[safe/jmp/linux-2.6] / fs / btrfs / extent-tree.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */
#include <linux/sched.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/sort.h>
#include <linux/rcupdate.h>
#include <linux/kthread.h>
#include "compat.h"
#include "hash.h"
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"
#include "transaction.h"
#include "volumes.h"
#include "locking.h"
#include "free-space-cache.h"

static int update_block_group(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              u64 bytenr, u64 num_bytes, int alloc,
                              int mark_free);
static int update_reserved_extents(struct btrfs_block_group_cache *cache,
                                   u64 num_bytes, int reserve);
static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                u64 bytenr, u64 num_bytes, u64 parent,
                                u64 root_objectid, u64 owner_objectid,
                                u64 owner_offset, int refs_to_drop,
                                struct btrfs_delayed_extent_op *extra_op);
static void __run_delayed_extent_op(struct btrfs_delayed_extent_op *extent_op,
                                    struct extent_buffer *leaf,
                                    struct btrfs_extent_item *ei);
static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root,
                                      u64 parent, u64 root_objectid,
                                      u64 flags, u64 owner, u64 offset,
                                      struct btrfs_key *ins, int ref_mod);
static int alloc_reserved_tree_block(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     u64 parent, u64 root_objectid,
                                     u64 flags, struct btrfs_disk_key *key,
                                     int level, struct btrfs_key *ins);
static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                          struct btrfs_root *extent_root, u64 alloc_bytes,
                          u64 flags, int force);
static int pin_down_bytes(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root,
                          struct btrfs_path *path,
                          u64 bytenr, u64 num_bytes,
                          int is_data, int reserved,
                          struct extent_buffer **must_clean);
static int find_next_key(struct btrfs_path *path, int level,
                         struct btrfs_key *key);
static void dump_space_info(struct btrfs_space_info *info, u64 bytes,
                            int dump_block_groups);

static noinline int
block_group_cache_done(struct btrfs_block_group_cache *cache)
{
        smp_mb();
        return cache->cached == BTRFS_CACHE_FINISHED;
}

static int block_group_bits(struct btrfs_block_group_cache *cache, u64 bits)
{
        return (cache->flags & bits) == bits;
}

/*
 * this adds the block group to the fs_info rb tree for the block group
 * cache
 */
static int btrfs_add_block_group_cache(struct btrfs_fs_info *info,
                                struct btrfs_block_group_cache *block_group)
{
        struct rb_node **p;
        struct rb_node *parent = NULL;
        struct btrfs_block_group_cache *cache;

        spin_lock(&info->block_group_cache_lock);
        p = &info->block_group_cache_tree.rb_node;

        while (*p) {
                parent = *p;
                cache = rb_entry(parent, struct btrfs_block_group_cache,
                                 cache_node);
                if (block_group->key.objectid < cache->key.objectid) {
                        p = &(*p)->rb_left;
                } else if (block_group->key.objectid > cache->key.objectid) {
                        p = &(*p)->rb_right;
                } else {
                        spin_unlock(&info->block_group_cache_lock);
                        return -EEXIST;
                }
        }

        rb_link_node(&block_group->cache_node, parent, p);
        rb_insert_color(&block_group->cache_node,
                        &info->block_group_cache_tree);
        spin_unlock(&info->block_group_cache_lock);

        return 0;
}

/*
 * This will return the block group at or after bytenr if contains is 0, else
 * it will return the block group that contains the bytenr
 */
static struct btrfs_block_group_cache *
block_group_cache_tree_search(struct btrfs_fs_info *info, u64 bytenr,
                              int contains)
{
        struct btrfs_block_group_cache *cache, *ret = NULL;
        struct rb_node *n;
        u64 end, start;

        spin_lock(&info->block_group_cache_lock);
        n = info->block_group_cache_tree.rb_node;

        while (n) {
                cache = rb_entry(n, struct btrfs_block_group_cache,
                                 cache_node);
                end = cache->key.objectid + cache->key.offset - 1;
                start = cache->key.objectid;

                if (bytenr < start) {
                        if (!contains && (!ret || start < ret->key.objectid))
                                ret = cache;
                        n = n->rb_left;
                } else if (bytenr > start) {
                        if (contains && bytenr <= end) {
                                ret = cache;
                                break;
                        }
                        n = n->rb_right;
                } else {
                        ret = cache;
                        break;
                }
        }
        if (ret)
                atomic_inc(&ret->count);
        spin_unlock(&info->block_group_cache_lock);

        return ret;
}

static int add_excluded_extent(struct btrfs_root *root,
                               u64 start, u64 num_bytes)
{
        u64 end = start + num_bytes - 1;
        set_extent_bits(&root->fs_info->freed_extents[0],
                        start, end, EXTENT_UPTODATE, GFP_NOFS);
        set_extent_bits(&root->fs_info->freed_extents[1],
                        start, end, EXTENT_UPTODATE, GFP_NOFS);
        return 0;
}

static void free_excluded_extents(struct btrfs_root *root,
                                  struct btrfs_block_group_cache *cache)
{
        u64 start, end;

        start = cache->key.objectid;
        end = start + cache->key.offset - 1;

        clear_extent_bits(&root->fs_info->freed_extents[0],
                          start, end, EXTENT_UPTODATE, GFP_NOFS);
        clear_extent_bits(&root->fs_info->freed_extents[1],
                          start, end, EXTENT_UPTODATE, GFP_NOFS);
}

static int exclude_super_stripes(struct btrfs_root *root,
                                 struct btrfs_block_group_cache *cache)
{
        u64 bytenr;
        u64 *logical;
        int stripe_len;
        int i, nr, ret;

        for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
                bytenr = btrfs_sb_offset(i);
                ret = btrfs_rmap_block(&root->fs_info->mapping_tree,
                                       cache->key.objectid, bytenr,
                                       0, &logical, &nr, &stripe_len);
                BUG_ON(ret);

                while (nr--) {
                        cache->bytes_super += stripe_len;
                        ret = add_excluded_extent(root, logical[nr],
                                                  stripe_len);
                        BUG_ON(ret);
                }

                kfree(logical);
        }
        return 0;
}

static struct btrfs_caching_control *
get_caching_control(struct btrfs_block_group_cache *cache)
{
        struct btrfs_caching_control *ctl;

        spin_lock(&cache->lock);
        if (cache->cached != BTRFS_CACHE_STARTED) {
                spin_unlock(&cache->lock);
                return NULL;
        }

        ctl = cache->caching_ctl;
        atomic_inc(&ctl->count);
        spin_unlock(&cache->lock);
        return ctl;
}

static void put_caching_control(struct btrfs_caching_control *ctl)
{
        if (atomic_dec_and_test(&ctl->count))
                kfree(ctl);
}

/*
 * this is only called by cache_block_group, since we could have freed extents
 * we need to check the pinned_extents for any extents that can't be used yet
 * since their free space will be released as soon as the transaction commits.
 */
static u64 add_new_free_space(struct btrfs_block_group_cache *block_group,
                              struct btrfs_fs_info *info, u64 start, u64 end)
{
        u64 extent_start, extent_end, size, total_added = 0;
        int ret;

        while (start < end) {
                ret = find_first_extent_bit(info->pinned_extents, start,
                                            &extent_start, &extent_end,
                                            EXTENT_DIRTY | EXTENT_UPTODATE);
                if (ret)
                        break;

                if (extent_start == start) {
                        start = extent_end + 1;
                } else if (extent_start > start && extent_start < end) {
                        size = extent_start - start;
                        total_added += size;
                        ret = btrfs_add_free_space(block_group, start,
                                                   size);
                        BUG_ON(ret);
                        start = extent_end + 1;
                } else {
                        break;
                }
        }

        if (start < end) {
                size = end - start;
                total_added += size;
                ret = btrfs_add_free_space(block_group, start, size);
                BUG_ON(ret);
        }

        return total_added;
}

static int caching_kthread(void *data)
{
        struct btrfs_block_group_cache *block_group = data;
        struct btrfs_fs_info *fs_info = block_group->fs_info;
        struct btrfs_caching_control *caching_ctl = block_group->caching_ctl;
        struct btrfs_root *extent_root = fs_info->extent_root;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        u64 total_found = 0;
        u64 last = 0;
        u32 nritems;
        int ret = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        exclude_super_stripes(extent_root, block_group);
        spin_lock(&block_group->space_info->lock);
        block_group->space_info->bytes_super += block_group->bytes_super;
        spin_unlock(&block_group->space_info->lock);

        last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);

        /*
         * We don't want to deadlock with somebody trying to allocate a new
         * extent for the extent root while also trying to search the extent
         * root to add free space.  So we skip locking and search the commit
         * root, since its read-only
         */
        path->skip_locking = 1;
        path->search_commit_root = 1;
        path->reada = 2;

        key.objectid = last;
        key.offset = 0;
        key.type = BTRFS_EXTENT_ITEM_KEY;
again:
        mutex_lock(&caching_ctl->mutex);
        /* need to make sure the commit_root doesn't disappear */
        down_read(&fs_info->extent_commit_sem);

        ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
        if (ret < 0)
                goto err;

        leaf = path->nodes[0];
        nritems = btrfs_header_nritems(leaf);

        while (1) {
                smp_mb();
                if (fs_info->closing > 1) {
                        last = (u64)-1;
                        break;
                }

                if (path->slots[0] < nritems) {
                        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                } else {
                        ret = find_next_key(path, 0, &key);
                        if (ret)
                                break;

                        caching_ctl->progress = last;
                        btrfs_release_path(extent_root, path);
                        up_read(&fs_info->extent_commit_sem);
                        mutex_unlock(&caching_ctl->mutex);
                        if (btrfs_transaction_in_commit(fs_info))
                                schedule_timeout(1);
                        else
                                cond_resched();
                        goto again;
                }

                if (key.objectid < block_group->key.objectid) {
                        path->slots[0]++;
                        continue;
                }

                if (key.objectid >= block_group->key.objectid +
                    block_group->key.offset)
                        break;

                if (key.type == BTRFS_EXTENT_ITEM_KEY) {
                        total_found += add_new_free_space(block_group,
                                                          fs_info, last,
                                                          key.objectid);
                        last = key.objectid + key.offset;

                        if (total_found > (1024 * 1024 * 2)) {
                                total_found = 0;
                                wake_up(&caching_ctl->wait);
                        }
                }
                path->slots[0]++;
        }
        ret = 0;

        total_found += add_new_free_space(block_group, fs_info, last,
                                          block_group->key.objectid +
                                          block_group->key.offset);
        caching_ctl->progress = (u64)-1;

        spin_lock(&block_group->lock);
        block_group->caching_ctl = NULL;
        block_group->cached = BTRFS_CACHE_FINISHED;
        spin_unlock(&block_group->lock);

err:
        btrfs_free_path(path);
        up_read(&fs_info->extent_commit_sem);

        free_excluded_extents(extent_root, block_group);

        mutex_unlock(&caching_ctl->mutex);
        wake_up(&caching_ctl->wait);

        put_caching_control(caching_ctl);
        atomic_dec(&block_group->space_info->caching_threads);
        return 0;
}

static int cache_block_group(struct btrfs_block_group_cache *cache)
{
        struct btrfs_fs_info *fs_info = cache->fs_info;
        struct btrfs_caching_control *caching_ctl;
        struct task_struct *tsk;
        int ret = 0;

        smp_mb();
        if (cache->cached != BTRFS_CACHE_NO)
                return 0;

        caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_KERNEL);
        BUG_ON(!caching_ctl);

        INIT_LIST_HEAD(&caching_ctl->list);
        mutex_init(&caching_ctl->mutex);
        init_waitqueue_head(&caching_ctl->wait);
        caching_ctl->block_group = cache;
        caching_ctl->progress = cache->key.objectid;
        /* one for caching kthread, one for caching block group list */
        atomic_set(&caching_ctl->count, 2);

        spin_lock(&cache->lock);
        if (cache->cached != BTRFS_CACHE_NO) {
                spin_unlock(&cache->lock);
                kfree(caching_ctl);
                return 0;
        }
        cache->caching_ctl = caching_ctl;
        cache->cached = BTRFS_CACHE_STARTED;
        spin_unlock(&cache->lock);

        down_write(&fs_info->extent_commit_sem);
        list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups);
        up_write(&fs_info->extent_commit_sem);

        atomic_inc(&cache->space_info->caching_threads);

        tsk = kthread_run(caching_kthread, cache, "btrfs-cache-%llu\n",
                          cache->key.objectid);
        if (IS_ERR(tsk)) {
                ret = PTR_ERR(tsk);
                printk(KERN_ERR "error running thread %d\n", ret);
                BUG();
        }

        return ret;
}

/*
 * return the block group that starts at or after bytenr
 */
static struct btrfs_block_group_cache *
btrfs_lookup_first_block_group(struct btrfs_fs_info *info, u64 bytenr)
{
        struct btrfs_block_group_cache *cache;

        cache = block_group_cache_tree_search(info, bytenr, 0);

        return cache;
}

/*
 * return the block group that contains the given bytenr
 */
struct btrfs_block_group_cache *btrfs_lookup_block_group(
                                                 struct btrfs_fs_info *info,
                                                 u64 bytenr)
{
        struct btrfs_block_group_cache *cache;

        cache = block_group_cache_tree_search(info, bytenr, 1);

        return cache;
}

void btrfs_put_block_group(struct btrfs_block_group_cache *cache)
{
        if (atomic_dec_and_test(&cache->count))
                kfree(cache);
}

static struct btrfs_space_info *__find_space_info(struct btrfs_fs_info *info,
                                                  u64 flags)
{
        struct list_head *head = &info->space_info;
        struct btrfs_space_info *found;

        rcu_read_lock();
        list_for_each_entry_rcu(found, head, list) {
                if (found->flags == flags) {
                        rcu_read_unlock();
                        return found;
                }
        }
        rcu_read_unlock();
        return NULL;
}

/*
 * after adding space to the filesystem, we need to clear the full flags
 * on all the space infos.
 */
void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
{
        struct list_head *head = &info->space_info;
        struct btrfs_space_info *found;

        rcu_read_lock();
        list_for_each_entry_rcu(found, head, list)
                found->full = 0;
        rcu_read_unlock();
}

static u64 div_factor(u64 num, int factor)
{
        if (factor == 10)
                return num;
        num *= factor;
        do_div(num, 10);
        return num;
}

u64 btrfs_find_block_group(struct btrfs_root *root,
                           u64 search_start, u64 search_hint, int owner)
{
        struct btrfs_block_group_cache *cache;
        u64 used;
        u64 last = max(search_hint, search_start);
        u64 group_start = 0;
        int full_search = 0;
        int factor = 9;
        int wrapped = 0;
again:
        while (1) {
                cache = btrfs_lookup_first_block_group(root->fs_info, last);
                if (!cache)
                        break;

                spin_lock(&cache->lock);
                last = cache->key.objectid + cache->key.offset;
                used = btrfs_block_group_used(&cache->item);

                if ((full_search || !cache->ro) &&
                    block_group_bits(cache, BTRFS_BLOCK_GROUP_METADATA)) {
                        if (used + cache->pinned + cache->reserved <
                            div_factor(cache->key.offset, factor)) {
                                group_start = cache->key.objectid;
                                spin_unlock(&cache->lock);
                                btrfs_put_block_group(cache);
                                goto found;
                        }
                }
                spin_unlock(&cache->lock);
                btrfs_put_block_group(cache);
                cond_resched();
        }
        if (!wrapped) {
                last = search_start;
                wrapped = 1;
                goto again;
        }
        if (!full_search && factor < 10) {
                last = search_start;
                full_search = 1;
                factor = 10;
                goto again;
        }
found:
        return group_start;
}

/* simple helper to search for an existing extent at a given offset */
int btrfs_lookup_extent(struct btrfs_root *root, u64 start, u64 len)
{
        int ret;
        struct btrfs_key key;
        struct btrfs_path *path;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        key.objectid = start;
        key.offset = len;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        ret = btrfs_search_slot(NULL, root->fs_info->extent_root, &key, path,
                                0, 0);
        btrfs_free_path(path);
        return ret;
}

/*
 * Back reference rules.  Back refs have three main goals:
 *
 * 1) differentiate between all holders of references to an extent so that
 *    when a reference is dropped we can make sure it was a valid reference
 *    before freeing the extent.
 *
 * 2) Provide enough information to quickly find the holders of an extent
 *    if we notice a given block is corrupted or bad.
 *
 * 3) Make it easy to migrate blocks for FS shrinking or storage pool
 *    maintenance.  This is actually the same as #2, but with a slightly
 *    different use case.
 *
 * There are two kinds of back refs. The implicit back refs is optimized
 * for pointers in non-shared tree blocks. For a given pointer in a block,
 * back refs of this kind provide information about the block's owner tree
 * and the pointer's key. These information allow us to find the block by
 * b-tree searching. The full back refs is for pointers in tree blocks not
 * referenced by their owner trees. The location of tree block is recorded
 * in the back refs. Actually the full back refs is generic, and can be
 * used in all cases the implicit back refs is used. The major shortcoming
 * of the full back refs is its overhead. Every time a tree block gets
 * COWed, we have to update back refs entry for all pointers in it.
 *
 * For a newly allocated tree block, we use implicit back refs for
 * pointers in it. This means most tree related operations only involve
 * implicit back refs. For a tree block created in old transaction, the
 * only way to drop a reference to it is COW it. So we can detect the
 * event that tree block loses its owner tree's reference and do the
 * back refs conversion.
 *
 * When a tree block is COW'd through a tree, there are four cases:
 *
 * The reference count of the block is one and the tree is the block's
 * owner tree. Nothing to do in this case.
 *
 * The reference count of the block is one and the tree is not the
 * block's owner tree. In this case, full back refs is used for pointers
 * in the block. Remove these full back refs, add implicit back refs for
 * every pointers in the new block.
 *
 * The reference count of the block is greater than one and the tree is
 * the block's owner tree. In this case, implicit back refs is used for
 * pointers in the block. Add full back refs for every pointers in the
 * block, increase lower level extents' reference counts. The original
 * implicit back refs are entailed to the new block.
 *
 * The reference count of the block is greater than one and the tree is
 * not the block's owner tree. Add implicit back refs for every pointer in
 * the new block, increase lower level extents' reference count.
 *
 * Back Reference Key composing:
 *
 * The key objectid corresponds to the first byte in the extent,
 * The key type is used to differentiate between types of back refs.
 * There are different meanings of the key offset for different types
 * of back refs.
 *
 * File extents can be referenced by:
 *
 * - multiple snapshots, subvolumes, or different generations in one subvol
 * - different files inside a single subvolume
 * - different offsets inside a file (bookend extents in file.c)
 *
 * The extent ref structure for the implicit back refs has fields for:
 *
 * - Objectid of the subvolume root
 * - objectid of the file holding the reference
 * - original offset in the file
 * - how many bookend extents
 *
 * The key offset for the implicit back refs is hash of the first
 * three fields.
 *
 * The extent ref structure for the full back refs has field for:
 *
 * - number of pointers in the tree leaf
 *
 * The key offset for the implicit back refs is the first byte of
 * the tree leaf
 *
 * When a file extent is allocated, The implicit back refs is used.
 * the fields are filled in:
 *
 *     (root_key.objectid, inode objectid, offset in file, 1)
 *
 * When a file extent is removed file truncation, we find the
 * corresponding implicit back refs and check the following fields:
 *
 *     (btrfs_header_owner(leaf), inode objectid, offset in file)
 *
 * Btree extents can be referenced by:
 *
 * - Different subvolumes
 *
 * Both the implicit back refs and the full back refs for tree blocks
 * only consist of key. The key offset for the implicit back refs is
 * objectid of block's owner tree. The key offset for the full back refs
 * is the first byte of parent block.
 *
 * When implicit back refs is used, information about the lowest key and
 * level of the tree block are required. These information are stored in
 * tree block info structure.
 */

#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
static int convert_extent_item_v0(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root,
                                  struct btrfs_path *path,
                                  u64 owner, u32 extra_size)
{
        struct btrfs_extent_item *item;
        struct btrfs_extent_item_v0 *ei0;
        struct btrfs_extent_ref_v0 *ref0;
        struct btrfs_tree_block_info *bi;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u32 new_size = sizeof(*item);
        u64 refs;
        int ret;

        leaf = path->nodes[0];
        BUG_ON(btrfs_item_size_nr(leaf, path->slots[0]) != sizeof(*ei0));

        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
        ei0 = btrfs_item_ptr(leaf, path->slots[0],
                             struct btrfs_extent_item_v0);
        refs = btrfs_extent_refs_v0(leaf, ei0);

        if (owner == (u64)-1) {
                while (1) {
                        if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                                ret = btrfs_next_leaf(root, path);
                                if (ret < 0)
                                        return ret;
                                BUG_ON(ret > 0);
                                leaf = path->nodes[0];
                        }
                        btrfs_item_key_to_cpu(leaf, &found_key,
                                              path->slots[0]);
                        BUG_ON(key.objectid != found_key.objectid);
                        if (found_key.type != BTRFS_EXTENT_REF_V0_KEY) {
                                path->slots[0]++;
                                continue;
                        }
                        ref0 = btrfs_item_ptr(leaf, path->slots[0],
                                              struct btrfs_extent_ref_v0);
                        owner = btrfs_ref_objectid_v0(leaf, ref0);
                        break;
                }
        }
        btrfs_release_path(root, path);

        if (owner < BTRFS_FIRST_FREE_OBJECTID)
                new_size += sizeof(*bi);

        new_size -= sizeof(*ei0);
        ret = btrfs_search_slot(trans, root, &key, path,
                                new_size + extra_size, 1);
        if (ret < 0)
                return ret;
        BUG_ON(ret);

        ret = btrfs_extend_item(trans, root, path, new_size);
        BUG_ON(ret);

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        btrfs_set_extent_refs(leaf, item, refs);
        /* FIXME: get real generation */
        btrfs_set_extent_generation(leaf, item, 0);
        if (owner < BTRFS_FIRST_FREE_OBJECTID) {
                btrfs_set_extent_flags(leaf, item,
                                       BTRFS_EXTENT_FLAG_TREE_BLOCK |
                                       BTRFS_BLOCK_FLAG_FULL_BACKREF);
                bi = (struct btrfs_tree_block_info *)(item + 1);
                /* FIXME: get first key of the block */
                memset_extent_buffer(leaf, 0, (unsigned long)bi, sizeof(*bi));
                btrfs_set_tree_block_level(leaf, bi, (int)owner);
        } else {
                btrfs_set_extent_flags(leaf, item, BTRFS_EXTENT_FLAG_DATA);
        }
        btrfs_mark_buffer_dirty(leaf);
        return 0;
}
#endif

static u64 hash_extent_data_ref(u64 root_objectid, u64 owner, u64 offset)
{
        u32 high_crc = ~(u32)0;
        u32 low_crc = ~(u32)0;
        __le64 lenum;

        lenum = cpu_to_le64(root_objectid);
        high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
        lenum = cpu_to_le64(owner);
        low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
        lenum = cpu_to_le64(offset);
        low_crc = crc32c(low_crc, &lenum, sizeof(lenum));

        return ((u64)high_crc << 31) ^ (u64)low_crc;
}

static u64 hash_extent_data_ref_item(struct extent_buffer *leaf,
                                     struct btrfs_extent_data_ref *ref)
{
        return hash_extent_data_ref(btrfs_extent_data_ref_root(leaf, ref),
                                    btrfs_extent_data_ref_objectid(leaf, ref),
                                    btrfs_extent_data_ref_offset(leaf, ref));
}

static int match_extent_data_ref(struct extent_buffer *leaf,
                                 struct btrfs_extent_data_ref *ref,
                                 u64 root_objectid, u64 owner, u64 offset)
{
        if (btrfs_extent_data_ref_root(leaf, ref) != root_objectid ||
            btrfs_extent_data_ref_objectid(leaf, ref) != owner ||
            btrfs_extent_data_ref_offset(leaf, ref) != offset)
                return 0;
        return 1;
}

static noinline int lookup_extent_data_ref(struct btrfs_trans_handle *trans,
                                           struct btrfs_root *root,
                                           struct btrfs_path *path,
                                           u64 bytenr, u64 parent,
                                           u64 root_objectid,
                                           u64 owner, u64 offset)
{
        struct btrfs_key key;
        struct btrfs_extent_data_ref *ref;
        struct extent_buffer *leaf;
        u32 nritems;
        int ret;
        int recow;
        int err = -ENOENT;

        key.objectid = bytenr;
        if (parent) {
                key.type = BTRFS_SHARED_DATA_REF_KEY;
                key.offset = parent;
        } else {
                key.type = BTRFS_EXTENT_DATA_REF_KEY;
                key.offset = hash_extent_data_ref(root_objectid,
                                                  owner, offset);
        }
again:
        recow = 0;
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0) {
                err = ret;
                goto fail;
        }

        if (parent) {
                if (!ret)
                        return 0;
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
                key.type = BTRFS_EXTENT_REF_V0_KEY;
                btrfs_release_path(root, path);
                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                if (ret < 0) {
                        err = ret;
                        goto fail;
                }
                if (!ret)
                        return 0;
#endif
                goto fail;
        }

        leaf = path->nodes[0];
        nritems = btrfs_header_nritems(leaf);
        while (1) {
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                err = ret;
                        if (ret)
                                goto fail;

                        leaf = path->nodes[0];
                        nritems = btrfs_header_nritems(leaf);
                        recow = 1;
                }

                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                if (key.objectid != bytenr ||
                    key.type != BTRFS_EXTENT_DATA_REF_KEY)
                        goto fail;

                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_data_ref);

                if (match_extent_data_ref(leaf, ref, root_objectid,
                                          owner, offset)) {
                        if (recow) {
                                btrfs_release_path(root, path);
                                goto again;
                        }
                        err = 0;
                        break;
                }
                path->slots[0]++;
        }
fail:
        return err;
}

static noinline int insert_extent_data_ref(struct btrfs_trans_handle *trans,
                                           struct btrfs_root *root,
                                           struct btrfs_path *path,
                                           u64 bytenr, u64 parent,
                                           u64 root_objectid, u64 owner,
                                           u64 offset, int refs_to_add)
{
        struct btrfs_key key;
        struct extent_buffer *leaf;
        u32 size;
        u32 num_refs;
        int ret;

        key.objectid = bytenr;
        if (parent) {
                key.type = BTRFS_SHARED_DATA_REF_KEY;
                key.offset = parent;
                size = sizeof(struct btrfs_shared_data_ref);
        } else {
                key.type = BTRFS_EXTENT_DATA_REF_KEY;
                key.offset = hash_extent_data_ref(root_objectid,
                                                  owner, offset);
                size = sizeof(struct btrfs_extent_data_ref);
        }

        ret = btrfs_insert_empty_item(trans, root, path, &key, size);
        if (ret && ret != -EEXIST)
                goto fail;

        leaf = path->nodes[0];
        if (parent) {
                struct btrfs_shared_data_ref *ref;
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_shared_data_ref);
                if (ret == 0) {
                        btrfs_set_shared_data_ref_count(leaf, ref, refs_to_add);
                } else {
                        num_refs = btrfs_shared_data_ref_count(leaf, ref);
                        num_refs += refs_to_add;
                        btrfs_set_shared_data_ref_count(leaf, ref, num_refs);
                }
        } else {
                struct btrfs_extent_data_ref *ref;
                while (ret == -EEXIST) {
                        ref = btrfs_item_ptr(leaf, path->slots[0],
                                             struct btrfs_extent_data_ref);
                        if (match_extent_data_ref(leaf, ref, root_objectid,
                                                  owner, offset))
                                break;
                        btrfs_release_path(root, path);
                        key.offset++;
                        ret = btrfs_insert_empty_item(trans, root, path, &key,
                                                      size);
                        if (ret && ret != -EEXIST)
                                goto fail;

