Btrfs: clean up find_free_extent

[deliverable/linux.git] / 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 "compat.h"
#include "hash.h"
#include "crc32c.h"
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"
#include "transaction.h"
#include "volumes.h"
#include "locking.h"
#include "ref-cache.h"

#define PENDING_EXTENT_INSERT 0
#define PENDING_EXTENT_DELETE 1
#define PENDING_BACKREF_UPDATE 2

struct pending_extent_op {
        int type;
        u64 bytenr;
        u64 num_bytes;
        u64 parent;
        u64 orig_parent;
        u64 generation;
        u64 orig_generation;
        int level;
        struct list_head list;
        int del;
};

static int __btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
                                         struct btrfs_root *root, u64 parent,
                                         u64 root_objectid, u64 ref_generation,
                                         u64 owner, struct btrfs_key *ins,
                                         int ref_mod);
static int update_reserved_extents(struct btrfs_root *root,
                                   u64 bytenr, u64 num, int reserve);
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 noinline int __btrfs_free_extent(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        u64 bytenr, u64 num_bytes, u64 parent,
                                        u64 root_objectid, u64 ref_generation,
                                        u64 owner_objectid, int pin,
                                        int ref_to_drop);

static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                          struct btrfs_root *extent_root, u64 alloc_bytes,
                          u64 flags, int force);

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;
}

/*
 * 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 int 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;
        int ret;

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

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

        if (start < end) {
                size = end - start;
                ret = btrfs_add_free_space(block_group, start, size);
                BUG_ON(ret);
        }
        mutex_unlock(&info->pinned_mutex);

        return 0;
}

static int remove_sb_from_cache(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--) {
                        btrfs_remove_free_space(cache, logical[nr],
                                                stripe_len);
                }
                kfree(logical);
        }
        return 0;
}

static int cache_block_group(struct btrfs_root *root,
                             struct btrfs_block_group_cache *block_group)
{
        struct btrfs_path *path;
        int ret = 0;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        int slot;
        u64 last;

        if (!block_group)
                return 0;

        root = root->fs_info->extent_root;

        if (block_group->cached)
                return 0;

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

        path->reada = 2;
        /*
         * we get into deadlocks with paths held by callers of this function.
         * since the alloc_mutex is protecting things right now, just
         * skip the locking here
         */
        path->skip_locking = 1;
        last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
        key.objectid = last;
        key.offset = 0;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;

        while (1) {
                leaf = path->nodes[0];
                slot = path->slots[0];
                if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto err;
                        if (ret == 0)
                                continue;
                        else
                                break;
                }
                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (key.objectid < block_group->key.objectid)
                        goto next;

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

                if (btrfs_key_type(&key) == BTRFS_EXTENT_ITEM_KEY) {
                        add_new_free_space(block_group, root->fs_info, last,
                                           key.objectid);

                        last = key.objectid + key.offset;
                }
next:
                path->slots[0]++;
        }

        add_new_free_space(block_group, root->fs_info, last,
                           block_group->key.objectid +
                           block_group->key.offset);

        block_group->cached = 1;
        remove_sb_from_cache(root, block_group);
        ret = 0;
err:
        btrfs_free_path(path);
        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 teh 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;
}

static inline void 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);
                                put_block_group(cache);
                                goto found;
                        }
                }
                spin_unlock(&cache->lock);
                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.
 *
 * 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 has fields for:
 *
 * - Objectid of the subvolume root
 * - Generation number of the tree holding the reference
 * - objectid of the file holding the reference
 * - number of references holding by parent node (alway 1 for tree blocks)
 *
 * Btree leaf may hold multiple references to a file extent. In most cases,
 * these references are from same file and the corresponding offsets inside
 * the file are close together.
 *
 * When a file extent is allocated the fields are filled in:
 *     (root_key.objectid, trans->transid, inode objectid, 1)
 *
 * When a leaf is cow'd new references are added for every file extent found
 * in the leaf.  It looks similar to the create case, but trans->transid will
 * be different when the block is cow'd.
 *
 *     (root_key.objectid, trans->transid, inode objectid,
 *      number of references in the leaf)
 *
 * When a file extent is removed either during snapshot deletion or
 * file truncation, we find the corresponding back reference and check
 * the following fields:
 *
 *     (btrfs_header_owner(leaf), btrfs_header_generation(leaf),
 *      inode objectid)
 *
 * Btree extents can be referenced by:
 *
 * - Different subvolumes
 * - Different generations of the same subvolume
 *
 * When a tree block is created, back references are inserted:
 *
 * (root->root_key.objectid, trans->transid, level, 1)
 *
 * When a tree block is cow'd, new back references are added for all the
 * blocks it points to. If the tree block isn't in reference counted root,
 * the old back references are removed. These new back references are of
 * the form (trans->transid will have increased since creation):
 *
 * (root->root_key.objectid, trans->transid, level, 1)
 *
 * When a backref is in deleting, the following fields are checked:
 *
 * if backref was for a tree root:
 *     (btrfs_header_owner(itself), btrfs_header_generation(itself), level)
 * else
 *     (btrfs_header_owner(parent), btrfs_header_generation(parent), level)
 *
 * Back Reference Key composing:
 *
 * The key objectid corresponds to the first byte in the extent, the key
 * type is set to BTRFS_EXTENT_REF_KEY, and the key offset is the first
 * byte of parent extent. If a extent is tree root, the key offset is set
 * to the key objectid.
 */

static noinline int lookup_extent_backref(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct btrfs_path *path,
                                          u64 bytenr, u64 parent,
                                          u64 ref_root, u64 ref_generation,
                                          u64 owner_objectid, int del)
{
        struct btrfs_key key;
        struct btrfs_extent_ref *ref;
        struct extent_buffer *leaf;
        u64 ref_objectid;
        int ret;

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

        ret = btrfs_search_slot(trans, root, &key, path, del ? -1 : 0, 1);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = -ENOENT;
                goto out;
        }

        leaf = path->nodes[0];
        ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_ref);
        ref_objectid = btrfs_ref_objectid(leaf, ref);
        if (btrfs_ref_root(leaf, ref) != ref_root ||
            btrfs_ref_generation(leaf, ref) != ref_generation ||
            (ref_objectid != owner_objectid &&
             ref_objectid != BTRFS_MULTIPLE_OBJECTIDS)) {
                ret = -EIO;
                WARN_ON(1);
                goto out;
        }
        ret = 0;
out:
        return ret;
}

static noinline int insert_extent_backref(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct btrfs_path *path,
                                          u64 bytenr, u64 parent,
                                          u64 ref_root, u64 ref_generation,
                                          u64 owner_objectid,
                                          int refs_to_add)
{
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_extent_ref *ref;
        u32 num_refs;
        int ret;

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

        ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*ref));
        if (ret == 0) {
                leaf = path->nodes[0];
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_ref);
                btrfs_set_ref_root(leaf, ref, ref_root);
                btrfs_set_ref_generation(leaf, ref, ref_generation);
                btrfs_set_ref_objectid(leaf, ref, owner_objectid);
                btrfs_set_ref_num_refs(leaf, ref, refs_to_add);
        } else if (ret == -EEXIST) {
                u64 existing_owner;

                BUG_ON(owner_objectid < BTRFS_FIRST_FREE_OBJECTID);
                leaf = path->nodes[0];
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_ref);
                if (btrfs_ref_root(leaf, ref) != ref_root ||
                    btrfs_ref_generation(leaf, ref) != ref_generation) {
                        ret = -EIO;
                        WARN_ON(1);
                        goto out;
                }

                num_refs = btrfs_ref_num_refs(leaf, ref);
                BUG_ON(num_refs == 0);
                btrfs_set_ref_num_refs(leaf, ref, num_refs + refs_to_add);

                existing_owner = btrfs_ref_objectid(leaf, ref);
                if (existing_owner != owner_objectid &&
                    existing_owner != BTRFS_MULTIPLE_OBJECTIDS) {
                        btrfs_set_ref_objectid(leaf, ref,
                                        BTRFS_MULTIPLE_OBJECTIDS);
                }
                ret = 0;
        } else {
                goto out;
        }
        btrfs_unlock_up_safe(path, 1);
        btrfs_mark_buffer_dirty(path->nodes[0]);
out:
        btrfs_release_path(root, path);
        return ret;
}

static noinline int remove_extent_backref(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct btrfs_path *path,
                                          int refs_to_drop)
{
        struct extent_buffer *leaf;
        struct btrfs_extent_ref *ref;
        u32 num_refs;
        int ret = 0;

        leaf = path->nodes[0];
        ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_ref);
        num_refs = btrfs_ref_num_refs(leaf, ref);
        BUG_ON(num_refs < refs_to_drop);
        num_refs -= refs_to_drop;
        if (num_refs == 0) {
                ret = btrfs_del_item(trans, root, path);
        } else {
                btrfs_set_ref_num_refs(leaf, ref, num_refs);
                btrfs_mark_buffer_dirty(leaf);
        }
        btrfs_release_path(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
}

