Fix windows WithDirLock to exclusive lock

We use LOCKFILE_FAIL_IMMEDIATELY, creating a shared lock that fail
immediately if the lock cannot be acquired. This does not match the
behavior of the unix version and does not make sense.

Using now LOCKFILE_EXCLUSIVE_LOCK to acquire exclusive lock blocking
until the lock can be acquired.

Add constants for the flags and add comments for the argument names to
prevent future errors.

Signed-off-by: Nir Soffer <[email protected]>

pkg/lockutil/lockutil_windows.go

@@ -33,20 +33,37 @@ var (
  procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
 )
 
+const (
+ // see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
+ LOCKFILE_EXCLUSIVE_LOCK = 0x00000002
+ LOCKFILE_FAIL_IMMEDIATELY = 0x00000001
+)
+
 func WithDirLock(dir string, fn func() error) error {
  dirFile, err := os.OpenFile(dir+".lock", os.O_CREATE, 0o644)
  if err != nil {
  return err
  }
  defer dirFile.Close()
- // see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
- // 1 lock immediately
- if err := lockFileEx(syscall.Handle(dirFile.Fd()), 1, 0, 1, 0, &syscall.Overlapped{}); err != nil {
+ if err := lockFileEx(
+ syscall.Handle(dirFile.Fd()), // hFile
+ LOCKFILE_EXCLUSIVE_LOCK, // dwFlags
+ 0, // dwReserved
+ 1, // nNumberOfBytesToLockLow
+ 0, // nNumberOfBytesToLockHigh
+ &syscall.Overlapped{}, // lpOverlapped
+ ); err != nil {
  return fmt.Errorf("failed to lock %q: %w", dir, err)
  }
 
  defer func() {
- if err := unlockFileEx(syscall.Handle(dirFile.Fd()), 0, 1, 0, &syscall.Overlapped{}); err != nil {
+ if err := unlockFileEx(
+ syscall.Handle(dirFile.Fd()), // hFile
+ 0, // dwReserved
+ 1, // nNumberOfBytesToLockLow
+ 0, // nNumberOfBytesToLockHigh
+ &syscall.Overlapped{}, // lpOverlapped
+ ); err != nil {
  logrus.WithError(err).Errorf("failed to unlock %q", dir)
  }
  }()