From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [45.144.208.40]) by lore.proxmox.com (Postfix) with ESMTPS id C36841FF0E4 for ; Tue, 14 Jul 2026 16:26:36 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 1CE5721429; Tue, 14 Jul 2026 16:26:36 +0200 (CEST) From: Fiona Ebner To: pve-devel@lists.proxmox.com Subject: [PATCH qemu-server 2/5] snapshot: document how consistency between multiple disks is achieved Date: Tue, 14 Jul 2026 16:25:58 +0200 Message-ID: <20260714142629.277917-3-f.ebner@proxmox.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260714142629.277917-1-f.ebner@proxmox.com> References: <20260714142629.277917-1-f.ebner@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1784039175793 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.282 Adjusted score from AWL reputation of From: address DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment (newer systems) RCVD_IN_DNSWL_LOW -0.7 Sender listed at https://www.dnswl.org/, low trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: POSSWDUU5EAFPB37LDORCGMREXIK6CYC X-Message-ID-Hash: POSSWDUU5EAFPB37LDORCGMREXIK6CYC X-MailFrom: f.ebner@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Document how the savevm-start and savevm-end QMP handlers affect the run-state of the VM and the block layer and how consistency between multiple disks is ensured. Signed-off-by: Fiona Ebner --- src/PVE/QemuConfig.pm | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/PVE/QemuConfig.pm b/src/PVE/QemuConfig.pm index 26f0fda2..cadcd9e9 100644 --- a/src/PVE/QemuConfig.pm +++ b/src/PVE/QemuConfig.pm @@ -321,6 +321,13 @@ sub __snapshot_create_vol_snapshots_hook { if ($running) { my $storecfg = PVE::Storage::config(); + # NOTE savevm-start is called even if no state is saved to ensure consistency between + # multiple disks. The savevm-start QMP handler does a vm_stop() which drains and flushes all + # block devices via QEMU's block layer. If the state is saved, vm_stop() is called when + # saving the state converges (right before the status from query-savevm becomes + # 'completed'). The savevm-end QMP handler resumes the VM if it was running (and not + # paused/suspended/etc.) before. + if ($hook eq "before") { if ($snap->{vmstate}) { my $path = PVE::Storage::path($storecfg, $snap->{vmstate}); -- 2.47.3