FSCTL_LOCK_VOLUME

The FSCTL_LOCK_VOLUME operation 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 using the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,        // handle to a file
  FSCTL_LOCK_VOLUME,       // dwIoControlCode, control code of
                           // operation to perform
  NULL,                    // lpInBuffer is not used; must be NULL
  0,                       // nInBufferSize is not used; must be zero
  NULL,                    // lpOutBuffer is not used; must be NULL
  0,                       // nOutBufferSize is not used; must be zero
  (LPDWORD) lpBytesReturned,   // pointer to receive output byte count
  (LPOVERLAPPED) lpOverlapped  // pointer to OVERLAPPED structure
                               // for asynchronous operation
);

Parameters

hDevice

Handle to the volume to be locked. To obtain a device handle, call the CreateFile function.

dwIoControlCode

Control code for the operation. This value identifies the specific operation to be performed and the type of device on which the operation is to be performed. Use FSCTL_LOCK_VOLUME for this operation.

lpInBuffer

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

nInBufferSize

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

lpOutBuffer

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

nOutBufferSize

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

lpBytesReturned

Pointer to a DWORD variable.

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

Pointer to an OVERLAPPED structure.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, this parameter 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, this parameter 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

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.

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

The 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 invokes the FSCTL_UNLOCK_VOLUME DeviceIoControl operation 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.

QuickInfo

  Windows NT: Requires version 3.5 or later.
  Windows: Unsupported.
  Windows CE: Unsupported.
  Header: Declared in winioctl.h.

See Also

Device Input and Output Overview, Device Input and Output Operations, CloseHandle, CreateFile, DeviceIoControl, FSCTL_UNLOCK_VOLUME