Btrfs: Add fallocate support v2
[safe/jmp/linux-2.6] / fs / btrfs / extent-tree.c
index f92b297..8af3952 100644 (file)
@@ -18,6 +18,7 @@
 #include <linux/sched.h>
 #include <linux/pagemap.h>
 #include <linux/writeback.h>
+#include <linux/blkdev.h>
 #include "hash.h"
 #include "crc32c.h"
 #include "ctree.h"
 #include "transaction.h"
 #include "volumes.h"
 #include "locking.h"
+#include "ref-cache.h"
 
-#define BLOCK_GROUP_DATA     EXTENT_WRITEBACK
-#define BLOCK_GROUP_METADATA EXTENT_UPTODATE
-#define BLOCK_GROUP_SYSTEM   EXTENT_NEW
+#define PENDING_EXTENT_INSERT 0
+#define PENDING_EXTENT_DELETE 1
+#define PENDING_BACKREF_UPDATE 2
 
-#define BLOCK_GROUP_DIRTY EXTENT_DIRTY
+struct pending_extent_op {
+       int type;
+       u64 bytenr;
+       u64 num_bytes;
+       u64 parent;
+       u64 orig_parent;
+       u64 generation;
+       u64 orig_generation;
+       int level;
+};
 
 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
-                                btrfs_root *extent_root);
+                                btrfs_root *extent_root, int all);
 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
-                              btrfs_root *extent_root);
+                              btrfs_root *extent_root, int all);
 static struct btrfs_block_group_cache *
 __btrfs_find_block_group(struct btrfs_root *root,
                         struct btrfs_block_group_cache *hint,
                         u64 search_start, int data, int owner);
 
-void maybe_lock_mutex(struct btrfs_root *root)
+static int block_group_bits(struct btrfs_block_group_cache *cache, u64 bits)
 {
-       if (root != root->fs_info->extent_root &&
-           root != root->fs_info->chunk_root &&
-           root != root->fs_info->dev_root) {
-               mutex_lock(&root->fs_info->alloc_mutex);
+       return (cache->flags & bits) == bits;
+}
+
+/*
+ * this adds the block group to the fs_info rb tree for the block group
+ * cache
+ */
+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;
 }
 
-void maybe_unlock_mutex(struct btrfs_root *root)
+/*
+ * 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)
 {
-       if (root != root->fs_info->extent_root &&
-           root != root->fs_info->chunk_root &&
-           root != root->fs_info->dev_root) {
-               mutex_unlock(&root->fs_info->alloc_mutex);
+       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;
+               }
+       }
+       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_lock(block_group, start,
+                                                       size);
+                       BUG_ON(ret);
+                       start = extent_end + 1;
+               } else {
+                       break;
+               }
+       }
+
+       if (start < end) {
+               size = end - start;
+               ret = btrfs_add_free_space_lock(block_group, start, size);
+               BUG_ON(ret);
        }
+       mutex_unlock(&info->pinned_mutex);
+
+       return 0;
 }
 
 static int cache_block_group(struct btrfs_root *root,
                             struct btrfs_block_group_cache *block_group)
 {
        struct btrfs_path *path;
-       int ret;
+       int ret = 0;
        struct btrfs_key key;
        struct extent_buffer *leaf;
-       struct extent_io_tree *free_space_cache;
        int slot;
        u64 last = 0;
-       u64 hole_size;
        u64 first_free;
        int found = 0;
 
@@ -78,7 +193,6 @@ static int cache_block_group(struct btrfs_root *root,
                return 0;
 
        root = root->fs_info->extent_root;
-       free_space_cache = &root->fs_info->free_space_cache;
 
        if (block_group->cached)
                return 0;
@@ -94,16 +208,17 @@ static int cache_block_group(struct btrfs_root *root,
         * skip the locking here
         */
        path->skip_locking = 1;
-       first_free = block_group->key.objectid;
+       first_free = max_t(u64, block_group->key.objectid,
+                          BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE);
        key.objectid = block_group->key.objectid;
        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)
-               return ret;
+               goto err;
        ret = btrfs_previous_item(root, path, 0, BTRFS_EXTENT_ITEM_KEY);
        if (ret < 0)
-               return ret;
+               goto err;
        if (ret == 0) {
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
@@ -117,32 +232,28 @@ static int cache_block_group(struct btrfs_root *root,
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto err;
-                       if (ret == 0) {
+                       if (ret == 0)
                                continue;
-                       } else {
+                       else
                                break;
-                       }
                }
                btrfs_item_key_to_cpu(leaf, &key, slot);
-               if (key.objectid < block_group->key.objectid) {
+               if (key.objectid < block_group->key.objectid)
                        goto next;
-               }
+
                if (key.objectid >= block_group->key.objectid +
-                   block_group->key.offset) {
+                   block_group->key.offset)
                        break;
-               }
 
                if (btrfs_key_type(&key) == BTRFS_EXTENT_ITEM_KEY) {
                        if (!found) {
                                last = first_free;
                                found = 1;
                        }
-                       if (key.objectid > last) {
-                               hole_size = key.objectid - last;
-                               set_extent_dirty(free_space_cache, last,
-                                                last + hole_size - 1,
-                                                GFP_NOFS);
-                       }
+
+                       add_new_free_space(block_group, root->fs_info, last,
+                                          key.objectid);
+
                        last = key.objectid + key.offset;
                }
 next:
@@ -151,179 +262,58 @@ next:
 
        if (!found)
                last = first_free;
-       if (block_group->key.objectid +
-           block_group->key.offset > last) {
-               hole_size = block_group->key.objectid +
-                       block_group->key.offset - last;
-               set_extent_dirty(free_space_cache, last,
-                                last + hole_size - 1, GFP_NOFS);
-       }
+
+       add_new_free_space(block_group, root->fs_info, last,
+                          block_group->key.objectid +
+                          block_group->key.offset);
+
        block_group->cached = 1;
+       ret = 0;
 err:
        btrfs_free_path(path);
-       return 0;
+       return ret;
 }
 
+/*
+ * return the block group that starts at or after bytenr
+ */
 struct btrfs_block_group_cache *btrfs_lookup_first_block_group(struct
                                                       btrfs_fs_info *info,
                                                         u64 bytenr)
 {
-       struct extent_io_tree *block_group_cache;
-       struct btrfs_block_group_cache *block_group = NULL;
-       u64 ptr;
-       u64 start;
-       u64 end;
-       int ret;
+       struct btrfs_block_group_cache *cache;
 
-       bytenr = max_t(u64, bytenr,
-                      BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE);
-       block_group_cache = &info->block_group_cache;
-       ret = find_first_extent_bit(block_group_cache,
-                                   bytenr, &start, &end,
-                                   BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA |
-                                   BLOCK_GROUP_SYSTEM);
-       if (ret) {
-               return NULL;
-       }
-       ret = get_state_private(block_group_cache, start, &ptr);
-       if (ret)
-               return NULL;
+       cache = block_group_cache_tree_search(info, bytenr, 0);
 
-       block_group = (struct btrfs_block_group_cache *)(unsigned long)ptr;
-       return block_group;
+       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 extent_io_tree *block_group_cache;
-       struct btrfs_block_group_cache *block_group = NULL;
-       u64 ptr;
-       u64 start;
-       u64 end;
-       int ret;
-
-       bytenr = max_t(u64, bytenr,
-                      BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE);
-       block_group_cache = &info->block_group_cache;
-       ret = find_first_extent_bit(block_group_cache,
-                                   bytenr, &start, &end,
-                                   BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA |
-                                   BLOCK_GROUP_SYSTEM);
-       if (ret) {
-               return NULL;
-       }
-       ret = get_state_private(block_group_cache, start, &ptr);
-       if (ret)
-               return NULL;
+       struct btrfs_block_group_cache *cache;
 
-       block_group = (struct btrfs_block_group_cache *)(unsigned long)ptr;
-       if (block_group->key.objectid <= bytenr && bytenr <
-           block_group->key.objectid + block_group->key.offset)
-               return block_group;
-       return NULL;
-}
+       cache = block_group_cache_tree_search(info, bytenr, 1);
 
-static int block_group_bits(struct btrfs_block_group_cache *cache, u64 bits)
-{
-       return (cache->flags & bits) == bits;
+       return cache;
 }
 
-static int noinline find_search_start(struct btrfs_root *root,
-                             struct btrfs_block_group_cache **cache_ret,
-                             u64 *start_ret, u64 num, int data)
+static struct btrfs_space_info *__find_space_info(struct btrfs_fs_info *info,
+                                                 u64 flags)
 {
-       int ret;
-       struct btrfs_block_group_cache *cache = *cache_ret;
-       struct extent_io_tree *free_space_cache;
-       struct extent_state *state;
-       u64 last;
-       u64 start = 0;
-       u64 cache_miss = 0;
-       u64 total_fs_bytes;
-       u64 search_start = *start_ret;
-       int wrapped = 0;
-
-       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
-       total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
-       free_space_cache = &root->fs_info->free_space_cache;
-
-       if (!cache)
-               goto out;
-
-again:
-       ret = cache_block_group(root, cache);
-       if (ret) {
-               goto out;
-       }
-
-       last = max(search_start, cache->key.objectid);
-       if (!block_group_bits(cache, data) || cache->ro)
-               goto new_group;
-
-       spin_lock_irq(&free_space_cache->lock);
-       state = find_first_extent_bit_state(free_space_cache, last, EXTENT_DIRTY);
-       while(1) {
-               if (!state) {
-                       if (!cache_miss)
-                               cache_miss = last;
-                       spin_unlock_irq(&free_space_cache->lock);
-                       goto new_group;
-               }
-
-               start = max(last, state->start);
-               last = state->end + 1;
-               if (last - start < num) {
-                       do {
-                               state = extent_state_next(state);
-                       } while(state && !(state->state & EXTENT_DIRTY));
-                       continue;
-               }
-               spin_unlock_irq(&free_space_cache->lock);
-               if (cache->ro) {
-                       goto new_group;
-               }
-               if (start + num > cache->key.objectid + cache->key.offset)
-                       goto new_group;
-               if (!block_group_bits(cache, data)) {
-                       printk("block group bits don't match %Lu %d\n", cache->flags, data);
-               }
-               *start_ret = start;
-               return 0;
-       }
-out:
-       cache = btrfs_lookup_block_group(root->fs_info, search_start);
-       if (!cache) {
-               printk("Unable to find block group for %Lu\n", search_start);
-               WARN_ON(1);
-       }
-       return -ENOSPC;
-
-new_group:
-       last = cache->key.objectid + cache->key.offset;
-wrapped:
-       cache = btrfs_lookup_first_block_group(root->fs_info, last);
-       if (!cache || cache->key.objectid >= total_fs_bytes) {
-no_cache:
-               if (!wrapped) {
-                       wrapped = 1;
-                       last = search_start;
-                       goto wrapped;
-               }
-               goto out;
-       }
-       if (cache_miss && !cache->cached) {
-               cache_block_group(root, cache);
-               last = cache_miss;
-               cache = btrfs_lookup_first_block_group(root->fs_info, last);
+       struct list_head *head = &info->space_info;
+       struct list_head *cur;
+       struct btrfs_space_info *found;
+       list_for_each(cur, head) {
+               found = list_entry(cur, struct btrfs_space_info, list);
+               if (found->flags == flags)
+                       return found;
        }
-       cache_miss = 0;
-       cache = btrfs_find_block_group(root, cache, last, data, 0);
-       if (!cache)
-               goto no_cache;
-       *cache_ret = cache;
-       goto again;
+       return NULL;
 }
 
 static u64 div_factor(u64 num, int factor)
@@ -335,53 +325,31 @@ static u64 div_factor(u64 num, int factor)
        return num;
 }
 
-static int block_group_state_bits(u64 flags)
-{
-       int bits = 0;
-       if (flags & BTRFS_BLOCK_GROUP_DATA)
-               bits |= BLOCK_GROUP_DATA;
-       if (flags & BTRFS_BLOCK_GROUP_METADATA)
-               bits |= BLOCK_GROUP_METADATA;
-       if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
-               bits |= BLOCK_GROUP_SYSTEM;
-       return bits;
-}
-
 static struct btrfs_block_group_cache *
 __btrfs_find_block_group(struct btrfs_root *root,
                         struct btrfs_block_group_cache *hint,
                         u64 search_start, int data, int owner)
 {
        struct btrfs_block_group_cache *cache;
-       struct extent_io_tree *block_group_cache;
        struct btrfs_block_group_cache *found_group = NULL;
        struct btrfs_fs_info *info = root->fs_info;
        u64 used;
        u64 last = 0;
-       u64 start;
-       u64 end;
        u64 free_check;
-       u64 ptr;
-       int bit;
-       int ret;
        int full_search = 0;
        int factor = 10;
        int wrapped = 0;
 
-       block_group_cache = &info->block_group_cache;
-
        if (data & BTRFS_BLOCK_GROUP_METADATA)
                factor = 9;
 
-       bit = block_group_state_bits(data);
-
        if (search_start) {
                struct btrfs_block_group_cache *shint;
                shint = btrfs_lookup_first_block_group(info, search_start);
                if (shint && block_group_bits(shint, data) && !shint->ro) {
                        spin_lock(&shint->lock);
                        used = btrfs_block_group_used(&shint->item);
-                       if (used + shint->pinned <
+                       if (used + shint->pinned + shint->reserved <
                            div_factor(shint->key.offset, factor)) {
                                spin_unlock(&shint->lock);
                                return shint;
@@ -392,7 +360,7 @@ __btrfs_find_block_group(struct btrfs_root *root,
        if (hint && !hint->ro && block_group_bits(hint, data)) {
                spin_lock(&hint->lock);
                used = btrfs_block_group_used(&hint->item);
-               if (used + hint->pinned <
+               if (used + hint->pinned + hint->reserved <
                    div_factor(hint->key.offset, factor)) {
                        spin_unlock(&hint->lock);
                        return hint;
@@ -406,26 +374,19 @@ __btrfs_find_block_group(struct btrfs_root *root,
                        last = search_start;
        }
 again:
-       while(1) {
-               ret = find_first_extent_bit(block_group_cache, last,
-                                           &start, &end, bit);
-               if (ret)
+       while (1) {
+               cache = btrfs_lookup_first_block_group(root->fs_info, last);
+               if (!cache)
                        break;
 
-               ret = get_state_private(block_group_cache, start, &ptr);
-               if (ret) {
-                       last = end + 1;
-                       continue;
-               }
-
-               cache = (struct btrfs_block_group_cache *)(unsigned long)ptr;
                spin_lock(&cache->lock);
                last = cache->key.objectid + cache->key.offset;
                used = btrfs_block_group_used(&cache->item);
 
                if (!cache->ro && block_group_bits(cache, data)) {
                        free_check = div_factor(cache->key.offset, factor);
-                       if (used + cache->pinned < free_check) {
+                       if (used + cache->pinned + cache->reserved <
+                           free_check) {
                                found_group = cache;
                                spin_unlock(&cache->lock);
                                goto found;
@@ -459,104 +420,22 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
        ret = __btrfs_find_block_group(root, hint, search_start, data, owner);
        return ret;
 }
-static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
-                          u64 owner, u64 owner_offset)
-{
-       u32 high_crc = ~(u32)0;
-       u32 low_crc = ~(u32)0;
-       __le64 lenum;
-       lenum = cpu_to_le64(root_objectid);
-       high_crc = btrfs_crc32c(high_crc, &lenum, sizeof(lenum));
-       lenum = cpu_to_le64(ref_generation);
-       low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
-       if (owner >= BTRFS_FIRST_FREE_OBJECTID) {
-               lenum = cpu_to_le64(owner);
-               low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
-               lenum = cpu_to_le64(owner_offset);
-               low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
-       }
-       return ((u64)high_crc << 32) | (u64)low_crc;
-}
 
-static int match_extent_ref(struct extent_buffer *leaf,
-                           struct btrfs_extent_ref *disk_ref,
-                           struct btrfs_extent_ref *cpu_ref)
+/* 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;
-       int len;
-
-       if (cpu_ref->objectid)
-               len = sizeof(*cpu_ref);
-       else
-               len = 2 * sizeof(u64);
-       ret = memcmp_extent_buffer(leaf, cpu_ref, (unsigned long)disk_ref,
-                                  len);
-       return ret == 0;
-}
-
-static int noinline lookup_extent_backref(struct btrfs_trans_handle *trans,
-                                         struct btrfs_root *root,
-                                         struct btrfs_path *path, u64 bytenr,
-                                         u64 root_objectid,
-                                         u64 ref_generation, u64 owner,
-                                         u64 owner_offset, int del)
-{
-       u64 hash;
        struct btrfs_key key;
-       struct btrfs_key found_key;
-       struct btrfs_extent_ref ref;
-       struct extent_buffer *leaf;
-       struct btrfs_extent_ref *disk_ref;
-       int ret;
-       int ret2;
-
-       btrfs_set_stack_ref_root(&ref, root_objectid);
-       btrfs_set_stack_ref_generation(&ref, ref_generation);
-       btrfs_set_stack_ref_objectid(&ref, owner);
-       btrfs_set_stack_ref_offset(&ref, owner_offset);
-
-       hash = hash_extent_ref(root_objectid, ref_generation, owner,
-                              owner_offset);
-       key.offset = hash;
-       key.objectid = bytenr;
-       key.type = BTRFS_EXTENT_REF_KEY;
+       struct btrfs_path *path;
 
-       while (1) {
-               ret = btrfs_search_slot(trans, root, &key, path,
-                                       del ? -1 : 0, del);
-               if (ret < 0)
-                       goto out;
-               leaf = path->nodes[0];
-               if (ret != 0) {
-                       u32 nritems = btrfs_header_nritems(leaf);
-                       if (path->slots[0] >= nritems) {
-                               ret2 = btrfs_next_leaf(root, path);
-                               if (ret2)
-                                       goto out;
-                               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)
-                               goto out;
-                       key.offset = found_key.offset;
-                       if (del) {
-                               btrfs_release_path(root, path);
-                               continue;
-                       }
-               }
-               disk_ref = btrfs_item_ptr(path->nodes[0],
-                                         path->slots[0],
-                                         struct btrfs_extent_ref);
-               if (match_extent_ref(path->nodes[0], disk_ref, &ref)) {
-                       ret = 0;
-                       goto out;
-               }
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-               key.offset = found_key.offset + 1;
-               btrfs_release_path(root, path);
-       }
-out:
+       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;
 }
 
@@ -577,7 +456,7 @@ out:
  * File extents can be referenced by:
  *
  * - multiple snapshots, subvolumes, or different generations in one subvol
- * - different files inside a single subvolume (in theory, not implemented yet)
+ * - different files inside a single subvolume
  * - different offsets inside a file (bookend extents in file.c)
  *
  * The extent ref structure has fields for:
@@ -585,146 +464,313 @@ out:
  * - Objectid of the subvolume root
  * - Generation number of the tree holding the reference
  * - objectid of the file holding the reference
- * - offset in the file corresponding to the key 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, offset in file)
+ *     (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 the same as the create case, but trans->transid
- * will be different when the block is cow'd.
+ * 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, offset in file)
+ *     (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, the corresponding back reference is found
- * by searching for:
+ * 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, offset in file)
+ *      inode objectid)
  *
  * Btree extents can be referenced by:
  *
  * - Different subvolumes
  * - Different generations of the same subvolume
  *
- * Storing sufficient information for a full reverse mapping of a btree
- * block would require storing the lowest key of the block in the backref,
- * and it would require updating that lowest key either before write out or
- * every time it changed.  Instead, the objectid of the lowest key is stored
- * along with the level of the tree block.  This provides a hint
- * about where in the btree the block can be found.  Searches through the
- * btree only need to look for a pointer to that block, so they stop one
- * level higher than the level recorded in the backref.
- *
- * Some btrees do not do reference counting on their extents.  These
- * include the extent tree and the tree of tree roots.  Backrefs for these
- * trees always have a generation of zero.
- *
  * When a tree block is created, back references are inserted:
  *
- * (root->root_key.objectid, trans->transid or zero, level, lowest_key_objectid)
+ * (root->root_key.objectid, trans->transid, level, 1)
  *
- * When a tree block is cow'd in a reference counted root,
- * new back references are added for all the blocks it points to.
- * These are of the form (trans->transid will have increased since creation):
+ * 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, lowest_key_objectid)
+ * (root->root_key.objectid, trans->transid, level, 1)
  *
- * Because the lowest_key_objectid and the level are just hints
- * they are not used when backrefs are deleted.  When a backref is deleted:
+ * When a backref is in deleting, the following fields are checked:
  *
  * if backref was for a tree root:
- *     root_objectid = root->root_key.objectid
+ *     (btrfs_header_owner(itself), btrfs_header_generation(itself), level)
  * else
- *     root_objectid = btrfs_header_owner(parent)
+ *     (btrfs_header_owner(parent), btrfs_header_generation(parent), level)
  *
- * (root_objectid, btrfs_header_generation(parent) or zero, 0, 0)
+ * Back Reference Key composing:
  *
- * Back Reference Key hashing:
- *
- * Back references have four fields, each 64 bits long.  Unfortunately,
- * This is hashed into a single 64 bit number and placed into the key offset.
- * The key objectid corresponds to the first byte in the extent, and the
- * key type is set to BTRFS_EXTENT_REF_KEY
+ * 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.
  */
-int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
-                                struct btrfs_root *root,
-                                struct btrfs_path *path, u64 bytenr,
-                                u64 root_objectid, u64 ref_generation,
-                                u64 owner, u64 owner_offset)
+
+static int noinline 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)
 {
-       u64 hash;
        struct btrfs_key key;
-       struct btrfs_extent_ref ref;
-       struct btrfs_extent_ref *disk_ref;
+       struct btrfs_extent_ref *ref;
+       struct extent_buffer *leaf;
+       u64 ref_objectid;
        int ret;
 
-       btrfs_set_stack_ref_root(&ref, root_objectid);
-       btrfs_set_stack_ref_generation(&ref, ref_generation);
-       btrfs_set_stack_ref_objectid(&ref, owner);
-       btrfs_set_stack_ref_offset(&ref, owner_offset);
-
-       hash = hash_extent_ref(root_objectid, ref_generation, owner,
-                              owner_offset);
-       key.offset = hash;
        key.objectid = bytenr;
        key.type = BTRFS_EXTENT_REF_KEY;
+       key.offset = parent;
 
-       ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(ref));
-       while (ret == -EEXIST) {
-               disk_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
-                                         struct btrfs_extent_ref);
-               if (match_extent_ref(path->nodes[0], disk_ref, &ref))
-                       goto out;
-               key.offset++;
-               btrfs_release_path(root, path);
-               ret = btrfs_insert_empty_item(trans, root, path, &key,
-                                             sizeof(ref));
+       ret = btrfs_search_slot(trans, root, &key, path, del ? -1 : 0, 1);
+       if (ret < 0)
+               goto out;
+       if (ret > 0) {
+               ret = -ENOENT;
+               goto out;
        }
-       if (ret)
+
+       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;
-       disk_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
-                                 struct btrfs_extent_ref);
-       write_extent_buffer(path->nodes[0], &ref, (unsigned long)disk_ref,
-                           sizeof(ref));
-       btrfs_mark_buffer_dirty(path->nodes[0]);
+       }
+       ret = 0;
 out:
-       btrfs_release_path(root, path);
        return ret;
 }
 
-static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
-                               struct btrfs_root *root,
-                               u64 bytenr, u64 num_bytes,
-                               u64 root_objectid, u64 ref_generation,
-                               u64 owner, u64 owner_offset)
+static int noinline 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)
 {
-       struct btrfs_path *path;
-       int ret;
        struct btrfs_key key;
-       struct extent_buffer *l;
-       struct btrfs_extent_item *item;
-       u32 refs;
-
-       WARN_ON(num_bytes < root->sectorsize);
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
+       struct extent_buffer *leaf;
+       struct btrfs_extent_ref *ref;
+       u32 num_refs;
+       int ret;
 
-       path->reada = 1;
        key.objectid = bytenr;
-       btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
-       key.offset = num_bytes;
-       ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key, path,
-                               0, 1);
-       if (ret < 0)
-               return ret;
-       if (ret != 0) {
-               BUG();
+       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, 1);
+       } 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 + 1);
+
+               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_mark_buffer_dirty(path->nodes[0]);
+out:
+       btrfs_release_path(root, path);
+       return ret;
+}
+
+static int noinline remove_extent_backref(struct btrfs_trans_handle *trans,
+                                         struct btrfs_root *root,
+                                         struct btrfs_path *path)
+{
+       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 == 0);
+       num_refs -= 1;
+       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;
+}
+
+static int __btrfs_update_extent_ref(struct btrfs_trans_handle *trans,
+                                    struct btrfs_root *root, u64 bytenr,
+                                    u64 orig_parent, u64 parent,
+                                    u64 orig_root, u64 ref_root,
+                                    u64 orig_generation, u64 ref_generation,
+                                    u64 owner_objectid)
+{
+       int ret;
+       struct btrfs_root *extent_root = root->fs_info->extent_root;
+       struct btrfs_path *path;
+
+       if (root == root->fs_info->extent_root) {
+               struct pending_extent_op *extent_op;
+               u64 num_bytes;
+
+               BUG_ON(owner_objectid >= BTRFS_MAX_LEVEL);
+               num_bytes = btrfs_level_size(root, (int)owner_objectid);
+               mutex_lock(&root->fs_info->extent_ins_mutex);
+               if (test_range_bit(&root->fs_info->extent_ins, bytenr,
+                               bytenr + num_bytes - 1, EXTENT_WRITEBACK, 0)) {
+                       u64 priv;
+                       ret = get_state_private(&root->fs_info->extent_ins,
+                                               bytenr, &priv);
+                       BUG_ON(ret);
+                       extent_op = (struct pending_extent_op *)
+                                                       (unsigned long)priv;
+                       BUG_ON(extent_op->parent != orig_parent);
+                       BUG_ON(extent_op->generation != orig_generation);
+
+                       extent_op->parent = parent;
+                       extent_op->generation = ref_generation;
+               } else {
+                       extent_op = kmalloc(sizeof(*extent_op), GFP_NOFS);
+                       BUG_ON(!extent_op);
+
+                       extent_op->type = PENDING_BACKREF_UPDATE;
+                       extent_op->bytenr = bytenr;
+                       extent_op->num_bytes = num_bytes;
+                       extent_op->parent = parent;
+                       extent_op->orig_parent = orig_parent;
+                       extent_op->generation = ref_generation;
+                       extent_op->orig_generation = orig_generation;
+                       extent_op->level = (int)owner_objectid;
+
+                       set_extent_bits(&root->fs_info->extent_ins,
+                                       bytenr, bytenr + num_bytes - 1,
+                                       EXTENT_WRITEBACK, GFP_NOFS);
+                       set_state_private(&root->fs_info->extent_ins,
+                                         bytenr, (unsigned long)extent_op);
+               }
+               mutex_unlock(&root->fs_info->extent_ins_mutex);
+               return 0;
        }
-       BUG_ON(ret != 0);
+
+       path = btrfs_alloc_path();
+       if (!path)
+               return -ENOMEM;
+       ret = lookup_extent_backref(trans, extent_root, path,
+                                   bytenr, orig_parent, orig_root,
+                                   orig_generation, owner_objectid, 1);
+       if (ret)
+               goto out;
+       ret = remove_extent_backref(trans, extent_root, path);
+       if (ret)
+               goto out;
+       ret = insert_extent_backref(trans, extent_root, path, bytenr,
+                                   parent, ref_root, ref_generation,
+                                   owner_objectid);
+       BUG_ON(ret);
+       finish_current_insert(trans, extent_root, 0);
+       del_pending_extents(trans, extent_root, 0);
+out:
+       btrfs_free_path(path);
+       return ret;
+}
+
+int btrfs_update_extent_ref(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root, u64 bytenr,
+                           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, 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 orig_parent, u64 parent,
+                                 u64 orig_root, u64 ref_root,
+                                 u64 orig_generation, u64 ref_generation,
+                                 u64 owner_objectid)
+{
+       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;
+       key.objectid = bytenr;
+       key.type = BTRFS_EXTENT_ITEM_KEY;
+       key.offset = (u64)-1;
+
+       ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key, path,
+                               0, 1);
+       if (ret < 0)
+               return ret;
+       BUG_ON(ret == 0 || path->slots[0] == 0);
+
+       path->slots[0]--;
        l = path->nodes[0];
+
+       btrfs_item_key_to_cpu(l, &key, path->slots[0]);
+       BUG_ON(key.objectid != bytenr);
+       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 + 1);
@@ -733,44 +779,45 @@ static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
        btrfs_release_path(root->fs_info->extent_root, path);
 
        path->reada = 1;
-       ret = btrfs_insert_extent_backref(trans, root->fs_info->extent_root,
-                                         path, bytenr, root_objectid,
-                                         ref_generation, owner, owner_offset);
+       ret = insert_extent_backref(trans, root->fs_info->extent_root,
+                                   path, bytenr, parent,
+                                   ref_root, ref_generation,
+                                   owner_objectid);
        BUG_ON(ret);
-       finish_current_insert(trans, root->fs_info->extent_root);
-       del_pending_extents(trans, root->fs_info->extent_root);
+       finish_current_insert(trans, root->fs_info->extent_root, 0);
+       del_pending_extents(trans, root->fs_info->extent_root, 0);
 
        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 root_objectid, u64 ref_generation,
-                               u64 owner, u64 owner_offset)
+                        struct btrfs_root *root,
+                        u64 bytenr, u64 num_bytes, u64 parent,
+                        u64 ref_root, u64 ref_generation,
+                        u64 owner_objectid)
 {
        int ret;
-
-       mutex_lock(&root->fs_info->alloc_mutex);
-       ret = __btrfs_inc_extent_ref(trans, root, bytenr, num_bytes,
-                                    root_objectid, ref_generation,
-                                    owner, owner_offset);
-       mutex_unlock(&root->fs_info->alloc_mutex);
+       if (ref_root == BTRFS_TREE_LOG_OBJECTID &&
+           owner_objectid < BTRFS_FIRST_FREE_OBJECTID)
+               return 0;
+       ret = __btrfs_inc_extent_ref(trans, root, bytenr, 0, parent,
+                                    0, ref_root, 0, ref_generation,
+                                    owner_objectid);
        return ret;
 }
 
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root)
 {
-       finish_current_insert(trans, root->fs_info->extent_root);
-       del_pending_extents(trans, root->fs_info->extent_root);
+       finish_current_insert(trans, root->fs_info->extent_root, 1);
+       del_pending_extents(trans, root->fs_info->extent_root, 1);
        return 0;
 }
 
-static int lookup_extent_ref(struct btrfs_trans_handle *trans,
-                            struct btrfs_root *root, u64 bytenr,
-                            u64 num_bytes, u32 *refs)
+int btrfs_lookup_extent_ref(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root, u64 bytenr,
+                           u64 num_bytes, u32 *refs)
 {
        struct btrfs_path *path;
        int ret;
@@ -801,70 +848,55 @@ out:
        return 0;
 }
 
-u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
-                                 struct btrfs_path *count_path,
-                                 u64 expected_owner,
-                                 u64 first_extent)
+int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans,
+                         struct btrfs_root *root, u64 bytenr)
 {
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_path *path;
-       u64 bytenr;
-       u64 found_objectid;
-       u64 found_owner;
-       u64 root_objectid = root->root_key.objectid;
-       u32 total_count = 0;
-       u32 extent_refs;
-       u32 cur_count;
-       u32 nritems;
-       int ret;
+       struct extent_buffer *leaf;
+       struct btrfs_extent_ref *ref_item;
        struct btrfs_key key;
        struct btrfs_key found_key;
-       struct extent_buffer *l;
-       struct btrfs_extent_item *item;
-       struct btrfs_extent_ref *ref_item;
-       int level = -1;
-
-       /* FIXME, needs locking */
-       BUG();
-
-       mutex_lock(&root->fs_info->alloc_mutex);
-       path = btrfs_alloc_path();
-again:
-       if (level == -1)
-               bytenr = first_extent;
-       else
-               bytenr = count_path->nodes[level]->start;
+       u64 ref_root;
+       u64 last_snapshot;
+       u32 nritems;
+       int ret;
 
-       cur_count = 0;
        key.objectid = bytenr;
-       key.offset = 0;
+       key.offset = (u64)-1;
+       key.type = BTRFS_EXTENT_ITEM_KEY;
 
-       btrfs_set_key_type(&key, 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);
 
-       l = path->nodes[0];
-       btrfs_item_key_to_cpu(l, &found_key, path->slots[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) {
+           found_key.type != BTRFS_EXTENT_ITEM_KEY)
                goto out;
-       }
 
