Re: [libvirt] [PATCHv2 3/3] snapshot: rudimentary qemu support for atomic disk snapshot

Taking an external snapshot of just one disk is atomic, without having to pause and resume the VM. This also paves the way for later patches to interact with the new qemu 'transaction' monitor command. The various scenarios when requesting atomic are: online, 1 disk, old qemu - safe, allowed by this patch online, more than 1 disk, old qemu - failure, this patch offline snapshot - safe, once a future patch implements offline disk snapshot online, 1 or more disks, new qemu - safe, once future patch uses transaction Taking an online system checkpoint snapshot is atomic, since it is done via a single 'savevm' monitor command. Taking an offline system checkpoint snapshot currently uses multiple qemu-img invocations with no provision for cleanup of partial failure, so for now we mark it unsupported. * src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Support new flag for single-disk setups. (qemuDomainSnapshotDiskPrepare): Check for atomic here. (qemuDomainSnapshotCreateDiskActive): Skip pausing the VM when atomic supported. (qemuDomainSnapshotIsAllowed): Use bool instead of int. --- Patches 1/3 and 2/3 unchanged. v2: consider interactions of atomic with non-disk-snapshots src/qemu/qemu_driver.c | 56 +++++++++++++++++++++++++++++++++-------------- 1 files changed, 39 insertions(+), 17 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 85f8cf7..9e62738 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -10279,6 +10295,12 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain, &vm, snap, flags)< 0) goto cleanup; } else if (!virDomainObjIsActive(vm)) { + if (flags& VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC) { + qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("atomic snapshots of inactive domains not " + "implemented yet")); + goto cleanup;

+ } if (qemuDomainSnapshotCreateInactive(driver, vm, snap)< 0) goto cleanup; } else {