rbd: remove snap_name arg from rbd_add_parse_args()

The snapshot name returned by rbd_add_parse_args() just gets saved
in the rbd_dev eventually.  So just do that inside that function and
do away with the snap_name argument, both in rbd_add_parse_args()
and rbd_dev_set_mapping().

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

drivers/block/rbd.c

@@ -665,23 +665,22 @@ static int snap_by_name(struct rbd_device *rbd_dev, const char *snap_name)
 	return -ENOENT;
 }
 
-static int rbd_dev_set_mapping(struct rbd_device *rbd_dev, char *snap_name)
+static int rbd_dev_set_mapping(struct rbd_device *rbd_dev)
 {
 	int ret;
 
-	if (!memcmp(snap_name, RBD_SNAP_HEAD_NAME,
+	if (!memcmp(rbd_dev->snap_name, RBD_SNAP_HEAD_NAME,
 		    sizeof (RBD_SNAP_HEAD_NAME))) {
 		rbd_dev->snap_id = CEPH_NOSNAP;
 		rbd_dev->mapping.size = rbd_dev->header.image_size;
 		rbd_dev->mapping.features = rbd_dev->header.features;
 		ret = 0;
 	} else {
-		ret = snap_by_name(rbd_dev, snap_name);
+		ret = snap_by_name(rbd_dev, rbd_dev->snap_name);
 		if (ret < 0)
 			goto done;
 		rbd_dev->mapping.read_only = true;
 	}
-	rbd_dev->snap_name = snap_name;
 	rbd_dev->exists = true;
 done:
 	return ret;
@@ -2843,8 +2842,7 @@ static inline char *dup_token(const char **buf, size_t *lenp)
  * Note: rbd_dev is assumed to have been initially zero-filled.
  */
 static struct ceph_options *rbd_add_parse_args(struct rbd_device *rbd_dev,
-						const char *buf,
-						char **snap_name)
+						const char *buf)
 {
 	size_t len;
 	const char *mon_addrs;
@@ -2893,11 +2891,11 @@ static struct ceph_options *rbd_add_parse_args(struct rbd_device *rbd_dev,
 		err_ptr = ERR_PTR(-ENAMETOOLONG);
 		goto out_err;
 	}
-	*snap_name = kmalloc(len + 1, GFP_KERNEL);
-	if (!*snap_name)
+	rbd_dev->snap_name = kmalloc(len + 1, GFP_KERNEL);
+	if (!rbd_dev->snap_name)
 		goto out_mem;
-	memcpy(*snap_name, buf, len);
-	*(*snap_name + len) = '\0';
+	memcpy(rbd_dev->snap_name, buf, len);
+	*(rbd_dev->snap_name + len) = '\0';
 
 	/* Initialize all rbd options to the defaults */
 
@@ -3132,7 +3130,6 @@ static ssize_t rbd_add(struct bus_type *bus,
 		       size_t count)
 {
 	struct rbd_device *rbd_dev = NULL;
-	char *snap_name;
 	struct ceph_options *ceph_opts;
 	struct ceph_osd_client *osdc;
 	int rc = -ENOMEM;
@@ -3151,7 +3148,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 	init_rwsem(&rbd_dev->header_rwsem);
 
 	/* parse add command */
-	ceph_opts = rbd_add_parse_args(rbd_dev, buf, &snap_name);
+	ceph_opts = rbd_add_parse_args(rbd_dev, buf);
 	if (IS_ERR(ceph_opts)) {
 		rc = PTR_ERR(ceph_opts);
 		goto err_out_mem;
@@ -3178,7 +3175,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 	if (rc)
 		goto err_out_probe;
 
-	rc = rbd_dev_set_mapping(rbd_dev, snap_name);
+	rc = rbd_dev_set_mapping(rbd_dev);
 	if (rc)
 		goto err_out_snaps;