btrfs: use dev_t to match device in device_matched

Commit "btrfs: add device major-minor info in the struct btrfs_device"
saved the device major-minor number in the struct btrfs_device upon
discovering it.

So no need to lookup_bdev() again just match, which means
device_matched() can go away.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -534,45 +534,6 @@ btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
 	return ret;
 }
 
-/*
- * Check if the device in the path matches the device in the given struct device.
- *
- * Returns:
- *   true  If it is the same device.
- *   false If it is not the same device or on error.
- */
-static bool device_matched(const struct btrfs_device *device, dev_t dev_new)
-{
-	char *device_name;
-	dev_t dev_old;
-	int ret;
-
-	/*
-	 * If we are looking for a device with the matching dev_t, then skip
-	 * device without a name (a missing device).
-	 */
-	if (!device->name)
-		return false;
-
-	device_name = kzalloc(BTRFS_PATH_NAME_MAX, GFP_KERNEL);
-	if (!device_name)
-		return false;
-
-	rcu_read_lock();
-	scnprintf(device_name, BTRFS_PATH_NAME_MAX, "%s", rcu_str_deref(device->name));
-	rcu_read_unlock();
-
-	ret = lookup_bdev(device_name, &dev_old);
-	kfree(device_name);
-	if (ret)
-		return false;
-
-	if (dev_old == dev_new)
-		return true;
-
-	return false;
-}
-
 /**
  *  Search and remove all stale devices (which are not mounted).
  *  When both inputs are NULL, it will search and release all stale devices.
@@ -604,7 +565,7 @@ static int btrfs_free_stale_devices(dev_t devt, struct btrfs_device *skip_device
 					 &fs_devices->devices, dev_list) {
 			if (skip_device && skip_device == device)
 				continue;
-			if (devt && !device_matched(device, devt))
+			if (devt && devt != device->devt)
 				continue;
 			if (fs_devices->opened) {
 				/* for an already deleted device return 0 */