Add 'nbd' as a valid filesystem driver type

The <filesystem> element can now accept a <driver type='nbd'/>
as an alternative to 'loop'. The benefit of NBD is support
for non-raw disk image formats.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

docs/formatdomain.html.in

@@ -1992,8 +1992,9 @@
             the <code>type</code> attribute selects the primary
             backend driver name, while the <code>format</code>
             attribute provides the format type. For example, LXC
-            supports a type of "loop", with a format of "raw". QEMU
-            supports a type of "path" or "handle", but no formats.
+            supports a type of "loop", with a format of "raw" or
+            "nbd" with any format. QEMU supports a type of "path"
+            or "handle", but no formats.
           </li>
         </ul>
       </dd>

docs/schemas/domaincommon.rng

@@ -1675,6 +1675,7 @@
             <value>path</value>
             <value>handle</value>
             <value>loop</value>
+            <value>nbd</value>
           </choice>
         </attribute>
       </optional>

src/conf/domain_conf.c

@@ -343,7 +343,8 @@ VIR_ENUM_IMPL(virDomainFSDriverType, VIR_DOMAIN_FS_DRIVER_TYPE_LAST,
               "default",
               "path",
               "handle",
-              "loop")
+              "loop",
+              "nbd")
 
 VIR_ENUM_IMPL(virDomainFSAccessMode, VIR_DOMAIN_FS_ACCESSMODE_LAST,
               "passthrough",

src/conf/domain_conf.h

@@ -801,6 +801,7 @@ enum virDomainFSDriverType {
     VIR_DOMAIN_FS_DRIVER_TYPE_PATH,
     VIR_DOMAIN_FS_DRIVER_TYPE_HANDLE,
     VIR_DOMAIN_FS_DRIVER_TYPE_LOOP,
+    VIR_DOMAIN_FS_DRIVER_TYPE_NBD,
 
     VIR_DOMAIN_FS_DRIVER_TYPE_LAST
 };

src/qemu/qemu_command.c

@@ -140,6 +140,7 @@ VIR_ENUM_IMPL(qemuDomainFSDriver, VIR_DOMAIN_FS_DRIVER_TYPE_LAST,
               "local",
               "local",
               "handle",
+              NULL,
               NULL);
 
 

tests/lxcxml2xmldata/lxc-disk-formats.xml

@@ -19,6 +19,11 @@
       <source file='/root/container.img'/>
       <target dir='/'/>
     </filesystem>
+    <filesystem type='file' accessmode='passthrough'>
+      <driver type='nbd' format='qcow2'/>
+      <source file='/root/container.qcow2'/>
+      <target dir='/home'/>
+    </filesystem>
     <console type='pty'>
       <target type='lxc' port='0'/>
     </console>