From patchwork Fri May 10 13:16:42 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Fiona Ebner X-Patchwork-Id: 13661584 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EB499C25B5F for ; Fri, 10 May 2024 13:17:51 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s5Q7m-0005bh-Gc; Fri, 10 May 2024 09:17:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s5Q7Y-0005VJ-IA; Fri, 10 May 2024 09:17:10 -0400 Received: from proxmox-new.maurer-it.com ([94.136.29.106]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s5Q7T-0002AO-RN; Fri, 10 May 2024 09:17:06 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 506C3473F7; Fri, 10 May 2024 15:16:52 +0200 (CEST) From: Fiona Ebner To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, armbru@redhat.com, eblake@redhat.com, hreitz@redhat.com, kwolf@redhat.com, vsementsov@yandex-team.ru, jsnow@redhat.com, f.gruenbichler@proxmox.com, t.lamprecht@proxmox.com, mahaocong@didichuxing.com, xiechanglong.d@gmail.com, wencongyang2@huawei.com Subject: [PATCH v3 0/5] mirror: allow specifying working bitmap Date: Fri, 10 May 2024 15:16:42 +0200 Message-Id: <20240510131647.1256467-1-f.ebner@proxmox.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Received-SPF: pass client-ip=94.136.29.106; envelope-from=f.ebner@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Changes from v2 (discussion here [2]): * Cluster size caveats only apply to non-COW diff image, adapt the cluster size check and documentation accordingly. * In the IO test, use backing files (rather than stand-alone diff images) in combination with copy-mode=write-blocking and larger cluster size for target images, to have a more realistic use-case and show that COW prevents ending up with cluster with partial data upon unaligned writes. * Create a separate patch for replacing is_none_mode with sync_mode in MirrorBlockJobx struct. * Disallow using read-only bitmap (cannot be used as working bitmap). * Require that bitmap is enabled at the start of the job. * Avoid IO test script potentially waiting on non-existent job when blockdev-mirror QMP command fails. * Fix pylint issues in IO test. * Rename IO test from sync-bitmap-mirror to mirror-bitmap. Changes from RFC/v1 (discussion here [0]): * Add patch to split BackupSyncMode and MirrorSyncMode. * Drop bitmap-mode parameter and use passed-in bitmap as the working bitmap instead. Users can get the desired behaviors by using the block-dirty-bitmap-clear and block-dirty-bitmap-merge calls (see commit message in patch 2/4 for how exactly). * Add patch to check whether target image's cluster size is at most mirror job's granularity. Optional, it's an extra safety check that's useful when the target is a "diff" image that does not have previously synced data. Use cases: * Possibility to resume a failed mirror later. * Possibility to only mirror deltas to a previously mirrored volume. * Possibility to (efficiently) mirror an drive that was previously mirrored via some external mechanism (e.g. ZFS replication). We are using the last one in production without any issues since about 4 years now. In particular, like mentioned in [1]: > - create bitmap(s) > - (incrementally) replicate storage volume(s) out of band (using ZFS) > - incrementally drive mirror as part of a live migration of VM > - drop bitmap(s) Now, the IO test added in patch 4/5 actually contains yet another use case, namely doing incremental mirrors to qcow2 "diff" images, that only contain the delta and can be rebased later. I had to adapt the IO test, because its output expected the mirror bitmap to still be dirty, but nowadays the mirror is apparently already done when the bitmaps are queried. So I thought, I'll just use 'write-blocking' mode to avoid any potential timing issues. Initially, the qcow2 diff image targets were stand-alone and that suffers from an issue when 'write-blocking' mode is used. If a write is not aligned to the granularity of the mirror target, then rebasing the diff image onto a backing image will not yield the desired result, because the full cluster is considered to be allocated and will "hide" some part of the base/backing image. The failure can be seen by either using 'write-blocking' mode in the IO test or setting the (bitmap) granularity to 32 KiB rather than the current 64 KiB. The test thus uses a more realistic approach where the qcow2 targets have backing images and a check is added in patch 5/5 for the cluster size for non-COW targets. However, with e.g. NBD, the cluster size cannot be queried and prohibiting all bitmap mirrors to NBD targets just to prevent the highly specific edge case seems not worth it, so the limitation is rather documented and the check ignores cases where querying the target image's cluster size returns -ENOTSUP. [0]: https://lore.kernel.org/qemu-devel/b91dba34-7969-4d51-ba40-96a91038cc54@yandex-team.ru/T/#m4ae27dc8ca1fb053e0a32cc4ffa2cfab6646805c [1]: https://lore.kernel.org/qemu-devel/1599127031.9uxdp5h9o2.astroid@nora.none/ [2]: https://lore.kernel.org/qemu-devel/20240307134711.709816-1-f.ebner@proxmox.com/ Fabian Grünbichler (1): iotests: add test for bitmap mirror Fiona Ebner (3): qapi/block-core: avoid the re-use of MirrorSyncMode for backup block/mirror: replace is_none_mode with sync_mode in MirrorBlockJob struct blockdev: mirror: check for target's cluster size when using bitmap John Snow (1): mirror: allow specifying working bitmap block/backup.c | 18 +- block/mirror.c | 101 +- block/monitor/block-hmp-cmds.c | 2 +- block/replication.c | 2 +- blockdev.c | 127 +- include/block/block_int-global-state.h | 7 +- qapi/block-core.json | 64 +- tests/qemu-iotests/tests/mirror-bitmap | 603 ++++ tests/qemu-iotests/tests/mirror-bitmap.out | 3198 ++++++++++++++++++++ tests/unit/test-block-iothread.c | 2 +- 10 files changed, 4055 insertions(+), 69 deletions(-) create mode 100755 tests/qemu-iotests/tests/mirror-bitmap create mode 100644 tests/qemu-iotests/tests/mirror-bitmap.out