FSCTL_OPLOCK_BREAK_ACKNOWLEDGE control code

Responds to notification that an exclusive opportunistic lock on a file is about to be broken. Use 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 
WINAPI 
DeviceIoControl( (HANDLE) hDevice,               // handle to file
                 FSCTL_OPLOCK_BREAK_ACKNOWLEDGE, // dwIoControlCode
                 NULL,                           // lpInBuffer
                 0,                              // nInBufferSize
                 NULL,                           // lpOutBuffer
                 0,                              // nOutBufferSize
                 (LPDWORD) lpBytesReturned,      // number of bytes returned
                 (LPOVERLAPPED) lpOverlapped );  // OVERLAPPED structure

Parameters

hDevice

A handle to the file or alternate stream on which the opportunistic lock is about to be broken. To retrieve 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

The control code for the operation. Use FSCTL_OPLOCK_BREAK_ACKNOWLEDGE for this operation.

lpInBuffer

Not used with this operation; set to NULL.

nInBufferSize

Not used with this operation; set to zero.

lpOutBuffer

Not used with this operation; set to NULL.

nOutBufferSize

Not used with this operation; set to zero.

lpBytesReturned

A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

This parameter is meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call GetOverlappedResult. If hDevice is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.

lpOverlapped

A pointer to an OVERLAPPED structure.

Because hDevice was opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. Therefore, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.

DeviceIoControl returns immediately, and the event object is signaled when the operation has been completed.

Return value

If the operation completes successfully, DeviceIoControl returns a nonzero value.

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

Remarks

This operation is used only by client applications that have requested an opportunistic lock from a local server. Client applications requesting opportunistic locks from remote servers must not request them directly—the network redirector transparently requests opportunistic locks for the application.

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 control code 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 control code.

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.

IIn Windows 8 and Windows Server 2012, this code is supported by the following technologies.

TechnologySupported

Server Message Block (SMB) 3.0 protocol

No

SMB 3.0 Transparent Failover (TFO)

No

SMB 3.0 with Scale-out File Shares (SO)

No

Cluster Shared Volume File System (CsvFS)

Yes

Resilient File System (ReFS)

Yes

 

Requirements

Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]

Header

WinIoCtl.h (include Windows.h)

See also

Oplock Semantics
CreateFile
DeviceIoControl
FSCTL_OPBATCH_ACK_CLOSE_PENDING
FSCTL_OPLOCK_BREAK_ACK_NO_2
GetOverlappedResult
HasOverlappedIoCompleted
Opportunistic Locks
OVERLAPPED

 

 

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