On Thu, Sep 24, 2020 at 01:43:49PM +0200, Peter Krempa wrote:
> Later patches will implement support for <transient/> disks in libvirt
> by installing an overlay on top of the configured image. This will
> require cleanup after the VM will be stopped so that the state is
> correctly discarded.
>
> Since the overlay will be installed only during the startup phase of the
> VM we need to ensure that qemuProcessStop doesn't delete the original
> file on some previous failure. This is solved by adding
> 'inhibitDiskTransientDelete' VM private data member which is set prior
> to any startup step and will be cleared once transient disk overlays are
> established.
>
> Based on that we can then delete the overlays for any <transient/> disk.
>
> Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
> ---
> src/qemu/qemu_domain.c | 2 ++
> src/qemu/qemu_domain.h | 4 ++++
> src/qemu/qemu_process.c | 22 ++++++++++++++++++++++
> 3 files changed, 28 insertions(+)
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 279de2997d..dc5949edfa 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -1792,6 +1792,8 @@ qemuDomainObjPrivateDataClear(qemuDomainObjPrivatePtr priv)
> priv->dbusVMStateIds = NULL;
>
> priv->dbusVMState = false;
> +
> + priv->inhibitDiskTransientDelete = false;
> }
>
>
> diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
> index c7c3c5c073..ec776ced72 100644
> --- a/src/qemu/qemu_domain.h
> +++ b/src/qemu/qemu_domain.h
> @@ -263,6 +263,10 @@ struct _qemuDomainObjPrivate {
> char **dbusVMStateIds;
> /* true if -object dbus-vmstate was added */
> bool dbusVMState;
> +
> + /* prevent deletion of <transient> disk overlay files between startup and
> + * succesful setup of the overlays */
> + bool inhibitDiskTransientDelete;
> };
>
> #define QEMU_DOMAIN_PRIVATE(vm) \
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index f21b8f1585..ffb3afa9c5 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -5616,6 +5616,9 @@ qemuProcessInit(virQEMUDriverPtr driver,
> if (virDomainObjSetDefTransient(driver->xmlopt, vm, priv->qemuCaps) < 0)
> goto cleanup;
>
> + /* don't clean up files for <transient> disks until we set them up */
> + priv->inhibitDiskTransientDelete = true;
> +
> if (flags & VIR_QEMU_PROCESS_START_PRETEND) {
> if (qemuDomainSetPrivatePaths(driver, vm) < 0) {
> virDomainObjRemoveTransientDef(vm);
> @@ -7710,6 +7713,18 @@ void qemuProcessStop(virQEMUDriverPtr driver,
> }
>
> qemuBlockRemoveImageMetadata(driver, vm, disk->dst, disk->src);
> +
> + /* for now transient disks are forbidden with migration so they
> + * can be handled here */
> + if (disk->transient &&
> + !priv->inhibitDiskTransientDelete) {
> + VIR_DEBUG("Removing transient overlay '%s' of disk '%s'",
> + disk->src->path, disk->dst);
> + if (qemuDomainStorageFileInit(driver, vm, disk->src, NULL) >= 0) {
> + virStorageFileUnlink(disk->src);
> + virStorageFileDeinit(disk->src);
> + }
> + }
> }
> }
>
> @@ -8125,6 +8140,10 @@ qemuProcessReconnect(void *opaque)
> cfg = virQEMUDriverGetConfig(driver);
> priv = obj->privateData;
>
> + /* expect that libvirt might have crashed during VM start, so prevent
> + * cleanup of transient disks */
> + priv->inhibitDiskTransientDelete = true;
> +
> if (qemuDomainObjBeginJob(driver, obj, QEMU_JOB_MODIFY) < 0)
> goto error;
> jobStarted = true;
> @@ -8228,6 +8247,9 @@ qemuProcessReconnect(void *opaque)
> goto error;
> }
>
> + /* vm startup complete, we can remove transient disks if required */
> + priv->inhibitDiskTransientDelete = false;
> +
> /* In case the domain shutdown while we were not running,
> * we need to finish the shutdown process. And we need to do it after
> * we have virQEMUCaps filled in.
> --
Tested-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
Thanks a lot!
Masa
