hotplug/Linux: fix same_vm check in block script

The original same_vm check has two bugs. When stubdom is in use because
it relies on numeric domid to check if two domains are in fact the same
one.  Another one is that the check would fail when two stubdoms are
checked against each other.

The first bug is fixed by using uuid to identify a domain. The second
bug is fixed by comparing the domains two stubdoms serve.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>

tools/hotplug/Linux/block-common.sh

@@ -112,14 +112,17 @@ same_vm()
                   "$FRONTEND_UUID")
   local target=$(xenstore_read_default  "/local/domain/$FRONTEND_ID/target"   \
                  "-1")
+  local targetvm=$(xenstore_read_default "/local/domain/$target/vm" "-1")
   local otarget=$(xenstore_read_default  "/local/domain/$otherdom/target"   \
                  "-1")
   local otvm=$(xenstore_read_default  "/local/domain/$otarget/vm"   \
                  "-1")
   otvm=${otvm%-1}
   othervm=${othervm%-1}
+  targetvm=${targetvm%-1}
   local frontend_uuid=${FRONTEND_UUID%-1}
   
-  [ "$frontend_uuid" = "$othervm" -o "$target" = "$otherdom" -o "$frontend_uuid" = "$otvm" ]
+  [ "$frontend_uuid" = "$othervm" -o "$targetvm" = "$othervm" -o \
+    "$frontend_uuid" = "$otvm" -o "$targetvm" = "$otvm" ]
 }