a key are
+ * well formed and in the proper order
+ */
+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;
+}
+
+/*
+ * extra checking to make sure all the items in a leaf are
+ * well formed and in the proper order
+ */
+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 noinline check_block(struct btrfs_root *root,
+                                struct btrfs_path *path, int level)
+{
+        u64 found_start;
+        return 0;
+        if (btrfs_header_level(path->nodes[level]) != level)
+            printk("warning: bad level %Lu wanted %d found %d\n",
+                   path->nodes[level]->start, level,
+                   btrfs_header_level(path->nodes[level]));
+        found_start = btrfs_header_bytenr(path->nodes[level]);
+        if (found_start != path->nodes[level]->start) {
+            printk("warning: bad bytentr %Lu found %Lu\n",
+                   path->nodes[level]->start, found_start);
+        }
+#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 noinline 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;
+}
+
+/* given a node and slot number, this reads the blocks it points to.  The
+ * extent buffer is returned with a reference taken (but unlocked).
+ * NULL is returned on error.
+ */
+static noinline struct extent_buffer *read_node_slot(struct btrfs_root *root,
+                                   struct extent_buffer *parent, int slot)
+{
+        int level = btrfs_header_level(parent);
+        if (slot < 0)
+                return NULL;
+        if (slot >= btrfs_header_nritems(parent))
+                return NULL;
+
+        BUG_ON(level == 0);
+
+        return read_tree_block(root, btrfs_node_blockptr(parent, slot),
+                       btrfs_level_size(root, level - 1),
+                       btrfs_node_ptr_generation(parent, slot));
+}
+
+/*
+ * node level balancing, used to make sure nodes are in proper order for
+ * item deletion.  We balance from the top down, so we have to make sure
+ * that a deletion won't leave an node completely empty later on.
+ */
+static noinline 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];
+        WARN_ON(!path->locks[level]);
+        WARN_ON(btrfs_header_generation(mid) != trans->transid);
+
+        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);
+                btrfs_tree_lock(child);
+                BUG_ON(!child);
+                ret = btrfs_cow_block(trans, root, child, mid, 0, &child, 0);
+                BUG_ON(ret);
+
+                spin_lock(&root->node_lock);
+                root->node = child;
+                spin_unlock(&root->node_lock);
+
+                ret = btrfs_update_extent_ref(trans, root, child->start,
+                                              mid->start, child->start,
+                                              root->root_key.objectid,
+                                              trans->transid, level - 1);
+                BUG_ON(ret);
+
+                add_root_to_dirty_list(root);
+                btrfs_tree_unlock(child);
+                path->locks[level] = 0;
+                path->nodes[level] = NULL;
+                clean_tree_block(trans, root, mid);
+                btrfs_tree_unlock(mid);
+                /* once for the path */
+                free_extent_buffer(mid);
+                ret = btrfs_free_extent(trans, root, mid->start, mid->len,
+                                        mid->start, root->root_key.objectid,
+                                        btrfs_header_generation(mid),
+                                        level, 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) {
+                btrfs_tree_lock(left);
+                wret = btrfs_cow_block(trans, root, left,
+                                       parent, pslot - 1, &left, 0);
+                if (wret) {
+                        ret = wret;
+                        goto enospc;
+                }
+        }
+        right = read_node_slot(root, parent, pslot + 1);
+        if (right) {
+                btrfs_tree_lock(right);
+                wret = btrfs_cow_block(trans, root, right,
+                                       parent, pslot + 1, &right, 0);
+                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, 1);
+                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, 1);
+                if (wret < 0 && wret != -ENOSPC)
+                        ret = wret;
+                if (btrfs_header_nritems(right) == 0) {
+                        u64 bytenr = right->start;
+                        u64 generation = btrfs_header_generation(parent);
+                        u32 blocksize = right->len;
+
+                        clean_tree_block(trans, root, right);
+                        btrfs_tree_unlock(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, parent->start,
+                                                 btrfs_header_owner(parent),
+                                                 generation, level, 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;
+                }
+                if (wret == 1) {
+                        wret = push_node_left(trans, root, left, mid, 1);
+                        if (wret < 0)
+                                ret = wret;
+                }
+                BUG_ON(wret == 1);
+        }
+        if (btrfs_header_nritems(mid) == 0) {
+                /* we've managed to empty the middle node, drop it */
+                u64 root_gen = btrfs_header_generation(parent);
+                u64 bytenr = mid->start;
+                u32 blocksize = mid->len;
+
+                clean_tree_block(trans, root, mid);
+                btrfs_tree_unlock(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,
+                                         parent->start,
+                                         btrfs_header_owner(parent),
+                                         root_gen, level, 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);
+                        /* left was locked after cow */
+                        path->nodes[level] = left;
+                        path->slots[level + 1] -= 1;
+                        path->slots[level] = orig_slot;
+                        if (mid) {
+                                btrfs_tree_unlock(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) {
+                btrfs_tree_unlock(right);
+                free_extent_buffer(right);
+        }
+        if (left) {
+                if (path->nodes[level] != left)
+                        btrfs_tree_unlock(left);
+                free_extent_buffer(left);
+        }
+        return ret;
+}
+
+/* Node balancing for insertion.  Here we only split or push nodes around
+ * when they are completely full.  This is also done top down, so we
+ * have to be pessimistic.
+ */
+static int noinline 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];
+        WARN_ON(btrfs_header_generation(mid) != trans->transid);
+        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;
+
+                btrfs_tree_lock(left);
+                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, 0);
+                        if (ret)
+                                wret = 1;
+                        else {
+                                wret = push_node_left(trans, root,
+                                                      left, mid, 0);
+                        }
+                }
+                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;
+                                btrfs_tree_unlock(mid);
+                                free_extent_buffer(mid);
+                        } else {
+                                orig_slot -=
+                                        btrfs_header_nritems(left);
+                                path->slots[level] = orig_slot;
+                                btrfs_tree_unlock(left);
+                                free_extent_buffer(left);
+                        }
+                        return 0;
+                }
+                btrfs_tree_unlock(left);
+                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;
+                btrfs_tree_lock(right);
+                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, 0);
+                        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);
+                                btrfs_tree_unlock(mid);
+                                free_extent_buffer(mid);
+                        } else {
+                                btrfs_tree_unlock(right);
+                                free_extent_buffer(right);
+                        }
+                        return 0;
+                }
+                btrfs_tree_unlock(right);
+                free_extent_buffer(right);
+        }
+        return 1;
+}
+
+/*
+ * readahead one full node of leaves, finding things that are close
+ * to the block in 'slot', and triggering ra on them.
