Fix fd leak in cache line checking

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/os/os-linux.h b/os/os-linux.h
index 1cd8272..b766cbf 100644
--- a/os/os-linux.h
+++ b/os/os-linux.h
@@ -263,10 +263,13 @@
 		return -1;
 
 	ret = read(fd, size, sizeof(size));
+
+	close(fd);
+
 	if (ret <= 0)
 		return -1;
-
-	return atoi(size);
+	else
+		return atoi(size);
 }
 
 #endif