                        leaf = path->nodes[0];
                }
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_data_ref);
                if (ret == 0) {
                        btrfs_set_extent_data_ref_root(leaf, ref,
                                                       root_objectid);
                        btrfs_set_extent_data_ref_objectid(leaf, ref, owner);
                        btrfs_set_extent_data_ref_offset(leaf, ref, offset);
                        btrfs_set_extent_data_ref_count(leaf, ref, refs_to_add);
                } else {
                        num_refs = btrfs_extent_data_ref_count(leaf, ref);
                        num_refs += refs_to_add;
                        btrfs_set_extent_data_ref_count(leaf, ref, num_refs);
                }
        }
        btrfs_mark_buffer_dirty(leaf);
        ret = 0;
fail:
        btrfs_release_path(root, path);
        return ret;
}

static noinline int remove_extent_data_ref(struct btrfs_trans_handle *trans,
                                           struct btrfs_root *root,
                                           struct btrfs_path *path,
                                           int refs_to_drop)
{
        struct btrfs_key key;
        struct btrfs_extent_data_ref *ref1 = NULL;
        struct btrfs_shared_data_ref *ref2 = NULL;
        struct extent_buffer *leaf;
        u32 num_refs = 0;
        int ret = 0;

        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

        if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
                ref1 = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_extent_data_ref);
                num_refs = btrfs_extent_data_ref_count(leaf, ref1);
        } else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
                ref2 = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_shared_data_ref);
                num_refs = btrfs_shared_data_ref_count(leaf, ref2);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        } else if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
                struct btrfs_extent_ref_v0 *ref0;
                ref0 = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_extent_ref_v0);
                num_refs = btrfs_ref_count_v0(leaf, ref0);
#endif
        } else {
                BUG();
        }

        BUG_ON(num_refs < refs_to_drop);
        num_refs -= refs_to_drop;

        if (num_refs == 0) {
                ret = btrfs_del_item(trans, root, path);
        } else {
                if (key.type == BTRFS_EXTENT_DATA_REF_KEY)
                        btrfs_set_extent_data_ref_count(leaf, ref1, num_refs);
                else if (key.type == BTRFS_SHARED_DATA_REF_KEY)
                        btrfs_set_shared_data_ref_count(leaf, ref2, num_refs);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
                else {
                        struct btrfs_extent_ref_v0 *ref0;
                        ref0 = btrfs_item_ptr(leaf, path->slots[0],
                                        struct btrfs_extent_ref_v0);
                        btrfs_set_ref_count_v0(leaf, ref0, num_refs);
                }
#endif
                btrfs_mark_buffer_dirty(leaf);
        }
        return ret;
}

static noinline u32 extent_data_ref_count(struct btrfs_root *root,
                                          struct btrfs_path *path,
                                          struct btrfs_extent_inline_ref *iref)
{
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_extent_data_ref *ref1;
        struct btrfs_shared_data_ref *ref2;
        u32 num_refs = 0;

        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
        if (iref) {
                if (btrfs_extent_inline_ref_type(leaf, iref) ==
                    BTRFS_EXTENT_DATA_REF_KEY) {
                        ref1 = (struct btrfs_extent_data_ref *)(&iref->offset);
                        num_refs = btrfs_extent_data_ref_count(leaf, ref1);
                } else {
                        ref2 = (struct btrfs_shared_data_ref *)(iref + 1);
                        num_refs = btrfs_shared_data_ref_count(leaf, ref2);
                }
        } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
                ref1 = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_extent_data_ref);
                num_refs = btrfs_extent_data_ref_count(leaf, ref1);
        } else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
                ref2 = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_shared_data_ref);
                num_refs = btrfs_shared_data_ref_count(leaf, ref2);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        } else if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
                struct btrfs_extent_ref_v0 *ref0;
                ref0 = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_extent_ref_v0);
                num_refs = btrfs_ref_count_v0(leaf, ref0);
#endif
        } else {
                WARN_ON(1);
        }
        return num_refs;
}

static noinline int lookup_tree_block_ref(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct btrfs_path *path,
                                          u64 bytenr, u64 parent,
                                          u64 root_objectid)
{
        struct btrfs_key key;
        int ret;

        key.objectid = bytenr;
        if (parent) {
                key.type = BTRFS_SHARED_BLOCK_REF_KEY;
                key.offset = parent;
        } else {
                key.type = BTRFS_TREE_BLOCK_REF_KEY;
                key.offset = root_objectid;
        }

        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret > 0)
                ret = -ENOENT;
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        if (ret == -ENOENT && parent) {
                btrfs_release_path(root, path);
                key.type = BTRFS_EXTENT_REF_V0_KEY;
                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                if (ret > 0)
                        ret = -ENOENT;
        }
#endif
        return ret;
}

static noinline int insert_tree_block_ref(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct btrfs_path *path,
                                          u64 bytenr, u64 parent,
                                          u64 root_objectid)
{
        struct btrfs_key key;
        int ret;

        key.objectid = bytenr;
        if (parent) {
                key.type = BTRFS_SHARED_BLOCK_REF_KEY;
                key.offset = parent;
        } else {
                key.type = BTRFS_TREE_BLOCK_REF_KEY;
                key.offset = root_objectid;
        }

        ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
        btrfs_release_path(root, path);
        return ret;
}

static inline int extent_ref_type(u64 parent, u64 owner)
{
        int type;
        if (owner < BTRFS_FIRST_FREE_OBJECTID) {
                if (parent > 0)
                        type = BTRFS_SHARED_BLOCK_REF_KEY;
                else
                        type = BTRFS_TREE_BLOCK_REF_KEY;
        } else {
                if (parent > 0)
                        type = BTRFS_SHARED_DATA_REF_KEY;
                else
                        type = BTRFS_EXTENT_DATA_REF_KEY;
        }
        return type;
}

static int find_next_key(struct btrfs_path *path, int level,
                         struct btrfs_key *key)

{
        for (; level < BTRFS_MAX_LEVEL; level++) {
                if (!path->nodes[level])
                        break;
                if (path->slots[level] + 1 >=
                    btrfs_header_nritems(path->nodes[level]))
                        continue;
                if (level == 0)
                        btrfs_item_key_to_cpu(path->nodes[level], key,
                                              path->slots[level] + 1);
                else
                        btrfs_node_key_to_cpu(path->nodes[level], key,
                                              path->slots[level] + 1);
                return 0;
        }
        return 1;
}

/*
 * look for inline back ref. if back ref is found, *ref_ret is set
 * to the address of inline back ref, and 0 is returned.
 *
 * if back ref isn't found, *ref_ret is set to the address where it
 * should be inserted, and -ENOENT is returned.
 *
 * if insert is true and there are too many inline back refs, the path
 * points to the extent item, and -EAGAIN is returned.
 *
 * NOTE: inline back refs are ordered in the same way that back ref
 *       items in the tree are ordered.
 */
static noinline_for_stack
int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_extent_inline_ref **ref_ret,
                                 u64 bytenr, u64 num_bytes,
                                 u64 parent, u64 root_objectid,
                                 u64 owner, u64 offset, int insert)
{
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        u64 flags;
        u64 item_size;
        unsigned long ptr;
        unsigned long end;
        int extra_size;
        int type;
        int want;
        int ret;
        int err = 0;

        key.objectid = bytenr;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = num_bytes;

        want = extent_ref_type(parent, owner);
        if (insert) {
                extra_size = btrfs_extent_inline_ref_size(want);
                path->keep_locks = 1;
        } else
                extra_size = -1;
        ret = btrfs_search_slot(trans, root, &key, path, extra_size, 1);
        if (ret < 0) {
                err = ret;
                goto out;
        }
        BUG_ON(ret);

        leaf = path->nodes[0];
        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        if (item_size < sizeof(*ei)) {
                if (!insert) {
                        err = -ENOENT;
                        goto out;
                }
                ret = convert_extent_item_v0(trans, root, path, owner,
                                             extra_size);
                if (ret < 0) {
                        err = ret;
                        goto out;
                }
                leaf = path->nodes[0];
                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
        }
#endif
        BUG_ON(item_size < sizeof(*ei));

        ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        flags = btrfs_extent_flags(leaf, ei);

        ptr = (unsigned long)(ei + 1);
        end = (unsigned long)ei + item_size;

        if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
                ptr += sizeof(struct btrfs_tree_block_info);
                BUG_ON(ptr > end);
        } else {
                BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
        }

        err = -ENOENT;
        while (1) {
                if (ptr >= end) {
                        WARN_ON(ptr > end);
                        break;
                }
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(leaf, iref);
                if (want < type)
                        break;
                if (want > type) {
                        ptr += btrfs_extent_inline_ref_size(type);
                        continue;
                }

                if (type == BTRFS_EXTENT_DATA_REF_KEY) {
                        struct btrfs_extent_data_ref *dref;
                        dref = (struct btrfs_extent_data_ref *)(&iref->offset);
                        if (match_extent_data_ref(leaf, dref, root_objectid,
                                                  owner, offset)) {
                                err = 0;
                                break;
                        }
                        if (hash_extent_data_ref_item(leaf, dref) <
                            hash_extent_data_ref(root_objectid, owner, offset))
                                break;
                } else {
                        u64 ref_offset;
                        ref_offset = btrfs_extent_inline_ref_offset(leaf, iref);
                        if (parent > 0) {
                                if (parent == ref_offset) {
                                        err = 0;
                                        break;
                                }
                                if (ref_offset < parent)
                                        break;
                        } else {
                                if (root_objectid == ref_offset) {
                                        err = 0;
                                        break;
                                }
                                if (ref_offset < root_objectid)
                                        break;
                        }
                }
                ptr += btrfs_extent_inline_ref_size(type);
        }
        if (err == -ENOENT && insert) {
                if (item_size + extra_size >=
                    BTRFS_MAX_EXTENT_ITEM_SIZE(root)) {
                        err = -EAGAIN;
                        goto out;
                }
                /*
                 * To add new inline back ref, we have to make sure
                 * there is no corresponding back ref item.
                 * For simplicity, we just do not add new inline back
                 * ref if there is any kind of item for this block
                 */
                if (find_next_key(path, 0, &key) == 0 &&
                    key.objectid == bytenr &&
                    key.type < BTRFS_BLOCK_GROUP_ITEM_KEY) {
                        err = -EAGAIN;
                        goto out;
                }
        }
        *ref_ret = (struct btrfs_extent_inline_ref *)ptr;
out:
        if (insert) {
                path->keep_locks = 0;
                btrfs_unlock_up_safe(path, 1);
        }
        return err;
}

/*
 * helper to add new inline back ref
 */
static noinline_for_stack
int setup_inline_extent_backref(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_path *path,
                                struct btrfs_extent_inline_ref *iref,
                                u64 parent, u64 root_objectid,
                                u64 owner, u64 offset, int refs_to_add,
                                struct btrfs_delayed_extent_op *extent_op)
{
        struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
        unsigned long ptr;
        unsigned long end;
        unsigned long item_offset;
        u64 refs;
        int size;
        int type;
        int ret;

        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        item_offset = (unsigned long)iref - (unsigned long)ei;

        type = extent_ref_type(parent, owner);
        size = btrfs_extent_inline_ref_size(type);

        ret = btrfs_extend_item(trans, root, path, size);
        BUG_ON(ret);

        ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        refs = btrfs_extent_refs(leaf, ei);
        refs += refs_to_add;
        btrfs_set_extent_refs(leaf, ei, refs);
        if (extent_op)
                __run_delayed_extent_op(extent_op, leaf, ei);

        ptr = (unsigned long)ei + item_offset;
        end = (unsigned long)ei + btrfs_item_size_nr(leaf, path->slots[0]);
        if (ptr < end - size)
                memmove_extent_buffer(leaf, ptr + size, ptr,
                                      end - size - ptr);

        iref = (struct btrfs_extent_inline_ref *)ptr;
        btrfs_set_extent_inline_ref_type(leaf, iref, type);
        if (type == BTRFS_EXTENT_DATA_REF_KEY) {
                struct btrfs_extent_data_ref *dref;
                dref = (struct btrfs_extent_data_ref *)(&iref->offset);
                btrfs_set_extent_data_ref_root(leaf, dref, root_objectid);
                btrfs_set_extent_data_ref_objectid(leaf, dref, owner);
                btrfs_set_extent_data_ref_offset(leaf, dref, offset);
                btrfs_set_extent_data_ref_count(leaf, dref, refs_to_add);
        } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
                struct btrfs_shared_data_ref *sref;
                sref = (struct btrfs_shared_data_ref *)(iref + 1);
                btrfs_set_shared_data_ref_count(leaf, sref, refs_to_add);
                btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
        } else if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
                btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
        } else {
                btrfs_set_extent_inline_ref_offset(leaf, iref, root_objectid);
        }
        btrfs_mark_buffer_dirty(leaf);
        return 0;
}

static int lookup_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_extent_inline_ref **ref_ret,
                                 u64 bytenr, u64 num_bytes, u64 parent,
                                 u64 root_objectid, u64 owner, u64 offset)
{
        int ret;

        ret = lookup_inline_extent_backref(trans, root, path, ref_ret,
                                           bytenr, num_bytes, parent,
                                           root_objectid, owner, offset, 0);
        if (ret != -ENOENT)
                return ret;

        btrfs_release_path(root, path);
        *ref_ret = NULL;

        if (owner < BTRFS_FIRST_FREE_OBJECTID) {
                ret = lookup_tree_block_ref(trans, root, path, bytenr, parent,
                                            root_objectid);
        } else {
                ret = lookup_extent_data_ref(trans, root, path, bytenr, parent,
                                             root_objectid, owner, offset);
        }
        return ret;
}

/*
 * helper to update/remove inline back ref
 */
static noinline_for_stack
int update_inline_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_extent_inline_ref *iref,
                                 int refs_to_mod,
                                 struct btrfs_delayed_extent_op *extent_op)
{
        struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
        struct btrfs_extent_data_ref *dref = NULL;
        struct btrfs_shared_data_ref *sref = NULL;
        unsigned long ptr;
        unsigned long end;
        u32 item_size;
        int size;
        int type;
        int ret;
        u64 refs;

        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        refs = btrfs_extent_refs(leaf, ei);
        WARN_ON(refs_to_mod < 0 && refs + refs_to_mod <= 0);
        refs += refs_to_mod;
        btrfs_set_extent_refs(leaf, ei, refs);
        if (extent_op)
                __run_delayed_extent_op(extent_op, leaf, ei);

        type = btrfs_extent_inline_ref_type(leaf, iref);

        if (type == BTRFS_EXTENT_DATA_REF_KEY) {
                dref = (struct btrfs_extent_data_ref *)(&iref->offset);
                refs = btrfs_extent_data_ref_count(leaf, dref);
        } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
                sref = (struct btrfs_shared_data_ref *)(iref + 1);
                refs = btrfs_shared_data_ref_count(leaf, sref);
        } else {
                refs = 1;
                BUG_ON(refs_to_mod != -1);
        }

        BUG_ON(refs_to_mod < 0 && refs < -refs_to_mod);
        refs += refs_to_mod;

        if (refs > 0) {
                if (type == BTRFS_EXTENT_DATA_REF_KEY)
                        btrfs_set_extent_data_ref_count(leaf, dref, refs);
                else
                        btrfs_set_shared_data_ref_count(leaf, sref, refs);
        } else {
                size =  btrfs_extent_inline_ref_size(type);
                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
                ptr = (unsigned long)iref;
                end = (unsigned long)ei + item_size;
                if (ptr + size < end)
                        memmove_extent_buffer(leaf, ptr, ptr + size,
                                              end - ptr - size);
                item_size -= size;
                ret = btrfs_truncate_item(trans, root, path, item_size, 1);
                BUG_ON(ret);
        }
        btrfs_mark_buffer_dirty(leaf);
        return 0;
}

static noinline_for_stack
int insert_inline_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 u64 bytenr, u64 num_bytes, u64 parent,
                                 u64 root_objectid, u64 owner,
                                 u64 offset, int refs_to_add,
                                 struct btrfs_delayed_extent_op *extent_op)
{
        struct btrfs_extent_inline_ref *iref;
        int ret;

        ret = lookup_inline_extent_backref(trans, root, path, &iref,
                                           bytenr, num_bytes, parent,
                                           root_objectid, owner, offset, 1);
        if (ret == 0) {
                BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID);
                ret = update_inline_extent_backref(trans, root, path, iref,
                                                   refs_to_add, extent_op);
        } else if (ret == -ENOENT) {
                ret = setup_inline_extent_backref(trans, root, path, iref,
                                                  parent, root_objectid,
                                                  owner, offset, refs_to_add,
                                                  extent_op);
        }
        return ret;
}

static int insert_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 u64 bytenr, u64 parent, u64 root_objectid,
                                 u64 owner, u64 offset, int refs_to_add)
{
        int ret;
        if (owner < BTRFS_FIRST_FREE_OBJECTID) {
                BUG_ON(refs_to_add != 1);
                ret = insert_tree_block_ref(trans, root, path, bytenr,
                                            parent, root_objectid);
        } else {
                ret = insert_extent_data_ref(trans, root, path, bytenr,
                                             parent, root_objectid,
                                             owner, offset, refs_to_add);
        }
        return ret;
}

static int remove_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_extent_inline_ref *iref,
                                 int refs_to_drop, int is_data)
{
        int ret;

        BUG_ON(!is_data && refs_to_drop != 1);
        if (iref) {
                ret = update_inline_extent_backref(trans, root, path, iref,
                                                   -refs_to_drop, NULL);
        } else if (is_data) {
                ret = remove_extent_data_ref(trans, root, path, refs_to_drop);
        } else {
                ret = btrfs_del_item(trans, root, path);
        }
        return ret;
}

#ifdef BIO_RW_DISCARD
static void btrfs_issue_discard(struct block_device *bdev,
                                u64 start, u64 len)
{
        blkdev_issue_discard(bdev, start >> 9, len >> 9, GFP_KERNEL);
}
#endif

static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
                                u64 num_bytes)
{
#ifdef BIO_RW_DISCARD
        int ret;
        u64 map_length = num_bytes;
        struct btrfs_multi_bio *multi = NULL;

        /* Tell the block device(s) that the sectors can be discarded */
        ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
                              bytenr, &map_length, &multi, 0);
        if (!ret) {
                struct btrfs_bio_stripe *stripe = multi->stripes;
                int i;

                if (map_length > num_bytes)
                        map_length = num_bytes;

                for (i = 0; i < multi->num_stripes; i++, stripe++) {
                        btrfs_issue_discard(stripe->dev->bdev,
                                            stripe->physical,
                                            map_length);
                }
                kfree(multi);
        }

        return ret;
#else
        return 0;
#endif
}

int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         u64 bytenr, u64 num_bytes, u64 parent,
                         u64 root_objectid, u64 owner, u64 offset)
{
        int ret;
        BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID &&
               root_objectid == BTRFS_TREE_LOG_OBJECTID);

        if (owner < BTRFS_FIRST_FREE_OBJECTID) {
                ret = btrfs_add_delayed_tree_ref(trans, bytenr, num_bytes,
                                        parent, root_objectid, (int)owner,
                                        BTRFS_ADD_DELAYED_REF, NULL);
        } else {
                ret = btrfs_add_delayed_data_ref(trans, bytenr, num_bytes,
                                        parent, root_objectid, owner, offset,
                                        BTRFS_ADD_DELAYED_REF, NULL);
        }
        return ret;
}

static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root,
                                  u64 bytenr, u64 num_bytes,
                                  u64 parent, u64 root_objectid,
                                  u64 owner, u64 offset, int refs_to_add,
                                  struct btrfs_delayed_extent_op *extent_op)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_extent_item *item;
        u64 refs;
        int ret;
        int err = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->reada = 1;
        path->leave_spinning = 1;
        /* this will setup the path even if it fails to insert the back ref */
        ret = insert_inline_extent_backref(trans, root->fs_info->extent_root,
                                           path, bytenr, num_bytes, parent,
                                           root_objectid, owner, offset,
                                           refs_to_add, extent_op);
        if (ret == 0)
                goto out;

        if (ret != -EAGAIN) {
                err = ret;
                goto out;
        }

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        refs = btrfs_extent_refs(leaf, item);
        btrfs_set_extent_refs(leaf, item, refs + refs_to_add);
        if (extent_op)
                __run_delayed_extent_op(extent_op, leaf, item);

        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(root->fs_info->extent_root, path);

        path->reada = 1;
        path->leave_spinning = 1;

        /* now insert the actual backref */
        ret = insert_extent_backref(trans, root->fs_info->extent_root,
                                    path, bytenr, parent, root_objectid,
                                    owner, offset, refs_to_add);
        BUG_ON(ret);
out:
        btrfs_free_path(path);
        return err;
}

static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_delayed_ref_node *node,
                                struct btrfs_delayed_extent_op *extent_op,
                                int insert_reserved)
{
        int ret = 0;
        struct btrfs_delayed_data_ref *ref;
        struct btrfs_key ins;
        u64 parent = 0;
        u64 ref_root = 0;
        u64 flags = 0;

        ins.objectid = node->bytenr;
        ins.offset = node->num_bytes;
        ins.type = BTRFS_EXTENT_ITEM_KEY;

        ref = btrfs_delayed_node_to_data_ref(node);
        if (node->type == BTRFS_SHARED_DATA_REF_KEY)
                parent = ref->parent;
        else
                ref_root = ref->root;

        if (node->action == BTRFS_ADD_DELAYED_REF && insert_reserved) {
                if (extent_op) {
                        BUG_ON(extent_op->update_key);
                        flags |= extent_op->flags_to_set;
                }
                ret = alloc_reserved_file_extent(trans, root,
                                                 parent, ref_root, flags,
                                                 ref->objectid, ref->offset,
                                                 &ins, node->ref_mod);
        } else if (node->action == BTRFS_ADD_DELAYED_REF) {
                ret = __btrfs_inc_extent_ref(trans, root, node->bytenr,
                                             node->num_bytes, parent,
                                             ref_root, ref->objectid,
                                             ref->offset, node->ref_mod,
                                             extent_op);
        } else if (node->action == BTRFS_DROP_DELAYED_REF) {
                ret = __btrfs_free_extent(trans, root, node->bytenr,
                                          node->num_bytes, parent,
                                          ref_root, ref->objectid,
                                          ref->offset, node->ref_mod,
                                          extent_op);
        } else {
                BUG();
        }
        return ret;
}

static void __run_delayed_extent_op(struct btrfs_delayed_extent_op *extent_op,
                                    struct extent_buffer *leaf,
                                    struct btrfs_extent_item *ei)
{
        u64 flags = btrfs_extent_flags(leaf, ei);
        if (extent_op->update_flags) {
                flags |= extent_op->flags_to_set;
                btrfs_set_extent_flags(leaf, ei, flags);
        }

        if (extent_op->update_key) {
                struct btrfs_tree_block_info *bi;
                BUG_ON(!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK));
                bi = (struct btrfs_tree_block_info *)(ei + 1);
                btrfs_set_tree_block_key(leaf, bi, &extent_op->key);
        }
}

static int run_delayed_extent_op(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_delayed_ref_node *node,
                                 struct btrfs_delayed_extent_op *extent_op)
{
        struct btrfs_key key;
        struct btrfs_path *path;
        struct btrfs_extent_item *ei;
        struct extent_buffer *leaf;
        u32 item_size;
        int ret;
        int err = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        key.objectid = node->bytenr;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = node->num_bytes;

        path->reada = 1;
        path->leave_spinning = 1;
        ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key,
                                path, 0, 1);
        if (ret < 0) {
                err = ret;
                goto out;
        }
        if (ret > 0) {
                err = -EIO;
                goto out;
        }

        leaf = path->nodes[0];
        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        if (item_size < sizeof(*ei)) {
                ret = convert_extent_item_v0(trans, root->fs_info->extent_root,
                                             path, (u64)-1, 0);
                if (ret < 0) {
                        err = ret;
                        goto out;
                }
                leaf = path->nodes[0];
                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
        }
#endif
        BUG_ON(item_size < sizeof(*ei));
        ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
        __run_delayed_extent_op(extent_op, leaf, ei);

        btrfs_mark_buffer_dirty(leaf);
out:
        btrfs_free_path(path);
        return err;
}

static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_delayed_ref_node *node,
                                struct btrfs_delayed_extent_op *extent_op,
                                int insert_reserved)
{
        int ret = 0;
        struct btrfs_delayed_tree_ref *ref;
        struct btrfs_key ins;
        u64 parent = 0;
        u64 ref_root = 0;

        ins.objectid = node->bytenr;
        ins.offset = node->num_bytes;
        ins.type = BTRFS_EXTENT_ITEM_KEY;

        ref = btrfs_delayed_node_to_tree_ref(node);
        if (node->type == BTRFS_SHARED_BLOCK_REF_KEY)
                parent = ref->parent;
        else
                ref_root = ref->root;

        BUG_ON(node->ref_mod != 1);
        if (node->action == BTRFS_ADD_DELAYED_REF && insert_reserved) {
                BUG_ON(!extent_op || !extent_op->update_flags ||
                       !extent_op->update_key);
                ret = alloc_reserved_tree_block(trans, root,
                                                parent, ref_root,
                                                extent_op->flags_to_set,
                                                &extent_op->key,
                                                ref->level, &ins);
        } else if (node->action == BTRFS_ADD_DELAYED_REF) {
                ret = __btrfs_inc_extent_ref(trans, root, node->bytenr,
                                             node->num_bytes, parent, ref_root,
                                             ref->level, 0, 1, extent_op);
        } else if (node->action == BTRFS_DROP_DELAYED_REF) {
                ret = __btrfs_free_extent(trans, root, node->bytenr,
                                          node->num_bytes, parent, ref_root,
                                          ref->level, 0, 1, extent_op);
        } else {
                BUG();
        }
        return ret;
}


/* helper function to actually process a single delayed ref entry */
static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct btrfs_delayed_ref_node *node,
                               struct btrfs_delayed_extent_op *extent_op,
                               int insert_reserved)
{
        int ret;
        if (btrfs_delayed_ref_is_head(node)) {
                struct btrfs_delayed_ref_head *head;
                /*
                 * we've hit the end of the chain and we were supposed
                 * to insert this extent into the tree.  But, it got
                 * deleted before we ever needed to insert it, so all
                 * we have to do is clean up the accounting
                 */
                BUG_ON(extent_op);
                head = btrfs_delayed_node_to_head(node);
                if (insert_reserved) {
                        int mark_free = 0;
                        struct extent_buffer *must_clean = NULL;

                        ret = pin_down_bytes(trans, root, NULL,
                                             node->bytenr, node->num_bytes,
                                             head->is_data, 1, &must_clean);
                        if (ret > 0)
                                mark_free = 1;

                        if (must_clean) {
                                clean_tree_block(NULL, root, must_clean);
                                btrfs_tree_unlock(must_clean);
                                free_extent_buffer(must_clean);
                        }
                        if (head->is_data) {
                                ret = btrfs_del_csums(trans, root,
                                                      node->bytenr,
                                                      node->num_bytes);
                                BUG_ON(ret);
                        }
                        if (mark_free) {
                                ret = btrfs_free_reserved_extent(root,
                                                        node->bytenr,
                                                        node->num_bytes);
                                BUG_ON(ret);
                        }
                }
                mutex_unlock(&head->mutex);
                return 0;
        }

        if (node->type == BTRFS_TREE_BLOCK_REF_KEY ||
            node->type == BTRFS_SHARED_BLOCK_REF_KEY)
                ret = run_delayed_tree_ref(trans, root, node, extent_op,
                                           insert_reserved);
        else if (node->type == BTRFS_EXTENT_DATA_REF_KEY ||
                 node->type == BTRFS_SHARED_DATA_REF_KEY)
                ret = run_delayed_data_ref(trans, root, node, extent_op,
                                           insert_reserved);
        else
                BUG();
        return ret;
}

static noinline struct btrfs_delayed_ref_node *
select_delayed_ref(struct btrfs_delayed_ref_head *head)
{
        struct rb_node *node;
        struct btrfs_delayed_ref_node *ref;
        int action = BTRFS_ADD_DELAYED_REF;
again:
        /*
         * select delayed ref of type BTRFS_ADD_DELAYED_REF first.
         * this prevents ref count from going down to zero when
         * there still are pending delayed ref.
         */
        node = rb_prev(&head->node.rb_node);
        while (1) {
                if (!node)
                        break;
                ref = rb_entry(node, struct btrfs_delayed_ref_node,
                                rb_node);
                if (ref->bytenr != head->node.bytenr)
                        break;
                if (ref->action == action)
                        return ref;
                node = rb_prev(node);
        }
        if (action == BTRFS_ADD_DELAYED_REF) {
                action = BTRFS_DROP_DELAYED_REF;
                goto again;
        }
        return NULL;
}

static noinline int run_clustered_refs(struct btrfs_trans_handle *trans,
                                       struct btrfs_root *root,
                                       struct list_head *cluster)
{
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_delayed_ref_node *ref;
        struct btrfs_delayed_ref_head *locked_ref = NULL;
        struct btrfs_delayed_extent_op *extent_op;
        int ret;
        int count = 0;
        int must_insert_reserved = 0;

        delayed_refs = &trans->transaction->delayed_refs;
        while (1) {
                if (!locked_ref) {
                        /* pick a new head ref from the cluster list */
                        if (list_empty(cluster))
                                break;

