9p doesn't handle renames between directories -- however, we were returning
EPERM instead of EXDEV when we detected this case.
Signed-off-by: Eric Van Hensbergren <ericvh@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>