[libvirt] [PATCHv3 18/43] snapshot: prevent migration from stranding snapshot data

Migration is another case of stranding metadata. And since snapshot metadata is arbitrarily large, there's no way to shoehorn it into the migration cookie of migration v3. A future patch will make it possible to manually recreate the snapshot metadata on the destination. But even that is limited, since if we delete the snapshot metadata prior to migration, then we won't know the name of the current snapshot to pass along; and if we delete the snapshot metadata after migration and use the v3 migration cookie to pass along the name of the current snapshot, then we need a way to bypass the fact that this patch refuses migration with snapshot metadata present. So eventually, we may have to introduce migration protocol v4 that allows feature negotiation and an arbitrary number of handshake exchanges, so as to pass as many rpc calls as needed to transfer all the snapshot xml hierarchy. But all of that is thoughts for the future; for now, the best course of action is to quit early, rather than get into a funky state of stale metadata. * src/qemu/qemu_driver.c (qemudDomainMigratePerform) (qemuDomainMigrateBegin3, qemuDomainMigratePerform3): Add restriction. --- src/qemu/qemu_driver.c | 24 ++++++++++++++++++++++++ 1 files changed, 24 insertions(+), 0 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index f79d9bc..8d769c9 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -7729,6 +7729,7 @@ qemudDomainMigratePerform (virDomainPtr dom, virDomainObjPtr vm; int ret = -1; const char *dconnuri = NULL; + int nsnapshots; virCheckFlags(QEMU_MIGRATION_FLAGS, -1); @@ -7749,6 +7750,13 @@ qemudDomainMigratePerform (virDomainPtr dom, goto cleanup; } + if ((nsnapshots = virDomainSnapshotObjListNum(&vm->snapshots, 0))) { + qemuReportError(VIR_ERR_OPERATION_INVALID, + _("cannot migrate domain with %d snapshots"), + nsnapshots); + goto cleanup; + } + if (flags & VIR_MIGRATE_PEER2PEER) { dconnuri = uri; uri = NULL; @@ -7825,6 +7833,7 @@ qemuDomainMigrateBegin3(virDomainPtr domain, struct qemud_driver *driver = domain->conn->privateData; virDomainObjPtr vm; char *xml = NULL; + int nsnapshots; virCheckFlags(QEMU_MIGRATION_FLAGS, NULL); @@ -7838,6 +7847,13 @@ qemuDomainMigrateBegin3(virDomainPtr domain, goto cleanup; } + if ((nsnapshots = virDomainSnapshotObjListNum(&vm->snapshots, 0))) { + qemuReportError(VIR_ERR_OPERATION_INVALID, + _("cannot migrate domain with %d snapshots"), + nsnapshots); + goto cleanup; + } + if ((flags & VIR_MIGRATE_CHANGE_PROTECTION)) { if (qemuMigrationJobStart(driver, vm, QEMU_ASYNC_JOB_MIGRATION_OUT) < 0) goto cleanup; @@ -7999,6 +8015,7 @@ qemuDomainMigratePerform3(virDomainPtr dom, struct qemud_driver *driver = dom->conn->privateData; virDomainObjPtr vm; int ret = -1; + int nsnapshots; virCheckFlags(QEMU_MIGRATION_FLAGS, -1); @@ -8012,6 +8029,13 @@ qemuDomainMigratePerform3(virDomainPtr dom, goto cleanup; } + if ((nsnapshots = virDomainSnapshotObjListNum(&vm->snapshots, 0))) { + qemuReportError(VIR_ERR_OPERATION_INVALID, + _("cannot migrate domain with %d snapshots"), + nsnapshots); + goto cleanup; + } + ret = qemuMigrationPerform(driver, dom->conn, vm, xmlin, dconnuri, uri, cookiein, cookieinlen, cookieout, cookieoutlen, -- 1.7.4.4