FSCTL_LOCK_VOLUME

The FSCTL_LOCK_VOLUME DeviceIoControl operation locks a volume. A locked volume can be accessed only through handles to the file object (*hDevice) that locks the volume.

dwIoControlCode = FSCTL_LOCK_VOLUME; // operation code

lpInBuffer = NULL; // pointer to input buffer; not used; must be NULL

nInBufferSize = 0; // size of input buffer; not used; must be zero

lpOutBuffer ; // pointer to output buffer; not used; must be NULL

nOutBufferSize ; // size of output buffer; not used; must be zero

lpBytesReturned ; // pointer to DWORD used by DeviceIoControl function

Parameters

lpInBuffer

Points to an input buffer. Not used with this operation. Set to NULL.

nInBufferSize

Specifies the size, in bytes, of the buffer pointed to by lpInBuffer. Not used with this operation. Set to zero.

lpOutBuffer

Points to an output buffer. Not used with this operation. Set to NULL.

nOutBufferSize

Specifies the size, in bytes, of the buffer pointed to by lpOutBuffer. Not used with this operation. Set to zero.

lpBytesReturned

Pointer to a DWORD. This value cannot be NULL. Although the FSCTL_LOCK_VOLUME operation produces no output data and lpOutBuffer should be NULL, the DeviceIoControl function uses the variable pointed to by lpBytesReturned. After the operation, the value of this variable is without meaning.

Return Values

If the operation succeeds, DeviceIoControl returns TRUE.

If the operation fails, DeviceIoControl returns FALSE. 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 timefor 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.

See Also

CloseHandle, CreateFile, DeviceIoControl, FSCTL_UNLOCK_VOLUME

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