OSError: Not enough disk space.
{'login': 'qqaatw', 'id': 24835382, 'node_id': 'MDQ6VXNlcjI0ODM1Mzgy', 'avatar_url': 'https://avatars.githubusercontent.com/u/24835382?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/qqaatw', 'html_url': 'https://github.com/qqaatw', 'followers_url': 'https://api.github.com/users/qqaatw/followers', 'following_url': 'https://api.github.com/users/qqaatw/following{/other_user}', 'gists_url': 'https://api.github.com/users/qqaatw/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/qqaatw/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/qqaatw/subscriptions', 'organizations_url': 'https://api.github.com/users/qqaatw/orgs', 'repos_url': 'https://api.github.com/users/qqaatw/repos', 'events_url': 'https://api.github.com/users/qqaatw/events{/privacy}', 'received_events_url': 'https://api.github.com/users/qqaatw/received_events', 'type': 'User', 'site_admin': False}
[{'id': 1935892857, 'node_id': 'MDU6TGFiZWwxOTM1ODkyODU3', 'url': 'https://api.github.com/repos/huggingface/datasets/labels/bug', 'name': 'bug', 'color': 'd73a4a', 'default': True, 'description': "Something isn't working"}]
{'login': 'albertvillanova', 'id': 8515462, 'node_id': 'MDQ6VXNlcjg1MTU0NjI=', 'avatar_url': 'https://avatars.githubusercontent.com/u/8515462?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/albertvillanova', 'html_url': 'https://github.com/albertvillanova', 'followers_url': 'https://api.github.com/users/albertvillanova/followers', 'following_url': 'https://api.github.com/users/albertvillanova/following{/other_user}', 'gists_url': 'https://api.github.com/users/albertvillanova/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/albertvillanova/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/albertvillanova/subscriptions', 'organizations_url': 'https://api.github.com/users/albertvillanova/orgs', 'repos_url': 'https://api.github.com/users/albertvillanova/repos', 'events_url': 'https://api.github.com/users/albertvillanova/events{/privacy}', 'received_events_url': 'https://api.github.com/users/albertvillanova/received_events', 'type': 'User', 'site_admin': False}
[{'login': 'albertvillanova', 'id': 8515462, 'node_id': 'MDQ6VXNlcjg1MTU0NjI=', 'avatar_url': 'https://avatars.githubusercontent.com/u/8515462?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/albertvillanova', 'html_url': 'https://github.com/albertvillanova', 'followers_url': 'https://api.github.com/users/albertvillanova/followers', 'following_url': 'https://api.github.com/users/albertvillanova/following{/other_user}', 'gists_url': 'https://api.github.com/users/albertvillanova/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/albertvillanova/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/albertvillanova/subscriptions', 'organizations_url': 'https://api.github.com/users/albertvillanova/orgs', 'repos_url': 'https://api.github.com/users/albertvillanova/repos', 'events_url': 'https://api.github.com/users/albertvillanova/events{/privacy}', 'received_events_url': 'https://api.github.com/users/albertvillanova/received_events', 'type': 'User', 'site_admin': False}]
["Maybe we can change the disk space calculating API from `shutil.disk_usage` to  `os.statvfs` in UNIX-like system, which can provide correct results.\r\n```\r\nstatvfs = os.statvfs('path')\r\navail_space_bytes = statvfs.f_frsize * statvfs.f_bavail\r\n```"
 'Hi @qqaatw, thanks for reporting.\r\n\r\nCould you please try:\r\n```python\r\ndataset = load_dataset("natural_questions", cache_dir=os.path.abspath(args.dataset_cache_dir))\r\n```'
 '@albertvillanova it works! Thanks for your suggestion. Is that a bug of `DownloadConfig`?'
 '`DownloadConfig` only sets the location to download the files. On the other hand, `cache_dir` sets the location for both downloading and caching the data. You can find more information here: https://huggingface.co/docs/datasets/loading_datasets.html#cache-directory']
## Describe the bug
I'm trying to download `natural_questions` dataset from the Internet, and I've specified the cache_dir which locates in a mounted disk and has enough disk space. However, even though the space is enough, the disk space checking function still reports the space of root `/` disk having no enough space. 

The file system structure is like below. The root `/` has `115G` disk space available, and the `sda1` is mounted to `/mnt`, which has `1.2T` disk space available:
```
/
/mnt/sda1/path/to/args.dataset_cache_dir 
```

## Steps to reproduce the bug
```python
dataset_config = DownloadConfig(
    cache_dir=os.path.abspath(args.dataset_cache_dir),
    resume_download=True,
)
dataset = load_dataset("natural_questions", download_config=dataset_config)
```

## Expected results

Can download the dataset without an error.

## Actual results

The following error raised:
```
OSError: Not enough disk space. Needed: 134.92 GiB (download: 41.97 GiB, generated: 92.95 GiB, post-processed: Unknown size)
```

## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.9.0
- Platform: Ubuntu 18.04
- Python version: 3.8.10
- PyArrow version:

{'url': 'https://api.github.com/repos/huggingface/datasets/issues/2972/reactions', 'total_count': 0, '+1': 0, '-1': 0, 'laugh': 0, 'hooray': 0, 'confused': 0, 'heart': 0, 'rocket': 0, 'eyes': 0}