zfs discuss - Jun 2007 - Question on clones and rollbacks

Hello,

I have the following situation:

1) A ZFS filesystem, created with zfs create:
    - multipack/u01
2) Data created in said filesystem
3) A snapshot taken of this filesystem:
    - multipack/u01 at initial
4) A clone filesystem created from the snapshot:
    - multipack/u09

multipack/u01                41.5K  57.9G  24.5K  /multipack/u01
multipack/u01 at initial          17K      -  24.5K  -
multipack/u09                20.0M  57.9G  20.0M  /multipack/u09

I discovered that if I had a regular user in the /multipack/u09
directory (ksh) and I try to rollback multipack/u01 at initial I get the
following error:

cannot unmount ''/multipack/u09'': Device busy

OK, so I get the reason behind this message but I do not understand
why we''re unmounting the clone filesystem in the first place?
Surely the filesystem is based on the read-only point in time snapshot
which isn''t changing.  Anything I add to this filesystem or delete
won''t affect the snapshot or the origin, multipack/u01 ... so why are
we attempting to unmount it for a rollback?



Many thanks in advance,

Jason
-- 
Jason Banham                               e-mail: jason.banham at sun.com
Kernel & Network Services                  phone : 0870 600 3222

             Solaris 10 : Why not install a copy today?
          http://www.sun.com/promotions/solaris10download/

> OK, so I get the reason behind this message but I do not understand
> why we''re unmounting the clone filesystem in the first place?
This is bug 6472202 "''zfs rollback'' and ''zfs
rename'' requires that clones be
unmounted".

Sorry about that,

--matt