FSCTL_OPLOCK_BREAK_ACKNOWLEDGE

The FSCTL_OPLOCK_BREAK_ACKNOWLEDGE operation responds to notification that an exclusive opportunistic lock on a file is about to be broken. An application uses this operation to indicate that the file should receive a level 2 opportunistic lock.

To perform this operation, call the DeviceIoControl function using the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,                // handle to file
  FSCTL_OPLOCK_BREAK_ACKNOWLEDGE,  // dwIoControlCode operation
  NULL,                            // lpInBuffer; must be NULL
  0,                               // nInBufferSize; must be zero
  NULL,                            // lpOutBuffer; must be NULL
  0,                               // nOutBufferSize; must be zero
  (LPDWORD) lpBytesReturned,       // number of bytes returned
  (LPOVERLAPPED) lpOverlapped      // OVERLAPPED structure
);

Parameters

hDevice

[in] Handle to the file or alternate stream on which the opportunistic lock is about to be broken. To obtain a handle, call the CreateFile function. The file or alternate stream must have been opened with the flag FILE_FLAG_OVERLAPPED. This handle must be the same one for which the opportunistic lock was originally requested.

dwIoControlCode

[in] Control code for the operation. This value identifies the specific operation to be performed and the type of device on which to perform it. Use FSCTL_OPLOCK_BREAK_ACKNOWLEDGE for this operation.

lpInBuffer

[in] Pointer to the input buffer. Not used; must be NULL.

nInBufferSize

[in] Size, in bytes, of the input buffer. Not used; must be zero.

lpOutBuffer

[out] Pointer to the output buffer. Not used; must be NULL.

nOutBufferSize

[in] Size, in bytes, of the output buffer. Not used; must be zero.

lpBytesReturned

[out] Pointer to a variable that receives the actual count of bytes returned by the function in the output buffer. The lpBytesReturned value is meaningless until the operation is complete or if there is no output buffer. With an asynchronous call, the programmer must provide a pointer to a valid value.

If lpOverlapped is NULL (nonoverlapped I/O), lpBytesReturned is used internally and cannot be NULL.

If lpOverlapped is not NULL (overlapped I/O), lpBytesReturned can be NULL.

lpOverlapped

[in] Pointer to an OVERLAPPED structure.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, lpOverlapped must point to a valid OVERLAPPED structure. In this case, DeviceIoControl is performed as an overlapped (asynchronous) operation. If the device was opened with the FILE_FLAG_OVERLAPPED flag and lpOverlapped is NULL, the function fails in unpredictable ways.

If hDevice was opened without specifying the FILE_FLAG_OVERLAPPED flag, lpOverlapped is ignored and the DeviceIoControl function does not return until the operation has been completed, or until an error occurs.

Return Values

If the operation succeeds, DeviceIoControl returns a nonzero value.

If the operation fails, DeviceIoControl returns zero. To get extended error information, call GetLastError.

Remarks

For the implications of overlapped I/O on this operation, see the Remarks section of the DeviceIoControl topic.

FSCTL_OPLOCK_BREAK_ACKNOWLEDGE is a response to notification that a level 1, batch, or filter opportunistic lock on an application's file has been broken. It indicates to the server that the application should receive a level 2 opportunistic lock. If the operation returns the error code ERROR_IO_PENDING, the server has granted the application a level 2 lock on the file.

One alternative to using FSCTL_OPLOCK_BREAK_ACKNOWLEDGE is to indicate that the application is about to close the file anyway. Use the FSCTL_OPBATCH_ACK_CLOSE_PENDING operation for this response.

Another alternative is to request to keep the file open but loose all locking, by means of the FSCTL_OPLOCK_BREAK_ACK_NO_2 operation.

Applications are notified that an opportunistic lock is broken by using the hEvent member of the OVERLAPPED structure associated with the file on which the opportunistic lock is broken. Applications may also use functions such as GetOverlappedResult and HasOverlappedIoCompleted.

Requirements

  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Unsupported.
  Header: Declared in Winioctl.h.

See Also

Device Input and Output Overview, Device Input and Output Control Codes, CreateFile, DeviceIoControl, FSCTL_OPBATCH_ACK_CLOSE_PENDING, FSCTL_OPLOCK_BREAK_ACK_NO_2, GetOverlappedResult, HasOverlappedIoCompleted, Opportunistic Locks, OVERLAPPED