conf: Introduce new XML tag "mode" for disk source

There are two ways to use a iSCSI LUN as disk source for qemu.

 * The LUN's path as it shows up on host, e.g.
   /dev/disk/by-path/ip-$ip:3260-iscsi-$iqn-fc18:iscsi.iscsi0-lun-1

 * The libiscsi URI from the storage pool source element host attribute, e.g.
   iscsi://demo.org:6000/iqn.1992-01.com.example/1

For a "volume" type disk, if the specified "pool" is of iscsi
type, we should support to use the LUN in either of above 2 ways.
That's why to introduce a new XML tag "mode" for the disk source
(libvirt should support iscsi pool with libiscsi, but it's another
new feature, which should be done later).

The "mode" can be either of "host" or "direct". Use "host" to indicate
use of the LUN with the path as it shows up on host. Use "direct" to
indicate to use it with the source pool host URI (future patches may support
to use network type libvirt storage too, e.g. Ceph)

docs/formatdomain.html.in

@@ -1601,7 +1601,16 @@
         <code>pool</code> and <code>volume</code>. Attribute <code>pool</code>
         specifies the name of storage pool (managed by libvirt) where the disk
         source resides, and attribute <code>volume</code> specifies the name of
-        storage volume (managed by libvirt) used as the disk source.
+        storage volume (managed by libvirt) used as the disk source. For a
+        "volume" type disk, if the underlying storage pool is "iscsi", attribute
+        <code>mode</code> (<span class="since">since 1.1.1</span>) can be used
+        to indicate how to represent the LUN as the disk source. The value
+        "host" indicates to use the LUN's path as it shows up on host, e.g.
+        /dev/disk/by-path/ip-10.11.12.9:3260-iscsi-iqn.2013-06.fc:iscsi.iscsi0-lun-1).
+        The value "direct" indicates to use the storage pool's
+        <code>source</code> element <code>host</code> attribute as the
+        disk source for the libiscsi URI, e.g.
+        file=iscsi://demo.org:6000/iqn.1992-01.com.example/1.
         <span class="since">Since 0.0.3; <code>type='dir'</code> since
         0.7.5; <code>type='network'</code> since
         0.8.7; <code>protocol='iscsi'</code> since 1.0.4;

docs/schemas/domaincommon.rng

@@ -1173,6 +1173,14 @@
                 <attribute name="volume">
                   <ref name="volName"/>
                 </attribute>
+                <optional>
+                  <attribute name="mode">
+                    <choice>
+                      <value>host</value>
+                      <value>direct</value>
+                    </choice>
+                  </attribute>
+                </optional>
                 <optional>
                   <ref name="startupPolicy"/>
                 </optional>

src/conf/domain_conf.c

@@ -761,6 +761,11 @@ VIR_ENUM_IMPL(virDomainDiskDiscard, VIR_DOMAIN_DISK_DISCARD_LAST,
               "default",
               "unmap",
               "ignore")
+VIR_ENUM_IMPL(virDomainDiskSourcePoolMode,
+              VIR_DOMAIN_DISK_SOURCE_POOL_MODE_LAST,
+              "default",
+              "host",
+              "direct")
 
 #define VIR_DOMAIN_XML_WRITE_FLAGS  VIR_DOMAIN_XML_SECURE
 #define VIR_DOMAIN_XML_READ_FLAGS   VIR_DOMAIN_XML_INACTIVE
@@ -4645,10 +4650,12 @@ virDomainDiskSourcePoolDefParse(xmlNodePtr node,
 {
     char *pool = NULL;
     char *volume = NULL;
+    char *mode = NULL;
     int ret = -1;
 
     pool = virXMLPropString(node, "pool");
     volume = virXMLPropString(node, "volume");
+    mode = virXMLPropString(node, "mode");
 
     /* CD-ROM and Floppy allows no source */
     if (!pool && !volume)
@@ -4664,6 +4671,14 @@ virDomainDiskSourcePoolDefParse(xmlNodePtr node,
     if (VIR_ALLOC(def->srcpool) < 0)
         goto cleanup;
 
+    if (mode && (def->srcpool->mode =
+                 virDomainDiskSourcePoolModeTypeFromString(mode)) <= 0) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("unknown source mode '%s' for volume type disk"),
+                       mode);
+        goto cleanup;
+    }
+
     def->srcpool->pool = pool;
     pool = NULL;
     def->srcpool->volume = volume;
@@ -4674,6 +4689,7 @@ virDomainDiskSourcePoolDefParse(xmlNodePtr node,
 cleanup:
     VIR_FREE(pool);
     VIR_FREE(volume);
+    VIR_FREE(mode);
     return ret;
 }
 
