storage: incorrect (0) usage information for unmounted btrfs subvolume

[KKoukiou]

Page: Storage

Before mounting:

After mounting:

Since we can't get this info before mounting maybe we should not show that at all?

[garrett]

It'd be great to have the usage without mounting, but if we can't do that, I agree that we shouldn't show it. We already have size.

Aside: Oddly, size and usage have different amounts. Size has 12.8 GB and usage shows 13 GB. Where does the 0.2 GB come from? Are there rounding-related errors?

[jkonecny12]

In general it's quite problematic for Anaconda that Cockpit Storage requires to mount volume before it can start working with subvolumes.
The issue is that volume is not really usable when mounted (at least not recommended) so forcing user to set mount point and everything is confusing. This is especially true in Anaconda where we are taking these mount points for installation and (correctly) skipping the volume mount.

[garrett]

In general it's quite problematic for Anaconda that Cockpit Storage requires to mount volume before it can start working with subvolumes. The issue is that volume is not really usable when mounted (at least not recommended) so forcing user to set mount point and everything is confusing. This is especially true in Anaconda where we are taking these mount points for installation and (correctly) skipping the volume mount.

Filed more generally about having to mount to perform operations @ #20855

(I consider this particular issue as different, as it would be solved by removing the usage when we can't show it. And the other is the more general case for all explicit actions that require mounting.)