Am 16.05.2013 um 10:36 hat Stefan Hajnoczi geschrieben:
> @drive-backup
>
> Start a point-in-time copy of a block device to a new destination. The
> status of ongoing drive-backup operations can be checked with
> query-block-jobs where the BlockJobInfo.type field has the value 'backup'.
> The operation can be stopped before it has completed using the
> block-job-cancel command.
>
> @device: the name of the device whose writes should be mirrored.
>
> @target: the target of the new image. If the file exists, or if it
> is a device, the existing file/device will be used as the new
> destination. If it does not exist, a new file will be created.
>
> @format: #optional the format of the new destination, default is to
> probe if @mode is 'existing', else the format of the source
>
> @mode: #optional whether and how QEMU should create a new image, default is
> 'absolute-paths'.
>
> @speed: #optional the maximum speed, in bytes per second
>
> Returns: nothing on success
> If @device is not a valid block device, DeviceNotFound
>
> Since 1.6
>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> blockdev.c | 92
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> qapi-schema.json | 32 ++++++++++++++++++++
> qmp-commands.hx | 37 +++++++++++++++++++++++
> 3 files changed, 161 insertions(+)
>
> diff --git a/blockdev.c b/blockdev.c
> index d1ec99a..c7a5e1e 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1353,6 +1353,98 @@ void qmp_block_commit(const char *device,
> drive_get_ref(drive_get_by_blockdev(bs));
> }
>
> +void qmp_drive_backup(const char *device, const char *target,
> + bool has_format, const char *format,
> + bool has_mode, enum NewImageMode mode,
> + bool has_speed, int64_t speed,
> + Error **errp)
> +{
> + BlockDriverState *bs;
> + BlockDriverState *target_bs;
> + BlockDriver *proto_drv;
> + BlockDriver *drv = NULL;
> + Error *local_err = NULL;
> + int flags;
> + uint64_t size;
> + int ret;
> +
> + if (!has_speed) {
> + speed = 0;
> + }
> + if (!has_mode) {
> + mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
> + }
> +
> + bs = bdrv_find(device);
> + if (!bs) {
> + error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> + return;
> + }
> +
> + if (!bdrv_is_inserted(bs)) {
> + error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
> + return;
> + }
> +
> + if (!has_format) {
> + format = mode == NEW_IMAGE_MODE_EXISTING ? NULL :
> bs->drv->format_name;
> + }
> + if (format) {
> + drv = bdrv_find_format(format);
> + if (!drv) {
> + error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
> + return;
> + }
> + }
> +
> + if (bdrv_in_use(bs)) {
> + error_set(errp, QERR_DEVICE_IN_USE, device);
> + return;
> + }
> +
> + flags = bs->open_flags | BDRV_O_RDWR;
> +
> + proto_drv = bdrv_find_protocol(target);
> + if (!proto_drv) {
> + error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
> + return;
> + }
I see that other block job commands are doing the same, but there are
two things unclear for me about this:
1. Shouldn't bdrv_img_create() and/or bdrv_open() already return an error
if the protocol can't be found? The error check is the only thing
that proto_drv is used for.
2. Why do we complain about a wrong _format_ here? If I ask for a qcow2
image called foo:bar.qcow2, qemu won't find the protocol "foo" and
complain that qcow2 is an invalid format.
> +
> + bdrv_get_geometry(bs, &size);
> + size *= 512;
I was going to suggest BDRV_SECTOR_SIZE at first, but...
Why not use bdrv_getlength() in the first place if you need it in bytes
anyway? As a nice bonus you would get -errno instead of size 0 on
failure.
> + if (mode != NEW_IMAGE_MODE_EXISTING) {
> + assert(format && drv);
> + bdrv_img_create(target, format,
> + NULL, NULL, NULL, size, flags, &local_err, false);
> + }
> +
> + if (error_is_set(&local_err)) {
> + error_propagate(errp, local_err);
> + return;
> + }
> +
> + target_bs = bdrv_new("");
> + ret = bdrv_open(target_bs, target, NULL, flags, drv);
> +
> + if (ret < 0) {
Why the empty line between bdrv_open and checking its return value?
> + bdrv_delete(target_bs);
> + error_set(errp, QERR_OPEN_FILE_FAILED, target);
> + return;
> + }
> +
> + backup_start(bs, target_bs, speed, block_job_cb, bs, &local_err);
> + if (local_err != NULL) {
> + bdrv_delete(target_bs);
> + error_propagate(errp, local_err);
> + return;
> + }
> +
> + /* Grab a reference so hotplug does not delete the BlockDriverState from
> + * underneath us.
> + */
> + drive_get_ref(drive_get_by_blockdev(bs));
> +}
> +
Kevin
