rbd: use GFP_NOIO in rbd_obj_request_create()

rbd: use GFP_NOIO in rbd_obj_request_create()

[ Upstream commit 5a60e87603c4c533492c515b7f62578189b03c9c ]

rbd_obj_request_create() is called on the main I/O path, so we need to
use GFP_NOIO to make sure allocation doesn't blow back on us.  Not all
callers need this, but I'm still hardcoding the flag inside rather than
making it a parameter because a) this is going to stable, and b) those
callers shouldn't really use rbd_obj_request_create() and will be fixed
in the future.

More memory allocation fixes will follow.

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>