On Fri, Aug 28, 2020 at 10:08:31 -0400, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
>
> Here is the implementation of transient option for qcow2 and raw format
> disk. This gets available <transient/> directive in domain xml file
> like as:
>
> <disk type='file' device='disk'>
> <driver name='qemu' type='qcow2'/>
> <source file='/var/lib/libvirt/images/guest.qcow2'/>
> <target dev='vda' bus='virtio'/>
> <transient/>
> </disk>
>
> When the qemu command line options are built, a new qcow2 image is
> created with backing qcow2 by using blockdev-snapshot command.
> The backing image is the qcow2 file which is set as <source>.
> The filename of the new qcow2 image is original-source-file.TRANSIENT.
>
> Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
> ---
> src/qemu/qemu_snapshot.c | 134 ++++++++++++++++++++++++++++++++++++++
> src/qemu/qemu_snapshot.h | 8 +++
> src/util/virstoragefile.h | 2 +
> 3 files changed, 144 insertions(+)
>
> diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
> index d310e6ff02..5c61d19f26 100644
> --- a/src/qemu/qemu_snapshot.c
> +++ b/src/qemu/qemu_snapshot.c
> @@ -2265,3 +2265,137 @@ qemuSnapshotDelete(virDomainObjPtr vm,
> cleanup:
> return ret;
> }
> +
> +static int
> +qemuTransientDiskPrepareOne(virQEMUDriverPtr driver,
This should be named with a qemuSnapshot... prefix:
qemuSnapshotDiskTransientPrepareOne for example.
> + virDomainObjPtr vm,
> + qemuSnapshotDiskDataPtr data,
> + virHashTablePtr blockNamedNodeData,
> + int asyncJob,
> + virJSONValuePtr actions)
> +{
> + int rc = -1;
> + virStorageSourcePtr dest;
You can use g_autoptr here.
> + virStorageSourcePtr src = data->disk->src;
> + qemuDomainObjPrivatePtr priv = vm->privateData;
> + g_autoptr(virQEMUDriverConfig) cfg = virQEMUDriverGetConfig(priv->driver);
> +
> + if (!strlen(src->path))
This will not work as expected. You must make sure that the source disk
is VIR_STORAGE_TYPE_FILE. presence of src->path does not guarantee it.
Also you can use virStorageSourceIsEmpty() here if you want to skip
empty cdroms, but transient cdrom/readonly disks should be rejected in
the config validator beforehand.
> + return rc;
Please always return constants right away. (rc is a constant at this
point).
> +
> + if (!(dest = virStorageSourceNew()))
> + return rc;
> +
> + dest->path = g_strdup_printf("%s.TRANSIENT", src->path);
> +
> + if (virFileExists(dest->path)) {
> + virReportError(VIR_ERR_INVALID_ARG,
> + _("Transient disk '%s' for '%s' exists"),
> + dest->path, src->path);
> + goto cleanup;
> + }
> +
> + dest->type = VIR_STORAGE_TYPE_FILE;
> + dest->format = VIR_STORAGE_FILE_QCOW2;
> + data->src = dest;
> +
> + if (qemuSnapshotDiskPrepareOne(driver, vm, cfg, data->disk,
> + NULL, data, blockNamedNodeData,
Create a virDomainSnapshotDiskDefPtr with the correct data from above
and pass it in here, rather than working around the addition to the data
structure.
> + false, true, asyncJob, actions) < 0)
> + goto cleanup;
> +
> + rc = 0;
> + cleanup:
> + if (rc < 0)
> + g_free(dest->path);
> +
> + return rc;
> +}
> +
> +static int
> +qemuWaitTransaction(virQEMUDriverPtr driver,
> + virDomainObjPtr vm,
> + int asyncJob,
> + virJSONValuePtr *actions)
This function isn't IMO necessary.