                        locked_ref = list_entry(cluster->next,
                                     struct btrfs_delayed_ref_head, cluster);

                        /* grab the lock that says we are going to process
                         * all the refs for this head */
                        ret = btrfs_delayed_ref_lock(trans, locked_ref);

                        /*
                         * we may have dropped the spin lock to get the head
                         * mutex lock, and that might have given someone else
                         * time to free the head.  If that's true, it has been
                         * removed from our list and we can move on.
                         */
                        if (ret == -EAGAIN) {
                                locked_ref = NULL;
                                count++;
                                continue;
                        }
                }

                /*
                 * record the must insert reserved flag before we
                 * drop the spin lock.
                 */
                must_insert_reserved = locked_ref->must_insert_reserved;
                locked_ref->must_insert_reserved = 0;

                extent_op = locked_ref->extent_op;
                locked_ref->extent_op = NULL;

                /*
                 * locked_ref is the head node, so we have to go one
                 * node back for any delayed ref updates
                 */
                ref = select_delayed_ref(locked_ref);
                if (!ref) {
                        /* All delayed refs have been processed, Go ahead
                         * and send the head node to run_one_delayed_ref,
                         * so that any accounting fixes can happen
                         */
                        ref = &locked_ref->node;

                        if (extent_op && must_insert_reserved) {
                                kfree(extent_op);
                                extent_op = NULL;
                        }

                        if (extent_op) {
                                spin_unlock(&delayed_refs->lock);

                                ret = run_delayed_extent_op(trans, root,
                                                            ref, extent_op);
                                BUG_ON(ret);
                                kfree(extent_op);

                                cond_resched();
                                spin_lock(&delayed_refs->lock);
                                continue;
                        }

                        list_del_init(&locked_ref->cluster);
                        locked_ref = NULL;
                }

                ref->in_tree = 0;
                rb_erase(&ref->rb_node, &delayed_refs->root);
                delayed_refs->num_entries--;

                spin_unlock(&delayed_refs->lock);

                ret = run_one_delayed_ref(trans, root, ref, extent_op,
                                          must_insert_reserved);
                BUG_ON(ret);

                btrfs_put_delayed_ref(ref);
                kfree(extent_op);
                count++;

                cond_resched();
                spin_lock(&delayed_refs->lock);
        }
        return count;
}

/*
 * this starts processing the delayed reference count updates and
 * extent insertions we have queued up so far.  count can be
 * 0, which means to process everything in the tree at the start
 * of the run (but not newly added entries), or it can be some target
 * number you'd like to process.
 */
int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root, unsigned long count)
{
        struct rb_node *node;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_delayed_ref_node *ref;
        struct list_head cluster;
        int ret;
        int run_all = count == (unsigned long)-1;
        int run_most = 0;

        if (root == root->fs_info->extent_root)
                root = root->fs_info->tree_root;

        delayed_refs = &trans->transaction->delayed_refs;
        INIT_LIST_HEAD(&cluster);
again:
        spin_lock(&delayed_refs->lock);
        if (count == 0) {
                count = delayed_refs->num_entries * 2;
                run_most = 1;
        }
        while (1) {
                if (!(run_all || run_most) &&
                    delayed_refs->num_heads_ready < 64)
                        break;

                /*
                 * go find something we can process in the rbtree.  We start at
                 * the beginning of the tree, and then build a cluster
                 * of refs to process starting at the first one we are able to
                 * lock
                 */
                ret = btrfs_find_ref_cluster(trans, &cluster,
                                             delayed_refs->run_delayed_start);
                if (ret)
                        break;

                ret = run_clustered_refs(trans, root, &cluster);
                BUG_ON(ret < 0);

                count -= min_t(unsigned long, ret, count);

                if (count == 0)
                        break;
        }

        if (run_all) {
                node = rb_first(&delayed_refs->root);
                if (!node)
                        goto out;
                count = (unsigned long)-1;

                while (node) {
                        ref = rb_entry(node, struct btrfs_delayed_ref_node,
                                       rb_node);
                        if (btrfs_delayed_ref_is_head(ref)) {
                                struct btrfs_delayed_ref_head *head;

                                head = btrfs_delayed_node_to_head(ref);
                                atomic_inc(&ref->refs);

                                spin_unlock(&delayed_refs->lock);
                                mutex_lock(&head->mutex);
                                mutex_unlock(&head->mutex);

                                btrfs_put_delayed_ref(ref);
                                cond_resched();
                                goto again;
                        }
                        node = rb_next(node);
                }
                spin_unlock(&delayed_refs->lock);
                schedule_timeout(1);
                goto again;
        }
out:
        spin_unlock(&delayed_refs->lock);
        return 0;
}

int btrfs_set_disk_extent_flags(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                u64 bytenr, u64 num_bytes, u64 flags,
                                int is_data)
{
        struct btrfs_delayed_extent_op *extent_op;
        int ret;

        extent_op = kmalloc(sizeof(*extent_op), GFP_NOFS);
        if (!extent_op)
                return -ENOMEM;

        extent_op->flags_to_set = flags;
        extent_op->update_flags = 1;
        extent_op->update_key = 0;
        extent_op->is_data = is_data ? 1 : 0;

        ret = btrfs_add_delayed_extent_op(trans, bytenr, num_bytes, extent_op);
        if (ret)
                kfree(extent_op);
        return ret;
}

static noinline int check_delayed_ref(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root,
                                      struct btrfs_path *path,
                                      u64 objectid, u64 offset, u64 bytenr)
{
        struct btrfs_delayed_ref_head *head;
        struct btrfs_delayed_ref_node *ref;
        struct btrfs_delayed_data_ref *data_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct rb_node *node;
        int ret = 0;

        ret = -ENOENT;
        delayed_refs = &trans->transaction->delayed_refs;
        spin_lock(&delayed_refs->lock);
        head = btrfs_find_delayed_ref_head(trans, bytenr);
        if (!head)
                goto out;

        if (!mutex_trylock(&head->mutex)) {
                atomic_inc(&head->node.refs);
                spin_unlock(&delayed_refs->lock);

                btrfs_release_path(root->fs_info->extent_root, path);

                mutex_lock(&head->mutex);
                mutex_unlock(&head->mutex);
                btrfs_put_delayed_ref(&head->node);
                return -EAGAIN;
        }

        node = rb_prev(&head->node.rb_node);
        if (!node)
                goto out_unlock;

        ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);

        if (ref->bytenr != bytenr)
                goto out_unlock;

        ret = 1;
        if (ref->type != BTRFS_EXTENT_DATA_REF_KEY)
                goto out_unlock;

        data_ref = btrfs_delayed_node_to_data_ref(ref);

        node = rb_prev(node);
        if (node) {
                ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
                if (ref->bytenr == bytenr)
                        goto out_unlock;
        }

        if (data_ref->root != root->root_key.objectid ||
            data_ref->objectid != objectid || data_ref->offset != offset)
                goto out_unlock;

        ret = 0;
out_unlock:
        mutex_unlock(&head->mutex);
out:
        spin_unlock(&delayed_refs->lock);
        return ret;
}

static noinline int check_committed_ref(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_path *path,
                                        u64 objectid, u64 offset, u64 bytenr)
{
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct extent_buffer *leaf;
        struct btrfs_extent_data_ref *ref;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_extent_item *ei;
        struct btrfs_key key;
        u32 item_size;
        int ret;

        key.objectid = bytenr;
        key.offset = (u64)-1;
        key.type = BTRFS_EXTENT_ITEM_KEY;

        ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        BUG_ON(ret == 0);

        ret = -ENOENT;
        if (path->slots[0] == 0)
                goto out;

        path->slots[0]--;
        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

        if (key.objectid != bytenr || key.type != BTRFS_EXTENT_ITEM_KEY)
                goto out;

        ret = 1;
        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        if (item_size < sizeof(*ei)) {
                WARN_ON(item_size != sizeof(struct btrfs_extent_item_v0));
                goto out;
        }
#endif
        ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);

        if (item_size != sizeof(*ei) +
            btrfs_extent_inline_ref_size(BTRFS_EXTENT_DATA_REF_KEY))
                goto out;

        if (btrfs_extent_generation(leaf, ei) <=
            btrfs_root_last_snapshot(&root->root_item))
                goto out;

        iref = (struct btrfs_extent_inline_ref *)(ei + 1);
        if (btrfs_extent_inline_ref_type(leaf, iref) !=
            BTRFS_EXTENT_DATA_REF_KEY)
                goto out;

        ref = (struct btrfs_extent_data_ref *)(&iref->offset);
        if (btrfs_extent_refs(leaf, ei) !=
            btrfs_extent_data_ref_count(leaf, ref) ||
            btrfs_extent_data_ref_root(leaf, ref) !=
            root->root_key.objectid ||
            btrfs_extent_data_ref_objectid(leaf, ref) != objectid ||
            btrfs_extent_data_ref_offset(leaf, ref) != offset)
                goto out;

        ret = 0;
out:
        return ret;
}

int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root,
                          u64 objectid, u64 offset, u64 bytenr)
{
        struct btrfs_path *path;
        int ret;
        int ret2;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOENT;

        do {
                ret = check_committed_ref(trans, root, path, objectid,
                                          offset, bytenr);
                if (ret && ret != -ENOENT)
                        goto out;

                ret2 = check_delayed_ref(trans, root, path, objectid,
                                         offset, bytenr);
        } while (ret2 == -EAGAIN);

        if (ret2 && ret2 != -ENOENT) {
                ret = ret2;
                goto out;
        }

        if (ret != -ENOENT || ret2 != -ENOENT)
                ret = 0;
out:
        btrfs_free_path(path);
        return ret;
}

#if 0
int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                    struct extent_buffer *buf, u32 nr_extents)
{
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        u64 root_gen;
        u32 nritems;
        int i;
        int level;
        int ret = 0;
        int shared = 0;

        if (!root->ref_cows)
                return 0;

        if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
                shared = 0;
                root_gen = root->root_key.offset;
        } else {
                shared = 1;
                root_gen = trans->transid - 1;
        }

        level = btrfs_header_level(buf);
        nritems = btrfs_header_nritems(buf);

        if (level == 0) {
                struct btrfs_leaf_ref *ref;
                struct btrfs_extent_info *info;

                ref = btrfs_alloc_leaf_ref(root, nr_extents);
                if (!ref) {
                        ret = -ENOMEM;
                        goto out;
                }

                ref->root_gen = root_gen;
                ref->bytenr = buf->start;
                ref->owner = btrfs_header_owner(buf);
                ref->generation = btrfs_header_generation(buf);
                ref->nritems = nr_extents;
                info = ref->extents;

                for (i = 0; nr_extents > 0 && i < nritems; i++) {
                        u64 disk_bytenr;
                        btrfs_item_key_to_cpu(buf, &key, i);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
                        fi = btrfs_item_ptr(buf, i,
                                            struct btrfs_file_extent_item);
                        if (btrfs_file_extent_type(buf, fi) ==
                            BTRFS_FILE_EXTENT_INLINE)
                                continue;
                        disk_bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
                        if (disk_bytenr == 0)
                                continue;

                        info->bytenr = disk_bytenr;
                        info->num_bytes =
                                btrfs_file_extent_disk_num_bytes(buf, fi);
                        info->objectid = key.objectid;
                        info->offset = key.offset;
                        info++;
                }

                ret = btrfs_add_leaf_ref(root, ref, shared);
                if (ret == -EEXIST && shared) {
                        struct btrfs_leaf_ref *old;
                        old = btrfs_lookup_leaf_ref(root, ref->bytenr);
                        BUG_ON(!old);
                        btrfs_remove_leaf_ref(root, old);
                        btrfs_free_leaf_ref(root, old);
                        ret = btrfs_add_leaf_ref(root, ref, shared);
                }
                WARN_ON(ret);
                btrfs_free_leaf_ref(root, ref);
        }
out:
        return ret;
}

/* when a block goes through cow, we update the reference counts of
 * everything that block points to.  The internal pointers of the block
 * can be in just about any order, and it is likely to have clusters of
 * things that are close together and clusters of things that are not.
 *
 * To help reduce the seeks that come with updating all of these reference
 * counts, sort them by byte number before actual updates are done.
 *
 * struct refsort is used to match byte number to slot in the btree block.
 * we sort based on the byte number and then use the slot to actually
 * find the item.
 *
 * struct refsort is smaller than strcut btrfs_item and smaller than
 * struct btrfs_key_ptr.  Since we're currently limited to the page size
 * for a btree block, there's no way for a kmalloc of refsorts for a
 * single node to be bigger than a page.
 */
struct refsort {
        u64 bytenr;
        u32 slot;
};

/*
 * for passing into sort()
 */
static int refsort_cmp(const void *a_void, const void *b_void)
{
        const struct refsort *a = a_void;
        const struct refsort *b = b_void;

        if (a->bytenr < b->bytenr)
                return -1;
        if (a->bytenr > b->bytenr)
                return 1;
        return 0;
}
#endif

static int __btrfs_mod_ref(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root,
                           struct extent_buffer *buf,
                           int full_backref, int inc)
{
        u64 bytenr;
        u64 num_bytes;
        u64 parent;
        u64 ref_root;
        u32 nritems;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int level;
        int ret = 0;
        int (*process_func)(struct btrfs_trans_handle *, struct btrfs_root *,
                            u64, u64, u64, u64, u64, u64);

        ref_root = btrfs_header_owner(buf);
        nritems = btrfs_header_nritems(buf);
        level = btrfs_header_level(buf);

        if (!root->ref_cows && level == 0)
                return 0;

        if (inc)
                process_func = btrfs_inc_extent_ref;
        else
                process_func = btrfs_free_extent;

        if (full_backref)
                parent = buf->start;
        else
                parent = 0;

        for (i = 0; i < nritems; i++) {
                if (level == 0) {
                        btrfs_item_key_to_cpu(buf, &key, i);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
                        fi = btrfs_item_ptr(buf, i,
                                            struct btrfs_file_extent_item);
                        if (btrfs_file_extent_type(buf, fi) ==
                            BTRFS_FILE_EXTENT_INLINE)
                                continue;
                        bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
                        if (bytenr == 0)
                                continue;

                        num_bytes = btrfs_file_extent_disk_num_bytes(buf, fi);
                        key.offset -= btrfs_file_extent_offset(buf, fi);
                        ret = process_func(trans, root, bytenr, num_bytes,
                                           parent, ref_root, key.objectid,
                                           key.offset);
                        if (ret)
                                goto fail;
                } else {
                        bytenr = btrfs_node_blockptr(buf, i);
                        num_bytes = btrfs_level_size(root, level - 1);
                        ret = process_func(trans, root, bytenr, num_bytes,
                                           parent, ref_root, level - 1, 0);
                        if (ret)
                                goto fail;
                }
        }
        return 0;
fail:
        BUG();
        return ret;
}

int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                  struct extent_buffer *buf, int full_backref)
{
        return __btrfs_mod_ref(trans, root, buf, full_backref, 1);
}

int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                  struct extent_buffer *buf, int full_backref)
{
        return __btrfs_mod_ref(trans, root, buf, full_backref, 0);
}

static int write_one_cache_group(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_block_group_cache *cache)
{
        int ret;
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        unsigned long bi;
        struct extent_buffer *leaf;

        ret = btrfs_search_slot(trans, extent_root, &cache->key, path, 0, 1);
        if (ret < 0)
                goto fail;
        BUG_ON(ret);

        leaf = path->nodes[0];
        bi = btrfs_item_ptr_offset(leaf, path->slots[0]);
        write_extent_buffer(leaf, &cache->item, bi, sizeof(cache->item));
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(extent_root, path);
fail:
        if (ret)
                return ret;
        return 0;

}

static struct btrfs_block_group_cache *
next_block_group(struct btrfs_root *root,
                 struct btrfs_block_group_cache *cache)
{
        struct rb_node *node;
        spin_lock(&root->fs_info->block_group_cache_lock);
        node = rb_next(&cache->cache_node);
        btrfs_put_block_group(cache);
        if (node) {
                cache = rb_entry(node, struct btrfs_block_group_cache,
                                 cache_node);
                atomic_inc(&cache->count);
        } else
                cache = NULL;
        spin_unlock(&root->fs_info->block_group_cache_lock);
        return cache;
}

int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root)
{
        struct btrfs_block_group_cache *cache;
        int err = 0;
        struct btrfs_path *path;
        u64 last = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        while (1) {
                if (last == 0) {
                        err = btrfs_run_delayed_refs(trans, root,
                                                     (unsigned long)-1);
                        BUG_ON(err);
                }

                cache = btrfs_lookup_first_block_group(root->fs_info, last);
                while (cache) {
                        if (cache->dirty)
                                break;
                        cache = next_block_group(root, cache);
                }
                if (!cache) {
                        if (last == 0)
                                break;
                        last = 0;
                        continue;
                }

                cache->dirty = 0;
                last = cache->key.objectid + cache->key.offset;

                err = write_one_cache_group(trans, root, path, cache);
                BUG_ON(err);
                btrfs_put_block_group(cache);
        }

        btrfs_free_path(path);
        return 0;
}

int btrfs_extent_readonly(struct btrfs_root *root, u64 bytenr)
{
        struct btrfs_block_group_cache *block_group;
        int readonly = 0;

        block_group = btrfs_lookup_block_group(root->fs_info, bytenr);
        if (!block_group || block_group->ro)
                readonly = 1;
        if (block_group)
                btrfs_put_block_group(block_group);
        return readonly;
}

static int update_space_info(struct btrfs_fs_info *info, u64 flags,
                             u64 total_bytes, u64 bytes_used,
                             struct btrfs_space_info **space_info)
{
        struct btrfs_space_info *found;

        found = __find_space_info(info, flags);
        if (found) {
                spin_lock(&found->lock);
                found->total_bytes += total_bytes;
                found->bytes_used += bytes_used;
                found->full = 0;
                spin_unlock(&found->lock);
                *space_info = found;
                return 0;
        }
        found = kzalloc(sizeof(*found), GFP_NOFS);
        if (!found)
                return -ENOMEM;

        INIT_LIST_HEAD(&found->block_groups);
        init_rwsem(&found->groups_sem);
        spin_lock_init(&found->lock);
        found->flags = flags;
        found->total_bytes = total_bytes;
        found->bytes_used = bytes_used;
        found->bytes_pinned = 0;
        found->bytes_reserved = 0;
        found->bytes_readonly = 0;
        found->bytes_delalloc = 0;
        found->full = 0;
        found->force_alloc = 0;
        *space_info = found;
        list_add_rcu(&found->list, &info->space_info);
        atomic_set(&found->caching_threads, 0);
        return 0;
}

static void set_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
{
        u64 extra_flags = flags & (BTRFS_BLOCK_GROUP_RAID0 |
                                   BTRFS_BLOCK_GROUP_RAID1 |
                                   BTRFS_BLOCK_GROUP_RAID10 |
                                   BTRFS_BLOCK_GROUP_DUP);
        if (extra_flags) {
                if (flags & BTRFS_BLOCK_GROUP_DATA)
                        fs_info->avail_data_alloc_bits |= extra_flags;
                if (flags & BTRFS_BLOCK_GROUP_METADATA)
                        fs_info->avail_metadata_alloc_bits |= extra_flags;
                if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
                        fs_info->avail_system_alloc_bits |= extra_flags;
        }
}

static void set_block_group_readonly(struct btrfs_block_group_cache *cache)
{
        spin_lock(&cache->space_info->lock);
        spin_lock(&cache->lock);
        if (!cache->ro) {
                cache->space_info->bytes_readonly += cache->key.offset -
                                        btrfs_block_group_used(&cache->item);
                cache->ro = 1;
        }
        spin_unlock(&cache->lock);
        spin_unlock(&cache->space_info->lock);
}

u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags)
{
        u64 num_devices = root->fs_info->fs_devices->rw_devices;

        if (num_devices == 1)
                flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0);
        if (num_devices < 4)
                flags &= ~BTRFS_BLOCK_GROUP_RAID10;

        if ((flags & BTRFS_BLOCK_GROUP_DUP) &&
            (flags & (BTRFS_BLOCK_GROUP_RAID1 |
                      BTRFS_BLOCK_GROUP_RAID10))) {
                flags &= ~BTRFS_BLOCK_GROUP_DUP;
        }

        if ((flags & BTRFS_BLOCK_GROUP_RAID1) &&
            (flags & BTRFS_BLOCK_GROUP_RAID10)) {
                flags &= ~BTRFS_BLOCK_GROUP_RAID1;
        }

        if ((flags & BTRFS_BLOCK_GROUP_RAID0) &&
            ((flags & BTRFS_BLOCK_GROUP_RAID1) |
             (flags & BTRFS_BLOCK_GROUP_RAID10) |
             (flags & BTRFS_BLOCK_GROUP_DUP)))
                flags &= ~BTRFS_BLOCK_GROUP_RAID0;
        return flags;
}

static u64 btrfs_get_alloc_profile(struct btrfs_root *root, u64 data)
{
        struct btrfs_fs_info *info = root->fs_info;
        u64 alloc_profile;

        if (data) {
                alloc_profile = info->avail_data_alloc_bits &
                        info->data_alloc_profile;
                data = BTRFS_BLOCK_GROUP_DATA | alloc_profile;
        } else if (root == root->fs_info->chunk_root) {
                alloc_profile = info->avail_system_alloc_bits &
                        info->system_alloc_profile;
                data = BTRFS_BLOCK_GROUP_SYSTEM | alloc_profile;
        } else {
                alloc_profile = info->avail_metadata_alloc_bits &
                        info->metadata_alloc_profile;
                data = BTRFS_BLOCK_GROUP_METADATA | alloc_profile;
        }

        return btrfs_reduce_alloc_profile(root, data);
}

void btrfs_set_inode_space_info(struct btrfs_root *root, struct inode *inode)
{
        u64 alloc_target;

        alloc_target = btrfs_get_alloc_profile(root, 1);
        BTRFS_I(inode)->space_info = __find_space_info(root->fs_info,
                                                       alloc_target);
}

static u64 calculate_bytes_needed(struct btrfs_root *root, int num_items)
{
        u64 num_bytes;
        int level;

        level = BTRFS_MAX_LEVEL - 2;
        /*
         * NOTE: these calculations are absolutely the worst possible case.
         * This assumes that _every_ item we insert will require a new leaf, and
         * that the tree has grown to its maximum level size.
         */

        /*
         * for every item we insert we could insert both an extent item and a
         * extent ref item.  Then for ever item we insert, we will need to cow
         * both the original leaf, plus the leaf to the left and right of it.
         *
         * Unless we are talking about the extent root, then we just want the
         * number of items * 2, since we just need the extent item plus its ref.
         */
        if (root == root->fs_info->extent_root)
                num_bytes = num_items * 2;
        else
                num_bytes = (num_items + (2 * num_items)) * 3;

        /*
         * num_bytes is total number of leaves we could need times the leaf
         * size, and then for every leaf we could end up cow'ing 2 nodes per
         * level, down to the leaf level.
         */
        num_bytes = (num_bytes * root->leafsize) +
                (num_bytes * (level * 2)) * root->nodesize;

        return num_bytes;
}

/*
 * Unreserve metadata space for delalloc.  If we have less reserved credits than
 * we have extents, this function does nothing.
 */
int btrfs_unreserve_metadata_for_delalloc(struct btrfs_root *root,
                                          struct inode *inode, int num_items)
{
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *meta_sinfo;
        u64 num_bytes;
        u64 alloc_target;
        bool bug = false;

        /* get the space info for where the metadata will live */
        alloc_target = btrfs_get_alloc_profile(root, 0);
        meta_sinfo = __find_space_info(info, alloc_target);

        num_bytes = calculate_bytes_needed(root->fs_info->extent_root,
                                           num_items);

        spin_lock(&meta_sinfo->lock);
        spin_lock(&BTRFS_I(inode)->accounting_lock);
        if (BTRFS_I(inode)->reserved_extents <=
            BTRFS_I(inode)->outstanding_extents) {
                spin_unlock(&BTRFS_I(inode)->accounting_lock);
                spin_unlock(&meta_sinfo->lock);
                return 0;
        }
        spin_unlock(&BTRFS_I(inode)->accounting_lock);

        BTRFS_I(inode)->reserved_extents--;
        BUG_ON(BTRFS_I(inode)->reserved_extents < 0);

        if (meta_sinfo->bytes_delalloc < num_bytes) {
                bug = true;
                meta_sinfo->bytes_delalloc = 0;
        } else {
                meta_sinfo->bytes_delalloc -= num_bytes;
        }
        spin_unlock(&meta_sinfo->lock);

        BUG_ON(bug);

        return 0;
}

static void check_force_delalloc(struct btrfs_space_info *meta_sinfo)
{
        u64 thresh;

        thresh = meta_sinfo->bytes_used + meta_sinfo->bytes_reserved +
                meta_sinfo->bytes_pinned + meta_sinfo->bytes_readonly +
                meta_sinfo->bytes_super + meta_sinfo->bytes_root +
                meta_sinfo->bytes_may_use;

        thresh = meta_sinfo->total_bytes - thresh;
        thresh *= 80;
        do_div(thresh, 100);
        if (thresh <= meta_sinfo->bytes_delalloc)
                meta_sinfo->force_delalloc = 1;
        else
                meta_sinfo->force_delalloc = 0;
}

struct async_flush {
        struct btrfs_root *root;
        struct btrfs_space_info *info;
        struct btrfs_work work;
};

static noinline void flush_delalloc_async(struct btrfs_work *work)
{
        struct async_flush *async;
        struct btrfs_root *root;
        struct btrfs_space_info *info;

        async = container_of(work, struct async_flush, work);
        root = async->root;
        info = async->info;

        btrfs_start_delalloc_inodes(root);
        wake_up(&info->flush_wait);
        btrfs_wait_ordered_extents(root, 0);

        spin_lock(&info->lock);
        info->flushing = 0;
        spin_unlock(&info->lock);
        wake_up(&info->flush_wait);

        kfree(async);
}

static void wait_on_flush(struct btrfs_space_info *info)
{
        DEFINE_WAIT(wait);
        u64 used;

        while (1) {
                prepare_to_wait(&info->flush_wait, &wait,
                                TASK_UNINTERRUPTIBLE);
                spin_lock(&info->lock);
                if (!info->flushing) {
                        spin_unlock(&info->lock);
                        break;
                }

                used = info->bytes_used + info->bytes_reserved +
                        info->bytes_pinned + info->bytes_readonly +
                        info->bytes_super + info->bytes_root +
                        info->bytes_may_use + info->bytes_delalloc;
                if (used < info->total_bytes) {
                        spin_unlock(&info->lock);
                        break;
                }
                spin_unlock(&info->lock);
                schedule();
        }
        finish_wait(&info->flush_wait, &wait);
}

static void flush_delalloc(struct btrfs_root *root,
                                 struct btrfs_space_info *info)
{
        struct async_flush *async;
        bool wait = false;

        spin_lock(&info->lock);

        if (!info->flushing) {
                info->flushing = 1;
                init_waitqueue_head(&info->flush_wait);
        } else {
                wait = true;
        }

        spin_unlock(&info->lock);

        if (wait) {
                wait_on_flush(info);
                return;
        }

        async = kzalloc(sizeof(*async), GFP_NOFS);
        if (!async)
                goto flush;

        async->root = root;
        async->info = info;
        async->work.func = flush_delalloc_async;

        btrfs_queue_worker(&root->fs_info->enospc_workers,
                           &async->work);
        wait_on_flush(info);
        return;

flush:
        btrfs_start_delalloc_inodes(root);
        btrfs_wait_ordered_extents(root, 0);

        spin_lock(&info->lock);
        info->flushing = 0;
        spin_unlock(&info->lock);
        wake_up(&info->flush_wait);
}

static int maybe_allocate_chunk(struct btrfs_root *root,
                                 struct btrfs_space_info *info)
{
        struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
        struct btrfs_trans_handle *trans;
        bool wait = false;
        int ret = 0;
        u64 min_metadata;
        u64 free_space;

        free_space = btrfs_super_total_bytes(disk_super);
        /*
         * we allow the metadata to grow to a max of either 5gb or 5% of the
         * space in the volume.
         */
        min_metadata = min((u64)5 * 1024 * 1024 * 1024,
                             div64_u64(free_space * 5, 100));
        if (info->total_bytes >= min_metadata) {
                spin_unlock(&info->lock);
                return 0;
        }

        if (info->full) {
                spin_unlock(&info->lock);
                return 0;
        }

        if (!info->allocating_chunk) {
                info->force_alloc = 1;
                info->allocating_chunk = 1;
                init_waitqueue_head(&info->allocate_wait);
        } else {
                wait = true;
        }

        spin_unlock(&info->lock);

        if (wait) {
                wait_event(info->allocate_wait,
                           !info->allocating_chunk);
                return 1;
        }

        trans = btrfs_start_transaction(root, 1);
        if (!trans) {
                ret = -ENOMEM;
                goto out;
        }

        ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                             4096 + 2 * 1024 * 1024,
                             info->flags, 0);
        btrfs_end_transaction(trans, root);
        if (ret)
                goto out;
out:
        spin_lock(&info->lock);
        info->allocating_chunk = 0;
        spin_unlock(&info->lock);
        wake_up(&info->allocate_wait);

        if (ret)
                return 0;
        return 1;
}

/*
 * Reserve metadata space for delalloc.
 */
int btrfs_reserve_metadata_for_delalloc(struct btrfs_root *root,
                                        struct inode *inode, int num_items)
{
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *meta_sinfo;
        u64 num_bytes;
        u64 used;
        u64 alloc_target;
        int flushed = 0;
        int force_delalloc;

        /* get the space info for where the metadata will live */
        alloc_target = btrfs_get_alloc_profile(root, 0);
        meta_sinfo = __find_space_info(info, alloc_target);

        num_bytes = calculate_bytes_needed(root->fs_info->extent_root,
                                           num_items);
again:
        spin_lock(&meta_sinfo->lock);

        force_delalloc = meta_sinfo->force_delalloc;

        if (unlikely(!meta_sinfo->bytes_root))
                meta_sinfo->bytes_root = calculate_bytes_needed(root, 6);

        if (!flushed)
                meta_sinfo->bytes_delalloc += num_bytes;

        used = meta_sinfo->bytes_used + meta_sinfo->bytes_reserved +
                meta_sinfo->bytes_pinned + meta_sinfo->bytes_readonly +
                meta_sinfo->bytes_super + meta_sinfo->bytes_root +
                meta_sinfo->bytes_may_use + meta_sinfo->bytes_delalloc;

        if (used > meta_sinfo->total_bytes) {
                flushed++;

                if (flushed == 1) {
                        if (maybe_allocate_chunk(root, meta_sinfo))
                                goto again;
                        flushed++;
                } else {
                        spin_unlock(&meta_sinfo->lock);
                }

                if (flushed == 2) {
                        filemap_flush(inode->i_mapping);
                        goto again;
                } else if (flushed == 3) {
                        flush_delalloc(root, meta_sinfo);
                        goto again;
                }
                spin_lock(&meta_sinfo->lock);
                meta_sinfo->bytes_delalloc -= num_bytes;
                spin_unlock(&meta_sinfo->lock);
                printk(KERN_ERR "enospc, has %d, reserved %d\n",
                       BTRFS_I(inode)->outstanding_extents,
                       BTRFS_I(inode)->reserved_extents);
                dump_space_info(meta_sinfo, 0, 0);
                return -ENOSPC;
        }

        BTRFS_I(inode)->reserved_extents++;
        check_force_delalloc(meta_sinfo);
        spin_unlock(&meta_sinfo->lock);

        if (!flushed && force_delalloc)
                filemap_flush(inode->i_mapping);

        return 0;
}

/*
 * unreserve num_items number of items worth of metadata space.  This needs to
 * be paired with btrfs_reserve_metadata_space.
 *
 * NOTE: if you have the option, run this _AFTER_ you do a
 * btrfs_end_transaction, since btrfs_end_transaction will run delayed ref
 * oprations which will result in more used metadata, so we want to make sure we
 * can do that without issue.
 */
int btrfs_unreserve_metadata_space(struct btrfs_root *root, int num_items)
{
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *meta_sinfo;
        u64 num_bytes;
        u64 alloc_target;
        bool bug = false;

        /* get the space info for where the metadata will live */
        alloc_target = btrfs_get_alloc_profile(root, 0);
        meta_sinfo = __find_space_info(info, alloc_target);

        num_bytes = calculate_bytes_needed(root, num_items);

        spin_lock(&meta_sinfo->lock);
        if (meta_sinfo->bytes_may_use < num_bytes) {
                bug = true;
                meta_sinfo->bytes_may_use = 0;
        } else {
                meta_sinfo->bytes_may_use -= num_bytes;
        }
        spin_unlock(&meta_sinfo->lock);

        BUG_ON(bug);

        return 0;
}

/*
 * Reserve some metadata space for use.  We'll calculate the worste case number
 * of bytes that would be needed to modify num_items number of items.  If we
 * have space, fantastic, if not, you get -ENOSPC.  Please call
 * btrfs_unreserve_metadata_space when you are done for the _SAME_ number of
 * items you reserved, since whatever metadata you needed should have already
 * been allocated.
 *
 * This will commit the transaction to make more space if we don't have enough
 * metadata space.  THe only time we don't do this is if we're reserving space
 * inside of a transaction, then we will just return -ENOSPC and it is the
 * callers responsibility to handle it properly.
 */
int btrfs_reserve_metadata_space(struct btrfs_root *root, int num_items)
{
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *meta_sinfo;
        u64 num_bytes;
        u64 used;
        u64 alloc_target;
        int retries = 0;

        /* get the space info for where the metadata will live */
        alloc_target = btrfs_get_alloc_profile(root, 0);
        meta_sinfo = __find_space_info(info, alloc_target);

        num_bytes = calculate_bytes_needed(root, num_items);
again:
        spin_lock(&meta_sinfo->lock);

        if (unlikely(!meta_sinfo->bytes_root))
                meta_sinfo->bytes_root = calculate_bytes_needed(root, 6);

        if (!retries)
                meta_sinfo->bytes_may_use += num_bytes;

        used = meta_sinfo->bytes_used + meta_sinfo->bytes_reserved +
                meta_sinfo->bytes_pinned + meta_sinfo->bytes_readonly +
                meta_sinfo->bytes_super + meta_sinfo->bytes_root +
                meta_sinfo->bytes_may_use + meta_sinfo->bytes_delalloc;

        if (used > meta_sinfo->total_bytes) {
                retries++;
                if (retries == 1) {
                        if (maybe_allocate_chunk(root, meta_sinfo))
                                goto again;
                        retries++;
                } else {
                        spin_unlock(&meta_sinfo->lock);
                }

                if (retries == 2) {
                        flush_delalloc(root, meta_sinfo);
                        goto again;
                }
                spin_lock(&meta_sinfo->lock);
                meta_sinfo->bytes_may_use -= num_bytes;
                spin_unlock(&meta_sinfo->lock);

                dump_space_info(meta_sinfo, 0, 0);
                return -ENOSPC;
        }

        check_force_delalloc(meta_sinfo);
        spin_unlock(&meta_sinfo->lock);

        return 0;
}

/*
 * This will check the space that the inode allocates from to make sure we have
 * enough space for bytes.
 */
int btrfs_check_data_free_space(struct btrfs_root *root, struct inode *inode,
                                u64 bytes)
{
        struct btrfs_space_info *data_sinfo;
        int ret = 0, committed = 0;

        /* make sure bytes are sectorsize aligned */
        bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);

        data_sinfo = BTRFS_I(inode)->space_info;
        if (!data_sinfo)
                goto alloc;

again:
        /* make sure we have enough space to handle the data first */
        spin_lock(&data_sinfo->lock);
        if (data_sinfo->total_bytes - data_sinfo->bytes_used -
            data_sinfo->bytes_delalloc - data_sinfo->bytes_reserved -
            data_sinfo->bytes_pinned - data_sinfo->bytes_readonly -
            data_sinfo->bytes_may_use - data_sinfo->bytes_super < bytes) {
                struct btrfs_trans_handle *trans;

                /*
                 * if we don't have enough free bytes in this space then we need
                 * to alloc a new chunk.
                 */
                if (!data_sinfo->full) {
                        u64 alloc_target;

                        data_sinfo->force_alloc = 1;
                        spin_unlock(&data_sinfo->lock);
alloc:
                        alloc_target = btrfs_get_alloc_profile(root, 1);
                        trans = btrfs_start_transaction(root, 1);
                        if (!trans)
                                return -ENOMEM;

                        ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                             bytes + 2 * 1024 * 1024,
                                             alloc_target, 0);
                        btrfs_end_transaction(trans, root);
                        if (ret)
                                return ret;

                        if (!data_sinfo) {
                                btrfs_set_inode_space_info(root, inode);
                                data_sinfo = BTRFS_I(inode)->space_info;
                        }
                        goto again;
                }
                spin_unlock(&data_sinfo->lock);

                /* commit the current transaction and try again */
                if (!committed && !root->fs_info->open_ioctl_trans) {
                        committed = 1;
                        trans = btrfs_join_transaction(root, 1);
                        if (!trans)
                                return -ENOMEM;
                        ret = btrfs_commit_transaction(trans, root);
                        if (ret)
                                return ret;
                        goto again;
                }

                printk(KERN_ERR "no space left, need %llu, %llu delalloc bytes"
                       ", %llu bytes_used, %llu bytes_reserved, "
                       "%llu bytes_pinned, %llu bytes_readonly, %llu may use "
                       "%llu total\n", (unsigned long long)bytes,
                       (unsigned long long)data_sinfo->bytes_delalloc,
                       (unsigned long long)data_sinfo->bytes_used,
                       (unsigned long long)data_sinfo->bytes_reserved,
                       (unsigned long long)data_sinfo->bytes_pinned,
                       (unsigned long long)data_sinfo->bytes_readonly,
                       (unsigned long long)data_sinfo->bytes_may_use,
                       (unsigned long long)data_sinfo->total_bytes);
                return -ENOSPC;
        }
        data_sinfo->bytes_may_use += bytes;
        BTRFS_I(inode)->reserved_bytes += bytes;
        spin_unlock(&data_sinfo->lock);

        return 0;
}

/*
 * if there was an error for whatever reason after calling
 * btrfs_check_data_free_space, call this so we can cleanup the counters.
 */
void btrfs_free_reserved_data_space(struct btrfs_root *root,
                                    struct inode *inode, u64 bytes)
{
        struct btrfs_space_info *data_sinfo;

        /* make sure bytes are sectorsize aligned */
        bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);

        data_sinfo = BTRFS_I(inode)->space_info;
        spin_lock(&data_sinfo->lock);
        data_sinfo->bytes_may_use -= bytes;
        BTRFS_I(inode)->reserved_bytes -= bytes;
        spin_unlock(&data_sinfo->lock);
}

/* called when we are adding a delalloc extent to the inode's io_tree */
void btrfs_delalloc_reserve_space(struct btrfs_root *root, struct inode *inode,
                                  u64 bytes)
{
        struct btrfs_space_info *data_sinfo;

        /* get the space info for where this inode will be storing its data */
        data_sinfo = BTRFS_I(inode)->space_info;

        /* make sure we have enough space to handle the data first */
        spin_lock(&data_sinfo->lock);
        data_sinfo->bytes_delalloc += bytes;

        /*
         * we are adding a delalloc extent without calling
         * btrfs_check_data_free_space first.  This happens on a weird
         * writepage condition, but shouldn't hurt our accounting
         */
        if (unlikely(bytes > BTRFS_I(inode)->reserved_bytes)) {
                data_sinfo->bytes_may_use -= BTRFS_I(inode)->reserved_bytes;
                BTRFS_I(inode)->reserved_bytes = 0;
        } else {
                data_sinfo->bytes_may_use -= bytes;
                BTRFS_I(inode)->reserved_bytes -= bytes;
        }

        spin_unlock(&data_sinfo->lock);
}

/* called when we are clearing an delalloc extent from the inode's io_tree */
void btrfs_delalloc_free_space(struct btrfs_root *root, struct inode *inode,
                              u64 bytes)
{
        struct btrfs_space_info *info;

        info = BTRFS_I(inode)->space_info;

        spin_lock(&info->lock);
        info->bytes_delalloc -= bytes;
        spin_unlock(&info->lock);
}

static void force_metadata_allocation(struct btrfs_fs_info *info)
{
        struct list_head *head = &info->space_info;
        struct btrfs_space_info *found;

        rcu_read_lock();
        list_for_each_entry_rcu(found, head, list) {
                if (found->flags & BTRFS_BLOCK_GROUP_METADATA)
                        found->force_alloc = 1;
        }
        rcu_read_unlock();
}

static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                          struct btrfs_root *extent_root, u64 alloc_bytes,
                          u64 flags, int force)
{
        struct btrfs_space_info *space_info;
        struct btrfs_fs_info *fs_info = extent_root->fs_info;
        u64 thresh;
        int ret = 0;

        mutex_lock(&fs_info->chunk_mutex);

        flags = btrfs_reduce_alloc_profile(extent_root, flags);

        space_info = __find_space_info(extent_root->fs_info, flags);
        if (!space_info) {
                ret = update_space_info(extent_root->fs_info, flags,
                                        0, 0, &space_info);
                BUG_ON(ret);
        }
        BUG_ON(!space_info);

        spin_lock(&space_info->lock);
        if (space_info->force_alloc)
                force = 1;
        if (space_info->full) {
                spin_unlock(&space_info->lock);
                goto out;
        }

        thresh = space_info->total_bytes - space_info->bytes_readonly;
        thresh = div_factor(thresh, 8);
        if (!force &&
           (space_info->bytes_used + space_info->bytes_pinned +
            space_info->bytes_reserved + alloc_bytes) < thresh) {
                spin_unlock(&space_info->lock);
                goto out;
        }
        spin_unlock(&space_info->lock);

        /*
         * if we're doing a data chunk, go ahead and make sure that
         * we keep a reasonable number of metadata chunks allocated in the
         * FS as well.
         */
        if (flags & BTRFS_BLOCK_GROUP_DATA && fs_info->metadata_ratio) {
                fs_info->data_chunk_allocations++;
                if (!(fs_info->data_chunk_allocations %
                      fs_info->metadata_ratio))
                        force_metadata_allocation(fs_info);
        }

        ret = btrfs_alloc_chunk(trans, extent_root, flags);
        spin_lock(&space_info->lock);
        if (ret)
                space_info->full = 1;
        space_info->force_alloc = 0;
        spin_unlock(&space_info->lock);
out:
        mutex_unlock(&extent_root->fs_info->chunk_mutex);
        return ret;
}

static int update_block_group(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              u64 bytenr, u64 num_bytes, int alloc,
                              int mark_free)
{
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *info = root->fs_info;
        u64 total = num_bytes;
        u64 old_val;
        u64 byte_in_group;

        /* block accounting for super block */
        spin_lock(&info->delalloc_lock);
        old_val = btrfs_super_bytes_used(&info->super_copy);
        if (alloc)
                old_val += num_bytes;
        else
                old_val -= num_bytes;
        btrfs_set_super_bytes_used(&info->super_copy, old_val);

        /* block accounting for root item */
        old_val = btrfs_root_used(&root->root_item);
        if (alloc)
                old_val += num_bytes;
        else
                old_val -= num_bytes;
        btrfs_set_root_used(&root->root_item, old_val);
        spin_unlock(&info->delalloc_lock);

        while (total) {
                cache = btrfs_lookup_block_group(info, bytenr);
                if (!cache)
                        return -1;
                byte_in_group = bytenr - cache->key.objectid;
                WARN_ON(byte_in_group > cache->key.offset);

                spin_lock(&cache->space_info->lock);
                spin_lock(&cache->lock);
                cache->dirty = 1;
                old_val = btrfs_block_group_used(&cache->item);
                num_bytes = min(total, cache->key.offset - byte_in_group);
                if (alloc) {
                        old_val += num_bytes;
                        btrfs_set_block_group_used(&cache->item, old_val);
                        cache->reserved -= num_bytes;
                        cache->space_info->bytes_used += num_bytes;
                        cache->space_info->bytes_reserved -= num_bytes;
                        if (cache->ro)
                                cache->space_info->bytes_readonly -= num_bytes;
                        spin_unlock(&cache->lock);
                        spin_unlock(&cache->space_info->lock);
                } else {
                        old_val -= num_bytes;
                        cache->space_info->bytes_used -= num_bytes;
                        if (cache->ro)
                                cache->space_info->bytes_readonly += num_bytes;
                        btrfs_set_block_group_used(&cache->item, old_val);
                        spin_unlock(&cache->lock);
                        spin_unlock(&cache->space_info->lock);
                        if (mark_free) {
                                int ret;

                                ret = btrfs_discard_extent(root, bytenr,
                                                           num_bytes);
                                WARN_ON(ret);

                                ret = btrfs_add_free_space(cache, bytenr,
                                                           num_bytes);
                                WARN_ON(ret);
                        }
                }
                btrfs_put_block_group(cache);
                total -= num_bytes;
                bytenr += num_bytes;
        }
        return 0;
}

static u64 first_logical_byte(struct btrfs_root *root, u64 search_start)
{
        struct btrfs_block_group_cache *cache;
        u64 bytenr;

        cache = btrfs_lookup_first_block_group(root->fs_info, search_start);
        if (!cache)
                return 0;

        bytenr = cache->key.objectid;
        btrfs_put_block_group(cache);

        return bytenr;
}

/*
 * this function must be called within transaction
 */
int btrfs_pin_extent(struct btrfs_root *root,
                     u64 bytenr, u64 num_bytes, int reserved)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_group_cache *cache;

        cache = btrfs_lookup_block_group(fs_info, bytenr);
        BUG_ON(!cache);

        spin_lock(&cache->space_info->lock);
        spin_lock(&cache->lock);
        cache->pinned += num_bytes;
        cache->space_info->bytes_pinned += num_bytes;
        if (reserved) {
                cache->reserved -= num_bytes;
                cache->space_info->bytes_reserved -= num_bytes;
        }
        spin_unlock(&cache->lock);
        spin_unlock(&cache->space_info->lock);

        btrfs_put_block_group(cache);

        set_extent_dirty(fs_info->pinned_extents,
                         bytenr, bytenr + num_bytes - 1, GFP_NOFS);
        return 0;
}

static int update_reserved_extents(struct btrfs_block_group_cache *cache,
                                   u64 num_bytes, int reserve)
{
        spin_lock(&cache->space_info->lock);
        spin_lock(&cache->lock);
        if (reserve) {
                cache->reserved += num_bytes;
                cache->space_info->bytes_reserved += num_bytes;
        } else {
                cache->reserved -= num_bytes;
                cache->space_info->bytes_reserved -= num_bytes;
        }
        spin_unlock(&cache->lock);
        spin_unlock(&cache->space_info->lock);
        return 0;
}

int btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_caching_control *next;
        struct btrfs_caching_control *caching_ctl;
        struct btrfs_block_group_cache *cache;

        down_write(&fs_info->extent_commit_sem);

        list_for_each_entry_safe(caching_ctl, next,
                                 &fs_info->caching_block_groups, list) {
                cache = caching_ctl->block_group;
                if (block_group_cache_done(cache)) {
                        cache->last_byte_to_unpin = (u64)-1;
                        list_del_init(&caching_ctl->list);
                        put_caching_control(caching_ctl);
                } else {
                        cache->last_byte_to_unpin = caching_ctl->progress;
                }
        }

        if (fs_info->pinned_extents == &fs_info->freed_extents[0])
                fs_info->pinned_extents = &fs_info->freed_extents[1];
        else
                fs_info->pinned_extents = &fs_info->freed_extents[0];

        up_write(&fs_info->extent_commit_sem);
        return 0;
}

static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_group_cache *cache = NULL;
        u64 len;

        while (start <= end) {
                if (!cache ||
                    start >= cache->key.objectid + cache->key.offset) {
                        if (cache)
                                btrfs_put_block_group(cache);
                        cache = btrfs_lookup_block_group(fs_info, start);
                        BUG_ON(!cache);
                }

                len = cache->key.objectid + cache->key.offset - start;
                len = min(len, end + 1 - start);

                if (start < cache->last_byte_to_unpin) {
                        len = min(len, cache->last_byte_to_unpin - start);
                        btrfs_add_free_space(cache, start, len);
                }

                spin_lock(&cache->space_info->lock);
                spin_lock(&cache->lock);
                cache->pinned -= len;
                cache->space_info->bytes_pinned -= len;
                spin_unlock(&cache->lock);
                spin_unlock(&cache->space_info->lock);

                start += len;
        }

        if (cache)
                btrfs_put_block_group(cache);
        return 0;
}

int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_io_tree *unpin;
        u64 start;
        u64 end;
        int ret;

        if (fs_info->pinned_extents == &fs_info->freed_extents[0])
                unpin = &fs_info->freed_extents[1];
        else
                unpin = &fs_info->freed_extents[0];

        while (1) {
                ret = find_first_extent_bit(unpin, 0, &start, &end,
                                            EXTENT_DIRTY);
                if (ret)
                        break;

                ret = btrfs_discard_extent(root, start, end + 1 - start);

                clear_extent_dirty(unpin, start, end, GFP_NOFS);
                unpin_extent_range(root, start, end);
                cond_resched();
        }

        return ret;
}

static int pin_down_bytes(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root,
                          struct btrfs_path *path,
                          u64 bytenr, u64 num_bytes,
                          int is_data, int reserved,
                          struct extent_buffer **must_clean)
{
        int err = 0;
        struct extent_buffer *buf;

        if (is_data)
                goto pinit;

        buf = btrfs_find_tree_block(root, bytenr, num_bytes);
        if (!buf)
                goto pinit;

        /* we can reuse a block if it hasn't been written
         * and it is from this transaction.  We can't
         * reuse anything from the tree log root because
         * it has tiny sub-transactions.
         */
        if (btrfs_buffer_uptodate(buf, 0) &&
            btrfs_try_tree_lock(buf)) {
                u64 header_owner = btrfs_header_owner(buf);
                u64 header_transid = btrfs_header_generation(buf);
                if (header_owner != BTRFS_TREE_LOG_OBJECTID &&
                    header_transid == trans->transid &&
                    !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
                        *must_clean = buf;
                        return 1;
                }
                btrfs_tree_unlock(buf);
        }
        free_extent_buffer(buf);
pinit:
        if (path)
                btrfs_set_path_blocking(path);
        /* unlocks the pinned mutex */
        btrfs_pin_extent(root, bytenr, num_bytes, reserved);

        BUG_ON(err < 0);
        return 0;
}

static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                u64 bytenr, u64 num_bytes, u64 parent,
                                u64 root_objectid, u64 owner_objectid,
                                u64 owner_offset, int refs_to_drop,
                                struct btrfs_delayed_extent_op *extent_op)
{
        struct btrfs_key key;
        struct btrfs_path *path;
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_root *extent_root = info->extent_root;
        struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        int ret;
        int is_data;
        int extent_slot = 0;
        int found_extent = 0;
        int num_to_del = 1;
        u32 item_size;
        u64 refs;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->reada = 1;
        path->leave_spinning = 1;

        is_data = owner_objectid >= BTRFS_FIRST_FREE_OBJECTID;
        BUG_ON(!is_data && refs_to_drop != 1);

        ret = lookup_extent_backref(trans, extent_root, path, &iref,
                                    bytenr, num_bytes, parent,
                                    root_objectid, owner_objectid,
                                    owner_offset);
        if (ret == 0) {
                extent_slot = path->slots[0];
                while (extent_slot >= 0) {
                        btrfs_item_key_to_cpu(path->nodes[0], &key,
                                              extent_slot);
                        if (key.objectid != bytenr)
                                break;
                        if (key.type == BTRFS_EXTENT_ITEM_KEY &&
                            key.offset == num_bytes) {
                                found_extent = 1;
                                break;
                        }
                        if (path->slots[0] - extent_slot > 5)
                                break;
                        extent_slot--;
                }
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
                item_size = btrfs_item_size_nr(path->nodes[0], extent_slot);
                if (found_extent && item_size < sizeof(*ei))
                        found_extent = 0;
#endif
                if (!found_extent) {
                        BUG_ON(iref);
                        ret = remove_extent_backref(trans, extent_root, path,
                                                    NULL, refs_to_drop,
                                                    is_data);
                        BUG_ON(ret);
                        btrfs_release_path(extent_root, path);
                        path->leave_spinning = 1;

                        key.objectid = bytenr;
                        key.type = BTRFS_EXTENT_ITEM_KEY;
                        key.offset = num_bytes;

                        ret = btrfs_search_slot(trans, extent_root,
                                                &key, path, -1, 1);
                        if (ret) {
                                printk(KERN_ERR "umm, got %d back from search"
                                       ", was looking for %llu\n", ret,
                                       (unsigned long long)bytenr);
                                btrfs_print_leaf(extent_root, path->nodes[0]);
                        }
                        BUG_ON(ret);
                        extent_slot = path->slots[0];
                }
        } else {
                btrfs_print_leaf(extent_root, path->nodes[0]);
                WARN_ON(1);
                printk(KERN_ERR "btrfs unable to find ref byte nr %llu "
                       "parent %llu root %llu  owner %llu offset %llu\n",
                       (unsigned long long)bytenr,
                       (unsigned long long)parent,
                       (unsigned long long)root_objectid,
                       (unsigned long long)owner_objectid,
                       (unsigned long long)owner_offset);
        }

        leaf = path->nodes[0];
        item_size = btrfs_item_size_nr(leaf, extent_slot);
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
        if (item_size < sizeof(*ei)) {
                BUG_ON(found_extent || extent_slot != path->slots[0]);
                ret = convert_extent_item_v0(trans, extent_root, path,
                                             owner_objectid, 0);
                BUG_ON(ret < 0);

                btrfs_release_path(extent_root, path);
                path->leave_spinning = 1;

                key.objectid = bytenr;
                key.type = BTRFS_EXTENT_ITEM_KEY;
                key.offset = num_bytes;

                ret = btrfs_search_slot(trans, extent_root, &key, path,
                                        -1, 1);
                if (ret) {
                        printk(KERN_ERR "umm, got %d back from search"
                               ", was looking for %llu\n", ret,
                               (unsigned long long)bytenr);
                        btrfs_print_leaf(extent_root, path->nodes[0]);
                }
                BUG_ON(ret);
                extent_slot = path->slots[0];
                leaf = path->nodes[0];
                item_size = btrfs_item_size_nr(leaf, extent_slot);
        }
#endif
        BUG_ON(item_size < sizeof(*ei));
        ei = btrfs_item_ptr(leaf, extent_slot,
                            struct btrfs_extent_item);
        if (owner_objectid < BTRFS_FIRST_FREE_OBJECTID) {
                struct btrfs_tree_block_info *bi;
                BUG_ON(item_size < sizeof(*ei) + sizeof(*bi));
                bi = (struct btrfs_tree_block_info *)(ei + 1);
                WARN_ON(owner_objectid != btrfs_tree_block_level(leaf, bi));
        }

        refs = btrfs_extent_refs(leaf, ei);
        BUG_ON(refs < refs_to_drop);
        refs -= refs_to_drop;

        if (refs > 0) {
                if (extent_op)
                        __run_delayed_extent_op(extent_op, leaf, ei);
                /*
                 * In the case of inline back ref, reference count will
                 * be updated by remove_extent_backref
                 */
                if (iref) {
                        BUG_ON(!found_extent);
                } else {
                        btrfs_set_extent_refs(leaf, ei, refs);
                        btrfs_mark_buffer_dirty(leaf);
                }
                if (found_extent) {
                        ret = remove_extent_backref(trans, extent_root, path,
                                                    iref, refs_to_drop,
                                                    is_data);
                        BUG_ON(ret);
                }
        } else {
                int mark_free = 0;
                struct extent_buffer *must_clean = NULL;

                if (found_extent) {
                        BUG_ON(is_data && refs_to_drop !=
                               extent_data_ref_count(root, path, iref));
                        if (iref) {
                                BUG_ON(path->slots[0] != extent_slot);
                        } else {
                                BUG_ON(path->slots[0] != extent_slot + 1);
                                path->slots[0] = extent_slot;
                                num_to_del = 2;
                        }
                }

                ret = pin_down_bytes(trans, root, path, bytenr,
                                     num_bytes, is_data, 0, &must_clean);
                if (ret > 0)
                        mark_free = 1;
                BUG_ON(ret < 0);
                /*
                 * it is going to be very rare for someone to be waiting
                 * on the block we're freeing.  del_items might need to
                 * schedule, so rather than get fancy, just force it
                 * to blocking here
                 */
                if (must_clean)
                        btrfs_set_lock_blocking(must_clean);

                ret = btrfs_del_items(trans, extent_root, path, path->slots[0],
                                      num_to_del);
                BUG_ON(ret);
                btrfs_release_path(extent_root, path);

                if (must_clean) {
                        clean_tree_block(NULL, root, must_clean);
                        btrfs_tree_unlock(must_clean);
                        free_extent_buffer(must_clean);
                }

                if (is_data) {
                        ret = btrfs_del_csums(trans, root, bytenr, num_bytes);
                        BUG_ON(ret);
                } else {
                        invalidate_mapping_pages(info->btree_inode->i_mapping,
                             bytenr >> PAGE_CACHE_SHIFT,
                             (bytenr + num_bytes - 1) >> PAGE_CACHE_SHIFT);
                }

                ret = update_block_group(trans, root, bytenr, num_bytes, 0,
                                         mark_free);
                BUG_ON(ret);
        }
        btrfs_free_path(path);
        return ret;
}

