QMP: add snapshot-blkdev-sync command

Add QMP bits for snapshot_blkdev command. This is the same as
snapshot_blkdev in the human monitor. The command is synchronous.

In the future async commands and or a break down of the functionality
into multiple commands might be added.

Also change the 'snapshot_file' argument to 'snapshot-file' in
the human monitor, so that it matches QMP.
Signed-off-by: NJes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@gmail.com>

blockdev.c

@@ -568,7 +568,7 @@ void do_commit(Monitor *mon, const QDict *qdict)
 int do_snapshot_blkdev(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
     const char *device = qdict_get_str(qdict, "device");
-    const char *filename = qdict_get_try_str(qdict, "snapshot_file");
+    const char *filename = qdict_get_try_str(qdict, "snapshot-file");
     const char *format = qdict_get_try_str(qdict, "format");
     BlockDriverState *bs;
     BlockDriver *drv, *old_drv, *proto_drv;
@@ -577,7 +577,7 @@ int do_snapshot_blkdev(Monitor *mon, const QDict *qdict, QObject **ret_data)
     char old_filename[1024];
 
     if (!filename) {
-        qerror_report(QERR_MISSING_PARAMETER, "snapshot_file");
+        qerror_report(QERR_MISSING_PARAMETER, "snapshot-file");
         ret = -1;
         goto out;
     }

hmp-commands.hx

@@ -840,7 +840,7 @@ ETEXI
 
     {
         .name       = "snapshot_blkdev",
-        .args_type  = "device:B,snapshot_file:s?,format:s?",
+        .args_type  = "device:B,snapshot-file:s?,format:s?",
         .params     = "device [new-image-file] [format]",
         .help       = "initiates a live snapshot\n\t\t\t"
                       "of device. If a new image file is specified, the\n\t\t\t"

qmp-commands.hx

@@ -691,6 +691,40 @@ Example:
 -> { "execute": "block_resize", "arguments": { "device": "scratch", "size": 1073741824 } }
 <- { "return": {} }
 
+EQMP
+
+    {
+        .name       = "blockdev-snapshot-sync",
+        .args_type  = "device:B,snapshot-file:s?,format:s?",
+        .params     = "device [new-image-file] [format]",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_snapshot_blkdev,
+    },
+
+SQMP
+blockdev-snapshot-sync
+----------------------
+
+Synchronous snapshot of a block device. snapshot-file specifies the
+target of the new image. If the file exists, or if it is a device, the
+snapshot will be created in the existing file/device. If does not
+exist, a new file will be created. format specifies the format of the
+snapshot image, default is qcow2.
+
+Arguments:
+
+- "device": device name to snapshot (json-string)
+- "snapshot-file": name of new image file (json-string)
+- "format": format of new image (json-string, optional)
+
+Example:
+
+-> { "execute": "blockdev-snapshot", "arguments": { "device": "ide-hd0",
+                                                    "snapshot-file":
+                                                    "/some/place/my-image",
+                                                    "format": "qcow2" } }
+<- { "return": {} }
+
 EQMP
 
     {