-       item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
-       extent_refs = btrfs_extent_refs(l, item);
+       last_snapshot = btrfs_root_last_snapshot(&root->root_item);
        while (1) {
-               l = path->nodes[0];
-               nritems = btrfs_header_nritems(l);
+               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(l, &found_key, path->slots[0]);
+               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != bytenr)
                        break;
 
@@ -873,80 +905,151 @@ again:
                        continue;
                }
 
-               cur_count++;
-               ref_item = btrfs_item_ptr(l, path->slots[0],
+               ref_item = btrfs_item_ptr(leaf, path->slots[0],
                                          struct btrfs_extent_ref);
-               found_objectid = btrfs_ref_root(l, ref_item);
-
-               if (found_objectid != root_objectid) {
-                       total_count = 2;
+               ref_root = btrfs_ref_root(leaf, ref_item);
+               if (ref_root != root->root_key.objectid &&
+                   ref_root != BTRFS_TREE_LOG_OBJECTID) {
+                       ret = 1;
                        goto out;
                }
-               if (level == -1) {
-                       found_owner = btrfs_ref_objectid(l, ref_item);
-                       if (found_owner != expected_owner) {
-                               total_count = 2;
-                               goto out;
-                       }
-                       /*
-                        * nasty.  we don't count a reference held by
-                        * the running transaction.  This allows nodatacow
-                        * to avoid cow most of the time
-                        */
-                       if (found_owner >= BTRFS_FIRST_FREE_OBJECTID &&
-                           btrfs_ref_generation(l, ref_item) ==
-                           root->fs_info->generation) {
-                               extent_refs--;
-                       }
+               if (btrfs_ref_generation(leaf, ref_item) <= last_snapshot) {
+                       ret = 1;
+                       goto out;
                }
-               total_count = 1;
+
                path->slots[0]++;
        }
-       /*
-        * if there is more than one reference against a data extent,
-        * we have to assume the other ref is another snapshot
-        */
-       if (level == -1 && extent_refs > 1) {
-               total_count = 2;
-               goto out;
-       }
-       if (cur_count == 0) {
-               total_count = 0;
-               goto out;
+       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;
        }
-       if (level >= 0 && root->node == count_path->nodes[level])
-               goto out;
-       level++;
-       btrfs_release_path(root, path);
-       goto again;
 
+       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:
-       btrfs_free_path(path);
-       mutex_unlock(&root->fs_info->alloc_mutex);
-       return total_count;
+       return ret;
 }
 
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
-                 struct extent_buffer *buf)
+                 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;
        u32 nritems;
+       u32 nr_file_extents = 0;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int level;
-       int ret;
-       int faili;
+       int ret = 0;
+       int faili = 0;
+       int (*process_func)(struct btrfs_trans_handle *, struct btrfs_root *,
+                           u64, u64, u64, u64, u64, u64, u64, u64);
 
-       if (!root->ref_cows)
-               return 0;
+       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);
        nritems = btrfs_header_nritems(buf);
+       level = btrfs_header_level(buf);
+
+       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;
+       }
+
        for (i = 0; i < nritems; i++) {
                cond_resched();
                if (level == 0) {
-                       u64 disk_bytenr;
                        btrfs_item_key_to_cpu(buf, &key, i);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
@@ -955,16 +1058,18 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                        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)
+                       bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
+                       if (bytenr == 0)
                                continue;
 
-                       mutex_lock(&root->fs_info->alloc_mutex);
-                       ret = __btrfs_inc_extent_ref(trans, root, disk_bytenr,
-                                   btrfs_file_extent_disk_num_bytes(buf, fi),
-                                   root->root_key.objectid, trans->transid,
-                                   key.objectid, key.offset);
-                       mutex_unlock(&root->fs_info->alloc_mutex);
+                       nr_file_extents++;
+
+                       ret = process_func(trans, root, bytenr,
+                                          orig_buf->start, buf->start,
+                                          orig_root, ref_root,
+                                          orig_generation, ref_generation,
+                                          key.objectid);
+
                        if (ret) {
                                faili = i;
                                WARN_ON(1);
@@ -972,15 +1077,11 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                        }
                } else {
                        bytenr = btrfs_node_blockptr(buf, i);
-                       btrfs_node_key_to_cpu(buf, &key, i);
-
-                       mutex_lock(&root->fs_info->alloc_mutex);
-                       ret = __btrfs_inc_extent_ref(trans, root, bytenr,
-                                          btrfs_level_size(root, level - 1),
-                                          root->root_key.objectid,
-                                          trans->transid,
-                                          level - 1, key.objectid);
-                       mutex_unlock(&root->fs_info->alloc_mutex);
+                       ret = process_func(trans, root, bytenr,
+                                          orig_buf->start, buf->start,
+                                          orig_root, ref_root,
+                                          orig_generation, ref_generation,
+                                          level - 1);
                        if (ret) {
                                faili = i;
                                WARN_ON(1);
@@ -988,37 +1089,90 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                        }
                }
        }
+out:
+       if (nr_extents) {
+               if (level == 0)
+                       *nr_extents = nr_file_extents;
+               else
+                       *nr_extents = nritems;
+       }
        return 0;
 fail:
        WARN_ON(1);
-#if 0
-       for (i =0; i < faili; i++) {
+       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) {
-                       u64 disk_bytenr;
-                       btrfs_item_key_to_cpu(buf, &key, i);
+                       btrfs_item_key_to_cpu(buf, &key, slot);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
-                       fi = btrfs_item_ptr(buf, i,
+                       fi = btrfs_item_ptr(buf, slot,
                                            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)
+                       bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
+                       if (bytenr == 0)
                                continue;
-                       err = btrfs_free_extent(trans, root, disk_bytenr,
-                                   btrfs_file_extent_disk_num_bytes(buf,
-                                                                     fi), 0);
-                       BUG_ON(err);
+                       ret = __btrfs_update_extent_ref(trans, root, bytenr,
+                                           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, i);
-                       err = btrfs_free_extent(trans, root, bytenr,
-                                       btrfs_level_size(root, level - 1), 0);
-                       BUG_ON(err);
+                       bytenr = btrfs_node_blockptr(buf, slot);
+                       ret = __btrfs_update_extent_ref(trans, root, bytenr,
+                                           orig_buf->start, buf->start,
+                                           orig_root, ref_root,
+                                           orig_generation, ref_generation,
+                                           level - 1);
+                       if (ret)
+                               goto fail;
                }
        }
-#endif
-       return ret;
+       return 0;
+fail:
+       WARN_ON(1);
+       return -1;
 }
 
 static int write_one_cache_group(struct btrfs_trans_handle *trans,
@@ -1043,8 +1197,8 @@ static int write_one_cache_group(struct btrfs_trans_handle *trans,
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(extent_root, path);
 fail:
-       finish_current_insert(trans, extent_root);
-       pending_ret = del_pending_extents(trans, extent_root);
+       finish_current_insert(trans, extent_root, 0);
+       pending_ret = del_pending_extents(trans, extent_root, 0);
        if (ret)
                return ret;
        if (pending_ret)
@@ -1056,34 +1210,37 @@ fail:
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root)
 {
-       struct extent_io_tree *block_group_cache;
-       struct btrfs_block_group_cache *cache;
-       int ret;
+       struct btrfs_block_group_cache *cache, *entry;
+       struct rb_node *n;
        int err = 0;
        int werr = 0;
        struct btrfs_path *path;
        u64 last = 0;
-       u64 start;
-       u64 end;
-       u64 ptr;
 
-       block_group_cache = &root->fs_info->block_group_cache;
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
 
-       mutex_lock(&root->fs_info->alloc_mutex);
        while(1) {
-               ret = find_first_extent_bit(block_group_cache, last,
-                                           &start, &end, BLOCK_GROUP_DIRTY);
-               if (ret)
-                       break;
-
-               last = end + 1;
-               ret = get_state_private(block_group_cache, start, &ptr);
-               if (ret)
+               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 = (struct btrfs_block_group_cache *)(unsigned long)ptr;
+
+               cache->dirty = 0;
+               last += cache->key.offset;
+
                err = write_one_cache_group(trans, root,
                                            path, cache);
                /*
@@ -1095,29 +1252,11 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                        werr = err;
                        continue;
                }
-               clear_extent_bits(block_group_cache, start, end,
-                                 BLOCK_GROUP_DIRTY, GFP_NOFS);
        }
        btrfs_free_path(path);
-       mutex_unlock(&root->fs_info->alloc_mutex);
        return werr;
 }
 
-static struct btrfs_space_info *__find_space_info(struct btrfs_fs_info *info,
-                                                 u64 flags)
-{
-       struct list_head *head = &info->space_info;
-       struct list_head *cur;
-       struct btrfs_space_info *found;
-       list_for_each(cur, head) {
-               found = list_entry(cur, struct btrfs_space_info, list);
-               if (found->flags == flags)
-                       return found;
-       }
-       return NULL;
-
-}
-
 static int update_space_info(struct btrfs_fs_info *info, u64 flags,
                             u64 total_bytes, u64 bytes_used,
                             struct btrfs_space_info **space_info)
@@ -1126,10 +1265,11 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
 
        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;
-               WARN_ON(found->total_bytes < found->bytes_used);
+               spin_unlock(&found->lock);
                *space_info = found;
                return 0;
        }
@@ -1138,10 +1278,14 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
                return -ENOMEM;
 
        list_add(&found->list, &info->space_info);
+       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->full = 0;
        found->force_alloc = 0;
        *space_info = found;
@@ -1200,7 +1344,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
        u64 thresh;
        u64 start;
        u64 num_bytes;
-       int ret;
+       int ret = 0, waited = 0;
 
        flags = reduce_alloc_profile(extent_root, flags);
 
@@ -1212,27 +1356,49 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
        }
        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)
+       if (space_info->full) {
+               spin_unlock(&space_info->lock);
                goto out;
+       }
 
        thresh = div_factor(space_info->total_bytes, 6);
        if (!force &&
-          (space_info->bytes_used + space_info->bytes_pinned + alloc_bytes) <
-           thresh)
+          (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 = mutex_trylock(&extent_root->fs_info->chunk_mutex);
+       if (!ret && !force) {
                goto out;
+       } else if (!ret) {
+               mutex_lock(&extent_root->fs_info->chunk_mutex);
+               waited = 1;
+       }
+
+       if (waited) {
+               spin_lock(&space_info->lock);
+               if (space_info->full) {
+                       spin_unlock(&space_info->lock);
+                       goto out_unlock;
+               }
+               spin_unlock(&space_info->lock);
+       }
 
-       mutex_lock(&extent_root->fs_info->chunk_mutex);
        ret = btrfs_alloc_chunk(trans, extent_root, &start, &num_bytes, flags);
-       if (ret == -ENOSPC) {
+       if (ret) {
 printk("space info full %Lu\n", flags);
                space_info->full = 1;
                goto out_unlock;
        }
-       BUG_ON(ret);
 
        ret = btrfs_make_block_group(trans, extent_root, 0, flags,
                     BTRFS_FIRST_CHUNK_TREE_OBJECTID, start, num_bytes);
@@ -1240,7 +1406,7 @@ printk("space info full %Lu\n", flags);
 out_unlock:
        mutex_unlock(&extent_root->fs_info->chunk_mutex);
 out:
-       return 0;
+       return ret;
 }
 
 static int update_block_group(struct btrfs_trans_handle *trans,
@@ -1253,10 +1419,7 @@ static int update_block_group(struct btrfs_trans_handle *trans,
        u64 total = num_bytes;
        u64 old_val;
        u64 byte_in_group;
-       u64 start;
-       u64 end;
 
-       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        while(total) {
                cache = btrfs_lookup_block_group(info, bytenr);
                if (!cache) {
@@ -1264,12 +1427,10 @@ static int update_block_group(struct btrfs_trans_handle *trans,
                }
                byte_in_group = bytenr - cache->key.objectid;
                WARN_ON(byte_in_group > cache->key.offset);
-               start = cache->key.objectid;
-               end = start + cache->key.offset - 1;
-               set_extent_bits(&info->block_group_cache, start, end,
-                               BLOCK_GROUP_DIRTY, GFP_NOFS);
 
+               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) {
@@ -1277,15 +1438,19 @@ static int update_block_group(struct btrfs_trans_handle *trans,
                        cache->space_info->bytes_used += 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;
                        btrfs_set_block_group_used(&cache->item, old_val);
                        spin_unlock(&cache->lock);
+                       spin_unlock(&cache->space_info->lock);
                        if (mark_free) {
-                               set_extent_dirty(&info->free_space_cache,
-                                                bytenr, bytenr + num_bytes - 1,
-                                                GFP_NOFS);
+                               int ret;
+                               ret = btrfs_add_free_space(cache, bytenr,
+                                                          num_bytes);
+                               if (ret)
+                                       return -1;
                        }
                }
                total -= num_bytes;
@@ -1296,27 +1461,23 @@ static int update_block_group(struct btrfs_trans_handle *trans,
 
 static u64 first_logical_byte(struct btrfs_root *root, u64 search_start)
 {
-       u64 start;
-       u64 end;
-       int ret;
-       ret = find_first_extent_bit(&root->fs_info->block_group_cache,
-                                   search_start, &start, &end,
-                                   BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA |
-                                   BLOCK_GROUP_SYSTEM);
-       if (ret)
+       struct btrfs_block_group_cache *cache;
+
+       cache = btrfs_lookup_first_block_group(root->fs_info, search_start);
+       if (!cache)
                return 0;
-       return start;
-}
 
+       return cache->key.objectid;
+}
 
-static int update_pinned_extents(struct btrfs_root *root,
+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->alloc_mutex));
+       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);
@@ -1326,29 +1487,24 @@ static int update_pinned_extents(struct btrfs_root *root,
        }
        while (num > 0) {
                cache = btrfs_lookup_block_group(fs_info, bytenr);
-               if (!cache) {
-                       u64 first = first_logical_byte(root, bytenr);
-                       WARN_ON(first < bytenr);
-                       len = min(first - bytenr, num);
-               } else {
-                       len = min(num, cache->key.offset -
-                                 (bytenr - cache->key.objectid));
-               }
+               BUG_ON(!cache);
+               len = min(num, cache->key.offset -
+                         (bytenr - cache->key.objectid));
                if (pin) {
-                       if (cache) {
-                               spin_lock(&cache->lock);
-                               cache->pinned += len;
-                               cache->space_info->bytes_pinned += len;
-                               spin_unlock(&cache->lock);
-                       }
+                       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 {
-                       if (cache) {
-                               spin_lock(&cache->lock);
-                               cache->pinned -= len;
-                               cache->space_info->bytes_pinned -= len;
-                               spin_unlock(&cache->lock);
-                       }
+                       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;
                }
                bytenr += len;
@@ -1357,6 +1513,36 @@ static int update_pinned_extents(struct btrfs_root *root,
        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);
+               bytenr += len;
+               num -= len;
+       }
+       return 0;
+}
+
 int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy)
 {
        u64 last = 0;
@@ -1365,6 +1551,7 @@ int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy)
        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);
@@ -1373,6 +1560,7 @@ int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy)
                set_extent_dirty(copy, start, end, GFP_NOFS);
                last = end + 1;
        }
+       mutex_unlock(&root->fs_info->pinned_mutex);
        return 0;
 }
 
@@ -1383,132 +1571,174 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
        u64 start;
        u64 end;
        int ret;
-       struct extent_io_tree *free_space_cache;
-       free_space_cache = &root->fs_info->free_space_cache;
+       struct btrfs_block_group_cache *cache;
 
-       mutex_lock(&root->fs_info->alloc_mutex);
+       mutex_lock(&root->fs_info->pinned_mutex);
        while(1) {
                ret = find_first_extent_bit(unpin, 0, &start, &end,
                                            EXTENT_DIRTY);
                if (ret)
                        break;
-               update_pinned_extents(root, start, end + 1 - start, 0);
+               btrfs_update_pinned_extents(root, start, end + 1 - start, 0);
                clear_extent_dirty(unpin, start, end, GFP_NOFS);
-               set_extent_dirty(free_space_cache, start, end, GFP_NOFS);
+               cache = btrfs_lookup_block_group(root->fs_info, start);
+               if (cache->cached)
+                       btrfs_add_free_space(cache, start, end - start + 1);
                if (need_resched()) {
-                       mutex_unlock(&root->fs_info->alloc_mutex);
+                       mutex_unlock(&root->fs_info->pinned_mutex);
                        cond_resched();
-                       mutex_lock(&root->fs_info->alloc_mutex);
+                       mutex_lock(&root->fs_info->pinned_mutex);
                }
        }
-       mutex_unlock(&root->fs_info->alloc_mutex);
+       mutex_unlock(&root->fs_info->pinned_mutex);
        return 0;
 }
 
 static int finish_current_insert(struct btrfs_trans_handle *trans,
-                                struct btrfs_root *extent_root)
+                                struct btrfs_root *extent_root, int all)
 {
        u64 start;
        u64 end;
+       u64 priv;
+       u64 search = 0;
        struct btrfs_fs_info *info = extent_root->fs_info;
-       struct extent_buffer *eb;
        struct btrfs_path *path;
-       struct btrfs_key ins;
-       struct btrfs_disk_key first;
+       struct btrfs_extent_ref *ref;
+       struct pending_extent_op *extent_op;
+       struct btrfs_key key;
        struct btrfs_extent_item extent_item;
        int ret;
-       int level;
        int err = 0;
 
