[dm-devel] dmsetup snapshot merge problem

[jjaing <jjaing 163 com>]

Hi All，
     "echo 0 $(blockdev --getsize /dev/loop0) snapshot /dev/loop0 /dev/loop1 n 64 | dmsetup create testcow"

      I use the above command to create a testcow, I dont find how to use snapshot on dmsetup, so in my understanding, testcow will be setup as /dev/loop0 for reading and  /dev/loop1 for writing. does it correct?  is there any manual on how to use snapshot?
     and could anyone tell me , how to merge this two device's contents after I made some writing on  testcow?
     Thanks!