On Tue, Jul 16, 2024 at 01:42:27AM +0300, Nikolai Barybin via Devel wrote:
> The usage of HMP commands are highly discouraged by qemu. Moreover,
> current snapshot creation routine does not provide flexibility in
> choosing target device for VM state snapshot.
>
> This patch makes use of QMP commands snapshot-save/delete and by
> default chooses first writable disk (if present) as target for VM
> state, NVRAM - otherwise.
>
> Signed-off-by: Nikolai Barybin <nikolai.barybin@xxxxxxxxxxxxx>
> ---
> src/qemu/qemu_snapshot.c | 158 ++++++++++++++++++++++++++++++++++++---
> 1 file changed, 148 insertions(+), 10 deletions(-)
>
> diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
> index f5260c4a22..83949a9a27 100644
> --- a/src/qemu/qemu_snapshot.c
> +++ b/src/qemu/qemu_snapshot.c
> @@ -308,6 +308,96 @@ qemuSnapshotCreateInactiveExternal(virQEMUDriver *driver,
> return ret;
> }
>
> +static int
> +qemuSnapshotActiveInternalGetWrdevListHelper(virDomainObj *vm,
> + char **wrdevs)
> +{
> + size_t wrdevCount = 0;
> + size_t i = 0;
> +
> + for (i = 0; i < vm->def->ndisks; i++) {
> + virDomainDiskDef *disk = vm->def->disks[i];
> + if (!disk->src->readonly) {
> + wrdevs[wrdevCount] = g_strdup(disk->src->nodenameformat);
> + wrdevCount++;
> + }
> + }
Being !readonly is not sufficient criteria form allowing use of internal
snapshots. It also must be !shareable. It also must be of a format that
permits snapshots, ie effectively only qcow2.
We should likely deny snapshots entirely if there are any shareable disks,
since I can't see it being conceptually sensible to snapshot a VM while
excluding shared writable disks.
Likewise dney snapshots if any writable disk is non-qcow2, as snapshots
need to be consistent across the entire VM writable storage set.
> +
> + if (wrdevCount == 0) {
> + if (vm->def->os.loader->nvram) {
> + wrdevs[0] = g_strdup(vm->def->os.loader->nvram->nodenameformat);
This doesn't make sense IMHO.
If there are not writable disks, we shouldn't be trying to snapshot at
all.
> + } else {
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> + _("no writable device for internal snapshot creation/deletion"));
> + return -1;
> + }
> + }
> +
> + return 0;
> +}
> +
> +
> +static int
> +qemuSnapshotCreateActiveInternalDone(virDomainObj *vm)
> +{
> + qemuBlockJobData *job = NULL;
> + qemuDomainObjPrivate *priv = vm->privateData;
> +
> + if (!(job = virHashLookup(priv->blockjobs, g_strdup_printf("snapsave%d", vm->def->id)))) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("failed to lookup blockjob 'snapsave%1$d'"), vm->def->id);
> + return -1;
> + }
> +
> + qemuBlockJobUpdate(vm, job, VIR_ASYNC_JOB_NONE);
> + if (job->state == VIR_DOMAIN_BLOCK_JOB_FAILED) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("snapshot-save job failed: %1$s"), NULLSTR(job->errmsg));
> + return -1;
> + }
> +
> + return job->state == VIR_DOMAIN_BLOCK_JOB_COMPLETED ? 1 : 0;
> +}
> +
> +
> +static int
> +qemuSnapshotCreateActiveInternalStart(virDomainObj *vm,
> + const char *name)
> +{
> + qemuBlockJobData *job = NULL;
> + g_autofree char** wrdevs = NULL;
> + int ret = -1;
> + int rc = 0;
> +
> + wrdevs = g_new0(char *, vm->def->ndisks + 1);
IMHO the qemuSnapshotActiveInternalGetWrdevListHelper method should be
allocating this, to the correct size it needs.
> + if (qemuSnapshotActiveInternalGetWrdevListHelper(vm, wrdevs) < 0)
> + return -1;
> +
> + if (!(job = qemuBlockJobDiskNew(vm, NULL, QEMU_BLOCKJOB_TYPE_SNAPSHOT_SAVE,
> + g_strdup_printf("snapsave%d", vm->def->id)))) {
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("failed to create new blockjob"));
> + return -1;
> + }
> +
> + qemuBlockJobSyncBegin(job);
> + if (qemuDomainObjEnterMonitorAsync(vm, VIR_ASYNC_JOB_SNAPSHOT) < 0) {
> + ret = -1;
> + goto cleanup;
> + }
> +
> + rc = qemuMonitorSnapshotSave(qemuDomainGetMonitor(vm), job->name,
> + name, wrdevs[0], wrdevs);
> + qemuDomainObjExitMonitor(vm);
> + if (rc == 0) {
> + qemuBlockJobStarted(job, vm);
> + ret = 0;
> + }
> +
> + cleanup:
> + qemuBlockJobStartupFinalize(vm, job);
> + return ret;
> +}
> +
With regards,
Daniel
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