zfs: using, then destroying a snapshot sometimes confuses zfs

[Stefan Bethke]

Sorry I can't be more precise at the moment, but while creating a  
script that mirrors some zfs filesystems to another machine, I've now  
twice gotten weird behaviour and then a panic.

The script iterates over a couple of zfs file systems:
- creates a snapshot with zfs snapshot tank/foo at mirror
- uses rsync to copy the contents of the snapshot with rsync /tank/ 
foo/.zfs/snapshot/mirror/ dest:...
- destroys the snapshot with zfs destroy tank/foo at mirror

During testing the script, I twice got to a point where, after the  
snapshot was created without an error message, rsync dropped out with  
an error message similar to "invalid file handle" on /tank/foo/.zfs/ 
snapshot.

At that point, I could cd to /tank/foo/.zfs, but ls produced the same  
error message.

I then tried to unmount the snapshot with zfs umount, and got a panic  
(which I also didn't manage to capture).

Is this a generally known issue, or should I try to capture more  
information when this happens again?

I'm running with these loader variables on amd64:
vfs.zfs.arc_max="512M"
vfs.zfs.prefetch_disable="1"
vfs.zfs.zil_disable="1"


Stefan

-- 
Stefan Bethke <stb at lassitu.de>   Fon +49 151 14070811