static int __btrfs_update_extent_ref(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root, u64 bytenr,
                                     u64 num_bytes,
                                     u64 orig_parent, u64 parent,
                                     u64 orig_root, u64 ref_root,
                                     u64 orig_generation, u64 ref_generation,
                                     u64 owner_objectid)
{
        int ret;
        int pin = owner_objectid < BTRFS_FIRST_FREE_OBJECTID;

        ret = btrfs_update_delayed_ref(trans, bytenr, num_bytes,
                                       orig_parent, parent, orig_root,
                                       ref_root, orig_generation,
                                       ref_generation, owner_objectid, pin);
        BUG_ON(ret);
        return ret;
}

int btrfs_update_extent_ref(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root, u64 bytenr,
                            u64 num_bytes, u64 orig_parent, u64 parent,
                            u64 ref_root, u64 ref_generation,
                            u64 owner_objectid)
{
        int ret;
        if (ref_root == BTRFS_TREE_LOG_OBJECTID &&
            owner_objectid < BTRFS_FIRST_FREE_OBJECTID)
                return 0;

        ret = __btrfs_update_extent_ref(trans, root, bytenr, num_bytes,
                                        orig_parent, parent, ref_root,
                                        ref_root, ref_generation,
                                        ref_generation, owner_objectid);
        return ret;
}
static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root, u64 bytenr,
                                  u64 num_bytes,
                                  u64 orig_parent, u64 parent,
                                  u64 orig_root, u64 ref_root,
                                  u64 orig_generation, u64 ref_generation,
                                  u64 owner_objectid)
{
        int ret;

        ret = btrfs_add_delayed_ref(trans, bytenr, num_bytes, parent, ref_root,
                                    ref_generation, owner_objectid,
                                    BTRFS_ADD_DELAYED_REF, 0);
        BUG_ON(ret);
        return ret;
}

static noinline_for_stack int add_extent_ref(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, u64 bytenr,
                          u64 num_bytes, u64 parent, u64 ref_root,
                          u64 ref_generation, u64 owner_objectid,
                          int refs_to_add)
{
        struct btrfs_path *path;
        int ret;
        struct btrfs_key key;
        struct extent_buffer *l;
        struct btrfs_extent_item *item;
        u32 refs;

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

        path->reada = 1;
        path->leave_spinning = 1;
        key.objectid = bytenr;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = num_bytes;

        /* first find the extent item and update its reference count */
        ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key,
                                path, 0, 1);
        if (ret < 0) {
                btrfs_set_path_blocking(path);
                return ret;
        }

        if (ret > 0) {
                WARN_ON(1);
                btrfs_free_path(path);
                return -EIO;
        }
        l = path->nodes[0];

        btrfs_item_key_to_cpu(l, &key, path->slots[0]);
        if (key.objectid != bytenr) {
                btrfs_print_leaf(root->fs_info->extent_root, path->nodes[0]);
                printk(KERN_ERR "btrfs wanted %llu found %llu\n",
                       (unsigned long long)bytenr,
                       (unsigned long long)key.objectid);
                BUG();
        }
        BUG_ON(key.type != BTRFS_EXTENT_ITEM_KEY);

        item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);

        refs = btrfs_extent_refs(l, item);
        btrfs_set_extent_refs(l, item, refs + refs_to_add);
        btrfs_unlock_up_safe(path, 1);

        btrfs_mark_buffer_dirty(path->nodes[0]);

        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,
                                    ref_root, ref_generation,
                                    owner_objectid, refs_to_add);
        BUG_ON(ret);
        btrfs_free_path(path);
        return 0;
}

int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         u64 bytenr, u64 num_bytes, u64 parent,
                         u64 ref_root, u64 ref_generation,
                         u64 owner_objectid)
{
        int ret;
        if (ref_root == BTRFS_TREE_LOG_OBJECTID &&
            owner_objectid < BTRFS_FIRST_FREE_OBJECTID)
                return 0;

        ret = __btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0, parent,
                                     0, ref_root, 0, ref_generation,
                                     owner_objectid);
        return ret;
}

static int drop_delayed_ref(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_delayed_ref_node *node)
{
        int ret = 0;
        struct btrfs_delayed_ref *ref = btrfs_delayed_node_to_ref(node);

        BUG_ON(node->ref_mod == 0);
        ret = __btrfs_free_extent(trans, root, node->bytenr, node->num_bytes,
                                  node->parent, ref->root, ref->generation,
                                  ref->owner_objectid, ref->pin, node->ref_mod);

        return ret;
}

/* helper function to actually process a single delayed ref entry */
static noinline int run_one_delayed_ref(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_delayed_ref_node *node,
                                        int insert_reserved)
{
        int ret;
        struct btrfs_delayed_ref *ref;

        if (node->parent == (u64)-1) {
                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
                 */
                if (insert_reserved) {
                        update_reserved_extents(root, node->bytenr,
                                                node->num_bytes, 0);
                }
                head = btrfs_delayed_node_to_head(node);
                mutex_unlock(&head->mutex);
                return 0;
        }

        ref = btrfs_delayed_node_to_ref(node);
        if (ref->action == BTRFS_ADD_DELAYED_REF) {
                if (insert_reserved) {
                        struct btrfs_key ins;

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

                        /* record the full extent allocation */
                        ret = __btrfs_alloc_reserved_extent(trans, root,
                                        node->parent, ref->root,
                                        ref->generation, ref->owner_objectid,
                                        &ins, node->ref_mod);
                        update_reserved_extents(root, node->bytenr,
                                                node->num_bytes, 0);
                } else {
                        /* just add one backref */
                        ret = add_extent_ref(trans, root, node->bytenr,
                                     node->num_bytes,
                                     node->parent, ref->root, ref->generation,
                                     ref->owner_objectid, node->ref_mod);
                }
                BUG_ON(ret);
        } else if (ref->action == BTRFS_DROP_DELAYED_REF) {
                WARN_ON(insert_reserved);
                ret = drop_delayed_ref(trans, root, node);
        }
        return 0;
}

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 (btrfs_delayed_node_to_ref(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;
        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;

                /*
                 * 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;
                        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,
                                          must_insert_reserved);
                BUG_ON(ret);
                btrfs_put_delayed_ref(ref);

                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_cross_ref_exist(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, u64 objectid, u64 bytenr)
{
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_extent_ref *ref_item;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u64 ref_root;
        u64 last_snapshot;
        u32 nritems;
        int ret;

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

        path = btrfs_alloc_path();
        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, &found_key, path->slots[0]);

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

        last_snapshot = btrfs_root_last_snapshot(&root->root_item);
        while (1) {
                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)
                                continue;
                        break;
                }
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != bytenr)
                        break;

                if (found_key.type != BTRFS_EXTENT_REF_KEY) {
                        path->slots[0]++;
                        continue;
                }

                ref_item = btrfs_item_ptr(leaf, path->slots[0],
                                          struct btrfs_extent_ref);
                ref_root = btrfs_ref_root(leaf, ref_item);
                if ((ref_root != root->root_key.objectid &&
                     ref_root != BTRFS_TREE_LOG_OBJECTID) ||
                     objectid != btrfs_ref_objectid(leaf, ref_item)) {
                        ret = 1;
                        goto out;
                }
                if (btrfs_ref_generation(leaf, ref_item) <= last_snapshot) {
                        ret = 1;
                        goto out;
                }

                path->slots[0]++;
        }
        ret = 0;
out:
        btrfs_free_path(path);
        return ret;
}

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;
}


noinline int btrfs_inc_ref(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root,
                           struct extent_buffer *orig_buf,
                           struct extent_buffer *buf, u32 *nr_extents)
{
        u64 bytenr;
        u64 ref_root;
        u64 orig_root;
        u64 ref_generation;
        u64 orig_generation;
        struct refsort *sorted;
        u32 nritems;
        u32 nr_file_extents = 0;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int level;
        int ret = 0;
        int faili = 0;
        int refi = 0;
        int slot;
        int (*process_func)(struct btrfs_trans_handle *, struct btrfs_root *,
                            u64, u64, u64, u64, u64, u64, u64, u64, u64);

        ref_root = btrfs_header_owner(buf);
        ref_generation = btrfs_header_generation(buf);
        orig_root = btrfs_header_owner(orig_buf);
        orig_generation = btrfs_header_generation(orig_buf);

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

        sorted = kmalloc(sizeof(struct refsort) * nritems, GFP_NOFS);
        BUG_ON(!sorted);

        if (root->ref_cows) {
                process_func = __btrfs_inc_extent_ref;
        } else {
                if (level == 0 &&
                    root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
                        goto out;
                if (level != 0 &&
                    root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID)
                        goto out;
                process_func = __btrfs_update_extent_ref;
        }

