Re: [Qemu-devel] [PATCH V2 07/10] snapshot: qmp use new internal API for external snapshot transaction

[Stefan Hajnoczi <stefanha@gmail.com>]

On Mon, Jan 07, 2013 at 03:28:06PM +0800, Wenchao Xia wrote:
>   This patch switch to internal common API to take group external
> snapshots from qmp_transaction interface. qmp layer simply does
> a translation from user input.
> 
> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
> ---
>  blockdev.c |  215 ++++++++++++++++++++++++------------------------------------
>  1 files changed, 87 insertions(+), 128 deletions(-)

An internal API for snapshots is not necessary.  qmp_transaction() is
already usable both from the monitor and C code.

The QAPI code generator creates structs that can be accessed directly
from C.  qmp_transaction(), BlockdevAction, and BlockdevActionList *is*
the snapshot API.  It just doesn't support internal snapshots yet, which
is what you are trying to add.

To add internal snapshot support, define a BlockdevInternalSnapshot type
in qapi-schema.json and add internal snapshot support in
qmp_transaction().

qmp_transaction() was designed with this in mind from the beginning and
dispatches based on BlockdevAction->kind.

The patch series will become much smaller while still adding internal
snapshot support.

Stefan