From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39711) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UrUMg-0007dV-JV for qemu-devel@nongnu.org; Tue, 25 Jun 2013 10:37:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UrUMe-0002CX-Uw for qemu-devel@nongnu.org; Tue, 25 Jun 2013 10:37:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52302) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UrUMe-0002CR-N6 for qemu-devel@nongnu.org; Tue, 25 Jun 2013 10:37:00 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r5PEaxKV009091 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 25 Jun 2013 10:36:59 -0400 Message-ID: <51C9AB05.8000902@redhat.com> Date: Tue, 25 Jun 2013 16:36:53 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1372163039-28332-1-git-send-email-stefanha@redhat.com> <20130625132638.GL3539@dhcp-200-207.str.redhat.com> <51C99FF7.5060705@redhat.com> <20130625140621.GN3539@dhcp-200-207.str.redhat.com> In-Reply-To: <20130625140621.GN3539@dhcp-200-207.str.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] block: add drive_backup HMP command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: imain@redhat.com, Fam Zheng , qemu-devel@nongnu.org, Stefan Hajnoczi Il 25/06/2013 16:06, Kevin Wolf ha scritto: > Am 25.06.2013 um 15:49 hat Paolo Bonzini geschrieben: >> Il 25/06/2013 15:26, Kevin Wolf ha scritto: >>>>> + if (!full) { >>>>> + error_setg(&errp, "-f is not yet implemented"); >>>>> + hmp_handle_error(mon, &errp); >>>>> + return; >>>>> + } >>> Then why make it a valid option and confuse users in the help text by >>> describing options that don't really exist? >> >> Because otherwise we're stuck with a meaning of the flag that is >> different between drive-mirror and block-backup. > > Do you mean when "otherwise" isn't only "we don't add -f now", but also > "we accidentally add a -f with different meaning later"? Not sure if > there's a real danger of that when we're aware that we want -f with the > same meaning as for mirroring. We have drive-mirror with: * the default is 'top' * -f gives 'full' block-backup for now only implements 'full'. If we do not force the user to add -f, the default is 'full' and we should not change it later. However, I would move the "not yet implemented" error from HMP to QMP. This way, both drive-mirror and block-backup will have a mandatory 'sync' argument. We plan to implement it anyway, and it makes sense imo to avoid gratuitous differences in the APIs. Paolo > Apart from that, it's HMP, so even in the unlikely case that we mess up, > fixing it is still an option. > > Kevin >