+ */
+static noinline void reada_for_search(struct btrfs_root *root,
+                                      struct btrfs_path *path,
+                                      int level, int slot, u64 objectid)
+{
+        struct extent_buffer *node;
+        struct btrfs_disk_key disk_key;
+        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;
+                }
+                if (path->reada < 0 && objectid) {
+                        btrfs_node_key(node, &disk_key, nr);
+                        if (btrfs_disk_key_objectid(&disk_key) != objectid)
+                                break;
+                }
+                search = btrfs_node_blockptr(node, nr);
+                if ((search >= lowest_read && search <= highest_read) ||
+                    (search < lowest_read && lowest_read - search <= 16384) ||
+                    (search > highest_read && search - highest_read <= 16384)) {
+                        readahead_tree_block(root, search, blocksize,
+                                     btrfs_node_ptr_generation(node, nr));
+                        nread += blocksize;
+                }
+                nscan++;
+                if (path->reada < 2 && (nread > (64 * 1024) || nscan > 32))
+                        break;
+                if(nread > (256 * 1024) || nscan > 128)
+                        break;
+
+                if (search < lowest_read)
+                        lowest_read = search;
+                if (search > highest_read)
+                        highest_read = search;
+        }
+}
+
+/*
+ * when we walk down the tree, it is usually safe to unlock the higher layers in
+ * the tree.  The exceptions are when our path goes through slot 0, because operations
+ * on the tree might require changing key pointers higher up in the tree.
+ *
+ * callers might also have set path->keep_locks, which tells this code to
+ * keep the lock if the path points to the last slot in the block.  This is
+ * part of walking through the tree, and selecting the next slot in the higher
+ * block.
+ *
+ * lowest_unlock sets the lowest level in the tree we're allowed to unlock.
+ * so if lowest_unlock is 1, level 0 won't be unlocked
+ */
+static noinline void unlock_up(struct btrfs_path *path, int level,
+                               int lowest_unlock)
+{
+        int i;
+        int skip_level = level;
+        int no_skips = 0;
+        struct extent_buffer *t;
+
+        for (i = level; i < BTRFS_MAX_LEVEL; i++) {
+                if (!path->nodes[i])
+                        break;
+                if (!path->locks[i])
+                        break;
+                if (!no_skips && path->slots[i] == 0) {
+                        skip_level = i + 1;
+                        continue;
+                }
+                if (!no_skips && path->keep_locks) {
+                        u32 nritems;
+                        t = path->nodes[i];
+                        nritems = btrfs_header_nritems(t);
+                        if (nritems < 1 || path->slots[i] >= nritems - 1) {
+                                skip_level = i + 1;
+                                continue;
+                        }
+                }
+                if (skip_level < i && i >= lowest_unlock)
+                        no_skips = 1;
+
+                t = path->nodes[i];
+                if (i >= lowest_unlock && i > skip_level && path->locks[i]) {
+                        btrfs_tree_unlock(t);
+                        path->locks[i] = 0;
+                }
+        }
+}
+
+/*
+ * 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;
+        struct extent_buffer *tmp;
+        int slot;
+        int ret;
+        int level;
+        int should_reada = p->reada;
+        int lowest_unlock = 1;
+        int blocksize;
+        u8 lowest_level = 0;
+        u64 blocknr;
+        u64 gen;
+        struct btrfs_key prealloc_block;
+
+        lowest_level = p->lowest_level;
+        WARN_ON(lowest_level && ins_len > 0);
+        WARN_ON(p->nodes[0] != NULL);
+
+        if (ins_len < 0)
+                lowest_unlock = 2;
+
+        prealloc_block.objectid = 0;
+
+again:
+        if (p->skip_locking)
+                b = btrfs_root_node(root);
+        else
+                b = btrfs_lock_root_node(root);
+
+        while (b) {
+                level = btrfs_header_level(b);
+
+                /*
+                 * setup the path here so we can release it under lock
+                 * contention with the cow code
+                 */
+                p->nodes[level] = b;
+                if (!p->skip_locking)
+                        p->locks[level] = 1;
+
+                if (cow) {
+                        int wret;
+
+                        /* is a cow on this block not required */
+                        spin_lock(&root->fs_info->hash_lock);
+                        if (btrfs_header_generation(b) == trans->transid &&
+                            btrfs_header_owner(b) == root->root_key.objectid &&
+                            !btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
+                                spin_unlock(&root->fs_info->hash_lock);
+                                goto cow_done;
+                        }
+                        spin_unlock(&root->fs_info->hash_lock);
+
+                        /* ok, we have to cow, is our old prealloc the right
+                         * size?
+                         */
+                        if (prealloc_block.objectid &&
+                            prealloc_block.offset != b->len) {
+                                btrfs_free_reserved_extent(root,
+                                           prealloc_block.objectid,
+                                           prealloc_block.offset);
+                                prealloc_block.objectid = 0;
+                        }
+
+                        /*
+                         * for higher level blocks, try not to allocate blocks
+                         * with the block and the parent locks held.
+                         */
+                        if (level > 1 && !prealloc_block.objectid &&
+                            btrfs_path_lock_waiting(p, level)) {
+                                u32 size = b->len;
+                                u64 hint = b->start;
+
+                                btrfs_release_path(root, p);
+                                ret = btrfs_reserve_extent(trans, root,
+                                                           size, size, 0,
+                                                           hint, (u64)-1,
+                                                           &prealloc_block, 0);
+                                BUG_ON(ret);
+                                goto again;
+                        }
+
+                        wret = btrfs_cow_block(trans, root, b,
+                                               p->nodes[level + 1],
+                                               p->slots[level + 1],
+                                               &b, prealloc_block.objectid);
+                        prealloc_block.objectid = 0;
+                        if (wret) {
+                                free_extent_buffer(b);
+                                ret = wret;
+                                goto done;
+                        }
+                }
+cow_done:
+                BUG_ON(!cow && ins_len);
+                if (level != btrfs_header_level(b))
+                        WARN_ON(1);
+                level = btrfs_header_level(b);
+
+                p->nodes[level] = b;
+                if (!p->skip_locking)
+                        p->locks[level] = 1;
+
+                ret = check_block(root, p, level);
+                if (ret) {
+                        ret = -1;
+                        goto done;
+                }
+
+                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) - 3) {
+                                int sret = split_node(trans, root, p, level);
+                                BUG_ON(sret > 0);
+                                if (sret) {
+                                        ret = sret;
+                                        goto done;
+                                }
+                                b = p->nodes[level];
+                                slot = p->slots[level];
+                        } else if (ins_len < 0) {
+                                int sret = balance_level(trans, root, p,
+                                                         level);
+                                if (sret) {
+                                        ret = sret;
+                                        goto done;
+                                }
+                                b = p->nodes[level];
+                                if (!b) {
+                                        btrfs_release_path(NULL, p);
+                                        goto again;
+                                }
+                                slot = p->slots[level];
+                                BUG_ON(btrfs_header_nritems(b) == 1);
+                        }
+                        unlock_up(p, level, lowest_unlock);
+
+                        /* this is only true while dropping a snapshot */
+                        if (level == lowest_level) {
+                                ret = 0;
+                                goto done;
+                        }
+
+                        blocknr = btrfs_node_blockptr(b, slot);
+                        gen = btrfs_node_ptr_generation(b, slot);
+                        blocksize = btrfs_level_size(root, level - 1);
+
+                        tmp = btrfs_find_tree_block(root, blocknr, blocksize);
+                        if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
+                                b = tmp;
+                        } else {
+                                /*
+                                 * reduce lock contention at high levels
+                                 * of the btree by dropping locks before
+                                 * we read.
