Comment 27 for bug 37768

Unless I'm mistaken the bug is caused by gparted telling the kernel to re-read the partition tables so that it knows that's it's resizing what it says it's resizing. If it's true that parted doesn't do that by itself then you've got an excellent argument against gparted doing that and I'd highly recommend suggesting it upstream. You can see, though, why it might be a good idea to make sure the tables haven't changed underneath you, but on the other hand if you're editing partition tables with two different programs at the same time you've got bigger problems.

The solution I'd like to see to this would be a d-bus interface for gparted to tell gnome-volume-manager to not mount partitions on the drive it's editing (or re-reading).