libceph: check reply num_data_items in setup_request_data()

setup_request_data() adds message data items to both request and reply
messages, but only checks request num_data_items before proceeding with
the loop.  This is wrong because if an op doesn't have any request data
items but has a reply data item (e.g. read), a duplicate data item gets
added to the message on every resend attempt.

This went unnoticed for years but now that message data items are
preallocated, it promptly crashes in ceph_msg_data_add().  Amend the
signature to make it clear that setup_request_data() operates on both
request and reply messages.  Also, remove data_len assert -- we have
another one in prepare_write_message().
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/osd_client.c

@@ -1917,48 +1917,48 @@ static bool should_plug_request(struct ceph_osd_request *req)
 /*
  * Keep get_num_data_items() in sync with this function.
  */
-static void setup_request_data(struct ceph_osd_request *req,
-			       struct ceph_msg *msg)
+static void setup_request_data(struct ceph_osd_request *req)
 {
-	u32 data_len = 0;
-	int i;
+	struct ceph_msg *request_msg = req->r_request;
+	struct ceph_msg *reply_msg = req->r_reply;
+	struct ceph_osd_req_op *op;
 
-	if (msg->num_data_items)
+	if (req->r_request->num_data_items || req->r_reply->num_data_items)
 		return;
 
-	WARN_ON(msg->data_length);
-	for (i = 0; i < req->r_num_ops; i++) {
-		struct ceph_osd_req_op *op = &req->r_ops[i];
-
+	WARN_ON(request_msg->data_length || reply_msg->data_length);
+	for (op = req->r_ops; op != &req->r_ops[req->r_num_ops]; op++) {
 		switch (op->op) {
 		/* request */
 		case CEPH_OSD_OP_WRITE:
 		case CEPH_OSD_OP_WRITEFULL:
 			WARN_ON(op->indata_len != op->extent.length);
-			ceph_osdc_msg_data_add(msg, &op->extent.osd_data);
+			ceph_osdc_msg_data_add(request_msg,
+					       &op->extent.osd_data);
 			break;
 		case CEPH_OSD_OP_SETXATTR:
 		case CEPH_OSD_OP_CMPXATTR:
 			WARN_ON(op->indata_len != op->xattr.name_len +
 						  op->xattr.value_len);
-			ceph_osdc_msg_data_add(msg, &op->xattr.osd_data);
+			ceph_osdc_msg_data_add(request_msg,
+					       &op->xattr.osd_data);
 			break;
 		case CEPH_OSD_OP_NOTIFY_ACK:
-			ceph_osdc_msg_data_add(msg,
+			ceph_osdc_msg_data_add(request_msg,
 					       &op->notify_ack.request_data);
 			break;
 
 		/* reply */
 		case CEPH_OSD_OP_STAT:
-			ceph_osdc_msg_data_add(req->r_reply,
+			ceph_osdc_msg_data_add(reply_msg,
 					       &op->raw_data_in);
 			break;
 		case CEPH_OSD_OP_READ:
-			ceph_osdc_msg_data_add(req->r_reply,
+			ceph_osdc_msg_data_add(reply_msg,
 					       &op->extent.osd_data);
 			break;
 		case CEPH_OSD_OP_LIST_WATCHERS:
-			ceph_osdc_msg_data_add(req->r_reply,
+			ceph_osdc_msg_data_add(reply_msg,
 					       &op->list_watchers.response_data);
 			break;
 
@@ -1967,25 +1967,23 @@ static void setup_request_data(struct ceph_osd_request *req,
 			WARN_ON(op->indata_len != op->cls.class_len +
 						  op->cls.method_len +
 						  op->cls.indata_len);
-			ceph_osdc_msg_data_add(msg, &op->cls.request_info);
+			ceph_osdc_msg_data_add(request_msg,
+					       &op->cls.request_info);
 			/* optional, can be NONE */
-			ceph_osdc_msg_data_add(msg, &op->cls.request_data);
+			ceph_osdc_msg_data_add(request_msg,
+					       &op->cls.request_data);
 			/* optional, can be NONE */
-			ceph_osdc_msg_data_add(req->r_reply,
+			ceph_osdc_msg_data_add(reply_msg,
 					       &op->cls.response_data);
 			break;
 		case CEPH_OSD_OP_NOTIFY:
-			ceph_osdc_msg_data_add(msg,
+			ceph_osdc_msg_data_add(request_msg,
 					       &op->notify.request_data);
-			ceph_osdc_msg_data_add(req->r_reply,
+			ceph_osdc_msg_data_add(reply_msg,
 					       &op->notify.response_data);
 			break;
 		}
-
-		data_len += op->indata_len;
 	}
-
-	WARN_ON(data_len != msg->data_length);
 }
 
 static void encode_pgid(void **p, const struct ceph_pg *pgid)
@@ -2033,7 +2031,7 @@ static void encode_request_partial(struct ceph_osd_request *req,
 			req->r_data_offset || req->r_snapc);
 	}
 
-	setup_request_data(req, msg);
+	setup_request_data(req);
 
 	encode_spgid(&p, &req->r_t.spgid); /* actual spg */
 	ceph_encode_32(&p, req->r_t.pgid.seed); /* raw hash */