From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36729) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UG0Qu-0000pY-TG for qemu-devel@nongnu.org; Thu, 14 Mar 2013 01:10:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UG0Qt-0000rz-UN for qemu-devel@nongnu.org; Thu, 14 Mar 2013 01:10:28 -0400 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:41756) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UG0Qt-0000rQ-CH for qemu-devel@nongnu.org; Thu, 14 Mar 2013 01:10:27 -0400 Received: from /spool/local by e28smtp02.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 14 Mar 2013 10:36:21 +0530 Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id 238E41258056 for ; Thu, 14 Mar 2013 10:41:21 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r2E5ACwP28835942 for ; Thu, 14 Mar 2013 10:40:12 +0530 Received: from d28av04.in.ibm.com (loopback [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r2E5AGG4016753 for ; Thu, 14 Mar 2013 16:10:16 +1100 Message-ID: <51415B52.1040409@linux.vnet.ibm.com> Date: Thu, 14 Mar 2013 13:08:34 +0800 From: Wenchao Xia MIME-Version: 1.0 References: <1357543689-11415-9-git-send-email-xiawenc@linux.vnet.ibm.com> <20130109124433.GA391@stefanha-thinkpad.redhat.com> <50EE33B2.4040504@linux.vnet.ibm.com> <20130110124109.GD30946@stefanha-thinkpad.redhat.com> <50EFAFA4.1030705@linux.vnet.ibm.com> <20130111091253.GA31400@stefanha-thinkpad.muc.redhat.com> <50F373DE.4060709@linux.vnet.ibm.com> <20130114100604.GH11260@stefanha-thinkpad.redhat.com> <50F4FF3C.9000706@linux.vnet.ibm.com> <513EE7B1.6060501@linux.vnet.ibm.com> <20130313101838.GD2309@dhcp-200-207.str.redhat.com> In-Reply-To: <20130313101838.GD2309@dhcp-200-207.str.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: Kevin Wolf Cc: aliguori@us.ibm.com, quintela@redhat.com, Stefan Hajnoczi , qemu-devel@nongnu.org, lcapitulino@redhat.com, pbonzini@redhat.com, dietmar@proxmox.com 于 2013-3-13 18:18, Kevin Wolf 写道: > Am 12.03.2013 um 09:30 hat Wenchao Xia geschrieben: >> I redesigned the structure, Following is the fake code: >> >> typedef struct BdrvActionOps { >> /* check the request's validation, allocate p_opaque if needed */ >> int (*check)(BlockdevAction *action, void **p_opaque, Error **errp); >> /* take the action */ >> int (*submit)(BlockdevAction *action, void *opaque, Error **errp); >> /* update emulator */ >> int (*commit)(BlockdevAction *action, void *opaque, Error **errp); >> /* cancel the action */ >> int (*rollback)(BlockdevAction *action, void *opaque, Error **errp); >> } BdrvActionOps; > > Why do you need the split of prepare into check/submit? > > If you have prepare/commit/abort, everybody will recognise this as the > standard transaction pattern because this is just how it's done. > Deviating from it needs a good justification in my opinion. > > Kevin > My thought is rejecting the request in *check if parameter invalid before take any action, while submit do the real action, to reduce the chance to of rolling back when some request not valid in the batch. -- Best Regards Wenchao Xia