rbd: void data pointers for rbd_obj_method_sync()

Make the inbound and outbound data parameters have void rather than
character type for rbd_obj_method_sync().  This makes it more clear
they don't expect typed data, and eliminates the need for some silly
type casts.

One more unrelated change: define the features buffer used in
_rbd_dev_v2_snap_features() to be a packed data structure.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

drivers/block/rbd.c

@@ -2623,9 +2623,9 @@ static int rbd_obj_method_sync(struct rbd_device *rbd_dev,
 			     const char *object_name,
 			     const char *class_name,
 			     const char *method_name,
-			     const char *outbound,
+			     const void *outbound,
 			     size_t outbound_size,
-			     char *inbound,
+			     void *inbound,
 			     size_t inbound_size,
 			     u64 *version)
 {
@@ -3578,8 +3578,8 @@ static int _rbd_dev_v2_snap_size(struct rbd_device *rbd_dev, u64 snap_id,
 
 	ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name,
 				"rbd", "get_size",
-				(char *) &snapid, sizeof (snapid),
-				(char *) &size_buf, sizeof (size_buf), NULL);
+				&snapid, sizeof (snapid),
+				&size_buf, sizeof (size_buf), NULL);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)
 		return ret;
@@ -3612,8 +3612,7 @@ static int rbd_dev_v2_object_prefix(struct rbd_device *rbd_dev)
 		return -ENOMEM;
 
 	ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name,
-				"rbd", "get_object_prefix",
-				NULL, 0,
+				"rbd", "get_object_prefix", NULL, 0,
 				reply_buf, RBD_OBJ_PREFIX_LEN_MAX, NULL);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)
@@ -3644,15 +3643,14 @@ static int _rbd_dev_v2_snap_features(struct rbd_device *rbd_dev, u64 snap_id,
 	struct {
 		__le64 features;
 		__le64 incompat;
-	} features_buf = { 0 };
+	} __attribute__ ((packed)) features_buf = { 0 };
 	u64 incompat;
 	int ret;
 
 	ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name,
 				"rbd", "get_features",
-				(char *) &snapid, sizeof (snapid),
-				(char *) &features_buf, sizeof (features_buf),
-				NULL);
+				&snapid, sizeof (snapid),
+				&features_buf, sizeof (features_buf), NULL);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)
 		return ret;
@@ -3706,15 +3704,15 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
 	snapid = cpu_to_le64(CEPH_NOSNAP);
 	ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name,
 				"rbd", "get_parent",
-				(char *) &snapid, sizeof (snapid),
-				(char *) reply_buf, size, NULL);
+				&snapid, sizeof (snapid),
+				reply_buf, size, NULL);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)
 		goto out_err;
 
 	ret = -ERANGE;
 	p = reply_buf;
-	end = (char *) reply_buf + size;
+	end = reply_buf + size;
 	ceph_decode_64_safe(&p, end, parent_spec->pool_id, out_err);
 	if (parent_spec->pool_id == CEPH_NOPOOL)
 		goto out;	/* No parent?  No problem. */
@@ -3767,7 +3765,7 @@ static char *rbd_dev_image_name(struct rbd_device *rbd_dev)
 		return NULL;
 
 	p = image_id;
-	end = (char *) image_id + image_id_size;
+	end = image_id + image_id_size;
 	ceph_encode_string(&p, end, rbd_dev->spec->image_id, (u32) len);
 
 	size = sizeof (__le32) + RBD_IMAGE_NAME_LEN_MAX;
@@ -3778,11 +3776,11 @@ static char *rbd_dev_image_name(struct rbd_device *rbd_dev)
 	ret = rbd_obj_method_sync(rbd_dev, RBD_DIRECTORY,
 				"rbd", "dir_get_name",
 				image_id, image_id_size,
-				(char *) reply_buf, size, NULL);
+				reply_buf, size, NULL);
 	if (ret < 0)
 		goto out;
 	p = reply_buf;
-	end = (char *) reply_buf + size;
+	end = reply_buf + size;
 	image_name = ceph_extract_encoded_string(&p, end, &len, GFP_KERNEL);
 	if (IS_ERR(image_name))
 		image_name = NULL;
@@ -3831,7 +3829,7 @@ static int rbd_dev_probe_update_spec(struct rbd_device *rbd_dev)
 
 	name = rbd_dev_image_name(rbd_dev);
 	if (name)
-		rbd_dev->spec->image_name = (char *) name;
+		rbd_dev->spec->image_name = (char *)name;
 	else
 		rbd_warn(rbd_dev, "unable to get image name");
 
@@ -3882,8 +3880,7 @@ static int rbd_dev_v2_snap_context(struct rbd_device *rbd_dev, u64 *ver)
 		return -ENOMEM;
 
 	ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name,
-				"rbd", "get_snapcontext",
-				NULL, 0,
+				"rbd", "get_snapcontext", NULL, 0,
 				reply_buf, size, ver);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)
@@ -3891,7 +3888,7 @@ static int rbd_dev_v2_snap_context(struct rbd_device *rbd_dev, u64 *ver)
 
 	ret = -ERANGE;
 	p = reply_buf;
-	end = (char *) reply_buf + size;
+	end = reply_buf + size;
 	ceph_decode_64_safe(&p, end, seq, out);
 	ceph_decode_32_safe(&p, end, snap_count, out);
 
@@ -3952,14 +3949,14 @@ static char *rbd_dev_v2_snap_name(struct rbd_device *rbd_dev, u32 which)
 	snap_id = cpu_to_le64(rbd_dev->header.snapc->snaps[which]);
 	ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name,
 				"rbd", "get_snapshot_name",
-				(char *) &snap_id, sizeof (snap_id),
+				&snap_id, sizeof (snap_id),
 				reply_buf, size, NULL);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)
 		goto out;
 
 	p = reply_buf;
-	end = (char *) reply_buf + size;
+	end = reply_buf + size;
 	snap_name = ceph_extract_encoded_string(&p, end, NULL, GFP_KERNEL);
 	if (IS_ERR(snap_name)) {
 		ret = PTR_ERR(snap_name);
@@ -4555,8 +4552,7 @@ static int rbd_dev_image_id(struct rbd_device *rbd_dev)
 	}
 
 	ret = rbd_obj_method_sync(rbd_dev, object_name,
-				"rbd", "get_id",
-				NULL, 0,
+				"rbd", "get_id", NULL, 0,
 				response, RBD_IMAGE_ID_LEN_MAX, NULL);
 	dout("%s: rbd_obj_method_sync returned %d\n", __func__, ret);
 	if (ret < 0)