Introduce <driver> under <filesystem> to support open-by-handle

VirtFS allows the user to choose between path/handle based fs driver.
As of now, libvirt hardcoded path based driver only. This patch provides
a solution to allow user to choose between path/handle based fs driver.

Sample:

    <filesystem type='mount'>
      <driver type='handle'/>
      <source dir='/folder/to/share1'/>
      <target dir='mount_tag1'/>
    </filesystem>

    <filesystem type='mount'>
      <driver type='path'/>
      <source dir='/folder/to/share2'/>
      <target dir='mount_tag2'/>
    </filesystem>

Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

docs/formatdomain.html.in

@@ -1156,6 +1156,7 @@
       <target dir='/'/>
     </filesystem>
     <filesystem type='mount' accessmode='passthrough'>
+      <driver type='path'/>
       <source dir='/export/to/guest'/>
       <target dir='/import/from/host'/>
       <readonly/>
@@ -1178,6 +1179,11 @@
         OpenVZ <span class="since">(since 0.6.2)</span>
         and QEMU/KVM <span class="since">(since 0.8.5)</span>.
         This is the default <code>type</code> if one is not specified.
+        This mode also has an optional
+        sub-element <code>driver</code>, with an
+        attribute <code>type='path'</code>
+        or <code>type='handle'</code> <span class="since">(since
+        0.9.7)</span>.
         </dd>
         <dt><code>type='template'</code></dt>
         <dd>

docs/schemas/domaincommon.rng

@@ -995,9 +995,12 @@
           </interleave>
         </group>
         <group>
-          <attribute name="type">
-            <value>mount</value>
-          </attribute>
+          <!-- type='mount' is default -->
+          <optional>
+            <attribute name="type">
+              <value>mount</value>
+            </attribute>
+          </optional>
           <interleave>
             <element name="source">
               <attribute name="dir">
@@ -1005,6 +1008,17 @@
               </attribute>
               <empty/>
             </element>
+            <optional>
+              <element name="driver">
+                <attribute name="type">
+                  <choice>
+                    <value>path</value>
+                    <value>handle</value>
+                  </choice>
+                </attribute>
+                <empty/>
+              </element>
+            </optional>
             <ref name="filesystemtgt"/>
           </interleave>
         </group>
@@ -1024,7 +1038,6 @@
         </group>
       </choice>
       <optional>
-        <ref name="address"/>
         <attribute name="accessmode">
         <choice>
           <value>passthrough</value>
@@ -1036,12 +1049,17 @@
     </element>
   </define>
   <define name="filesystemtgt">
-    <element name="target">
-      <attribute name="dir">
-        <ref name="absDirPath"/>
-      </attribute>
-      <empty/>
-    </element>
+    <interleave>
+      <optional>
+        <ref name="address"/>
+      </optional>
+      <element name="target">
+        <attribute name="dir">
+          <ref name="absDirPath"/>
+        </attribute>
+        <empty/>
+      </element>
+    </interleave>
   </define>
   <!--
       An interface description can either be of type bridge in which case

src/conf/domain_conf.c

@@ -238,6 +238,11 @@ VIR_ENUM_IMPL(virDomainFS, VIR_DOMAIN_FS_TYPE_LAST,
               "file",
               "template")
 
+VIR_ENUM_IMPL(virDomainFSDriverType, VIR_DOMAIN_FS_DRIVER_TYPE_LAST,
+              "default",
+              "path",
+              "handle")
+
 VIR_ENUM_IMPL(virDomainFSAccessMode, VIR_DOMAIN_FS_ACCESSMODE_LAST,
               "passthrough",
               "mapped",
@@ -2828,6 +2833,7 @@ virDomainFSDefParseXML(xmlNodePtr node,
     virDomainFSDefPtr def;
     xmlNodePtr cur;
     char *type = NULL;
+    char *fsdriver = NULL;
     char *source = NULL;
     char *target = NULL;
     char *accessmode = NULL;
@@ -2878,11 +2884,21 @@ virDomainFSDefParseXML(xmlNodePtr node,
                 target = virXMLPropString(cur, "dir");
             } else if (xmlStrEqual(cur->name, BAD_CAST "readonly")) {
                 def->readonly = 1;
+            } else if ((fsdriver == NULL) && (xmlStrEqual(cur->name, BAD_CAST "driver"))) {
+                fsdriver = virXMLPropString(cur, "type");
             }
         }
         cur = cur->next;
     }
 
+    if (fsdriver) {
+        if ((def->fsdriver = virDomainFSDriverTypeTypeFromString(fsdriver)) <= 0) {
+            virDomainReportError(VIR_ERR_INTERNAL_ERROR,
+                                 _("unknown fs driver type '%s'"), fsdriver);
+            goto error;
+        }
+    }
+
     if (source == NULL) {
         virDomainReportError(VIR_ERR_NO_SOURCE,
                              target ? "%s" : NULL, target);
@@ -2905,6 +2921,7 @@ virDomainFSDefParseXML(xmlNodePtr node,
 
 cleanup:
     VIR_FREE(type);
+    VIR_FREE(fsdriver);
     VIR_FREE(target);
     VIR_FREE(source);
     VIR_FREE(accessmode);
@@ -9351,6 +9368,7 @@ virDomainFSDefFormat(virBufferPtr buf,
 {
     const char *type = virDomainFSTypeToString(def->type);
     const char *accessmode = virDomainFSAccessModeTypeToString(def->accessmode);
+    const char *fsdriver = virDomainFSDriverTypeTypeToString(def->fsdriver);
 
     if (!type) {
         virDomainReportError(VIR_ERR_INTERNAL_ERROR,
@@ -9369,6 +9387,10 @@ virDomainFSDefFormat(virBufferPtr buf,
                       "    <filesystem type='%s' accessmode='%s'>\n",
                       type, accessmode);
 
