block: add drive_backup HMP command

Make "drive_backup" available on the HMP monitor:

  drive_backup [-n] [-f] device target [format]

The -n flag requests QEMU to reuse the image found in new-image-file,
instead of recreating it from scratch.

The -f flag requests QEMU to copy the whole disk, so that the result
does not need a backing file.  Note that this flag *must* currently be
passed since the other sync modes ('none' and 'top') have not been
implemented yet.  Requiring it ensures that "drive_backup" behaves like
"drive_mirror".
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hmp-commands.hx

@@ -1056,6 +1056,26 @@ STEXI
 @findex drive_mirror
 Start mirroring a block device's writes to a new destination,
 using the specified target.
+ETEXI
+
+    {
+        .name       = "drive_backup",
+        .args_type  = "reuse:-n,full:-f,device:B,target:s,format:s?",
+        .params     = "[-n] [-f] device target [format]",
+        .help       = "initiates a point-in-time\n\t\t\t"
+                      "copy for a device. The device's contents are\n\t\t\t"
+                      "copied to the new image file, excluding data that\n\t\t\t"
+                      "is written after the command is started.\n\t\t\t"
+                      "The -n flag requests QEMU to reuse the image found\n\t\t\t"
+                      "in new-image-file, instead of recreating it from scratch.\n\t\t\t"
+                      "The -f flag requests QEMU to copy the whole disk,\n\t\t\t"
+                      "so that the result does not need a backing file.\n\t\t\t",
+        .mhandler.cmd = hmp_drive_backup,
+    },
+STEXI
+@item drive_backup
+@findex drive_backup
+Start a point-in-time copy of a block device to a specificed target.
 ETEXI
 
     {

hmp.c

@@ -907,6 +907,34 @@ void hmp_drive_mirror(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &errp);
 }
 
+void hmp_drive_backup(Monitor *mon, const QDict *qdict)
+{
+    const char *device = qdict_get_str(qdict, "device");
+    const char *filename = qdict_get_str(qdict, "target");
+    const char *format = qdict_get_try_str(qdict, "format");
+    int reuse = qdict_get_try_bool(qdict, "reuse", 0);
+    int full = qdict_get_try_bool(qdict, "full", 0);
+    enum NewImageMode mode;
+    Error *errp = NULL;
+
+    if (!filename) {
+        error_set(&errp, QERR_MISSING_PARAMETER, "target");
+        hmp_handle_error(mon, &errp);
+        return;
+    }
+
+    if (reuse) {
+        mode = NEW_IMAGE_MODE_EXISTING;
+    } else {
+        mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
+    }
+
+    qmp_drive_backup(device, filename, !!format, format,
+                     full ? MIRROR_SYNC_MODE_FULL : MIRROR_SYNC_MODE_TOP,
+                     true, mode, false, 0, false, 0, false, 0, &errp);
+    hmp_handle_error(mon, &errp);
+}
+
 void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict)
 {
     const char *device = qdict_get_str(qdict, "device");

hmp.h

@@ -55,6 +55,7 @@ void hmp_balloon(Monitor *mon, const QDict *qdict);
 void hmp_block_resize(Monitor *mon, const QDict *qdict);
 void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict);
 void hmp_drive_mirror(Monitor *mon, const QDict *qdict);
+void hmp_drive_backup(Monitor *mon, const QDict *qdict);
 void hmp_migrate_cancel(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict);