From 7dc44eb059fc976e7c88091477a981a4a90bf2f5 Mon Sep 17 00:00:00 2001
From: Eric Blake <eblake@redhat.com>
Date: Sat, 27 Aug 2011 13:48:19 -0600
Subject: [PATCH] snapshot: fine-tune qemu snapshot revert states

For a system checkpoint of a running or paused domain, it's fairly
easy to honor new flags for altering which state to use after the
revert.  For an inactive snapshot, the revert has to be done while
there is no qemu process, so do back-to-back transitions; this also
lets us revert to inactive snapshots even for transient domains.

* src/qemu/qemu_driver.c (qemuDomainRevertToSnapshot): Support new
flags.
---
 src/qemu/qemu_driver.c | 59 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 51 insertions(+), 8 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 53bf5bfe2e..43cb4c04eb 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -8921,7 +8921,8 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
     qemuDomainObjPrivatePtr priv;
     int rc;
 
-    virCheckFlags(0, -1);
+    virCheckFlags(VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING |
+                  VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED, -1);
 
     /* We have the following transitions, which create the following events:
      * 1. inactive -> inactive: none
@@ -8953,6 +8954,17 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         goto cleanup;
     }
 
+    if (!vm->persistent &&
+        snap->def->state != VIR_DOMAIN_RUNNING &&
+        snap->def->state != VIR_DOMAIN_PAUSED &&
+        (flags & (VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING |
+                  VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED)) == 0) {
+        qemuReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                        _("transient domain needs to request run or pause "
+                          "to revert to inactive snapshot"));
+        goto cleanup;
+    }
+
     if (vm->current_snapshot) {
         vm->current_snapshot->def->current = false;
         if (qemuDomainSnapshotWriteMetadata(vm, vm->current_snapshot,
@@ -9026,7 +9038,9 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         }
 
         /* Touch up domain state.  */
-        if (snap->def->state == VIR_DOMAIN_PAUSED) {
+        if (!(flags & VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING) &&
+            (snap->def->state == VIR_DOMAIN_PAUSED ||
+             (flags & VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED))) {
             /* Transitions 3, 6, 9 */
             virDomainObjSetState(vm, VIR_DOMAIN_PAUSED,
                                  VIR_DOMAIN_PAUSED_FROM_SNAPSHOT);
@@ -9080,20 +9094,49 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
             event = virDomainEventNewFromObj(vm,
                                              VIR_DOMAIN_EVENT_STOPPED,
                                              detail);
+        }
+
+        if (qemuDomainSnapshotRevertInactive(vm, snap) < 0) {
             if (!vm->persistent) {
-                /* XXX For transient domains, enforce that one of the
-                 * flags is set to get domain running again. For now,
-                 * reverting to offline on a transient domain ends up
-                 * killing the domain, without reverting any disk state. */
                 if (qemuDomainObjEndJob(driver, vm) > 0)
                     virDomainRemoveInactive(&driver->domains, vm);
                 vm = NULL;
                 goto cleanup;
             }
+            goto endjob;
         }
 
-        if (qemuDomainSnapshotRevertInactive(vm, snap) < 0)
-            goto endjob;
+        if (flags & (VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING |
+                     VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED)) {
+            /* Flush first event, now do transition 2 or 3 */
+            bool paused = (flags & VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED) != 0;
+
+            if (event)
+                qemuDomainEventQueue(driver, event);
+            rc = qemuProcessStart(snapshot->domain->conn, driver, vm, NULL,
+                                  paused, false, -1, NULL, NULL,
+                                  VIR_VM_OP_CREATE);
+            virDomainAuditStart(vm, "from-snapshot", rc >= 0);
+            if (rc < 0) {
+                if (!vm->persistent) {
+                    if (qemuDomainObjEndJob(driver, vm) > 0)
+                        virDomainRemoveInactive(&driver->domains, vm);
+                    vm = NULL;
+                    goto cleanup;
+                }
+                goto endjob;
+            }
+            detail = VIR_DOMAIN_EVENT_STARTED_FROM_SNAPSHOT;
+            event = virDomainEventNewFromObj(vm,
+                                             VIR_DOMAIN_EVENT_STARTED,
+                                             detail);
+            if (paused) {
+                detail = VIR_DOMAIN_EVENT_SUSPENDED_FROM_SNAPSHOT;
+                event2 = virDomainEventNewFromObj(vm,
+                                                  VIR_DOMAIN_EVENT_SUSPENDED,
+                                                  detail);
+            }
+        }
     }
 
     ret = 0;
-- 
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