+                                 */
+                                if (level > 1) {
+                                        btrfs_release_path(NULL, p);
+                                        if (tmp)
+                                                free_extent_buffer(tmp);
+                                        if (should_reada)
+                                                reada_for_search(root, p,
+                                                                 level, slot,
+                                                                 key->objectid);
+
+                                        tmp = read_tree_block(root, blocknr,
+                                                         blocksize, gen);
+                                        if (tmp)
+                                                free_extent_buffer(tmp);
+                                        goto again;
+                                } else {
+                                        if (tmp)
+                                                free_extent_buffer(tmp);
+                                        if (should_reada)
+                                                reada_for_search(root, p,
+                                                                 level, slot,
+                                                                 key->objectid);
+                                        b = read_node_slot(root, b, slot);
+                                }
+                        }
+                        if (!p->skip_locking)
+                                btrfs_tree_lock(b);
+                } 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) {
+                                        ret = sret;
+                                        goto done;
+                                }
+                        }
+                        unlock_up(p, level, lowest_unlock);
+                        goto done;
+                }
+        }
+        ret = 1;
+done:
+        if (prealloc_block.objectid) {
+                btrfs_free_reserved_extent(root,
+                           prealloc_block.objectid,
+                           prealloc_block.offset);
+        }
+
+        return ret;
+}
+
+int btrfs_merge_path(struct btrfs_trans_handle *trans,
+                     struct btrfs_root *root,
+                     struct btrfs_key *node_keys,
+                     u64 *nodes, int lowest_level)
+{
+        struct extent_buffer *eb;
+        struct extent_buffer *parent;
+        struct btrfs_key key;
+        u64 bytenr;
+        u64 generation;
+        u32 blocksize;
+        int level;
+        int slot;
+        int key_match;
+        int ret;
+
+        eb = btrfs_lock_root_node(root);
+        ret = btrfs_cow_block(trans, root, eb, NULL, 0, &eb, 0);
+        BUG_ON(ret);
+
+        parent = eb;
+        while (1) {
+                level = btrfs_header_level(parent);
+                if (level == 0 || level <= lowest_level)
+                        break;
+
+                ret = bin_search(parent, &node_keys[lowest_level], level,
+                                 &slot);
+                if (ret && slot > 0)
+                        slot--;
+
+                bytenr = btrfs_node_blockptr(parent, slot);
+                if (nodes[level - 1] == bytenr)
+                        break;
+
+                blocksize = btrfs_level_size(root, level - 1);
+                generation = btrfs_node_ptr_generation(parent, slot);
+                btrfs_node_key_to_cpu(eb, &key, slot);
+                key_match = !memcmp(&key, &node_keys[level - 1], sizeof(key));
+
+                if (generation == trans->transid) {
+                        eb = read_tree_block(root, bytenr, blocksize,
+                                             generation);
+                        btrfs_tree_lock(eb);
+                }
+
+                /*
+                 * if node keys match and node pointer hasn't been modified
+                 * in the running transaction, we can merge the path. for
+                 * blocks owened by reloc trees, the node pointer check is
+                 * skipped, this is because these blocks are fully controlled
+                 * by the space balance code, no one else can modify them.
+                 */
+                if (!nodes[level - 1] || !key_match ||
+                    (generation == trans->transid &&
+                     btrfs_header_owner(eb) != BTRFS_TREE_RELOC_OBJECTID)) {
+                        if (level == 1 || level == lowest_level + 1) {
+                                if (generation == trans->transid) {
+                                        btrfs_tree_unlock(eb);
+                                        free_extent_buffer(eb);
+                                }
+                                break;
+                        }
+
+                        if (generation != trans->transid) {
+                                eb = read_tree_block(root, bytenr, blocksize,
+                                                generation);
+                                btrfs_tree_lock(eb);
+                        }
+
+                        ret = btrfs_cow_block(trans, root, eb, parent, slot,
+                                              &eb, 0);
+                        BUG_ON(ret);
+
+                        if (root->root_key.objectid ==
+                            BTRFS_TREE_RELOC_OBJECTID) {
+                                if (!nodes[level - 1]) {
+                                        nodes[level - 1] = eb->start;
+                                        memcpy(&node_keys[level - 1], &key,
+                                               sizeof(node_keys[0]));
+                                } else {
+                                        WARN_ON(1);
+                                }
+                        }
+
+                        btrfs_tree_unlock(parent);
+                        free_extent_buffer(parent);
+                        parent = eb;
+                        continue;
+                }
+
+                btrfs_set_node_blockptr(parent, slot, nodes[level - 1]);
+                btrfs_set_node_ptr_generation(parent, slot, trans->transid);
+                btrfs_mark_buffer_dirty(parent);
+
+                ret = btrfs_inc_extent_ref(trans, root,
+                                        nodes[level - 1],
+                                        blocksize, parent->start,
+                                        btrfs_header_owner(parent),
+                                        btrfs_header_generation(parent),
+                                        level - 1);
+                BUG_ON(ret);
+
+                /*
+                 * If the block was created in the running transaction,
+                 * it's possible this is the last reference to it, so we
+                 * should drop the subtree.
+                 */
+                if (generation == trans->transid) {
+                        ret = btrfs_drop_subtree(trans, root, eb, parent);
+                        BUG_ON(ret);
+                        btrfs_tree_unlock(eb);
+                        free_extent_buffer(eb);
+                } else {
+                        ret = btrfs_free_extent(trans, root, bytenr,
+                                        blocksize, parent->start,
+                                        btrfs_header_owner(parent),
+                                        btrfs_header_generation(parent),
+                                        level - 1, 1);
+                        BUG_ON(ret);
+                }
+                break;
+        }
+        btrfs_tree_unlock(parent);
+        free_extent_buffer(parent);
+        return 0;
+}
+
+/*
+ * 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;
+}
+
+/*
+ * update item key.
