From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53552) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1evmJo-0001He-Rc for qemu-devel@nongnu.org; Tue, 13 Mar 2018 11:58:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1evmJn-0001yt-Ta for qemu-devel@nongnu.org; Tue, 13 Mar 2018 11:58:28 -0400 Date: Tue, 13 Mar 2018 16:58:19 +0100 From: Kevin Wolf Message-ID: <20180313155819.GG4642@localhost.localdomain> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH v3 1/1] block/mirror: change the semantic of 'force' of block-job-cancel List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, jsnow@redhat.com, liliang.opensource@gmail.com Am 13.03.2018 um 13:12 hat Jeff Cody geschrieben: > From: Liang Li > > When doing drive mirror to a low speed shared storage, if there was heavy > BLK IO write workload in VM after the 'ready' event, drive mirror block job > can't be canceled immediately, it would keep running until the heavy BLK IO > workload stopped in the VM. > > Libvirt depends on the current block-job-cancel semantics, which is that > when used without a flag after the 'ready' event, the command blocks > until data is in sync. However, these semantics are awkward in other > situations, for example, people may use drive mirror for realtime > backups while still wanting to use block live migration. Libvirt cannot > start a block live migration while another drive mirror is in progress, > but the user would rather abandon the backup attempt as broken and > proceed with the live migration than be stuck waiting for the current > drive mirror backup to finish. > > The drive-mirror command already includes a 'force' flag, which libvirt > does not use, although it documented the flag as only being useful to > quit a job which is paused. However, since quitting a paused job has > the same effect as abandoning a backup in a non-paused job (namely, the > destination file is not in sync, and the command completes immediately), > we can just improve the documentation to make the force flag obviously > useful. > > Cc: Paolo Bonzini > Cc: Jeff Cody > Cc: Kevin Wolf > Cc: Max Reitz > Cc: Eric Blake > Cc: John Snow > Reported-by: Huaitong Han > Signed-off-by: Huaitong Han > Signed-off-by: Liang Li > Signed-off-by: Jeff Cody > --- > > N.B.: This was rebased on top of Kevin's block branch, > and the 'force' flag added to block_job_user_cancel Thanks, applied to the block branch. Kevin