libceph: isolate other message data fields

Define ceph_msg_data_set_pagelist(), ceph_msg_data_set_bio(), and
ceph_msg_data_set_trail() to clearly abstract the assignment of the
remaining data-related fields in a ceph message structure.  Use the
new functions in the osd client and mds client.

This partially resolves:
    http://tracker.ceph.com/issues/4263Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

fs/ceph/mds_client.c

@@ -2603,7 +2603,7 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
 			goto fail;
 	}
 
-	reply->pagelist = pagelist;
+	ceph_msg_data_set_pagelist(reply, pagelist);
 	if (recon_state.flock)
 		reply->hdr.version = cpu_to_le16(2);
 	reply->hdr.data_len = cpu_to_le32(pagelist->length);

include/linux/ceph/messenger.h

@@ -221,6 +221,11 @@ extern void ceph_con_keepalive(struct ceph_connection *con);
 
 extern void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
 				size_t length, size_t alignment);
+extern void ceph_msg_data_set_pagelist(struct ceph_msg *msg,
+				struct ceph_pagelist *pagelist);
+extern void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio);
+extern void ceph_msg_data_set_trail(struct ceph_msg *msg,
+				struct ceph_pagelist *trail);
 
 extern struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
 				     bool can_fail);

net/ceph/messenger.c

@@ -2701,6 +2701,34 @@ void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
 }
 EXPORT_SYMBOL(ceph_msg_data_set_pages);
 
+void ceph_msg_data_set_pagelist(struct ceph_msg *msg,
+				struct ceph_pagelist *pagelist)
+{
+	/* BUG_ON(!pagelist); */
+	/* BUG_ON(msg->pagelist); */
+
+	msg->pagelist = pagelist;
+}
+EXPORT_SYMBOL(ceph_msg_data_set_pagelist);
+
+void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio)
+{
+	/* BUG_ON(!bio); */
+	/* BUG_ON(msg->bio); */
+
+	msg->bio = bio;
+}
+EXPORT_SYMBOL(ceph_msg_data_set_bio);
+
+void ceph_msg_data_set_trail(struct ceph_msg *msg, struct ceph_pagelist *trail)
+{
+	/* BUG_ON(!trail); */
+	/* BUG_ON(msg->trail); */
+
+	msg->trail = trail;
+}
+EXPORT_SYMBOL(ceph_msg_data_set_trail);
+
 /*
  * construct a new message with given type, size
  * the new msg has a ref count of 1.

net/ceph/osd_client.c

@@ -1763,12 +1763,12 @@ int ceph_osdc_start_request(struct ceph_osd_client *osdc,
 			osd_data->length, osd_data->alignment);
 #ifdef CONFIG_BLOCK
 	} else if (osd_data->type == CEPH_OSD_DATA_TYPE_BIO) {
-		req->r_request->bio = osd_data->bio;
+		ceph_msg_data_set_bio(req->r_request, osd_data->bio);
 #endif
 	} else {
 		BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_NONE);
 	}
-	req->r_request->trail = &req->r_trail;
+	ceph_msg_data_set_trail(req->r_request, &req->r_trail);
 
 	register_request(osdc, req);
 
@@ -2132,7 +2132,7 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
 				osd_data->length, osd_data->alignment);
 #ifdef CONFIG_BLOCK
 		} else if (osd_data->type == CEPH_OSD_DATA_TYPE_BIO) {
-			m->bio = osd_data->bio;
+			ceph_msg_data_set_bio(m, osd_data->bio);
 #endif
 		}
 	}