rbd: don't assign extent info in rbd_req_sync_op()

Move the assignment of the extent offset and length and payload
length out of rbd_req_sync_op() and into its caller in the one spot
where a read (and note--no write) operation might be initiated.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

drivers/block/rbd.c

@@ -1025,19 +1025,15 @@ static struct bio *bio_chain_clone_range(struct bio **bio_src,
 	return NULL;
 }
 
-static struct ceph_osd_req_op *rbd_create_rw_op(int opcode, u32 payload_len)
+static struct ceph_osd_req_op *rbd_create_rw_op(int opcode, u64 ofs, u64 len)
 {
 	struct ceph_osd_req_op *op;
 
 	op = kzalloc(sizeof (*op), GFP_NOIO);
 	if (!op)
 		return NULL;
-	/*
-	 * op extent offset and length will be set later on
-	 * after ceph_calc_file_object_mapping().
-	 */
+
 	op->op = opcode;
-	op->payload_len = payload_len;
 
 	return op;
 }
@@ -1047,6 +1043,42 @@ static void rbd_destroy_op(struct ceph_osd_req_op *op)
 	kfree(op);
 }
 
+struct ceph_osd_req_op *rbd_osd_req_op_create(u16 opcode, ...)
+{
+	struct ceph_osd_req_op *op;
+	va_list args;
+
+	op = kzalloc(sizeof (*op), GFP_NOIO);
+	if (!op)
+		return NULL;
+	op->op = opcode;
+	va_start(args, opcode);
+	switch (opcode) {
+	case CEPH_OSD_OP_READ:
+	case CEPH_OSD_OP_WRITE:
+		/* rbd_osd_req_op_create(READ, offset, length) */
+		/* rbd_osd_req_op_create(WRITE, offset, length) */
+		op->extent.offset = va_arg(args, u64);
+		op->extent.length = va_arg(args, u64);
+		if (opcode == CEPH_OSD_OP_WRITE)
+			op->payload_len = op->extent.length;
+		break;
+	default:
+		rbd_warn(NULL, "unsupported opcode %hu\n", opcode);
+		kfree(op);
+		op = NULL;
+		break;
+	}
+	va_end(args);
+
+	return op;
+}
+
+static void rbd_osd_req_op_destroy(struct ceph_osd_req_op *op)
+{
+	kfree(op);
+}
+
 static void rbd_coll_end_req_index(struct request *rq,
 				   struct rbd_req_coll *coll,
 				   int index,
@@ -1262,13 +1294,6 @@ static int rbd_req_sync_op(struct rbd_device *rbd_dev,
 	if (IS_ERR(pages))
 		return PTR_ERR(pages);
 
-	if (op->op == CEPH_OSD_OP_READ || op->op == CEPH_OSD_OP_WRITE) {
-		op->extent.offset = ofs;
-		op->extent.length = inbound_size;
-		if (op->op == CEPH_OSD_OP_WRITE)
-			op->payload_len = inbound_size;
-	}
-
 	ret = rbd_do_request(NULL, rbd_dev, NULL, CEPH_NOSNAP,
 			  object_name, ofs, inbound_size, NULL,
 			  pages, num_pages,
@@ -1304,7 +1329,6 @@ static int rbd_do_op(struct request *rq,
 	u64 seg_len;
 	int ret;
 	struct ceph_osd_req_op *op;
-	u32 payload_len;
 	int opcode;
 	int flags;
 	u64 snapid;
@@ -1319,22 +1343,17 @@ static int rbd_do_op(struct request *rq,
 		opcode = CEPH_OSD_OP_WRITE;
 		flags = CEPH_OSD_FLAG_WRITE|CEPH_OSD_FLAG_ONDISK;
 		snapid = CEPH_NOSNAP;
-		payload_len = seg_len;
 	} else {
 		opcode = CEPH_OSD_OP_READ;
 		flags = CEPH_OSD_FLAG_READ;
 		rbd_assert(!snapc);
 		snapid = rbd_dev->spec->snap_id;
-		payload_len = 0;
 	}
 
 	ret = -ENOMEM;
-	op = rbd_create_rw_op(opcode, payload_len);
+	op = rbd_osd_req_op_create(opcode, seg_ofs, seg_len);
 	if (!op)
 		goto done;
-	op->extent.offset = seg_ofs;
-	op->extent.length = seg_len;
-	op->payload_len = payload_len;
 
 	/* we've taken care of segment sizes earlier when we
 	   cloned the bios. We should never have a segment
@@ -1352,7 +1371,7 @@ static int rbd_do_op(struct request *rq,
 	if (ret < 0)
 		rbd_coll_end_req_index(rq, coll, coll_index,
 					(s32)ret, seg_len);
-	rbd_destroy_op(op);
+	rbd_osd_req_op_destroy(op);
 done:
 	kfree(seg_name);
 	return ret;
@@ -1370,13 +1389,13 @@ static int rbd_req_sync_read(struct rbd_device *rbd_dev,
 	struct ceph_osd_req_op *op;
 	int ret;
 
-	op = rbd_create_rw_op(CEPH_OSD_OP_READ, 0);
+	op = rbd_osd_req_op_create(CEPH_OSD_OP_READ, ofs, len);
 	if (!op)
 		return -ENOMEM;
 
 	ret = rbd_req_sync_op(rbd_dev, CEPH_OSD_FLAG_READ,
 			       op, object_name, ofs, len, buf, NULL, ver);
-	rbd_destroy_op(op);
+	rbd_osd_req_op_destroy(op);
 
 	return ret;
 }
@@ -1391,7 +1410,7 @@ static int rbd_req_sync_notify_ack(struct rbd_device *rbd_dev,
 	struct ceph_osd_req_op *op;
 	int ret;
 
-	op = rbd_create_rw_op(CEPH_OSD_OP_NOTIFY_ACK, 0);
+	op = rbd_create_rw_op(CEPH_OSD_OP_NOTIFY_ACK, 0, 0);
 	if (!op)
 		return -ENOMEM;
 
@@ -1442,7 +1461,7 @@ static int rbd_req_sync_watch(struct rbd_device *rbd_dev, int start)
 	__le64 version = 0;
 	int ret;
 
-	op = rbd_create_rw_op(CEPH_OSD_OP_WATCH, 0);
+	op = rbd_create_rw_op(CEPH_OSD_OP_WATCH, 0, 0);
 	if (!op)
 		return -ENOMEM;
 
@@ -1505,9 +1524,10 @@ static int rbd_req_sync_exec(struct rbd_device *rbd_dev,
 	 * operation.
 	 */
 	payload_size = class_name_len + method_name_len + outbound_size;
-	op = rbd_create_rw_op(CEPH_OSD_OP_CALL, payload_size);
+	op = rbd_create_rw_op(CEPH_OSD_OP_CALL, 0, 0);
 	if (!op)
 		return -ENOMEM;
+	op->payload_len = payload_size;
 
 	op->cls.class_name = class_name;
 	op->cls.class_len = (__u8) class_name_len;