+ *
+ * This function isn't completely safe. It's the caller's responsibility
+ * that the new key won't break the order
+ */
+int btrfs_set_item_key_safe(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root, struct btrfs_path *path,
+                            struct btrfs_key *new_key)
+{
+        struct btrfs_disk_key disk_key;
+        struct extent_buffer *eb;
+        int slot;
+
+        eb = path->nodes[0];
+        slot = path->slots[0];
+        if (slot > 0) {
+                btrfs_item_key(eb, &disk_key, slot - 1);
+                if (comp_keys(&disk_key, new_key) >= 0)
+                        return -1;
+        }
+        if (slot < btrfs_header_nritems(eb) - 1) {
+                btrfs_item_key(eb, &disk_key, slot + 1);
+                if (comp_keys(&disk_key, new_key) <= 0)
+                        return -1;
+        }
+
+        btrfs_cpu_key_to_disk(&disk_key, new_key);
+        btrfs_set_item_key(eb, &disk_key, slot);
+        btrfs_mark_buffer_dirty(eb);
+        if (slot == 0)
+                fixup_low_keys(trans, root, path, &disk_key, 1);
+        return 0;
+}
+
+/*
+ * 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 empty)
+{
+        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;
+        WARN_ON(btrfs_header_generation(src) != trans->transid);
+        WARN_ON(btrfs_header_generation(dst) != trans->transid);
+
+        if (!empty && src_nritems <= 8)
+                return 1;
+
+        if (push_items <= 0) {
+                return 1;
+        }
+
+        if (empty) {
+                push_items = min(src_nritems, push_items);
+                if (push_items < src_nritems) {
+                        /* leave at least 8 pointers in the node if
+                         * we aren't going to empty it
+                         */
+                        if (src_nritems - push_items < 8) {
+                                if (push_items <= 8)
+                                        return 1;
+                                push_items -= 8;
+                        }
+                }
+        } else
+                push_items = min(src_nritems - 8, push_items);
+
+        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);
+
+        ret = btrfs_update_ref(trans, root, src, dst, dst_nritems, push_items);
+        BUG_ON(ret);
+
+        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;
+
+        WARN_ON(btrfs_header_generation(src) != trans->transid);
+        WARN_ON(btrfs_header_generation(dst) != trans->transid);
+
+        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 < 4) {
+                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);
+
+        ret = btrfs_update_ref(trans, root, src, dst, 0, push_items);
+        BUG_ON(ret);
+
+        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 noinline insert_new_root(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           struct btrfs_path *path, int level)
+{
+        u64 lower_gen;
+        struct extent_buffer *lower;
+        struct extent_buffer *c;
+        struct extent_buffer *old;
+        struct btrfs_disk_key lower_key;
+        int ret;
+
+        BUG_ON(path->nodes[level]);
+        BUG_ON(path->nodes[level-1] != root->node);
+
+        lower = path->nodes[level-1];
+        if (level == 1)
+                btrfs_item_key(lower, &lower_key, 0);
+        else
+                btrfs_node_key(lower, &lower_key, 0);
+
+        c = btrfs_alloc_free_block(trans, root, root->nodesize, 0,
+                                   root->root_key.objectid, trans->transid,
+                                   level, 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);
+
+        write_extent_buffer(c, root->fs_info->fsid,
+                            (unsigned long)btrfs_header_fsid(c),
+                            BTRFS_FSID_SIZE);
+
+        write_extent_buffer(c, root->fs_info->chunk_tree_uuid,
+                            (unsigned long)btrfs_header_chunk_tree_uuid(c),
+                            BTRFS_UUID_SIZE);
+
+        btrfs_set_node_key(c, &lower_key, 0);
+        btrfs_set_node_blockptr(c, 0, lower->start);
+        lower_gen = btrfs_header_generation(lower);
+        WARN_ON(lower_gen != trans->transid);
+
+        btrfs_set_node_ptr_generation(c, 0, lower_gen);
+
+        btrfs_mark_buffer_dirty(c);
+
+        spin_lock(&root->node_lock);
+        old = root->node;
+        root->node = c;
+        spin_unlock(&root->node_lock);
+
+        ret = btrfs_update_extent_ref(trans, root, lower->start,
+                                      lower->start, c->start,
+                                      root->root_key.objectid,
+                                      trans->transid, level - 1);
+        BUG_ON(ret);
+
+        /* the super has an extra ref to root->node */
+        free_extent_buffer(old);
+
+        add_root_to_dirty_list(root);
+        extent_buffer_get(c);
+        path->nodes[level] = c;
+        path->locks[level] = 1;
+        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);
+        WARN_ON(trans->transid == 0);
+        btrfs_set_node_ptr_generation(lower, slot, trans->transid);
+        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 noinline 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];
+        WARN_ON(btrfs_header_generation(c) != trans->transid);
+        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) - 3)
+                        return 0;
+                if (ret < 0)
+                        return ret;
+        }
+
+        c_nritems = btrfs_header_nritems(c);
+
+        split = btrfs_alloc_free_block(trans, root, root->nodesize,
+                                        path->nodes[level + 1]->start,
+                                        root->root_key.objectid,
+                                        trans->transid, level, 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);
+        btrfs_set_header_flags(split, 0);
+        write_extent_buffer(split, root->fs_info->fsid,
+                            (unsigned long)btrfs_header_fsid(split),
+                            BTRFS_FSID_SIZE);
+        write_extent_buffer(split, root->fs_info->chunk_tree_uuid,
+                            (unsigned long)btrfs_header_chunk_tree_uuid(split),
+                            BTRFS_UUID_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;
+
+        ret = btrfs_update_ref(trans, root, c, split, 0, c_nritems - mid);
+        BUG_ON(ret);
+
+        if (path->slots[level] >= mid) {
+                path->slots[level] -= mid;
+                btrfs_tree_unlock(c);
+                free_extent_buffer(c);
+                path->nodes[level] = split;
+                path->slots[level + 1] += 1;
+        } else {
+                btrfs_tree_unlock(split);
+                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 noinline 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,
+                           int empty)
+{
+        struct extent_buffer *left = path->nodes[0];
+        struct extent_buffer *right;
+        struct extent_buffer *upper;
+        struct btrfs_disk_key disk_key;
+        int slot;
+        u32 i;
+        int free_space;
+        int push_space = 0;
+        int push_items = 0;
+        struct btrfs_item *item;
+        u32 left_nritems;
+        u32 nr;
+        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;
+
+        WARN_ON(!btrfs_tree_locked(path->nodes[1]));
+
+        right = read_node_slot(root, upper, slot + 1);
+        btrfs_tree_lock(right);
+        free_space = btrfs_leaf_free_space(root, right);
+        if (free_space < data_size + sizeof(struct btrfs_item))
+                goto out_unlock;
+
+        /* cow and double check */
+        ret = btrfs_cow_block(trans, root, right, upper,
+                              slot + 1, &right, 0);
+        if (ret)
+                goto out_unlock;
+
+        free_space = btrfs_leaf_free_space(root, right);
+        if (free_space < data_size + sizeof(struct btrfs_item))
+                goto out_unlock;
+
+        left_nritems = btrfs_header_nritems(left);
+        if (left_nritems == 0)
+                goto out_unlock;
+
+        if (empty)
+                nr = 0;
