When retrying a read request, we need to "Reset" the bio.  It is easiest to
get this right if we discard the bio we have and re-clone it.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>