From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38815) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Us9tN-0000iy-5U for qemu-devel@nongnu.org; Thu, 27 Jun 2013 06:57:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Us9tM-0003eA-2G for qemu-devel@nongnu.org; Thu, 27 Jun 2013 06:57:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57627) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Us9tL-0003dy-QV for qemu-devel@nongnu.org; Thu, 27 Jun 2013 06:57:31 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r5RAvTbo022622 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 27 Jun 2013 06:57:30 -0400 Message-ID: <51CC1A8F.3070004@redhat.com> Date: Thu, 27 Jun 2013 12:57:19 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1372219161-12209-1-git-send-email-famz@redhat.com> <1372219161-12209-2-git-send-email-famz@redhat.com> <20130627081536.GE13780@stefanha-thinkpad.redhat.com> <20130627094134.GA8076@t430s.nay.redhat.com> In-Reply-To: <20130627094134.GA8076@t430s.nay.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 1/3] block: add target-id option to drive-backup QMP command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: famz@redhat.com Cc: kwolf@redhat.com, obarenbo@redhat.com, armbru@redhat.com, roliveri@redhat.com, hbrock@redhat.com, qemu-devel@nongnu.org, rjones@redhat.com, pmyers@redhat.com, imain@redhat.com, Stefan Hajnoczi Il 27/06/2013 11:41, Fam Zheng ha scritto: > On Thu, 06/27 10:15, Stefan Hajnoczi wrote: >> On Wed, Jun 26, 2013 at 11:59:19AM +0800, Fam Zheng wrote: >>> Add target-id (optional) to drive-backup command, to make the target bs >>> a named drive so that we can operate on it (e.g. export with NBD). >>> >>> Signed-off-by: Fam Zheng >>> --- >>> blockdev.c | 4 +++- >>> qapi-schema.json | 7 +++++-- >>> qmp-commands.hx | 3 ++- >>> 3 files changed, 10 insertions(+), 4 deletions(-) >>> >>> diff --git a/blockdev.c b/blockdev.c >>> index b3a57e0..5e694f3 100644 >>> --- a/blockdev.c >>> +++ b/blockdev.c >>> @@ -935,6 +935,7 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp) >>> backup = common->action->drive_backup; >>> >>> qmp_drive_backup(backup->device, backup->target, >>> + backup->has_target_id, backup->target_id, >>> backup->has_format, backup->format, >>> backup->has_mode, backup->mode, >>> backup->has_speed, backup->speed, >>> @@ -1420,6 +1421,7 @@ void qmp_block_commit(const char *device, >>> } >>> >>> void qmp_drive_backup(const char *device, const char *target, >>> + bool has_target_id, const char *target_id, >>> bool has_format, const char *format, >>> bool has_mode, enum NewImageMode mode, >>> bool has_speed, int64_t speed, >>> @@ -1494,7 +1496,7 @@ void qmp_drive_backup(const char *device, const char *target, >>> return; >>> } >>> >>> - target_bs = bdrv_new(""); >>> + target_bs = bdrv_new(has_target_id ? target_id : ""); >> >> This raises a new issue: >> >> Now that the target can be named, what happens when the user issues a >> monitor command, e.g. drive-del, block-resize, or drive-backup :)? >> >> We have a clumsy form of protection with bdrv_set_in_use(). It makes >> several monitor commands refuse with -EBUSY. >> >> Perhaps we should have a command permission set so it's possible to >> allow/deny specific commands. >> > > Yes, this makes me realize that ref count it not a solution to retire > bs->in_use, because we can't tell if drive-del or block-resize is safe > with only reference number. But I can't think of two situations to deny > different subsets of commands, shouldn't a general blocker, like in_use > does, be good enough? For example, right now nbd-server-add does not check bdrv_in_use. But shrinking a device that is exposed via NBD could be surprising to the NBD clients. Paolo