core: fix template-based HVM disk handling

We use only one device-mapper layer for HVMs, and this isn't the same as
for PV - it is that one, which PV does in initramfs.
Device-mapper layers summary for template-based VMs:
PV: root.img+root-cow.img (dom0) -> xvda, xvda+volatile.img (VM)
HVM: root.img+volatile.img (dom0)

core-modules/01QubesHVm.py

@@ -96,7 +96,7 @@ class QubesHVm(QubesVm):
             (not 'xml_element' in kwargs or kwargs['xml_element'].get('guiagent_installed') is None):
             self.services['meminfo-writer'] = False
 
-        self.storage.volatile_img = None
+        self.storage.rootcow_img = None
 
     @property
     def type(self):
@@ -233,9 +233,7 @@ class QubesHVm(QubesVm):
         if self.is_running():
             raise NotImplementedError("Online resize of HVM's private.img not implemented, shutdown the VM first")
 
-        f_private = open (self.private_img, "a+b")
+        self.storage.resize_private_img(size)
-        f_private.truncate (size)
-        f_private.close ()
 
     def resize_root_img(self, size):
         if self.template:
@@ -255,14 +253,6 @@ class QubesHVm(QubesVm):
         f_root.truncate (size)
         f_root.close ()
 
-    def get_rootdev(self, source_template=None):
-        if self.template:
-            return "'script:snapshot:{template_root}:{volatile},xvda,w',".format(
-                    template_root=self.template.root_img,
-                    volatile=self.volatile_img)
-        else:
-            return "'script:file:{root_img},xvda,w',".format(root_img=self.root_img)
-
     def get_config_params(self):
 
         params = super(QubesHVm, self).get_config_params()
@@ -295,34 +285,6 @@ class QubesHVm(QubesVm):
 
         return True
 
-    def reset_volatile_storage(self, **kwargs):
-        assert not self.is_running(), "Attempt to clean volatile image of running VM!"
-
-        source_template = kwargs.get("source_template", self.template)
-
-        if source_template is None:
-            # Nothing to do on non-template based VM
-            return
-
-        if os.path.exists (self.volatile_img):
-            if self.debug:
-                if os.path.getmtime(self.template.root_img) > os.path.getmtime(self.volatile_img):
-                    if kwargs.get("verbose", False):
-                        print >>sys.stderr, "--> WARNING: template have changed, resetting root.img"
-                else:
-                    if kwargs.get("verbose", False):
-                        print >>sys.stderr, "--> Debug mode: not resetting root.img"
-                        print >>sys.stderr, "--> Debug mode: if you want to force root.img reset, either update template VM, or remove volatile.img file"
-                    return
-            os.remove (self.volatile_img)
-
-        f_volatile = open (self.volatile_img, "w")
-        f_root = open (self.template.root_img, "r")
-        f_root.seek(0, os.SEEK_END)
-        f_volatile.truncate (f_root.tell()) # make empty sparse file of the same size as root.img
-        f_volatile.close ()
-        f_root.close()
-
     @property
     def vif(self):
         if self.xid < 0:
@@ -463,7 +425,6 @@ class QubesHVm(QubesVm):
                         guid_pid = open(guid_pidfile).read().strip()
                         os.kill(int(guid_pid), 15)
 
-
     def suspend(self):
         if dry_run:
             return

core/storage/xen.py

@@ -76,7 +76,18 @@ class QubesXenVmStorage(QubesVmStorage):
                     "{dir}/root.img:{dir}/root-cow.img".format(
                         dir=self.vmdir),
                     "block-origin", self.root_dev, True)
+        elif self.vm.template and not self.vm.template.storage.rootcow_img:
+            # HVM template-based VM - template doesn't have own
+            # root-cow.img, only one device-mapper layer
+            return self._format_disk_dev(
+                    "{tpldir}/root.img:{vmdir}/volatile.img".format(
+                        tpldir=self.vm.template.dir_path,
+                        vmdir=self.vmdir),
+                    "block-snapshot", self.root_dev, True)
         elif self.vm.template:
+            # any other template-based VM - two device-mapper layers: one
+            # in dom0 (here) from root+root-cow, and another one from
+            # this+volatile.img
             return self._format_disk_dev(
                     "{dir}/root.img:{dir}/root-cow.img".format(
                         dir=self.vm.template.dir_path),
@@ -170,7 +181,8 @@ class QubesXenVmStorage(QubesVmStorage):
 
     def commit_template_changes(self):
         assert self.vm.is_template()
-        # TODO: move rootcow_img to this class; the same for vm.is_outdated()
+        if not self.rootcow_img:
+            return
         if os.path.exists (self.rootcow_img):
            os.rename (self.rootcow_img, self.rootcow_img + '.old')
 
@@ -183,3 +195,34 @@ class QubesXenVmStorage(QubesVmStorage):
         f_root.close()
         os.umask(old_umask)
 
+    def reset_volatile_storage(self, verbose = False, source_template = None):
+        if source_template is None:
+            source_template = self.vm.template
+
+        if source_template is not None:
+            # template-based VM with only one device-mapper layer -
+            # volatile.img used as upper layer on root.img, no root-cow.img
+            # intermediate layer
+            if not source_template.storage.rootcow_img:
+                if os.path.exists(self.volatile_img):
+                    if self.vm.debug:
+                        if os.path.getmtime(source_template.storage.root_img)\
+                                > os.path.getmtime(self.volatile_img):
+                            if verbose:
+                                print >>sys.stderr, "--> WARNING: template have changed, resetting root.img"
+                        else:
+                            if verbose:
+                                print >>sys.stderr, "--> Debug mode: not resetting root.img"
+                                print >>sys.stderr, "--> Debug mode: if you want to force root.img reset, either update template VM, or remove volatile.img file"
+                            return
+                    os.remove(self.volatile_img)
+
+                f_volatile = open(self.volatile_img, "w")
+                f_root = open(source_template.storage.root_img, "r")
+                f_root.seek(0, os.SEEK_END)
+                f_volatile.truncate(f_root.tell()) # make empty sparse file of the same size as root.img
+                f_volatile.close()
+                f_root.close()
+                return
+        super(QubesXenVmStorage, self).reset_volatile_storage(
+            verbose=verbose, source_template=source_template)