# attempt 1: open fd WITH namecache entry (file linked)
file: 4194304 bytes
holder: opened+unlinked... (attempt 1 used plain open holder)
before umount: 4194304 bytes
umount: unmount of /mnt/df3181 failed: Device busy
umount rc=1 (16 == EBUSY)
after  umount: 4194304 bytes (mount still present: 1)