From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38921) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z3Qk5-0001tj-6a for qemu-devel@nongnu.org; Fri, 12 Jun 2015 11:19:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z3Qjw-0007DW-Df for qemu-devel@nongnu.org; Fri, 12 Jun 2015 11:19:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54022) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z3Qjw-0007Cs-7o for qemu-devel@nongnu.org; Fri, 12 Jun 2015 11:19:28 -0400 Message-ID: <557AF87D.1050207@redhat.com> Date: Fri, 12 Jun 2015 11:19:25 -0400 From: John Snow MIME-Version: 1.0 References: <1433776886-27239-1-git-send-email-vsementsov@virtuozzo.com> <1433776886-27239-2-git-send-email-vsementsov@virtuozzo.com> <20150609170325.GI3181@stefanha-thinkpad.redhat.com> <5577F312.9040502@virtuozzo.com> <20150610132420.GD2430@stefanha-thinkpad.home> <557960AC.4080607@virtuozzo.com> <20150611130309.GD9425@stefanha-thinkpad.redhat.com> <5579B58B.6020408@redhat.com> <20150612102815.GC623@stefanha-thinkpad.redhat.com> In-Reply-To: <20150612102815.GC623@stefanha-thinkpad.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/8] spec: add qcow2-dirty-bitmaps specification List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: kwolf@redhat.com, Vladimir Sementsov-Ogievskiy , Stefan Hajnoczi , qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy , den@openvz.org, pbonzini@redhat.com On 06/12/2015 06:28 AM, Stefan Hajnoczi wrote: > On Thu, Jun 11, 2015 at 12:21:31PM -0400, John Snow wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA256 >> >> >> >> On 06/11/2015 09:03 AM, Stefan Hajnoczi wrote: >>> On Thu, Jun 11, 2015 at 01:19:24PM +0300, Vladimir >>> Sementsov-Ogievskiy wrote: >>>> On 10.06.2015 16:24, Stefan Hajnoczi wrote: >>>>> On Wed, Jun 10, 2015 at 11:19:30AM +0300, Vladimir >>>>> Sementsov-Ogievskiy wrote: >>>>>> On 09.06.2015 20:03, Stefan Hajnoczi wrote: >>>>>>> On Mon, Jun 08, 2015 at 06:21:19PM +0300, Vladimir >>>>>>> Sementsov-Ogievskiy wrote: >>>>>>>> @@ -166,6 +167,19 @@ the header extension data. Each >>>>>>>> entry look like this: terminated if it has full length) >>>>>>>> +== Dirty bitmaps == + +Dirty bitmaps is an optional >>>>>>>> header extension. It provides a possibility of +storing >>>>>>>> dirty bitmaps in qcow2 image. The fields are: + + >>>>>>>> 0 - 3: nb_dirty_bitmaps + Number of >>>>>>>> dirty bitmaps contained in the image >>>>>>> Is there a maximum? >>>>>> hmm. any proposals for this? >>>>> 65535 seems practical. >>>> >>>> So, you suggest to reduce this field width to 2b? And additional >>>> 2 bytes reserved field, to achieve 8b-alignment? >>> >>> No, I would leave it 32-bit but impose a little (which can be > > s/little/limit/ > >>> increased later if necessary). That's how nb_snapshots works too. >>> >> >> Doesn't the code already limit the number of bitmaps via +#define >> QCOW_MAX_DIRTY_BITMAPS 65536, from patch 2? > > It needs to be in the specification. > Yes, but the way the replies read made it sound like we hadn't decided on what the limit *was*, so I was just trying to clarify for myself, here.