From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38829) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SfX6E-0002IT-67 for qemu-devel@nongnu.org; Fri, 15 Jun 2012 10:02:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SfX68-0004vX-UA for qemu-devel@nongnu.org; Fri, 15 Jun 2012 10:02:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1318) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SfX68-0004vH-Kh for qemu-devel@nongnu.org; Fri, 15 Jun 2012 10:02:00 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q5FE1xqo012603 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 15 Jun 2012 10:01:59 -0400 Date: Fri, 15 Jun 2012 11:02:17 -0300 From: Luiz Capitulino Message-ID: <20120615110217.58ceff71@doriath.home> In-Reply-To: <4FDA0188.4080705@redhat.com> References: <806c66b2f071f03bec0b7d45a71512e394386885.1339617170.git.phrdina@redhat.com> <4FD9D67F.5080505@redhat.com> <4FD9FB83.8050208@redhat.com> <4FD9FD6A.2080702@redhat.com> <4FDA0188.4080705@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] qapi: converted commit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Pavel Hrdina Cc: kwolf@redhat.com, Jeff Cody , Eric Blake , qemu-devel@nongnu.org On Thu, 14 Jun 2012 17:21:44 +0200 Pavel Hrdina wrote: > On 06/14/2012 05:04 PM, Eric Blake wrote: > > On 06/14/2012 08:56 AM, Pavel Hrdina wrote: > >> On 06/14/2012 02:18 PM, Eric Blake wrote: > >>> On 06/14/2012 01:35 AM, Pavel Hrdina wrote: > >>>> Signed-off-by: Pavel Hrdina > >>>> --- > >>>> +++ b/qapi-schema.json > >>>> @@ -1169,6 +1169,21 @@ > >>>> { 'command': 'block_resize', 'data': { 'device': 'str', 'size': > >>>> 'int' }} > >>>> > >>>> ## > >>>> +# @commit > >>>> +# > >>>> +# Commit changes to the disk images (if -snapshot is used) or > >>>> backing files. > >>>> +# > >>>> +# @device: the name of the device or the "all" to commit all devices > >>>> +# > >>>> +# Returns: nothing on success > >>>> +# If @device is not a valid block device, DeviceNotFound > >>>> +# If a long-running operation is using the device, DeviceInUse > >>>> +# > >>>> +# Since: 1.2 > >>>> +## > >>>> +{ 'command': 'commit', 'data': { 'device': 'str' }} > >>> Should we use this as an opportunity to make the command more powerful? > >>> For example, integrating this with the 'transaction' command or a block > >>> job queried by 'query-block-jobs' to track its progress would be useful. > >>> Also, suppose I have A<- B<- C. Does 'commit' only do one layer (C > >>> into B), or all layers (B and C into A)? That argues that we need an > >>> optional parameter that says how deep to commit (committing C into B > >>> only to repeat and commit B into A is more time-consuming than directly > >>> committing both B and C into A to start with). When a commit is > >>> complete, which file is backing the device - is it still C (which > >>> continues to diverge, but now from the point of the commit) or does qemu > >>> pivot things to have the device now backed by B (and C can be discarded, > >>> particularly true if changes are now going into B which invalidate C). > >> What i find out is that 'commit' will commit changes only from C to B > >> and qemu continues with C from the new commit point. I couldn't find a > >> way to commit changes and go back to backing file. This should be > >> supported by parameter and also as you mention that commit all changes > >> through all snapshots should be supported by another parameter. > >> The 'transaction' feature would be nice to have too. > > Which makes it sound like we're starting to overlap with Jeff's work on > > 'block-commit'. > > > > If 'block-commit' proves to be better all around at doing what we want, > > do we even need to keep 'commit' in QMP, or would it be okay for HMP only? > If the 'block-commit' will be better I think that we could drop the > 'commit' completely. And have only 'block-commit' for both QMP and HMP. I completely agree about the QMP part, but for HMP it's a good idea to maintain the commit command. To achieve this, we can implement hmp_commit() in terms of block-commit. Jeff, can you answer us here? Does block-commit supersedes the commit command we have today?