rbd: pass length, not op for osd completions

The only thing type-specific osd completion functions do with their
osd op parameter is (in some cases) extract the number of bytes
transferred from it.  In the other cases, the xferred bytes field
is not used, and total message data transfer byte count (which may
well be zero) is used.

Just set the object request transfer count in the main osd request
callback function and provide that to the other routines.  There is
then no longer any need to pass the op pointer to the type-specific
completion routines, so drop those parameters.

Stop doing anything with the total message data length.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

drivers/block/rbd.c

@@ -1274,42 +1274,30 @@ static void rbd_obj_request_complete(struct rbd_obj_request *obj_request)
 		complete_all(&obj_request->completion);
 }
 
-static void rbd_osd_trivial_callback(struct rbd_obj_request *obj_request,
-				struct ceph_osd_op *op)
+static void rbd_osd_trivial_callback(struct rbd_obj_request *obj_request)
 {
 	dout("%s: obj %p\n", __func__, obj_request);
 	obj_request_done_set(obj_request);
 }
 
-static void rbd_osd_read_callback(struct rbd_obj_request *obj_request,
-				struct ceph_osd_op *op)
+static void rbd_osd_read_callback(struct rbd_obj_request *obj_request)
 {
-	u64 xferred;
 
-	/*
-	 * We support a 64-bit length, but ultimately it has to be
-	 * passed to blk_end_request(), which takes an unsigned int.
-	 */
-	xferred = le64_to_cpu(op->extent.length);
-	rbd_assert(xferred < (u64) UINT_MAX);
 	dout("%s: obj %p result %d %llu/%llu\n", __func__, obj_request,
-		obj_request->result, xferred, obj_request->length);
+		obj_request->result, obj_request->xferred, obj_request->length);
 	if (obj_request->result == (s32) -ENOENT) {
 		zero_bio_chain(obj_request->bio_list, 0);
 		obj_request->result = 0;
-	} else if (xferred < obj_request->length && !obj_request->result) {
-		zero_bio_chain(obj_request->bio_list, xferred);
-		xferred = obj_request->length;
+	} else if (obj_request->xferred < obj_request->length &&
+			!obj_request->result) {
+		zero_bio_chain(obj_request->bio_list, obj_request->xferred);
+		obj_request->xferred = obj_request->length;
 	}
-	obj_request->xferred = xferred;
 	obj_request_done_set(obj_request);
 }
 
-static void rbd_osd_write_callback(struct rbd_obj_request *obj_request,
-				struct ceph_osd_op *op)
+static void rbd_osd_write_callback(struct rbd_obj_request *obj_request)
 {
-
-	obj_request->xferred = le64_to_cpu(op->extent.length);
 	dout("%s: obj %p result %d %llu/%llu\n", __func__, obj_request,
 		obj_request->result, obj_request->xferred, obj_request->length);
 
@@ -1331,8 +1319,7 @@ static void rbd_osd_write_callback(struct rbd_obj_request *obj_request,
  * For a simple stat call there's nothing to do.  We'll do more if
  * this is part of a write sequence for a layered image.
  */
-static void rbd_osd_stat_callback(struct rbd_obj_request *obj_request,
-				struct ceph_osd_op *op)
+static void rbd_osd_stat_callback(struct rbd_obj_request *obj_request)
 {
 	dout("%s: obj %p\n", __func__, obj_request);
 	obj_request_done_set(obj_request);
@@ -1352,7 +1339,6 @@ static void rbd_osd_req_callback(struct ceph_osd_request *osd_req,
 	rbd_assert(!!obj_request->img_request ^
 				(obj_request->which == BAD_WHICH));
 
-	obj_request->xferred = le32_to_cpu(msg->hdr.data_len);
 	reply_head = msg->front.iov_base;
 	obj_request->result = (s32) le32_to_cpu(reply_head->result);
 	obj_request->version = le64_to_cpu(osd_req->r_reassert_version.version);
@@ -1360,22 +1346,29 @@ static void rbd_osd_req_callback(struct ceph_osd_request *osd_req,
 	num_ops = le32_to_cpu(reply_head->num_ops);
 	WARN_ON(num_ops != 1);	/* For now */
 
+	/*
+	 * We support a 64-bit length, but ultimately it has to be
+	 * passed to blk_end_request(), which takes an unsigned int.
+	 */
 	op = &reply_head->ops[0];
+	obj_request->xferred = le64_to_cpu(op->extent.length);
+	rbd_assert(obj_request->xferred < (u64) UINT_MAX);
+
 	opcode = le16_to_cpu(op->op);
 	switch (opcode) {
 	case CEPH_OSD_OP_READ:
-		rbd_osd_read_callback(obj_request, op);
+		rbd_osd_read_callback(obj_request);
 		break;
 	case CEPH_OSD_OP_WRITE:
-		rbd_osd_write_callback(obj_request, op);
+		rbd_osd_write_callback(obj_request);
 		break;
 	case CEPH_OSD_OP_STAT:
-		rbd_osd_stat_callback(obj_request, op);
+		rbd_osd_stat_callback(obj_request);
 		break;
 	case CEPH_OSD_OP_CALL:
 	case CEPH_OSD_OP_NOTIFY_ACK:
 	case CEPH_OSD_OP_WATCH:
-		rbd_osd_trivial_callback(obj_request, op);
+		rbd_osd_trivial_callback(obj_request);
 		break;
 	default:
 		rbd_warn(NULL, "%s: unsupported op %hu\n",