add mode field to blockdev-snapshot-sync transaction item
The mode field lets a management application create the snapshot
destination outside QEMU.
Right now, the only modes are "existing" and "absolute-paths". Mirroring
introduces "no-backing-file". In the future "relative-paths" could be
implemented too.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 88730c1..0a6edc3 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -748,9 +748,10 @@
BlockDriver *proto_drv;
BlockDriver *drv;
int flags;
+ enum NewImageMode mode;
+ const char *new_image_file;
const char *device;
const char *format = "qcow2";
- const char *new_image_file = NULL;
dev_info = dev_entry->value;
dev_entry = dev_entry->next;
@@ -761,10 +762,14 @@
switch (dev_info->kind) {
case BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
device = dev_info->blockdev_snapshot_sync->device;
+ if (!dev_info->blockdev_snapshot_sync->has_mode) {
+ dev_info->blockdev_snapshot_sync->mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
+ }
+ new_image_file = dev_info->blockdev_snapshot_sync->snapshot_file;
if (dev_info->blockdev_snapshot_sync->has_format) {
format = dev_info->blockdev_snapshot_sync->format;
}
- new_image_file = dev_info->blockdev_snapshot_sync->snapshot_file;
+ mode = dev_info->blockdev_snapshot_sync->mode;
break;
default:
abort();
@@ -805,13 +810,15 @@
}
/* create new image w/backing file */
- ret = bdrv_img_create(new_image_file, format,
- states->old_bs->filename,
- states->old_bs->drv->format_name,
- NULL, -1, flags);
- if (ret) {
- error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
- goto delete_and_fail;
+ if (mode != NEW_IMAGE_MODE_EXISTING) {
+ ret = bdrv_img_create(new_image_file, format,
+ states->old_bs->filename,
+ states->old_bs->drv->format_name,
+ NULL, -1, flags);
+ if (ret) {
+ error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
+ goto delete_and_fail;
+ }
}
/* We will manually add the backing_hd field to the bs later */
diff --git a/qapi-schema.json b/qapi-schema.json
index 85de38e..0882f43 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1118,6 +1118,22 @@
{ 'command': 'block_resize', 'data': { 'device': 'str', 'size': 'int' }}
##
+# @NewImageMode
+#
+# An enumeration that tells QEMU how to set the backing file path in
+# a new image file.
+#
+# @existing: QEMU should look for an existing image file.
+#
+# @absolute-paths: QEMU should create a new image with absolute paths
+# for the backing file.
+#
+# Since: 1.1
+##
+{ 'enum': 'NewImageMode'
+ 'data': [ 'existing', 'absolute-paths' ] }
+
+##
# @BlockdevSnapshot
#
# @device: the name of the device to generate the snapshot from.
@@ -1127,7 +1143,8 @@
# @format: #optional the format of the snapshot image, default is 'qcow2'.
##
{ 'type': 'BlockdevSnapshot',
- 'data': { 'device': 'str', 'snapshot-file': 'str', '*format': 'str' } }
+ 'data': { 'device': 'str', 'snapshot-file': 'str', '*format': 'str',
+ '*mode': 'NewImageMode' } }
##
# @BlockdevAction
diff --git a/qmp-commands.hx b/qmp-commands.hx
index fb4f1df..7c03b62 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -705,6 +705,13 @@
For snapshots this is the device, the file to use for the new snapshot,
and the format. The default format, if not specified, is qcow2.
+Each new snapshot defaults to being created by QEMU (wiping any
+contents if the file already exists), but it is also possible to reuse
+an externally-created file. In the latter case, you should ensure that
+the new image file has the same contents as the current one; QEMU cannot
+perform any meaningful check. Typically this is achieved by using the
+current image file as the backing file for the new image.
+
Arguments:
actions array:
@@ -715,6 +722,8 @@
- "device": device name to snapshot (json-string)
- "snapshot-file": name of new image file (json-string)
- "format": format of new image (json-string, optional)
+ - "mode": whether and how QEMU should create the snapshot file
+ (NewImageMode, optional, default "absolute-paths")
Example:
@@ -725,6 +734,7 @@
"format": "qcow2" } },
{ 'type': 'blockdev-snapshot-sync', 'data' : { "device": "ide-hd1",
"snapshot-file": "/some/place/my-image2",
+ "mode": "existing",
"format": "qcow2" } } ] } }
<- { "return": {} }