+        else
+                nr = 1;
+
+        if (path->slots[0] >= left_nritems)
+                push_space += data_size + sizeof(*item);
+
+        i = left_nritems - 1;
+        while (i >= nr) {
+                item = btrfs_item_nr(left, i);
+
+                if (!empty && push_items > 0) {
+                        if (path->slots[0] > i)
+                                break;
+                        if (path->slots[0] == i) {
+                                int space = btrfs_leaf_free_space(root, left);
+                                if (space + push_space * 2 > free_space)
+                                        break;
+                        }
+                }
+
+                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 (i == 0)
+                        break;
+                i--;
+        }
+        if (left->map_token) {
+                unmap_extent_buffer(left, left->map_token, KM_USER1);
+                left->map_token = NULL;
+        }
+
+        if (push_items == 0)
+                goto out_unlock;
+
+        if (!empty && 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);
+
+        if (left_nritems)
+                btrfs_mark_buffer_dirty(left);
+        btrfs_mark_buffer_dirty(right);
+
+        ret = btrfs_update_ref(trans, root, left, right, 0, push_items);
+        BUG_ON(ret);
+
+        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;
+                if (btrfs_header_nritems(path->nodes[0]) == 0)
+                        clean_tree_block(trans, root, path->nodes[0]);
+                btrfs_tree_unlock(path->nodes[0]);
+                free_extent_buffer(path->nodes[0]);
+                path->nodes[0] = right;
+                path->slots[1] += 1;
+        } else {
+                btrfs_tree_unlock(right);
+                free_extent_buffer(right);
+        }
+        return 0;
+
+out_unlock:
+        btrfs_tree_unlock(right);
+        free_extent_buffer(right);
+        return 1;
+}
+
+/*
+ * 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,
+                          int empty)
+{
+        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;
+        u32 nr;
+        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;
+        }
+
+        WARN_ON(!btrfs_tree_locked(path->nodes[1]));
+
+        left = read_node_slot(root, path->nodes[1], slot - 1);
+        btrfs_tree_lock(left);
+        free_space = btrfs_leaf_free_space(root, left);
+        if (free_space < data_size + sizeof(struct btrfs_item)) {
+                ret = 1;
+                goto out;
+        }
+
+        /* cow and double check */
+        ret = btrfs_cow_block(trans, root, left,
+                              path->nodes[1], slot - 1, &left, 0);
+        if (ret) {
+                /* we hit -ENOSPC, but it isn't fatal here */
+                ret = 1;
+                goto out;
+        }
+
+        free_space = btrfs_leaf_free_space(root, left);
+        if (free_space < data_size + sizeof(struct btrfs_item)) {
+                ret = 1;
+                goto out;
+        }
+
+        if (empty)
+                nr = right_nritems;
+        else
+                nr = right_nritems - 1;
+
+        for (i = 0; i < nr; 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 (!empty && push_items > 0) {
+                        if (path->slots[0] < i)
+                                break;
+                        if (path->slots[0] == i) {
+                                int space = btrfs_leaf_free_space(root, right);
+                                if (space + push_space * 2 > free_space)
+                                        break;
+                        }
+                }
+
+                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) {
+                ret = 1;
+                goto out;
+        }
+        if (!empty && 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 */
+        if (push_items > right_nritems) {
+                printk("push items %d nr %u\n", push_items, right_nritems);
+                WARN_ON(1);
+        }
+
+        if (push_items < right_nritems) {
+                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 -= 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);
+        if (right_nritems)
+                btrfs_mark_buffer_dirty(right);
+
+        ret = btrfs_update_ref(trans, root, right, left,
+                               old_left_nritems, push_items);
+        BUG_ON(ret);
+
+        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;
+                if (btrfs_header_nritems(path->nodes[0]) == 0)
+                        clean_tree_block(trans, root, path->nodes[0]);
+                btrfs_tree_unlock(path->nodes[0]);
+                free_extent_buffer(path->nodes[0]);
+                path->nodes[0] = left;
+                path->slots[1] -= 1;
+        } else {
+                btrfs_tree_unlock(left);
+                free_extent_buffer(left);
+                path->slots[0] -= push_items;
+        }
+        BUG_ON(path->slots[0] < 0);
+        return ret;
+out:
+        btrfs_tree_unlock(left);
+        free_extent_buffer(left);
+        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 noinline 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, 0);
+                if (wret < 0) {
+                        return wret;
+                }
+                if (wret) {
+                        wret = push_leaf_left(trans, root, path, data_size, 0);
+                        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,
+                                        path->nodes[1]->start,
+                                        root->root_key.objectid,
+                                        trans->transid, 0, l->start, 0);
+        if (IS_ERR(right)) {
+                BUG_ON(1);
+                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);
+
+        write_extent_buffer(right, root->fs_info->chunk_tree_uuid,
+                            (unsigned long)btrfs_header_chunk_tree_uuid(right),
+                            BTRFS_UUID_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;
+
+                                btrfs_tree_unlock(path->nodes[0]);
+                                free_extent_buffer(path->nodes[0]);
+                                path->nodes[0] = right;
+                                path->slots[0] = 0;
+                                path->slots[1] += 1;
+                                btrfs_mark_buffer_dirty(right);
+                                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;
+                                btrfs_tree_unlock(path->nodes[0]);
+                                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;
+                                }
+                                btrfs_mark_buffer_dirty(right);
+                                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);
+
+        ret = btrfs_update_ref(trans, root, l, right, 0, nritems);
+        BUG_ON(ret);
+
+        if (mid <= slot) {
+                btrfs_tree_unlock(path->nodes[0]);
+                free_extent_buffer(path->nodes[0]);
+                path->nodes[0] = right;
+                path->slots[0] -= mid;
+                path->slots[1] += 1;
+        } else {
+                btrfs_tree_unlock(right);
+                free_extent_buffer(right);
+        }
+
+        BUG_ON(path->slots[0] < 0);
+
+        if (double_split) {
+                BUG_ON(num_doubles != 0);
+                num_doubles++;
+                goto again;
+        }
+        return ret;
+}
+
+/*
+ * make the item pointed to by the path smaller.  new_size indicates
+ * how small to make it, and from_end tells us if we just chop bytes
+ * off the end of the item or if we shift the item to chop bytes off
+ * the front.
+ */
+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;
+}
+
+/*
+ * make the item pointed to by the path bigger, data_size is the new size.
+ */
+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 items into the tree.
+ * This does all the path init required, making room in the tree if needed.
+ * Returns the number of keys that were inserted.
+ */
+int btrfs_insert_some_items(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root,
+                            struct btrfs_path *path,
+                            struct btrfs_key *cpu_key, u32 *data_size,
+                            int nr)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_item *item;
+        int ret = 0;
+        int slot;
+        int i;
+        u32 nritems;
+        u32 total_data = 0;
+        u32 total_size = 0;
+        unsigned int data_end;
+        struct btrfs_disk_key disk_key;
+        struct btrfs_key found_key;
+
+        found_key.objectid = 0;
+        nr = min_t(int, nr, BTRFS_NODEPTRS_PER_BLOCK(root));
+
+        for (i = 0; i < nr; i++)
+                total_data += data_size[i];
+
+        total_data = min_t(u32, total_data, BTRFS_LEAF_DATA_SIZE(root));
+        total_size = total_data + (nr * sizeof(struct btrfs_item));
+        ret = btrfs_search_slot(trans, root, cpu_key, path, total_size, 1);
+        if (ret == 0)
+                return -EEXIST;
+        if (ret < 0)
+                goto out;
+
+        leaf = path->nodes[0];
+
+        nritems = btrfs_header_nritems(leaf);
+        data_end = leaf_data_end(root, leaf);
+
+        if (btrfs_leaf_free_space(root, leaf) < total_size) {
+                for (i = nr; i >= 0; i--) {
+                        total_data -= data_size[i];
+                        total_size -= data_size[i] + sizeof(struct btrfs_item);
+                        if (total_size < btrfs_leaf_free_space(root, leaf))
+                                break;
+                }
+                nr = i;
+        }
+
+        slot = path->slots[0];
+        BUG_ON(slot < 0);
+
+        if (slot != nritems) {
+                unsigned int old_data = btrfs_item_end_nr(leaf, slot);
+
+                item = btrfs_item_nr(leaf, slot);
+                btrfs_item_key_to_cpu(leaf, &found_key, slot);
+
+                /* figure out how many keys we can insert in here */
+                total_data = data_size[0];
+                for (i = 1; i < nr; i++) {
+                        if (comp_cpu_keys(&found_key, cpu_key + i) <= 0)
+                                break;
+                        total_data += data_size[i];
+                }
+                nr = i;
+
+                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 - total_data);
+                }
+                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 + nr),
+                              btrfs_item_nr_offset(slot),
+                              (nritems - slot) * sizeof(struct btrfs_item));
+
+                /* shift the data */
+                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
+                              data_end - total_data, btrfs_leaf_data(leaf) +
+                              data_end, old_data - data_end);
+                data_end = old_data;
+        } else {
+                /*
+                 * this sucks but it has to be done, if we are inserting at
+                 * the end of the leaf only insert 1 of the items, since we
+                 * have no way of knowing whats on the next leaf and we'd have
+                 * to drop our current locks to figure it out
+                 */
+                nr = 1;
+        }
+
+        /* setup the item for the new data */
+        for (i = 0; i < nr; i++) {
+                btrfs_cpu_key_to_disk(&disk_key, cpu_key + i);
+                btrfs_set_item_key(leaf, &disk_key, slot + i);
+                item = btrfs_item_nr(leaf, slot + i);
+                btrfs_set_item_offset(leaf, item, data_end - data_size[i]);
+                data_end -= data_size[i];
+                btrfs_set_item_size(leaf, item, data_size[i]);
+        }
+        btrfs_set_header_nritems(leaf, nritems + nr);
+        btrfs_mark_buffer_dirty(leaf);
+
+        ret = 0;
+        if (slot == 0) {
+                btrfs_cpu_key_to_disk(&disk_key, cpu_key);
+                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:
+        if (!ret)
+                ret = nr;
+        return ret;
+}
+
+/*
+ * Given a key and some data, insert items into the tree.
+ * This does all the path init required, making room in the tree if needed.
+ */
+int btrfs_insert_empty_items(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root,
+                            struct btrfs_path *path,
+                            struct btrfs_key *cpu_key, u32 *data_size,
+                            int nr)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_item *item;
+        int ret = 0;
+        int slot;
+        int slot_orig;
+        int i;
+        u32 nritems;
+        u32 total_size = 0;
+        u32 total_data = 0;
+        unsigned int data_end;
+        struct btrfs_disk_key disk_key;
+
+        for (i = 0; i < nr; i++) {
+                total_data += data_size[i];
+        }
+
+        total_size = total_data + (nr * sizeof(struct btrfs_item));
+        ret = btrfs_search_slot(trans, root, cpu_key, path, total_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) < total_size) {
+                btrfs_print_leaf(root, leaf);
+                printk("not enough freespace need %u have %d\n",
+                       total_size, btrfs_leaf_free_space(root, leaf));
+                BUG();
+        }
+
+        slot = path->slots[0];
+        BUG_ON(slot < 0);
+
+        if (slot != nritems) {
+                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 - total_data);
+                }
+                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 + nr),
+                              btrfs_item_nr_offset(slot),
+                              (nritems - slot) * sizeof(struct btrfs_item));
+
+                /* shift the data */
+                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
+                              data_end - total_data, btrfs_leaf_data(leaf) +
+                              data_end, old_data - data_end);
+                data_end = old_data;
+        }
+
+        /* setup the item for the new data */
+        for (i = 0; i < nr; i++) {
+                btrfs_cpu_key_to_disk(&disk_key, cpu_key + i);
+                btrfs_set_item_key(leaf, &disk_key, slot + i);
+                item = btrfs_item_nr(leaf, slot + i);
+                btrfs_set_item_offset(leaf, item, data_end - data_size[i]);
+                data_end -= data_size[i];
+                btrfs_set_item_size(leaf, item, data_size[i]);
+        }
+        btrfs_set_header_nritems(leaf, nritems + nr);
+        btrfs_mark_buffer_dirty(leaf);
+
+        ret = 0;
+        if (slot == 0) {
+                btrfs_cpu_key_to_disk(&disk_key, cpu_key);
+                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.
+ *
+ * the tree should have been previously balanced so the deletion does not
+ * empty a node.
+ */
+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;
+}
+
+/*
+ * a helper function to delete the leaf pointed to by path->slots[1] and
+ * path->nodes[1].  bytenr is the node block pointer, but since the callers
+ * already know it, it is faster to have them pass it down than to
+ * read it out of the node again.
+ *
+ * This deletes the pointer in path->nodes[1] and frees the leaf
+ * block extent.  zero is returned if it all worked out, < 0 otherwise.
+ *
+ * The path must have already been setup for deleting the leaf, including
+ * all the proper balancing.  path->nodes[1] must be locked.
