rbd: define rbd_dev_{create,destroy}() helpers

Encapsulate the creation/initialization and destruction of rbd
device structures.  The rbd_client and the rbd_spec structures
provided on creation hold references whose ownership is transferred
to the new rbd_device structure.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

drivers/block/rbd.c

@@ -504,6 +504,7 @@ static void rbd_client_release(struct kref *kref)
  */
 static void rbd_put_client(struct rbd_client *rbdc)
 {
+	if (rbdc)
 		kref_put(&rbdc->kref, rbd_client_release);
 }
 
@@ -2166,6 +2167,34 @@ static void rbd_spec_free(struct kref *kref)
 	kfree(spec);
 }
 
+struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
+				struct rbd_spec *spec)
+{
+	struct rbd_device *rbd_dev;
+
+	rbd_dev = kzalloc(sizeof (*rbd_dev), GFP_KERNEL);
+	if (!rbd_dev)
+		return NULL;
+
+	spin_lock_init(&rbd_dev->lock);
+	INIT_LIST_HEAD(&rbd_dev->node);
+	INIT_LIST_HEAD(&rbd_dev->snaps);
+	init_rwsem(&rbd_dev->header_rwsem);
+
+	rbd_dev->spec = spec;
+	rbd_dev->rbd_client = rbdc;
+
+	return rbd_dev;
+}
+
+static void rbd_dev_destroy(struct rbd_device *rbd_dev)
+{
+	kfree(rbd_dev->header_name);
+	rbd_put_client(rbd_dev->rbd_client);
+	rbd_spec_put(rbd_dev->spec);
+	kfree(rbd_dev);
+}
+
 static bool rbd_snap_registered(struct rbd_snap *snap)
 {
 	bool ret = snap->dev.type == &rbd_snap_device_type;
@@ -3242,7 +3271,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 		rc = PTR_ERR(rbdc);
 		goto err_out_args;
 	}
-	ceph_opts = NULL;	/* ceph_opts now owned by rbd_dev client */
+	ceph_opts = NULL;	/* rbd_dev client now owns this */
 
 	/* pick the pool */
 	osdc = &rbdc->client->osdc;
@@ -3251,22 +3280,19 @@ static ssize_t rbd_add(struct bus_type *bus,
 		goto err_out_client;
 	spec->pool_id = (u64) rc;
 
-	rbd_dev = kzalloc(sizeof (*rbd_dev), GFP_KERNEL);
+	rbd_dev = rbd_dev_create(rbdc, spec);
 	if (!rbd_dev)
 		goto err_out_client;
-
-	spin_lock_init(&rbd_dev->lock);
-	INIT_LIST_HEAD(&rbd_dev->node);
-	INIT_LIST_HEAD(&rbd_dev->snaps);
-	init_rwsem(&rbd_dev->header_rwsem);
-	rbd_dev->rbd_client = rbdc;
-	rbd_dev->spec = spec;
+	rbdc = NULL;		/* rbd_dev now owns this */
+	spec = NULL;		/* rbd_dev now owns this */
 
 	rbd_dev->mapping.read_only = rbd_opts->read_only;
+	kfree(rbd_opts);
+	rbd_opts = NULL;	/* done with this */
 
 	rc = rbd_dev_probe(rbd_dev);
 	if (rc < 0)
-		goto err_out_mem;
+		goto err_out_rbd_dev;
 
 	/* no need to lock here, as rbd_dev is not registered yet */
 	rc = rbd_dev_snaps_update(rbd_dev);
@@ -3317,8 +3343,6 @@ static ssize_t rbd_add(struct bus_type *bus,
 	if (rc)
 		goto err_out_bus;
 
-	kfree(rbd_opts);
-
 	/* Everything's ready.  Announce the disk to the world. */
 
 	add_disk(rbd_dev->disk);
@@ -3332,7 +3356,6 @@ static ssize_t rbd_add(struct bus_type *bus,
 	/* this will also clean up rest of rbd_dev stuff */
 
 	rbd_bus_del_dev(rbd_dev);
-	kfree(rbd_opts);
 
 	return rc;
 
@@ -3346,9 +3369,8 @@ static ssize_t rbd_add(struct bus_type *bus,
 	rbd_remove_all_snaps(rbd_dev);
 err_out_probe:
 	rbd_header_free(&rbd_dev->header);
-	kfree(rbd_dev->header_name);
-err_out_mem:
-	kfree(rbd_dev);
+err_out_rbd_dev:
+	rbd_dev_destroy(rbd_dev);
 err_out_client:
 	rbd_put_client(rbdc);
 err_out_args:
@@ -3394,7 +3416,6 @@ static void rbd_dev_release(struct device *dev)
 	if (rbd_dev->watch_event)
 		rbd_req_sync_unwatch(rbd_dev);
 
-	rbd_put_client(rbd_dev->rbd_client);
 
 	/* clean up and free blkdev */
 	rbd_free_disk(rbd_dev);
@@ -3404,10 +3425,9 @@ static void rbd_dev_release(struct device *dev)
 	rbd_header_free(&rbd_dev->header);
 
 	/* done with the id, and with the rbd_dev */
-	kfree(rbd_dev->header_name);
 	rbd_dev_id_put(rbd_dev);
-	rbd_spec_put(rbd_dev->spec);
-	kfree(rbd_dev);
+	rbd_assert(rbd_dev->rbd_client != NULL);
+	rbd_dev_destroy(rbd_dev);
 
 	/* release module ref */
 	module_put(THIS_MODULE);