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Lunev" , qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Kevin Wolf , qemu-stable@nongnu.org References: <20260828222005.2888213-1-den@openvz.org> <05df98ca-e5d7-4cb2-99d2-74a1a276f58a@proxmox.com> Content-Language: en-US From: "Denis V. 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envelope-from=den@virtuozzo.com; helo=DB3PR0202CU003.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-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: qemu development 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 On 9/1/26 14:23, Fiona Ebner wrote: > Hi Denis, > > Am 29.08.26 um 12:20 AM schrieb Denis V. Lunev: >> From: Denis V. Lunev >> >> it->bs is the cursor into monitor_bdrv_states for the second phase of >> bdrv_next(), so it has to be NULL when that phase starts. Commit >> f6d38c9f6d made the first phase store the node it returns there, to >> unreference the right one when the graph changes underneath. The cursor >> is now left pointing at the last BlockBackend root, so the second phase >> resumes from there instead of from the head of the list and never >> returns a node added before it. >> >> A skipped node drops out of the vm_stop and migration handover paths: >> not flushed, not inactivated, not snapshotted. bdrv_inactivate_all() >> still reports success, so the node keeps its image lock and the >> migration target cannot open the image. Only detached nodes are hit in >> practice, as these callers also recurse into children. >> >> Reset the cursor when the second phase starts. old_bs is taken at the >> top of the function, so f6d38c9f6d keeps working. >> >> Fixes: f6d38c9f6d ("block-backend: fix edge case in bdrv_next() where BDS associated to BB changes") >> Signed-off-by: Denis V. Lunev >> Cc: Fiona Ebner >> Cc: Kevin Wolf > thank you for the fix! > > Reviewed-by: Fiona Ebner > Tested-by: Fiona Ebner > > Should also go into stable I suppose? Unsure. We do not know real consequences, there are no reports. I found this problem by accident only testing migration with big trees a lot. Den