CA-393578: Fix vbd cleanup in metadata scripts

The xe-[backup,restore]-metadata scripts have cleanup logic designed to ensure
we do not leave any vbd objects etc behind.

This logic calls `vbd-unplug` with a 20s timeout, and then (regardless of the
result) allows up to 10s for any device specified in the VBD to disappear - if
it does not, it does not trigger a `vbd-destroy`.

This logic fails in the case where a VDI is attached to a VM running on the same
host, as the `device` field in the new VBD will be populated with the backend
device for the running VM. In this case, the `vbd-unplug` fails immediately (as
the vbd is not plugged because the original `vbd-plug` attempt fails as the VDI
is in use), but then we sit waiting for 10s for the device to disappear (which
is obviously does not), and then fail to trigger a `vbd-destroy`, leaving the
VBD behind.

Fix this by simply removing the wait for the device to disappear and always
attempting a `vbd-destroy`, as I am not aware of any situation where this
additional 10s wait will give any benefit given current behaviours.

Signed-off-by: Alex Brett <[email protected]>

scripts/xe-backup-metadata

@@ -118,25 +118,8 @@ function cleanup {
    if [ ! -z "${vbd_uuid}" ]; then
       ${debug} echo -n "Unplugging VBD: "
       ${XE} vbd-unplug uuid="${vbd_uuid}" timeout=20
-      # poll for the device to go away if we know its name
-      if [ "${device}" != "" ]; then
-          device_gone=0
-          for ((i=0; i<10; i++)); do
-              ${debug} echo -n "."
-              if [ ! -b "${device}" ]; then
-                  ${debug} echo " done"
-                  device_gone=1
-                  break
-              fi
-              sleep 1
-          done
-          if [ ${device_gone} -eq 0 ]; then
-              ${debug} echo " failed"
-              echo "Please destroy VBD ${vbd_uuid} manually."
-          else
-              ${XE} vbd-destroy uuid="${vbd_uuid}"
-          fi
-      fi
+      ${debug} echo -n "Destroying VBD: "
+      ${XE} vbd-destroy uuid="${vbd_uuid}"
    fi
    if [ ${fs_uninitialised} -eq 1 -a -n "${vdi_uuid}" ] ; then
       ${XE} vdi-destroy uuid="${vdi_uuid}"

scripts/xe-restore-metadata

@@ -202,26 +202,9 @@ function cleanup {
    if [ ! -z "${vbd_uuid}" ]; then
       ${debug} echo -n "Unplugging VBD: " >&2
       ${XE} vbd-unplug uuid="${vbd_uuid}" timeout=20
-      # poll for the device to go away if we know its name
-      if [ "${device}" != "" ]; then
-          device_gone=0
-          for ((i=0; i<10; i++)); do
-              ${debug} echo -n "." >&2
-              if [ ! -b "${device}" ]; then
-                  ${debug} echo " done" >&2
-                  device_gone=1
-                  break
-              fi
-              sleep 1
-          done
-          if [ ${device_gone} -eq 0 ]; then
-              ${debug} echo " failed" >&2
-              ${debug} echo "Please destroy VBD ${vbd_uuid} manually." >&2
-          else
-              ${XE} vbd-destroy uuid="${vbd_uuid}"
-              vbd_uuid=""
-          fi
-      fi
+      ${debug} echo -n "Destroying VBD: " >&2
+      ${XE} vbd-destroy uuid="${vbd_uuid}"
+      vbd_uuid=""
       device=""
    fi
 }