Btrfs subvolume quota still in its infancy with btrfs version 4.2.2

Ever tried to dive into the btrfs subvolume topic, especially in combination with quotas (not snapshots here)? Looks really promising… administring subvolumes in hierarchies automagically offers managing quotas on (summed up) top- and on (dedicated) sub-levels by design, see : Btrfs SysadminGuide Subvolumes or Btrfs: Subvolumes and snapshots for example. With the later 4.x kernels there is btrfs 4.2.2, representing a huge step forward in btrfs development, so thought to give it another try on a red hat / oracle uek based 7.2 system.

Following, I’m going to show what I attempted to achive, the how-to’s, the workarounds I tried and, intermixed, the quite odd behaviour that I observed. Odd to an magnitude, that makes me recommed everyone to stay averse against employing this promising but still semifinished (?) technology.

The setup of a subvolume, dedicated for quota control is quite easy and takes only a couple of keystrokes. Understand though, that quota control with btrfs can only be enabled throughout the entire filesystem but can then be set to a value dedicatetly.