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From: Scott Moser [mailto:ssmoser2 at gmail.com] On Behalf Of Scott Moser
Sent: den 11 juni 2012 23:16

>...Without digging around on older versions of OS's and their included kernel/udev/kpartx.... i'd have to say that from your message above, and my testing that running 'kpartx' is no longer necessary.  That can reasonably be expected to be created by >the kernel or some other plumbing bits automatically...

I just now tested to remove the kpartx invocation from /nova/virt/disk/mount.py, like this:

diff --git a/nova/virt/disk/mount.py b/nova/virt/disk/mount.py
index 11959b2..4d9527b 100644
--- a/nova/virt/disk/mount.py
+++ b/nova/virt/disk/mount.py
@@ -61,25 +61,9 @@ class Mount(object):
         if self.partition == -1:
             self.error = _('partition search unsupported with %s') % self.mode
         elif self.partition:
-            map_path = '/dev/mapper/%sp%s' % (os.path.basename(self.device),
-                                              self.partition)
-            assert(not os.path.exists(map_path))
-
-            # Note kpartx can output warnings to stderr and succeed
-            # Also it can output failures to stderr and "succeed"
-            # So we just go on the existence of the mapped device
-            _out, err = utils.trycmd('kpartx', '-a', self.device,
-                                     run_as_root=True, discard_warnings=True)
-
-            # Note kpartx does nothing when presented with a raw image,
-            # so given we only use it when we expect a partitioned image, fail
-            if not os.path.exists(map_path):
-                if not err:
-                    err = _('partition %s not found') % self.partition
-                self.error = _('Failed to map partitions: %s') % err
-            else:
-                self.mapped_device = map_path
-                self.mapped = True
+            #qemu-nbd already has mapped the partition for mounting
+            self.mapped_device = '%sp%s' % (self.device, self.partition)
+            self.mapped = True
         else:
             self.mapped_device = self.device
             self.mapped = True
@@ -90,8 +74,7 @@ class Mount(object):
         """Remove partitions of the device from the file system namespace."""
         if not self.mapped:
             return
-        if self.partition:
-            utils.execute('kpartx', '-d', self.device, run_as_root=True)
+        #No need to run kpartx
         self.mapped = False

to rely on the qemu-nbd mapping. With the above change, file injection works fine with the CirrOS qcow2 image (I have not tested with any other image yet).
I run Ubuntu 12.04 Desktop with the 3.2.0-24-generic kernel and qemu-utils package version 1.0+noroms-0ubuntu13

Best Regards,
Fredric