From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56340) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bpBEo-0001Al-Bv for qemu-devel@nongnu.org; Wed, 28 Sep 2016 05:33:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bpBEn-0001o4-E9 for qemu-devel@nongnu.org; Wed, 28 Sep 2016 05:33:14 -0400 From: "Pavel Dovgalyuk" References: <20160926080757.6992.74311.stgit@PASHA-ISP> <20160926080838.6992.95614.stgit@PASHA-ISP> <20160926092346.GE6093@noname.str.redhat.com> <002001d217db$845fc030$8d1f4090$@ru> <20160926131721.GH6093@noname.str.redhat.com> <001101d218c8$67aa1010$36fe3030$@ru> <20160928083620.GD5236@noname.redhat.com> In-Reply-To: <20160928083620.GD5236@noname.redhat.com> Date: Wed, 28 Sep 2016 12:32:52 +0300 Message-ID: <001501d2196b$496b4e90$dc41ebb0$@ru> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Language: ru Subject: Re: [Qemu-devel] [PATCH v5 7/9] block: don't make snapshots for filters List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: 'Kevin Wolf' Cc: 'Pavel Dovgalyuk' , qemu-devel@nongnu.org, peter.maydell@linaro.org, quintela@redhat.com, jasowang@redhat.com, mst@redhat.com, pbonzini@redhat.com, mreitz@redhat.com, qemu-block@nongnu.org > From: Kevin Wolf [mailto:kwolf@redhat.com] > Am 27.09.2016 um 16:06 hat Pavel Dovgalyuk geschrieben: > > > From: Kevin Wolf [mailto:kwolf@redhat.com] > > > Am 26.09.2016 um 11:51 hat Pavel Dovgalyuk geschrieben: > > > > > From: Kevin Wolf [mailto:kwolf@redhat.com] > > > > > Am 26.09.2016 um 10:08 hat Pavel Dovgalyuk geschrieben: > > > Originally, we only called bdrv_goto_snapshot() for all _top level_ > > > BDSes, and this is still what you normally get. However, if you > > > explicitly create a BDS (e.g. with its own -drive option), it is > > > considered a top level BDS without actually being top level for the > > > guest, and therefore the snapshotting function is called for it. > > > > > > Of course, this is highly inefficient because the goto_snapshot request > > > is passed by the filter driver and then called another time for the > > > lower node, effectively loading the snapshot a second time. Maybe double-saving/loading does the smallest damage then? And we should just document how to use blkreplay effectively? > > > > > > On the other hand if you use a single -drive option to create both the > > > qcow2 BDS and the blkreplay filter, we do need to pass down the > > > goto_snapshot request because it won't be called for the qcow2 layer > > > otherwise. > > > > How this can be specified in command line? > > I believed that separate -drive option is required. > > Something like this: > > -drive driver=blkreplay,image.driver=file,image.filename=test.img > I tried the following command line, but VM does not detect the hard drive and cannot boot. -drive driver=blkreplay,if=none,image.driver=file,image.filename=testdisk.qcow,id=img-blkreplay -device ide-hd,drive=img-blkreplay Pavel Dovgalyuk