int btrfs_update_block_group(struct btrfs_trans_handle *trans,
			     u64 bytenr, u64 num_bytes, int alloc)
{
	struct btrfs_fs_info *info = trans->fs_info;
	struct btrfs_block_group *cache = NULL;
	u64 total = num_bytes;
	u64 old_val;
	u64 byte_in_group;
	int factor;
	int ret = 0;

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

	while (total) {
		cache = btrfs_lookup_block_group(info, bytenr);
		if (!cache) {
			ret = -ENOENT;
			break;
		}
		factor = btrfs_bg_type_to_factor(cache->flags);

		/*
		 * If this block group has free space cache written out, we
		 * need to make sure to load it if we are removing space.  This
		 * is because we need the unpinning stage to actually add the
		 * space back to the block group, otherwise we will leak space.
		 */
		if (!alloc && !btrfs_block_group_done(cache))
			btrfs_cache_block_group(cache, 1);

		byte_in_group = bytenr - cache->start;
		WARN_ON(byte_in_group > cache->length);

		spin_lock(&cache->space_info->lock);
		spin_lock(&cache->lock);

		if (btrfs_test_opt(info, SPACE_CACHE) &&
		    cache->disk_cache_state < BTRFS_DC_CLEAR)
			cache->disk_cache_state = BTRFS_DC_CLEAR;

		old_val = cache->used;
		num_bytes = min(total, cache->length - byte_in_group);
		if (alloc) {
			old_val += num_bytes;
			cache->used = old_val;
			cache->reserved -= num_bytes;
			cache->space_info->bytes_reserved -= num_bytes;
			cache->space_info->bytes_used += num_bytes;
			cache->space_info->disk_used += num_bytes * factor;
			spin_unlock(&cache->lock);
			spin_unlock(&cache->space_info->lock);
		} else {
			old_val -= num_bytes;
			cache->used = old_val;
			cache->pinned += num_bytes;
			btrfs_space_info_update_bytes_pinned(info,
					cache->space_info, num_bytes);
			cache->space_info->bytes_used -= num_bytes;
			cache->space_info->disk_used -= num_bytes * factor;
			spin_unlock(&cache->lock);
			spin_unlock(&cache->space_info->lock);

			set_extent_dirty(&trans->transaction->pinned_extents,
					 bytenr, bytenr + num_bytes - 1,
					 GFP_NOFS | __GFP_NOFAIL);
		}

		spin_lock(&trans->transaction->dirty_bgs_lock);
		if (list_empty(&cache->dirty_list)) {
			list_add_tail(&cache->dirty_list,
				      &trans->transaction->dirty_bgs);
			trans->delayed_ref_updates++;
			btrfs_get_block_group(cache);
		}
		spin_unlock(&trans->transaction->dirty_bgs_lock);

		/*
		 * No longer have used bytes in this block group, queue it for
		 * deletion. We do this after adding the block group to the
		 * dirty list to avoid races between cleaner kthread and space
		 * cache writeout.
		 */
		if (!alloc && old_val == 0) {
			if (!btrfs_test_opt(info, DISCARD_ASYNC))
				btrfs_mark_bg_unused(cache);
		}

		btrfs_put_block_group(cache);
		total -= num_bytes;
		bytenr += num_bytes;
	}

	/* Modified block groups are accounted for in the delayed_refs_rsv. */
	btrfs_update_delayed_refs_rsv(trans);
	return ret;
}
int btrfs_update_block_group(struct btrfs_trans_handle *trans,
			     u64 bytenr, u64 num_bytes, int alloc)
{
	struct btrfs_fs_info *info = trans->fs_info;
	struct btrfs_block_group *cache = NULL;
	u64 total = num_bytes;
	u64 old_val;
	u64 byte_in_group;
	int factor;
	int ret = 0;

	 
	spin_lock(&info->delalloc_root_lock);
	old_val = btrfs_super_bytes_used(info->super_copy);
	if (alloc)
		old_val += num_bytes;
	else
		old_val -= num_bytes;
	btrfs_set_super_bytes_used(info->super_copy, old_val);
	spin_unlock(&info->delalloc_root_lock);

	while (total) {
		cache = btrfs_lookup_block_group(info, bytenr);
		if (!cache) {
			ret = -ENOENT;
			break;
		}
		factor = btrfs_bg_type_to_factor(cache->flags);

		 
		if (!alloc && !btrfs_block_group_done(cache))
			btrfs_cache_block_group(cache, 1);

		byte_in_group = bytenr - cache->start;
		WARN_ON(byte_in_group > cache->length);

		spin_lock(&cache->space_info->lock);
		spin_lock(&cache->lock);

		if (btrfs_test_opt(info, SPACE_CACHE) &&
		    cache->disk_cache_state < BTRFS_DC_CLEAR)
			cache->disk_cache_state = BTRFS_DC_CLEAR;

		old_val = cache->used;
		num_bytes = min(total, cache->length - byte_in_group);
		if (alloc) {
			old_val += num_bytes;
			cache->used = old_val;
			cache->reserved -= num_bytes;
			cache->space_info->bytes_reserved -= num_bytes;
			cache->space_info->bytes_used += num_bytes;
			cache->space_info->disk_used += num_bytes * factor;
			spin_unlock(&cache->lock);
			spin_unlock(&cache->space_info->lock);
		} else {
			old_val -= num_bytes;
			cache->used = old_val;
			cache->pinned += num_bytes;
			btrfs_space_info_update_bytes_pinned(info,
					cache->space_info, num_bytes);
			cache->space_info->bytes_used -= num_bytes;
			cache->space_info->disk_used -= num_bytes * factor;
			spin_unlock(&cache->lock);
			spin_unlock(&cache->space_info->lock);

			set_extent_dirty(&trans->transaction->pinned_extents,
					 bytenr, bytenr + num_bytes - 1,
					 GFP_NOFS | __GFP_NOFAIL);
		}

		spin_lock(&trans->transaction->dirty_bgs_lock);
		if (list_empty(&cache->dirty_list)) {
			list_add_tail(&cache->dirty_list,
				      &trans->transaction->dirty_bgs);
			trans->delayed_ref_updates++;
			btrfs_get_block_group(cache);
		}
		spin_unlock(&trans->transaction->dirty_bgs_lock);

		 
		if (!alloc && old_val == 0) {
			if (!btrfs_test_opt(info, DISCARD_ASYNC))
				btrfs_mark_bg_unused(cache);
		}

		btrfs_put_block_group(cache);
		total -= num_bytes;
		bytenr += num_bytes;
	}

	 
	btrfs_update_delayed_refs_rsv(trans);
	return ret;
}