Re: [Qemu-devel] [RFC PATCH v3 2/2] qmp: add command 'blockdev-backup'

[Paolo Bonzini]

Il 17/10/2013 07:36, Fam Zheng ha scritto:
> Similar to drive-backup, but this command uses a device id as target
> instead of creating/opening an image file.
> 
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  blockdev.c       | 63 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qapi-schema.json | 49 +++++++++++++++++++++++++++++++++++++++++++
>  qmp-commands.hx  | 46 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 158 insertions(+)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 4f76e28..c53d597 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1937,6 +1937,69 @@ void qmp_drive_backup(const char *device, const char 
> *target,
>      }
>  }
>  
> +void qmp_blockdev_backup(const char *device, const char *target,
> +                       enum MirrorSyncMode sync,
> +                       bool has_speed, int64_t speed,
> +                       bool has_on_source_error,
> +                       BlockdevOnError on_source_error,
> +                       bool has_on_target_error,
> +                       BlockdevOnError on_target_error,
> +                       Error **errp)
> +{
> +    BlockDriverState *bs;
> +    BlockDriverState *target_bs;
> +    Error *local_err = NULL;
> +
> +    if (!has_speed) {
> +        speed = 0;
> +    }
> +    if (!has_on_source_error) {
> +        on_source_error = BLOCKDEV_ON_ERROR_REPORT;
> +    }
> +    if (!has_on_target_error) {
> +        on_target_error = BLOCKDEV_ON_ERROR_REPORT;
> +    }
> +
> +    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 (bdrv_in_use(bs)) {
> +        error_set(errp, QERR_DEVICE_IN_USE, device);
> +        return;
> +    }

Should these two checks be moved to backup_start?

> +    target_bs = bdrv_find(target);
> +    if (!target_bs) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, target);
> +        return;
> +    }
> +
> +    if (!bdrv_is_inserted(target_bs)) {
> +        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, target);
> +        return;
> +    }
> +
> +    if (bdrv_in_use(target_bs)) {
> +        error_set(errp, QERR_DEVICE_IN_USE, target);
> +        return;
> +    }

Same for these two.

> +    bdrv_ref(target_bs);
> +    backup_start(bs, target_bs, speed, sync, on_source_error, 
> on_target_error,
> +                 block_job_cb, bs, &local_err);
> +    if (local_err != NULL) {
> +        error_propagate(errp, local_err);

Missing bdrv_unref.

Otherwise looks good!

Paolo

> +    }
> +}
> +
>  #define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
>  
>  void qmp_drive_mirror(const char *device, const char *target,
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 60f3fd1..89bc510 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -1794,6 +1794,40 @@
>              '*on-target-error': 'BlockdevOnError' } }
>  
>  ##
> +# @BlockdevBackup
> +#
> +# @device: the name of the device which should be copied.
> +#
> +# @target: the name of the backup target device
> +#
> +# @sync: what parts of the disk image should be copied to the destination
> +#        (all the disk, only the sectors allocated in the topmost image, or
> +#        only new I/O).
> +#
> +# @speed: #optional the maximum speed, in bytes per second
> +#
> +# @on-source-error: #optional the action to take on an error on the source,
> +#                   default 'report'.  'stop' and 'enospc' can only be used
> +#                   if the block device supports io-status (see BlockInfo).
> +#
> +# @on-target-error: #optional the action to take on an error on the target,
> +#                   default 'report' (no limitations, since this applies to
> +#                   a different block device than @device).
> +#
> +# Note that @on-source-error and @on-target-error only affect background I/O.
> +# If an error occurs during a guest write request, the device's rerror/werror
> +# actions will be used.
> +#
> +# Since: 1.7
> +##
> +{ 'type': 'BlockdevBackup',
> +  'data': { 'device': 'str', 'target': 'str',
> +            'sync': 'MirrorSyncMode',
> +            '*speed': 'int',
> +            '*on-source-error': 'BlockdevOnError',
> +            '*on-target-error': 'BlockdevOnError' } }
> +
> +##
>  # @Abort
>  #
>  # This action can be used to test transaction failure.
> @@ -1983,6 +2017,21 @@
>  { 'command': 'drive-backup', 'data': 'DriveBackup' }
>  
>  ##
> +# @blockdev-backup
> +#
> +# Block device version for drive-backup command. Use existing device as 
> target
> +# of backup.
> +#
> +# For the arguments, see the documentation of BlockdevBackup.
> +#
> +# Returns: nothing on success
> +#          If @device or @target is not a valid block device, DeviceNotFound
> +#
> +# Since 1.7
> +##
> +{ 'command': 'blockdev-backup', 'data': 'BlockdevBackup' }
> +
> +##
>  # @drive-mirror
>  #
>  # Start mirroring a block device's writes to a new destination.
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index fba15cd..4116a8d 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -963,6 +963,52 @@ Example:
>                                                 "sync": "full",
>                                                 "target": "backup.img" } }
>  <- { "return": {} }
> +
> +EQMP
> +
> +    {
> +        .name       = "blockdev-backup",
> +        .args_type  = "sync:s,device:B,target:B,speed:i?,"
> +                      "on-source-error:s?,on-target-error:s?",
> +        .mhandler.cmd_new = qmp_marshal_input_blockdev_backup,
> +    },
> +
> +SQMP
> +blockdev-backup
> +------------
> +
> +The device version of drive-backup: this command takes a existing named 
> device
> +as backup target.
> +
> +Arguments:
> +
> +- "device": the name of the device which should be copied.
> +            (json-string)
> +- "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.
> +            (json-string)
> +- "sync": what parts of the disk image should be copied to the destination;
> +  possibilities include "full" for all the disk, "top" for only the sectors
> +  allocated in the topmost image, or "none" to only replicate new I/O
> +  (MirrorSyncMode).
> +- "mode": whether and how QEMU should create a new image
> +          (NewImageMode, optional, default 'absolute-paths')
> +- "speed": the maximum speed, in bytes per second (json-int, optional)
> +- "on-source-error": the action to take on an error on the source, default
> +                     'report'.  'stop' and 'enospc' can only be used
> +                     if the block device supports io-status.
> +                     (BlockdevOnError, optional)
> +- "on-target-error": the action to take on an error on the target, default
> +                     'report' (no limitations, since this applies to
> +                     a different block device than device).
> +                     (BlockdevOnError, optional)
> +
> +Example:
> +-> { "execute": "blockdev-backup", "arguments": { "device": "src-id",
> +                                                  "target": "tgt-id" } }
> +<- { "return": {} }
> +
>  EQMP
>  
>      {
>