Unable to umount union-parts after umounting unionfs

From: Philip Paeps (philip_at_freebsd.org)
Date: 06/22/05

  • Next message: Philip Paeps: "Re: acpi_fujitsu not working" 
    Date: Wed, 22 Jun 2005 08:53:57 +0200
To: freebsd-current@freebsd.org

    When playing with union filesystems this morning, I noticed that it's not
    possible to unmount the directory mounted on union cleanly, even after the
    union has been cleanly unmounted, once you've read from the union:

    Setup:

    # touch fs1 fs2
    # mkdir tstfs
    # mdconfig -a -t vnode -f fs1 -s 16M
    # mdconfig -a -t vnode -f fs2 -s 16M
    # newfs /dev/md0
    # newfs /dev/md1
    # mount /dev/md0 tstfs/
    # mount /dev/md1 /mnt
    # mount -t unionfs /mnt tstfs/

    Trying to umount /mnt now fails as expected:

    # umount /mnt
    umount: unmount of /mnt failed: Device busy

    Unmounting after the union has been unmounted without anything having been
    read from it or written to it, is no problem either:

    # umount tstfs/
    # umount /mnt

    When something has been written to the union, but nothing has been read from
    it, there's not problem either:

    # touch tstfs/foo
    # umount tstfs/
    # umount /mnt

    When something has been read, however:

    # ls tstfs/
    .snap/ foo
    # umount tstfs/
    # umount /mnt
    umount: unmount of /mnt failed: Device busy

    Strangely, when an 'empty' union is read from, there's no problem unmounting
    it. It's only when it's read when there's something on it. In other words,
    from a clean setup:

    # ls tstfs/
    .snap/
    # umount tstfs/
    # umount /mnt

    But (continuing on the clean setup):

    # mount /dev/md1 /mnt
    # mount -t unionfs /mnt tstfs/
    # touch tstfs/foo
    # umount tstfs/
    # umount /mnt
    # mount /dev/md1 /mnt
    # mount -t unionfs /mnt tstfs/
    # ls tstfs/
    .snap/ foo
    # umount tstfs/
    # umount /mnt
    umount: unmount of /mnt failed: Device busy

    Is anyone else seeing this? :-)

     - Philip 

    -- 
Philip Paeps                                    Please don't Cc me, I am
philip@freebsd.org                               subscribed to the list.
  BOFH Excuse #237:
    Plate voltage too low on demodulator tube
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  • Next message: Philip Paeps: "Re: acpi_fujitsu not working"

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