[dm-devel] Snapshot/VFS-lock tests

[Kevin Corry]

On Thursday 31 July 2003 12:28, Erik Tews wrote:
> I think xfs uses a uuid in its filesystem so that you don't mount a
> filesystem twich when you got multiple paths to this filesystem.
>
> There is a special mount-option called nouuid which makes the kernel
> ignore the uuid. Because the uuid of the original filesystem is the same
> as the snapshot-uuid you will have to use this option to mount an
> xfs-snapshot.

Yes, I know. I mentioned this in my original posting. I did use this option 
when trying to mount the snapshots of XFS.

> And I used xfs-evms-snapshots with evms 1.2.1 for a long time without
> any problems with the vfs-lock-patch which came with evms 1.2.1.

I'm using the latest XFS snapshot for 2.4.21. Perhaps something has changed 
from the version you were using.

> Very old kernels had a problem with ro-xfs-filesystems but this has been
> resolved now.
>
> Perhaps you will have to add the option ro to the mount too when
> mounting a ro-snapshot.

Just to be fair, I'm running the XFS tests again. And strangely enough, I'm 
getting different results. :-(  Not sure how to explain that, other than I 
must have mixed up the kernels I thought I was running. Although...if that 
were the case, the read-only-with-VFS-lock case should have been 
different...so I'm not entirely sure what the problem was.

In any case, the new results make much more sense. Snapshots will work with 
XFS as long as you have the VFS-lock patch.



XFS:

writeable snapshot:

with VFS-lock:
XFS mounting filesystem device-mapper(254,17)
Ending clean XFS mount for filesystem: device-mapper(254,17)

without VFS-lock:
mount: wrong fs type, bad option, bad superblock on /dev/evms/snap1,
       or too many mounted file systems
XFS mounting filesystem device-mapper(254,17)
Starting XFS recovery on filesystem: device-mapper(254,17) (dev: 254/17)
XFS: xlog_recover_process_data: bad clientid
XFS: log mount/recovery failed
XFS: log mount failed

read-only snapshot:

with VFS-lock:
XFS mounting filesystem device-mapper(254,17)
Ending clean XFS mount for filesystem: device-mapper(254,17)

without VFS-lock:
mount: wrong fs type, bad option, bad superblock on /dev/evms/snap1,
       or too many mounted file systems
XFS mounting filesystem device-mapper(254,17)
XFS: recovery required required on read-only device.
XFS: write access unavailable, cannot proceed.
XFS: log mount/recovery failed
XFS: log mount failed

-- 
Kevin Corry
kevcorry at us.ibm.com
http://evms.sourceforge.net/