Date: Wed, 22 Jun 2005 08:53:57 +0200 From: Philip Paeps <philip@freebsd.org> To: freebsd-current@freebsd.org Subject: Unable to umount union-parts after umounting unionfs Message-ID: <20050622065357.GA694@loge.nixsys.be>
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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
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