[Bug 1875863] Re: ceph -- Unable to mount ceph volume on s390x
James Page
james.page at ubuntu.com
Wed Apr 29 15:24:36 UTC 2020
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Changed in: ceph (Ubuntu)
Status: New => Invalid
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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
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