[Bug 1783542] Re: OSD creation on bcache device not working

[James Page]

The bcache check is specific to the 10.2.9 release currently in updates
- 10.2.10 which is currently in proposed reverts this feature, so Ubuntu
is aligned with upstream Ceph, but we're not quite as up-to-date on
point releases yet.

I guess the tl;dr is if you want to use bcache devices with ceph Jewel,
use the HWE kernel.

I'm going to mark this as Won't Fix (as its already fixed in the point
release) but this should flush through shortly.


** Changed in: ceph (Ubuntu)
       Status: New => Won't Fix

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https://bugs.launchpad.net/bugs/1783542

Title:
  OSD creation on bcache device not working

Status in ceph package in Ubuntu:
  Won't Fix

Bug description:
  Using the ceph-osd charm on xenial hwe.

  The charm successfully calls out for the regular ceph-disk prepare
  command, but that fails since it thinks of that device being a
  partition and doesn't create partition on top of bcache.

  The log ends up with failing:
  2018-07-24 14:41:40 INFO juju-log osdize cmd: ['ceph-disk', 'prepare', '--fs-type', 'xfs', '/dev/bcache4', '/dev/sdd']
  2018-07-24 14:41:42 DEBUG add-disk set_data_partition: incorrect partition UUID: None, expected ['4fbd7e29-9d25-41b8-afd0-5ec00ceff05d', '4fbd7e29-9d25-41b8-afd0-062c0ceff05d', '4fbd7e29-8ae0-4982-bf9d-5a8d867af560', '4fbd7e29-9d25-41b8-afd0-35865ceff05d']

  Full log:
  https://pastebin.canonical.com/p/8JMM9JbhxZ/

  After inspecting the ceph-disk source, I've found out where it is failing:
  ceph/xenial-updates,now 10.2.9-0ubuntu0.16.04.1 amd64 [installed]
  /usr/lib/python2.7/dist-packages/ceph_disk/main.py:#763

  def is_partition(dev):
      """
      Check whether a given device path is a partition or a full disk.
      """
      if is_mpath(dev):
          return is_partition_mpath(dev)

      dev = os.path.realpath(dev)
      st = os.lstat(dev)
      if not stat.S_ISBLK(st.st_mode):
          raise Error('not a block device', dev)

      name = get_dev_name(dev)
      if is_bcache(name):
          return True
      if os.path.exists(os.path.join('/sys/block', name)):
          return False

  If I remove the is_bcache check, it tries to create the partition on
  top and succeeds with in only with running on xenial-hwe kernel
  (4.13.0-45-generic at the moment).

  However patches that support partitioning of bcache devices are not
  available on the mainline kernel, so I suspect it would fail when not
  having our patches applied. [0]

  Note that this is probably related to the LP#1667078 fix [1] (bcache device numbers increase by 16) and 
  https://launchpadlibrarian.net/309401983/0001-bcache-Fix-bcache-device-names.patch

  Also note that this issue is not related to LP#1729145 or LP#1728742
  as I'm already running on the fixed kernel and the sympthoms are
  different. [2]. Also MAAS is up to date. [3]

  I assume this patch has been accepted by Canonical (not mainline ceph)
  and causing us the issue [4].

  [0]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b8c0d911ac5285e6be8967713271a51bdc5a936a
  [1]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1667078
  [2]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1729145
  [3]: https://bugs.launchpad.net/curtin/+bug/1728742
  [4]: http://tracker.ceph.com/issues/13278

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