block/rnbd-clt: Dynamically alloc buffer for pathname & blk_symlink_name

For every rnbd_clt_dev, we alloc the pathname and blk_symlink_name
statically to NAME_MAX which is 255 bytes. In most of the cases we only
need less than 10 bytes, so 500 bytes per block device are wasted.

This commit dynamically allocates memory buffer for pathname and
blk_symlink_name.

Signed-off-by: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: Lutz Pogrell <lutz.pogrell@cloud.ionos.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rnbd/rnbd-clt-sysfs.c

@@ -434,6 +434,7 @@ void rnbd_clt_remove_dev_symlink(struct rnbd_clt_dev *dev)
 	 */
 	if (strlen(dev->blk_symlink_name) && try_module_get(THIS_MODULE)) {
 		sysfs_remove_link(rnbd_devs_kobj, dev->blk_symlink_name);
+		kfree(dev->blk_symlink_name);
 		module_put(THIS_MODULE);
 	}
 }
@@ -492,10 +493,17 @@ static int rnbd_clt_get_path_name(struct rnbd_clt_dev *dev, char *buf,
 static int rnbd_clt_add_dev_symlink(struct rnbd_clt_dev *dev)
 {
 	struct kobject *gd_kobj = &disk_to_dev(dev->gd)->kobj;
-	int ret;
+	int ret, len;
+
+	len = strlen(dev->pathname) + strlen(dev->sess->sessname) + 2;
+	dev->blk_symlink_name = kzalloc(len, GFP_KERNEL);
+	if (!dev->blk_symlink_name) {
+		rnbd_clt_err(dev, "Failed to allocate memory for blk_symlink_name\n");
+		goto out_err;
+	}
 
 	ret = rnbd_clt_get_path_name(dev, dev->blk_symlink_name,
-				      sizeof(dev->blk_symlink_name));
+				      len);
 	if (ret) {
 		rnbd_clt_err(dev, "Failed to get /sys/block symlink path, err: %d\n",
 			      ret);

drivers/block/rnbd/rnbd-clt.c

@@ -59,6 +59,7 @@ static void rnbd_clt_put_dev(struct rnbd_clt_dev *dev)
 	ida_simple_remove(&index_ida, dev->clt_device_id);
 	mutex_unlock(&ida_lock);
 	kfree(dev->hw_queues);
+	kfree(dev->pathname);
 	rnbd_clt_put_sess(dev->sess);
 	mutex_destroy(&dev->lock);
 	kfree(dev);
@@ -1387,10 +1388,17 @@ static struct rnbd_clt_dev *init_dev(struct rnbd_clt_session *sess,
 		       pathname, sess->sessname, ret);
 		goto out_queues;
 	}
+
+	dev->pathname = kzalloc(strlen(pathname) + 1, GFP_KERNEL);
+	if (!dev->pathname) {
+		ret = -ENOMEM;
+		goto out_queues;
+	}
+	strlcpy(dev->pathname, pathname, strlen(pathname) + 1);
+
 	dev->clt_device_id	= ret;
 	dev->sess		= sess;
 	dev->access_mode	= access_mode;
-	strlcpy(dev->pathname, pathname, sizeof(dev->pathname));
 	mutex_init(&dev->lock);
 	refcount_set(&dev->refcount, 1);
 	dev->dev_state = DEV_STATE_INIT;
@@ -1422,8 +1430,8 @@ static bool __exists_dev(const char *pathname, const char *sessname)
 			continue;
 		mutex_lock(&sess->lock);
 		list_for_each_entry(dev, &sess->devs_list, list) {
-			if (!strncmp(dev->pathname, pathname,
-				     sizeof(dev->pathname))) {
+			if (strlen(dev->pathname) == strlen(pathname) &&
+			    !strcmp(dev->pathname, pathname)) {
 				found = true;
 				break;
 			}

drivers/block/rnbd/rnbd-clt.h

@@ -108,7 +108,7 @@ struct rnbd_clt_dev {
 	u32			clt_device_id;
 	struct mutex		lock;
 	enum rnbd_clt_dev_state	dev_state;
-	char			pathname[NAME_MAX];
+	char			*pathname;
 	enum rnbd_access_mode	access_mode;
 	bool			read_only;
 	bool			rotational;
@@ -126,7 +126,7 @@ struct rnbd_clt_dev {
 	struct list_head        list;
 	struct gendisk		*gd;
 	struct kobject		kobj;
-	char			blk_symlink_name[NAME_MAX];
+	char			*blk_symlink_name;
 	refcount_t		refcount;
 	struct work_struct	unmap_on_rmmod_work;
 };