xenapi: separate disk for cinder volumes

Some kernels have lockup issues while serving cinder volumes from
file-loopback-lvm kind of cinder setup. This patch provides a way to
create an additional drive to the OpenStack VM, and use that to store
cinder volumes, thus eliminating the lockup issue. It will help when
testing XenServer. Now, you can specify devices for stack-volumes
through:

    VOLUME_BACKING_DEVICE

In case you are using CINDER_MULTI_LVM_BACKEND, you can use

    VOLUME_BACKING_DEVICE2

as well.

Xenserver:
Should you whish to use a 10 gig disk backend for your cinder volumes,
specify:

    XEN_XVDB_SIZE_GB=10
    VOLUME_BACKING_DEVICE=/dev/xvdb

Citrix is using this approach on its internal CI system to run tests
against OpenStack. This is a workaround for this bug:

  https://bugs.launchpad.net/cinder/+bug/1023755

Related to blueprint xenapi-devstack-cleanup

Change-Id: Iee633d2704185bfbf9234882654c47b850fa168a

lib/cinder

@@ -69,10 +69,12 @@ CINDER_PERIODIC_INTERVAL=${CINDER_PERIODIC_INTERVAL:-60}
 # Name of the lvm volume groups to use/create for iscsi volumes
 VOLUME_GROUP=${VOLUME_GROUP:-stack-volumes}
 VOLUME_BACKING_FILE=${VOLUME_BACKING_FILE:-$DATA_DIR/${VOLUME_GROUP}-backing-file}
+VOLUME_BACKING_DEVICE=${VOLUME_BACKING_DEVICE:-}
 
 # VOLUME_GROUP2 is used only if CINDER_MULTI_LVM_BACKEND = True
 VOLUME_GROUP2=${VOLUME_GROUP2:-stack-volumes2}
 VOLUME_BACKING_FILE2=${VOLUME_BACKING_FILE2:-$DATA_DIR/${VOLUME_GROUP2}-backing-file}
+VOLUME_BACKING_DEVICE2=${VOLUME_BACKING_DEVICE2:-}
 
 VOLUME_NAME_PREFIX=${VOLUME_NAME_PREFIX:-volume-}
 
@@ -335,20 +337,24 @@ create_cinder_volume_group() {
     # ``/opt/stack/data``.
 
     if ! sudo vgs $VOLUME_GROUP; then
+        if [ -z "$VOLUME_BACKING_DEVICE" ]; then
             # Only create if the file doesn't already exists
             [[ -f $VOLUME_BACKING_FILE ]] || truncate -s $VOLUME_BACKING_FILE_SIZE $VOLUME_BACKING_FILE
-
             DEV=`sudo losetup -f --show $VOLUME_BACKING_FILE`
 
             # Only create if the loopback device doesn't contain $VOLUME_GROUP
             if ! sudo vgs $VOLUME_GROUP; then
                 sudo vgcreate $VOLUME_GROUP $DEV
             fi
+        else
+            sudo vgcreate $VOLUME_GROUP $VOLUME_BACKING_DEVICE
+        fi
     fi
     if [ "$CINDER_MULTI_LVM_BACKEND" = "True" ]; then
         #set up the second volume if CINDER_MULTI_LVM_BACKEND is enabled
 
         if ! sudo vgs $VOLUME_GROUP2; then
+            if [ -z "$VOLUME_BACKING_DEVICE2" ]; then
                 # Only create if the file doesn't already exists
                 [[ -f $VOLUME_BACKING_FILE2 ]] || truncate -s $VOLUME_BACKING_FILE_SIZE $VOLUME_BACKING_FILE2
 
@@ -358,6 +364,9 @@ create_cinder_volume_group() {
                 if ! sudo vgs $VOLUME_GROUP2; then
                     sudo vgcreate $VOLUME_GROUP2 $DEV
                 fi
+            else
+                sudo vgcreate $VOLUME_GROUP2 $VOLUME_BACKING_DEVICE2
+            fi
         fi
     fi
 

tools/xen/install_os_domU.sh

@@ -259,6 +259,19 @@ fi
 FLAT_NETWORK_BRIDGE=$(bridge_for "$VM_BRIDGE_OR_NET_NAME")
 append_kernel_cmdline "$GUEST_NAME" "flat_network_bridge=${FLAT_NETWORK_BRIDGE}"
 
+# Add a separate xvdb, if it was requested
+if [[ "0" != "$XEN_XVDB_SIZE_GB" ]]; then
+    vm=$(xe vm-list name-label="$GUEST_NAME" --minimal)
+
+    # Add a new disk
+    localsr=$(get_local_sr)
+    extra_vdi=$(xe vdi-create \
+        name-label=xvdb-added-by-devstack \
+        virtual-size="${XEN_XVDB_SIZE_GB}GiB" \
+        sr-uuid=$localsr type=user)
+    xe vbd-create vm-uuid=$vm vdi-uuid=$extra_vdi device=1
+fi
+
 # create a snapshot before the first boot
 # to allow a quick re-run with the same settings
 xe vm-snapshot vm="$GUEST_NAME" new-name-label="$SNAME_FIRST_BOOT"

tools/xen/xenrc

@@ -76,4 +76,14 @@ UBUNTU_INST_NAMESERVERS=""
 UBUNTU_INST_NETMASK=""
 UBUNTU_INST_GATEWAY=""
 
+# Create a separate xvdb. Tis could be used as a backing device for cinder
+# volumes. Specify
+#   XEN_XVDB_SIZE_GB=10
+#   VOLUME_BACKING_DEVICE=/dev/xvdb
+# in your localrc to avoid kernel lockups:
+#   https://bugs.launchpad.net/cinder/+bug/1023755
+#
+# Set the size to 0 to avoid creation of additional disk.
+XEN_XVDB_SIZE_GB=0
+
 source ../../stackrc