+ */
+noinline int btrfs_del_leaf(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root,
+                            struct btrfs_path *path, u64 bytenr)
+{
+        int ret;
+        u64 root_gen = btrfs_header_generation(path->nodes[1]);
+
+        ret = del_ptr(trans, root, path, 1, path->slots[1]);
+        if (ret)
+                return ret;
+
+        ret = btrfs_free_extent(trans, root, bytenr,
+                                btrfs_level_size(root, 0),
+                                path->nodes[1]->start,
+                                btrfs_header_owner(path->nodes[1]),
+                                root_gen, 0, 1);
+        return ret;
+}
+/*
+ * delete the item at the leaf level in path.  If that empties
+ * the leaf, remove it from the tree
+ */
+int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+                    struct btrfs_path *path, int slot, int nr)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_item *item;
+        int last_off;
+        int dsize = 0;
+        int ret = 0;
+        int wret;
+        int i;
+        u32 nritems;
+
+        leaf = path->nodes[0];
+        last_off = btrfs_item_offset_nr(leaf, slot + nr - 1);
+
+        for (i = 0; i < nr; i++)
+                dsize += btrfs_item_size_nr(leaf, slot + i);
+
+        nritems = btrfs_header_nritems(leaf);
+
+        if (slot + nr != nritems) {
+                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,
+                              last_off - data_end);
+
+                for (i = slot + nr; 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 + nr),
+                              sizeof(struct btrfs_item) *
+                              (nritems - slot - nr));
+        }
+        btrfs_set_header_nritems(leaf, nritems - nr);
+        nritems -= nr;
+
+        /* delete the leaf if we've emptied it */
+        if (nritems == 0) {
+                if (leaf == root->node) {
+                        btrfs_set_header_level(leaf, 0);
+                } else {
+                        ret = btrfs_del_leaf(trans, root, path, leaf->start);
+                        BUG_ON(ret);
+                }
+        } 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) / 4) {
+                        /* 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_left(trans, root, path, 1, 1);
+                        if (wret < 0 && wret != -ENOSPC)
+                                ret = wret;
+
+                        if (path->nodes[0] == leaf &&
+                            btrfs_header_nritems(leaf)) {
+                                wret = push_leaf_right(trans, root, path, 1, 1);
+                                if (wret < 0 && wret != -ENOSPC)
+                                        ret = wret;
+                        }
+
+                        if (btrfs_header_nritems(leaf) == 0) {
+                                path->slots[1] = slot;
+                                ret = btrfs_del_leaf(trans, root, path, leaf->start);
+                                BUG_ON(ret);
+                                free_extent_buffer(leaf);
+                        } else {
+                                /* if we're still in the path, make sure
+                                 * we're dirty.  Otherwise, one of the
+                                 * push_leaf functions must have already
+                                 * dirtied this buffer
+                                 */
+                                if (path->nodes[0] == leaf)
+                                        btrfs_mark_buffer_dirty(leaf);
+                                free_extent_buffer(leaf);
+                        }
+                } else {
+                        btrfs_mark_buffer_dirty(leaf);
+                }
+        }
+        return ret;
+}
+
+/*
+ * search the tree again to find a leaf with lesser keys
+ * returns 0 if it found something or 1 if there are no lesser leaves.
+ * returns < 0 on io errors.
+ *
+ * This may release the path, and so you may lose any locks held at the
+ * time you call it.
+ */
+int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
+{
+        struct btrfs_key key;
+        struct btrfs_disk_key found_key;
+        int ret;
+
+        btrfs_item_key_to_cpu(path->nodes[0], &key, 0);
+
+        if (key.offset > 0)
+                key.offset--;
+        else if (key.type > 0)
+                key.type--;
+        else if (key.objectid > 0)
+                key.objectid--;
+        else
+                return 1;
+
+        btrfs_release_path(root, path);
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (ret < 0)
+                return ret;
+        btrfs_item_key(path->nodes[0], &found_key, 0);
+        ret = comp_keys(&found_key, &key);
+        if (ret < 0)
+                return 0;
+        return 1;
+}
+
+/*
+ * A helper function to walk down the tree starting at min_key, and looking
+ * for nodes or leaves that are either in cache or have a minimum
+ * transaction id.  This is used by the btree defrag code, and tree logging
+ *
+ * This does not cow, but it does stuff the starting key it finds back
+ * into min_key, so you can call btrfs_search_slot with cow=1 on the
+ * key and get a writable path.
+ *
+ * This does lock as it descends, and path->keep_locks should be set
+ * to 1 by the caller.
+ *
+ * This honors path->lowest_level to prevent descent past a given level
+ * of the tree.
+ *
+ * min_trans indicates the oldest transaction that you are interested
+ * in walking through.  Any nodes or leaves older than min_trans are
+ * skipped over (without reading them).
+ *
+ * returns zero if something useful was found, < 0 on error and 1 if there
+ * was nothing in the tree that matched the search criteria.
+ */
+int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
+                         struct btrfs_key *max_key,
+                         struct btrfs_path *path, int cache_only,
+                         u64 min_trans)
+{
+        struct extent_buffer *cur;
+        struct btrfs_key found_key;
+        int slot;
+        int sret;
+        u32 nritems;
+        int level;
+        int ret = 1;
+
+again:
+        cur = btrfs_lock_root_node(root);
+        level = btrfs_header_level(cur);
+        WARN_ON(path->nodes[level]);
+        path->nodes[level] = cur;
+        path->locks[level] = 1;
+
+        if (btrfs_header_generation(cur) < min_trans) {
+                ret = 1;
+                goto out;
+        }
+        while(1) {
+                nritems = btrfs_header_nritems(cur);
+                level = btrfs_header_level(cur);
+                sret = bin_search(cur, min_key, level, &slot);
+
+                /* at the lowest level, we're done, setup the path and exit */
+                if (level == path->lowest_level) {
+                        if (slot >= nritems)
+                                goto find_next_key;
+                        ret = 0;
+                        path->slots[level] = slot;
+                        btrfs_item_key_to_cpu(cur, &found_key, slot);
+                        goto out;
+                }
+                if (sret && slot > 0)
+                        slot--;
+                /*
+                 * check this node pointer against the cache_only and
+                 * min_trans parameters.  If it isn't in cache or is too
+                 * old, skip to the next one.
