root->objectid = objectid;
        root->last_trans = 0;
        root->highest_objectid = 0;
+       root->nr_delalloc_inodes = 0;
        root->name = NULL;
        root->inode_tree = RB_ROOT;
        INIT_RADIX_TREE(&root->delayed_nodes_tree, GFP_ATOMIC);
 
        INIT_LIST_HEAD(&root->dirty_list);
        INIT_LIST_HEAD(&root->root_list);
+       INIT_LIST_HEAD(&root->delalloc_inodes);
+       INIT_LIST_HEAD(&root->delalloc_root);
        INIT_LIST_HEAD(&root->logged_list[0]);
        INIT_LIST_HEAD(&root->logged_list[1]);
        spin_lock_init(&root->orphan_lock);
        spin_lock_init(&root->inode_lock);
+       spin_lock_init(&root->delalloc_lock);
        spin_lock_init(&root->accounting_lock);
        spin_lock_init(&root->log_extents_lock[0]);
        spin_lock_init(&root->log_extents_lock[1]);
        INIT_LIST_HEAD(&fs_info->trans_list);
        INIT_LIST_HEAD(&fs_info->dead_roots);
        INIT_LIST_HEAD(&fs_info->delayed_iputs);
-       INIT_LIST_HEAD(&fs_info->delalloc_inodes);
+       INIT_LIST_HEAD(&fs_info->delalloc_roots);
        INIT_LIST_HEAD(&fs_info->caching_block_groups);
-       spin_lock_init(&fs_info->delalloc_lock);
+       spin_lock_init(&fs_info->delalloc_root_lock);
        spin_lock_init(&fs_info->trans_lock);
        spin_lock_init(&fs_info->fs_roots_radix_lock);
        spin_lock_init(&fs_info->delayed_iput_lock);
 
        INIT_LIST_HEAD(&splice);
 
-       spin_lock(&root->fs_info->delalloc_lock);
-       list_splice_init(&root->fs_info->delalloc_inodes, &splice);
+       spin_lock(&root->delalloc_lock);
+       list_splice_init(&root->delalloc_inodes, &splice);
 
        while (!list_empty(&splice)) {
-               btrfs_inode = list_entry(splice.next, struct btrfs_inode,
-                                   delalloc_inodes);
+               btrfs_inode = list_first_entry(&splice, struct btrfs_inode,
+                                              delalloc_inodes);
 
                list_del_init(&btrfs_inode->delalloc_inodes);
                clear_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                          &btrfs_inode->runtime_flags);
-               spin_unlock(&root->fs_info->delalloc_lock);
+               spin_unlock(&root->delalloc_lock);
 
                btrfs_invalidate_inodes(btrfs_inode->root);
 
-               spin_lock(&root->fs_info->delalloc_lock);
+               spin_lock(&root->delalloc_lock);
        }
 
-       spin_unlock(&root->fs_info->delalloc_lock);
+       spin_unlock(&root->delalloc_lock);
+}
+
+static void btrfs_destroy_all_delalloc_inodes(struct btrfs_fs_info *fs_info)
+{
+       struct btrfs_root *root;
+       struct list_head splice;
+
+       INIT_LIST_HEAD(&splice);
+
+       spin_lock(&fs_info->delalloc_root_lock);
+       list_splice_init(&fs_info->delalloc_roots, &splice);
+       while (!list_empty(&splice)) {
+               root = list_first_entry(&splice, struct btrfs_root,
+                                        delalloc_root);
+               list_del_init(&root->delalloc_root);
+               root = btrfs_grab_fs_root(root);
+               BUG_ON(!root);
+               spin_unlock(&fs_info->delalloc_root_lock);
+
+               btrfs_destroy_delalloc_inodes(root);
+               btrfs_put_fs_root(root);
+
+               spin_lock(&fs_info->delalloc_root_lock);
+       }
+       spin_unlock(&fs_info->delalloc_root_lock);
 }
 
 static int btrfs_destroy_marked_extents(struct btrfs_root *root,
                btrfs_destroy_delayed_inodes(root);
                btrfs_assert_delayed_root_empty(root);
 