/*
 * when we free an extent, it is possible (and likely) that we free the last
 * delayed ref for that extent as well.  This searches the delayed ref tree for
 * a given extent, and if there are no other delayed refs to be processed, it
 * removes it from the tree.
 */
static noinline int check_ref_cleanup(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root, u64 bytenr)
{
        struct btrfs_delayed_ref_head *head;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_delayed_ref_node *ref;
        struct rb_node *node;
        int ret;

        delayed_refs = &trans->transaction->delayed_refs;
        spin_lock(&delayed_refs->lock);
        head = btrfs_find_delayed_ref_head(trans, bytenr);
        if (!head)
                goto out;

        node = rb_prev(&head->node.rb_node);
        if (!node)
                goto out;

        ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);

        /* there are still entries for this ref, we can't drop it */
        if (ref->bytenr == bytenr)
                goto out;

        if (head->extent_op) {
                if (!head->must_insert_reserved)
                        goto out;
                kfree(head->extent_op);
                head->extent_op = NULL;
        }

        /*
         * waiting for the lock here would deadlock.  If someone else has it
         * locked they are already in the process of dropping it anyway
         */
        if (!mutex_trylock(&head->mutex))
                goto out;

        /*
         * at this point we have a head with no other entries.  Go
         * ahead and process it.
         */
        head->node.in_tree = 0;
        rb_erase(&head->node.rb_node, &delayed_refs->root);

        delayed_refs->num_entries--;

        /*
         * we don't take a ref on the node because we're removing it from the
         * tree, so we just steal the ref the tree was holding.
         */
        delayed_refs->num_heads--;
        if (list_empty(&head->cluster))
                delayed_refs->num_heads_ready--;

        list_del_init(&head->cluster);
        spin_unlock(&delayed_refs->lock);

        ret = run_one_delayed_ref(trans, root->fs_info->tree_root,
                                  &head->node, head->extent_op,
                                  head->must_insert_reserved);
        BUG_ON(ret);
        btrfs_put_delayed_ref(&head->node);
        return 0;
out:
        spin_unlock(&delayed_refs->lock);
        return 0;
}

int btrfs_free_extent(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      u64 bytenr, u64 num_bytes, u64 parent,
                      u64 root_objectid, u64 owner, u64 offset)
{
        int ret;

        /*
         * tree log blocks never actually go into the extent allocation
         * tree, just update pinning info and exit early.
         */
        if (root_objectid == BTRFS_TREE_LOG_OBJECTID) {
                WARN_ON(owner >= BTRFS_FIRST_FREE_OBJECTID);
                /* unlocks the pinned mutex */
                btrfs_pin_extent(root, bytenr, num_bytes, 1);
                ret = 0;
        } else if (owner < BTRFS_FIRST_FREE_OBJECTID) {
                ret = btrfs_add_delayed_tree_ref(trans, bytenr, num_bytes,
                                        parent, root_objectid, (int)owner,
                                        BTRFS_DROP_DELAYED_REF, NULL);
                BUG_ON(ret);
                ret = check_ref_cleanup(trans, root, bytenr);
                BUG_ON(ret);
        } else {
                ret = btrfs_add_delayed_data_ref(trans, bytenr, num_bytes,
                                        parent, root_objectid, owner,
                                        offset, BTRFS_DROP_DELAYED_REF, NULL);
                BUG_ON(ret);
        }
        return ret;
}

static u64 stripe_align(struct btrfs_root *root, u64 val)
{
        u64 mask = ((u64)root->stripesize - 1);
        u64 ret = (val + mask) & ~mask;
        return ret;
}

/*
 * when we wait for progress in the block group caching, its because
 * our allocation attempt failed at least once.  So, we must sleep
 * and let some progress happen before we try again.
 *
 * This function will sleep at least once waiting for new free space to
 * show up, and then it will check the block group free space numbers
 * for our min num_bytes.  Another option is to have it go ahead
 * and look in the rbtree for a free extent of a given size, but this
 * is a good start.
 */
static noinline int
wait_block_group_cache_progress(struct btrfs_block_group_cache *cache,
                                u64 num_bytes)
{
        struct btrfs_caching_control *caching_ctl;
        DEFINE_WAIT(wait);

        caching_ctl = get_caching_control(cache);
        if (!caching_ctl)
                return 0;

        wait_event(caching_ctl->wait, block_group_cache_done(cache) ||
                   (cache->free_space >= num_bytes));

        put_caching_control(caching_ctl);
        return 0;
}

static noinline int
wait_block_group_cache_done(struct btrfs_block_group_cache *cache)
{
        struct btrfs_caching_control *caching_ctl;
        DEFINE_WAIT(wait);

        caching_ctl = get_caching_control(cache);
        if (!caching_ctl)
                return 0;

        wait_event(caching_ctl->wait, block_group_cache_done(cache));

        put_caching_control(caching_ctl);
        return 0;
}

enum btrfs_loop_type {
        LOOP_CACHED_ONLY = 0,
        LOOP_CACHING_NOWAIT = 1,
        LOOP_CACHING_WAIT = 2,
        LOOP_ALLOC_CHUNK = 3,
        LOOP_NO_EMPTY_SIZE = 4,
};

/*
 * walks the btree of allocated extents and find a hole of a given size.
 * The key ins is changed to record the hole:
 * ins->objectid == block start
 * ins->flags = BTRFS_EXTENT_ITEM_KEY
 * ins->offset == number of blocks
 * Any available blocks before search_start are skipped.
 */
static noinline int find_free_extent(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *orig_root,
                                     u64 num_bytes, u64 empty_size,
                                     u64 search_start, u64 search_end,
                                     u64 hint_byte, struct btrfs_key *ins,
                                     u64 exclude_start, u64 exclude_nr,
                                     int data)
{
        int ret = 0;
        struct btrfs_root *root = orig_root->fs_info->extent_root;
        struct btrfs_free_cluster *last_ptr = NULL;
        struct btrfs_block_group_cache *block_group = NULL;
        int empty_cluster = 2 * 1024 * 1024;
        int allowed_chunk_alloc = 0;
        struct btrfs_space_info *space_info;
        int last_ptr_loop = 0;
        int loop = 0;
        bool found_uncached_bg = false;
        bool failed_cluster_refill = false;
        bool failed_alloc = false;

        WARN_ON(num_bytes < root->sectorsize);
        btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY);
        ins->objectid = 0;
        ins->offset = 0;

        space_info = __find_space_info(root->fs_info, data);

        if (orig_root->ref_cows || empty_size)
                allowed_chunk_alloc = 1;

        if (data & BTRFS_BLOCK_GROUP_METADATA) {
                last_ptr = &root->fs_info->meta_alloc_cluster;
                if (!btrfs_test_opt(root, SSD))
                        empty_cluster = 64 * 1024;
        }

        if ((data & BTRFS_BLOCK_GROUP_DATA) && btrfs_test_opt(root, SSD)) {
                last_ptr = &root->fs_info->data_alloc_cluster;
        }

        if (last_ptr) {
                spin_lock(&last_ptr->lock);
                if (last_ptr->block_group)
                        hint_byte = last_ptr->window_start;
                spin_unlock(&last_ptr->lock);
        }

        search_start = max(search_start, first_logical_byte(root, 0));
        search_start = max(search_start, hint_byte);

        if (!last_ptr)
                empty_cluster = 0;

        if (search_start == hint_byte) {
                block_group = btrfs_lookup_block_group(root->fs_info,
                                                       search_start);
                /*
                 * we don't want to use the block group if it doesn't match our
                 * allocation bits, or if its not cached.
                 */
                if (block_group && block_group_bits(block_group, data) &&
                    block_group_cache_done(block_group)) {
                        down_read(&space_info->groups_sem);
                        if (list_empty(&block_group->list) ||
                            block_group->ro) {
                                /*
                                 * someone is removing this block group,
                                 * we can't jump into the have_block_group
                                 * target because our list pointers are not
                                 * valid
                                 */
                                btrfs_put_block_group(block_group);
                                up_read(&space_info->groups_sem);
                        } else
                                goto have_block_group;
                } else if (block_group) {
                        btrfs_put_block_group(block_group);
                }
        }

search:
        down_read(&space_info->groups_sem);
        list_for_each_entry(block_group, &space_info->block_groups, list) {
                u64 offset;
                int cached;

                atomic_inc(&block_group->count);
                search_start = block_group->key.objectid;

have_block_group:
                if (unlikely(block_group->cached == BTRFS_CACHE_NO)) {
                        /*
                         * we want to start caching kthreads, but not too many
                         * right off the bat so we don't overwhelm the system,
                         * so only start them if there are less than 2 and we're
                         * in the initial allocation phase.
                         */
                        if (loop > LOOP_CACHING_NOWAIT ||
                            atomic_read(&space_info->caching_threads) < 2) {
                                ret = cache_block_group(block_group);
                                BUG_ON(ret);
                        }
                }

                cached = block_group_cache_done(block_group);
                if (unlikely(!cached)) {
                        found_uncached_bg = true;

                        /* if we only want cached bgs, loop */
                        if (loop == LOOP_CACHED_ONLY)
                                goto loop;
                }

                if (unlikely(block_group->ro))
                        goto loop;

                /*
                 * Ok we want to try and use the cluster allocator, so lets look
                 * there, unless we are on LOOP_NO_EMPTY_SIZE, since we will
                 * have tried the cluster allocator plenty of times at this
                 * point and not have found anything, so we are likely way too
                 * fragmented for the clustering stuff to find anything, so lets
                 * just skip it and let the allocator find whatever block it can
                 * find
                 */
                if (last_ptr && loop < LOOP_NO_EMPTY_SIZE) {
                        /*
                         * the refill lock keeps out other
                         * people trying to start a new cluster
                         */
                        spin_lock(&last_ptr->refill_lock);
                        if (last_ptr->block_group &&
                            (last_ptr->block_group->ro ||
                            !block_group_bits(last_ptr->block_group, data))) {
                                offset = 0;
                                goto refill_cluster;
                        }

                        offset = btrfs_alloc_from_cluster(block_group, last_ptr,
                                                 num_bytes, search_start);
                        if (offset) {
                                /* we have a block, we're done */
                                spin_unlock(&last_ptr->refill_lock);
                                goto checks;
                        }

                        spin_lock(&last_ptr->lock);
                        /*
                         * whoops, this cluster doesn't actually point to
                         * this block group.  Get a ref on the block
                         * group is does point to and try again
                         */
                        if (!last_ptr_loop && last_ptr->block_group &&
                            last_ptr->block_group != block_group) {

                                btrfs_put_block_group(block_group);
                                block_group = last_ptr->block_group;
                                atomic_inc(&block_group->count);
                                spin_unlock(&last_ptr->lock);
                                spin_unlock(&last_ptr->refill_lock);

                                last_ptr_loop = 1;
                                search_start = block_group->key.objectid;
                                /*
                                 * we know this block group is properly
                                 * in the list because
                                 * btrfs_remove_block_group, drops the
                                 * cluster before it removes the block
                                 * group from the list
                                 */
                                goto have_block_group;
                        }
                        spin_unlock(&last_ptr->lock);
refill_cluster:
                        /*
                         * this cluster didn't work out, free it and
                         * start over
                         */
                        btrfs_return_cluster_to_free_space(NULL, last_ptr);

                        last_ptr_loop = 0;

                        /* allocate a cluster in this block group */
                        ret = btrfs_find_space_cluster(trans, root,
                                               block_group, last_ptr,
                                               offset, num_bytes,
                                               empty_cluster + empty_size);
                        if (ret == 0) {
                                /*
                                 * now pull our allocation out of this
                                 * cluster
                                 */
                                offset = btrfs_alloc_from_cluster(block_group,
                                                  last_ptr, num_bytes,
                                                  search_start);
                                if (offset) {
                                        /* we found one, proceed */
                                        spin_unlock(&last_ptr->refill_lock);
                                        goto checks;
                                }
                        } else if (!cached && loop > LOOP_CACHING_NOWAIT
                                   && !failed_cluster_refill) {
                                spin_unlock(&last_ptr->refill_lock);

                                failed_cluster_refill = true;
                                wait_block_group_cache_progress(block_group,
                                       num_bytes + empty_cluster + empty_size);
                                goto have_block_group;
                        }

                        /*
                         * at this point we either didn't find a cluster
                         * or we weren't able to allocate a block from our
                         * cluster.  Free the cluster we've been trying
                         * to use, and go to the next block group
                         */
                        btrfs_return_cluster_to_free_space(NULL, last_ptr);
                        spin_unlock(&last_ptr->refill_lock);
                        goto loop;
                }

                offset = btrfs_find_space_for_alloc(block_group, search_start,
                                                    num_bytes, empty_size);
                /*
                 * If we didn't find a chunk, and we haven't failed on this
                 * block group before, and this block group is in the middle of
                 * caching and we are ok with waiting, then go ahead and wait
                 * for progress to be made, and set failed_alloc to true.
                 *
                 * If failed_alloc is true then we've already waited on this
                 * block group once and should move on to the next block group.
                 */
                if (!offset && !failed_alloc && !cached &&
                    loop > LOOP_CACHING_NOWAIT) {
                        wait_block_group_cache_progress(block_group,
                                                num_bytes + empty_size);
                        failed_alloc = true;
                        goto have_block_group;
                } else if (!offset) {
                        goto loop;
                }
checks:
                search_start = stripe_align(root, offset);
                /* move on to the next group */
                if (search_start + num_bytes >= search_end) {
                        btrfs_add_free_space(block_group, offset, num_bytes);
                        goto loop;
                }

                /* move on to the next group */
                if (search_start + num_bytes >
                    block_group->key.objectid + block_group->key.offset) {
                        btrfs_add_free_space(block_group, offset, num_bytes);
                        goto loop;
                }

                if (exclude_nr > 0 &&
                    (search_start + num_bytes > exclude_start &&
                     search_start < exclude_start + exclude_nr)) {
                        search_start = exclude_start + exclude_nr;

                        btrfs_add_free_space(block_group, offset, num_bytes);
                        /*
                         * if search_start is still in this block group
                         * then we just re-search this block group
                         */
                        if (search_start >= block_group->key.objectid &&
                            search_start < (block_group->key.objectid +
                                            block_group->key.offset))
                                goto have_block_group;
                        goto loop;
                }

                ins->objectid = search_start;
                ins->offset = num_bytes;

                if (offset < search_start)
                        btrfs_add_free_space(block_group, offset,
                                             search_start - offset);
                BUG_ON(offset > search_start);

                update_reserved_extents(block_group, num_bytes, 1);

                /* we are all good, lets return */
                break;
loop:
                failed_cluster_refill = false;
                failed_alloc = false;
                btrfs_put_block_group(block_group);
        }
        up_read(&space_info->groups_sem);

        /* LOOP_CACHED_ONLY, only search fully cached block groups
         * LOOP_CACHING_NOWAIT, search partially cached block groups, but
         *                      dont wait foR them to finish caching
         * LOOP_CACHING_WAIT, search everything, and wait if our bg is caching
         * LOOP_ALLOC_CHUNK, force a chunk allocation and try again
         * LOOP_NO_EMPTY_SIZE, set empty_size and empty_cluster to 0 and try
         *                      again
         */
        if (!ins->objectid && loop < LOOP_NO_EMPTY_SIZE &&
            (found_uncached_bg || empty_size || empty_cluster ||
             allowed_chunk_alloc)) {
                if (found_uncached_bg) {
                        found_uncached_bg = false;
                        if (loop < LOOP_CACHING_WAIT) {
                                loop++;
                                goto search;
                        }
                }

                if (loop == LOOP_ALLOC_CHUNK) {
                        empty_size = 0;
                        empty_cluster = 0;
                }

                if (allowed_chunk_alloc) {
                        ret = do_chunk_alloc(trans, root, num_bytes +
                                             2 * 1024 * 1024, data, 1);
                        allowed_chunk_alloc = 0;
                } else {
                        space_info->force_alloc = 1;
                }

                if (loop < LOOP_NO_EMPTY_SIZE) {
                        loop++;
                        goto search;
                }
                ret = -ENOSPC;
        } else if (!ins->objectid) {
                ret = -ENOSPC;
        }

        /* we found what we needed */
        if (ins->objectid) {
                if (!(data & BTRFS_BLOCK_GROUP_DATA))
                        trans->block_group = block_group->key.objectid;

                btrfs_put_block_group(block_group);
                ret = 0;
        }

        return ret;
}

static void dump_space_info(struct btrfs_space_info *info, u64 bytes,
                            int dump_block_groups)
{
        struct btrfs_block_group_cache *cache;

        spin_lock(&info->lock);
        printk(KERN_INFO "space_info has %llu free, is %sfull\n",
               (unsigned long long)(info->total_bytes - info->bytes_used -
                                    info->bytes_pinned - info->bytes_reserved -
                                    info->bytes_super),
               (info->full) ? "" : "not ");
        printk(KERN_INFO "space_info total=%llu, pinned=%llu, delalloc=%llu,"
               " may_use=%llu, used=%llu, root=%llu, super=%llu, reserved=%llu"
               "\n",
               (unsigned long long)info->total_bytes,
               (unsigned long long)info->bytes_pinned,
               (unsigned long long)info->bytes_delalloc,
               (unsigned long long)info->bytes_may_use,
               (unsigned long long)info->bytes_used,
               (unsigned long long)info->bytes_root,
               (unsigned long long)info->bytes_super,
               (unsigned long long)info->bytes_reserved);
        spin_unlock(&info->lock);

        if (!dump_block_groups)
                return;

        down_read(&info->groups_sem);
        list_for_each_entry(cache, &info->block_groups, list) {
                spin_lock(&cache->lock);
                printk(KERN_INFO "block group %llu has %llu bytes, %llu used "
                       "%llu pinned %llu reserved\n",
                       (unsigned long long)cache->key.objectid,
                       (unsigned long long)cache->key.offset,
                       (unsigned long long)btrfs_block_group_used(&cache->item),
                       (unsigned long long)cache->pinned,
                       (unsigned long long)cache->reserved);
                btrfs_dump_free_space(cache, bytes);
                spin_unlock(&cache->lock);
        }
        up_read(&info->groups_sem);
}

int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         u64 num_bytes, u64 min_alloc_size,
                         u64 empty_size, u64 hint_byte,
                         u64 search_end, struct btrfs_key *ins,
                         u64 data)
{
        int ret;
        u64 search_start = 0;
        struct btrfs_fs_info *info = root->fs_info;

        data = btrfs_get_alloc_profile(root, data);
again:
        /*
         * the only place that sets empty_size is btrfs_realloc_node, which
         * is not called recursively on allocations
         */
        if (empty_size || root->ref_cows) {
                if (!(data & BTRFS_BLOCK_GROUP_METADATA)) {
                        ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                     2 * 1024 * 1024,
                                     BTRFS_BLOCK_GROUP_METADATA |
                                     (info->metadata_alloc_profile &
                                      info->avail_metadata_alloc_bits), 0);
                }
                ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                     num_bytes + 2 * 1024 * 1024, data, 0);
        }

        WARN_ON(num_bytes < root->sectorsize);
        ret = find_free_extent(trans, root, num_bytes, empty_size,
                               search_start, search_end, hint_byte, ins,
                               trans->alloc_exclude_start,
                               trans->alloc_exclude_nr, data);

        if (ret == -ENOSPC && num_bytes > min_alloc_size) {
                num_bytes = num_bytes >> 1;
                num_bytes = num_bytes & ~(root->sectorsize - 1);
                num_bytes = max(num_bytes, min_alloc_size);
                do_chunk_alloc(trans, root->fs_info->extent_root,
                               num_bytes, data, 1);
                goto again;
        }
        if (ret == -ENOSPC) {
                struct btrfs_space_info *sinfo;

                sinfo = __find_space_info(root->fs_info, data);
                printk(KERN_ERR "btrfs allocation failed flags %llu, "
                       "wanted %llu\n", (unsigned long long)data,
                       (unsigned long long)num_bytes);
                dump_space_info(sinfo, num_bytes, 1);
        }

        return ret;
}

int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len)
{
        struct btrfs_block_group_cache *cache;
        int ret = 0;

        cache = btrfs_lookup_block_group(root->fs_info, start);
        if (!cache) {
                printk(KERN_ERR "Unable to find block group for %llu\n",
                       (unsigned long long)start);
                return -ENOSPC;
        }

        ret = btrfs_discard_extent(root, start, len);

        btrfs_add_free_space(cache, start, len);
        update_reserved_extents(cache, len, 0);
        btrfs_put_block_group(cache);

        return ret;
}

static int alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root,
                                      u64 parent, u64 root_objectid,
                                      u64 flags, u64 owner, u64 offset,
                                      struct btrfs_key *ins, int ref_mod)
{
        int ret;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_extent_item *extent_item;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int type;
        u32 size;

        if (parent > 0)
                type = BTRFS_SHARED_DATA_REF_KEY;
        else
                type = BTRFS_EXTENT_DATA_REF_KEY;

        size = sizeof(*extent_item) + btrfs_extent_inline_ref_size(type);

        path = btrfs_alloc_path();
        BUG_ON(!path);

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_item(trans, fs_info->extent_root, path,
                                      ins, size);
        BUG_ON(ret);

        leaf = path->nodes[0];
        extent_item = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_item);
        btrfs_set_extent_refs(leaf, extent_item, ref_mod);
        btrfs_set_extent_generation(leaf, extent_item, trans->transid);
        btrfs_set_extent_flags(leaf, extent_item,
                               flags | BTRFS_EXTENT_FLAG_DATA);

        iref = (struct btrfs_extent_inline_ref *)(extent_item + 1);
        btrfs_set_extent_inline_ref_type(leaf, iref, type);
        if (parent > 0) {
                struct btrfs_shared_data_ref *ref;
                ref = (struct btrfs_shared_data_ref *)(iref + 1);
                btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
                btrfs_set_shared_data_ref_count(leaf, ref, ref_mod);
        } else {
                struct btrfs_extent_data_ref *ref;
                ref = (struct btrfs_extent_data_ref *)(&iref->offset);
                btrfs_set_extent_data_ref_root(leaf, ref, root_objectid);
                btrfs_set_extent_data_ref_objectid(leaf, ref, owner);
                btrfs_set_extent_data_ref_offset(leaf, ref, offset);
                btrfs_set_extent_data_ref_count(leaf, ref, ref_mod);
        }

        btrfs_mark_buffer_dirty(path->nodes[0]);
        btrfs_free_path(path);

        ret = update_block_group(trans, root, ins->objectid, ins->offset,
                                 1, 0);
        if (ret) {
                printk(KERN_ERR "btrfs update block group failed for %llu "
                       "%llu\n", (unsigned long long)ins->objectid,
                       (unsigned long long)ins->offset);
                BUG();
        }
        return ret;
}

static int alloc_reserved_tree_block(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     u64 parent, u64 root_objectid,
                                     u64 flags, struct btrfs_disk_key *key,
                                     int level, struct btrfs_key *ins)
{
        int ret;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_extent_item *extent_item;
        struct btrfs_tree_block_info *block_info;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        u32 size = sizeof(*extent_item) + sizeof(*block_info) + sizeof(*iref);

        path = btrfs_alloc_path();
        BUG_ON(!path);

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_item(trans, fs_info->extent_root, path,
                                      ins, size);
        BUG_ON(ret);

        leaf = path->nodes[0];
        extent_item = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_item);
        btrfs_set_extent_refs(leaf, extent_item, 1);
        btrfs_set_extent_generation(leaf, extent_item, trans->transid);
        btrfs_set_extent_flags(leaf, extent_item,
                               flags | BTRFS_EXTENT_FLAG_TREE_BLOCK);
        block_info = (struct btrfs_tree_block_info *)(extent_item + 1);

        btrfs_set_tree_block_key(leaf, block_info, key);
        btrfs_set_tree_block_level(leaf, block_info, level);

        iref = (struct btrfs_extent_inline_ref *)(block_info + 1);
        if (parent > 0) {
                BUG_ON(!(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));
                btrfs_set_extent_inline_ref_type(leaf, iref,
                                                 BTRFS_SHARED_BLOCK_REF_KEY);
                btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
        } else {
                btrfs_set_extent_inline_ref_type(leaf, iref,
                                                 BTRFS_TREE_BLOCK_REF_KEY);
                btrfs_set_extent_inline_ref_offset(leaf, iref, root_objectid);
        }

        btrfs_mark_buffer_dirty(leaf);
        btrfs_free_path(path);

        ret = update_block_group(trans, root, ins->objectid, ins->offset,
                                 1, 0);
        if (ret) {
                printk(KERN_ERR "btrfs update block group failed for %llu "
                       "%llu\n", (unsigned long long)ins->objectid,
                       (unsigned long long)ins->offset);
                BUG();
        }
        return ret;
}

int btrfs_alloc_reserved_file_extent(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     u64 root_objectid, u64 owner,
                                     u64 offset, struct btrfs_key *ins)
{
        int ret;

        BUG_ON(root_objectid == BTRFS_TREE_LOG_OBJECTID);

        ret = btrfs_add_delayed_data_ref(trans, ins->objectid, ins->offset,
                                         0, root_objectid, owner, offset,
                                         BTRFS_ADD_DELAYED_EXTENT, NULL);
        return ret;
}

/*
 * this is used by the tree logging recovery code.  It records that
 * an extent has been allocated and makes sure to clear the free
 * space cache bits as well
 */
int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   u64 root_objectid, u64 owner, u64 offset,
                                   struct btrfs_key *ins)
{
        int ret;
        struct btrfs_block_group_cache *block_group;
        struct btrfs_caching_control *caching_ctl;
        u64 start = ins->objectid;
        u64 num_bytes = ins->offset;

        block_group = btrfs_lookup_block_group(root->fs_info, ins->objectid);
        cache_block_group(block_group);
        caching_ctl = get_caching_control(block_group);

        if (!caching_ctl) {
                BUG_ON(!block_group_cache_done(block_group));
                ret = btrfs_remove_free_space(block_group, start, num_bytes);
                BUG_ON(ret);
        } else {
                mutex_lock(&caching_ctl->mutex);

                if (start >= caching_ctl->progress) {
                        ret = add_excluded_extent(root, start, num_bytes);
                        BUG_ON(ret);
                } else if (start + num_bytes <= caching_ctl->progress) {
                        ret = btrfs_remove_free_space(block_group,
                                                      start, num_bytes);
                        BUG_ON(ret);
                } else {
                        num_bytes = caching_ctl->progress - start;
                        ret = btrfs_remove_free_space(block_group,
                                                      start, num_bytes);
                        BUG_ON(ret);

