void check_system_chunk(struct btrfs_trans_handle *trans, u64 type)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_space_info *info;
	u64 left;
	u64 thresh;
	int ret = 0;
	u64 num_devs;

	/*
	 * Needed because we can end up allocating a system chunk and for an
	 * atomic and race free space reservation in the chunk block reserve.
	 */
	lockdep_assert_held(&fs_info->chunk_mutex);

	info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
	spin_lock(&info->lock);
	left = info->total_bytes - btrfs_space_info_used(info, true);
	spin_unlock(&info->lock);

	num_devs = get_profile_num_devs(fs_info, type);

	/* num_devs device items to update and 1 chunk item to add or remove */
	thresh = btrfs_calc_metadata_size(fs_info, num_devs) +
		btrfs_calc_insert_metadata_size(fs_info, 1);

	if (left < thresh && btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
		btrfs_info(fs_info, "left=%llu, need=%llu, flags=%llu",
			   left, thresh, type);
		btrfs_dump_space_info(fs_info, info, 0, 0);
	}

	if (left < thresh) {
		u64 flags = btrfs_system_alloc_profile(fs_info);

		/*
		 * Ignore failure to create system chunk. We might end up not
		 * needing it, as we might not need to COW all nodes/leafs from
		 * the paths we visit in the chunk tree (they were already COWed
		 * or created in the current transaction for example).
		 */
		ret = btrfs_alloc_chunk(trans, flags);
	}

	if (!ret) {
		ret = btrfs_block_rsv_add(fs_info->chunk_root,
					  &fs_info->chunk_block_rsv,
					  thresh, BTRFS_RESERVE_NO_FLUSH);
		if (!ret)
			trans->chunk_bytes_reserved += thresh;
	}
}
void check_system_chunk(struct btrfs_trans_handle *trans, u64 type)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_space_info *info;
	u64 left;
	u64 thresh;
	int ret = 0;
	u64 num_devs;

	 
	lockdep_assert_held(&fs_info->chunk_mutex);

	info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
	spin_lock(&info->lock);
	left = info->total_bytes - btrfs_space_info_used(info, true);
	spin_unlock(&info->lock);

	num_devs = get_profile_num_devs(fs_info, type);

	 
	thresh = btrfs_calc_metadata_size(fs_info, num_devs) +
		btrfs_calc_insert_metadata_size(fs_info, 1);

	if (left < thresh && btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
		btrfs_info(fs_info, "left=%llu, need=%llu, flags=%llu",
			   left, thresh, type);
		btrfs_dump_space_info(fs_info, info, 0, 0);
	}

	if (left < thresh) {
		u64 flags = btrfs_system_alloc_profile(fs_info);

		 
		ret = btrfs_alloc_chunk(trans, flags);
	}

	if (!ret) {
		ret = btrfs_block_rsv_add(fs_info->chunk_root,
					  &fs_info->chunk_block_rsv,
					  thresh, BTRFS_RESERVE_NO_FLUSH);
		if (!ret)
			trans->chunk_bytes_reserved += thresh;
	}
}