WebUI feature request: grow btrfs filesystem on expanded Virtual Disk

[Hooverdan96]

Reported by @goremaker on the Rockstor forum: (https://forum.rockstor.com/t/rockstor-not-recognizing-expanded-storage-size/9340)

When using Rockstor in a VM setup (Proxmox, Virtualbox, etc.) and an existing btrfs storage disk is increased in size, there is currently no option to automatically or manually increase the filesystem to the enlarged portion of the disk. This was not considered a valid scenario originally (due to the design intent of offering Rockstor as an appliance with its own dedicated hardware, aka built on bar metal).

However, as observed in the forum in this and other threads, users are starting to multi-purpose server hardware (due to increased capabilities/performance that has become more affordable compared to 10 years ago) which can be addressed by virtualizing appliances like Rockstor.

The current approach to expand a filesystem to the full disk after a resizing of said virtual disk is to execute this at the command line using

btrfs filesystem resize <devid> max <mnt>

as described here: btrfs filesystem resize

Request is to incorporate this into the WebUI:

• recognize the changed device size on the disk page
• allow for expansion of filesystem to increased size
• optional: create a workflow that allows for automatic resizing of the filesystem, if the underlying device is "grown"