                        start = caching_ctl->progress;
                        num_bytes = ins->objectid + ins->offset -
                                    caching_ctl->progress;
                        ret = add_excluded_extent(root, start, num_bytes);
                        BUG_ON(ret);
                }

                mutex_unlock(&caching_ctl->mutex);
                put_caching_control(caching_ctl);
        }

        update_reserved_extents(block_group, ins->offset, 1);
        btrfs_put_block_group(block_group);
        ret = alloc_reserved_file_extent(trans, root, 0, root_objectid,
                                         0, owner, offset, ins, 1);
        return ret;
}

/*
 * finds a free extent and does all the dirty work required for allocation
 * returns the key for the extent through ins, and a tree buffer for
 * the first block of the extent through buf.
 *
 * returns 0 if everything worked, non-zero otherwise.
 */
static int alloc_tree_block(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            u64 num_bytes, u64 parent, u64 root_objectid,
                            struct btrfs_disk_key *key, int level,
                            u64 empty_size, u64 hint_byte, u64 search_end,
                            struct btrfs_key *ins)
{
        int ret;
        u64 flags = 0;

        ret = btrfs_reserve_extent(trans, root, num_bytes, num_bytes,
                                   empty_size, hint_byte, search_end,
                                   ins, 0);
        if (ret)
                return ret;

        if (root_objectid == BTRFS_TREE_RELOC_OBJECTID) {
                if (parent == 0)
                        parent = ins->objectid;
                flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
        } else
                BUG_ON(parent > 0);

        if (root_objectid != BTRFS_TREE_LOG_OBJECTID) {
                struct btrfs_delayed_extent_op *extent_op;
                extent_op = kmalloc(sizeof(*extent_op), GFP_NOFS);
                BUG_ON(!extent_op);
                if (key)
                        memcpy(&extent_op->key, key, sizeof(extent_op->key));
                else
                        memset(&extent_op->key, 0, sizeof(extent_op->key));
                extent_op->flags_to_set = flags;
                extent_op->update_key = 1;
                extent_op->update_flags = 1;
                extent_op->is_data = 0;

                ret = btrfs_add_delayed_tree_ref(trans, ins->objectid,
                                        ins->offset, parent, root_objectid,
                                        level, BTRFS_ADD_DELAYED_EXTENT,
                                        extent_op);
                BUG_ON(ret);
        }
        return ret;
}

struct extent_buffer *btrfs_init_new_buffer(struct btrfs_trans_handle *trans,
                                            struct btrfs_root *root,
                                            u64 bytenr, u32 blocksize,
                                            int level)
{
        struct extent_buffer *buf;

        buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
        if (!buf)
                return ERR_PTR(-ENOMEM);
        btrfs_set_header_generation(buf, trans->transid);
        btrfs_set_buffer_lockdep_class(buf, level);
        btrfs_tree_lock(buf);
        clean_tree_block(trans, root, buf);

        btrfs_set_lock_blocking(buf);
        btrfs_set_buffer_uptodate(buf);

        if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID) {
                set_extent_dirty(&root->dirty_log_pages, buf->start,
                         buf->start + buf->len - 1, GFP_NOFS);
        } else {
                set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
                         buf->start + buf->len - 1, GFP_NOFS);
        }
        trans->blocks_used++;
        /* this returns a buffer locked for blocking */
        return buf;
}

/*
 * helper function to allocate a block for a given tree
 * returns the tree buffer or NULL.
 */
struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root, u32 blocksize,
                                        u64 parent, u64 root_objectid,
                                        struct btrfs_disk_key *key, int level,
                                        u64 hint, u64 empty_size)
{
        struct btrfs_key ins;
        int ret;
        struct extent_buffer *buf;

        ret = alloc_tree_block(trans, root, blocksize, parent, root_objectid,
                               key, level, empty_size, hint, (u64)-1, &ins);
        if (ret) {
                BUG_ON(ret > 0);
                return ERR_PTR(ret);
        }

        buf = btrfs_init_new_buffer(trans, root, ins.objectid,
                                    blocksize, level);
        return buf;
}

struct walk_control {
        u64 refs[BTRFS_MAX_LEVEL];
        u64 flags[BTRFS_MAX_LEVEL];
        struct btrfs_key update_progress;
        int stage;
        int level;
        int shared_level;
        int update_ref;
        int keep_locks;
        int reada_slot;
        int reada_count;
};

#define DROP_REFERENCE  1
#define UPDATE_BACKREF  2

static noinline void reada_walk_down(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct walk_control *wc,
                                     struct btrfs_path *path)
{
        u64 bytenr;
        u64 generation;
        u64 refs;
        u64 flags;
        u64 last = 0;
        u32 nritems;
        u32 blocksize;
        struct btrfs_key key;
        struct extent_buffer *eb;
        int ret;
        int slot;
        int nread = 0;

        if (path->slots[wc->level] < wc->reada_slot) {
                wc->reada_count = wc->reada_count * 2 / 3;
                wc->reada_count = max(wc->reada_count, 2);
        } else {
                wc->reada_count = wc->reada_count * 3 / 2;
                wc->reada_count = min_t(int, wc->reada_count,
                                        BTRFS_NODEPTRS_PER_BLOCK(root));
        }

        eb = path->nodes[wc->level];
        nritems = btrfs_header_nritems(eb);
        blocksize = btrfs_level_size(root, wc->level - 1);

        for (slot = path->slots[wc->level]; slot < nritems; slot++) {
                if (nread >= wc->reada_count)
                        break;

                cond_resched();
                bytenr = btrfs_node_blockptr(eb, slot);
                generation = btrfs_node_ptr_generation(eb, slot);

                if (slot == path->slots[wc->level])
                        goto reada;

                if (wc->stage == UPDATE_BACKREF &&
                    generation <= root->root_key.offset)
                        continue;

                /* We don't lock the tree block, it's OK to be racy here */
                ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,
                                               &refs, &flags);
                BUG_ON(ret);
                BUG_ON(refs == 0);

                if (wc->stage == DROP_REFERENCE) {
                        if (refs == 1)
                                goto reada;

                        if (wc->level == 1 &&
                            (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
                                continue;
                        if (!wc->update_ref ||
                            generation <= root->root_key.offset)
                                continue;
                        btrfs_node_key_to_cpu(eb, &key, slot);
                        ret = btrfs_comp_cpu_keys(&key,
                                                  &wc->update_progress);
                        if (ret < 0)
                                continue;
                } else {
                        if (wc->level == 1 &&
                            (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
                                continue;
                }
reada:
                ret = readahead_tree_block(root, bytenr, blocksize,
                                           generation);
                if (ret)
                        break;
                last = bytenr + blocksize;
                nread++;
        }
        wc->reada_slot = slot;
}

/*
 * hepler to process tree block while walking down the tree.
 *
 * when wc->stage == UPDATE_BACKREF, this function updates
 * back refs for pointers in the block.
 *
 * NOTE: return value 1 means we should stop walking down.
 */
static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   struct btrfs_path *path,
                                   struct walk_control *wc, int lookup_info)
{
        int level = wc->level;
        struct extent_buffer *eb = path->nodes[level];
        u64 flag = BTRFS_BLOCK_FLAG_FULL_BACKREF;
        int ret;

        if (wc->stage == UPDATE_BACKREF &&
            btrfs_header_owner(eb) != root->root_key.objectid)
                return 1;

        /*
         * when reference count of tree block is 1, it won't increase
         * again. once full backref flag is set, we never clear it.
         */
        if (lookup_info &&
            ((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||
             (wc->stage == UPDATE_BACKREF && !(wc->flags[level] & flag)))) {
                BUG_ON(!path->locks[level]);
                ret = btrfs_lookup_extent_info(trans, root,
                                               eb->start, eb->len,
                                               &wc->refs[level],
                                               &wc->flags[level]);
                BUG_ON(ret);
                BUG_ON(wc->refs[level] == 0);
        }

        if (wc->stage == DROP_REFERENCE) {
                if (wc->refs[level] > 1)
                        return 1;

                if (path->locks[level] && !wc->keep_locks) {
                        btrfs_tree_unlock(eb);
                        path->locks[level] = 0;
                }
                return 0;
        }

        /* wc->stage == UPDATE_BACKREF */
        if (!(wc->flags[level] & flag)) {
                BUG_ON(!path->locks[level]);
                ret = btrfs_inc_ref(trans, root, eb, 1);
                BUG_ON(ret);
                ret = btrfs_dec_ref(trans, root, eb, 0);
                BUG_ON(ret);
                ret = btrfs_set_disk_extent_flags(trans, root, eb->start,
                                                  eb->len, flag, 0);
                BUG_ON(ret);
                wc->flags[level] |= flag;
        }

        /*
         * the block is shared by multiple trees, so it's not good to
         * keep the tree lock
         */
        if (path->locks[level] && level > 0) {
                btrfs_tree_unlock(eb);
                path->locks[level] = 0;
        }
        return 0;
}

/*
 * hepler to process tree block pointer.
 *
 * when wc->stage == DROP_REFERENCE, this function checks
 * reference count of the block pointed to. if the block
 * is shared and we need update back refs for the subtree
 * rooted at the block, this function changes wc->stage to
 * UPDATE_BACKREF. if the block is shared and there is no
 * need to update back, this function drops the reference
 * to the block.
 *
 * NOTE: return value 1 means we should stop walking down.
 */
static noinline int do_walk_down(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct walk_control *wc, int *lookup_info)
{
        u64 bytenr;
        u64 generation;
        u64 parent;
        u32 blocksize;
        struct btrfs_key key;
        struct extent_buffer *next;
        int level = wc->level;
        int reada = 0;
        int ret = 0;

        generation = btrfs_node_ptr_generation(path->nodes[level],
                                               path->slots[level]);
        /*
         * if the lower level block was created before the snapshot
         * was created, we know there is no need to update back refs
         * for the subtree
         */
        if (wc->stage == UPDATE_BACKREF &&
            generation <= root->root_key.offset) {
                *lookup_info = 1;
                return 1;
        }

        bytenr = btrfs_node_blockptr(path->nodes[level], path->slots[level]);
        blocksize = btrfs_level_size(root, level - 1);

        next = btrfs_find_tree_block(root, bytenr, blocksize);
        if (!next) {
                next = btrfs_find_create_tree_block(root, bytenr, blocksize);
                reada = 1;
        }
        btrfs_tree_lock(next);
        btrfs_set_lock_blocking(next);

        ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,
                                       &wc->refs[level - 1],
                                       &wc->flags[level - 1]);
        BUG_ON(ret);
        BUG_ON(wc->refs[level - 1] == 0);
        *lookup_info = 0;

        if (wc->stage == DROP_REFERENCE) {
                if (wc->refs[level - 1] > 1) {
                        if (level == 1 &&
                            (wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))
                                goto skip;

                        if (!wc->update_ref ||
                            generation <= root->root_key.offset)
                                goto skip;

                        btrfs_node_key_to_cpu(path->nodes[level], &key,
                                              path->slots[level]);
                        ret = btrfs_comp_cpu_keys(&key, &wc->update_progress);
                        if (ret < 0)
                                goto skip;

                        wc->stage = UPDATE_BACKREF;
                        wc->shared_level = level - 1;
                }
        } else {
                if (level == 1 &&
                    (wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))
                        goto skip;
        }

        if (!btrfs_buffer_uptodate(next, generation)) {
                btrfs_tree_unlock(next);
                free_extent_buffer(next);
                next = NULL;
                *lookup_info = 1;
        }

        if (!next) {
                if (reada && level == 1)
                        reada_walk_down(trans, root, wc, path);
                next = read_tree_block(root, bytenr, blocksize, generation);
                btrfs_tree_lock(next);
                btrfs_set_lock_blocking(next);
        }

        level--;
        BUG_ON(level != btrfs_header_level(next));
        path->nodes[level] = next;
        path->slots[level] = 0;
        path->locks[level] = 1;
        wc->level = level;
        if (wc->level == 1)
                wc->reada_slot = 0;
        return 0;
skip:
        wc->refs[level - 1] = 0;
        wc->flags[level - 1] = 0;
        if (wc->stage == DROP_REFERENCE) {
                if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
                        parent = path->nodes[level]->start;
                } else {
                        BUG_ON(root->root_key.objectid !=
                               btrfs_header_owner(path->nodes[level]));
                        parent = 0;
                }

                ret = btrfs_free_extent(trans, root, bytenr, blocksize, parent,
                                        root->root_key.objectid, level - 1, 0);
                BUG_ON(ret);
        }
        btrfs_tree_unlock(next);
        free_extent_buffer(next);
        *lookup_info = 1;
        return 1;
}

/*
 * hepler to process tree block while walking up the tree.
 *
 * when wc->stage == DROP_REFERENCE, this function drops
 * reference count on the block.
 *
 * when wc->stage == UPDATE_BACKREF, this function changes
 * wc->stage back to DROP_REFERENCE if we changed wc->stage
 * to UPDATE_BACKREF previously while processing the block.
 *
 * NOTE: return value 1 means we should stop walking up.
 */
static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct walk_control *wc)
{
        int ret = 0;
        int level = wc->level;
        struct extent_buffer *eb = path->nodes[level];
        u64 parent = 0;

        if (wc->stage == UPDATE_BACKREF) {
                BUG_ON(wc->shared_level < level);
                if (level < wc->shared_level)
                        goto out;

                ret = find_next_key(path, level + 1, &wc->update_progress);
                if (ret > 0)
                        wc->update_ref = 0;

                wc->stage = DROP_REFERENCE;
                wc->shared_level = -1;
                path->slots[level] = 0;

                /*
                 * check reference count again if the block isn't locked.
                 * we should start walking down the tree again if reference
                 * count is one.
                 */
                if (!path->locks[level]) {
                        BUG_ON(level == 0);
                        btrfs_tree_lock(eb);
                        btrfs_set_lock_blocking(eb);
                        path->locks[level] = 1;

                        ret = btrfs_lookup_extent_info(trans, root,
                                                       eb->start, eb->len,
                                                       &wc->refs[level],
                                                       &wc->flags[level]);
                        BUG_ON(ret);
                        BUG_ON(wc->refs[level] == 0);
                        if (wc->refs[level] == 1) {
                                btrfs_tree_unlock(eb);
                                path->locks[level] = 0;
                                return 1;
                        }
                }
        }

        /* wc->stage == DROP_REFERENCE */
        BUG_ON(wc->refs[level] > 1 && !path->locks[level]);

        if (wc->refs[level] == 1) {
                if (level == 0) {
                        if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF)
                                ret = btrfs_dec_ref(trans, root, eb, 1);
                        else
                                ret = btrfs_dec_ref(trans, root, eb, 0);
                        BUG_ON(ret);
                }
                /* make block locked assertion in clean_tree_block happy */
                if (!path->locks[level] &&
                    btrfs_header_generation(eb) == trans->transid) {
                        btrfs_tree_lock(eb);
                        btrfs_set_lock_blocking(eb);
                        path->locks[level] = 1;
                }
                clean_tree_block(trans, root, eb);
        }

        if (eb == root->node) {
                if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF)
                        parent = eb->start;
                else
                        BUG_ON(root->root_key.objectid !=
                               btrfs_header_owner(eb));
        } else {
                if (wc->flags[level + 1] & BTRFS_BLOCK_FLAG_FULL_BACKREF)
                        parent = path->nodes[level + 1]->start;
                else
                        BUG_ON(root->root_key.objectid !=
                               btrfs_header_owner(path->nodes[level + 1]));
        }

        ret = btrfs_free_extent(trans, root, eb->start, eb->len, parent,
                                root->root_key.objectid, level, 0);
        BUG_ON(ret);
out:
        wc->refs[level] = 0;
        wc->flags[level] = 0;
        return ret;
}

static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   struct btrfs_path *path,
                                   struct walk_control *wc)
{
        int level = wc->level;
        int lookup_info = 1;
        int ret;

        while (level >= 0) {
                if (path->slots[level] >=
                    btrfs_header_nritems(path->nodes[level]))
                        break;

                ret = walk_down_proc(trans, root, path, wc, lookup_info);
                if (ret > 0)
                        break;

                if (level == 0)
                        break;

                ret = do_walk_down(trans, root, path, wc, &lookup_info);
                if (ret > 0) {
                        path->slots[level]++;
                        continue;
                }
                level = wc->level;
        }
        return 0;
}

static noinline int walk_up_tree(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct walk_control *wc, int max_level)
{
        int level = wc->level;
        int ret;

        path->slots[level] = btrfs_header_nritems(path->nodes[level]);
        while (level < max_level && path->nodes[level]) {
                wc->level = level;
                if (path->slots[level] + 1 <
                    btrfs_header_nritems(path->nodes[level])) {
                        path->slots[level]++;
                        return 0;
                } else {
                        ret = walk_up_proc(trans, root, path, wc);
                        if (ret > 0)
                                return 0;

                        if (path->locks[level]) {
                                btrfs_tree_unlock(path->nodes[level]);
                                path->locks[level] = 0;
                        }
                        free_extent_buffer(path->nodes[level]);
                        path->nodes[level] = NULL;
                        level++;
                }
        }
        return 1;
}

/*
 * drop a subvolume tree.
 *
 * this function traverses the tree freeing any blocks that only
 * referenced by the tree.
 *
 * when a shared tree block is found. this function decreases its
 * reference count by one. if update_ref is true, this function
 * also make sure backrefs for the shared block and all lower level
 * blocks are properly updated.
 */
int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref)
{
        struct btrfs_path *path;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *tree_root = root->fs_info->tree_root;
        struct btrfs_root_item *root_item = &root->root_item;
        struct walk_control *wc;
        struct btrfs_key key;
        int err = 0;
        int ret;
        int level;

        path = btrfs_alloc_path();
        BUG_ON(!path);

        wc = kzalloc(sizeof(*wc), GFP_NOFS);
        BUG_ON(!wc);

        trans = btrfs_start_transaction(tree_root, 1);

        if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
                level = btrfs_header_level(root->node);
                path->nodes[level] = btrfs_lock_root_node(root);
                btrfs_set_lock_blocking(path->nodes[level]);
                path->slots[level] = 0;
                path->locks[level] = 1;
                memset(&wc->update_progress, 0,
                       sizeof(wc->update_progress));
        } else {
                btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
                memcpy(&wc->update_progress, &key,
                       sizeof(wc->update_progress));

                level = root_item->drop_level;
                BUG_ON(level == 0);
                path->lowest_level = level;
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                path->lowest_level = 0;
                if (ret < 0) {
                        err = ret;
                        goto out;
                }
                WARN_ON(ret > 0);

                /*
                 * unlock our path, this is safe because only this
                 * function is allowed to delete this snapshot
                 */
                btrfs_unlock_up_safe(path, 0);

                level = btrfs_header_level(root->node);
                while (1) {
                        btrfs_tree_lock(path->nodes[level]);
                        btrfs_set_lock_blocking(path->nodes[level]);

                        ret = btrfs_lookup_extent_info(trans, root,
                                                path->nodes[level]->start,
                                                path->nodes[level]->len,
                                                &wc->refs[level],
                                                &wc->flags[level]);
                        BUG_ON(ret);
                        BUG_ON(wc->refs[level] == 0);

                        if (level == root_item->drop_level)
                                break;

                        btrfs_tree_unlock(path->nodes[level]);
                        WARN_ON(wc->refs[level] != 1);
                        level--;
                }
        }

        wc->level = level;
        wc->shared_level = -1;
        wc->stage = DROP_REFERENCE;
        wc->update_ref = update_ref;
        wc->keep_locks = 0;
        wc->reada_count = BTRFS_NODEPTRS_PER_BLOCK(root);

        while (1) {
                ret = walk_down_tree(trans, root, path, wc);
                if (ret < 0) {
                        err = ret;
                        break;
                }

                ret = walk_up_tree(trans, root, path, wc, BTRFS_MAX_LEVEL);
                if (ret < 0) {
                        err = ret;
                        break;
                }

                if (ret > 0) {
                        BUG_ON(wc->stage != DROP_REFERENCE);
                        break;
                }

                if (wc->stage == DROP_REFERENCE) {
                        level = wc->level;
                        btrfs_node_key(path->nodes[level],
                                       &root_item->drop_progress,
                                       path->slots[level]);
                        root_item->drop_level = level;
                }

                BUG_ON(wc->level == 0);
                if (trans->transaction->in_commit ||
                    trans->transaction->delayed_refs.flushing) {
                        ret = btrfs_update_root(trans, tree_root,
                                                &root->root_key,
                                                root_item);
                        BUG_ON(ret);

                        btrfs_end_transaction(trans, tree_root);
                        trans = btrfs_start_transaction(tree_root, 1);
                } else {
                        unsigned long update;
                        update = trans->delayed_ref_updates;
                        trans->delayed_ref_updates = 0;
                        if (update)
                                btrfs_run_delayed_refs(trans, tree_root,
                                                       update);
                }
        }
        btrfs_release_path(root, path);
        BUG_ON(err);

        ret = btrfs_del_root(trans, tree_root, &root->root_key);
        BUG_ON(ret);

        if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
                ret = btrfs_find_last_root(tree_root, root->root_key.objectid,
                                           NULL, NULL);
                BUG_ON(ret < 0);
                if (ret > 0) {
                        ret = btrfs_del_orphan_item(trans, tree_root,
                                                    root->root_key.objectid);
                        BUG_ON(ret);
                }
        }

        if (root->in_radix) {
                btrfs_free_fs_root(tree_root->fs_info, root);
        } else {
                free_extent_buffer(root->node);
                free_extent_buffer(root->commit_root);
                kfree(root);
        }
out:
        btrfs_end_transaction(trans, tree_root);
        kfree(wc);
        btrfs_free_path(path);
        return err;
}

/*
 * drop subtree rooted at tree block 'node'.
 *
 * NOTE: this function will unlock and release tree block 'node'
 */
int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
                        struct extent_buffer *node,
                        struct extent_buffer *parent)
{
        struct btrfs_path *path;
        struct walk_control *wc;
        int level;
        int parent_level;
        int ret = 0;
        int wret;

        BUG_ON(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);

        path = btrfs_alloc_path();
        BUG_ON(!path);

        wc = kzalloc(sizeof(*wc), GFP_NOFS);
        BUG_ON(!wc);

        btrfs_assert_tree_locked(parent);
        parent_level = btrfs_header_level(parent);
        extent_buffer_get(parent);
        path->nodes[parent_level] = parent;
        path->slots[parent_level] = btrfs_header_nritems(parent);

        btrfs_assert_tree_locked(node);
        level = btrfs_header_level(node);
        path->nodes[level] = node;
        path->slots[level] = 0;
        path->locks[level] = 1;

        wc->refs[parent_level] = 1;
        wc->flags[parent_level] = BTRFS_BLOCK_FLAG_FULL_BACKREF;
        wc->level = level;
        wc->shared_level = -1;
        wc->stage = DROP_REFERENCE;
        wc->update_ref = 0;
        wc->keep_locks = 1;
        wc->reada_count = BTRFS_NODEPTRS_PER_BLOCK(root);

        while (1) {
                wret = walk_down_tree(trans, root, path, wc);
                if (wret < 0) {
                        ret = wret;
                        break;
                }

                wret = walk_up_tree(trans, root, path, wc, parent_level);
                if (wret < 0)
                        ret = wret;
                if (wret != 0)
                        break;
        }

        kfree(wc);
        btrfs_free_path(path);
        return ret;
}

#if 0
static unsigned long calc_ra(unsigned long start, unsigned long last,
                             unsigned long nr)
{
        return min(last, start + nr - 1);
}

static noinline int relocate_inode_pages(struct inode *inode, u64 start,
                                         u64 len)
{
        u64 page_start;
        u64 page_end;
        unsigned long first_index;
        unsigned long last_index;
        unsigned long i;
        struct page *page;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct file_ra_state *ra;
        struct btrfs_ordered_extent *ordered;
        unsigned int total_read = 0;
        unsigned int total_dirty = 0;
        int ret = 0;

        ra = kzalloc(sizeof(*ra), GFP_NOFS);

        mutex_lock(&inode->i_mutex);
        first_index = start >> PAGE_CACHE_SHIFT;
        last_index = (start + len - 1) >> PAGE_CACHE_SHIFT;

        /* make sure the dirty trick played by the caller work */
        ret = invalidate_inode_pages2_range(inode->i_mapping,
                                            first_index, last_index);
        if (ret)
                goto out_unlock;

        file_ra_state_init(ra, inode->i_mapping);

        for (i = first_index ; i <= last_index; i++) {
                if (total_read % ra->ra_pages == 0) {
                        btrfs_force_ra(inode->i_mapping, ra, NULL, i,
                                       calc_ra(i, last_index, ra->ra_pages));
                }
                total_read++;
again:
                if (((u64)i << PAGE_CACHE_SHIFT) > i_size_read(inode))
                        BUG_ON(1);
                page = grab_cache_page(inode->i_mapping, i);
                if (!page) {
                        ret = -ENOMEM;
                        goto out_unlock;
                }
                if (!PageUptodate(page)) {
                        btrfs_readpage(NULL, page);
                        lock_page(page);
                        if (!PageUptodate(page)) {
                                unlock_page(page);
                                page_cache_release(page);
                                ret = -EIO;
                                goto out_unlock;
                        }
                }
                wait_on_page_writeback(page);

                page_start = (u64)page->index << PAGE_CACHE_SHIFT;
                page_end = page_start + PAGE_CACHE_SIZE - 1;
                lock_extent(io_tree, page_start, page_end, GFP_NOFS);

                ordered = btrfs_lookup_ordered_extent(inode, page_start);
                if (ordered) {
                        unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
                        unlock_page(page);
                        page_cache_release(page);
                        btrfs_start_ordered_extent(inode, ordered, 1);
                        btrfs_put_ordered_extent(ordered);
                        goto again;
                }
                set_page_extent_mapped(page);

                if (i == first_index)
                        set_extent_bits(io_tree, page_start, page_end,
                                        EXTENT_BOUNDARY, GFP_NOFS);
                btrfs_set_extent_delalloc(inode, page_start, page_end);

                set_page_dirty(page);
                total_dirty++;

                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
                unlock_page(page);
                page_cache_release(page);
        }

out_unlock:
        kfree(ra);
        mutex_unlock(&inode->i_mutex);
        balance_dirty_pages_ratelimited_nr(inode->i_mapping, total_dirty);
        return ret;
}

static noinline int relocate_data_extent(struct inode *reloc_inode,
                                         struct btrfs_key *extent_key,
                                         u64 offset)
{
        struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
        struct extent_map_tree *em_tree = &BTRFS_I(reloc_inode)->extent_tree;
        struct extent_map *em;
        u64 start = extent_key->objectid - offset;
        u64 end = start + extent_key->offset - 1;

        em = alloc_extent_map(GFP_NOFS);
        BUG_ON(!em || IS_ERR(em));

        em->start = start;
        em->len = extent_key->offset;
        em->block_len = extent_key->offset;
        em->block_start = extent_key->objectid;
        em->bdev = root->fs_info->fs_devices->latest_bdev;
        set_bit(EXTENT_FLAG_PINNED, &em->flags);

