[dm-devel] Re: Snapshot merging

[Mikulas Patocka <mpatocka redhat com>]

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.

Otherwise, the code seems stable, I didn't see anything wrong, I tried to 
crash it while merging and it resumed without data corruption.

Mikulas