-               btrfs_destroy_delalloc_inodes(root);
+               btrfs_destroy_all_delalloc_inodes(root->fs_info);
 
                spin_lock(&root->fs_info->trans_lock);
                root->fs_info->running_transaction = NULL;
 
        spin_unlock(&BTRFS_I(inode)->lock);
 }
 
+static void btrfs_add_delalloc_inodes(struct btrfs_root *root,
+                                     struct inode *inode)
+{
+       spin_lock(&root->delalloc_lock);
+       if (list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
+               list_add_tail(&BTRFS_I(inode)->delalloc_inodes,
+                             &root->delalloc_inodes);
+               set_bit(BTRFS_INODE_IN_DELALLOC_LIST,
+                       &BTRFS_I(inode)->runtime_flags);
+               root->nr_delalloc_inodes++;
+               if (root->nr_delalloc_inodes == 1) {
+                       spin_lock(&root->fs_info->delalloc_root_lock);
+                       BUG_ON(!list_empty(&root->delalloc_root));
+                       list_add_tail(&root->delalloc_root,
+                                     &root->fs_info->delalloc_roots);
+                       spin_unlock(&root->fs_info->delalloc_root_lock);
+               }
+       }
+       spin_unlock(&root->delalloc_lock);
+}
+
+static void btrfs_del_delalloc_inode(struct btrfs_root *root,
+                                    struct inode *inode)
+{
+       spin_lock(&root->delalloc_lock);
+       if (!list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
+               list_del_init(&BTRFS_I(inode)->delalloc_inodes);
+               clear_bit(BTRFS_INODE_IN_DELALLOC_LIST,
+                         &BTRFS_I(inode)->runtime_flags);
+               root->nr_delalloc_inodes--;
+               if (!root->nr_delalloc_inodes) {
+                       spin_lock(&root->fs_info->delalloc_root_lock);
+                       BUG_ON(list_empty(&root->delalloc_root));
+                       list_del_init(&root->delalloc_root);
+                       spin_unlock(&root->fs_info->delalloc_root_lock);
+               }
+       }
+       spin_unlock(&root->delalloc_lock);
+}
+
 /*
  * extent_io.c set_bit_hook, used to track delayed allocation
  * bytes in this file, and to maintain the list of inodes that
                spin_lock(&BTRFS_I(inode)->lock);
                BTRFS_I(inode)->delalloc_bytes += len;
                if (do_list && !test_bit(BTRFS_INODE_IN_DELALLOC_LIST,
-                                        &BTRFS_I(inode)->runtime_flags)) {
-                       spin_lock(&root->fs_info->delalloc_lock);
-                       if (list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
-                               list_add_tail(&BTRFS_I(inode)->delalloc_inodes,
-                                             &root->fs_info->delalloc_inodes);
-                               set_bit(BTRFS_INODE_IN_DELALLOC_LIST,
-                                       &BTRFS_I(inode)->runtime_flags);
-                       }
-                       spin_unlock(&root->fs_info->delalloc_lock);
-               }
+                                        &BTRFS_I(inode)->runtime_flags))
+                       btrfs_add_delalloc_inodes(root, inode);
                spin_unlock(&BTRFS_I(inode)->lock);
        }
 }
                BTRFS_I(inode)->delalloc_bytes -= len;
                if (do_list && BTRFS_I(inode)->delalloc_bytes == 0 &&
                    test_bit(BTRFS_INODE_IN_DELALLOC_LIST,
-                            &BTRFS_I(inode)->runtime_flags)) {
-                       spin_lock(&root->fs_info->delalloc_lock);
-                       if (!list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
-                               list_del_init(&BTRFS_I(inode)->delalloc_inodes);
-                               clear_bit(BTRFS_INODE_IN_DELALLOC_LIST,
-                                         &BTRFS_I(inode)->runtime_flags);
-                       }
-                       spin_unlock(&root->fs_info->delalloc_lock);
-               }
+                            &BTRFS_I(inode)->runtime_flags))
+                       btrfs_del_delalloc_inode(root, inode);
                spin_unlock(&BTRFS_I(inode)->lock);
        }
 }
  * some fairly slow code that needs optimization. This walks the list
  * of all the inodes with pending delalloc and forces them to disk.
  */
-int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
+static int __start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
 {
        struct btrfs_inode *binode;
        struct inode *inode;
        struct list_head splice;
        int ret = 0;
 
-       if (root->fs_info->sb->s_flags & MS_RDONLY)
-               return -EROFS;
-
        INIT_LIST_HEAD(&works);
        INIT_LIST_HEAD(&splice);
 
-       spin_lock(&root->fs_info->delalloc_lock);
-       list_splice_init(&root->fs_info->delalloc_inodes, &splice);
+       spin_lock(&root->delalloc_lock);
+       list_splice_init(&root->delalloc_inodes, &splice);
        while (!list_empty(&splice)) {
                binode = list_entry(splice.next, struct btrfs_inode,
                                    delalloc_inodes);
 
