[Bug 1875863] Comment bridged from LTC Bugzilla

[bugproxy]

------- Comment From Eduard.Shishkin at ibm.com 2020-04-29 17:30 EDT-------
(In reply to comment #12)
> Oh, just noticed that this is a kernel issue and fix.
> In this case we need of course an upstream accepted kernel patch.
> I didn't found anything like "ceph: fix up endian bug in managing feature
> bits" in linux-next yet.
> Is it available at some staging tree?

Hi, It was queued for Linux-5.7-rcX (don't look for this in staging trees):
https://marc.info/?l=ceph-devel&m=158817653611155&w=2

-- 
You received this bug notification because you are a member of Ubuntu
OpenStack, which is a bug assignee.
https://bugs.launchpad.net/bugs/1875863

Title:
  ceph -- Unable to mount ceph volume on s390x

Status in Ubuntu on IBM z Systems:
  Incomplete
Status in ceph package in Ubuntu:
  Invalid
Status in linux package in Ubuntu:
  New

Bug description:
  When mounting a ceph volume, mount operation fails with an IO error.
  The problem is always reproducible.

  Identified potential root cause as kernel endian bug:

  In the function handle_session() variable @features always
  contains little endian order of bytes. Just because The feature
  mask sent by the MDS is little-endian (bits are packed bytewise
  from left to right in encode_supported_features()).

  However, test_bit(), called to check features availability, assumes
  the host order of bytes in that variable. This leads to problems on
  big endian architectures. Specifically it is impossible to mount
  ceph volume on s390.

  A fixup was proposed to convert little-endian order of bytes to the
  host one. That fixup was modified by ceph maintainers to use existing
  unpacking means for the conversion. The resulted patch attached.

  Related discussion in the ceph-development mailing list:
  https://marc.info/?l=ceph-devel&m=158815357301332&w=2

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-z-systems/+bug/1875863/+subscriptions