        /* setup extent map to cheat btrfs_readpage */
        lock_extent(&BTRFS_I(reloc_inode)->io_tree, start, end, GFP_NOFS);
        while (1) {
                int ret;
                write_lock(&em_tree->lock);
                ret = add_extent_mapping(em_tree, em);
                write_unlock(&em_tree->lock);
                if (ret != -EEXIST) {
                        free_extent_map(em);
                        break;
                }
                btrfs_drop_extent_cache(reloc_inode, start, end, 0);
        }
        unlock_extent(&BTRFS_I(reloc_inode)->io_tree, start, end, GFP_NOFS);

        return relocate_inode_pages(reloc_inode, start, extent_key->offset);
}

struct btrfs_ref_path {
        u64 extent_start;
        u64 nodes[BTRFS_MAX_LEVEL];
        u64 root_objectid;
        u64 root_generation;
        u64 owner_objectid;
        u32 num_refs;
        int lowest_level;
        int current_level;
        int shared_level;

        struct btrfs_key node_keys[BTRFS_MAX_LEVEL];
        u64 new_nodes[BTRFS_MAX_LEVEL];
};

struct disk_extent {
        u64 ram_bytes;
        u64 disk_bytenr;
        u64 disk_num_bytes;
        u64 offset;
        u64 num_bytes;
        u8 compression;
        u8 encryption;
        u16 other_encoding;
};

static int is_cowonly_root(u64 root_objectid)
{
        if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
            root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
            root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
            root_objectid == BTRFS_DEV_TREE_OBJECTID ||
            root_objectid == BTRFS_TREE_LOG_OBJECTID ||
            root_objectid == BTRFS_CSUM_TREE_OBJECTID)
                return 1;
        return 0;
}

static noinline int __next_ref_path(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *extent_root,
                                    struct btrfs_ref_path *ref_path,
                                    int first_time)
{
        struct extent_buffer *leaf;
        struct btrfs_path *path;
        struct btrfs_extent_ref *ref;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u64 bytenr;
        u32 nritems;
        int level;
        int ret = 1;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        if (first_time) {
                ref_path->lowest_level = -1;
                ref_path->current_level = -1;
                ref_path->shared_level = -1;
                goto walk_up;
        }
walk_down:
        level = ref_path->current_level - 1;
        while (level >= -1) {
                u64 parent;
                if (level < ref_path->lowest_level)
                        break;

                if (level >= 0)
                        bytenr = ref_path->nodes[level];
                else
                        bytenr = ref_path->extent_start;
                BUG_ON(bytenr == 0);

                parent = ref_path->nodes[level + 1];
                ref_path->nodes[level + 1] = 0;
                ref_path->current_level = level;
                BUG_ON(parent == 0);

                key.objectid = bytenr;
                key.offset = parent + 1;
                key.type = BTRFS_EXTENT_REF_KEY;

                ret = btrfs_search_slot(trans, extent_root, &key, path, 0, 0);
                if (ret < 0)
                        goto out;
                BUG_ON(ret == 0);

                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(extent_root, path);
                        if (ret < 0)
                                goto out;
                        if (ret > 0)
                                goto next;
                        leaf = path->nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid == bytenr &&
                    found_key.type == BTRFS_EXTENT_REF_KEY) {
                        if (level < ref_path->shared_level)
                                ref_path->shared_level = level;
                        goto found;
                }
next:
                level--;
                btrfs_release_path(extent_root, path);
                cond_resched();
        }
        /* reached lowest level */
        ret = 1;
        goto out;
walk_up:
        level = ref_path->current_level;
        while (level < BTRFS_MAX_LEVEL - 1) {
                u64 ref_objectid;

                if (level >= 0)
                        bytenr = ref_path->nodes[level];
                else
                        bytenr = ref_path->extent_start;

                BUG_ON(bytenr == 0);

                key.objectid = bytenr;
                key.offset = 0;
                key.type = BTRFS_EXTENT_REF_KEY;

                ret = btrfs_search_slot(trans, extent_root, &key, path, 0, 0);
                if (ret < 0)
                        goto out;

                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(extent_root, path);
                        if (ret < 0)
                                goto out;
                        if (ret > 0) {
                                /* the extent was freed by someone */
                                if (ref_path->lowest_level == level)
                                        goto out;
                                btrfs_release_path(extent_root, path);
                                goto walk_down;
                        }
                        leaf = path->nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != bytenr ||
                                found_key.type != BTRFS_EXTENT_REF_KEY) {
                        /* the extent was freed by someone */
                        if (ref_path->lowest_level == level) {
                                ret = 1;
                                goto out;
                        }
                        btrfs_release_path(extent_root, path);
                        goto walk_down;
                }
found:
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_extent_ref);
                ref_objectid = btrfs_ref_objectid(leaf, ref);
                if (ref_objectid < BTRFS_FIRST_FREE_OBJECTID) {
                        if (first_time) {
                                level = (int)ref_objectid;
                                BUG_ON(level >= BTRFS_MAX_LEVEL);
                                ref_path->lowest_level = level;
                                ref_path->current_level = level;
                                ref_path->nodes[level] = bytenr;
                        } else {
                                WARN_ON(ref_objectid != level);
                        }
                } else {
                        WARN_ON(level != -1);
                }
                first_time = 0;

                if (ref_path->lowest_level == level) {
                        ref_path->owner_objectid = ref_objectid;
                        ref_path->num_refs = btrfs_ref_num_refs(leaf, ref);
                }

                /*
                 * the block is tree root or the block isn't in reference
                 * counted tree.
                 */
                if (found_key.objectid == found_key.offset ||
                    is_cowonly_root(btrfs_ref_root(leaf, ref))) {
                        ref_path->root_objectid = btrfs_ref_root(leaf, ref);
                        ref_path->root_generation =
                                btrfs_ref_generation(leaf, ref);
                        if (level < 0) {
                                /* special reference from the tree log */
                                ref_path->nodes[0] = found_key.offset;
                                ref_path->current_level = 0;
                        }
                        ret = 0;
                        goto out;
                }

                level++;
                BUG_ON(ref_path->nodes[level] != 0);
                ref_path->nodes[level] = found_key.offset;
                ref_path->current_level = level;

                /*
                 * the reference was created in the running transaction,
                 * no need to continue walking up.
                 */
                if (btrfs_ref_generation(leaf, ref) == trans->transid) {
                        ref_path->root_objectid = btrfs_ref_root(leaf, ref);
                        ref_path->root_generation =
                                btrfs_ref_generation(leaf, ref);
                        ret = 0;
                        goto out;
                }

                btrfs_release_path(extent_root, path);
                cond_resched();
        }
        /* reached max tree level, but no tree root found. */
        BUG();
out:
        btrfs_free_path(path);
        return ret;
}

static int btrfs_first_ref_path(struct btrfs_trans_handle *trans,
                                struct btrfs_root *extent_root,
                                struct btrfs_ref_path *ref_path,
                                u64 extent_start)
{
        memset(ref_path, 0, sizeof(*ref_path));
        ref_path->extent_start = extent_start;

        return __next_ref_path(trans, extent_root, ref_path, 1);
}

static int btrfs_next_ref_path(struct btrfs_trans_handle *trans,
                               struct btrfs_root *extent_root,
                               struct btrfs_ref_path *ref_path)
{
        return __next_ref_path(trans, extent_root, ref_path, 0);
}

static noinline int get_new_locations(struct inode *reloc_inode,
                                      struct btrfs_key *extent_key,
                                      u64 offset, int no_fragment,
                                      struct disk_extent **extents,
                                      int *nr_extents)
{
        struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
        struct btrfs_path *path;
        struct btrfs_file_extent_item *fi;
        struct extent_buffer *leaf;
        struct disk_extent *exts = *extents;
        struct btrfs_key found_key;
        u64 cur_pos;
        u64 last_byte;
        u32 nritems;
        int nr = 0;
        int max = *nr_extents;
        int ret;

        WARN_ON(!no_fragment && *extents);
        if (!exts) {
                max = 1;
                exts = kmalloc(sizeof(*exts) * max, GFP_NOFS);
                if (!exts)
                        return -ENOMEM;
        }

        path = btrfs_alloc_path();
        BUG_ON(!path);

        cur_pos = extent_key->objectid - offset;
        last_byte = extent_key->objectid + extent_key->offset;
        ret = btrfs_lookup_file_extent(NULL, root, path, reloc_inode->i_ino,
                                       cur_pos, 0);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = -ENOENT;
                goto out;
        }

        while (1) {
                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto out;
                        if (ret > 0)
                                break;
                        leaf = path->nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.offset != cur_pos ||
                    found_key.type != BTRFS_EXTENT_DATA_KEY ||
                    found_key.objectid != reloc_inode->i_ino)
                        break;

                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(leaf, fi) !=
                    BTRFS_FILE_EXTENT_REG ||
                    btrfs_file_extent_disk_bytenr(leaf, fi) == 0)
                        break;

                if (nr == max) {
                        struct disk_extent *old = exts;
                        max *= 2;
                        exts = kzalloc(sizeof(*exts) * max, GFP_NOFS);
                        memcpy(exts, old, sizeof(*exts) * nr);
                        if (old != *extents)
                                kfree(old);
                }

                exts[nr].disk_bytenr =
                        btrfs_file_extent_disk_bytenr(leaf, fi);
                exts[nr].disk_num_bytes =
                        btrfs_file_extent_disk_num_bytes(leaf, fi);
                exts[nr].offset = btrfs_file_extent_offset(leaf, fi);
                exts[nr].num_bytes = btrfs_file_extent_num_bytes(leaf, fi);
                exts[nr].ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
                exts[nr].compression = btrfs_file_extent_compression(leaf, fi);
                exts[nr].encryption = btrfs_file_extent_encryption(leaf, fi);
                exts[nr].other_encoding = btrfs_file_extent_other_encoding(leaf,
                                                                           fi);
                BUG_ON(exts[nr].offset > 0);
                BUG_ON(exts[nr].compression || exts[nr].encryption);
                BUG_ON(exts[nr].num_bytes != exts[nr].disk_num_bytes);

                cur_pos += exts[nr].num_bytes;
                nr++;

                if (cur_pos + offset >= last_byte)
                        break;

                if (no_fragment) {
                        ret = 1;
                        goto out;
                }
                path->slots[0]++;
        }

        BUG_ON(cur_pos + offset > last_byte);
        if (cur_pos + offset < last_byte) {
                ret = -ENOENT;
                goto out;
        }
        ret = 0;
out:
        btrfs_free_path(path);
        if (ret) {
                if (exts != *extents)
                        kfree(exts);
        } else {
                *extents = exts;
                *nr_extents = nr;
        }
        return ret;
}

static noinline int replace_one_extent(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_path *path,
                                        struct btrfs_key *extent_key,
                                        struct btrfs_key *leaf_key,
                                        struct btrfs_ref_path *ref_path,
                                        struct disk_extent *new_extents,
                                        int nr_extents)
{
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        struct inode *inode = NULL;
        struct btrfs_key key;
        u64 lock_start = 0;
        u64 lock_end = 0;
        u64 num_bytes;
        u64 ext_offset;
        u64 search_end = (u64)-1;
        u32 nritems;
        int nr_scaned = 0;
        int extent_locked = 0;
        int extent_type;
        int ret;

        memcpy(&key, leaf_key, sizeof(key));
        if (ref_path->owner_objectid != BTRFS_MULTIPLE_OBJECTIDS) {
                if (key.objectid < ref_path->owner_objectid ||
                    (key.objectid == ref_path->owner_objectid &&
                     key.type < BTRFS_EXTENT_DATA_KEY)) {
                        key.objectid = ref_path->owner_objectid;
                        key.type = BTRFS_EXTENT_DATA_KEY;
                        key.offset = 0;
                }
        }

        while (1) {
                ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
                if (ret < 0)
                        goto out;

                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
next:
                if (extent_locked && ret > 0) {
                        /*
                         * the file extent item was modified by someone
                         * before the extent got locked.
                         */
                        unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
                                      lock_end, GFP_NOFS);
                        extent_locked = 0;
                }

                if (path->slots[0] >= nritems) {
                        if (++nr_scaned > 2)
                                break;

                        BUG_ON(extent_locked);
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto out;
                        if (ret > 0)
                                break;
                        leaf = path->nodes[0];
                        nritems = btrfs_header_nritems(leaf);
                }

                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

                if (ref_path->owner_objectid != BTRFS_MULTIPLE_OBJECTIDS) {
                        if ((key.objectid > ref_path->owner_objectid) ||
                            (key.objectid == ref_path->owner_objectid &&
                             key.type > BTRFS_EXTENT_DATA_KEY) ||
                            key.offset >= search_end)
                                break;
                }

                if (inode && key.objectid != inode->i_ino) {
                        BUG_ON(extent_locked);
                        btrfs_release_path(root, path);
                        mutex_unlock(&inode->i_mutex);
                        iput(inode);
                        inode = NULL;
                        continue;
                }

                if (key.type != BTRFS_EXTENT_DATA_KEY) {
                        path->slots[0]++;
                        ret = 1;
                        goto next;
                }
                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                extent_type = btrfs_file_extent_type(leaf, fi);
                if ((extent_type != BTRFS_FILE_EXTENT_REG &&
                     extent_type != BTRFS_FILE_EXTENT_PREALLOC) ||
                    (btrfs_file_extent_disk_bytenr(leaf, fi) !=
                     extent_key->objectid)) {
                        path->slots[0]++;
                        ret = 1;
                        goto next;
                }

                num_bytes = btrfs_file_extent_num_bytes(leaf, fi);
                ext_offset = btrfs_file_extent_offset(leaf, fi);

                if (search_end == (u64)-1) {
                        search_end = key.offset - ext_offset +
                                btrfs_file_extent_ram_bytes(leaf, fi);
                }

                if (!extent_locked) {
                        lock_start = key.offset;
                        lock_end = lock_start + num_bytes - 1;
                } else {
                        if (lock_start > key.offset ||
                            lock_end + 1 < key.offset + num_bytes) {
                                unlock_extent(&BTRFS_I(inode)->io_tree,
                                              lock_start, lock_end, GFP_NOFS);
                                extent_locked = 0;
                        }
                }

                if (!inode) {
                        btrfs_release_path(root, path);

                        inode = btrfs_iget_locked(root->fs_info->sb,
                                                  key.objectid, root);
                        if (inode->i_state & I_NEW) {
                                BTRFS_I(inode)->root = root;
                                BTRFS_I(inode)->location.objectid =
                                        key.objectid;
                                BTRFS_I(inode)->location.type =
                                        BTRFS_INODE_ITEM_KEY;
                                BTRFS_I(inode)->location.offset = 0;
                                btrfs_read_locked_inode(inode);
                                unlock_new_inode(inode);
                        }
                        /*
                         * some code call btrfs_commit_transaction while
                         * holding the i_mutex, so we can't use mutex_lock
                         * here.
                         */
                        if (is_bad_inode(inode) ||
                            !mutex_trylock(&inode->i_mutex)) {
                                iput(inode);
                                inode = NULL;
                                key.offset = (u64)-1;
                                goto skip;
                        }
                }

                if (!extent_locked) {
                        struct btrfs_ordered_extent *ordered;

                        btrfs_release_path(root, path);

                        lock_extent(&BTRFS_I(inode)->io_tree, lock_start,
                                    lock_end, GFP_NOFS);
                        ordered = btrfs_lookup_first_ordered_extent(inode,
                                                                    lock_end);
                        if (ordered &&
                            ordered->file_offset <= lock_end &&
                            ordered->file_offset + ordered->len > lock_start) {
                                unlock_extent(&BTRFS_I(inode)->io_tree,
                                              lock_start, lock_end, GFP_NOFS);
                                btrfs_start_ordered_extent(inode, ordered, 1);
                                btrfs_put_ordered_extent(ordered);
                                key.offset += num_bytes;
                                goto skip;
                        }
                        if (ordered)
                                btrfs_put_ordered_extent(ordered);

                        extent_locked = 1;
                        continue;
                }

                if (nr_extents == 1) {
                        /* update extent pointer in place */
                        btrfs_set_file_extent_disk_bytenr(leaf, fi,
                                                new_extents[0].disk_bytenr);
                        btrfs_set_file_extent_disk_num_bytes(leaf, fi,
                                                new_extents[0].disk_num_bytes);
                        btrfs_mark_buffer_dirty(leaf);

                        btrfs_drop_extent_cache(inode, key.offset,
                                                key.offset + num_bytes - 1, 0);

                        ret = btrfs_inc_extent_ref(trans, root,
                                                new_extents[0].disk_bytenr,
                                                new_extents[0].disk_num_bytes,
                                                leaf->start,
                                                root->root_key.objectid,
                                                trans->transid,
                                                key.objectid);
                        BUG_ON(ret);

                        ret = btrfs_free_extent(trans, root,
                                                extent_key->objectid,
                                                extent_key->offset,
                                                leaf->start,
                                                btrfs_header_owner(leaf),
                                                btrfs_header_generation(leaf),
                                                key.objectid, 0);
                        BUG_ON(ret);

                        btrfs_release_path(root, path);
                        key.offset += num_bytes;
                } else {
                        BUG_ON(1);
#if 0
                        u64 alloc_hint;
                        u64 extent_len;
                        int i;
                        /*
                         * drop old extent pointer at first, then insert the
                         * new pointers one bye one
                         */
                        btrfs_release_path(root, path);
                        ret = btrfs_drop_extents(trans, root, inode, key.offset,
                                                 key.offset + num_bytes,
                                                 key.offset, &alloc_hint);
                        BUG_ON(ret);

                        for (i = 0; i < nr_extents; i++) {
                                if (ext_offset >= new_extents[i].num_bytes) {
                                        ext_offset -= new_extents[i].num_bytes;
                                        continue;
                                }
                                extent_len = min(new_extents[i].num_bytes -
                                                 ext_offset, num_bytes);

                                ret = btrfs_insert_empty_item(trans, root,
                                                              path, &key,
                                                              sizeof(*fi));
                                BUG_ON(ret);

                                leaf = path->nodes[0];
                                fi = btrfs_item_ptr(leaf, path->slots[0],
                                                struct btrfs_file_extent_item);
                                btrfs_set_file_extent_generation(leaf, fi,
                                                        trans->transid);
                                btrfs_set_file_extent_type(leaf, fi,
                                                        BTRFS_FILE_EXTENT_REG);
                                btrfs_set_file_extent_disk_bytenr(leaf, fi,
                                                new_extents[i].disk_bytenr);
                                btrfs_set_file_extent_disk_num_bytes(leaf, fi,
                                                new_extents[i].disk_num_bytes);
                                btrfs_set_file_extent_ram_bytes(leaf, fi,
                                                new_extents[i].ram_bytes);

                                btrfs_set_file_extent_compression(leaf, fi,
                                                new_extents[i].compression);
                                btrfs_set_file_extent_encryption(leaf, fi,
                                                new_extents[i].encryption);
                                btrfs_set_file_extent_other_encoding(leaf, fi,
                                                new_extents[i].other_encoding);

                                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        extent_len);
                                ext_offset += new_extents[i].offset;
                                btrfs_set_file_extent_offset(leaf, fi,
                                                        ext_offset);
                                btrfs_mark_buffer_dirty(leaf);

                                btrfs_drop_extent_cache(inode, key.offset,
                                                key.offset + extent_len - 1, 0);

                                ret = btrfs_inc_extent_ref(trans, root,
                                                new_extents[i].disk_bytenr,
                                                new_extents[i].disk_num_bytes,
                                                leaf->start,
                                                root->root_key.objectid,
                                                trans->transid, key.objectid);
                                BUG_ON(ret);
                                btrfs_release_path(root, path);

                                inode_add_bytes(inode, extent_len);

                                ext_offset = 0;
                                num_bytes -= extent_len;
                                key.offset += extent_len;

                                if (num_bytes == 0)
                                        break;
                        }
                        BUG_ON(i >= nr_extents);
#endif
                }

                if (extent_locked) {
                        unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
                                      lock_end, GFP_NOFS);
                        extent_locked = 0;
                }
skip:
                if (ref_path->owner_objectid != BTRFS_MULTIPLE_OBJECTIDS &&
                    key.offset >= search_end)
                        break;

                cond_resched();
        }
        ret = 0;
out:
        btrfs_release_path(root, path);
        if (inode) {
                mutex_unlock(&inode->i_mutex);
                if (extent_locked) {
                        unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
                                      lock_end, GFP_NOFS);
                }
                iput(inode);
        }
        return ret;
}

int btrfs_reloc_tree_cache_ref(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct extent_buffer *buf, u64 orig_start)
{
        int level;
        int ret;

        BUG_ON(btrfs_header_generation(buf) != trans->transid);
        BUG_ON(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);

        level = btrfs_header_level(buf);
        if (level == 0) {
                struct btrfs_leaf_ref *ref;
                struct btrfs_leaf_ref *orig_ref;

                orig_ref = btrfs_lookup_leaf_ref(root, orig_start);
                if (!orig_ref)
                        return -ENOENT;

                ref = btrfs_alloc_leaf_ref(root, orig_ref->nritems);
                if (!ref) {
                        btrfs_free_leaf_ref(root, orig_ref);
                        return -ENOMEM;
                }

                ref->nritems = orig_ref->nritems;
                memcpy(ref->extents, orig_ref->extents,
                        sizeof(ref->extents[0]) * ref->nritems);

                btrfs_free_leaf_ref(root, orig_ref);

                ref->root_gen = trans->transid;
                ref->bytenr = buf->start;
                ref->owner = btrfs_header_owner(buf);
                ref->generation = btrfs_header_generation(buf);

                ret = btrfs_add_leaf_ref(root, ref, 0);
                WARN_ON(ret);
                btrfs_free_leaf_ref(root, ref);
        }
        return 0;
}

static noinline int invalidate_extent_cache(struct btrfs_root *root,
                                        struct extent_buffer *leaf,
                                        struct btrfs_block_group_cache *group,
                                        struct btrfs_root *target_root)
{
        struct btrfs_key key;
        struct inode *inode = NULL;
        struct btrfs_file_extent_item *fi;
        u64 num_bytes;
        u64 skip_objectid = 0;
        u32 nritems;
        u32 i;

        nritems = btrfs_header_nritems(leaf);
        for (i = 0; i < nritems; i++) {
                btrfs_item_key_to_cpu(leaf, &key, i);
                if (key.objectid == skip_objectid ||
                    key.type != BTRFS_EXTENT_DATA_KEY)
                        continue;
                fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(leaf, fi) ==
                    BTRFS_FILE_EXTENT_INLINE)
                        continue;
                if (btrfs_file_extent_disk_bytenr(leaf, fi) == 0)
                        continue;
                if (!inode || inode->i_ino != key.objectid) {
                        iput(inode);
                        inode = btrfs_ilookup(target_root->fs_info->sb,
                                              key.objectid, target_root, 1);
                }
                if (!inode) {
                        skip_objectid = key.objectid;
                        continue;
                }
                num_bytes = btrfs_file_extent_num_bytes(leaf, fi);

                lock_extent(&BTRFS_I(inode)->io_tree, key.offset,
                            key.offset + num_bytes - 1, GFP_NOFS);
                btrfs_drop_extent_cache(inode, key.offset,
                                        key.offset + num_bytes - 1, 1);
                unlock_extent(&BTRFS_I(inode)->io_tree, key.offset,
                              key.offset + num_bytes - 1, GFP_NOFS);
                cond_resched();
        }
        iput(inode);
        return 0;
}

static noinline int replace_extents_in_leaf(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct extent_buffer *leaf,
                                        struct btrfs_block_group_cache *group,
                                        struct inode *reloc_inode)
{
        struct btrfs_key key;
        struct btrfs_key extent_key;
        struct btrfs_file_extent_item *fi;
        struct btrfs_leaf_ref *ref;
        struct disk_extent *new_extent;
        u64 bytenr;
        u64 num_bytes;
        u32 nritems;
        u32 i;
        int ext_index;
        int nr_extent;
        int ret;

        new_extent = kmalloc(sizeof(*new_extent), GFP_NOFS);
        BUG_ON(!new_extent);

        ref = btrfs_lookup_leaf_ref(root, leaf->start);
        BUG_ON(!ref);

        ext_index = -1;
        nritems = btrfs_header_nritems(leaf);
        for (i = 0; i < nritems; i++) {
                btrfs_item_key_to_cpu(leaf, &key, i);
                if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                        continue;
                fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(leaf, fi) ==
                    BTRFS_FILE_EXTENT_INLINE)
                        continue;
                bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
                if (bytenr == 0)
                        continue;

                ext_index++;
                if (bytenr >= group->key.objectid + group->key.offset ||
                    bytenr + num_bytes <= group->key.objectid)
                        continue;

                extent_key.objectid = bytenr;
                extent_key.offset = num_bytes;
                extent_key.type = BTRFS_EXTENT_ITEM_KEY;
                nr_extent = 1;
                ret = get_new_locations(reloc_inode, &extent_key,
                                        group->key.objectid, 1,
                                        &new_extent, &nr_extent);
                if (ret > 0)
                        continue;
                BUG_ON(ret < 0);

                BUG_ON(ref->extents[ext_index].bytenr != bytenr);
                BUG_ON(ref->extents[ext_index].num_bytes != num_bytes);
                ref->extents[ext_index].bytenr = new_extent->disk_bytenr;
                ref->extents[ext_index].num_bytes = new_extent->disk_num_bytes;

                btrfs_set_file_extent_disk_bytenr(leaf, fi,
                                                new_extent->disk_bytenr);
                btrfs_set_file_extent_disk_num_bytes(leaf, fi,
                                                new_extent->disk_num_bytes);
                btrfs_mark_buffer_dirty(leaf);

                ret = btrfs_inc_extent_ref(trans, root,
                                        new_extent->disk_bytenr,
                                        new_extent->disk_num_bytes,
                                        leaf->start,
                                        root->root_key.objectid,
                                        trans->transid, key.objectid);
                BUG_ON(ret);

                ret = btrfs_free_extent(trans, root,
                                        bytenr, num_bytes, leaf->start,
                                        btrfs_header_owner(leaf),
                                        btrfs_header_generation(leaf),
                                        key.objectid, 0);
                BUG_ON(ret);
                cond_resched();
        }
        kfree(new_extent);
        BUG_ON(ext_index + 1 != ref->nritems);
        btrfs_free_leaf_ref(root, ref);
        return 0;
}

int btrfs_free_reloc_root(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root)
{
        struct btrfs_root *reloc_root;
        int ret;

        if (root->reloc_root) {
                reloc_root = root->reloc_root;
                root->reloc_root = NULL;
                list_add(&reloc_root->dead_list,
                         &root->fs_info->dead_reloc_roots);

                btrfs_set_root_bytenr(&reloc_root->root_item,
                                      reloc_root->node->start);
                btrfs_set_root_level(&root->root_item,
                                     btrfs_header_level(reloc_root->node));
                memset(&reloc_root->root_item.drop_progress, 0,
                        sizeof(struct btrfs_disk_key));
                reloc_root->root_item.drop_level = 0;

                ret = btrfs_update_root(trans, root->fs_info->tree_root,
                                        &reloc_root->root_key,
                                        &reloc_root->root_item);
                BUG_ON(ret);
        }
        return 0;
}

int btrfs_drop_dead_reloc_roots(struct btrfs_root *root)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *reloc_root;
        struct btrfs_root *prev_root = NULL;
        struct list_head dead_roots;
        int ret;
        unsigned long nr;

        INIT_LIST_HEAD(&dead_roots);
        list_splice_init(&root->fs_info->dead_reloc_roots, &dead_roots);

        while (!list_empty(&dead_roots)) {
                reloc_root = list_entry(dead_roots.prev,
                                        struct btrfs_root, dead_list);
                list_del_init(&reloc_root->dead_list);

                BUG_ON(reloc_root->commit_root != NULL);
                while (1) {
                        trans = btrfs_join_transaction(root, 1);
                        BUG_ON(!trans);

                        mutex_lock(&root->fs_info->drop_mutex);
                        ret = btrfs_drop_snapshot(trans, reloc_root);
                        if (ret != -EAGAIN)
                                break;
                        mutex_unlock(&root->fs_info->drop_mutex);