+                 */
+                while(slot < nritems) {
+                        u64 blockptr;
+                        u64 gen;
+                        struct extent_buffer *tmp;
+                        struct btrfs_disk_key disk_key;
+
+                        blockptr = btrfs_node_blockptr(cur, slot);
+                        gen = btrfs_node_ptr_generation(cur, slot);
+                        if (gen < min_trans) {
+                                slot++;
+                                continue;
+                        }
+                        if (!cache_only)
+                                break;
+
+                        if (max_key) {
+                                btrfs_node_key(cur, &disk_key, slot);
+                                if (comp_keys(&disk_key, max_key) >= 0) {
+                                        ret = 1;
+                                        goto out;
+                                }
+                        }
+
+                        tmp = btrfs_find_tree_block(root, blockptr,
+                                            btrfs_level_size(root, level - 1));
+
+                        if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
+                                free_extent_buffer(tmp);
+                                break;
+                        }
+                        if (tmp)
+                                free_extent_buffer(tmp);
+                        slot++;
+                }
+find_next_key:
+                /*
+                 * we didn't find a candidate key in this node, walk forward
+                 * and find another one
+                 */
+                if (slot >= nritems) {
+                        path->slots[level] = slot;
+                        sret = btrfs_find_next_key(root, path, min_key, level,
+                                                  cache_only, min_trans);
+                        if (sret == 0) {
+                                btrfs_release_path(root, path);
+                                goto again;
+                        } else {
+                                goto out;
+                        }
+                }
+                /* save our key for returning back */
+                btrfs_node_key_to_cpu(cur, &found_key, slot);
+                path->slots[level] = slot;
+                if (level == path->lowest_level) {
+                        ret = 0;
+                        unlock_up(path, level, 1);
+                        goto out;
+                }
+                cur = read_node_slot(root, cur, slot);
+
+                btrfs_tree_lock(cur);
+                path->locks[level - 1] = 1;
+                path->nodes[level - 1] = cur;
+                unlock_up(path, level, 1);
+        }
+out:
+        if (ret == 0)
+                memcpy(min_key, &found_key, sizeof(found_key));
+        return ret;
+}
+
+/*
+ * this is similar to btrfs_next_leaf, but does not try to preserve
+ * and fixup the path.  It looks for and returns the next key in the
+ * tree based on the current path and the cache_only and min_trans
+ * parameters.
+ *
+ * 0 is returned if another key is found, < 0 if there are any errors
+ * and 1 is returned if there are no higher keys in the tree
+ *
+ * path->keep_locks should be set to 1 on the search made before
+ * calling this function.
+ */
+int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
+                        struct btrfs_key *key, int lowest_level,
+                        int cache_only, u64 min_trans)
+{
+        int level = lowest_level;
+        int slot;
+        struct extent_buffer *c;
+
+        while(level < BTRFS_MAX_LEVEL) {
+                if (!path->nodes[level])
+                        return 1;
+
+                slot = path->slots[level] + 1;
+                c = path->nodes[level];
+next:
+                if (slot >= btrfs_header_nritems(c)) {
+                        level++;
+                        if (level == BTRFS_MAX_LEVEL) {
+                                return 1;
+                        }
+                        continue;
+                }
+                if (level == 0)
+                        btrfs_item_key_to_cpu(c, key, slot);
+                else {
+                        u64 blockptr = btrfs_node_blockptr(c, slot);
+                        u64 gen = btrfs_node_ptr_generation(c, slot);
+
+                        if (cache_only) {
+                                struct extent_buffer *cur;
+                                cur = btrfs_find_tree_block(root, blockptr,
+                                            btrfs_level_size(root, level - 1));
+                                if (!cur || !btrfs_buffer_uptodate(cur, gen)) {
+                                        slot++;
+                                        if (cur)
+                                                free_extent_buffer(cur);
+                                        goto next;
+                                }
+                                free_extent_buffer(cur);
+                        }
+                        if (gen < min_trans) {
+                                slot++;
+                                goto next;
+                        }
+                        btrfs_node_key_to_cpu(c, key, slot);
+                }
+                return 0;
+        }
+        return 1;
+}
+
+/*
+ * search the tree again to find a leaf with greater keys
+ * 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;
+        struct extent_buffer *c;
+        struct extent_buffer *next = NULL;
+        struct btrfs_key key;
+        u32 nritems;
+        int ret;
+
+        nritems = btrfs_header_nritems(path->nodes[0]);
+        if (nritems == 0) {
+                return 1;
+        }
+
+        btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
+
+        btrfs_release_path(root, path);
+        path->keep_locks = 1;
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        path->keep_locks = 0;
+
+        if (ret < 0)
+                return ret;
+
+        nritems = btrfs_header_nritems(path->nodes[0]);
+        /*
+         * by releasing the path above we dropped all our locks.  A balance
+         * could have added more items next to the key that used to be
+         * at the very end of the block.  So, check again here and
+         * advance the path if there are now more items available.
+         */
+        if (nritems > 0 && path->slots[0] < nritems - 1) {
+                path->slots[0]++;
+                goto done;
+        }
+
+        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++;
+                        if (level == BTRFS_MAX_LEVEL) {
+                                return 1;
+                        }
+                        continue;
+                }
+
+                if (next) {
+                        btrfs_tree_unlock(next);
+                        free_extent_buffer(next);
+                }
+
+                if (level == 1 && (path->locks[1] || path->skip_locking) &&
+                    path->reada)
+                        reada_for_search(root, path, level, slot, 0);
+
+                next = read_node_slot(root, c, slot);
+                if (!path->skip_locking) {
+                        WARN_ON(!btrfs_tree_locked(c));
+                        btrfs_tree_lock(next);
+                }
+                break;
+        }
+        path->slots[level] = slot;
+        while(1) {
+                level--;
+                c = path->nodes[level];
+                if (path->locks[level])
+                        btrfs_tree_unlock(c);
+                free_extent_buffer(c);
+                path->nodes[level] = next;
+                path->slots[level] = 0;
+                if (!path->skip_locking)
+                        path->locks[level] = 1;
+                if (!level)
+                        break;
+                if (level == 1 && path->locks[1] && path->reada)
+                        reada_for_search(root, path, level, slot, 0);
+                next = read_node_slot(root, next, 0);
+                if (!path->skip_locking) {
+                        WARN_ON(!btrfs_tree_locked(path->nodes[level]));
+                        btrfs_tree_lock(next);
+                }
+        }
+done:
+        unlock_up(path, 0, 1);
+        return 0;
+}
+
+/*
+ * this uses btrfs_prev_leaf to walk backwards in the tree, and keeps
+ * searching until it gets past min_objectid or finds an item of 'type'
+ *
+ * returns 0 if something is found, 1 if nothing was found and < 0 on error
+ */
+int btrfs_previous_item(struct btrfs_root *root,
+                        struct btrfs_path *path, u64 min_objectid,
+                        int type)
+{
+        struct btrfs_key found_key;
+        struct extent_buffer *leaf;
+        u32 nritems;
+        int ret;
+
+        while(1) {
+                if (path->slots[0] == 0) {
+                        ret = btrfs_prev_leaf(root, path);
+                        if (ret != 0)
+                                return ret;
+                } else {
+                        path->slots[0]--;
+                }
+                leaf = path->nodes[0];
+                nritems = btrfs_header_nritems(leaf);
+                if (nritems == 0)
+                        return 1;
+                if (path->slots[0] == nritems)
+                        path->slots[0]--;
+
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                if (found_key.type == type)
+                        return 0;
+                if (found_key.objectid < min_objectid)
+                        break;
+                if (found_key.objectid == min_objectid &&
+                    found_key.type < type)
+                        break;
+        }
+        return 1;
+}