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[libvirt] [RFC: PATCH 4/4] snapshot: new XML for external system checkpoint



Each <domainsnapshot> can now contain an optional <memory>
element that describes how the VM state was handled, similar
to disk snapshots.  The new element will always appear in
output; for back-compat, an input that lacks the element will
assume 'no' or 'internal' according to the domain state.

Along with this change, it is now possible to pass <disks> in
the XML for an offline snapshot; this also needs to be wired up
in a future patch, to make it possible to choose internal vs.
external on a per-disk basis for each disk in an offline domain.
At that point, using the --disk-only flag for an offline domain
will be able to work.

For some examples below, remember that qemu supports the
following snapshot actions:

qemu-img: offline external and internal disk
savevm: online internal VM and disk
migrate: online external VM
transaction: online external disk

=====
<domainsnapshot>
  <memory snapshot='no'/>
  ...
</domainsnapshot>

implies that there is no VM state saved (mandatory for
offline and disk-only snapshots, not possible otherwise);
using qemu-img for offline domains and transaction for online.

=====
<domainsnapshot>
  <memory snapshot='internal'/>
  ...
</domainsnapshot>

state is saved inside one of the disks (as in qemu's 'savevm'
system checkpoint implementation).  If needed in the future,
we can also add an attribute pointing out _which_ disk saved
the internal state; maybe disk='vda'.

=====
<domainsnapshot>
  <memory snapshot='external' file='/path/to/state'/>
  ...
</domainsnapshot>

This is not wired up yet, but future patches will allow this to
control a combination of 'virsh save /path/to/state' plus disk
snapshots from the same point in time.

=====

So for 0.10.0, I plan to implement this table of combinations,
with '*' designating new code and '+' designating existing code
reached through new combinations of xml and/or the existing
DISK_ONLY flag:

domain  memory  disk   disk-only | result
-----------------------------------------
offline omit    omit   any       | memory=no disk=int, via qemu-img
offline no      omit   any       |+memory=no disk=int, via qemu-img
offline omit/no no     any       | invalid combination (nothing to snapshot)
offline omit/no int    any       |+memory=no disk=int, via qemu-img
offline omit/no ext    any       |*memory=no disk=ext, via qemu-img
offline int/ext any    any       | invalid combination (no memory to save)
online  omit    omit   off       | memory=int disk=int, via savevm
online  omit    omit   on        | memory=no disk=default, via transaction
online  omit    no/ext off       | unsupported for now
online  omit    no     on        | invalid combination (nothing to snapshot)
online  omit    ext    on        | memory=no disk=ext, via transaction
online  omit    int    off       |+memory=int disk=int, via savevm
online  omit    int    on        | unsupported for now
online  no      omit   any       |+memory=no disk=default, via transaction
online  no      no     any       | invalid combination (nothing to snapshot)
online  no      int    any       | unsupported for now
online  no      ext    any       |+memory=no disk=ext, via transaction
online  int/ext any    on        | invalid combination (disk-only vs. memory)
online  int     omit   off       |+memory=int disk=int, via savevm
online  int     no/ext off       | unsupported for now
online  int     int    off       |+memory=int disk=int, via savevm
online  ext     omit   off       |*memory=ext disk=default, via migrate+trans
online  ext     no     off       |+memory=ext disk=no, via migrate
online  ext     int    off       | unsupported for now
online  ext     ext    off       |*memory=ext disk=ext, via migrate+transaction