@@ -14157,9 +14173,13 @@ virDomainDiskSourceDefFormat(virBufferPtr buf,
         case VIR_DOMAIN_DISK_TYPE_VOLUME:
             virBufferAddLit(buf, "      <source");
 
-            if (def->srcpool)
+            if (def->srcpool) {
                 virBufferAsprintf(buf, " pool='%s' volume='%s'",
                                   def->srcpool->pool, def->srcpool->volume);
+                if (def->srcpool->mode)
+                    virBufferAsprintf(buf, " mode='%s'",
+                                      virDomainDiskSourcePoolModeTypeToString(def->srcpool->mode));
+            }
             if (def->startupPolicy)
                 virBufferEscapeString(buf, " startupPolicy='%s'", startupPolicy);
 

src/conf/domain_conf.h

@@ -652,11 +652,32 @@ struct _virDomainBlockIoTuneInfo {
 };
 typedef virDomainBlockIoTuneInfo *virDomainBlockIoTuneInfoPtr;
 
+/*
+ * Used for volume "type" disk to indicate how to represent
+ * the disk source if the specified "pool" is of iscsi type.
+ */
+enum virDomainDiskSourcePoolMode {
+    VIR_DOMAIN_DISK_SOURCE_POOL_MODE_DEFAULT = 0,
+
+    /* Use the path as it shows up on host, e.g.
+     * /dev/disk/by-path/ip-$ip-iscsi-$iqn:iscsi.iscsi-pool0-lun-1
+     */
+    VIR_DOMAIN_DISK_SOURCE_POOL_MODE_HOST,
+
+    /* Use the URI from the storage pool source element host attribute. E.g.
+     * file=iscsi://demo.org:6000/iqn.1992-01.com.example/1.
+     */
+    VIR_DOMAIN_DISK_SOURCE_POOL_MODE_DIRECT,
+
+    VIR_DOMAIN_DISK_SOURCE_POOL_MODE_LAST
+};
+
 typedef struct _virDomainDiskSourcePoolDef virDomainDiskSourcePoolDef;
 struct _virDomainDiskSourcePoolDef {
     char *pool; /* pool name */
     char *volume; /* volume name */
     int voltype; /* enum virStorageVolType, internal only */
+    int mode; /* enum virDomainDiskSourcePoolMode */
 };
 typedef virDomainDiskSourcePoolDef *virDomainDiskSourcePoolDefPtr;
 
@@ -2554,6 +2575,7 @@ VIR_ENUM_DECL(virDomainDiskSecretType)
 VIR_ENUM_DECL(virDomainDeviceSGIO)
 VIR_ENUM_DECL(virDomainDiskTray)
 VIR_ENUM_DECL(virDomainDiskDiscard)
+VIR_ENUM_DECL(virDomainDiskSourcePoolMode)
 VIR_ENUM_DECL(virDomainIoEventFd)
 VIR_ENUM_DECL(virDomainVirtioEventIdx)
 VIR_ENUM_DECL(virDomainDiskCopyOnRead)

tests/qemuxml2argvdata/qemuxml2argv-disk-source-pool-mode.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>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='volume' device='cdrom'>
+      <source pool='blk-pool0' volume='blk-pool0-vol0' mode='host' startupPolicy='optional'>
+        <seclabel model='selinux' relabel='yes'>
+          <label>system_u:system_r:public_content_t:s0</label>
+        </seclabel>
+      </source>
+      <target dev='hda' bus='ide'/>
+      <readonly/>
+      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
+    </disk>
+    <disk type='volume' device='cdrom'>
+      <source pool='blk-pool0' volume='blk-pool0-vol1' mode='direct' startupPolicy='optional'>
+        <seclabel model='selinux' relabel='yes'>
+          <label>system_u:system_r:public_content_t:s0</label>
+        </seclabel>
+      </source>
+      <target dev='hda' bus='ide'/>
+      <readonly/>
+      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
+    </disk>
+    <disk type='file' device='disk'>
+      <source file='/tmp/idedisk.img'/>
+      <target dev='hdc' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='3'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='ide' index='1'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2xmltest.c

@@ -264,6 +264,7 @@ mymain(void)
 
     DO_TEST("disk-scsi-disk-vpd");
     DO_TEST("disk-source-pool");
+    DO_TEST("disk-source-pool-mode");
 
     DO_TEST("disk-drive-discard");