FSCTL_LOCK_VOLUME

Using the FSCTL_LOCK_VOLUME control code locks a volume. A locked volume can be accessed only through handles to the file object (*hDevice) that locks the volume.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,            // handle to a volume
  FSCTL_LOCK_VOLUME,           // 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 volume to be locked. To obtain a device handle, call the CreateFile function.

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_LOCK_VOLUME 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.

If the output buffer is too small to return any data, then the call fails, GetLastError returns the error code ERROR_INSUFFICIENT_BUFFER, and the returned byte count is zero.

If the output buffer is too small to hold all of the data but can hold some entries, then the operating system returns as much as fits, the call fails, GetLastError returns the error code ERROR_MORE_DATA, and lpBytesReturned indicates the amount of data returned. Your application should call DeviceIoControl again with the same operation, specifying a new starting point.

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, the operation 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 DeviceIoControl 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

The hDevice handle passed to DeviceIoControl must be a handle to a volume, opened for direct access. An application can obtain such a handle by calling CreateFile with lpFileName set to a string that looks like this:

\\.\X: 

where X is a hard-drive partition letter, floppy disk drive, or CD-ROM drive. The application must also specify the FILE_SHARE_READ and FILE_SHARE_WRITE flags in the dwShareMode parameter of CreateFile.

This operation fails if there are any open files on the volume. Conversely, success of this operation indicates there are no open files.

This operation is useful for applications that need exclusive access to a volume for a period of time—for example, disk utility programs.

A locked volume remains locked until one of the following occurs:

• The application uses the FSCTL_UNLOCK_VOLUME control code to unlock the volume.
• The handle closes, either directly through CloseHandle, or indirectly when a process terminates.

The system flushes all cached data to the volume before locking it. For example, any data held in a lazy-write cache is written to the volume.

Requirements

  Windows NT/2000: Requires Windows NT 3.5 or later.
  Windows 95/98: Unsupported.
  Header: Declared in Winioctl.h.

See Also

Device Input and Output Overview, Device Input and Output Control Codes, CloseHandle, CreateFile, DeviceIoControl, FSCTL_UNLOCK_VOLUME