                        nr = trans->blocks_used;
                        ret = btrfs_end_transaction(trans, root);
                        BUG_ON(ret);
                        btrfs_btree_balance_dirty(root, nr);
                }

                free_extent_buffer(reloc_root->node);

                ret = btrfs_del_root(trans, root->fs_info->tree_root,
                                     &reloc_root->root_key);
                BUG_ON(ret);
                mutex_unlock(&root->fs_info->drop_mutex);

                nr = trans->blocks_used;
                ret = btrfs_end_transaction(trans, root);
                BUG_ON(ret);
                btrfs_btree_balance_dirty(root, nr);

                kfree(prev_root);
                prev_root = reloc_root;
        }
        if (prev_root) {
                btrfs_remove_leaf_refs(prev_root, (u64)-1, 0);
                kfree(prev_root);
        }
        return 0;
}

int btrfs_add_dead_reloc_root(struct btrfs_root *root)
{
        list_add(&root->dead_list, &root->fs_info->dead_reloc_roots);
        return 0;
}

int btrfs_cleanup_reloc_trees(struct btrfs_root *root)
{
        struct btrfs_root *reloc_root;
        struct btrfs_trans_handle *trans;
        struct btrfs_key location;
        int found;
        int ret;

        mutex_lock(&root->fs_info->tree_reloc_mutex);
        ret = btrfs_find_dead_roots(root, BTRFS_TREE_RELOC_OBJECTID, NULL);
        BUG_ON(ret);
        found = !list_empty(&root->fs_info->dead_reloc_roots);
        mutex_unlock(&root->fs_info->tree_reloc_mutex);

        if (found) {
                trans = btrfs_start_transaction(root, 1);
                BUG_ON(!trans);
                ret = btrfs_commit_transaction(trans, root);
                BUG_ON(ret);
        }

        location.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID;
        location.offset = (u64)-1;
        location.type = BTRFS_ROOT_ITEM_KEY;

        reloc_root = btrfs_read_fs_root_no_name(root->fs_info, &location);
        BUG_ON(!reloc_root);
        btrfs_orphan_cleanup(reloc_root);
        return 0;
}

static noinline int init_reloc_tree(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root)
{
        struct btrfs_root *reloc_root;
        struct extent_buffer *eb;
        struct btrfs_root_item *root_item;
        struct btrfs_key root_key;
        int ret;

        BUG_ON(!root->ref_cows);
        if (root->reloc_root)
                return 0;

        root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
        BUG_ON(!root_item);

        ret = btrfs_copy_root(trans, root, root->commit_root,
                              &eb, BTRFS_TREE_RELOC_OBJECTID);
        BUG_ON(ret);

        root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
        root_key.offset = root->root_key.objectid;
        root_key.type = BTRFS_ROOT_ITEM_KEY;

        memcpy(root_item, &root->root_item, sizeof(root_item));
        btrfs_set_root_refs(root_item, 0);
        btrfs_set_root_bytenr(root_item, eb->start);
        btrfs_set_root_level(root_item, btrfs_header_level(eb));
        btrfs_set_root_generation(root_item, trans->transid);

        btrfs_tree_unlock(eb);
        free_extent_buffer(eb);

        ret = btrfs_insert_root(trans, root->fs_info->tree_root,
                                &root_key, root_item);
        BUG_ON(ret);
        kfree(root_item);

        reloc_root = btrfs_read_fs_root_no_radix(root->fs_info->tree_root,
                                                 &root_key);
        BUG_ON(!reloc_root);
        reloc_root->last_trans = trans->transid;
        reloc_root->commit_root = NULL;
        reloc_root->ref_tree = &root->fs_info->reloc_ref_tree;

        root->reloc_root = reloc_root;
        return 0;
}

/*
 * Core function of space balance.
 *
 * The idea is using reloc trees to relocate tree blocks in reference
 * counted roots. There is one reloc tree for each subvol, and all
 * reloc trees share same root key objectid. Reloc trees are snapshots
 * of the latest committed roots of subvols (root->commit_root).
 *
 * To relocate a tree block referenced by a subvol, there are two steps.
 * COW the block through subvol's reloc tree, then update block pointer
 * in the subvol to point to the new block. Since all reloc trees share
 * same root key objectid, doing special handing for tree blocks owned
 * by them is easy. Once a tree block has been COWed in one reloc tree,
 * we can use the resulting new block directly when the same block is
 * required to COW again through other reloc trees. By this way, relocated
 * tree blocks are shared between reloc trees, so they are also shared
 * between subvols.
 */
static noinline int relocate_one_path(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root,
                                      struct btrfs_path *path,
                                      struct btrfs_key *first_key,
                                      struct btrfs_ref_path *ref_path,
                                      struct btrfs_block_group_cache *group,
                                      struct inode *reloc_inode)
{
        struct btrfs_root *reloc_root;
        struct extent_buffer *eb = NULL;
        struct btrfs_key *keys;
        u64 *nodes;
        int level;
        int shared_level;
        int lowest_level = 0;
        int ret;

        if (ref_path->owner_objectid < BTRFS_FIRST_FREE_OBJECTID)
                lowest_level = ref_path->owner_objectid;

        if (!root->ref_cows) {
                path->lowest_level = lowest_level;
                ret = btrfs_search_slot(trans, root, first_key, path, 0, 1);
                BUG_ON(ret < 0);
                path->lowest_level = 0;
                btrfs_release_path(root, path);
                return 0;
        }

        mutex_lock(&root->fs_info->tree_reloc_mutex);
        ret = init_reloc_tree(trans, root);
        BUG_ON(ret);
        reloc_root = root->reloc_root;

        shared_level = ref_path->shared_level;
        ref_path->shared_level = BTRFS_MAX_LEVEL - 1;

        keys = ref_path->node_keys;
        nodes = ref_path->new_nodes;
        memset(&keys[shared_level + 1], 0,
               sizeof(*keys) * (BTRFS_MAX_LEVEL - shared_level - 1));
        memset(&nodes[shared_level + 1], 0,
               sizeof(*nodes) * (BTRFS_MAX_LEVEL - shared_level - 1));

        if (nodes[lowest_level] == 0) {
                path->lowest_level = lowest_level;
                ret = btrfs_search_slot(trans, reloc_root, first_key, path,
                                        0, 1);
                BUG_ON(ret);
                for (level = lowest_level; level < BTRFS_MAX_LEVEL; level++) {
                        eb = path->nodes[level];
                        if (!eb || eb == reloc_root->node)
                                break;
                        nodes[level] = eb->start;
                        if (level == 0)
                                btrfs_item_key_to_cpu(eb, &keys[level], 0);
                        else
                                btrfs_node_key_to_cpu(eb, &keys[level], 0);
                }
                if (nodes[0] &&
                    ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                        eb = path->nodes[0];
                        ret = replace_extents_in_leaf(trans, reloc_root, eb,
                                                      group, reloc_inode);
                        BUG_ON(ret);
                }
                btrfs_release_path(reloc_root, path);
        } else {
                ret = btrfs_merge_path(trans, reloc_root, keys, nodes,
                                       lowest_level);
                BUG_ON(ret);
        }

        /*
         * replace tree blocks in the fs tree with tree blocks in
         * the reloc tree.
         */
        ret = btrfs_merge_path(trans, root, keys, nodes, lowest_level);
        BUG_ON(ret < 0);

        if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                ret = btrfs_search_slot(trans, reloc_root, first_key, path,
                                        0, 0);
                BUG_ON(ret);
                extent_buffer_get(path->nodes[0]);
                eb = path->nodes[0];
                btrfs_release_path(reloc_root, path);
                ret = invalidate_extent_cache(reloc_root, eb, group, root);
                BUG_ON(ret);
                free_extent_buffer(eb);
        }

        mutex_unlock(&root->fs_info->tree_reloc_mutex);
        path->lowest_level = 0;
        return 0;
}

static noinline int relocate_tree_block(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_path *path,
                                        struct btrfs_key *first_key,
                                        struct btrfs_ref_path *ref_path)
{
        int ret;

        ret = relocate_one_path(trans, root, path, first_key,
                                ref_path, NULL, NULL);
        BUG_ON(ret);

        return 0;
}

static noinline int del_extent_zero(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *extent_root,
                                    struct btrfs_path *path,
                                    struct btrfs_key *extent_key)
{
        int ret;

        ret = btrfs_search_slot(trans, extent_root, extent_key, path, -1, 1);
        if (ret)
                goto out;
        ret = btrfs_del_item(trans, extent_root, path);
out:
        btrfs_release_path(extent_root, path);
        return ret;
}

static noinline struct btrfs_root *read_ref_root(struct btrfs_fs_info *fs_info,
                                                struct btrfs_ref_path *ref_path)
{
        struct btrfs_key root_key;

        root_key.objectid = ref_path->root_objectid;
        root_key.type = BTRFS_ROOT_ITEM_KEY;
        if (is_cowonly_root(ref_path->root_objectid))
                root_key.offset = 0;
        else
                root_key.offset = (u64)-1;

        return btrfs_read_fs_root_no_name(fs_info, &root_key);
}

static noinline int relocate_one_extent(struct btrfs_root *extent_root,
                                        struct btrfs_path *path,
                                        struct btrfs_key *extent_key,
                                        struct btrfs_block_group_cache *group,
                                        struct inode *reloc_inode, int pass)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *found_root;
        struct btrfs_ref_path *ref_path = NULL;
        struct disk_extent *new_extents = NULL;
        int nr_extents = 0;
        int loops;
        int ret;
        int level;
        struct btrfs_key first_key;
        u64 prev_block = 0;


        trans = btrfs_start_transaction(extent_root, 1);
        BUG_ON(!trans);

        if (extent_key->objectid == 0) {
                ret = del_extent_zero(trans, extent_root, path, extent_key);
                goto out;
        }

        ref_path = kmalloc(sizeof(*ref_path), GFP_NOFS);
        if (!ref_path) {
                ret = -ENOMEM;
                goto out;
        }

        for (loops = 0; ; loops++) {
                if (loops == 0) {
                        ret = btrfs_first_ref_path(trans, extent_root, ref_path,
                                                   extent_key->objectid);
                } else {
                        ret = btrfs_next_ref_path(trans, extent_root, ref_path);
                }
                if (ret < 0)
                        goto out;
                if (ret > 0)
                        break;

                if (ref_path->root_objectid == BTRFS_TREE_LOG_OBJECTID ||
                    ref_path->root_objectid == BTRFS_TREE_RELOC_OBJECTID)
                        continue;

                found_root = read_ref_root(extent_root->fs_info, ref_path);
                BUG_ON(!found_root);
                /*
                 * for reference counted tree, only process reference paths
                 * rooted at the latest committed root.
                 */
                if (found_root->ref_cows &&
                    ref_path->root_generation != found_root->root_key.offset)
                        continue;

                if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                        if (pass == 0) {
                                /*
                                 * copy data extents to new locations
                                 */
                                u64 group_start = group->key.objectid;
                                ret = relocate_data_extent(reloc_inode,
                                                           extent_key,
                                                           group_start);
                                if (ret < 0)
                                        goto out;
                                break;
                        }
                        level = 0;
                } else {
                        level = ref_path->owner_objectid;
                }

                if (prev_block != ref_path->nodes[level]) {
                        struct extent_buffer *eb;
                        u64 block_start = ref_path->nodes[level];
                        u64 block_size = btrfs_level_size(found_root, level);

                        eb = read_tree_block(found_root, block_start,
                                             block_size, 0);
                        btrfs_tree_lock(eb);
                        BUG_ON(level != btrfs_header_level(eb));

                        if (level == 0)
                                btrfs_item_key_to_cpu(eb, &first_key, 0);
                        else
                                btrfs_node_key_to_cpu(eb, &first_key, 0);

                        btrfs_tree_unlock(eb);
                        free_extent_buffer(eb);
                        prev_block = block_start;
                }

                mutex_lock(&extent_root->fs_info->trans_mutex);
                btrfs_record_root_in_trans(found_root);
                mutex_unlock(&extent_root->fs_info->trans_mutex);
                if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                        /*
                         * try to update data extent references while
                         * keeping metadata shared between snapshots.
                         */
                        if (pass == 1) {
                                ret = relocate_one_path(trans, found_root,
                                                path, &first_key, ref_path,
                                                group, reloc_inode);
                                if (ret < 0)
                                        goto out;
                                continue;
                        }
                        /*
                         * use fallback method to process the remaining
                         * references.
                         */
                        if (!new_extents) {
                                u64 group_start = group->key.objectid;
                                new_extents = kmalloc(sizeof(*new_extents),
                                                      GFP_NOFS);
                                nr_extents = 1;
                                ret = get_new_locations(reloc_inode,
                                                        extent_key,
                                                        group_start, 1,
                                                        &new_extents,
                                                        &nr_extents);
                                if (ret)
                                        goto out;
                        }
                        ret = replace_one_extent(trans, found_root,
                                                path, extent_key,
                                                &first_key, ref_path,
                                                new_extents, nr_extents);
                } else {
                        ret = relocate_tree_block(trans, found_root, path,
                                                  &first_key, ref_path);
                }
                if (ret < 0)
                        goto out;
        }
        ret = 0;
out:
        btrfs_end_transaction(trans, extent_root);
        kfree(new_extents);
        kfree(ref_path);
        return ret;
}
#endif

static u64 update_block_group_flags(struct btrfs_root *root, u64 flags)
{
        u64 num_devices;
        u64 stripped = BTRFS_BLOCK_GROUP_RAID0 |
                BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10;

        num_devices = root->fs_info->fs_devices->rw_devices;
        if (num_devices == 1) {
                stripped |= BTRFS_BLOCK_GROUP_DUP;
                stripped = flags & ~stripped;

                /* turn raid0 into single device chunks */
                if (flags & BTRFS_BLOCK_GROUP_RAID0)
                        return stripped;

                /* turn mirroring into duplication */
                if (flags & (BTRFS_BLOCK_GROUP_RAID1 |
                             BTRFS_BLOCK_GROUP_RAID10))
                        return stripped | BTRFS_BLOCK_GROUP_DUP;
                return flags;
        } else {
                /* they already had raid on here, just return */
                if (flags & stripped)
                        return flags;

                stripped |= BTRFS_BLOCK_GROUP_DUP;
                stripped = flags & ~stripped;

                /* switch duplicated blocks with raid1 */
                if (flags & BTRFS_BLOCK_GROUP_DUP)
                        return stripped | BTRFS_BLOCK_GROUP_RAID1;

                /* turn single device chunks into raid0 */
                return stripped | BTRFS_BLOCK_GROUP_RAID0;
        }
        return flags;
}

static int __alloc_chunk_for_shrink(struct btrfs_root *root,
                     struct btrfs_block_group_cache *shrink_block_group,
                     int force)
{
        struct btrfs_trans_handle *trans;
        u64 new_alloc_flags;
        u64 calc;

        spin_lock(&shrink_block_group->lock);
        if (btrfs_block_group_used(&shrink_block_group->item) +
            shrink_block_group->reserved > 0) {
                spin_unlock(&shrink_block_group->lock);

                trans = btrfs_start_transaction(root, 1);
                spin_lock(&shrink_block_group->lock);

                new_alloc_flags = update_block_group_flags(root,
                                                   shrink_block_group->flags);
                if (new_alloc_flags != shrink_block_group->flags) {
                        calc =
                             btrfs_block_group_used(&shrink_block_group->item);
                } else {
                        calc = shrink_block_group->key.offset;
                }
                spin_unlock(&shrink_block_group->lock);

                do_chunk_alloc(trans, root->fs_info->extent_root,
                               calc + 2 * 1024 * 1024, new_alloc_flags, force);

                btrfs_end_transaction(trans, root);
        } else
                spin_unlock(&shrink_block_group->lock);
        return 0;
}


int btrfs_prepare_block_group_relocation(struct btrfs_root *root,
                                         struct btrfs_block_group_cache *group)

{
        __alloc_chunk_for_shrink(root, group, 1);
        set_block_group_readonly(group);
        return 0;
}

/*
 * checks to see if its even possible to relocate this block group.
 *
 * @return - -1 if it's not a good idea to relocate this block group, 0 if its
 * ok to go ahead and try.
 */
int btrfs_can_relocate(struct btrfs_root *root, u64 bytenr)
{
        struct btrfs_block_group_cache *block_group;
        struct btrfs_space_info *space_info;
        struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
        struct btrfs_device *device;
        int full = 0;
        int ret = 0;

        block_group = btrfs_lookup_block_group(root->fs_info, bytenr);

        /* odd, couldn't find the block group, leave it alone */
        if (!block_group)
                return -1;

        /* no bytes used, we're good */
        if (!btrfs_block_group_used(&block_group->item))
                goto out;

        space_info = block_group->space_info;
        spin_lock(&space_info->lock);

        full = space_info->full;

        /*
         * if this is the last block group we have in this space, we can't
         * relocate it unless we're able to allocate a new chunk below.
         *
         * Otherwise, we need to make sure we have room in the space to handle
         * all of the extents from this block group.  If we can, we're good
         */
        if ((space_info->total_bytes != block_group->key.offset) &&
           (space_info->bytes_used + space_info->bytes_reserved +
            space_info->bytes_pinned + space_info->bytes_readonly +
            btrfs_block_group_used(&block_group->item) <
            space_info->total_bytes)) {
                spin_unlock(&space_info->lock);
                goto out;
        }
        spin_unlock(&space_info->lock);

        /*
         * ok we don't have enough space, but maybe we have free space on our
         * devices to allocate new chunks for relocation, so loop through our
         * alloc devices and guess if we have enough space.  However, if we
         * were marked as full, then we know there aren't enough chunks, and we
         * can just return.
         */
        ret = -1;
        if (full)
                goto out;

        mutex_lock(&root->fs_info->chunk_mutex);
        list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) {
                u64 min_free = btrfs_block_group_used(&block_group->item);
                u64 dev_offset, max_avail;

                /*
                 * check to make sure we can actually find a chunk with enough
                 * space to fit our block group in.
                 */
                if (device->total_bytes > device->bytes_used + min_free) {
                        ret = find_free_dev_extent(NULL, device, min_free,
                                                   &dev_offset, &max_avail);
                        if (!ret)
                                break;
                        ret = -1;
                }
        }
        mutex_unlock(&root->fs_info->chunk_mutex);
out:
        btrfs_put_block_group(block_group);
        return ret;
}

static int find_first_block_group(struct btrfs_root *root,
                struct btrfs_path *path, struct btrfs_key *key)
{
        int ret = 0;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
        int slot;

        ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
        if (ret < 0)
                goto out;

        while (1) {
                slot = path->slots[0];
                leaf = path->nodes[0];
                if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret == 0)
                                continue;
                        if (ret < 0)
                                goto out;
                        break;
                }
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                if (found_key.objectid >= key->objectid &&
                    found_key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
                        ret = 0;
                        goto out;
                }
                path->slots[0]++;
        }
        ret = -ENOENT;
out:
        return ret;
}

int btrfs_free_block_groups(struct btrfs_fs_info *info)
{
        struct btrfs_block_group_cache *block_group;
        struct btrfs_space_info *space_info;
        struct btrfs_caching_control *caching_ctl;
        struct rb_node *n;

        down_write(&info->extent_commit_sem);
        while (!list_empty(&info->caching_block_groups)) {
                caching_ctl = list_entry(info->caching_block_groups.next,
                                         struct btrfs_caching_control, list);
                list_del(&caching_ctl->list);
                put_caching_control(caching_ctl);
        }
        up_write(&info->extent_commit_sem);

        spin_lock(&info->block_group_cache_lock);
        while ((n = rb_last(&info->block_group_cache_tree)) != NULL) {
                block_group = rb_entry(n, struct btrfs_block_group_cache,
                                       cache_node);
                rb_erase(&block_group->cache_node,
                         &info->block_group_cache_tree);
                spin_unlock(&info->block_group_cache_lock);

                down_write(&block_group->space_info->groups_sem);
                list_del(&block_group->list);
                up_write(&block_group->space_info->groups_sem);

                if (block_group->cached == BTRFS_CACHE_STARTED)
                        wait_block_group_cache_done(block_group);

                btrfs_remove_free_space_cache(block_group);

                WARN_ON(atomic_read(&block_group->count) != 1);
                kfree(block_group);

                spin_lock(&info->block_group_cache_lock);
        }
        spin_unlock(&info->block_group_cache_lock);

        /* now that all the block groups are freed, go through and
         * free all the space_info structs.  This is only called during
         * the final stages of unmount, and so we know nobody is
         * using them.  We call synchronize_rcu() once before we start,
         * just to be on the safe side.
         */
        synchronize_rcu();

        while(!list_empty(&info->space_info)) {
                space_info = list_entry(info->space_info.next,
                                        struct btrfs_space_info,
                                        list);

                list_del(&space_info->list);
                kfree(space_info);
        }
        return 0;
}

int btrfs_read_block_groups(struct btrfs_root *root)
{
        struct btrfs_path *path;
        int ret;
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *space_info;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;

        root = info->extent_root;
        key.objectid = 0;
        key.offset = 0;
        btrfs_set_key_type(&key, BTRFS_BLOCK_GROUP_ITEM_KEY);
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        while (1) {
                ret = find_first_block_group(root, path, &key);
                if (ret > 0) {
                        ret = 0;
                        goto error;
                }
                if (ret != 0)
                        goto error;

                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                cache = kzalloc(sizeof(*cache), GFP_NOFS);
                if (!cache) {
                        ret = -ENOMEM;
                        break;
                }

                atomic_set(&cache->count, 1);
                spin_lock_init(&cache->lock);
                spin_lock_init(&cache->tree_lock);
                cache->fs_info = info;
                INIT_LIST_HEAD(&cache->list);
                INIT_LIST_HEAD(&cache->cluster_list);

                /*
                 * we only want to have 32k of ram per block group for keeping
                 * track of free space, and if we pass 1/2 of that we want to
                 * start converting things over to using bitmaps
                 */
                cache->extents_thresh = ((1024 * 32) / 2) /
                        sizeof(struct btrfs_free_space);

                read_extent_buffer(leaf, &cache->item,
                                   btrfs_item_ptr_offset(leaf, path->slots[0]),
                                   sizeof(cache->item));
                memcpy(&cache->key, &found_key, sizeof(found_key));

                key.objectid = found_key.objectid + found_key.offset;
                btrfs_release_path(root, path);
                cache->flags = btrfs_block_group_flags(&cache->item);
                cache->sectorsize = root->sectorsize;

                /*
                 * check for two cases, either we are full, and therefore
                 * don't need to bother with the caching work since we won't
                 * find any space, or we are empty, and we can just add all
                 * the space in and be done with it.  This saves us _alot_ of
                 * time, particularly in the full case.
                 */
                if (found_key.offset == btrfs_block_group_used(&cache->item)) {
                        exclude_super_stripes(root, cache);
                        cache->last_byte_to_unpin = (u64)-1;
                        cache->cached = BTRFS_CACHE_FINISHED;
                        free_excluded_extents(root, cache);
                } else if (btrfs_block_group_used(&cache->item) == 0) {
                        exclude_super_stripes(root, cache);
                        cache->last_byte_to_unpin = (u64)-1;
                        cache->cached = BTRFS_CACHE_FINISHED;
                        add_new_free_space(cache, root->fs_info,
                                           found_key.objectid,
                                           found_key.objectid +
                                           found_key.offset);
                        free_excluded_extents(root, cache);
                }

                ret = update_space_info(info, cache->flags, found_key.offset,
                                        btrfs_block_group_used(&cache->item),
                                        &space_info);
                BUG_ON(ret);
                cache->space_info = space_info;
                spin_lock(&cache->space_info->lock);
                cache->space_info->bytes_super += cache->bytes_super;
                spin_unlock(&cache->space_info->lock);

                down_write(&space_info->groups_sem);
                list_add_tail(&cache->list, &space_info->block_groups);
                up_write(&space_info->groups_sem);

                ret = btrfs_add_block_group_cache(root->fs_info, cache);
                BUG_ON(ret);

                set_avail_alloc_bits(root->fs_info, cache->flags);
                if (btrfs_chunk_readonly(root, cache->key.objectid))
                        set_block_group_readonly(cache);
        }
        ret = 0;
error:
        btrfs_free_path(path);
        return ret;
}

int btrfs_make_block_group(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root, u64 bytes_used,
                           u64 type, u64 chunk_objectid, u64 chunk_offset,
                           u64 size)
{
        int ret;
        struct btrfs_root *extent_root;
        struct btrfs_block_group_cache *cache;

        extent_root = root->fs_info->extent_root;

        root->fs_info->last_trans_log_full_commit = trans->transid;

        cache = kzalloc(sizeof(*cache), GFP_NOFS);
        if (!cache)
                return -ENOMEM;

        cache->key.objectid = chunk_offset;
        cache->key.offset = size;
        cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
        cache->sectorsize = root->sectorsize;

        /*
         * we only want to have 32k of ram per block group for keeping track
         * of free space, and if we pass 1/2 of that we want to start
         * converting things over to using bitmaps
         */
        cache->extents_thresh = ((1024 * 32) / 2) /
                sizeof(struct btrfs_free_space);
        atomic_set(&cache->count, 1);
        spin_lock_init(&cache->lock);
        spin_lock_init(&cache->tree_lock);
        INIT_LIST_HEAD(&cache->list);
        INIT_LIST_HEAD(&cache->cluster_list);

        btrfs_set_block_group_used(&cache->item, bytes_used);
        btrfs_set_block_group_chunk_objectid(&cache->item, chunk_objectid);
        cache->flags = type;
        btrfs_set_block_group_flags(&cache->item, type);

        cache->last_byte_to_unpin = (u64)-1;
        cache->cached = BTRFS_CACHE_FINISHED;
        exclude_super_stripes(root, cache);

        add_new_free_space(cache, root->fs_info, chunk_offset,
                           chunk_offset + size);

        free_excluded_extents(root, cache);

        ret = update_space_info(root->fs_info, cache->flags, size, bytes_used,
                                &cache->space_info);
        BUG_ON(ret);

        spin_lock(&cache->space_info->lock);
        cache->space_info->bytes_super += cache->bytes_super;
        spin_unlock(&cache->space_info->lock);

        down_write(&cache->space_info->groups_sem);
        list_add_tail(&cache->list, &cache->space_info->block_groups);
        up_write(&cache->space_info->groups_sem);

        ret = btrfs_add_block_group_cache(root->fs_info, cache);
        BUG_ON(ret);

        ret = btrfs_insert_item(trans, extent_root, &cache->key, &cache->item,
                                sizeof(cache->item));
        BUG_ON(ret);

        set_avail_alloc_bits(extent_root->fs_info, type);

        return 0;
}

int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root, u64 group_start)
{
        struct btrfs_path *path;
        struct btrfs_block_group_cache *block_group;
        struct btrfs_free_cluster *cluster;
        struct btrfs_key key;
        int ret;

        root = root->fs_info->extent_root;

        block_group = btrfs_lookup_block_group(root->fs_info, group_start);
        BUG_ON(!block_group);
        BUG_ON(!block_group->ro);

        memcpy(&key, &block_group->key, sizeof(key));

        /* make sure this block group isn't part of an allocation cluster */
        cluster = &root->fs_info->data_alloc_cluster;
        spin_lock(&cluster->refill_lock);
        btrfs_return_cluster_to_free_space(block_group, cluster);
        spin_unlock(&cluster->refill_lock);

        /*
         * make sure this block group isn't part of a metadata
         * allocation cluster
         */
        cluster = &root->fs_info->meta_alloc_cluster;
        spin_lock(&cluster->refill_lock);
        btrfs_return_cluster_to_free_space(block_group, cluster);
        spin_unlock(&cluster->refill_lock);

        path = btrfs_alloc_path();
        BUG_ON(!path);

        spin_lock(&root->fs_info->block_group_cache_lock);
        rb_erase(&block_group->cache_node,
                 &root->fs_info->block_group_cache_tree);
        spin_unlock(&root->fs_info->block_group_cache_lock);

        down_write(&block_group->space_info->groups_sem);
        /*
         * we must use list_del_init so people can check to see if they
         * are still on the list after taking the semaphore
         */
        list_del_init(&block_group->list);
        up_write(&block_group->space_info->groups_sem);

        if (block_group->cached == BTRFS_CACHE_STARTED)
                wait_block_group_cache_done(block_group);

        btrfs_remove_free_space_cache(block_group);

        spin_lock(&block_group->space_info->lock);
        block_group->space_info->total_bytes -= block_group->key.offset;
        block_group->space_info->bytes_readonly -= block_group->key.offset;
        spin_unlock(&block_group->space_info->lock);

        btrfs_clear_space_info_full(root->fs_info);

        btrfs_put_block_group(block_group);
        btrfs_put_block_group(block_group);

        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret > 0)
                ret = -EIO;
        if (ret < 0)
                goto out;

        ret = btrfs_del_item(trans, root, path);
out:
        btrfs_free_path(path);
        return ret;
}