Rewrite upgrade-simple to C++

src/disk_tool_udev.cpp

@@ -1,6 +1,7 @@
 // Copyright (c) Vitaliy Filippov, 2019+
 // License: VNPL-1.1 (see README.md for details)
 
+#include <sys/file.h>
 #include <dirent.h>
 
 #include "disk_tool.h"
@@ -109,6 +110,11 @@ uint32_t disk_tool_t::write_osd_superblock(std::string device, json11::Json para
         free(buf);
         return 0;
     }
+    // Lock the file
+    if (flock(fd, LOCK_EX|LOCK_NB) < 0)
+    {
+        fprintf(stderr, "Warning: Failed to lock %s with flock - udev autodetection may fail. Error: %s\n", device.c_str(), strerror(errno));
+    }
     int r = write_blocking(fd, buf, buf_len);
     if (r < 0)
     {