* docs/schemas/domainsnapshot.rng (memory): New RNG element.
* docs/formatsnapshot.html.in: Document it.
* src/conf/snapshot_conf.h (virDomainSnapshotDef): New fields.
* src/conf/domain_conf.c (virDomainSnapshotDefFree)
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Manage new fields.
* tests/domainsnapshotxml2xmltest.c: New test.
* tests/domainsnapshotxml2xmlin/*.xml: Update existing tests.
* tests/domainsnapshotxml2xmlout/*.xml: Likewise.
---
 docs/formatsnapshot.html.in                        | 11 +++++
 docs/schemas/domainsnapshot.rng                    | 23 +++++++++
 src/conf/snapshot_conf.c                           | 55 ++++++++++++++++++++--
 src/conf/snapshot_conf.h                           |  3 ++
 tests/domainsnapshotxml2xmlin/external_vm.xml      | 10 ++++
 tests/domainsnapshotxml2xmlin/noparent.xml         |  9 ++++
 tests/domainsnapshotxml2xmlout/all_parameters.xml  |  1 +
 tests/domainsnapshotxml2xmlout/disk_snapshot.xml   |  1 +
 tests/domainsnapshotxml2xmlout/external_vm.xml     | 43 +++++++++++++++++
 tests/domainsnapshotxml2xmlout/full_domain.xml     |  1 +
 tests/domainsnapshotxml2xmlout/metadata.xml        |  1 +
 tests/domainsnapshotxml2xmlout/noparent.xml        |  1 +
 .../noparent_nodescription.xml                     |  1 +
 .../noparent_nodescription_noactive.xml            |  1 +
 tests/domainsnapshotxml2xmltest.c                  |  1 +
 15 files changed, 159 insertions(+), 3 deletions(-)
 create mode 100644 tests/domainsnapshotxml2xmlin/external_vm.xml
 create mode 100644 tests/domainsnapshotxml2xmlin/noparent.xml
 create mode 100644 tests/domainsnapshotxml2xmlout/external_vm.xml

diff --git a/docs/formatsnapshot.html.in b/docs/formatsnapshot.html.in
index ec5ebf3..e2dd9a2 100644
--- a/docs/formatsnapshot.html.in
+++ b/docs/formatsnapshot.html.in
@@ -106,6 +106,17 @@
         description is omitted when initially creating the snapshot,
         then this field will be empty.
       </dd>
+      <dt><code>memory</code></dt>
+      <dd>On input, this is an optional request for how to handle VM
+        state.  For an offline domain or a disk-only snapshot,
+        attribute <code>snapshot</code> must be <code>no</code>, since
+        there is no VM state saved; otherwise, the attribute can
+        be <code>internal</code> if the VM state is piggy-backed with
+        other internal disk state, or <code>external</code> along with
+        a second attribute <code>file</code> giving the absolute path
+        of the file holding the VM state.  <span class="since">Since
+        0.10.0</span>
+      </dd>
       <dt><code>disks</code></dt>
       <dd>On input, this is an optional listing of specific
         instructions for disk snapshots; it is needed when making a
diff --git a/docs/schemas/domainsnapshot.rng b/docs/schemas/domainsnapshot.rng
index 0ef0631..230833d 100644
--- a/docs/schemas/domainsnapshot.rng
+++ b/docs/schemas/domainsnapshot.rng
@@ -31,6 +31,29 @@
           </element>
         </optional>
         <optional>
+          <element name='memory'>
+            <choice>
+              <attribute name='snapshot'>
+                <choice>
+                  <value>no</value>
+                  <value>internal</value>
+                </choice>
+              </attribute>
+              <group>
+                <optional>
+                  <attribute name='snapshot'>
+                    <value>external</value>
+                  </attribute>
+                </optional>
+                <attribute name='file'>
+                  <ref name='absFilePath'/>
+                </attribute>
+              </group>
+            </choice>
+            <empty/>
+          </element>
+        </optional>
+        <optional>
           <element name='disks'>
             <zeroOrMore>
               <ref name='disksnapshot'/>
diff --git a/src/conf/snapshot_conf.c b/src/conf/snapshot_conf.c
index b9eb74c..ce40724 100644
--- a/src/conf/snapshot_conf.c
+++ b/src/conf/snapshot_conf.c
@@ -96,6 +96,7 @@ void virDomainSnapshotDefFree(virDomainSnapshotDefPtr def)
     VIR_FREE(def->name);
     VIR_FREE(def->description);
     VIR_FREE(def->parent);
+    VIR_FREE(def->file);
     for (i = 0; i < def->ndisks; i++)
         virDomainSnapshotDiskDefClear(&def->disks[i]);
     VIR_FREE(def->disks);
@@ -175,6 +176,8 @@ virDomainSnapshotDefParseString(const char *xmlStr,
     int active;
     char *tmp;
     int keepBlanksDefault = xmlKeepBlanksDefault(0);
+    char *memorySnapshot = NULL;
+    char *memoryFile = NULL;

     xml = virXMLParseCtxt(NULL, xmlStr, _("(domain_snapshot)"), &ctxt);
     if (!xml) {
@@ -267,11 +270,48 @@ virDomainSnapshotDefParseString(const char *xmlStr,
         def->creationTime = tv.tv_sec;
     }