        /*
         * we make two passes through the items.  In the first pass we
         * only record the byte number and slot.  Then we sort based on
         * byte number and do the actual work based on the sorted results
         */
        for (i = 0; i < nritems; i++) {
                cond_resched();
                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;

                        nr_file_extents++;
                        sorted[refi].bytenr = bytenr;
                        sorted[refi].slot = i;
                        refi++;
                } else {
                        bytenr = btrfs_node_blockptr(buf, i);
                        sorted[refi].bytenr = bytenr;
                        sorted[refi].slot = i;
                        refi++;
                }
        }
        /*
         * if refi == 0, we didn't actually put anything into the sorted
         * array and we're done
         */
        if (refi == 0)
                goto out;

        sort(sorted, refi, sizeof(struct refsort), refsort_cmp, NULL);

        for (i = 0; i < refi; i++) {
                cond_resched();
                slot = sorted[i].slot;
                bytenr = sorted[i].bytenr;

                if (level == 0) {
                        btrfs_item_key_to_cpu(buf, &key, slot);
                        fi = btrfs_item_ptr(buf, slot,
                                            struct btrfs_file_extent_item);

                        bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
                        if (bytenr == 0)
                                continue;

                        ret = process_func(trans, root, bytenr,
                                   btrfs_file_extent_disk_num_bytes(buf, fi),
                                   orig_buf->start, buf->start,
                                   orig_root, ref_root,
                                   orig_generation, ref_generation,
                                   key.objectid);

                        if (ret) {
                                faili = slot;
                                WARN_ON(1);
                                goto fail;
                        }
                } else {
                        ret = process_func(trans, root, bytenr, buf->len,
                                           orig_buf->start, buf->start,
                                           orig_root, ref_root,
                                           orig_generation, ref_generation,
                                           level - 1);
                        if (ret) {
                                faili = slot;
                                WARN_ON(1);
                                goto fail;
                        }
                }
        }
out:
        kfree(sorted);
        if (nr_extents) {
                if (level == 0)
                        *nr_extents = nr_file_extents;
                else
                        *nr_extents = nritems;
        }
        return 0;
fail:
        kfree(sorted);
        WARN_ON(1);
        return ret;
}

int btrfs_update_ref(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root, struct extent_buffer *orig_buf,
                     struct extent_buffer *buf, int start_slot, int nr)

{
        u64 bytenr;
        u64 ref_root;
        u64 orig_root;
        u64 ref_generation;
        u64 orig_generation;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int ret;
        int slot;
        int level;

        BUG_ON(start_slot < 0);
        BUG_ON(start_slot + nr > btrfs_header_nritems(buf));

        ref_root = btrfs_header_owner(buf);
        ref_generation = btrfs_header_generation(buf);
        orig_root = btrfs_header_owner(orig_buf);
        orig_generation = btrfs_header_generation(orig_buf);
        level = btrfs_header_level(buf);

        if (!root->ref_cows) {
                if (level == 0 &&
                    root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
                        return 0;
                if (level != 0 &&
                    root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID)
                        return 0;
        }

        for (i = 0, slot = start_slot; i < nr; i++, slot++) {
                cond_resched();
                if (level == 0) {
                        btrfs_item_key_to_cpu(buf, &key, slot);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
                        fi = btrfs_item_ptr(buf, slot,
                                            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;
                        ret = __btrfs_update_extent_ref(trans, root, bytenr,
                                    btrfs_file_extent_disk_num_bytes(buf, fi),
                                    orig_buf->start, buf->start,
                                    orig_root, ref_root, orig_generation,
                                    ref_generation, key.objectid);
                        if (ret)
                                goto fail;
                } else {
                        bytenr = btrfs_node_blockptr(buf, slot);
                        ret = __btrfs_update_extent_ref(trans, root, bytenr,
                                            buf->len, orig_buf->start,
                                            buf->start, orig_root, ref_root,
                                            orig_generation, ref_generation,
                                            level - 1);
                        if (ret)
                                goto fail;
                }
        }
        return 0;
fail:
        WARN_ON(1);
        return -1;
}

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;

}

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

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

        while (1) {
                cache = NULL;
                spin_lock(&root->fs_info->block_group_cache_lock);
                for (n = rb_first(&root->fs_info->block_group_cache_tree);
                     n; n = rb_next(n)) {
                        entry = rb_entry(n, struct btrfs_block_group_cache,
                                         cache_node);
                        if (entry->dirty) {
                                cache = entry;
                                break;
                        }
                }
                spin_unlock(&root->fs_info->block_group_cache_lock);

                if (!cache)
                        break;

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

                err = write_one_cache_group(trans, root,
                                            path, cache);
                /*
                 * if we fail to write the cache group, we want
                 * to keep it marked dirty in hopes that a later
                 * write will work
                 */
                if (err) {
                        werr = err;
                        continue;
                }
        }
        btrfs_free_path(path);
        return werr;
}

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)
                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);
        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);
}

/*
 * for now this just makes sure we have at least 5% of our metadata space free
 * for use.
 */
int btrfs_check_metadata_free_space(struct btrfs_root *root)
{
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *meta_sinfo;
        u64 alloc_target, thresh;
        int committed = 0, ret;

        /* 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);

again:
        spin_lock(&meta_sinfo->lock);
        if (!meta_sinfo->full)
                thresh = meta_sinfo->total_bytes * 80;
        else
                thresh = meta_sinfo->total_bytes * 95;

        do_div(thresh, 100);

        if (meta_sinfo->bytes_used + meta_sinfo->bytes_reserved +
            meta_sinfo->bytes_pinned + meta_sinfo->bytes_readonly > thresh) {
                struct btrfs_trans_handle *trans;
                if (!meta_sinfo->full) {
                        meta_sinfo->force_alloc = 1;
                        spin_unlock(&meta_sinfo->lock);

                        trans = btrfs_start_transaction(root, 1);
                        if (!trans)
                                return -ENOMEM;

                        ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                             2 * 1024 * 1024, alloc_target, 0);
                        btrfs_end_transaction(trans, root);
                        goto again;
                }
                spin_unlock(&meta_sinfo->lock);

                if (!committed) {
                        committed = 1;
                        trans = btrfs_join_transaction(root, 1);
                        if (!trans)
                                return -ENOMEM;
                        ret = btrfs_commit_transaction(trans, root);
                        if (ret)
                                return ret;
                        goto again;
                }
                return -ENOSPC;
        }
        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;
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 < 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_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;
                        goto again;
                }
                spin_unlock(&data_sinfo->lock);

                /* commit the current transaction and try again */
                if (!committed) {
                        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", bytes, data_sinfo->bytes_delalloc,
                       data_sinfo->bytes_used, data_sinfo->bytes_reserved,
                       data_sinfo->bytes_pinned, data_sinfo->bytes_readonly,
                       data_sinfo->bytes_may_use, data_sinfo->total_bytes);
                return -ENOSPC;
        }
        data_sinfo->bytes_may_use += bytes;
        BTRFS_I(inode)->reserved_bytes += bytes;
        spin_unlock(&data_sinfo->lock);

        return btrfs_check_metadata_free_space(root);
}

/*
 * 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 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;
        u64 thresh;
        int ret = 0;

        mutex_lock(&extent_root->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;
                space_info->force_alloc = 0;
        }
        if (space_info->full) {
                spin_unlock(&space_info->lock);
                goto out;
        }

        thresh = space_info->total_bytes - space_info->bytes_readonly;
        thresh = div_factor(thresh, 6);
        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);

        ret = btrfs_alloc_chunk(trans, extent_root, flags);
        if (ret)
                space_info->full = 1;
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;

        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;
                        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);
                } 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);
                        }
                }
                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;
        put_block_group(cache);

        return bytenr;
}

int btrfs_update_pinned_extents(struct btrfs_root *root,
                                u64 bytenr, u64 num, int pin)
{
        u64 len;
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *fs_info = root->fs_info;

