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Wed, 19 Aug 2020 16:50:37 +0000 (UTC) Date: Wed, 19 Aug 2020 18:50:36 +0200 From: Kevin Wolf To: Max Reitz Subject: Re: [PATCH v7 33/47] mirror: Deal with filters Message-ID: <20200819165036.GH10272@linux.fritz.box> References: <20200625152215.941773-1-mreitz@redhat.com> <20200625152215.941773-34-mreitz@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200625152215.941773-34-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=kwolf@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 04:00:34 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 25.06.2020 um 17:22 hat Max Reitz geschrieben: > This includes some permission limiting (for example, we only need to > take the RESIZE permission for active commits where the base is smaller > than the top). > > Use this opportunity to rename qmp_drive_mirror()'s "source" BDS to > "target_backing_bs", because that is what it really refers to. > > Signed-off-by: Max Reitz > @@ -1682,6 +1721,7 @@ static BlockJob *mirror_start_job( > s->zero_target = zero_target; > s->copy_mode = copy_mode; > s->base = base; > + s->base_overlay = bdrv_find_overlay(bs, base); > s->granularity = granularity; > s->buf_size = ROUND_UP(buf_size, granularity); > s->unmap = unmap; Is this valid without freezing the links between base_overlay and base? Actually, I guess we should freeze everything between bs and base (for base != NULL) and it's a preexisting problem that just happens to affect this code, too. Or maybe freezing everything is too much. We only want to make sure that no non-filter is inserted between base and base_overlay and that base (and now base_overlay) always stay in the backing chain of bs. But what options apart from freezing do we have to achieve this? Why is using base_overlay even better than using base? Assuming there is a good reason, maybe the commit message could spell it out. Kevin