xend: improve psudeo-bootloader support for external block scripts

Userspace tools support external block scripts (e.g. block-drbd
provided by drbd project).  The psuedo-bootloader setup code in
xend has a few limitations wrt external block scripts, which this
patch addresses.

blkif.py: parse_uname() utility function should be able to parse a
disk specifier understood by the rest of the tools.

XendDomainInfo.py: Block devices using external block scripts must
be attached to dom0 before running the psuedo-bootloader.

Signed-off-by: Jim Fehlig <jfehlig@novell.com>
Tested-by: Shriram Rajagopalan <rshriram@gmail.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/python/xen/util/blkif.py

@@ -66,8 +66,8 @@ def blkdev_segment(name):
                 'type'         : 'Disk' }
     return val
 
-def _parse_uname(uname):
-    fn = taptype = None
+def parse_uname(uname):
+    fn = typ = taptype = None
     if uname.find(":") != -1:
         (typ, fn) = uname.split(":", 1)
 
@@ -76,15 +76,18 @@ def _parse_uname(uname):
                
         if typ in ("tap", "tap2"):
             (taptype, fn) = fn.split(":", 1)
-    return (fn, taptype)
+            if taptype in ("tapdisk", "ioemu"):
+                (taptype, fn) = fn.split(":", 1)
+    return (fn, (typ,taptype))
+
 
 def blkdev_uname_to_file(uname):
     """Take a blkdev uname and return the corresponding filename."""
-    return _parse_uname(uname)[0]
+    return parse_uname(uname)[0]
 
 def blkdev_uname_to_taptype(uname):
     """Take a blkdev uname and return the blktap type."""
-    return _parse_uname(uname)[1]
+    return parse_uname(uname)[1]
 
 def mount_mode(name):
     mode = None

tools/python/xen/xend/XendDomainInfo.py

@@ -38,7 +38,7 @@ from types import StringTypes
 
 import xen.lowlevel.xc
 from xen.util import asserts, auxbin, mkdir
-from xen.util.blkif import blkdev_uname_to_file, blkdev_uname_to_taptype
+from xen.util.blkif import parse_uname
 import xen.util.xsm.xsm as security
 from xen.util import xsconstants
 from xen.util import mkdir
@@ -3248,9 +3248,18 @@ class XendDomainInfo:
             devtype = devinfo[0]
             disk = devinfo[1]['uname']
 
-            fn = blkdev_uname_to_file(disk)
-            taptype = blkdev_uname_to_taptype(disk)
-            mounted = devtype in ['tap', 'tap2'] and taptype != 'aio' and taptype != 'sync' and not os.stat(fn).st_rdev
+            (fn, types) = parse_uname(disk)
+            def _shouldMount(types):
+                if types[0] in ('file', 'phy'):
+                    return False
+                if types[0] in ('tap', 'tap2'):
+                    if types[1] in ('aio', 'sync'):
+                        return False
+                    else:
+                        return True
+                return os.access('/etc/xen/scripts/block-%s' % types[0], os.X_OK)
+
+            mounted = _shouldMount(types)
             mounted_vbd_uuid = 0
             if mounted:
                 # This is a file, not a device.  pygrub can cope with a