P at draigBrady
Jul 13, 2012, 5:35 PM
Post #21 of 22
On 07/14/2012 12:09 AM, Mark Moseley wrote:
> On Tue, Jun 12, 2012 at 8:20 AM, Pádraig Brady <P [at] draigbrady> wrote:
>> On 06/12/2012 04:07 PM, Fredric Morenius wrote:
>>> From: Scott Moser [mailto:ssmoser2 [at] gmail] 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
>> Looks good. That should also support raw through the /dev/loop%s devices.
>> It might be safer to fallback to kpartx if not exists ...
>> '%sp%s' % (self.device, self.partition)
>> That would support kernels before 3.2
>> I'd also add a comment in the code, that nbd must be mounted with param
>> max_part=16 or whatever.
> Might be totally unrelated to the above issues but I figured I'd throw
> it out there. I was messing with file injection today and was getting
> odd errors.
> Some were due to hitting errors on a previous boot and partitions not
> getting cleaned up (e.g. kpartx -d never ran and the /dev/mapper/nbd*
> entries were still there, or qemu-nbd was still running). Some of
> those were likely a result of my own circumstances.
> More interesting though, and what might be of use to other people, the
> "kpartx -a" calls get run and then the code in nova/virt/disk/mount.py
> immediately checks for whether or not the newly created
> /dev/mapper/nbdXXpX partitions exist. They'd actually get created but
> the os.exists call would fail. Apparently the os.exists call was
> getting run too soon. I added a time.sleep() after both the 'kpartx
> -a' and 'kpartx -d' calls, to give things time to catch up before the
> os.exists calls and things worked much better.
The amount of synchronization bugs I've noticed in lower
Linux layers lately is worrying.
Anyway I've created a bug for this:
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