-       WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
        btrfs_set_stack_extent_refs(&extent_item, 1);
-       btrfs_set_key_type(&ins, BTRFS_EXTENT_ITEM_KEY);
        path = btrfs_alloc_path();
 
        while(1) {
-               ret = find_first_extent_bit(&info->extent_ins, 0, &start,
-                                           &end, EXTENT_LOCKED);
-               if (ret)
+               mutex_lock(&info->extent_ins_mutex);
+               ret = find_first_extent_bit(&info->extent_ins, search, &start,
+                                           &end, EXTENT_WRITEBACK);
+               if (ret) {
+                       mutex_unlock(&info->extent_ins_mutex);
+                       if (search && all) {
+                               search = 0;
+                               continue;
+                       }
                        break;
+               }
 
-               ins.objectid = start;
-               ins.offset = end + 1 - start;
-               err = btrfs_insert_item(trans, extent_root, &ins,
+               ret = try_lock_extent(&info->extent_ins, start, end, GFP_NOFS);
+               if (!ret) {
+                       search = end + 1;
+                       mutex_unlock(&info->extent_ins_mutex);
+                       cond_resched();
+                       continue;
+               }
+               BUG_ON(ret < 0);
+
+               ret = get_state_private(&info->extent_ins, start, &priv);
+               BUG_ON(ret);
+               extent_op = (struct pending_extent_op *)(unsigned long)priv;
+
+               mutex_unlock(&info->extent_ins_mutex);
+
+               if (extent_op->type == PENDING_EXTENT_INSERT) {
+                       key.objectid = start;
+                       key.offset = end + 1 - start;
+                       key.type = BTRFS_EXTENT_ITEM_KEY;
+                       err = btrfs_insert_item(trans, extent_root, &key,
                                        &extent_item, sizeof(extent_item));
-               clear_extent_bits(&info->extent_ins, start, end, EXTENT_LOCKED,
-                                 GFP_NOFS);
+                       BUG_ON(err);
 
-               eb = btrfs_find_tree_block(extent_root, ins.objectid,
-                                          ins.offset);
+                       mutex_lock(&info->extent_ins_mutex);
+                       clear_extent_bits(&info->extent_ins, start, end,
+                                         EXTENT_WRITEBACK, GFP_NOFS);
+                       mutex_unlock(&info->extent_ins_mutex);
 
-               if (!btrfs_buffer_uptodate(eb, trans->transid)) {
-                       mutex_unlock(&extent_root->fs_info->alloc_mutex);
-                       btrfs_read_buffer(eb, trans->transid);
-                       mutex_lock(&extent_root->fs_info->alloc_mutex);
-               }
+                       err = insert_extent_backref(trans, extent_root, path,
+                                               start, extent_op->parent,
+                                               extent_root->root_key.objectid,
+                                               extent_op->generation,
+                                               extent_op->level);
+                       BUG_ON(err);
+               } else if (extent_op->type == PENDING_BACKREF_UPDATE) {
+                       err = lookup_extent_backref(trans, extent_root, path,
+                                               start, extent_op->orig_parent,
+                                               extent_root->root_key.objectid,
+                                               extent_op->orig_generation,
+                                               extent_op->level, 0);
+                       BUG_ON(err);
 
-               btrfs_tree_lock(eb);
-               level = btrfs_header_level(eb);
-               if (level == 0) {
-                       btrfs_item_key(eb, &first, 0);
+                       mutex_lock(&info->extent_ins_mutex);
+                       clear_extent_bits(&info->extent_ins, start, end,
+                                         EXTENT_WRITEBACK, GFP_NOFS);
+                       mutex_unlock(&info->extent_ins_mutex);
+
+                       key.objectid = start;
+                       key.offset = extent_op->parent;
+                       key.type = BTRFS_EXTENT_REF_KEY;
+                       err = btrfs_set_item_key_safe(trans, extent_root, path,
+                                                     &key);
+                       BUG_ON(err);
+                       ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                            struct btrfs_extent_ref);
+                       btrfs_set_ref_generation(path->nodes[0], ref,
+                                                extent_op->generation);
+                       btrfs_mark_buffer_dirty(path->nodes[0]);
+                       btrfs_release_path(extent_root, path);
                } else {
-                       btrfs_node_key(eb, &first, 0);
-               }
-               btrfs_tree_unlock(eb);
-               free_extent_buffer(eb);
-               /*
-                * the first key is just a hint, so the race we've created
-                * against reading it is fine
-                */
-               err = btrfs_insert_extent_backref(trans, extent_root, path,
-                                         start, extent_root->root_key.objectid,
-                                         0, level,
-                                         btrfs_disk_key_objectid(&first));
-               BUG_ON(err);
-               if (need_resched()) {
-                       mutex_unlock(&extent_root->fs_info->alloc_mutex);
-                       cond_resched();
-                       mutex_lock(&extent_root->fs_info->alloc_mutex);
+                       BUG_ON(1);
                }
+               kfree(extent_op);
+               unlock_extent(&info->extent_ins, start, end, GFP_NOFS);
+               if (all)
+                       search = 0;
+               else
+                       search = end + 1;
+
+               cond_resched();
        }
        btrfs_free_path(path);
        return 0;
 }
 
-static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
-                         int pending)
+static int pin_down_bytes(struct btrfs_trans_handle *trans,
+                         struct btrfs_root *root,
+                         u64 bytenr, u64 num_bytes, int is_data)
 {
        int err = 0;
+       struct extent_buffer *buf;
 
-       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
-       if (!pending) {
-               struct extent_buffer *buf;
-               buf = btrfs_find_tree_block(root, bytenr, num_bytes);
-               if (buf) {
-                       if (btrfs_try_tree_lock(buf) &&
-                           btrfs_buffer_uptodate(buf, 0)) {
-                               u64 transid =
-                                   root->fs_info->running_transaction->transid;
-                               u64 header_transid =
-                                       btrfs_header_generation(buf);
-                               if (header_transid == transid &&
-                                   !btrfs_header_flag(buf,
-                                              BTRFS_HEADER_FLAG_WRITTEN)) {
-                                       clean_tree_block(NULL, root, buf);
-                                       btrfs_tree_unlock(buf);
-                                       free_extent_buffer(buf);
-                                       return 1;
-                               }
-                               btrfs_tree_unlock(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_transid == trans->transid &&
+                   !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
+                       clean_tree_block(NULL, root, buf);
+                       btrfs_tree_unlock(buf);
                        free_extent_buffer(buf);
+                       return 1;
                }
-               update_pinned_extents(root, bytenr, num_bytes, 1);
-       } else {
-               set_extent_bits(&root->fs_info->pending_del,
-                               bytenr, bytenr + num_bytes - 1,
-                               EXTENT_LOCKED, GFP_NOFS);
+               btrfs_tree_unlock(buf);
        }
+       free_extent_buffer(buf);
+pinit:
+       btrfs_update_pinned_extents(root, bytenr, num_bytes, 1);
+
        BUG_ON(err < 0);
        return 0;
 }
@@ -1516,11 +1746,11 @@ static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
 /*
  * 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,
+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, u64 owner_offset, int pin,
-                        int mark_free)
+                        u64 owner_objectid, int pin, int mark_free)
 {
        struct btrfs_path *path;
        struct btrfs_key key;
@@ -1534,7 +1764,6 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
        struct btrfs_extent_item *ei;
        u32 refs;
 
-       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        key.objectid = bytenr;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        key.offset = num_bytes;
@@ -1544,9 +1773,8 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 
        path->reada = 1;
        ret = lookup_extent_backref(trans, extent_root, path,
-                                   bytenr, root_objectid,
-                                   ref_generation,
-                                   owner_objectid, owner_offset, 1);
+                                   bytenr, parent, root_objectid,
+                                   ref_generation, owner_objectid, 1);
        if (ret == 0) {
                struct btrfs_key found_key;
                extent_slot = path->slots[0];
@@ -1564,23 +1792,21 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                        if (path->slots[0] - extent_slot > 5)
                                break;
                }
-               if (!found_extent)
-                       ret = btrfs_del_item(trans, extent_root, path);
+               if (!found_extent) {
+                       ret = remove_extent_backref(trans, extent_root, path);
+                       BUG_ON(ret);
+                       btrfs_release_path(extent_root, path);
+                       ret = btrfs_search_slot(trans, extent_root,
+                                               &key, path, -1, 1);
+                       BUG_ON(ret);
+                       extent_slot = path->slots[0];
+               }
        } else {
                btrfs_print_leaf(extent_root, path->nodes[0]);
                WARN_ON(1);
                printk("Unable to find ref byte nr %Lu root %Lu "
-                      " gen %Lu owner %Lu offset %Lu\n", bytenr,
-                      root_objectid, ref_generation, owner_objectid,
-                      owner_offset);
-       }
-       if (!found_extent) {
-               btrfs_release_path(extent_root, path);
-               ret = btrfs_search_slot(trans, extent_root, &key, path, -1, 1);
-               if (ret < 0)
-                       return ret;
-               BUG_ON(ret);
-               extent_slot = path->slots[0];
+                      "gen %Lu owner %Lu\n", bytenr,
+                      root_objectid, ref_generation, owner_objectid);
        }
 
        leaf = path->nodes[0];
@@ -1594,6 +1820,10 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
        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) != 1);
                /* if the back ref and the extent are next to each other
                 * they get deleted below in one shot
                 */
@@ -1601,15 +1831,13 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                num_to_del = 2;
        } else if (found_extent) {
                /* otherwise delete the extent back ref */
-               ret = btrfs_del_item(trans, extent_root, path);
+               ret = remove_extent_backref(trans, extent_root, path);
                BUG_ON(ret);
                /* if refs are 0, we need to setup the path for deletion */
                if (refs == 0) {
                        btrfs_release_path(extent_root, path);
                        ret = btrfs_search_slot(trans, extent_root, &key, path,
                                                -1, 1);
-                       if (ret < 0)
-                               return ret;
                        BUG_ON(ret);
                }
        }
@@ -1617,9 +1845,16 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
        if (refs == 0) {
                u64 super_used;
                u64 root_used;
+#ifdef BIO_RW_DISCARD
+               u64 map_length = num_bytes;
+               struct btrfs_multi_bio *multi = NULL;
+#endif
 
                if (pin) {
-                       ret = pin_down_bytes(root, bytenr, num_bytes, 0);
+                       mutex_lock(&root->fs_info->pinned_mutex);
+                       ret = pin_down_bytes(trans, root, bytenr, num_bytes,
+                               owner_objectid >= BTRFS_FIRST_FREE_OBJECTID);
+                       mutex_unlock(&root->fs_info->pinned_mutex);
                        if (ret > 0)
                                mark_free = 1;
                        BUG_ON(ret < 0);
@@ -1638,15 +1873,34 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                                           root_used - num_bytes);
                ret = btrfs_del_items(trans, extent_root, path, path->slots[0],
                                      num_to_del);
-               if (ret) {
-                       return ret;
-               }
+               BUG_ON(ret);
+               btrfs_release_path(extent_root, path);
                ret = update_block_group(trans, root, bytenr, num_bytes, 0,
                                         mark_free);
                BUG_ON(ret);
+
+#ifdef BIO_RW_DISCARD
+               /* 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++) {
+                               blkdev_issue_discard(stripe->dev->bdev,
+                                                    stripe->physical >> 9,
+                                                    map_length >> 9);
+                       }
+                       kfree(multi);
+               }
+#endif
        }
        btrfs_free_path(path);
-       finish_current_insert(trans, extent_root);
+       finish_current_insert(trans, extent_root, 0);
        return ret;
 }
 
@@ -1655,46 +1909,98 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
  * them from the extent map
  */
 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
-                              btrfs_root *extent_root)
+                              btrfs_root *extent_root, int all)
 {
        int ret;
        int err = 0;
        u64 start;
        u64 end;
+       u64 priv;
+       u64 search = 0;
        struct extent_io_tree *pending_del;
-       struct extent_io_tree *pinned_extents;
+       struct extent_io_tree *extent_ins;
+       struct pending_extent_op *extent_op;
+       struct btrfs_fs_info *info = extent_root->fs_info;
 
-       WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
+       extent_ins = &extent_root->fs_info->extent_ins;
        pending_del = &extent_root->fs_info->pending_del;
-       pinned_extents = &extent_root->fs_info->pinned_extents;
 
        while(1) {
-               ret = find_first_extent_bit(pending_del, 0, &start, &end,
-                                           EXTENT_LOCKED);
-               if (ret)
+               mutex_lock(&info->extent_ins_mutex);
+               ret = find_first_extent_bit(pending_del, search, &start, &end,
+                                           EXTENT_WRITEBACK);
+               if (ret) {
+                       mutex_unlock(&info->extent_ins_mutex);
+                       if (all && search) {
+                               search = 0;
+                               continue;
+                       }
                        break;
-               clear_extent_bits(pending_del, start, end, EXTENT_LOCKED,
+               }
+
+               ret = try_lock_extent(extent_ins, start, end, GFP_NOFS);
+               if (!ret) {
+                       search = end+1;
+                       mutex_unlock(&info->extent_ins_mutex);
+                       cond_resched();
+                       continue;
+               }
+               BUG_ON(ret < 0);
+
+               ret = get_state_private(pending_del, start, &priv);
+               BUG_ON(ret);
+               extent_op = (struct pending_extent_op *)(unsigned long)priv;
+
+               clear_extent_bits(pending_del, start, end, EXTENT_WRITEBACK,
                                  GFP_NOFS);
-               if (!test_range_bit(&extent_root->fs_info->extent_ins,
-                                   start, end, EXTENT_LOCKED, 0)) {
-                       update_pinned_extents(extent_root, start,
-                                             end + 1 - start, 1);
+               if (!test_range_bit(extent_ins, start, end,
+                                   EXTENT_WRITEBACK, 0)) {
+                       mutex_unlock(&info->extent_ins_mutex);
+free_extent:
                        ret = __free_extent(trans, extent_root,
-                                            start, end + 1 - start,
-                                            extent_root->root_key.objectid,
-                                            0, 0, 0, 0, 0);
+                                           start, end + 1 - start,
+                                           extent_op->orig_parent,
+                                           extent_root->root_key.objectid,
+                                           extent_op->orig_generation,
+                                           extent_op->level, 1, 0);
+                       kfree(extent_op);
                } else {
-                       clear_extent_bits(&extent_root->fs_info->extent_ins,
-                                         start, end, EXTENT_LOCKED, GFP_NOFS);
+                       kfree(extent_op);
+
+                       ret = get_state_private(&info->extent_ins, start,
+                                               &priv);
+                       BUG_ON(ret);
+                       extent_op = (struct pending_extent_op *)
+                                               (unsigned long)priv;
+
+                       clear_extent_bits(&info->extent_ins, start, end,
+                                         EXTENT_WRITEBACK, GFP_NOFS);
+
+                       mutex_unlock(&info->extent_ins_mutex);
+
+                       if (extent_op->type == PENDING_BACKREF_UPDATE)
+                               goto free_extent;
+
+                       mutex_lock(&extent_root->fs_info->pinned_mutex);
+                       ret = pin_down_bytes(trans, extent_root, start,
+                                            end + 1 - start, 0);
+                       mutex_unlock(&extent_root->fs_info->pinned_mutex);
+
+                       ret = update_block_group(trans, extent_root, start,
+                                               end + 1 - start, 0, ret > 0);
+
+                       BUG_ON(ret);
+                       kfree(extent_op);
                }
                if (ret)
                        err = ret;
+               unlock_extent(extent_ins, start, end, GFP_NOFS);
 
