rbd: do not duplicate ceph_client pointer in rbd_device

The rbd_device structure maintains a duplicate copy of the
ceph_client pointer maintained in its rbd_client structure.  There
appears to be no good reason for this, and its presence presents a
risk of them getting out of synch or otherwise misused.  So kill it
off, and use the rbd_client copy only.
Signed-off-by: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>

drivers/block/rbd.c

@@ -140,7 +140,6 @@ struct rbd_device {
 	struct gendisk		*disk;		/* blkdev's gendisk and rq */
 	struct request_queue	*q;
 
-	struct ceph_client	*client;
 	struct rbd_client	*rbd_client;
 
 	char			name[DEV_NAME_LEN]; /* blkdev name, e.g. rbd3 */
@@ -388,7 +387,6 @@ static int rbd_get_client(struct rbd_device *rbd_dev, const char *mon_addr,
 		/* using an existing client */
 		kref_get(&rbdc->kref);
 		rbd_dev->rbd_client = rbdc;
-		rbd_dev->client = rbdc->client;
 		spin_unlock(&node_lock);
 		return 0;
 	}
@@ -401,7 +399,6 @@ static int rbd_get_client(struct rbd_device *rbd_dev, const char *mon_addr,
 	}
 
 	rbd_dev->rbd_client = rbdc;
-	rbd_dev->client = rbdc->client;
 	return 0;
 done_err:
 	kfree(rbd_opts);
@@ -435,7 +432,6 @@ static void rbd_put_client(struct rbd_device *rbd_dev)
 	kref_put(&rbd_dev->rbd_client->kref, rbd_client_release);
 	spin_unlock(&node_lock);
 	rbd_dev->rbd_client = NULL;
-	rbd_dev->client = NULL;
 }
 
 /*
@@ -858,6 +854,7 @@ static int rbd_do_request(struct request *rq,
 	struct rbd_request *req_data;
 	struct ceph_osd_request_head *reqhead;
 	struct rbd_image_header *header = &dev->header;
+	struct ceph_osd_client *osdc;
 
 	req_data = kzalloc(sizeof(*req_data), GFP_NOIO);
 	if (!req_data) {
@@ -876,11 +873,9 @@ static int rbd_do_request(struct request *rq,
 
 	down_read(&header->snap_rwsem);
 
-	req = ceph_osdc_alloc_request(&dev->client->osdc, flags,
-				      snapc,
-				      ops,
-				      false,
-				      GFP_NOIO, pages, bio);
+	osdc = &dev->rbd_client->client->osdc;
+	req = ceph_osdc_alloc_request(osdc, flags, snapc, ops,
+					false, GFP_NOIO, pages, bio);
 	if (!req) {
 		up_read(&header->snap_rwsem);
 		ret = -ENOMEM;
@@ -909,8 +904,8 @@ static int rbd_do_request(struct request *rq,
 	layout->fl_object_size = cpu_to_le32(1 << RBD_MAX_OBJ_ORDER);
 	layout->fl_pg_preferred = cpu_to_le32(-1);
 	layout->fl_pg_pool = cpu_to_le32(dev->poolid);
-	ceph_calc_raw_layout(&dev->client->osdc, layout, snapid,
-			     ofs, &len, &bno, req, ops);
+	ceph_calc_raw_layout(osdc, layout, snapid, ofs, &len, &bno,
+				req, ops);
 
 	ceph_osdc_build_request(req, ofs, &len,
 				ops,
@@ -920,16 +915,16 @@ static int rbd_do_request(struct request *rq,
 	up_read(&header->snap_rwsem);
 
 	if (linger_req) {
-		ceph_osdc_set_request_linger(&dev->client->osdc, req);
+		ceph_osdc_set_request_linger(osdc, req);
 		*linger_req = req;
 	}
 
-	ret = ceph_osdc_start_request(&dev->client->osdc, req, false);
+	ret = ceph_osdc_start_request(osdc, req, false);
 	if (ret < 0)
 		goto done_err;
 
 	if (!rbd_cb) {
-		ret = ceph_osdc_wait_request(&dev->client->osdc, req);
+		ret = ceph_osdc_wait_request(osdc, req);
 		if (ver)
 			*ver = le64_to_cpu(req->r_reassert_version.version);
 		dout("reassert_ver=%lld\n",
@@ -1227,7 +1222,7 @@ static int rbd_req_sync_watch(struct rbd_device *dev,
 			      u64 ver)
 {
 	struct ceph_osd_req_op *ops;
-	struct ceph_osd_client *osdc = &dev->client->osdc;
+	struct ceph_osd_client *osdc = &dev->rbd_client->client->osdc;
 
 	int ret = rbd_create_rw_ops(&ops, 1, CEPH_OSD_OP_WATCH, 0);
 	if (ret < 0)
@@ -1314,7 +1309,7 @@ static int rbd_req_sync_notify(struct rbd_device *dev,
 		          const char *obj)
 {
 	struct ceph_osd_req_op *ops;
-	struct ceph_osd_client *osdc = &dev->client->osdc;
+	struct ceph_osd_client *osdc = &dev->rbd_client->client->osdc;
 	struct ceph_osd_event *event;
 	struct rbd_notify_info info;
 	int payload_len = sizeof(u32) + sizeof(u32);
@@ -1623,13 +1618,14 @@ static int rbd_header_add_snap(struct rbd_device *dev,
 	int ret;
 	void *data, *p, *e;
 	u64 ver;
+	struct ceph_mon_client *monc;
 
 	/* we should create a snapshot only if we're pointing at the head */
 	if (dev->cur_snap)
 		return -EINVAL;
 
-	ret = ceph_monc_create_snapid(&dev->client->monc, dev->poolid,
-				      &new_snapid);
+	monc = &dev->rbd_client->client->monc;
+	ret = ceph_monc_create_snapid(monc, dev->poolid, &new_snapid);
 	dout("created snapid=%lld\n", new_snapid);
 	if (ret < 0)
 		return ret;
@@ -1809,7 +1805,8 @@ static ssize_t rbd_client_id_show(struct device *dev,
 {
 	struct rbd_device *rbd_dev = dev_to_rbd(dev);
 
-	return sprintf(buf, "client%lld\n", ceph_client_id(rbd_dev->client));
+	return sprintf(buf, "client%lld\n",
+			ceph_client_id(rbd_dev->rbd_client->client));
 }
 
 static ssize_t rbd_pool_show(struct device *dev,
@@ -2233,7 +2230,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 	mutex_unlock(&ctl_mutex);
 
 	/* pick the pool */
-	osdc = &rbd_dev->client->osdc;
+	osdc = &rbd_dev->rbd_client->client->osdc;
 	rc = ceph_pg_poolid_by_name(osdc->osdmap, rbd_dev->pool_name);
 	if (rc < 0)
 		goto err_out_client;
@@ -2312,9 +2309,12 @@ static void rbd_dev_release(struct device *dev)
 	struct rbd_device *rbd_dev =
 			container_of(dev, struct rbd_device, dev);
 
-	if (rbd_dev->watch_request)
-		ceph_osdc_unregister_linger_request(&rbd_dev->client->osdc,
+	if (rbd_dev->watch_request) {
+		struct ceph_client *client = rbd_dev->rbd_client->client;
+
+		ceph_osdc_unregister_linger_request(&client->osdc,
 						    rbd_dev->watch_request);
+	}
 	if (rbd_dev->watch_event)
 		rbd_req_sync_unwatch(rbd_dev, rbd_dev->obj_md_name);