[libvirt] [PATCH v7 18/23] backup: qemu: Implement metadata tracking for checkpoint APIs

[Peter Krempa]

On Wed, Mar 27, 2019 at 05:10:49 -0500, Eric Blake wrote:
> A lot of this work heavily copies from the existing snapshot
> APIs.  The interaction with qemu during create/delete still
> needs to be implemented, but this takes care of all the libvirt
> metadata (saving and restoring XML, and tracking the relations
> between multiple checkpoints).
> 
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
>  src/qemu/qemu_block.h  |   3 +
>  src/qemu/qemu_conf.h   |   2 +
>  src/qemu/qemu_domain.h |  15 +
>  src/qemu/qemu_block.c  |  12 +
>  src/qemu/qemu_conf.c   |   5 +
>  src/qemu/qemu_domain.c | 133 +++++++
>  src/qemu/qemu_driver.c | 843 +++++++++++++++++++++++++++++++++++++++++
>  7 files changed, 1013 insertions(+)

[...]

> +static char *
> +qemuDomainCheckpointGetXMLDesc(virDomainCheckpointPtr checkpoint,
> +                               unsigned int flags)
> +{
> +    virQEMUDriverPtr driver = checkpoint->domain->conn->privateData;
> +    virDomainObjPtr vm = NULL;
> +    char *xml = NULL;
> +    virDomainMomentObjPtr chk = NULL;
> +    qemuDomainObjPrivatePtr priv;
> +    int rc;
> +    size_t i;
> +    virDomainCheckpointDefPtr chkdef;
> +
> +    virCheckFlags(VIR_DOMAIN_CHECKPOINT_XML_SECURE |
> +                  VIR_DOMAIN_CHECKPOINT_XML_NO_DOMAIN |
> +                  VIR_DOMAIN_CHECKPOINT_XML_SIZE, NULL);
> +
> +    if (!(vm = qemuDomObjFromCheckpoint(checkpoint)))
> +        return NULL;
> +
> +    if (virDomainCheckpointGetXMLDescEnsureACL(checkpoint->domain->conn, vm->def, flags) < 0)
> +        goto cleanup;
> +
> +    if (!(chk = qemuCheckObjFromCheckpoint(vm, checkpoint)))
> +        goto cleanup;
> +    chkdef = virDomainCheckpointObjGetDef(chk);
> +
> +    if (flags & VIR_DOMAIN_CHECKPOINT_XML_SIZE) {
> +        /* TODO: for non-current checkpoint, this requires a QMP sequence per
> +           disk, since the stat of one bitmap in isolation is too low,
> +           and merely adding bitmap sizes may be too high:
> +             block-dirty-bitmap-create tmp
> +             for each bitmap from checkpoint to current:
> +               add bitmap to src_list
> +             block-dirty-bitmap-merge dst=tmp src_list
> +             query-block and read tmp size
> +             block-dirty-bitmap-remove tmp
> +           So for now, go with simpler query-blocks only for current.
> +        */
> +        if (virDomainCheckpointGetCurrent(vm->checkpoints) != chk) {
> +            virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
> +                           _("cannot compute size for non-current checkpoint '%s'"),
> +                           checkpoint->name);
> +            goto cleanup;
> +        }
> +
> +        if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_QUERY) < 0)
> +            goto cleanup;
> +
> +        if (virDomainObjCheckActive(vm) < 0)
> +            goto endjob;
> +
> +        if (qemuBlockNodeNamesDetect(driver, vm, QEMU_ASYNC_JOB_NONE) < 0)
> +            goto endjob;
> +
> +        /* TODO: Shouldn't need to recompute node names. */

I'm not quite sure what you mean by this comment, but note that my
blockdev implementation does not suppose that node names are consistent
accors separate qemu runs.

The main point is that if we are detecting the backing chain which whill
still be supported the detected files get random nodenames. (well
sequential, but that does not matter).

> +        for (i = 0; i < chkdef->ndisks; i++) {
> +            virDomainCheckpointDiskDef *disk = &chkdef->disks[i];
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20190327/aa7feb81/attachment-0001.sig>