        WARN_ON(!mutex_is_locked(&root->fs_info->pinned_mutex));
        if (pin) {
                set_extent_dirty(&fs_info->pinned_extents,
                                bytenr, bytenr + num - 1, GFP_NOFS);
        } else {
                clear_extent_dirty(&fs_info->pinned_extents,
                                bytenr, bytenr + num - 1, GFP_NOFS);
        }
        mutex_unlock(&root->fs_info->pinned_mutex);

        while (num > 0) {
                cache = btrfs_lookup_block_group(fs_info, bytenr);
                BUG_ON(!cache);
                len = min(num, cache->key.offset -
                          (bytenr - cache->key.objectid));
                if (pin) {
                        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);
                        fs_info->total_pinned += len;
                } else {
                        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);
                        fs_info->total_pinned -= len;
                        if (cache->cached)
                                btrfs_add_free_space(cache, bytenr, len);
                }
                put_block_group(cache);
                bytenr += len;
                num -= len;
        }
        return 0;
}

static int update_reserved_extents(struct btrfs_root *root,
                                   u64 bytenr, u64 num, int reserve)
{
        u64 len;
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *fs_info = root->fs_info;

        while (num > 0) {
                cache = btrfs_lookup_block_group(fs_info, bytenr);
                BUG_ON(!cache);
                len = min(num, cache->key.offset -
                          (bytenr - cache->key.objectid));

                spin_lock(&cache->space_info->lock);
                spin_lock(&cache->lock);
                if (reserve) {
                        cache->reserved += len;
                        cache->space_info->bytes_reserved += len;
                } else {
                        cache->reserved -= len;
                        cache->space_info->bytes_reserved -= len;
                }
                spin_unlock(&cache->lock);
                spin_unlock(&cache->space_info->lock);
                put_block_group(cache);
                bytenr += len;
                num -= len;
        }
        return 0;
}

int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy)
{
        u64 last = 0;
        u64 start;
        u64 end;
        struct extent_io_tree *pinned_extents = &root->fs_info->pinned_extents;
        int ret;

        mutex_lock(&root->fs_info->pinned_mutex);
        while (1) {
                ret = find_first_extent_bit(pinned_extents, last,
                                            &start, &end, EXTENT_DIRTY);
                if (ret)
                        break;
                set_extent_dirty(copy, start, end, GFP_NOFS);
                last = end + 1;
        }
        mutex_unlock(&root->fs_info->pinned_mutex);
        return 0;
}

int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct extent_io_tree *unpin)
{
        u64 start;
        u64 end;
        int ret;

        while (1) {
                mutex_lock(&root->fs_info->pinned_mutex);
                ret = find_first_extent_bit(unpin, 0, &start, &end,
                                            EXTENT_DIRTY);
                if (ret)
                        break;

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

                /* unlocks the pinned mutex */
                btrfs_update_pinned_extents(root, start, end + 1 - start, 0);
                clear_extent_dirty(unpin, start, end, GFP_NOFS);

                cond_resched();
        }
        mutex_unlock(&root->fs_info->pinned_mutex);
        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,
                          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_owner != BTRFS_TREE_RELOC_OBJECTID &&
                    header_owner != BTRFS_DATA_RELOC_TREE_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:
        btrfs_set_path_blocking(path);
        mutex_lock(&root->fs_info->pinned_mutex);
        /* unlocks the pinned mutex */
        btrfs_update_pinned_extents(root, bytenr, num_bytes, 1);

        BUG_ON(err < 0);
        return 0;
}

/*
 * remove an extent from the root, returns 0 on success
 */
static int __free_extent(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         u64 bytenr, u64 num_bytes, u64 parent,
                         u64 root_objectid, u64 ref_generation,
                         u64 owner_objectid, int pin, int mark_free,
                         int refs_to_drop)
{
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_root *extent_root = info->extent_root;
        struct extent_buffer *leaf;
        int ret;
        int extent_slot = 0;
        int found_extent = 0;
        int num_to_del = 1;
        struct btrfs_extent_item *ei;
        u32 refs;

        key.objectid = bytenr;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        key.offset = num_bytes;
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->reada = 1;
        path->leave_spinning = 1;
        ret = lookup_extent_backref(trans, extent_root, path,
                                    bytenr, parent, root_objectid,
                                    ref_generation, owner_objectid, 1);
        if (ret == 0) {
                struct btrfs_key found_key;
                extent_slot = path->slots[0];
                while (extent_slot > 0) {
                        extent_slot--;
                        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                                              extent_slot);
                        if (found_key.objectid != bytenr)
                                break;
                        if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
                            found_key.offset == num_bytes) {
                                found_extent = 1;
                                break;
                        }
                        if (path->slots[0] - extent_slot > 5)
                                break;
                }
                if (!found_extent) {
                        ret = remove_extent_backref(trans, extent_root, path,
                                                    refs_to_drop);
                        BUG_ON(ret);
                        btrfs_release_path(extent_root, path);
                        path->leave_spinning = 1;
                        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 gen %llu owner %llu\n",
                       (unsigned long long)bytenr,
                       (unsigned long long)parent,
                       (unsigned long long)root_objectid,
                       (unsigned long long)ref_generation,
                       (unsigned long long)owner_objectid);
        }

        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, extent_slot,
                            struct btrfs_extent_item);
        refs = btrfs_extent_refs(leaf, ei);

        /*
         * we're not allowed to delete the extent item if there
         * are other delayed ref updates pending
         */

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

        if (refs == 0 && found_extent &&
            path->slots[0] == extent_slot + 1) {
                struct btrfs_extent_ref *ref;
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_extent_ref);
                BUG_ON(btrfs_ref_num_refs(leaf, ref) != refs_to_drop);
                /* if the back ref and the extent are next to each other
                 * they get deleted below in one shot
                 */
                path->slots[0] = extent_slot;
                num_to_del = 2;
        } else if (found_extent) {
                /* otherwise delete the extent back ref */
                ret = remove_extent_backref(trans, extent_root, path,
                                            refs_to_drop);
                BUG_ON(ret);
                /* if refs are 0, we need to setup the path for deletion */
                if (refs == 0) {
                        btrfs_release_path(extent_root, path);
                        path->leave_spinning = 1;
                        ret = btrfs_search_slot(trans, extent_root, &key, path,
                                                -1, 1);
                        BUG_ON(ret);
                }
        }

        if (refs == 0) {
                u64 super_used;
                u64 root_used;
                struct extent_buffer *must_clean = NULL;

                if (pin) {
                        ret = pin_down_bytes(trans, root, path,
                                bytenr, num_bytes,
                                owner_objectid >= BTRFS_FIRST_FREE_OBJECTID,
                                &must_clean);
                        if (ret > 0)
                                mark_free = 1;
                        BUG_ON(ret < 0);
                }

                /* block accounting for super block */
                spin_lock(&info->delalloc_lock);
                super_used = btrfs_super_bytes_used(&info->super_copy);
                btrfs_set_super_bytes_used(&info->super_copy,
                                           super_used - num_bytes);

                /* block accounting for root item */
                root_used = btrfs_root_used(&root->root_item);
                btrfs_set_root_used(&root->root_item,
                                           root_used - num_bytes);
                spin_unlock(&info->delalloc_lock);

                /*
                 * 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 (owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                        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;
}

/*
 * remove an extent from the root, returns 0 on success
 */
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 ref_generation,
                                        u64 owner_objectid, int pin,
                                        int refs_to_drop)
{
        WARN_ON(num_bytes < root->sectorsize);

        /*
         * if metadata always pin
         * if data pin when any transaction has committed this
         */
        if (owner_objectid < BTRFS_FIRST_FREE_OBJECTID ||
            ref_generation != trans->transid)
                pin = 1;

        if (ref_generation != trans->transid)
                pin = 1;

        return __free_extent(trans, root, bytenr, num_bytes, parent,
                            root_objectid, ref_generation,
                            owner_objectid, pin, pin == 0, refs_to_drop);
}

/*
 * 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;

        /*
         * 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->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 ref_generation,
                      u64 owner_objectid, int pin)
{
        int ret;

        /*
         * tree log blocks never actually go into the extent allocation
         * tree, just update pinning info and exit early.
         *
         * data extents referenced by the tree log do need to have
         * their reference counts bumped.
         */
        if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID &&
            owner_objectid < BTRFS_FIRST_FREE_OBJECTID) {
                mutex_lock(&root->fs_info->pinned_mutex);

                /* unlocks the pinned mutex */
                btrfs_update_pinned_extents(root, bytenr, num_bytes, 1);
                update_reserved_extents(root, bytenr, num_bytes, 0);
                ret = 0;
        } else {
                ret = btrfs_add_delayed_ref(trans, bytenr, num_bytes, parent,
                                       root_objectid, ref_generation,
                                       owner_objectid,
                                       BTRFS_DROP_DELAYED_REF, 1);
                BUG_ON(ret);
                ret = check_ref_cleanup(trans, root, bytenr);
                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;
}

/*
 * 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;
        u64 total_needed = num_bytes;
        u64 *last_ptr = NULL;
        struct btrfs_block_group_cache *block_group = NULL;
        int empty_cluster = 2 * 1024 * 1024;
        int allowed_chunk_alloc = 0;
        int using_hint = 0;
        struct btrfs_space_info *space_info;

        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->last_alloc;
                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->last_data_alloc;

        if (last_ptr) {
                if (*last_ptr)
                        hint_byte = *last_ptr;
                else
                        empty_size += empty_cluster;
        } else {
                empty_cluster = 0;
        }
        search_start = max(search_start, first_logical_byte(root, 0));
        search_start = max(search_start, hint_byte);

        if (search_start == hint_byte) {
                using_hint = 1;
                block_group = btrfs_lookup_block_group(root->fs_info,
                                                       search_start);
                if (block_group && block_group_bits(block_group, data)) {
                        total_needed += empty_size;
                        down_read(&space_info->groups_sem);
                        goto have_block_group;
                } else if (block_group) {
                        put_block_group(block_group);
                }

                empty_size += empty_cluster;
                using_hint = 0;
        }

search:
        down_read(&space_info->groups_sem);
        list_for_each_entry(block_group, &space_info->block_groups, list) {
                struct btrfs_free_space *free_space;

