glnx-fdio: handle EOPNOTSUPP for copy_file_range
When using copy_file_range
to target a source and dest on the same NFS
mount on some older kernel versions, it's possible that we can get
EOPNOTSUPP
e.g. if the NFS server doesn't support server-side copy.
We hit this in the FCOS release pipeline where we run ostree pull-local
to pull content between two repos on the same mount from
inside an OpenShift cluster on top of RHEL7.
Nowadays, it seems like the kernel itself falls back to a more generic
version of copy_file_range()
at least. Though to be compatible with
older kernels, let's add EOPNOTSUPP
to the list of errors we interpret
as "cfr possibly available, but can't be done for this specific
operation".