From patchwork Wed Nov 29 15:26:22 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 842620 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3yn4Gk5WMCz9sRn for ; Thu, 30 Nov 2017 02:30:06 +1100 (AEDT) Received: from localhost ([::1]:43657 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eK4JI-00052D-SC for incoming@patchwork.ozlabs.org; Wed, 29 Nov 2017 10:30:04 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54305) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eK4G6-0001zg-1G for qemu-devel@nongnu.org; Wed, 29 Nov 2017 10:26:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eK4G4-0007VY-P0 for qemu-devel@nongnu.org; Wed, 29 Nov 2017 10:26:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:20809) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eK4Fz-0007Tl-Nv; Wed, 29 Nov 2017 10:26:39 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D695973C; Wed, 29 Nov 2017 15:26:38 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-117-153.ams2.redhat.com [10.36.117.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8EFE860561; Wed, 29 Nov 2017 15:26:37 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Wed, 29 Nov 2017 16:26:22 +0100 Message-Id: <20171129152628.14906-5-kwolf@redhat.com> In-Reply-To: <20171129152628.14906-1-kwolf@redhat.com> References: <20171129152628.14906-1-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Wed, 29 Nov 2017 15:26:38 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 04/10] QAPI & interop: Clarify events emitted by 'block-job-cancel' X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Kashyap Chamarthy When you cancel an in-progress 'mirror' job (or "active `block-commit`") with QMP `block-job-cancel`, it emits the event: BLOCK_JOB_CANCELLED. However, when `block-job-cancel` is issued *after* `drive-mirror` has indicated (via the event BLOCK_JOB_READY) that the source and destination have reached synchronization: [...] # Snip `drive-mirror` invocation & outputs { "execute":"block-job-cancel", "arguments":{ "device":"virtio0" } } {"return": {}} It (`block-job-cancel`) will counterintuitively emit the event 'BLOCK_JOB_COMPLETED': { "timestamp":{ "seconds":1510678024, "microseconds":526240 }, "event":"BLOCK_JOB_COMPLETED", "data":{ "device":"virtio0", "len":41126400, "offset":41126400, "speed":0, "type":"mirror" } } But this is expected behaviour, where the _COMPLETED event indicates that synchronization has successfully ended (and the destination now has a point-in-time copy, which is at the time of cancel). So add a small note to this effect in 'block-core.json'. While at it, also update the "Live disk synchronization -- drive-mirror and blockdev-mirror" section in 'live-block-operations.rst'. (Thanks: Max Reitz for reminding me of this caveat on IRC.) Signed-off-by: Kashyap Chamarthy Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf --- qapi/block-core.json | 6 ++++ docs/interop/live-block-operations.rst | 50 ++++++++++++++++++++++------------ 2 files changed, 38 insertions(+), 18 deletions(-) diff --git a/qapi/block-core.json b/qapi/block-core.json index 76bf50f813..dd763dcf87 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -2065,6 +2065,12 @@ # BLOCK_JOB_CANCELLED event. Before that happens the job is still visible when # enumerated using query-block-jobs. # +# Note that if you issue 'block-job-cancel' after 'drive-mirror' has indicated +# (via the event BLOCK_JOB_READY) that the source and destination are +# synchronized, then the event triggered by this command changes to +# BLOCK_JOB_COMPLETED, to indicate that the mirroring has ended and the +# destination now has a point-in-time copy tied to the time of the cancellation. +# # For streaming, the image file retains its backing file unless the streaming # operation happens to complete just as it is being cancelled. A new streaming # operation can be started at a later time to finish copying all data from the diff --git a/docs/interop/live-block-operations.rst b/docs/interop/live-block-operations.rst index 5f0179749f..734252bc80 100644 --- a/docs/interop/live-block-operations.rst +++ b/docs/interop/live-block-operations.rst @@ -506,26 +506,40 @@ Again, given our familiar disk image chain:: [A] <-- [B] <-- [C] <-- [D] -The ``drive-mirror`` (and its newer equivalent ``blockdev-mirror``) allows -you to copy data from the entire chain into a single target image (which -can be located on a different host). - -Once a 'mirror' job has started, there are two possible actions while a -``drive-mirror`` job is active: - -(1) Issuing the command ``block-job-cancel`` after it emits the event - ``BLOCK_JOB_CANCELLED``: will (after completing synchronization of - the content from the disk image chain to the target image, [E]) - create a point-in-time (which is at the time of *triggering* the - cancel command) copy, contained in image [E], of the the entire disk +The ``drive-mirror`` (and its newer equivalent ``blockdev-mirror``) +allows you to copy data from the entire chain into a single target image +(which can be located on a different host), [E]. + +.. note:: + + When you cancel an in-progress 'mirror' job *before* the source and + target are synchronized, ``block-job-cancel`` will emit the event + ``BLOCK_JOB_CANCELLED``. However, note that if you cancel a + 'mirror' job *after* it has indicated (via the event + ``BLOCK_JOB_READY``) that the source and target have reached + synchronization, then the event emitted by ``block-job-cancel`` + changes to ``BLOCK_JOB_COMPLETED``. + + Besides the 'mirror' job, the "active ``block-commit``" is the only + other block device job that emits the event ``BLOCK_JOB_READY``. + The rest of the block device jobs ('stream', "non-active + ``block-commit``", and 'backup') end automatically. + +So there are two possible actions to take, after a 'mirror' job has +emitted the event ``BLOCK_JOB_READY``, indicating that the source and +target have reached synchronization: + +(1) Issuing the command ``block-job-cancel`` (after it emits the event + ``BLOCK_JOB_COMPLETED``) will create a point-in-time (which is at + the time of *triggering* the cancel command) copy of the entire disk image chain (or only the top-most image, depending on the ``sync`` - mode). + mode), contained in the target image [E]. One use case for this is + live VM migration with non-shared storage. -(2) Issuing the command ``block-job-complete`` after it emits the event - ``BLOCK_JOB_COMPLETED``: will, after completing synchronization of - the content, adjust the guest device (i.e. live QEMU) to point to - the target image, and, causing all the new writes from this point on - to happen there. One use case for this is live storage migration. +(2) Issuing the command ``block-job-complete`` (after it emits the event + ``BLOCK_JOB_COMPLETED``) will adjust the guest device (i.e. live + QEMU) to point to the target image, [E], causing all the new writes + from this point on to happen there. About synchronization modes: The synchronization mode determines *which* part of the disk image chain will be copied to the target.