live_commit.txt

==================================live commit==================================
1.live commit of data from overlay image nodes into backing nodes
i.e. writes data between 'top' and 'base' into 'base'.
base-->sn1-->sn2-->sn3-->sn4
->{ "execute": "__com.redhat_block-commit", "arguments": { "device": "drive-virtio-disk0", "base": "/root/sn1", "top": "/root/sn3", "speed": 1000000000 } }
<-{"return": {}}
<-{"timestamp": {"seconds": 1333951164, "microseconds": 797571}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "drive-virtio-disk0", "len": 10737418240, "offset": 8279556096, "speed": 1000000000, "type": "commit"}}
# @device:  the name of the device
#
# @base:   #optional The file name of the backing image to write data into,
#                    If not specified, this is the deepest backing image.
#
# @top:              The file name of the backing image within the image chain,
#                    which contains the topmost data to be committed down.
#                    Note, the active layer as 'top' is currently unsupported.
#
#                    If top == base, that is an error.
#
# @speed:  #optional the maximum speed, in bytes per second.
#
# Returns: Nothing on success
#          If commit or stream is already active on this device, DeviceInUse
#          If @device does not exist, DeviceNotFound
#          If image commit is not supported by this device, NotSupported
#          If @base or @top is invalid, a generic error is returned
#          If @top is the active layer, or omitted, a generic error is returned
#          If @speed is invalid, InvalidParameter

2.cancel live commit.
->{ "execute": "block_job_cancel", "arguments": { "device": "drive-virtio-disk0" } }
<-{"return": {}}

3.query live commit job status.
->{ "execute" : "query-block-jobs", "arguments" : {} }
<-{"return": [{"device": "drive-virtio-disk0", "len": 10737418240, "offset": 10737418240, "speed": 1000000000, "type": "commit"}]}

4.set live commit speed limit.
->{ "execute": "block_job_set_speed", "arguments": { "device": "drive-virtio-disk0", "speed": 1024000 } }

5.tell different commit.
- offline commit (static): 
# qemu-img commit -f qcow2 /dev/vg-90.100-sluo/sluo-snap1
(qemu) ? commit
commit device|all -- commit changes to the disk images (if -snapshot is used) or backing files
- live commit (dynamic).
  - via HMP: (qemu) ? __com.redhat_block-commit
             __com.redhat_block-commit (null) -- (null)
  - via QMP: { "execute": "__com.redhat_block-commit", "arguments": { "device": "drive-virtio-disk0", "base": "/root/sn1", "top": "/root/sn3", "speed": 1000000000 } }