# attempt 2: holder opens the file then UNLINKS it (no namecache entry, fd only)
file: 4194304 bytes
holder: opened+unlinked, initial st_size=4194304
=== attempting non-forced umount ===
umount: unmount of /mnt/df3181 failed: Device busy
umount rc=1
--- holder:
holder: opened+unlinked, initial st_size=4194304
holder: t+1..t+16 st_size=4194304        (NEVER truncated)
--- mounts: 1
cleanup umount rc=0
# console at cleanup: "unmount(/mnt/df3181): forced umount of (null) - 1 namecache refs, 1 mount refs"
# => dounmount bailed at its mnt_refs loop BEFORE VFS_UNMOUNT; tmpfs_unmount never ran.