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

have_block_group:
                if (unlikely(!block_group->cached)) {
                        mutex_lock(&block_group->cache_mutex);
                        ret = cache_block_group(root, block_group);
                        mutex_unlock(&block_group->cache_mutex);
                        if (ret) {
                                put_block_group(block_group);
                                break;
                        }
                }

                mutex_lock(&block_group->alloc_mutex);

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

                free_space = btrfs_find_free_space(block_group, search_start,
                                                   total_needed);
                if (!free_space)
                        goto loop;

                search_start = stripe_align(root, free_space->offset);

                /* move on to the next group */
                if (search_start + num_bytes >= search_end)
                        goto loop;

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

                if (using_hint && search_start > hint_byte)
                        goto loop;

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

                        /*
                         * 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)) {
                                mutex_unlock(&block_group->alloc_mutex);
                                goto have_block_group;
                        }
                        goto loop;
                }

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

                btrfs_remove_free_space_lock(block_group, search_start,
                                             num_bytes);
                /* we are all good, lets return */
                mutex_unlock(&block_group->alloc_mutex);
                break;
loop:
                mutex_unlock(&block_group->alloc_mutex);
                put_block_group(block_group);
                if (using_hint) {
                        empty_size += empty_cluster;
                        total_needed += empty_cluster;
                        using_hint = 0;
                        up_read(&space_info->groups_sem);
                        goto search;
                }
        }
        up_read(&space_info->groups_sem);

        if (!ins->objectid && (empty_size || allowed_chunk_alloc)) {
                int try_again = empty_size;

                total_needed -= empty_size;
                empty_size = 0;

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

                if (try_again)
                        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;

                if (last_ptr)
                        *last_ptr = ins->objectid + ins->offset;
                put_block_group(block_group);
                ret = 0;
        }

        return ret;
}

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

        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->full) ? "" : "not ");
        printk(KERN_INFO "space_info total=%llu, pinned=%llu, delalloc=%llu,"
               " may_use=%llu, used=%llu\n", info->total_bytes,
               info->bytes_pinned, info->bytes_delalloc, info->bytes_may_use,
               info->bytes_used);

        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);
}

static 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) {
                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);
                BUG();
        }

        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);
        put_block_group(cache);
        update_reserved_extents(root, start, len, 0);

        return ret;
}

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;
        ret = __btrfs_reserve_extent(trans, root, num_bytes, min_alloc_size,
                                     empty_size, hint_byte, search_end, ins,
                                     data);
        update_reserved_extents(root, ins->objectid, ins->offset, 1);
        return ret;
}

static int __btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
                                         struct btrfs_root *root, u64 parent,
                                         u64 root_objectid, u64 ref_generation,
                                         u64 owner, struct btrfs_key *ins,
                                         int ref_mod)
{
        int ret;
        u64 super_used;
        u64 root_used;
        u64 num_bytes = ins->offset;
        u32 sizes[2];
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_root *extent_root = info->extent_root;
        struct btrfs_extent_item *extent_item;
        struct btrfs_extent_ref *ref;
        struct btrfs_path *path;
        struct btrfs_key keys[2];

        if (parent == 0)
                parent = ins->objectid;

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

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

        memcpy(&keys[0], ins, sizeof(*ins));
        keys[1].objectid = ins->objectid;
        keys[1].type = BTRFS_EXTENT_REF_KEY;
        keys[1].offset = parent;
        sizes[0] = sizeof(*extent_item);
        sizes[1] = sizeof(*ref);

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

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_items(trans, extent_root, path, keys,
                                       sizes, 2);
        BUG_ON(ret);

        extent_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                     struct btrfs_extent_item);
        btrfs_set_extent_refs(path->nodes[0], extent_item, ref_mod);
        ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
                             struct btrfs_extent_ref);

        btrfs_set_ref_root(path->nodes[0], ref, root_objectid);
        btrfs_set_ref_generation(path->nodes[0], ref, ref_generation);
        btrfs_set_ref_objectid(path->nodes[0], ref, owner);
        btrfs_set_ref_num_refs(path->nodes[0], ref, ref_mod);

        btrfs_mark_buffer_dirty(path->nodes[0]);

        trans->alloc_exclude_start = 0;
        trans->alloc_exclude_nr = 0;
        btrfs_free_path(path);

        if (ret)
                goto out;

        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();
        }
out:
        return ret;
}

int btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, u64 parent,
                                u64 root_objectid, u64 ref_generation,
                                u64 owner, struct btrfs_key *ins)
{
        int ret;

        if (root_objectid == BTRFS_TREE_LOG_OBJECTID)
                return 0;

        ret = btrfs_add_delayed_ref(trans, ins->objectid,
                                    ins->offset, parent, root_objectid,
                                    ref_generation, owner,
                                    BTRFS_ADD_DELAYED_EXTENT, 0);
        BUG_ON(ret);
        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_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, u64 parent,
                                u64 root_objectid, u64 ref_generation,
                                u64 owner, struct btrfs_key *ins)
{
        int ret;
        struct btrfs_block_group_cache *block_group;

        block_group = btrfs_lookup_block_group(root->fs_info, ins->objectid);
        mutex_lock(&block_group->cache_mutex);
        cache_block_group(root, block_group);
        mutex_unlock(&block_group->cache_mutex);

        ret = btrfs_remove_free_space(block_group, ins->objectid,
                                      ins->offset);
        BUG_ON(ret);
        put_block_group(block_group);
        ret = __btrfs_alloc_reserved_extent(trans, root, parent, root_objectid,
                                            ref_generation, owner, 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.
 */
int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       u64 num_bytes, u64 parent, u64 min_alloc_size,
                       u64 root_objectid, u64 ref_generation,
                       u64 owner_objectid, u64 empty_size, u64 hint_byte,
                       u64 search_end, struct btrfs_key *ins, u64 data)
{
        int ret;
        ret = __btrfs_reserve_extent(trans, root, num_bytes,
                                     min_alloc_size, empty_size, hint_byte,
                                     search_end, ins, data);
        BUG_ON(ret);
        if (root_objectid != BTRFS_TREE_LOG_OBJECTID) {
                ret = btrfs_add_delayed_ref(trans, ins->objectid,
                                            ins->offset, parent, root_objectid,
                                            ref_generation, owner_objectid,
                                            BTRFS_ADD_DELAYED_EXTENT, 0);
                BUG_ON(ret);
        }
        update_reserved_extents(root, ins->objectid, ins->offset, 1);
        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,
                                             u64 ref_generation,
                                             int level,
                                             u64 hint,
                                             u64 empty_size)
{
        struct btrfs_key ins;
        int ret;
        struct extent_buffer *buf;

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

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

int btrfs_drop_leaf_ref(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root, struct extent_buffer *leaf)
{
        u64 leaf_owner;
        u64 leaf_generation;
        struct refsort *sorted;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int nritems;
        int ret;
        int refi = 0;
        int slot;

        BUG_ON(!btrfs_is_leaf(leaf));
        nritems = btrfs_header_nritems(leaf);
        leaf_owner = btrfs_header_owner(leaf);
        leaf_generation = btrfs_header_generation(leaf);

        sorted = kmalloc(sizeof(*sorted) * nritems, GFP_NOFS);
        /* we do this loop twice.  The first time we build a list
         * of the extents we have a reference on, then we sort the list
         * by bytenr.  The second time around we actually do the
         * extent freeing.
         */
        for (i = 0; i < nritems; i++) {
                u64 disk_bytenr;
                cond_resched();

                btrfs_item_key_to_cpu(leaf, &key, i);

                /* only extents have references, skip everything else */
                if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                        continue;

                fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);

                /* inline extents live in the btree, they don't have refs */
                if (btrfs_file_extent_type(leaf, fi) ==
                    BTRFS_FILE_EXTENT_INLINE)
                        continue;

                disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);

                /* holes don't have refs */
                if (disk_bytenr == 0)
                        continue;

                sorted[refi].bytenr = disk_bytenr;
                sorted[refi].slot = i;
                refi++;
        }

        if (refi == 0)
                goto out;

        sort(sorted, refi, sizeof(struct refsort), refsort_cmp, NULL);

        for (i = 0; i < refi; i++) {
                u64 disk_bytenr;

                disk_bytenr = sorted[i].bytenr;
                slot = sorted[i].slot;

                cond_resched();

