When calculating VG size and free space in the VG, blivet doesn't check the size of the LVM PV format, but assumes it has the same size as the underlying device. This leads to wrong assumption about VG size and free space when the PV format is smaller than the device when for example the underlying block device was resized.

Example of wrong values for a 5 GiB VG:

# vgs test
  VG   #PV #LV #SN Attr   VSize  VFree 
  test   1   0   0 wz--n- <5.00g <5.00g

blivet values:

In [1]: import blivet; b=blivet.Blivet(); b.reset()
In [2]: test = b.devicetree.get_device_by_name("test")
In [3]: test.size
Out[3]: Size (9.99609375 GiB)
In [4]: test.free_space
Out[4]: Size (9.99609375 GiB)

See also this upstream issue: https://github.com/storaged-project/blivet/issues/1320