+    memorySnapshot = virXPathString("string(./memory/@snapshot)", ctxt);
+    memoryFile = virXPathString("string(./memory/@file)", ctxt);
+    if (memorySnapshot) {
+        def->memory = virDomainSnapshotLocationTypeFromString(memorySnapshot);
+        if (def->memory <= 0) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("unknown memory snapshot setting '%s'"),
+                           memorySnapshot);
+            goto cleanup;
+        }
+        if (memoryFile &&
+            def->memory != VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("memory filename '%s' requires external snapshot"),
+                           memoryFile);
+            goto cleanup;
+        }
+    } else if (memoryFile) {
+        def->memory = VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL;
+    } else {
+        def->memory = ((flags & VIR_DOMAIN_SNAPSHOT_PARSE_DISKS ||
+                        (flags & VIR_DOMAIN_SNAPSHOT_PARSE_REDEFINE &&
+                         def->state == VIR_DOMAIN_DISK_SNAPSHOT)) ?
+                       VIR_DOMAIN_SNAPSHOT_LOCATION_NONE :
+                       VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL);
+    }
+    if ((def->state == VIR_DOMAIN_SHUTOFF ||
+         def->state == VIR_DOMAIN_DISK_SNAPSHOT) &&
+        def->memory != VIR_DOMAIN_SNAPSHOT_LOCATION_NONE) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("memory state cannot be saved with offline snapshot"));
+        goto cleanup;
+    }
+    def->file = memoryFile;
+    memoryFile = NULL;
+
     if ((i = virXPathNodeSet("./disks/*", ctxt, &nodes)) < 0)
         goto cleanup;
     if (flags & VIR_DOMAIN_SNAPSHOT_PARSE_DISKS ||
         (flags & VIR_DOMAIN_SNAPSHOT_PARSE_REDEFINE &&
-         def->state == VIR_DOMAIN_DISK_SNAPSHOT)) {
+         def->state == VIR_DOMAIN_DISK_SNAPSHOT) ||
+        def->memory == VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL) {
         def->ndisks = i;
         if (def->ndisks && VIR_ALLOC_N(def->disks, def->ndisks) < 0) {
             virReportOOMError();
@@ -303,6 +343,8 @@ cleanup:
     VIR_FREE(creation);
     VIR_FREE(state);
     VIR_FREE(nodes);
+    VIR_FREE(memorySnapshot);
+    VIR_FREE(memoryFile);
     xmlXPathFreeContext(ctxt);
     if (ret == NULL)
         virDomainSnapshotDefFree(def);
@@ -524,8 +566,15 @@ char *virDomainSnapshotDefFormat(const char *domain_uuid,
     }
     virBufferAsprintf(&buf, "  <creationTime>%lld</creationTime>\n",
                       def->creationTime);
-    /* For now, only output <disks> on disk-snapshot */
-    if (def->state == VIR_DOMAIN_DISK_SNAPSHOT) {
+    if (def->memory) {
+        virBufferAsprintf(&buf, "  <memory snapshot='%s'",
+                          virDomainSnapshotLocationTypeToString(def->memory));
+        virBufferEscapeString(&buf, " file='%s'", def->file);
+        virBufferAddLit(&buf, "/>\n");
+    }
+    /* Only output <disks> on disk-snapshot or external memory snapshot */
+    if (def->state == VIR_DOMAIN_DISK_SNAPSHOT ||
+        def->memory == VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL) {
         virBufferAddLit(&buf, "  <disks>\n");
         for (i = 0; i < def->ndisks; i++) {
             virDomainSnapshotDiskDefPtr disk = &def->disks[i];
diff --git a/src/conf/snapshot_conf.h b/src/conf/snapshot_conf.h
index 7d46a82..d17b3ff 100644
--- a/src/conf/snapshot_conf.h
+++ b/src/conf/snapshot_conf.h
@@ -66,6 +66,9 @@ struct _virDomainSnapshotDef {
     long long creationTime; /* in seconds */
     int state; /* enum virDomainSnapshotState */