                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                        continue;

                fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);

                ret = btrfs_free_extent(trans, root, disk_bytenr,
                                btrfs_file_extent_disk_num_bytes(leaf, fi),
                                leaf->start, leaf_owner, leaf_generation,
                                key.objectid, 0);
                BUG_ON(ret);

                atomic_inc(&root->fs_info->throttle_gen);
                wake_up(&root->fs_info->transaction_throttle);
                cond_resched();
        }
out:
        kfree(sorted);
        return 0;
}

static noinline int cache_drop_leaf_ref(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_leaf_ref *ref)
{
        int i;
        int ret;
        struct btrfs_extent_info *info;
        struct refsort *sorted;

        if (ref->nritems == 0)
                return 0;

        sorted = kmalloc(sizeof(*sorted) * ref->nritems, GFP_NOFS);
        for (i = 0; i < ref->nritems; i++) {
                sorted[i].bytenr = ref->extents[i].bytenr;
                sorted[i].slot = i;
        }
        sort(sorted, ref->nritems, sizeof(struct refsort), refsort_cmp, NULL);

        /*
         * the items in the ref were sorted when the ref was inserted
         * into the ref cache, so this is already in order
         */
        for (i = 0; i < ref->nritems; i++) {
                info = ref->extents + sorted[i].slot;
                ret = btrfs_free_extent(trans, root, info->bytenr,
                                          info->num_bytes, ref->bytenr,
                                          ref->owner, ref->generation,
                                          info->objectid, 0);

                atomic_inc(&root->fs_info->throttle_gen);
                wake_up(&root->fs_info->transaction_throttle);
                cond_resched();

                BUG_ON(ret);
                info++;
        }

        kfree(sorted);
        return 0;
}

static int drop_snap_lookup_refcount(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root, u64 start,
                                     u64 len, u32 *refs)
{
        int ret;

        ret = btrfs_lookup_extent_ref(trans, root, start, len, refs);
        BUG_ON(ret);

#if 0 /* some debugging code in case we see problems here */
        /* if the refs count is one, it won't get increased again.  But
         * if the ref count is > 1, someone may be decreasing it at
         * the same time we are.
         */
        if (*refs != 1) {
                struct extent_buffer *eb = NULL;
                eb = btrfs_find_create_tree_block(root, start, len);
                if (eb)
                        btrfs_tree_lock(eb);

                mutex_lock(&root->fs_info->alloc_mutex);
                ret = lookup_extent_ref(NULL, root, start, len, refs);
                BUG_ON(ret);
                mutex_unlock(&root->fs_info->alloc_mutex);

                if (eb) {
                        btrfs_tree_unlock(eb);
                        free_extent_buffer(eb);
                }
                if (*refs == 1) {
                        printk(KERN_ERR "btrfs block %llu went down to one "
                               "during drop_snap\n", (unsigned long long)start);
                }

        }
#endif

        cond_resched();
        return ret;
}

/*
 * this is used while deleting old snapshots, and it drops the refs
 * on a whole subtree starting from a level 1 node.
 *
 * The idea is to sort all the leaf pointers, and then drop the
 * ref on all the leaves in order.  Most of the time the leaves
 * will have ref cache entries, so no leaf IOs will be required to
 * find the extents they have references on.
 *
 * For each leaf, any references it has are also dropped in order
 *
 * This ends up dropping the references in something close to optimal
 * order for reading and modifying the extent allocation tree.
 */
static noinline int drop_level_one_refs(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_path *path)
{
        u64 bytenr;
        u64 root_owner;
        u64 root_gen;
        struct extent_buffer *eb = path->nodes[1];
        struct extent_buffer *leaf;
        struct btrfs_leaf_ref *ref;
        struct refsort *sorted = NULL;
        int nritems = btrfs_header_nritems(eb);
        int ret;
        int i;
        int refi = 0;
        int slot = path->slots[1];
        u32 blocksize = btrfs_level_size(root, 0);
        u32 refs;

        if (nritems == 0)
                goto out;

        root_owner = btrfs_header_owner(eb);
        root_gen = btrfs_header_generation(eb);
        sorted = kmalloc(sizeof(*sorted) * nritems, GFP_NOFS);

        /*
         * step one, sort all the leaf pointers so we don't scribble
         * randomly into the extent allocation tree
         */
        for (i = slot; i < nritems; i++) {
                sorted[refi].bytenr = btrfs_node_blockptr(eb, i);
                sorted[refi].slot = i;
                refi++;
        }

        /*
         * nritems won't be zero, but if we're picking up drop_snapshot
         * after a crash, slot might be > 0, so double check things
         * just in case.
         */
        if (refi == 0)
                goto out;

        sort(sorted, refi, sizeof(struct refsort), refsort_cmp, NULL);

        /*
         * the first loop frees everything the leaves point to
         */
        for (i = 0; i < refi; i++) {
                u64 ptr_gen;

                bytenr = sorted[i].bytenr;

                /*
                 * check the reference count on this leaf.  If it is > 1
                 * we just decrement it below and don't update any
                 * of the refs the leaf points to.
                 */
                ret = drop_snap_lookup_refcount(trans, root, bytenr,
                                                blocksize, &refs);
                BUG_ON(ret);
                if (refs != 1)
                        continue;

                ptr_gen = btrfs_node_ptr_generation(eb, sorted[i].slot);

                /*
                 * the leaf only had one reference, which means the
                 * only thing pointing to this leaf is the snapshot
                 * we're deleting.  It isn't possible for the reference
                 * count to increase again later
                 *
                 * The reference cache is checked for the leaf,
                 * and if found we'll be able to drop any refs held by
                 * the leaf without needing to read it in.
                 */
                ref = btrfs_lookup_leaf_ref(root, bytenr);
                if (ref && ref->generation != ptr_gen) {
                        btrfs_free_leaf_ref(root, ref);
                        ref = NULL;
                }
                if (ref) {
                        ret = cache_drop_leaf_ref(trans, root, ref);
                        BUG_ON(ret);
                        btrfs_remove_leaf_ref(root, ref);
                        btrfs_free_leaf_ref(root, ref);
                } else {
                        /*
                         * the leaf wasn't in the reference cache, so
                         * we have to read it.
                         */
                        leaf = read_tree_block(root, bytenr, blocksize,
                                               ptr_gen);
                        ret = btrfs_drop_leaf_ref(trans, root, leaf);
                        BUG_ON(ret);
                        free_extent_buffer(leaf);
                }
                atomic_inc(&root->fs_info->throttle_gen);
                wake_up(&root->fs_info->transaction_throttle);
                cond_resched();
        }

        /*
         * run through the loop again to free the refs on the leaves.
         * This is faster than doing it in the loop above because
         * the leaves are likely to be clustered together.  We end up
         * working in nice chunks on the extent allocation tree.
         */
        for (i = 0; i < refi; i++) {
                bytenr = sorted[i].bytenr;
                ret = btrfs_free_extent(trans, root, bytenr,
                                        blocksize, eb->start,
                                        root_owner, root_gen, 0, 1);
                BUG_ON(ret);

                atomic_inc(&root->fs_info->throttle_gen);
                wake_up(&root->fs_info->transaction_throttle);
                cond_resched();
        }
out:
        kfree(sorted);

        /*
         * update the path to show we've processed the entire level 1
         * node.  This will get saved into the root's drop_snapshot_progress
         * field so these drops are not repeated again if this transaction
         * commits.
         */
        path->slots[1] = nritems;
        return 0;
}

/*
 * helper function for drop_snapshot, this walks down the tree dropping ref
 * counts as it goes.
 */
static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   struct btrfs_path *path, int *level)
{
        u64 root_owner;
        u64 root_gen;
        u64 bytenr;
        u64 ptr_gen;
        struct extent_buffer *next;
        struct extent_buffer *cur;
        struct extent_buffer *parent;
        u32 blocksize;
        int ret;
        u32 refs;

        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);
        ret = drop_snap_lookup_refcount(trans, root, path->nodes[*level]->start,
                                path->nodes[*level]->len, &refs);
        BUG_ON(ret);
        if (refs > 1)
                goto out;

        /*
         * walk down to the last node level and free all the leaves
         */
        while (*level >= 0) {
                WARN_ON(*level < 0);
                WARN_ON(*level >= BTRFS_MAX_LEVEL);
                cur = path->nodes[*level];

                if (btrfs_header_level(cur) != *level)
                        WARN_ON(1);

                if (path->slots[*level] >=
                    btrfs_header_nritems(cur))
                        break;

                /* the new code goes down to level 1 and does all the
                 * leaves pointed to that node in bulk.  So, this check
                 * for level 0 will always be false.
                 *
                 * But, the disk format allows the drop_snapshot_progress
                 * field in the root to leave things in a state where
                 * a leaf will need cleaning up here.  If someone crashes
                 * with the old code and then boots with the new code,
                 * we might find a leaf here.
                 */
                if (*level == 0) {
                        ret = btrfs_drop_leaf_ref(trans, root, cur);
                        BUG_ON(ret);
                        break;
                }

                /*
                 * once we get to level one, process the whole node
                 * at once, including everything below it.
                 */
                if (*level == 1) {
                        ret = drop_level_one_refs(trans, root, path);
                        BUG_ON(ret);
                        break;
                }