-               if (need_resched()) {
-                       mutex_unlock(&extent_root->fs_info->alloc_mutex);
-                       cond_resched();
-                       mutex_lock(&extent_root->fs_info->alloc_mutex);
-               }
+               if (all)
+                       search = 0;
+               else
+                       search = end + 1;
+               cond_resched();
        }
        return err;
 }
@@ -1703,45 +2009,79 @@ static int del_pending_extents(struct btrfs_trans_handle *trans, struct
  * 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 root_objectid,
-                              u64 ref_generation, u64 owner_objectid,
-                              u64 owner_offset, int pin)
+                              struct btrfs_root *root,
+                              u64 bytenr, u64 num_bytes, u64 parent,
+                              u64 root_objectid, u64 ref_generation,
+                              u64 owner_objectid, int pin)
 {
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        int pending_ret;
        int ret;
 
        WARN_ON(num_bytes < root->sectorsize);
-       if (!root->ref_cows)
-               ref_generation = 0;
-
        if (root == extent_root) {
-               pin_down_bytes(root, bytenr, num_bytes, 1);
+               struct pending_extent_op *extent_op;
+
+               extent_op = kmalloc(sizeof(*extent_op), GFP_NOFS);
+               BUG_ON(!extent_op);
+
+               extent_op->type = PENDING_EXTENT_DELETE;
+               extent_op->bytenr = bytenr;
+               extent_op->num_bytes = num_bytes;
+               extent_op->parent = parent;
+               extent_op->orig_parent = parent;
+               extent_op->generation = ref_generation;
+               extent_op->orig_generation = ref_generation;
+               extent_op->level = (int)owner_objectid;
+
+               mutex_lock(&root->fs_info->extent_ins_mutex);
+               set_extent_bits(&root->fs_info->pending_del,
+                               bytenr, bytenr + num_bytes - 1,
+                               EXTENT_WRITEBACK, GFP_NOFS);
+               set_state_private(&root->fs_info->pending_del,
+                                 bytenr, (unsigned long)extent_op);
+               mutex_unlock(&root->fs_info->extent_ins_mutex);
                return 0;
        }
-       ret = __free_extent(trans, root, bytenr, num_bytes, root_objectid,
-                           ref_generation, owner_objectid, owner_offset,
-                           pin, pin == 0);
+       /* if metadata always pin */
+       if (owner_objectid < BTRFS_FIRST_FREE_OBJECTID) {
+               if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID) {
+                       struct btrfs_block_group_cache *cache;
+
+                       /* btrfs_free_reserved_extent */
+                       cache = btrfs_lookup_block_group(root->fs_info, bytenr);
+                       BUG_ON(!cache);
+                       btrfs_add_free_space(cache, bytenr, num_bytes);
+                       update_reserved_extents(root, bytenr, num_bytes, 0);
+                       return 0;
+               }
+               pin = 1;
+       }
 
-       finish_current_insert(trans, root->fs_info->extent_root);
-       pending_ret = del_pending_extents(trans, root->fs_info->extent_root);
+       /* if data pin when any transaction has committed this */
+       if (ref_generation != trans->transid)
+               pin = 1;
+
+       ret = __free_extent(trans, root, bytenr, num_bytes, parent,
+                           root_objectid, ref_generation,
+                           owner_objectid, pin, pin == 0);
+
+       finish_current_insert(trans, root->fs_info->extent_root, 0);
+       pending_ret = del_pending_extents(trans, root->fs_info->extent_root, 0);
        return ret ? ret : pending_ret;
 }
 
 int btrfs_free_extent(struct btrfs_trans_handle *trans,
-                     struct btrfs_root *root, u64 bytenr,
-                     u64 num_bytes, u64 root_objectid,
-                     u64 ref_generation, u64 owner_objectid,
-                     u64 owner_offset, int pin)
+                     struct btrfs_root *root,
+                     u64 bytenr, u64 num_bytes, u64 parent,
+                     u64 root_objectid, u64 ref_generation,
+                     u64 owner_objectid, int pin)
 {
        int ret;
 
-       maybe_lock_mutex(root);
-       ret = __btrfs_free_extent(trans, root, bytenr, num_bytes,
+       ret = __btrfs_free_extent(trans, root, bytenr, num_bytes, parent,
                                  root_objectid, ref_generation,
-                                 owner_objectid, owner_offset, pin);
-       maybe_unlock_mutex(root);
+                                 owner_objectid, pin);
        return ret;
 }
 
@@ -1768,21 +2108,22 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                                     u64 exclude_start, u64 exclude_nr,
                                     int data)
 {
-       int ret;
-       u64 orig_search_start;
+       int ret = 0;
        struct btrfs_root * root = orig_root->fs_info->extent_root;
-       struct btrfs_fs_info *info = root->fs_info;
        u64 total_needed = num_bytes;
        u64 *last_ptr = NULL;
-       struct btrfs_block_group_cache *block_group;
-       int full_scan = 0;
-       int wrapped = 0;
+       struct btrfs_block_group_cache *block_group = NULL;
        int chunk_alloc_done = 0;
        int empty_cluster = 2 * 1024 * 1024;
        int allowed_chunk_alloc = 0;
+       struct list_head *head = NULL, *cur = NULL;
+       int loop = 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;
 
        if (orig_root->ref_cows || empty_size)
                allowed_chunk_alloc = 1;
@@ -1792,163 +2133,182 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                empty_cluster = 256 * 1024;
        }
 
-       if ((data & BTRFS_BLOCK_GROUP_DATA) && btrfs_test_opt(root, SSD)) {
+       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 {
+               else
                        empty_size += empty_cluster;
-               }
        }
-
        search_start = max(search_start, first_logical_byte(root, 0));
-       orig_search_start = search_start;
-
-       if (search_end == (u64)-1)
-               search_end = btrfs_super_total_bytes(&info->super_copy);
-
-       if (hint_byte) {
-               block_group = btrfs_lookup_first_block_group(info, hint_byte);
-               if (!block_group)
-                       hint_byte = search_start;
-               block_group = btrfs_find_block_group(root, block_group,
-                                                    hint_byte, data, 1);
-               if (last_ptr && *last_ptr == 0 && block_group)
-                       hint_byte = block_group->key.objectid;
-       } else {
-               block_group = btrfs_find_block_group(root,
-                                                    trans->block_group,
-                                                    search_start, data, 1);
-       }
        search_start = max(search_start, hint_byte);
-
        total_needed += empty_size;
 
-check_failed:
-       if (!block_group) {
-               block_group = btrfs_lookup_first_block_group(info,
+       block_group = btrfs_lookup_block_group(root->fs_info, search_start);
+       if (!block_group)
+               block_group = btrfs_lookup_first_block_group(root->fs_info,
                                                             search_start);
-               if (!block_group)
-                       block_group = btrfs_lookup_first_block_group(info,
-                                                      orig_search_start);
-       }
-       if (full_scan && !chunk_alloc_done) {
-               if (allowed_chunk_alloc) {
-                       do_chunk_alloc(trans, root,
-                                    num_bytes + 2 * 1024 * 1024, data, 1);
-                       allowed_chunk_alloc = 0;
-               } else if (block_group && block_group_bits(block_group, data)) {
-                       block_group->space_info->force_alloc = 1;
-               }
-               chunk_alloc_done = 1;
-       }
-       ret = find_search_start(root, &block_group, &search_start,
-                               total_needed, data);
-       if (ret == -ENOSPC && last_ptr && *last_ptr) {
-               *last_ptr = 0;
-               block_group = btrfs_lookup_first_block_group(info,
-                                                            orig_search_start);
-               search_start = orig_search_start;
-               ret = find_search_start(root, &block_group, &search_start,
-                                       total_needed, data);
-       }
-       if (ret == -ENOSPC)
-               goto enospc;
-       if (ret)
-               goto error;
+       space_info = __find_space_info(root->fs_info, data);
 
-       if (last_ptr && *last_ptr && search_start != *last_ptr) {
-               *last_ptr = 0;
-               if (!empty_size) {
-                       empty_size += empty_cluster;
-                       total_needed += empty_size;
-               }
-               block_group = btrfs_lookup_first_block_group(info,
-                                                      orig_search_start);
-               search_start = orig_search_start;
-               ret = find_search_start(root, &block_group,
-                                       &search_start, total_needed, data);
-               if (ret == -ENOSPC)
-                       goto enospc;
-               if (ret)
-                       goto error;
-       }
+       down_read(&space_info->groups_sem);
+       while (1) {
+               struct btrfs_free_space *free_space;
+               /*
+                * the only way this happens if our hint points to a block
+                * group thats not of the proper type, while looping this
+                * should never happen
+                */
+               WARN_ON(!block_group);
+               mutex_lock(&block_group->alloc_mutex);
+               if (unlikely(!block_group_bits(block_group, data)))
+                       goto new_group;
 
-       search_start = stripe_align(root, search_start);
-       ins->objectid = search_start;
-       ins->offset = num_bytes;
+               ret = cache_block_group(root, block_group);
+               if (ret) {
+                       mutex_unlock(&block_group->alloc_mutex);
+                       break;
+               }
 
-       if (ins->objectid + num_bytes >= search_end)
-               goto enospc;
+               if (block_group->ro)
+                       goto new_group;
 
-       if (ins->objectid + num_bytes >
-           block_group->key.objectid + block_group->key.offset) {
-               search_start = block_group->key.objectid +
-                       block_group->key.offset;
-               goto new_group;
-       }
+               free_space = btrfs_find_free_space(block_group, search_start,
+                                                  total_needed);
+               if (free_space) {
+                       u64 start = block_group->key.objectid;
+                       u64 end = block_group->key.objectid +
+                               block_group->key.offset;
+
+                       search_start = stripe_align(root, free_space->offset);
+
+                       /* move on to the next group */
+                       if (search_start + num_bytes >= search_end)
+                               goto new_group;
+
+                       /* move on to the next group */
+                       if (search_start + num_bytes > end)
+                               goto new_group;
+
+                       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 >= start &&
+                                   search_start < end) {
+                                       mutex_unlock(&block_group->alloc_mutex);
+                                       continue;
+                               }
 
-       if (test_range_bit(&info->extent_ins, ins->objectid,
-                          ins->objectid + num_bytes -1, EXTENT_LOCKED, 0)) {
-               search_start = ins->objectid + num_bytes;
-               goto new_group;
-       }
+                               /* else we go to the next block group */
+                               goto new_group;
+                       }
 
-       if (test_range_bit(&info->pinned_extents, ins->objectid,
-                          ins->objectid + num_bytes -1, EXTENT_DIRTY, 0)) {
-               search_start = ins->objectid + num_bytes;
-               goto new_group;
-       }
+                       ins->objectid = search_start;
+                       ins->offset = num_bytes;
 
-       if (exclude_nr > 0 && (ins->objectid + num_bytes > exclude_start &&
-           ins->objectid < exclude_start + exclude_nr)) {
-               search_start = exclude_start + exclude_nr;
-               goto new_group;
-       }
+                       btrfs_remove_free_space_lock(block_group, search_start,
+                                                    num_bytes);
+                       /* we are all good, lets return */
+                       mutex_unlock(&block_group->alloc_mutex);
+                       break;
+               }
+new_group:
+               mutex_unlock(&block_group->alloc_mutex);
+               /*
+                * Here's how this works.
+                * loop == 0: we were searching a block group via a hint
+                *              and didn't find anything, so we start at
+                *              the head of the block groups and keep searching
+                * loop == 1: we're searching through all of the block groups
+                *              if we hit the head again we have searched
+                *              all of the block groups for this space and we
+                *              need to try and allocate, if we cant error out.
+                * loop == 2: we allocated more space and are looping through
+                *              all of the block groups again.
+                */
+               if (loop == 0) {
+                       head = &space_info->block_groups;
+                       cur = head->next;
 
-       if (!(data & BTRFS_BLOCK_GROUP_DATA)) {
-               block_group = btrfs_lookup_block_group(info, ins->objectid);
-               if (block_group)
-                       trans->block_group = block_group;
-       }
-       ins->offset = num_bytes;
-       if (last_ptr) {
-               *last_ptr = ins->objectid + ins->offset;
-               if (*last_ptr ==
-                   btrfs_super_total_bytes(&root->fs_info->super_copy)) {
-                       *last_ptr = 0;
+                       if (last_ptr && *last_ptr) {
+                               total_needed += empty_cluster;
+                               *last_ptr = 0;
+                       }
+                       loop++;
+               } else if (loop == 1 && cur == head) {
+                       if (allowed_chunk_alloc && !chunk_alloc_done) {
+                               up_read(&space_info->groups_sem);
+                               ret = do_chunk_alloc(trans, root, num_bytes +
+                                                    2 * 1024 * 1024, data, 1);
+                               if (ret < 0)
+                                       break;
+                               down_read(&space_info->groups_sem);
+                               loop++;
+                               head = &space_info->block_groups;
+                               cur = head->next;
+                               chunk_alloc_done = 1;
+                       } else if (!allowed_chunk_alloc) {
+                               space_info->force_alloc = 1;
+                               break;
+                       } else {
+                               break;
+                       }
+               } else if (cur == head) {
+                       break;
                }
+
+               block_group = list_entry(cur, struct btrfs_block_group_cache,
+                                        list);
+               search_start = block_group->key.objectid;
+               cur = cur->next;
        }
-       return 0;
 
-new_group:
-       if (search_start + num_bytes >= search_end) {
-enospc:
-               search_start = orig_search_start;
-               if (full_scan) {
-                       ret = -ENOSPC;
-                       goto error;
-               }
-               if (wrapped) {
-                       if (!full_scan)
-                               total_needed -= empty_size;
-                       full_scan = 1;
-               } else
-                       wrapped = 1;
+       /* we found what we needed */
+       if (ins->objectid) {
+               if (!(data & BTRFS_BLOCK_GROUP_DATA))
+                       trans->block_group = block_group;
+
+               if (last_ptr)
+                       *last_ptr = ins->objectid + ins->offset;
+               ret = 0;
+       } else if (!ret) {
+               ret = -ENOSPC;
        }
-       block_group = btrfs_lookup_first_block_group(info, search_start);
-       cond_resched();
-       block_group = btrfs_find_block_group(root, block_group,
-                                            search_start, data, 0);
-       goto check_failed;
 
-error:
+       up_read(&space_info->groups_sem);
        return ret;
 }
 
+static void dump_space_info(struct btrfs_space_info *info, u64 bytes)
+{
+       struct btrfs_block_group_cache *cache;
+       struct list_head *l;
+
+       printk(KERN_INFO "space_info has %Lu free, is %sfull\n",
+              info->total_bytes - info->bytes_used - info->bytes_pinned -
+              info->bytes_reserved, (info->full) ? "" : "not ");
+
+       down_read(&info->groups_sem);
+       list_for_each(l, &info->block_groups) {
+               cache = list_entry(l, struct btrfs_block_group_cache, list);
+               spin_lock(&cache->lock);
+               printk(KERN_INFO "block group %Lu has %Lu bytes, %Lu used "
+                      "%Lu pinned %Lu reserved\n",
+                      cache->key.objectid, cache->key.offset,
+                      btrfs_block_group_used(&cache->item),
+                      cache->pinned, 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,
@@ -1987,11 +2347,9 @@ again:
                                     BTRFS_BLOCK_GROUP_METADATA |
                                     (info->metadata_alloc_profile &
                                      info->avail_metadata_alloc_bits), 0);
-                       BUG_ON(ret);
                }
                ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                     num_bytes + 2 * 1024 * 1024, data, 0);
-               BUG_ON(ret);
        }
 
        WARN_ON(num_bytes < root->sectorsize);
@@ -2002,22 +2360,40 @@ again:
 
        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) {
-               printk("allocation failed flags %Lu\n", data);
+               struct btrfs_space_info *sinfo;
+
+               sinfo = __find_space_info(root->fs_info, data);
+               printk("allocation failed flags %Lu, wanted %Lu\n",
+                      data, num_bytes);
+               dump_space_info(sinfo, num_bytes);
                BUG();
        }
-       clear_extent_dirty(&root->fs_info->free_space_cache,
-                          ins->objectid, ins->objectid + ins->offset - 1,
-                          GFP_NOFS);
-       return 0;
+
+       return ret;
 }
 