> +{
> + qemuDomainObjPrivatePtr priv = vm->privateData;
> +
> + if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
> + return -1;
> +
> + if (qemuMonitorTransaction(priv->mon, actions) < 0)
> + return -1;
> +
> + if (qemuDomainObjExitMonitor(driver, vm) < 0)
> + return -1;
> +
> + rturn 0;
> +}
> +
> +int
> +qemuTransientCreatetDisk(virQEMUDriverPtr driver,
> + virDomainObjPtr vm,
> + int asyncJob)
> +{
> + size_t i;
> + int rc = -1;
> + size_t ndata = 0;
> + qemuSnapshotDiskDataPtr data = NULL;
> + g_autoptr(virJSONValue) actions = NULL;
> + qemuDomainObjPrivatePtr priv = vm->privateData;
> + g_autoptr(virHashTable) blockNamedNodeData = NULL;
> + bool blockdev = virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_BLOCKDEV);
Imo it will be better to factor out the common parts from this and
qemuSnapshotCreateDiskActive and then just use the disjunct logic in
this function.
> +
> + if (!blockdev)
> + return rc;
This breaks startup of VMs with pre-blockdev qemu as it returns -1 here
directly when blockdev is not supported.
> + if (VIR_ALLOC_N(data, vm->def->ndisks) < 0)
> + return rc;
> +
> + if (!(blockNamedNodeData = qemuBlockGetNamedNodeData(vm, asyncJob)))
> + goto cleanup;
> +
> + if (!(actions = virJSONValueNewArray()))
> + goto cleanup;
> +
> + for (i = 0; i < vm->def->ndisks; i++) {
> + virDomainDiskDefPtr disk = vm->def->disks[i];
> +
> + if (disk->src->readonly)
> + continue;
This transient+readonly should be a hard error and validated in the
config validator rather than here.
> +
> + if (disk->transient) {
> + data[ndata].disk = disk;
> + if (qemuTransientDiskPrepareOne(driver, vm, &data[ndata], blockNamedNodeData,
> + asyncJob, actions) < 0)
misaligned code.
> + goto cleanup;
> + ndata++;
> + }
> + }
> +
> + if (qemuWaitTransaction(driver, vm, asyncJob, &actions) < 0)
> + goto cleanup;
> +
> + for (i = 0; i < ndata; i++) {
> + qemuSnapshotDiskDataPtr dd = &data[i];
> +
> + qemuSnapshotDiskUpdateSource(driver, vm, dd, blockdev);
> + dd->disk->src->transientEstablished = true;
> + }
These both can be factored out and shared with the snapshot code.
> +
> + VIR_FREE(data);
> + rc = 0;
> + cleanup:
> + qemuSnapshotDiskCleanup(data, vm->def->ndisks, driver, vm, asyncJob);
> +
> + return rc;
> +}
> +
> +void
> +qemuTransientRemoveDisk(virDomainDiskDefPtr disk)
This doesn't belong into this helper file. Removal of the snapshot
images is not related to snapshots.
> +{
> + if (disk->src->transientEstablished) {
> + VIR_DEBUG("unlink transient disk: %s", disk->src->path);
> + unlink(disk->src->path);
> + }
> +}
> diff --git a/src/qemu/qemu_snapshot.h b/src/qemu/qemu_snapshot.h
> index 8b3ebe87b1..aecb1762d2 100644
> --- a/src/qemu/qemu_snapshot.h
> +++ b/src/qemu/qemu_snapshot.h
> @@ -53,3 +53,11 @@ int
> qemuSnapshotDelete(virDomainObjPtr vm,
> virDomainSnapshotPtr snapshot,
> unsigned int flags);
> +
> +int
> +qemuTransientCreatetDisk(virQEMUDriverPtr driver,
> + virDomainObjPtr vm,
> + int asyncJob);
> +
> +void
> +qemuTransientRemoveDisk(virDomainDiskDefPtr disk);
> diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
> index f73b3ee005..fd42d017f3 100644
> --- a/src/util/virstoragefile.h
> +++ b/src/util/virstoragefile.h
> @@ -383,6 +383,8 @@ struct _virStorageSource {
> /* these must not be used apart from formatting the output JSON in the qemu driver */
> char *ssh_user;
> bool ssh_host_key_check_disabled;
> +
> + bool transientEstablished;
The deep copy function is not updated with this new member. Also you
should document this variable.
> };
>
> G_DEFINE_AUTOPTR_CLEANUP_FUNC(virStorageSource, virObjectUnref);
> --
> 2.27.0
>