                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
                blocksize = btrfs_level_size(root, *level - 1);

                ret = drop_snap_lookup_refcount(trans, root, bytenr,
                                                blocksize, &refs);
                BUG_ON(ret);

                /*
                 * if there is more than one reference, we don't need
                 * to read that node to drop any references it has.  We
                 * just drop the ref we hold on that node and move on to the
                 * next slot in this level.
                 */
                if (refs != 1) {
                        parent = path->nodes[*level];
                        root_owner = btrfs_header_owner(parent);
                        root_gen = btrfs_header_generation(parent);
                        path->slots[*level]++;

                        ret = btrfs_free_extent(trans, root, bytenr,
                                                blocksize, parent->start,
                                                root_owner, root_gen,
                                                *level - 1, 1);
                        BUG_ON(ret);

                        atomic_inc(&root->fs_info->throttle_gen);
                        wake_up(&root->fs_info->transaction_throttle);
                        cond_resched();

                        continue;
                }

                /*
                 * we need to keep freeing things in the next level down.
                 * read the block and loop around to process it
                 */
                next = read_tree_block(root, bytenr, blocksize, ptr_gen);
                WARN_ON(*level <= 0);
                if (path->nodes[*level-1])
                        free_extent_buffer(path->nodes[*level-1]);
                path->nodes[*level-1] = next;
                *level = btrfs_header_level(next);
                path->slots[*level] = 0;
                cond_resched();
        }
out:
        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);

        if (path->nodes[*level] == root->node) {
                parent = path->nodes[*level];
                bytenr = path->nodes[*level]->start;
        } else {
                parent = path->nodes[*level + 1];
                bytenr = btrfs_node_blockptr(parent, path->slots[*level + 1]);
        }

        blocksize = btrfs_level_size(root, *level);
        root_owner = btrfs_header_owner(parent);
        root_gen = btrfs_header_generation(parent);

        /*
         * cleanup and free the reference on the last node
         * we processed
         */
        ret = btrfs_free_extent(trans, root, bytenr, blocksize,
                                  parent->start, root_owner, root_gen,
                                  *level, 1);
        free_extent_buffer(path->nodes[*level]);
        path->nodes[*level] = NULL;

        *level += 1;
        BUG_ON(ret);

        cond_resched();
        return 0;
}

/*
 * helper function for drop_subtree, this function is similar to
 * walk_down_tree. The main difference is that it checks reference
 * counts while tree blocks are locked.
 */
static noinline int walk_down_subtree(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root,
                                      struct btrfs_path *path, int *level)
{
        struct extent_buffer *next;
        struct extent_buffer *cur;
        struct extent_buffer *parent;
        u64 bytenr;
        u64 ptr_gen;
        u32 blocksize;
        u32 refs;
        int ret;

        cur = path->nodes[*level];
        ret = btrfs_lookup_extent_ref(trans, root, cur->start, cur->len,
                                      &refs);
        BUG_ON(ret);
        if (refs > 1)
                goto out;

        while (*level >= 0) {
                cur = path->nodes[*level];
                if (*level == 0) {
                        ret = btrfs_drop_leaf_ref(trans, root, cur);
                        BUG_ON(ret);
                        clean_tree_block(trans, root, cur);
                        break;
                }
                if (path->slots[*level] >= btrfs_header_nritems(cur)) {
                        clean_tree_block(trans, root, cur);
                        break;
                }

                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                blocksize = btrfs_level_size(root, *level - 1);
                ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);

                next = read_tree_block(root, bytenr, blocksize, ptr_gen);
                btrfs_tree_lock(next);
                btrfs_set_lock_blocking(next);

                ret = btrfs_lookup_extent_ref(trans, root, bytenr, blocksize,
                                              &refs);
                BUG_ON(ret);
                if (refs > 1) {
                        parent = path->nodes[*level];
                        ret = btrfs_free_extent(trans, root, bytenr,
                                        blocksize, parent->start,
                                        btrfs_header_owner(parent),
                                        btrfs_header_generation(parent),
                                        *level - 1, 1);
                        BUG_ON(ret);
                        path->slots[*level]++;
                        btrfs_tree_unlock(next);
                        free_extent_buffer(next);
                        continue;
                }

                *level = btrfs_header_level(next);
                path->nodes[*level] = next;
                path->slots[*level] = 0;
                path->locks[*level] = 1;
                cond_resched();
        }
out:
        parent = path->nodes[*level + 1];
        bytenr = path->nodes[*level]->start;
        blocksize = path->nodes[*level]->len;

        ret = btrfs_free_extent(trans, root, bytenr, blocksize,
                        parent->start, btrfs_header_owner(parent),
                        btrfs_header_generation(parent), *level, 1);
        BUG_ON(ret);

        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 += 1;
        cond_resched();
        return 0;
}

/*
 * helper for dropping snapshots.  This walks back up the tree in the path
 * to find the first node higher up where we haven't yet gone through
 * all the slots
 */
static noinline int walk_up_tree(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 int *level, int max_level)
{
        u64 root_owner;
        u64 root_gen;
        struct btrfs_root_item *root_item = &root->root_item;
        int i;
        int slot;
        int ret;

        for (i = *level; i < max_level && path->nodes[i]; i++) {
                slot = path->slots[i];
                if (slot < btrfs_header_nritems(path->nodes[i]) - 1) {
                        struct extent_buffer *node;
                        struct btrfs_disk_key disk_key;

                        /*
                         * there is more work to do in this level.
                         * Update the drop_progress marker to reflect
                         * the work we've done so far, and then bump
                         * the slot number
                         */
                        node = path->nodes[i];
                        path->slots[i]++;
                        *level = i;
                        WARN_ON(*level == 0);
                        btrfs_node_key(node, &disk_key, path->slots[i]);
                        memcpy(&root_item->drop_progress,
                               &disk_key, sizeof(disk_key));
                        root_item->drop_level = i;
                        return 0;
                } else {
                        struct extent_buffer *parent;

                        /*
                         * this whole node is done, free our reference
                         * on it and go up one level
                         */
                        if (path->nodes[*level] == root->node)
                                parent = path->nodes[*level];
                        else
                                parent = path->nodes[*level + 1];

                        root_owner = btrfs_header_owner(parent);
                        root_gen = btrfs_header_generation(parent);

                        clean_tree_block(trans, root, path->nodes[*level]);
                        ret = btrfs_free_extent(trans, root,
                                                path->nodes[*level]->start,
                                                path->nodes[*level]->len,
                                                parent->start, root_owner,
                                                root_gen, *level, 1);
                        BUG_ON(ret);
                        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 = i + 1;
                }
        }
        return 1;
}

/*
 * drop the reference count on the tree rooted at 'snap'.  This traverses
 * the tree freeing any blocks that have a ref count of zero after being
 * decremented.
 */
int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                        *root)
{
        int ret = 0;
        int wret;
        int level;
        struct btrfs_path *path;
        int i;
        int orig_level;
        int update_count;
        struct btrfs_root_item *root_item = &root->root_item;

        WARN_ON(!mutex_is_locked(&root->fs_info->drop_mutex));
        path = btrfs_alloc_path();
        BUG_ON(!path);

        level = btrfs_header_level(root->node);
        orig_level = level;
        if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
                path->nodes[level] = root->node;
                extent_buffer_get(root->node);
                path->slots[level] = 0;
        } else {
                struct btrfs_key key;
                struct btrfs_disk_key found_key;
                struct extent_buffer *node;

                btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
                level = root_item->drop_level;
                path->lowest_level = level;
                wret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (wret < 0) {
                        ret = wret;
                        goto out;
                }
                node = path->nodes[level];
                btrfs_node_key(node, &found_key, path->slots[level]);
                WARN_ON(memcmp(&found_key, &root_item->drop_progress,
                               sizeof(found_key)));
                /*
                 * unlock our path, this is safe because only this
                 * function is allowed to delete this snapshot
                 */
                for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
                        if (path->nodes[i] && path->locks[i]) {
                                path->locks[i] = 0;
                                btrfs_tree_unlock(path->nodes[i]);
                        }
                }
        }
        while (1) {
                unsigned long update;
                wret = walk_down_tree(trans, root, path, &level);
                if (wret > 0)
                        break;
                if (wret < 0)
                        ret = wret;

                wret = walk_up_tree(trans, root, path, &level,
                                    BTRFS_MAX_LEVEL);
                if (wret > 0)
                        break;
                if (wret < 0)
                        ret = wret;
                if (trans->transaction->in_commit ||
                    trans->transaction->delayed_refs.flushing) {
                        ret = -EAGAIN;
                        break;
                }
                atomic_inc(&root->fs_info->throttle_gen);
                wake_up(&root->fs_info->transaction_throttle);
                for (update_count = 0; update_count < 16; update_count++) {
                        update = trans->delayed_ref_updates;
                        trans->delayed_ref_updates = 0;
                        if (update)
                                btrfs_run_delayed_refs(trans, root, update);
                        else
                                break;
                }
        }
        for (i = 0; i <= orig_level; i++) {
                if (path->nodes[i]) {
                        free_extent_buffer(path->nodes[i]);
                        path->nodes[i] = NULL;
                }
        }
out:
        btrfs_free_path(path);
        return ret;
}

