@@ -35,6 +35,11 @@ STEXI
@item commit
@findex commit
Commit changes to the disk images (if -snapshot is used) or backing files.
+If the backing file is smaller than the snapshot, then the backing file will be
+resized to be the same size as the snapshot. If the snapshot is smaller than
+the backing file, the backing file will not be truncated. If you want the
+backing file to match the size of the smaller snapshot, you can safely truncate
+it yourself once the commit operation successfully completes.
ETEXI
{
@@ -1973,6 +1973,13 @@
# user needs to complete the job with the block-job-complete
# command after getting the ready event. (Since 2.0)
#
+# If the base image is smaller than top, then the base image
+# will be resized to be the same size as top. If top is
+# smaller than the base image, the base will not be
+# truncated. If you want the base image size to match the
+# size of the smaller top, you can safely truncate it
+# yourself once the commit operation successfully completes.
+#
#
# @speed: #optional the maximum speed, in bytes per second
#
@@ -140,7 +140,12 @@ it doesn't need to be specified separately in this case.
@item commit [-f @var{fmt}] [-t @var{cache}] @var{filename}
-Commit the changes recorded in @var{filename} in its base image.
+Commit the changes recorded in @var{filename} in its base image or backing file.
+If the backing file is smaller than the snapshot, then the backing file will be
+resized to be the same size as the snapshot. If the snapshot is smaller than
+the backing file, the backing file will not be truncated. If you want the
+backing file to match the size of the smaller snapshot, you can safely truncate
+it yourself once the commit operation successfully completes.
@item compare [-f @var{fmt}] [-F @var{fmt}] [-p] [-s] [-q] @var{filename1} @var{filename2}
@@ -965,6 +965,45 @@ EQMP
.mhandler.cmd_new = qmp_marshal_input_block_commit,
},
+SQMP
+block-commit
+------------
+
+Live commit of data from overlay image nodes into backing nodes - i.e., writes
+data between 'top' and 'base' into 'base'.
+
+Arguments:
+
+- "device": The device's ID, must be unique (json-string)
+- "base": The file name of the backing image to write data into.
+ If not specified, this is the deepest backing image
+ (json-string, optional)
+- "top": The file name of the backing image within the image chain,
+ which contains the topmost data to be committed down.
+
+ If top == base, that is an error.
+ If top == active, the job will not be completed by itself,
+ user needs to complete the job with the block-job-complete
+ command after getting the ready event. (Since 2.0)
+
+ If the base image is smaller than top, then the base image
+ will be resized to be the same size as top. If top is
+ smaller than the base image, the base will not be
+ truncated. If you want the base image size to match the
+ size of the smaller top, you can safely truncate it
+ yourself once the commit operation successfully completes.
+ (json-string)
+- "speed": the maximum speed, in bytes per second (json-int, optional)
+
+
+Example:
+
+-> { "execute": "block-commit", "arguments": { "device": "virtio0",
+ "top": "/tmp/snap1.qcow2" } }
+<- { "return": {} }
+
+EQMP
+
{
.name = "drive-backup",
.args_type = "sync:s,device:B,target:s,speed:i?,mode:s?,format:s?,"