btrfs: cleanup btrfs_find_device_by_devspec()

btrfs_find_device_by_devspec() finds the device by @devid or by
@device_path. This patch makes code flow easy to read by open coding the
else part and renames devpath to device_path.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -2402,7 +2402,8 @@ static struct btrfs_device *btrfs_find_device_by_path(
  * Lookup a device given by device id, or the path if the id is 0.
  */
 struct btrfs_device *btrfs_find_device_by_devspec(
-		struct btrfs_fs_info *fs_info, u64 devid, const char *devpath)
+		struct btrfs_fs_info *fs_info, u64 devid,
+		const char *device_path)
 {
 	struct btrfs_device *device;
 
@@ -2410,24 +2411,24 @@ struct btrfs_device *btrfs_find_device_by_devspec(
 		device = btrfs_find_device(fs_info, devid, NULL, NULL);
 		if (!device)
 			return ERR_PTR(-ENOENT);
-	} else {
-		if (!devpath || !devpath[0])
-			return ERR_PTR(-EINVAL);
-
-		if (strcmp(devpath, "missing") == 0) {
-			list_for_each_entry(device, &fs_info->fs_devices->devices,
-					    dev_list) {
-				if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
-					     &device->dev_state) &&
-					     !device->bdev)
-					return device;
-			}
-			return ERR_PTR(-ENOENT);
-		} else {
-			device = btrfs_find_device_by_path(fs_info, devpath);
+		return device;
+	}
+
+	if (!device_path || !device_path[0])
+		return ERR_PTR(-EINVAL);
+
+	if (strcmp(device_path, "missing") == 0) {
+		/* Find first missing device */
+		list_for_each_entry(device, &fs_info->fs_devices->devices,
+				    dev_list) {
+			if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
+				     &device->dev_state) && !device->bdev)
+				return device;
 		}
+		return ERR_PTR(-ENOENT);
 	}
-	return device;
+
+	return btrfs_find_device_by_path(fs_info, device_path);
 }
 
 /*