ext2: check err when partial != NULL

Check err when partial == NULL is meaningless because
partial == NULL means getting branch successfully without
error.

CC: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191105045100.7104-1-cgxu519@mykernel.net
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/inode.c

@@ -701,10 +701,13 @@ static int ext2_get_blocks(struct inode *inode,
 		if (!partial) {
 			count++;
 			mutex_unlock(&ei->truncate_mutex);
-			if (err)
-				goto cleanup;
 			goto got_it;
 		}
+
+		if (err) {
+			mutex_unlock(&ei->truncate_mutex);
+			goto cleanup;
+		}
 	}
 
 	/*