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;
        int level;
        int parent_level;
        int ret = 0;
        int wret;

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

        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);
        extent_buffer_get(node);
        path->nodes[level] = node;
        path->slots[level] = 0;

        while (1) {
                wret = walk_down_subtree(trans, root, path, &level);
                if (wret < 0)
                        ret = wret;
                if (wret != 0)
                        break;

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

        btrfs_free_path(path);
        return ret;
}

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;
                spin_lock(&em_tree->lock);
                ret = add_extent_mapping(em_tree, em);
                spin_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;
}

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) > 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;
}

static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 u64 objectid, u64 size)
{
        struct btrfs_path *path;
        struct btrfs_inode_item *item;
        struct extent_buffer *leaf;
        int ret;

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

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_inode(trans, root, path, objectid);
        if (ret)
                goto out;

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
        memset_extent_buffer(leaf, 0, (unsigned long)item, sizeof(*item));
        btrfs_set_inode_generation(leaf, item, 1);
        btrfs_set_inode_size(leaf, item, size);
        btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
        btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(root, path);
out:
        btrfs_free_path(path);
        return ret;
}

static noinline struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
                                        struct btrfs_block_group_cache *group)
{
        struct inode *inode = NULL;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root;
        struct btrfs_key root_key;
        u64 objectid = BTRFS_FIRST_FREE_OBJECTID;
        int err = 0;

        root_key.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID;
        root_key.type = BTRFS_ROOT_ITEM_KEY;
        root_key.offset = (u64)-1;
        root = btrfs_read_fs_root_no_name(fs_info, &root_key);
        if (IS_ERR(root))
                return ERR_CAST(root);

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

        err = btrfs_find_free_objectid(trans, root, objectid, &objectid);
        if (err)
                goto out;

        err = __insert_orphan_inode(trans, root, objectid, group->key.offset);
        BUG_ON(err);

        err = btrfs_insert_file_extent(trans, root, objectid, 0, 0, 0,
                                       group->key.offset, 0, group->key.offset,
                                       0, 0, 0);
        BUG_ON(err);

        inode = btrfs_iget_locked(root->fs_info->sb, objectid, root);
        if (inode->i_state & I_NEW) {
                BTRFS_I(inode)->root = root;
                BTRFS_I(inode)->location.objectid = 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);
                BUG_ON(is_bad_inode(inode));
        } else {
                BUG_ON(1);
        }
        BTRFS_I(inode)->index_cnt = group->key.objectid;

        err = btrfs_orphan_add(trans, inode);
out:
        btrfs_end_transaction(trans, root);
        if (err) {
                if (inode)
                        iput(inode);
                inode = ERR_PTR(err);
        }
        return inode;
}

int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
{

        struct btrfs_ordered_sum *sums;
        struct btrfs_sector_sum *sector_sum;
        struct btrfs_ordered_extent *ordered;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct list_head list;
        size_t offset;
        int ret;
        u64 disk_bytenr;

        INIT_LIST_HEAD(&list);

        ordered = btrfs_lookup_ordered_extent(inode, file_pos);
        BUG_ON(ordered->file_offset != file_pos || ordered->len != len);

        disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
        ret = btrfs_lookup_csums_range(root->fs_info->csum_root, disk_bytenr,
                                       disk_bytenr + len - 1, &list);

        while (!list_empty(&list)) {
                sums = list_entry(list.next, struct btrfs_ordered_sum, list);
                list_del_init(&sums->list);

                sector_sum = sums->sums;
                sums->bytenr = ordered->start;

                offset = 0;
                while (offset < sums->len) {
                        sector_sum->bytenr += ordered->start - disk_bytenr;
                        sector_sum++;
                        offset += root->sectorsize;
                }

                btrfs_add_ordered_sum(inode, ordered, sums);
        }
        btrfs_put_ordered_extent(ordered);
        return 0;
}

int btrfs_relocate_block_group(struct btrfs_root *root, u64 group_start)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_path *path;
        struct btrfs_fs_info *info = root->fs_info;
        struct extent_buffer *leaf;
        struct inode *reloc_inode;
        struct btrfs_block_group_cache *block_group;
        struct btrfs_key key;
        u64 skipped;
        u64 cur_byte;
        u64 total_found;
        u32 nritems;
        int ret;
        int progress;
        int pass = 0;

        root = root->fs_info->extent_root;

        block_group = btrfs_lookup_block_group(info, group_start);
        BUG_ON(!block_group);

        printk(KERN_INFO "btrfs relocating block group %llu flags %llu\n",
               (unsigned long long)block_group->key.objectid,
               (unsigned long long)block_group->flags);

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

        reloc_inode = create_reloc_inode(info, block_group);
        BUG_ON(IS_ERR(reloc_inode));

        __alloc_chunk_for_shrink(root, block_group, 1);
        set_block_group_readonly(block_group);

        btrfs_start_delalloc_inodes(info->tree_root);
        btrfs_wait_ordered_extents(info->tree_root, 0);
again:
        skipped = 0;
        total_found = 0;
        progress = 0;
        key.objectid = block_group->key.objectid;
        key.offset = 0;
        key.type = 0;
        cur_byte = key.objectid;

        trans = btrfs_start_transaction(info->tree_root, 1);
        btrfs_commit_transaction(trans, info->tree_root);

        mutex_lock(&root->fs_info->cleaner_mutex);
        btrfs_clean_old_snapshots(info->tree_root);
        btrfs_remove_leaf_refs(info->tree_root, (u64)-1, 1);
        mutex_unlock(&root->fs_info->cleaner_mutex);

        trans = btrfs_start_transaction(info->tree_root, 1);
        btrfs_commit_transaction(trans, info->tree_root);

        while (1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0)
                        goto out;
next:
                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 == 1) {
                                ret = 0;
                                break;
                        }
                        leaf = path->nodes[0];
                        nritems = btrfs_header_nritems(leaf);
                }

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

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

                if (progress && need_resched()) {
                        btrfs_release_path(root, path);
                        cond_resched();
                        progress = 0;
                        continue;
                }
                progress = 1;

                if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY ||
                    key.objectid + key.offset <= cur_byte) {
                        path->slots[0]++;
                        goto next;
                }

                total_found++;
                cur_byte = key.objectid + key.offset;
                btrfs_release_path(root, path);

                __alloc_chunk_for_shrink(root, block_group, 0);
                ret = relocate_one_extent(root, path, &key, block_group,
                                          reloc_inode, pass);
                BUG_ON(ret < 0);
                if (ret > 0)
                        skipped++;

                key.objectid = cur_byte;
                key.type = 0;
                key.offset = 0;
        }

        btrfs_release_path(root, path);

        if (pass == 0) {
                btrfs_wait_ordered_range(reloc_inode, 0, (u64)-1);
                invalidate_mapping_pages(reloc_inode->i_mapping, 0, -1);
        }

        if (total_found > 0) {
                printk(KERN_INFO "btrfs found %llu extents in pass %d\n",
                       (unsigned long long)total_found, pass);
                pass++;
                if (total_found == skipped && pass > 2) {
                        iput(reloc_inode);
                        reloc_inode = create_reloc_inode(info, block_group);
                        pass = 0;
                }
                goto again;
        }

        /* delete reloc_inode */
        iput(reloc_inode);

        /* unpin extents in this range */
        trans = btrfs_start_transaction(info->tree_root, 1);
        btrfs_commit_transaction(trans, info->tree_root);

        spin_lock(&block_group->lock);
        WARN_ON(block_group->pinned > 0);
        WARN_ON(block_group->reserved > 0);
        WARN_ON(btrfs_block_group_used(&block_group->item) > 0);
        spin_unlock(&block_group->lock);
        put_block_group(block_group);
        ret = 0;
out:
        btrfs_free_path(path);
        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 rb_node *n;

        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);

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

                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);
                mutex_init(&cache->alloc_mutex);
                mutex_init(&cache->cache_mutex);
                INIT_LIST_HEAD(&cache->list);
                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);

                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;
                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;
        atomic_set(&cache->count, 1);
        spin_lock_init(&cache->lock);
        mutex_init(&cache->alloc_mutex);
        mutex_init(&cache->cache_mutex);
        INIT_LIST_HEAD(&cache->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);

        ret = update_space_info(root->fs_info, cache->flags, size, bytes_used,
                                &cache->space_info);
        BUG_ON(ret);
        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_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));

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

        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);
        block_group->space_info->full = 0;

        put_block_group(block_group);
        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;
}