From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:59552) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tt8i6-0008Sj-32 for qemu-devel@nongnu.org; Wed, 09 Jan 2013 22:21:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Tt8i2-0003n6-83 for qemu-devel@nongnu.org; Wed, 09 Jan 2013 22:21:42 -0500 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:41952) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tt8i1-0003lo-Kj for qemu-devel@nongnu.org; Wed, 09 Jan 2013 22:21:38 -0500 Received: from /spool/local by e28smtp08.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 10 Jan 2013 08:49:52 +0530 Received: from d28relay04.in.ibm.com (d28relay04.in.ibm.com [9.184.220.61]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id 7CF5D125804F for ; Thu, 10 Jan 2013 08:51:44 +0530 (IST) Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay04.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r0A3LSFs62652532 for ; Thu, 10 Jan 2013 08:51:29 +0530 Received: from d28av02.in.ibm.com (loopback [127.0.0.1]) by d28av02.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r0A3LTZe031651 for ; Thu, 10 Jan 2013 14:21:30 +1100 Message-ID: <50EE33B2.4040504@linux.vnet.ibm.com> Date: Thu, 10 Jan 2013 11:21:22 +0800 From: Wenchao Xia MIME-Version: 1.0 References: <1357543689-11415-1-git-send-email-xiawenc@linux.vnet.ibm.com> <1357543689-11415-9-git-send-email-xiawenc@linux.vnet.ibm.com> <20130109124433.GA391@stefanha-thinkpad.redhat.com> In-Reply-To: <20130109124433.GA391@stefanha-thinkpad.redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH V2 07/10] snapshot: qmp use new internal API for external snapshot transaction List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: kwolf@redhat.com, aliguori@us.ibm.com, quintela@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, pbonzini@redhat.com, dietmar@proxmox.com 于 2013-1-9 20:44, Stefan Hajnoczi 写道: > 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 >> --- >> 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 > As API, qmp_transaction have following disadvantages: 1) interface is based on string not data type inside qemu, that means other function calling it result in: bdrv->string->bdrv 2) all capability are forced to be exposed. 3) need structure to record each transaction state, such as BlkTransactionStates. Extending it is equal to add an internal layer. Actually I started up by use qmp_transaction as API, but soon found that work is almost done around BlkTransactionStates, so added a layer around it clearly. -- Best Regards Wenchao Xia