libceph: evaluate osd_req_op_data() arguments only once

This patch changes the osd_req_op_data() macro to not evaluate
arguments more than once in order to follow the kernel coding style.
Signed-off-by: Ioana Ciornei <ciorneiioana@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
[idryomov@gmail.com: changelog, formatting]
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/osd_client.c

@@ -121,10 +121,12 @@ static void ceph_osd_data_bio_init(struct ceph_osd_data *osd_data,
 #endif /* CONFIG_BLOCK */
 
 #define osd_req_op_data(oreq, whch, typ, fld)				\
-	({						\
-		BUG_ON(whch >= (oreq)->r_num_ops);	\
-		&(oreq)->r_ops[whch].typ.fld;		\
-	})
+({									\
+	struct ceph_osd_request *__oreq = (oreq);			\
+	unsigned int __whch = (whch);					\
+	BUG_ON(__whch >= __oreq->r_num_ops);				\
+	&__oreq->r_ops[__whch].typ.fld;					\
+})
 
 static struct ceph_osd_data *
 osd_req_op_raw_data_in(struct ceph_osd_request *osd_req, unsigned int which)