Re: [libvirt] [PATCH v2 10/10] blockcommit: turn on active commit

With this in place, I can (finally!) now do: virsh blockcommit $dom vda --shallow --wait --verbose --pivot and watch qemu shorten the backing chain by one, followed by libvirt automatically updating the dumpxml output, effectively undoing the work of virsh snapshot-commit --no-metadata --disk-only. Commit is SOOOO much faster than blockpull, when I'm still fairly close in time to when the temporary qcow2 wrapper file was created via a snapshot operation! * src/qemu/qemu_driver.c (qemuDomainBlockCommit): Implement live commit to regular files. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- src/qemu/qemu_driver.c | 45 +++++++++++++++++++++++++++++++++++++++------ 1 file changed, 39 insertions(+), 6 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 5903144..c0fc5e9 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c

@@ -15540,13 +15542,14 @@ qemuDomainBlockCommit(virDomainPtr dom, &top_parent))) goto endjob; - /* FIXME: qemu 2.0 supports active commit, but as a two-stage - * process; qemu 2.1 is further improving active commit. We need - * to start supporting it in libvirt. */ if (topSource == disk->src) { /* We assume that no one will backport qemu 2.0 active commit * to an earlier qemu without also backporting the block job - * ready event; but this makes sure of that fact */ + * ready event; but this makes sure of that fact. + * + * XXX Also need to check other capability bit(s): qemu 1.7 + * supports async blockjob but not active commit; and qemu 2.0 + * active commit misbehaves on 0-byte file. */ if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_BLOCKJOB_ASYNC)) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("active commit not supported with this QEMU binary"));