GParted 0.8.1 --enable-libparted-dmraid

Libparted 2.3
Format /dev/sdb5 as linux-swap  00:00:01    ( ERROR )

calibrate /dev/sdb5  00:00:00    ( SUCCESS )

path: /dev/sdb5
start: 29298688
end: 37296127
size: 7997440 (3.81 GiB)
set partition type on /dev/sdb5  00:00:01    ( SUCCESS )

new partition type: linux-swap(v1)
create new linux-swap file system  00:00:00    ( ERROR )

mkswap -L "" /dev/sdb5

/dev/sdb5: Device or resource busy

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