+    if (def->fsdriver) {
+        virBufferAsprintf(buf, "      <driver type='%s'/>\n", fsdriver);
+    }
+
     if (def->src) {
         switch (def->type) {
         case VIR_DOMAIN_FS_TYPE_MOUNT:

src/conf/domain_conf.h

@@ -368,6 +368,15 @@ enum virDomainFSType {
     VIR_DOMAIN_FS_TYPE_LAST
 };
 
+/* Filesystem driver type */
+enum virDomainFSDriverType {
+    VIR_DOMAIN_FS_DRIVER_TYPE_DEFAULT = 0,
+    VIR_DOMAIN_FS_DRIVER_TYPE_PATH,
+    VIR_DOMAIN_FS_DRIVER_TYPE_HANDLE,
+
+    VIR_DOMAIN_FS_DRIVER_TYPE_LAST
+};
+
 /* Filesystem mount access mode  */
 enum virDomainFSAccessMode {
     VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH,
@@ -381,6 +390,7 @@ typedef struct _virDomainFSDef virDomainFSDef;
 typedef virDomainFSDef *virDomainFSDefPtr;
 struct _virDomainFSDef {
     int type;
+    int fsdriver;
     int accessmode;
     char *src;
     char *dst;
@@ -1865,6 +1875,7 @@ VIR_ENUM_DECL(virDomainController)
 VIR_ENUM_DECL(virDomainControllerModelSCSI)
 VIR_ENUM_DECL(virDomainControllerModelUSB)
 VIR_ENUM_DECL(virDomainFS)
+VIR_ENUM_DECL(virDomainFSDriverType)
 VIR_ENUM_DECL(virDomainFSAccessMode)
 VIR_ENUM_DECL(virDomainNet)
 VIR_ENUM_DECL(virDomainNetBackend)

src/qemu/qemu_command.c

@@ -100,6 +100,12 @@ VIR_ENUM_IMPL(qemuControllerModelUSB, VIR_DOMAIN_CONTROLLER_MODEL_USB_LAST,
               "vt82c686b-usb-uhci",
               "pci-ohci");
 
+VIR_ENUM_DECL(qemuDomainFSDriver)
+VIR_ENUM_IMPL(qemuDomainFSDriver, VIR_DOMAIN_FS_DRIVER_TYPE_LAST,
+              "local",
+              "local",
+              "handle");
+
 
 static void
 uname_normalize (struct utsname *ut)
@@ -1811,6 +1817,7 @@ char *qemuBuildFSStr(virDomainFSDefPtr fs,
                      virBitmapPtr qemuCaps ATTRIBUTE_UNUSED)
 {
     virBuffer opt = VIR_BUFFER_INITIALIZER;
+    const char *driver = qemuDomainFSDriverTypeToString(fs->fsdriver);
 
     if (fs->type != VIR_DOMAIN_FS_TYPE_MOUNT) {
         qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
@@ -1818,7 +1825,13 @@ char *qemuBuildFSStr(virDomainFSDefPtr fs,
         goto error;
     }
 
-    virBufferAddLit(&opt, "local");
+    if (!driver) {
+        qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                        _("Filesystem driver type not supported"));
+        goto error;
+    }
+    virBufferAdd(&opt, driver, -1);
+
     if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_MAPPED) {
         virBufferAddLit(&opt, ",security_model=mapped");
     } else if(fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH) {

tests/qemuxml2argvdata/qemuxml2argv-fs9p.args

@@ -3,5 +3,8 @@ pc -m 214 -smp 1 -nographic -nodefconfig -nodefaults -monitor \
 unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -hda \
 /dev/HostVG/QEMUGuest1 -fsdev local,security_model=passthrough,id=fsdev-fs0,\
 path=/export/to/guest -device virtio-9p-pci,id=fs0,fsdev=fsdev-fs0,\
-mount_tag=/import/from/host,bus=pci.0,addr=0x3 -usb -device virtio-balloon-pci,\
-id=balloon0,bus=pci.0,addr=0x4
+mount_tag=/import/from/host,bus=pci.0,addr=0x3 \
+-fsdev handle,security_model=mapped,id=fsdev-fs1,\
+path=/export/to/guest2 -device virtio-9p-pci,id=fs1,fsdev=fsdev-fs1,\
+mount_tag=/import/from/host2,bus=pci.0,addr=0x4 \
+-usb -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5

tests/qemuxml2argvdata/qemuxml2argv-fs9p.xml

@@ -24,5 +24,10 @@
       <source dir='/export/to/guest'/>
       <target dir='/import/from/host'/>
     </filesystem>
+    <filesystem accessmode='mapped'>
+      <driver type='handle'/>
+      <source dir='/export/to/guest2'/>
+      <target dir='/import/from/host2'/>
+    </filesystem>
   </devices>
 </domain>