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[Rafael David Tinoco <rafael.tinoco@xxxxxxxxxxxxx>]

Okay, following instructions already provided by Chris Arges -
responsible for the kernel bisection so far - and Ed - working on the
case since its beginning - I was able to create another reproducer - not
openstack dependant - that fails close to 100% of times.

Output:

# running test

----

inaddy@alien:test$ ./teste.sh
% RUN: 1
+ Creating disk 0: /dev/vdb
+ Creating disk 1: /dev/vdc
! Starting virtual machine
! Adding disk 0: /dev/vdb
! Adding disk 1: /dev/vdc
! Waiting virtual machine network to be up
! Checking if disk is online:
* Found 0 extra disks online
$ Missing disk(s) exiting

# checking results

inaddy@alien:test$ ssh sf00068947precise
Last login: Tue Aug 11 14:07:11 2015 from 192.168.128.1
inaddy@sf00068947precise:~$ ls -lah /dev/vd*
brw-rw---- 1 root disk 253, 0 Aug 11 14:29 /dev/vda
brw-rw---- 1 root disk 253, 1 Aug 11 14:29 /dev/vda1
brw-rw---- 1 root disk 253, 2 Aug 11 14:29 /dev/vda2
brw-rw---- 1 root disk 253, 5 Aug 11 14:29 /dev/vda5
inaddy@sf00068947precise:~$ echo 1 | sudo tee /sys/bus/pci/rescan
1
inaddy@sf00068947precise:~$ ls -lah /dev/vd*
brw-rw---- 1 root disk 253,  0 Aug 11 14:29 /dev/vda
brw-rw---- 1 root disk 253,  1 Aug 11 14:29 /dev/vda1
brw-rw---- 1 root disk 253,  2 Aug 11 14:29 /dev/vda2
brw-rw---- 1 root disk 253,  5 Aug 11 14:29 /dev/vda5
brw-rw---- 1 root disk 253, 16 Aug 11 14:29 /dev/vdb
brw-rw---- 1 root disk 253, 32 Aug 11 14:29 /dev/vdc

----

Attaching files for this "second" reproducer. This will guide me on
verifying a possible fix.

-- 
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Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1479031

Title:
  attached block devices not showing up

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Precise:
  In Progress

Bug description:
  I have Ubuntu Precise guests running in kvm to which I attach volumes
  immediately after boot. Sometimes I notice that the devices do not
  show up in the guest e.g. they are not visible in /proc/partitions and
  dmesg boot log shows no sign of then being noticed. Qemu itself shows
  that the devices are attached and if I do a rescan within the guest
  the devices appear. A reboot also cause the devices to appear. So, it
  feels like there is enough evidence to suggest that the devices were
  properly attached by qemu/seabios but they just didn't get noticed by
  the guest.

  This issue is reproducible with Precise running 3.2, 3.5 (lts-quantal)
  and 3.8 (lts-raring) kernels but not as of 3.11 (lts-saucy) so it
  would appear that something changed between 3.8 and 3.11 that resolved
  this issue and if we can identify it we should backport to 3.2.

  I am able to reproduce this issue using Openstack to spin up vms and
  attach volumes using the following script:

  http://pastebin.ubuntu.com/11954253/

  I hit this issue with 1/2 instances.

  As a workaround one can rescan and the device shows up:
  echo 1 | sudo tee /sys/bus/pci/rescan

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