-int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
+int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len)
+{
+       struct btrfs_block_group_cache *cache;
+
+       cache = btrfs_lookup_block_group(root->fs_info, start);
+       if (!cache) {
+               printk(KERN_ERR "Unable to find block group for %Lu\n", start);
+               return -ENOSPC;
+       }
+       btrfs_add_free_space(cache, start, len);
+       update_reserved_extents(root, start, len, 0);
+       return 0;
+}
+
+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,
@@ -2025,19 +2401,17 @@ int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
                                  u64 data)
 {
        int ret;
-       maybe_lock_mutex(root);
        ret = __btrfs_reserve_extent(trans, root, num_bytes, min_alloc_size,
                                     empty_size, hint_byte, search_end, ins,
                                     data);
-       maybe_unlock_mutex(root);
+       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,
+                                        struct btrfs_root *root, u64 parent,
                                         u64 root_objectid, u64 ref_generation,
-                                        u64 owner, u64 owner_offset,
-                                        struct btrfs_key *ins)
+                                        u64 owner, struct btrfs_key *ins)
 {
        int ret;
        int pending_ret;
@@ -2052,6 +2426,9 @@ static int __btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
        struct btrfs_path *path;
        struct btrfs_key keys[2];
 
+       if (parent == 0)
+               parent = ins->objectid;
+
        /* block accounting for super block */
        spin_lock_irq(&info->delalloc_lock);
        super_used = btrfs_super_bytes_used(&info->super_copy);
@@ -2063,17 +2440,34 @@ static int __btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
        btrfs_set_root_used(&root->root_item, root_used + num_bytes);
 
        if (root == extent_root) {
+               struct pending_extent_op *extent_op;
+
+               extent_op = kmalloc(sizeof(*extent_op), GFP_NOFS);
+               BUG_ON(!extent_op);
+
+               extent_op->type = PENDING_EXTENT_INSERT;
+               extent_op->bytenr = ins->objectid;
+               extent_op->num_bytes = ins->offset;
+               extent_op->parent = parent;
+               extent_op->orig_parent = 0;
+               extent_op->generation = ref_generation;
+               extent_op->orig_generation = 0;
+               extent_op->level = (int)owner;
+
+               mutex_lock(&root->fs_info->extent_ins_mutex);
                set_extent_bits(&root->fs_info->extent_ins, ins->objectid,
                                ins->objectid + ins->offset - 1,
-                               EXTENT_LOCKED, GFP_NOFS);
+                               EXTENT_WRITEBACK, GFP_NOFS);
+               set_state_private(&root->fs_info->extent_ins,
+                                 ins->objectid, (unsigned long)extent_op);
+               mutex_unlock(&root->fs_info->extent_ins_mutex);
                goto update_block;
        }
 
        memcpy(&keys[0], ins, sizeof(*ins));
-       keys[1].offset = hash_extent_ref(root_objectid, ref_generation,
-                                        owner, owner_offset);
        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);
 
@@ -2082,8 +2476,8 @@ static int __btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
 
        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, 1);
@@ -2093,15 +2487,15 @@ static int __btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
        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_offset(path->nodes[0], ref, owner_offset);
+       btrfs_set_ref_num_refs(path->nodes[0], ref, 1);
 
        btrfs_mark_buffer_dirty(path->nodes[0]);
 
        trans->alloc_exclude_start = 0;
        trans->alloc_exclude_nr = 0;
        btrfs_free_path(path);
-       finish_current_insert(trans, extent_root);
-       pending_ret = del_pending_extents(trans, extent_root);
+       finish_current_insert(trans, extent_root, 0);
+       pending_ret = del_pending_extents(trans, extent_root, 0);
 
        if (ret)
                goto out;
@@ -2122,19 +2516,46 @@ out:
 }
 
 int btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
-                               struct btrfs_root *root,
+                               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_alloc_reserved_extent(trans, root, parent, root_objectid,
+                                           ref_generation, owner, ins);
+       update_reserved_extents(root, ins->objectid, ins->offset, 0);
+       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, u64 owner_offset,
-                               struct btrfs_key *ins)
+                               u64 owner, struct btrfs_key *ins)
 {
        int ret;
-       maybe_lock_mutex(root);
-       ret = __btrfs_alloc_reserved_extent(trans, root, root_objectid,
-                                           ref_generation, owner,
-                                           owner_offset, ins);
-       maybe_unlock_mutex(root);
+       struct btrfs_block_group_cache *block_group;
+
+       block_group = btrfs_lookup_block_group(root->fs_info, ins->objectid);
+       mutex_lock(&block_group->alloc_mutex);
+       cache_block_group(root, block_group);
+
+       ret = btrfs_remove_free_space_lock(block_group, ins->objectid,
+                                          ins->offset);
+       mutex_unlock(&block_group->alloc_mutex);
+       BUG_ON(ret);
+       ret = __btrfs_alloc_reserved_extent(trans, root, parent, root_objectid,
+                                           ref_generation, owner, ins);
        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
@@ -2144,38 +2565,62 @@ int btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
  */
 int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
-                      u64 num_bytes, u64 min_alloc_size,
+                      u64 num_bytes, u64 parent, u64 min_alloc_size,
                       u64 root_objectid, u64 ref_generation,
-                      u64 owner, u64 owner_offset,
-                      u64 empty_size, u64 hint_byte,
+                      u64 owner_objectid, u64 empty_size, u64 hint_byte,
                       u64 search_end, struct btrfs_key *ins, u64 data)
 {
        int ret;
 
-       maybe_lock_mutex(root);
-
        ret = __btrfs_reserve_extent(trans, root, num_bytes,
                                     min_alloc_size, empty_size, hint_byte,
                                     search_end, ins, data);
        BUG_ON(ret);
-       ret = __btrfs_alloc_reserved_extent(trans, root, root_objectid,
-                                           ref_generation, owner,
-                                           owner_offset, ins);
-       BUG_ON(ret);
+       if (root_objectid != BTRFS_TREE_LOG_OBJECTID) {
+               ret = __btrfs_alloc_reserved_extent(trans, root, parent,
+                                       root_objectid, ref_generation,
+                                       owner_objectid, ins);
+               BUG_ON(ret);
 
-       maybe_unlock_mutex(root);
+       } else {
+               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)
+{
+       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_tree_lock(buf);
+       clean_tree_block(trans, root, 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++;
+       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,
+                                            u32 blocksize, u64 parent,
                                             u64 root_objectid,
                                             u64 ref_generation,
-                                            u64 first_objectid,
                                             int level,
                                             u64 hint,
                                             u64 empty_size)
@@ -2184,40 +2629,20 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
        int ret;
        struct extent_buffer *buf;
 
-       ret = btrfs_alloc_extent(trans, root, blocksize, blocksize,
-                                root_objectid, ref_generation,
-                                level, first_objectid, empty_size, hint,
-                                (u64)-1, &ins, 0);
+       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_find_create_tree_block(root, ins.objectid, blocksize);
-       if (!buf) {
-               btrfs_free_extent(trans, root, ins.objectid, blocksize,
-                                 root->root_key.objectid, ref_generation,
-                                 0, 0, 0);
-               return ERR_PTR(-ENOMEM);
-       }
-       btrfs_set_header_generation(buf, trans->transid);
-       btrfs_tree_lock(buf);
-       clean_tree_block(trans, root, buf);
-       btrfs_set_buffer_uptodate(buf);
-
-       if (PageDirty(buf->first_page)) {
-               printk("page %lu dirty\n", buf->first_page->index);
-               WARN_ON(1);
-       }
 
-       set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
-                        buf->start + buf->len - 1, GFP_NOFS);
-       trans->blocks_used++;
+       buf = btrfs_init_new_buffer(trans, root, ins.objectid, blocksize);
        return buf;
 }
 
-static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
-                                 struct btrfs_root *root,
-                                 struct extent_buffer *leaf)
+int btrfs_drop_leaf_ref(struct btrfs_trans_handle *trans,
+                       struct btrfs_root *root, struct extent_buffer *leaf)
 {
        u64 leaf_owner;
        u64 leaf_generation;
@@ -2232,8 +2657,6 @@ static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
        leaf_owner = btrfs_header_owner(leaf);
        leaf_generation = btrfs_header_generation(leaf);
 
-       mutex_unlock(&root->fs_info->alloc_mutex);
-
        for (i = 0; i < nritems; i++) {
                u64 disk_bytenr;
                cond_resched();
@@ -2253,77 +2676,82 @@ static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
                if (disk_bytenr == 0)
                        continue;
 
-               mutex_lock(&root->fs_info->alloc_mutex);
                ret = __btrfs_free_extent(trans, root, disk_bytenr,
                                btrfs_file_extent_disk_num_bytes(leaf, fi),
-                               leaf_owner, leaf_generation,
-                               key.objectid, key.offset, 0);
-               mutex_unlock(&root->fs_info->alloc_mutex);
+                               leaf->start, leaf_owner, leaf_generation,
+                               key.objectid, 0);
                BUG_ON(ret);
-       }
 
-       mutex_lock(&root->fs_info->alloc_mutex);
+               atomic_inc(&root->fs_info->throttle_gen);
+               wake_up(&root->fs_info->transaction_throttle);
+               cond_resched();
+       }
        return 0;
 }
 
-static void noinline reada_walk_down(struct btrfs_root *root,
-                                    struct extent_buffer *node,
-                                    int slot)
+static int noinline cache_drop_leaf_ref(struct btrfs_trans_handle *trans,
+                                       struct btrfs_root *root,
+                                       struct btrfs_leaf_ref *ref)
 {
-       u64 bytenr;
-       u64 last = 0;
-       u32 nritems;
-       u32 refs;
-       u32 blocksize;
-       int ret;
        int i;
-       int level;
-       int skipped = 0;
+       int ret;
+       struct btrfs_extent_info *info = ref->extents;
 
-       nritems = btrfs_header_nritems(node);
-       level = btrfs_header_level(node);
-       if (level)
-               return;
+       for (i = 0; i < ref->nritems; i++) {
+               ret = __btrfs_free_extent(trans, root, info->bytenr,
+                                         info->num_bytes, ref->bytenr,
+                                         ref->owner, ref->generation,
+                                         info->objectid, 0);
 
-       for (i = slot; i < nritems && skipped < 32; i++) {
-               bytenr = btrfs_node_blockptr(node, i);
-               if (last && ((bytenr > last && bytenr - last > 32 * 1024) ||
-                            (last > bytenr && last - bytenr > 32 * 1024))) {
-                       skipped++;
-                       continue;
-               }
-               blocksize = btrfs_level_size(root, level - 1);
-               if (i != slot) {
-                       ret = lookup_extent_ref(NULL, root, bytenr,
-                                               blocksize, &refs);
-                       BUG_ON(ret);
-                       if (refs != 1) {
-                               skipped++;
-                               continue;
-                       }
-               }
-               ret = readahead_tree_block(root, bytenr, blocksize,
-                                          btrfs_node_ptr_generation(node, i));
-               last = bytenr + blocksize;
+               atomic_inc(&root->fs_info->throttle_gen);
+               wake_up(&root->fs_info->transaction_throttle);
                cond_resched();
-               if (ret)
-                       break;
+
+               BUG_ON(ret);
+               info++;
        }
+
+       return 0;
 }
 
-/*
- * we want to avoid as much random IO as we can with the alloc mutex
- * held, so drop the lock and do the lookup, then do it again with the
- * lock held.
- */
 int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,
                              u32 *refs)
 {
-       mutex_unlock(&root->fs_info->alloc_mutex);
-       lookup_extent_ref(NULL, root, start, len, refs);
+       int ret;
+
+       ret = btrfs_lookup_extent_ref(NULL, 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("block %llu went down to one during drop_snap\n",
+                              (unsigned long long)start);
+               }
+
+       }
+#endif
+
        cond_resched();
-       mutex_lock(&root->fs_info->alloc_mutex);
-       return lookup_extent_ref(NULL, root, start, len, refs);
+       return ret;
 }
 
 /*
@@ -2341,12 +2769,11 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
        struct extent_buffer *next;
        struct extent_buffer *cur;
        struct extent_buffer *parent;
+       struct btrfs_leaf_ref *ref;
        u32 blocksize;
        int ret;
        u32 refs;
 
-       mutex_lock(&root->fs_info->alloc_mutex);
-
        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);
        ret = drop_snap_lookup_refcount(root, path->nodes[*level]->start,
@@ -2370,7 +2797,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                    btrfs_header_nritems(cur))
                        break;
                if (*level == 0) {
-                       ret = drop_leaf_ref(trans, root, cur);
+                       ret = btrfs_drop_leaf_ref(trans, root, cur);
                        BUG_ON(ret);
                        break;
                }
@@ -2385,43 +2812,62 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                        root_owner = btrfs_header_owner(parent);
                        root_gen = btrfs_header_generation(parent);
                        path->slots[*level]++;
+
                        ret = __btrfs_free_extent(trans, root, bytenr,
-                                               blocksize, root_owner,
-                                               root_gen, 0, 0, 1);
+                                               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;
                }
+               /*
+                * at this point, we have a single ref, and since the
+                * only place referencing this extent is a dead root
+                * the reference count should never go higher.
+                * So, we don't need to check it again
+                */
+               if (*level == 1) {
+                       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);
+                               *level = 0;
+                               break;
+                       }
+                       if (printk_ratelimit()) {
+                               printk("leaf ref miss for bytenr %llu\n",
+                                      (unsigned long long)bytenr);
+                       }
+               }
                next = btrfs_find_tree_block(root, bytenr, blocksize);
                if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
                        free_extent_buffer(next);
-                       mutex_unlock(&root->fs_info->alloc_mutex);
-
-                       if (path->slots[*level] == 0)
-                               reada_walk_down(root, cur, path->slots[*level]);
 
                        next = read_tree_block(root, bytenr, blocksize,
                                               ptr_gen);
                        cond_resched();
-                       mutex_lock(&root->fs_info->alloc_mutex);
-
-                       /* we've dropped the lock, double check */
+#if 0
+                       /*
+                        * this is a debugging check and can go away
+                        * the ref should never go all the way down to 1
+                        * at this point
+                        */
                        ret = lookup_extent_ref(NULL, root, bytenr, blocksize,
                                                &refs);
                        BUG_ON(ret);
-                       if (refs != 1) {
-                               parent = path->nodes[*level];
-                               root_owner = btrfs_header_owner(parent);
-                               root_gen = btrfs_header_generation(parent);
-
-                               path->slots[*level]++;
-                               free_extent_buffer(next);
-                               ret = __btrfs_free_extent(trans, root, bytenr,
-                                                       blocksize,
-                                                       root_owner,
-                                                       root_gen, 0, 0, 1);
-                               BUG_ON(ret);
-                               continue;
-                       }
+                       WARN_ON(refs != 1);
+#endif
                }
                WARN_ON(*level <= 0);
                if (path->nodes[*level-1])
@@ -2429,28 +2875,121 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                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) {
-               root_owner = root->root_key.objectid;
                parent = path->nodes[*level];
+               bytenr = path->nodes[*level]->start;
        } else {
                parent = path->nodes[*level + 1];
-               root_owner = btrfs_header_owner(parent);
+               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);
-       ret = __btrfs_free_extent(trans, root, path->nodes[*level]->start,
-                               path->nodes[*level]->len,
-                               root_owner, root_gen, 0, 0, 1);
+
+       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);
-       mutex_unlock(&root->fs_info->alloc_mutex);
+
+       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 int noinline 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);
+
+               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;
 }
@@ -2462,7 +3001,8 @@ out:
  */
 static int noinline walk_up_tree(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
-                                struct btrfs_path *path, int *level)
+                                struct btrfs_path *path,
+                                int *level, int max_level)
 {
        u64 root_owner;
        u64 root_gen;
@@ -2471,7 +3011,7 @@ static int noinline walk_up_tree(struct btrfs_trans_handle *trans,
        int slot;
        int ret;
 
-       for(i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
+       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;
@@ -2486,21 +3026,26 @@ static int noinline walk_up_tree(struct btrfs_trans_handle *trans,
                        root_item->drop_level = i;
                        return 0;
                } else {
-                       if (path->nodes[*level] == root->node) {
-                               root_owner = root->root_key.objectid;
-                               root_gen =
-                                  btrfs_header_generation(path->nodes[*level]);
-                       } else {
-                               struct extent_buffer *node;
-                               node = path->nodes[*level + 1];
-                               root_owner = btrfs_header_owner(node);
-                               root_gen = btrfs_header_generation(node);
-                       }
+                       struct extent_buffer *parent;
+                       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,
-                                               root_owner, root_gen, 0, 0, 1);
+                                               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;
@@ -2570,7 +3115,8 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                if (wret < 0)
                        ret = wret;
 
-               wret = walk_up_tree(trans, root, path, &level);
+               wret = walk_up_tree(trans, root, path, &level,
+                                   BTRFS_MAX_LEVEL);
                if (wret > 0)
                        break;
                if (wret < 0)
@@ -2579,6 +3125,8 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                        ret = -EAGAIN;
                        break;
                }
+               atomic_inc(&root->fs_info->throttle_gen);
+               wake_up(&root->fs_info->transaction_throttle);
        }
        for (i = 0; i <= orig_level; i++) {
                if (path->nodes[i]) {
@@ -2591,35 +3139,48 @@ out:
        return ret;
 }
 