+    int memory; /* enum virDomainMemorySnapshot */
+    char *file; /* memory state file when snapshot is external */
+
     size_t ndisks; /* should not exceed dom->ndisks */
     virDomainSnapshotDiskDef *disks;

diff --git a/tests/domainsnapshotxml2xmlin/external_vm.xml b/tests/domainsnapshotxml2xmlin/external_vm.xml
new file mode 100644
index 0000000..3bcd150
--- /dev/null
+++ b/tests/domainsnapshotxml2xmlin/external_vm.xml
@@ -0,0 +1,10 @@
+<domainsnapshot>
+  <name>my snap name</name>
+  <description>! #$%^</description>
+  <state>running</state>
+  <memory snapshot='external' file='/dev/HostVG/GuestMemory'/>
+  <parent>
+    <name>earlier_snap</name>
+  </parent>
+  <creationTime>1272917631</creationTime>
+</domainsnapshot>
diff --git a/tests/domainsnapshotxml2xmlin/noparent.xml b/tests/domainsnapshotxml2xmlin/noparent.xml
new file mode 100644
index 0000000..cbac0d8
--- /dev/null
+++ b/tests/domainsnapshotxml2xmlin/noparent.xml
@@ -0,0 +1,9 @@
+<domainsnapshot>
+  <name>my snap name</name>
+  <description>! #$%^</description>
+  <state>running</state>
+  <creationTime>1272917631</creationTime>
+  <domain>
+    <uuid>9d37b878-a7cc-9f9a-b78f-49b3abad25a8</uuid>
+  </domain>
+</domainsnapshot>
diff --git a/tests/domainsnapshotxml2xmlout/all_parameters.xml b/tests/domainsnapshotxml2xmlout/all_parameters.xml
index eb2ee85..4178ac6 100644
--- a/tests/domainsnapshotxml2xmlout/all_parameters.xml
+++ b/tests/domainsnapshotxml2xmlout/all_parameters.xml
@@ -6,6 +6,7 @@
     <name>earlier_snap</name>
   </parent>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='internal'/>
   <domain>
     <uuid>9d37b878-a7cc-9f9a-b78f-49b3abad25a8</uuid>
   </domain>
diff --git a/tests/domainsnapshotxml2xmlout/disk_snapshot.xml b/tests/domainsnapshotxml2xmlout/disk_snapshot.xml
index 0a4b179..57aef16 100644
--- a/tests/domainsnapshotxml2xmlout/disk_snapshot.xml
+++ b/tests/domainsnapshotxml2xmlout/disk_snapshot.xml
@@ -6,6 +6,7 @@
     <name>earlier_snap</name>
   </parent>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='no'/>
   <disks>
     <disk name='hda' snapshot='no'/>
     <disk name='hdb' snapshot='no'/>
diff --git a/tests/domainsnapshotxml2xmlout/external_vm.xml b/tests/domainsnapshotxml2xmlout/external_vm.xml
new file mode 100644
index 0000000..8814bce
--- /dev/null
+++ b/tests/domainsnapshotxml2xmlout/external_vm.xml
@@ -0,0 +1,43 @@
+<domainsnapshot>
+  <name>my snap name</name>
+  <description>! #$%^</description>
+  <state>running</state>
+  <parent>
+    <name>earlier_snap</name>
+  </parent>
+  <creationTime>1272917631</creationTime>
+  <memory snapshot='external' file='/dev/HostVG/GuestMemory'/>
+  <disks>
+    <disk name='hda' snapshot='no'/>
+  </disks>
+  <domain type='qemu'>
+    <name>QEMUGuest1</name>
+    <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+    <metadata>
+      <app1:foo xmlns:app1="http://foo.org/";>fooish</app1:foo>
+      <app2:bar xmlns:app2="http://bar.com/"; maman="baz">barish</app2:bar>
+    </metadata>
+    <memory unit='KiB'>219100</memory>
+    <currentMemory unit='KiB'>219100</currentMemory>
+    <vcpu placement='static' cpuset='1-4,8-20,525'>1</vcpu>
+    <os>
+      <type arch='i686' machine='pc'>hvm</type>
+      <boot dev='hd'/>
+    </os>
+    <clock offset='utc'/>
+    <on_poweroff>destroy</on_poweroff>
+    <on_reboot>restart</on_reboot>
+    <on_crash>destroy</on_crash>
+    <devices>
