Worker volumes out of disk space

I have 64G on /opt/concourse/worker
The worker has created /opt/concourse/worker/volumes on /dev/loop2 with only 5.7G of space and now 1.5G free

Now when I run a pipeline /dev/loop2 get filled.

How do I persuade the worker to allocate more space for its volumes ?

Ah, if anyone else has this problem do

btrfs filesystem resize max /opt/concourse/worker/volumes

When you grow the underlying ext filesystem concourse does not grow its loop filesystem

I believe by default it sizes the volumes mount to 90% of the disk size. (Leaving 10% free)

Thanks @eedwards-sk,
what happened is that I ran out of space so I grew the ext filesystem. It seems that concourse allocated the additional space to the volume because the image file was larger. However it did not automatically grow the btrfs filesystem inside the image.
I had to do that manually.