fs: RWF_NOWAIT should imply IOCB_NOIO

With the change allowing read-ahead for IOCB_NOWAIT, we changed the
RWF_NOWAIT semantics of only doing cached reads. Since we know have
IOCB_NOIO to manage that specific side of it, just make RWF_NOWAIT
imply IOCB_NOIO as well to restore the previous behavior.

Fixes: 2e85abf ("mm: allow read-ahead with IOCB_NOWAIT set")
Reported-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/fs.h

@@ -3293,7 +3293,7 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
 	if (flags & RWF_NOWAIT) {
 		if (!(ki->ki_filp->f_mode & FMODE_NOWAIT))
 			return -EOPNOTSUPP;
-		kiocb_flags |= IOCB_NOWAIT;
+		kiocb_flags |= IOCB_NOWAIT | IOCB_NOIO;
 	}
 	if (flags & RWF_HIPRI)
 		kiocb_flags |= IOCB_HIPRI;