def _initDMinfo(self):
self._mapLVtuple2dm = {}<EOL>self._mapLVname2dm = {}<EOL>self._vgTree = {}<EOL>if self._dmMajorNum is None:<EOL><INDENT>self._initBlockMajorMap()<EOL><DEDENT>for file in os.listdir(devmapperDir):<EOL><INDENT>mobj = re.match('<STR_LIT>', file)<EOL>if mobj:<EOL><INDENT>path = os.path.join(devmapperDir, file)<EOL>(major, minor) = self._getDevMajorMinor(path)<EOL>if major == self._dmMajorNum:<EOL><INDENT>vg = mobj.group(<NUM_LIT:1>).replace('<STR_LIT>', '<STR_LIT:->')<EOL>lv = mobj.group(<NUM_LIT:2>).replace('<STR_LIT>', '<STR_LIT:->')<EOL>dmdev = "<STR_LIT>" % minor<EOL>self._mapLVtuple2dm[(vg,lv)] = dmdev<EOL>self._mapLVname2dm[file] = dmdev<EOL>if not vg in self._vgTree:<EOL><INDENT>self._vgTree[vg] = []<EOL><DEDENT>self._vgTree[vg].append(lv)<EOL><DEDENT><DEDENT><DEDENT>
Check files in /dev/mapper to initialize data structures for 
        mappings between device-mapper devices, minor device numbers, VGs 
        and LVs.