[PATCH v3 06/10] qemu snapshot: use QMP snapshot-save for internal snapshots creation

[Peter Krempa <pkrempa@xxxxxxxxxx>]

From: Nikolai Barybin via Devel <devel@xxxxxxxxxxxxxxxxx>

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 and by
default chooses first writable non-shared qcow2 disk (if present)
as target for VM state.

Signed-off-by: Nikolai Barybin <nikolai.barybin@xxxxxxxxxxxxx>
Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---
 src/qemu/qemu_snapshot.c | 124 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 116 insertions(+), 8 deletions(-)

diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
index f5260c4a22..d4602d386f 100644
--- a/src/qemu/qemu_snapshot.c
+++ b/src/qemu/qemu_snapshot.c
@@ -309,6 +309,99 @@ qemuSnapshotCreateInactiveExternal(virQEMUDriver *driver,
 }


+static char **
+qemuSnapshotActiveInternalCreateGetDevices(virDomainObj *vm,
+                                           virDomainSnapshotDef *snapdef)
+{
+    g_auto(GStrv) devices = g_new0(char *, vm->def->ndisks + 2);
+    size_t ndevs = 0;
+    size_t i = 0;
+
+    /* This relies on @snapdef being aligned and validated via
+     * virDomainSnapshotAlignDisks() and qemuSnapshotPrepare(), which also
+     * ensures that all disks are backed by qcow2. */
+    for (i = 0; i < snapdef->ndisks; i++) {
+        virDomainSnapshotDiskDef *snapdisk = snapdef->disks + i;
+        virDomainDiskDef *domdisk = vm->def->disks[i];
+
+        switch (snapdisk->snapshot) {
+        case VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL:
+            devices[ndevs++] = g_strdup(qemuBlockStorageSourceGetFormatNodename(domdisk->src));
+            break;
+
+        case VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL:
+        case VIR_DOMAIN_SNAPSHOT_LOCATION_MANUAL:
+        case VIR_DOMAIN_SNAPSHOT_LOCATION_NO:
+        case VIR_DOMAIN_SNAPSHOT_LOCATION_DEFAULT:
+        case VIR_DOMAIN_SNAPSHOT_LOCATION_LAST:
+            continue;
+        }
+    }
+
+    if (vm->def->os.loader &&
+        vm->def->os.loader->nvram &&
+        vm->def->os.loader->nvram->format == VIR_STORAGE_FILE_QCOW2) {
+        devices[ndevs++] = g_strdup(qemuBlockStorageSourceGetFormatNodename(vm->def->os.loader->nvram));
+    }
+
+    return g_steal_pointer(&devices);
+}
+
+
+static int
+qemuSnapshotCreateActiveInternalDone(virDomainObj *vm,
+                                     qemuBlockJobData *job)
+{
+    qemuBlockJobUpdate(vm, job, VIR_ASYNC_JOB_SNAPSHOT);
+
+    if (job->state == VIR_DOMAIN_BLOCK_JOB_FAILED) {
+        virReportError(VIR_ERR_OPERATION_FAILED,
+                       _("snapshot-save job failed: %1$s"), NULLSTR(job->errmsg));
+        return -1;
+    }
+
+    return job->state == VIR_DOMAIN_BLOCK_JOB_COMPLETED ? 1 : 0;
+}
+
+
+static qemuBlockJobData *
+qemuSnapshotCreateActiveInternalStart(virDomainObj *vm,
+                                      virDomainSnapshotDef *snapdef)
+{
+    g_autofree char *jobname = g_strdup_printf("internal-snapshot-save-%s", snapdef->parent.name);
+    qemuBlockJobData *job = NULL;
+    g_auto(GStrv) devices = NULL;
+    int rc = 0;
+
+    if (!(devices = qemuSnapshotActiveInternalCreateGetDevices(vm, snapdef)))
+        return NULL;
+
+    if (!(job = qemuBlockJobDiskNew(vm, NULL, QEMU_BLOCKJOB_TYPE_SNAPSHOT_SAVE,
+                                    jobname)))
+        return NULL;
+
+    qemuBlockJobSyncBegin(job);
+
+    if (qemuDomainObjEnterMonitorAsync(vm, VIR_ASYNC_JOB_SNAPSHOT) < 0)
+        goto error;
+
+    rc = qemuMonitorSnapshotSave(qemuDomainGetMonitor(vm), jobname, snapdef->parent.name,
+                                 devices[0], (const char **) devices);
+    qemuDomainObjExitMonitor(vm);
+
+    if (rc < 0)
+        goto error;
+
+    qemuBlockJobStarted(job, vm);
+
+    return job;
+
+ error:
+    qemuBlockJobStartupFinalize(vm, job);
+    return NULL;
+}
+
+
 /* The domain is expected to be locked and active. */
 static int
 qemuSnapshotCreateActiveInternal(virQEMUDriver *driver,
@@ -321,6 +414,7 @@ qemuSnapshotCreateActiveInternal(virQEMUDriver *driver,
     bool resume = false;
     virDomainSnapshotDef *snapdef = virDomainSnapshotObjGetDef(snap);
     int ret = -1;
+    int rv = 0;

     if (!qemuMigrationSrcIsAllowed(vm, false, VIR_ASYNC_JOB_SNAPSHOT, 0))
         goto cleanup;
@@ -342,15 +436,29 @@ qemuSnapshotCreateActiveInternal(virQEMUDriver *driver,
         }
     }

-    if (qemuDomainObjEnterMonitorAsync(vm, VIR_ASYNC_JOB_SNAPSHOT) < 0) {
-        resume = false;
-        goto cleanup;
-    }
+    if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_SNAPSHOT_INTERNAL_QMP)) {
+        g_autoptr(qemuBlockJobData) job = NULL;

-    ret = qemuMonitorCreateSnapshot(priv->mon, snap->def->name);
-    qemuDomainObjExitMonitor(vm);
-    if (ret < 0)
-        goto cleanup;
+        if (!(job = qemuSnapshotCreateActiveInternalStart(vm, snapdef)))
+            goto cleanup;
+
+        while ((rv = qemuSnapshotCreateActiveInternalDone(vm, job)) != 1) {
+            if (rv < 0 || qemuDomainObjWait(vm) < 0)
+                goto cleanup;
+        }
+
+        ret = 0;
+    } else {
+        if (qemuDomainObjEnterMonitorAsync(vm, VIR_ASYNC_JOB_SNAPSHOT) < 0) {
+            resume = false;
+            goto cleanup;
+        }
+
+        ret = qemuMonitorCreateSnapshot(priv->mon, snap->def->name);
+        qemuDomainObjExitMonitor(vm);
+        if (ret < 0)
+            goto cleanup;
+    }

     if (!(snapdef->cookie = (virObject *) qemuDomainSaveCookieNew(vm)))
         goto cleanup;
-- 
2.46.0