On 06/06/14 00:52, Eric Blake wrote:
> 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@xxxxxxxxxx>
> ---
> 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"));
ACK once you figure out the detection of the capability.
Peter
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