-int btrfs_free_block_groups(struct btrfs_fs_info *info)
+int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
+                       struct btrfs_root *root,
+                       struct extent_buffer *node,
+                       struct extent_buffer *parent)
 {
-       u64 start;
-       u64 end;
-       u64 ptr;
-       int ret;
+       struct btrfs_path *path;
+       int level;
+       int parent_level;
+       int ret = 0;
+       int wret;
 
-       mutex_lock(&info->alloc_mutex);
-       while(1) {
-               ret = find_first_extent_bit(&info->block_group_cache, 0,
-                                           &start, &end, (unsigned int)-1);
-               if (ret)
+       path = btrfs_alloc_path();
+       BUG_ON(!path);
+
+       BUG_ON(!btrfs_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);
+
+       BUG_ON(!btrfs_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;
-               ret = get_state_private(&info->block_group_cache, start, &ptr);
-               if (!ret)
-                       kfree((void *)(unsigned long)ptr);
-               clear_extent_bits(&info->block_group_cache, start,
-                                 end, (unsigned int)-1, GFP_NOFS);
-       }
-       while(1) {
-               ret = find_first_extent_bit(&info->free_space_cache, 0,
-                                           &start, &end, EXTENT_DIRTY);
-               if (ret)
+
+               wret = walk_up_tree(trans, root, path, &level, parent_level);
+               if (wret < 0)
+                       ret = wret;
+               if (wret != 0)
                        break;
-               clear_extent_dirty(&info->free_space_cache, start,
-                                  end, GFP_NOFS);
        }
-       mutex_unlock(&info->alloc_mutex);
-       return 0;
+
+       btrfs_free_path(path);
+       return ret;
 }
 
 static unsigned long calc_ra(unsigned long start, unsigned long last,
@@ -2633,37 +3194,43 @@ static int noinline relocate_inode_pages(struct inode *inode, u64 start,
 {
        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;
-       unsigned long total_read = 0;
-       unsigned long ra_pages;
        struct btrfs_ordered_extent *ordered;
-       struct btrfs_trans_handle *trans;
+       unsigned int total_read = 0;
+       unsigned int total_dirty = 0;
+       int ret = 0;
 
        ra = kzalloc(sizeof(*ra), GFP_NOFS);
 
        mutex_lock(&inode->i_mutex);
-       i = start >> PAGE_CACHE_SHIFT;
+       first_index = start >> PAGE_CACHE_SHIFT;
        last_index = (start + len - 1) >> PAGE_CACHE_SHIFT;
 
-       ra_pages = BTRFS_I(inode)->root->fs_info->bdi.ra_pages;
+       /* 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 <= last_index; i++) {
-               if (total_read % ra_pages == 0) {
+       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_pages));
+                                      calc_ra(i, last_index, ra->ra_pages));
                }
                total_read++;
 again:
                if (((u64)i << PAGE_CACHE_SHIFT) > i_size_read(inode))
-                       goto truncate_racing;
+                       BUG_ON(1);
                page = grab_cache_page(inode->i_mapping, i);
                if (!page) {
+                       ret = -ENOMEM;
                        goto out_unlock;
                }
                if (!PageUptodate(page)) {
@@ -2672,6 +3239,7 @@ again:
                        if (!PageUptodate(page)) {
                                unlock_page(page);
                                page_cache_release(page);
+                               ret = -EIO;
                                goto out_unlock;
                        }
                }
@@ -2692,10 +3260,13 @@ again:
                }
                set_page_extent_mapped(page);
 
+               btrfs_set_extent_delalloc(inode, page_start, page_end);
+               if (i == first_index)
+                       set_extent_bits(io_tree, page_start, page_end,
+                                       EXTENT_BOUNDARY, GFP_NOFS);
 
-               set_extent_delalloc(io_tree, page_start,
-                                   page_end, GFP_NOFS);
                set_page_dirty(page);
+               total_dirty++;
 
                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
                unlock_page(page);
@@ -2703,347 +3274,1393 @@ again:
        }
 
 out_unlock:
-       /* we have to start the IO in order to get the ordered extents
-        * instantiated.  This allows the relocation to code to wait
-        * for all the ordered extents to hit the disk.
-        *
-        * Otherwise, it would constantly loop over the same extents
-        * because the old ones don't get deleted  until the IO is
-        * started
-        */
-       btrfs_fdatawrite_range(inode->i_mapping, start, start + len - 1,
-                              WB_SYNC_NONE);
        kfree(ra);
-       trans = btrfs_start_transaction(BTRFS_I(inode)->root, 1);
-       if (trans) {
-               btrfs_end_transaction(trans, BTRFS_I(inode)->root);
-               mark_inode_dirty(inode);
-       }
        mutex_unlock(&inode->i_mutex);
-       return 0;
-
-truncate_racing:
-       vmtruncate(inode, inode->i_size);
-       balance_dirty_pages_ratelimited_nr(inode->i_mapping,
-                                          total_read);
-       goto out_unlock;
+       balance_dirty_pages_ratelimited_nr(inode->i_mapping, total_dirty);
+       return ret;
 }
 
-/*
- * The back references tell us which tree holds a ref on a block,
- * but it is possible for the tree root field in the reference to
- * reflect the original root before a snapshot was made.  In this
- * case we should search through all the children of a given root
- * to find potential holders of references on a block.
- *
- * Instead, we do something a little less fancy and just search
- * all the roots for a given key/block combination.
- */
-static int find_root_for_ref(struct btrfs_root *root,
-                            struct btrfs_path *path,
-                            struct btrfs_key *key0,
-                            int level,
-                            int file_key,
-                            struct btrfs_root **found_root,
-                            u64 bytenr)
-{
-       struct btrfs_key root_location;
-       struct btrfs_root *cur_root = *found_root;
-       struct btrfs_file_extent_item *file_extent;
-       u64 root_search_start = BTRFS_FS_TREE_OBJECTID;
-       u64 found_bytenr;
-       int ret;
-
-       root_location.offset = (u64)-1;
-       root_location.type = BTRFS_ROOT_ITEM_KEY;
-       path->lowest_level = level;
-       path->reada = 0;
-       while(1) {
-               ret = btrfs_search_slot(NULL, cur_root, key0, path, 0, 0);
-               found_bytenr = 0;
-               if (ret == 0 && file_key) {
-                       struct extent_buffer *leaf = path->nodes[0];
-                       file_extent = btrfs_item_ptr(leaf, path->slots[0],
-                                            struct btrfs_file_extent_item);
-                       if (btrfs_file_extent_type(leaf, file_extent) ==
-                           BTRFS_FILE_EXTENT_REG) {
-                               found_bytenr =
-                                       btrfs_file_extent_disk_bytenr(leaf,
-                                                              file_extent);
-                      }
-               } else if (!file_key) {
-                       if (path->nodes[level])
-                               found_bytenr = path->nodes[level]->start;
-               }
-
-               btrfs_release_path(cur_root, path);
-
-               if (found_bytenr == bytenr) {
-                       *found_root = cur_root;
-                       ret = 0;
-                       goto out;
-               }
-               ret = btrfs_search_root(root->fs_info->tree_root,
-                                       root_search_start, &root_search_start);
-               if (ret)
-                       break;
-
-               root_location.objectid = root_search_start;
-               cur_root = btrfs_read_fs_root_no_name(root->fs_info,
-                                                     &root_location);
-               if (!cur_root) {
-                       ret = 1;
+static int noinline 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);
        }
-out:
-       path->lowest_level = 0;
-       return ret;
+       unlock_extent(&BTRFS_I(reloc_inode)->io_tree, start, end, GFP_NOFS);
+
+       return relocate_inode_pages(reloc_inode, start, extent_key->offset);
 }
 
-/*
- * note, this releases the path
- */
-static int noinline relocate_one_reference(struct btrfs_root *extent_root,
-                                 struct btrfs_path *path,
-                                 struct btrfs_key *extent_key,
-                                 u64 *last_file_objectid,
-                                 u64 *last_file_offset,
-                                 u64 *last_file_root,
-                                 u64 last_extent)
-{
-       struct inode *inode;
-       struct btrfs_root *found_root;
-       struct btrfs_key root_location;
-       struct btrfs_key found_key;
+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)
+               return 1;
+       return 0;
+}
+
+static int noinline __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;
-       u64 ref_root;
-       u64 ref_gen;
-       u64 ref_objectid;
-       u64 ref_offset;
-       int ret;
+       struct btrfs_key key;
+       struct btrfs_key found_key;
+       u64 bytenr;
+       u32 nritems;
        int level;
+       int ret = 1;
 
-       WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
+       path = btrfs_alloc_path();
+       if (!path)
+               return -ENOMEM;
 
-       ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
-                            struct btrfs_extent_ref);
-       ref_root = btrfs_ref_root(path->nodes[0], ref);
-       ref_gen = btrfs_ref_generation(path->nodes[0], ref);
-       ref_objectid = btrfs_ref_objectid(path->nodes[0], ref);
-       ref_offset = btrfs_ref_offset(path->nodes[0], ref);
-       btrfs_release_path(extent_root, path);
+       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;
 
-       root_location.objectid = ref_root;
-       if (ref_gen == 0)
-               root_location.offset = 0;
-       else
-               root_location.offset = (u64)-1;
-       root_location.type = BTRFS_ROOT_ITEM_KEY;
-
-       found_root = btrfs_read_fs_root_no_name(extent_root->fs_info,
-                                               &root_location);
-       BUG_ON(!found_root);
-       mutex_unlock(&extent_root->fs_info->alloc_mutex);
-
-       if (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
-               found_key.objectid = ref_objectid;
-               found_key.type = BTRFS_EXTENT_DATA_KEY;
-               found_key.offset = ref_offset;
-               level = 0;
-
-               if (last_extent == extent_key->objectid &&
-                   *last_file_objectid == ref_objectid &&
-                   *last_file_offset == ref_offset &&
-                   *last_file_root == ref_root)
-                       goto out;
+               if (level >= 0) {
+                       bytenr = ref_path->nodes[level];
+               } else {
+                       bytenr = ref_path->extent_start;
+               }
+               BUG_ON(bytenr == 0);
 
-               ret = find_root_for_ref(extent_root, path, &found_key,
-                                       level, 1, &found_root,
-                                       extent_key->objectid);
+               parent = ref_path->nodes[level + 1];
+               ref_path->nodes[level + 1] = 0;
+               ref_path->current_level = level;
+               BUG_ON(parent == 0);
 
-               if (ret)
+               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;
 
-               if (last_extent == extent_key->objectid &&
-                   *last_file_objectid == ref_objectid &&
-                   *last_file_offset == ref_offset &&
-                   *last_file_root == ref_root)
+               ret = btrfs_search_slot(trans, extent_root, &key, path, 0, 0);
+               if (ret < 0)
                        goto out;
 
-               inode = btrfs_iget_locked(extent_root->fs_info->sb,
-                                         ref_objectid, found_root);
-               if (inode->i_state & I_NEW) {
-                       /* the inode and parent dir are two different roots */
-                       BTRFS_I(inode)->root = found_root;
-                       BTRFS_I(inode)->location.objectid = ref_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);
+               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);
                }
-               /* this can happen if the reference is not against
-                * the latest version of the tree root
+
+               /*
+                * the block is tree root or the block isn't in reference
+                * counted tree.
                 */
-               if (is_bad_inode(inode))
+               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;
+               }
 
-               *last_file_objectid = inode->i_ino;
-               *last_file_root = found_root->root_key.objectid;
-               *last_file_offset = ref_offset;
+               level++;
+               BUG_ON(ref_path->nodes[level] != 0);
+               ref_path->nodes[level] = found_key.offset;
+               ref_path->current_level = level;
 
-               relocate_inode_pages(inode, ref_offset, extent_key->offset);
-               iput(inode);
-       } else {
-               struct btrfs_trans_handle *trans;
-               struct extent_buffer *eb;
-               int needs_lock = 0;
+               /*
+                * 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;
+               }
 
-               eb = read_tree_block(found_root, extent_key->objectid,
-                                    extent_key->offset, 0);
-               btrfs_tree_lock(eb);
-               level = btrfs_header_level(eb);
+               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;
+}
 
-               if (level == 0)
-                       btrfs_item_key_to_cpu(eb, &found_key, 0);
-               else
-                       btrfs_node_key_to_cpu(eb, &found_key, 0);
+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;
 
-               btrfs_tree_unlock(eb);
-               free_extent_buffer(eb);
+       return __next_ref_path(trans, extent_root, ref_path, 1);
+}
 
-               ret = find_root_for_ref(extent_root, path, &found_key,
-                                       level, 0, &found_root,
-                                       extent_key->objectid);
+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);
+}
 
-               if (ret)
+static int noinline 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]++;
+       }
 
-               /*
-                * right here almost anything could happen to our key,
-                * but that's ok.  The cow below will either relocate it
-                * or someone else will have relocated it.  Either way,
-                * it is in a different spot than it was before and
-                * we're happy.
-                */
+       WARN_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 int noinline 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 first_pos;
+       u32 nritems;
+       int nr_scaned = 0;
+       int extent_locked = 0;
+       int extent_type;
+       int ret;
+
+       memcpy(&key, leaf_key, sizeof(key));
+       first_pos = INT_LIMIT(loff_t) - extent_key->offset;
+       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 >= first_pos + extent_key->offset))
+                               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 (first_pos > key.offset - ext_offset)
+                       first_pos = key.offset - ext_offset;
+
+               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 >= first_pos + extent_key->offset)
+                       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 int noinline 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 int noinline 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 int noinline 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 int noinline 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 (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);
+       }
 
-               trans = btrfs_start_transaction(found_root, 1);
+       /*
+        * 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 (found_root == extent_root->fs_info->extent_root ||
-                   found_root == extent_root->fs_info->chunk_root ||
-                   found_root == extent_root->fs_info->dev_root) {
-                       needs_lock = 1;
-                       mutex_lock(&extent_root->fs_info->alloc_mutex);
-               }
+       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);
+       }
 
-               path->lowest_level = level;
-               path->reada = 2;
-               ret = btrfs_search_slot(trans, found_root, &found_key, path,
-                                       0, 1);
-               path->lowest_level = 0;
-               btrfs_release_path(found_root, path);
+       mutex_unlock(&root->fs_info->tree_reloc_mutex);
+       path->lowest_level = 0;
+       return 0;
+}
+
+static int noinline 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;
 
-               if (found_root == found_root->fs_info->extent_root)
-                       btrfs_extent_post_op(trans, found_root);
-               if (needs_lock)
-                       mutex_unlock(&extent_root->fs_info->alloc_mutex);
+       ret = relocate_one_path(trans, root, path, first_key,
+                               ref_path, NULL, NULL);
+       BUG_ON(ret);
 
-               btrfs_end_transaction(trans, found_root);
+       if (root == root->fs_info->extent_root)
+               btrfs_extent_post_op(trans, root);
 
-       }
-out:
-       mutex_lock(&extent_root->fs_info->alloc_mutex);
        return 0;
 }
 
-static int noinline del_extent_zero(struct btrfs_root *extent_root,
+static int noinline del_extent_zero(struct btrfs_trans_handle *trans,
+                                   struct btrfs_root *extent_root,
                                    struct btrfs_path *path,
                                    struct btrfs_key *extent_key)
 {
        int ret;
-       struct btrfs_trans_handle *trans;
 
-       trans = btrfs_start_transaction(extent_root, 1);
        ret = btrfs_search_slot(trans, extent_root, extent_key, path, -1, 1);
-       if (ret > 0) {
-               ret = -EIO;
-               goto out;
-       }
-       if (ret < 0)
+       if (ret)
                goto out;
        ret = btrfs_del_item(trans, extent_root, path);
 out:
-       btrfs_end_transaction(trans, extent_root);
+       btrfs_release_path(extent_root, path);
        return ret;
 }
 
+static struct btrfs_root noinline *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 int noinline relocate_one_extent(struct btrfs_root *extent_root,
                                        struct btrfs_path *path,
-                                       struct btrfs_key *extent_key)
+                                       struct btrfs_key *extent_key,
+                                       struct btrfs_block_group_cache *group,
+                                       struct inode *reloc_inode, int pass)
 {
-       struct btrfs_key key;
-       struct btrfs_key found_key;
-       struct extent_buffer *leaf;
-       u64 last_file_objectid = 0;
-       u64 last_file_root = 0;
-       u64 last_file_offset = (u64)-1;
-       u64 last_extent = 0;
-       u32 nritems;
-       u32 item_size;
-       int ret = 0;
+       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(extent_root, path, extent_key);
+               ret = del_extent_zero(trans, extent_root, path, extent_key);
                goto out;
        }
-       key.objectid = extent_key->objectid;
-       key.type = BTRFS_EXTENT_REF_KEY;
-       key.offset = 0;
 
