Both R1BIO_Barrier and R1BIO_Returned are 4 !!!!

This means that barrier requests don't get returned (i.e.  b_endio called)
because it looks like they already have been.
Signed-off-by: NNeil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>