+      <emulator>/usr/bin/qemu</emulator>
+      <disk type='block' device='disk' snapshot='no'>
+        <source dev='/dev/HostVG/QEMUGuest1'/>
+        <target dev='hda' bus='ide'/>
+        <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+      </disk>
+      <controller type='usb' index='0'/>
+      <controller type='ide' index='0'/>
+      <memballoon model='virtio'/>
+    </devices>
+  </domain>
+</domainsnapshot>
diff --git a/tests/domainsnapshotxml2xmlout/full_domain.xml b/tests/domainsnapshotxml2xmlout/full_domain.xml
index 27cf41d..65d1469 100644
--- a/tests/domainsnapshotxml2xmlout/full_domain.xml
+++ b/tests/domainsnapshotxml2xmlout/full_domain.xml
@@ -6,6 +6,7 @@
     <name>earlier_snap</name>
   </parent>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='internal'/>
   <domain type='qemu'>
     <name>QEMUGuest1</name>
     <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
diff --git a/tests/domainsnapshotxml2xmlout/metadata.xml b/tests/domainsnapshotxml2xmlout/metadata.xml
index 93c9f39..f961458 100644
--- a/tests/domainsnapshotxml2xmlout/metadata.xml
+++ b/tests/domainsnapshotxml2xmlout/metadata.xml
@@ -6,6 +6,7 @@
     <name>earlier_snap</name>
   </parent>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='internal'/>
   <domain type='qemu'>
     <name>QEMUGuest1</name>
     <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
diff --git a/tests/domainsnapshotxml2xmlout/noparent.xml b/tests/domainsnapshotxml2xmlout/noparent.xml
index cbac0d8..0cbbb65 100644
--- a/tests/domainsnapshotxml2xmlout/noparent.xml
+++ b/tests/domainsnapshotxml2xmlout/noparent.xml
@@ -3,6 +3,7 @@
   <description>! #$%^</description>
   <state>running</state>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='internal'/>
   <domain>
     <uuid>9d37b878-a7cc-9f9a-b78f-49b3abad25a8</uuid>
   </domain>
diff --git a/tests/domainsnapshotxml2xmlout/noparent_nodescription.xml b/tests/domainsnapshotxml2xmlout/noparent_nodescription.xml
index 0de202d..4eb4016 100644
--- a/tests/domainsnapshotxml2xmlout/noparent_nodescription.xml
+++ b/tests/domainsnapshotxml2xmlout/noparent_nodescription.xml
@@ -3,5 +3,6 @@
   <description>! #$%^</description>
   <state>running</state>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='internal'/>
   <active>1</active>
 </domainsnapshot>
diff --git a/tests/domainsnapshotxml2xmlout/noparent_nodescription_noactive.xml b/tests/domainsnapshotxml2xmlout/noparent_nodescription_noactive.xml
index 25b60f3..94d59a3 100644
--- a/tests/domainsnapshotxml2xmlout/noparent_nodescription_noactive.xml
+++ b/tests/domainsnapshotxml2xmlout/noparent_nodescription_noactive.xml
@@ -3,4 +3,5 @@
   <description>! #$%^</description>
   <state>running</state>
   <creationTime>1272917631</creationTime>
+  <memory snapshot='no'/>
 </domainsnapshot>
diff --git a/tests/domainsnapshotxml2xmltest.c b/tests/domainsnapshotxml2xmltest.c
index e363c99..84278d6 100644
--- a/tests/domainsnapshotxml2xmltest.c
+++ b/tests/domainsnapshotxml2xmltest.c
@@ -110,6 +110,7 @@ mymain(void)
     DO_TEST("noparent_nodescription", NULL, 1);
     DO_TEST("noparent", "9d37b878-a7cc-9f9a-b78f-49b3abad25a8", 0);
     DO_TEST("metadata", "c7a5fdbd-edaf-9455-926a-d65c16db1809", 0);
+    DO_TEST("external_vm", "c7a5fdbd-edaf-9455-926a-d65c16db1809", 0);

     virCapabilitiesFree(driver.caps);

-- 
1.7.11.2


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