[dm-devel] Re: Snapshot merging
Mike Snitzer
snitzer at redhat.com
Wed Sep 9 15:56:43 UTC 2009
On Wed, Sep 09 2009 at 11:47am -0400,
Mikulas Patocka <mpatocka at redhat.com> wrote:
> Hi
>
> I found one bug in the userspace code --- start merging, then from the
> other console deactivate the origin volume with lvchange -an, then wait
> next 15 seconds for the next poll interval:
>
> the poll process will think that the merging finished, removing the
> snapshot, leaving partially merged origin and causing data corruption:
>
> [slunicko:~]# lvconvert -M vg1/lv2_snap1
> Merging of volume lv2_snap1 started.
> lv2: Merged: 13.1%
> ( .... deactivate the volume from the other console ....)
> lv2: Merged: -1.0%
> Merge into logical volume lv2 finished.
> Logical volume "snapshot4" successfully removed
>
> Maybe this bug was in my code too, I don't remember.
Likely, considering I merely ported your LVM2 patches to the latest
version. That said, I could've introduced this issue by missing
something in the port. Regardless, I'll have a look at preventing the
origin LV from being deactivated during a merge.
> Otherwise, the code seems stable, I didn't see anything wrong, I tried to
> crash it while merging and it resumed without data corruption.
Great, thanks for the feedback and testing!
Mike
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