[libvirt] [PATCH v2 3/5] qemu: Track domain quiesced status

[Tomoki Sekiyama]

Adds an quiesced flag into qemuDomainObjPrivate that tracks whether guest
filesystems of the domain is quiesced of not.
It also modify error code from qemuDomainSnapshotFSFreeze and
qemuDomainSnapshotFSThaw, so that a caller can know whether the command is
actually sent to the guest agent. If the error is caused before sending a
freeze command, a counterpart thaw command shouldn't be sent to avoid
confusing the tracking of quiesced status.
---
 src/qemu/qemu_domain.h |    2 ++
 src/qemu/qemu_driver.c |   41 +++++++++++++++++++++++++++++++----------
 2 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index 0bed50b..8a79a00 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -176,6 +176,8 @@ struct _qemuDomainObjPrivate {
     char **qemuDevices; /* NULL-terminated list of devices aliases known to QEMU */
 
     bool hookRun;  /* true if there was a hook run over this domain */
+
+    bool quiesced; /* true if the domain filesystems are quiesced */
 };
 
 typedef enum {
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 9aad2dc..8109e46 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -12040,6 +12040,8 @@ cleanup:
 }
 
 
+/* Return -1 if request is not sent to agent due to misconfig, -2 on agent
+ * failure, and number of frozen filesystems on success. */
 static int
 qemuDomainSnapshotFSFreeze(virDomainObjPtr vm) {
     qemuDomainObjPrivatePtr priv = vm->privateData;
@@ -12056,14 +12058,24 @@ qemuDomainSnapshotFSFreeze(virDomainObjPtr vm) {
                        _("QEMU guest agent is not configured"));
         return -1;
     }
+    if (priv->quiesced) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("domain is already quiesced"));
+        return -1;
+    }
 
     qemuDomainObjEnterAgent(vm);
     freezed = qemuAgentFSFreeze(priv->agent);
     qemuDomainObjExitAgent(vm);
 
-    return freezed;
+    if (freezed >= 0)
+        priv->quiesced = true;
+
+    return freezed < 0 ? -2 : freezed;
 }
 
+/* Return -1 if request is not sent to agent due to misconfig, -2 on agent
+ * failure, and number of thawed filesystems on success. */
 static int
 qemuDomainSnapshotFSThaw(virDomainObjPtr vm, bool report)
 {
@@ -12084,6 +12096,11 @@ qemuDomainSnapshotFSThaw(virDomainObjPtr vm, bool report)
                            _("QEMU guest agent is not configured"));
         return -1;
     }
+    if (!priv->quiesced && report) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("domain is not quiesced"));
+        return -1;
+    }
 
     qemuDomainObjEnterAgent(vm);
     if (!report)
@@ -12093,8 +12110,11 @@ qemuDomainSnapshotFSThaw(virDomainObjPtr vm, bool report)
         virSetError(err);
     qemuDomainObjExitAgent(vm);
 
+    if (thawed >= 0)
+        priv->quiesced = false;
+
     virFreeError(err);
-    return thawed;
+    return thawed < 0 ? -2 : thawed;
 }
 
 /* The domain is expected to be locked and inactive. */
@@ -13069,17 +13089,18 @@ qemuDomainSnapshotCreateActiveExternal(virConnectPtr conn,
         goto cleanup;
 
     /* If quiesce was requested, then issue a freeze command, and a
-     * counterpart thaw command, no matter what.  The command will
-     * fail if the guest is paused or the guest agent is not
-     * running.  */
+     * counterpart thaw command when the it is actually sent to agent.
+     * The command will fail if the guest is paused or the guest agent is not
+     * running, or is already quiesced.  */
     if (flags & VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE) {
-        if (qemuDomainSnapshotFSFreeze(vm) < 0) {
-            /* helper reported the error */
-            thaw = -1;
+        int freeze = qemuDomainSnapshotFSFreeze(vm);
+        if (freeze < 0) {
+            /* the helper reported the error */
+            if (freeze != -1)
+                thaw = -1; /* the command is sent but agent failed */
             goto endjob;
-        } else {
-            thaw = 1;
         }
+        thaw = 1;
     }
 
     /* We need to track what state the guest is in, since taking the