From mboxrd@z Thu Jan 1 00:00:00 1970 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 16394C25B10 for ; Mon, 13 May 2024 06:47:27 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s6PSM-00016B-82; Mon, 13 May 2024 02:46:42 -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 1s6PSK-00014N-SK for qemu-devel@nongnu.org; Mon, 13 May 2024 02:46:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s6PSH-0006Qt-Mu for qemu-devel@nongnu.org; Mon, 13 May 2024 02:46:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1715582796; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/pxScFYb3oXIhvjEh8s6hm0zLJA/zdXbZdHZoeTVr18=; b=fkZE2yyVADcLx+NHkMi2qHP2vWMajfNd0zEcFQlm4l5+LoCcTiTb7Wquh+OswcP0pWfrZT vW6UEg/gkNhTNbLLcKhKjCUsBjo90LxqqUSFV2VXjqC1I28FhC1oktPVbpCT9w8QS74NxT hTTPnWWuITsO+ZIJ2OLz1uJJL0zM8EQ= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-125-c_UhaXzMOE-pbUYbU9uL7A-1; Mon, 13 May 2024 02:46:32 -0400 X-MC-Unique: c_UhaXzMOE-pbUYbU9uL7A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0400D29AA2C4; Mon, 13 May 2024 06:46:32 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C96BC41D; Mon, 13 May 2024 06:46:30 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id A46EA21E66E5; Mon, 13 May 2024 08:46:29 +0200 (CEST) From: Markus Armbruster To: Fiona Ebner Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, 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: Re: [PATCH v3 3/5] mirror: allow specifying working bitmap In-Reply-To: <20240510131647.1256467-4-f.ebner@proxmox.com> (Fiona Ebner's message of "Fri, 10 May 2024 15:16:45 +0200") References: <20240510131647.1256467-1-f.ebner@proxmox.com> <20240510131647.1256467-4-f.ebner@proxmox.com> Date: Mon, 13 May 2024 08:46:29 +0200 Message-ID: <87h6f2cipm.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.332, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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 Fiona Ebner writes: > From: John Snow > > for the mirror job. The bitmap's granularity is used as the job's > granularity. > > The new @bitmap parameter is marked unstable in the QAPI and can > currently only be used for @sync=3Dfull mode. > > Clusters initially dirty in the bitmap as well as new writes are > copied to the target. > > Using block-dirty-bitmap-clear and block-dirty-bitmap-merge API, > callers can simulate the three kinds of @BitmapSyncMode (which is used > by backup): > 1. always: default, just pass bitmap as working bitmap. > 2. never: copy bitmap and pass copy to the mirror job. > 3. on-success: copy bitmap and pass copy to the mirror job and if > successful, merge bitmap into original afterwards. > > When the target image is a non-COW "diff image", i.e. one that was not > used as the target of a previous mirror and the target image's cluster > size is larger than the bitmap's granularity, or when > @copy-mode=3Dwrite-blocking is used, there is a pitfall, because the > cluster in the target image will be allocated, but not contain all the > data corresponding to the same region in the source image. > > An idea to avoid the limitation would be to mark clusters which are > affected by unaligned writes and are not allocated in the target image > dirty, so they would be copied fully later. However, for migration, > the invariant that an actively synced mirror stays actively synced > (unless an error happens) is useful, because without that invariant, > migration might inactivate block devices when mirror still got work > to do and run into an assertion failure [0]. > > Another approach would be to read the missing data from the source > upon unaligned writes to be able to write the full target cluster > instead. > > But certain targets like NBD do not allow querying the cluster size. > To avoid limiting/breaking the use case of syncing to an existing > target, which is arguably more common than the diff image use case, > document the limitation in QAPI. > > This patch was originally based on one by Ma Haocong, but it has since > been modified pretty heavily, first by John and then again by Fiona. > > [0]: https://lore.kernel.org/qemu-devel/1db7f571-cb7f-c293-04cc-cd856e060= c3f@proxmox.com/ > > Suggested-by: Ma Haocong > Signed-off-by: Ma Haocong > Signed-off-by: John Snow > [FG: switch to bdrv_dirty_bitmap_merge_internal] > Signed-off-by: Fabian Gr=C3=BCnbichler > Signed-off-by: Thomas Lamprecht > [FE: rebase for 9.1 > get rid of bitmap mode parameter > use caller-provided bitmap as working bitmap > turn bitmap parameter experimental] > Signed-off-by: Fiona Ebner [...] > diff --git a/include/block/block_int-global-state.h b/include/block/block= _int-global-state.h > index 54f8c8cbcb..8b93db017e 100644 > --- a/include/block/block_int-global-state.h > +++ b/include/block/block_int-global-state.h > @@ -138,6 +138,8 @@ BlockJob *commit_active_start(const char *job_id, Blo= ckDriverState *bs, > * @granularity: The chosen granularity for the dirty bitmap. > * @buf_size: The amount of data that can be in flight at one time. > * @mode: Whether to collapse all images in the chain to the target. > + * @bitmap: Use this bitmap as a working bitmap, i.e. non-dirty clusters= are > + only mirrored if written to later. > * @backing_mode: How to establish the target's backing chain after comp= letion. > * @zero_target: Whether the target should be explicitly zero-initialized > * @on_source_error: The action to take upon error reading from the sour= ce. > @@ -158,7 +160,8 @@ void mirror_start(const char *job_id, BlockDriverStat= e *bs, > BlockDriverState *target, const char *replaces, > int creation_flags, int64_t speed, > uint32_t granularity, int64_t buf_size, > - MirrorSyncMode mode, BlockMirrorBackingMode backing_mo= de, > + MirrorSyncMode mode, BdrvDirtyBitmap *bitmap, > + BlockMirrorBackingMode backing_mode, > bool zero_target, > BlockdevOnError on_source_error, > BlockdevOnError on_target_error, > diff --git a/qapi/block-core.json b/qapi/block-core.json > index 9d94129ea2..5ddebe71ee 100644 > --- a/qapi/block-core.json > +++ b/qapi/block-core.json > @@ -2191,6 +2191,18 @@ > # destination (all the disk, only the sectors allocated in the > # topmost image, or only new I/O). > # > +# @bitmap: The name of a bitmap to use as a working bitmap for > +# sync=3Dfull mode. This argument must be not be present for other > +# sync modes and not at the same time as @granularity. The > +# bitmap's granularity is used as the job's granularity. When > +# the target does not support COW and is a diff image, i.e. one > +# that should only contain the delta and was not synced to > +# previously, the target's cluster size must not be larger than > +# the bitmap's granularity and copy-mode=3Dwrite-blocking should not Comma before "and", please. > +# be used. That is, because unaligned writes will lead to Two spaces between sentences for consistency, please. Suggest "Otherwise, unaligned writes ..." > +# allocated clusters with partial data in the target image! > +# (Since 9.1) > +# > # @granularity: granularity of the dirty bitmap, default is 64K if the > # image format doesn't have clusters, 4K if the clusters are > # smaller than that, else the cluster size. Must be a power of 2 > @@ -2228,12 +2240,18 @@ > # disappear from the query list without user intervention. > # Defaults to true. (Since 3.1) > # > +# Features: > +# > +# @unstable: Member @bitmap is experimental. > +# > # Since: 1.3 > ## > { 'struct': 'DriveMirror', > 'data': { '*job-id': 'str', 'device': 'str', 'target': 'str', > '*format': 'str', '*node-name': 'str', '*replaces': 'str', > - 'sync': 'MirrorSyncMode', '*mode': 'NewImageMode', > + 'sync': 'MirrorSyncMode', > + '*bitmap': { 'type': 'str', 'features': [ 'unstable' ] }, > + '*mode': 'NewImageMode', > '*speed': 'int', '*granularity': 'uint32', > '*buf-size': 'int', '*on-source-error': 'BlockdevOnError', > '*on-target-error': 'BlockdevOnError', > @@ -2513,6 +2531,18 @@ > # destination (all the disk, only the sectors allocated in the > # topmost image, or only new I/O). > # > +# @bitmap: The name of a bitmap to use as a working bitmap for > +# sync=3Dfull mode. This argument must be not be present for other > +# sync modes and not at the same time as @granularity. The > +# bitmap's granularity is used as the job's granularity. When > +# the target does not support COW and is a diff image, i.e. one > +# that should only contain the delta and was not synced to > +# previously, the target's cluster size must not be larger than > +# the bitmap's granularity and copy-mode=3Dwrite-blocking should not > +# be used. That is, because unaligned writes will lead to > +# allocated clusters with partial data in the target image! > +# (Since 9.1) Comments above apply. > +# > # @granularity: granularity of the dirty bitmap, default is 64K if the > # image format doesn't have clusters, 4K if the clusters are > # smaller than that, else the cluster size. Must be a power of 2 > @@ -2548,6 +2578,10 @@ > # disappear from the query list without user intervention. > # Defaults to true. (Since 3.1) > # > +# Features: > +# > +# @unstable: Member @bitmap is experimental. > +# > # Since: 2.6 > # > # Example: > @@ -2562,6 +2596,7 @@ > 'data': { '*job-id': 'str', 'device': 'str', 'target': 'str', > '*replaces': 'str', > 'sync': 'MirrorSyncMode', > + '*bitmap': { 'type': 'str', 'features': [ 'unstable' ] }, > '*speed': 'int', '*granularity': 'uint32', > '*buf-size': 'int', '*on-source-error': 'BlockdevOnError', > '*on-target-error': 'BlockdevOnError', [...] With my comments addressed, Acked-by: Markus Armbruster