[dm-devel] How to determine when a snapshot has finished merging?

[Wicher Minnaard]

Hi, I'm new to the list.
I'm experimenting with the snapshot-merge target on a 2.6.33_rc4 kernel:

echo 0 $(blockdev --getsize /dev/mapper/original) snapshot-merge
/dev/mapper/original /dev/loop1 p 8 | dmsetup create mergeomatic

where /dev/loop1 is a COW volume I created earlier (with the
'snapshot' target, against /dev/mapper/original, of course).
I wait for some time and then I just 'dmsetup remove' to break down
the device stack, starting with the 'mergeomatic' device. I then take
a look at /dev/mapper/original, and, much to my delight, I see stuff
that has been merged back in from the snapshot.

But I don't know how to determine whether the merge has completed. I
looked around in /proc and /sys, but those contained no obvious clues
(not obvious to me, that is). My kernel logs never mention any dm
activity (whereas the md driver is quite chatty and features
/proc/mdstat).
Any suggestions greatly appreciated.

Regards, Wicher