[libvirt] [PATCHv4 39/51] snapshot: allow halting after snapshot
Eric Blake
eblake at redhat.com
Fri Sep 2 04:25:16 UTC 2011
Since a snapshot is fully recoverable, it is useful to have a
snapshot as a means of hibernating a guest, then reverting to
the snapshot to wake the guest up. This mode of usage is
similar to 'virsh save/virsh restore', except that virsh
save uses an external file while virsh snapshot keeps the
vm state internal to a qcow2 file. However, it only works on
persistent domains.
In the usage pattern of snapshot/revert for hibernating a guest,
there is no need to keep the guest running between the two points
in time, especially since that would generate runtime state that
would just be discarded. Add a flag to make it possible to
stop the domain after the snapshot has completed.
* include/libvirt/libvirt.h.in (VIR_DOMAIN_SNAPSHOT_CREATE_HALT):
New flag.
* src/libvirt.c (virDomainSnapshotCreateXML): Document it.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML)
(qemuDomainSnapshotCreateActive): Implement it.
---
include/libvirt/libvirt.h.in | 2 ++
src/libvirt.c | 12 ++++++++++++
src/qemu/qemu_driver.c | 33 +++++++++++++++++++++++++++++----
3 files changed, 43 insertions(+), 4 deletions(-)
diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 64441d9..b35042c 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -2565,6 +2565,8 @@ typedef enum {
snapshot current */
VIR_DOMAIN_SNAPSHOT_CREATE_NO_METADATA = (1 << 2), /* Make snapshot without
remembering it */
+ VIR_DOMAIN_SNAPSHOT_CREATE_HALT = (1 << 3), /* Stop running guest
+ after snapshot */
} virDomainSnapshotCreateFlags;
/* Take a snapshot of the current VM state */
diff --git a/src/libvirt.c b/src/libvirt.c
index 9b3d2b6..0ae6cc2 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -15632,6 +15632,12 @@ error:
* the just-created snapshot has its metadata deleted. This flag is
* incompatible with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE.
*
+ * If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_HALT, then the domain
+ * will be inactive after the snapshot completes, regardless of whether
+ * it was active before; otherwise, a running domain will still be
+ * running after the snapshot. This flag is invalid on transient domains,
+ * and is incompatible with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE.
+ *
* Returns an (opaque) virDomainSnapshotPtr on success, NULL on failure.
*/
virDomainSnapshotPtr
@@ -15675,6 +15681,12 @@ virDomainSnapshotCreateXML(virDomainPtr domain,
_("redefine and no metadata flags are mutually exclusive"));
goto error;
}
+ if ((flags & VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE) &&
+ (flags & VIR_DOMAIN_SNAPSHOT_CREATE_HALT)) {
+ virLibDomainError(VIR_ERR_INVALID_ARG,
+ _("redefine and halt flags are mutually exclusive"));
+ goto error;
+ }
if (conn->driver->domainSnapshotCreateXML) {
virDomainSnapshotPtr ret;
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 3aefaef..d3968cf 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -8678,7 +8678,8 @@ static int
qemuDomainSnapshotCreateActive(virConnectPtr conn,
struct qemud_driver *driver,
virDomainObjPtr *vmptr,
- virDomainSnapshotObjPtr snap)
+ virDomainSnapshotObjPtr snap,
+ unsigned int flags)
{
virDomainObjPtr vm = *vmptr;
qemuDomainObjPrivatePtr priv = vm->privateData;
@@ -8708,6 +8709,24 @@ qemuDomainSnapshotCreateActive(virConnectPtr conn,
qemuDomainObjEnterMonitorWithDriver(driver, vm);
ret = qemuMonitorCreateSnapshot(priv->mon, snap->def->name);
qemuDomainObjExitMonitorWithDriver(driver, vm);
+ if (ret < 0)
+ goto cleanup;
+
+ if (flags & VIR_DOMAIN_SNAPSHOT_CREATE_HALT) {
+ virDomainEventPtr event;
+
+ event = virDomainEventNewFromObj(vm, VIR_DOMAIN_EVENT_STOPPED,
+ VIR_DOMAIN_EVENT_STOPPED_FROM_SNAPSHOT);
+ qemuProcessStop(driver, vm, 0, VIR_DOMAIN_SHUTOFF_FROM_SNAPSHOT);
+ virDomainAuditStop(vm, "from-snapshot");
+ /* We already filtered the _HALT flag for persistent domains
+ * only, so this end job never drops the last reference. */
+ ignore_value(qemuDomainObjEndJob(driver, vm));
+ resume = false;
+ vm = NULL;
+ if (event)
+ qemuDomainEventQueue(driver, event);
+ }
cleanup:
if (resume && virDomainObjIsActive(vm) &&
@@ -8719,7 +8738,7 @@ cleanup:
_("resuming after snapshot failed"));
}
- if (qemuDomainObjEndJob(driver, vm) == 0) {
+ if (vm && qemuDomainObjEndJob(driver, vm) == 0) {
/* Only possible if a transient vm quit while our locks were down,
* in which case we don't want to save snapshot metadata. */
*vmptr = NULL;
@@ -8746,7 +8765,8 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
virCheckFlags(VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE |
VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT |
- VIR_DOMAIN_SNAPSHOT_CREATE_NO_METADATA, NULL);
+ VIR_DOMAIN_SNAPSHOT_CREATE_NO_METADATA |
+ VIR_DOMAIN_SNAPSHOT_CREATE_HALT, NULL);
if (((flags & VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE) &&
!(flags & VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT)) ||
@@ -8769,6 +8789,11 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
"%s", _("domain is marked for auto destroy"));
goto cleanup;
}
+ if (!vm->persistent && (flags & VIR_DOMAIN_SNAPSHOT_CREATE_HALT)) {
+ qemuReportError(VIR_ERR_OPERATION_INVALID, "%s",
+ _("cannot halt after transient domain snapshot"));
+ goto cleanup;
+ }
if (!(def = virDomainSnapshotDefParseString(xmlDesc, driver->caps,
QEMU_EXPECTED_VIRT_TYPES,
@@ -8841,7 +8866,7 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
goto cleanup;
} else {
if (qemuDomainSnapshotCreateActive(domain->conn, driver,
- &vm, snap) < 0)
+ &vm, snap, flags) < 0)
goto cleanup;
}
--
1.7.4.4
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