The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.

4.5 Resizing a Btrfs File System

You can use the btrfs command to increase the size of a mounted btrfs file system if there is space on the underlying devices to accommodate the change, or to decrease its size if the file system has sufficient available free space. The command does not have any effect on the layout or size of the underlying devices.

For example, to increase the size of /mybtrfs1 by 2 GB:

# btrfs filesystem resize +2g /mybtrfs1

Decrease the size of /mybtrfs2 by 4 GB:

# btrfs filesystem resize -4g /mybtrfs2

Set the size of /mybtrfs3 to 20 GB:

# btrfs filesystem resize 20g /mybtrfs3