int btrfs_balance(struct btrfs_fs_info *fs_info,
		  struct btrfs_balance_control *bctl,
		  struct btrfs_ioctl_balance_args *bargs)
{
	u64 meta_target, data_target;
	u64 allowed;
	int mixed = 0;
	int ret;
	u64 num_devices;
	unsigned seq;
	bool reducing_redundancy;
	int i;

	if (btrfs_fs_closing(fs_info) ||
	    atomic_read(&fs_info->balance_pause_req) ||
	    btrfs_should_cancel_balance(fs_info)) {
		ret = -EINVAL;
		goto out;
	}

	allowed = btrfs_super_incompat_flags(fs_info->super_copy);
	if (allowed & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
		mixed = 1;

	/*
	 * In case of mixed groups both data and meta should be picked,
	 * and identical options should be given for both of them.
	 */
	allowed = BTRFS_BALANCE_DATA | BTRFS_BALANCE_METADATA;
	if (mixed && (bctl->flags & allowed)) {
		if (!(bctl->flags & BTRFS_BALANCE_DATA) ||
		    !(bctl->flags & BTRFS_BALANCE_METADATA) ||
		    memcmp(&bctl->data, &bctl->meta, sizeof(bctl->data))) {
			btrfs_err(fs_info,
	  "balance: mixed groups data and metadata options must be the same");
			ret = -EINVAL;
			goto out;
		}
	}

	/*
	 * rw_devices will not change at the moment, device add/delete/replace
	 * are exclusive
	 */
	num_devices = fs_info->fs_devices->rw_devices;

	/*
	 * SINGLE profile on-disk has no profile bit, but in-memory we have a
	 * special bit for it, to make it easier to distinguish.  Thus we need
	 * to set it manually, or balance would refuse the profile.
	 */
	allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
	for (i = 0; i < ARRAY_SIZE(btrfs_raid_array); i++)
		if (num_devices >= btrfs_raid_array[i].devs_min)
			allowed |= btrfs_raid_array[i].bg_flag;

	if (!validate_convert_profile(fs_info, &bctl->data, allowed, "data") ||
	    !validate_convert_profile(fs_info, &bctl->meta, allowed, "metadata") ||
	    !validate_convert_profile(fs_info, &bctl->sys,  allowed, "system")) {
		ret = -EINVAL;
		goto out;
	}

	/*
	 * Allow to reduce metadata or system integrity only if force set for
	 * profiles with redundancy (copies, parity)
	 */
	allowed = 0;
	for (i = 0; i < ARRAY_SIZE(btrfs_raid_array); i++) {
		if (btrfs_raid_array[i].ncopies >= 2 ||
		    btrfs_raid_array[i].tolerated_failures >= 1)
			allowed |= btrfs_raid_array[i].bg_flag;
	}
	do {
		seq = read_seqbegin(&fs_info->profiles_lock);

		if (((bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
		     (fs_info->avail_system_alloc_bits & allowed) &&
		     !(bctl->sys.target & allowed)) ||
		    ((bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
		     (fs_info->avail_metadata_alloc_bits & allowed) &&
		     !(bctl->meta.target & allowed)))
			reducing_redundancy = true;
		else
			reducing_redundancy = false;

		/* if we're not converting, the target field is uninitialized */
		meta_target = (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
			bctl->meta.target : fs_info->avail_metadata_alloc_bits;
		data_target = (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
			bctl->data.target : fs_info->avail_data_alloc_bits;
	} while (read_seqretry(&fs_info->profiles_lock, seq));

	if (reducing_redundancy) {
		if (bctl->flags & BTRFS_BALANCE_FORCE) {
			btrfs_info(fs_info,
			   "balance: force reducing metadata redundancy");
		} else {
			btrfs_err(fs_info,
	"balance: reduces metadata redundancy, use --force if you want this");
			ret = -EINVAL;
			goto out;
		}
	}

	if (btrfs_get_num_tolerated_disk_barrier_failures(meta_target) <
		btrfs_get_num_tolerated_disk_barrier_failures(data_target)) {
		btrfs_warn(fs_info,
	"balance: metadata profile %s has lower redundancy than data profile %s",
				btrfs_bg_type_to_raid_name(meta_target),
				btrfs_bg_type_to_raid_name(data_target));
	}

	ret = insert_balance_item(fs_info, bctl);
	if (ret && ret != -EEXIST)
		goto out;

	if (!(bctl->flags & BTRFS_BALANCE_RESUME)) {
		BUG_ON(ret == -EEXIST);
		BUG_ON(fs_info->balance_ctl);
		spin_lock(&fs_info->balance_lock);
		fs_info->balance_ctl = bctl;
		spin_unlock(&fs_info->balance_lock);
	} else {
		BUG_ON(ret != -EEXIST);
		spin_lock(&fs_info->balance_lock);
		update_balance_args(bctl);
		spin_unlock(&fs_info->balance_lock);
	}

	ASSERT(!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
	set_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
	describe_balance_start_or_resume(fs_info);
	mutex_unlock(&fs_info->balance_mutex);

	ret = __btrfs_balance(fs_info);

	mutex_lock(&fs_info->balance_mutex);
	if (ret == -ECANCELED && atomic_read(&fs_info->balance_pause_req))
		btrfs_info(fs_info, "balance: paused");
	/*
	 * Balance can be canceled by:
	 *
	 * - Regular cancel request
	 *   Then ret == -ECANCELED and balance_cancel_req > 0
	 *
	 * - Fatal signal to "btrfs" process
	 *   Either the signal caught by wait_reserve_ticket() and callers
	 *   got -EINTR, or caught by btrfs_should_cancel_balance() and
	 *   got -ECANCELED.
	 *   Either way, in this case balance_cancel_req = 0, and
	 *   ret == -EINTR or ret == -ECANCELED.
	 *
	 * So here we only check the return value to catch canceled balance.
	 */
	else if (ret == -ECANCELED || ret == -EINTR)
		btrfs_info(fs_info, "balance: canceled");
	else
		btrfs_info(fs_info, "balance: ended with status: %d", ret);

	clear_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);

	if (bargs) {
		memset(bargs, 0, sizeof(*bargs));
		btrfs_update_ioctl_balance_args(fs_info, bargs);
	}

	if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
	    balance_need_close(fs_info)) {
		reset_balance_state(fs_info);
		btrfs_exclop_finish(fs_info);
	}

	wake_up(&fs_info->balance_wait_q);

	return ret;
out:
	if (bctl->flags & BTRFS_BALANCE_RESUME)
		reset_balance_state(fs_info);
	else
		kfree(bctl);
	btrfs_exclop_finish(fs_info);

	return ret;
}