-               list_del_init(&binode->delalloc_inodes);
-
+               list_move_tail(&binode->delalloc_inodes,
+                              &root->delalloc_inodes);
                inode = igrab(&binode->vfs_inode);
                if (!inode) {
-                       clear_bit(BTRFS_INODE_IN_DELALLOC_LIST,
-                                 &binode->runtime_flags);
+                       cond_resched_lock(&root->delalloc_lock);
                        continue;
                }
-
-               list_add_tail(&binode->delalloc_inodes,
-                             &root->fs_info->delalloc_inodes);
-               spin_unlock(&root->fs_info->delalloc_lock);
+               spin_unlock(&root->delalloc_lock);
 
                work = btrfs_alloc_delalloc_work(inode, 0, delay_iput);
                if (unlikely(!work)) {
                                   &work->work);
 
                cond_resched();
-               spin_lock(&root->fs_info->delalloc_lock);
+               spin_lock(&root->delalloc_lock);
        }
-       spin_unlock(&root->fs_info->delalloc_lock);
+       spin_unlock(&root->delalloc_lock);
 
        list_for_each_entry_safe(work, next, &works, list) {
                list_del_init(&work->list);
                btrfs_wait_and_free_delalloc_work(work);
        }
+       return 0;
+out:
+       list_for_each_entry_safe(work, next, &works, list) {
+               list_del_init(&work->list);
+               btrfs_wait_and_free_delalloc_work(work);
+       }
+
+       if (!list_empty_careful(&splice)) {
+               spin_lock(&root->delalloc_lock);
+               list_splice_tail(&splice, &root->delalloc_inodes);
+               spin_unlock(&root->delalloc_lock);
+       }
+       return ret;
+}
 
-       /* the filemap_flush will queue IO into the worker threads, but
+int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
+{
+       int ret;
+
+       if (root->fs_info->sb->s_flags & MS_RDONLY)
+               return -EROFS;
+
+       ret = __start_delalloc_inodes(root, delay_iput);
+       /*
+        * the filemap_flush will queue IO into the worker threads, but
         * we have to make sure the IO is actually started and that
         * ordered extents get created before we return
         */
                    atomic_read(&root->fs_info->async_delalloc_pages) == 0));
        }
        atomic_dec(&root->fs_info->async_submit_draining);
-       return 0;
-out:
-       list_for_each_entry_safe(work, next, &works, list) {
-               list_del_init(&work->list);
-               btrfs_wait_and_free_delalloc_work(work);
+       return ret;
+}
+
+int btrfs_start_all_delalloc_inodes(struct btrfs_fs_info *fs_info,
+                                   int delay_iput)
+{
+       struct btrfs_root *root;
+       struct list_head splice;
+       int ret;
+
+       if (fs_info->sb->s_flags & MS_RDONLY)
+               return -EROFS;
+
+       INIT_LIST_HEAD(&splice);
+
+       spin_lock(&fs_info->delalloc_root_lock);
+       list_splice_init(&fs_info->delalloc_roots, &splice);
+       while (!list_empty(&splice)) {
+               root = list_first_entry(&splice, struct btrfs_root,
+                                       delalloc_root);
+               root = btrfs_grab_fs_root(root);
+               BUG_ON(!root);
+               list_move_tail(&root->delalloc_root,
+                              &fs_info->delalloc_roots);
+               spin_unlock(&fs_info->delalloc_root_lock);
+
+               ret = __start_delalloc_inodes(root, delay_iput);
+               btrfs_put_fs_root(root);
+               if (ret)
+                       goto out;
+
+               spin_lock(&fs_info->delalloc_root_lock);
        }
+       spin_unlock(&fs_info->delalloc_root_lock);
 
+       atomic_inc(&fs_info->async_submit_draining);
+       while (atomic_read(&fs_info->nr_async_submits) ||
+             atomic_read(&fs_info->async_delalloc_pages)) {
+               wait_event(fs_info->async_submit_wait,
+                  (atomic_read(&fs_info->nr_async_submits) == 0 &&
+                   atomic_read(&fs_info->async_delalloc_pages) == 0));
+       }
+       atomic_dec(&fs_info->async_submit_draining);
+       return 0;
+out:
        if (!list_empty_careful(&splice)) {
-               spin_lock(&root->fs_info->delalloc_lock);
-               list_splice_tail(&splice, &root->fs_info->delalloc_inodes);
-               spin_unlock(&root->fs_info->delalloc_lock);
+               spin_lock(&fs_info->delalloc_root_lock);
+               list_splice_tail(&splice, &fs_info->delalloc_roots);
+               spin_unlock(&fs_info->delalloc_root_lock);
        }
        return ret;
 }