-       while(1) {
-               ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
+       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;
 
-               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) {
-                               ret = 0;
-                               goto out;
+               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;
                        }
-                       if (ret < 0)
-                               goto out;
-                       leaf = path->nodes[0];
+                       level = 0;
+               } else {
+                       level = ref_path->owner_objectid;
                }
 
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-               if (found_key.objectid != extent_key->objectid) {
-                       break;
-               }
+               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);
 
-               if (found_key.type != BTRFS_EXTENT_REF_KEY) {
-                       break;
+                       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;
                }
 
-               key.offset = found_key.offset + 1;
-               item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+               if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID &&
+                   pass >= 2) {
+                       /*
+                        * 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;
+                       }
+                       btrfs_record_root_in_trans(found_root);
+                       ret = replace_one_extent(trans, found_root,
+                                               path, extent_key,
+                                               &first_key, ref_path,
+                                               new_extents, nr_extents);
+                       if (ret < 0)
+                               goto out;
+                       continue;
+               }
 
-               ret = relocate_one_reference(extent_root, path, extent_key,
-                                            &last_file_objectid,
-                                            &last_file_offset,
-                                            &last_file_root, last_extent);
-               if (ret)
+               btrfs_record_root_in_trans(found_root);
+               if (ref_path->owner_objectid < BTRFS_FIRST_FREE_OBJECTID) {
+                       ret = relocate_tree_block(trans, found_root, path,
+                                                 &first_key, ref_path);
+               } else {
+                       /*
+                        * try to update data extent references while
+                        * keeping metadata shared between snapshots.
+                        */
+                       ret = relocate_one_path(trans, found_root, path,
+                                               &first_key, ref_path,
+                                               group, reloc_inode);
+               }
+               if (ret < 0)
                        goto out;
-               last_extent = extent_key->objectid;
        }
        ret = 0;
 out:
-       btrfs_release_path(extent_root, path);
+       btrfs_end_transaction(trans, extent_root);
+       kfree(new_extents);
+       kfree(ref_path);
        return ret;
 }
 
@@ -3096,10 +4713,8 @@ int __alloc_chunk_for_shrink(struct btrfs_root *root,
        spin_lock(&shrink_block_group->lock);
        if (btrfs_block_group_used(&shrink_block_group->item) > 0) {
                spin_unlock(&shrink_block_group->lock);
-               mutex_unlock(&root->fs_info->alloc_mutex);
 
                trans = btrfs_start_transaction(root, 1);
-               mutex_lock(&root->fs_info->alloc_mutex);
                spin_lock(&shrink_block_group->lock);
 
                new_alloc_flags = update_block_group_flags(root,
@@ -3115,86 +4730,159 @@ int __alloc_chunk_for_shrink(struct btrfs_root *root,
                do_chunk_alloc(trans, root->fs_info->extent_root,
                               calc + 2 * 1024 * 1024, new_alloc_flags, force);
 
-               mutex_unlock(&root->fs_info->alloc_mutex);
                btrfs_end_transaction(trans, root);
-               mutex_lock(&root->fs_info->alloc_mutex);
        } else
                spin_unlock(&shrink_block_group->lock);
        return 0;
 }
 
-int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 shrink_start)
+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;
+
+       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_NODATASUM |
+                                         BTRFS_INODE_NOCOMPRESS);
+       btrfs_mark_buffer_dirty(leaf);
+       btrfs_release_path(root, path);
+out:
+       btrfs_free_path(path);
+       return ret;
+}
+
+static struct inode noinline *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);
+       }
+
+       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_relocate_block_group(struct btrfs_root *root, u64 group_start)
 {
        struct btrfs_trans_handle *trans;
-       struct btrfs_root *tree_root = root->fs_info->tree_root;
        struct btrfs_path *path;
-       u64 cur_byte;
-       u64 total_found;
-       u64 shrink_last_byte;
-       struct btrfs_block_group_cache *shrink_block_group;
        struct btrfs_fs_info *info = root->fs_info;
-       struct btrfs_key key;
-       struct btrfs_key found_key;
        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;
 
-       mutex_lock(&root->fs_info->alloc_mutex);
-       shrink_block_group = btrfs_lookup_block_group(root->fs_info,
-                                                     shrink_start);
-       BUG_ON(!shrink_block_group);
-
-       shrink_last_byte = shrink_block_group->key.objectid +
-               shrink_block_group->key.offset;
-
-       shrink_block_group->space_info->total_bytes -=
-               shrink_block_group->key.offset;
-       path = btrfs_alloc_path();
        root = root->fs_info->extent_root;
-       path->reada = 2;
+
+       block_group = btrfs_lookup_block_group(info, group_start);
+       BUG_ON(!block_group);
 
        printk("btrfs relocating block group %llu flags %llu\n",
-              (unsigned long long)shrink_start,
-              (unsigned long long)shrink_block_group->flags);
+              (unsigned long long)block_group->key.objectid,
+              (unsigned long long)block_group->flags);
 
-       __alloc_chunk_for_shrink(root, shrink_block_group, 1);
+       path = btrfs_alloc_path();
+       BUG_ON(!path);
 
-again:
+       reloc_inode = create_reloc_inode(info, block_group);
+       BUG_ON(IS_ERR(reloc_inode));
 
-       shrink_block_group->ro = 1;
+       __alloc_chunk_for_shrink(root, block_group, 1);
+       block_group->ro = 1;
+       block_group->space_info->total_bytes -= block_group->key.offset;
 
+       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 = shrink_start;
+       key.objectid = block_group->key.objectid;
        key.offset = 0;
        key.type = 0;
        cur_byte = key.objectid;
 
-       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-       if (ret < 0)
-               goto out;
-
-       ret = btrfs_previous_item(root, path, 0, BTRFS_EXTENT_ITEM_KEY);
-       if (ret < 0)
-               goto out;
+       trans = btrfs_start_transaction(info->tree_root, 1);
+       btrfs_commit_transaction(trans, info->tree_root);
 
-       if (ret == 0) {
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-               if (found_key.objectid + found_key.offset > shrink_start &&
-                   found_key.objectid < shrink_last_byte) {
-                       cur_byte = found_key.objectid;
-                       key.objectid = cur_byte;
-               }
-       }
-       btrfs_release_path(root, path);
+       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);
 
        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);
@@ -3210,102 +4898,77 @@ next:
                        nritems = btrfs_header_nritems(leaf);
                }
 
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 
-               if (found_key.objectid >= shrink_last_byte)
+               if (key.objectid >= block_group->key.objectid +
+                   block_group->key.offset)
                        break;
 
                if (progress && need_resched()) {
-                       memcpy(&key, &found_key, sizeof(key));
-                       cond_resched();
                        btrfs_release_path(root, path);
-                       btrfs_search_slot(NULL, root, &key, path, 0, 0);
+                       cond_resched();
                        progress = 0;
-                       goto next;
+                       continue;
                }
                progress = 1;
 
-               if (btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY ||
-                   found_key.objectid + found_key.offset <= cur_byte) {
-                       memcpy(&key, &found_key, sizeof(key));
-                       key.offset++;
+               if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY ||
+                   key.objectid + key.offset <= cur_byte) {
                        path->slots[0]++;
                        goto next;
                }
 
                total_found++;
-               cur_byte = found_key.objectid + found_key.offset;
-               key.objectid = cur_byte;
+               cur_byte = key.objectid + key.offset;
                btrfs_release_path(root, path);
-               ret = relocate_one_extent(root, path, &found_key);
-               __alloc_chunk_for_shrink(root, shrink_block_group, 0);
-       }
 
-       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++;
 
-       if (total_found > 0) {
-               printk("btrfs relocate found %llu last extent was %llu\n",
-                      (unsigned long long)total_found,
-                      (unsigned long long)found_key.objectid);
-               mutex_unlock(&root->fs_info->alloc_mutex);
-               trans = btrfs_start_transaction(tree_root, 1);
-               btrfs_commit_transaction(trans, tree_root);
+               key.objectid = cur_byte;
+               key.type = 0;
+               key.offset = 0;
+       }
 
-               btrfs_clean_old_snapshots(tree_root);
+       btrfs_release_path(root, path);
 
-               btrfs_wait_ordered_extents(tree_root);
+       if (pass == 0) {
+               btrfs_wait_ordered_range(reloc_inode, 0, (u64)-1);
+               invalidate_mapping_pages(reloc_inode->i_mapping, 0, -1);
+               WARN_ON(reloc_inode->i_mapping->nrpages);
+       }
 
-               trans = btrfs_start_transaction(tree_root, 1);
-               btrfs_commit_transaction(trans, tree_root);
-               mutex_lock(&root->fs_info->alloc_mutex);
+       if (total_found > 0) {
+               printk("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;
        }
 
-       /*
-        * we've freed all the extents, now remove the block
-        * group item from the tree
-        */
-       mutex_unlock(&root->fs_info->alloc_mutex);
-
-       trans = btrfs_start_transaction(root, 1);
-
-       mutex_lock(&root->fs_info->alloc_mutex);
-       memcpy(&key, &shrink_block_group->key, sizeof(key));
-
-       ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
-       if (ret > 0)
-               ret = -EIO;
-       if (ret < 0)
-               goto out;
-
-       clear_extent_bits(&info->block_group_cache, key.objectid,
-                         key.objectid + key.offset - 1,
-                         (unsigned int)-1, GFP_NOFS);
-
-
-       clear_extent_bits(&info->free_space_cache,
-                          key.objectid, key.objectid + key.offset - 1,
-                          (unsigned int)-1, GFP_NOFS);
-
-       memset(shrink_block_group, 0, sizeof(*shrink_block_group));
-       kfree(shrink_block_group);
-
-       btrfs_del_item(trans, root, path);
-       btrfs_release_path(root, path);
-       mutex_unlock(&root->fs_info->alloc_mutex);
-       btrfs_commit_transaction(trans, root);
+       /* delete reloc_inode */
+       iput(reloc_inode);
 
-       mutex_lock(&root->fs_info->alloc_mutex);
+       /* unpin extents in this range */
+       trans = btrfs_start_transaction(info->tree_root, 1);
+       btrfs_commit_transaction(trans, info->tree_root);
 
-       /* the code to unpin extents might set a few bits in the free
-        * space cache for this range again
-        */
-       clear_extent_bits(&info->free_space_cache,
-                          key.objectid, key.objectid + key.offset - 1,
-                          (unsigned int)-1, GFP_NOFS);
+       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);
+       ret = 0;
 out:
        btrfs_free_path(path);
-       mutex_unlock(&root->fs_info->alloc_mutex);
        return ret;
 }
 
@@ -3346,20 +5009,42 @@ out:
        return ret;
 }
 
+int btrfs_free_block_groups(struct btrfs_fs_info *info)
+{
+       struct btrfs_block_group_cache *block_group;
+       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);
+               kfree(block_group);
+
+               spin_lock(&info->block_group_cache_lock);
+       }
+       spin_unlock(&info->block_group_cache_lock);
+       return 0;
+}
+
 int btrfs_read_block_groups(struct btrfs_root *root)
 {
        struct btrfs_path *path;
        int ret;
-       int bit;
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_space_info *space_info;
-       struct extent_io_tree *block_group_cache;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
 
-       block_group_cache = &info->block_group_cache;
        root = info->extent_root;
        key.objectid = 0;
        key.offset = 0;
@@ -3368,7 +5053,6 @@ int btrfs_read_block_groups(struct btrfs_root *root)
        if (!path)
                return -ENOMEM;
 
-       mutex_lock(&root->fs_info->alloc_mutex);
        while(1) {
                ret = find_first_block_group(root, path, &key);
                if (ret > 0) {
@@ -3387,6 +5071,8 @@ int btrfs_read_block_groups(struct btrfs_root *root)
                }
 
                spin_lock_init(&cache->lock);
+               mutex_init(&cache->alloc_mutex);
+               INIT_LIST_HEAD(&cache->list);
                read_extent_buffer(leaf, &cache->item,
                                   btrfs_item_ptr_offset(leaf, path->slots[0]),
                                   sizeof(cache->item));
@@ -3395,39 +5081,24 @@ int btrfs_read_block_groups(struct btrfs_root *root)
                key.objectid = found_key.objectid + found_key.offset;
                btrfs_release_path(root, path);
                cache->flags = btrfs_block_group_flags(&cache->item);
-               bit = 0;
-               if (cache->flags & BTRFS_BLOCK_GROUP_DATA) {
-                       bit = BLOCK_GROUP_DATA;
-               } else if (cache->flags & BTRFS_BLOCK_GROUP_SYSTEM) {
-                       bit = BLOCK_GROUP_SYSTEM;
-               } else if (cache->flags & BTRFS_BLOCK_GROUP_METADATA) {
-                       bit = BLOCK_GROUP_METADATA;
-               }
-               set_avail_alloc_bits(info, cache->flags);
 
                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);
 
-               /* use EXTENT_LOCKED to prevent merging */
-               set_extent_bits(block_group_cache, found_key.objectid,
-                               found_key.objectid + found_key.offset - 1,
-                               EXTENT_LOCKED, GFP_NOFS);
-               set_state_private(block_group_cache, found_key.objectid,
-                                 (unsigned long)cache);
-               set_extent_bits(block_group_cache, found_key.objectid,
-                               found_key.objectid + found_key.offset - 1,
-                               bit | EXTENT_LOCKED, GFP_NOFS);
-               if (key.objectid >=
-                   btrfs_super_total_bytes(&info->super_copy))
-                       break;
+               ret = btrfs_add_block_group_cache(root->fs_info, cache);
+               BUG_ON(ret);
+
+               set_avail_alloc_bits(root->fs_info, cache->flags);
        }
        ret = 0;
 error:
        btrfs_free_path(path);
-       mutex_unlock(&root->fs_info->alloc_mutex);
        return ret;
 }
 
@@ -3437,20 +5108,22 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
                           u64 size)
 {
        int ret;
-       int bit = 0;
        struct btrfs_root *extent_root;
        struct btrfs_block_group_cache *cache;
-       struct extent_io_tree *block_group_cache;
 
-       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        extent_root = root->fs_info->extent_root;
-       block_group_cache = &root->fs_info->block_group_cache;
+
+       root->fs_info->last_trans_new_blockgroup = trans->transid;
 
        cache = kzalloc(sizeof(*cache), GFP_NOFS);
-       BUG_ON(!cache);
+       if (!cache)
+               return -ENOMEM;
+
        cache->key.objectid = chunk_offset;
        cache->key.offset = size;
        spin_lock_init(&cache->lock);
+       mutex_init(&cache->alloc_mutex);
+       INIT_LIST_HEAD(&cache->list);
        btrfs_set_key_type(&cache->key, BTRFS_BLOCK_GROUP_ITEM_KEY);
 
        btrfs_set_block_group_used(&cache->item, bytes_used);
@@ -3461,25 +5134,63 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
        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);
 
-       bit = block_group_state_bits(type);
-       set_extent_bits(block_group_cache, chunk_offset,
-                       chunk_offset + size - 1,
-                       EXTENT_LOCKED, GFP_NOFS);
-       set_state_private(block_group_cache, chunk_offset,
-                         (unsigned long)cache);
-       set_extent_bits(block_group_cache, chunk_offset,
-                       chunk_offset + size - 1,
-                       bit | EXTENT_LOCKED, GFP_NOFS);
+       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);
 
-       finish_current_insert(trans, extent_root);
-       ret = del_pending_extents(trans, extent_root);
+       finish_current_insert(trans, extent_root, 0);
+       ret = del_pending_extents(trans, extent_root, 0);
        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);
+
+       memcpy(&key, &block_group->key, sizeof(key));
+
+       path = btrfs_alloc_path();
+       BUG_ON(!path);
+
+       btrfs_remove_free_space_cache(block_group);
+       rb_erase(&block_group->cache_node,
+                &root->fs_info->block_group_cache_tree);
+       down_write(&block_group->space_info->groups_sem);
+       list_del(&block_group->list);
+       up_write(&block_group->space_info->groups_sem);
+
+       /*
+       memset(shrink_block_group, 0, sizeof(*shrink_block_group));
+       kfree(shrink_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;
+}