cross-partition mv fails with "Operation not supported" due to ACLs

[Jim Meyering]

FYI, on a system like this,

  $ head -1 /etc/issue
  Red Hat Enterprise Linux AS release 4 (Nahant Update 6)
  $ rpm -q glibc-devel
  glibc-devel-2.3.4-2.39
  $ uname -r
  2.6.9-67.ELsmp

The coreutils test, tests/mv/part-symlink, fails with this output:

-0 mv rem_reg loc_sl (loc_sl) ()
-0 mv -b rem_reg loc_sl (loc_sl loc_sl~ -> rem_reg) ()
+0 mv rem_reg loc_sl [mv: preserving permissions for `loc_sl': Operation not 
supported ](loc_sl) ()
+0 mv -b rem_reg loc_sl [mv: preserving permissions for `loc_sl': Operation not 
supported ](loc_sl loc_sl~ -> rem_reg) ()

In spite of the name of that test, the failure is unrelated to symlinks.
Any cross-partition move of a regular file elicits the
"Operation not supported" diagnostic, *but*, and here's the
part that matters:

  It happens only when moving from an NFS-mounted partition (which
  is Solaris 10 ZFS, I think) to a partition without those newer ACLs.
  E.g., when moving to an ext3 /tmp or to /dev/shm, which is tmpfs,
  there's no problem, because acl_*get*_fd fails.

Investigating shows that the diagnostic is due to acl_set_fd failing,
which is because it does this:

  fsetxattr(4, "system.posix_acl_access"..., "\x02...", 36, 0) = -1
    EOPNOTSUPP (Operation not supported)

Since coreutils-5.2.1 works the same way on that system, this
isn't even a regression.